Production method for preventing thick plate holes in thick die steel
By optimizing the entire production process, the problem of hole defects in thick plates of thick-gauge mold steel was solved, resulting in improved product quality and pass rate, and reduced production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEBEI PUYANG IRON & STEEL
- Filing Date
- 2026-02-11
- Publication Date
- 2026-05-12
AI Technical Summary
In the production of thick mold steel plates, common defects such as holes are difficult to effectively suppress, which affects product quality and pass rate, and increases production costs.
By systematically optimizing the entire process, including raw material handling, smelting, continuous casting, rolling, and post-rolling cooling, including processes such as baking, deep deoxidation, low-speed continuous casting, heavy pressure reduction, and slow cooling, the purity and density of molten steel and billets are ensured, grains are refined, and internal defects are avoided.
It significantly reduces hole defects, improves product quality and pass rate, and lowers enterprise production costs, resulting in good economic benefits.
Abstract
Description
Technical Field
[0001] This invention relates to the field of mold steel technology, and in particular to a production method for preventing holes in thick plates of thick mold steel. Background Technology
[0002] Thick-gauge mold steel plates, due to their superior properties such as high strength, high hardness, good wear resistance, and toughness, are widely used in high-end equipment manufacturing fields such as machinery manufacturing, automotive industry, and aerospace. However, in the production process of thick-gauge mold steel plates, porosity is one of the more common and difficult problems to solve. These pores mainly include gas pores, shrinkage cavities, and looseness, and their causes are complex, mainly related to factors such as excessive moisture content in raw materials, insufficient deoxidation during smelting, uneven solidification during continuous casting, unreasonable rolling heating and reduction process parameters, and uneven cooling after rolling.
[0003] The presence of voids severely reduces the mechanical properties and reliability of thick-gauge mold steel plates, leading to breakage and failure during subsequent processing or service. This significantly impacts product quality and yield, increasing production costs for enterprises. Currently, existing production technologies employ fragmented control measures for voids in thick-gauge mold steel plates, lacking a systematic solution and making it difficult to effectively suppress voids.
[0004] Therefore, developing a production method that can comprehensively and effectively prevent the formation of holes in thick-gauge mold steel plates is of great practical significance for improving the quality of thick-gauge mold steel plates and increasing the economic benefits of enterprises. Summary of the Invention
[0005] In view of this, the present invention provides a production method for preventing voids in thick-gauge die steel plates. The present invention systematically optimizes the entire production process, including raw material processing, smelting, continuous casting, rolling, and post-rolling cooling, thereby suppressing the generation of void defects at their source and significantly improving the product quality and yield of thick-gauge die steel plates.
[0006] The first aspect of this invention is to provide a production method for preventing holes in thick plates of thick die steel, comprising the following steps: S1. Raw material pretreatment: Molten iron and scrap steel are used as raw materials. The scrap steel is baked at a temperature of 280~800℃ for 1.5~2.5 hours. The moisture content of the baked scrap steel is strictly controlled to not exceed 5%. Alternatively, the scrap steel can be added to an empty furnace for baking to remove moisture and prevent moisture from decomposing into hydrogen, oxygen and other gases during the smelting process. This reduces the gas content in the molten steel and lowers the risk of porosity defects. S2. Smelting: A converter smelting process is adopted, and conventional high-carbon and low-residual-oxygen operations are implemented to ensure that the carbon content of the molten steel reaches the target value of 0.10~0.20% at the end point, while controlling the residual oxygen content of the molten steel at a low level of 140~280 ppm. Before alloying, aluminum blocks of 0.35~0.65 kg / t steel are added to the molten steel for pre-deoxidation treatment to ensure the quality of deep deoxidation and ensure that the oxygen content of qualified molten steel after alloying is less than 10 ppm. This fully removes oxygen elements from the molten steel, avoids oxygen from combining with other elements to form oxide inclusions, and reduces residual gas in the molten steel. S3. Continuous Casting: Qualified molten steel is continuously cast. During continuous casting, the casting speed is controlled within a low range of 0.6~0.65 m / min, and the argon seal flow rate of the tundish sliding nozzle is 1~3 L / min. This ensures that the initial solidification thickness of the billet shell in the crystallizer meets the process requirements and avoids the absorption of excess gas, thereby reducing or eliminating shrinkage cavities, porosity, and center segregation and negative segregation of the billet generated during solidification. The solidification end position of the billet (solid fraction fs=0.3~0.85) is determined by dynamic light reduction technology. A heavy reduction process is used in the solidification end region, with a reduction of 15~18 mm. The heavy reduction eliminates the internal voids formed during the solidification process of the billet and improves the density of the billet. After continuous casting, the billet undergoes a slow cooling treatment for 72 hours. The temperature in the slow cooling pit is not lower than 100℃ to reduce the temperature gradient and stress inside the billet, avoid microcracks caused by stress concentration, and promote the diffusion and escape of hydrogen inside the billet. S4. Rolling: The slowly cooled billet is fed into a heating furnace for heating. A low-temperature, slow-heating approach is adopted to control the heating rate and ensure uniform temperature rise, guaranteeing the heating quality of the medium plate. The heating temperature is controlled at 1250~1270℃, and the heating time is 8~9 min / cm billet thickness, ensuring uniform internal temperature and improving the plasticity and machinability of the steel. In the rough rolling stage, a high-temperature, high-reduction, 6-pass rolling process is used. The reduction rate in the first three passes is controlled to be greater than 15%. This high reduction rate breaks down coarse grains and any loose as-cast structures within the billet, increasing the billet density. In the finish rolling stage, at least two passes have a reduction rate greater than 12% to further refine the grains, optimize the steel's microstructure and properties, and eliminate any internal defects that may occur during the rolling process. S5. Post-rolling cooling: After rolling, the medium-thick plate is first air-cooled for 1.5~2 hours, and then subjected to a slow cooling treatment for 48 hours. The air cooling rapidly reduces the surface temperature of the steel plate, and the subsequent slow cooling treatment can reduce the temperature difference between the inside and the surface of the steel plate, avoiding thermal stress cracks caused by excessive temperature difference; at the same time, the slow cooling process is conducive to the full diffusion and escape of hydrogen inside the steel plate, preventing hydrogen accumulation and hydrogen-induced cracks, and further avoiding the formation of porosity defects.
[0007] The second aspect of the present invention is to provide a thick die steel plate product produced by the above method.
[0008] Preferably, the thickness of the die steel plate is 100~160 mm.
[0009] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention systematically optimizes parameters throughout the entire production process, from raw material pretreatment, smelting, continuous casting, rolling to post-rolling cooling, which can fundamentally solve the problem of void defects and effectively improve product quality.
[0010] This invention controls the moisture content of scrap steel by baking it, and, in conjunction with high carbon extraction, low residual oxygen, and deep deoxidation with aluminum addition during the smelting process, significantly reduces the gas and impurity content in the molten steel, thereby reducing the generation of porosity and oxide inclusions.
[0011] The continuous casting process of this invention adopts low casting speed, argon sealing of the sliding nozzle in the tundish to control the flow rate, electromagnetic stirring in the secondary cooling section, heavy pressure at the end of solidification and slow cooling process, which ensures the full solidification and density improvement of the billet, while reducing the internal stress and hydrogen content of the billet, and avoiding defects such as shrinkage cavities, porosity and microcracks generated in the billet stage.
[0012] The present invention strictly controls the heating temperature and uniformity during the rolling process. By using large reduction rates in rough rolling and large reduction rates in specific passes of finish rolling, the coarse structure of the billet is broken up, the grains are refined, and internal defects are further eliminated. The air cooling and slow cooling process after rolling effectively avoids hydrogen accumulation and stress cracking, ensuring the performance stability of the final product.
[0013] The production method of this invention has clear process parameters and strong operability, making it suitable for large-scale industrial production. It can significantly improve the pass rate of thick-gauge mold steel plates and reduce enterprise production costs, thus having good economic benefits and application value. Detailed Implementation
[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0015] Unless otherwise specified, all experiments were repeated three times. Results are expressed as mean ± standard deviation, and P < 0.05 indicates a significant difference.
[0016] Example 1: A production method for preventing holes in thick-gauge mold steel plates, comprising the following steps: S1. Raw material pretreatment: High-quality molten iron and scrap steel are selected as raw materials. The scrap steel is sent to a baking device for baking treatment. The baking temperature is 300℃±20℃ and the baking time is 2 hours. After baking, the moisture content of the scrap steel is tested and found to be 3%. S2. Smelting: A converter smelting process is adopted, and high carbon and low residual oxygen operation is implemented. The carbon content of the molten steel at the end point is controlled to be 0.20%, and the residual oxygen content in the furnace is 140 ppm. During the tapping process, aluminum blocks are added to the molten steel for deoxidation. The aluminum blocks are added at 0.35 kg / t of steel, and the mixture is stirred thoroughly to ensure that the aluminum blocks react completely with the molten steel to complete the deep deoxidation treatment. S3. Continuous Casting: Qualified molten steel is injected into the continuous casting machine for continuous casting operation, and the casting speed is controlled at 0.62 m / min. The solidification end position of the billet (solid fraction fs=0.5) is determined by thermodynamic simulation calculation and dynamic light reduction equipment. At this position, a heavy reduction device is set up to carry out heavy reduction operation, and the heavy reduction amount is 15 mm. After the billet is continuously cast, it is sent to a slow cooling pit for 72 h of slow cooling treatment. The temperature in the slow cooling pit is greater than 100℃. S4. Rolling: The slowly cooled billet is fed into a heating furnace for heating. The heating rate is controlled to ensure uniform temperature rise using a low-temperature, slow-heating heating concept. The furnace heating temperature is 1250℃, and the heating time is 9 min / cm billet thickness. The heated billet is then fed into a roughing mill for rough rolling. The reduction rates for the first three passes are 16%, 17%, and 16.5%, respectively. After rough rolling, the billet is fed into a finishing mill for finishing rolling. The reduction rates for the second and fourth passes are 12.5% and 13%, respectively. The reduction rates for the remaining passes are adjusted reasonably according to the target thickness. S5. Post-rolling cooling: After rolling, the medium-thick plate is first placed in the air for air cooling for 2 hours; then it is sent to a slow cooling pit for 48 hours of slow cooling treatment. The temperature of the slow cooling pit is 200℃. After the slow cooling is completed, it is naturally cooled to room temperature to obtain 120 mm die steel medium-thick plate products.
[0017] Ultrasonic testing was performed on the thick mold steel plates produced in this embodiment. The results showed that there were no defects such as pores, shrinkage cavities, or looseness inside the steel plates, and the mechanical properties test results met the relevant standard requirements.
[0018] Example 2 The difference from Example 1 is as follows: the scrap steel baking temperature is 350℃±20℃, the baking time is 1.5 h, and the moisture content of the scrap steel after baking is 2%; the final carbon content of the molten steel is 0.14%, and the residual oxygen content in the furnace is 200 ppm; the amount of aluminum blocks added is 0.5 kg / t; the continuous casting speed is 0.65 m / min, and the total reduction during the heavy pressing process is 18 mm; the furnace heating temperature is 1270℃; the reduction rates of the first three passes of rough rolling are 15.5%, 16.8%, and 17.2%, respectively; the reduction rates of the first and third passes of finishing rolling are 12.2% and 12.8%, respectively; and the air cooling time is 1.5 h.
[0019] Ultrasonic testing was performed on the thick mold steel plates produced in this embodiment. The results showed that there were no defects such as pores, shrinkage cavities, or looseness inside the steel plates, and the mechanical properties test results met the relevant standard requirements.
[0020] Example 3 The difference from Example 1 is as follows: the scrap steel baking temperature is 280℃±20℃, the baking time is 2.5 h, and the moisture content of the scrap steel after baking is 4%; the final carbon content of the molten steel is 0.16%, and the residual oxygen content in the furnace is 180 ppm; the amount of aluminum blocks added is 0.45 kg / t steel, the continuous casting speed is 0.6 m / min, the total reduction during the heavy pressing process is 16 mm, and the temperature in the slow cooling pit is greater than 100℃; the furnace heating temperature is 1260℃, and the heating time is 8.5 minutes / cm billet thickness; the reduction rates of the first three passes of rough rolling are 15.2%, 16.3%, and 15.8%, respectively; the reduction rates of the third and fifth passes of finishing rolling are 12.1% and 12.3%, respectively; and the air cooling time is 1.8 h.
[0021] Ultrasonic testing was performed on the thick mold steel plates produced in this embodiment. The results showed that there were no defects such as pores, shrinkage cavities, or looseness inside the steel plates, and the mechanical properties test results met the relevant standard requirements.
[0022] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A production method for preventing holes in thick-gauge mold steel plates, characterized in that, Includes the following steps: S1. Raw material pretreatment: Use scrap steel and molten iron with a moisture content of ≤5% as raw materials; S2. Smelting: The final carbon content of the molten steel is 0.10~0.20% and the residual oxygen content is 140~280 ppm through converter smelting. Pre-deoxidation treatment is carried out before alloying the steel. S3. Continuous casting: The qualified molten steel is continuously cast at a casting speed of 0.6~0.65 m / min. The solidification end position of the billet is determined by dynamic light pressure calculation. Heavy pressure process is used in the solidification end area. After the billet is continuously cast, it is slowly cooled. S4. Rolling: The slowly cooled billet is sent into a heating furnace for heating. The heating time is 8~9 min / cm billet thickness to ensure that the billet is heated evenly. Then, rough rolling and finish rolling are performed in sequence to ensure that there are no double strands on the edge of the rolled plate. S5. Post-rolling cooling: After rolling, the steel is first air-cooled and then slowly cooled to obtain thick-gauge mold steel.
2. The production method for preventing holes in thick-gauge mold steel plates according to claim 1, characterized in that, In step S1, the scrap steel is baked to reduce its moisture content. The baking temperature is 280~800℃ and the baking time is 1.5~2.5 h.
3. The production method for preventing holes in thick-gauge mold steel plates according to claim 1, characterized in that, In step S2, the pre-deoxidation treatment method involves adding aluminum blocks at a rate of 0.35~0.65 kg / t of steel to the molten steel.
4. The production method for preventing holes in thick-gauge mold steel plates according to claim 1, characterized in that, In step S3, the reduction amount of the heavy pressure process is 15~18 mm.
5. The production method for preventing holes in thick-gauge mold steel plates according to claim 1, characterized in that, In step S3, the slow cooling time is 72 hours, and the temperature inside the slow cooling pit is ≥100℃.
6. The production method for preventing holes in thick-gauge mold steel plates according to claim 1, characterized in that, In step S4, the uniform heating temperature after heating is 1250~1270℃.
7. The production method for preventing holes in thick-gauge mold steel plates according to claim 1, characterized in that, In step S4, the reduction rate of the first three passes of rough rolling is greater than 15%, and the reduction rate of at least two passes of finish rolling is greater than 12%.
8. A production method for preventing holes in thick-gauge mold steel plates according to claim 1, characterized in that, In step S5, the air cooling time is 1.5~2 hours, and the slow cooling time is 48 hours.
9. Thick-gauge mold steel medium-thick plate products obtained by the method according to any one of claims 1-8.
10. The medium-thick plate of mold steel according to claim 9, characterized in that, The thickness of the medium-thick plate of the mold steel is 100~160 mm.