Equivalent cooling control method in continuous casting process of stainless steel plate blank

Abstract

The invention discloses an equivalent cooling control method in the continuous casting process of a stainless steel slab, which introduces an equivalent cooling concept, replaces the real-time pulling speed in the existing water quantity control, and creates an equivalent cooling water quantity control model to adapt to the conditions of pulling speed reduction by tundish heat exchange or accident short pause speed, so that the water quantity in the process is automatically controlled, and the production efficiency is improved. And the problem of casting blank supercooling caused by quick change of the tundish is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting technology for stainless steel slabs, and specifically relates to an equivalent cooling control method for the continuous casting process of stainless steel slabs. Background Technology

[0002] During continuous casting, when the casting speed is reduced due to heat exchange in the tundish or during a brief stoppage due to an emergency, the temperature of the billet inside the casting machine decreases. During the speed increase process after heat exchange or after the discharge of runners, the dynamic secondary cooling water is sprayed according to a function of the casting speed. This causes the surface of the billet distributed within the casting machine during the heat exchange or brief stoppage to be lower than the normal casting state. This results in billets requiring hot delivery temperatures failing to meet hot testing requirements, making it easy for low-temperature brittle steel grades such as ferritic stainless steel to break during continuous casting.

[0003] In actual production, users adjust the temperature drop caused by the tundish quick change or the extended residence time of the billet in the casting machine due to an accidental pause by manually reducing the water volume in the secondary cooling zone. If the automatic water distribution of the secondary cooling zone is not restored when the machine is restarted, the billet may not be completely solidified after exiting the fan-shaped section, causing an accident.

[0004] Furthermore, manually reducing the water volume in the secondary cooling zone relies on the operator's experience, which cannot guarantee stability and can easily lead to problems with the quality of the cast billet. Summary of the Invention

[0005] The purpose of this invention is to provide an equivalent cooling control method for the continuous casting process of stainless steel slabs to address the problem of undercooling of the slab caused by heat exchange or restarting after an accidental speed reduction.

[0006] The objective of this invention is achieved through the following technical means: an equivalent cooling control method for a continuous casting process of stainless steel slabs, comprising the following steps: Obtain the metallurgical length of the rolls in each sector of the continuous casting machine; When the continuous casting machine is undergoing heat exchange or is interrupted due to an accident, record the current time T0 and reduce the casting speed to the set speed υ0; Calculate the equivalent pulling speed of each sector segment. Where i represents the i-th sector segment, , In the formula The metallurgical length of the outlet roller of the i-th sector segment at the end of heat exchange or accident suspension; e is the metallurgical length of the inlet roller of the i-th sector when the heat exchange or accident pause ends; T0 is the time when heat exchange or accident temporary start-up occurs; T1 is the time when the heat exchanger or accident temporarily ends; When a heat exchanger or accident has temporarily ended and production is about to be accelerated, each sector segment will adjust its production speed according to the calculated equivalent pulling speed. The water volume in each sector segment is controlled. The specific method for controlling the water volume of each sector segment through equivalent pulling speed is as follows: water volume Q = A ( ) 2 +B +C, where A, B, and C are preset coefficients.

[0007] Starting from the second sector segment, the metallurgical length of the exit roller of the previous sector segment is taken as the metallurgical length of the inlet roller of the current sector segment.

[0008] When heat exchange is not performed or an accident occurs causing a shutdown, i.e. during normal operation, the water volume Q=A in each sector segment. 2 +B +C, where A, B, and C are preset coefficients. For real-time pulling speed.

[0009] If multiple sector segments are controlled by the same nozzle, then these sector segments are grouped together, and the water flow of this group of sector segments... The metallurgical length of the last sector exit roller in the group at the end of a heat exchanger or accidental shutdown. e represents the metallurgical length of the inlet roller of the first sector of the group at the end of a heat exchange or accidental shutdown.

[0010] If there is another sector segment before the current sector segment group, the metallurgical length of the exit roller of the previous sector segment is used as the metallurgical length of the inlet roller of the current sector segment group. If there is another group of sector segments before this group of sector segments, then the metallurgical length of the exit roller of the last sector segment of the previous group of sector segments is used as the metallurgical length of the inlet roller of the current group of sector segments.

[0011] When the continuous casting machine is undergoing heat exchange or experiencing an accident and pausing, the position of the billet at the entrance of the sector segment is recorded and denoted as point a. When point a enters the i-th sector segment, all sector segments before the i-th segment switch to water flow control based on real-time casting speed, Q=A. 2 +B +C, where A, B, and C are preset coefficients. For real-time pulling speed.

[0012] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the method described in the foregoing technical solutions.

[0013] The beneficial effects of this invention are as follows: by analyzing the heat balance relationship of the secondary cooling zone during continuous casting, the water volume of the fan-shaped section controlled by each nozzle is adjusted in real time according to the data before the speed reduction, and the casting speed is controlled according to the equivalent casting speed control based on the residence time of the billet in each cooling zone, i.e., the fan-shaped section, so as to overcome the adverse factors of large temperature drop of the billet. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the sector segment partitioning; Figure 2 This is a heat balance diagram for the continuous casting process; Figure 3 This is a heat balance diagram of the secondary cooling zone during the continuous casting process. Figure 4 Flowchart of equivalent cooling control method for continuous casting process of stainless steel slab; The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0015] Traditional solidification theory of cast billets follows a "square root relationship" where the thickness of the billet shell is directly proportional to the square root of the solidification time of the molten steel, that is:

[0016] In the formula: ------Blank shell thickness, mm; K------Consolidation coefficient, mm / min 0.5 ; t-------Settling time, min; like Figure 2 As shown, according to the experimental evaluation, in the continuous casting process, from the solidification and cooling of molten steel to the room temperature billet stage, from the crystallizer to the secondary cooling zone and then to the radiation zone, the heat released accounts for about 40% of the total heat, and the heat released after the billet is cut off and cooled accounts for about 60%.

[0017] like Figure 3 The heat balance diagram of the secondary cooling zone in the continuous casting process is shown below. In the thermal equilibrium of the two cooling zones: (1) Heat is radiated from the surface of the billet to the air, accounting for about 25% of the secondary cooling zone; (2) The heat transfer between air and the billet is relatively small in the secondary cooling zone; (3) The support rollers contact the surface of the billet for heat transfer, accounting for approximately 17% of the secondary cooling zone; (4) The water vapor sprayed onto the billet carries away heat (convection), accounting for about 33% of the secondary cooling zone; (5) The heat carried away by the water droplets flowing along the inner arc accounts for approximately 25% of the heat in the second cooling zone; Based on the above analysis, the secondary cooling water carries away 58% of the heat of the billet in the secondary cooling zone. By controlling the amount of cooling water in this zone, the surface temperature of the billet and the solidification rate of the billet can be adjusted appropriately.

[0018] Based on the above experimental data analysis of the heat balance in the secondary cooling zone, an equivalent cooling control method for the continuous casting process of stainless steel slabs is proposed, which replaces the real-time casting speed with an equivalent casting speed.

[0019] like Figure 4 As shown, an equivalent cooling control method for continuous casting of stainless steel slabs includes the following steps: Obtain the metallurgical length of the rolls in each sector of the continuous casting machine; First, obtain the metallurgical length corresponding to each roll in each sector of the continuous casting machine.

[0020] The sector segment is a structural division of the continuous casting machine itself.

[0021] When the continuous casting machine is undergoing heat exchange or is stopped due to an accident, the current time T0 is recorded and the casting speed is reduced to the set speed υ0. When the continuous casting machine is undergoing heat exchange or is stopped due to an accident, its speed is often not directly reduced to zero, but is reduced to a set low speed, i.e., υ0.

[0022] Calculate the equivalent pulling speed of each sector segment. Where i represents the i-th sector segment, , In the formula The metallurgical length of the outlet roller of the i-th sector segment at the end of heat exchange or accident suspension; e is the metallurgical length of the inlet roller of the i-th sector when the heat exchange or accident pause ends; T0 is the time when heat exchange or accident temporary start-up occurs; T1 is the time when the heat exchanger or accident temporarily ends; The equivalent pulling speed is calculated for each sector segment. For example, if the continuous casting machine has a total of 10 sector segments, then calculate... to The equivalent pulling speed of each of the 10 sector segments is obtained.

[0023] by to For example, , in The metallurgical length of the exit roller of the first sector segment. e represents the metallurgical length of the first sector entry roller at the end of the heat exchange or accident pause.

[0024] , in The metallurgical length of the exit roller of the second sector segment. e represents the metallurgical length of the second sector entry roller at the end of the heat exchange or accident pause.

[0025] This step allows us to determine the equivalent pulling speed of each sector segment.

[0026] When a heat exchanger or accident has temporarily ended and production is about to be accelerated, each sector segment will adjust its production speed according to the calculated equivalent pulling speed. The water volume in each sector segment is controlled. When the heat exchange or accident is temporarily resolved and acceleration begins, the equivalent acceleration rate calculated previously should be used. The water volume in each sector segment is controlled.

[0027] The specific method for controlling the water volume of each sector segment through equivalent pulling speed is as follows: Water volume Q = A ( ) 2 +B +C, where A, B, and C are preset coefficients.

[0028] Starting from the second sector segment, the metallurgical length of the exit roller of the previous sector segment is taken as the metallurgical length of the inlet roller of the current sector segment.

[0029] As in the original second sector segment, it is That is, the metallurgical length of the exit roller of the second sector section minus the metallurgical length of the inlet roller of the second sector section; Optimized to That is, the metallurgical length of the exit roller of the second sector segment minus the metallurgical length of the exit roller of the first sector segment.

[0030] When heat exchange is not performed or an accident occurs causing a shutdown, i.e. during normal operation, the water volume Q=A in each sector segment. 2 +B +C, where A, B, and C are preset coefficients. For real-time pulling speed.

[0031] During normal operation of the fan-shaped section, the water volume is controlled according to the real-time speed. However, for non-fan-shaped sections such as the crystallizer foot roll area and the curved section in the continuous casting machine, the water volume of the corresponding nozzles is always controlled by the real-time casting speed.

[0032] If multiple sector segments are controlled by the same nozzle, then these sector segments are grouped together, and the water flow of this group of sector segments... The metallurgical length of the last sector exit roller in the group at the end of a heat exchanger or accidental shutdown. e represents the metallurgical length of the inlet roller of the first sector of the group at the end of a heat exchange or accidental shutdown.

[0033] In the actual structure of the sector segment, such as Figure 1 As shown, if multiple sector segments are controlled by the same nozzle, then these multiple sector segments are divided into the same group.

[0034] The calculation method then becomes: calculate the equivalent pulling speed of each group of sector segments. Where i represents the i-th sector segment, , In the formula When the heat exchanger or accidental interruption ends, the metallurgical length of the outlet roller of the last sector of the i-th group of sector segments; e represents the metallurgical length of the inlet roller of the first sector segment in the i-th group when the heat exchanger or accident pause ends. like Figure 1 As shown, in the continuous casting machine used in this embodiment, the distance from the inlet of sector 1 to the liquid level of the crystallizer is 4298mm. The metallurgical length of the inlet roller of sector 1 is L1e, the metallurgical length of the outlet roller is L1f=L1e+1980, the metallurgical length of the outlet roller of sector 2 is L2f=L1e+3973, the metallurgical length of the outlet roller of the third group of sector sections (i.e., the outlet roller of sector 4) is L3f=L1e+8054, the metallurgical length of the outlet roller of the fourth group of sector sections (i.e., the outlet roller of sector 6) is L4f=L1e+12230, the metallurgical length of the outlet roller of the fifth group of sector sections (i.e., the outlet roller of sector 8) is L5f=L1e+16802, and the metallurgical length of the outlet roller of the sixth group of sector sections (i.e., the outlet roller of sector 10) is L6f=L1e+21982.

[0035] like Figure 1 As shown, there are a total of 6 groups of sector segments: the first group is sector segment 1, the second group is sector segment 2, the third group is sector segments 3 and 4, the fourth group is sector segments 5 and 6, the fifth group is sector segments 7 and 8, and the sixth group is sector segments 9 and 10.

[0036] Taking the third group of sector segments as an example, , In the formula When the heat exchanger or accidental interruption ends, the metallurgical length of the exit roller of the third group of sector sections, the last sector section (i.e., sector section 4); e represents the metallurgical length of the inlet roller of the first sector (i.e., sector 3) in the third group of sector segments when the heat exchanger or accident pause ends.

[0037] If there is another sector segment before the current sector segment group, the metallurgical length of the exit roller of the previous sector segment is used as the metallurgical length of the inlet roller of the current sector segment group. If there is another group of sector segments before this group of sector segments, then the metallurgical length of the exit roller of the last sector segment of the previous group of sector segments is used as the metallurgical length of the inlet roller of the current group of sector segments.

[0038] Taking the third group of sector segments as an example, it becomes , In the formula When the heat exchanger or accidental interruption ends, the metallurgical length of the exit roller of the third group of sector sections, the last sector section (i.e., sector section 4); 2f is the metallurgical length of the inlet roller of the second group of sector sections, the first sector section (i.e., sector section 2), when the heat exchange or accident pause ends.

[0039] When the continuous casting machine is undergoing heat exchange or experiencing an accident and pausing, the position of the billet at the entrance of the sector segment is recorded and denoted as point a. When point a enters the i-th sector segment, all sector segments before the i-th segment switch to water flow control based on real-time casting speed, Q=A. 2 +B +C, where A, B, and C are preset coefficients. For real-time pulling speed.

[0040] When the continuous casting machine is undergoing heat exchange or is stopped due to an accident, record the position of the billet at the entrance of the sector section and mark it as point a. Monitor the position of point a. When point a enters the next sector section, all previous sector sections are switched to control the water volume based on the real-time casting speed.

[0041] by Figure 1 For example, as the equipment operates, point a will continuously move backward, moving from sector 1 into other sector segments.

[0042] When point a enters the third group of sector segments (sector segments 3 and 4), the third to sixth groups of sector segments still use the equivalent pulling speed to control the water volume, while the first to second groups of sector segments before the third group are changed to control the water volume Q through real-time pulling speed.

[0043] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the method described in the foregoing technical solutions.

Claims

1. An equivalent cooling control method for continuous casting of stainless steel slabs, characterized in that, Includes the following steps: Obtain the metallurgical length of the rolls in each sector of the continuous casting machine; When the continuous casting machine is undergoing heat exchange or is interrupted due to an accident, record the current time T0 and reduce the casting speed to the set speed υ0; Calculate the equivalent pulling speed of each sector segment. Where i represents the i-th sector segment, ， In the formula The metallurgical length of the outlet roller of the i-th sector segment at the end of heat exchange or accident suspension; e is the metallurgical length of the inlet roller of the i-th sector when the heat exchange or accident pause ends; T0 is the time when heat exchange or accident temporary start-up occurs; T1 is the time when the heat exchanger or accident temporarily ends; When a heat exchanger or accident has temporarily ended and production is about to be accelerated, each sector segment will adjust its production speed according to the calculated equivalent pulling speed. The water volume in each sector segment is controlled.

2. The equivalent cooling control method for continuous casting process of stainless steel slabs according to claim 1, characterized in that: The specific method for controlling the water volume of each sector segment through equivalent pulling speed is as follows: water volume Q = A ( ) 2 +B +C, where A, B, and C are preset coefficients.

3. The equivalent cooling control method for continuous casting process of stainless steel slabs according to claim 1, characterized in that: Starting from the second sector segment, the metallurgical length of the exit roller of the previous sector segment is taken as the metallurgical length of the inlet roller of the current sector segment.

4. The equivalent cooling control method for continuous casting process of stainless steel slabs according to claim 1, characterized in that: When heat exchange is not performed or an accident occurs causing a shutdown, i.e. during normal operation, the water volume Q=A in each sector segment. 2 +B +C, where A, B, and C are preset coefficients. For real-time pulling speed.

5. The equivalent cooling control method for continuous casting process of stainless steel slabs according to claim 1, characterized in that: If multiple sector segments are controlled by the same nozzle, then these sector segments are grouped together, and the water flow of this group of sector segments... The metallurgical length of the last sector exit roller in the group at the end of a heat exchanger or accidental shutdown. e represents the metallurgical length of the inlet roller of the first sector of the group at the end of a heat exchange or accidental shutdown.

6. The equivalent cooling control method for continuous casting process of stainless steel slabs according to claim 5, characterized in that: If there is another sector segment before the current sector segment group, the metallurgical length of the exit roller of the previous sector segment is used as the metallurgical length of the inlet roller of the current sector segment group. If there is another group of sector segments before this group of sector segments, then the metallurgical length of the exit roller of the last sector segment of the previous group of sector segments is used as the metallurgical length of the inlet roller of the current group of sector segments.

7. The equivalent cooling control method for continuous casting process of stainless steel slabs according to claim 1, characterized in that: When the continuous casting machine is undergoing heat exchange or experiencing an accident and pausing, the position of the billet at the entrance of the sector segment is recorded and denoted as point a. When point a enters the i-th sector segment, all sector segments before the i-th segment switch to water flow control based on real-time casting speed, Q=A. 2 +B +C, where A, B, and C are preset coefficients. For real-time pulling speed.

8. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the method as described in any one of claims 1-7.

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