Preparation method of ultra-high strength C250 ultra-large size vacuum consumable steel ingot

Abstract

This application relates to the technical field of metal material manufacturing and specifically discloses a method for preparing ultra-high-strength C250 ultra-large vacuum consumable steel ingots. This preparation method includes vacuum induction smelting and vacuum consumable remelting; the alloying process in a vacuum induction furnace involves precise control of the chemical composition, specifically C0.006±0.001wt%, Ni18.0±0.20wt%, Co8.0±0.05wt%, Mo5.0±0.10wt%, Ti0.40±0.01wt%, and Al0.10±0.02wt%. This application addresses issues such as controlling the chemical composition points and uniformity of ultra-large C250 vacuum induction Φ710mm electrodes and Φ810mm vacuum consumable steel ingots, achieving a metallurgical quality of the ultra-large vacuum consumable steel ingots that fully matches the physical quality of small-sized steel bars.

Description

Technical Field

[0001] The present application relates to the technical field of metal material manufacturing, and more specifically, to a method for preparing ultra-high strength C250 ultra-large size vacuum consumable steel ingots. Background Art

[0002] An aircraft engine is a highly complex and sophisticated thermal machine that provides the power required for aircraft to fly. As the heart of the aircraft, it is known as the "flower of industry" and directly affects the performance, reliability and economy of the aircraft. It is an important manifestation of a country's scientific and technological, industrial and national defense strength.

[0003] With the rapid development of my country's national defense construction and the accelerated upgrading of weapons and equipment, aircraft are developing towards larger and longer-range capabilities, and the raw materials used for engine shafts are developing towards larger specifications and sizes. Currently, the C250 steel used for my country's civil aviation engine shafts is produced using vacuum induction and vacuum consumable steel production processes. The steel bar production specifications are mainly Φ≤304mm, and the vacuum consumable steel ingots used are Φ660mm in size. To meet the demand for large-scale production, the specifications of the raw materials are required to be significantly increased from the original Φ≤304mm to Φ≤375mm. At the same time, in order to improve the utilization rate of forgings in each batch of furnaces, it is necessary to increase the size and weight of the steel ingots to increase the weight of the delivered finished steel bars from the original Φ660mm steel ingots to Φ810mm steel ingots.

[0004] There is no mature technology for the vacuum induction smelting and consumable remelting production of ultra-large vacuum consumable ingots of C250 steel. It is necessary to conduct process exploration, testing and trial production of each production process of vacuum smelting of 12-ton vacuum induction Φ710mm electrode rods and consumable remelting of Φ810mm steel ingots, so that the comprehensive metallurgical quality of ultra-large C250 steel bars can fully meet the technical specifications of small-sized Φ300mm round bars, which makes production extremely difficult. Summary of the Invention

[0005] In view of the above relevant analysis, this application aims to provide a method for preparing ultra-high strength C250 ultra-large size vacuum consumable steel ingots, which can prominently solve the following technical problems: (1) precise point control of the chemical composition of Φ710mm electrode rods produced by a 12-ton vacuum induction furnace; (2) low segregation control of the composition structure of Φ810mm steel ingots produced by a 12-ton vacuum consumable furnace, ensuring the uniformity of the chemical composition of the head and tail of the ultra-large size steel ingots.

[0006] The present application provides a preparation method of ultra-high strength C250 ultra-large size vacuum consumable steel ingot, which adopts a smelting method of a vacuum induction furnace + a vacuum consumable furnace to produce a chemical composition of C0.006±0.001wt%, Ni18.0±0.20wt%, Co8.0±0.05wt%, Mo5.0±0.10wt%, Ti0.40±0.01wt%, and Al0.10±0.02wt%.

[0007] The preparation method includes vacuum induction smelting and vacuum consumable remelting;

[0008] In the vacuum induction smelting, the chemical composition requirements are as follows: C 0.006±0.001wt%; Mn≤0.05wt%; Si≤0.05wt%; S≤0.001wt%; P≤0.005wt%; Ni 18.0±0.20wt%; Co 8.0±0.05wt%; Ti 0.40±0.01wt%; Mo 5.0±0.10wt%; AI 0.10±0.02wt%; O≤0.0010wt%; N≤0.0010wt%;

[0009] Vacuum induction melting process: full melting temperature T is 1490-1540℃;

[0010] Vacuum induction refining process: refining temperature T is 1540-1610℃, vacuum degree ≤5Pa;

[0011] Alloying process in vacuum induction furnace: precise control of chemical composition, specifically C0.006±0.001wt%, Ni18.0±0.20wt%, Co8.0±0.05wt%, Mo5.0±0.10wt%, Ti0.40±0.01wt%, Al0.10±0.02wt%;

[0012] Vacuum induction pouring process: pouring temperature T is 1550-1580℃, vacuum degree ≤300Pa;

[0013] Cooling process of vacuum induction electrode rod: The cooling time t of electrode rod in mold is 1-3h, and air cooling is carried out after demoulding;

[0014] Vacuum induction electrode rod surface polishing;

[0015] In the vacuum consumable remelting, the vacuum consumable melting stage: melting rate R = 5.5-6.5Kg / min;

[0016] Vacuum consumable steel ingots are air-cooled and surface-polished.

[0017] Optionally, the raw materials for the vacuum induction smelting are composed of refined steel, alloy materials, and metal materials, and the raw materials are required to have accurate composition and be free of rust, oil, and dirt on the surface.

[0018] Optionally, the chemical composition of the vacuum consumable steel ingot is precisely controlled to ensure uniform chemical composition.

[0019] In summary, this application has the following beneficial effects:

[0020] (1) This application uses a 12-ton vacuum induction furnace. Through precise batching and accurate calculation, it realizes the control of chemical element points in steel. By controlling the content of Mn, Si, S, and P in steel, it reduces the generation and aggregation of inclusions in steel, improves the purity of steel, and achieves a high match between the strength and toughness of steel.

[0021] (2) During the refining process in the vacuum induction furnace, the present application adopts a low vacuum stirring method to continuously remove O and N from the steel, thereby improving the purity of the molten steel and the uniformity of the chemical composition of the electrode rod.

[0022] (3) This application adopts low-temperature pouring during the pouring process of the vacuum induction furnace to reduce the shrinkage holes of the oversized electrode rods, move the chemical composition segregation area upward, and achieve uniform chemical composition consistency of the oversized electrode rods.

[0023] (4) In the vacuum consumable remelting process, the present application strictly controls the electrode melting rate (R=5.5-6.5Kg / min) to improve the uniformity of macrostructure of ultra-large steel bars and solve the problems of radial segregation and excessive annular patterns of macrostructure. DETAILED DESCRIPTION

[0024] Before describing the embodiments of the present application in detail, it should be understood that the terminology used herein is only for the purpose of describing particular embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the term belongs.

[0025] Currently, C250 steel for civil aviation engine shafts in my country is manufactured using a vacuum induction and vacuum consumable smelting method. To meet the demands of large-scale and long-distance development, the Φ≤304mm steel bars produced from the current mature Φ660mm steel ingots are no longer sufficient. The need arises to increase the size and weight of the steel ingots, thereby increasing the size of the finished steel bars, increasing the delivered weight of the steel bars, and improving the utilization rate of each batch of forgings to further meet the demands of large-scale tasks.

[0026] As ingot sizes continue to expand, inclusions and chemical composition segregation become increasingly severe, significantly impacting the performance of oversized ingots. To meet the performance specifications of smaller ingots, the production of ultra-high-strength C250 oversized ingots is an urgent need in my country.

[0027] This application achieves precise point control of the composition of large-size Φ710mm electrode rods and low segregation control of Φ810mm vacuum consumable steel ingots by precisely controlling the steps of the vacuum induction smelting production process. The comprehensive mechanical properties of the ultra-large-size steel ingots can meet the technical specifications and are stable.

[0028] This application provides a method for preparing ultra-high strength C250 ultra-large vacuum consumable steel ingots using a 12-ton vacuum induction furnace. The preparation method comprises:

[0029] (1) Vacuum induction smelting

[0030] The raw materials used in vacuum induction furnace smelting are C250 steel, a special ultra-pure refined steel; Ni plate, M-Co, M-Mo, M-Ti, M-Al, and other metal materials. The raw materials must have accurate chemical composition and be free of rust, oil, and dirt. The specific chemical composition (wt%) control requirements for the electrode rods are as follows: C 0.006±0.001wt%; Mn ≤ 0.05wt%; Si ≤ 0.05wt%; S ≤ 0.001wt%; P ≤ 0.005wt%; Ni 18.0±0.20wt%; Co 8.0±0.05wt%; Ti 0.40±0.01wt%; Mo 5.0±0.10wt%; Al 0.10±0.02wt%; O ≤ 0.0010wt%; N ≤ 0.0010wt%.

[0031] Vacuum induction melting process: the full melting temperature T is 1490-1540℃.

[0032] Vacuum induction refining process: refining temperature T is 1540-1610℃, vacuum degree ≤5Pa.

[0033] Alloying process in a vacuum induction furnace: The chemical composition (wt%) is precisely controlled, specifically C0.006±0.001wt%, Ni18.0±0.20wt%, Co8.0±0.05wt%, Mo5.0±0.10wt%, Ti0.40±0.01wt%, and Al0.10±0.02wt%.

[0034] Vacuum induction pouring process: pouring temperature T is 1550-1580℃, vacuum degree ≤300Pa.

[0035] Vacuum induction electrode rod cooling process: The electrode rod in-mold cooling time t is 1-3h, and air cooling is performed after demoulding.

[0036] The surface of the vacuum induction electrode rod is polished.

[0037] (2) Vacuum consumable remelting

[0038] Vacuum self-consumption starting stage: voltage 21.0-24.0V; current 6-16KA.

[0039] Vacuum consumable melting stage: melting rate R = 5.5-6.5Kg / min; vacuum degree 0.35-045Pa.

[0040] Vacuum consumable steel ingots are air-cooled and surface-polished.

[0041] Compared with the current C250 double vacuum technology, this application provides the vacuum induction smelting technology for ultra-large Φ810mm steel ingots for the first time, which is an unprecedented breakthrough in metallurgical technology.

[0042] The strict control of the vacuum consumable remelting process in this application solves the problem of low-magnification microstructure uniformity, chemical composition, and inclusion segregation in ultra-large-sized steel ingots. The preparation method of this application can produce ultra-pure, ultra-high-strength C250 ultra-large-sized steel ingots that pass magnetic particle inspection.

[0043] By adopting the preparation method of the present application, the heat treatment mechanical properties of the super-large size steel ingots are excellent, which can fully meet the technical index requirements of small size bars, and at the same time the yield rate of the steel ingots is greatly improved.

[0044] To make the purpose, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0045] The present application is further described in detail below in conjunction with the embodiments and performance test results. Example Example 1

[0046] This embodiment provides a method for preparing ultra-high strength C250 ultra-large size vacuum consumable steel ingots. This embodiment uses a 12-ton vacuum induction furnace.

[0047] The preparation method specifically comprises the following steps:

[0048] (1) Vacuum induction furnace smelting

[0049] 1. The raw materials used in vacuum induction furnace smelting are C250 steel, a special ultra-pure refined steel; Ni plate, M-Co, M-Mo, M-Ti, M-Al, and other metal materials. The raw materials must have accurate chemical composition and be free of rust, oil, and contamination. Specific control requirements for the chemical composition of the electrode rods are shown in Table 1.

[0050] 2. Vacuum induction melting process: The raw materials are added to the crucible in batches and melted by electricity. The full melting temperature T is 1530℃.

[0051] 3. Vacuum induction refining process: After the charge is fully melted, the furnace is evacuated for refining. The refining temperature T is 1575℃, stirring is performed, and the vacuum degree is 3.5Pa.

[0052] 4. Vacuum Induction Alloying Process: After melting and refining the charge, samples were taken for analysis, revealing C 0.005%, Ni 17.89%, Mo 5.05%, Ti 0.35%, and Al 0.12%. Accurate calculations and adjustments were made to the control points required for the chemical composition, completing the alloying process to ensure the chemical composition met technical standards.

[0053] 5. Vacuum induction pouring process: pouring is carried out after the chemical composition meets the technical standard requirements, the pouring temperature is 1555℃ and the vacuum degree is 230Pa.

[0054] 6. Cooling process of vacuum induction electrode rod: The electrode rod is mold-cooled for 2 hours and then air-cooled.

[0055] 7. Polishing the surface of vacuum induction electrode rod.

[0056] The chemical composition of the finished vacuum induction electrode rod is shown in Table 1.

[0057] Table 1 Chemical composition of finished electrode rod (wt%)

[0058]

[0059] (2) Vacuum consumable remelting

[0060] 1. Vacuum self-consumption starting stage: voltage 21.0-24.0V; current 6-16KA.

[0061] 2. Vacuum consumable melting stage: melting rate R = 6.5Kg / min; vacuum degree 0.41Pa.

[0062] 3. Vacuum self-consumable hot capping stage: the starting weight of the steel ingot hot capping is 500Kg; the ending weight of the steel ingot hot capping is 120Kg.

[0063] 4. Heat treatment process of vacuum consumable steel ingot: vacuum consumable steel ingot is air-cooled and the surface is polished. Example 2

[0064] This embodiment provides a method for preparing ultra-high strength C250 ultra-large size vacuum consumable steel ingot.

[0065] The differences between this embodiment and embodiment 1 are as follows:

[0066] (1) The chemical composition of the finished vacuum induction electrode rod is shown in Table 1. The differences in vacuum induction furnace smelting are as follows:

[0067] The total melting temperature T in the vacuum induction melting process is 1525°C.

[0068] The refining temperature T of the vacuum induction refining process is 1580°C and the vacuum degree is 3.6Pa.

[0069] Vacuum induction alloying process: After melting and refining the charge, sampling and analysis revealed C 0.006%, Ni 17.83%, Mo 4.97%, Ti 0.37%, and Al 0.07%. Accurate calculations and adjustments were made to the electrode rod's chemical composition control requirements to complete the alloying process, ensuring the chemical composition met technical standards.

[0070] The pouring temperature of the vacuum induction pouring process is 1560°C and the vacuum degree is 220Pa.

[0071] (2) The differences between vacuum consumable remelting are as follows:

[0072] Vacuum consumable melting stage: melting rate R = 6.4Kg / min; vacuum degree 0.40Pa. Example 3

[0073] This embodiment provides a method for preparing ultra-high strength C250 ultra-large size vacuum consumable steel ingot.

[0074] The differences between this embodiment and embodiment 1 are as follows:

[0075] (1) The chemical composition of the finished vacuum induction electrode rod is shown in Table 1. The differences in vacuum induction furnace smelting are as follows:

[0076] The total melting temperature T in the vacuum induction melting process is 1528°C.

[0077] The refining temperature T of the vacuum induction refining process is 1578°C and the vacuum degree is 3.5Pa.

[0078] Vacuum induction alloying process: After melting and refining the charge, sampling and analysis revealed C 0.006%, Ni 17.99%, Mo 5.09%, Ti 0.37%, and Al 0.11%. Accurate calculations and adjustments were made to the electrode rod's chemical composition control requirements to complete the alloying process, ensuring the chemical composition met technical standards.

[0079] The pouring temperature of the vacuum induction pouring process is 1560°C and the vacuum degree is 225Pa.

[0080] (2) The differences between vacuum consumable remelting are as follows:

[0081] Vacuum consumable melting stage: melting rate R = 6.3Kg / min; vacuum degree 0.45Pa.

[0082] Performance testing

[0083] The following performance tests were performed on the ultra-high strength C250 ultra-large size vacuum consumable steel ingots prepared in the above examples.

[0084] (1) Chemical composition analysis and testing

[0085] The detection method refers to "3 Sampling and sample preparation methods for finished product analysis" and "5 Permissible deviations of chemical composition of finished products" in GB / T222-2006 "Permissible tolerances for chemical composition of finished products of steel" and GB / T223 "Chemical analysis methods for steel and alloys".

[0086] The test results are shown in Table 2.

[0087] Table 2 Chemical composition of steel ingot (wt%)

[0088]

[0089] (2) Low-magnification tissue detection

[0090] The test method refers to ASTM A604-2007 "Standard Practice for Macroetch Testing of Consumable Electrode Remelted Steel Bars and Billets".

[0091] The test results are shown in Table 3.

[0092] Table 3 Low-magnification tissue detection results

[0093]

[0094] (3) Mechanical properties testing

[0095] The test methods refer to GB / T 228 "Metallic Materials Room Temperature Tensile Test Method", GB / T 229 "Metal Charpy Notch Impact Test Method", GB / T 230 "Metal Rockwell Hardness Test Method", and GB / T4161 "Metallic Materials Plane Strain Fracture Toughness KIC Test Method".

[0096] The test results are shown in Table 4.

[0097] Table 4 Mechanical properties test results

[0098]

[0099] (IV) Non-metallic debris and grain size detection

[0100] The detection method refers to GB / T 10561 "Determination of non-metallic inclusion content in steel - Standard rating chart microscopic examination method".

[0101] The test results are shown in Table 5.

[0102] Table 5 Non-metallic impurities and grain size

[0103]

[0104] According to the test results in Tables 2 to 5, the chemical composition, macrostructure, mechanical properties, non-metallic impurities and grain size of the ultra-high strength C250 ultra-large size vacuum consumable steel ingot prepared by the preparation method of the present application can meet the requirements of the technical standards. Comparative Example

[0105] This comparative example provides a method for preparing an ultra-high-strength C250 ultra-large vacuum consumable steel ingot. This comparative example differs from Example 1 in that: (II) during the vacuum consumable remelting step, the melting rate R during the vacuum consumable remelting phase is 7.0 kg / min. The remaining steps remain the same as in Example 1.

[0106] The ultra-high strength C250 ultra-large vacuum consumable steel ingot prepared in the above preparation example was subjected to macroscopic microstructure testing. The testing method was based on ASTM A604-2007, "Standard Practice for Macroscopic Etching of Consumable Electrode Remelted Steel Bars and Billets."

[0107] The test results are shown in Table 6.

[0108] Table 6 Macroscopic tissue test results of Example 1 and Comparative Example

[0109]

[0110] As can be seen from Table 6, by comparing the macrostructure test results of Example 1 and the comparative example, it can be seen that when the melting rate R=7.0Kg / min in the vacuum consumable melting stage in the vacuum consumable remelting step, it will obviously affect the radial segregation and annular pattern results of the ultra-high strength C250 ultra-large size vacuum consumable steel ingot, thereby failing to meet the requirements of the corresponding technical standards.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing ultra-high strength C250 ultra-large size vacuum consumable steel ingot, characterized in that: The preparation method includes vacuum induction smelting and vacuum consumable remelting; In the vacuum induction smelting, the chemical composition requirements are as follows: C 0.006±0.001wt%; Mn≤0.05wt%; Si≤0.05wt%; S≤0.001wt%; P≤0.005wt%; Ni 18.0±0.20wt%; Co 8.0±0.05wt%; Ti0.40±0.01wt%; Mo 5.0±0.10wt%; Al 0.10±0.02wt%; O≤0.0010wt%; N≤0.0010wt%; The vacuum induction smelting adopts a 12-ton vacuum induction furnace; Vacuum induction melting process: full melting temperature T is 1490-1540℃; Vacuum induction refining process: refining temperature T is 1540-1610℃, vacuum degree ≤5Pa; Alloying process in a vacuum induction furnace: precise control of chemical composition, specifically C 0.006±0.001wt%, Ni18.0±0.20wt%, Co 8.0±0.05wt%, Mo 5.0±0.10wt%, Ti 0.40±0.01wt%, Al 0.10±0.02wt%; Vacuum induction pouring process: pouring temperature T is 1550-1580℃, vacuum degree ≤300Pa; Vacuum induction electrode rod cooling process: The electrode rod in-mold cooling time t is 1-3h, and air cooling is performed after demoulding; Vacuum induction electrode rod surface polishing; In the vacuum consumable remelting, the vacuum consumable melting stage: melting rate R = 5.5-6.5 kg / min; Vacuum consumable steel ingots are air-cooled and surface-polished.

2. The method for preparing ultra-high strength C250 ultra-large size vacuum consumable steel ingot according to claim 1, characterized in that: The raw materials for vacuum induction smelting are composed of refined steel, alloy materials, and metal materials, and the raw materials are required to have accurate composition and be free of rust, oil, and dirt on the surface.

3. The method for preparing the ultra-high strength C250 ultra-large size vacuum consumable steel ingot according to claim 1, characterized in that: The chemical composition of the vacuum consumable steel ingot is ensured to be precisely controlled to ensure uniform chemical composition.

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