A high-strength alloy structural steel for shafts and its preparation method

Abstract

This invention discloses a high-strength alloy structural steel for shafts and its preparation method, belonging to the technical field of alloy structural steel, and solving the problem of low strength in existing shaft materials. The high-strength alloy structural steel for shafts comprises, by mass percentage: C 0.40%–0.50%, Mn 0.20%–1.00%, Si 0.15%–0.60%, Mo 0.30%–0.80%, Cr 1.30%–3.00%, Ni 2.50%–5.00%, P ≤0.01%, S ≤0.01%, Al ≤0.03%, O ≤0.002%, with the remainder being Fe and unavoidable impurities. The high-strength alloy structural steel for shafts of this invention possesses both high strength and high toughness.

Description

Technical Field

[0001] This invention relates to the field of alloy structural steel technology, and in particular to a high-strength alloy structural steel for shafts and its preparation method. Background Technology

[0002] The commonly used stainless steel for shafts is 3Cr13. Its common chemical composition by mass percentage is as follows: carbon (C) 0.26-0.35%, silicon (Si) ≤1.00%, manganese (Mn) ≤1.00%, chromium (Cr) 12.00-14.00%, nickel (Ni) ≤0.60%, phosphorus (P) ≤0.04%, sulfur (S) ≤0.03%, with the remainder being iron and unavoidable impurities. The tensile strength of 3Cr13 after heat treatment is 1604 MPa, and the yield strength is 913 MPa.

[0003] With the development of industry, the working environment and intensity of shaft materials have put forward higher strength requirements. The strength of 3Cr13 can no longer meet the needs of shaft materials. Therefore, providing a high-strength shaft alloy material is an urgent technical problem to be solved. Summary of the Invention

[0004] In view of the above, the present invention aims to provide a high-strength alloy structural steel for shafts and its preparation method, in order to solve the problem of low strength of existing shaft materials.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] This invention provides a high-strength alloy structural steel for shafts. The composition of the high-strength alloy structural steel for shafts, by mass percentage, includes: C 0.40%–0.50%, Mn 0.20%–1.00%, Si 0.15%–0.60%, Mo 0.30%–0.80%, Cr 1.30%–3.00%, Ni 2.50%–5.00%, P ≤0.01%, S ≤0.01%, Al ≤0.03%, O ≤0.002%, with the remainder being Fe and unavoidable impurities.

[0007] Furthermore, the composition of the high-strength shaft alloy structural steel, by mass percentage, is: C 0.42%–0.50%, Mn 0.50%–1.00%, Si 0.30%–0.60%, Mo 0.40%–0.75%, Cr 2.0%–3.0%, Ni 2.50%–4.50%, P ≤0.005%, S ≤0.002%, O ≤0.002%, with the balance being Fe and unavoidable trace impurities.

[0008] Furthermore, the microstructure of high-strength alloy structural steel for shafts includes a martensitic matrix and uniformly dispersed Cr. 23C6 and G are equal, and Cr is guaranteed by elements such as C, Cr, Mo, Ni, Mn and Si. 23 The number of precipitated phases, such as C6 and G, ultimately improves the mechanical properties of steel through the interaction between these phases.

[0009] Furthermore, the average tensile strength of high-strength alloy structural steel for shafts is 1840–1854 MPa, and the average yield strength is 1421–1432 MPa.

[0010] The present invention also provides a method for preparing the above-mentioned high-strength alloy structural steel for shafts, the method comprising the following steps:

[0011] Step 1, Raw material preparation: Prepare the raw materials according to the mass percentage of each component of the high-strength shaft alloy structural steel;

[0012] Step 2, Vacuum Induction Melting: The raw materials are loaded into a vacuum induction furnace for melting, and then refined to obtain molten steel;

[0013] Step 3, Casting: Cast the molten steel into electrode rods;

[0014] Step 4, Vacuum self-consumption: After surface treatment of the electrode rod, vacuum self-consumption is performed to obtain a consumable ingot;

[0015] Step 5, Forging: Forging the consumable ingot, then air-cooling it to room temperature to obtain a forged billet;

[0016] Step 6, Heat treatment: Heat the forging billet to 850-900℃, hold for 2-4 hours, air cool to no more than 80℃, then perform deep cryogenic treatment, and finally perform low-temperature tempering; then air cool to below 50℃ to obtain high-strength alloy structural steel for shafts.

[0017] Furthermore, in step 2, melting is carried out at 1500–1530°C.

[0018] Furthermore, in step 2, refining is carried out at 1530–1550°C under a vacuum of 1–5 Pa.

[0019] Furthermore, in step 3, the electrode rod is cast at a temperature of 1550–1580°C and a casting speed of 100–300 kg / min.

[0020] Furthermore, in step 6, the cryogenic treatment includes: holding at -70 to -80°C for 2 to 3 hours.

[0021] Furthermore, in step 6, the low-temperature tempering process is as follows: holding at 200-250℃ for 2-4 hours.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] a) The high-strength alloy structural steel for shafts of the present invention, through strict control of the content of chemical elements, especially C, Cr, and Mo, can obtain a uniformly distributed, C-containing, dispersed strengthening precipitate Cr on a martensitic matrix. 23 The C6 and G phases, along with uniformly distributed Mo, can enhance the strength and tempering stability of alloy materials through solid solution strengthening. The amount of Cr in the steel can be controlled by rationally managing the addition of each element. 23 The content of C6 and G phases is controlled to ensure the strength of the steel. This high-strength alloy structural steel achieves its strength by strictly controlling the content of each element in the steel, so that the elements cooperate with each other to effectively improve the segregation of chemical elements, the segregation of precipitated phases, and the uniformity of the microstructure, thereby improving the mechanical properties of the alloy material, especially its room temperature strength.

[0024] b) The high-strength alloy structural steel for shafts of the present invention has high strength and high toughness, for example: the average tensile strength is 1840-1854 MPa and the average yield strength is 1421-1432 MPa.

[0025] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of what is particularly pointed out in the written description and claims. Detailed Implementation

[0026] The preferred embodiments of the present invention will now be described in detail. These embodiments are used to illustrate the principles of the present invention.

[0027] This invention provides a high-strength alloy structural steel for shafts. The composition of the high-strength alloy structural steel for shafts, by mass percentage, includes: C 0.40%–0.50%, Mn 0.20%–1.00%, Si 0.15%–0.60%, Mo 0.30%–0.80%, Cr 1.30%–3.00%, Ni 2.50%–5.00%, P ≤0.01%, S ≤0.01%, Al ≤0.03%, O ≤0.002%, with the remainder being Fe and unavoidable impurities.

[0028] The following details the function and dosage selection of the components contained in this invention:

[0029] C: As one of the alloying strengthening elements, C can form Cr with Cr in steel. 23 C6 precipitates diffusely at grain boundaries, playing a role in precipitation strengthening. However, with increasing C content, the precipitated Cr phase... 23 C6 will aggregate and grow, when Cr 23The strengthening effect of C6 on steel gradually weakens as the size of C6 reaches a certain level. Therefore, the C content in steel needs to be controlled within a certain range to better utilize the precipitation strengthening effect of C to improve the strength and hardness of the steel. Therefore, in this invention, the C content is controlled at 0.40% to 0.50%.

[0030] Mn: Mn can improve the hot plasticity of steel and eliminate the hot brittleness of sulfur in steel. Furthermore, adding a small amount of Mn to steel can improve its wear resistance. Generally, an Mn content of around 0.8% is optimal for both hot plasticity and wear resistance. As the Mn content increases further, its wear resistance and hot plasticity hardly increase, but increasing the Mn content leads to increased steel production costs. Therefore, in this invention, the Mn content is controlled at 0.20% to 1.00%.

[0031] Si: As one of the ferrite-forming elements, Si can stabilize the ferrite structure. Moreover, a small amount of Si can also improve the aging hardness of steel. If the Si content in steel is too high, it will significantly increase the sensitivity of steel to intergranular corrosion. Therefore, the Si content in steel needs to be controlled within a certain range. Thus, in this invention, the Si content is controlled to be 0.15% to 0.60%.

[0032] Mo: The addition of Mo can improve the tempering stability of steel, increasing its strength while maintaining its toughness. However, as the Mo content increases, the hardness of the steel increases significantly while decreasing its toughness, making it impossible to guarantee both strength and toughness. Therefore, in this invention, the Mo content is controlled at 0.30% to 0.80%.

[0033] Cr: As one of the main corrosion-resistant elements, Cr can not only improve the corrosion resistance of steel, but also interact with C to form Cr. 23 C6 intergranular dispersed phases are used to improve the strength and hardness of steel, but the Cr content must be controlled. 23 Size of C6 precipitate, Cr 23 Excessive C6 precipitate size can lead to a decrease in the strength and hardness of steel. Therefore, in this invention, the Cr content is controlled to be 1.30% to 3.00%.

[0034] Ni: The addition of Ni can effectively improve the toughness and elongation of steel. However, as the Ni content increases, it will have an adverse effect on the strength of steel. Therefore, in this invention, the Ni content is controlled to be 2.50% to 5.00%.

[0035] To further improve the overall performance of the aforementioned high-strength alloy structural steel for shafts, the composition of the aforementioned high-strength alloy structural steel for shafts, by mass percentage, is as follows: C 0.42%–0.50%, Mn 0.50%–1.00%, Si 0.30%–0.60%, Mo 0.40%–0.75%, Cr 2.0%–3.0%, Ni 2.50%–4.50%, P≤0.005%, S≤0.002%, O≤0.002%, with the balance being Fe and unavoidable trace impurities.

[0036] Specifically, the microstructure of the aforementioned high-strength shaft alloy structural steel includes a martensitic matrix and uniformly dispersed Cr. 23 C6 and G are equal, and Cr is guaranteed by elements such as C, Cr, Mo, Ni, Mn and Si. 23 The number of precipitated phases, such as C6 and G, ultimately improves the mechanical properties of steel through the interaction between these phases.

[0037] Specifically, in the microstructure of the aforementioned high-strength shaft alloy structural steel, Cr 23 The volume percentage of C6 and G phases is 5% to 9.5%.

[0038] Specifically, the high-strength shaft alloy structural steel mentioned above has uniform and fine grains, with a grain size of 7 to 8.5.

[0039] The present invention also provides a method for preparing the above-mentioned high-strength alloy structural steel for shafts, comprising the following steps:

[0040] Step 1, Raw material preparation: Prepare the raw materials according to the mass percentage of each component of the high-strength shaft alloy structural steel;

[0041] Step 2, Vacuum Induction Melting: The raw materials are loaded into a vacuum induction furnace for melting, and then refined to obtain molten steel;

[0042] Step 3, Casting: Cast the molten steel into electrode rods;

[0043] Step 4, Vacuum self-consumption: After the surface of the electrode rod is machined and polished, vacuum self-consumption is performed to obtain a consumable ingot;

[0044] Step 5, Forging: The consumable ingot is forged at an initial forging temperature of 1150-1200℃ and a final forging temperature of 840-950℃. After two upsettings and two drawings, and six heatings, the ingot is forged and then air-cooled to room temperature to obtain a forged billet.

[0045] Step 6, Heat treatment: Heat the forging billet to 850-900℃, hold for 2-4 hours, air cool to no more than 80℃, then perform deep cryogenic treatment, and finally perform low-temperature tempering; then air cool to below 50℃ to obtain high-strength alloy structural steel for shafts.

[0046] Specifically, in step 2 above, melting is carried out at 1500–1530°C.

[0047] Specifically, in step 2 above, refining is carried out at 1530–1550°C under a vacuum of 1–5 Pa.

[0048] Specifically, in step 2 above, if the refining time is too short, the degassing in the steel will be incomplete; if the refining time is too long, the refractory material of the crucible will enter the molten steel and contaminate it. Both too long and too short a refining time will contaminate the molten steel, affecting its purity and ultimately its mechanical properties. Therefore, in this invention, the refining time is controlled to be 25 to 40 minutes.

[0049] Specifically, in step 3 above, the casting speed and casting temperature are controlled in combination to improve the ingot yield of the cast electrode rod and reduce production costs. If the casting speed is too fast or the temperature is too high, energy consumption will increase; if the casting speed is too slow or the temperature is too low, the element distribution will be uneven. Therefore, the electrode rod is cast at a temperature of 1550–1580℃ (e.g., 1560℃, 1570℃) and a casting speed of 100–300 kg / min.

[0050] Specifically, in step 3 above, the casting process is carried out in an argon atmosphere. Because the steel contains Mn, if the argon pressure is too low during casting, a large amount of Mn will volatilize, and in severe cases, it will contaminate the casting chamber. While a higher argon pressure can also reduce Mn volatilization, its effect on inhibiting Mn volatilization is not significantly different from that of a lower pressure, but higher pressure increases production costs. Therefore, the argon pressure is controlled at 3000–8000 Pa.

[0051] Specifically, in step 4 above, the initial stage of vacuum self-consumption has a current of 2.5–7.5 kA, a voltage of 22.5–25.5 V, and a melting rate of 1–9 drops / s; the melting rate in the smelting stage is 1.8–3 kg / min, and the dripping rate is 2–4 drops / s; the current in the hot capping stage is 1.8–2.5 kA, and the melting rate is 1–4 drops / s.

[0052] Specifically, in step 6 above, considering that excessively high temperatures will cause the steel grains to grow rapidly and affect the mechanical properties of the steel, while excessively low temperatures will prevent the microstructure from completely transforming into austenite; excessively long holding times will cause the grains to grow excessively, while excessively short holding times will prevent the microstructure from completely transforming into austenite, the temperature is controlled at 850–900℃ for 2–4 hours.

[0053] Specifically, in step 6 above, the temperature is increased to 850-900℃ at a heating rate of 80-100℃ / h.

[0054] Specifically, in step 6 above, in order to improve the toughness of the steel while ensuring its strength, the cryogenic treatment includes: holding at -70 to -80°C for 2 to 3 hours.

[0055] Specifically, in step 6 above, in order to remove the stress of the alloy, a low-temperature tempering process is performed. The low-temperature tempering process is as follows: hold at 200-250℃ for 2-4 hours.

[0056] Specifically, in step 6 above, the high-strength alloy structural steel for shafts has high strength and high toughness, for example: the average tensile strength is 1840-1854 MPa and the average yield strength is 1421-1432 MPa.

[0057] Examples 1-3

[0058] The advantages of precise control of the composition and process parameters of the steel of the present invention will be demonstrated below with specific embodiments and comparative examples.

[0059] Examples 1-3 of the present invention provide a high-strength alloy structural steel for shafts and a method for preparing the same. The chemical composition of the steel in Examples 1-3 is shown in Table 1.

[0060] The preparation method of Example 1 includes:

[0061] Step 1, Raw material preparation: Prepare the raw materials according to the mass percentage of each component of the high-strength shaft alloy structural steel;

[0062] Step 2, Vacuum Induction Melting: The raw materials are loaded into a vacuum induction furnace and melted at 1510-1520℃, and then refined at 1530-1540℃ and 2-4Pa for 30 minutes to obtain molten steel.

[0063] Step 3, Casting: The molten steel is cast into an electrode rod (250 mm in diameter) at a casting speed of 150 kg / min at 1550-1560℃. Argon gas protection is used throughout the casting process, with an argon purging rate of 4000 Pa.

[0064] Step 4, Vacuum Consumable Ingot: After machining the surface of the electrode rod, vacuum consumable ingot is obtained; in the initial stage of vacuum consumable ingot, the smelting current is controlled at 2.5-3.5KA, the smelting voltage is 22.5-23.5V, and the melting rate is 2-5 drops / s; in the melting stage, the melting rate is 3kg / min and the melting drop rate is 3 drops / s; in the hot sealing stage, the current is 2-2.5KA and the melting rate is 1-3 drops / s, resulting in a consumable ingot (diameter 305mm);

[0065] Step 5, Forging: The consumable ingot is forged at an initial forging temperature of 1170-1180℃ and a final forging temperature of 840-850℃. After two upsettings and two drawings, and six heatings, the ingot is forged and then air-cooled to room temperature to obtain a forged billet.

[0066] Step 6, Heat treatment: Heat the forging billet to 850℃ at a heating rate of 85℃ / h, hold for 2 hours, and air cool to 70℃; then hold at -75℃ for 2 hours, and finally hold at 200℃ for 2 hours, and air cool to room temperature to obtain high-strength alloy structural steel for shafts.

[0067] The preparation method of Example 2 includes:

[0068] Step 1, Raw material preparation: Prepare the raw materials according to the mass percentage of each component of the high-strength shaft alloy structural steel;

[0069] Step 2, Vacuum Induction Melting: The raw materials are loaded into a vacuum induction furnace and melted at 1515-1520℃, and then refined at 1540-1550℃ and 2-5Pa for 40 minutes to obtain molten steel.

[0070] Step 3, Casting: Molten steel is cast into electrode rods (250 mm in diameter) at a casting speed of 200 kg / min at 1570-1580℃. Argon gas protection is used throughout the casting process, with an argon purging rate of 6000 Pa.

[0071] Step 4, Vacuum Consumable Ingot: After machining the surface of the electrode rod, vacuum consumable ingot is obtained; in the initial stage of vacuum consumable ingot, the smelting current is controlled at 3-4 kA, the smelting voltage is 22.5-23.5 V, and the melting rate is 3-5 drops / s; in the melting stage, the melting rate is 3 kg / min and the melting drop rate is 3 drops / s; in the hot sealing stage, the current is 1.8-2.2 kA and the melting rate is 1-3 drops / s, resulting in a consumable ingot (diameter 305 mm);

[0072] Step 5, Forging: The consumable ingot is forged at an initial forging temperature of 1180-1200℃ and a final forging temperature of 880-900℃. After two forgings and two drawings, the ingot is forged and then air-cooled to room temperature to obtain a forged billet.

[0073] Step 6, Heat treatment: Heat the forging billet to 880℃ at a heating rate of 85℃ / h, hold for 3 hours, and air cool to 50℃; then hold at -75℃ for 3 hours, and finally hold at 250℃ for 3 hours, and air cool to room temperature to obtain high-strength alloy structural steel for shafts.

[0074] The preparation method of Example 3 includes:

[0075] Step 1, Raw material preparation: Prepare the raw materials according to the mass percentage of each component of the high-strength shaft alloy structural steel;

[0076] Step 2, Vacuum Induction Melting: The raw materials are loaded into a vacuum induction furnace and melted at 1520-1530℃, and then refined at 1545-1550℃ and 2-5Pa for 40 minutes to obtain molten steel.

[0077] Step 3, Casting: Molten steel is cast into electrode rods (250mm in diameter) at a casting speed of 250kg / min at 1560~1570℃. Argon gas protection is used throughout the casting process, with argon purging at 8000Pa.

[0078] Step 4, Vacuum Consumable Ingot: After machining the surface of the electrode rod, vacuum consumable ingot is obtained; in the initial stage of vacuum consumable ingot, the smelting current is controlled at 5.5-7KA, the smelting voltage is 23.5-24.5V, and the melting rate is 5-7 drops / s; in the melting stage, the melting rate is 3kg / min and the melting drop rate is 3 drops / s; in the hot sealing stage, the current is 2-2.5KA and the melting rate is 1-3 drops / s, resulting in a consumable ingot (diameter 305mm);

[0079] Step 5, Forging: The consumable ingot is forged at an initial forging temperature of 1160-1180℃ and a final forging temperature of 920-950℃. After two forgings and two drawings, and six heatings, the ingot is forged and then air-cooled to room temperature to obtain a forged billet.

[0080] Step 6, Heat treatment: Heat the forging billet to 890℃ at a heating rate of 85℃ / h, hold for 4 hours, and air cool to 50℃; then hold at -75℃ for 4 hours, and finally hold at 250℃ for 4 hours, and air cool to room temperature to obtain high-strength alloy structural steel for shafts.

[0081] The microstructures of Examples 1-3 are shown in Table 2 below. The main performance test results of Examples 1-3 are shown in Table 3.

[0082] Table 1 Chemical composition, wt%

[0083]

[0084] Table 2 Microstructure of Steel

[0085]

[0086]

[0087] Table 3 shows some performance test results.

[0088] Example 1 1840 1421 16.5 Example 2 1854 1432 16 Example 3 1848 1427 16 Comparative Example 1 1748 1378 18 Comparative Example 2 1783 1382 18.5

[0089] The inventors conducted extensive experimental research during the research process, and some poorly performing solutions are now presented as comparative examples.

[0090] Comparative Example 1

[0091] This comparative example provides an alloy structural steel for shafts and its preparation method. The composition is shown in Table 1 above. The preparation method is the same as that in Example 1, and will not be repeated here.

[0092] Comparative Example 2

[0093] This comparative example provides an alloy structural steel for shafts and its preparation method. The composition is shown in Table 1 above. The preparation method is the same as that in Example 1, and will not be repeated here.

[0094] In summary, the high-strength alloy structural steel for shafts provided by this invention, through strict control of the content of chemical elements, especially C, Cr, and Mo, can produce a uniformly distributed, C-containing, dispersed strengthening precipitate on a martensitic matrix. 23 The C6 and G phases, along with uniformly distributed Mo, can enhance the strength and tempering stability of alloy materials through solid solution strengthening. The amount of Cr in the steel can be controlled by rationally managing the addition of each element. 23 The content of C6 and G phases, Cr 23 Too much C6 will lead to the precipitation of Cr at grain boundaries. 23 C6 has a larger particle size, which weakens the dispersion strengthening effect. 23 A low C6 content also leads to fewer grain boundary precipitates, resulting in poor dispersion strengthening and consequently affecting the strength of the alloy material. This high-strength alloy structural steel, through strict control of the content of each element, achieves synergistic effects between the elements to effectively improve the segregation of chemical elements and precipitated phases, as well as the uniformity of the microstructure, thereby enhancing the mechanical properties of the alloy material, especially its room temperature strength. Compared with existing stainless steel for shafts, the high-strength alloy structural steel for shafts provided by this invention increases the tensile strength and yield strength by more than 15% and 56%, respectively, meeting the high-strength performance requirements of current working environments for shaft metal materials, while also extending the service life of the alloy shaft.

[0095] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-strength alloy structural steel for shafts, characterized in that, The high-strength alloy structural steel for shafts comprises, by mass percentage: C 0.47%~0.50%, Mn 0.85%~0.95%, Si 0.15%~0.45%, Mo 0.60%~0.80%, Cr 1.30%~3.00%, Ni 2.50%~5.00%, P ≤0.01%, S ≤0.01%, Al ≤0.03%, O ≤0.002%, with the remainder being Fe and unavoidable impurities; The microstructure of the high-strength alloy structural steel for shafts includes a martensitic matrix and uniformly dispersed Cr. 23 C6 and G phases, the Cr 23 The volume percentage of C6 and G phases is 5%~9.5%; the grain size is 7~8.

5. The high-strength alloy structural steel for shafts has an average tensile strength of 1840~1854 MPa and an average yield strength of 1421~1432 MPa. The method for preparing the high-strength alloy structural steel for shafts includes the following steps: Step 1, Raw material preparation: Prepare the raw materials according to the mass percentage of each component of the high-strength shaft alloy structural steel; Step 2, Vacuum Induction Melting: The raw materials are loaded into a vacuum induction furnace for melting, and then refined to obtain molten steel; Step 3, Casting: Cast the molten steel into electrode rods; Step 4, Vacuum self-consumption: After surface treatment of the electrode rod, vacuum self-consumption is performed to obtain a consumable ingot; Step 5, Forging: Forging the consumable ingot, then air-cooling it to room temperature to obtain a forged billet; Step 6, Heat treatment: Heat the forging billet to 850~900℃, hold for 2~4 hours, air cool to no more than 80℃, then hold at -70~-80℃ for 2~3 hours for deep cryogenic treatment; finally, hold at 200~250℃ for 2~4 hours for low-temperature tempering; then air cool to below 50℃ to obtain high-strength alloy structural steel for shafts.

2. The high-strength alloy structural steel for shafts according to claim 1, characterized in that, The high-strength alloy structural steel for shafts comprises, by mass percentage: C 0.47%~0.50%, Mn 0.85%~0.95%, Si 0.15%~0.45%, Mo 0.60%~0.75%, Cr 2.0%~3.0%, Ni 2.50%~4.50%, P ≤0.005%, S ≤0.002%, O ≤0.002%, with the balance being Fe and unavoidable trace impurities.

3. A method for preparing high-strength alloy structural steel for shafts according to any one of claims 1 to 2, characterized in that, The preparation method includes the following steps: Step 1, Raw material preparation: Prepare the raw materials according to the mass percentage of each component of the high-strength shaft alloy structural steel; Step 2, Vacuum Induction Melting: The raw materials are loaded into a vacuum induction furnace for melting, and then refined to obtain molten steel; Step 3, Casting: Cast the molten steel into electrode rods; Step 4, Vacuum self-consumption: After surface treatment of the electrode rod, vacuum self-consumption is performed to obtain a consumable ingot; Step 5, Forging: Forging the consumable ingot, then air-cooling it to room temperature to obtain a forged billet; Step 6, Heat treatment: Heat the forging billet to 850~900℃, hold for 2~4 hours, air cool to no more than 80℃, then perform deep cryogenic treatment, and finally perform low-temperature tempering; then air cool to below 50℃ to obtain high-strength alloy structural steel for shafts.

4. The preparation method according to claim 3, characterized in that, In step 2, melting is carried out at 1500~1530℃.

5. The preparation method according to claim 3, characterized in that, In step 2, refining is carried out at 1530~1550℃ under a vacuum of 1~5Pa.

6. The preparation method according to claim 3, characterized in that, In step 3, the electrode rod is cast at a temperature of 1550~1580℃ and a casting speed of 100~300kg / min.

7. The preparation method according to claim 3, characterized in that, In step 6, the cryogenic treatment includes: maintaining the temperature at -75~-80℃ for 2~3 hours.

8. The preparation method according to any one of claims 3 to 7, characterized in that, In step 6, the low-temperature tempering process is as follows: holding at 200~250℃ for 2~3 hours.

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