Method for controlling the crown of a thin strip by means of the temperature of the crystallization rolls

Abstract

The present application belongs to the field of thin strip continuous casting thin strip shape control technology, and relates to a method for controlling the convexity of thin strip steel through the temperature of a crystallization roller. By controlling the N content and H content in the continuous casting molten steel, the contact and heat transfer performance between the molten steel and the crystallization roller are improved, and the effective heat transfer between the molten steel and the crystallization roller and the solidification rate of the molten steel are ensured. At the same time, the temperature of the crystallization roller during the continuous casting of the molten steel is monitored in real time by a temperature measuring device, the convexity of the continuous casting thin strip steel is monitored in real time by a thickness measuring device, and the target convexity is compared with the measured convexity, the difference between the target convexity and the measured convexity is calculated, and the crystallization roller temperature required to reach the target convexity is fed back through a fitting formula. The water flow of the cooling water required to adjust the crystallization roller cooling to reach the target crystallization roller temperature is fed back through the fitting formula. The present application adjusts the temperature of the crystallization roller in real time by adjusting the water flow of the cooling water of the crystallization roller in real time, and achieves the purpose of real-time control of the shape and convexity of the continuous casting thin strip steel.

Description

Technical Field

[0001] This invention belongs to the field of thin strip continuous casting and relates to the plate shape control technology of thin strip steel, specifically to a method for controlling the crown of thin strip steel by means of the temperature of the crystallizing roll. Background Technology

[0002] The twin-roll continuous casting process for thin strip involves introducing molten steel through a flow outlet into a molten pool formed by a pair of counter-rotating crystallizing rolls. The molten steel contacts the cooler surface of the crystallizing rolls, forming a solid shell. As the rolls rotate, the steel is discharged from the surface of the crystallizing rolls, forming a continuous cast strip. The cast strip is then hot-rolled into hot-rolled thin strip steel through one or two hot rolling passes. The stability of the cast strip's crown is crucial to the stability of the crown of the finished hot-rolled strip steel.

[0003] In existing technologies, strip crown control techniques are all geared towards the hot continuous rolling process. These methods control the crown of hot-rolled strip by adjusting the bending roll force of each stand in the hot continuous rolling mill, or by using hot-roll crown feedback control to control the crown of the next coil of strip. Therefore, existing technologies cannot currently be used to control the crown of the cast strip in the process of directly forming the cast strip from molten steel in twin-roll continuous casting.

[0004] In other words, controlling the crown of the strip in twin-roll continuous casting remains a technological gap. In particular, methods for controlling the crown of thin strip steel through the temperature of the crystallizing rolls are a promising area for further research. Summary of the Invention

[0005] This invention solves the problem of unstable crown of continuously cast thin strip steel during twin-roll continuous casting by designing the roll shape of the crystallizing roll and controlling the position of the core nozzle. It improves the crown stability of hot-rolled thin strip steel after the subsequent hot rolling, and also improves the stability of the strip shape and the stability of the hot rolling process, thereby improving the product strip shape quality.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] According to the present invention, a method for controlling the crown of thin strip steel includes:

[0008] (1) Steel with qualified composition is obtained by steelmaking in electric furnace or converter. The N content of the steel is controlled within the range of 5-80 ppm and the H content is controlled within the range of less than 3.5 ppm.

[0009] (2) Molten steel solidifies into a solid thin strip steel by passing through a pair of rotating crystallizing rolls. Cooling channels are provided inside the crystallizing rolls to cool them, and the temperature T of the crystallizing rolls is measured in real time by temperature sensors. act ;

[0010] (3) The convexity C of the thin strip steel is measured in real time using a convexity measuring device. act And calculate the measured convexity C. actWith the design target convexity C in The difference ΔC, ΔC = C in -C act ,

[0011] (4) Through formula T in =T act -δ△C, the required temperature value of the crystallizing roller can be calculated.

[0012] In the formula, δ is an empirical parameter for adjusting the temperature of the crystallizing roller, and the value of δ ranges from 0.01 to 3.

[0013] (5) Monitor the water flow rate F of the cooling water in the internal water-cooling channel of the crystallizing roller in real time using a water flow detection device. act And through formula F in =F act +β(T in -T act The required cooling water flow rate for the crystallizing roller is calculated.

[0014] In the formula, β is an empirical parameter for regulating cooling water flow rate, and the value of β ranges from 0.1 to 15.

[0015] (6) By timely feedback and adjustment of cooling water flow rate, the temperature of the crystallizing roll is corrected so that the crown of the continuously cast thin strip is controlled at the target crown C. in Within ±5μm.

[0016] According to the method for controlling the crown of thin strip steel of the present invention, preferably, the molten steel is low-carbon steel, high-carbon steel, low-alloy steel, high-alloy steel, etc.

[0017] According to the method for controlling the crown of thin strip steel according to the present invention, preferably, the cooling water in the water-cooling channel inside the crystallizing roller is circulating water and is cooled by a cooling device.

[0018] According to the method for controlling the crown of thin strip steel according to the present invention, preferably, the inlet temperature of the cooling water is controlled within the range of 5-40°C.

[0019] According to the method for controlling the crown of thin strip steel according to the present invention, preferably, the temperature of the crystallizing roller is controlled at 100-600°C.

[0020] According to the method for controlling the crown of thin strip steel according to the present invention, preferably, the crown of continuously cast thin strip steel is controlled within ±5μm of the target crown.

[0021] Beneficial technical effects

[0022] Compared with the prior art, the technical advantages and beneficial effects of the present invention include at least the following:

[0023] The present application fully considers the reasons of the shape and crown change of the continuous casting thin strip steel in the double-roller thin strip casting process, controls the casting strip shape of the thin strip steel directly casted from the molten steel for the first time, and particularly relates to the real-time control of the thin strip crown in the thin strip casting process. By controlling the N content and H content in the molten steel for casting thin strip steel, the heat conduction performance between the molten steel and the crystallization roller is controlled, the effective solidification of the molten steel and the overall shape quality in the width direction of the strip are improved. By real-time measuring the crown of the continuous casting thin strip steel and the temperature of the crystallization roller, and comparing with the target crown, the water flow of the crystallization roller and the temperature of the crystallization roller are adjusted in real time according to the temperature feedback control and the feedback control equation of the crystallization roller cooling water flow, the thermal expansion of the crystallization roller and the surface profile of the crystallization roller are controlled by adjusting the temperature of the crystallization roller, the shape between the roller gap composed of a pair of crystallization rollers is controlled, and the purpose of real-time controlling the shape and crown of the thin strip casting thin strip steel is achieved. Through the control of the trace elements N and H content in the molten steel, the control of the cooling water flow of the crystallization roller, and the control of the temperature of the crystallization roller, the problem that the shape and crown of the continuous casting thin strip steel cannot be controlled in real time is solved, the shape stability and crown stability of the thin strip casting thin strip steel are improved, and the shape quality of the continuous casting thin strip steel is improved. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor belong to the scope of protection of the present application.

[0025] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those of ordinary skill in the art to which the present application belongs.

[0026] Example 1

[0027] After the steel is smelted by the electric furnace or converter and treated by VD degassing and LF refining, the molten steel with qualified composition is obtained, the N content in the molten steel is controlled in the range of 25 ppm, and the H content is controlled in the range of 2 ppm. The molten steel is cast into thin strip steel by a pair of opposite rotating crystallization rollers, the crystallization roller is provided with a cooling water channel to cool and control the temperature of the crystallization roller. The temperature of the crystallization roller is detected in real time by the temperature sensor arranged on the crystallization roller as T act = 360℃, the cooling water inlet temperature is 30℃, and the crown C act of the continuous casting thin strip steel is detected in real time by the crown measuring device as 30μm. According to the target crown C in = 36μm, the crown difference ΔC between the detected crown and the target crown is calculated as 6. According to T in = Tact -δΔC is used to calculate the temperature T of the crystallizing roller under feedback control. in The temperature is 353.4℃, and the value of δ in the formula is 1.1. The flow rate F of the cooling water in the water-cooling channel inside the crystallizing roller is monitored in real time by a water flow detection device. act 1200m 3 / h, and according to formula F in =F act +β(T in -T act The water flow rate F under feedback control is calculated. in It is 1160.4m 3 / h, where β is 6. After adjusting the water flow rate, the crown of the continuously cast thin strip steel in this embodiment is within ±5μm of 36μm, achieving real-time, stable, and precise control of the crown of the continuously cast thin strip steel.

[0028] Example 2

[0029] After steelmaking in an electric furnace or converter, and following VD degassing and LF refining, molten steel with acceptable composition is obtained. The nitrogen content in the molten steel is controlled within the range of 16 ppm, and the hydrogen content within the range of 3.1 ppm. The molten steel is then cast into thin strip steel through a pair of counter-rotating crystallizing rolls. Cooling water channels are installed inside the crystallizing rolls for cooling and temperature control. Temperature sensors installed on the crystallizing rolls continuously monitor the temperature (T) in real time. act The temperature is 430℃, the cooling water inlet temperature is 15℃, and the crown C of the continuously cast thin strip steel is detected in real time using a crown measuring device. act It is 86 μm. Based on the target convexity C... in The convexity is 45 μm, and the calculated convexity difference ΔC between the detected convexity and the target convexity is -41. According to T... in =T act -δΔC is used to calculate the temperature T of the crystallizing roller under feedback control. in The temperature is 542.8℃, and the value of δ in the formula is 2.75. The flow rate F of the cooling water in the water-cooling channel inside the crystallizing roller is monitored in real time by a water flow detection device. act 1180m 3 / h, and according to formula F in =F act +β(T in -T act The water flow rate F under feedback control is calculated. in 1315.3m 3 / h, where β is 1.2. After adjusting the water flow rate, the crown of the continuously cast thin strip steel in this embodiment is within ±5μm of 45μm, achieving real-time, stable, and precise control of the crown of the continuously cast thin strip steel.

[0030] Example 3

[0031] After steelmaking in an electric furnace or converter, and following VD degassing and LF refining, molten steel with acceptable composition is obtained. The nitrogen content in the molten steel is controlled within the range of 68 ppm, and the hydrogen content within the range of 1.6 ppm. The molten steel is then cast into thin strip steel through a pair of counter-rotating crystallizing rolls. Cooling water channels are installed inside the crystallizing rolls for cooling and temperature control. Temperature sensors installed on the crystallizing rolls continuously monitor the temperature (T) in real time. act The temperature is 285℃, the cooling water inlet temperature is 20℃, and the crown C of the continuously cast thin strip steel is detected in real time using a crown measuring device. act It is 16 μm. Based on the target convexity C... in The convexity is 36 μm, and the calculated convexity difference ΔC between the detected convexity and the target convexity is 20. According to T... in =T act -δΔC is used to calculate the temperature T of the crystallizing roller under feedback control. in The temperature is 271℃, and the value of δ in the formula is 0.7. The flow rate F of the cooling water in the water-cooling channel inside the crystallizing roller is monitored in real time by a water flow detection device. act 1350m 3 / h, and according to formula F in =F act +β(T in -T act The water flow rate F under feedback control is calculated. in It is 1341.6m 3 / h, where β is 0.6. After adjusting the water flow rate, the crown of the continuously cast thin strip steel in this embodiment is within ±5μm of 36μm, achieving real-time, stable, and precise control of the crown of the continuously cast thin strip steel.

[0032] The above description is only a specific embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of controlling the crown of a thin strip, characterized by, The method comprises: (1) obtaining a qualified steel melt by an electric furnace or converter steelmaking, the N content of the steel melt is controlled in a range of 5-80 ppm, and the H content is controlled in a range of less than 3.5 ppm; (2) The molten steel is solidified into solid thin strip steel through a pair of rotating crystallization rollers, the crystallization rollers are internally provided with cooling channels to cool the crystallization rollers, and the temperature T of the crystallization rollers is measured in real time through a temperature sensor act ; (3) The crown C of the thin strip steel is measured in real time by a crown measuring device act , and the difference ΔC between the measured crown C act and the design target crown C in is calculated, ΔC = C in -C act , (4) The value of the desired adjusted crystallizer roll temperature is calculated by the equation T in = T act - δΔC, In the formula, δ is an experience parameter for adjusting the temperature of the crystallization roller, and the value range of δ is 0.01-3; (5) Real-time monitoring of the water flow value F of the cooling water in the internal water cooling channel of the crystallization roller by the water flow detection device act , and the required water flow of the cooling water of the crystallization roller is calculated by the formula F in = F act + β (T in - T act ) In the formula, β is an experience parameter for adjusting the water flow of the cooling water, and the value range of β is 0.1-15; (6) By timely feedback and adjustment of cooling water flow, the temperature of the crystallization roller is corrected, so that the crown of the continuously cast thin strip steel is controlled within ±5 μm of the target crown C in .

2. The method for controlling the crown of a thin strip steel according to claim 1, characterized in that, The steel melt is a low-carbon steel, high-carbon steel, low-alloy steel, or high-alloy steel melt.

3. The method for controlling the crown of a thin strip steel according to claim 1, characterized in that, The cooling water in the internal water cooling channel of the crystallization roller is circulating water, and is cooled by a cooling device.

4. The method for controlling the crown of a thin strip steel according to claim 1, characterized in that, The water inlet temperature of the cooling water is controlled in a range of 5-40 ℃.

5. The method for controlling the crown of a thin strip steel according to claim 1, characterized in that, The temperature of the crystallization roller is controlled in a range of 100-600 ℃.