JPS6050122A - Cooling method of high temperature steel sheet - Google Patents

Abstract

PURPOSE:To prevent generation of cooling strain by segmenting the range of cooling start temp. and stop temp. to plural temp. regions, and cooling a steel sheet while changing the spray pattern of cooling water from the top and bottom surfaces in the transverse direction of the steel sheet in accordance with the temp. region in each segment. CONSTITUTION:A high-temp. steel sheet formed by hot rolling is cooled with water from the top and bottom surfaces thereof. Water cooling of the high- temp. steel sheet is accomplished while the range of cooling start temp. and stop temp., for example, the water spray pattern in the distribution A of the water flow rate in the transverse direction, is changed to a pattern I , pattern IIand pattern III. More specifically, the pattern I is the same as in the conventional method but the distribution of the water flow at the edge is made slightly higher like in the pattern II unlike the pattern I in the temp. distribution in the transverse direction from the cooling start temp. of about 550 deg.C to the cooling stop temp. of about 300 deg.C. The distributions of the water flow in most of the transverse direction are made the same in the pattern III.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for water cooling a co-rolled high-temperature steel plate from its upper and lower surfaces.

This type of cooling method is technically difficult, and there are many problems to be solved, and various research and developments have been carried out from various fields in the industry, and some methods have been put into practical use.

That is, since the cooling speed is not uniform in the thickness direction from the front surface to the center to the back surface, deformations such as buckling waves and warping are likely to occur.

Because the board is wide, a large amount of water collects on the top surface of the board.

Because of the outflow, the cooling uniformity in the upper and lower surfaces and in the width direction is likely to be disrupted, and deformations such as buckling waves and warping are likely to occur.

Rolled steel plates are not uniform in temperature, size (plate crown, etc.), shape, and surface texture, and are prone to variations in cooling.

There are many topics that need to be resolved.

By the way, in online controlled cooling of high-temperature steel plates, the current state of conventional technology is shown in Figure 1 (al As shown in the figure, the shape of the steel plate at room temperature is deformed at the edges.

As a measure to prevent this cooling distortion, as shown in Fig. 1 fbl,
By creating a distribution of cooling water in the width direction of the steel plate, which is smaller on the edge side of the plate, the cooling start temperature, i.e., the temperature distribution in the width direction of the steel plate before cooling, changes from approximately 800°C to the cooling stop temperature, i.e., after cooling. With the temperature distribution in the width direction of the steel sheet, only large cooling strain occurs when cooling to about 550°C.

By the way, if the cooling start temperature is lower than it should be, cooling distortion will increase as shown in Figure 2, which will not only result in a defective product, but also cause operational troubles such as not being able to use a hot repeller.

On the other hand, from the material side, as shown in Figure @6, there is a relationship between mechanical properties and cooling stop temperature.

In other words, the cooling stop temperature? Lowering yield stress (YS),.

This results in an improvement in tensile stress (TS), and also increases Ceq
A decrease in the amount of added components leads to a decrease in the amount of added components, resulting in significant benefits such as improved weldability.

That is, by lowering Ceq'z and lowering the cooling stop temperature, a material that satisfies mechanical properties can be manufactured.

The ingredient list in FIG. 6 is as follows.

In this way, although it is effective to lower Ceq 'j (and lower the cooling stop temperature), as mentioned above, there is the problem of cooling distortion, and there is a limit to lowering the cooling stop temperature to a total of 550°C or less. There is.

In other words, if we consider a plate factory, if cooling is completely stopped at about 500°C and straightened with a hot leveler, steel plates with good flatness can be manufactured, but if cooling is stopped at a lower temperature than that, the conventional technology It is impossible to manufacture it for the following reasons.

■ For example, when the temperature is 600°C, the steel plate is deformed before the hot leveler, requiring strong straightening, and even if straightening is possible, a large uneven temperature distribution will occur on the steel plate. Therefore, when the steel plate is cooled to room temperature, it becomes defective in shape.

■ When the steel plate is cooled to near room temperature, the temperature distribution of the steel plate is nearly uniform, but the deformation that occurs during the cooling process is large and the strength of the steel plate increases, so that it cannot be straightened sufficiently and the shape becomes defective.

Figure 4, foil figure 5? Referring to the conventional example, I will explain it once again.
In FIG. 4, (5) is the water volume distribution in the width direction, and the water injection distribution is such that the water volume is smaller on the edge side.

fBl is the temperature distribution in the width direction, approximately 00℃ → approximately 550℃
℃→approximately 300℃→100℃→room temperature, (C
) shows the entire shape of the steel plate, and ■) shows the hot leveler.

That is, in Fig. 4, by setting the water flow distribution in the width direction (N) and setting the cooling stop temperature from the cooling start temperature of about 800°C to about 550°C, the
) and then air cooled, the shape of the steel sheet at room temperature becomes normal, but in this case, the cooling stop temperature is not that low, so it cannot be said that the mechanical properties and CeqO point are fully satisfied.

Therefore, the width direction water amount distribution (3)! Cooling start temperature of about 800℃, cooling stop temperature of about 550℃, about 600℃
If the cooling stop temperature is set to , deformation will occur before the hot leveler is applied. Even if it can be straightened, it will deform when air cooled, and it cannot be straightened with a hot leveler.

The cause of this is the cooling of the cooling water poured into the steel plate and the cooling when the cooled water flows over the steel plate.
The relationship shown in the figure becomes clear, and this result also shows that when cooling at temperatures below about 500°C, as shown in Figure 4, adding water to the width distribution causes uneven temperature distribution in the width direction. This is because it will happen.

By the way, regarding the temperature distribution allowable value in the width direction of the steel plate, the 14th
When considered with reference to the figure, the horizontal axis is the steel plate width, and the vertical axis shows the relationship with the temperature difference in the width direction (temperature difference between the center of the steel plate width and both ends of the steel plate). For example, even if the temperature difference in the width direction is large, the flatness of the steel plate is good, but if the plate width is large, buckling deformation occurs even if the temperature difference in the width direction is small.

In view of the above-mentioned phenomena and findings, the present invention has been developed to reduce Ceq'i and reduce the cooling stop temperature. Is there a cooling method for high-temperature steel plates that causes less cooling distortion even at low temperatures? This is what we are trying to provide.

That is, in the present invention, a hot-rolled high-temperature steel plate is cooled with water from its upper and lower surfaces.

In the process of cooling a high-temperature steel plate with water, the range of cooling start temperature and cooling stop temperature is divided into multiple temperature ranges, and cooling is performed while changing the cooling water injection pattern in the width direction of the steel plate corresponding to each temperature range. It is a feature of all that it does.

Is there a drawing regarding the method for cooling high-temperature steel sheets according to the present invention? Refer to and explain in detail.

Is Fig. 6 a schematic diagram of an embodiment of the present invention? As is clear from FIG. 6, in this example, cooling is performed while changing the water injection pattern in the width direction water amount distribution (3) to pattern E, pattern (2), and pattern (2).

That is, pattern (2) is similar to the conventional example shown in FIG. 4, but unlike pattern I, pattern H Is the water volume distribution of the edge like this? In addition, in pattern m, the water amount distribution in the width direction is almost the same.

The outline of the cooling method of the present invention is as described above, and the control method will be described later.
This will be explained with reference to Figure 10.

In FIG. 7, (1) is a steel plate to be cooled, which is cooled by simultaneous water injection during the process of being threaded in the direction of the arrow.

(2) is a table roller, which is arranged in rows at predetermined intervals in the sheet passing direction, and the roller (2) and the VCrfi lower spray nozzle (7)? A lower cooling header (4) is provided.

(3) is the upper cooling header, and the upper hairpin nozzle (6)? Is there cooling water on the top surface of the steel plate to be cooled (1)? These are injected and are arranged in parallel in the width direction of the steel plate (1). (5) is an auxiliary header for upper cooling, and has a hairpin nozzle (8).

That is, in the present invention, since the case where water is injected from the upper surface of the steel plate has a large influence and is important, the lower cooling device has the same configuration as the conventional example, but the upper cooling device is configured as shown in Fig. 8. ing.

That is, in Figure 8, the upper cooling header (fasteners such as 311 kU bolts + 10
In addition to fixing the installation with +, the upper cooling header (3
) Between the upper auxiliary header (11) and the upper auxiliary header (11), the M auxiliary header (5) is fully fixedly installed using fasteners such as U-holts.

That is, Funkisiple piping 03)? It is connected to the upper supply water pipe (I41) shown in Figure @10 through the upper cooling header (3) and the upper cooling auxiliary header (5)? Alternate plate passing direction?
As is clear from the water supply system diagram shown in Figure 10, the three-way switching valve σ5]
'Water injection pattern as shown in the figure? In this example, it is possible to change to pattern (2) or pattern (H).

In addition, in Fig. 9, (a) shows the upper part of the
l ld Upper upper auxiliary header center comes, ○ mark is upper hairpin nozzle position, Δ mark is upper auxiliary hairpin nozzle position,
The black vO mark indicates that the upper hairpin nozzle is not used.

That is, as shown in FIG. 11, the steel plate to be cooled 11)? In order to cool the steel plate by passing it through a cooling device Oη that injects water all at once from the upper and lower surfaces, the range of cooling start temperature and cooling stop brightness is divided into multiple temperature ranges, and the steel plate width is adjusted according to the temperature range of each division. Directional cooling water injection pattern? To cool while changing, the 11th
The explanation will be based on the functional outline diagram shown in the figure and the flowchart in FIG. 12.

There are thermometers (18
) (I9), a steel plate tracking sensor (20) is provided on the entry side, and a steel plate tracking function 21J1 is provided.
Water injection amount calculation and cooling time calculation function allow water injection command,
The water injection stop command 1231 is given to the cooling device (lη), and the water injection amount distribution change function (241
, expected temperature actual value C5I, etc. are possible.

The 70-chart from the start of cooling to the end of cooling will be explained with reference to FIG. 12.

In the broom 12 diagram, block A is the actual cooling start temperature Ts.
It is a Glock with expected data such as cT, target cooling stop temperature TFcTo, plate thickness t, plate width, plate length, etc.

[F]) is a block that determines the target cooling rate cR'r22, which is set experimentally and empirically according to the steel type, plate thickness, etc.

fc] is the calculation block for the same time when cooling, which is
It can be found in the following calculation.

fDl is a calculation block for the required water density W, and this W is calculated by the following formula.

Here, CRTC℃/s), w Ci/miH, i)
, and A and n are coefficients, respectively.

(El is a block for calculating the required total water amount wT and calculating the threading speed V, !l), and WT is calculated by the following formula.

WT = WX Aw) 17! Xriiw: Cooling sawn, It-e; Cooling sawn length,
l; Correction value taking into account water injection distribution in the upper part, etc.

Also, ■ is calculated using the following formula.

7ICT-Steel plate dog (tip) protrusion amount, jICB
i Steel plate bottom (rear end) protrusion amount A Switching valve 'J5)
An order issued to IJη? Glock [G] When the r output is %NO, it is Deiay (delay).

Then, the water injection pattern ■ is performed as described above, but when there is a water injection pattern change command as in issue C,
Time 11 until fl water injection pattern change? Calculation block, fJ) water injection time integration block, (K) water injection pattern change time judgment block, (Ll upper auxiliary header three-way valve opening command block, (M judgment whether cooling has ended, (The command block to close the three-way valves of the upper and lower main headers and upper auxiliary header of Nl, the command block to transfer the steel plate (0) to the outside of the cooling system, the block to estimate the actual temperature of the steel plate after cooling the cod, and then the end. It is.

Therefore, τ is calculated using the following formula.

Note that if the steel plate temperature at the time of changing the water injection pattern is Tchi, and the average cooling rate kCRTChi thus far is taken, then CRTchi = CRTo:f (Tchi).

However, m may be performed after fE).

In addition, at fL+, a three-way valve is used in this example, but since the amount of water injected from the auxiliary header is small, 0N-
It may also be an OFF type butterfly valve or the like.

@ Figures 7 to 11 show an example of an upper cooling device with an auxiliary header attached, but as shown in Figure 13, the upper cooling device may be a hairpin-shaped nozzle with a two-stage structure, upper and lower? In addition, the upper and lower sections may have two types of water injection putter feet in the width direction, the cooling temperature range may be divided by the above-mentioned Tchi, and the entire header of the upper section and the lower section may be separated.

Control 70-chart in this case is [G
l becomes the three-way valve opening command of the upper and lower pattern ■, and
< (L) is the pattern ■ Header three-way valve open command do pattern 7
II is the header three-way valve open command, [Nl is the upper and lower use three-way valve close command, and the rest! This is the same as the illustrated example in FIG.

In addition, Fig. 15 and Fig. 16 are examples of changes in the injection pattern of cooling water for the assembly board, and both are examples in which the cooling start temperature of 800°C and the cooling stop temperature of 600°C are divided into two ranges. The figure shows six examples where the water density at the center of the board width is constant and the water density at both ends of the board width is changed in pattern I and pattern ■. Figure @16 shows the water volume at the center of the board width. Pattern■ and pattern■ when density is changed
Six examples are shown. In addition, is pattern ■ in the figure an example of increasing the water volume density? As shown, the pattern ■
You can make it smaller.

As shown in Figure 17, in the conventional example of cooling in one pattern from a cooling start temperature of 800°C to a cooling stop temperature of 600°C, as mentioned above, the cooling stop temperature was 500°C.
In contrast, in the case of A-1 in Fig. 15, the average deformation of the steel plate becomes significantly large in the vicinity of 550°C, whereas in the case of A-1 in Fig. 15, the cooling stop temperature is as low as 200°C or less. However, the occurrence of cooling strain is significantly reduced, and this can be said to be a method for cooling high-temperature steel sheets that prevents cooling strain even though Ceq f is lowered and mechanical properties are fully satisfied.

In addition, in the case of the above example, the cooling start temperature is 800°C.
In the above example, the cooling stop temperature is divided into two categories up to around 300°C, but if the cooling start temperature is around 800°C and the cooling stop temperature is around 100°C, it is divided into three categories, and the temperature of each division is Cooling water injection pattern in the width direction of the copper plate corresponding to the area? You may change it. In addition, the cooling start temperature is not limited to around 800°C, but generally it is sufficient to be around the Ars tipping point or higher, and the cooling stop temperature is also around 550°C.
It is sufficient if the temperature is below ℃.

That is, in the above example, Pattern I is the same as the conventional example, but it is divided into a plurality of temperature ranges from a cooling start temperature of around 800°C to a cooling stop temperature of 500°C to 550°C. The cooling water injection pattern in the width direction of the steel plate may be changed depending on each classification, and this is particularly effective for steel plates with a thickness of 50 mm or more.

Next, an embodiment of the present invention will be described in comparison with a conventional example.

<Conventional example> Steel plate size (cocoon)...11.8X"+190x14.
800 Cooling start temperature (d... 750 Cooling stop temperature rcl... 650 Cooling water Itt (rrVmin, i) -0,26〈
Examples of the present invention> Steel plate size (strength)...10.3X3210X14.8
00 Cooling start temperature rcl... 770 Pattern change temperature (c)... 520 Cooling stop temperature (
℃)... 330 Cooling water water!・= 0.26 姶′min, rd The cooling stop temperature distribution of the above-mentioned conventional example and the embodiment of the present invention is @1
The temperature distribution is uneven in the board width direction with the distribution shown in Fig. 8 (aHbl, and in the conventional example Fig. 18 fa), whereas in the embodiment of the present invention, the temperature distribution is as shown in Fig. 18 fa. fbl
As shown in , the temperature distribution in the width direction of the plate becomes uniform.

Therefore, as shown in Reference Photo 1, in the conventional example, the edges of the steel plate are deformed into a corrugated plate shape during actual operation, whereas in the embodiment of the present invention, the steel plate is in good condition during actual operation. It can be seen that cooling has been applied to show the flatness of the entire surface.

In summary, in the present invention, when cooling a high-temperature copper plate, in the process of water-cooling a high-temperature steel plate, the range of the cooling start temperature and the cooling stop temperature is divided into a plurality of temperature ranges, and the range of the cooling start temperature and the cooling stop temperature is divided into multiple temperature ranges. Corresponding cooling water injection pattern in the width direction of the steel plate?
Since cooling is performed while changing the temperature, even if the cooling stop temperature is lowered, the occurrence of cooling distortion can be reduced. It is possible to exhibit the advantage of improving weldability by reducing the amount of additive components by reducing Ceq, which can be lowered, and also to significantly improve mechanical properties such as yield stress and tensile stress.

[Brief explanation of drawings]

@Figure 1 (a) (BL is a diagram explaining the current state of the conventional technology, Figure 2 is a diagram showing the relationship between the cooling stop temperature and cooling strain of a steel plate, and Figure 6 is a complete explanation of the effect of the cooling stop temperature on the material quality. Fig. 4 is a schematic diagram of the conventional example, Fig. 5 is an explanatory diagram of the conventional example showing the steel plate temperature and secondary cooling/direct cooling, and Fig. 6 of the foil is a schematic diagram showing the embodiment of the present invention. Fig. 7 is a side view of an example of the cooling device used in the present invention, Fig. 8 is a plan view of the upper cooling device in Fig. 7, and Fig. 9 is an example of the use of the upper hairpin nozzle in the present invention and a pattern change. An explanatory diagram of an example of the use of the auxiliary nozzle, Figure 10 is a water supply system diagram to the cooling device used in the present invention, Figure 11 is a functional overview diagram of the cooling method of the present invention, and Figure 12 is an example of the Kihatsu F!A embodiment. 70-Chart-An explanatory diagram of an example, Fig. 13 is a sectional view of the upper cooling device in the second embodiment of the present invention, @14 diagram is an explanatory diagram showing an example of temperature distribution tolerance in the width direction of the steel plate, @15 diagram Is the water density at the center of the board width? An explanatory diagram showing three examples of water injection patterns of the steel sheet cooling water of the present invention when it is constant, and Figure 16 is the water density at the center of the board width? Wooden F when changed? An explanatory diagram showing 6 examples of injection patterns of A steel plate cooling water, Figure 17 is a graph diagram showing the results of pattern 8-1 in Figure 15, and Figures 18 [a] and (b) are conventional examples and examples of the present invention. The cooling stop temperature distribution r is shown, fa) is the conventional example, and [bl is the wood F! This is an example of fJ. fi+...Steel plate to be cooled, (3)...Upper cooling header, (4)...Lower cooling header, (5)...Upper cooling auxiliary header, (6)...Upper hairpin nozzle,
(7j...lower sagure nozzle, (8)...upper auxiliary hairpin nozzle. Export of the 4th and 6th figure procedures amendments) Dear Commissioner of the Japan Patent Office 1, Display of 731 Showa phrases Patent application no. No. 159891 8 2 Name of the invention Method for cooling high-temperature steel plates 3, relationship to the amended case Patent applicant (119) Kobe Steel, Ltd. 4 Agent address 1013 Mikuriya, Higashiosaka-shi, Osaka Kan-Osaka +0
6171121 (381KM Showa year, month, day (self-motivated) Character erasure 6, subject of amendment, Zan-Eiichisho, full text of Dansei Threat 7, contents of amendment (1) Specification @ page 2, lines 6 to 7 The size of the eyes
... shape," is corrected to "size, shape (plate crown, etc.)." (2) “In cooling water” on page 2, line 17,
Correct the cooling water distribution. (3) "Also" and rc&lJ on page 3, line 11
Insert the sentence "For steel plates with the same strength level as conventional" between. (4) On page 3 of the same page, line m12, “the decrease in the amount is due to the added component” c.
It is corrected as "additional components that can reduce the amount of." (“Steel plate tfJ member center” on page 6, line 9 of the same statement is “
Corrected to "center of steel plate." (6) "Settings" on page 10, line 19 will be corrected to "calculation." (7) "Cooling zone" on page 11, line 13. Correct as "cooling zone width." 1g+ "Expected" in line 17 of page 12 will be corrected to "intake." (9) In the attached drawings, Figures 3, 5, 6, and 12 have been corrected as shown in the attached sheet.

Claims (1)

[Scope of Claims] L In a method of cooling a hot rolled high temperature steel plate with water from its upper and lower surfaces, in the process of water cooling the high temperature steel plate, cooling) 15 Range of starting temperature and cooling stop temperature and a plurality of temperatures. A method for cooling a high-temperature steel sheet, characterized in that the cooling water is divided into zones, and the cooling water is cooled while changing the cooling water injection bagoon in the width direction of the steel sheet corresponding to the temperature range of each zone.