WO2009107865A1

WO2009107865A1 - Method for detecting breakouts in continuous casting and an apparatus therefor, breakout prevention apparatus, method for estimating solidification shell thickness and an apparatus therefor, and a continuous casting method for steel

Info

Publication number: WO2009107865A1
Application number: PCT/JP2009/054118
Authority: WO
Inventors: 飯嶋寛昌; 久保田淳
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2008-02-28
Filing date: 2009-02-26
Publication date: 2009-09-03
Also published as: TW200946265A; TWI389749B

Abstract

Disclosed is a method and an apparatus for detecting breakouts in continuous casting and an apparatus therefor, for precisely detecting breakouts that occur in slabs during the continuous casting of molten steel, wherein: a heat flux q1 of heat input to the solidification interface from when the molten steel in the mold is at bath level to when it reaches the mold exit, is measured; a steady solidification interface heat input q2_reg, caused by the flow of molten steel in mold in a steady state, is obtained based on the formula below (1); a heat flux profile is obtained for the difference between heat flux q1 and the steady solidification interface heat input q2_reg (q1-q2_reg) from when the molten steel is at bath level to when it reaches the mold exit; and whether a breakout occurred and whether the breakout is due to resolubility or heat extraction deficiency, is determined, based on the heat flux profile. q2reg=h⋅Δθ …………(1) Where: h = heat transfer coefficient between molten steel and solidification shell; and Δθ = degree of superheat of molten steel

Description

Description Breakout detection method and apparatus in continuous forging, breakout prevention apparatus, solidified shell thickness estimation method and apparatus, and steel continuous forging method TECHNICAL FIELD

The present invention relates to a method and an apparatus for accurately detecting and further preventing a breakout generated in a piece in continuous casting of molten copper. The present invention also relates to a continuous steel forging method using the breakout detection method.

The invention further relates to a method and apparatus for estimating the solidification shell thickness in the continuous casting of molten steel. Background art

In continuous forging, the molten steel poured into the mold is cooled in the mold to form a solidified shell and is drawn out of the mold. However, if for some reason the formation of the solidified shell becomes insufficient and there is a portion with a thin solidified shell thickness, the solidified shell will be broken when this thinned solid shell portion comes to the vertical outlet (bottom lower end). As a result, there is a risk of a so-called breakout of molten steel.

If a breakout occurs, the operation must be stopped, and it is necessary to select an operating condition that does not cause a breakout. Is not preferable because the operation efficiency deteriorates. Against this background, development of a method that can accurately determine the risk of breakout while performing high-speed fabrication is desired, and various methods have been proposed.

For example, Patent Document 1 (Japanese Patent Publication No. 63-53903) discloses the following technology.

In a method for preventing breakout in continuous forging by measuring the heat flux according to the heat extraction of mold with a thin plate type surface heat flux meter placed on the outer surface of the saddle. The local heat flux of each part of the saddle type is measured with several heat flux meters, and the entrainment speed is measured when the wave height of the heat flux waveform representing the temporal change of the heat flux suddenly exceeds a predetermined value. A breakout prevention method in continuous fabrication, wherein the occurrence of breakout is prevented by lowering and slowing in until the wave height returns to its original state. Disclosure of the invention

[Problems to be solved by the invention]

The technique disclosed in Patent Document 1 is a breakout prevention method by detecting a change in heat flux using a heat flux meter. The local heat flux of each part of the saddle shape means the amount of heat removed from the saddle shape, and the amount of heat removal is related to the formation of the solidified shell. Therefore, it is reasonable to predict that when there is an abnormality in the change in heat flux, there is an abnormality in the formation of the solidified shell thickness and there is a risk of breakout.

However, considering that the occurrence of breakout occurs when the thickness of the solidified shell does not reach the prescribed thickness at the vertical outlet, the risk of an accurate breakout can be grasped only by the change in heat flux. It's not always enough to do that. This is because even if there is an abnormality in the heat flux in the early stage of the solidified shell formation process in the vertical mold, a solidified shell is formed in the subsequent stage of the solidified shell formation process, If a solidified shell with a thickness is formed, it may be judged that there is no risk of breakout.

In other words, predicting the risk of breakout based only on the change in local heat flux shown in the conventional example was not a sufficiently accurate indicator.

As described above, the occurrence of breakout is directly related to the thickness of the solidified shell at the vertical outlet, and if the thickness of the solidified shell can be estimated accurately, the risk of breakout can be accurately determined. That is, the inventor considered that it is important to find an index closely related to whether the solidified shell thickness at the vertical outlet reaches a predetermined thickness.

Accordingly, an object of the present invention is to provide a method and an apparatus for detecting breakout generated in a piece more accurately and preventing it in continuous forging of molten steel. Another object of the present invention is to provide a method and apparatus for estimating the thickness of the solidified shell at the vertical outlet more accurately.

[Means for solving the problems]

The thickness of the solidified shell is closely related to the heat removal state between the saddle mold and the scissors. In other words, if the solidified shell thickness is thin, the amount of heat transferred from the piece to the bowl increases and the amount of heat removed increases. Conversely, if the thickness of the solidified shell is thick, the amount of heat transferred to the piece cup and bowl decreases. The amount of heat is reduced. The inventor decided to examine this fact in more detail and to examine the specific heat removal state in the actual saddle type.

In order to detect the heat removal state, it is necessary to obtain the heat flux at each part of the saddle type. This can be done as follows. Fig. 2 is a cross-sectional view of vertical mold 1, which is connected to the bottom of tundish 40, and molten steel 5 is discharged from immersion nozzle 3 installed in vertical mold 1 (arrow) Is shown. Mold powder 7 (shown as a layer) is added to the molten metal surface, and this mold powder 7 flows into the gap between the mold 1 and the molten steel 5 to act as a lubricant. The molten steel 5 is extracted by the mold 1 through the mold powder 7, and is pulled out toward the vertical mold outlet without forming the solidified shell 9.

FIG. 3 is an enlarged cross-sectional view showing a part of the vertical copper plate 11 forming the vertical mold 1. In order to obtain the heat flux, it is necessary to detect the temperature gradient in the vertical copper plate 11, and a thermocouple 17 is used to detect this. As shown in FIG. 3, the thermocouple 17 has a hole 15 formed in the bottom of the cooling water passage 13 formed on the outer surface of the vertical copper plate 11, and a certain distance in the depth direction 2 is formed therein. It is buried in the place. A temperature gradient is detected from the output of the embedded thermocouple 17, and the heat flux can be obtained by calculation based on this temperature gradient.

The local heat flux ql (J Vm ² ) is calculated by calculating the detection temperature of the two thermocouples 17 (T1 C), T2 CC), the embedding interval d (m), and the thermal conductivity of the vertical type 1; L As (jZs'm '^), use the following formula.

ql = λ (Tl— T2) Zd

According to the inventor's research, a pair of thermocouples 17 arranged in the vertical direction of the vertical shape is a vertical short piece (for example, the shorter side in a vertical shape with a horizontal cross section). As shown by the black circles in Fig. 4, a total of nine places were installed at a height of 40 to 200 mm below the normal surface position. Based on the output signal from these thermocouples 17, the local heat flux was obtained by the above equation, and the relationship between the local heat flux and the position of the molten metal surface force was investigated. Fig. 5 is a graph showing an example of the results of this investigation. The vertical axis shows the local heat flux (unit: jZs'm ² ), and the horizontal axis shows the distance from the molten metal surface (unit: mm). In this specification, the shape of the graph showing the relationship between the local heat flux and the distance from the molten metal surface is shown as the heat flux profile, where the vertical axis is the local heat flux and the horizontal axis is the distance from the molten metal surface. Yeah.

As shown in the graph of Fig. 5, the local heat flux decreases in the direction of the molten metal surface force toward the vertical outlet, takes a local minimum in the vicinity of the distance force S400mm from the molten metal surface, and then once shows an increasing trend. The increasing tendency shows a maximum value when the distance from the molten metal surface is about 600 mm, and then decreases again.

The inventor paid attention to the fact that the local heat flux turned from a decreasing tendency toward a vertical outlet toward the vertical outlet direction, and further studied.

The position where the local heat flux shows the minimum value is a distance from the molten metal surface of about 400 mm. The position of the discharge flow of the molten steel 5 (flow from the spout: arrow) of the immersion nozzle 3 is vertical. It coincides with the position where it collides with the short side (see Fig. 2). The relationship between such changes in local heat flux and molten steel discharge flow is as follows. Tells the following: -As shown in Fig. 5, the local heat flux decreases in the direction of the hot water surface force toward the vertical outlet, because the thermal resistance increased, that is, the solidified shell thickness gradually increased as shown in Fig. 2. It shows that it is getting thicker.

Then, at the position where the discharge flow of the molten steel 5 discharged from the immersion nozzle 3 collides with the solidified shell 9, the solidified shell 9 is remelted, the thickness of the solidified shell is reduced, and the thinned solidified shell 9 is solidified. It is thought that the heat generated by the molten steel flow is applied to the solid interface and the local heat flux is increased. .

Further, as it goes further downstream in the forging direction, the influence of molten steel flow disappears, and the local heat flux decreases again, which is considered to increase the thickness of the solidified shell.

From the above considerations, the shape of the solidified shell 9 at a certain moment is shown in Fig. 2. The thickness of the solidified shell 9 increases from the molten metal surface to the position of the local heat flux, and the local heat flux From the minimum value to the maximum value, the thickness of the solidified shell 9 decreases, and after the local heat flux maximum value, the thickness of the solidified shell 9 increases again.

In the vertical shape, the thickness of the solidified shell at the vertical shape outlet is determined through the process of increasing or decreasing the thickness of the solidified shell.

The relationship between the extent to which the solidified seal thickness grows in the mold and the degree to which the solidified shell 9 formed by re-dissolution of the solidified seal 9 becomes thinner is directly related to the solidified shell thickness at the mold outlet. It seems to be related. Furthermore, considering that the occurrence of breakout is related to the thickness of the solidified shell at the vertical outlet, the above two relationships are considered to be deeply related to the presence or absence of breakout.

Therefore, the inventor conducted further studies to investigate the relationship between the above-mentioned two levels, that is, the degree of growth of the solidified shell thickness and the degree of thinning of the solidified shell 9 once formed, and the occurrence of breakout.

<Introduction of solidification interface heat input>,

If the phenomenon of remelting of the solidified shell due to the molten copper flow does not occur in the vertical mold, for example, when there is no discharge from the immersion nozzle and only the molten steel in the vertical mold is pulled out, the solidified shell is removed from the molten metal surface. It is thought that the thickness gradually increases toward the mold outlet.

Assuming that the phenomenon of remelting of the solidified shell due to the molten steel flow does not occur, and assuming a graph where the horizontal axis is the distance from the molten metal surface and the vertical axis is the local heat flux, as in Fig. 5. In the case of Fig. 5, it is assumed that there will be a gradual rise and a gentle decrease curve.

In this case, the thickness of the solidified shell at the vertical outlet is considered to be proportional to the sum of the heat removal. In other words, if the situation is such an assumption, the heat flux profile in the above graph is blurred. It can be said that it can be easily used as an indicator of the occurrence of a breakout.

On the other hand, in an actual vertical mold, remelting of the solidified shell occurs due to the influence of the molten steel flow (hereinafter simply referred to as “molten steel flow”) due to the discharge flow from the submerged nozzle. As a result, the phenomenon of increased heat removal has occurred.

Therefore, in a state where there is an influence of the molten steel flow, the degree of growth of the solidified shell thickness is not proportional to the amount of heat removal but is proportional to the measured amount of heat removal minus the amount of heat removal due to the influence of the molten steel flow. Conceivable. The amount of heat removal due to the influence of the molten steel flow can be evaluated as heat input to the solidification interface by the molten steel flow (hereinafter simply referred to as “solidification interface heat input”).

Considering this, in the operating state in which molten steel is discharged from the immersion nozzle, the degree to which the solidified shell becomes thin can be evaluated by solidification interface heat input, while the degree to which the solidified shell grows depends on the thermocouple. Local heat flux force that can be measured Solidification interface Λ It can be evaluated by subtracting heat.

Therefore, by comparing these two evaluation quantities, it can be used as an indicator of breakout occurrence. By the way, if the solidification interface heat input is c ^ iZs'm ² ), this solidification interface heat input q2 is the heat transfer coefficient from the molten steel to the solidification interface h (in J / Vm ² '), and the degree of superheat of the molten copper Let be Δ Θ (in) and it can be expressed by the following equation.

q2 = h- Δ Θ (1)

However, h = l. 22 X 10 ⁵ XV ° ⁸

V: Molten steel flow velocity (mZs)

厶 0 = T ₀ -T _S (° C)

T _0: vertical type molten copper temperature (in)

T _s: Molten copper solidus temperature (° C)

The mold inner molten steel temperature T ₀ (° C) may be obtained by actually measuring the mold inner molten steel temperature, for example, based on the tundish (TD) molten steel temperature (actually measured value) You may calculate with a temperature estimation formula.

T ₀ = 705.156 + 0.544086T _TD ― 2.35053Vc-0.00303W + 18.12663 (0.10181nFC-0.3362)

However, T _TD : Temperature of molten steel in TD (° C) (actual value)

Vc: Forging speed (mz min) '

W: Forging width (m) (actual value)

FC: Applied current value (A) (actual value)

As described above, the solidification interface heat input q2 is related to the heat transfer coefficient h, and the heat transfer coefficient h is an amount related to the molten copper flow velocity V. Therefore, in order to measure the solidification interface heat input q2 online, it is necessary to measure the molten steel flow velocity V in the vertical mold online. While operating, the molten steel flow velocity V can be It is difficult to measure.

Therefore, the inventor samples the pieces produced in advance at various forging speeds, obtains the molten steel flow velocity values at each forging speed from the dendrite angle in the pieces, and based on the molten steel flow velocity values. We considered obtaining the solidification interface heat input q2. Here, the dendrite inclination is the inclination of the primary branch of the dendrite extending in the surface force thickness direction with respect to the normal direction to the surface of the slab, and is known to correlate with the molten steel flow velocity value.

The solidification interface heat input q2 obtained in advance is referred to as “solidification interface heat input q2j in a steady state, and is expressed as steady solidification interface heat input q2 _res . The purpose of using the term steady state is as follows. The purpose is to eliminate an abnormal state where the immersion nozzle is clogged and has a drift in the molten steel flow velocity.

Then, the inventor wanted to estimate the thickness of the solidified shell at the vertical outlet or evaluate the occurrence of breakout, and subtracted the steady-state solidification interface heat input q2 _reg from the local heat flux measured by the thermocouple in the operating state. A heat flux profile was obtained for the amount of heat, and based on this heat flux profile, it was considered to evaluate the thickness of the solidified shell at the vertical outlet or the occurrence of breakout. The reasons for considering the steady-state solidification interface heat input q2 _reg from the measured local heat flux in this way are as follows.

If the heat flux profile for the amount of heat obtained by subtracting the steady solidification interface heat input q2 _reg from the measured local heat flux in the operating state becomes a gradually decreasing curve, this heat flux profile is the above-mentioned immersion nozzle. This means that it is the same as the heat flow rate profile in the case where the molten steel in the mold is simply drawn out without discharging from the mold. This means that the solidification interface heat input q2 in the operating state is the same as the steady state solidification interface heat input q2 _res . In other words, in this state, the degree of thinning of the solidified shell is the same as in the steady state, that is, due to the molten steel flow from the normal immersion nozzle. It can be evaluated that breakout does not occur if the solidified shell grows normally. In this situation, the steady-state solidification interface heat input q2 _reg is subtracted from the measured local heat flux, and the solidification shell thickness at the vertical outlet is calculated based on the heat flux profile for the amount of heat. Can be estimated.

It should be noted that when the solidification interface heat input q2 is the same as the steady solidification interface heat input q2 _reg , the breakout caused by the solidification interface remelting due to the increase in the solidification interface heat input q2 (hereinafter referred to as “ In this case, it contributes to the growth of the solidified shell thickness while moving from the molten steel caniscus to the vertical bottom exit. If the solidified shell does not grow sufficiently during this movement when the amount of heat removal is small and the thickness is thin, a breakout due to the small amount of heat removal contributing to the growth of the solidified shell thickness (hereinafter simply referred to as “heat removal”). There is a risk of occurrence of deficiency breakout J). On the other hand, if the heat flux profile related to the amount of heat obtained by subtracting the steady solidification interface heat input q2 _reg from the local heat flux measured by the thermocouple rises at a certain distance from the molten metal surface, that is, the heat flux profile has a minimum value. This means that the actual solidification interface heat input q2 is larger than the steady solidification interface heat input q2 _reg , and in this state, the degree of remelting of the solidified shell is less than in the steady state. It is considered high. For example, a drift in the molten steel flow occurs in the vertical mold due to the clogging of the immersion nozzle, and the heat input at the vertical interface that is the object to be measured increases more than usual.

In this case, it is considered that the size of the bumps represents a heat input larger than the normal solidification interface heat input q2. In other words, it can be evaluated that the degree of the size of the bumps is such that the solidified shell caused by the abnormal molten steel flow is remelted and the thickness of the solidified shell is reduced, and if this is large, vertical cooling is performed as usual. Even so, it can be evaluated that there is a risk of occurrence of a remeltable breakout.

In this way, by subtracting the steady-state solidification interface heat input q2 _res from the measured local heat flux and obtaining the heat flux profile for the amount of heat, solidification depends on the presence or absence of bumps and the magnitude of the heat flux profile. It is possible to clearly grasp the degree of shell remelting compared to the steady state, and it is possible to estimate the thickness of the solidified shell at the vertical outlet, and the remeltability based on the thickness etc. The risk of breakout can be evaluated.

In addition, it is possible to evaluate the risk of a heat-out insufficient breakout by obtaining the heat removal amount excluding the bumps.

Therefore, the inventor obtained the molten steel flow velocity from the dendritic tilt angle for various forging speeds, obtained the steady solidification interface heat input q2 _res for each case, and obtained this steady solidification interface heat input q2 _reg for the operating conditions. The heat flux profile subtracted by the thermocouple in the state was obtained, and the heat flux profile was obtained. The solidified shell thickness was estimated based on the heat flux profile, and the occurrence of breakout was further investigated.

Hereinafter, the contents of the examination will be specifically described.

Figure 6 shows the relationship between the molten steel flow velocity (mZs) and the distance from the molten metal surface (mm) based on the dendrite tilt angle of the slab when the forging speed Vc = 2.54 mZmin and the forging width W = 1100 mm. The graph is graphed with the molten metal flow velocity on the vertical axis and the distance of the molten metal surface on the horizontal axis.

The molten steel flow velocity V (m / s) is obtained from this graph, and the steady solidification interface heat input q2 _res is obtained based on the above equation (1). Then, the local heat flux in the operating state is measured with a thermocouple, and the steady-state solidification interface heat input q2 _re8 at the same forging speed as the measured operating state is subtracted from the measured value force to obtain the heat flux profile for the subtracted heat amount. In Fig. 7, the vertical axis shows the local heat flux (jZs' m ² ), the horizontal axis shows the distance (mm) from the molten metal surface, and the black circle value (D1) in the graph shows the value measured by the thermocouple. The white circle value (D2) indicates the value measured by the thermocouple, the steady-state solidification interface heat input q2 _reg , and the value (ql-q2 _reg ).

Fig. 8 is a graph schematically showing the heat flux profile of (ql-q2 _res ) drawn by the white circles in Fig. 7. The area enclosed by the graph, that is, the integrated value of the local heat flux (overall heat It is explanatory drawing explaining an example of how to obtain | require (flux).

Hereinafter, the method for obtaining the overall heat flux will be described with reference to FIG.

First, as shown in FIG. 8, the graph is divided into a plurality of trapezoids to obtain the area of each trapezoid (Q1-1 to Q1-7), and the total area Q is obtained by adding them.

The minimum point in the graph is A, the maximum point is B, the saddle-shaped exit point is C, the triangle ABC is regarded as a bump, and the area of this bump, that is, the area Q2 of the triangle ABC is obtained as follows (Fig. 9). reference). The point on the horizontal axis corresponding to point A is A ', the point on the horizontal axis corresponding to point C is C', and the area Q1-8 of trapezoid AC TA 'is obtained, and this Q1-8 and Ql-1 ~ Q1— If the area obtained by adding 3 is Q1, Q2 = Q-Q1.

Based on Q1 and Q2 obtained in this way, we examined the relationship between the occurrence of breakout in each forging condition. The results are shown in Table 1. With regard to the presence or absence of breakout, it was determined that a breakout occurred when the shell thickness was 6mm or less.

Q1 Q2 Breakout Example

Occurrence

1 19000 1200 None

2 17900 1450 None

3 25000 540 None

4 27000 Τ500 None

5 28000 3500 None

6 31500 5000 None

7 33500 8500 None

8 27500 6850 None

9 26000 10050 None

10 19500 3550 None

11 18900 4090

Ε None

12 17800 3950

Μ (None

13 17900 4500 Y

14 19000 5700 Yes y

t5 19070 5950 Yes

16 19 450 7500 Yes

17 20570 8500 Yes

ΐ & 14000 1000 Yes

19 ί3300 100 Yes

20 12500-1020 CM available

21 11700 1500 Yes

22 10500 3200 Yes

23 9750 1500 Yes

24 8050 300 Yes y

25 7650 450 Yes

26 6500 270 Yes

27 5450 55 Yes

28 4890 150 Yes

29 14500 108Q0 Yes

30 13000 9000 Yes

31 12700 9500 Yes

32 10700 8000 Yes

33 10 200 7500 Yes

34 9000 6000 Yes

35 7050 5500 Yes

36 8650 8200 Yes

37 7400 4500 Y

38 5100 4700 Yes y

39 7150 6800 Yes

40 6950 6500 Yes y

Figure 10 plots the numerical values shown in Table 1 on the coordinate plane with the horizontal axis Ql (kjZm ² ) and the vertical axis Q2 (kjZm ² ), and the coordinate plane in relation to the occurrence of breakout. Is divided into five areas. The boundaries of the region are: Q l (al) = 15000 (kj / m ² ), Q l (a 2) = 21000 (kj / m ² ), Q2 (i3) = 4500 (kjZm ² ).

In the area shown in FIG. 10, areas (1) to (3) are areas where there is a risk of breakout occurrence (that is, areas where the breakout judgment is “Yes” in the above investigation), and areas ( 4) and (5) are areas where there is no risk of breakout. First, we will compare and examine the common areas (1) to (3) where there is a risk of breakout. Area (1)>

Region (1) (Ql <a 1 and Q2≥) Q 1 is small and it can be evaluated that both the risk of insufficient heat removal breakout and the risk of occurrence of remeltable breakout are large. . And since there was actually a breakout in region (1), it can be said that this breakout has the properties of both an underheated breakout and a remeltable breakout.

From the viewpoint of the solidified shell thickness in the state of region (1), since Q1 is small, the total solidified shell thickness is thin and Q2 is large. It is thought that there is a part that is connected and the degree of thinning is large.

Area (2)>

Region (2) (Q l <a 1 and Q2 <J3) has a small Q1 and there is a risk of inadequate heat removal breakout. Since force Q2 is also small, the risk of remelting breakout is small. Can be evaluated. And since there was actually a breakout in region (2), it can be said that this breakout has the property of an insufficient heat release breakout.

In terms of the state of region (2) from the viewpoint of the solidified shell thickness, since Q1 is small, the total thickness of the solidified shell is thin, but since Q2 is small, the thickness of the solidified shell is locally thin. It is considered that there is no part that exists, or even if it exists, the degree of thinning is small.

Area (3)>

Region (3) (a 1≤Q1≤ α ₂ and Q2≥] 3) is less danger of Q 1 is relatively large heat extraction lack of breakout generation, the re-solubility breakout occurs because Q2 is large It can be evaluated as a dangerous area. Since breakout actually occurred in the region (3), it can be said that this breakout has the property of re-dissolvable breakout.

From the viewpoint of the solidified shell thickness in the state of region (3), since Q1 is large, the total thickness of the solidified shell is relatively thick, but since Q2 is large, the thickness of the solidified shell is locally increased. There is a part where the thickness is thin, and the degree of thinning is considered to be large. Next, we will compare the areas (4) and (5) where no breakout occurs. <Area (4)>

Region (4) (Ql> α 2 and Q2≥ / 3) is a region where Ql is large and there is little risk of underheated breakout, but because Q2 is large, there is a risk of remeltable breakout. It can be evaluated that there is. In this region (4), the breakout generation was ineffective, and the amount of heat removal that contributed to the growth of the solidified shell thickness was sufficiently large. Even if there is a hot spot, it is considered that the breakout was extremely powerful.

Area (5)>

Region (5) (Ql> α 1 and Q2 <0) is a region where Q1 is relatively large and there is little risk of occurrence of incomplete heat breakout. Since Q2 is small, there is no risk of remeltable breakout. Can be evaluated. In addition, the absence of breakout in this region (5) means that the amount of heat removal contributing to the growth of the solidified seal thickness was large, and therefore there was no portion where the solidified shell was locally thin because the thickness of the entire solidified shell was thick. It was thought that it was hard enough to make it thin even if it was hot. As can be seen from the examination of the above regions (4) and (5), when the state of region (4) and the state of region (5) are compared, the state of region (5) is more preferable. Therefore, in order to change the state of the areas (1) to (3) where the breakout occurred to a state where no breakout occurred, it is effective to change the state to the area (4). It is more preferable to control the operating conditions so as to achieve the state of (5).

Specifically, if it is in the state of region (1), operate to increase Q1 to the state of region (4) or further decrease Q2 to the state of region (5). The condition may be controlled. In the state of the region (2), the operating conditions may be controlled so that Q 1 is increased to the state of the region (5). In addition, when in the state of region (3), the operating conditions should be set so that Q2 is reduced to force the state of region (5) or Q 1 is increased to the state of region (4). If you control.

Controlling operating conditions that increase Q1 includes reducing the forging speed and / or increasing the vertical cooling. In order to control the operating conditions for reducing Q2, electromagnetic brake devices are placed, for example, above and below the immersion nozzle discharge hole in a vertical type, and the flow rate of molten steel is reduced by applying a DC magnetic field. Can be mentioned. The basic method of the above explanation is to determine the heat flux ql that enters the solidification interface from the molten steel surface to the vertical outlet and the steady solidification interface heat input q2 _res to obtain (ql _q2 _res ) To determine whether a breakout can occur based on the heat flux profile. The description other than this is an example, and the present invention is not limited to the above contents.

For example, the heat flux ql can be obtained by a method such as a method of obtaining from the inlet and outlet temperatures of the vertical cooling water. good. Further, the steady-state solidification interface heat input (12 ^ may be obtained based on the result of the estimated value of the molten steel flow velocity by, for example, numerical simulation within the vertical mold.

The method of analyzing the heat flux profile of (ql-q2 _reg ) is most preferably performed by calculating Q 1 and Q 2 described above, but is not limited to this. For example, the height and position of the bumps may simply be used as a criterion for determining the risk of breakout (for example, it is considered effective in the case of a facility with a strong molten steel flow that hits the solidification interface and a large fluctuation). .

When analyzing using Q1 and Q2, if there is no minimum value or bumps in the heat flux profile, Q1 = Q (Fig. 8) and Q2 = 0 may be used. If the minimum value of (ql—q2 _reg ) is difficult (partially ambiguous, two or more locations are found, etc.), draw an approximate curve as close as possible to the pattern shown in FIG. q2 _reg ) reduction curve (the curve corresponding to Q1 in Fig. 9, that is, the lower the local heat flux the closer to the molten metal surface, the larger the curve).

Although it is preferable to consider both Q1 and Q2, it is also possible to use only Q1 for estimation of shell thickness and judgment of breakout. For example, it is difficult for molten copper to reach the solidification interface. When Q2 fluctuation is expected to be small, it is expected that there will be little decrease in estimation and judgment accuracy without considering Q2.

Needless to say, integration means other than the above-described method (trapezoidal method) may be used to obtain Q l and Q2. In the analysis of Fig. 9, the boundary line AC between Q1 and Q2 need not be a straight line. For example, the curve from the molten metal surface to A may be taken into account as an approximate curve.

The specific breakout determination using Q1 and Q2 is not limited to the method described above, and Q1 is an index of heat removal due to solidification (that is, a factor that reduces the risk of breakout by increasing the value). Q2 can be used appropriately as an indicator of solidification interface heat input exceeding the steady state (ie, a factor that increases the risk of breakout by increasing the numerical value).

However, Q l <α 1 corresponding to the case where the solidified shell thickness growth is insufficient regardless of Q2 (region (1) and region (2) above), and the solidified shell thickness growth is a breakout regardless of Q2. Q 1> α 2 corresponding to the region (5) where Ql> a 2 and region (4)) are often present. It is preferable to predetermine the ground α 1 and α 2 (α 1 <α 2).

In this case, the region of a 1 ≤ Q1 ≤ α 2 is a region affected by the magnitude of Q2, so it may be determined that there is a risk of breakout depending on the value of Q2. That is, in this case, it is preferable to determine that there is a risk of breakout when a predetermined threshold value is exceeded. The threshold value of Q2 is preferably determined based on Q1, but as a result, it may be a constant value throughout al≤Q l≤α2. This corresponds to the β force in the example in Table 1 above. As another method, it is conceivable to further subdivide a 1≤Q1≤ «2 and set a threshold value for each region. For example, if α3 and α4 are set (α1 <α3 <α4 <α2), then Q≥] 31 if α1≤Q1 <α3, Q2 if a3≤Ql <α4, if a4≤Ql≤ α2 In addition, Q≥j33 can be a condition corresponding to the occurrence of breakout. In this case, generally: 31 <β2 <β3.

In addition, in the region of al≤Ql≤ α2, Q2≥f (Ql) (f is a function) can be set as a condition corresponding to the occurrence of a breakout. For example, in Table 1, in the range of α 1 (15000kjZm ² ) to α 2 (21000kj / m ² ) (Examination Examples 1, 2, 10 to 17), the criterion of Q2≥ aQl (a = 0.25) It is also possible to use. Depending on the equipment, it may be sufficient to make a breakout judgment by simply using Q2 ≥ a Ql (α: 0.25), for example, without providing the above-mentioned boundary due to α 1 and α 2 (Q 1 depending on operating conditions) If the fluctuation is small, etc.)

Q1 and Q2 do not have an upper limit, but this is because there is an upper limit to the values that Q1 and Q2 can take depending on the equipment.

It should be noted that the values of α1, α2, J3, and α exemplified above agree well when the molten steel is an extremely low carbon steel. Here, the extremely low carbon steel with molten steel refers to steel with C≤0.01% at the stage of forging molten steel. In the above breakout judgment method, the basic part of the analysis of the solidified shell formation phenomenon does not depend on the steel type. Therefore, it can be applied to other steel types without problems by calibrating coefficients and thresholds as necessary. As described above, the inventor believes that each value of Ql and Q2 is closely related to the occurrence of breakout, and each force value is related to the cause of occurrence of a different breakout. By using the value of Q2 as an indicator of the occurrence of breakouts, breakout occurrences can be detected accurately, and control to avoid the risk of breakouts can be appropriately performed based on the cause of breakout occurrences. I found. <Estimation of solidified shell thickness>

By the way, the overall heat flux Q1 obtained in this way can be evaluated as the amount of heat consumed for solidification of the molten steel, and the overall heat flux Q2 re-melts the solidified shell by collision of the molten steel flow with the solidified shell. It can be evaluated that it is the sensible heat of the molten steel flow that is the amount of heat. In other words, if the thickness of the solidified shell at the vertical outlet is estimated based on the overall heat flux Q1, the solidified shell thickness can be accurately estimated. Therefore, we determined the solidified shell thickness from Q1 and examined the possibility of quantitatively evaluating the risk of breakout from the solidified shell thickness. Hereinafter, a method for estimating the thickness of the solidified shell at the vertical outlet using the overall heat flux Q1 will be described. First, considering the physical process of solidification of the molten steel in the vertical mold, the molten steel injected from the immersion nozzle into the vertical mold has an enthalpy: H ₀ (heat content) including sensible heat and latent heat of solidification. . The molten copper having this enthalby: H ₀ loses the enthalpy of heat dissipation: AH _sur by dissipating the heat of the hot water surface, and is removed by vertical cooling between the hot water surface and the vertical outlet. Enthalpy drop of enthalpy drop corresponding to the amount of heat removed, and finally the bow I is punched from the bowl as a solidified shell with enthalpy at the bowl exit. . This enthalpy relationship from the immersion nozzle to the molten metal injected into the vertical mold reaches the molten metal surface vertical outlet is expressed by the following equation (4).

^^ = ^^ + △ 11 + 厶 H _sur (4)

However, H ₀ : Enthalpy of molten steel in a vertical mold O kg)

Hi: Enthalpy of solidified shell at the vertical outlet (jZkg)

Δ H: タルピーピーピータル (jZkg) per unit weight of solidified shell at the vertical outlet 厶 H molten metal surface heat dissipation a / kg)

Here, ¾ and Δ Η H ₀ can be obtained as follows. Gu! How to find ^>

The enthalpy of the solidified shell at the vertical outlet can be obtained from the following equation (5).

H! = 670. 27T _lave + 11958 (5)

Equation (5) expresses the enthalpy by integrating the specific heat of solid-phase steel with temperature and expresses it as a function of temperature. T _{lave in} Eq. (5) represents the average temperature of the solidified shell at the vertical outlet, and this T _Iave is obtained from Eq. (6) shown below.

T _lave = 28. 75Vc + 1234. 275 (6)

Vc: Forging speed (mZmin)

Equation (6) calculates the heat transfer solidification in the vertical mold at Vc = 1.4m / min 1.8m / min 2.2m / min 2.6m / min, and the calculated average temperature of the vertical outlet seal Vc It is expressed as a linear expression of Figure 11 shows the graph used to derive Eq. (6). In Fig. 11, the vertical axis shows the vertical outlet shell thickness direction average temperature C), and the horizontal axis shows the forging speed (m / min).

The enthalpy: Δ H _sur corresponding to the heat release from the molten metal surface can be obtained from the following equation (7).

厶 H _sur = (10000Z7100). (60ZVc) (7)

Vc: Forging speed (mZmin)

Equation (7) is the amount of heat released from the molten metal surface, and how much enthalpy is released per unit volume of molten steel. It is calculated. If the discharge enthalpy per unit surface area of the molten metal is AH _sur '(unit W / m ² ), the amount of enthalpy release per unit volume of molten steel Δ H _sur (J / kg) is expressed as the rate of forging per unit time Δ H _sur Since it suffices to divide by the determined molten steel weight, AH _sur = ^/ (density 7100 ¥ (; / 60 1 (= unit area)), and AH _SU / is set to 10000 W / m ² (7) It is.

<H. How to find>

The enthalpy of vertical molten steel: H ₀ is obtained by integrating the specific heat of liquid phase steel with temperature to obtain the enthalpy and expressing it as a function of temperature based on equation (8). Can do.

_{^{H 0 = (1 X 10- 10}} XT 0 4 -4X 10 "7 XT 0 3 + 0.0005 XT 0 2 - 0.0098 XT 0 + 4.5508)

X 4.19 X 1000 (8)

However, T ₀ : Temperature of molten steel in vertical mold (° C)

In addition, the molten copper temperature T ₀ in Eq. (8) is the following (9), where the molten steel temperature in the eaves was actually measured with a thermocouple in the existing equipment, and the multiple regression equation was calculated under the operating conditions at that time. ) Expression force can be obtained.

T ₀ = 705.156 + 0.544086T _XD -2.35053Vc-0.00303W

+18.12663 (0.10181-ln (FC) -0.3362) (9)

However, T _TD : Tundish (TZD: tundish) internal steel temperature (° C)

(Vc: Forging speed, m / min)

W: Mold (M / D) width (m)

FC: FC (flow control) current (A) As described above, Hi, AH _sur , and H ₀ can be obtained. Therefore, ΔΗ can be obtained from the following equation (10) obtained by modifying equation (4). .

Since ΔΗ is an enthalpy equivalent to the amount of heat removed by removing heat from the hot water surface to the vertical outlet, the solidified shell thickness D at the vertical outlet is calculated using the overall heat flux Q1. It can be expressed by equation (2).

Where p: density of solidified shell at the vertical outlet (kgZm ³ )

In addition, p can be obtained from the following equation (11), which is a recursive equation that obtains the density of solid iron from 20 to 1500 at 5 points and makes it a function of temperature.

_{^{P = (- 1.686 X 10- 10}} T lave 3 +2.7069 X 10- 7 T lave 2 - 5.2909 X lO _ T lave +7.9106) X 1000 ... (11) It should be noted, AH _sur, for H _0, how to obtain the p Is not limited to the method described above. In the above examination, the overall heat flux Q2 is excluded from the overall heat flux for estimating the solidified shell thickness, assuming that the molten steel flow collides with the solidified shell and is a molten steel flow collision sensible heat that remelts the solidified shell. I did it.

However, when the molten steel discharge flow temporarily increases from the immersion nozzle during forging, that is, when the overall heat flux Q2 is present, the solidified shell is remelted by the molten steel flow, and solidification delay is considered to occur. . For this reason, it is conceivable that the thickness of the solidified shell becomes thinner than the thickness of the solidified shell obtained by simply excluding the overall heat flux Q2.

Therefore, in the following, a more accurate estimation method of the solidified shell thickness in consideration of the solidification delay due to remelting will be described.

The inventor considered that even if remelting due to the overall heat flux Q2 occurs, not all of the overall heat flux Q2 acts to remelt the solidified shell, but some of it acts to remelt. . Considering that, the solidified shell thickness estimated based on the overall heat flux Q1 is considered to be D, and the solidified shell thickness considering remelting due to the overall heat flux Q2 is considered to be that X1 of Q1 and Q2 acts as remelting. The following proportional relationship is established.

Q1: D = (Q1 -X-Q2): D1

If the above proportional expression is arranged for D1, D1 = D (1—X'Q2 / Q1).

Therefore, if X can be obtained, D1 can be obtained.

Therefore, if the above proportional expression is arranged with respect to X, X = (D_D1) ZD'Q1ZQ2. The value of (D—Dl) ZD that appears in this equation is the solidification delay RS (Retardation of Solidification), which is a well-known document “Effects of Molten Steel Flow and Molten Superheat” (( Germany) Japan Society for the Promotion of Science, Steel 19th Committee Solidification Process Study Group presentation materials: p.8-9), it is shown that it can be obtained by the following formula (3).

RS = | 3 X (V ⁰ · ⁸ · 厶 0) · '· · (3)

β: Coagulation delay constant (unitless)

V: Molten steel flow velocity (m / s)

厶 Θ: Molten steel superheat (° C)

RS: Solidification delay (no unit)

As described above, the degree of superheat of molten steel Δ 0 can be determined as Δ Θ = T ₀ — T _S (T .: Molten steel temperature (in), T _s: Molten steel solidus temperature (° C)) Therefore, if the molten steel flow velocity V is obtained, RS can be obtained. The molten steel flow velocity V ( _{m <} s) can be obtained from the force of equation (13) using the overall heat flux Q2.

V = (Q2 / (a -t- A θ)) ¹ ²⁵ * (13) a: Molten steel flow rate constant (no unit)

t: Time required for the solidification seal to pass through the minimum point in the profile to reach the force-type outlet)

X = (D—D ZD.Q1ZQ2 In the equation, if (D—D1) ZD is replaced with RS, then X = RS-Q1 ZQ2. This value of X is the above-mentioned Dl = D (1—X.Q2ZQ1) Substituting into, Dl = D (1-RS), so that the solidification shell thickness D1 can be obtained in consideration of the solidification delay As described above, the solidification delay RS shown in the above equation (14) can be obtained. Therefore, the solidification seal thickness D1 considering the solidification delay due to the overall heat flux Q2 can be obtained as D1 = D (1 – RS).

In order to verify the validity of the above examination, D and D1 were obtained under some operating conditions and compared with values obtained by other methods.

As a comparison method, the following D ′ and D1 ′ were calculated.

Shell thickness calculated from only the amount of heat removed using a heat flux profile with D '= ql only. In other words, ql is used instead of ql q2 _res , and a value corresponding to the overall heat flux Q is calculated (referred to as Q ′), and D ′ = Q ′ Z (AH ′) according to the above equation (2) ρ)

Shell thickness considering solidification delay in Dl '== D'. That is, the value obtained from Dl '= D' (1—RS) from RS.

D _real = Internal crack location force of the shell Estimated shell thickness

Table 2

Vc: Forging speed

W: Forged width

T _TD : Temperature of molten steel in TD

Δ 0: Molten steel superheat

FC: Upper pole FC DC current

RS: Solidification delay As a result, the component force D and D1 are stable and close to the measured values, and D1 is particularly improved. In this way, the solidified shell thickness D at the vertical outlet can be obtained using the overall heat flux Q1, and further, the solidified shell thickness D1 in consideration of the solidification delay can be obtained.

If the thickness of the solidified shell can be obtained, the relationship between the thickness of the solidified shell and the presence / absence of occurrence of breakout can be obtained in advance to provide an index for the presence / absence of occurrence of breakout. For example, when the predicted thickness D exceeds the threshold, it can be determined that the breakout occurs, or when the predicted thickness D1 exceeds the threshold, it can be determined that the breakout occurs. . The threshold may be set in advance from examples or calculated by theoretical calculation according to the steel type, equipment, and operating conditions. Moreover, this breakout occurrence index is based on the thickness of the solidified shell at the vertical outlet, and is a more direct index than that based solely on the change in heat flux described above. It can be said that the accuracy is high.

In addition, the breakout generation detection method based on Q1 or based on Q1 and Q2 as illustrated in FIG. 10 may be omitted while apparently omitting the process of actually calculating the solidified shell thickness. Since the presence or absence of breakout is predicted based on the effect on Ql and Q2 on the thickness of the solid shell, high accuracy can be obtained as well. The present invention has been made based on the above knowledge, and specifically has the following constitutional power.

(1) The step of measuring the heat flux ql that enters the solidification interface between the molten steel in the mold from the molten metal surface to the mold outlet in continuous forging, and the steady state due to the molten steel flow in the mold in the steady state The solidification interface heat input q2 _res is calculated based on the following equation (1), and the difference between the heat flux ql and the steady solidification interface heat input q2 _res (ql-q2 _reg ) A breakout detection method in continuous fabrication, comprising: a step of obtaining a heat flux profile up to and a step of determining whether or not there is a risk of occurrence of a breakout based on the heat flux profile.

q2 _reg = h- Δ Θ. (1)

Where h: heat transfer coefficient between molten steel and solidified shell

ΔΘ: degree of superheat of molten steel. (2) The breakout detection method in continuous fabrication as described in (1) above, wherein whether or not there is a risk of occurrence of breakout is determined based on the heat flux profile obtained for (ql-q2 _res ) The steps to do are:

A step of obtaining overall heat fluxes Q1 and Q2 by the following method based on the heat flux profile; that is, (i) if there is a minimum point showing a minimum value in the heat flux profile, When the local heat flux value at the vertical outlet is connected with a straight line, the overall heat flux corresponding to the area above the straight line is defined as Q2, and the heat flux from the hot water surface to the vertical outlet is defined as Q2. The total heat flux corresponding to the total area enclosed by the entire profile curve Q2 is the total heat flux corresponding to the area minus Q2, and (ii) there is no minimum point indicating the minimum value in the heat flux profile. In this case, the step of setting the total heat flux corresponding to the entire area surrounded by the entire curve of the heat flux profile between the molten metal surface force 铸 type outlet as the total heat flux Q1 and Q2 as zero; and

Determining whether there is a risk of occurrence of breakout based on the overall heat flux Q1 or based on Q1 and Q2.

The overall heat flux is obtained by integrating the local heat flux as is apparent from the above description.

(3) The breakout detection method in continuous fabrication as described in (2) above, wherein Q1 is defined as an index of heat removal due to solidification, and Q2 is defined in the step of determining whether there is a risk of occurrence of breakout. Breakout detection method characterized by determining whether there is a risk of breakout based on Q1 or based on Q1 and Q2 as an indicator of solidification interface heat input exceeding normal.

The present invention is also the breakout detection method in continuous fabrication as described in (2) above, wherein in the step of determining whether or not there is a risk of occurrence of the breakout, the risk of breakout is reduced by increasing Q1. It is characterized by the fact that Q2 is treated as a factor that increases the risk of breakout by increasing the numerical value, and whether there is a breakout risk based on Q1 or based on Q1 and Q2. It is also a breakout detection method.

(4) The breakout detection method in continuous fabrication as described in (2) or (3) above, wherein in the step of determining whether there is a risk of occurrence of breakout based on the overall heat flux Q1, With regard to the predetermined threshold values α 1 and α 2 (α 1 <α 2), it is determined that there is a breakout risk when (i) Q l <a 1, and (ii) al≤Ql≤ A breakout detection method, characterized by determining that there is a risk of breakout according to the value of Q2 when α2.

Here, it is determined that there is a risk of breakout when the value exceeds a predetermined threshold (al ≤ Q l ≤ ο: may be a constant value over the entire range of 2) based on Q2 force Q 1 It is preferable. (5) The breakout detection method in continuous fabrication according to any one of (2) to (4) above, wherein the minimum value indicates a minimum value in the heat flux profile obtained for (ql-q2 _res ) In the case where there are points, (i) Ql <α 1 and Q2 ≥ β, or (ii) for the thresholds α1, α2 (α1 <α2) and Q2 ) Ql <α1 and Q2 <β, or (iii) a breakout detection method in fabrication, wherein it is determined that there is a risk of breakout when a1≤Q1≤a2 and Q2≥j3.

That is, the breakout detection method in continuous forging according to the present invention measures the heat flux ql that is input to the solidification interface during the time from the molten metal in the mold to the mold outlet in the continuous casting, The steady-state solidification interface heat input q2 _reg due to the flow of molten copper in the vertical mold is obtained based on the above equation (1), and the difference between these heat flux ql and steady-state solidification interface heat input q2 _re8 (ql− q2 _res ) The heat flux profile from the molten steel surface to the vertical outlet is obtained for the molten steel, and the local heat flux value at the local minimum and the vertical outlet is present when there are local minimum points indicating the minimum value in the thermal flux profile. The total heat flux corresponding to the area above the straight line is Q2, and the total area surrounded by the entire curve of the heat flux profile file from the hot water surface position to the vertical outlet is Q2. Subtracting Q2 from the overall heat flux equivalent to Q1 is the overall heat flux corresponding to the product, and Q1 <a1 and Q2 ≥ β for the thresholds α1 and α2 (α1 <α2) and Q2 It is characterized by determining that there is a risk of breakout when Ql <a1 and Q2 <β, or a1≤Q1≤a2 and Q2≥j3.

(6) A breakout detection method in continuous forging as described in (5) above, wherein the molten steel is an ultra-low carbon steel, al is 15000 (kJ / m ² ), a 2 1000 (kjZm ² ),] 3 force S4500 (kjZm ² ) Breakout detection method in continuous fabrication, characterized by

(7) The breakout detection method in continuous fabrication as described in (2) or (3) above, wherein step power for determining whether or not there is a risk of occurrence of breakout based on the overall heat flux Q1 Based on the following formula (2) using the bundle Q1, the step of estimating the solidified shell thickness D at the vertical outlet, and the relationship between the estimated solidified shell thickness D and the risk of occurrence of breakout was obtained in advance. And determining whether there is a risk of occurrence of breakout based on the threshold value.

D = QlZ (AH.p) (2)

D: Thickness of the solidified shell at the vertical outlet (m) Ql: Overall heat flux (j / m ² )

Δ Η: enthalpy drop per unit weight of solidified shell at vertical outlet (jZkg) p: solidified shell density at vertical outlet (kg / m

Further, the unit of ql is j / s'm ² , the unit of q ² _reg in the above formula (1) is jZs'rn ² h, the unit of JZ sm ² −, and the unit of ΔΘ. C.

(8) The breakout detection method in continuous fabrication as described in (2) or (3) above, wherein a minimum point indicating a minimum value in the heat flux profile obtained for the (q 1 -q2 _reg ) If present, the step of determining the presence or absence of a breakout risk based on the overall heat flux Q1 and Q2 is performed by solidifying the vertical outlet based on the following equation (2) using the overall heat flux Q1. Estimating the shell thickness D and the solidification shell thickness D1 taking into account the solidification delay caused by remelting by the overall heat flux Q2, using the solidification delay RS determined based on the following equation (3), Dl = Presence / absence of breakout risk based on the estimated step based on the relationship D (l-RS), the estimated solidified shell thickness D1, and the threshold value previously determined in relation to the risk of breakout occurrence Judgment And a breakout detecting method.

D = Q1 / (厶 Η ・ ρ) (2)

D: Thickness of the solidified shell at the vertical outlet (m)

• Ql: Overall heat flux (jZm ² )

ΔΗ: enthalpy drop per unit weight of solidified shell at vertical outlet (jZkg) P: solidified shell density at vertical outlet (kgZm ³ )

RS = X (V ⁰ ⁸ Δ 0) (3)

However, RS: solidification delay (no unit)

β: Coagulation delay constant (unitless)

V: Molten steel flow velocity (m / s)

Δ Θ: Molten steel superheat (in)

Where V = (Q2 (α.ΐ · Δ 0)) ¹ · ²⁵

Q2: Overall heat flux (jZm ² )

α: Flow rate constant of molten steel (unitless)

t: Time required for the solidified shell to pass through the minimum point in the heat flux profile to reach the vertical outlet (S)

Further, jZs'm ² units of the ql, the formula (1) in q2 units of _reg jZs'm ^2, the units of h JZ s'm ² '° C, the unit of delta theta. C. When there is no minimum point showing a minimum value in the heat flux profile obtained for (ql−q2 _res ), the minimum point showing a minimum value in the heat flux profile is determined by the method described in (7) above. In the case where there is, the solidification shell thickness at the vertical outlet is estimated by the method described in (8) above, and whether there is a risk of occurrence of breakout can be determined based on the estimated value and the threshold value. preferable.

(9) The breakout detection method in continuous fabrication as described in any one of (1) to (6) above, wherein the heat flux ql differs in the embedding depth in the saddle thickness in the saddle shape. A plurality of pairs of thermocouples embedded between points are installed in the vertical forging direction, and the local heat flux is obtained by the following equation (4) based on the output of the pair of thermocouples. A breakout detection method.

ql = λ (Tl -T2) / d (4)

Where λ is a bowl-shaped thermal conductivity

Tl, Τ2: Thermocouple detection temperature

d: Thermocouple burying interval

(10) The breakout detection method in continuous fabrication as described in (7) or (8) above, wherein the heat flux ql is embedded between two points having different embedding depths in the vertical direction in the vertical shape. Breakout detection, characterized in that a plurality of pairs of thermocouples are installed in the vertical forging direction and the local heat flux is obtained by the following equation (4) based on the output of the pair of thermocouples Method. .

ql = l (Tl -T2) / d (4)

However, L: 錶 -shaped thermal conductivity (in jZs'm ')'

(Tl, T2: Thermocouple detection temperature CC)

d: Thermocouple burying interval (m)

(11) By inputting a pair of thermocouples embedded in two points at different depths in the vertical thickness direction, the thermocouple group installed in the vertical forging direction, and temperature information from the thermocouple group The local heat flux calculation means to determine the local heat flux ql at each thermocouple installation site, and the steady solidification interface heat input q2 _res due to the molten steel flow of the vertical bowl in the steady state are the data obtained from the following equation (1). Memorize the steady solidification interface heat input memorization and the difference between the heat flux ql and the steady solidification interface heat input q2 _res (ql-q2 _res ) Profile calculation means and breakout judgment means for judging whether or not there is a risk of occurrence of breakout based on the obtained heat flux profile. Breakout detection device for continuous mirror construction.

q2 _reg = h- Δ Θ (1)

Where h: Heat transfer coefficient between molten copper and solidified shell

ΔΘ: degree of superheat of molten steel.

(12) The breakout detection device for continuous fabrication according to (1 1) above, wherein the breakout determination means includes:

Based on the heat flux profile, the overall heat fluxes Q1 and Q2 are obtained by the following method; that is, (0 When there is a minimum point indicating a minimum value in the heat flux profile, the minimum point and the vertical outlet When the local heat flux value is connected with a straight line, the overall heat flux corresponding to the area above the straight line is defined as Q2, and it is surrounded by the entire curve of the heat flux profile from the molten metal surface position to the vertical outlet. If the total heat flux force Q2 corresponding to the total area is deducted, the total heat flux corresponding to the area is Q1, and (ii) there is no minimum point indicating the minimum value in the heat flux profile file Is the overall heat flux corresponding to the entire area surrounded by the entire curve of the heat flux profile between the hot water surface position and the vertical outlet, and the overall heat flux Q 1 and Q2 is zero;

A breakout detection device, which is a breakout determination means, characterized by determining whether or not there is a risk of occurrence of a breakout based on the overall heat flux Q1 or based on Q1 and Q2.

(13) The breakout detection device for continuous fabrication as described in (12) above, wherein the breakout determination means uses the overall heat flux Q1 as an index of heat removal due to solidification, and if necessary, Q2 Is a breakout detection device that is a breakout determination means that determines whether there is a risk of breakout based on Q1 or based on Q1 and Q2 .

The present invention is also the breakout detection device for continuous fabrication as described in (12) above, wherein the breakout determination means power Q 1 is treated as a factor for reducing the risk of breakout by increasing the numerical value. Treating Q2 as a factor that increases the risk of breakout by increasing the numerical value, it is a breakout judgment means that determines whether there is a risk of breakout based on Q1 or based on Q1 and Q2. This is a breakout detection device.

(14) The breakout detection device in continuous fabrication as described in (12) or (13) above, wherein the breakout determination means has a predetermined threshold value α 1, α for the overall heat flux Q 1. 2 For (α.1 <α 2), (i) When Q l a a 1, it is determined that there is a risk of breakout. (Ii) When a 1 ≤ Q 1 ≤ α 2 The breakout detection device, which is a breakout determination means, determines that there is a risk of breakout according to the value of Q2.

Here, when Q2 is equal to or greater than a predetermined threshold based on Q1 (which may be a constant value across a1≤Q1≤α2), it is determined that there is a risk of breakout. preferable.

(15) according to the above (12) or (13), a breakout detector in continuous鍀造, before Symbol breakout judging means, wherein (ql- q2 _ree) the heat flux profile obtained for If there is a minimum point indicating a minimum value in Q1, the thresholds α1, α2 (a1 <Q! 2) for Q1 and the thresholds for Q2 <a 1 and Q2≥) 3, or (ii) Q l <a 1 and Q2 </ 3, or (iii) o: risk of breakout when 1≤Q 1≤ α 2 and Q2≥ β A breakout detection device for determining whether or not

That is, the breakout detection device in continuous fabrication according to the present invention includes a thermocouple group in which a plurality of pairs of thermocouples embedded at two points having different depths in the vertical thickness direction are installed in the vertical fabrication direction. The local heat flux calculation means to obtain the local heat flux ql at each thermocouple installation site by inputting the temperature information from the thermocouple group, and the steady solidification interface heat input due to the molten copper flow in the bowl in the steady state q2 _reg The steady solidification interface heat input storage means for storing the data obtained from the above equation (1) and the difference between the heat flux ql and the steady solidification interface heat input q2 _reg (ql _ q2 _res ) The profile calculation means for obtaining the heat flux profile up to the heel-shaped outlet, and when there is a minimum point indicating the minimum value in the heat flux profile obtained by the profile calculation means, the minimum point and the mirror-type outlet The overall heat flux corresponding to the area above this straight line is Q2 when connected to the local heat flux value of this line with a straight line, and is surrounded by the entire curve of the heat flux profile between the hot water surface position and the vertical outlet Q1 is the total heat flux force corresponding to the total area Q2 and Q1 is the total heat flux equivalent to the total area I, and the predetermined threshold values α1, α2 (α1 <α2) and Q2 for Q1 There is a risk of breakout when Q l <α 1 and Q2≥, or Ql <α 1 and Q2 <β, or α 1 ≤ Ql ≤ a 2 and Q2 ≥ j3 And a breakout determination means for determining the above.

(16) The breakout detection device for continuous forging as described in (15) above, where the al force is 5000 (kjZm ² ), 0; 2 is 21000 (¾1 111) when the molten steel is extremely low carbon copper. ² ), Breakout detection device characterized by being set to force 4500 (kjZm ² ).

(17) The breakout detection device for continuous fabrication as described in (12) or (13) above, wherein the breakout determination means is based on the following equation (2) using the overall heat flux Q1. Congeal at the vertical exit The solidified shell thickness calculating means for calculating the solid shell thickness D and the calculated value of the solidified shell thickness calculating means are input, and the calculated value D and the threshold value obtained in advance in relation to the risk of occurrence of breakout are used. A breakout detection device comprising: a breakout determination means main body for determining whether there is a risk of occurrence of breakout based on the breakout determination main body.

D = Q1Z (厶 Η ・ ρ) (2)

D: Thickness of the solidified shell at the vertical outlet (m)

Q1: Overall heat flux (jZm ² )

厶 H: enthalpy drop per unit weight of solidified shell at vertical outlet (jZkg) p: solidified shell density at vertical outlet (kgZm ³ )

In addition, the unit of ql is jZs'm ² , the unit of q2 _reg is L s'm ^ h in the above formula (1), and the unit of JZ sm ² '° C, Δ 0. C.

(18) The breakout detection device for continuous fabrication as described in (12) or (13) above, wherein the breakout determination means is based on the following equation (2) using the overall heat flux Q1. Calculate the solidified shell thickness D at the mold outlet, and further consider the solidification shell thickness D1 taking into account the solidification delay caused by remelting by the overall heat flux Q2, and the solidification delay RS obtained based on the following equation (3): The calculated value of the solidified shell thickness calculating means and the calculated value of the solidified shell thickness calculating means are calculated according to the relationship D1 = D (1 RS), and the calculated value D1 and the risk of occurrence of breakout in advance A breakout detection device comprising: a breakout determination means main body that determines whether or not there is a risk of occurrence of breakout based on a threshold value obtained in relation to

D = Q1Z (厶 Η ・ ρ) (2)

D: Thickness of the solidified shell at the vertical outlet (m)

Ql: Overall heat flux (jZm ² )

RS = β X (V ⁰ ^{8 8} 0) (3)

However, RS: solidification delay (no unit)

0: Coagulation delay constant (no unit)

V: Molten steel flow velocity (m / s)

厶 Θ: Molten copper superheat (° C) ―

Where V = (Q2Z ( "'t- Δ Θ)) 1 - 25

02: Overall heat flux (1! ^) α: Molten steel flow rate constant (no unit)

t: Time required for the solidified shell to pass through the minimum point in the heat flux profile and reach the vertical outlet (S)

In addition, the unit of ql is J s 'm ² , the unit of q ² _res is jZs' m ² , the unit of h is JZ s 'm ² ' ° C, and the unit of ΔΘ is To do. The solidification shell computing means shows the minimum value in the heat flux profile by the method of (17) when there is no minimum point showing the minimum value in the heat flux profile of (ql−q2 _res ). In the case where there is a minimum point, it is preferable that the calculation means is for calculating the thickness of the solidified shell at the saddle type outlet by the method (18).

(19) A breakout prevention device using the breakout detection device according to any one of (11) to (18) above, wherein the breakout determination unit inputs a signal from the breakout determination unit and the breakout determination unit When it is determined that there is a risk of out, control conditions are provided to control the operating conditions so as to reduce the forging speed, or in addition to this control, to reduce the molten copper flow velocity in the mold. Breakout prevention device in continuous manufacturing.

(20) A breakout prevention device using the breakout detection device according to any one of (11) to (18) above, wherein the breakout determination unit inputs a signal from the breakout determination unit and the breakout determination unit A breakout prevention device for continuous forging, comprising control means for controlling to reduce the forging speed when it is determined that there is a risk of out.

(21) A breakout prevention device using the breakout detection device according to (15) or (16) above,

When a breakout determination means signal is input and the breakout determination means determines that there is a risk of breakout, (i) this risk determination is based on Ql <a 1 and Q2 ≥ β In this case, (a) the operating conditions are controlled so as to lower the forming speed and strengthen the dredging or dredging cooling, or (b) in addition to the control, control to lower the molten steel flow velocity in the dredging. (Ii) In the case of risk judgment based on QK α 1 and Q2 and β, control the operating conditions so as to reduce the forging speed and increase the dredging or vertical cooling, and (iii) a 1≤Q1≤ α 2 and in the case of risk judgment based on Q2≥β, (i) control means to reduce the molten steel flow velocity in the mold, or (B) to control the steelmaking speed and / or to increase the mold cooling. A breakout prevention device in continuous fabrication characterized by comprising. (22) A continuous steel forging method using the breakout detection method described in (4) above, wherein (i) Q l> α 2 or (ii) a I Ql ≤ α 2 and Q2 A continuous forging method of steel, characterized by controlling the operating conditions so that the value is reduced so that it is not determined that there is a risk of out.

(23) A continuous steel forging method using the breakout detection method described in (5) or (6) above, wherein Q l> α 2 and Q 2 ≥ β, or Q l ≥ a 1 and Q 2 A continuous copper production method characterized by controlling the operating conditions so as to be β.

(24) The continuous steel forging method as described in (23) above, wherein (i) when Ql <α 1 and Q2 ≥ β during operation, (a) reduce the forging speed and Alternatively, control the operating conditions so as to enhance the vertical cooling, or in addition to the control, (b) control the operating conditions so as to decrease the molten steel flow velocity in the vertical mold, and (ii) Q l <α 1 When Q2 <j3, the operating conditions were controlled so as to reduce the forging speed and increase Z or vertical cooling. (Iii) a 1≤Q 1≤ α 2 and Q2≥ β In this case, (iii) the molten steel flow velocity in the vertical mold is decreased, or (B) the operating conditions are controlled so as to lower the forging speed and / or increase the vertical cooling. , Continuous forging method of steel.

(25) The steel continuous forging method as described in (22) to (24) above, wherein the heat flux ql is embedded in the mold between two points with different embedding depths in the mold thickness direction. A steel continuous forging method, in which a plurality of a pair of thermocouples are arranged in the vertical forging direction and the local heat flux is obtained by the following equation (4) based on the output of the pair of thermocouples.

ql = X (Tl -T2) / d (4)

Where λ is a bowl-shaped thermal conductivity

Τ1, Τ2: Thermocouple detection temperature

d: Thermocouple burying interval

(26) A continuous steel forging method using the breakout detection method described in (7) above, in which the estimated solidified shell thickness D force is smaller than the threshold value determined in advance in relation to the risk of breakout occurrence. A continuous forging method for steel that controls the operating conditions.

(27) A continuous steel forging method using the breakout detection method described in (8) above, in which the estimated solidified shell thickness D1 is determined in advance from a threshold value determined in relation to the risk of breakout occurrence. Become smaller Steel continuous forging method to control the operating conditions. If the minimum point of the heat flux profile of (ql-q2 _reg ) does not exist, continuous fabrication is performed by the method described in (26) above, and if the minimum point exists, the method described in (27) above. It is preferable to continuously forge.

(28) The step of measuring the heat flux ql that enters the solidification interface before the molten steel in the mold reaches the mold surface force in the continuous forging, and the steady state due to the molten steel flow in the mold in the steady state The step of obtaining the solidification interface heat input q2 _reg based on the following equation (1) and the difference between the heat flux ql O / s' m ² ) and the steady solidification interface heat input q2 _reg (ql-q2 _res ) A step of obtaining a heat flux profile from the surface to the vertical outlet, and G) if there is a minimum point indicating a minimum value in the heat flux profile, the local heat flux value at the minimum point and the vertical outlet The total heat flux corresponding to the area above this straight line is defined as Q2, and the molten metal surface force is equivalent to the total area surrounded by the entire curve of the heat flux profile between the vertical outlets. The total heat flux force Q2 is bowed. Qii, and (ii) when there is no local minimum point indicating the minimum value in the heat flux profile, the total heat corresponding to the entire area surrounded by the entire curve of the heat flux profile from the molten metal surface position to the vertical outlet Let the flux be the overall heat flux Q1,

And a step of estimating the solidified shell thickness D at the vertical outlet based on the following formula (2) using the overall heat flux Q 1.

q2 _reg = h- Δ Θ (1)

Where q2 _reg: steady-state solidification interface heat input (j / s'm ² )

h: Heat transfer coefficient between molten steel and solidified shell (J / s · m ² · ° C)

厶 Θ: Molten steel superheat CC)

D = Q1 ^/ (AH- p) (2)

D: Solidified shell thickness at the vertical outlet (m)

Q1: Overall heat flux (jZm ² )

厶 H: enthalpy drop per unit weight of solidified shell at the vertical outlet (jZkg) P: solidified shell density at the mold outlet (kgZm ³ )

(29) A method for estimating the solidified shell thickness D1 in consideration of the solidification delay caused by remelting by the overall heat flux Q2 when there is a local minimum point showing a minimum value in the heat flux profile, according to (28) above. If the calculated thickness of the solidified shell is D, D1 = D (1—RS). A method for estimating the thickness of a solidified shell in continuous forging.

RS-β X (V ⁰ ⁸ Δ Θ) (3)

RS: Freezing delay (no unit)

β: Coagulation delay constant (unitless)

V: Molten steel flow velocity (m / s)

厶 Θ: Molten steel superheat (° C)

Where V = (Q2Z ( _α -t. Δ 0)) ^{1 25}

Q2: Overall heat flux (L m2)

a: Molten copper flow rate constant (no unit)

t: Time required for the solidified shell to pass through the minimum point in the heat flux profile to reach the force saddle type outlet (S) Note that if there is no minimum point in the heat flux profile of (ql-q2 _res ) By estimating the solidified shell thickness (D) by the method described in (28) above, and when there is a minimum point, by estimating the solidified shell thickness (D1) by the method described in (29) above, It is preferable to estimate the thickness of each solidified shell.

(30) The method for estimating the thickness of a solidified shell in continuous casting as described in (28) or (29) above, wherein the heat flux ql is between two points having different embedding depths in the vertical direction of the vertical shape in the vertical shape. Solidification in continuous forging characterized by a local heat flux obtained by the following equation (4) based on the output of the pair of thermocouples by installing a plurality of embedded thermocouples in the vertical forging direction. Shell thickness estimation method.

ql = λ (Tl -T2) / d (4)

Where ql: Heat flux (J Vm ² )

λ: vertical thermal conductivity (j / s 'm' ^)

Tl, T2: Thermocouple detection temperature (t)

d: Embedment interval of thermocouple (m)

(31) A thermocouple group in which a plurality of thermocouples embedded in two points at different depths in the vertical thickness direction are installed in the vertical fabrication direction, and temperature information from the thermocouple counter is input. The local heat flux calculation means for determining the local heat flux ql at each thermocouple installation site and the steady solidification interface heat input q2 _reB by the molten steel flow in the mold in the steady state. The memorized steady solidification interface heat input memory and the difference between the heat flux ql and the steady solidification interface heat input q2 _ree (ql-q2 _reg ) Profile calculation means for obtaining a heat flux profile up to the mouth,

(i) When there is no local minimum point indicating the minimum value in the heat flux profile obtained by the profile calculation means, the entire area surrounded by the entire curve of the heat flux profile between the molten metal surface position and the vertical ffl port Gi) If there is a local minimum point indicating the minimum value in the heat flux profile obtained by the profile calculation means, the total heat flux corresponding to Q1 is defined as Q1 and the local heat flux value at the vertical outlet Q2 is the total heat flux corresponding to the area above the straight line, and corresponds to the entire area surrounded by the entire curve of the heat flux profile between the molten metal surface and the vertical outlet. By subtracting Q2 from the overall heat flux force, the overall heat flux corresponding to the area is Q1,

A solidification shell thickness estimation device in continuous forging characterized by comprising solidification shell thickness calculation means for calculating the solidification shell thickness D at the vertical outlet based on the following formula (2) using the general heat flux Q1 .

q2 _reg = h- Δ Θ (1)

Where q2 _reg : Steady solidification interface heat input (J / m ² )

h: Heat transfer coefficient between molten steel and solidified shell (jZs'm ² '^)

厶 Θ: Molten steel superheat (° C)

D = QlZ (AH 'p) (2)

D: Solidified shell thickness at the mirror exit (m)

Ql: Overall heat flux (jZm ² )

ΔΗ: enthalpy drop per unit weight of solidified shell at vertical outlet O / kg) p: solidified shell density at vertical outlet (kgZm ³ )

(32) In the solidified shell thickness estimation device described in (31) above, the solidified shell thickness calculation means uses D1 = D (1 when D1 is the solidified shell thickness considering the solidification delay caused by remelting by the overall heat flux Q2. — RS), a solidified shell thickness estimation device for continuous forging.

However, RS = i3 Χ (ν ° · 8 · Δ 0) (3)

j3: Solidification delay constant (no unit) '

V: Flow velocity of molten steel (m / s)

Δ Θ: Molten copper superheat (° C)

RS: Freezing delay (no unit)

Here V = (Q2Z (a. Δ 0)) 1 · 25

Q2: Overall heat flux (JZm ² )

α: Flow rate constant of molten steel (unitless) t: Time required for the solidified shell to pass through the minimum point in the heat flux profile to reach the force saddle type exit (S) Note that the solidified shell thickness estimation device is the minimum point of the heat flux profile of (ql-q2 _reg ). In the case where the solidified shell thickness (D1) does not exist, the solidified shell thickness (D) is estimated by the method described in (31) above. It is preferable to estimate the thickness of the solidified shell in each case. Brief Description of Drawings

FIG. 1 is an explanatory diagram of a continuous forging facility provided with a breakout prevention device according to an embodiment of the present invention.

FIG. 2 is an explanatory view for explaining means for solving the problem, and is a cross-sectional view showing an example of a continuous forging mold in which a thermocouple is embedded.

FIG. 3 is an explanatory diagram for explaining means for solving the problem, and is an explanatory diagram showing an example of a thermocouple embedding method.

FIG. 4 is an explanatory view for explaining means for solving the problem, and is an explanatory view showing an example of a thermocouple mounting position.

Fig. 5 is an explanatory diagram for explaining the means for solving the problem, and shows an example of the relationship between the local heat flux (vertical axis: jZs' m ² ) and the distance from the molten metal surface (horizontal axis: mm). It is a graph.

FIG. 6 is an explanatory diagram for explaining the means for solving the problem, and is a graph showing an example of the relationship between the molten steel flow velocity (vertical axis: mZs) and the distance from the molten metal surface (horizontal axis: mm).

Fig. 7 is an explanatory diagram for explaining the means for solving the problem. The local heat flux ql (black circle) and (ql -q2 _reg ) (white circle) (vertical axis: JZs' m ² ) It is a graph which shows an example of the relationship with distance (horizontal axis: mm).

FIG. 8 is an explanatory diagram for explaining the means for solving the problem, and shows an example of how to obtain the area of the heat flux profile indicated by the graph showing the relationship between the local heat flux and the distance from the molten metal surface. It is a figure.

Fig. 9 is an explanatory diagram for explaining the means for solving the problem. An example of how to determine the area of the heat flux profiles Q1 and Q2 shown by the graph showing the relationship between the local heat flux and the distance from the molten metal surface FIG.

FIG. 10 is an explanatory diagram for explaining an example of means for solving the problem. The horizontal axis is Ql (kj / m ² ), and the vertical axis is

Plot the numerical values shown in Table 1 on the coordinate plane, and breakout occurs The coordinate plane is divided into five regions in relation to the presence or absence of.

FIG. 11 is an explanatory diagram for explaining the means for solving the problem, and is a graph showing an example of the relationship between the forging speed and the average temperature in the shell thickness direction at the vertical outlet, and the vertical axis indicates the vertical outlet shell thickness. The direction average temperature (in) and the horizontal axis shows the forging speed (m / min).

FIG. 12 is an explanatory view of a continuous forging apparatus provided with a breakout prevention device according to another embodiment of the present invention. ·

FIG. 13 is an explanatory diagram of a continuous forging facility in which a breakout prevention device according to still another embodiment of the present invention is installed.

(Explanation of symbols)

1 vertical

3 Immersion nozzle

5 Molten steel

7 Monored powder

9 Solidified shell

11 Vertical copper plate

13 Cooling water passage

15 Hole (at the bottom of the cooling water passage)

17 Thermocouple

19 pieces

21 Guide roller

23 Pinch roll

25 motor

27 Pinch roll control device

29 Local heat flux calculation means

31 Steady solidification interface heat input memory

32 Heat flux profile calculation means

33 Breakout judgment means

33A Breakout judgment means body

34 Solidified shell thickness calculation means

35 Control unit

37 Alarm device 40 tundish

41 Electromagnetic brake device BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1, FIG. 12 and FIG. 13 are explanatory diagrams of a continuous forging facility provided with a breakout detection and prevention device and a solidified shell thickness estimation device according to an embodiment of the present invention. The same parts as those in Fig. 2 are given the same reference numerals.

Continuous forging equipment

Type 1 and

An immersion nozzle 3 connected to the bottom of the tundish 40 and installed in the mold 1 to discharge the molten steel 5 from the tundish 40;

-Guide roller 21 that guides the piece 19 from the bowl 1 and

-Pinch roll 23 for pulling out the piece 19

'A motor 25 for rotationally driving the pinch roll 23,

• Pinch roll control device 27 to control the motor 25 and

It has.

The continuous fabrication facility having such a configuration is provided with a breakout prevention device (including a breakout detection device and a solidified shell thickness estimation device) having the following constitutional power.

Breakout prevention device

-A thermocouple group in which a plurality of thermocouples 17 embedded in two points at different depths in a vertical copper plate 11 forming a vertical mold 1 are installed in the vertical direction of the vertical dimension and the manufacturing direction;

A local heat flux calculating means 29 for calculating the local heat flux ql at each thermocouple installation site by inputting temperature information from the thermocouple group 17 in the vertical thickness direction;

• Steady solidification interface heat input storage means 31 for storing data obtained from steady solidification interface heat input q2 _res based on the following equation (1) due to molten steel flow in the mold in the steady state;

'The heat flux profile calculation means 32 for obtaining the heat flux profile from the molten steel to the hot metal surface 铸 type outlet for the difference between the heat flux ql and the steady-state solidification interface heat input q2 _ree (ql-q2 _res ),

• Breakout determination means 33 for determining whether there is a risk of breakout based on the obtained heat flux profile;

• When the signal of breakout determination means 33 is input and breakout determination means 33 determines that there is a risk of breakout,

(0 Control to reduce the forging speed (Fig. 13), (ii) Control to reduce the forging speed and / or control to reduce the flow rate of molten steel in the mold 1 (Fig. 12), or

(iii) Control the operating conditions so as to lower the casting speed and strengthen Z or vertical cooling, or in addition to the control, control to reduce the molten copper flow rate in the vertical mold (Fig. 1),

Control means 35;

-It is provided with an alarm device 37 that issues an alarm when the breakout determination means 33 determines that there is a risk of breakout.

q2 _reg = h- Δ Θ (1)

Where h: heat transfer coefficient between molten copper and solidified shell

厶 Θ: Degree of superheat of molten steel In the breakout prevention device of Fig. 1, breakout judgment means 33

-Calculate the overall heat flux Q1 and Q2 based on the heat flux profile obtained by the profile calculation means 32, and use the overall heat flux Q1 or Q1 and Q2 to calculate the vertical outlet f of the solidified shell 9. Solidified shell thickness calculating means 34 for calculating the thickness (solid shell thickness)

Breakout determination that inputs the calculated value of the solidified shell thickness calculation means 34 and determines whether there is a risk of breakout occurrence based on the calculated value and the threshold value obtained in advance in relation to the risk of breakout occurrence Means body 33Α,

Have Hereinafter, each configuration will be described in more detail. Gu thermocouple>

The thermocouple 17 is embedded in the vertical copper plate ii in the same manner as shown in FIGS. In other words, a hole 15 is made in the bottom of the cooling water passage 13 formed on the outer surface of the mm copper plate 11 (see Fig. 3), and a thermocouple 17 is embedded in the hole 15 so as to have a certain distance in the depth direction 2 A pair of thermocouples 17 buried in the place are installed in nine places (18 in total) in the vertical production direction.

In this embodiment, the thermocouple 17 is embedded on the short side and the long side of the saddle (the longer side in the saddle shape where the horizontal cross section is a rectangular parallelepiped), and is measured for each side of the saddle shape. Then, the presence or absence of breakout is determined based on the measured value for each side.

<Local heat flux calculation means> The local heat flux calculating means 29 inputs the signal of the thermocouple 17 and calculates the local heat flux ql. The local heat flux calculation means 29 is realized by the CPU executing a predetermined program. As described above, the local heat flux calculation means 29 includes the detected temperatures of the two thermocouples 17 as Tl, Τ2, The following equation (4) is written to calculate the local heat flux, where d is the embedding interval and λ is the thermal conductivity of 及 type 1.

ql = A (Τ1 -Τ2) / ά (4) Steady solidification interface heat storage means>

The steady solidification interface heat input storage means 31 stores the data of the steady solidification interface heat input q2 _res by the molten steel flow in the mold in the steady state, which is obtained based on the following equation (1).

q2 _reg = h- Δ Θ (1)

^{However, h = l 22 X 10 5} XV ° -. 8

V: Molten steel flow velocity (mZs)

厶 Θ = T ₀ -T _S

T ₀ : Temperature of molten copper in mold (° C)

T _s: Molten steel solidus temperature (° C)

Note that the steady-state solidification interface heat input q2 _res is obtained by obtaining the molten steel flow velocity from the dendrite inclination angle of the slab produced when operating at a predetermined forging speed, and using the molten steel flow velocity as described in (1) above. A method for obtaining the steady-state solidification interface heat input q2 _reg based on the equation is preferred.

The heat flux profile calculation means 32 receives the heat flux ql calculated by the local heat flux calculation means 29 and the steady solidification interface heat input q2 _reg stored in the steady solidification interface heat storage means 31 from each device. For these differences (ql _q2 _res ), the heat flux profile from the molten steel force to the vertical outlet is obtained.

Similar to the local heat flux calculation means 29, the heat flux profile calculation means 32 is realized by the CPU executing a predetermined program. This program has a logic for calculating the above-mentioned heat flux profile. Has been written.

The solidification seal thickness calculation means 34 provided in the breakout prevention device of FIG. 1 calculates the solidification shell thickness D at the vertical outlet based on the heat flux profile obtained by the heat flux profile calculation means 32. A specific calculation method is as follows. If there is no local minimum point indicating the minimum value in the heat flux profile obtained by the heat flux profile calculation means 32, it corresponds to the entire area surrounded by the entire curve of the heat flux profile between the molten metal surface position and the vertical outlet. Let Q1 be the overall heat flux to be calculated, and use this overall heat flux Q1 to calculate the solidification seal thickness D at the vertical outlet based on the following equation (2).

In addition, when there is a local minimum point that shows a minimum value in the heat flux profile obtained by the heat flux profile calculating means 32, this local point is connected to the local heat flux value at the vertical outlet by a straight line. The total surface heat flux corresponding to the area above the straight line is defined as Q2, and the surface heat force between the vertical outlets is the heat flux pro between the vertical outlets: Q2 is calculated from the total heat flux corresponding to the entire area surrounded by the entire curve of 7 isles. The total heat flux corresponding to the subtracted area is defined as Q1, and the total heat flux Q1 is used to calculate the solidified shell thickness D at the vertical outlet based on the following equation (2) (see Fig. 9).

D = Q1 / (A H- p) (2)

However, hi: solidified shell thickness at the vertical outlet (m)

厶 H: enthalpy drop per unit weight of solidified shell at vertical outlet (j / kg)

P: Solidified shell density at the vertical outlet (kgZm ³ ) As a calculation method with improved accuracy, the solidified shell thickness calculation means 34 is generated by remelting with the overall heat flux Q2. The shell thickness D1 may be calculated by the equation D1 = D (1−RS) using the setting delay RS obtained by the following equation (3). If there is no minimum point in the heat flux profile, either the algorithm for obtaining D instead of D1 or the algorithm for obtaining D1 with Q2 = 0 can obtain the same result.

RS = β X (V ⁰ ⁸ Δ Δ θ) (3)

β: Coagulation delay constant (unitless)

V: Molten copper flow velocity (m / s)

Δ Θ: Molten steel superheat CC)

RS: Coagulation delay (no unit)

Where V = (QS ^ a10 厶 0)) ¹ ²⁵

Q2: Overall heat flux CjZm ² )

a: Molten steel flow rate constant (no unit)

<Breakout judgment method> In the breakout prevention device of FIG. 1, the breakout determination means 33 includes the solidified shell thickness calculation means 34 and a breakout determination means body 33A. In the breakout prevention devices shown in FIGS. 12 and 13, the breakout judging means 33 does not go through the solidified shell thickness calculation, but directly determines whether there is a risk of breakout occurrence from the heat flux profile calculated by the heat flux profile calculating means 32. judge. Hereinafter, each case will be described separately. In the case of the breakout prevention device shown in FIG. 1, the breakout judging means body 33A inputs the calculated value (solidified shell thickness D or D1) of the solidified shell thickness calculating means 34 and generates the breakout in advance. Whether or not there is a risk of occurrence of breakout is determined based on the threshold value obtained in relation to the risk of occurrence of the breakout. The threshold values are obtained by acquiring data in simulation experiments and actual operations in advance about various Q l and Q2, the thickness of the solidified shell, and the occurrence of breakout at the solidified shell thickness. For example, if the target solidified shell thickness at the vertical outlet is a numerical value (or numerical range) within the range of 20-30mrn, the numerical value within the range of the solidified shell thickness of 5-7mm is below this value, there is a risk of breakout The threshold value is determined to be present. In the case of the breakout prevention device of FIGS. 12 and 13, the breakout determination means 33 is based on the heat flux profile calculated by the heat flux profile calculation means 32, for example, the relationship between Q1 and Q2 shown in 囪 9 above. And determine whether or not there is a risk of occurrence of these threshold values and a predetermined threshold force breakout.

For example, Q 1 and Q 2 shown in FIG. 9 described above are obtained, and a predetermined threshold value α ΐ. Α 2 (α 1 <a 2) and Q 2 with a predetermined threshold value / 3 are obtained. From the relationship, determine whether there is a risk of breakout based on the criteria shown in Figure 10.

Specifically, when (i) Q l <a 1 and Q2 ≥ β, or (ii) Q l <α 1 and Q2 β, (iii) or a 1 ≤Q 1 ≤ a 2 and Q2 β Determine that there is a risk of breakout. When the breakout determination means 33 determines that there is a risk of breakout, the breakout determination means 33 outputs the fact to the control means 35. At that time, the risk of breakout is a force based on Q 1 a 1 and Q2 ≥ β \ or a force based on Q 1 a 1 and Q2 <, or alternatively α 1 ≤Q 1 ≤ α 2 and Q2 ≥ β It is preferable that the output is based on the

The threshold alpha 1, alpha 2, J3 are those determined by the type of molten steel, for example, when the molten steel is extremely low carbon steel, α 1 = 15000 (kj / m 2), α 2 = 21000 (kj / m ² ), = 4500 (kj / m ² ). Note that the ultra-low carbon steel has a carbon content of 0.01 mass% or less.

Standards based on Q1 or other criteria based on the relationship between Q1 and Q2 may be used. For example In the above example, if _a l ≤ Ql ≤ α 2, it may be determined whether there is a risk of breakout if Q2 is greater than or equal to the threshold that is more sensible based on Q 1.

As another method, for example, when the value of the ratio of Q2 and Q1 Q2ZQ1 is equal to or greater than a predetermined threshold, it may be determined that there is a risk of breakout. This threshold is determined by the type of molten steel. For example, when the molten steel is an extremely low carbon steel, it is 0.25. The breakout determination means 33 or breakout determination means 33A is also realized by the CPU executing a predetermined program, and the determination logic described above is written in this program. Control means>

When the breakout determination means 33 determines that there is a risk of breakout, the control means 35 controls various devices to avoid breakout based on the determination result.

For example, in the case of the breakout prevention device shown in FIG. 12, specifically, there is a risk of breakout due to Q 1 <α 1 and Q2≥β from the breakout judging means 33 with respect to α 1, << 2 and / 3. Is input to the pinch roll control device 27 to instruct the motor 25 to reduce the rotational speed of the motor 25. In addition to this, it is also possible to output a signal for applying a DC magnetic field to the electromagnetic brake device 41 so as to reduce the molten steel flow velocity in the mold 1. When the control means 35 inputs a signal from the breakout determination means 33 that there is a risk of breakout due to Q 1 α 1 and Q 2 β, the rotation of the motor 25 to the pinch roll control device 27 Outputs a command to decelerate the speed. Furthermore, when the control means 35 inputs a signal from the breakout judging means 33 that there is a risk of breakout due to a 1≤Q1≤α2 and Q2≥13, the control means 35 sends a type 1 signal to the electromagnetic brake device 41. The signal which applies the direct current magnetic field which lowers the molten steel flow velocity inside is output.

Further, in the case of the breakout prevention device of FIG. 1, specifically, when a signal indicating that there is a risk of breakout is input from the breakout judging means 34, the rotation speed of the motor 25 is controlled to the pinch roll control device 27. Outputs a signal to command deceleration. In addition to this, a signal for applying a DC magnetic field that lowers the molten steel flow velocity in the mirror mold 1 may be output to the electromagnetic brake device 41.

In the case of the breakout prevention device shown in FIG. 13, when a signal indicating that there is a risk of breakout is input from the breakout judging means 33, the forging speed is simply controlled to be reduced, that is, to the pinch roll control device 27. This can be done by outputting a signal to command the motor 25 to reduce the rotational speed.

In addition, although not shown in any figure, the vertical cooling control means for controlling vertical cooling water etc. Control may be performed to send a signal to enhance saddle cooling and increase the thickness of the solidified shell. This is particularly effective for countermeasures against the lack of heat removal due to insufficient Q1. The control means 35 outputs a command signal so as to issue an alarm to the alarm device 37 when a signal indicating that there is a danger of breakout is input. The control means 35 is also realized by the CPU executing a predetermined program, and logic for outputting the above-described command signal is written in this program.

The alarm device 37 issues an alarm when a signal from the breakout determination means 33 is input. There are no restrictions on the type of alarm, but examples include alarm sounds, lighting of alarm lamps, and combinations thereof. The operation of the present embodiment configured as described above will be described.

In the operation of discharging molten steel 5 from the immersion nozzle 3 and cooling it with the mold 1 to continuously produce the piece 19, the signal from the thermocouple 17 is input to the local heat flux calculating means 29 to calculate the local heat flux. Then, the calculation result is input to the profile calculation means 32. The heat flux profile calculation means 32 is based on the local heat flux ql input from the local heat flux calculation means 29 and the steady solidification interface heat input memory means 31 stored on the steady solidification interface heat input q2 _reg . ql—Calculates q2 _reg and calculates the heat flux profile based on the result. Then, for example, Ql and Q2 as shown in FIG. 9 are obtained for the calculated heat flux profile, and these calculated values Q1 and Q2 are input to the breakout determination means 33.

In the case of the breakout prevention device shown in FIG. 12 or FIG. 13, the breakout determination means 33 determines whether or not there is a risk of occurrence of a breakout according to a predetermined rule for the input Ql or Q2. For example, the presence or absence of a breakout risk is determined based on the relationship between the values of Q1 and Q2 in FIG.

In the case of the breakout prevention device shown in FIG. 1, the solidified shell thickness calculating means 34 first calculates the overall heat flux Ql or Q2 by the above-described method based on the heat flux profile obtained by the heat flux profile calculating means 32. Ask for. The solidified shell thickness calculating means 34 further calculates the solidified shell thickness D or D1 at the vertical outlet by the above-described method based on the overall heat flux Ql or Q2. Furthermore, breakout judgment means body 33A force Solidified shell thickness D or D1 calculated by solidified shell thickness calculating means 34 is input, and whether there is a risk of breakout occurring or not in relation to this value and a predetermined threshold value Determine. As a result of the determination, if there is no risk of breakout, the operation is continued as it is.

On the other hand, if it is determined that there is a risk of breakout as a result of the determination, the breakout determination means 33 outputs a signal to the control means 35 that there is a risk of breakout. At the same time, a command signal for issuing an alarm to the alarm device 37 is output.

In the case of the breakout prevention device shown in FIGS. 12 and 13, the breakout determination means 33 may further output the type of breakout danger to the control means 35. For example, with respect to << 1, α2, | 3 above, is it in the danger zone of the heat-insufficient breakout (Q 1 and α1 and Q2 <] 3), or the power in the danger zone of the re-dissolvable breakout? (A 1 ≤ Q 1 ≤ α 2 and Q2 ≥), or both of them are in danger (Q l <a 1 and Q2 β). When the signal from the breakout determination means 33 is input, the control means 35 performs control for, for example, reducing the forging speed and the molten steel flow velocity.

Specifically, as the control for reducing the forging speed, the control means 35 outputs a signal for instructing the pinch roll control device 27 to decelerate the rotational speed of the motor 25. The pinch roll control device 27 receiving this signal controls the motor 25 to reduce the rotational speed. By reducing the number of revolutions of the motor 25, the forging speed is reduced and the thickness of the solidified shell in the mold 1 is increased, so that the risk of breakout can be avoided.

Specifically, as the control for reducing the molten steel flow velocity, the control means 35 outputs a signal for applying a DC magnetic field to the electromagnetic brake device 41 so as to reduce the molten steel flow velocity in the mold 1. When this signal is output, the electromagnetic brake device 41 applies a DC magnetic field to the mold 1 and the molten steel flow speed in the mold 1 decreases. When the molten steel flow velocity decreases, the velocity at which the molten steel collides with the solidified shell interface decreases, and the degree of remelting of the solidified shell decreases, so that the thickness of the solidified shell increases and the risk of breakout can be avoided. . In the case of the breakout prevention device of FIG. 12, more detailed processing as described below can be performed in response to the determination using _α1 , _α2 , and J3.

When the control means 35 receives the signal from the breakout determination means 33 and it is based on Q 1 a 1 and Q 2 ≥ β, the heat release insufficient breakout occurs and the remeltability occurs. Since there is a risk of both breakout occurrences, control is performed to reduce the forging speed and the molten steel flow velocity.

As a control for reducing the forging speed, specifically, the control means 35 is a pinch roll control device. Outputs a signal to command the motor 27 to reduce the rotational speed of the motor 25. The pinch roll control device 27 receiving this signal controls the motor 25 to reduce the rotational speed. By reducing the number of revolutions of the motor 25, the forging speed is reduced and the thickness of the solidified shell in the mold 1 is increased, so that the risk of a breakout due to insufficient heat removal can be avoided.

Specifically, the control for lowering the molten copper flow velocity is such that the control means 35 outputs a signal that applies a DC magnetic field to the electromagnetic brake device 41 to lower the molten steel flow velocity of the vertical type 1 內, When this signal is output, the electromagnetic brake device 41 applies a DC magnetic field to the mold 1 and the molten steel flow velocity in the mold 1 decreases. When the molten steel flow velocity decreases, the velocity at which the molten steel collides with the solidified shell interface decreases, and the degree of remelting of the solidified shell decreases, thus avoiding the risk of breakout due to remelting of the solidified shell. it can.

If the signal from breakout judging means 33 is based on Q 1, a 1, Q2, and β, it means that there is a risk of breakout due to insufficient heat removal. Outputs a signal to the pinch roll control device 27 to command the motor 25 to reduce its rotational speed. As a result, the forging speed is reduced and the thickness of the solidified shell in the mold 1 is increased, so that it is possible to avoid the risk of a breakout due to insufficient heat removal.

If the signal from breakout judging means 33 is based on a1≤Q1≤α2 and Q2≥J3, there is a risk of remeltable breakout. 35 outputs a signal for applying a DC magnetic field to the electromagnetic brake device 41 so as to reduce the flow velocity of the molten steel in the mold 1 so that remelting breakout can be avoided as described above. In addition, the alarm device issues an alarm when a signal from the breakout determination means 33 is input. This can inform the operator of the danger of a breakout. In FIGS. 1, 12, and 13, the thermocouple group consisting of thermocouples 17, local heat flux calculation means 29, steady-solidification interface heat input storage means 31, heat flux profile calculation means 32, and breakout are shown in FIGS. The determination means 33 (or the alarm device 37) constitutes a breakout detection device. Further, in FIG. 1, the thermocouple group consisting of thermocouples 17, the local heat flux calculating means 29, the steady solidification interface heat input memory means 31, the heat flux profile calculating means 32, and the solidification seal thickness calculating means 34 are solidified. Construct shell thickness estimation device. For example, using a communication鍀Installation according to FIG. 12, for ultra low carbon steel, 2. was going to steering business in铸造rate of OmZ min, Q2 rather was the 4500KjZm ^2, the value of Q 1 is Q 1 lSOOOkj / m ² There was a risk of a heat deficient breakout. Thus, when the forging speed was reduced to 0.5'5 min, Ql ≥ 15000kj / m ² , and a sufficient solidified shell thickness was obtained, preventing the occurrence of breakout. After the solidified shell is sufficiently thick, high-speed forging can be performed by increasing the forging speed again.

In addition, using the continuous equipment shown in Fig. 12, when operating extremely low carbon copper at a forging rate of 2.5 m / min, the value of Q1 was 15000¾J / m ² ≤Ql≤21000kjZm ² , The value of Q2, became Q2≥4500 kL m ² , and there was a risk of remelting breakout. Therefore, when the electromagnetic brake device 41 was operated, the value of Q2 could be reduced to a value smaller than ASOOkjZm ² and remeltable breakout could be prevented. Furthermore, using the continuous equipment shown in Fig. 13, the operation of ultra-low carbon copper was conducted at a production speed of 2. OmZ, under the condition that it does not deviate from 15000 / ^ ² ≤01 ≤21000 kjZm ² The value of Q2 ZQ1 exceeded 0.25. For this reason, when the forging speed was reduced to 0.5 mZ, it became Q2 / QK 0.25, a sufficient solidified shell thickness could be obtained, and the occurrence of breakout could be prevented. After the solidified shell thickness is sufficiently increased, high-speed forging can be performed by increasing the forging speed again. According to this embodiment, it is determined whether there is a risk of breakout based on the heat flux profile directly related to the thickness of the solidified shell at the vertical outlet, or directly related to breakout from the profile. Since the thickness of the solidified shell at the vertical outlet can be obtained and the presence or absence of breakout can be judged based on this solidified shell thickness, the occurrence of breakout can be detected easily and reliably with high sensitivity under various operating conditions. As a result, breakout can be reliably prevented. In addition, since it is possible to determine the risk of breakout, including whether it is a remeltable breakout or an underheated breakout, it is possible to select an optimal prevention measure. In the contents and embodiments of the present invention described above, the geometrically performed method is mainly used as a method for obtaining the integrated value of the heat flux corresponding to the overall heat flux and the size of the bump from the heat flux profile. Indicated. However, the present invention is not limited to this. For example, the overall heat flux may be obtained by integrating the dull. Industrial applicability

In the present invention, the molten copper in the mold in the continuous casting is between the hot water surface and the mold outlet. The heat flux ql input to the solidification interface was measured, and the difference between the heat flux ql and the steady solidification interface heat input q2 _{reg due} to the molten steel flow in the mold in the steady state (ql-q2 _reg ) Since the heat flux profile from the top to the vertical outlet was obtained and the risk of breakout occurrence was determined based on this heat flux profile, the occurrence of breakout under various operating conditions It is easy and reliable to predict with high sensitivity, and breakout can be prevented reliably. In addition, by determining and analyzing the overall heat flux Q1 and Q2 based on the heat flux profile, it is possible to further determine the cause of each breakout, making it possible to take appropriate measures to avoid breakout based on the cause. .

Further, since the solidified shell thickness at the vertical outlet is estimated using the overall heat flux Ql or further Q2, the solidified shell thickness can be accurately estimated.

As described above, the present invention has various excellent effects in the field of continuous forging control.

Claims

The scope of the claims

1. a step of measuring a heat flux ql that is input to the solidification interface from the hot metal surface force to the vertical outlet in the continuous molding,

The step of obtaining the steady-state solidification interface heat input q2 _reg by the molten steel flow in the mold in the steady state based on the following equation (1):

A step of obtaining a heat flux profile from the molten steel surface to the vertical outlet for the difference between the heat flux ql and the steady-state solidification interface heat input q2 _res (ql-q2 _res ),

A step of determining whether there is a risk of breakout based on the heat flux profile,

Breakout detection method in continuous fabrication. '

q2 _reg = h- 厶 Θ (1)

Where h: heat transfer coefficient between molten copper and solidified shell

ΔΘ: degree of superheat of molten steel.

2. A breakout detection method in continuous fabrication according to claim 1,

Determining whether there is a risk of occurrence of breakout based on the heat flux profile determined for (ql-q2 _ree ),

A step of determining overall heat fluxes Q1 and Q2 by the following method based on the heat flux profile;

If there is a minimum point indicating a minimum value in the heat flux profile, the area of the portion above this line when the minimum point and the local heat flux value at the saddle-shaped outlet are connected by a straight line Q2 is the total heat flux corresponding to, and the total heat flux force Q2 corresponding to the entire area surrounded by the entire curve of the heat flux profile from the molten metal surface position to the vertical outlet is equivalent to the area of the bow IV The overall heat flux is Q 1

When there is no local minimum point indicating the minimum value in the heat flux profile, the overall heat flux corresponding to the entire area surrounded by the entire curve of the heat flux profile between the vertical outlets and the molten metal surface force is determined as the overall heat flow. Bundling Q1 and Q2 being zero; and

A breakout detection method comprising: determining whether there is a risk of occurrence of breakout based on the overall heat flux Q1 or based on Q1 and Q2.

3. The breakout detection method in continuous fabrication according to claim 2,

In the step of determining whether there is a risk of breakout, Q1 is removed by solidification As an indicator of quantity, as an indicator of solidification interface heat input exceeding Q2

A breakout detection method that determines whether there is a risk of breakout based on Q1 or based on Q1 and Q2.

4. A breakout detection method in continuous fabrication according to claim 2,

In the step of determining whether or not there is a risk of breakout based on the overall heat flux Q1, V1 is set to V1 and thresholds α1 and α2 (αΚα2) are set in advance!

When Ql <a 1, it is determined that there is a risk of breakout,

Breakout detection method that determines that there is a risk of breakout according to the value of Q2 when al≤Ql≤ α2.

5. A breakout detection method in continuous fabrication according to claim 2,

In the case where there is a minimum point indicating a minimum value in the heat flux profile obtained for (ql−q2 _reg ),

Q1 α1 and Q2 ≥ β, or Ql a1 and Q2 <β, or a1≤Q1≤ a Breakout detection method that determines that there is a danger of breakout when Q2 ≥ β.

6. The breakout detection method in continuous mirror construction according to claim 5,

A breakout detection method in which the molten steel is an extremely low carbon steel, αΐ is 15000 (kjZm ² ), (^ ??? ^^ hi] /! ^), And J3 force 500 (kJ no m ² ).

7. The breakout detection method in continuous fabrication according to claim 2,

The step of determining whether there is a risk of occurrence of breakout based on the overall heat flux Q1 is a step of estimating the solidified shell thickness D at the vertical outlet based on the following equation (2) using the overall heat flux Q1. When,

A breakout detection method comprising: determining whether there is a risk of occurrence of breakout based on the estimated solidified shell thickness D and a threshold value obtained in advance in relation to the risk of occurrence of breakout.

D = Q1 / (AH- p) (2)

D: Thickness of the solidified shell at the vertical outlet (m)

Ql: Overall heat flux (J / m ² ) 厶 H: enthalpy drop per unit weight of solidified shell at vertical outlet (jZkg) p: solidified shell density at vertical outlet (kgZm ³ )

Further, the unit of ql is J Vm ² , the unit of q2 _reg is J / s'm ² h in the formula (1), JZ s'm ² '° C, and the unit of ΔΘ. C.

8. A breakout detection method in continuous fabrication according to claim 2,

In the case where there is a minimum point indicating a minimum value in the heat flux profile obtained for (ql_q2 _rei! ),

Step force for determining the risk of breakout based on the overall heat flux Q1 and Q2

Estimating the solidified shell thickness D at the vertical outlet based on the following equation (2) using the overall heat flux Q1;

The relationship of D1 = D (1 _ RS) using the solidification delay RS obtained based on the following formula (3) as the solidification shell thickness D1 considering the solidification delay caused by remelting by the overall heat flux Q2. Estimating with

A breakout detection method comprising: determining whether or not there is a risk of breakout occurrence based on the estimated solidified shell thickness D1 and a threshold value obtained in advance in relation to the risk of breakout occurrence.

D = QlZ (A H. p) (2)

D: Thickness of the solidified shell at the vertical outlet (m)

Q1: Overall heat flux (j / m ² )

Δ H: enthalpy drop per unit weight of solidified shell at vertical outlet (jZkg)

P: Solidified shell density at the vertical outlet (kgZm ³ )

RS: Solidification delay (no unit)

J3: Solidification delay constant (no unit)

V: Molten steel flow velocity (m / s)

Δ Θ: Molten steel superheat (° C)

Here V = (Q2Z 't'厶0)) ¹ - ²⁵

Q2: Overall heat flux (jZm ² )

α: Flow rate constant of molten steel (unitless)

t: The solidified shell passes through the minimum point in the heat flux profile until it reaches the vertical outlet Time required for (S)

The unit of ql is jZs'm ^{2 in the} above formula (1), the unit of q2 _reg is jZs'm ² , the unit of h is JZ s'm ² ° C, and the unit of Δ 0 is C.

9. A breakout detection method in continuous fabrication according to claim 2,

For (ql-q2 _re6 ), there is no minimum point indicating the minimum value in the heat flux profile obtained! /, In the case described in claim 7,

In the case where there is a minimum point indicating a minimum value in the heat flux profile obtained for (ql−q2 _reg ), the method according to claim 8,

Breakout detection method for estimating the thickness of the solidified shell at the mirror exit.

10. The breakout detection method in continuous fabrication according to any one of claims 1 to 6, wherein the heat flux ql is embedded between two points having different embedding depths in the vertical thickness direction in the vertical shape. A breakout detection method, wherein a plurality of a pair of thermocouples are installed in a vertical forging direction and a local heat flux is obtained by the following equation (4) based on the output of the pair of thermocouples.

ql = (Tl -T2) / d (4)

Where λ is a bowl-shaped thermal conductivity

Τ1, Τ2: Thermocouple detection temperature

d: Thermocouple burying interval

11. The breakout detection method according to any one of claims 7 to 9, wherein the heat flux ql is embedded between two points having different embedding depths in the vertical thickness direction in the vertical mold. A breakout detection method, wherein a plurality of a pair of thermocouples are installed in a vertical forging direction and a local heat flux is obtained by the following equation (4) based on the output of the pair of thermocouples.

_¾ 1 = λ (Tl -T2) / d (4)

However, λ: vertical thermal conductivity (in jZs'm *)

Tl, Τ2: Thermocouple detection temperature (in)

d: Thermocouple burying interval (m)

12. A thermocouple group in which a pair of thermocouples embedded at two points with different depths in the vertical thickness direction are installed in the vertical direction.

The temperature information from the thermocouple group is input to determine the local heat flux ql at each thermocouple installation site. Local heat flux calculation means;

Steady solidification interface heat input storage means for storing the data obtained from steady solidification interface heat input q2 _reg based on the following equation (1) due to molten steel flow in the mold in the steady state:

Profile calculation means to obtain the heat flux profile from the molten steel surface to the vertical outlet for the difference between the heat flux ql and the steady-state solidification interface heat input q2 _reg (ql-q2 _reg ),

• A breakout detection device for continuous fabrication, comprising breakout determination means for determining whether there is a risk of breakout occurrence based on the obtained heat flux profile.

q2 _reg = h- Δ Θ (1)

Where h: heat transfer coefficient between molten steel and solidified shell

ΘΘ: Degree of superheat of molten steel.

13. A breakout detection device for continuous fabrication according to claim 12,

The breakout determination means is

Based on the heat flux profile, the overall heat fluxes Q1 and Q2 are determined by the following method;

If there is a minimum point indicating a minimum value in the heat flux profile, it corresponds to the area above this line when the minimum point and the local heat flux value at the vertical outlet are connected by a straight line. The total heat flux corresponding to the area obtained by subtracting Q2 from the total heat flux corresponding to the total area surrounded by the entire curve of the heat flux profile between the molten metal surface position and the vertical outlet is Q2. Is Q 1 and

When there is no minimum point indicating a minimum value in the heat flux profile, the total heat flux corresponding to the total area surrounded by the entire curve of the heat flux profile between the molten steel surface force 力 type outlet is determined as the total heat flux. Bundle Q1, Q2 is zero;

A breakout detection device, which is a breakout determination means for determining whether or not there is a risk of occurrence of a breakout based on the overall heat flux Q1 or based on Q1 and Q2.

14. The breakout detection device for continuous fabrication according to claim 13,

The breakout determination means uses the overall heat flux Q1 as an index of heat removal by solidification, and if necessary, Q2 as an index of solidification interface heat input exceeding the steady state.

A breakout detection device that is a breakout determination means that determines whether there is a risk of breakout occurrence based on Q1 or based on Q1 and Q2. The breakout detection device for continuous fabrication according to claim 13, The breakout determination means, for the predetermined threshold α 1 α2 (α 1 <α2) for the overall heat flux Q1,

When Ql <a 1, it is determined that there is a risk of breakout,

a Breakout detection device that is a breakout determination means that determines that there is a risk of breakout according to the value of Q2 when 1≤Q1≤ α2.

16. The breakout detection device for continuous fabrication according to claim 13,

In the case where the breakout determining means has a local minimum point indicating a local minimum in the heat flux profile obtained for (ql_q2 _reg ),

Predetermined threshold for Q1 α1 α2 (α1 <ο: 2) and for the predetermined threshold for Q2, Ql <α 1 and Q2 ≥ j3, or Ql a 1 and Q2 β, or α 1≤ A breakout detection device that is a breakout determination means that determines that there is a risk of breakout when Q1≤ α 2 and Q2 ≥ 0.

17. The breakout detection device for continuous mirror construction according to claim 16, comprising:

When the molten copper is an ultra-low carbon steel, αΐ is set to 15000 (kj / m ² ), 0; 2 is set to 21000 (1 ^ / ^/ 1 ^),] 3 is set to 4500 (kjZm ² ) Out detection device.

18. The breakout detection device for continuous fabrication according to claim 13,

The breakout determination means is

Solidification shell thickness calculation means for calculating the solidification shell thickness D at the vertical outlet based on the following equation (2) using the overall heat flux Q1,

The calculation value of the solidified shell thickness calculation means is input, and the presence or absence of breakout occurrence risk is determined based on the calculation value D and a threshold value obtained in advance in relation to the risk of breakout occurrence. A breakout detection device having a determination means main body.

D = QlZ (AH '; o) (2)

D: Thickness of the solidified shell at the vertical outlet (m)

Ql: Overall heat flux (jZm ² )

厶 H: enthalpy drop per unit weight of solidified shell at vertical outlet (j / kg) P: solidified shell density at vertical outlet (kgZm ³ )

Further, the unit of ql is J / s'm ² , the unit of q2 _ree is j / s'm ² h in the formula (1), and the unit of J / s'm ² '° C Δ 0 is And

19. The breakout detection device for continuous fabrication according to claim 13, wherein the breakout determination means includes:

Using the overall heat flux Q1, calculate the solidified shell thickness D at the vertical outlet based on the following equation (2), and further reduce the solidified shell thickness D1 considering the solidification delay caused by remelting by the overall heat flux Q2. Solidification shell thickness calculation means for calculating from the relationship of D1 == D (1−RS) using the solidification delay degree RS obtained based on the equation (3),

A calculation value of the solidification thickness calculating means is input, and a breakout risk is determined based on the calculated value D1 and a threshold value obtained in advance in relation to the risk of breakout occurrence. A breakout detection device comprising a quatout determination means main body.

D = Q1 / (A H- p) (2)

D: Thickness of the solidified shell at the vertical outlet (m)

Q1: Overall heat flux (j / m ² )

Δ H: enthalpy drop per unit weight of the solidified shell at the shaping outlet (jZkg)

P: Solidified shell density at the vertical outlet (kgZm ³ )

RS = β X (V ⁰⁸ · Δ θ) (3)

RS: Solidification delay (no unit)

β: Coagulation delay constant (unitless)

V: Molten copper flow velocity (m / s)

厶 Θ: Molten copper superheat CC)

Where \ = ((32 ^/ (0: -1; '厶 Θ)) ¹ · ²⁵

Q2: Overall heat flux (jZm ² )

α: Molten copper flow rate constant (no unit)

In addition, the unit of ql is J Vm ² , the unit of q2 _reg is jZs'm ² in the formula (1), the unit of h is jZ s'm ² '° C, and the unit of Δ0. C.

20. The breakout detection device for continuous fabrication according to claim 13, wherein the solidified shell thickness calculating means comprises:

The method according to claim 18, wherein there is no local minimum indicating a local minimum in the heat flux profile obtained for (ql-q2 _reg ), If there is a local minimum indicating a local minimum in the heat flux profile determined for (ql-q2 _reg ),

Breakout detection devices, each of which is a calculation means for calculating the thickness of the solidified shell at the vertical outlet.

21. A breakout prevention apparatus using the breakout detection device according to any one of claims 12 to 20, wherein the breakout determination means inputs a signal of the breakout determination means and the breakout determination means has a risk of breakout In the continuous forging, including a control means for controlling the operating conditions so as to reduce the forging speed, or in addition to the control, for reducing the flow rate of the molten steel in the mold. .

22. A breakout prevention device using the breakout detection device according to any one of claims 12 to 20,

Breakout ^ Breakout prevention device in continuous forging with control means to control the speed of forging to be reduced when the breakout judging means judges that there is a risk of breakout by inputting the signal of the fixing means .

23. A breakout prevention device using the breakout detection device according to claim 16 or 17,

When a breakout determination means signal is input and the breakout determination means determines that there is a risk of breakout,

If the risk determination is based on Q l <a 1 and Q2 ≥ | 3, control the operating conditions to reduce the forging speed and / or increase the vertical cooling, or the control In addition to controlling the flow velocity of molten steel in the vertical mold,

In the case of a hazard judgment based on QK a 1 and Q2 and β, the operating conditions are controlled so as to reduce the forging speed and strengthen the dredging or vertical cooling,

a In case of risk judgment based on 1≤Q1≤α2 and Q2≥β, control to lower the molten steel flow velocity in the mold, or to further reduce the forging speed and strengthen the mold or mold cooling.

Breakout prevention device in continuous fabrication with control means.

24. A method for continuously forging steel using the breakout detection method according to claim 4, Ql> a 2 or

a Continuous steel forging method in which the operating conditions are controlled so that a 1 ≤ Q 1 ≤ α 2 and Q 2 have a reduced value so that they are not judged to be at risk of breakout.

25. A continuous steel forging method using the breakout detection method according to claim 5 or 6, wherein Q l> α 2 and Q2 ≥ β, or Ql ≥ α 1 and Q2 <β. A continuous steel forging method that controls operating conditions.

26. The method of continuous forging steel according to claim 25, wherein the steel is in operation.

When QK a 1 and Q2 ≥ β, the operating conditions are controlled so as to reduce the forging speed and / or to increase the vertical cooling, or in addition to this control, to decrease the molten steel flow velocity in the vertical mold. Control the operating conditions,

If Ql <a 1 and Q2 <J3, control the operating conditions to lower the forging speed g and increase Z or vertical cooling,

If a1≤Q1≤a2 and Q2≥β, then control the operating conditions to lower the molten steel flow velocity in the mold, or further reduce the forging speed and / or increase the mold cooling. Steel continuous forging method.

27. A method of continuous forging steel according to claim 24,

A plurality of pairs of thermocouples embedded between two points with different embedding depths in the saddle mold thickness direction in the saddle mold are installed in the saddle mold fabrication direction to output the pair of thermocouples. Based on the local heat flux obtained by the following equation (4) based on the steel continuous forging method.

ql = X (Tl -T2) / d (4)

Where λ is a bowl-shaped thermal conductivity

Τ1, Τ2: Thermocouple detection temperature

d: Thermocouple burying interval

28. A method for continuously forging steel using the breakout detection method according to claims 7 to 9, wherein the estimated solidified shell thickness is smaller than a threshold value obtained in advance in relation to the risk of occurrence of breakout. A continuous steel forging method that controls the operating conditions.

29. Heat input to the solidification interface between the molten steel in the mold and the mold outlet in continuous casting Measuring the heat flux ql to

The step of obtaining the steady solidification interface heat input q2 _reg by the molten steel flow in the mold in the steady state based on the following equation (1):

Obtaining the heat flux profile from the molten steel surface to the vertical outlet for the difference between the heat flux ql (j Vm ² ) and the steady solidification interface heat input q2 _reg (ql-q2 _reg ),

If there is a minimum point indicating a minimum value in the heat flux profile, a portion above this line when the minimum point and the local heat flux value at the vertical outlet are connected by a straight line. Q2 is the total heat flux corresponding to the total area, and Q2 is the total heat flux corresponding to the entire area surrounded by the entire curve of the heat flux profile between the vertical outlet and the molten steel surface position force as Q2. Let Q 1 be the corresponding overall heat flux,

When there is no local minimum point indicating the minimum value in the heat flux profile, the total heat flux corresponding to the entire area surrounded by the entire curve of the heat flux profile from the molten metal surface position to the vertical outlet is determined as the total heat flow. Bundle Q1,

A method for estimating the solidified shell thickness in continuous casting, comprising the step of estimating the solidified shell thickness D at the vertical outlet based on the following equation (2) using the overall heat flux Q1.

q2 _reg = h- Δ Θ (1) · where q2 _reg : heat input at steady-state solidification interface 0 / s' m ² )

h: Heat transfer coefficient between molten copper and solidified shell (in L * m ² ')

Δ Θ: Superheat degree of molten steel (° C)

D = Q1Z (厶 Η ・ ρ) (2)

D: Solidified shell thickness at the vertical outlet (m)

Ql: Overall heat flux (jZm ² )

厶 H: enthalpy drop per unit weight of solidified shell at vertical outlet (L kg) p: solidified shell density at vertical outlet (kgZm ³ )

30. A method for estimating the solidified shell thickness D1 taking into account the solidification delay caused by remelting by the overall heat flux Q2 when there is a local minimum point in the heat flux profile.

30. A method for estimating a solidified shell thickness in continuous fabrication, wherein Dl = D (1—RS), where D is a solidified shell thickness obtained according to claim 29.

However, RS = β X (V ⁰ ^{8 8} 9) (3)

RS: Freezing delay (no unit)

J3: Solidification delay constant (no unit) V: Molten steel flow velocity (πι / s)

厶 Θ: Molten steel superheat (° C)

Where _{V = (Q2Z (a .t '} A 0)) 1 · 25

Q2: Overall heat flux (jZm ² )

a: Molten steel flow rate constant (unitless)

31. a step of measuring a heat flux ql that enters the solidification interface between the molten steel in the mold in the continuous casting and the mold outlet,

A step of obtaining a steady solidification interface heat input q2 _res based on the following equation (1) by a molten steel flow in the mold in a steady state:

The step of obtaining the heat flux profile from the hot metal surface to the vertical outlet for the difference between the heat flux ql α / sm ² ) and the steady solidification interface heat input q2 _res (ql-q2 _reg ),

Estimating the solidified shell thickness from the heat flux profile, comprising the steps of:

If there is no local minimum point indicating the local minimum in the heat flux profile, the solidified shell thickness is estimated by the method of claim 29,

If there is a minimum point showing a minimum value in the heat flux profile, the solidified shell thickness is estimated by the method according to claim 30.

Solidified shell thickness estimation method in continuous forging.

32. The method for estimating a solidified shell thickness in continuous forging according to any one of claims 29 to 31_, wherein the heat flux ql is between two points having different embedding depths in the saddle thickness direction in the saddle shape. Estimating the thickness of the solidified shell in continuous forging, which is a local heat flux obtained by the following equation (4) based on the output of the pair of thermocouples by installing multiple embedded thermocouples in the vertical forging direction Method.

ql = λ (Tl-T2) / d (4)

Where ql: heat flux (jZs'm ² )

λ: vertical thermal conductivity (jZs'm '° C)

Tl, T2: Thermocouple detection temperature CC)

d: Thermocouple burying interval (m)

33. A thermocouple group in which a pair of thermocouples embedded in two points at different depths in the vertical thickness direction are installed in the vertical direction,

Input the temperature information from the thermocouple group and obtain the local heat flux ql at each thermocouple installation site;

Profile calculation means for obtaining the heat flux profile from the molten steel surface to the vertical outlet for the difference between the heat flux ql and the steady-state solidification interface heat input q2 _reg (ql-q2 _reg ),

When there is no local minimum point indicating the minimum value in the heat flux profile obtained by the profile calculation means, a summary corresponding to the entire area surrounded by the entire curve of the heat flux profile between the molten metal surface position and the vertical outlet. When the heat flux is Q1, and there is a minimum point that shows the minimum value in the heat flux profile obtained by the profile calculation means, the minimum point and the local heat flux value at the vertical outlet are connected by a straight line. The overall heat flux corresponding to the area above this straight line is defined as Q2, and the overall heat flux force Q2 corresponding to the entire area surrounded by the entire curve of the heat flux profile from the molten metal surface position to the vertical outlet The total heat flux corresponding to the area is Q1, and the total heat flux Q1 is used to calculate the solidified shell thickness D at the vertical outlet based on the following equation (2) using the total heat flux Q1. Solidified shell thickness estimation device in a continuous 鎵造 with an arithmetic hand stage.

q2 _reg = h- Δ Θ (1)

Where q2 _reg: steady-state solidification interface heat input ClZs'm ² )

h: Heat transfer coefficient between molten steel and solidified shell (j / sππ ² °

厶 Θ: Molten steel superheat (° C)

D = Ql / (AH-p) (2)

D: Thickness of the solidified shell at the vertical outlet (m)

Ql: Overall heat flux ClZm ² )

厶 H: enthalpy drop per unit weight of solidified shell at vertical outlet (J / kg) P: solidified shell density at vertical outlet (kg / m ³ )

34. The solidification shell thickness calculation means includes: D1 = D (1—RS), where D1 is a solidification shell thickness in consideration of a solidification delay caused by remelting by the overall heat flux Q2, in the continuous forging according to claim 33. Solid shell thickness estimation device.

RS = 0 Χ (ν ° ' ⁸ · Δ 0) (3)

J3: Solidification delay constant (no unit) V: Flow velocity of molten steel (m / _S )

厶 Θ: Molten copper superheat (° C)

RS: Coagulation delay (no unit)

Where _{V = (Q2 / (a -t} 'A 0)) 1 · 25

Q2: Overall heat flux (j / m ² )

a: Molten steel flow rate constant (unitless), t: Time required for the solidified shell to pass through the minimum point in the heat flux profile to reach the vertical outlet (S)

35. A thermocouple group in which a plurality of pairs of thermocouples embedded in two points at different depths in the vertical thickness direction are arranged in the vertical direction,

A profile calculating means for calculating the heat flux profile to the difference between these heat fluxes ql and steady solidification interface heat input q2 _{_reg} (ql- q2 _reg) molten steel for reaches the melt surface force铸型outlet,

A solidified shell thickness estimation device comprising solidified shell thickness calculating means for calculating the solidified shell thickness D at the vertical outlet based on the heat flux profile obtained by the profile calculating means,

The solidified shell thickness calculating means is

If there is no local minimum point indicating the local minimum in the heat flux profile, the solidified shell thickness D is calculated by the method of claim 33, and

If there is a minimum point indicating a minimum value in the heat flux profile, the solidified shell thickness D1 is calculated by the method described in claim 34.

Is an arithmetic means,

Solidified shell thickness estimation device in continuous forging.