A method for preparing a vacuum double consumable steel ingot of super-high strength SF1900 steel

Abstract

This application relates to the technical field of ultra-high strength steel materials, specifically disclosing a method for preparing ultra-high strength SF1900 steel vacuum double-consumable steel ingots. The method disclosed in this application involves: vacuum induction melting, primary vacuum consumable remelting, and secondary vacuum consumable remelting. The technical solution disclosed in this application, through VIM+VAR+VAR smelting, produces vacuum consumable steel ingots with high purity, low segregation, and extremely high uniformity in composition and microstructure.

Description

Technical Field

[0001] This application relates to the technical field of ultra-high strength steel materials, specifically to a method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot. Background Technology

[0002] Ultra-high strength SF1900 steel possesses ultra-high strength, high toughness, and long fatigue life. Currently, the smelting of ultra-high strength SF1900 steel for aerospace applications generally employs a dual-smelting process, namely vacuum induction melting + protective atmosphere electroslag remelting or vacuum induction melting + vacuum arc remelting.

[0003] However, during protective atmosphere electroslag remelting, the loss of Al is difficult to control; slight misjudgments in the selection of slag materials and smelting parameters can easily lead to large fluctuations in the Al content of the steel ingot, affecting the uniformity and stability of the chemical composition. In vacuum arc remelting, the desulfurization capacity and the modification effect of oxide inclusions are relatively poor. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingots.

[0005] This application provides a method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot, which specifically includes the following steps in sequence: vacuum induction melting, primary vacuum consumable remelting, and secondary vacuum consumable remelting;

[0006] The process parameters for the single vacuum self-consumable remelting are as follows: melting rate is 5.5-6.5 kg / min; helium is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 230-280 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 230-280 ml / min to 15-25 ml / min within 30 minutes.

[0007] The process parameters for the secondary vacuum self-consuming remelting are as follows: melting rate is 4.5-5.5 kg / min; helium is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 160-220 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 160-220 ml / min to 15-25 ml / min within 30 minutes.

[0008] This application discloses a smelting process for ultra-high strength SF1900 steel, with the aim of smelting ultra-high strength vacuum double consumable steel ingots with low raw material costs, good hot working performance, and ultra-high purity in industrial production.

[0009] This application employs a dual-vacuum arc remelting process, eliminating the risk of contamination from foreign slag systems. It also results in superior and more uniform solidification structure control, and the high uniformity of chemical composition and microstructure leads to stable mechanical properties and low dispersion. Therefore, the successful use of the triple process of vacuum induction melting (VIM) + vacuum arc remelting (VAR) + vacuum arc remelting (VAR) in steelmaking not only fills the gap in my country's ultra-high strength SF1900 steel smelting technology but also improves the metallurgical quality of domestic ultra-high strength SF1900 steel.

[0010] Preferably, the process parameters for vacuum induction melting are as follows: full melting temperature: 1500℃-1550℃; refining temperature: 1520℃-1570℃; tapping temperature: 1540℃-1570℃; vacuum degree during full melting: 20-40Pa; vacuum degree during refining: less than 3Pa, maintained for more than 50 minutes.

[0011] Preferably, in the vacuum induction melting step, the tapping temperature > refining temperature > total melting temperature.

[0012] Preferably, in the vacuum induction melting step, the refining temperature = total melting temperature + (10-30℃) and the tapping temperature = refining temperature + (5-20℃).

[0013] Preferably, in the vacuum induction melting step, the raw materials include No. 0 Ni or No. 1 Ni, Co metal, Cr metal, Mo metal, Al metal, low-carbon steel, and carbon electrode; the electrode prepared by the vacuum induction melting step has an ingot size of Φ550-600mm and a weight of 5000-6000kg.

[0014] In one specific implementation, the electrode ingot dimensions are: Φ580mm, 5600kg.

[0015] Preferably, the process parameters for the single vacuum consumable remelting are: vacuum degree of 0.1-1 Pa, melting rate of 5.7-6.3 kg / min; helium gas is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 240-260 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 240-260 ml / min to 17-23 ml / min within 30 minutes.

[0016] Preferably, the process parameters for the single vacuum self-consuming remelting are: vacuum degree of 0.5-1 Pa, melting rate of 5.8-6.2 kg / min; during melting, helium gas is introduced for cooling, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 245-255 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 245-255 ml / min to 18-22 ml / min within 30 minutes.

[0017] Preferably, the process parameters for the secondary vacuum consumable remelting are: vacuum degree of 0.1-1 Pa, melting rate of 4.7-5.3 kg / min; helium gas is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 170-210 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 170-210 ml / min to 18-22 ml / min within 30 minutes.

[0018] Preferably, the process parameters for the secondary vacuum consumable remelting are: vacuum degree of 0.1-0.4 Pa, melting rate of 4.8-5.2 kg / min; helium gas is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 180-200 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 180-200 ml / min to 18-22 ml / min within 30 minutes.

[0019] Preferably, the chemical composition of the ultra-high strength SF1900 steel vacuum double consumable steel ingot, by weight percentage, is as follows: C 0.14-0.25%, Ni 13.00-15.00%, Mo 1.00-2.00%, Cr 1.5-3.0%, Co 9.00-11.00%, Al 0.85-0.95%, Si≤0.10%, Mn≤0.10%, Cu≤0.05%, S≤0.001%, P≤0.005%, O≤0.0005%, N≤0.001%, with the remainder being Fe and unavoidable impurities.

[0020] Preferably, the steel ingot prepared by this method has a shape of Φ650-700mm alloy ingot.

[0021] In one specific implementation, the steel ingot prepared by this method has a diameter of Φ660mm.

[0022] In summary, the technical solution of this application has the following effects:

[0023] This application employs a triple smelting process of vacuum induction furnace (VIM) + vacuum arc remelting furnace (VAR) + vacuum arc remelting furnace (VAR) for production. After the first VAR process, the electrodes prepared by VIM may still contain a small amount of minute inclusions or inclusions with densities close to molten metal. The second VIM remelting allows these inclusions more opportunities to float or dissolve, further removing residual inclusions and gases (H, O, N). For steels with an alloy content of 27% or higher, the two directional solidification processes significantly eliminate macroscopic and microscopic defects such as segregation, porosity, and shrinkage cavities, resulting in a fine and uniform solidification structure with the highest purity. This also prevents the loss of C and Al during electroslag remelting, which can cause differences in chemical composition between the beginning and end of the process. VIM+VAR+VAR smelting is an effective method for producing high-purity, low-segregation, and highly uniform vacuum arc remelting steel ingots in terms of composition and structure.

[0024] This application employs a triple smelting process of vacuum induction furnace (VIM) + vacuum arc remelting furnace (VAR) + vacuum arc remelting furnace (VAR) to manufacture Φ660mm steel ingots. The VIM process uses high vacuum smelting, controls the gas content in the steel before Al addition, and performs low-temperature casting under vacuum to ensure that non-metallic inclusions and impurity elements such as S, P, Si, Mn, Ti, O, and N are controlled at low levels. The VAR remelting process uses high vacuum and low melting rate to achieve further degassing, inclusion removal, and uniform microstructure. Steel ingots are forged using a high-speed forging machine to produce steel bars such as Φ200mm. Inspection shows that their low-magnification microstructure—white spots, dark spots, radial segregation, and annular patterns—all reach AAAA level. In the non-metallic inclusions, the number of inclusions in the A fine series (grade 0) and B fine series (grade 0.5) is less than one; the number of inclusions in the C fine series (grade 0) and D fine series (grade 0.5) is less than 1.5. Furthermore, the impurity elements are Si≤0.10%, Mn≤0.10%, Cu≤0.05%, S≤0.001%, P≤0.005%, O≤0.0005%, and N≤0.001%, achieving high purity and low segregation. Attached Figure Description

[0025] Figure 1 This is a photograph of the steel Φ660mm consumable ingot prepared in Example 1. Detailed Implementation

[0026] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0027] Example

[0028] Example 1

[0029] Example 1 provides a vacuum double consumable steel ingot and its preparation method.

[0030] The method for preparing steel in this embodiment is as follows:

[0031] (1) Vacuum induction melting

[0032] Raw materials: Ni (grade 0), Co, Cr, Mo, Al, low-carbon steel, and carbon electrodes;

[0033] a) Full melting temperature: 1520℃;

[0034] b) Refining temperature: 1555℃;

[0035] c) Tap temperature: 1565℃;

[0036] d) Vacuum level during full melting period: 30 Pa;

[0037] e) Vacuum degree during refining: 2 Pa, maintain for 100 min.

[0038] Ingot type: Φ580mm, 5600kg; the chemical composition of the induction electrode is shown in Table 1 below.

[0039] Table 1 Chemical composition of the induction electrode in Example 1

[0040]

[0041] (2) Vacuum self-consumption remelting

[0042] Vacuum level: 0.7 Pa;

[0043] Melting rate: 6.01 kg / min;

[0044] During smelting, helium is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 250 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 250 ml / min to 20 ml / min within 30 minutes.

[0045] The chemical composition of a vacuum arc remelted steel ingot is shown in Table 2 below.

[0046] Table 2 Chemical composition of the vacuum arc remelting steel ingot in Example 1

[0047]

[0048] (3) Secondary vacuum consumable remelting

[0049] Vacuum degree: 0.3 Pa;

[0050] Melting rate: 5.02 kg / min;

[0051] During the smelting process, helium gas is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 190 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 190 ml / min to 20 ml / min within 30 minutes.

[0052] Casting: Φ660mm alloy ingot.

[0053] Figure 1 The image shows a Φ660mm consumable steel ingot prepared in Example 1, exhibiting good appearance quality. The chemical composition of the vacuum consumable remelted steel ingot is shown in Table 3 below.

[0054] Table 3 Chemical composition of the secondary vacuum arc remelting steel ingot in Example 1

[0055]

[0056] The steel ingots prepared in this embodiment have qualified composition, and the control is precise and stable; the surface of the steel ingots is good.

[0057] Example 2

[0058] Example 2 provides a vacuum double consumable steel ingot and its preparation method.

[0059] The method for preparing steel in this embodiment is as follows:

[0060] (1) Vacuum induction melting

[0061] Raw materials: Ni (grade 0), Co, Cr, Mo, Al, low-carbon steel, and carbon electrodes;

[0062] a) Full melting temperature: 1510℃;

[0063] b) Refining temperature: 1550℃;

[0064] c) Tap temperature: 1570℃;

[0065] d) Vacuum level during full melting period: 30 Pa;

[0066] e) Vacuum level during refining: 2 Pa, maintained for 100 minutes.

[0067] Ingot type: Φ580mm, 5600kg; the chemical composition of the induction electrode is shown in Table 4 below.

[0068] Table 4 Chemical composition of the induction electrode in Example 2

[0069]

[0070] (2) Vacuum self-consumption remelting

[0071] Vacuum degree: 0.3 Pa;

[0072] Melting rate: 5.52 kg / min;

[0073] During smelting, helium is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 250 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 250 ml / min to 20 ml / min within 30 minutes.

[0074] The chemical composition of a vacuum arc remelted steel ingot is shown in Table 5 below.

[0075] Table 5 Chemical composition of the vacuum arc remelting steel ingot in Example 2

[0076]

[0077] (3) Secondary vacuum consumable remelting

[0078] Vacuum level: 0.7 Pa;

[0079] Melting rate: 5.46 kg / min;

[0080] During smelting, helium is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 190 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 190 ml / min to 6 ml / min within 30 minutes.

[0081] Casting: Φ660mm alloy ingot.

[0082] The chemical composition of vacuum arc remelting steel ingots is shown in Table 6 below.

[0083] Table 6 Chemical composition of the secondary vacuum arc remelting steel ingot in Example 2

[0084]

[0085] The steel ingots prepared in this embodiment have qualified composition, and the control is precise and stable; the surface of the steel ingots is good.

[0086] Example 3

[0087] Example 3 provides a vacuum double consumable steel ingot and its preparation method.

[0088] The method for preparing steel in this embodiment is as follows:

[0089] (1) Vacuum induction melting

[0090] Raw materials: Ni (grade 0), Co, Cr, Mo, Al, low-carbon steel, and carbon electrodes;

[0091] a) Full melting temperature: 1520℃;

[0092] b) Refining temperature: 1530℃;

[0093] c) Tap temperature: 1570℃;

[0094] d) Vacuum level during full melting period: 30 Pa;

[0095] e) Vacuum level during refining: 2 Pa, maintained for 100 minutes.

[0096] Ingot type: Φ580mm, 5600kg; the chemical composition of the induction electrode is shown in Table 7 below.

[0097] Table 7 Chemical composition of the induction electrode in Example 3

[0098]

[0099] (2) Vacuum self-consumption remelting

[0100] Vacuum level: 0.4 Pa;

[0101] Melting rate: 6.48 kg / min;

[0102] During smelting, helium is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 250 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 250 ml / min to 20 ml / min within 30 minutes.

[0103] The chemical composition of a vacuum arc remelted steel ingot is shown in Table 8 below.

[0104] Table 8 Chemical composition of the vacuum arc remelting steel ingot in Example 3

[0105]

[0106] (3) Secondary vacuum consumable remelting

[0107] Vacuum level: 0.7 Pa;

[0108] Melting rate: 4.58 kg / min;

[0109] During the smelting process, helium gas is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 220 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 220 ml / min to 20 ml / min within 30 minutes.

[0110] Casting: Φ660mm alloy ingot.

[0111] The chemical composition of vacuum arc remelted steel ingots is shown in Table 9 below.

[0112] Table 9 Chemical composition of the secondary vacuum arc remelting steel ingot in Example 3

[0113]

[0114] The steel ingots prepared in this embodiment have qualified composition, and the control is precise and stable; the surface of the steel ingots is good.

[0115] Comparative Example

[0116] Comparative Example 1

[0117] Comparative Example 1 provides a vacuum double consumable steel ingot and its preparation method.

[0118] The difference between this comparative example and Example 1 is that the smelting process is a combined process of vacuum induction melting and vacuum consumable remelting.

[0119] The method for preparing steel in this comparative example is as follows:

[0120] (1) Vacuum induction melting

[0121] Raw materials: Ni (grade 0), Co, Cr, Mo, Al, low-carbon steel, and carbon electrodes;

[0122] a) Full melting temperature: 1520℃;

[0123] b) Refining temperature: 1555℃;

[0124] c) Tap temperature: 1565℃;

[0125] d) Vacuum level during full melting period: 30 Pa;

[0126] e) Vacuum degree during refining: 2 Pa, maintain for 100 min.

[0127] Ingot type: Φ580mm, 5600kg; the chemical composition of the induction electrode is shown in Table 10 below.

[0128] Table 10 Chemical composition of the induction electrode in Comparative Example 1

[0129]

[0130] (2) Vacuum consumable remelting

[0131] Vacuum level: 2.5 Pa;

[0132] Melting rate: 6.01 kg / min;

[0133] During smelting, helium is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 250 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 250 ml / min to 20 ml / min within 30 minutes.

[0134] The chemical composition of vacuum arc remelting steel ingots is shown in Table 11 below.

[0135] Table 11 Chemical composition of the secondary vacuum arc remelting steel ingot in Comparative Example 1

[0136]

[0137] The steel ingots prepared in this comparative example have high contents of O and N impurities, and poor uniformity of C chemical composition.

[0138] Comparative Example 2

[0139] Comparative Example 2 provides a vacuum double consumable steel ingot and its preparation method.

[0140] The difference between this comparative example and Example 1 is that the processes for the first vacuum arc remelting and the second vacuum arc remelting are different.

[0141] The method for preparing steel in this comparative example is as follows:

[0142] (1) Vacuum induction melting

[0143] Raw materials: Ni (grade 0), Co, Cr, Mo, Al, low-carbon steel, and carbon electrodes;

[0144] a) Full melting temperature: 1520℃;

[0145] b) Refining temperature: 1555℃;

[0146] c) Tap temperature: 1565℃;

[0147] d) Vacuum level during full melting period: 30 Pa;

[0148] e) Vacuum degree during refining: 2 Pa, maintain for 100 min.

[0149] Ingot type: Φ580mm, 5600kg; the chemical composition of the induction electrode is shown in Table 12 below.

[0150] Table 12 Chemical composition of the induction electrode in Comparative Example 2

[0151]

[0152] (2) Vacuum self-consumption remelting

[0153] Vacuum degree: 2.3 Pa;

[0154] Melting rate: 7.32 kg / min;

[0155] During smelting, helium is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 190 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 190 ml / min to 6 ml / min within 30 minutes.

[0156] The chemical composition of a vacuum arc remelted steel ingot is shown in Table 2 below.

[0157] Table 13 Chemical composition of the vacuum arc remelting steel ingot in Comparative Example 2

[0158]

[0159] (3) Secondary vacuum consumable remelting

[0160] Vacuum degree: 2.3 Pa;

[0161] Melting rate: 6.81 kg / min;

[0162] During smelting, helium is introduced for cooling. The flow rate is controlled according to the helium pressure reference. During the initial stage of helium cooling, the flow rate increases from 0 ml / min to 250 ml / min within 30 minutes. During the hot capping stage, the flow rate decreases from 250 ml / min to 20 ml / min within 30 minutes.

[0163] Casting: Φ660mm alloy ingot.

[0164] The chemical composition of vacuum arc remelting steel ingots is shown in Table 14 below.

[0165] Table 14 Chemical composition of the secondary vacuum arc remelting steel ingot in Comparative Example 2

[0166]

[0167] The steel ingots prepared in this comparative example have high contents of O and N impurities, and poor uniformity of C chemical composition.

[0168] Performance testing

[0169] The ultra-high strength SF1900 steel ingots with a diameter of 660mm from Examples 1, 2, and 3 were forged into 200mm steel bars using a high-speed forging mill. According to ASTM A604-93, the white spots, dark spots, radial segregation, and annular patterns in their low-magnification microstructure all reached AAAA grade. Their low-magnification microstructure ratings are shown in Table 15. Non-metallic inclusions were detected according to Method E in ASTM E 45, and the inclusion content in the steel was rated as shown in Table 16.

[0170] Table 15 Low-magnification microstructure ratings of ultra-high strength SF1900 steel in Examples 1, 2, and 3

[0171]

[0172] Table 16 Inclusion content in ultra-high strength SF1900 steel of Examples 1, 2 and 3

[0173]

[0174] Combining the test results in Tables 15-16 above and Tables 3, 6, and 9 of Examples 1-3, it can be seen that the ultra-high strength SF1900 steel Φ660mm ingots forged into Φ200mm steel bars using the triple smelting process of vacuum induction furnace (VIM) + vacuum arc remelting furnace (VAR) + vacuum arc remelting furnace (VAR) provided in this application have the following low-magnification microstructure: white spots, dark spots, radial segregation, and annular patterns all reach AAAA level. The number of non-metallic inclusions is less than 1 for A fine series 0 and B fine series 0.5; and less than 2 for C fine series 0 and D fine series 0.5. Moreover, the impurity elements are S < 0.001%, P < 0.006%, Si ≤ 0.02%, Mn ≤ 0.02%, Ti < 0.01%, O ≤ 0.0005%, and N ≤ 0.001%. This indicates that the steel ingots prepared by the technical solution of this application have achieved the goal of high purity and low segregation.

[0175] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot, characterized in that, Specifically, the process includes the following steps in sequence: vacuum induction melting, primary vacuum consumable remelting, and secondary vacuum consumable remelting. The process parameters for the single vacuum self-consumable remelting are as follows: melting rate is 5.5-6.5 kg / min; helium is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 230-280 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 230-280 ml / min to 15-25 ml / min within 30 minutes. The process parameters for the secondary vacuum consumable remelting are as follows: melting rate is 4.5-5.5 kg / min; helium is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 160-220 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 160-220 ml / min to 15-25 ml / min within 30 minutes. The chemical composition of the ultra-high strength SF1900 steel vacuum double consumable steel ingot, by weight percentage, is as follows: C 0.14-0.25%, Ni 13.00-15.00%, Mo 1.00-2.00%, Cr 1.5-3.0%, Co 9.00-11.00%, Al 0.85-0.95%, Si≤0.10%, Mn≤0.10%, Cu≤0.05%, S≤0.001%, P≤0.005%, O≤0.0005%, N≤0.001%, with the remainder being Fe and unavoidable impurities.

2. The method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot according to claim 1, characterized in that, In the vacuum induction melting step, the raw materials include No. 0 Ni or No. 1 Ni, Co metal, Cr metal, Mo metal, Al metal, low-carbon steel, and carbon electrode; the electrode is prepared by the vacuum induction melting step, and the ingot size of the electrode is Φ550-600mm and 5000-6000kg.

3. The method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot according to claim 2, characterized in that, The electrode ingot dimensions are: Φ580mm, 5600kg.

4. The method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot according to claim 1, characterized in that, The process parameters for the single vacuum self-consumable remelting are as follows: vacuum degree is 0.1-1 Pa, melting rate is 5.7-6.3 kg / min; helium is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 240-260 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 240-260 ml / min to 17-23 ml / min within 30 minutes.

5. The method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot according to claim 4, characterized in that, The process parameters for the single vacuum self-consumable remelting are as follows: vacuum degree is 0.5-1 Pa, melting rate is 5.8-6.2 kg / min; helium is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 245-255 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 245-255 ml / min to 18-22 ml / min within 30 minutes.

6. The method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot according to claim 1, characterized in that, The process parameters for the secondary vacuum self-consuming remelting are as follows: vacuum degree is 0.1-1 Pa, melting rate is 4.7-5.3 kg / min; helium gas is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 170-210 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 170-210 ml / min to 18-22 ml / min within 30 minutes.

7. The method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot according to claim 6, characterized in that, The process parameters for the secondary vacuum self-consuming remelting are as follows: vacuum degree is 0.1-0.4 Pa, melting rate is 4.8-5.2 kg / min; helium gas is introduced for cooling during melting, and during the initial stage of helium cooling, the flow rate increases from 0 ml / min to 180-200 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 180-200 ml / min to 18-22 ml / min within 30 minutes.

8. The method for preparing ultra-high strength SF1900 steel vacuum double consumable steel ingot according to claim 1, characterized in that, The steel ingots prepared by this method have an ingot size of Φ650-700mm alloy casting.

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