Preparation method of low-segregation high-carbon stainless steel billet

Abstract

The present invention relates to the field of metallurgy and discloses a method for preparing a low-segregation, high-carbon stainless steel billet, comprising: sequentially performing electric furnace smelting, LF furnace refining, VD furnace refining, and casting to obtain an electrode rod; performing electroslag remelting on the electrode rod to obtain an ingot; and performing annealing on the ingot to obtain a low-segregation, high-carbon stainless steel billet. The electroslag remelting comprises a preparation stage, an arc starting stage, a steady-state remelting stage, and a filling stage. During the steady-state remelting stage, the melting rate is controlled according to the weight of the ingot to be prepared and ensured to be stable. When the weight of the ingot to be prepared is 2.5 to 3.5 tons, the melting rate is controlled to be 4.5 to 5.5 kg / min; when the weight of the ingot to be prepared is 4.5 to 5.5 tons, the melting rate is controlled to be 6 to 7 kg / min; and when the weight of the ingot to be prepared is 6.5 to 7.5 tons, the melting rate is controlled to be 7 to 8 kg / min. The present invention can control element segregation, reduce shrinkage cavity depth, and improve the surface quality of the billet.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a method for preparing a low-segregation high-carbon stainless steel billet. Background Art

[0002] High-carbon stainless steel, characterized by high hardness, wear resistance, and corrosion resistance, is widely used in bearings, piston rings, and other fields. However, the high content of elements such as C and Cr in this series of steels can easily lead to element segregation, affecting the processing and service life of components.

[0003] Based on this, the existing technology still needs to be improved. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for preparing a low-segregation high-carbon stainless steel billet, so as to at least solve the problem of element segregation in the high-carbon stainless steel billet.

[0005] According to one aspect of the present invention, a method for preparing a low-segregation high-carbon stainless steel billet is provided, comprising:

[0006] The electrode rod is obtained by sequentially carrying out electric furnace smelting, LF furnace refining, VD furnace refining and casting;

[0007] Electroslag remelting is performed on the electrode rod to obtain a steel ingot;

[0008] Annealing the steel ingot to obtain a low-segregation high-carbon stainless steel billet;

[0009] Among them, electroslag remelting includes a preparation stage, an arc starting stage, a steady-state remelting stage and a filling stage; in the steady-state remelting stage, the melting rate is controlled according to the weight of the steel ingot to be prepared and the melting rate is ensured to be stable; when the weight of the steel ingot to be prepared is 2.5~3.5 tons, the melting rate is controlled to be 4.5~5.5kg / min; when the weight of the steel ingot to be prepared is 4.5~5.5 tons, the melting rate is controlled to be 6~7kg / min; when the weight of the steel ingot to be prepared is 6.5~7.5 tons, the melting rate is controlled to be 7~8kg / min.

[0010] According to one embodiment of the present invention, during the steady-state remelting stage, the outlet water temperature of the crystallizer is controlled to be 30-45° C., and the outlet water temperature of the crystallizer and the flow rate of the protective gas are ensured to be stable.

[0011] According to one embodiment of the present invention, during the arc starting stage, a protective gas is introduced into the electroslag furnace until the oxygen content in the furnace drops below 5000 ppm, and then the arc is started;

[0012] In the arc starting stage, the control current is 7000~13000A and the control voltage is 30~45V;

[0013] During the arc starting stage, if the instantaneous current is lower than the corresponding threshold, the slag adding speed is reduced; if the instantaneous current is higher than the corresponding threshold, the slag adding speed is increased.

[0014] According to one embodiment of the present invention, during the filling stage, the power or melting speed is gradually reduced, the filling time is ≥45 minutes, and the furnace cooling time is 50-90 minutes.

[0015] According to one embodiment of the present invention, during electroslag remelting, the slag used contains 65-75% CaF2 and 25-35% Al2O3 by weight, and the slag usage is 22-30 kg / ton of steel; 25-35% of the slag is added in the preparation stage, and the remaining slag is added in the arc starting stage.

[0016] According to one embodiment of the present invention, before electroslag remelting, the method further includes: baking and heating the electrode rod, with the baking heating temperature being 820-860°C, the heating rate being ≤60°C / h, and the baking heating time being 6-8h.

[0017] According to one embodiment of the present invention, argon blowing is ensured in the pouring pipe for 15 to 30 minutes within 35 minutes before pouring, the argon pressure is controlled to be 0.20 to 0.50 MPa during the pouring process, the height between the ladle nozzle and the center pouring pipe gate is controlled to be ≤150 mm, the amount of protective slag is 1.5 to 2.5 kg / t, the ingot body pouring time is 420 to 600 seconds, and the riser pouring time is 240 to 300 seconds.

[0018] According to one embodiment of the present invention, during the VD furnace refining process, the argon blowing flow rate is maintained at ≥120L / min for 15~20 minutes, the argon blowing flow rate is reduced before breaking the vacuum, and the lid is closed and stirred for 5~10 minutes after breaking the vacuum. The static argon blowing is ≥15 minutes, and the bag temperature is 1490~1500℃.

[0019] According to one embodiment of the present invention, during the annealing process, the heating rate is 30~50℃ / h, the heating temperature is 840~860℃, the holding time is 13~15h, and after the holding is completed, it is slowly cooled to ≤400℃ at a cooling rate of ≤20℃ / h before being taken out of the furnace.

[0020] According to one embodiment of the present invention, the carbon content of the low-segregation high-carbon stainless steel billet is greater than 0.5%, the carbon segregation index is 1.5-2.0, the central porosity level is 0, the central shrinkage level is 0, and the central segregation level is 0.

[0021] In the technical solution of the present invention, by controlling the melting rate in the steady-state remelting stage during the electroslag remelting process and combining the setting of relevant parameters in each step, the element segregation can be effectively controlled, and the shrinkage cavity depth can be reduced, the surface quality of the steel billet can be improved, and the yield rate can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A flow chart of a method for preparing a low-segregation high-carbon stainless steel billet according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0025] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. Subsequent embodiments will not explain this one by one.

[0026] refer to Figure 1 The present invention provides a method for preparing a low-segregation high-carbon stainless steel billet, comprising:

[0027] The electrode rod is obtained by sequentially carrying out electric furnace smelting, LF furnace refining, VD furnace refining and casting;

[0028] Electroslag remelting is performed on the electrode rod to obtain a steel ingot; wherein the electroslag remelting includes a preparation stage, an arc starting stage, a steady-state remelting stage and a filling stage;

[0029] The steel ingot is annealed to obtain a low-segregation high-carbon stainless steel billet.

[0030] In an embodiment of the present invention, the carbon content of the high-carbon stainless steel billet may be greater than 0.5%, for example, greater than 0.6%, greater than 0.7%, greater than 0.8%, or greater than 0.9%. In a specific embodiment, the high-carbon stainless steel is 95Cr18 stainless steel, which comprises, by mass percentage, the following: C: 0.90-1.00%; Si: ≤0.80%; Mn: ≤0.80%; S: ≤0.030%; P: ≤0.035%; Cr: 17.00-19.00%; Ni: ≤0.60%; Mo: ≤0.75%.

[0031] In embodiments of the present invention, by configuring relevant parameters for various steps, including the electroslag remelting step, the synergistic effect of multiple parameters across multiple steps can effectively control element segregation, reduce shrinkage cavity depth, improve billet surface quality, and increase yield rate. The inventors of this application recognized that, during the electrode rod casting process, using lower pouring temperatures and higher cooling intensity can improve element segregation. However, higher cooling intensity (shorter solidification time) can also result in deeper shrinkage cavities, reducing yield rate. Therefore, by properly matching pouring temperature (determined by the ladle temperature) and pouring time, this application can both control segregation and ensure shallow shrinkage cavity depth, providing high-quality electrode rods for the electroslag remelting process. The inventors of this application also recognized that, during the electroslag remelting process, the melting rate during the steady-state remelting stage and the filling stage (the filling stage is controlled by time) directly affects the segregation and surface quality of the steel ingot. Generally, lower melting rates result in shallower molten pool depths, which can improve element segregation but also lead to poorer surface quality. Therefore, the present application can effectively control element segregation while ensuring good surface quality by matching reasonable parameters in the steady-state remelting stage and the filling stage.

[0032] Each step is described below.

[0033] Electric furnace smelting: Lime is placed on the furnace bottom before charging, and then pure iron and alloy raw materials are charged into the furnace according to the composition ratio of the target steel (such as 95Cr18 stainless steel); after the charge is fully melted, oxygen is blown at a temperature ≥1600℃ to remove carbon, degas and remove inclusions, and reasonably control the carbon content; lime, fluorite, CaSi, Al blocks and carbon powder are added for reduction for ≥10 minutes, and nitrogen is blown for stirring. The steel tapping temperature is ≥1650℃.

[0034] LF furnace refining: The molten steel obtained after electric furnace smelting is sent to the LF furnace and sent for electric refining for reduction. The whole process is reduced with steel slag and baked carbon powder to make the chemical composition close to the target value. When the temperature is ≥1580℃, Al is fed to the Al content of 0.06~0.08%, and the bag is hung.

[0035] VD furnace refining: Maintain an argon flow rate of ≥120 L / min for 15-20 minutes. Reduce the argon flow rate before breaking vacuum. If the Al content is ≤0.005% after breaking vacuum, feed Al wire until the Al content reaches 0.04%. Then, close the lid and stir for 5-10 minutes. Add 10-15 kg of rare earths per furnace. Maintain an argon purge time of ≥15 minutes. Maintain a ladle temperature of 1490-1500°C.

[0036] Pouring: Ensure argon is flushed through the pouring nozzle for 15-30 minutes within 35 minutes before pouring. Use a slit-type nozzle for argon protection during pouring. Maintain the argon pressure between 0.20-0.50 MPa during pouring. Ensure accurate alignment between the ladle nozzle and the center pouring nozzle, maintaining the height between them ≤150 mm. Maintain a steady rise in the liquid level when pouring the ingot body and cap. Use 1.5-2.5 kg / t mold slag. The ingot body pouring time is 420-600 seconds, and the riser pouring time is 240-300 seconds. Electrode rods are cast.

[0037] Electroslag remelting:

[0038] ① Electrode rod processing

[0039] The high-carbon stainless steel electrode rods are peeled to ensure that there is no black skin or cracks on the surface, and the weld nodules and weld scars on the end faces and surfaces of the electrode rods are cleaned. The electrode rods are baked and heated at a temperature of 820-860°C, a heating rate of ≤60°C / h, and a baking time of 6-8h.

[0040] ②Slag preparation

[0041] The slag used should contain 65-75% CaF2 and 25-35% Al2O3 by weight (for example, a 70% CaF2 + 30% Al2O3 pre-melted slag). The slag usage is 22-30 kg per ton of steel. After unpacking the pre-melted slag, add it to the ESC through the protective atmosphere slag inlet within 15 minutes to prevent it from absorbing moisture from the air.

[0042] ③Electroslag remelting (using protective atmosphere electroslag furnace for remelting)

[0043] During the preparation phase, a 10-15 mm thick starter plate for this steel grade is placed on a water-cooled base below the mold. The starter plate's diameter is slightly smaller than the mold's inner diameter. Slag at a concentration of 25-35 wt% (e.g., 30 wt%) is then added to the mold through the slag inlet. The electrode rod is then lowered to a position close to the starter plate.

[0044] During the arc starting phase, the ESC uses current and voltage control, with a control current of 7,000 to 13,000A and a control voltage of 30 to 45V. Shielding gas is first introduced into the furnace through the shielding gas control valve until the oxygen content drops below 5,000 ppm. Arc starting is then initiated. During the arc starting process, the remaining slag is added to the furnace through the slag feed port, depending on current and voltage fluctuations. If the instantaneous current falls below the threshold, the slag addition rate is reduced; if it exceeds the threshold, the slag addition rate is increased. Once the current and voltage stabilize, a slag pool has formed within the furnace, marking the end of the arc starting phase. All slag must be added during this phase.

[0045] During the steady-state remelting phase, the electroslag furnace uses melt rate control, which is based on the weight of the ingot to be prepared, ensuring a stable melt rate without drastic fluctuations. For ingots weighing 2.5 to 3.5 tons, the melt rate is controlled at 4.5 to 5.5 kg / min; for ingots weighing 4.5 to 5.5 tons, the melt rate is controlled at 6 to 7 kg / min; and for ingots weighing 6.5 to 7.5 tons, the melt rate is controlled at 7 to 8 kg / min. Furthermore, the mold outlet water temperature is controlled at 30 to 45°C, and both the mold outlet water temperature and the shielding gas flow rate are maintained stable without drastic fluctuations.

[0046] During the filling stage, power or melting rate reduction control is adopted to gradually reduce the power or melting rate. The filling time is ≥45min and the furnace cooling time is 50~90min.

[0047] Ingot annealing: heating rate is 30 ~ 50℃ / h, heating temperature is 840~860℃, holding time is 13~15h, after holding, slowly cool to ≤400℃ at a cooling rate of ≤20℃ / h and then take out of the furnace.

[0048] In some embodiments, the low-segregation, high-carbon stainless steel billet produced using the above-described method of the present invention has a carbon segregation index of 1.5 to 2.0, a central porosity level of 0, a central shrinkage level of 0, and a central segregation level of 0. The produced billet has high purity, effectively improved segregation, a shallow melt pool depth, and good surface quality.

[0049] The following describes the specific embodiments.

[0050] Example 1

[0051] The following steps are used to prepare low segregation high carbon stainless steel billets:

[0052] 1. Electrode rod preparation

[0053] ① Before charging, place lime on the bottom of the furnace, then charge the pure iron and alloy raw materials into the furnace according to the composition ratio of 95Cr18; after the charge is fully melted, blow oxygen at a temperature of 1610℃ to remove carbon, degas and remove inclusions, and reasonably control the carbon content; add lime, fluorite, CaSi, Al blocks and carbon powder for reduction for 15 minutes, blow nitrogen for stirring, and the steel tapping temperature is 1658℃.

[0054] ② Enter the LF furnace and send it for electric refining for reduction. The whole process is reduced with steel slag and baked carbon powder to make the chemical composition close to the target value. When the temperature is 1590℃, feed Al to 0.06% and hang the bag.

[0055] ③ VD furnace refining: Maintain an argon flow rate of 130 L / min for 18 minutes. Reduce the argon flow rate before breaking vacuum. Feed Al wire until the Al content reaches 0.04%, then close the lid and stir for 8 minutes. Add 12 kg of rare earth per furnace, maintain a static argon flow time of 18 minutes, and maintain a ladle temperature of 1493°C.

[0056] ④ Within 35 minutes before pouring, argon was blown through the pouring nozzle for 20 minutes. A slot-type nozzle was used for argon protection during pouring, and the argon pressure was controlled at 0.3 MPa during the pouring process. The ladle nozzle and the center pouring nozzle were accurately aligned, and the height between the nozzle and the pouring nozzle was controlled at 145 mm. During pouring of the ingot body and cap, the liquid level was controlled to rise steadily. The mold casting flux dosage was 2.0 kg / t. The ingot body pouring time was 450 seconds, and the riser pouring time was 280 seconds. Electrode rods were cast.

[0057] 2. Electroslag Remelting

[0058] ① Electrode rod processing

[0059] The high-carbon stainless steel electrode rods are subjected to surface peeling treatment to ensure that there is no black skin or cracks on the surface. The end faces and surface weld nodules and weld scars of the electrode rods must be cleaned. The electrode rods are baked and heated at a temperature of 830°C, a heating rate of 55°C / h, and a baking time of 6 hours.

[0060] ②Slag preparation

[0061] Use 70% CaF2 + 30% Al2O3 pre-melted slag, with a slag usage of 25kg / ton of steel. Add the pre-melted slag to the electroslag furnace through the protective atmosphere slag inlet within 10 minutes after unpacking to prevent the slag from absorbing water in the air.

[0062] ③Electroslag remelting

[0063] Remelting is performed in a protective atmosphere electroslag furnace. During the preparatory stage, a 12mm-thick dummy plate for this steel grade is placed on a water-cooled base below the mold. The diameter of the dummy plate is slightly smaller than the mold's inner diameter. 30% of the slag is then added to the mold through the slag inlet. Subsequently, the electrode rod is lowered to a position close to the dummy plate. During the arc-starting stage, the electroslag furnace is controlled using current and voltage control, with a control current of 8000A and a control voltage of 40V. Shielding gas is first introduced into the furnace through the shielding gas control valve until the oxygen content in the furnace drops below 5000ppm. Arcing is then initiated. During the arc-starting process, the remaining 70% of the slag is added through the slag inlet. When the current and voltage stabilize, a slag pool has formed within the furnace, and the arc-starting stage is concluded. During the steady-state remelting stage, the electroslag furnace is controlled using melting rate control. For a 3-ton ingot to be produced, the melting rate is controlled at 4.5kg / min to ensure a stable melting rate without drastic fluctuations. The gas flow rate is also maintained to ensure stability without drastic fluctuations. During the steady-state phase, the outlet water temperature of the crystallizer is controlled at 35°C to ensure stability without drastic fluctuations. During the filling phase, power or melting rate control is adopted to gradually reduce the power or melting rate. The filling time is 50 minutes and the furnace cooling time is 60 minutes.

[0064] 3. Ingot annealing

[0065] The heating rate is 40℃ / h, the heating temperature is 840℃, the holding time is 13h, and after the holding time is completed, it is slowly cooled to 400℃ at a cooling rate of 15℃ / h and then taken out of the furnace.

[0066] The low-segregation high-carbon stainless steel billet produced has high purity, and the segregation is effectively improved. The carbon segregation index K is about 1.5, the central porosity is level 0, the central shrinkage is level 0, the central segregation is level 0, the molten pool depth is shallow, and the surface quality is good.

[0067] Example 2

[0068] The following steps are used to prepare low segregation high carbon stainless steel billets:

[0069] 1. Electrode rod preparation

[0070] ① Before charging, place lime on the bottom of the furnace, then charge the pure iron and alloy raw materials into the furnace according to the composition ratio of 95Cr18; after the charge is fully melted, blow oxygen at 1608℃ to remove carbon, degas and remove inclusions, and reasonably control the carbon content; add lime, fluorite, CaSi, Al blocks and carbon powder for reduction for 15 minutes, blow nitrogen for stirring, and the tapping temperature is 1655℃.

[0071] ② Enter the LF furnace and send it for electric refining for reduction. The whole process is reduced with steel slag and baked carbon powder to make the chemical composition close to the target value. When the temperature is 1586℃, feed Al to 0.08% and hang the bag.

[0072] ③ VD furnace refining: Maintain an argon flow rate of 125 L / min for 19 minutes. Reduce the argon flow rate before breaking vacuum. Feed Al wire until the Al content reaches 0.04%, then close the lid and stir for 6 minutes. Add 15 kg of rare earth per furnace, maintain argon flow for 20 minutes, and maintain a ladle temperature of 1499°C.

[0073] ④ Within 35 minutes before pouring, argon was blown through the pouring nozzle for 22 minutes. A slot-type nozzle was used for argon protection during pouring, and the argon pressure was controlled at 0.4 MPa. The ladle nozzle and the center pouring nozzle were accurately aligned, and the height between the nozzle and the pouring nozzle was controlled at 148 mm. During pouring of the ingot body and cap, the liquid level was controlled to rise steadily. The mold casting flux dosage was 1.8 kg / t. The ingot body pouring time was 580 seconds, and the riser pouring time was 245 seconds. Electrode rods were cast.

[0074] 2. Electroslag Remelting

[0075] ① Electrode rod processing

[0076] The high-carbon stainless steel electrode rods were peeled to ensure that there was no black skin or cracks on the surface, and the weld nodules and weld scars on the end faces and surfaces of the electrode rods were cleaned. The electrode rods were baked at a temperature of 855°C, a heating rate of 60°C / h, and a baking time of 7.5h.

[0077] ②Slag preparation

[0078] Use 70% CaF2 + 30% Al2O3 pre-melted slag, with a slag usage of 28kg / ton of steel. After unpacking the pre-melted slag, add it to the electroslag furnace through the protective atmosphere slag inlet within 12 minutes to prevent the slag from absorbing water in the air.

[0079] ③Electroslag remelting

[0080] Remelting is performed in a protective atmosphere electroslag furnace. During the preparatory stage, a 15mm-thick dummy plate for this steel grade is placed on a water-cooled base below the mold. The diameter of the dummy plate is slightly smaller than the mold's inner diameter. 30% of the slag is then added to the mold through the slag inlet. Subsequently, the electrode rod is lowered to a position close to the dummy plate. During the arc-starting stage, the electroslag furnace is controlled using current and voltage control, with a control current of 9000A and a control voltage of 38V. Shielding gas is first introduced into the furnace through the shielding gas control valve until the oxygen content in the furnace drops below 5000ppm. Arcing is then initiated. During the arc-starting process, the remaining 70% of the slag is added through the slag inlet depending on current and voltage fluctuations. When the current and voltage stabilize, a slag pool has formed within the furnace, and the arc-starting stage is concluded. During the steady-state remelting stage, the electroslag furnace is controlled using melting rate control. For a 5-ton ingot to be produced, the melting rate is controlled at 6.5kg / min to ensure a stable melting rate without significant fluctuations. The shielding gas flow rate was maintained stable without drastic fluctuations. During the steady-state phase, the mold outlet water temperature was controlled at 38°C to ensure stability without drastic fluctuations. During the filling phase, power or melt rate control was employed, gradually reducing the power or melt rate. The filling time was 70 minutes, and the furnace cooling time was 80 minutes.

[0081] 3. Ingot annealing

[0082] The heating rate is 50℃ / h, the heating temperature is 860℃, the holding time is 15h, and after the holding time is completed, it is slowly cooled to 380℃ at a cooling rate of 15℃ / h and then taken out of the furnace.

[0083] The low-segregation high-carbon stainless steel billet produced has high purity, and the segregation is effectively improved. The carbon segregation index K is about 1.6, the central porosity is level 0, the central shrinkage is level 0, the central segregation is level 0, the molten pool depth is shallow, and the surface quality is good.

[0084] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to limit the scope of the disclosure of the present invention (including the claims) to these examples. Within the spirit of the present invention, the technical features of the above embodiments or different embodiments may be combined, and many other variations exist in different aspects of the present invention as described above, which are not provided in detail for the sake of clarity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a low-segregation high-carbon stainless steel billet, characterized in that: The low-segregation high-carbon stainless steel billet comprises, by mass percentage, 0.90-1.00% C and 17.00-19.00% Cr. The method comprises: The electrode rod is obtained by sequentially carrying out electric furnace smelting, LF furnace refining, VD furnace refining and casting; performing electroslag remelting on the electrode rod to obtain a steel ingot; Annealing the steel ingot to obtain the low-segregation high-carbon stainless steel billet; The electroslag remelting includes a preparation stage, an arc starting stage, a steady-state remelting stage, and a filling stage. During the steady-state remelting stage, the melting rate is controlled according to the weight of the steel ingot to be prepared and the melting rate is ensured to be stable. When the weight of the steel ingot to be prepared is 2.5-3.5 tons, the melting rate is controlled to be 4.5-5.5 kg / min; when the weight of the steel ingot to be prepared is 4.5-5.5 tons, the melting rate is controlled to be 6-7 kg / min; when the weight of the steel ingot to be prepared is 6.5-7.5 tons, the melting rate is controlled to be 7-8 kg / min. In the arc starting stage, the control current is 7000~13000A, and the control voltage is 30~45V; if the instantaneous current is lower than the corresponding threshold, the slag addition speed is reduced, and if the instantaneous current is higher than the corresponding threshold, the slag addition speed is increased; During the steady-state remelting stage, the outlet water temperature of the crystallizer is controlled to be 30-38°C, and the outlet water temperature of the crystallizer and the flow rate of the protective gas are ensured to be stable; During the filling stage, the power or melting speed is gradually reduced, the filling time is ≥45 minutes, and the furnace cooling time is 50-90 minutes; During the VD furnace refining process, the ladle temperature is 1490~1500℃; The ingot casting time is 420~600s, and the riser casting time is 240~300s.

2. The method according to claim 1, characterized in that During the arc starting stage, protective gas is introduced into the electroslag furnace until the oxygen content in the furnace drops below 5000 ppm, and then the arc is started.

3. The method according to claim 1, characterized in that During electroslag remelting, the slag used contains 65-75% CaF2 and 25-35% Al2O3 by weight, and the slag usage is 22-30 kg per ton of steel; 25-35% of the slag is added in the preparation stage, and the remaining slag is added in the arc starting stage.

4. The method according to claim 1, wherein Before electroslag remelting, the method further includes: baking and heating the electrode rod, wherein the baking heating temperature is 820-860° C., the heating rate is ≤60° C. / h, and the baking heating time is 6-8 hours.

5. The method according to claim 1, wherein Ensure that the injection pipe is purged with argon for 15 to 30 minutes within 35 minutes before pouring. During the pouring process, the argon pressure is controlled at 0.20 to 0.50 MPa. The height between the ladle nozzle and the center injection pipe gate is controlled to be ≤150 mm. The amount of protective slag is 1.5 to 2.5 kg / t.

6. The method according to claim 1, characterized in that During the VD furnace refining process, the argon blowing flow rate is maintained at ≥120L / min for 15~20min. The argon blowing flow rate is reduced before breaking the vacuum. After breaking the vacuum, close the lid and stir for 5~10min. The static argon blowing time is ≥15min.

7. The method according to claim 1, characterized in that During the annealing process, the heating rate is 30~50℃ / h, the heating temperature is 840~860℃, the holding time is 13~15h, and after the holding is completed, it is slowly cooled to ≤400℃ at a cooling rate of ≤20℃ / h before being taken out of the furnace.

8. The method according to claim 1, characterized in that The carbon segregation index is 1.5~2.0, the central porosity grade is 0, the central shrinkage grade is 0, and the central segregation grade is 0.

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