Machining method of small-deformation gear steel and gear piece

Abstract

The embodiment of the invention relates to a machining method of small-deformation gear steel and a gear piece, and belongs to the technical field of gear steel. The machining method comprises the following steps: S1, carrying out microalloying treatment on the gear steel by adopting Ti and / or Nb; s2, the gear steel subjected to microalloying treatment is rolled, and a gear steel bar is obtained; s3, the gear steel bar is sequentially subjected to blank forging, heat treatment after forging and machining, and a to-be-carburized gear is obtained; s4, the gear to be carburized is subjected to carburizing treatment and diffusion treatment, and a gear piece is obtained; s5, the gear part is subjected to gas quenching treatment, and the gear part is cooled to the room temperature in stages; and S6, the gear piece subjected to gas quenching treatment is subjected to tempering treatment. According to the invention, through the microalloying treatment of the gear steel and the staged gas quenching treatment of the gear piece, the quenching deformation of the gear piece is controlled, and the deformation after quenching is greatly reduced, so that the gear piece with good dimensional precision control is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of gear steel, and in particular to a processing method of gear steel with less deformation and a gear part. Background Art

[0002] The production of master and driven gears for gearboxes of various types of automobiles and rail transit locomotives, the production of gears and gear shafts for reducers of new energy vehicles, and the production of other heavy-duty types of gears generally require quenching of the gears. However, quenching deformation has always been a difficult point to control in the heat treatment process, especially the quenching deformation of carburized gear parts. Due to the inconsistent composition from the surface to the core of the gear parts after carburizing, the thermal deformation is more complicated during quenching, resulting in severe quenching deformation, which increases the amount of subsequent processing and affects the stability of part performance; and abnormally severe deformation may directly lead to the scrapping of parts, affecting the product qualification rate.

[0003] At present, the control of carburizing and quenching deformation is mainly based on die press quenching, reverse shaping, straightening after quenching and other means. However, die press quenching cannot correct the tooth shape and tooth direction of the gear workpiece, and reverse shaping and straightening after quenching are likely to cause additional damage to the material or produce microcracks. Summary of the invention

[0004] In view of the above analysis, the embodiments of the present invention aim to provide a method for processing gear steel with less deformation and a gear part, so as to solve the problem of severe deformation of gear parts after carburizing and quenching.

[0005] On the one hand, an embodiment of the present invention provides a method for processing gear steel with less deformation, comprising:

[0006] S1. Microalloying of gear steel with Ti and / or Nb;

[0007] S2, rolling the micro-alloyed gear steel to obtain a gear steel bar;

[0008] S3, sequentially performing forging, post-forging heat treatment and machining on the gear steel bar to obtain the gear to be carburized;

[0009] S4, performing carburizing treatment and diffusion treatment on the gear to be carburized to obtain a gear part;

[0010] S5, performing gas quenching treatment on the gear parts, and cooling the gear parts to room temperature in stages;

[0011] S6. Tempering the gear parts after gas quenching.

[0012] Furthermore, in step S1, when Ti is used for microalloying treatment, the mass percentage of Ti is controlled to be 0.035-0.065% of the gear steel; when Nb is used for microalloying treatment, the mass percentage of Nb is controlled to be 0.02-0.06% of the gear steel; when Ti and Nb are used for composite microalloying treatment, the total mass percentage of Ti and Nb in the gear steel is controlled to be 0.025-0.085%.

[0013] Furthermore, in step S1, when Ti is used for microalloying, the mass percentage of N in the gear steel is controlled to be 0.003-0.006%; when Ti and Nb are used for composite microalloying, the mass percentage of N in the gear steel is controlled to be within 0.005%.

[0014] Furthermore, in step S5, when the gear part is subjected to gas quenching treatment, an inert gas is used for quenching cooling; after the surface of the gear part is cooled to 430-440°C, the supply of the inert gas is stopped; after waiting for 10-20 seconds, the inert gas is supplied again for quenching cooling until the gear steel workpiece is cooled to room temperature.

[0015] Furthermore, when the inert gas is transported, the gas pressure of the inert gas is 3 to 5 bar.

[0016] Furthermore, in step S2, when the gear steel is rolled, the heating temperature is not less than 1200° C., and the holding time is not less than 60 minutes.

[0017] Furthermore, in step S2, when the gear steel is rolled, the final rolling temperature is not less than 850°C; after rolling is completed, the gear steel bars are placed on a cooling bed for cooling, and the interval between each gear steel bar is more than 300mm; when the surface temperature of the gear steel bar drops to 400-500°C, the gear steel bar is pile cooled or pit cooled.

[0018] Furthermore, when the gear steel to be carburized is carburized, the carburizing temperature is 930-980°C.

[0019] Furthermore, in step S4, during the diffusion treatment, the diffusion temperature is 900-960° C., and the diffusion time is 25-30 minutes.

[0020] On the other hand, an embodiment of the present invention further provides a gear part with less deformation, which can be processed by the method of the above embodiment. Compared with before carburizing treatment, the precision loss of the gear steel workpiece after carburizing and quenching treatment does not exceed 3 levels.

[0021] The present invention can achieve at least one of the following beneficial effects:

[0022] 1. The present invention uses Ti and / or Nb elements to perform microalloying treatment on gear steel, which can refine the gear steel structure and grains, ensure the uniformity of the structure of the gear to be carburized, and help reduce the quenching deformation of the carburized gear steel.

[0023] 2. The present invention adopts a gas quenching treatment method, and the cooling speed is controllable, which can effectively reduce the stress inside the steel, control the quenching deformation of the gear parts, and avoid large deformation of the gear parts after quenching; and the surface cleanliness of the workpiece after treatment is high, and no subsequent cleaning and shot blasting cleaning procedures are required, which simplifies the process. In addition, during the gas quenching treatment process, the gear parts are cooled to room temperature in stages to avoid excessive cooling speed, thereby reducing carburizing quenching deformation.

[0024] 3. The present invention controls the starting rolling temperature, the final rolling temperature and the cooling process of the steel after rolling, thereby ensuring that the gear steel has a sufficient number of precipitated phases with appropriate sizes, so that the proportion of precipitated phases with a size of 5 to 200 nm reaches more than 60%, so that the grain size of the gear steel can be controlled to be sufficiently small and uniform, which is beneficial to reducing the subsequent quenching deformation of the gear steel.

[0025] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are only for the purpose of illustrating particular embodiments and are not to be construed as limiting the invention.

[0027] Figure 1 The figure is a comparison result of the precision loss of gear parts after carburizing and quenching according to various embodiments of the present invention and comparative examples.

[0028] Figure 2 The figure is a comparison result of the deformation of gear parts after carburizing and quenching according to various embodiments of the present invention and comparative examples. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, exemplary embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. For the sake of clarity and conciseness, not all features of the actual implementation are described in the specification.

[0030] An embodiment of the present invention provides a method for processing gear steel with less deformation, comprising the following steps:

[0031] S1. Microalloying of gear steel with Ti and / or Nb;

[0032] S2, rolling the micro-alloyed gear steel to obtain a gear steel bar;

[0033] S3, sequentially performing forging, post-forging heat treatment and machining on the gear steel bar to obtain the gear to be carburized;

[0034] S4, performing carburizing treatment and diffusion treatment on the gear to be carburized to obtain a gear part;

[0035] S5, performing gas quenching treatment on the gear parts, and cooling the gear parts to room temperature in stages;

[0036] S6. Tempering the gear parts after gas quenching.

[0037] The present invention uses Ti and / or Nb elements to perform microalloying treatment on gear steel, which can refine the gear steel structure and grains, ensure the uniformity of the structure of the gear to be carburized, and is beneficial to reducing the quenching deformation of the carburized gear steel.

[0038] Compared with traditional water quenching and oil quenching, the gas quenching treatment adopted by the present invention has a controllable cooling speed, can effectively reduce the stress inside the steel, can control the quenching deformation of the gear parts, and avoid large deformation of the gear parts after quenching; and the surface cleanliness of the workpiece after treatment is high, and no subsequent cleaning and shot blasting cleaning procedures are required, which simplifies the process. In addition, during the gas quenching treatment process, the gear parts are cooled to room temperature in stages to avoid excessive cooling speed, thereby reducing carburizing quenching deformation.

[0039] The present invention realizes the control of quenching deformation of gear parts by microalloying the gear steel and performing staged gas quenching on the gear parts, greatly reduces the deformation after quenching, and thus obtains gear parts with good dimensional accuracy control.

[0040] Compared with traditional mold press quenching, reverse shaping, straightening after quenching and other methods, the method of the present invention will not cause additional damage to the gear parts, will not produce defects such as microcracks, and the deformation of the gear teeth can also be well controlled.

[0041] In some embodiments, in step S1, when Ti is used for microalloying treatment, the mass percentage of Ti is controlled to be 0.035-0.065% of the gear steel. Among them, too low Ti content may result in too little TiC formed in the gear steel, too little precipitation phase, which may lead to insufficient organization and grain refinement and homogenization of the steel; and when the Ti content is too high, large particles of TiC or TiN will be formed in the gear steel, affecting the fatigue performance of the gear, and improper subsequent heat treatment may lead to abnormal organization, such as the appearance of mixed crystals. Therefore, when using Ti microalloying treatment, the Ti content in the gear steel should be controlled to be 0.035-0.065%, for example, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, etc.

[0042] Furthermore, when Ti is used for microalloying, the mass percentage of N in the gear steel is controlled to be 0.003-0.006%, for example, 0.003%, 0.004%, 0.005%, 0.006%, etc., to avoid excessive N content and the formation of a large number of TiN inclusions.

[0043] In some embodiments, when Nb is used for microalloying, the mass percentage of Nb is controlled to be 0.02-0.06% of the gear steel. If the Nb content is too low, it will affect the gear steel structure and grain refinement effect; if the Nb content is too high, it will cause waste of the Nb element and may affect the homogenization of the grain size. Therefore, it is necessary to ensure that the Nb content is in the range of 0.02-0.06%, for example, the Nb content can be 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, etc.

[0044] In some embodiments, when Ti and Nb are used for composite microalloying treatment, the total mass percentage of Ti and Nb is controlled to be 0.025-0.085% of the gear steel, for example, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, etc.

[0045] Furthermore, when Ti and Nb are used for composite microalloying treatment, the mass percentage of N in the gear steel is controlled within 0.005% to avoid the formation of large TiN inclusions and a large number of large Ti(C,N) and Nb(C,N) precipitates or composite Ti and Nb precipitates, which affect the gear steel structure and grain refinement effect.

[0046] In some embodiments, in step S2, when the micro-alloyed gear steel is rolled, the gear steel is first heated and kept warm, wherein the heating temperature is not less than 1200°C and the holding time is not less than 60 minutes, so as to ensure the dissolution of key alloying elements such as C, Ti, Nb, Al in the gear steel, make the alloying elements more uniform, reduce component segregation, and be more conducive to reducing subsequent quenching deformation.

[0047] In some embodiments, in step S2, when rolling the gear steel, the starting rolling temperature is controlled at 1050-1150°C, and the final rolling temperature is not lower than 850°C; after rolling is completed, the gear steel bars are placed on a cooling bed for cooling, and the interval between each gear steel bar is more than 300mm; when the surface temperature of the gear steel bar drops to 400-500°C, the gear steel bar is pile cooled or pit cooled.

[0048] The present invention controls the start rolling temperature, the final rolling temperature and the cooling process of the steel after rolling, so as to ensure that the gear steel has a sufficient number of precipitates of appropriate size, so that the precipitates of 5-200nm account for more than 60%, so that the grain size of the gear steel can be controlled to be sufficiently small and uniform, which is conducive to reducing the subsequent quenching deformation of the gear steel. If the process parameters of the rolling process and the cooling process after rolling are not within the above range, the quenching deformation of the gear steel may increase.

[0049] In step S3, the gear steel bar is subjected to forging, post-forging heat treatment, machining and other steps to be processed into the required gear steel, and then carburized.

[0050] In some embodiments, when the gear steel to be carburized is carburized in step S4, a vacuum low-pressure carburizing process may be used for the carburizing process.

[0051] Acetylene gas may be used for pulse carburizing treatment, and the flow rate of acetylene gas during treatment may be controlled at 135 to 165 L / h, for example, 135 L / h, 140 L / h, 145 L / h, 150 L / h, 155 L / h, 160 L / h, 165 L / h, etc. Specifically, the gear steel to be carburized is placed in a vacuum low-pressure carburizing furnace, and acetylene gas is introduced into the carburizing furnace at a flow rate of 135 to 165 L / h, and heated.

[0052] In some embodiments, in step S4, the carburizing temperature during carburizing treatment is 930-980°C, for example, 930°C, 935°C, 940°C, 945°C, 950°C, 955°C, 960°C, 965°C, 970°C, 975°C, 980°C, etc.

[0053] The present invention can improve the uniformity of carbon concentration of the carburized layer by performing pulse carburizing treatment on the gear part; at the same time, by controlling the carburizing temperature and the carburizing gas pressure, the carburizing process can be accurately controlled, and the deformation of the workpiece can be better controlled. In addition, pulse carburizing can reduce the carburizing time and improve the carburizing treatment efficiency.

[0054] In some embodiments, in step S4, when the diffusion treatment is performed, the diffusion temperature is 900-960°C, and the diffusion time is 25-30 minutes. Specifically, the diffusion temperature can be 900°C, 905°C, 910°C, 915°C, 920°C, 925°C, 930°C, 935°C, 940°C, 945°C, 950°C, 955°C, 960°C, etc.; the diffusion time can be 25min, 26min, 27min, 28min, 29min, 30min, etc.

[0055] The present invention uses diffusion treatment to make the carbon on the surface of the gear part diffuse rapidly toward the centripetal part, which helps to evenly distribute the carbon in the gear part; and the diffusion treatment can make the structure in the gear steel more uniform, reduce the internal stress in the subsequent quenching process, and thus reduce deformation. The present invention controls the diffusion temperature and diffusion time during the diffusion treatment, thereby avoiding the increase of the quenching deformation of the gear part caused by inappropriate diffusion temperature and time, and affecting the control effect of the quenching deformation of the gear part.

[0056] In some embodiments, in step S5, when the gear part is subjected to gas quenching treatment, an inert gas is used for quenching cooling, for example, an inert gas such as nitrogen or helium.

[0057] In some embodiments, during gas quenching treatment, the surface of the gear part is first cooled to 430-440°C, and then the supply of inert gas is stopped; after waiting for 10-20 seconds, the inert gas is supplied again for quenching cooling until the gear part is cooled to room temperature. In the present invention, during the gas quenching treatment, the gear part is cooled to room temperature in stages. Compared with directly cooling to room temperature, the cooling rate of the gear part can be controlled, the internal stress caused by rapid cooling can be reduced, and the deformation of the gear part can be reduced. In addition, the gear part of the present invention pauses cooling when it is cooled to 430-440°C, which can reduce the temperature difference between the surface and the core of the gear part, thereby better controlling the deformation of the gear part.

[0058] In some embodiments, when the inert gas is delivered during the gas quenching process, the gas pressure of the inert gas is 3 to 5 bar, for example, 3 bar, 3.5 bar, 4 bar, 4.5 bar, 5 bar, etc. The present invention can significantly reduce the deformation of the gear part by controlling the gas pressure, thereby better controlling the dimensional accuracy of the gear part, and avoiding the quenching deformation of the gear part being unable to be controlled due to excessive or insufficient gas pressure, thereby increasing the deformation of the gear part.

[0059] In some embodiments, when the tempering treatment is performed in step S6, the tempering temperature is 170-200°C and the holding time is 60-150 minutes. In the present invention, after the gear part is quenched, the internal stress generated by rapid cooling during quenching can be reduced by tempering the gear part and controlling the temperature and time of the tempering treatment, thereby reducing the deformation and cracking risks of the gear part and improving the dimensional stability of the gear part. If the tempering temperature or the tempering time exceeds the above range, the deformation of the gear part will increase.

[0060] Specifically, the tempering temperature can be 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, etc.; the tempering time can be 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, etc.

[0061] The present invention obtains gear steel with a controlled specific composition range by microalloying the gear steel; then, the gear steel is rolled and the gear is processed to obtain a gear part to be carburized with a suitable structure control; the gear part is carburized by a vacuum low-pressure carburizing process; then, the carburizing and quenching deformation is reduced by controlling the gas quenching process, and a gear part with good dimensional accuracy control is obtained.

[0062] The gear parts after tempering heat treatment are inspected for dimensions, including tooth shape and tooth phase, and compared with the dimensions of the gear parts to be carburized before carburizing and quenching heat treatment. The precision loss of the gear parts during quenching treatment of the present invention can be controlled to ≤3 levels.

[0063] The carburizing and quenching deformation of the gear steel quenching process of the present invention was tested using a C-shaped specimen. The deformation of the notch width at the opening of the C-shaped specimen after carburizing, quenching and tempering was controlled to be ≤0.2 mm compared to the C-shaped specimen before carburizing.

[0064] An embodiment of the present invention further provides a gear part with less deformation, which is processed by the method of the above embodiment. Compared with before carburizing treatment, the precision loss of the gear steel workpiece of the present invention after carburizing and quenching treatment does not exceed 3 levels.

[0065] The specific implementation method of the present invention is further described below through specific examples.

[0066] Example 1

[0067] Gear steel processing methods include:

[0068] S1, using Ti for microalloying treatment: in the gear steel smelting process, after LF smelting is completed, Ti element is added to the gear steel, the gear steel is microalloyed, and the mass percentage of Ti is controlled to be 0.058% of the gear steel, and the mass percentage of N in the gear steel is 0.0053%.

[0069] S2, rolling the gear steel. During heating and heat preservation, the heating temperature is 1250℃, and the heating time is 100min; after heating, the gear steel ingot is rolled, and the final rolling temperature is controlled at 920~950℃; after rolling, the steel is placed on a cooling bed for cooling, and each steel is placed at a distance of 400~900mm, and pit cooling is performed when the surface temperature drops to 400~500℃, and after pit cooling, the gear steel bar is obtained.

[0070] S3, using gear steel bars, through forging, post-forging heat treatment, machining and other links to process into gear parts to be carburized, and at the same time using gear steel bars to process into C-shaped specimens;

[0071] S4, the gear parts and C-shaped samples were carburized in a vacuum low-pressure carburizing furnace. During carburizing, acetylene gas was introduced into the carburizing furnace at a flow rate of 135L / h, and carburizing was performed in a pulse form at a carburizing temperature of 950°C. After the pulse carburizing, the gear parts and C-shaped samples were diffused for 26 minutes at a diffusion temperature of 930°C.

[0072] S5, after the diffusion is completed, the gear parts and C-shaped specimens are moved to the cooling room for gas quenching treatment. The nitrogen gas pressure is 4 Bar. After the gear surface is cooled to 430-440 ° C, the ventilation is stopped and waited for 14 seconds. After that, the quenching cooling is carried out again with 4 Bar gas pressure and cooled to room temperature.

[0073] S6, the gear parts and C-shaped specimens after carburizing and quenching were tempered at 180 °C and the holding time was 110 min.

[0074] The gear parts after tempering were inspected for size. Compared with the gear dimensions before carburizing, the dimensional accuracy loss was 2 levels. The opening width of the C-shaped specimen notch after tempering was measured, and the deformation was 0.18mm compared with the dimensions before carburizing.

[0075] Example 2

[0076] Gear steel processing methods include:

[0077] S1, using Nb for micro-alloying treatment: in the gear steel smelting process, after LF smelting is completed, Nb element is added to the gear steel to perform micro-alloying treatment on the gear steel, and the mass percentage of Nb is controlled to be 0.036% of the gear steel.

[0078] S2, rolling the gear steel. During heating and heat preservation, the heating temperature is 1200℃, and the heating time is 90min; after heating, the gear steel ingot is rolled, and the final rolling temperature is controlled at 940~970℃; after rolling, the steel is placed on a cooling bed for cooling, and each steel is placed at a distance of 500~1100mm, and pit cooling is performed when the surface temperature drops to 400~500℃, and after pit cooling, the gear steel bar is obtained.

[0079] S3, using gear steel bars, through forging, post-forging heat treatment, machining and other links to process into gear parts to be carburized, and at the same time using gear steel bars to process into C-shaped specimens;

[0080] S4, the gear parts and C-shaped samples were carburized in a vacuum low-pressure carburizing furnace. During carburizing, acetylene gas was introduced into the carburizing furnace at a flow rate of 150L / h, and carburizing was performed in a pulse form at a carburizing temperature of 980°C. After the pulse carburizing, the gear parts and C-shaped samples were diffused for 30 minutes at a diffusion temperature of 960°C.

[0081] S5, after the diffusion is completed, the gear parts and C-shaped specimens are moved to the cooling room for gas quenching treatment. The nitrogen gas pressure is 3.5 Bar. After the gear surface is cooled to 430-440 ° C, the ventilation is stopped and waited for 17 seconds. After that, the quenching cooling is performed again with 4 Bar gas pressure and cooled to room temperature.

[0082] S6, the gear parts and C-shaped specimens after carburizing and quenching were tempered at a tempering temperature of 170 °C and a holding time of 150 min.

[0083] The gear parts after tempering were inspected for size. Compared with the gear size before carburizing, the loss of dimensional accuracy was 1 level. The opening width of the notch of the C-shaped specimen after tempering was measured, and the deformation was 0.11mm compared with the size before carburizing.

[0084] Example 3

[0085] Gear steel processing methods include:

[0086] S1, composite microalloying treatment with Ti and Nb: in the gear steel smelting process, after LF smelting, Ti and Nb elements are added to the gear steel for microalloying treatment, and the mass percentage of Ti is controlled to be 0.05% of the gear steel, the mass percentage of Nb is controlled to be 0.03% of the gear steel, and the N content in the gear steel is 0.0044%.

[0087] S2, rolling the gear steel. During heating and heat preservation, the heating temperature is 1230℃, and the heating time is 120min; after heating, the gear steel ingot is rolled, and the final rolling temperature is controlled at 900-950℃; after rolling, the steel is placed on a cooling bed for cooling, and each steel is placed at a distance of 600-1500mm, and pit cooling is performed when the surface temperature drops to 400-500℃, and after pit cooling, the gear steel bar is obtained.

[0088] S3, using gear steel bars, through forging, post-forging heat treatment, machining and other links to process into gear parts to be carburized, and at the same time using gear steel bars to process into C-shaped specimens;

[0089] S4, the gear parts and C-shaped samples were carburized in a vacuum low-pressure carburizing furnace. During carburizing, acetylene gas was introduced into the carburizing furnace at a flow rate of 165L / h, and carburizing was performed in a pulse form at a carburizing temperature of 930°C. After the pulse carburizing, the gear parts and C-shaped samples were diffused for 25 minutes at a diffusion temperature of 900°C.

[0090] S5, after the diffusion is completed, the gear parts and C-shaped specimens are moved to the cooling room for gas quenching treatment. The nitrogen gas pressure is 4 Bar. After the gear surface is cooled to 430-440 ° C, the ventilation is stopped and waited for 15 seconds. After that, the gas pressure is 5 Bar again for quenching cooling and cooled to room temperature.

[0091] S6, the gear parts and C-shaped specimens after carburizing and quenching are tempered at a tempering temperature of 200°C and a holding time of 60 minutes.

[0092] The gear parts after tempering were inspected for size. Compared with the gear size before carburizing, the dimensional accuracy loss was 2 levels. The opening width of the C-shaped specimen notch after tempering was measured, and the deformation was 0.13mm compared with the size before carburizing.

[0093] Comparative Example 1

[0094] Gear steel processing methods include:

[0095] S1, using Ti for microalloying treatment: in the gear steel smelting process, after LF smelting is completed, Ti element is added to the gear steel, the gear steel is microalloyed, and the mass percentage of Ti is controlled to be 0.052% of the gear steel, and the N content in the gear steel is 0.0068%, and the N content is too high.

[0096] S2, rolling the gear steel. During heating and heat preservation, the heating temperature is too low, 1180℃, and the heating time is 100min; after heating, the gear steel ingot is rolled, and the final rolling temperature is too low, controlled at 830-840℃; after rolling, the steel is placed on a cooling bed for cooling, and each steel is placed at a small interval of 100-200mm; when the surface temperature drops to 350-400℃, pit cooling is carried out, and after pit cooling, the gear steel bar is obtained.

[0097] S3, using gear steel bars, through forging, post-forging heat treatment, machining and other links to process into gear parts to be carburized, and at the same time using gear steel bars to process into C-shaped specimens;

[0098] S4, the gear parts and C-shaped samples were carburized in a vacuum low-pressure carburizing furnace. Acetylene gas was introduced into the carburizing furnace during carburizing, and the carburizing was carried out in a strong carburizing and diffusion mode. The carbon potential during strong carburizing was 1.0%, the carbon potential during diffusion was 0.80%, and the carburizing temperature was 930°C. After carburizing, the gear parts and C-shaped samples were diffused, with a diffusion time of 90 minutes and a diffusion temperature of 930°C. The diffusion time was too long and the diffusion temperature was too low.

[0099] S5, after the diffusion is completed, the gear parts and C-shaped specimens are placed in oil for quenching and cooled to room temperature.

[0100] S6, the gear parts and C-shaped specimens after carburizing and quenching were tempered at 180℃ and the holding time was 120min.

[0101] The gear parts after tempering were inspected for size. Compared with the gear size before carburizing, the dimensional accuracy loss was 4 levels. The opening width of the C-shaped sample notch after tempering was measured, and the deformation was 0.38 mm compared with the size before carburizing. Compared with Examples 1 to 3, the method of this comparative example resulted in larger gear quenching deformation.

[0102] Comparative Example 2

[0103] Gear steel processing methods include:

[0104] S1, using Ti for microalloying treatment: in the gear steel smelting process, after LF smelting is completed, Ti element is added to the gear steel, the gear steel is microalloyed, and the mass percentage of Ti is controlled to be 0.052% of the gear steel, and the N content in the gear steel is 0.0068%, and the N content is too high.

[0105] S2, rolling the gear steel. During heating and heat preservation, the heating temperature is 1180℃, and the heating time is 100min; after heating, the gear steel ingot is rolled, and the final rolling temperature is controlled at 830-860℃; after rolling, the steel is placed on a cooling bed for cooling, and each steel is placed at a distance of 100-200mm, and pit cooling is performed when the surface temperature drops to 350-390℃, and after pit cooling, the gear steel bar is obtained.

[0106] S3, using gear steel bars, through forging, post-forging heat treatment, machining and other links to process into gear parts to be carburized, and at the same time using gear steel bars to process into C-shaped specimens;

[0107] S4, the gear parts and C-shaped samples were carburized in a vacuum low-pressure carburizing furnace. During carburizing, acetylene gas was introduced into the carburizing furnace at a flow rate of 115L / h, and the gas flow rate was too small; and the carburizing treatment was performed in the form of pulses, and the carburizing temperature was 950°C. After the pulse carburizing, the gear parts and C-shaped samples were diffused, and the diffusion time was 20min, and the diffusion temperature was 920°C.

[0108] S5, after the diffusion is completed, the gear parts and C-shaped specimens are moved to the cooling chamber for gas quenching treatment with a nitrogen gas pressure of 7 Bar and cooled to room temperature without adopting a staged cooling method.

[0109] S6, the gear parts and C-shaped specimens after carburizing and quenching were tempered at 180℃ and the holding time was 120min.

[0110] The gear parts after tempering were inspected for size. Compared with the gear size before carburizing, the dimensional accuracy loss was 4 levels. The opening width of the C-shaped sample notch after tempering was measured, and the deformation was 0.31 mm compared with the size before carburizing. Compared with Examples 1 to 3, the method of this comparative example resulted in larger gear quenching deformation.

[0111] Figure 1 and Figure 2 The figure shows the comparison of the precision loss and deformation of the gear parts after quenching in each embodiment and comparative example. Figure 1 and Figure 2 It can be seen that by adopting the processing method of the present invention and controlling the various process parameters in the processing process within an appropriate range, the deformation of the gear part can be controlled within 0.2 mm, and the dimensional accuracy loss is below level 2. However, when the quenching treatment method of the present invention is not adopted or the process parameters are not within the range set by the present invention, the deformation of the gear part is significantly increased, exceeding 0.3 mm, and the dimensional accuracy loss is above level 4.

[0112] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for processing gear steel with less deformation, characterized in that: include: S1. Microalloying the gear steel with Ti and / or Nb; S2, rolling the gear steel that has undergone the microalloying treatment to obtain a gear steel bar; S3, subjecting the gear steel bar to forging, post-forging heat treatment and machining in sequence to obtain a gear to be carburized; S4, performing carburizing treatment and diffusion treatment on the gear to be carburized to obtain a gear part; S5, performing gas quenching treatment on the gear part, and cooling the gear part to room temperature in stages; S6. Tempering the gear part after gas quenching.

2. The method according to claim 1, characterized in that In step S1, When Ti is used for the microalloying treatment, the mass percentage of Ti is controlled to be 0.035-0.065% of the gear steel; When Nb is used for the microalloying treatment, the mass percentage of Nb is controlled to be 0.02-0.06% of the gear steel; When Ti and Nb are used for composite microalloying treatment, the total mass percentage of Ti and Nb in the gear steel is controlled to be 0.025-0.085%.

3. The method according to claim 2, characterized in that In step S1, when Ti is used for the microalloying treatment, the mass percentage of N in the gear steel is controlled to be 0.003-0.006%; When Ti and Nb are used for composite microalloying, the mass percentage of N in the gear steel is controlled within 0.005%.

4. The method according to claim 1, characterized in that In step S5, when the gear part is subjected to gas quenching treatment, an inert gas is used for quenching cooling; After the surface of the gear part is cooled to 430-440° C., the supply of the inert gas is stopped; After waiting for 10 to 20 seconds, the inert gas is delivered again for quenching cooling until the gear steel workpiece is cooled to room temperature.

5. The method according to claim 4, characterized in that When the inert gas is transported, the gas pressure of the inert gas is 3 to 5 bar.

6. The method according to claim 1, characterized in that In step S2, when the gear steel is rolled, the heating temperature is not less than 1200° C. and the holding time is not less than 60 minutes.

7. The method according to claim 6, characterized in that In step S2, when rolling the gear steel, the final rolling temperature is not less than 850° C.; After rolling is completed, the gear steel bars are placed on a cooling bed for cooling, and the interval between each gear steel bar is more than 300 mm; When the surface temperature of the gear steel bar material drops to 400-500° C., the gear steel bar material is pile cooled or pit cooled.

8. The method according to claim 1, characterized in that In step S4, when the gear steel to be carburized is carburized, the carburizing temperature is 930-980°C.

9. The method according to claim 8, characterized in that In step S4, during the diffusion treatment, the diffusion temperature is 900-960° C. and the diffusion time is 25-30 minutes.

10. A gear part with less deformation, characterized in that: The gear steel workpiece is processed by the method according to any one of claims 1 to 9, and the precision loss of the gear steel workpiece after carburizing and quenching treatment is no more than 3 levels compared with that before carburizing treatment.

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