Steel plate shape defect control method after quenching of thin-gauge quenched and tempered steel

Abstract

The invention relates to a steel plate shape defect control method after quenching of thin-gauge quenched and tempered steel, which comprises the following steps: dividing head and tail shape defects of a quenched steel plate into three types, and providing corresponding solutions for the three defect types; and according to the quenching tail plate shape state, the time t required by discharging the steel plate to a certain position away from the tail is calculated, and then the secondary model automatically adjusts the water flow of the upper surface after the steel plate is discharged from the furnace and starts quenching t, so that the ratio of water supply to water is changed, and the quenching tail plate shape is improved. According to the method, the head and tail plate shape defects are improved by improving the head and tail quenching cooling uniformity; by adopting the method, the unevenness of the head and the tail of the quenched steel plate is reduced to 3-5 / 1000 from 10-15 / 1000 on average; after the quenched steel plate is tempered and straightened, the maximum value of one-time unevenness is reduced to be within 3 / 1000 from 5 / 1000; and the unevenness of the quenched steel plate after tempering and straightening is improved from 85% to 3 / 1000 to 95% to 2 / 1000.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy production and manufacturing, and in particular to a method for controlling shape defects of thin-gauge quenched and tempered steel plates after quenching. Background Art

[0002] The current mainstream production method for obtaining ultra-high-strength steel is to use a nitrogen-protected radiation tube roller-hearth furnace to heat a single steel plate to above the austenitizing temperature, keep it warm for a certain period of time, and then quench it after it comes out of the furnace.

[0003] The performance and shape of the steel plate after quenching are the core indicators of quenched and tempered high-strength steel. Generally speaking, to achieve the performance indicators, it is only necessary to quickly cool the steel plate at a rate greater than the critical cooling rate of the martensitic phase transformation to obtain a martensitic structure. However, due to the differences in the heat exchange process between different parts of the steel plate and the fluid during the quenching process, plate shape defects have always been a common technical problem in the industry. In particular, the stable flow field at the head and tail of the steel plate is different from that in the middle, and the head and tail parts have no external constraints and are extremely easy to deform; therefore, in actual production, there is often a problem that the shape of the middle part of the steel plate is good after quenching, but the head and tail of the steel plate have problems such as warping and knocking.

[0004] Specifically, there are single defects or two combined defects, such as both the head and tail are warped, both the head and tail are knocked down, and the head is warped and the tail is knocked down, or the head is knocked and the tail is warped. The head and tail are warped up and knocked down, which often leads to the unevenness of the head and tail of the steel plate after straightening cannot meet the user's requirements and needs to be revised, causing great losses to the production enterprises.

[0005] Chinese Patent CN 117107017A: A method for controlling the head-to-tail reverse deformation defect of thin-gauge martensitic wear-resistant steel after quenching. The invention mainly solves the head-to-tail reverse deformation defect by adjusting the roll gap value of the quenching machine and changing the residual water volume on the upper surface of the head and tail during the cooling process of the steel plate. The invention only solves one type of head-to-tail reverse deformation defect, and the method is not very applicable and cannot solve multiple types of head-to-tail plate shape defect problems.

[0006] Chinese Patent CN 110129543A: A quenching process method for ultra-thin strip steel based on a roller quenching machine. This invention improves the flatness of ultra-thin high-strength strip steel after quenching, eliminates quenching deformation of strip steel, eliminates edge waves, middle waves and other strip steel quenching shape problems, and improves the longitudinal head and tail warping and buckling of strip steel after quenching. This invention does not specifically solve the head and tail warping and buckling problems, but is a common means of quenching shape control. It has been proven by a large number of practices that it cannot solve the problem of head and tail shape defects of quenched plates.

[0007] Chinese Patent CN 117187503A: A quenching production line and production method. This invention is a new quenching production line. It uses steel coils as raw materials, and after heating and quenching, a laser cutting machine is used to cut the strip into fixed-length steel plates. Although this method solves the problem of warping at the head and tail of the strip, it is different from the raw material state used in the present invention. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a method for controlling the shape defects of thin-gauge quenched and tempered steel plates after quenching, thereby improving the uniformity of head and tail quenching cooling and achieving improvement of head and tail shape defects.

[0009] The technical solution adopted by the present invention is: a method for controlling the shape defects of thin-gauge quenched and tempered steel plates after quenching, characterized in that it comprises the following steps:

[0010] S1. Identify the head and tail defect characteristics and measure the amplitude value of the quenched steel plate;

[0011] S2. Formulate a quenching process optimization plan based on the head and tail shape defect characteristics of the steel plate identified in step S1;

[0012] S3. Identify the head and tail defect characteristics of the steel plate produced after the quenching process optimization plan and measure the amplitude value;

[0013] S4, comparing the head and tail defect characteristics and amplitude values ​​of the steel plate in step S1 and step S3, and adjusting the quenching process plan accordingly according to the comparison results until the head and tail plate shape defect characteristics and amplitude values ​​meet the target requirements.

[0014] Preferably, in step S1, the types of plate shape feature recognition of the head and tail of the steel plate are divided into: the head and tail are warped in the same direction, the head and tail are warped in opposite directions, and only one end of the head and tail is warped.

[0015] Preferably, if the warping direction of the head and tail of the steel plate is consistent, the quenching process optimization plan is: first, adjust the water ratio of the upper and lower surfaces during the quenching process, and the adjustment range is: -0.05 to +0.05; secondly, adjust the quenching speed of the steel plate, and the adjustment range is: -3 to +3m / min; adjust the defect of the warping direction of the head and tail of the steel plate to the target requirement, or adjust it to only one end of the head and tail to warp.

[0016] Preferably, if the warping of the head and tail of the steel plate is opposite, the quenching process optimization plan is: adjust the water ratio of the upper and lower surfaces during the quenching process, where if the plate head is warped, increase the upper and lower water ratio by 0.01 to 0.05, and if the plate head is downward, reduce the upper and lower water ratio by -0.01 to -0.05; adjust the defect of opposite warping of the head and tail of the steel plate to the target requirement, or adjust it to only one end of the head and tail is warped.

[0017] Preferably, if only one end of the steel plate is warped, the quenching process optimization solution is: using the secondary system of the quenching machine, the quenching process is set to a time-triggered variable water quenching process.

[0018] Preferably, the specific method of the time-triggered variable water quenching process is: according to the quenching speed and the length of the steel plate, the time t required for the steel plate to pass through the slit nozzle from the position of the tail L is calculated;

[0019] In the secondary system, it is set that after the steel plate out of the furnace signal is turned on, the upper and lower water volumes of the slit nozzle begin to adjust. The adjustment plan is: when the tail quenching plate shape is an upward defect, the lower surface water flow rate is kept unchanged, and on the basis of the current upper and lower water ratio, the upper surface water flow rate is reset by increasing the upper and lower water ratio by 0.01~0.03; when the tail quenching plate shape is a downward defect, the lower surface water flow rate is kept unchanged, and the upper surface water volume is reset by reducing the upper and lower water ratio by 0.01~0.03.

[0020] Preferably, the calculation formula for time t is: t=(d+l-4) / v, where: d is the distance from the position where the quenching machine is connected when the steel plate exits the furnace signal triggers the quenching machine to the slit nozzle, in m; l is the length of the steel plate, in m; v is the quenching speed, in m / s.

[0021] Preferably, L=4m.

[0022] Preferably, a shape meter is used after quenching to identify the head and tail defect characteristics and measure the amplitude value of the steel plate.

[0023] Preferably, the target requirement for adjusting the quenching process is to achieve an unevenness of the head and tail of the steel plate after quenching of ≤3 / 1000.

[0024] The beneficial effects achieved by the present invention are: the present invention has the following advantages:

[0025] 1. The head and tail shape defects of quenched steel plates are divided into three types, and corresponding solutions for the three types of defects are proposed;

[0026] 2. According to the plate shape at the tail of quenching, by calculating the time t required for the steel plate to be taken out of the furnace to a certain position at the tail, the secondary model automatically adjusts the upper surface water flow rate t after the steel plate is taken out of the furnace and starts quenching to change the upper and lower water ratio and improve the plate shape at the tail of quenching. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] A method for controlling shape defects of a thin-gauge quenched and tempered steel plate after quenching of the present invention comprises the following steps:

[0029] S1. Identification of defect characteristics of the head and tail of the steel plate after quenching and measurement of amplitude value; the types of plate shape characteristics of the head and tail of the steel plate are divided into the following categories: the first category, the warping direction of the head and tail is consistent: both the head and tail are warped upward, and both the head and tail are knocked down; the second category, the warping directions of the head and tail are opposite: the head is warped and the tail is knocked down, and the head is knocked down and the tail is warped; the third category, only one end of the head and tail is warped: the head is straight and the tail is knocked down, the head is straight and the tail is warped upward, the head is warped and the tail is straight, and the head is knocked down and the tail is straight;

[0030] S2. Formulate a quenching process optimization plan based on the head and tail shape defect characteristics of the steel plate identified in step S1;

[0031] Category 1: The improvement method for the head and tail warping direction is: according to the head and tail warping direction, the water ratio of the upper and lower surfaces is adjusted first, and the adjustment range is: -0.05~+0.05; secondly, the quenching speed of the steel plate is adjusted, and the adjustment range is: -3~+3m / min; this type of defect is adjusted to the third type of defect form with the head and tail unevenness ≤3 / 1000 or the head is straight and the tail is warped;

[0032] The second type: The improvement method for the opposite warping of the head and tail is: according to the warping direction of the plate head, adjust the water ratio of the upper and lower surfaces during the quenching process. If the plate head is warped, increase the upper and lower water ratio by 0.01 to 0.05; if the plate head is knocked down, reduce the upper and lower water ratio by -0.01 to -0.05, and adjust this type of defect to the third type of defect with a straight head and a warped tail;

[0033] The third category: The improvement method for warping at only one end is to use the secondary system of the quenching machine to set the quenching process to a variable water volume quenching process that can be triggered by time. The specific method is: according to the quenching speed and the length of the steel plate, calculate the time t (unit: second) required for the steel plate to pass through the slit nozzle from a position about 4.0m away from the tail (the calculation formula for time t is: t = (d + l-4) / v, where d: the distance from the position where the steel plate exits the furnace signal triggers the quenching machine to the slit nozzle, unit: meter; l: steel plate length, unit: meter; v: quenching speed, unit: meter / second), and set it in the secondary system so that t seconds after the steel plate exits the furnace signal is connected, the upper and lower water volumes of the slit nozzle begin to adjust. The adjustment scheme is as follows: when the tail quenching plate shape is an upward defect, the water flow rate on the lower surface is kept unchanged, and on the basis of the current upper and lower water ratio, the upper surface water flow rate is reset by increasing the upper and lower water ratio by 0.01 to 0.03; on the contrary, for the tail knocking defect, the adjustment scheme is the opposite: keep the water flow rate on the lower surface unchanged, and reset the upper surface water volume by reducing the upper and lower water ratio by 0.01 to 0.03; in particular, in order to optimize the solution of the head and tail plate shape defects, it is necessary to detect the tail defect characteristics and amplitude values ​​of the steel plate after process improvement according to the plate shape meter and compare them with the characteristics and amplitude values ​​of the previous steel plate, and then decide the amount of increase or decrease in the upper surface water volume during the process of the next steel plate passing through the slit nozzle in the tail area; after the quenching of each steel plate is completed, the secondary system needs to readjust the quenching process to the original process and prepare for the quenching of the next steel plate;

[0034] S3. Identify the head and tail defect characteristics of the steel plate produced after the quenching process optimization plan and measure the amplitude value;

[0035] S4. Compare the head and tail defect characteristics and amplitude values ​​of the steel plate in step S1 and step S3, and adjust the quenching process plan accordingly according to the comparison results (adjust according to the quenching process optimization plan of step S2) until the head and tail plate shape defect characteristics and amplitude values ​​meet the target requirements.

[0036] In this embodiment, the shape meter after quenching is used to identify the head and tail defect characteristics of the steel plate and measure the amplitude value.

[0037] In this embodiment, the target requirement for adjusting the quenching process is to achieve an unevenness of the head and tail of the steel plate after quenching of ≤3 / 1000.

[0038] By adopting the method for controlling the shape defects of thin-gauge quenched and tempered steel plates after quenching of the present invention, the head and tail unevenness of the quenched steel plates is reduced from an average of 10 to 15 / 1000 to 3 to 5 / 1000; the maximum unevenness of the quenched steel plates after tempering + straightening is reduced from 5 / 1000 to within 3 / 1000; the unevenness of the quenched steel plates after tempering + straightening is increased from 85% to 3 / 1000 to 95% to 2 / 1000.

[0039] Example:

[0040] Table 1 Main process parameter values ​​under the original quenching process (steel type: Q960, center roughness after quenching ≤ 3 / 1000)

[0041]

[0042] Table 2 Optimized process parameter values ​​for primary quenching process

[0043]

[0044] Table 3 Optimized process parameter values ​​for the second quenching process

[0045]

[0046]

[0047] Table 4 Roughness value and qualified rate of finished steel plates before and after process optimization (steel type: Q960)

[0048]

[0049] It should be noted that the description of the above technical solutions is exemplary, and this specification can be embodied in different forms and should not be interpreted as being limited to the technical solutions set forth herein. On the contrary, providing these descriptions will make the disclosure of the present invention thorough and complete, and will fully convey the scope disclosed in this specification to those skilled in the art. In addition, the technical solutions of the present invention are limited only by the scope of the claims.

[0050] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention should be considered to belong to the protection scope of the present invention.

Claims

1. A method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching, characterized in that: The following steps are involved: S1. Identify the head and tail defect characteristics and measure the amplitude value of the quenched steel plate; S2. Formulate a quenching process optimization plan based on the head and tail shape defect characteristics of the steel plate identified in step S1; S3. Identify the head and tail defect characteristics of the steel plate produced after the quenching process optimization plan and measure the amplitude value; S4, comparing the head and tail defect characteristics and amplitude values ​​of the steel plate in step S1 and step S3, and adjusting the quenching process plan accordingly according to the comparison results until the head and tail plate shape defect characteristics and amplitude values ​​meet the target requirements.

2. The method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching according to claim 1, characterized in that: In step S1, the types of plate shape feature recognition at the head and tail of the steel plate are divided into: the head and tail are warped in the same direction, the head and tail are warped in opposite directions, and only one end of the head and tail is warped.

3. The method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching according to claim 2, characterized in that: If the warping direction of the steel plate is consistent at the head and tail, the quenching process optimization plan is: first, adjust the water ratio of the upper and lower surfaces during the quenching process, with an adjustment range of -0.05 to +0.05; secondly, adjust the quenching speed of the steel plate, with an adjustment range of -3 to +3m / min; adjust the defect of consistent warping direction at the head and tail of the steel plate to the target requirement, or adjust it to warping at only one end of the head and tail.

4. The method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching according to claim 2, characterized in that: If the warping of the steel plate at the head and tail is opposite, the quenching process optimization plan is: adjust the water ratio of the upper and lower surfaces during the quenching process. If the plate head is warped, increase the upper and lower water ratio by 0.01 to 0.

05. If the plate head is downward, reduce the upper and lower water ratio by -0.01 to -0.05; adjust the defect of opposite warping of the steel plate at the head and tail to the target requirement, or adjust it to only one end of the head and tail to be warped.

5. The method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching according to claim 2, characterized in that: If only one end of the steel plate is warped, the optimization plan for the quenching process is: use the secondary system of the quenching machine to set the quenching process to a time-triggered variable water quenching process.

6. The method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching according to claim 5, characterized in that: The specific method of the time-triggered variable water quenching process is as follows: according to the quenching speed and the length of the steel plate, the time t required for the steel plate to pass through the slit nozzle from the position L at the tail end is calculated; In the secondary system, it is set that after the steel plate out of the furnace signal is turned on, the upper and lower water volumes of the slit nozzle begin to adjust. The adjustment plan is: when the tail quenching plate shape is an upward defect, the lower surface water flow rate is kept unchanged, and on the basis of the current upper and lower water ratio, the upper surface water flow rate is reset by increasing the upper and lower water ratio by 0.01~0.03; when the tail quenching plate shape is a downward defect, the lower surface water flow rate is kept unchanged, and the upper surface water volume is reset by reducing the upper and lower water ratio by 0.01~0.

03.

7. The method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching according to claim 6, characterized in that: The calculation formula for time t is: t=(d+l-4) / v, where: d is the distance from the steel plate out-of-furnace signal triggering the quenching machine to the slit nozzle, unit m; l is the steel plate length, unit m; v is the quenching speed, unit m / s.

8. The method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching according to claim 6, characterized in that: L=4m.

9. The method for controlling shape defects of thin gauge quenched and tempered steel plates after quenching according to claim 1, characterized in that: The shape meter after quenching is used to identify the head and tail defect characteristics and measure the amplitude value of the steel plate.

10. The method for controlling shape defects of thin gauge quenched and tempered steel plate after quenching according to claim 1, characterized in that: The target requirement for adjusting the quenching process is to achieve an unevenness of the head and tail of the steel plate after quenching of ≤3 / 1000.

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