Method for eliminating middle cracks of oriented silicon steel continuous casting billet

Abstract

The invention belongs to the technical field of metallurgy, and provides a method for eliminating middle cracks of oriented silicon steel continuous casting billets.The method comprises the steps that the cooling mode of a secondary cooling area of a continuous casting machine is optimized, nozzles of a bent section and a fan-shaped section of the continuous casting machine are arranged to be efficient anti-blocking type aerial fog nozzles, and periodic tracking detection and calibration are conducted on roller rows of the fan-shaped section of the continuous casting machine; according to the method, through the synergistic effect of optimization of cooling and optimization of equipment stress, the middle crack defect of the casting blank is fundamentally eliminated or remarkably reduced, measures are specific, operability is high, the problem of pain points in the production process of products of the type is solved, the surface quality of a hot-rolled coil is improved, and the production cost is reduced. And a foundation is laid for obtaining high and stable magnetic performance of a final oriented silicon steel product.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology and relates to the production of high-quality grain-oriented silicon steel and the optimization of its continuous casting process, specifically a method for eliminating intermediate cracks in grain-oriented silicon steel continuous casting billets. Background Technology

[0002] Grain-oriented silicon steel is an important soft magnetic material mainly used in the manufacture of transformer cores. Its surface quality and the uniformity of its internal structure directly affect the magnetic properties and lamination factor of the final product. During the production process, "bulge" defects often occur on the surface of hot-rolled coils, which manifest as local bulges on the surface of the rolled steel plate. This seriously affects the smooth progress of subsequent cold rolling processes, the uniformity of the surface coating, and the quality of the final product.

[0003] Research has found that the root cause of bulging defects in hot-rolled coils can often be traced back to internal cracks in the continuously cast slab. Inadequate secondary cooling design and poor casting machine roll gap precision make the slab more prone to internal defects such as intermediate cracks. These defects cannot be completely welded together during subsequent hot rolling and remain in the slab as uneven stress, ultimately manifesting as surface bulges on the hot-rolled coil. Existing continuous casting processes have shortcomings in the uniformity of secondary cooling water distribution and equipment precision, which are key reasons for internal quality problems in the slab. Therefore, a systematic method to solve the problem of intermediate cracks in grain-oriented silicon steel continuously cast slabs is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for eliminating intermediate cracks in continuously cast oriented silicon steel billets. By systematically optimizing the secondary cooling process of continuous casting and improving the functional precision of key equipment, the internal quality of the billet is significantly improved.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows: A method for eliminating intermediate cracks in continuously cast oriented silicon steel billets, including S1. Optimize the cooling method of the secondary cooling zone of the continuous casting machine: The cooling method is set to strong cooling in the middle and weak cooling at the edges to enhance the cooling of the foot roller and the bending section. S2. Set the nozzles of the curved section and fan-shaped section of the continuous casting machine as high-efficiency anti-clogging aerosol nozzles; S3. Periodically track and calibrate the fan-shaped section of the continuous casting machine's rolls, and control the roll gap accuracy within ±0.5mm.

[0006] Furthermore, the specific settings in S1 include: the secondary cooling water volume in the secondary cooling zone of the continuous casting machine is 1.4-1.6 L / kg, and the proportions of secondary cooling water volume in the foot roll zone, bending section, arc section, straightening section, and horizontal section are 10-15%, 40-50%, 25-30%, 10-15%, and 2-5%, respectively. At the same time, the side water volume is set to (0.4-0.6) × the middle water volume.

[0007] Furthermore, the online usage standards for sector segments are standardized, specifying that sector segments should be replaced when the measured roll gap deviation exceeds ±0.5mm at 20% of the points; the roll gap should be measured and adjusted before each batch of production.

[0008] The beneficial effects of this invention are: The method of this invention is systematic and synergistic: cooling optimization and equipment precision improvement complement each other. Differentiated cooling takes into account both the internal quality and corner quality of the billet, while high-precision equipment reduces mechanical stress, ensuring stable and uniform solidification of the billet in the vulnerable temperature range.

[0009] The method of this invention is applicable to specific production lines: it is designed for wide-width slab casting machines and the high alloy characteristics of grain-oriented silicon steel. The measures are specific, highly operable, and solve the pain points in the production process of such products.

[0010] The method of this invention improves overall benefits: while eliminating cracks in the middle of the product, it also improves the center segregation, which not only improves the surface quality of hot-rolled coils, but also lays the foundation for the final grain-oriented silicon steel product to obtain high and stable magnetic properties. Attached Figure Description

[0011] Figure 1 This is a low-magnification microstructure view of a billet cast using a conventional process; Figure 2 This is a low-magnification microstructure view of the cast billet after the implementation of the method of the present invention. Detailed Implementation

[0012] The present invention will be further described in detail below with reference to specific production examples. This embodiment is implemented based on the technical solution of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0013] A method for eliminating intermediate cracks in continuously cast slabs of grain-oriented silicon steel includes: S1. Optimize the cooling method of the secondary cooling zone of the continuous casting machine: The secondary cooling water zone in the width direction of the billet is finely controlled. In combination with the characteristics of the oriented silicon steel billet, the original uniform cooling mode is adjusted to a differentiated cooling mode with strong cooling in the middle and weak cooling at the edge, especially strengthening the cooling of the foot roll and the bending section. The specific settings include: the secondary cooling water volume in the secondary cooling zone of the continuous casting machine is 1.4-1.6 L / kg; the proportions of secondary cooling water volume in the foot roll area, bending section, arc section, straightening section, and horizontal section are 10-15%, 40-50%, 25-30%, 10-15%, and 2-5%, respectively; and the side water volume is set to (0.4-0.6) × the middle water volume. This adjustment aims to enhance the cooling intensity of the first half of the secondary cooling stage, improve and reduce bulging between the billet rolls, thereby effectively suppressing the initiation of cracks in the middle of the billet.

[0014] S2. Set the nozzles of the curved section and fan-shaped section of the continuous casting machine as high-efficiency anti-clogging aerosol nozzles; The high-efficiency anti-clogging aerosol nozzle has a larger flow orifice and a self-cleaning design, ensuring uniform atomization of cooling water, stable spray angle, and resistance to clogging during long-term operation. This ensures uniform and controllable cooling of the billet in critical areas subjected to bending / straightening stress, avoiding stress concentration and cracks induced by insufficient cooling due to nozzle clogging.

[0015] S3. Periodically track and calibrate the fan-shaped section of the continuous casting machine's rolls through regular inspections, and control the roll gap accuracy within ±0.5mm. Standardize the online use of sector sections, specifying that sector sections should be replaced when the measured roll gap deviation exceeds ±0.5mm at 20% of the points. Before each batch of production, the roll gap should be measured and adjusted to eliminate the additional mechanical stress on the billet caused by roll gap misalignment, thus creating a stable mechanical environment for the solidification and growth of the billet shell.

[0016] By systematically implementing the above steps, the combined effect of thermodynamics (optimized cooling) and mechanics (optimized equipment stress) can fundamentally eliminate or significantly reduce intermediate crack defects in the cast billet. Example

[0017] On a production line equipped with a Voestalpine (VAI) 230×2150mm slab continuous casting machine, typical composition grain-oriented silicon steel (containing 3.45% Si and 0.06% C) with a specification of 230×1200mm and a casting speed of 1.05m / min is produced.

[0018] S1. Optimize the cooling method of the secondary cooling zone of the continuous casting machine: In the secondary dynamic water distribution model, the water distribution curve is reset. In the foot roll section and bending section, the cooling water flow rate in the middle area of ​​the billet is increased to a total of 1150-1200 L / min, while the cooling water flow rate in the edge section is reduced to a total of 600-620 L / min.

[0019] S2. Set the nozzles of the curved section and fan-shaped section of the continuous casting machine to high-efficiency anti-clogging aerosol nozzles; establish a strict nozzle inspection system, and replace the curved section with all nozzles that have been inspected and are normal before each batch of production.

[0020] S3. Before production, use a roll gap meter to perform a tracking test and calibration on the arc and roll gap of the fan-shaped roll column of the continuous casting machine to ensure that the roll gap accuracy is controlled within ±0.5mm.

[0021] After 16 heats were produced continuously using the above-described method, samples of the cast billets were subjected to low-magnification acid leaching inspection. The results are as follows: Figure 1 and Figure 2 The data shows that the average rating of intermediate cracks in the billet has decreased from the original 2.0 (medium) to below 0.5 (slight); after the corresponding batch of billets is hot-rolled into coils, the detection rate of surface bulge defects on the hot-rolled coils has decreased from the original 9.7% to below 0.3%.

Claims

1. A method for eliminating intermediate cracks in continuously cast oriented silicon steel billets, characterized in that: include: S1. Optimize the cooling method of the secondary cooling zone of the continuous casting machine: The cooling method is set to strong cooling in the middle and weak cooling at the edges to enhance the cooling of the foot roller and the bending section. S2. Set the nozzles of the curved section and fan-shaped section of the continuous casting machine as high-efficiency anti-clogging aerosol nozzles; S3. Periodically track and calibrate the fan-shaped section of the continuous casting machine's rolls, and control the roll gap accuracy within ±0.5mm.

2. The method for eliminating intermediate cracks in continuously cast oriented silicon steel billets according to claim 1, characterized in that: The specific settings in S1 include: the secondary cooling water volume in the secondary cooling zone of the continuous casting machine is 1.4-1.6 L / kg, and the proportions of secondary cooling water volume in the foot roll zone, bending section, arc section, straightening section, and horizontal section are 10-15%, 40-50%, 25-30%, 10-15%, and 2-5%, respectively. At the same time, the side water volume is set to (0.4-0.6) × the middle water volume.

3. The method for eliminating intermediate cracks in continuously cast oriented silicon steel billets according to claim 1, characterized in that: In S3, when the measured roll gap deviation exceeds ±0.5mm at 20% of the points, the sector section is replaced and taken off the production line. The roll gap is measured and adjusted before each batch of production.

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