Heat treatment method for A-100 steel forge piece and A-100 steel part

Abstract

The invention provides a heat treatment method of an A-100 steel forge piece and an A-100 steel part, and relates to the field of forging.The method comprises the steps that based on the strength requirement of the A-100 steel forge piece, a target tempering temperature is determined from a strength relation curve; the strength relation curve comprises a tensile strength curve and a yield strength curve; the tensile strength curve is used for representing the corresponding relation between the tempering temperature and the tensile strength of the A-100 steel forge piece; the yield strength curve is used for representing the corresponding relation between the tempering temperature and the yield strength of the A-100 steel forge piece; and the A-100 steel forging is subjected to tempering treatment according to the target tempering temperature. The method is suitable for the heat treatment process of A-100 steel forgings and is used for selecting a proper tempering temperature.

Description

Technical Field

[0001] The present application relates to the field of forging, and particularly to a heat treatment method for A-100 steel forgings and A-100 steel parts. Background Art

[0002] With the development of the aviation industry, new requirements have been put forward for the service performance of ultra-high strength steel. It should not only have ultra-high strength, but also have good fracture toughness at the same time. A-100 steel is a new type of ultra-high strength steel proposed in response to the development needs of the situation, and has excellent strength and toughness. In addition, this steel also has excellent ductility, excellent ability to resist fatigue crack fracture, and high hardness, and is considered the preferred material for key aircraft components and landing gears. Through heat treatment, its tensile strength can reach 1930 MPa to 2070 MPa, and its fracture toughness can reach 110 MPa·m 1 / 2 ~161.5 MPa·m 1 / 2 .

[0003] Therefore, how to select the heat treatment parameters of A-100 steel forgings has become our need. Summary of the Invention

[0004] The present application provides a heat treatment method for A-100 steel forgings to reasonably select the heat treatment parameters of A-100 steel forgings.

[0005] In a first aspect, the present application provides a heat treatment method for A-100 steel forgings, characterized in that the method includes: determining a target tempering temperature from a strength relationship curve based on the strength requirement of the A-100 steel forging; the strength relationship curve includes a tensile strength curve and a yield strength curve; the tensile strength curve is used to characterize the corresponding relationship between the tempering temperature and the tensile strength of the A-100 steel forging; the yield strength curve is used to characterize the corresponding relationship between the tempering temperature and the yield strength of the A-100 steel forging; tempering the A-100 steel forging according to the target tempering temperature.

[0006] The heat treatment method for A-100 steel forgings provided by the present application can determine the target tempering temperature from the strength relationship curve based on the strength requirement of the A-100 steel forging. The strength relationship curve includes a tensile strength curve and a yield strength curve. The tensile strength curve is used to characterize the corresponding relationship between the tempering temperature and the tensile strength of the A-100 steel forging, and the yield strength curve is used to characterize the corresponding relationship between the tempering temperature and the yield strength of the A-100 steel forging. In this way, the selected target tempering temperature is the tempering temperature that matches the strength requirement. According to the tempering temperature that matches the strength requirement, the desired strength requirement can be obtained through tempering treatment, thereby providing a solution for selecting a suitable tempering temperature.

[0007] Optionally, before tempering the A-100 steel forging according to the target tempering temperature, the method further includes: heat-treating the A-100 steel forging according to a first heat treatment process.

[0008] Optionally, heat-treating the A-100 steel forging according to the first heat treatment process includes: heating the A-100 steel forging to 855°C ± 15°C, holding for 60 min to 75 min, oil quenching, tempering back to -73°C ± 8°C, and holding for 60 min ± 5 min.

[0009] Optionally, before heat-treating the A-100 steel forging according to the first heat treatment process, the method further includes: performing preliminary heat treatment on the A-100 steel forging according to a second heat treatment process.

[0010] Optionally, performing preliminary heat treatment on the A-100 steel forging according to the second heat treatment process includes: heating the A-100 steel forging to 900°C ± 10°C and holding for at least 60 min, air cooling, then heating to 680°C ± 10°C and holding for at least 16 h, air cooling.

[0011] Optionally, the A-100 steel forging is obtained by forging an A-100 steel billet; the A-100 steel billet includes 0.24% carbon, 0.052% silicon, 3.04% chromium, 11.21% nickel, 1.24% molybdenum, and 84.218% iron.

[0012] Optionally, the A-100 steel billet is obtained by vacuum induction and vacuum consumable melting.

[0013] Optionally, the A-100 steel billet is subjected to normalizing and high-temperature tempering treatments.

[0014] Optionally, the method further includes: forging the A-100 steel bar into a cubic billet in one heat, slow cooling after forging; heating the cubic billet to 900°C ± 10°C and holding for at least 60 min, air cooling, then heating to 680°C ± 10°C and holding for at least 16 h, air cooling; cutting the cubic billet into multiple specimens; heating the multiple specimens to 855°C ± 15°C and holding for 60 min to 75 min, oil quenching, tempering back to -73°C ± 8°C and holding for 60 min ± 5 min; performing tempering treatments on the multiple specimens according to different tempering temperatures respectively, and testing the tensile strength and yield strength of the specimens tempered according to each tempering temperature; plotting a strength relationship curve based on the tensile strength and yield strength of the specimens tempered according to each tempering temperature.

[0015] In a second aspect, the present application further provides an A-100 steel part, which is obtained by heat-treating an A-100 steel forging using the heat treatment method described in the first aspect above.

[0016] The beneficial effects of the second aspect above can be referred to those described in the first aspect above and will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 Strength curves of A-100 steel at different tempering temperatures provided by the embodiments of the present application; Figure 2 Fracture toughness curves of A-100 steel tempered at different temperatures provided by the embodiments of the present application; Figure 3 Performance curves of A-100 steel tempered at different temperatures provided by the embodiments of the present application; Figure 4 Schematic flow chart of the heat treatment method for A-100 steel forgings provided by the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0020] It should be noted that in the embodiments of the present application, words such as "exemplarily" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplarily" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Exactly speaking, using words such as "exemplarily" or "for example" aims to present relevant concepts in a specific way.

[0021] In order to facilitate the clear description of the technical solutions in the embodiments of the present application, in the embodiments of the present application, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order.

[0022] With the development of the aviation industry, new requirements have been put forward for the service performance of ultra-high-strength steel. It should not only have ultra-high strength but also good fracture toughness at the same time. A-100 steel is a new type of ultra-high-strength steel proposed in line with the development needs of the situation, with excellent strength and toughness. In addition, this steel also has excellent ductility, excellent ability to resist fatigue crack fracture, and high hardness, and is considered the preferred material for key aircraft components and landing gears. Through heat treatment, its tensile strength can reach 1930 MPa to 2070 MPa, and its fracture toughness can reach 110 MPa·m 1 / 2 ~161.5 MPa·m 1 / 2 。

[0023] Therefore, how to select the heat treatment parameters of A-100 steel forgings has become our need.

[0024] First, an experimental analysis was carried out on the relationship between the heat treatment parameters and strength of A-100 steel forgings.

[0025] The experimental materials were A-100 bars with a diameter of 200 millimeters (mm) produced by a certain steel plant. The bars were smelted by vacuum induction + vacuum consumable, and were subjected to normalizing + high-temperature tempering treatment. Its chemical composition is specifically shown in Table 1 below: Table 1 As shown in Table 1, the A-100 bar includes 0.24% carbon, 0.052% silicon, 3.04% chromium, 11.21% nickel, and 1.24% molybdenum. The remaining components are all iron, that is, it includes 84.218% iron.

[0026] Then, a 3t free forging hammer was used to forge the A-100 bar into 120 mm × 100 mm × 320 mm, completed in one heat, and slowly cooled after forging. Then the forgings were subjected to preliminary heat treatment to improve the machining performance of A-100. Its preliminary heat treatment process was (900 ± 10) °C × (holding for ≥ 60 min) air cooling + (680 ± 10) °C × (holding for ≥ 16 h) air cooling. Wire cutting was used to cut samples for mechanical property testing for final heat treatment. Its heat treatment process was (885 ± 15) °C × (holding for 60 + 150 min) oil cooling, (-73 ± 8) °C × (holding for 60 ± 5 min) air tempering, (464 - 510) °C × (holding for 5 - 8 h) air cooling.

[0027] The heat-treated samples were processed into standard tensile samples with d0 = 5 mm and standard fracture toughness samples with B = 15 mm. The tensile samples were tested on an electronic universal testing machine, and the fracture toughness was tested on an electro-hydraulic servo fatigue testing machine. A hardness tester was used to measure the hardness values of different heat-treated samples. Five points were detected for hardness, and the average value was taken as the measurement result.

[0028] After the sample is oil quenched at (885 ± 15) °C and cryogenically treated at (-73 ± 8) °C, and then undergoes secondary hardening at different temperatures, the curves of strength and fracture toughness varying with the tempering temperature can be obtained.

[0029] Exemplarily, Figure 1 This is the strength curve of A-100 steel at different tempering temperatures provided by the embodiment of the present application. As Figure 1 shown, when the tempering temperature is 464 °C, the tensile strength of A-100 steel is 2089 MPa and the yield strength is 1863 MPa; when the tempering temperature is 470 °C, the tensile strength of A-100 steel is 2040 MPa and the yield strength is 1840 MPa; when the tempering temperature is 476 °C, the tensile strength of A-100 steel is 2008 MPa and the yield strength is 1808 MPa; when the tempering temperature is 482 °C, the tensile strength of A-100 steel is 1970 MPa and the yield strength is 1770 MPa; when the tempering temperature is 488 °C, the tensile strength of A-100 steel is 1895 MPa and the yield strength is 1735 MPa; when the tempering temperature is 494 °C, the tensile strength of A-100 steel is 2090 MPa and the yield strength is 1803 MPa; when the tempering temperature is 500 °C, the tensile strength of A-100 steel is 1735 MPa and the yield strength is 1650 MPa; when the tempering temperature is 510 °C, the tensile strength of A-100 steel is 1609.5 MPa and the yield strength is 1548 MPa.

[0030] From the above Figure 1 it can be seen that the tempering temperature has an obvious influence on the tensile strength of A-100 steel. In the temperature range of 464 °C to 510 °C, with the increase of the tempering temperature, the tensile strength and yield strength of A-100 steel gradually decrease. When the tempering temperature increases from 500 °C to 510 °C, the strength of A-100 steel decreases most significantly. When the tempering temperature drops by 10 °C, the tensile strength drops by 133 MPa, a decrease of about 7.6%; the yield strength drops by 105 MPa, a decrease of about 6.35%. And when the tempering temperature is 464 °C, the strength is the highest, with a tensile strength of 2089 MPa and a yield strength of 1863 MPa. When the tempering temperature is 510 °C, the strength is the lowest, with a tensile strength of 1609.5 MPa and a yield strength of 1548 MPa.

[0031] Exemplarily, Figure 2 This is the fracture toughness curve of A-100 steel tempered at different temperatures provided by the embodiment of the present application. As Figure 2As shown, in the temperature range of (464 - 510)°C, with the increase of tempering temperature, the fracture toughness of A-100 steel increases gradually. When the tempering temperature increases from 464°C to 470°C, the fracture toughness of A-100 steel increases most significantly. When the tempering temperature increases by 6°C, the fracture toughness increases by 29 MPa·m 1 / 2 , an increase of about 33.5%. However, after the tempering temperature reaches 482°C, the change in fracture toughness tends to be stable. This is mainly because the lath martensites are arranged crosswise with each other, making it difficult for cracks to propagate. And when the tempering temperature is 464°C, the fracture toughness is the lowest, which is 86.5 MPa·m 1 / 2 . When the tempering temperature is 510°C, the fracture toughness is the highest, which is 161.5 MPa·m 1 / 2 .

[0032] Exemplarily, Figure 3 is the performance curve of A-100 steel tempered at different temperatures provided by the embodiment of the present application. As Figure 3 shown, when the tempering temperature is below 494°C, with the increase of tempering temperature, the elongation first increases and then decreases, while the reduction of area increases gradually, but the increase amplitude is not large. In the temperature range of 464°C - 510°C, with the increase of tempering temperature, the hardness of A-100 steel decreases gradually.

[0033] Based on the understanding of the above experimental analysis, the embodiment of the present application also provides a heat treatment method for A-100 steel forgings. Figure 4 is the flow schematic diagram of the heat treatment method for A-100 steel forgings provided by the embodiment of the present application. As Figure 4 shown, the method includes the following steps: S101. Based on the strength requirement of the A-100 steel forging, determine the target tempering temperature from the strength relationship curve.

[0034] Among them, the strength relationship curve includes the tensile strength curve and the yield strength curve. The tensile strength curve is used to characterize the corresponding relationship between the tempering temperature and the tensile strength of the A-100 steel forging, and the yield strength curve is used to characterize the corresponding relationship between the tempering temperature and the yield strength of the A-100 steel forging.

[0035] The tensile strength curve and the yield strength curve can specifically refer to the above Figure 1 shown, and will not be elaborated here.

[0036] For example, when the strength requirement of the A-100 steel forging is a tensile strength of 2040 MPa, then according to the strength curve above Figure 1 , 470°C can be selected as the target tempering temperature.

[0037] For another example, when the strength requirement of the A-100 steel forging is a yield strength of 1735 MPa, then according to the above Figure 1From the strength curve, 488 °C can be selected as the target tempering temperature.

[0038] Optionally, the A-100 steel forging is obtained by forging based on an A-100 steel billet, and the A-100 steel billet includes 0.24% carbon, 0.052% silicon, 3.04% chromium, 11.21% nickel, 1.24% molybdenum, and 84.218% iron.

[0039] Optionally, the A-100 steel billet is obtained by vacuum induction and vacuum consumable melting.

[0040] Optionally, the A-100 steel billet is subjected to normalizing and high-temperature tempering treatments.

[0041] S102. Temper the A-100 steel forging according to the target tempering temperature.

[0042] For example, the A-100 steel forging can be heated to the target tempering temperature, held for 5 - 8 hours (h), and then air-cooled.

[0043] In some possible embodiments, before tempering the A-100 steel forging according to the target tempering temperature, the A-100 steel forging can also be heat-treated according to a first heat treatment process.

[0044] For example, the A-100 steel forging can be heated to 855 °C ± 15 °C, held for 60 min to 75 min, oil-cooled, and then reheated to -73 °C ± 8 °C and held for 60 min ± 5 min.

[0045] In some other possible embodiments, before heat-treating the A-100 steel forging according to the first heat treatment process, the A-100 steel forging can also be subjected to preliminary heat treatment according to a second heat treatment process.

[0046] For example, the A-100 steel forging can be heated to 900 °C ± 10 °C and held for at least 60 min, air-cooled, and then heated to 680 °C ± 10 °C and held for at least 16 h, air-cooled.

[0047] In still some other possible embodiments, after heat-treating the A-100 steel forging according to the first heat treatment process, the A-100 steel forging can also be cryogenically treated according to a third heat treatment process.

[0048] For example, the A-100 steel can be heated to 885 °C ± 15 °C, then oil-quenched, and then cooled to -73 °C ± 8 °C.

[0049] The heat treatment method for A-100 steel forgings provided by the embodiments of the present application can determine the target tempering temperature from the strength relationship curve based on the strength requirements of the A-100 steel forgings. The strength relationship curve includes the tensile strength curve and the yield strength curve. The tensile strength curve is used to characterize the corresponding relationship between the tempering temperature and the tensile strength of the A-100 steel forgings, and the yield strength curve is used to characterize the corresponding relationship between the tempering temperature and the yield strength of the A-100 steel forgings. In this way, the selected target tempering temperature is the tempering temperature that matches the strength requirements. According to the tempering temperature that matches the strength requirements, the desired strength requirements can be obtained through tempering treatment, thereby providing a solution for selecting an appropriate tempering temperature.

[0050] In some possible embodiments, before the above S101, the strength relationship curve can also be obtained. In this case, before the above S101, the method can further include the following steps: Step 1: Forge the A-100 steel bar into a cubic billet in one heat and slow cool after forging.

[0051] Step 2: Heat the cubic billet to 900°C ± 10°C and hold for at least 60 min, then air cool. Then heat it to 680°C ± 10°C and hold for at least 16 h, and then air cool.

[0052] Step 3: Cut the cubic billet into multiple specimens.

[0053] Step 4: Heat the multiple specimens to 855°C ± 15°C and hold for 60 min to 75 min, then oil cool. Then warm back to -73°C ± 8°C and hold for 60 min ± 5 min.

[0054] Step 5: Temper the multiple specimens at different tempering temperatures respectively, and test the tensile strength and yield strength of the specimens tempered at each tempering temperature.

[0055] Step 6: Draw the strength relationship curve according to the tensile strength and yield strength of the specimens tempered at each tempering temperature.

[0056] Steps 1 to 6 can be referred to the process of experimental analysis of the relationship between the heat treatment parameters and strength of A-100 steel forgings described above, and will not be elaborated here.

[0057] The technical solutions of the embodiments of the present application have been introduced from the perspective of the method. In an exemplary embodiment, the embodiments of the present application also provide an A-100 steel part, which is obtained by heat treating the A-100 steel forging using the heat treatment method in the above embodiment.

[0058] Based on the understanding of the above embodiments, the following conclusions can be drawn: 1) The A-100 steel is oil quenched at (885±15)°C for (60 - 75 min) of heat preservation, and after being reheated in air at (-73±8)°C for (60±5 min) of heat preservation, tempering treatment is carried out at (464 - 510)°C for (5 - 8 h) of heat preservation. With the increase of the tempering temperature, the strength and hardness of the A-100 steel decrease, the fracture toughness and reduction of area increase, while the elongation change is not obvious.

[0059] (2) Tempering at a temperature of (470 - 488)°C results in a good match between strength and fracture toughness, providing a reference for the determination of the process.

[0060] Although the present application has been described in connection with specific features and their embodiments, it is obvious that various modifications and combinations can be made without departing from the spirit and scope of the present application. Accordingly, the present specification and the drawings are merely exemplary illustrations of the present application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations or equivalents within the scope of the present application. Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these changes and modifications.

[0061] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any change or replacement within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A heat treatment method for A-100 steel forgings, characterized in that: The method comprises: Based on the strength requirement of the A-100 steel forging, the target tempering temperature is determined from the strength relationship curve; the strength relationship curve includes a tensile strength curve and a yield strength curve; the tensile strength curve is used to characterize the corresponding relationship between the tempering temperature and the tensile strength of the A-100 steel forging; the yield strength curve is used to characterize the corresponding relationship between the tempering temperature and the yield strength of the A-100 steel forging; The A-100 steel forging is tempered according to the target tempering temperature.

2. The method according to claim 1, characterized in that Before tempering the A-100 steel forging according to the target tempering temperature, the method further includes: The A-100 steel forging is heat treated according to a first heat treatment process.

3. The method according to claim 2, characterized in that The step of heat treating the A-100 steel forging according to the first heat treatment process comprises: The A-100 steel forging is heated to 855°C ± 15°C and kept at this temperature for 60 to 75 minutes, oil-cooled, returned to the temperature of -73°C ± 8°C, and kept at this temperature for 60 minutes ± 5 minutes.

4. The method according to claim 2, characterized in that: Before heat treating the A-100 steel forging according to the first heat treatment process, the method further includes: The A-100 steel forging is subjected to preliminary heat treatment according to a second heat treatment process.

5. The method according to claim 4, characterized in that The step of performing preliminary heat treatment on the A-100 steel forging according to the second heat treatment process comprises: The A-100 steel forging is heated to 900°C±10°C, kept at this temperature for at least 60 minutes, and air-cooled, and then heated to 680°C±10°C, kept at this temperature for at least 16 hours, and air-cooled.

6. The method according to any one of claims 1 to 5, characterized in that: The A-100 steel forging is forged based on an A-100 steel billet; the A-100 steel billet includes 0.24% carbon, 0.052% silicon, 3.04% chromium, 11.21% nickel, 1.24% molybdenum, and 84.218% iron.

7. The method according to claim 6, characterized in that The A-100 steel billet is obtained by vacuum induction and vacuum consumable smelting.

8. The method according to claim 6, characterized in that The A-100 steel billet is subjected to normalizing and high temperature tempering treatments.

9. The method according to claim 1, characterized in that: The method further comprises: The A-100 steel bar is forged into a cubic billet, which is completed in one fire and slowly cooled after forging; The cubic blank is heated to 900°C±10°C, kept at this temperature for at least 60 minutes, air-cooled, and then heated to 680°C±10°C, kept at this temperature for at least 16 hours, and air-cooled; cutting the cubic blank into a plurality of specimens; The plurality of samples are heated to 855°C ± 15°C, and kept at this temperature for 60 to 75 minutes, oil-cooled, returned to the temperature of -73°C ± 8°C, and kept at this temperature for 60 minutes ± 5 minutes; Tempering the plurality of samples at different tempering temperatures, respectively, and testing the tensile strength and yield strength of the samples tempered at each tempering temperature; The strength relationship curve is drawn according to the tensile strength and yield strength of the sample tempered at each tempering temperature.

10. An A-100 steel part, characterized in that: The A-100 steel parts are obtained by heat treating A-100 steel forgings using the heat treatment method described in any one of claims 1 to 9.

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