An electroslag remelting method for controlling d-type inclusions of hot work die steel

Abstract

This invention discloses an electroslag remelting method for controlling Class D inclusions in hot work die steel. The method includes: (1) selecting consumable electrodes for welding and surface treatment; (2) selecting slag material for preheating and baking; (3) placing the preheated slag material from step (2) and the consumable electrodes from step (1) into an atmosphere-protected ingot-pulling electroslag furnace for arc slag melting, and after feeding, placing the billet into an annealing furnace for heat preservation and annealing; (4) forging the annealed electroslag ingot from step (3) into forging products. This invention utilizes an argon atmosphere-protected ingot-pulling electroslag furnace to achieve stable control of Class D inclusions in hot work die steel without sacrificing the surface quality of the electroslag ingot, solving the problem of large fluctuations in the Class D inclusion level of hot work die steel in electroslag remelting production, and steadily improving the quality of high-end hot work die steel. The method of this invention is simple and easy to operate, and is worth promoting and applying.

Description

Technical Field

[0001] This invention belongs to the field of electroslag remelting technology, specifically relating to an electroslag remelting method for controlling Class D inclusions in hot work die steel. Background Technology

[0002] Electroslag remelting (ESR) is a process that utilizes the resistance heat generated by molten slag to melt, refine, and solidify metal consumable electrodes in a crystallizer. ESR effectively removes non-metallic inclusions from steel, reduces its oxygen content, and improves its cleanliness. As a specialized metallurgical process, ESR is widely used in the smelting and production of many high-quality steel grades.

[0003] Electroslag furnaces are generally divided into stationary electroslag furnaces and ingot-pulling electroslag furnaces, with stationary electroslag furnaces accounting for the majority. Ingot-pulling electroslag furnaces have advantages such as longer ingot shapes and higher yield, but because ingot-pulling electroslag furnaces need to ensure both the internal quality and surface quality of the electroslag ingots, their actual smelting operations differ significantly from those of stationary slag furnaces, requiring higher control over various operating parameters.

[0004] With the rapid development of my country's mold industry, the output of mold steel has increased rapidly, and the requirements for quality are becoming increasingly stringent. Hot work mold steels such as 4Cr5MoSiV, 4Cr5MoSiV1, 4Cr5Mo2V, and 4Cr5Mo3V are widely used in the manufacture of die-casting molds, extrusion molds, and other molds, requiring high thermal wear resistance, thermal fatigue resistance, and resistance to hot crack propagation under certain hardening conditions. Non-metallic inclusions in steel disrupt the continuity of the metal, especially hard, non-deformable inclusions, which easily cause stress concentration. Under external stress, crack propagation can easily develop and expand, leading to mold failure. High-performance hot work mold steels typically require electroslag remelting processes for production. With the continuous advancement of steelmaking technology, the oxygen content in hot work die steel can be easily controlled below 20 ppm, even below 10 ppm, and the sulfur content below 50 ppm or even lower. This significantly improves the purity of the steel. Inclusions of types A and C can reach grade 0, and inclusions of type B can be controlled within grade 1.0 or 0.5. However, inclusions of type D fluctuate considerably, with most fine inclusions around grade 1.5, and even some type DS inclusions appearing. Although some articles report that inclusions of type D can reach grade 0, this is rarely achieved in actual production, inspection, and testing of foreign samples. Achieving stable control of inclusions of type D in hot work die steel is of great significance for improving its purity and performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for controlling the electroslag remelting of Class D inclusions in hot work die steel.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] An electroslag remelting method for controlling Class D inclusions in hot work die steel, the method comprising the following steps:

[0008] (1) Select consumable electrode welding and perform surface treatment;

[0009] (2) Select appropriate slag materials and preheat and bake them before use;

[0010] (3) The slag material after preheating and baking in step (2) and the self-consumable electrode in step (1) are placed in an atmosphere-protected ingot-drawing electroslag furnace for arc ignition and slag melting. After the feeding is completed, the billet is taken out and placed in an annealing furnace for heat preservation and annealing.

[0011] (4) Forge the annealed electroslag ingot in step (3) into forging products, and take samples for testing and analysis.

[0012] In step (1) of this invention, the self-consumable electrode composition requirements are [O]≤0.0020%, 0.015≤[Al]≤0.025%, and [Ca]≤0.0005%; the equivalent diameter of the self-consumable electrode meets the requirement of a filling ratio of 23-33%.

[0013] In step (1) of this invention, after the consumable electrode is welded, it is processed on a shot blasting machine with a shot blasting particle size of 1 mm. Then, the electrode tip is preheated to 700-750℃ in an argon protective atmosphere and held for 30-35 minutes.

[0014] The slag material in step (2) of the present invention includes electrofused pre-melted slag and silica. The slag material composition ratio is: CaF2: 30-40%, CaO: 15-25%, MgO: 3-5%, Al2O3: 30-35%, SiO2: 8-15%, and the binary basicity is between 1.5 and 2.5.

[0015] In step (2) of the present invention, the total amount of slag material is 1-1.5% of the weight of the electroslag ingot.

[0016] In step (3) of the present invention, slag melting is carried out in a crystallizer of an electroslag furnace under full argon atmosphere protection, with cooling water pressure of 0.5-0.6MPa, slag resistance of 5.5-6.5mΩ, and melting rate of 300-400kg / h.

[0017] In step (3) of the present invention, aluminum particles are not used for deoxidation during the electroslag remelting process.

[0018] In step (3) of the present invention, the atmosphere protection pressure is controlled at 10-15 mbar during slag formation and at 2-3 mbar during normal smelting. The flue gas dust discharge adopts an intermittent pressure self-discharge method.

[0019] In step (3) of this invention, after the electroslag ingot is melted and the billet is produced, it is subjected to stress-relief annealing according to conventional process.

[0020] In step (4) of this invention, the annealed electroslag ingot is forged into modules by high-temperature diffusion + three upsetting and three drawing + ultra-fine processing + spheroidizing annealing process, and the inclusions are sampled and tested according to GB / T10561 standard.

[0021] The method of this invention achieves stable control of Class D inclusions in hot work die steel produced by electroslag remelting process.

[0022] The beneficial effects of adopting the above technical solution are as follows: 1. This invention utilizes a fully argon atmosphere-protected ingot-pulling electroslag furnace to achieve stable control of Class D inclusions in hot work die steel without sacrificing the surface quality of the electroslag ingot, thus solving the problem of large fluctuations in the level of Class D inclusions in hot work die steel during electroslag remelting and steadily improving the quality of high-end hot work die steel. 2. This invention's consumable electrode has relatively clear requirements for elements such as oxygen, aluminum, and calcium. Through refined control of the surface quality of the consumable electrode, atmosphere-protected preheating of the electrode, and control of different atmosphere protection pressures at different stages, the low oxygen potential of the electroslag furnace is controlled. 3. During the electroslag remelting process, this invention optimizes parameters such as small filling ratio, low basicity slag system, low melting rate, and high water pressure, ensuring slag pool temperature and cooling intensity, and improving the adsorption, removal, and fine control capabilities of Class D inclusions. 4. This invention's method is simple and easy to operate, meeting the higher purity requirements of high-end hot work die steel, and is worthy of widespread application. Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0024] This embodiment describes a method for controlling type D inclusions in hot work die steel (4Cr5MoSiV) via electroslag remelting, including the following steps:

[0025] (1) Select consumable electrode steel: 4Cr5MoSiV; consumable electrode diameter: Φ310mm; composition meets national standard requirements, of which [O]: 0.0018%, [Al]: 0.022%, [Ca]: 0.0004%. After welding, the surface and end are shot blasted on a shot blasting machine with a shot blasting particle size of 1mm. The electrode end is preheated to 750℃ in an argon protective atmosphere and held for 30min. Filling ratio 26.69%.

[0026] (2) Slag composition ratio: CaF2: 32%, CaO: 20%, MgO: 4%, Al2O3: 34%, SiO2: 10%, binary basicity 2.0; total slag amount 100kg, producing 10 tons of ingots, slag amount to ingot weight ratio 1%. The slag material is prepared by mixing different amounts of electrofused pre-melted slag and silica and then baked according to the conventional baking system before use.

[0027] (3) The slag material preheated and baked in step (2) and the consumable electrode in step (1) are placed into a Φ600mm crystallizer of an electroslag remelting furnace under full argon atmosphere protection for arc slag melting. The argon protection pressure during slag melting is 12mbar, and the argon protection pressure during normal melting is 2mbar. The flue gas is discharged by intermittent pressure self-discharge. The cooling water pressure during the production process is 0.55-0.6MPa, the slag resistance is 5.7-6.2mΩ, and the melting rate is 320-360kg / h. Aluminum particles are not used for deoxidation during electroslag remelting. After normal melting and feeding, the billet is placed in an annealing furnace and annealed according to the conventional stress relief process.

[0028] (4) The electroslag ingot after annealing in step (3) is forged into a module of 800mm×160mm×L using a 3150-ton press according to the high temperature diffusion + three upsetting and three drawing + ultra-fine + spheroidizing annealing process. The inclusions are sampled and tested according to GB / T10561 standard.

[0029] The inclusions in the 4Cr5MoSiV forging module are inspected as follows:

[0030]

[0031] This embodiment can obtain hot work die steel that meets the inclusion requirements of NADCA#207 high-quality steel. Example 2

[0032] The electroslag remelting method for controlling type D inclusions in hot work die steel (4Cr5MoSiV1) in this embodiment includes the following steps:

[0033] (1) Select consumable electrode steel: 4Cr5MoSiV1; equivalent diameter of consumable electrode: Φ330mm; composition meets national standard requirements, of which [O]: 0.0015%, [Al]: 0.019%, [Ca]: 0.0002%. After welding, surface and end shot blasting treatment is performed on a shot blasting machine with a shot blasting particle size ≤1mm. The electrode end is preheated to 720℃ in an argon protective atmosphere and held for 32min. Filling ratio 30.25%.

[0034] (2) Slag composition ratio: CaF2: 35%, CaO: 15%, MgO: 3%, Al2O3: 35%, SiO2: 12%, binary basicity 1.51; total slag amount 110kg, producing 8.4 tons of ingots, slag amount to ingot weight ratio 1.3%. The slag material is prepared by mixing different amounts of electrofused pre-melted slag and silica and then baked according to the conventional baking system before use.

[0035] (3) The slag material preheated and baked in step (2) and the consumable electrode in step (1) are placed into a Φ600mm crystallizer of an electroslag remelting furnace under full argon atmosphere protection for arc slag melting. The argon protection pressure during slag melting is 13mbar, and the argon protection pressure during normal melting is 3mbar. The flue gas is discharged by intermittent pressure self-discharge. The cooling water pressure during the production process is 0.54-0.59MPa, the slag resistance is 5.6-6.2mΩ, and the melting rate is 330-380kg / h. Aluminum particles are not used for deoxidation during electroslag remelting. After normal melting and feeding, the billet is placed in an annealing furnace and annealed according to the conventional stress relief process.

[0036] (4) The electroslag ingot after annealing in step (3) is forged into a module of 700mm×220mm×L using a 3150-ton press according to the high temperature diffusion + three upsetting and three drawing + ultra-fine + spheroidizing annealing process. The inclusions are sampled and tested according to GB / T10561 standard.

[0037] The inclusions in the 4Cr5MoSiV1 forging module are inspected as follows:

[0038]

[0039] This embodiment can obtain hot work die steel that meets the inclusion requirements of NADCA#207 high-quality steel. Example 3

[0040] The electroslag remelting method for controlling Class D inclusions in hot work die steel (4Cr5Mo2V) in this embodiment includes the following steps:

[0041] (1) Select consumable electrode steel: 4Cr5Mo2V; consumable electrode equivalent diameter: Φ340mm; composition meets national standard requirements, of which [O]: 0.0012%, [Al]: 0.017%, [Ca]: 0%. After welding, surface and end shot blasting treatment is performed on a shot blasting machine with a shot blasting particle size of 1mm. The electrode end is preheated to 740℃ in an argon protective atmosphere and held for 33min. Filling ratio 32.11%.

[0042] (2) Slag composition ratio: CaF2: 39%, CaO: 18%, MgO: 5%, Al2O3: 30%, SiO2: 8%, binary basicity 2.25; total slag amount 106kg, producing 8.6 tons of ingots, slag amount to ingot weight ratio 1.23%. The slag material is prepared by mixing different amounts of electrofused pre-melted slag and silica and then baked according to the conventional baking system before use.

[0043] (3) The slag material preheated and baked in step (2) and the consumable electrode in step (1) are placed into a Φ600mm crystallizer of an electroslag remelting furnace under full argon atmosphere protection for arc slag melting. The argon protection pressure during slag melting is 15mbar, and the argon protection pressure during normal melting is 3mbar. The flue gas is discharged by intermittent pressure self-discharge. The cooling water pressure during the production process is 0.53-0.59MPa, the slag resistance is 5.8-6.3mΩ, and the melting rate is 340-400kg / h. Aluminum particles are not used for deoxidation during electroslag remelting. After normal melting and feeding, the billet is placed in an annealing furnace and annealed under conventional stress relief process.

[0044] (4) The electroslag ingot after annealing in step (3) is forged into a module of 760mm×200mm×L using a 3150-ton press according to the high temperature diffusion + three upsetting and three drawing + ultra-fine + spheroidizing annealing process. The inclusions are sampled and tested according to GB / T10561 standard.

[0045] The inclusions in the 4Cr5Mo2V forging module are inspected as follows:

[0046]

[0047] This embodiment can obtain hot work die steel that meets the inclusion requirements of NADCA#207 high-quality steel. Example 4

[0048] The electroslag remelting method for controlling Class D inclusions in hot work die steel (4Cr5Mo3V) in this embodiment includes the following steps:

[0049] (1) Select consumable electrode steel: 4Cr5Mo3V; consumable electrode equivalent diameter: Φ288mm; composition meets national standard requirements, of which [O]: 0.020%, [Al]: 0.025%, [Ca]: 0.0005%. After welding, surface and end shot blasting treatment is performed on a shot blasting machine with a shot blasting particle size of 1mm. The electrode end is preheated to 750℃ in an argon protective atmosphere and held for 30min. Filling ratio 23.04%.

[0050] (2) Slag composition ratio: CaF2: 40%, CaO: 25%, MgO: 5%, Al2O3: 30%, SiO2: 8%, binary basicity 2.48; total slag amount 135kg, producing 9 tons of ingots, slag amount to ingot weight ratio 1.5%. The slag material is prepared by mixing different amounts of electrofused pre-melted slag and silica and then baked according to the conventional baking system before use.

[0051] (3) The slag material preheated and baked in step (2) and the consumable electrode in step (1) are placed into a Φ600mm crystallizer of an electroslag remelting furnace under full argon atmosphere protection for arc slag melting. The argon protection pressure is 10mbar during slag melting and 2mbar during normal melting. The flue gas is discharged by intermittent pressure self-discharge. The cooling water pressure during the production process is 0.50-0.56MPa, the slag resistance is 5.5-5.9mΩ, and the melting rate is 300-340kg / h. Aluminum particles are not used for deoxidation during electroslag remelting. After normal melting and feeding, the billet is placed in an annealing furnace and annealed under conventional stress relief process.

[0052] (4) The electroslag ingot after annealing in step (3) is forged into a module of 710mm×180mm×L using a 3150-ton press according to the high temperature diffusion + three upsetting and three drawing + ultra-fine + spheroidizing annealing process. The inclusions are sampled and tested according to GB / T10561 standard.

[0053] The inclusions in the 4Cr5Mo3V forging module are inspected as follows:

[0054]

[0055] This embodiment can obtain hot work die steel that meets the inclusion requirements of NADCA#207 high-quality steel.

[0056] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An electroslag remelting process for controlling D-type inclusions in hot work die steel, characterized by, The method includes the following steps: (1) Select consumable electrode welding and perform surface treatment; (2) Select appropriate slag materials and preheat and bake them before use; (3) The slag material after preheating and baking in step (2) and the self-consumable electrode in step (1) are placed in an atmosphere-protected ingot-drawing electroslag furnace for arc ignition and slag melting. After the feeding is completed, the billet is taken out and placed in an annealing furnace for heat preservation and annealing. (4) Forge the annealed electroslag ingot from step (3) into forging products, and take samples for testing and analysis; In step (1), the self-consumable electrode composition requirements are: [O] ≤ 0.0020%, 0.015 ≤ [Al] ≤ 0.025%, and [Ca] ≤ 0.0005%. In step (1), the fill ratio of the consumable electrode equivalent diameter is 23-33%; The slag material in step (2) includes electrofused pre-melted slag and silica, which is conventionally baked; the slag material composition ratio is: CaF2: 30-40%, CaO: 15-25%, MgO: 3-5%, Al2O3: 30-35%, SiO2: 8-15%, and the binary basicity is between 1.5 and 2.

5. In step (2), the total amount of slag is 1-1.5% of the weight of the electroslag ingot. In step (3), aluminum particles are not used for deoxidation during the electroslag remelting process; In step (3), slag melting is carried out in a crystallizer of an electroslag furnace under full argon atmosphere protection, with cooling water pressure of 0.5-0.6MPa, slag resistance of 5.5-6.5mΩ, and melting rate of 300-400kg / h.

2. The electroslag remelting method for controlling Class D inclusions in hot work die steel according to claim 1, characterized in that, In step (1), after the consumable electrode is welded, it is processed on a shot blasting machine with a shot blasting particle size of 1 mm. Then, the electrode tip is preheated to 700-750℃ in an argon protective atmosphere and held for 30-35 minutes.

3. The electroslag remelting method for controlling Class D inclusions in hot work die steel according to claim 1, characterized in that, In step (3), the atmosphere protection pressure is controlled at 10-15 mbar during slag formation and at 2-3 mbar during normal smelting. The flue gas dust discharge adopts an intermittent pressure self-discharge method.

4. The electroslag remelting method for controlling Class D inclusions in hot work die steel according to claim 1, characterized in that, In step (4), the annealed electroslag ingot is forged into modules by high-temperature diffusion + three upsetting and three drawing + ultra-fine processing + spheroidizing annealing process, and the inclusions are sampled and tested according to GB / T10561 standard.