Forming method for achieving high performance and low damage of aircraft engine M50 bearing steel

Abstract

The invention discloses a forming method for realizing high performance and low damage of aircraft engine M50 bearing steel, which comprises the following steps: S1, putting a prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heating to 200-600 DEG C, and carrying out heat preservation treatment after heating to the final temperature; s2, the ring blank subjected to heat preservation is placed on a ring rolling machine, the deformation amount and the deformation rate are set through the ring rolling machine, then the ring blank is rolled, deformation of the ring blank is completed, and air cooling treatment is conducted after deformation is completed; and S3, high-energy pulse current is introduced into the air-cooled ring blank, so that an electroplastic effect is generated in the ring blank, micro-nano defects generated in the warm forming rolling process are repaired, and internal crystal grains are further refined. According to the method, warm forming rolling machining is conducted on the aircraft engine M50 bearing steel within the range of 200-600 DEG C, micro-nano defects can be reduced, the machining time can be shortened, high-energy pulse current repairing treatment is further conducted on a finished product workpiece obtained after warm forming rolling, the micro-nano defects are repaired, and the mechanical performance and strength of a formed component are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of material processing and forming, and particularly to a forming method for realizing high performance and low damage of aeroengine M50 bearing steel. Background Art

[0002] The main shaft bearing of an aeroengine is a key component of an aircraft and an important cutting-edge equipment with a highly complex and precise thermo-mechanical structure. As a key component for bearing capacity and transmitting motion, it supports the most core rotor system of the engine, and the working conditions are extremely harsh, requiring high speed, high precision, high load-bearing capacity and high reliability. In the forming manufacturing process of M50 bearing steel, ring rolling is a continuous local plastic forming method, which has the advantages of high efficiency and energy saving compared with other bearing ring manufacturing processes. At present, the production of M50 bearing rings mainly relies on cold rolling and hot rolling. Cold rolling at room temperature is a way for metal materials to undergo plastic deformation. Cold rolling at room temperature can refine the microstructure, and the refined microstructure shows great potential in improving the comprehensive mechanical properties. However, the workpieces obtained by cold rolling are extremely prone to microcrack defects. For M50 bearing steel with poor formability, hot rolling can make it show good plastic deformation effect, which is very effective for the forming of ring parts with complex cross-sectional profile shapes. Therefore, hot rolling is usually used to manufacture large ring parts. However, since it is necessary to keep warm at high temperature for a long time after the hot rolling process, it usually causes the grains of the material to become coarse. Therefore, a new processing method is needed to optimize the traditional compression process and realize the high-performance and low-damage forming of M50 bearing steel.

[0003] At present, the research on the ring rolling forming of M50 bearing steel mainly focuses on room temperature and high temperature conditions. There is relatively little research on warm forming at intermediate temperatures, and the research on the forming law content under these temperature conditions still needs to be supplemented. Chinese Patent CN107138660A discloses a warm ring rolling forming method for high-carbon chromium bearing steel to achieve spheroidization of the structure, including: S1. Low-temperature austenitizing heating: placing the processed ring blank into a heating furnace and heating it to 10°C to 40°C above the critical temperature Ac1 of the material, and holding for 5 to 10 minutes; S2. Slow cooling in the furnace: slowly cooling the ring blank that has completed heat preservation in the heating furnace to within 50°C below the critical temperature Ar1 of the material, and controlling the cooling rate at 100°C / h to 200°C / h; S3. Warm rolling forming: quickly transferring the cooled ring blank from the heating furnace to a ring rolling machine for rolling, controlling the deformation amount of the ring blank at 40% to 70%, and controlling the final rolling temperature within 100°C below Ar1. This method is used for the warm ring rolling forming of high-carbon chromium bearing steel. At a temperature lower than the forging temperature of the material, the structure of the material is directly spheroidized through warm ring rolling deformation, realizing the integration of forming and spheroidization, which can eliminate the traditional spheroidizing annealing process, improve efficiency and reduce energy consumption. However, the current forming temperature of this process is still in the high-temperature range. During the rolling process, the temperature of the ring blank needs to be monitored in real time. When the temperature of the ring blank is lower than the final rolling temperature, rolling is immediately terminated, and the ring blank is reheated to the preset initial rolling temperature in the furnace and then rolling is continued to ensure the acquisition of spheroidized structure. It is still not suitable for the high-performance and low-damage rapid forming of M50 bearing steel. Summary of the Invention

[0004] The main purpose of the present invention is to propose a forming method for achieving high performance and low damage of aero-engine M50 bearing steel. The warm ring rolling can well integrate the advantages of cold rolling and hot rolling processes, reduce the formation of micro-nano defects, and shorten the processing time. In addition, the warm ring rolling of M50 bearing steel is subjected to high-energy pulsed current repair treatment. The two processes are asynchronously processed. The overall process flow is short, the process time is shortened, the processing efficiency is enhanced, and the introduction of high-energy pulsed current will further refine the grains, repair the micro-nano defects generated during the processing of the material, promote the dissolution of carbides, and further enhance the mechanical properties and strength of the formed component. Therefore, the M50 bearing steel formed by the method of the present invention fully meets the current strength requirements and can greatly improve the efficiency of bearing forming manufacturing.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A forming method for achieving high performance and low damage of aero-engine M50 bearing steel, including the following steps:

[0007] S1. Place the prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heat it to 200 to 600°C, and perform heat preservation treatment after reaching the final temperature;

[0008] S2. Place the ring blank after heat preservation on a ring rolling mill, set the deformation amount and deformation rate through the ring rolling mill, and then roll the ring blank to complete the deformation. After the deformation is completed, perform air cooling treatment;

[0009] S3. Pass a high-energy pulsed current into the air-cooled ring blank to generate an electroplastic effect inside the ring blank, repair the micro-nano defects generated during the warm forming rolling process, and further refine the internal grains.

[0010] In the above solution, in step S1, the heat preservation treatment time is 3 - 5 min.

[0011] In the above solution, in step S2, the deformation amount is set to 20% - 40%.

[0012] In the above solution, in step S2, the deformation rate is set to 0.1 mm / s - 2 mm / s.

[0013] In the above solution, in step S2, the air cooling treatment is natural cooling to room temperature.

[0014] In the above solution, in step S3, the current density of the passed high-energy pulsed current is 50 - 100 A / mm 2 , the single pulse time is 0.02 s, 10 pulses are passed in once, and the number of power-on times is 1 - 5 times.

[0015] The beneficial effects produced by the present invention are:

[0016] The method of the present invention performs warm forming rolling processing on the aeroengine M50 bearing steel in the range of 200 - 600 °C. Compared with the cold ring rolling process that will generate a large number of micro-nano defects such as pores, and the hot ring rolling process that uses a large amount of time and has coarse grains, warm ring rolling can well integrate the advantages of the two forming processes, reduce the formation of micro-nano defects, and shorten the processing time, thereby achieving the short-time and rapid obtaining of finished workpieces with extremely few defects. Some micro-nano defects still appear during the warm forming rolling processing of M50 bearing steel. The method of the present invention further performs high-energy pulsed current repair treatment on the finished workpieces of warm forming rolling. The high-energy pulsed current can directly refine the metal grains, repair the micro-nano defects, and further promote the dissolution of carbides, further enhancing the mechanical properties and strength of the formed components. And the high-energy pulsed current repair treatment has a short time and high efficiency. Therefore, by combining the two processes of warm forming rolling and high-energy pulsed current repair, and using high-energy pulsed current to regulate the tissue properties of M50 bearing steel under the warm forming process, the defects generated by compression forming can be perfectly compensated. Description of the Drawings

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 is the process flow chart of the embodiment of the present invention;

[0019] Figure 2 is the schematic diagram of micro-nano defects in the existing cold ring rolling;

[0020] Figure 3 is the schematic diagram of defects and the statistical chart of the number of defects in the warm ring rolling in the embodiment of the present invention; among them, (a) the ring rolling sample at 200 °C, (b) the ring rolling sample at 400 °C, (c) the ring rolling sample at 600 °C, (d) the statistical chart of defects of cold rolling and warm rolling samples;

[0021] Figure 4 is the comparison diagram of micro-nano defects of the ring rolling sample at 400 °C before and after the repair by high-energy pulsed current in the embodiment of the present invention; among them, (a) the un-repaired sample, (b) 100 A / mm 2 ;

[0022] Figure 5 is the comparison diagram of the grain size of the ring rolling sample at 400 °C before and after the repair by high-energy pulsed current in the embodiment of the present invention; among them, (a) the un-repaired sample, (b) 100 A / mm 2 . Detailed implementation manners

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] The present invention proposes a forming method for achieving high performance and low damage of aero-engine M50 bearing steel, as Figure 1 shown, including the following steps:

[0025] S1. Place the prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heat it up to 200 - 600 °C, and perform heat preservation after reaching the final temperature to ensure the temperature stability during rolling;

[0026] S2. Place the heat-preserved ring blank on a ring rolling machine, set the deformation amount and deformation rate through the ring rolling machine, then roll the ring blank to complete the deformation, and perform air cooling after the deformation is completed;

[0027] S3. Pass a high-energy pulsed current into the ring blank after air cooling to generate an electroplastic effect inside the ring blank, repair the micro-nano defects generated during the warm forming rolling process, and further refine the internal grains.

[0028] After being treated with a high-energy pulsed current, the high-strength and fine-grained aerospace bearing material M50 bearing steel with high performance has been prepared. Compared with the traditional hot rolling and cold rolling processes, the metal material prepared by this process has healed micro-nano defects, refined grain size, better mechanical properties and strength, and the process is simpler and takes less time.

[0029] In a preferred embodiment of the present invention, in step S1, the heat preservation treatment time is 3 - 5 min.

[0030] In a preferred embodiment of the present invention, in step S2, the deformation amount is set to 20% - 40%.

[0031] In a preferred embodiment of the present invention, in step S2, the deformation rate is set to 0.1 mm / s - 2 mm / s.

[0032] In a preferred embodiment of the present invention, in step S2, the air cooling treatment is natural cooling to room temperature.

[0033] In a preferred embodiment of the present invention, in step S3, the current density of the high-energy pulsed current passed in is 50 - 100 A / mm 2 , the duration of a single pulse is 0.02 s, 10 pulses are passed in at a time, and the number of power-on times is 1 - 5 times.

[0034] Next, the method of the present invention will be further described through 6 examples.

[0035] Select the annealed M50 steel of aero-engine bearings as the raw material, prepare multiple M50 bearing steel ring blanks, with dimensions of inner diameter 44 mm, outer diameter 60 mm, axial thickness 8 mm, and radial height 8 mm. Rolling ratio: Rolling ratio = (original cross-sectional area - final cross-sectional area) / original cross-sectional area. Since the axial thickness of the ring blank hardly changes during the ring rolling process, the rolling ratio in this patent = (initial radial height - final radial height) / initial radial height (i.e., the rolling ratio is the deformation amount in the experiment). If the rolling ratio is too small, the stored energy of deformation will be small and recrystallization is not likely to occur; if the rolling ratio is too large, more microcracks or even fractures will occur in the ring blank.

[0036] Example 1:

[0037] A forming method for achieving high performance and low damage of aero-engine M50 bearing steel, comprising the following steps:

[0038] S1. Place the prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heat it up to 200 °C, and hold for 5 min after reaching the final temperature;

[0039] S2. Place the ring blank after heat preservation on a ring rolling mill, set the deformation amount to 30% and the deformation rate to 0.1 mm / s through the ring rolling mill, then roll the ring blank to complete the deformation, and perform air cooling treatment after the deformation is completed;

[0040] S3. Pass a high-energy pulsed current into the ring blank after air cooling, with a current density of 50 A / mm 2 , and the duration is 0.2 s to repair the micro-nano defects generated during the warm forming rolling process.

[0041] Example 2:

[0042] A forming method for achieving high performance and low damage of aero-engine M50 bearing steel includes the following steps:

[0043] S1. Place the prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heat it up to 400 °C, and hold for 5 min after reaching the final temperature;

[0044] S2. Place the ring blank after heat preservation on a ring rolling mill, set the deformation amount to 30% and the deformation rate to 0.1 mm / s through the ring rolling mill, then roll the ring blank to complete the deformation, and perform air cooling treatment after the deformation is completed;

[0045] S3. Pass a high-energy pulsed current into the ring blank after air cooling, with a current density of 50 A / mm 2 , and the duration is 0.2 s to repair the micro-nano defects generated during the warm forming rolling process.

[0046] Example 3:

[0047] A forming method for achieving high performance and low damage of aero-engine M50 bearing steel includes the following steps:

[0048] S1. Place the prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heat it up to 600 °C, and hold for 5 min after reaching the final temperature;

[0049] S2. Place the ring blank after heat preservation on a ring rolling mill, set the deformation amount to 30% and the deformation rate to 0.1 mm / s through the ring rolling mill, then roll the ring blank to complete the deformation, and perform air cooling treatment after the deformation is completed;

[0050] S3. Pass a high-energy pulsed current into the ring blank after air cooling, with a current density of 50 A / mm 2 , and the duration is 0.2 s to repair the micro-nano defects generated during the warm forming rolling process.

[0051] Figure 2 It is a schematic diagram of room temperature cold rolling defects. Figure 3 It is a schematic diagram of warm rolling defects and a statistical chart of the number of defects. By comparison, it can be seen that the number of warm rolling defects (the positions marked in red in the figure) is significantly less than that of cold rolling defects, and as the rolling temperature increases, the defects in the specimen significantly decrease, indicating that warm rolling can effectively reduce the generation of defects.

[0052] Example 4:

[0053] A forming method for achieving high performance and low damage of aeroengine M50 bearing steel, comprising the following steps:

[0054] S1. Place the prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heat it to 200 °C, and hold for 5 min after reaching the final temperature;

[0055] S2. Place the ring blank after heat preservation on a ring rolling mill, set the deformation amount to 30% and the deformation rate to 0.1 mm / s through the ring rolling mill, then roll the ring blank to complete the deformation, and perform air cooling treatment after the deformation is completed;

[0056] S3. Pass a high-energy pulsed current into the ring blank after air cooling, with a current density of 100 A / mm 2 , and a duration of 0.2 s, to repair the micro-nano defects generated during the warm forming rolling process.

[0057] Example 5:

[0058] A forming method for achieving high performance and low damage of aeroengine M50 bearing steel, comprising the following steps:

[0059] S1. Place the prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heat it to 400 °C, and hold for 5 min after reaching the final temperature;

[0060] S2. Place the ring blank after heat preservation on a ring rolling mill, set the deformation amount to 30% and the deformation rate to 0.1 mm / s through the ring rolling mill, then roll the ring blank to complete the deformation, and perform air cooling treatment after the deformation is completed;

[0061] S3. Pass a high-energy pulsed current into the ring blank after air cooling, with a current density of 100 A / mm 2 , and a duration of 0.2 s, to repair the micro-nano defects generated during the warm forming rolling process.

[0062] Figure 4 It is a comparison diagram of micro-nano defects of a ring rolling specimen at 400 °C before and after repair by high-energy pulsed current. In the figure, (a) is the specimen without repair, and (b) is the current density of 100 A / mm 2As can be seen from the figure, after the pulsed current is introduced, the number of defects in the specimen is significantly reduced, indicating that the pulsed current can effectively repair the micro-nano defects in the material.

[0063] Figure 5 Figure for comparing the grain sizes of the 400°C ring-rolled specimens before and after repair by high-energy pulsed current. In the figure, (a) is the unrepaired specimen; (b) the current density is 100 A / mm 2 As can be seen from the figure, after the pulsed current is introduced, the grains are significantly refined, indicating that the high-energy pulsed current can significantly promote grain refinement.

[0064] Example Six:

[0065] A forming method for achieving high performance and low damage of aero-engine M50 bearing steel, comprising the following steps:

[0066] S1. Place the prepared M50 bearing steel ring blank into a heat treatment atmosphere furnace, heat it up to 600°C, and hold it for 5 minutes after reaching the final temperature;

[0067] S2. Place the ring blank after heat preservation on a ring rolling mill, set the deformation amount to 30% and the deformation rate to 0.1 mm / s through the ring rolling mill, then roll the ring blank to complete the deformation, and perform air cooling treatment after the deformation is completed;

[0068] S3. Pass a high-energy pulsed current into the ring blank after air cooling, with a current density of 100 A / mm 2 , and the duration is 0.2 s, to repair the micro-nano defects generated during the warm forming rolling process.

[0069] It should be noted that according to the needs of implementation, each step / component described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0070] The sequence numbers of the steps in the above embodiments do not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0071] It should be understood that those of ordinary skill in the art can make improvements or transformations according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A forming method for achieving high performance and low damage of aircraft engine M50 bearing steel, characterized in that: The following steps are involved: S1. Place the prepared M50 bearing steel ring blank in a heat treatment atmosphere furnace, heat it to 200-600°C, and perform heat preservation treatment after reaching the final temperature; S2, placing the heat-insulated ring blank on a ring rolling machine, setting the deformation amount and deformation rate through the ring rolling machine, and then rolling the ring blank to complete the deformation, and performing air cooling after the deformation is completed; S3. A high-energy pulse current is passed through the air-cooled ring blank to generate an electroplastic effect inside the ring blank, repair the micro-nano defects generated during the warm forming rolling process, and further refine the internal grains.

2. The forming method for achieving high performance and low damage of aircraft engine M50 bearing steel according to claim 1 is characterized in that: In step S1, the heat preservation treatment time is 3-5 minutes.

3. The forming method for achieving high performance and low damage of aircraft engine M50 bearing steel according to claim 1 is characterized in that: In step S2, the deformation amount is set to 20%-40%.

4. The forming method for achieving high performance and low damage of aircraft engine M50 bearing steel according to claim 1 is characterized in that: In step S2, the deformation rate is set to 0.1 mm / s-2 mm / s.

5. The forming method for achieving high performance and low damage of aircraft engine M50 bearing steel according to claim 1 is characterized in that: In step S2, the air cooling treatment is natural cooling to room temperature.

6. The forming method for achieving high performance and low damage of aircraft engine M50 bearing steel according to claim 1 is characterized in that: In step S3, the current density of the high energy pulse current is 50-100A / mm 2 The single pulse time is 0.02s, 10 pulses are input at a time, and the number of power-on times is 1-5 times.

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