CN113278769A

CN113278769A - Carburizing steel expansion process and carburizing steel gear

Info

Publication number: CN113278769A
Application number: CN202110551014.2A
Authority: CN
Inventors: 党军玲; 马宏利; 贺志付; 黄文鹏; 仲博颖; 胡云权
Original assignee: Chongqing Gearbox Co Ltd
Current assignee: Chongqing Gearbox Co Ltd
Priority date: 2021-05-20
Filing date: 2021-05-20
Publication date: 2021-08-20

Abstract

The invention discloses a carburizing steel expansion process, which is characterized in that after rough turning or gear hobbing, when the problem that the size of a gear blank (steel billet) is smaller is faced, an applicant creatively applies a quenching and high-temperature tempering mode to expand the gear blank. The method is convenient to implement, and the applicant finds that the gear blank subjected to the expansion treatment can completely meet the machining size requirement of the gear. Compared with the carburized billet, the non-carburized billet is not influenced by a high carbon area of the surface layer in the quenching process, so that the expansion amount is larger, and the size requirement is easily met. Therefore, the applicant has chosen to subject the gear blank to an expansion process prior to carburization. The billet is subjected to expansion treatment before carburization, so that the billet can meet the requirement of machining size in the later period, and the billet subjected to expansion treatment is more beneficial to the later-period carburization quenching. The invention also discloses a carburizing steel gear.

Description

Carburizing steel expansion process and carburizing steel gear

Technical Field

The invention relates to the field of carburizing steel, in particular to a carburizing steel expansion process and a carburizing steel gear.

Background

In the prior art, gears are usually machined from carburized steel. The processing steps of the gear mainly comprise: forging a blank, roughly turning, hobbing, carburizing, quenching and machining. Wherein, blank forging, rough turning and hobbing belong to cold processing.

However, in the gear machining process, after rough turning or hobbing, the common normal line and the addendum circle of the gear blank may be small in size. If the common normal line and the addendum circle of the gear blank are small in size, gears meeting the requirements cannot be machined in subsequent machining. Therefore, if the common normal line and the addendum circle of the gear blank are smaller after rough turning and gear hobbing, the gear blank can only be scrapped, so that the material waste is caused, and the production efficiency is reduced.

Therefore, how to remedy the gear blank which does not meet the size requirement so as to enable the size of the gear blank to meet the requirement and avoid scrapping is a critical problem to be solved urgently by the technical personnel in the field.

Disclosure of Invention

The invention aims to remedy gear blanks which do not meet the size requirement, so that the size of the gear blanks meets the requirement, and scrapping is avoided. In order to achieve the purpose, the invention provides the following technical scheme:

a carburizing steel expansion process comprises the following steps: before carburizing, the billet is subjected to an expansion treatment, and the expansion treatment comprises quenching and high-temperature tempering.

Preferably, the expansion process is located after rough turning or after hobbing.

Preferably, the upscaling process includes the steps of:

s1: quenching;

s2: high-temperature tempering;

s3: detecting whether the common normal line and the addendum circle of the billet meet the size requirement or not, and if so, entering a subsequent processing procedure; if not, the process proceeds to step S1.

Preferably, the step temperature (650 ± 30) ° c and the quenching temperature during quenching in step S1 are T1, and T1 is (Ac3+30 to 50) ° c, where Ac3 is calculated based on the material of the slab.

Preferably, if the requirement for the amount of the billet to rise is large, T1 is a value close to an upper limit value; if the demand for the amount of increase in the billet is small, T1 is a value close to the lower limit value.

Preferably, the diameter of the steel billet is d, the holding time during quenching in the step S1 is t1, and if d is less than or equal to 250mm, t1 is d/100; if d > 250mm, t1 ═ 0.5 (d/100).

Preferably, the tempering temperature of the high-temperature tempering in the step S2 is T2, and T2 ═ 650 ± 30 ℃.

Preferably, the diameter of the billet is d, the holding time for the high-temperature tempering in the step S2 is t2, and t2 is 1+ (d/50).

Preferably, in the high temperature tempering in step S2, the billet is cooled by air cooling.

The invention also provides a carburizing steel gear which comprises an expansion part, wherein the expansion part is formed by any one carburizing steel expansion process.

The processing technology of the carburized steel gear comprises the following steps: forging blank, rough turning, hobbing, carburizing and quenching and machining. After rough turning or gear hobbing, when the problem that the size of a gear blank (billet) is smaller exists, the applicant creatively applies a mode of quenching and high-temperature tempering to expand the gear blank. The method is convenient to implement, and the applicant finds that the gear blank subjected to the expansion treatment can completely meet the machining size requirement of the gear.

Compared with the carburized billet, the non-carburized billet is not influenced by a high carbon area of the surface layer in the quenching process, so that the expansion amount is larger, and the size requirement is easily met. Therefore, the applicant has chosen to subject the gear blank to an expansion process prior to carburization. The billet is subjected to expansion treatment before carburization, so that the billet can meet the requirements of machining size in the later period, and the billet subjected to expansion treatment is beneficial to subsequent machining and cutting and dispersion distribution of a carburized and quenched metallographic structure.

Drawings

In order to more clearly illustrate the solution of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without inventive efforts.

Fig. 1 is a flowchart of the upscaling process according to an embodiment of the present invention.

Detailed Description

The invention discloses a carburizing steel expansion process, which can expand the size of a steel billet so that the steel billet meets the size requirement of later machining. The invention also discloses a carburizing steel gear.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

The processing technology of the carburized steel gear comprises the following steps: forging blank, rough turning, hobbing, carburizing, quenching and machining. After rough turning or gear hobbing, when the problem that the size of a gear blank (billet) is smaller exists, the applicant creatively applies a mode of quenching and high-temperature tempering to expand the gear blank. The method is convenient to implement, and the applicant finds that the gear blank subjected to the expansion treatment can completely meet the machining size requirement of the gear.

Then the following problem is whether the swelling treatment is performed before carburizing or after carburizing. In order to solve this problem, the applicant has made intensive studies and found the following:

if the billet after carburization is subjected to expansion treatment, the carburized steel (billet after carburization) generates two opposite stresses between the core and the case coat in the quenching cooling zone. The surface carburized layer has high-carbon austenite, and obvious thermal shrinkage can occur when the surface carburized layer is cooled from the quenching temperature of about 830 ℃ to the Ms (the starting temperature of martensite transformation) point temperature range. At this time, the core is transformed from low carbon austenite to ferrite, lower bainite, and martensite, and the core volume increases. Therefore, large internal stress is generated between the core and the surface-permeated layer. In this case, whether the surface-permeated layer compresses the core or the core stretches the surface-permeated layer depends mainly on the degree of plasticity of the phase-change product of the core. If the core is hardened to be low-carbon bainite or martensite, the surface carburized layer can generate tensile plastic deformation under the action of core expansion stress, so that the main stress direction of the carburized steel after being quenched is expanded.

If the core part can only obtain ferrite with good plasticity condition after quenching, the main stress direction of the carburized steel generates shrinkage deformation under the action of the compressive stress of the thermal shrinkage of the surface carburization layer. Even if the surface layer carburized layer is continuously cooled to below the Ms point temperature, the martensite transformation volume is increased, and only partial size shrinkage can be compensated.

Compared with the carburized billet, the non-carburized billet is not influenced by a high carbon area of the surface layer in the quenching process, so that the expansion amount is larger, and the size requirement is easily met. Therefore, the applicant has chosen to subject the gear blank to an expansion process prior to carburization. Table 1 shows a comparison of the magnitude of the increase in carburized and non-carburized steel billets of different outer diameters. As can be seen from table 1, the amount of expansion of the billet in the case of non-carburization is significantly larger than the amount of expansion of the billet in the case of carburization.

TABLE 1

Remarking: the billet referred to in the present invention is an external gear ring billet or a disk-shaped gear ring billet.

The expansion process may be performed after rough turning or after hobbing.

It should be noted that, the billet is subjected to the expansion treatment before carburization, so that the billet can meet the requirements of machining size in the later period, and the billet subjected to the expansion treatment is beneficial to the subsequent machining and cutting processing and the dispersion distribution of the carburized and quenched metallographic structure.

The specific steps of the swelling treatment comprise the following steps:

s1: and (6) quenching. The step temperature of the steel billet before quenching is 650 +/-30) DEG C, and the quenching temperature during quenching is T1 ═ Ac3+ 30-50℃, wherein Ac3 is calculated according to the material of the steel billet. The quenching includes heating, holding, and cooling, the quenching temperature T1 specifically refers to the holding temperature, and Ac3 is the transformation point of each steel material.

The upper limit of T1 is (Ac3+50) deg.C, and the lower limit of T1 is (Ac3+30) deg.C. If the demand for the increased amount of billet is large, T1 is a value close to the upper limit value. If the demand for the amount of increase in billet is small, T1 is a value close to the lower limit value.

The heat preservation time t1 during quenching is related to the effective diameter d of the steel billet, and if d is less than or equal to 250mm, t1 is d/100; if d > 250mm, t1 ═ 0.5 (d/100). The effective diameter D is 1.5 × (ψ D0- ψ D1)/2, where D0 is the outer diameter of the billet and D1 is the inner diameter of the billet.

S2: and (4) high-temperature tempering. The tempering temperature T2 of high-temperature tempering is 650 +/-30 ℃. The tempering temperature T2 here is the holding temperature during tempering, and the holding time T2 for high-temperature tempering is 1+ (d/50). In the high-temperature tempering, the billet is cooled by air cooling.

The invention also discloses a carburizing steel gear which comprises an expansion part, wherein the expansion part is formed by any one of the carburizing steel expansion processes. The carburizing steel expansion process has the above effects, and the carburizing steel gear formed by the carburizing steel expansion process also has the above effects, so the details are not repeated herein.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A carburizing steel expansion process is characterized by comprising the following steps: before carburizing, the billet is subjected to an expansion treatment, and the expansion treatment comprises quenching and high-temperature tempering.

2. The carburizing steel expansion process according to claim 1, wherein the expansion treatment is located after rough turning or after hobbing.

3. The carburizing steel expansion process according to claim 1, wherein the expansion treatment includes the steps of:

s1: quenching;

s2: high-temperature tempering;

4. The carburizing steel expansion process according to claim 3, wherein the step mean temperature at the quenching in the step S1 is (650 ± 30) ° C, and the quenching temperature T1 is (Ac3+ 30-50) ° C, wherein Ac3 is calculated according to the material of the steel slab.

5. The carburizing steel expansion process according to claim 4, wherein if the requirement for the expansion amount of the steel slab is large, T1 is a value close to an upper limit value; if the demand for the amount of increase in the billet is small, T1 is a value close to the lower limit value.

6. The carburizing steel expansion process according to claim 3, wherein the diameter of the steel billet is d, the holding time during quenching in the step S1 is t1, and if d is less than or equal to 250mm, t1 is d/100; if d > 250mm, t1 ═ 0.5 (d/100).

7. The carburizing steel expansion process according to claim 3, wherein the tempering temperature of the high-temperature tempering in the step S2 is T2, and T2 is (650 ± 30) DEG C.

8. The carburizing steel expansion process according to claim 3, wherein the diameter of the steel billet is d, the holding time of the high-temperature tempering in the step S2 is t2, and t2 is 1+ (d/50).

9. The carburizing steel expansion process according to claim 3, wherein the steel slab is cooled by air cooling in the high-temperature tempering in the step S2.

10. A carburized steel gear comprising an enlarged portion, characterized in that the enlarged portion is formed by a carburized steel enlarging process according to any one of claims 1 to 9.