阅读说明：本技术 由齿轮圆钢加工齿轮零件的方法以及齿轮零件 (Method for machining gear part from round gear steel and gear part ) 是由 刘年富 赵贺楠 吴学兴 杨伟光 董凤奎 王银国 于 2020-06-16 设计创作，主要内容包括：本申请涉及钢铁制造领域,具体而言,涉及一种由齿轮圆钢加工齿轮零件的方法以及齿轮零件。该方法,包括将多个齿轮零件垂直放置在试样框中进行加热均化,齿轮零件之间间隔70～90mm；采用冷风冷却180～220s,风冷流量调节阀的开启度为15～25％,回流热风冷却时间为280～320s；温度降至655～665℃,保温290～310min。将多个齿轮零件垂直放置在试样框中进行加热均化,齿轮零件之间间隔70～90mm,相互之间不接触,同时采取适当的等温正火工艺,能够将齿轮零件的组织控制为F+P,组织≤3级,且同一齿坯零件不同位置的硬度散差控制≤4HBW,同框中,齿坯零件硬度散差控制≤6HBW。(The application relates to the field of steel manufacturing, in particular to a method for machining a gear part by gear round steel and the gear part. The method comprises the steps of vertically placing a plurality of gear parts in a sample frame for heating homogenization, wherein the interval between the gear parts is 70-90 mm; cooling by cold air for 180-220 s, wherein the opening degree of an air-cooled flow regulating valve is 15-25%, and the cooling time of the backflow hot air is 280-320 s; the temperature is reduced to 655-665 ℃, and the temperature is kept for 290-310 min. A plurality of gear parts are vertically placed in a sample frame for heating homogenization, the gear parts are spaced by 70-90 mm and are not in contact with each other, meanwhile, a proper isothermal normalizing process is adopted, the structure of the gear parts can be controlled to be F + P, the structure is less than or equal to 3 grades, the hardness variation of different positions of the same gear blank part is controlled to be less than or equal to 4HBW, and the hardness variation of the gear blank part in the same frame is controlled to be less than or equal to 6 HBW.)

1. A method for processing gear parts by gear round steel is characterized in that the banded structure of the gear round steel is less than or equal to 2.0 level; the hardenability of the gear round steel comprises: j9 is 38-43HRC, J15 is 32-37 HRC; the cross section carbon segregation of the gear round steel is less than or equal to 0.025 percent; the structure of the gear round steel is F + P and is less than or equal to 3 grades; the normalizing hardness of the round gear steel is 165-180 HBW;

the method comprises the following steps: heating the gear round steel, then forging the gear round steel into a gear part, and carrying out isothermal normalizing on the gear part;

the isothermal normalizing comprises: heating, homogenizing, air cooling and air cooling;

the heating and homogenizing step comprises the steps of vertically placing a plurality of gear parts in a sample frame for heating and homogenizing, wherein the gear parts are spaced by 70-90 mm and are not in contact with each other;

the air cooling step comprises cooling by cold air for 180-220 s, wherein the opening degree of an air cooling flow regulating valve is 15-25%, and the cooling time of backflow hot air is 280-320 s;

and the air cooling comprises the steps of reducing the temperature of the gear part subjected to air cooling to 655-665 ℃ in a furnace, preserving the temperature for 290-310 min, and discharging and air cooling.

2. The method for machining gear parts from round gear steel according to claim 1,

the temperature of the heating and homogenizing step is 940-960 ℃; the time is 80-100 min.

3. The method for machining gear parts from round gear steel according to claim 1,

the step of heating the gear round steel comprises the following steps:

blanking the round gear steel into gear blanks with the length of 310-330 mm, controlling the heating temperature at 1250-1270 ℃ and the heating time at 30-50 s.

4. The method for machining a gear part from round gear steel according to claim 3,

the step of forging the gear round steel comprises the following steps:

the forging temperature is 1240-1260 ℃, the finish forging temperature is 985-1015 ℃, and the gear blank is forged into a gear part with the diameter of 120-430 mm.

5. A method of machining a gear part from round gear steel as claimed in any one of claims 1 to 4, wherein the step of preparing the round gear steel comprises:

the first step is as follows: smelting in a converter;

the second step is that: refining outside the furnace;

the third step: RH vacuum degassing;

the fourth step: continuously casting a square billet;

the fifth step: heating and rolling;

and in the fourth step, when the square billet is continuously cast, the electromagnetic stirring parameter of the crystallizer is controlled to be 195-205A/2.0 Hz, and the electromagnetic stirring parameter of the tail end is controlled to be 590-610A/5.0 Hz.

6. The method for machining a gear part from round gear steel according to claim 5,

in the fourth step, during square billet continuous casting, secondary cooling is carried out in four sections, wherein forced cooling is adopted in the first section and the second section, and cooling water in the first section and the second section accounts for 25-35% of the total cooling water amount; and the third section and the fourth section both adopt weak cooling, the cooling water of the third section accounts for 22-28% of the total cooling water amount, and the cooling water of the fourth section accounts for 12-18% of the total cooling water amount.

7. The method for machining a gear part from round gear steel according to claim 5,

in the fifth step, during heating and rolling, the reduction rate of the rough rolling single pass is more than or equal to 15%, and the accumulated reduction of the rough rolling section accounts for 45-55% of the total reduction of the casting blank.

8. The method for machining a gear part from round gear steel according to claim 5,

and in the fifth step, the temperature of a high-temperature section is controlled to be 1240-1260 ℃ and the time of the high-temperature section is controlled to be 250-350min during heating and rolling.

9. The method for machining gear parts from round gear steel according to claim 1,

the gear round steel comprises the following components in percentage by weight: c: 0.22-0.26%, Si: 0.20-0.35%, Mn: 0.70-1.00%, P is less than or equal to 0.025%, S: 0.017-0.030%, Cr: 1.00-1.25%, Mo: 0.30-0.40%, Ni: 0.40-0.60%, Al: 0.020-0.035%, Ti 0.005-0.030%, N: 0.0080-0.0120% and the balance of Fe;

wherein Al/N is 2.0-3.5, and Ti/N is 1.7-3.5.

10. A gear part is characterized in that the structure of the gear part is F + P and is less than or equal to 3 grades;

the hardness dispersion difference of different positions of the same gear part is less than or equal to 4 HBW.

Technical Field

The application relates to the field of steel manufacturing, in particular to a method for machining a gear part by gear round steel and the gear part.

Background

Isothermal normalizing heat treatment is generally required to be carried out on a carburized gear forging blank to obtain a uniform structure and proper processing hardness, and the structure preparation is made for subsequent carburization so as to reduce quenching deformation.

Some known methods for improving the structural uniformity of gear steel include:

(1) normalizing by using waste heat after forging: carrying out waste heat normalizing treatment on the gear forging after the hot forging forming;

(2) machining: turning the outer circle, the inner hole and the end face, inserting the key slot and removing burrs;

(3) cleaning: cleaning and removing grease dirt and oxide skin on the surface of the gear forging;

(4) pre-oxidation: pushing the cleaned gear forging into a pre-oxidation furnace chamber of a continuous carburizing furnace for pre-oxidation treatment;

(5) high-temperature carburization: pushing the gear forging subjected to the pre-oxidation treatment into a carburizing furnace chamber of a continuous carburizing furnace for high-temperature carburizing treatment, wherein the carburizing adopts a two-section carburizing method, the first section is a strong carburizing stage, and the second section is a diffusion stage;

(6) pre-normalizing: pushing the gear forging subjected to carburization into a normalizing furnace chamber of a continuous carburizing furnace, and carrying out pre-normalizing treatment on the gear forging through a fan arranged around the furnace chamber;

(7) reheating: pushing the gear forging with the waste heat after being pre-normalized into a reheating furnace chamber of a continuous carburizing furnace, reheating to 815-835 ℃ and preserving heat for 2-3 hours; in the reheating process, the carbon potential in the furnace chamber is controlled to be 0.55 +/-0.05 percent;

(8) quenching: directly and vertically immersing the reheated and insulated gear forging into quenching oil, wherein a stirrer is arranged in the quenching oil, so that the temperature of the quenching oil is uniform, and the temperature of the quenching oil is controlled to be 60 +/-5 ℃;

(9) tempering: the quenched gear is subjected to heat preservation for 2-3 hours at the temperature of 180-200 ℃ for tempering, and then is discharged from a furnace for air cooling;

(10) shot blasting: and carrying out surface shot blasting treatment on the gear forging subjected to the carburizing heat treatment.

The main process control points of the method are as follows: waste heat normalizing, high-temperature carburizing, pre-normalizing, reheating and quenching. The process control method has the advantages of excessive process conditions required to be controlled, large variability, large uncontrollable risk for round steel with different performance compositions, incapability of effectively improving the tissue uniformity of the gear steel and further incapability of effectively reducing the hardness dispersion difference of the gear.

Disclosure of Invention

An object of the embodiment of the application is to provide a method for machining a gear part by gear round steel and the gear part, which can aim at the gear round steel with a specific structure, improve the structure uniformity of the gear part made of the gear round steel in a targeted manner, and reduce the hardness dispersion difference of the gear part.

In a first aspect, the application provides a method for processing gear parts by gear round steel, wherein the banded structure of the gear round steel is less than or equal to 2.0 level; the hardenability of the gear round steel comprises: j9 is 38-43HRC, J15 is 32-37 HRC; the cross section carbon segregation of the gear round steel is less than or equal to 0.025 percent; the structure of the gear round steel is F (ferrite phase) + P (pearlite structure), and is less than or equal to grade 3; the normalizing hardness of the round steel gear is 165-180 HBW;

the method comprises the following steps: heating the round gear steel, forging the round gear steel into a gear part, and carrying out isothermal normalizing on the gear part;

isothermal normalizing comprises the following steps: heating, homogenizing, air cooling and air cooling;

the heating and homogenizing step comprises the steps of vertically placing a plurality of gear parts in a sample frame for heating and homogenizing, wherein the gear parts are spaced by 70-90 mm and are not in contact with each other;

the air cooling step comprises cooling by cold air for 180-220 s, wherein the opening degree of an air cooling flow control valve is 15-25%, and the cooling time of backflow hot air is 280-320 s;

and air cooling comprises the steps of reducing the temperature of the gear part subjected to air cooling to 655-665 ℃ in a furnace, preserving the temperature for 290-310 min, discharging and air cooling.

For a round steel of a specific structure: the banded structure of the gear round steel is less than or equal to 2.0 grade; the hardenability of the gear round steel comprises: j9 is 38-43HRC, J15 is 32-37 HRC; the cross section carbon segregation of the gear round steel is less than or equal to 0.025 percent; the structure of the gear round steel is F (ferrite phase) + P (pearlite structure), and is less than or equal to grade 3; the normalizing hardness of the round steel gear is 165-180 HBW; a proper gear blank part framing system is adopted, a plurality of gear parts are vertically placed in a sample frame for heating homogenization, the gear parts are spaced by 70-90 mm and are not in contact with each other, meanwhile, a proper isothermal normalizing process is adopted, the structure of the gear blank parts can be controlled to be F + P, the structure is not more than 3 grade, the hardness dispersion difference of different positions of the same gear blank part is controlled to be not more than 4HBW, and the hardness dispersion difference of the gear blank parts in the same sample frame is controlled to be not more than 6 HBW. Therefore, the structure uniformity of the gear part manufactured by the gear round steel can be improved in a targeted manner, and the hardness variation of the gear part is reduced.

In a second aspect, the present application provides a gear part, the structure of which is F + P and is no greater than 3 stages;

the hardness dispersion difference of the same gear part at different positions is less than or equal to 4 HBW.

The gear part has uniform F + P structure, and the same gear part has poor hardness dispersion at different positions and excellent performance.

Drawings

In order to more clearly explain the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that for those skilled in the art, other related drawings can be obtained from these drawings without inventive effort.

FIG. 1 shows the micro-topography of a gear part provided in example 2;

FIG. 2 shows the micro-topography of the gear part provided in comparative example 6.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments.

Thus, the following detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.

The embodiment of the application provides a method for processing gear parts by round gear steel, wherein the banded structure of the round gear steel is less than or equal to 2.0 level; the hardenability of the gear round steel comprises: j9 is 38-43HRC, J15 is 32-37 HRC; the cross section carbon segregation of the gear round steel is less than or equal to 0.025 percent; the structure of the gear round steel is F + P and is less than or equal to 3 grades; the normalizing hardness of the round steel gear is 165-180 HBW;

the method comprises the following steps: heating the round gear steel, forging the round gear steel into a gear part, and carrying out isothermal normalizing on the gear part;

isothermal normalizing comprises the following steps: heating, homogenizing, air cooling and air cooling;

the heating and homogenizing step comprises the steps of vertically placing a plurality of gear parts in a sample frame for heating and homogenizing, wherein the gear parts are spaced by 70-90 mm and are not in contact with each other;

the air cooling step comprises cooling by cold air for 180-220 s, wherein the opening degree of an air cooling flow control valve is 15-25%, and the cooling time of backflow hot air is 280-320 s;

and air cooling comprises the steps of reducing the temperature of the gear part subjected to air cooling to 655-665 ℃ in a furnace, preserving the temperature for 290-310 min, discharging and air cooling.

A proper gear blank part framing system is adopted for the round steel with the specific structure, a plurality of gear parts are vertically placed in a sample frame for heating and homogenizing, the gear parts are spaced by 70-90 mm and are not in contact with each other, meanwhile, a proper isothermal normalizing process is adopted, the structure of the gear blank parts can be controlled to be F + P, the structure is not more than 3 grade, the hardness dispersion difference of different positions of the same gear blank part is not more than 4HBW, and the hardness dispersion difference of the gear blank parts in the same sample frame is not more than 6 HBW. Therefore, the structure uniformity of the gear part manufactured by the gear round steel can be improved in a targeted manner, and the hardness variation of the gear part is reduced.

In some embodiments of the present application, a method of machining a gear part from gear round steel comprises:

and step S1, preparing gear round steel.

The gear round steel comprises the following components in percentage by weight: c: 0.22-0.26%, Si: 0.20-0.35%, Mn: 0.70-1.00%, P is less than or equal to 0.025%, S: 0.017-0.030%, Cr: 1.00-1.25%, Mo: 0.30-0.40%, Ni: 0.40-0.60%, Al: 0.020-0.035%, Ti 0.005-0.030%, N: 0.0080-0.0120% and the balance of Fe;

wherein Al/N is 2.0-3.5, and Ti/N is 1.7-3.5.

Further, the gear round steel comprises the following components in percentage by weight: c: 0.23-0.25%, Si: 0.21-0.34%, Mn: 0.71-0.99%, P is less than or equal to 0.025%, S: 0.018-0.029%, Cr: 1.01-1.24%, Mo: 0.31-0.39%, Ni: 0.41-0.59%, Al: 0.021-0.034%, Ti 0.004-0.029%, N: 0.0079-0.0110% and the balance Fe;

wherein Al/N is 2.1-3.4, and Ti/N is 1.8-3.4.

Illustratively, the gear round steel comprises the following components in percentage by weight: c: 0.24%, Si: 0.25%, Mn: 0.80%, P is less than or equal to 0.025%, S: 0.020%, Cr: 1.10%, Mo: 0.35%, Ni: 0.45%, Al: 0.030%, Ti: 0.015%, N: 0.01 percent, and the balance of Fe;

wherein Al/N is 2.5 and Ti/N is 3.0.

Further, the preparation method of the round gear steel comprises the following steps:

the first step is as follows: smelting in a converter;

the second step is that: refining outside the furnace;

the third step: RH vacuum degassing;

the fourth step: continuously casting a square billet;

the fifth step: and (4) heating and rolling.

Furthermore, in the fourth step, during the square billet continuous casting, the electromagnetic stirring parameter of the crystallizer is controlled to be 195-205A/2.0 Hz, and the electromagnetic stirring parameter of the tail end is controlled to be 590-610A/5.0 Hz.

Furthermore, in the fourth step, during the square billet continuous casting, the electromagnetic stirring parameter of the crystallizer is controlled to be 196-204A/2.0 Hz, and the electromagnetic stirring parameter of the tail end is controlled to be 591-611A/5.0 Hz.

Illustratively, in the fourth step, during the billet continuous casting, the electromagnetic stirring parameter of the crystallizer is controlled to be 200A/2.0Hz, and the electromagnetic stirring parameter of the tail end is controlled to be 600A/5.0 Hz.

Furthermore, in the fourth step, during square billet continuous casting, secondary cooling is carried out in four sections, the first section and the second section both adopt forced cooling, and cooling water of the first section and the second section both accounts for 25-35% of the total cooling water; and the third section and the fourth section both adopt weak cooling, the cooling water of the third section accounts for 22-28% of the total cooling water amount, and the cooling water of the fourth section accounts for 12-18% of the total cooling water amount.

Furthermore, the cooling water of the first section and the cooling water of the second section both account for 26-34% of the total cooling water; the third section of cooling water accounts for 23-27% of the total cooling water amount, and the fourth section of cooling water accounts for 13-17% of the total cooling water amount.

Illustratively, the cooling water of the first and second sections each accounts for 30% of the total cooling water amount; the cooling water of the third section accounts for 25% of the total cooling water amount, and the cooling water of the fourth section accounts for 15% of the total cooling water amount.

In the continuous casting process, the electromagnetic stirring parameters of the crystallizer are controlled within the range, and the process parameters of secondary cooling are controlled within the range, so that the composition segregation can be effectively reduced, the uniformity of the components of a casting blank can be ensured, and the subsequent influence on the composition and the structure uniformity of the cross section of the gear can be reduced.

Further, the continuous casting process adopts a large square billet section for production, the superheat degree of the molten steel is controlled to be 15-30 ℃, and the constant drawing speed is controlled to be 0.45-0.55 m/min.

Further, the continuous casting process adopts a large square billet section for production, the superheat degree of the molten steel is controlled at 16-28 ℃, and the constant drawing speed is controlled at 0.46-0.54 m/min.

Illustratively, the continuous casting process adopts a large square billet section for production, the superheat degree of molten steel is controlled at 20 ℃, and the constant drawing speed is controlled at 0.5 m/min.

Furthermore, in the fifth step, during the heating and rolling, the temperature of the high temperature section (the temperature of the heating second section and the temperature of the soaking section) is controlled at 1250 + -10 ℃, and the time of the high temperature section is controlled at 250-.

Furthermore, during the heating rolling, the temperature of the high temperature section (the temperature of the heating second section and the temperature of the soaking section) is controlled at 1250 +/-5 ℃, and the time of the high temperature section is controlled at 260-340 min.

For example, in the heating rolling, the temperature of the high temperature section (the temperature of the second heating section and the temperature of the soaking section) is controlled at 1250 ℃, and the time of the high temperature section is controlled at 300 min.

Furthermore, in the fifth step, during heating rolling, the rough rolling adopts single-pass large reduction, the single-pass reduction rate of the rough rolling is more than or equal to 15%, and the accumulated reduction of the rough rolling section accounts for 45-55% of the total reduction of the casting blank.

By controlling the process conditions of heating and rolling within the range, the casting blank structure can be ensured to be fully deformed and to be deformed and permeated to the core of the casting blank, the dendrite of the core of the casting blank is ensured to be crushed, recrystallization is promoted to occur, the fine and uniform grain size is obtained, and the structure is uniform when the subsequent round steel cooling structure is changed.

Further, during heating rolling, the reduction rate of a single pass of rough rolling is 15% -30%, and the accumulated reduction of a rough rolling section accounts for 46% -54% of the total reduction of the casting blank.

Illustratively, the rough rolling single-pass reduction rate is 20%, and the cumulative reduction of the rough rolling section accounts for 50% of the total reduction of the cast slab.

In step S1, the composition and structure of the gear round steel are ensured to be uniform by controlling the conditions of the continuous casting process and the heating and rolling process.

Detecting the structure and the performance of the gear round steel prepared in the step S1, taking a sample with the height of 15-20mm at the D/4 and the center part of the rolled round steel, and preserving the temperature of the sample for 60 +/-5 min at 930 +/-5 ℃; air cooling to 650 +/-5 ℃ in a holding furnace, holding for 90min, and then detecting the banded structure of the sample according to GB/T13299 after air cooling; sampling at the D/4 position of rolled round steel according to the GB/T225 requirement, quenching at the temperature of 930 +/-5 ℃ according to the normalizing temperature, and then quenching at the temperature of 925 +/-5 ℃, and detecting the hardenability value of the round steel according to the GB/T225 requirement; sampling according to the 9-point method usingThe drill bit is used for drilling samples, and a carbon-sulfur analyzer is used for analyzing the carbon segregation condition of the cross section of the round steel.

And (3) detection results: the banded structure of the gear round steel prepared according to the step S1 is less than or equal to 2.0 grade; the hardenability of the gear round steel comprises: j9 is 38-43HRC, J15 is 32-37 HRC; the cross section carbon segregation of the gear round steel is less than or equal to 0.025 percent; the structure of the gear round steel is F + P and is less than or equal to 3 grades; the normalizing hardness of the round gear steel is 165-180 HBW.

In other alternative embodiments of the present application, the machining of the gear steel may also be performed by directly purchasing round steel having the above-described properties.

And S2, machining the round gear steel obtained in the S1 into gear parts.

The gear round steel manufactured in the step S1 is processed into the gear part, so that the uniformity of the components and the structure of the cross section of the gear part can be effectively ensured.

Further, the method for machining the gear part from the gear round steel comprises the following steps: and heating the round gear steel, forging the round gear steel into a gear part, and carrying out isothermal normalizing on the gear part.

Further, the step of heating the gear round steel comprises the following steps:

blanking the round gear steel into gear blanks with the length of 310-330 mm, controlling the heating temperature at 1250-1270 ℃ and the heating time at 30-50 s.

Further, the step of heating the gear round steel comprises the following steps:

blanking round gear steel into gear blanks with the length of 315-325 mm, controlling the heating temperature to be 1255-1265 ℃ and the heating time to be 35-45 s.

Illustratively, the round gear steel is blanked into a gear blank with the length of 320mm, the heating temperature is controlled to be 1260 ℃, and the heating time is controlled to be 40 s.

Further, the step of forging the gear round steel comprises the following steps:

the forging temperature is 1240-1260 ℃, the finish forging temperature is 985-1015 ℃, and the gear blank is forged into a gear part with the diameter of 120-430 mm.

Furthermore, the forging temperature is 1245-1255 ℃, the finish forging temperature is 986-1016 ℃, and the forging diameter of the gear blank is 125-425 mm.

Illustratively, the open forging temperature is 1250 ℃ and the finish forging temperature is 1000 ℃, and the gear blank is forged into a gear part having a diameter of 300 mm.

Further, isothermal normalizing comprises: heating and homogenizing, air cooling and air cooling.

Further, the heating homogenization step comprises the step of vertically placing a plurality of gear parts in the sample frame for heating homogenization, wherein the gear parts are spaced by 70-90 mm and are not in contact with each other.

Furthermore, a plurality of gear parts are vertically placed in the sample frame for heating homogenization, and the interval between the gear parts is 75-85 mm.

Illustratively, a plurality of gear parts are vertically placed in a sample frame for heat homogenization, with 80mm spacing between the gear parts.

Further, the temperature of the heating and homogenizing step is 940-960 ℃; the time is 80-100 min.

Further optionally, the temperature of the heating and homogenizing step is 945 to 955 ℃; the time is 85-95 min.

Illustratively, the temperature of the heat homogenization step is 950 ℃; the time is 90 min.

Further, the air cooling step comprises cooling by cold air for 180-220 s, wherein the opening degree of an air cooling flow regulating valve is 15-25%, and the cooling time of the backflow hot air is 280-320 s;

further, the air cooling step comprises cooling with cold air for 185-215 s, wherein the opening degree of the air cooling flow regulating valve is 16-24%, the proportion and time of the backflow hot air are controlled, and the cooling time of the backflow hot air is 285-315 s.

Illustratively, cold air cooling is adopted for 200s, the opening degree of an air-cooled flow regulating valve is 20%, and the cooling time of return hot air is 300 s.

Further, the air cooling comprises the steps of reducing the temperature of the gear part subjected to air cooling to 655-665 ℃ in a furnace, preserving the temperature for 290-310 min, and discharging and air cooling.

Further, air cooling comprises the steps of reducing the temperature of the gear part subjected to air cooling to 656-664 ℃ in a furnace, preserving the heat for 295-305 min, and discharging the gear part out of the furnace for air cooling.

Illustratively, the air cooling comprises the steps of reducing the temperature of the gear part subjected to air cooling to 660 ℃ in a furnace, keeping the temperature for 300min, and discharging and air cooling.

Further, the gear part obtained is subjected to press quenching.

Illustratively, 2 gear parts of the same frame are taken randomly, 3 samples (15mm +/-3 min) are taken in the circumferential direction of each gear part, and the hardness and the structure of the isothermal normalizing gear blank are detected according to GB/T13320.

The detection result shows that the structure of the gear part prepared by the method is F + P and is less than or equal to 3 grades.

Furthermore, in the gear part prepared by the method, the hardness difference of a plurality of gear parts is less than or equal to 6HBW in the same sample frame.

Furthermore, the hardness difference of the same gear part and different positions of the gear part prepared by the method is less than or equal to 4 HBW.

Some embodiments of the present application also provide a gear part having a structure of F + P and ≦ 3 stage.

Furthermore, the hardness dispersion difference of different positions of the same gear part is less than or equal to 4 HBW.

In some embodiments of the present application, the gear part may be manufactured according to the method for machining a gear part from round gear steel provided in the previous embodiments.

The features and properties of the present application will be described in detail below with reference to examples and comparative examples.