Machining method for large-torque shaft blank

Abstract

The invention relates to a machining method for a large-torque shaft blank. The technical problems that a blank manufactured through a traditional method is large in follow-up machining difficulty, high in tool cost, large in residual stress and large in heat treatment deformation are solved. A cross wedge rolling process is selected, a blank with high dimensional precision is obtained through wedging, forming and finishing, and the obtained forging blank is high in dimensional precision, small in machining allowance and good in metallographic structure uniformity; the hardness is ensured to range from 170 HBW to 185 HBW; forging and heat treatment processes are simple in process and low in cost, and particularly, the heat treatment process is suitable for various furnace types. The preparation heat treatment process is an isothermal normalizing process and can be completed by a periodic furnace or a continuous furnace with the heating temperature meeting 900 DEG C, the heat treatment process is time-saving and labor-saving, the cost is low, the quality is stable, and the process reliability is high.

Description

Technical Field

[0001] The present invention relates to forging technology, and specifically to a processing method for large-torque shaft blanks. Background Art

[0002] In order to manufacture shaft parts with large transmission torque, excellent wear resistance and impact resistance, low-carbon alloy steel materials with relatively high alloy content and hardenability are generally required. A commonly used material with excellent strength and toughness is 20Cr2Ni4A. The round bar of this raw material is usually manufactured into the required blank through four processes of "blanking - forging - normalizing - high-temperature tempering".

[0003] In the manufacturing process of this traditional blank process, forging equipment such as hammer forging and crank presses are generally selected, with low forging efficiency, high cost, and large machining allowance after forming (unilateral machining allowance of 2 mm - 5 mm); at the same time, a heat treatment method of normalizing + high-temperature tempering is generally selected, with many process steps, long cycle, and high cost.

[0004] Due to the high hardenability of this material, the blanks manufactured by traditional methods, such as large-torque shaft forging blanks, have a relatively high hardness (above 220 HBW), so there are problems such as difficult subsequent processing, high tool cost, and large residual stress in the machined parts. At the same time, the metallographic structure of the blank is a non-equilibrium structure, generally pearlite + sorbite + ferrite structure, and there is also a large deformation during subsequent heat treatment.

[0005] Chinese Patent CN106826142 A discloses a manufacturing method for the intermediate shaft of an automotive transmission, achieving the technical effects of efficient manufacturing of the intermediate shaft and uniform metallographic structure, and improving production efficiency. However, bainite will appear due to the too-fast cooling rate in the subsequent heat normalizing step, and the ferrite content is small, so the requirement of low hardness cannot be achieved.

[0006] Chinese Patent CN110343823 A discloses an isothermal normalizing heat treatment process, which regenerates austenite, reduces the banded structure of the workpiece, and the generated structure is more uniform, improving the machinability of the workpiece and enhancing the mechanical properties of the workpiece, while reducing production costs. However, the temperature in the sixth stage of this process is too low and the time in the seventh stage is too short, which cannot meet the pearlite transformation conditions and will result in the metallographic structure and hardness of the blank not meeting the requirements. Summary of the Invention

[0007] The object of the present invention is to solve the technical problems that the blanks manufactured by traditional methods have difficult subsequent processing, high tool cost, large residual stress, and large heat treatment deformation, and to provide a processing method for large-torque shaft blanks.

[0008] In order to achieve the above object and complete the above concept, the technical solution provided by the present invention is as follows:

[0009] A processing method for a large-torque shaft blank, characterized in that it includes the following steps:

[0010] S0, stock preparation

[0011] Prepare a round bar stock that meets the processing requirements;

[0012] S1, blanking

[0013] Saw the round bar stock into multiple short bar stocks as needed;

[0014] S2, cross wedge rolling

[0015] Heat the short bar stock and feed the short bar stock heated to the forging temperature into the die of the cross wedge rolling forging equipment. After passing through three sections of wedging, forming, and finishing, a forging is obtained;

[0016] S3, isothermal normalizing

[0017] Load the forging into a heat treatment furnace for isothermal normalizing process to obtain a large-torque shaft blank;

[0018] When the heat treatment furnace is a batch furnace:

[0019] During the cycle, it is sequentially divided into a heating stage, a high-temperature isothermal stage, an intermediate cooling and temperature reduction stage, a low-temperature isothermal stage, and an out-of-furnace cooling stage according to time; during the heating stage, the forging is heated in the furnace to 870 - 930 °C and maintained for 90 - 150 min in the high-temperature isothermal stage; during the intermediate cooling and temperature reduction stage, the forging is cooled in the furnace to 570 - 630 °C and maintained for 330 - 390 min in the low-temperature isothermal stage; finally, the forging is cooled in the furnace in the out-of-furnace cooling stage; the duration of the intermediate cooling and temperature reduction stage is 40 - 80 min;

[0020] When the heat treatment furnace is a continuous furnace:

[0021] Set the stepping time, feeding cycle or conveyor speed so that the forging stays in the low-temperature furnace at 570 - 630 °C for 330 - 390 min and the forging is maintained in the high-temperature furnace at 870 - 930 °C for 70 - 140 min; at the same time, control the temperature in the intermediate cooling stage and cool slowly so that the temperature after cooling is not lower than 650 °C;

[0022] S4, acceptance

[0023] Accept the large-torque shaft blank obtained after the isothermal normalizing process: When the hardness of the large-torque shaft blank is between 170 HBW - 185 HBW, the hardness scatter of the whole batch of blanks is less than 15 HB, and the hardness scatter of a single blank is less than 6 HB, the processing of the large-torque shaft blank is completed; otherwise, it is sent back to the furnace for treatment.

[0024] Further, in step S0, the round bar stock is made of high hardenability carburizing alloy steel 20Cr2Ni4A.

[0025] Further, in step S3, when the heat treatment furnace is a batch furnace, the forging is heated in the furnace to 900 °C during the heating-up stage and maintained for 120 min in the high-temperature isothermal stage; the forging is cooled in the furnace to 600 °C during the intermediate cooling-down stage and maintained for 360 min in the low-temperature isothermal stage; the duration of the intermediate cooling-down stage is 60 min.

[0026] When the heat treatment furnace is a continuous furnace, the forging is maintained in a low-temperature furnace at 600 °C for 360 min, and the forgings are classified: when the cross-sectional thickness of the forging exceeds 80 mm, it is maintained in a high-temperature furnace at 900 °C for 120 min; when the cross-sectional thickness of the forging does not exceed 80 mm, it is maintained in a high-temperature furnace at 900 °C for 90 min.

[0027] Further, in step S3, during the intermediate cooling-down stage, the rapid cooling system or the method of opening the furnace door is used for heat dissipation; during the furnace discharging and cooling stage, the method of opening the furnace door is used for heat dissipation.

[0028] Further, step S2 is specifically as follows:

[0029] S2-1, Heating

[0030] The short bar stocks are heated one by one to the forging temperature to make the core of the short bar stocks fully heated and the temperature uniform. The judgment method is that the colors at the ends of the short bar stocks are the same and there is no obvious darker color.

[0031] S2-2, Forming

[0032] The heated short bar stocks are put into a cross wedge rolling forging equipment, and at the same time, the upper and lower rolls are operated to complete the three processes of wedging, forming, and finishing; then the stock head is automatically cut off by the die cutter before discharging to obtain the forging.

[0033] S2-3, Sorting

[0034] The forgings are inspected and accepted: when the forgings have no surface defects and the central porosity by ultrasonic flaw detection is not greater than grade 3, the forgings are stacked in the material box and waiting for the next process; otherwise, they are discarded.

[0035] Further, in step S2-1, the short bar stocks are heated by an intermediate frequency induction heating equipment, and the temperature is measured in combination with an infrared thermometer; the induction area of the intermediate frequency induction heating equipment includes a heating area and a heat preservation area; the forging temperature is between 1120 °C and 1180 °C.

[0036] Further, in step S2-3, the surface defects include folding, crack, scale, unfilled, spiral indentation, and deep pit.

[0037] Further, in step S1, the round bar stock is cut into short bar stocks by a band saw or a circular saw, and the following conditions are met: the slope of the saw cut surface is not greater than 0.5 degrees and there are no burrs on the cross section.

[0038] Further, in step S0, the length of the round bar stock is (6000 ± 30) mm, and the diameter is Φ(85 ± 3) mm;

[0039] In step S1, the length of the short bar stock is (720 ± 3) mm, the diameter is Φ(85 ± 3) mm, and the weight is (32.07 ± 0.03) kg.

[0040] Advantages of the present invention compared with the prior art:

[0041] 1. A processing method for large torque shaft blanks provided by the present invention is different from traditional crank press or hammer forging hot plastic forming methods. The cross wedge rolling process is selected. After the short bar stock heated to the forging temperature is fed into the die through the cross wedge rolling forging equipment and formed through three sections of wedging, forming, and finishing, the obtained forging blank has high dimensional accuracy and small machining allowance (within 2 mm on one side); and the metallographic structure is a balanced structure: pearlite + ferrite, with good metallographic structure uniformity; the hardness is guaranteed to be within 170 HBW - 185 HBW, and the hardness scatter of the whole batch of blanks is within 15 HB, and the hardness scatter of a single blank is within 6 HB; the processes of forging and heat treatment are simple and low-cost, especially the heat treatment process is applicable to various furnace types.

[0042] 2. A processing method for large torque shaft blanks provided by the present invention, the preliminary heat treatment process is an isothermal normalizing process, which can be completed by a periodic furnace or a continuous furnace with a heating temperature meeting 900 °C. The heat treatment process saves time and effort, has low cost, and has stable quality and high process reliability, and is suitable for machining and subsequent heat treatment. Brief Description of the Drawings

[0043] Figure 1 is a schematic structural diagram of a typical existing large torque shaft forging blank;

[0044] Figure 2 is a schematic diagram of the heat treatment process of traditional normalizing + high temperature tempering;

[0045] Figure 3 is a schematic diagram of the heat treatment process of isothermal normalizing in step S3 of the embodiment of the processing method for large torque shaft blanks of the present invention;

[0046] Figure 4 is a comparison diagram of the metallographic structures obtained by using the isothermal normalizing heat treatment process of the present invention and the traditional normalizing + high temperature tempering heat treatment process, where (a) is the metallographic structure obtained by using the isothermal normalizing heat treatment process, and (b) is the metallographic structure obtained by using the traditional normalizing + high temperature tempering heat treatment process;

[0047] Figure 5 It is a schematic diagram of a continuous isothermal normalizing furnace production line to which the present invention can be applied. Specific embodiments

[0048] Next, specific technical solutions in the embodiments of the present invention will be further described in conjunction with the accompanying drawings.

[0049] The processing method of the large-torque shaft blank of the present invention can be used to manufacture blanks of large-torque transmission shaft parts, such as Figure 1 As shown in a typical existing large-torque shaft forging blank (referred to as a blank), its maximum outer diameter is 87 mm and its length is 401.9 mm. The blank material is high hardenability carburizing alloy steel 20Cr2Ni4A.

[0050] In the method provided by the present invention, the blank is manufactured through three processes of "blanking - cross wedge rolling - isothermal annealing".

[0051] Different from the traditional crank press or hammer forging hot plastic forming method, the forming method of the present invention is the cross wedge rolling process, that is, a cross wedge rolling forging equipment (such as the cross wedge rolling forging equipment with the model D46-125*1200 manufactured by Beijing Institute of Mechanical and Electrical Engineering) is used to feed the round bar stock heated to the forging temperature (1120 °C - 1180 °C) into the die and obtain the forging after forming through three sections of wedging, forming, and finishing.

[0052] The post-forging heat treatment method is also different from the traditional method. Generally, the preliminary heat treatment of the forging blank of high hardenability steel 20Cr2Ni4A is "normalizing + high temperature tempering", as Figure 2 shown, the heat treatment process is complex, the cycle time is long, and the energy consumption and labor cost are high; in addition, "normalizing + one or two high temperature temperings" often results in incomplete phase transformation, leading to the hardness of the workpiece after heat treatment being higher than 220 HB. The heat treatment process of the present invention is the isothermal normalizing process, which can be completed by a periodic furnace or a continuous furnace with a heating temperature meeting 900 °C. The process is as Figure 3 shown, the heat treatment process saves time and effort (one-time loading, one-time furnace entry), has low cost, and has stable quality and high process reliability.

[0053] The metallographic structure of the blank obtained by the traditional process of "normalizing + high temperature tempering" of the forging is as Figure 4 (b) shown, which is a pearlite + sorbite + ferrite structure; the metallographic structure of the blank obtained by this method is as Figure 4As shown in (a), it is the equilibrium state structure, including evenly distributed ferrite + pearlite. The blanks processed by the present invention meet the standards of Grade 1 - 3 in GB / T 13320-2007 "Metallographic Structure Rating Diagram and Evaluation Method for Steel Die Forgings", and the banding grade meets the standards of Grade 1 - 3 in GB / T 34474.1-2017 "Evaluation of Banded Structure in Steel - Part 1: Standard Rating Diagram Method". The surface hardness and core hardness of the blanks are detected according to the standards of GB / T 231.1-2018 "Metallic Materials - Brinell Hardness Test - Part 1: Test Method", and the results are 170HBW - 185HBW, which are easy to machine. The hardness dispersion of the whole batch of blanks is within 15HB, and the hardness dispersion of a single blank is within 6HB.

[0054] An embodiment of the processing method for large - torque shaft - type blanks provided by the present invention, the process: blanking - cross - wedge rolling - isothermal normalizing, includes the following steps:

[0055] S0, stock preparation

[0056] Prepare round bar materials that meet the processing requirements; the round bar materials are high - hardenability carburizing alloy steel 20Cr2Ni4A; the length of the round bar materials is about 6000mm, and the diameter is Φ85mm.

[0057] S1, blanking

[0058] Saw the round bar materials into multiple short bar materials by a band saw or a circular saw according to needs, and meet the conditions: the slope of the sawing surface is not more than 0.5 degrees and the cross - section has no burrs; the length of the short bar materials is (720 ± 0.3)mm, the diameter is Φ(85 ± 0.3)mm, and the weight is about 32.07kg.

[0059] S2, cross - wedge rolling

[0060] Heat the short bar materials, and feed the short bar materials heated to the forging temperature into the die of the cross - wedge rolling forging equipment. After forming through three sections of wedging, forming, and finishing, forgings are obtained. Specifically:

[0061] S2 - 1, heating

[0062] Heat the short bar materials one by one to the forging temperature (1120℃ - 1180℃) through an intermediate - frequency induction heating device, and measure the temperature in combination with an infrared thermometer. The heating process should meet the conditions: the core of the short bar materials is fully heated and the temperature is uniform. The judgment method is: the colors at the ends of the short bar materials are the same, without obvious darker color; the induction area of the intermediate - frequency induction heating device includes a heating area and a heat - preservation area.

[0063] S2 - 2, forming

[0064] Put the heated short bar stock into the cross wedge rolling forging equipment, and operate the upper and lower rolls simultaneously to complete the three processes of wedging, forming, and finishing; then automatically cut off the stock head with the die cutter before discharging to obtain the forging.

[0065] S2-3, Sorting

[0066] Inspect the forging: When the forging has no surface defects (such as folding, cracks, scale, incomplete filling, spiral indentation, and deep pits, etc.) and the central porosity detected by ultrasonic flaw detection is not greater than grade 3 (based on GB / T 1979-2001

[0067] "Rating of Macrostructure Defects of Structural Steel"), neatly stack the forgings in the material box and wait for the next process; otherwise, dispose of them as waste.

[0068] S3, Isothermal Normalizing

[0069] Load the forging into the heat treatment furnace for isothermal normalizing process; regardless of the equipment used for the isothermal normalizing process of the large torque shaft blank, the process must comply with Figure 3 the process curve in it. Especially, the isothermal time must be guaranteed to make the structure transform into an equilibrium structure (uniformly distributed pearlite + ferrite), so as to ensure that the hardness is between 170HBW - 185HBW, and the hardness scatter of the whole batch of blanks is within 15HB, and the hardness scatter of a single blank is within 6HB.

[0070] When the heat treatment furnace is a batch furnace:

[0071] In the intermediate cooling and temperature reduction stage, use a rapid cooling system or open the furnace door to dissipate heat; in the furnace discharging and cooling stage, use the air cooling method with the furnace door open to dissipate heat. If the heat treatment furnace has excellent heat preservation performance and the temperature reduction is slow, the isothermal time can also be appropriately shortened according to the actual situation. In addition, for equipment with a rapid cooling function, the rapid cooling system can be turned on, and it is best to control the cooling time within about 1 hour. The longer the intermediate cooling stage, the lower the hardness of the heat-treated blank; to improve production efficiency, the furnace door can also be appropriately opened to accelerate heat dissipation and speed up the furnace cooling rate.

[0072] Specifically:

[0073] The loading method is not limited. During the cycle, it is divided into a heating-up stage, a high-temperature isothermal stage, an intermediate cooling and temperature reduction stage, a low-temperature isothermal stage, and a furnace discharging and cooling stage in sequence according to time. In the heating-up stage, heat the forging in the furnace to 900°C and maintain it for 120 min in the high-temperature isothermal stage; in the intermediate cooling and temperature reduction stage, cool the forging in the furnace to 600°C and maintain it for 360 min in the low-temperature isothermal stage; finally, cool the forging in the furnace in the furnace discharging and cooling stage; the duration of the intermediate cooling and temperature reduction stage is 60 min.

[0074] When the heat treatment furnace is a continuous furnace:

[0075] A continuous furnace (continuous isothermal normalizing furnace production line) generally includes a loading and unloading area, a high-temperature furnace, a rapid cooling chamber, and a low-temperature furnace (also called an isothermal furnace). The designed maximum operating temperature of the high-temperature furnace is generally 970°C, and that of the low-temperature furnace is generally 750°C.

[0076] In the present invention, the set temperature of the high-temperature furnace is 900°C, and that of the low-temperature furnace is 600°C. Generally, the rapid cooling chamber does not require blowing for cooling. Just turn off the fan and let it cool by natural air. The forging loading method is not limited. Parameters such as the stepping time of the continuous furnace (the time required for the pallet to advance one station) or the conveying speed (the advancing speed of the mesh belt of the mesh belt furnace or the motor frequency) are inversely deduced from the holding time of the forging in the low-temperature furnace being 6 hours, and the temperature settings of each zone of the high-temperature furnace are adjusted correspondingly so that the forging can be held at 900°C for 1.5 to 2 hours.

[0077] Take Figure 5 the shown continuous isothermal normalizing furnace production line as an example.

[0078] Calculation process of the stepping time of the isothermal furnace: The isothermal furnace has 12 stations. The forging needs to stay in the isothermal furnace for 6 hours, that is, 360 minutes have passed from entering the isothermal furnace to leaving it. For 12 stations, the time required for the forging to advance 1 station in the furnace (stepping time) is 360 / 12 = 30 minutes.

[0079] Calculation process of the temperature setting of the high-temperature furnace: The temperature of the high-temperature furnace is controlled by zone in 6 zones. Zone 1 has 3 stations, and each of zones 2 - 6 has 2 stations. Then the process requires holding at 900°C for 2 hours (120 minutes). It is necessary to divide 120 minutes by the stepping time of 30 minutes, that is, 120 / 30 = 4 stations. Then the last two zones of the high-temperature furnace, zone 5 and zone 6, need to be determined as the holding zones with the temperature set at 900°C. The first 4 zones are heating zones. For example, zone 1 is 650°C, zone 2 is 750°C, zone 3 is 830°C, and zone 4 is 880°C, with step-by-step temperature increase.

[0080] In addition, the austenitizing holding time at 900°C can be slightly adjusted according to the cross-sectional thickness of the workpiece. For a cross-section exceeding 80 mm, the upper limit time can be selected; for a cross-section less than 80 mm, the lower limit time can be selected according to the degree. Since the stepping time is longer than that of ordinary forgings, the fan can be turned off during the intermediate cooling stage of the forging in the rapid cooling chamber and air-cooled for a certain time to control the temperature during the intermediate cooling stage and ensure that the cooling temperature is not lower than 650°C to prevent the temperature from continuing to drop to the bainite transformation zone during the transfer process and forming bainite structure, resulting in high hardness.

[0081] Specifically:

[0082] Set the stepping time, feeding cycle or conveyor speed so that the forging stays in the low-temperature furnace at 600 °C for 360 min, and classify the forgings: when the cross-sectional thickness of the forging exceeds 80 mm, keep it in the high-temperature furnace at 900 °C for 120 min; when the cross-sectional thickness of the forging does not exceed 80 mm, keep it in the high-temperature furnace at 900 °C for 90 min. At the same time, control the temperature in the intermediate cooling stage and cool slowly so that the temperature after cooling is not lower than 650 °C.

[0083] S4, acceptance

[0084] Accept the large-torque shaft blanks obtained after the isothermal normalizing process: when the hardness of the large-torque shaft blanks is between 170 HBW - 185 HBW, the hardness scatter of the whole batch of blanks is less than 15 HB, and the hardness scatter of a single blank is less than 6 HB, the processing of the large-torque shaft blanks is completed; otherwise, send them back to the furnace for treatment.

[0085] The above content is only one embodiment of the present invention and does not limit the protection scope of the present invention. Any equivalent transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A processing method for a large-torque shaft blank, characterized in that It includes the following steps: S0, Stock preparation Prepare round bar stock meeting the processing requirements; S1, Blanking Saw the round bar stock into multiple short bar stocks as needed; S2, Cross wedge rolling Heat the short bar stocks, and feed the short bar stocks heated to the forging temperature into the die of the cross wedge rolling forging equipment. After forming through three sections of wedging, forming, and finishing, forgings are obtained; S3, Isothermal normalizing Load the forgings into a heat treatment furnace for isothermal normalizing process to obtain large torque shaft blanks; When the heat treatment furnace is a batch furnace: In the cycle, it is successively divided into a heating stage, a high temperature holding stage, an intermediate cooling and temperature reduction stage, a low temperature isothermal stage, and an out-of-furnace cooling stage in chronological order; in the heating stage, the forgings are heated in the furnace to 870 - 930 °C and maintained for 90 - 150 min in the high temperature holding stage; in the intermediate cooling and temperature reduction stage, the forgings are cooled in the furnace to 570 - 630 °C and maintained for 330 - 390 min in the low temperature isothermal stage; finally, the forgings are cooled to room temperature in the out-of-furnace cooling stage; the duration of the intermediate cooling and temperature reduction stage is 40 - 80 min; there is no time limit for the heating stage; When the heat treatment furnace is a continuous furnace: Set the stepping time, feeding cycle or conveyor speed so that the forgings stay in the low temperature furnace at 570 - 630 °C for 330 - 390 min and stay in the high temperature furnace at 870 - 930 °C for 70 - 140 min; at the same time, control the temperature in the intermediate cooling stage so that the temperature after cooling is not lower than 650 °C; S4, Inspection Inspect the large torque shaft blanks obtained after the isothermal normalizing process: When the hardness of the large torque shaft blanks is between 170 HBW - 185 HBW, the hardness scatter of the whole batch of blanks is less than 15 HB, and the hardness scatter of a single blank is less than 6 HB, the processing of the large torque shaft blanks is completed; otherwise, they are sent back to the furnace for treatment.

2. A processing method for large torque shaft blanks according to claim 1, characterized in that: In step S0, the round bar stock is high hardenability carburizing alloy steel 20Cr2Ni4A.

3. A processing method for large torque shaft blanks according to claim 2, characterized in that: In step S3, when the heat treatment furnace is a batch furnace, in the heating stage, the forgings are heated in the furnace to 900 °C and maintained for 120 min in the high temperature isothermal stage; in the intermediate cooling and temperature reduction stage, the forgings are cooled in the furnace to 600 °C and maintained for 360 min in the low temperature isothermal stage; the duration of the intermediate cooling and temperature reduction stage is 60 min; When the heat treatment furnace is a continuous furnace, keep the forgings in the low temperature furnace at 600 °C for 360 min and classify the forgings: When the cross-sectional thickness of the forgings exceeds 80 mm, keep them in the high temperature furnace at 900 °C for 120 min; when the cross-sectional thickness of the forgings does not exceed 80 mm, keep them in the high temperature furnace at 900 °C for 90 min.

4. A processing method for large torque shaft blanks according to claim 3, characterized in that: In step S3, in the intermediate cooling and temperature reduction stage, a rapid temperature reduction system or the method of opening the furnace door is used for heat dissipation; in the out-of-furnace cooling stage, the method of opening the furnace door is used for heat dissipation.

5. The processing method of a large-torque shaft blank according to claim 4, characterized in that, Step S2 is specifically as follows: S2-1, Heating Heat each short bar stock to the forging temperature one by one, so that the core of the short bar stock is thoroughly heated and the temperature is uniform. The judgment method is that the colors at the ends of the short bar stocks are the same and there is no obvious darker color; S2-2, Forming Put the heated short bar stock into the cross wedge rolling forging equipment, and operate the upper and lower rolls simultaneously to complete the three processes of wedging, forming, and finishing; then automatically cut off the stock head through the die cutter before discharging to obtain the forging; S2-3, Sorting Inspect the forgings: When the forgings have no surface defects and the central porosity detected by ultrasonic flaw detection is not greater than grade 3, stack the forgings in the bins and wait for the next process; otherwise, discard them.

6. A processing method for a large torque shaft blank according to claim 5, characterized in that: In step S2-1, the short bar stock is heated by an intermediate frequency induction heating device, and the temperature is measured in combination with an infrared thermometer; the induction area of the intermediate frequency induction heating device includes a heating area and a heat preservation area; the forging temperature is between 1120°C and 1180°C.

7. A processing method for a large torque shaft blank according to claim 6, characterized in that: In step S2-3, the surface defects include folds, cracks, skin pressing, non-filling, spiral indentations, and deep pits.

8. A processing method for a large torque shaft blank according to claim 7, characterized in that: In step S1, the round bar stock is cut into short bar stocks by a band saw or a circular saw, and the conditions are met: the slope of the saw cut surface is not greater than 0.5 degrees and there is no burr on the cross section.

9. A processing method for a large torque shaft blank according to claim 1, characterized in that: In step S0, the length of the round bar stock is (6000±30) mm, and the diameter is Φ(85±3) mm; In step S1, the length of the short bar stock is (720±3) mm, the diameter is Φ(85±3) mm, and the weight is (32.07±0.03) kg.

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