JPS6030565A - Method for stabilizing surface shape of ingot with heated casting mold type continuous casting method - Google Patents

Abstract

PURPOSE:To enable continuous casting of a casting ingot having a stable surface condition by controlling the drawing speed of the casting ingot in such a way that the position to form the initially solidified surface of the casting ingot detected by the measured value of the temp. near the inside wall at the outlet end of a heated casting mold attains a prescribed standard value. CONSTITUTION:The temp. of the molten metal 1 in a holding furnace 2 in which a molten metal is held roughly at a specified melt level by supplying the molten metal through an inflow port 3 and discharging the same through an overflow port 4 is held constant via a heater 11 by a thermocouple 10 and a temp. controller 20 and the temp. of the inside wall of a casting mold 5 is maintained at the solidifying temp. of the metal 1 or above in continuous casting for the metal by supplying the molten metal 1 in the furnace 2 into the mold 5, cooling the solidified metal drawn via a dummy casting ingot from the outlet of the mold 5 by a cooler 13 and drawing out continuously the same in the form of a casting ingot 12 by pinch rollers 18. The temp. near the inside wall at the outlet end of the mold 5 is further detected with a thermocouple 9 and the position to form the initially solidified surface of the ingot 12 is detected. The drawing speed of the ingot 12 is controlled via a driving motor 19 of the rollers 18 by a speed controller 22 in such a way that said position attains a standard value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuous casting of metals, more particularly having an outlet opening for withdrawing the ingot and an inlet opening for supplying the molten metal, the inner wall temperature being adjusted to the solidification temperature of the metal to be cast. Molten metal is supplied into the mold held in the above manner, and a dummy ingot kept at a temperature below the solidification temperature of the molten metal is brought into contact with the surface of the molten metal, and then this dummy ingot is pulled out from the mold outlet to form a dummy ingot. Concerning the control of various factors related to the casting speed to stabilize the surface condition of the ingot in a continuous metal casting method in which a metal solidified body is continuously formed at the tip. The law has Patent No. 10491
Although proposed in No. 46, very strict speed control was required to perform this f'L.

Moreover, the casting speed varies depending on the type of metal and the cross-sectional shape of the ingot, as well as the ingot cooling capacity, hot water supply temperature, mold inner wall temperature, and mold outlet end il? - The casting speed is also influenced by the molten metal pressure, and these factors are not always constant, but take values that fluctuate within a certain range. Therefore, if the ingot is drawn at a constant speed without taking into account the fluctuations of these factors, the surface condition of the obtained ingot will not always be constant, and there will be cases where there are hanging scratches on the surface or stairs. In addition to visible stripes, breakouts may occur or the ingot and mold may stick together, forcing continuous casting to be interrupted.

Therefore, as a result of intensive research, the inventor has found that continuous casting of an ingot with a stable surface condition is possible by controlling the initial solidification surface profile e of the ingot to be within the range specified below. I discovered that. The condition in which the surface of the ingot is maintained depends on the intended use of the ingot; in some cases, a smooth and beautiful ingot is required, and in other cases, It may not be a problem even if there are slight scratches from hanging. However, if cracks or step-like stripes appear on the casting surface, the ingot can no longer be used as a product, and it will be necessary to melt and cast it again. Therefore, the present invention provides a method for stably and continuously casting an ingot having the required casting surface. The present invention will be described in detail below along with examples.

First of all, what most strongly controls the surface condition of the ingot is the combination of metal type and mold material, but there are also other factors such as the degree of cleanliness of the mold inner wall surface, the initial solidification surface formation position, the molten metal temperature, the mold inner wall temperature, It is also affected by the molten metal pressure applied to the mold outlet end, the ingot cooling capacity, and the ingot cross-sectional shape. Therefore, when carrying out the heated mold continuous casting method, it is necessary to select the mold material according to the type of metal and at the same time to experimentally find the optimal conditions for various operating factors according to the cross-sectional shape of the ingot. When selecting the mold material, it is necessary to select one that allows a smooth and beautiful ingot to be obtained and that has a wide range of initial solidification surface formation positions.

For example, when silicon carbide is used as a mold material for 918% aluminum, the initial solidification surface formation position at which a smooth and beautiful ingot is obtained is between the mold outlet end and 1.5 holes inside the mold. If the initial solidification surface formation position enters the mold more than 1.5 rm, slight hanging scratches will appear on the casting surface, and if it enters the mold more than 3 rms, the pulling scratches on the casting surface will become stronger, causing the casting surface to deteriorate. The metallic luster of the metal will be lost, and if it enters the mold for more than 1.5 degrees, cracks will occur on the casting surface. On the other hand, if the initial solidification surface formation position is outside the mold, step-like stripes will appear on the casting surface, and if it moves beyond the mold outlet end for more than one stroke, these stripes will become stronger, and in some cases breakout may occur. Continuous casting would have to be interrupted. On the other hand, when alumina is used as the mold material for 998% aluminum, deep cracks will occur in the casting surface if the initial solidification surface formation position is even slightly inside the mold; On the outside, step-like stripes appear on the casting surface. Therefore, if alumina is used as the mold material for 99.8φ aluminum, an ingot with a good surface condition cannot be obtained. By the way, if you choose boron nitride as the mold material for 99t8% aluminum, silicon carbide for aluminum alloy containing 1t silicon, and graphite for 99t steel,
The initial solidification surface formation position range is widened to obtain an ingot with a good surface condition. Furthermore, for tin alloys containing 99 tin and 10 titanium lead (stainless steel is suitable as a mold). For example, when graphite casting is used with 999% copper, the molten metal temperature (from 1530℃ to IJ5
If the temperature of the inner wall at one end is in the range of 1,140°C from 1,520°C, an ingot with a good casting surface can be obtained, but if the temperature of the molten metal is 1,200°C, Even if the temperature is set to 1,130°C, it is not possible to obtain an ingot with no hanging scratches or step-like stripes.Therefore, the initial solidification surface formation position of the ingot is controlled to be within the range. In order to do this, it is necessary to quantitatively evaluate the effects of the molten metal temperature, the calorific value of the heating element for heating the mold, and the ingot cooling capacity on the ingot solidification rate according to the metal type, g-type material, mold structure, and ingot cross-sectional shape. You need to understand it. As a result of research conducted by the inventor, these factors were quantified without affecting the solidification rate of the ingot. Figure 1 shows the solidification of an ingot when a round bar with a diameter of 20 m was cast using 99.99 thialuminum. The relationship between speed and molten metal temperature is shown. Curve A in the figure is when cooling water is applied to the ingot at a rate of 12/min at a position 40m away from the mold outlet end, and curve B is 60m/min.
C is the curve when cooling water is used at 127 per minute at a position of 80° and D is 100°. As is clear from Figure 1, the ingot solidification rate changes almost linearly with changes in molten metal temperature.
Round bar 'f' between 0 and 0: Curve E in the 0 figure showing the relationship between the heater output for mold heating and the solidification rate of the ingot during casting indicates the case where the bath water temperature is 680°C, F is 700'C, G is 720℃
, ■ is a curve at a molten metal temperature of 740°C. As is clear from Figure 2, there is an almost linear relationship between the 1jvJ block solidification rate and the solidification rate of the 1jvJ lump when the heater output for heating the mold is between 100W and 250W. The curve ■ in Figure 0, which shows the relationship between the amount of cooling water used to cool the ingot and the solidification rate of the ingot when casting a round bar, shows the relationship between the amount of cooling water used to cool the ingot and the solidification rate of the ingot. J is 60 because it was 4 when I guessed it.
rtas K is the curve when cooling water is applied to the ingot at the 80° position, and Ll is the curve when cooling water is applied to the ingot at the 100° position.As is clear from Figure 3, the ingot solidification rate (ζ It can also be seen that the change has a large effect on the solidification rate of the ingot.0 Next, Figure 4 shows the relationship between the solidification rate of the ingot and the temperature of the molten metal when casting a plate fr of 999-chip copper with a thickness of 3 mm and @20 m. The curve M in the diagram showing the relationship is when cooling air is applied to the ingot at a rate of 150 tons per minute at a position 60 tons away from the mold outlet end.
This is the curve when cooling air of t is applied to the ingot.

Figure 5 shows the relationship between the solidification rate of the ingot and the output of the heater for heating the mold when casting a sheet metal of 99 mm copper with a thickness of 3 mm and a width of 20 mm. Indicates the gap relationship, Q is molten metal temperature 1,140'C, RU molten metal temperature 1,
What is the relationship at 160℃? The 0 figure shown is 99.9elj
si! in Figure 0 shows the relationship between the ingot withdrawal speed and the cooling air volume when casting a copper plate with a thickness of 3 mm and a width of 20+ m. :
Curve 1゛, T is 8O-1U when cooling air is applied to the ingot at a rate of 150 tons per minute at a position 60 stitches away from the mold exit end.
is the curve when cooling air is applied to the ingot at a rate of 150 tons per minute at a position 100 meters away. It is clear that the same speed changes almost linearly.

When controlling this ζ within the range of 1 solidification surface formation position 12 from the beginning of the ingot, it is possible to change the ingot drawing speed itself or completely change the casting solidification speed itself. At the same time, it shows that it is possible to absorb some changes in the molten metal temperature and ingot cooling capacity as a total disturbance.Furthermore, the inventor investigated the molten metal pressure and the force exerted at the mold outlet end. We also investigated the relationship with the solidification rate and found that the solidification rate of the ingot was hardly affected by changes in molten metal pressure. No breakout occurs when pulling horizontally,
This shows that it is possible to absorb the disturbance as long as it does not deteriorate the flow of the mold.

Therefore, in order to control the initial solidification surface formation position of the ingot within a certain range, it is necessary to detect the change in the ingot. There are two methods: a method of detecting the temperature of self-molten metal in the mold, and a method of detecting the frictional force between the mold and the ingot.

However, it is actually extremely difficult to detect the temperature of the inner wall of the mold. Therefore, the inventor found the following three methods that are actually practicable: 0, a method to detect the temperature near the inner wall of the mold while keeping the output of the built-in heater constant in the mold; There is a method of controlling the output of the built-in heater in the mold and detecting its calorific value, and a method of detecting the temperature of the mold at the exposed part near the end of the mold using a non-contact thermometer. When measuring nearby temperature, a method is usually adopted in which a thermocouple is embedded near the inner wall of the mold outlet end.
This shows the relationship between the temperature near the mold inner wall and the initial solidification surface formation position of the ingot during continuous casting of round bars. A chromel-alumel thermocouple 9 was placed at a distance of 16 degrees from the inner wall of the five-ring mold, and the output of the heater 6 for heating the mold was maintained at 11.100 W.

Note that 12 indicates the ingot. As is clear from Figure 7 (G), as the initial solidification surface formation position of the ingot moves into the mold, the temperature near the inner wall of the mold decreases. Although it is not greatly affected by the solidification rate or molten metal temperature, it is greatly affected by the mold material and the temperature detection position. Therefore,
When detecting the initial solidification surface formation position of an ingot using this method, it is necessary to decide the temperature detection position by taking into consideration the thermal resistance from the built-in heater of the mold to the inner wall of the mold. The relationship between the calorific value of the heater built into the mold and the initial solidification surface shape position 11 of the ingot is shown when a round bar with a diameter of 20 gourds is cast. At this time, the heat generation value of the built-in mold heater is 511 II m from the mold outlet end. A chromel alumel thermocouple is installed at a position 3 circles away from the inner wall of the mold, and the temperature of the thermocouple is 700 IIm.
Differential-integral proportional control is performed to keep the temperature within ±1°C. As is clear from FIG. 8, the amount of heat generated by the mold heater increases as the initial solidification surface forming position of the ingot moves into the mold.

Figure 9 shows the relationship between the temperature of the exposed part of the mold obtained using a non-contact thermometer and the initial solidification surface formation position of the ingot when a plate of 99.9% copper, 3mm thick and 20m+ wide was cast. shows. As is clear from the figure, as the initial solidification surface formation position of the ingot moves into the mold, the temperature of the exposed mold part decreases. In addition, to detect the temperature of the inner wall of the mold, it is sufficient to install a thermocouple in the part of the molten metal near the position where the initial solidification surface of the ingot is formed in the mold. However, the temperature of the self-molten metal in the mold depends on the temperature of the molten metal supplied to the mold. Therefore, if the hot water supply temperature fluctuates greatly, the initial solidification surface formation must also be detected at I-position in combination with the hot water supply temperature. Further, this method can only be implemented if a temperature detection terminal can be installed within the mold.

FIG. 10 shows the relationship between the mold self-molten metal temperature and the initial solidification surface formation position of the ingot when a round bar with a diameter of 30 holes was cast using 99.99% aluminum. The thermocouple at this time has a height of 22III
It was installed at a position that entered the mold 12 from the outlet end of the mold 11. Curve V in the figure shows the hot water supply temperature at 740°C, and W shows the hot water temperature at 720°C.
This is the case. As is clear from the figure, as the initial solidification surface forming position of the ingot enters the mold, the temperature of the mold self-molten metal decreases. Note that it is extremely difficult to detect the ingot temperature at the mold outlet end.

Therefore, the inventors have discovered a method for detecting all the initial solidification surface formation positions of ingots by detecting the surface temperature of the ingot preventer near the mouth end of the mold using a non-contact thermometer. This method is effective for high-melting point metals such as cast iron and steel.Recently, contact thermometers that can measure temperature even when the temperature sensing element is in operation have been commercially available.

Figure 11 shows a cast iron containing 3.5% carbon and 2.1% silicon, which is 2 mm from the mold outlet end when a round bar with a diameter of 12+ m is cast.
The relationship between the ingot surface temperature and the initial solidification surface formation position of the ingot at a distance of 0 m is shown. Curve X in the figure shows the case where the casting speed is 24 m/min, and curve Y shows the case where the casting speed is 26 m/min. As is clear from the figure, as the ingot solidifies into the mold, the ingot surface temperature also decreases.

Figure 12 shows a diameter of 2 mm in 99.99% aluminum.
The relationship between the frictional force between the mold and the ingot and the initial solidification surface formation position of the ingot is shown when a 0 m round bar is continuously cast. Curve a in the figure
The curved line is when silicon carbide is used as the mold material, and the curved line is when boron nitride is used as the mold material.

In this way, the frictional force has different values depending on the combination of metal type and mold material. As is clear from the figure, the frictional force between the mold and the ingot increases as the initial solidification surface formation position of the ingot moves into the mold. In addition, when measuring the values shown in Figure 12, the amount of heat generated by the heater for heating the mold was set to 0 using a strain gauge installed on the mouth of the mold fixing mechanism at the position where the frictional force between the mold and the ingot is applied. If the initial solidification surface formation position P of the ingot and the temperature t1 near the inner wall of the mold are kept constant, there exists a relationship P=F1(tl n (1)). Fl is a function that depends on the type of metal to be cast, the structure of the mold, and the installation position of the temperature sensor.Next, the amount of heat generated by the heater for heating the mold is determined so that the temperature t2 near the inner wall of the mold is constant. When controlling, the initial solidification surface formation position P of the ingot and the calorific value q2 of the mold heater
There is a relationship between P = F 2 (q 2 , t 2 ) (2).

Furthermore, there is a relationship p=F3 (t3. t3') (3) between the initial solidification surface formation position P of the ingot, the mold self-molten metal temperature t3, and the molten metal temperature ta/ supplied to the mold. There is a relationship between the initial solidification surface formation position P of the ingot and the ingot surface temperature t4 as follows: P=F4(t4) (4) 0 Furthermore, the initial solidification surface formation position P of the ingot, the mold and the ingot The relationship p = F 5 (tq s ) (5) exists between the frictional force tq and 5.0 Putting equations (1) to (5) together, the initial solidification surface formation position P of the ingot can be expressed as P=Fi(αi)' (6)0where i=1.2.3.4.
5 Now, in order for the ingot to have a stable surface condition, the initial solidification surface formation position P of the ingot must be determined depending on the type of metal to be cast, the mold material, and the cross-sectional shape of the ingot. It is only necessary to control the ingot withdrawal speed or ingot solidification rate so that the ingot solidification rate is within a range determined empirically. The method of changing the total calorific value of the heater and the method of changing the cooling capacity of the ingot are difficult to think of. However, the method of changing the molten metal temperature according to the change in the initial solidification surface formation position of the molten metal requires a complete change in the temperature of the molten metal, which usually has a large heat capacity, resulting in a slow response.
．． The same applies to the method of changing the amount of cooling water or the amount of cooling air for cooling the ingot, which has a strong risk of not being able to sufficiently control the initial solidification surface formation position of the ingot.

As a result of our research, we have found that the molten metal temperature and ingot cooling capacity are independently controlled in advance to standard values determined empirically, taking into account the type of metal to be cast, the material of the mold, the cross-sectional shape of the ingot, etc. Even if this changes slightly, if the change is absorbed as a disturbance by changing the ingot drawing speed, l':r, and the amount of heat generated by the mold heater, the initial solidification surface formation position of the ingot can be accurately adjusted. The conclusion was reached that it is possible to control the temperature well, and as a result, an ingot with a stable and good casting surface can be obtained.Another method is to set the temperature near the inner wall of the ingot to a predetermined standard value. The heat generated by the heater for heating the mold in order to keep the metals that should be cast in advance,
Based on experience, we consider the cross-sectional shape of the ingot, the mold structure, etc.
The ingot withdrawal speed is not changed while the ingot is within the range of the upper and lower limits, and when the exothermic bone is outside this range,
It has been found that a method of varying the ingot withdrawal speed so that the calorific value falls within this range is very effective. This method makes it possible to accurately control the initial solidification surface shape u of the ingot even if the ingot solidification rate varies widely, so after bringing the dummy ingot into contact with the molten metal in the mold, It can be applied even in situations where the initial solidification rate of the ingot, which is obtained by drawing out the ingot and passing it through this dummy ingot to obtain a metal solidified body, fluctuates considerably. By detecting changes in the ingot cooling capacity and ingot cooling capacity, and controlling the initial solidification surface shape of the ingot using the above three methods, while considering the influence that the range of change has on the ingot 8 speed. It is effective to do so.

Here, the relationship between the ingot solidification rate ■ and the molten metal temperature t7 is V = F7 (t7) (7), and the ingot solidification rate V and a5 ingot cooling capacity C
8 has the following relationship: V = F 8 (CB) (81).

Furthermore, the ingot solidification rate V and the calorific value of the heater for heating the mold q9
There is a relationship between V = F 9 (q g ) (9).

A method for controlling the initial solidification surface formation position of an ingot by organizing all the relationships described above will be described below.

The first method is to determine the heat generated by the heater for heating the mold (including O?), a standard value determined empirically, taking into account the metal to be cast in advance, the material of the ingot, the cross-sectional shape of the ingot, etc. While controlling the temperature in the vicinity of the mold inner wall, the initial solidification surface formation position is determined by controlling the initial solid surface formation position of the weak ingot by changing the ingot withdrawal speed. It is a method of control.

Here, by changing the ingot withdrawal speed υ, 1 initial solidification li!・1
One method for setting the surface forming position P to a predetermined standard value po will be described. That is, from equation (1), p-F
l(tl), there is a method of bringing the initial solidification surface formation position P closer to the standard value PO by Δp=c(po-p) αq within the time ΔT. Here, C(0(c)) is a proportionality constant.

In this case, the ingot withdrawal speed τ should satisfy the ingot solidification rate v Kongo and ΔP − (v−V ) ts T (I+)? + = V + c (POP) / △T (
The ingot solidification rate V varies depending on the ingot cooling capacity and the hot water supply temperature, and also varies slightly depending on the molten metal pressure applied to the mold outlet end.

However, if continuous casting is performed while controlling the ingot withdrawal speed so that the initial solidification surface formation position P becomes accurately the standard value PO, the ingot # within time T1 at time T will be ! The same speed V can be captured by the average value of the casting speed υ as v=/T, ydt/ll Q3.

Furthermore, if we consider all the effects of the melt temperature t7 and the ingot cooling capacity C8 on the ingot solidification rate V, T7 and T8 can be expressed as As an average value, the ingot solidification rate V is v=/T, Jt/'rx+(p7(t7)-F7(t7
)) + (F8 (c8) - F8 (c8)) (Can be caught at 141.

Here, in order to prevent the ingot withdrawal speed v2 from changing suddenly,
Proportionality constant C and time constant ΔTf of Equation 03: It is necessary to take values determined empirically as appropriate. Further, the time constant T1 of Equation 03 and Equation 03 may be set to a time sufficient to calculate @clump solidification rate (■).

The second method is to set the temperature near the inner wall of the mold to a standard value determined empirically in consideration of the type of metal to be cast, the material of the mold, the cross-sectional shape of the ingot, etc., and calculate the amount of heat generated by the mold heater. In this method, the initial solidification surface shape position B is controlled by controlling the total amount of heat generated, detecting the initial solidification surface formation position of the ingot, and changing the ingot withdrawal speed. Since the initial solidification surface formation position of a certain 0 ingot is given by equation (2), similarly to the first method, equation 03 or 0
The ingot solidification rate is calculated using Equation 4, and the ingot withdrawal speed υ is given using Equation H.

The third method is to detect the initial solidification surface formation position of the ingot by detecting the ingot surface temperature just outside the mold mouth end, and control this initial solidification surface formation position by changing the ingot withdrawal speed. This is the way to do it. That is, from equation (4), P-p'4(+
4) Therefore, similarly to the first method, the ingot withdrawal speed τ is given by equation 02 using the time constant ΔT and the proportionality constant C.

Note that the ingot solidification rate V is given using the u equation or the (141 equation).

The fourth method is to detect the temperature of the self-molten metal in the mold to detect the initial solidification surface formation position of the ingot, and to control this initial solidification surface formation position by changing the ingot withdrawal speed.

Note that the initial solidification surface formation position of the ingot is given by equation (3), so similarly to the first method, the ingot solidification rate is calculated using equation 03 or equation 1, and the ingot is pulled out using equation 03. The velocity τ is given.

The fifth method is to detect the stress applied to the mold fixing mechanism, calculate the frictional force between the ingot and the mold, detect the initial solidification surface formation position of the ingot, and change the ingot withdrawal speed. This is a method of controlling the bottom position of this initial solidification surface shape. In addition, the initial solidification surface type position of the ingot is given by equation (5), and as in the first method, the ingot solidification rate is calculated using equation 03 or 04, and equation (12) is The ingot withdrawal speed υ is given using

The sixth method is to detect the initial solidification surface formation position of the ingot by detecting the ingot surface temperature just outside the mold mouth end, and to change the amount of heat generated by the heater for heating the mold. By controlling the forming position, the ingot withdrawal speed τ is independently controlled to be constant.

Also, the initial solidification surface shape @P of the ingot is p=F4 from equation (4).
It is given by (+4). Here, one method for changing the calorific value qk of the mold heating heating element so that the initial solidification surface formation position P of the ingot becomes a predetermined standard value PO will be described.

Now) If continuous casting is performed while controlling the calorific value qt of the mold heater so that the initial solidification surface formation position P becomes accurately the standard value PO, the ingot solidification rate vit is equal to the ingot withdrawal rate τ. . Here, the proportionality constant C (0<c) Kongo is 6
Initial solidification surface shape alignment [G, P Th standard value P
In order to approach O by ΔP=c(PG-P), the ingot solidification rate should be set to vt-V=v-c(POP)/ΔT 69 . This a [exist] formula is F9 using formula (9).
Since it is expressed as (q)=t'-c(PG-P)/△TH, this can be expressed in terms of the calorific value q of the heater for heating the mold: q=F9Cυ-c (PO-P)/6T) LJn
get. Here, if we consider the shadow 471Ik of the molten metal temperature t7 and the ingot cooling capacity c8, the time T
Molten metal temperature t7 and ingot cooling capacity C within T1 time in
As the average value of &, V-'1l-e(PG
P)/6T-F(F7(+7)-F'7(T7))+
(F'8(e8)-F8(c8))
-P) AT-1-(F7(+7)-F?(T7))+(
F8(c8)-F8(';'8))) α■ and n 0 The seventh method is to detect the initial solidification surface formation position of the ingot by detecting the temperature of the molten metal in mold m, and This method controls the initial solidification surface formation position by changing the calorific value of the heating heater, and the initial solidification surface formation position of the zero ingot is controlled independently so that the ingot withdrawal speed is constant. Since it is given by equation 3), the calorific value of the mold heating heater can be given using equation 071 or equation 1, as in the sixth method.

The eighth method is to detect the stress applied to the mold fixing mechanism,
This method controls the initial solidification surface formation position by calculating the frictional force between the ingot and the mold, detecting the initial solidification surface formation position of the ingot, and changing the amount of heat generated by the mold heater. Since the initial solidification surface formation position of the ingot, which is independently controlled so that the ingot drawing speed is constant, is given by equation (5), the an equation or (19 equation) is used as in the sixth method. The calorific value of the heater for heating the mold is given by

The ninth method is that in the above-mentioned methods 6 to 8, the calorific value of the heater for heating the mold necessary for setting the initial solidification surface formation position of the ingot to a standard value is set to an upper limit predetermined by the mold structure. If it does not fall within the range between and the lower limit, the method is to change the ingot withdrawal speed so that the calorific value falls within this range.

In other words, the initial solidification surface formation position P of the ingot is determined by equation (3) or (4).
Here, when the solidification rate V of the ingot is in a steady state, that is, the solidification rate V is given by the molten metal temperature L7, the iron ingot cooling capacity C8, and the force applied to the mold outlet end. If the change is due only to fluctuations in pressure, etc., the calorific value of the heater for heating the mold is set to the intermediate value qg between the predetermined upper limit value q1 and lower limit value q2, and the time T1 within T1 time when the limit is reached. The solidification rate ■ of fA'5 ingot is calculated using the ingot withdrawal speed τ and equation (9): ■ - fT - 1 □ fτ + (F9 (q) - F9 (qO)))
It is expressed as dT/TI O■. Here, the value changes depending on the one lump withdrawal speed τ and the heat generation profile qVi of the mold heating heater time TK. Furthermore, if changes in the molten metal temperature t7 and the ingot cooling capacity C8 are taken into account, T7 and 100 8 as the average value of the molten metal n12liniL7 and the ingot cooling capacity c8 within T1 time, the solidification rate V of the ingot is V=/T, □[V+(F9(q)-F9(QO)))d
T/TI+(F7(t7)-F7(t7))+(FB(
c8) FB (c8)) (21). 211
In the formula, t7 and c8 are instantaneous values at time T.

Here, using the proportionality constant c (0<c)t-, the time constant 61
Set the initial solidification surface formation position P of the ingot to the standard value PO within the time△
In order to bring p=c (po-p) closer, the heater for heating the mold should be set to 1 q=Fq [V-C(PQ-P)/ΔT]. Here, V is the formula 00. The solidification speed of the ingot was 11E.

@Formula V (If the heat generation fkq of the heater for heating the mold is between the predetermined upper limit q□ and lower limit q2, then only q is changed without changing the rυ lump withdrawal speed υ. On the other hand, when q>Q□ or q<Q2, the ingot withdrawal speed is changed by △υ−F9 (,q)−F9 (qO) (c), and the mold heating The amount of heat generated by the heater q is q =
q 6 C! 4 〇Next, when the solidification rate V of the ingot is in an unsteady state, that is, immediately after the start of casting, it is necessary to detect the change in ■.0For this, use formula 09. Using the solidification rate v1 at time T obtained from , and the solidification rate V2i at time T-72 using the time constant T2, V = V 1 + [(Vl-V2)/(T-T2)
)(Tl/2) @ Solidification rate V' at time T
All you have to do is find i.

The reason for this is that the solidification rate v1 at time T determined using formula 09 is the average value within five hours of time constant T, so it is necessary to fully correct the first-order differential coefficient of ■ using formula (c). It is. Next is the @ style? Calculate the calorific value q of the heater for heating the mold using can do.

The above example is basically a proportional operation, but it is also possible to increase the accuracy of control by performing a proportional, integral, and differential (PID) operation, and as a result, the initial solidification surface of the ingot is formed. Since the range of change in the position P can be narrowed, it is possible to keep the surface condition of the ingot more stable and smooth.◇The initial solidification surface formation position P of the ingot is determined empirically in advance. If the upper limit value P1 or lower limit value P2 is exceeded, a circuit may be installed to notify the farmer through a bamboo report and at the same time switch the control to manual mode.

Next, a description based on the drawings will be added for the purpose of further clarifying the content of the present invention.

FIG. 13 shows a first embodiment of the method for stabilizing the surface shape of an ingot in the heated mold continuous casting method of the present invention, in particular, a configuration in which the entire temperature near the inner wall of the mold is detected in the vertical upward drawing method to control the ingot withdrawal speed. It is a diagram. In the figure, molten metal 1 flows into the holding furnace 2 from a molten metal flow port 3 and flows out from an overflow port 4. As a result, the molten metal level remains almost constant, and the molten metal pressure applied to the mold outlet flame also decreases to l'! remains constant. 5 is a mold, which has a built-in heater 6 and is connected to a fixing mechanism 7. 8 is a board that shields radiant heat from the hot water surface, and 9 is a thermocouple for measuring the temperature near the inner wall of the mold. 10 is a thermocouple for measuring the melt temperature,
The heater 11 for heating the holding furnace is controlled by the molten metal temperature regulator 20.
The temperature of the molten metal is controlled by controlling the molten metal temperature. 012 is a metal ingot. 013 is an ingot cooling device. The flow rate of cooling water is adjusted by a regulating pulp 14, and flows into a cooling water reservoir through an inlet 15. , n01 discharged from the overflow port 16
Reference numeral 7 denotes a cooling device face leg mechanism, 18 a pinch roller, and 119 a pinch roller driving motor.The mold heating heater 6 is controlled by an output regulator 21 so that its output is constant.

22 is a motor rotation speed regulator that detects the thermoelectromotive force of the thermocouple 9 for temperature measurement near the inner wall of the mold, converts this n into temperature, and calculates equations (1), (13) and (L). Figure 14 is a second embodiment of the method of the present invention, and is a block diagram showing another example of the vertical upward pull type. The devices are given the same reference numerals. 23 in the figure.
is an ingot air cooling device, in which cooling air enters from the inlet 24,
The oR type heating heater 6, which is blown upward along the slit 25 and the ingot 12, is connected to a thermocouple 9 for measuring the temperature near the inner wall of the mold by a temperature controller 26 and a power adjustment unit 27.
The voltage is controlled so that the temperature detected by the sensor remains constant. 28 is a wattmeter, motor speed regulator 2
2. Detect the power required to keep the temperature constant,
Calculate equation (2), a-temperature equation, and 03 equation, and motor 1
Controls the number of revolutions at 90.

FIG. 15 is a third embodiment of the method of the present invention, which is a block diagram of a horizontal horizontal drawing method. That is, the surface temperature of the ingot is detected by the non-contact thermometer 29, and the motor speed regulator 22 calculates equations (4), 09, and a2, and the motor 1
90 rotation speed''! is controlled. Note that 30 indicates a cooling water shielding plate.

FIG. 16 is a fourth embodiment of the method of the present invention, which is a block diagram of the vertical subtraction type. As shown in the figure, the temperature of the molten metal in the mold is determined by converting the thermoelectromotive force generated by the thermocouple 31 into the converter 32.
The temperature is converted and sent to the motor speed regulator 22 as temperature data.

On the other hand, the temperature of the molten metal is controlled to be constant by controlling the thermoelectromotive force generated by the thermocouple 10 with the temperature regulator 20 and the holding furnace heater 11. At the same time, temperature data is sent to the fast reaction regulator 22. In the 0 speed regulator 22, the formula (3) is
03 formula and 0'IJ formula are calculated to control the number of rotations of the motor 19.0 Figure 17 shows the fifth method of the present invention method as well.
A configuration diagram of a vertical downward pull type using a siphon tube is shown in the embodiment. As shown in the figure, the electromotive force sent from the strain gauge 33 attached to the mold identification mechanism 7 is converted into a frictional force between the mold 5 and the ingot 12 by the all-analog-to-digital converter 34, and the motor speed controller 22 0 to control the rotation speed of the motor 19 by calculating equations (5), 03, and 03.
35 is a hot water supply pipe, 36 is a heater, 37 is a thermocouple, and 38 is a temperature regulator.Next, based on the present invention (example 1 illustrating an example) using a vertical upward drawing type continuous casting equipment@ Three sheets of 99.9-inch copper and 20 m wide were continuously cast into the mold. All graphite was used in the mold, and the mold was immersed in the molten metal, and no heater was used to heat the mold. . The temperature of the molten metal is determined by using a platinum-platinum rhodium thermocouple in a protection tube as a temperature measuring element, and using a temperature controller as a PI.
The mass cooling system was operated in D and kept at 1,140℃±2℃, and the air cooling system was installed at a position 80cm away from the top of the J-type, using 150 tons of cooling air per minute. did. A platinum-platinum rhodium thermocouple for measuring the temperature near the inner wall of the mold is installed at a position 3 #I below the upper end of the mold and 2 + III + away from the inner wall, and the ingot withdrawal speed is fully controlled so that this temperature is ID 75 ° C. The standard value for the initial solidification surface formation position of the ingot is the upper end of casting! It was lowered by 90.5ran. In this case, equation (1) is P Cm)' = 0.25 t, ("L 2 (
39,25 were used. In addition, the ingot solidification rate V in the θ temperature type
The time constant Tl for calculating 2 was set to 60 seconds. Furthermore, 03
Proportionality constant C for calculating the ingot withdrawal speed v2 according to the formula
#'i0.4 The stapling time constant ΔT was set to 30 seconds. As a result, the ingot withdrawal speed υ was controlled within 505 ± 2 Ω per minute, and the resulting ingot had a good and fine casting surface. As a result of looking at cast skin,
Initial solidification surface formation position of ingot H - Standard A1 [± for 1
It was within the range of 0.5 prisoners.

Example-2 3.5% carbon and 2
．． A round bar with a diameter of 12 mm was cast from cast iron containing 1 h of silicon.

Zirconia was used for the mold, molybdenum was used for the heater, and the output 'i was kept at 250 W. Note that the molten metal temperature was not measured, and the calorific value of the holding furnace heater was kept constant. Cooling is done by air cooling, using the full air volume of 300 tons per minute and 20 tons per minute.
Cooling air hit the ingot at a position 60 mm from the upper end of the mold and was blown upward along the ingot. Then, while observing the temperature of the ingot 20 degrees above the upper end of the mold using an optical pyrometer, the ingot withdrawal speed was manually controlled so that the temperature was within the range of 780'C7) to 785°C. As a result, the ingot drawing speed was 22 ± 1 head per minute, and the surface condition of the obtained ingot was generally good, although thin step-like waves were observed in some parts, and the initial solidification surface of the ingot was formed. It was found that the location was within ±1m+ of the top of the dove shape.

Example-3 A round bar with a diameter of 20 m1 was manufactured using a vertical down-drawing continuous casting machine (9999%) using a full mini ram (L7). 5
Silicon carbide was used for the mold L-1t; Nickel comb wire was used as the type 5 heater. 1 per minute for ingot cooling
2J: Using 0.5t of cooling water, 60cm from the mold outlet end.
Cooling water was made to hit the ingot below. A chromel-alumel thermocouple was installed in a thermostatic tube as a thermometer in the mold 10 mm above the mold. The calorific value of the holding furnace heater was controlled using a temperature controller so that the molten metal temperature was 720°C and 3°C.

Here, the ingot drawing speed is maintained at Vt- for 48 minutes per minute, and Gi
The system uses a method that changes the amount of heat generated by the heater for heating the mold. The initial n-coplanar formation position of the ingot was detected based on the mold self-molten metal temperature. In this case, equation (3) is p”'==10(t' 3-2t3+660), /(
t'3-j3) or equation (9) used v'R/min=-OJ)4qW+54. In addition, in the measurement, the proportional constant C was set to 0.5, the time constant △T was set to 1 minute, and as a result, the output of the mold heating heater was changed from 70 V/ to 2
The surface condition of the ingot that was controlled between 50W and 0 was generally good although some thin hanging scratches were observed.As a result of the observation of the casting surface of the ingot, it was found that the initial katted solid surface shape of the gun ingot was The standard value for position P is 2.0, and it is 1.5 for the position P that entered the mold before.
It was found that the mold was controlled at a position 2.5 m from the pus into the mold.0 LOL Example-4 Using a horizontal horizontal drawing type continuous casting machine, 99B'l; full mini ram with a thickness of 5a + i, A plate with a width of 100N was continuously cast.At this time, ETJK used boron nitride and nickel chrome metal as a heater for heating the mold.The molten metal temperature U was kept at 710℃ and 3℃, and the ingot cooling water was poured into the mold. Use 12±1 per minute at a position 40-away from the bottom end, and place chromel alumel at a position 5 degrees from the bottom end of the mold and 3 degrees from the inner wall. A thermocouple was installed. Furthermore, a strain gauge was attached to the mold fixing mechanism to detect the frictional force between the ingot and the mold. At this time, the equation (9) using the formula (5) is as follows: v tm /min = 0.03qw + 106 The upper limit q1 of the output of the heater for heating the mold using gold is 300VJ,
The lower limit value q2 is the 100W intermediate value q. is 0 with 200W
Furthermore, in equation (g), the time constant T1 for increasing the ingot solidification rate V was set to 60 seconds. In addition, in equation (a), the proportionality constant C for calculating the output q of the heater for heating the mold is 0.3, the time constant ΔT is 30 seconds, and the standard value of the initial solidification surface formation position P of the ingot is -2D m. The temperature near the inner wall of the mold was 7.
Initially, the ingot drawing speed was controlled manually while maintaining the temperature at 00±1°C, and when the speed reached 90 m/min, the output q of the mold heating heater exceeded the upper or lower limit. As a result, the ingot drawing speed was automatically adjusted using formula (c) and was controlled between 90 and 110 points per minute.The cast surface of the obtained ingot was very smooth and beautiful. By observing the casting surface, it was found that the initial solidification surface formation position of the ingot was equal to the standard value PO.

[Brief explanation of the drawing]

Figure 1 shows the characteristic curve of ingot solidification rate and molten metal temperature when casting a 99991% 9991% aluminum + w + round bar, and Figure 2 shows the characteristic curve of mold heating heater output and ingot solidification rate. Figure 3 shows the characteristic curve of the amount of cooling water for cooling the ingot and the solidification rate of the ingot, and Figure 4 shows the solidification rate of the ingot and the molten metal when casting a plate of 999% steel with a thickness of AW and a width of 20mm. Figure 5 shows the characteristic curve of the solidification rate of the ingot and the output of the heater for heating the mold. Figure 6 shows the characteristic curve of the solidification rate and the amount of cooling air It. The seventh droplet amount is 9999. The relationship curve between the temperature near the mold inner wall and the initial gH surface formation position of the g The explanatory diagram, Figure @8, is the relationship curve between the calorific value of the heater built into the mold and the initial solidification surface formation position of the ingot, and the fs9 diagram shows the relationship curve when a plate of 999V copper with a thickness of 3cm and 1 da 20 days is cast. Relationship curve between mold self-molten metal temperature and ingot solidification surface formation position, Figure 10 shows the mold self-molten metal temperature and ingot initial solidification surface formation position when a round bar with a diameter of 30 mm was cast with 99.99 thialium. The relationship curve in Figure 11 is 3.5%.
The relationship curve between the surface temperature of the ingot and the initial solidification surface formation position of the ingot when a round bar with a diameter of 12 mm is made from cast iron containing carbon and 2.1% silicon. Figure 13 shows the relationship curve between the P friction between the mold and the ingot and the initial solidification surface formation position of the ingot when continuously casting a round bar.
FIGS. 14, 15, 16, and 37 are diagrams showing a structure 5V, respectively, of an embodiment of the method for stabilizing the surface shape of an ingot in the heated mold continuous casting method of the present invention. 1... Molten % 2... Holding furnace 3... Molten metal flow population 4
... Molten metal overflow port 5 ... Mold 6 ... Heater for heating the mold 7 ... fl, I-type fixing mechanism 8 ... Molten metal surface shielding board 9 ... Thermocouple for measuring temperature near the inner wall of the mold 1o
... Thermocouple for measuring molten metal temperature 11 ... Heater for heating the holding furnace J2 ... Ingot J3, ingot cooling device 14.
・Cooling water adjustment valve 15...Cooling water inlet 16・
・Cooling water overflow port 17... Leg mechanism for cooling device 18・
- Pinch roller - 19... Motor 2o... Molten metal temperature regulator 21... Mold heating heater output regulator - 22... Motor rotational speed regulator 23... Ingot air cooling device 24...・Cooling air inlet 25...
Nurit 26... Temperature controller 27... Power adjustment unit 28... Power meter 29... Non-contact thermometer 3
0... Cooling water shielding plate 31... Thermocouple 32... Converter 33... Load detection end 34... Analog-digital converter 35... Hot water pipe 36... Heater 37...
...Thermocouple 38...Temperature controller Patent applicant O.C.C. Co., Ltd. Nippon Light Metal Co., Ltd. Sugar 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. Molten metal is supplied into a mold having an outlet opening for drawing out an ingot and an inlet opening for supplying molten metal, and whose inner wall temperature is maintained at a temperature higher than the solidification temperature of the metal to be cast. Then, a dummy ingot kept at a temperature below the solidification temperature of the molten metal is brought into contact with the surface of the molten metal, and then the dummy ingot is pulled out from the mold outlet, thereby continuously depositing a solidified metal at the tip of the dummy ingot. In continuous casting of the metal to be formed, the initial solidification surface formation position of the metal solidified body is detected by detecting the temperature near the inner wall of the mold outlet end while keeping the calorific value of the W, type 1 heating element constant. An ingot surface in a heated mold continuous casting method characterized by fully controlling the ingot withdrawal speed so that the initial solidification surface formation position is a standard value determined in advance according to the type of metal to be cast and the material of the mold. Shape stabilization method. 2. While controlling the amount of heat generated by the heating element for heating the mold so that the temperature near the inner wall at the end of the mold becomes a standard value determined in advance according to the type of metal to be cast and the material of the mold, the amount of heat required for this is detected. Method for stabilizing the surface shape of an ingot according to claim 1, which detects the initial solidification surface formation position of the solidified metal by detecting the surface temperature of the solidified metal just outside the outlet end of the mold. The method for stabilizing the surface shape of an ingot according to claim 1, which detects the initial solidified surface formation position of the solidified metal, o = 4, detects the initial solidified surface formation position of the solidified metal by detecting the temperature of the self-molten metal in the mold. A method for stabilizing the surface shape of an ingot according to claim 1 which detects the solidification surface formation position 05, a patent claim which detects the initial solidification surface formation position of the metal solidified body by detecting the stress applied to the mold fixing mechanism. A method for stabilizing the surface shape of an ingot according to item 1. 6. Controlling the amount of heat generated by the heating element for heating the mold so that the detected initial solidification surface formation position becomes a standard value determined in advance according to the type of metal to be cast and the material of the mold. The method for stabilizing the surface shape of an ingot according to items 3 to 5. 7. The amount of heat generated by the heating element for heating the mold is controlled so that the detected initial solidification surface formation position becomes a standard value predetermined according to the type of metal to be cast and the material of the mold. A method for stabilizing the surface shape of an ingot according to claims 3 to 5, wherein the ingot drawing speed is controlled to be within a range between an upper limit value and a lower limit value determined by the structure of the heating element for heating the mold.