Process control method for improving cooling slab shape of a high tmcp steel plate

Abstract

The application discloses a process control method for improving a cooling plate type of a strong TMCP steel plate, and specifically comprises the following steps: (1) placing a blank into a heating furnace for heating, wherein the heating temperature is 1180-1220 DEG C, and the heating time is set according to the blank thickness and the furnace charging temperature; (2) setting a final rolling temperature according to the blank thickness, and controlling the last pass reduction ratio to be 10-12%; (3) selecting the flow of a single header according to the blank thickness and a red temperature setting; and (4) adjusting the cooling acceleration and the head and tail shielding according to the plate type of the steel plate. The application can greatly reduce the straightening rescue amount of the steel plate, and the performance uniformity of the steel plate is more stable.

Description

TECHNICAL FIELD

[0001] The present application relates to a process control method for improving the cooling plate shape of a strong TMCP steel plate. BACKGROUND

[0002] Existing medium plate production lines are equipped with ultra-fast cooling equipment. In order to compete in the market price, low alloy series steel plates mainly containing C and Mn reduce the Mn content to below 0.9%, and the re-red temperature to below 600°C. This process design route requires high uniformity of cooling. The uniformity of the current cooling system is difficult to control the overall temperature uniformity of the steel plate within 20°C, so that the flatness of the low alloy series steel plate designed in this way cannot meet the national standard, and needs to be straightened or flattened, resulting in cost waste. High alloy series steel generally adds Cr, Ni, V, Ti and other alloys. This kind of variety needs high cooling speed and large flow cooling process to meet the performance requirements. High cooling speed will also cause uneven deformation of the steel plate, and the steel plate may even be rejected, especially for pipeline steel below 20mm and high-strength series steel plate, which is more sensitive to cooling. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a process control method for improving the cooling plate shape of a strong TMCP steel plate, which greatly reduces the straightening and saving amount of the steel plate, and the performance uniformity of the steel plate is more stable.

[0004] The technical solution for solving the above technical problems is: a process control method for improving the cooling plate shape of a strong TMCP steel plate, which specifically includes the following steps:

[0005] (1) Put the blank into the heating furnace for heating, the heating temperature is 1180-1220°C, and the heating time is set according to the blank thickness and the furnace temperature;

[0006] (2) Set the final rolling temperature according to the blank thickness, and control the last pass reduction rate to 10-12%;

[0007] (3) Select the appropriate flow of a single header according to the blank thickness and the re-red temperature setting;

[0008] (4) Adjust the cooling acceleration and head and tail shielding according to the plate shape of the steel plate.

[0009] The present application further limits the scheme:

[0010] Preferably, the heating time in (1) is set according to the blank thickness and the charging temperature, the charging temperature is 400 DEG C as a boundary, the in-furnace time is set to be ≥ (1.0H-30) min below 400 DEG C, the in-furnace time is set to be ≥ (0.9H-20) min above 400 DEG C, H is the thickness of the steel plate, unit: mm.

[0011] Preferably, the finishing temperature in (2) is set according to the blank thickness, specifically, the finishing temperature is 800-860 DEG C when the thickness is below 20 mm, the finishing temperature is 760-820 DEG C when the thickness is 20-40 mm, and the finishing temperature is 800-820 DEG C when the thickness is above 40 mm.

[0012] Preferably, the flow rate of the single header in (3) is set according to the blank thickness and the re-red temperature, for the ferrite+pearlite structure alloy steel, the flow rate L of the single header of the steel plate with a thickness of 10-25 mm is selected to be 200±20 m3 / h, the flow rate of the single header above 25 mm is selected to be 240±20 m3 / h, and the flow rate can be reduced by 20 m3 / h if the cooling water temperature is below 24 DEG C, for the steel plate requiring bainite or martensite, the flow rate L of the single header of the steel plate with a thickness of 10-25 mm is selected to be 260±20 m3 / h, and the flow rate of the single header above 25 mm is selected to be 300±20 m3 / h.

[0013] Preferably, the re-red temperature of the blank in (3) is controlled by the cooling roller speed, the cooling roller speed is 0.6-0.9 m / s when the blank thickness is above 25 mm, and the cooling roller speed is 0.9-1.2 m / s when the blank thickness is below 25 mm.

[0014] Preferably, the cooling acceleration and the head-tail shielding in (4) are adjusted according to the plate shape of the steel plate, the tail water ratio is reduced if the plate shape of the steel plate is concave, the tail water ratio is increased if the plate shape of the steel plate is convex, the water ratio is set to be 1.25-1.35 for the steel plate below 25 mm, the water ratio is set to be 1.3-1.45 for the steel plate above 25 mm, the cooling acceleration is set to be 0.01-0.015 m / s2, the head-tail water ratio should be reduced if the plate shape of the steel plate is concave, that is, the cooling water amount of the head-tail shielding is reduced by 20%-40%, and the head-tail does not need to be shielded if the plate shape of the steel plate is convex.

[0015] The present application has the beneficial effects that the straightening rescue amount of the steel plate is greatly reduced, and the performance uniformity of the steel plate is more stable, the cooling acceleration is set to be 0.01-0.015 m / s2, which is to ensure that the tail temperature of the steel plate is not too low when entering the water, so as to cause the strength to be weak, and also to control the temperature uniformity of the head, the middle and the tail within 40 DEG C after cooling, and the last pass reduction rate is controlled to be 10-12%, so as to ensure good rolling wave shape. Embodiment Example

[0016] The embodiment provides a process control method for improving a cooling plate type of a strong TMCP steel plate, and the method specifically comprises the following steps.

[0017] (1) Put the blank into a heating furnace for heating, the heating temperature is 1200℃, and the heating time is set according to the blank thickness and the furnace charging temperature, the furnace charging temperature is taken as a boundary, the in-furnace time is set to be ≥(1.0H-30) min when the furnace charging temperature is below 400℃, and the in-furnace time is set to be ≥(0.9H-20) min when the furnace charging temperature is above 400℃, H is the thickness of the steel plate, and the unit is mm;

[0018] (2) The finish rolling temperature is set according to the blank thickness, the finish rolling temperature is 860℃ when the thickness is below 20 mm, the finish rolling temperature is 820℃ when the thickness is 20-40 mm, the finish rolling temperature is 800℃ when the thickness is above 40 mm, and the last pass reduction rate is controlled to be 12%;

[0019] (3) The flow rate of a single header is selected according to the blank thickness and the re-red temperature, the re-red temperature is controlled by the cooling roller speed, the cooling roller speed is 0.9 m / s when the blank thickness is above 25 mm, and the cooling roller speed is 1.2 m / s when the blank thickness is below 25 mm, and appropriate flow rate of the single header is selected, wherein the flow rate L of the single header of the steel plate with a ferrite+pearlite structure and with a thickness of 10-25 mm is 200±20 m3 / h, the flow rate of the single header of the steel plate with a thickness above 25 mm is 240±20 m3 / h, meanwhile, if the cooling water temperature is below 24℃, the flow rate can be reduced by 20 m3 / h, the flow rate L of the single header of the steel plate with a thickness of 10-25 mm is 260±20 m3 / h if the steel plate requires bainite or martensite, and the flow rate of the single header of the steel plate with a thickness above 25 mm is 300±20 m3 / h;

[0020] (4) The cooling acceleration and the head and tail shielding are adjusted according to the plate type of the steel plate, the tail water ratio is reduced if the plate type of the steel plate is concave, the tail water ratio is increased if the plate type of the steel plate is convex, the water ratio is set to be 1.25 for the steel plate with a thickness below 25 mm, the water ratio is set to be 1.35 for the steel plate with a thickness above 25 mm, the cooling acceleration is set to be 0.01 m / s2, the head and tail water ratio should be reduced if the plate type of the steel plate is concave, that is, the cooling water amount of the lower part of the head and tail shielding is reduced, and the head and tail do not need to be shielded if the plate type of the steel plate is convex.

[0021] In addition to the above embodiment, the present application can also have other implementation manners. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A process control method for improving a cooling sheet shape of a high TMCP steel sheet, characterized by: The method specifically comprises the following steps: (1) Put the blank into the heating furnace for heating, the heating temperature is 1180-1220℃, the heating time is set according to the blank thickness and the furnace temperature, specifically, the furnace temperature is taken as the boundary of 400℃, when less than 400℃, the in-furnace time is set to ≥(1.0H-30)min, when >400℃, the in-furnace time is set to ≥(0.9H-20)min, H is the thickness of the steel plate, unit mm; (2) Set the finishing temperature according to the blank thickness, the final pass reduction rate is controlled at 10-12%; (3) According to the thickness of the blank, select the appropriate flow of single header, while adjusting the red temperature setting, wherein for ferrite + pearlite microstructure of alloy steel, the flow L of single header of steel plate with thickness ≥10mm and less than 25mm is selected to be 200±20m 3 / h, the flow of single header of steel plate with thickness greater than 25mm is selected to be 240±20m 3 / h, and if the cooling water temperature is lower than 24℃, the flow is reduced by 20m 3 / h; for steel plate requiring bainite or martensite, the flow L of single header of steel plate with thickness ≥10mm and less than 25mm is selected to be 260±20m 3 / h, the flow of single header of steel plate with thickness greater than 25mm is selected to be 300±20m 3 / h; The blank red temperature is controlled by the cooling roller speed, that is, when the blank thickness is greater than 25mm, the cooling roller speed is 0.6-0.9m / s, when the thickness is less than 25mm, the cooling roller speed is 0.9-1.2m / s; (4) Adjust the cooling acceleration and the head and tail shielding according to the plate shape of the steel plate.

2. A process control method for improving a cooling sheet type of a high TMCP steel sheet according to claim 1, characterized in that: The (2) sets the finishing temperature according to the blank thickness, specifically, when the thickness is less than 20mm, the finishing temperature is 800-860℃, when the thickness is 20-40mm, the finishing temperature is 760-820℃, when the thickness is higher than 40mm, the finishing temperature is 800-820℃.