Austenitic stainless steel bolt and strengthening process thereof

Abstract

The invention relates to the technical field of fasteners, and discloses an austenitic stainless steel bolt and a strengthening process thereof. The strengthening technology of the austenitic stainless steel bolt comprises the steps that raw materials are smelted in vacuum and poured into a round bar blank; the round bar blank is subjected to solution treatment at the temperature of 1000-1100 DEG C; the blank obtained after solution treatment is rolled at the temperature ranging from 300 DEG C to 850 DEG C; carrying out blank surface short-time solution treatment on the rolled blank at the temperature of 1000-1100 DEG C under the protection atmosphere; and the blank obtained after surface solution treatment is cut into the required length, chamfering and gear hobbing are conducted, and the austenitic stainless steel bolt is obtained. According to the method, a process of fully matching solution treatment, medium-temperature deformation rolling processing and short-time solution treatment on the surface of the blank is adopted, so that the austenitic stainless steel bolt can be well strengthened, and the method is also suitable for strengthening the large-diameter austenitic stainless steel bolt.

Description

Technical Field

[0001] The present invention relates to the technical field of fasteners, and particularly to an austenitic stainless steel bolt and its strengthening process. Background Art

[0002] Austenitic stainless steel bolts are commonly used in complex working conditions such as high temperature, high pressure, and corrosive environments. Through strengthening treatment, it can ensure that the bolts maintain good mechanical properties and durability under these harsh conditions.

[0003] Since austenitic stainless steel is prone to precipitate carbides at the grain boundaries in the temperature range of 425 - 850°C, hot working in this temperature range is avoided as much as possible in engineering. Therefore, the commonly used strengthening treatment methods for austenitic stainless steel bolts currently include: solution treatment, and the method combining solution treatment and cold sizing.

[0004] After solution treatment, the strength of the solid-state bolts is still low, and the fastening performance of high-pressure bolts cannot be guaranteed. Cold sizing is to perform diameter-changing extrusion forming at room temperature, and its strength and hardness can be greatly improved. However, as the extrusion deformation amount of the bolt during cold sizing increases, the difficulty of diameter change also increases. Usually, the diameter reduction amount does not exceed 0.5 mm. Therefore, although the strength and hardness of the bolts can be greatly improved, the effect of strain strengthening is limited to the range of about 0.5 mm on the bolt surface and cannot play a role in strain strengthening the bolt core. Moreover, the larger the diameter of the bolt, the worse the cold sizing effect, and the effect can be almost negligible.

[0005] The engineering application of large-diameter austenitic stainless steel bolts is greatly restricted, resulting in that the use environment of many high-temperature and high-pressure austenitic stainless steel equipment basically cannot use conventional austenitic stainless steel, but expensive nickel-based stainless steel bolts are selected. Summary of the Invention

[0006] The main object of the present invention is to provide an austenitic stainless steel bolt and its preparation process, aiming to solve the problems in the prior art that the core of the austenitic stainless steel bolt cannot be effectively strengthened, and the large-diameter austenitic stainless steel bolt cannot be effectively strengthened.

[0007] To achieve the above object, the present invention proposes a strengthening process for an austenitic stainless steel bolt, including the following steps: S10. Melting an austenitic stainless steel raw material with the grade of 06Cr18Ni11Nb in vacuum and casting it into a round bar blank; S20. Subjecting the round bar blank in step S10 to sufficient solution treatment at 1000 - 1100°C and cooling it to room temperature with water; S30. Roll the billet after solution treatment in step S20 at 300 - 850°C, with the final cross-sectional diameter reduction ≥ 5%, and water-cool or air-cool to room temperature; S40. Under the condition of protective atmosphere, subject the rolled billet in step S30 to surface solution treatment at 1000 - 1100°C, with the solution treatment duration not exceeding 5 min, and water-cool to room temperature; S50. Cut the billet after surface solution treatment in step S40 into the required length, perform chamfering and hobbing, to obtain the austenitic stainless steel bolt.

[0008] Optionally, in step S30, the billet is rolled at 400 - 550°C.

[0009] Preferably, in step S30, the billet is rolled at 500 - 510°C.

[0010] Optionally, in step S30, the number of times the billet is rolled is two. After the first rolling, it is sent back to the furnace for heat preservation, and then the second rolling is carried out.

[0011] Optionally, in step S30, the temperature for heat preservation in the furnace is the same as the temperature during the second rolling, and the heat preservation duration is 5 - 20 min.

[0012] Optionally, in step S30, after the first rolling, the cross-sectional diameter reduction is 5 - 7.5%, and after the second rolling, the final cross-sectional diameter reduction is 7 - 10%.

[0013] Preferably, in step S30, after the first rolling, the cross-sectional diameter reduction is 7.0%, and after the second rolling, the final cross-sectional diameter reduction is 10.0%.

[0014] Optionally, in step S40, the surface solution treatment includes: heating the heat treatment furnace to 1100°C, feeding the billet into the heat treatment furnace, closing the furnace door, introducing argon into the furnace, waiting for the surface of the billet to heat up to 1000 - 1100°C, keeping warm for 2 - 5 min, taking the billet out of the furnace and water-cooling to room temperature.

[0015] Optionally, in step S40, during the surface solution treatment of the billet, when the surface of the billet heats up to 1040 - 1060°C, keep warm for 3 - 4 min.

[0016] Optionally, in step S10, the diameter of the round bar billet is 24 - 48 mm.

[0017] Optionally, in step S20, the duration of the solution treatment is 2 - 5 h.

[0018] The present invention also provides an austenitic stainless steel bolt, which is obtained by using the strengthening process of the austenitic stainless steel bolt described in any one of the above.

[0019] In the technical solution of the present invention, a round bar blank is made of an austenitic stainless steel raw material with the grade of 06Cr18Ni11Nb. The raw material components contain the stabilizing element niobium. Due to the presence of this stabilizing element, when hot working is carried out in an appropriate temperature range below the solution temperature, carbides precipitate dispersedly in the grains and will not be distributed at the grain boundaries, ensuring the effect of reducing the diameter and deforming the workpiece within an appropriate temperature range.

[0020] The round bar blank is fully solution-treated at 1000 - 1100 °C, which can make the structure and chemical composition of the austenitic stainless steel more uniform. By heating to the high-temperature single-phase region and holding for a certain time, carbides and alloying elements are fully dissolved in austenite, and a uniform single-phase structure is obtained after cooling. This helps to improve the overall performance of the material.

[0021] The billet after full solution treatment is subjected to medium-temperature deformation rolling at 300 - 850 °C, which can effectively improve the strength and hardness of the billet, and can also better strengthen the core of the billet, and is suitable for the strengthening of large-diameter bolts.

[0022] After the billet is subjected to medium-temperature deformation rolling, the hardened state on its surface will be hardened again at the tooth crest after hobbing. The superposition of multiple hardening processes is likely to cause microcracks at the tooth crest. Therefore, in the present invention, the billet after medium-temperature deformation rolling is subjected to a short-time solution treatment of no more than 5 minutes to soften the processing stress in the range of about 2 mm of the billet surface layer. And due to the low thermal conductivity of austenitic stainless steel, the short-time heat treatment will not spread the solution treatment temperature to the core of the billet, thus ensuring that while the processing stress on the billet surface layer is eliminated, the strength of the core remains unchanged, so as to better meet the reliability of thread processing quality.

[0023] The present invention uses the raw material of austenitic stainless steel with the grade of 06Cr18Ni11Nb to make bolts, and with full solution treatment, medium-temperature deformation rolling, and surface short-time solution treatment, it can better strengthen the austenitic stainless steel bolts, and can also better strengthen the core of the bolts. The bolts obtained have excellent hardness and strength, and are also suitable for the strengthening of large-diameter austenitic stainless steel bolts. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention 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 invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0025] Figure 1 It is the Vickers hardness test result diagram of Performance Test 1 of the present invention; Figure 2 It is the metallographic diagram of the bolt obtained in Example 1 in the tooth crest part in Performance Test 2 of the present invention; Figure 3 It is the metallographic diagram of the bolt obtained in Comparative Example 2 in the tooth crest part in Performance Test 2 of the present invention; Figure 4 It is the structural schematic diagram of 6 test positions in Performance Test 1 of the present invention.

[0026] Explanation of the reference numerals in the attached drawings: 1. Cylindrical structure; 11. The first group of test positions; 12. The second group of test positions; 13. The third group of test positions; 14. The fourth group of test positions; 15. The fifth group of test positions; 16. The sixth group of test positions.

[0027] The realization, functional characteristics and advantages of the purpose of the present invention will be further described in conjunction with the embodiments with reference to the attached drawings. Specific embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the attached drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0029] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, then the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the attached drawings). If the specific posture changes, the directional indications will also change accordingly.

[0030] In addition, if there are descriptions such as "first", "second", etc. involved in the embodiments of the present invention, then the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes the A solution, or the B solution, or the solution where A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] The present invention provides a strengthening process for austenitic stainless steel bolts, comprising the following steps: S10. Melting an austenitic stainless steel raw material of grade 06Cr18Ni11Nb in vacuum and casting it into a round bar blank; S20. Subjecting the round bar blank in step S10 to full solution treatment at 1000 - 1100 °C and water-cooling it to room temperature; S30. Rolling the blank after solution treatment in step S20 at 300 - 850 °C, with the final cross-sectional diameter reduction ≥ 5%, and water-cooling or air-cooling it to room temperature; S40. Under the condition of a protective atmosphere, subjecting the rolled blank in step S30 to surface solution treatment at 1000 - 1100 °C, with the solution treatment duration not exceeding 5 min, and water-cooling it to room temperature; S50. Cutting the blank after surface solution treatment in step S40 into the required length, chamfering and hobbing it to obtain the austenitic stainless steel bolt.

[0032] In the technical solution of the present invention, a round bar blank with a diameter of 24 - 48 mm is made of an austenitic stainless steel raw material of grade 06Cr18Ni11Nb. The raw material components contain the stabilizing element niobium. Due to the presence of this stabilizing element, when hot working is carried out in an appropriate temperature range below the solution temperature, carbides are precipitated dispersedly in the crystal grains and will not be distributed at the grain boundaries, ensuring the effect of diameter reduction deformation processing in an appropriate temperature range.

[0033] Subjecting the round bar blank to solution treatment at 1000 - 1100 °C for 2 - 5 h can make the structure and chemical composition of the austenitic stainless steel more uniform. By heating to the high-temperature single-phase region and holding for a certain time, carbides and alloying elements are fully dissolved in austenite, and a uniform single-phase structure is obtained after cooling. This helps to improve the overall performance of the material.

[0034] Carrying out medium-temperature deformation rolling processing on the blank after full solution treatment at 300 - 850 °C can effectively improve the strength and hardness of the blank, and can also better strengthen the core of the blank, and is suitable for the strengthening of large-diameter bolts.

[0035] After the blank is subjected to medium-temperature deformation rolling, hardening occurs again at the tooth crest after hobbing processing on its surface. The superposition of multiple hardening processes can easily lead to the generation of microcracks at the tooth crest. Therefore, in the present invention, the blank after medium-temperature deformation rolling is subjected to a short-time solution treatment of no more than 5 minutes to soften the processing stress in the range of about 2 mm in the surface layer of the blank. And due to the low thermal conductivity of austenitic stainless steel, the short-time heat treatment will not spread the solution heat treatment temperature to the core of the blank, thus ensuring that while the processing stress on the surface layer of the blank is eliminated, the strength of the core remains unchanged, so as to better meet the reliability of thread processing quality.

[0036] It should be noted that in step S30, the "cross-sectional diameter reduction amount" means that the diameter of the cross-section of the original blank is D0, and after the nth deformation rolling process, the diameter of the cross-section of the blank is Dn, where n is a positive integer. For example, n can take values such as 1, 2, etc. Then, after the nth deformation rolling process, the calculation formula for the cross-sectional diameter reduction amount is: Cross-sectional diameter reduction amount 。

[0037] Specifically, in the said step S30, the number of times the blank is rolled is two. After the first rolling is completed, it is sent back to the furnace for heat preservation, and then the second rolling is carried out. And the heat preservation temperature in the furnace when sent back is the same as the temperature during the second rolling, and the heat preservation duration is 5 - 20 minutes. Among them, after the first rolling, the cross-sectional diameter reduction amount is 5 - 7.5%, and after the second rolling, the final cross-sectional diameter reduction amount is 7 - 10%. Through two specific medium-temperature deformation rolling processes, the austenitic stainless steel bolt can be effectively strengthened.

[0038] Specifically, in the said step S40, the solution treatment of the blank surface includes: heating the heat treatment furnace to 1100°C, sending the blank into the heat treatment furnace, closing the furnace door, introducing argon gas into the furnace. When the surface of the blank is heated to 1000 - 1100°C, keep it warm for 2 - 5 minutes, then the blank is taken out of the furnace and cooled to room temperature by water.

[0039] The present invention also proposes an austenitic stainless steel bolt prepared by using the strengthening process of the austenitic stainless steel bolt described in any one of the above. The specific preparation process of the strengthening process of this austenitic stainless steel bolt refers to the above embodiments. Since this austenitic stainless steel bolt adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated here one by one.

[0040] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments and the drawings. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention. Embodiment 1

[0041] A strengthening process for an austenitic stainless steel bolt includes the following steps: S10. Melt the austenitic stainless steel raw material with the grade of 06Cr18Ni11Nb under vacuum and cast it into a round bar blank with a diameter of 48 mm. The chemical components of the raw material are shown in Table 1 below; S20. Solution-treat the round bar blank in step S10 at 1050 - 1060 °C for 3 h, and water-cool it to room temperature (25 °C); S30. Perform the first rolling on the blank after solution treatment in step S20 at 500 - 510 °C. After the first rolling, the cross-sectional diameter reduction of the blank is 7.0%, and water-cool it to room temperature (25 °C); S40. Heat the heat treatment furnace to 1100 °C, send the blank after rolling treatment in step S30 into the heat treatment furnace, close the furnace door, introduce argon into the furnace. Wait until the surface temperature of the blank rises to 1045 - 1055 °C, hold for 4 min, then take the blank out of the furnace and water-cool it to room temperature (25 °C); S50. Cut the blank after surface solution treatment in step S40 into the required length, chamfer and gear-hobbing process it to obtain the austenitic stainless steel bolt.

[0042] Table 1 Chemical components of the raw material (unit: wt%) C Si Mn P S Cr Ni Nb Fe and impurities Content 0.05 0.85 1.50 0.040 0.025 18.00 11.00 0.80 Balance Examples 2 - 5 Examples 2 - 5 are based on Example 1, and the difference is that: in step S30, the first rolling is carried out under different temperature conditions, and the others are the same as Example 1.

[0043] Example 2: In step S30, the first rolling is carried out at 300 - 310 °C.

[0044] Example 3: In step S30, the first rolling is carried out at 420 - 430 °C.

[0045] Example 4: In step S30, the first rolling is carried out at 660 - 670 °C.

[0046] Example 5: In step S30, the first rolling is carried out at 840 - 850 °C. Example 6

[0047] This example is based on Example 1, and the difference is that: in step S30, after the first rolling, the cross-sectional diameter reduction of the blank is 7.0%. Send the blank after the first rolling into a heat treatment furnace at 510 °C. Wait until the surface temperature of the blank rises to 500 - 510 °C, hold for 10 min. Then perform the second rolling on the blank at 500 - 510 °C. After the second rolling, the final cross-sectional diameter reduction of the blank (the cumulative diameter reduction of the first and second times) is 10%, and water-cool it to room temperature (25 °C).

[0048] Examples - 7 to 8 Examples 7 to 8 are based on Example 6, and the difference lies in that: in step S30, after the first rolling, the cross-sectional diameter reduction of the blank is different, and the others are the same as those in Example 6.

[0049] Example 7: In step S30, after the first rolling, the cross-sectional diameter reduction of the blank is 5.0%.

[0050] Example 8: In step S30, after the first rolling, the cross-sectional diameter reduction of the blank is 7.5%.

[0051] Comparative Example 1 This comparative example is based on Example 1, and the difference lies in that: step S30 is not included, that is, the blank after solution treatment in step S20 is directly processed according to step S40, and the others are the same as those in Example 1.

[0052] Comparative Example 2 This comparative example is based on Example 1, and the difference lies in that: step S40 is not included, that is, the blank after the first rolling is directly processed according to step S50, and the others are the same as those in Example 1.

[0053] Performance Test 1 The bolts prepared in Example 1, Example 6 and Comparative Example 1 were subjected to Vickers hardness test with reference to GB / T 4340.1 - 2009 "Metallic materials - Vickers hardness test - Part 1: Test method". During the test, the ends of the corresponding bolts were intercepted along the radial direction to obtain a cylindrical structure 1 with a thickness of 1 cm, and this cylindrical structure was used as the specimen. When testing, the first group of test positions 11 were 3 points at a distance of 50 μm from the tooth root, the second group of test positions 12 were 3 points at a distance of 1 mm from the tooth root, the third group of test positions 13 were 3 points at a distance of 2 mm from the tooth root, the fourth group of test positions 14 were 3 points at a distance of 3 mm from the tooth root, the fifth group of test positions 15 were 3 points at a distance of 4 mm from the tooth root, and the sixth group of test positions 16 were 3 points in the middle (i.e., the core). A total of 6 groups of data were detected, and the test results of each group were the average values of the test data of the corresponding 3 points. For the three test groups of Example 1, Example 6 and Comparative Example 1, each test group had 6 test positions, and each test position corresponded to 3 points. The test results are as Figure 1 shown.

[0054] Among them, Figure 1The yellow broken line corresponds to Comparative Example 1, the blue broken line corresponds to Example 1, and the gray broken line corresponds to Example 6. Among them, "1" in the table corresponds to the 1st group of test positions, and so on, "6" corresponds to the 6th group of test positions. Only the average data of Vickers hardness are shown in the table, and the unit is not recorded. It can be understood that the unit is HV. For example, for the column corresponding to "1", the "330.60" of the corresponding yellow broken line indicates that the Vickers hardness is 330.60 HV.

[0055] From Figure 1 the test structure of, it can be seen that by fully solution treatment, combined with medium-temperature rolling deformation processing and surface short-time solution treatment, the hardness of large-diameter austenitic stainless steel bolts can be effectively improved. The hardness of the tooth root part can reach above 410 HV, and the hardness of the core part can reach above 260 HV, which has a good strengthening effect on the core part. From Figure 1 it can also be seen that compared with Example 1, Example 6 can further increase the strengthening effect through two hot rolling treatments.

[0056] Performance Test 2 The metallographic diagram of the bolt obtained in Example 1 at the tooth top is as Figure 2 shown, and the metallographic diagram of the bolt obtained in Comparative Example 2 at the tooth top is as Figure 3 shown. From Figure 2 and Figure 3 it can be seen that in Comparative Example 2, due to the lack of surface short-time solution treatment, cracking appears at the tooth top, while in Example 1, due to the surface short-time solution treatment, no cracking phenomenon is observed at the tooth top. It shows that after the bar material is strengthened by medium-temperature rolling, when gear hobbing is carried out, the shear stress of the die gear is superimposed on the original strengthening stress, and the internal stress is huge. The extrusion streamline of the internal grains of the metal instantly gushes like molten slurry, and tiny cracks are extremely likely to appear at the tooth top of the tooth pattern under the action of shear stress. These microcracks that appear at the tooth top are also extremely likely to expand and tear during the preloading of the bolt, squeezing into the thread to form foreign objects and jamming the nut. After the bar material is strengthened by medium-temperature rolling, short-time solution heat treatment is carried out on the shallow surface layer of the bar material to eliminate the processing stress on the shallow surface layer of the bar material. When gear hobbing is carried out, the shear stress of the die gear has no superposition with the original strengthening stress, the metal streamline direction is consistent, no conventional cracks will appear at the tooth top of the tooth pattern, and the bolt performance is greatly improved.

[0057] Performance Test 3 The bolts obtained in Examples 1 to 8 and Comparative Example 1 were subjected to a yield strength test according to GB / T 228.2-2015 "Metallic materials - Tensile testing - Part 2: Testing methods at elevated temperatures". During the test, the ends of the corresponding bolts were intercepted along the radial direction to obtain a cylindrical structure with a thickness of 5 mm, and this cylindrical structure was used as the specimen. The test temperature was 600 °C, and the test results are shown in Table 2 below.

[0058] Table 2 Bolt Yield Strength Yield strength (MPa) Example 1 424 Example 2 357 Example 3 388 Example 4 421 Example 5 413 Example 6 429 Example 7 425 Example 8 427 Comparative Example 1 189 As can be seen from the high-temperature test results in Table 2, the medium-temperature rolling and short-time surface solution treatment adopted in the present invention can effectively improve the yield strength of bolts, and the bolts thus prepared can be preferably applied to high-temperature environments.

[0059] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the patent protection scope of the present invention.

Claims

1. A strengthening process for an austenitic stainless steel bolt, characterized in that It includes the following steps: S10. Melting an austenitic stainless steel raw material with the grade of 06Cr18Ni11Nb under vacuum and casting it into a round bar blank; S20. Subjecting the round bar blank in the step S10 to full solution treatment at 1000 - 1100 °C and cooling it to room temperature with water; S30. Rolling the blank after solution treatment in the step S20 at 300 - 850 °C, with the final cross-sectional diameter reduction ≥ 5%, and cooling it to room temperature with water or air; S40. Under the condition of a protective atmosphere, subjecting the blank after rolling in the step S30 to surface solution treatment at 1000 - 1100 °C, with the surface solution treatment not exceeding 5 min, and cooling it to room temperature with water; S50. Cutting the blank after surface solution treatment in the step S40 into the required length, chamfering and hobbing it to obtain the austenitic stainless steel bolt.

2. The strengthening process of the austenitic stainless steel bolt according to claim 1, characterized in that, In the step S30, the blank is rolled at 400 - 550 °C.

3. The strengthening process of the austenitic stainless steel bolt according to claim 2, wherein, In the step S30, the number of rolling times of the blank is two. After the first rolling is completed, it is returned to the furnace for heat preservation and then the second rolling is carried out.

4. The strengthening process of the austenitic stainless steel bolt according to claim 3, characterized in that, In the step S30, the temperature of heat preservation in the furnace is the same as the temperature during the second rolling, and the heat preservation duration is 5 - 20 min.

5. The strengthening process of the austenitic stainless steel bolt according to claim 3, characterized in that, In the step S30, after the first rolling, the cross-sectional diameter reduction is 5 - 7.5%, and after the second rolling, the final cross-sectional diameter reduction is 7 - 10%.

6. The strengthening process of the austenitic stainless steel bolt according to claim 1, characterized in that, In the step S40, the surface solution treatment includes: heating the heat treatment furnace to 1100 °C, feeding the blank into the heat treatment furnace, closing the furnace door, introducing argon into the furnace, waiting for the surface of the blank to rise to 1000 - 1100 °C, keeping it warm for 2 - 5 min, taking the blank out of the furnace and cooling it to room temperature with water.

7. The strengthening process of the austenitic stainless steel bolt according to claim 6, characterized in that, In the step S40, during the surface solution treatment of the blank, when the surface of the blank rises to 1040 - 1060 °C, keep it warm for 3 - 4 min.

8. The strengthening process of the austenitic stainless steel bolt according to claim 1, characterized in that, In the step S10, the diameter of the round bar blank is 24 - 48 mm.

9. The strengthening process of the austenitic stainless steel bolt according to claim 1, characterized in that, In the step S20, the duration of the solution treatment is 2 - 5 h.

10. An austenitic stainless steel bolt, characterized in that, It is obtained by using the strengthening process of the austenitic stainless steel bolt according to any one of claims 1 - 9.

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