Gear steel carburizing heat treatment grain size control method and gear part

Abstract

The invention relates to the technical field of metal heat treatment and forming, in particular to a gear steel carburizing heat treatment grain size control method and a gear part. The gear blank is subjected to annealing treatment, and an annealed gear is obtained; the gear subjected to annealing treatment is subjected to carburizing quenching and tempering treatment, and a gear part is obtained; wherein the temperature of the annealing treatment is 600-800 DEG C. According to the method, growth and crystal mixing of crystal grains in the gear steel carburizing treatment process are effectively controlled, and the deformation, the operation quality and the operation life of the gear can be controlled easily after carburizing treatment.

Description

Technical Field

[0001] The invention relates to the technical field of metal heat treatment and forming, and in particular to a method for controlling the grain size of gear steel during carburizing heat treatment and a gear part. Background Art

[0002] Gears are mechanical components with teeth on the rim that can continuously mesh to transmit motion and power. They are important basic parts of mechanical equipment and the main transmission parts of most complete sets of mechanical equipment. Gear products can be roughly divided into two categories: vehicle gears and industrial gears, both of which are obtained by carburizing heat treatment of gear steel. Among them, the grain size of the carburizing heat treatment of gear steel directly affects the dimensional accuracy and deformation size of the gear after carburizing heat treatment, which in turn determines the operating quality and life of the gear set, and finally reflects in the high performance, low noise, long life and comfortable driving experience of the car.

[0003] Therefore, controlling the uniform and fine grain size of automobile gears after carburizing and reducing gear heat treatment deformation have become issues that need to be urgently addressed. Summary of the invention

[0004] The present invention aims to provide a method for controlling the grain size of gear steel during carburizing heat treatment and a gear part. The method can control the grain size of automobile gears after carburizing to be uniform and fine, reduce gear heat treatment deformation, and thus improve the gear running quality and service life.

[0005] To achieve the above object, the present invention provides a method for controlling the grain size of gear steel during carburizing heat treatment, the method comprising:

[0006] Processing the gear steel to obtain a gear blank;

[0007] Performing annealing treatment on the gear blank to obtain an annealed gear;

[0008] Carburizing, quenching and tempering the annealed gear to obtain a gear part;

[0009] The annealing temperature is 600-800°C.

[0010] The present invention also provides a gear part prepared based on the method for controlling the grain size of gear steel during carburizing heat treatment.

[0011] Technical effects and advantages of the present invention:

[0012] The present invention provides a method for controlling the grain size of gear steel during carburizing heat treatment, the method comprising: processing the gear steel to obtain a gear blank; annealing the gear blank to obtain an annealed gear; carburizing quenching and tempering the annealed gear to obtain a gear part; wherein the annealing temperature is 600-800°C.

[0013] The method effectively controls the growth of grains and mixed crystals during the carburizing process of gear steel, and is beneficial to controlling the deformation, operating quality and operating life of the gear after the carburizing process.

[0014] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 This is a flow chart of the method for controlling the grain size of gear steel during carburizing heat treatment;

[0017] Figure 2 This is the process parameter diagram for carburizing, quenching and tempering;

[0018] Figure 3 This is a diagram after the prior art is applied to situation A;

[0019] Figure 4 This is a diagram after the technology of the present invention is used for situation A;

[0020] Figure 5 This is a diagram after the prior art is applied to situation B;

[0021] Figure 6 This is a diagram after the technology of the present invention is used for situation B;

[0022] Figure 7 This is a diagram after the technology of the present invention is adopted for situation C. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0025] In order to solve the deficiencies of the prior art, the present invention discloses a method for controlling the grain size of gear steel during carburizing heat treatment, such as Figure 1 As shown, the method includes: processing gear steel to obtain gear blanks; annealing the gear blanks to obtain annealed gears; carburizing, quenching and tempering the annealed gears to obtain gear parts; wherein the annealing temperature is 600-800°C.

[0026] Specifically, annealing the gear blank to obtain the annealed gear includes:

[0027] Normalizing the gear blank;

[0028] The gear blank after normalizing treatment is subjected to rough turning, recrystallization annealing and finish turning in sequence to obtain the gear after annealing treatment.

[0029] Specifically, annealing the gear blank to obtain the annealed gear includes:

[0030] The gear blank is obtained by die forging the gear blank;

[0031] The gear blank is subjected to rough turning, annealing and finish turning in sequence to obtain the annealed gear.

[0032] Specifically, after the annealed gear is carburized and quenched, the method further includes: tempering and finishing the carburized and quenched gear to obtain a gear part.

[0033] The annealing treatment is performed at a temperature of 600-800° C. and for a time of 4-6 hours.

[0034] Among them, the temperature of carburizing and quenching treatment is 0-905℃; the temperature of tempering treatment is 0-180℃. Figure 2 shown.

[0035] In order to better understand the above scheme, the above scheme can be divided into three situations, specifically:

[0036] A. For the gear parts production process of "gear steel bar (raw material) cutting - normalizing - rough turning, finish turning - carburizing and quenching", annealing treatment is added between rough turning and finish turning. The specific steps include:

[0037] 1.1 Saw or shear the gear steel (cylindrical raw material) into segments to obtain gear blanks.

[0038] 1.2 The gear blank is normalized. The normalizing treatment parameters include: temperature of 830-900°C and time of 30-60 minutes.

[0039] 1.3 Rough turning the gear blank after normalizing treatment to obtain a gear rough blank.

[0040] 1.4 The gear rough blank is subjected to recrystallization annealing at 600-800℃ to eliminate the energy accumulated by dislocation and distortion caused by machining on the surface layer of the gear fine blank, which can effectively control the grain size consistency of the gear blank surface under carburizing heat treatment conditions.

[0041] 1.5 Finish turning the rough gear blank to obtain the fine gear blank.

[0042] 1.6 The gear blank is subjected to carburizing quenching + tempering + finishing to obtain the gear parts.

[0043] B. For the gear parts production process of "die forging gear blank - rough turning, fine turning - carburizing treatment", annealing treatment is added between rough turning and fine turning. Specifically, the following steps are included:

[0044] 2.1 Saw or shear the gear steel (cylindrical raw material) into segments to obtain gear blanks.

[0045] 2.2 The gear blank is obtained by die forging.

[0046] 2.3 The gear blank is rough turned to obtain the gear blank.

[0047] 2.4 The gear blank is annealed at 600-800℃ to eliminate the stress caused by hot working and the energy accumulated by dislocation and distortion of the surface layer caused by machining, which can effectively control the consistency of the grain size of the surface and core of the gear blank under carburizing heat treatment conditions.

[0048] 2.5 Finish turning the rough gear blank to obtain the fine gear blank.

[0049] 2.6 The gear blank is subjected to carburizing quenching + tempering + finishing to obtain the gear parts.

[0050] C. The gear parts production process of "die forging gear blank - rough turning - annealing instead of isothermal normalizing - fine turning - carburizing treatment" specifically includes the following steps:

[0051] 3.1 Saw or shear the gear steel (cylindrical raw material) into segments to obtain gear blanks.

[0052] 3.2 The gear blank is obtained by die forging and rough turning.

[0053] 3.3 The gear blank is annealed at 600-800℃ to eliminate the stress caused by hot working and the energy accumulated by dislocation and distortion of the surface layer caused by machining, which can effectively control the consistency of the grain size of the surface and core of the gear blank under carburizing heat treatment conditions.

[0054] 3.4 The annealed gear blank is subjected to fine turning to obtain a fine gear blank.

[0055] 3.5 The gear blank is subjected to carburizing quenching + tempering + finishing to obtain the gear parts.

[0056] It should be noted that the gear part can be either a vehicle gear or an industrial gear.

[0057] The present invention provides a method for controlling the grain size of gear steel during carburizing heat treatment, the method comprising: processing the gear steel to obtain a gear blank; annealing the gear blank to obtain an annealed gear; carburizing, quenching and tempering the annealed gear to obtain a gear part; wherein the annealing temperature is 600-800°C. The method effectively controls the growth and mixed crystal of the grains during the carburizing treatment of the gear steel, and is conducive to controlling the deformation, operating quality and operating life of the gear after the carburizing treatment.

[0058] In order to verify the feasibility of this solution, an example is provided below.

[0059] Example 1

[0060] This example is a result verification for the above-mentioned case A. Among them, the grain size of the gear steel hot-rolled material under simulated carburizing heat treatment conditions is as follows Figure 3 The gear steel material of the present invention is normalized (845℃, 45min) and annealed (650℃, 2h) and then carburized and quenched (900℃, 3h) and tempered (170℃, 3h) under the conditions of simulated carburization heat treatment. The grain size is 8.5 without mixed crystals, which is qualified. Figure 4 .

[0061] Example 2

[0062] This embodiment is a result verification for the above-mentioned case B. Among them, the grain size of the gear steel hot-rolled material under simulated carburizing heat treatment conditions is as follows Figure 5 The grain size is 2-8.5, the extreme difference is large, and it is unqualified. The gear steel material after annealing (680℃, 2h) is carburized and quenched (900℃, 3h) and tempered (170℃, 3h) under the conditions of simulated carburizing heat treatment. The grain size is 8.5 without mixed crystals, which is qualified. Figure 6 .

[0063] Example 3

[0064] This example is a result verification for the above C case. After annealing (760℃, 2h) instead of isothermal normalizing (900℃, 45min-cooling to 610℃ isothermal 2h), the gear steel material simulates carburizing heat treatment conditions, carburizing quenching (900℃, 3h) and tempering (170℃, 3h). The grain size is 8.5 without mixed crystals, and the qualified Figure 7 .

[0065] The present invention also provides a gear part prepared based on the gear steel carburizing heat treatment grain size control method.

[0066] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling the grain size of gear steel during carburizing heat treatment, characterized in that: The method comprises: Processing the gear steel to obtain a gear blank; Performing annealing treatment on the gear blank to obtain an annealed gear; Carburizing, quenching and tempering the annealed gear to obtain a gear part; The annealing temperature is 600-800°C.

2. The method for controlling the grain size of gear steel during carburizing heat treatment according to claim 1, characterized in that: Annealing the gear blank to obtain the annealed gear includes: Normalizing the gear blank; The gear blank after normalizing treatment is subjected to rough turning, recrystallization annealing and finish turning in sequence to obtain the gear after annealing treatment.

3. The method for controlling the grain size of gear steel during carburizing heat treatment according to claim 1, characterized in that: Annealing the gear blank to obtain the annealed gear includes: The gear blank is obtained by die forging the gear blank; The gear blank is subjected to rough turning, annealing and finish turning in sequence to obtain the annealed gear.

4. The method for controlling the grain size of gear steel during carburizing heat treatment according to claim 2, characterized in that: The normalizing treatment conditions include: temperature of 830-900°C and time of 30-60 minutes.

5. The method for controlling the grain size of gear steel during carburizing heat treatment according to claim 1, characterized in that: After the annealed gear is carburized and quenched, the method further includes: tempering and finishing the carburized and quenched gear to obtain a gear part.

6. The method for controlling the grain size of gear steel during carburizing heat treatment according to claim 1, characterized in that: The temperature of carburizing and quenching treatment is 0-905℃.

7. The method for controlling the grain size of gear steel during carburizing heat treatment according to claim 1, characterized in that: The temperature of the tempering treatment is 0-180°C.

8. The method for controlling the grain size of gear steel during carburizing heat treatment according to claim 1, characterized in that: The gear steel is cut into sections to obtain gear blanks.

9. A gear part manufactured based on the method for controlling the grain size of gear steel during carburizing heat treatment according to any one of claims 1 to 8.

Images