Method for controlling transverse cracks of high silicon steel and continuous casting large round billet of high silicon steel

Abstract

The invention relates to a control method for transverse cracks of high-silicon steel and continuous casting large round billets of the high-silicon steel, and belongs to the technical field of steel continuous casting. In order to solve the problem that transverse cracks are prone to occurring in the production process of high-silicon steel continuous casting large round billets, the invention provides a method for controlling the transverse cracks of the high-silicon steel and the continuous casting large round billets of the high-silicon steel, the method comprises a multi-parameter cooperative control method, and the parameters comprise component optimization, equipment precision control and continuous casting process control. According to the method, through comprehensive measures such as Ti microalloying, low P / S control, precise centering control and straightening temperature optimization, on the basis of low-cost improvement, the transverse crack occurrence rate of the high-silicon steel continuous casting large round billet is remarkably reduced. Experimental results show that the transverse crack occurrence rate of the high-silicon steel continuous casting large round billet is reduced to 0% and is remarkably improved compared with 37% of a traditional process, only a small amount of titanium alloy elements are needed, the cost advantage is obvious, and a reliable solution is provided for efficient and stable production of the high-silicon steel continuous casting billet.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel continuous casting, and particularly relates to a high-silicon steel and a control method for transverse cracks of the high-silicon steel in continuous casting of a large round billet. BACKGROUND

[0002] In the production process of the continuous casting large round billet, the high-silicon steel (C≥0.50%, Si≥1.60%) is prone to transverse cracks on the inner arc side in the straightening process due to its poor hot plasticity caused by the special composition. At present, the straightening temperature of the continuous casting large round billet is generally controlled at 750-830 DEG C, and the high-silicon steel is in the brittle temperature range of 750-817 DEG C, and the high-temperature plasticity of the high-silicon steel sharply decreases, and the section shrinkage rate is less than 40% at 750 DEG C, so that the straightening stress is concentrated, and the transverse cracks are caused. These cracks are inherited to the surface of the steel in the subsequent rolling process, and form the "Y crack" defects, which seriously affect the product quality, and even lead to scrap, and reduce the yield.

[0003] At present, the industry mainly adopts two methods to alleviate the transverse crack problem: one is to optimize the straightening process parameters, such as reducing the straightening temperature or adjusting the straightening speed, to avoid the brittle range; the other is to improve the high-temperature plasticity of the steel by micro-alloying, such as adding B, Ti and other elements. However, these methods have obvious deficiencies. The straightening temperature that is too low may cause the billet to bulge or the equipment load to be too large, which affects the production stability; and the alloying method can partially improve the plasticity, but may introduce new metallurgical problems, such as increased precipitated phase, and increase the production cost. More importantly, the traditional method cannot fundamentally change the phase change behavior of the high-silicon steel in the brittle temperature range, and the crack sensitivity is still high. SUMMARY

[0004] In order to solve the problem that the high-silicon steel continuous casting large round billet is prone to transverse crack defects in the production process, the application provides a high-silicon steel and a control method for transverse cracks of the high-silicon steel continuous casting large round billet.

[0005] The technical scheme of the application is as follows:

[0006] A high-silicon steel, the chemical composition includes, by weight percentage: C: 0.59-0.63%, Si: 1.70-1.80%, Mn: 0.43-0.48%, P≤0.015%, S≤0.005%, Cr: 0.95-1.05%, V: 0.11-0.14%, Ti: 0.0150-0.0200%, and the rest is Fe and inevitable impurities.

[0007] The application discloses a control method for transverse cracks of high-silicon steel continuous casting large round billets.

[0008] Further, the component optimization further comprises controlling P≤0.015%, S≤0.005% in the steel.

[0009] Further, the chemical components of the high-silicon steel include, in percentage by weight, C: 0.59-0.63%, Si: 1.70-1.80%, Mn: 0.43-0.48%, P≤0.015%, S≤0.005%, Cr: 0.95-1.05%, V: 0.11-0.14%, Ti: 0.0150-0.0200%, and the rest is Fe and inevitable impurities.

[0010] Further, the superheat of the continuous casting process is 25-40 DEG C.

[0011] Further, the straightening temperature of the continuous casting process is 830-860 DEG C.

[0012] Further, the straightening pull-straightening machine group used in the continuous casting process is provided with seven pull-straightening machines, the straightening pressure of the first pull-straightening machine is 0 MPa, the straightening pressure of the second pull-straightening machine is 0.8 MPa, the straightening pressure of the third pull-straightening machine is 0.8 MPa, the straightening pressure of the fourth pull-straightening machine is 1.2 MPa, the straightening pressure of the fifth pull-straightening machine is 2 MPa, the straightening pressure of the sixth pull-straightening machine is 2.8 MPa, and the straightening pressure of the seventh pull-straightening machine is 3.2 MPa.

[0013] Further, during the straightening process of the continuous casting process, the fluctuation of the straightening pressure is ≤0.3 MPa.

[0014] The application has the following beneficial effects:

[0015] The present application significantly reduces the transverse crack occurrence rate of high silicon steel continuous casting large round billets through multi-parameter collaborative control on the basis of low-cost improvement. First, the present application adds 150-200 ppm of Ti element in the steel, utilizes the TiN preferential precipitation characteristics, plays a role in nitrogen fixation, inhibits the formation of brittle precipitates such as Nb(C, N) and AlN, and at the same time, the TiN particles pin the austenite grain boundary, refine the grain structure, effectively reduce the width and depth of the third brittle temperature zone, and greatly reduce the crack sensitivity. Secondly, the present application strictly controls P≤0.015%, S≤0.005% in the steel, reduces the influence of thermal embrittlement and cold embrittlement. In addition, the laser centering system is used to accurately adjust the fan segment foot roller deviation (deviation≤0.5mm), and ensure the uniform stress of the casting billet.

[0016] The present application optimizes the straightening process combined with the high temperature plasticity curve, and controls the straightening temperature at 830-860℃ through dynamic compensation of the continuous casting speed, avoids the adverse effects of the brittle zone, and at the same time optimizes the straightening pressure distribution and reduces stress concentration.

[0017] The experimental results show that the present application reduces the transverse crack occurrence rate of high silicon steel continuous casting large round billets to 0% through multi-parameter collaborative control, which is significantly improved compared with the traditional process of 37%, and only a small amount of titanium alloy elements are needed, and the cost advantage is obvious, which provides a reliable solution for efficient and stable production of high silicon steel continuous casting billets. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The appearance photo of the high silicon steel continuous casting large round billet prepared in Example 1 is shown in the figure.

[0019] Figure 2 The appearance photo of the high silicon steel continuous casting large round billet prepared in Comparative Example 1 is shown in the figure. DETAILED DESCRIPTION

[0020] The technical solutions of the present application are further described below in combination with examples, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present application without departing from the spirit and scope of the technical solutions of the present application shall be covered in the protection scope of the present application. The process equipment or device not specifically mentioned in the following examples is the conventional equipment or device in the art, and the raw materials used in the examples of the present application can be obtained from the market if not specifically mentioned. The technical means used in the examples of the present application is the conventional means familiar to those skilled in the art if not specifically mentioned.

[0021] Example 1

[0022] The present embodiment provides a control method for transverse cracks of high silicon steel continuous casting large round billets.

[0023] The internal control chemical composition of the high silicon steel in the embodiment includes, in terms of weight percentage: C: 0.59-0.63%, Si: 1.70-1.80%, Mn: 0.43-0.48%, P≤0.015%, S≤0.005%, Cr: 0.95-1.05%, V: 0.11-0.14%, Ti: 0.0150-0.0200%, and the rest is Fe and inevitable impurities.

[0024] The embodiment provides a method for controlling transverse cracks of high silicon steel continuous casting large round billets with a specification of Φ550 mm, which includes a multi-parameter coordinated control method, and the parameters include composition optimization, equipment precision control and continuous casting process control.

[0025] The composition optimization of the high silicon steel is to control the Ti content in the steel at 150-200 ppm, P≤0.015% and S≤0.005%. The Ti added in the steel forms titanium nitride to be preferentially precipitated, the solid nitrogen effect reduces the precipitation temperature of niobium carbon nitride and aluminum nitride, and the grain refinement effect of TiN pinning austenite effectively reduces the width and depth of the third brittle temperature zone, and the crack sensitivity is obviously reduced. The P content in the steel is controlled to be ≤0.015%, and the S content is controlled to be ≤0.005%, so as to reduce the hot brittleness / cold brittleness of the steel.

[0026] The equipment precision control in the continuous casting process is to use a laser centering system, to check and adjust the axis centering deviation of the sector segment foot roller before casting, to monitor and adjust the deviation in real time, and to control the centering deviation to be ≤0.5 mm.

[0027] The superheat degree of the continuous casting process is 25-40 ℃, the continuous casting speed is controlled at 0.30 m / min, the straightening temperature can be directly increased by 20-30 ℃, the straightening temperature of each furnace is measured, and the straightening temperature range is increased to 830-860 ℃.

[0028] In the embodiment, the total straightening pressure of the straightening and tension leveling unit is controlled at 1.08 MPa, there are 7 tension leveling machines in the straightening and tension leveling unit, the straightening pressure of the first tension leveling machine is 0 MPa, the straightening pressure of the second tension leveling machine is 0.8 MPa, the straightening pressure of the third tension leveling machine is 0.8 MPa, the straightening pressure of the fourth tension leveling machine is 1.2 MPa, the straightening pressure of the fifth tension leveling machine is 2 MPa, the straightening pressure of the sixth tension leveling machine is 2.8 MPa, and the straightening pressure of the seventh tension leveling machine is 3.2 MPa. In the straightening process of the continuous casting process, the fluctuation of the straightening pressure is ≤3.0 MPa.

[0029] Comparative Example 1

[0030] The comparative example provides a high silicon steel and a preparation method of a continuous casting large round billet thereof.

[0031] The internal control chemical composition of the high silicon steel in the present comparative example includes, in terms of weight percentage: C: 0.58-0.66%, Si: 1.60-2.00%, Mn: 0.40-0.70%, P≤0.025%, S≤0.020%, Cr: 0.90-1.20%, V: 0.10-0.20%, and the rest is Fe and inevitable impurities.

[0032] The overheat in the preparation process of the transverse crack of the high silicon steel continuous casting large round billet with a specification of Φ550mm in the present comparative example is 15-40℃, the continuous casting pulling speed is controlled at 0.26m / min, and the straightening temperature range is 800-820℃.

[0033] The total straightening pressure of the straightening and drawing unit in the present comparative example is controlled at 1.1MPa, and the straightening and drawing unit is provided with 7 straightening and drawing machines. The straightening pressure of the first straightening and drawing machine is 0MPa, the straightening pressure of the second straightening and drawing machine is 1.5MPa, the straightening pressure of the third straightening and drawing machine is 0MPa, the straightening pressure of the fourth straightening and drawing machine is 1.5MPa, the straightening pressure of the fifth straightening and drawing machine is 2.5MPa, the straightening pressure of the sixth straightening and drawing machine is 2.5MPa, and the straightening pressure of the seventh straightening and drawing machine is 3.0MPa.

[0034] Figure 1 The appearance photo of the high silicon steel continuous casting large round billet prepared in Example 1; as shown in Figure 1 , the surface of the casting billet is free of any visible transverse crack defects. Figure 2 The appearance photo of the high silicon steel continuous casting large round billet prepared in Comparative Example 1; as shown in Figure 2 , it can be clearly observed that there are obvious transverse cracks on the surface of the casting billet, and these cracks are mainly distributed on the inner arc side of the casting billet.

[0035] Figure 1 and Figure 2 , which fully proves the effectiveness of the comprehensive measures of Ti micro-alloying (150-200ppm), low P / S control (P≤0.015%, S≤0.005%), precise centering control (deviation≤0.5mm), and optimized straightening temperature (830-860℃) in the present application. The results show that the present application successfully solves the plasticity deterioration problem of high silicon steel in the brittle temperature range, and realizes the production of defect-free continuous casting billet.

Claims

1. A high silicon steel, characterized in that, The chemical composition includes, by weight percentage: C: 0.59-0.63%, Si: 1.70-1.80%, Mn: 0.43-0.48%, P≤0.015%, S≤0.005%, Cr: 0.95-1.05%, V: 0.11-0.14%, Ti: 0.0150-0.0200%, and the rest is Fe and inevitable impurities.

2. A method for controlling transverse cracking of a high silicon steel continuously cast bloom, characterized by, The method includes multi-parameter collaborative control, the parameters including composition optimization, equipment precision and continuous casting process control, the composition optimization is to control the Ti content in the steel at 150-200ppm, the equipment precision is to control the axis alignment deviation of the fan-shaped segment foot roller within 0.5mm, and the continuous casting process control is to control the continuous casting speed at 0.30m / min and the total straightening pressure of the straightening and tension leveling unit at 10.8Mpa.

3. The method according to claim 2, wherein the method is characterized by: The composition optimization further includes controlling P≤0.015% and S≤0.005% in the steel.

4. The method according to claim 3, wherein the method is characterized by: The chemical composition of the high-silicon steel includes, by weight percentage: C: 0.59-0.63%, Si: 1.70-1.80%, Mn: 0.43-0.48%, P≤0.015%, S≤0.005%, Cr: 0.95-1.05%, V: 0.11-0.14%, Ti: 0.0150-0.0200%, and the rest is Fe and inevitable impurities.

5. The method according to claim 4, wherein the method is characterized by: The superheat of the continuous casting process is 25-40℃.

6. The method according to claim 5, wherein the method is characterized by: The straightening temperature of the continuous casting process is 830-860℃.

7. The method according to claim 6, wherein the method is characterized by: The straightening and tension leveling unit used in the continuous casting process is provided with 7 straightening and tension leveling machines, the straightening pressure of the first straightening and tension leveling machine is 0MPa, the straightening pressure of the second straightening and tension leveling machine is 0.8MPa, the straightening pressure of the third straightening and tension leveling machine is 0.8MPa, the straightening pressure of the fourth straightening and tension leveling machine is 1.2MPa, the straightening pressure of the fifth straightening and tension leveling machine is 2MPa, the straightening pressure of the sixth straightening and tension leveling machine is 2.8MPa, and the straightening pressure of the seventh straightening and tension leveling machine is 3.2MPa.

8. The method according to claim 7, wherein the method is characterized by: During the straightening process of the continuous casting process, the fluctuation of the straightening pressure is ≤0.3MPa.

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