A forming method for the influence of alloy element content on the internal structure of forgings

Abstract

This invention belongs to the field of forging hot working and relates to a method for determining the influence of alloy element content on the internal structure of forgings. The method includes: determining the Al element content level of a billet; and forging the billet using different forging schemes based on the Al element content in the billet to obtain forgings.

Description

Technical Field

[0001] This invention belongs to the field of forging hot working and relates to a forming method for the influence of alloy element content on the internal structure of forgings. Background Technology

[0002] 18Cr2Ni4WA is a stainless steel material with alloying elements C, Si, Mn, P, S, Cr, Mo, W, V, Ni, Al, and Cu, and gaseous contents of H, O, and N. According to standard GJB1951-94, the Al content should be ≤0.01%. However, in actual production, the Al content in raw materials often exceeds this standard, significantly impacting the final mechanical properties of the forgings and causing them to fail physical and chemical tests. It is used for high tensile and creep strength and good oxidation resistance in the temperature range of 650–900℃, making it suitable for manufacturing high-temperature parts for aerospace engines requiring high strength below 870℃ and oxidation resistance below 980℃. Due to its excellent comprehensive performance, it is widely used in aerospace and other fields and is one of the most widely used stainless steel materials in foreign aero-engines.

[0003] Because 18Cr2Ni4WA alloy forgings have different requirements for internal structure and high requirements for raw material elements, especially the content of AL element, the production parameter control requirements for forgings will vary. If the production parameters are not controlled properly, the change of each parameter will directly affect the internal structure of the forging, making the product unable to meet the final requirements, resulting in product scrap and a great waste of resources.

[0004] 18Cr2Ni4WA steel is generally used in aerospace for high-speed rotating load-bearing or rotating parts. In use, high tensile and impact resistance of forgings are required. However, during the forging process, the forging temperature and the number of heating cycles have a significant impact on these values.

[0005] The conventional forging method is as follows:

[0006] Material preparation, forming, heat treatment, and physical and chemical analysis are all completed within one forging cycle for ordinary parts. Physical and chemical testing is then performed on the forgings.

[0007] Conventional processing often fails to meet the required low-magnification and high-magnification grain size of the internal microstructure of forgings. Therefore, selecting a suitable forging method based on the Al content is crucial to the microstructure and properties of this material. In particular, adding a billet preparation step to free-form forgings is essential to ensure that the final forging deformation amount and rate meet the requirements for the final physicochemical testing results. Otherwise, a large number of defective forgings will be generated, leading to their scrap. Summary of the Invention

[0008] The purpose of this invention is to provide different forging methods for 18Cr2Ni4WA based on the amount of Al element in the raw material, to improve the internal structure of the forging by controlling the forging method, and to use the forging method to meet the design requirements of the forging and obtain a reasonable forging forming scheme to obtain a qualified and stable internal structure.

[0009] Technical solution:

[0010] A forming method for the influence of alloy element content on the internal microstructure of forgings, comprising:

[0011] The Al element content of the billet was determined to be at a certain level.

[0012] Depending on the Al content in the billet, different forging schemes are used to forge the billet to obtain forgings.

[0013] When the Al content is less than or equal to 0.02% and greater than 0.01%, the forging scheme adopts a first-stage forging + forming; when the Al content is less than or equal to 0.03% and greater than 0.02%, the forging scheme adopts a second-stage forging + forming; when the Al content is greater than 0.03%, the forging scheme adopts a third-stage forging + forming.

[0014] Level 1 forging includes:

[0015] The billet is fed into the furnace at a temperature ≤800℃ and held at 800℃ for 0.4 min / mm to 0.6 min / mm. Then, the furnace temperature is increased to 1110℃ to 1115℃ and heated to the set time with a holding coefficient of 0.6 min / mm. The billet is then immediately removed from the furnace and upset once on a free forging hammer. It is then returned to the furnace and heated to 1130℃ with a holding coefficient of 0.6 min / mm to the set time. The billet is then immediately removed from the furnace and forged to the desired shape on a free forging hammer, while controlling the intermediate and final forging temperatures. The forging ratio of upsetting to drawing per forging is 1.0 to 1.5.

[0016] Secondary forging includes:

[0017] The billet is fed into the furnace at a temperature ≤800℃ and held at 800℃ for 0.4 min / mm to 0.6 min / mm. Then, the furnace temperature is raised to 1115℃ to 1120℃ and heated to the set time with a holding coefficient of 0.6 min / mm. The billet is then immediately removed from the furnace and upset twice on a free forging hammer. It is then returned to the furnace and heated to 1130℃ with a holding coefficient of 0.6 min / mm to the set time. The billet is then immediately removed from the furnace and forged to the desired shape on a free forging hammer, while controlling the intermediate and final forging temperatures. The forging ratio of upsetting to drawing per forging is 1.5 to 2.0.

[0018] Level 3 reforging includes:

[0019] The billet is fed into the furnace at a temperature ≤800℃ and held at 800℃ for 0.4 min / mm to 0.6 min / mm. Then, the furnace temperature is raised to 1120℃ to 1125℃ and heated to the set time with a holding coefficient of 0.6 min / mm. The billet is then immediately removed from the furnace and upset three times on a free forging hammer. It is then returned to the furnace and heated to 1130℃ with a holding coefficient of 0.6 min / mm to the set time. The billet is then immediately removed from the furnace and forged to the pre-formed shape on a free forging hammer, while controlling the intermediate and final forging temperatures. The forging ratio of upsetting to drawing per forging is 2.0 to 2.5.

[0020] Molding includes:

[0021] The preform is heated to 1113℃~1140℃, and the heat preservation coefficient is calculated as 0.6min / mm. While the preform is being heated, the tooling mold is preheated to 250℃~350℃. After the preform is held at the set temperature, it is immediately taken out of the furnace for forging, and the transfer time is less than or equal to 20 seconds.

[0022] The method further includes:

[0023] The formed parts are subjected to quenching and tempering treatment. The quenching process is as follows: hold at 800℃ for 1.5 hours and then cool with oil, hold at 170℃ for 2.5 hours and then air cool.

[0024] When the Al content is less than or equal to 0.01%, the method further includes:

[0025] The forging is placed in the furnace at a temperature of ≤800℃ and held at 800℃. The temperature is increased to 1130℃ at a rate of 0.4min / mm to 0.6min / mm, with a holding coefficient of 0.6min / mm. After the forging is held at the set temperature for the set time, it is immediately taken out of the furnace and forged on a free forging hammer until it is formed, while controlling the intermediate and final forging temperatures.

[0026] The beneficial effects are as follows: 18Cr2Ni4WA steel belongs to martensitic-ferritic stainless steel. By determining the AL element content of the raw materials, different forging methods for 18Cr2Ni4WA can be provided to improve the internal structure of the forgings. The forging method can meet the design requirements of the forgings and provide a reasonable forging forming scheme to obtain a qualified and stable internal structure. This will improve the pass rate of the internal structure of the forgings by improving the physical and chemical analysis, thereby reducing scrap loss and greatly improving the pass rate of the forgings. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a forging.

[0028] Figure 2 This is a schematic diagram of the mold. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, a technical solution of one embodiment of the present invention will be clearly and completely described below in conjunction with the implementation of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The features of various aspects of the embodiments of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can also be practiced without these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples. The invention is not limited to any specific setups and methods provided below, but covers all improvements, substitutions, etc., to product structures and methods without departing from the spirit of the invention.

[0031] The Al content of the raw material was determined to provide different forging methods for 18Cr2Ni4WA. The typical Al content of the 18Cr2Ni4WA raw material, according to GJB1951-94, is ≤0.01%. The actual measured content range is shown in Table 1.

[0032] Table 1

[0033] Content Classification A B C D AL element content ≤0.01％ ≤0.02％ ≤0.03％ ≤0.04％ Forging method conventional Level 1 forging + forming Secondary forging + forming Level 3 reforging + forming

[0034] By controlling the forging method, the internal structure of the forging can be improved, and the forging method can be used to meet the requirements of the forging. Figure 1 The design requires a reasonable forging and forming scheme to obtain a qualified and stable internal structure.

[0035] The method includes the following steps:

[0036] Step 1: Determine the AL element content level of the raw materials to determine the forging method.

[0037] Step 2: Classify forging methods; forging is classified into four categories: A, B, C, and D; AL content ≤ 0.01% corresponds to conventional forging; AL content ≤ 0.02% corresponds to first-level modified forging + forming; AL content ≤ 0.03% corresponds to second-level modified forging + forming; AL content ≤ 0.04% corresponds to third-level modified forging + forming.

[0038] Step 3: Forging.

[0039] The conventional method is to forge the billet at a temperature of ≤800℃, hold it at 800℃, and then raise the temperature to 1130℃ at a rate of 0.4min / mm to 0.6min / mm, with a holding coefficient of 0.6min / mm. After the forging is held at the set temperature for the set time, it is immediately taken out of the furnace and forged on a free forging hammer until it is formed, while controlling the intermediate and final forging temperatures.

[0040] Forging of the first-stage forging and forming into billets involves placing the forging in a furnace at a temperature ≤800℃, holding it at 800℃, and then heating it in the furnace at a rate of 0.4 min / mm~0.6 min / mm until it reaches 1110℃~1115℃, with a holding coefficient of 0.6 min / mm. After holding the forging at the set temperature, it is immediately removed from the furnace and upset once on a free forging hammer, then returned to the furnace and heated to 1130℃ with a holding coefficient of 0.6 min / mm. After holding the forging at the set temperature, it is immediately removed from the furnace and forged in the free forging hammer until it reaches the final shape, while controlling the intermediate and final forging temperatures. The forging ratio of upsetting to drawing in the forging is 1.0~1.5.

[0041] For the secondary forging and forming of the billet, the forging process involves placing the billet in a furnace at a temperature ≤800℃, holding it at 800℃, and then heating it in the furnace at a rate of 0.4 min / mm~0.6 min / mm until it reaches 1115℃~1120℃, with a holding coefficient of 0.6 min / mm. After holding the forging at the set temperature, the forging is immediately removed from the furnace and upset twice on a free forging hammer before being returned to the furnace and heated to 1130℃, with a holding coefficient of 0.6 min / mm. After holding the forging at the set temperature, the forging is immediately removed from the furnace and forged into shape on a free forging hammer, while controlling the intermediate and final forging temperatures. The forging ratio of upsetting to drawing is 1.5~2.0.

[0042] For the three-stage reforging and forming of the billet, the forging process involves placing the billet in the furnace at a temperature ≤800℃, holding it at 800℃, and then heating it in the furnace at a rate of 0.4 min / mm~0.6 min / mm until it reaches 1120℃~1125℃, with a holding coefficient of 0.6 min / mm. After holding the forging at the set temperature, the forging is immediately removed from the furnace and upset three times on a free forging hammer before being returned to the furnace and heated to 1130℃, with a holding coefficient of 0.6 min / mm. After holding the forging at the set temperature, the forging is immediately removed from the furnace and forged on a free forging hammer until it reaches the desired shape, while controlling the intermediate and final forging temperatures. The forging ratio of upsetting to drawing is 2.0~2.5.

[0043] The billet is forged at a temperature of 1110℃~1125℃ with a holding coefficient of 0.6min / mm. The anvil is preheated to 200℃~350℃. After the forging is held at the set temperature for a set time, it is immediately taken out of the furnace and upset and reforged on a free forging hammer, while controlling the intermediate and final forging temperatures. The forging ratio of upsetting to drawing is 1.0~2.5.

[0044] Step 4: Forming and forging.

[0045] The preformed part is heated to 1113℃~1140℃, with a heat retention coefficient calculated at 0.6min / mm. The tooling mold is preheated simultaneously with the preformed part heating. Figure 2 The temperature should be increased to 250℃~350℃; after the formed part is kept at the set temperature for the set time, it should be taken out of the furnace for forging immediately, and the transfer time should be less than or equal to 20 seconds.

[0046] Step 5: Heat treatment of the molded part.

[0047] The formed parts are subjected to quenching and tempering treatment. The quenching process is as follows: hold at 800℃ for 1.5 hours and then cool with oil, hold at 170℃ for 2.5 hours and then cool with air.

[0048] Step 6: Perform 100% mechanical property checks.

[0049] Example 1:

[0050] (1) Design process flow: forging bar stock → determination of AL element content of raw materials → sawing to the required length of the process → determination of forging scheme → modification forging → forming forging → heat treatment → physical and chemical treatment.

[0051] (2) For production furnace number 15E293; the AL element content was determined to be ≤0.03%; the forging method was determined to be the corresponding secondary forging + forming; the required billet size (Φ250×150) was specified.

[0052] (3) Forge the bar stock by 2 upsetting and 2 drawing (Φ250×150)

[0053] First forging: Φ250x150 axially elongated, forged square, chamfered, and shaped to: ~Φ160x355 (strictly control the 355 dimension).

[0054] Second forging: Φ160x355 axial upsetting, rounding, and shaping to: Φ245x160 (strictly controlling 170% of the p3 dimension).

[0055] Third forming: Φ245x160 axial elongation, forging, and chamfering to: ~Φ160x355 (strictly control 170% of the p3 dimension).

[0056] Fourth stage reforging: Φ160x355 axial upsetting, rounding, and shaping to: Φ230x170 (strictly controlling 170% of the p3 dimension).

[0057] (4) After the forgings underwent final heat treatment, samples were taken for physical and chemical analysis. The results showed that both the low-magnification microstructure and the high-magnification grain size were qualified.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A forming method for the influence of alloy element content on the internal structure of a forging, wherein the forging material is 18Cr2Ni4WA steel, characterized in that, include: The Al element content of the billet was determined to be at a certain level. Based on the Al content in the billet, different forging schemes are used to forge the billet to obtain forgings; Specifically: When the Al content is less than or equal to 0.02% and greater than 0.01%, the forging scheme adopts a single-stage forging + forming process; when the Al content is less than or equal to 0.03% and greater than 0.02%, the forging scheme adopts a two-stage forging + forming process. When the Al content is greater than 0.03%, the forging scheme adopts three-stage modified forging + forming; Level 1 forging includes: The billet, with a temperature ≤800℃, is fed into the furnace and held at 800℃ for 0.4 min / mm to 0.6 min / mm. The furnace temperature is then increased to 1110℃ to 1115℃ and heated for the set time at a holding rate of 0.6 min / mm. The billet is immediately removed from the furnace and upset once on a free forging hammer. It is then returned to the furnace and heated to 1130℃, held for the set time at a holding rate of 0.6 min / mm. The billet is then immediately removed from the furnace and forged on a free forging hammer until pre-formed, while controlling the final forging temperature. The forging ratio of upsetting to drawing per forging pass is 1.0 to 1.

5. Secondary forging includes: The billet is fed into the furnace at a temperature ≤800℃ and held at 800℃ for 0.4 min / mm to 0.6 min / mm. Then, the furnace temperature is increased to 1115℃ to 1120℃ and heated to the set time with a holding coefficient of 0.6 min / mm. The billet is then immediately removed from the furnace and upset twice on a free forging hammer. It is then returned to the furnace and heated to 1130℃ with a holding coefficient of 0.6 min / mm to the set time. The billet is then immediately removed from the furnace and forged on a free forging hammer to the pre-formed shape, while controlling the final forging temperature. The forging ratio of upsetting to drawing per forging pass is 1.5 to 2.

0. Level 3 reforging includes: The billet, with a temperature ≤800℃, is fed into the furnace and held at 800℃ for 0.4 min / mm to 0.6 min / mm. Then, the furnace temperature is raised to 1120℃ to 1125℃ and heated to the set time with a holding coefficient of 0.6 min / mm. The billet is then immediately removed from the furnace and upset three times on a free forging hammer. It is then returned to the furnace and heated to 1130℃, heated to the set time with a holding coefficient of 0.6 min / mm. The billet is then immediately removed from the furnace and forged to the pre-formed shape on a free forging hammer, while controlling the final forging temperature. The forging ratio of upsetting to drawing per forging is 2.0 to 2.

5.

2. The method according to claim 1, characterized in that, molding include: The preform is heated to 1113℃~1140℃. The heat preservation coefficient is calculated as 0.6min / mm. While the preform is being heated, the tooling mold is preheated to 250℃~350℃. After the preform is held at the set temperature, it is immediately taken out of the furnace for forging. The transfer time is less than or equal to 20 seconds to obtain the formed part.

3. The method according to claim 2, characterized in that, The method further includes: The formed parts are subjected to quenching and tempering treatment. The quenching process is as follows: hold at 800℃ for 1.5 hours and then cool with oil, hold at 170℃ for 2.5 hours and then air cool.

4. The method according to claim 1, characterized in that, When the Al content is less than or equal to 0.01%, the method further includes: The forging is placed in the furnace at a temperature ≤ 800℃ and held at 800℃ for 0.4 min / mm to 0.6 min / mm. The furnace temperature is then increased to 1130℃ and held for a holding time of 0.6 min / mm. After the forging is held for the set time, it is immediately removed from the furnace and forged on a free forging hammer until it is formed, while controlling the final forging temperature.

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