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

Abstract

The application relates to the technical field of ultrahigh-strength steel materials, and particularly discloses a preparation method of an ultrahigh-strength SF1900 steel vacuum consumable ingot. The preparation method of the ultrahigh-strength SF1900 steel vacuum consumable ingot comprises vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting. The application is produced by adopting a vacuum induction furnace + protective atmosphere electroslag + vacuum consumable furnace three-in-one smelting process, realizes comprehensive optimization of purity, inclusion control, composition uniformity and solidification structure, and improves the solidification structure, macrosegregation and chemical composition uniformity consistency of the ingot.

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 consumable steel ingots. 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-process smelting method: vacuum induction melting + protective atmosphere electroslag remelting or vacuum induction melting + vacuum arc remelting. In the dual-process smelting of vacuum induction melting + protective atmosphere electroslag remelting, the protective atmosphere electroslag remelting has unique advantages in desulfurization and inclusion removal, but it is inferior in terms of steel purity, gas control, and solidification structure control. In the dual-process smelting of vacuum induction melting + vacuum arc remelting, the desulfurization capacity and oxide inclusion modification effect during remelting are relatively poor. Summary of the Invention

[0003] To address the aforementioned technical problems, this application provides a method for preparing ultra-high strength SF1900 steel vacuum consumable steel ingots.

[0004] This application provides a method for preparing ultra-high strength SF1900 steel vacuum consumable steel ingot, which specifically includes the following steps in sequence: vacuum induction melting, protective atmosphere electroslag remelting, and vacuum consumable remelting;

[0005] The process parameters for the protective atmosphere electroslag remelting are as follows: the slag material is pre-melted slag, and the slag system and ratio by weight percentage are CaF2:Al2O3:CaO:MgO=60-70%:15-25%:8-12%:3-7%; the melting rate is 5.0-7.0 kg / h; and the protective atmosphere is Ar gas.

[0006] The process parameters for 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 220-280 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 220-280 ml / min to 15-25 ml / min within 30 minutes.

[0007] The purpose of the smelting process of the ultra-high strength SF1900 steel provided in this application is to smelt a new type of ultra-high strength SF1900 steel consumable ingot with low raw material cost, good hot working performance and ultra-high purity in industrial production.

[0008] The successful smelting of ultra-high strength SF1900 steel using a triple process of vacuum induction melting, protective atmosphere electroslag remelting, and vacuum arc remelting 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.

[0009] 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.

[0010] Preferably, in the vacuum induction melting step, the refining temperature = total melting temperature + (10-20℃) and the tapping temperature = total melting temperature + (30-40℃).

[0011] In one specific implementation, in the vacuum induction melting step, the full melting temperature is 1530℃; the refining temperature is 1545℃; the tapping temperature is 1565℃; the vacuum degree during the full melting period is 20-40Pa; and the vacuum degree during the refining period is 2Pa, maintained for 100min.

[0012] In one specific implementation, in the vacuum induction melting step, the full melting temperature is 1535℃; the refining temperature is 1540℃; the tapping temperature is 1570℃; the vacuum degree during the full melting period is 20-40Pa; and the vacuum degree during the refining period is 2Pa, maintained for 100min.

[0013] In one specific implementation, in the vacuum induction melting step, the full melting temperature is 1525℃; the refining temperature is 1550℃; the tapping temperature is 1570℃; the vacuum degree during the full melting period is 20-40Pa; and the vacuum degree during the refining period is 2Pa, maintained for 100min.

[0014] 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.

[0015] Preferably, in the protective atmosphere electroslag remelting step, the pre-melted slag, by weight percentage, has a slag system and ratio of CaF2:Al2O3:CaO:MgO = 62-67%:16-23%:9-11%:4-6%.

[0016] In one specific implementation, in the protective atmosphere electroslag remelting step, the pre-melted slag, by weight percentage, has a slag system and ratio of CaF2:Al2O3:CaO:MgO=65%:20%:10%:5%.

[0017] Preferably, in the protective atmosphere electroslag remelting step, the melting rate is 5.5-6.5 kg / h.

[0018] Preferably, in the protective atmosphere electroslag remelting step, the melting rate is 5.7-6.2 kg / h.

[0019] Preferably, in the vacuum consumable remelting, the melting rate is 4.7-5.3 kg / min; during the melting process, helium gas is introduced for cooling, 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 17-22 ml / min within 30 minutes.

[0020] In the specific implementation scheme, the chemical composition of the ultra-high strength SF1900 steel vacuum 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%, Ti < 0.01%, Si: ≤ 0.10%, Mn: ≤ 0.10%, Cu ≤ 0.05%, S ≤ 0.0007%, P ≤ 0.006%, O ≤ 15 ppm, N ≤ 15 ppm, with the remainder being Fe and unavoidable impurities.

[0021] In summary, the technical solution of this application has the following effects:

[0022] This application employs a triple smelting process: vacuum induction furnace (VIM), protective atmosphere electroslag remelting (PESR), and vacuum arc remelting (VAR). The unique advantages of PESR in desulfurization and inclusion removal are perfectly combined with the advantages of VIM and VAR in purity, gas control, and solidification structure. This achieves comprehensive optimization of purity, inclusion control, compositional uniformity, and solidification structure. By selecting appropriate slag materials and process parameters, the S content is reduced to a low level, sulfide and some oxide inclusions are removed, and the hard, angular Al2O3 oxides are transformed into softer, more spherical calcium aluminates, significantly reducing the detrimental effects of inclusions on fatigue performance. The PESR protective atmosphere electroslag remelting prevents secondary oxidation during the smelting process, allowing for precise control of the Al content. The subsequent VAR (vacuum arc remelting) process is carried out under vacuum to further remove gases (H, O, N) and provide an additional opportunity to remove any tiny inclusions that may remain after PESR, thereby improving the uniformity of the solidification structure, macrosegregation, and chemical composition of the steel ingot.

[0023] This application employs a triple (VIM+PESR+VAR) smelting process to manufacture Φ660mm steel ingots. VIM utilizes high-vacuum smelting, controlling the gas content in the steel before Al addition, and 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 kept at low levels. PESR uses an Ar-protected atmosphere electroslag quaternary slag system to avoid air pollution, further stabilize deoxidation and desulfurization, and the slag pool can also adsorb some gases and non-metallic inclusions. VAR remelting uses high vacuum and a low melting rate to achieve further degassing, inclusion removal, and uniform microstructure. Steel ingots are forged using a high-speed forging mill to produce steel bars of Φ200mm. Inspection shows that their low-magnification microstructure—including white spots, dark spots, radial segregation, and annular patterns—all reach AAAA level. Among non-metallic inclusions, the number of inclusions in the A fine series (grade 0), 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 two. Impurity elements are categorized as follows: S < 0.0007%, P < 0.006%, Ti < 0.01%, Si ≤ 0.10%, Mn ≤ 0.10%, O ≤ 15ppm, and N ≤ 15ppm. This achieves high purity and low segregation. Furthermore, the VIM-PESR-VAR triple process has a cost advantage over the VIM-VAR-VAR triple process. Detailed Implementation

[0024] 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. Example Example 1

[0025] Example 1 provides a method for preparing ultra-high strength SF1900 steel vacuum consumable steel ingot.

[0026] The preparation method of ultra-high strength SF1900 steel in this embodiment is as follows:

[0027] (1) Vacuum induction melting

[0028] The raw materials used are No. 0 Ni, metallic Co, metallic Cr, metallic Mo, metallic Al, low-carbon high-quality steel, and carbon electrodes.

[0029] a) Full melting temperature: 1530℃;

[0030] b) Refining temperature: 1545℃;

[0031] c) Tap temperature: 1565℃;

[0032] d) Vacuum level during full melting period: 25 Pa;

[0033] e) Vacuum degree during refining: 2 Pa, maintain for 100 min.

[0034] Ingot type: Φ580mm, 5600kg; the chemical composition of the induction electrode is shown in Table 1 below.

[0035] Table 1 Chemical composition of the induction electrode in Example 1

[0036]

[0037] (2) Protective atmosphere electroslag remelting

[0038] The slag mix ratio is CaF2:Al2O3:CaO:MgO = 65%:20%:10%:5%;

[0039] Melting rate: 6.08 kg / min.

[0040] Protective atmosphere: Ar gas protection.

[0041] The chemical composition of electroslag ingots is shown in Table 2 below.

[0042] Table 2 Chemical composition of electroslag ingots in Example 1

[0043]

[0044] (3) Vacuum consumable remelting

[0045] Melting speed: 5.03kg / min;

[0046] 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.

[0047] Casting: Φ660mm steel ingot; the chemical composition of the vacuum arc remelted steel ingot is shown in Table 3 below.

[0048] Table 3 Chemical composition of vacuum arc remelted steel ingots in Example 1

[0049]

[0050] 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. Example 2

[0051] Example 2 provides a method for preparing ultra-high strength SF1900 steel vacuum consumable steel ingots.

[0052] The preparation method of ultra-high strength SF1900 steel in this embodiment is as follows:

[0053] (1) Vacuum induction melting

[0054] a) Full melting temperature: 1535℃;

[0055] b) Refining temperature: 1540℃;

[0056] c) Tap temperature: 1570℃;

[0057] d) Vacuum level during full melting period: 25 Pa;

[0058] e) Vacuum degree during refining: 2 Pa, maintain for 100 min.

[0059] The chemical composition of the induction electrode is shown in Table 4 below.

[0060] Table 4 Chemical composition of the induction electrode in Example 2

[0061]

[0062] (2) Protective atmosphere electroslag remelting

[0063] The slag mix ratio is CaF2:Al2O3:CaO:MgO = 65%:20%:10%:5%;

[0064] Melting rate: 6.68 kg / min.

[0065] Protective atmosphere: Ar gas protection

[0066] The chemical composition of electroslag ingots is shown in Table 5 below.

[0067] Table 5 Chemical composition of electroslag ingots in Example 2

[0068]

[0069] (3) Vacuum consumable remelting

[0070] Melting rate: 4.65 kg / min;

[0071] 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.

[0072] Casting: Φ660mm steel ingot; the chemical composition of the vacuum arc remelted steel ingot is shown in Table 6 below.

[0073] Table 6 Chemical composition of vacuum arc remelted steel ingots in Example 2

[0074]

[0075] The steel ingots prepared in this embodiment have qualified composition, and the control is precise and stable. Example 3

[0076] Example 3 provides a method for preparing ultra-high strength SF1900 steel vacuum consumable steel ingot.

[0077] The preparation method of ultra-high strength SF1900 steel in this embodiment is as follows:

[0078] (1) Vacuum induction melting

[0079] a) Full melting temperature: 1525℃;

[0080] b) Refining temperature: 1550℃;

[0081] c) Tap temperature: 1570℃;

[0082] d) Vacuum level during full melting period: 25 Pa;

[0083] e) Vacuum degree during refining: 2 Pa, maintain for 100 min.

[0084] The chemical composition of the induction electrode is shown in Table 7 below.

[0085] Table 7 Chemical composition of the induction electrode in Example 3

[0086]

[0087] (2) Protective atmosphere electroslag remelting

[0088] The slag mix ratio is CaF2:Al2O3:CaO:MgO = 65%:20%:10%:5%;

[0089] Melting rate: 5.12 kg / min.

[0090] Protective atmosphere: Ar gas protection

[0091] The chemical composition of electroslag ingots is shown in Table 8 below.

[0092] Table 8 Chemical composition of electroslag ingots in Example 3

[0093]

[0094] (3) Vacuum consumable remelting

[0095] Melting rate: 5.42 kg / min;

[0096] 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.

[0097] Casting: Φ660mm steel ingot; the chemical composition of the vacuum arc remelted steel ingot is shown in Table 9 below.

[0098] Table 9 Chemical composition of vacuum arc remelted steel ingots in Example 3

[0099] Comparative Example Comparative Example 1

[0100] Comparative Example 1 provides a method for preparing ultra-high strength SF1900 steel vacuum consumable steel ingots.

[0101] The difference between this comparative example and Example 1 is that no protective atmosphere electroslag remelting was performed.

[0102] The preparation method of ultra-high strength SF1900 steel in this comparative example is as follows:

[0103] (1) Vacuum induction melting

[0104] a) Full melting temperature: 1530℃;

[0105] b) Refining temperature: 1545℃;

[0106] c) Tap temperature: 1565℃;

[0107] d) Vacuum level during full melting period: 25 Pa;

[0108] e) Vacuum degree during refining: 2 Pa, maintain for 100 min.

[0109] The chemical composition of the induction electrode is shown in Table 10 below.

[0110] Table 10 Chemical composition of the induction electrode in Comparative Example 1

[0111]

[0112] (2) Vacuum consumable remelting

[0113] Melting speed: 5.03kg / min;

[0114] 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.

[0115] Casting: Φ660mm steel ingot; the chemical composition of the vacuum arc remelted steel ingot is shown in Table 3 below.

[0116] Table 11 Chemical composition of vacuum arc remelted steel ingots in Comparative Example 1

[0117]

[0118] The steel ingots prepared in this comparative example have a high content of S impurity elements and poor uniformity in the chemical composition of C and Al. Comparative Example 2

[0119] Comparative Example 2 provides a method for preparing ultra-high strength SF1900 steel vacuum consumable steel ingots.

[0120] The difference between this comparative example and Example 1 is that the process parameters for protective atmosphere electroslag remelting and vacuum arc remelting are different.

[0121] The preparation method of ultra-high strength SF1900 steel in this comparative example is as follows:

[0122] (1) Vacuum induction melting

[0123] a) Full melting temperature: 1530℃;

[0124] b) Refining temperature: 1545℃;

[0125] c) Tap temperature: 1565℃;

[0126] d) Vacuum level during full melting period: 25 Pa;

[0127] e) Vacuum degree during refining: 2 Pa, maintain for 100 min.

[0128] The chemical composition of the induction electrode is shown in Table 12 below.

[0129] Table 12 Chemical composition of the induction electrode in Comparative Example 2

[0130]

[0131] (2) Protective atmosphere electroslag remelting

[0132] The slag mix ratio is CaF2:Al2O3:CaO:MgO = 65%:15%:15%:5%;

[0133] Melting rate: 7.32 kg / min.

[0134] Protective atmosphere: Ar gas protection.

[0135] The chemical composition of electroslag ingots is shown in Table 13 below.

[0136] Table 13 Chemical composition of electroslag ingots in Comparative Example 2

[0137]

[0138] (3) Vacuum consumable remelting

[0139] Melting rate: 5.83 kg / min;

[0140] 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.

[0141] Casting: Φ660mm steel ingot; the chemical composition of the vacuum arc remelted steel ingot is shown in Table 14 below.

[0142] Table 14 Chemical composition of vacuum arc remelted steel ingots in Comparative Example 2

[0143]

[0144] The steel ingots prepared in this comparative example have high contents of S, O, and N impurities, and poor uniformity of Al chemical composition.

[0145] Performance testing

[0146] The ultra-high strength SF1900 steel ingots with a diameter of 660mm from Examples 1-3 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.

[0147] Table 15 Low-magnification microstructure rating of ultra-high strength SF1900 steel in Examples 1-3

[0148]

[0149] Table 16 Inclusion content in ultra-high strength SF1900 steel of Examples 1-3

[0150]

[0151] 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 VIM+PESR+VAR triple smelting process provided in this application have low-magnification microstructures: 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-series fine inclusions (0 grade) and B-series fine inclusions (0.5 grade); and less than 2 for C-series fine inclusions and D-series fine inclusions (0 grade). Furthermore, the impurity elements are: S < 0.0007%, P < 0.004%, Si ≤ 0.02%, Mn ≤ 0.02%, Ti < 0.01%, O ≤ 5ppm, and N ≤ 7ppm. This indicates that the steel ingots prepared by the technical solution of this application achieve high purity and low segregation.

[0152] 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 consumable steel ingot, characterized in that, Specifically, the process includes the following steps in sequence: vacuum induction melting, protective atmosphere electroslag remelting, and vacuum consumable remelting. The process parameters for the protective atmosphere electroslag remelting are as follows: the slag material is pre-melted slag, and the slag system and ratio by weight percentage are CaF2:Al2O3:CaO:MgO=60-70%:15-25%:8-12%:3-7%; the melting rate is 5.0-7.0 kg / h; and the protective atmosphere is Ar gas. The process parameters for vacuum self-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 220-280 ml / min within 30 minutes, and during the hot capping stage, the flow rate decreases from 220-280 ml / min to 15-25 ml / min within 30 minutes. The chemical composition of the ultra-high strength SF1900 steel vacuum 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%, Ti < 0.01%, Si: ≤ 0.10%, Mn: ≤ 0.10%, Cu ≤ 0.05%, S ≤ 0.0007%, P ≤ 0.006%, O ≤ 15 ppm, N ≤ 15 ppm, with the remainder being Fe and unavoidable impurities.

2. The method for preparing ultra-high strength SF1900 steel vacuum consumable 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 Φ550-660mm and 5000-6000kg.

3. The method for preparing ultra-high strength SF1900 steel vacuum consumable ingot according to claim 1, characterized in that, In the protective atmosphere electroslag remelting step, the pre-melted slag, by weight percentage, has a slag system and ratio of CaF2:Al2O3:CaO:MgO=62-67%:16-23%:9-11%:4-6%.

4. The method for preparing ultra-high strength SF1900 steel vacuum consumable ingot according to claim 1, wherein the method for preparing the ultra-high strength SF1900 steel vacuum consumable ingot is characterized in that, In the protective atmosphere electroslag remelting step, the melting rate is 5.5-6.5 kg / h.

5. The method for preparing ultra-high strength SF1900 steel vacuum consumable ingot according to claim 1, wherein the method for preparing the ultra-high strength SF1900 steel vacuum consumable ingot is characterized in that, In the protective atmosphere electroslag remelting step, the melting rate is 5.7-6.2 kg / h.

6. The method for preparing ultra-high strength SF1900 steel vacuum consumable ingot according to claim 1, characterized in that, In the vacuum self-consuming remelting process, the melting rate is 4.7-5.3 kg / min; during the melting process, helium gas is introduced for cooling. In the initial stage of helium cooling, the flow rate increases from 0 ml / min to 240-260 ml / min within 30 minutes, and in the hot capping stage, the flow rate decreases from 240-260 ml / min to 17-22 ml / min within 30 minutes.

7. The method for preparing ultra-high strength SF1900 steel vacuum consumable ingot according to claim 1, characterized in that, The chemical composition of the ultra-high strength SF1900 steel vacuum 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%, Ti < 0.01%, Si: ≤ 0.02%, Mn: ≤ 0.02%, Cu ≤ 0.05%, S ≤ 0.0007%, P ≤ 0.004%, O ≤ 5 ppm, N ≤ 7 ppm, with the remainder being Fe and unavoidable impurities.

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