CN111910050A - Heat treatment method for reducing gear tooth direction angle variation - Google Patents
Heat treatment method for reducing gear tooth direction angle variation Download PDFInfo
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- CN111910050A CN111910050A CN201910383099.0A CN201910383099A CN111910050A CN 111910050 A CN111910050 A CN 111910050A CN 201910383099 A CN201910383099 A CN 201910383099A CN 111910050 A CN111910050 A CN 111910050A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
- C23C8/22—Carburising of ferrous surfaces
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
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- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Heat Treatment Of Articles (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
Abstract
A heat treatment method for reducing the tooth direction angle variation of a gear is characterized in that a lining ring matched with a gear weight reduction groove is arranged outside an easily deformable area of the gear, the heat treatment is realized by carburizing and quenching after preheating, and the quenching process is that the heat treatment is realized by standing in an oil bath after carburizing and then stirring. The invention optimizes the heat treatment process from preheating, carburizing, quenching parameters and the like, and improves the qualification rate of the gear tooth direction angle error on the premise of ensuring that the metallographic index of the heat treatment is basically unchanged.
Description
Technical Field
The invention relates to a technology in the field of heat treatment of automobile gearbox gears, in particular to a heat treatment method for reducing gear tooth direction angle variation.
Background
In the production process of the automobile gearbox gear, heat treatment is a very important link. The gear can obtain good wear resistance and fatigue resistance after carburizing and quenching, but heat treatment deformation is also avoided, which directly influences the transmission efficiency, NVH, service life and the like of the gear. In the prior art, the gear is generally heated to a high temperature of more than 900 ℃ for carburizing, which causes large distortion in the gear heat treatment process, so a finishing process is usually required to be arranged after the heat treatment for correcting, but the precision grade and the mechanical property of the gear can be influenced. Among various gear precision indexes, the tooth direction angle error is extremely sensitive to heat treatment, and if the heat treatment process is improperly controlled, the reject ratio of the tooth direction angle error of the heat-treated gear can reach more than 50%.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a heat treatment method for reducing the tooth direction angle variation of the gear, optimizes the heat treatment process by starting from preheating, carburizing, quenching parameters and the like, and improves the qualification rate of the tooth direction angle error of the gear on the premise of ensuring that the metallographic index of the heat treatment is basically unchanged.
The invention is realized by the following technical scheme:
the invention realizes heat treatment by arranging a lining ring matched with a gear weight reduction groove outside the easy-deformation area of the gear, and performing carburization and quenching after preheating.
The easily deformable area refers to: a weight-reducing slot region.
The shape of the lining ring is matched with the annular lightening groove of the gear, and a gap is arranged on the side edge of the lining ring.
The clearance between the lining ring and the single side of the gear weight-reducing groove is 0.6-1.0 mm.
The preheating temperature is 400-450 ℃.
Preferably, the carburizing is carried out by adopting a controlled atmosphere box type multipurpose furnace and adopting a nitrogen-methanol atmosphere and propane as enriching gases.
The carburizing temperature is preferably 830-850 ℃.
Preferably, the quenching is performed by carburizing, then standing and then stirring; further preferably, the mixture is left standing in the oil pool for 10-20s without stirring and then stirred at 900rpm for 580-600 s.
The quenching process is preferably controlled by the quenching oil temperature and the rotating speed of the oil pool stirring motor, wherein the quenching oil temperature is 130-.
Technical effects
Compared with the prior art, the invention improves the traditional three-stage (high-temperature carburization, high-temperature diffusion and low-temperature quenching) heat treatment carburization mode, adopts single-stage low-temperature heat treatment, avoids thermal deformation caused by high-temperature carburization, controls the quenching oil temperature and the rotating speed of a stirring motor to reduce quenching deformation, is assisted by an additional lining ring, well controls the tooth direction angle variation of the gear under the premise of ensuring that the metallographic index of the heat treatment is basically unchanged, does not need to reserve reverse deformation amount before the heat treatment and finish machining correction after the heat treatment, and reduces the rejection rate of the gear.
Drawings
FIG. 1 is a heat-treated gear and its backing ring of example 1;
FIG. 2 is a view showing a gear and its backing ring heat-treated according to example 2;
FIG. 3 is heat-treated gear of embodiment 3;
in the figure: a is a heat-treated gear, and B is a liner ring.
Detailed Description
Example 1
As shown in fig. 1A, the heat-treated gear selected in this embodiment has the following basic dimensions: the outer diameter phi is 107.8mm, the bore diameter phi is 46.8mm, the depth of the weight-reducing groove is 11mm, the width is 15mm, and the wall thickness of the gear at the weight-reducing groove is 6 mm. The heat treatment deformation of the gear is easily caused by the wall thickness change of the weight reduction groove area, and the gear precision is influenced. The gear material is 20MnCr5, the weight is 1.1kg, and the depth requirement of a carburized layer is as follows: 550HV1:0.50-0.70mm, the metallurgical structure of the carburized layer is 1-4 grade carbide and 1-5 grade retained austenite, the tooth surface is not finished after heat treatment, and the tooth direction angle error is required to be within 11 mu m.
When the gear is mounted, the lining ring shown in the figure 1B is placed on the material rack, then the gear shown in the figure 1A is placed on the lining ring, so that the weight reduction groove area of the gear is matched with the lining ring, the stability is ensured by utilizing the self weight of the gear, and the heat deformation of the weight reduction groove area during heat treatment is reduced. The unilateral clearance between the lining ring and the weight-reducing groove is 1.0 mm.
The gear needs to be preheated before heat treatment, the preheating temperature is 420 ℃, and the time is more than 30 minutes.
After preheating, carburizing and quenching the gear, selecting 4 groups of parameters shown in the following table for full-furnace heat treatment, setting the quenching oil temperature at 130 ℃, and controlling the quenching of the gear by changing the rotating speed and the stirring time of a stirring motor of an oil pool.
| Scheme number | Carburizing temperature/. degree.C | Quenching stirring speed and time |
| 1 | 840 | 600s 900rpm stirring |
| 2 | 840 | 10s no stirring +590s 800rpm stirring |
| 3 | 850 | 10s no stirring +590s 800rpm stirring |
| 4 | 850 | 20s no stirring +580s 800rpm stirring |
The diameter of the weight-reducing groove and the tooth-direction angle error of different schemes are measured after heat treatment, and the results are shown in the following table:
compared with the measurement result before implementation of the invention, the gear tooth direction angle variation qualification rate of the gear teeth of different heat treatment schemes is greatly improved, the rejection rate of the gear is reduced, and the problem of heat treatment deformation of the heat treatment gear caused by the wall thickness variation of the weight reduction groove area is improved. Compared with the results of 4 groups of heat treatment schemes, the increase of the carburizing temperature and the increase of the quenching stirring speed both can cause the reduction of the gear tooth direction angle error qualification rate, and the scheme 2 result is optimal according to the heat treatment result.
The full-scale heat treatment was carried out without adding an auxiliary liner ring according to the heat treatment parameters of the scheme 2, which is denoted as scheme 5, and the results are shown in the following table. The qualification rate of the tooth direction angle error is also improved only by adjusting the heat treatment process, but because the wall thickness of the gear at the lightening groove is smaller than the depth of the groove, if no lining ring is used for supporting and compensating, deformation is easy to generate during heat treatment, and the precision of the gear is influenced.
Example 2
Fig. 2A shows a heat-treated gear selected according to the present embodiment, the basic dimensions of the gear are: the outer diameter phi is 141.6mm, the aperture phi is 49.8mm, the depth of the weight-reducing groove is 6mm, the width is 25mm, and the wall thickness of the weight-reducing groove is 10 mm. The gear is overall flatter and has relatively less wall thickness variation. The gear material is 20MnCr5, the weight is 1.5kg, and the depth requirement of a carburized layer is as follows: 550HV1:0.50-0.70mm, the metallurgical structure of the carburized layer is 1-4 grade carbide and 1-5 grade retained austenite, the tooth surface is not finished after heat treatment, and the tooth direction angle error is required to be within 12 mu m.
When the gear is mounted, the lining ring shown in fig. 2B is placed on the material rack, then the gear shown in fig. 2A is placed on the lining ring, the weight reduction groove area of the gear is matched with the lining ring, and the stability is ensured by using the self weight of the gear, so that the thermal deformation of the weight reduction groove area during thermal treatment is reduced. The unilateral clearance between the lining ring and the weight-reducing groove is 0.8 mm.
The gear needs to be preheated before heat treatment, the preheating temperature is 450 ℃, and the time is more than 30 minutes.
After preheating, carburizing and quenching the gear, selecting 4 groups of parameters shown in the following table for full-furnace heat treatment, setting the quenching oil temperature at 140 ℃, and controlling the quenching of the gear by changing the rotating speed and the stirring time of a stirring motor of an oil pool.
The diameter of the weight-reducing groove and the tooth-direction angle error of different schemes are measured after heat treatment, and the results are shown in the following table:
compared with the measurement result before implementation of the invention, the gear tooth direction angle variation qualification rate of the gear teeth of different heat treatment schemes is greatly improved, the rejection rate of the gear is reduced, and the problem of heat treatment deformation of the heat treatment gear caused by the wall thickness variation of the weight reduction groove area is improved. Compared with the results of 4 heat treatment schemes, the results of the schemes 1 to 3 are relatively similar, and compared with the schemes 1 and 2, the scheme 3 increases the non-stirring time during quenching, relatively slows down the cooling speed during quenching and is beneficial to reducing the quenching stress.
The full-furnace heat treatment was carried out without additional auxiliary liner ring according to the heat treatment parameters of scheme 3, as scheme 5, and the results are shown in the following table. Only the heat treatment process is improved, the difference between the qualification rate of the tooth direction angle error and the result of using the additional lining ring is not large, the wall thickness of the heat treatment gear weight-reducing groove is larger than the depth of the weight-reducing groove, and the influence on the gear precision is small during the heat treatment.
Example 3
As shown in fig. 3, the heat-treated gear selected for the present embodiment has the following basic dimensions: the outer diameter phi is 82.8mm, and the aperture phi is 49.8 mm. The gear structure is simpler, does not have the obvious part of wall thickness change, and the gear material is 20MnCr5, and weight 0.64kg, and the carburized layer degree of depth requirement is: 550HV1:0.50-0.70mm, the metallurgical structure of the carburized layer is 1-4 grade carbide and 1-5 grade retained austenite, the tooth surface is not finished after heat treatment, and the tooth direction angle error is required to be within 11 mu m.
The gear needs to be preheated before heat treatment, the preheating temperature is 420 ℃, and the time is more than 30 minutes.
After preheating, carburizing and quenching the gear, selecting 4 groups of parameters shown in the following table for full-furnace heat treatment, setting the quenching oil temperature at 130 ℃, and controlling the quenching of the gear by changing the rotating speed and the stirring time of a stirring motor of an oil pool.
The tooth orientation angle errors for the different protocols were measured after heat treatment and the results are shown in the following table:
compared with the measurement result before the implementation of the invention, the qualification rate of the gear tooth direction angle variation of the gear teeth of different heat treatment schemes is improved, the rejection rate of the gear is reduced, and the problem of thermal deformation of the gear with simple structure and uniform wall thickness can be improved by adjusting the heat treatment process. Comparing the results of the 4 heat treatment schemes, we prefer scheme 3 to be an optimized process for this gear.
The heat treatment deformation is mainly from the thermal stress and the structural stress of the gear, and for the carburized gear steel, the thermal deformation is mainly caused by the thermal stress generated by the high-temperature heating of the gear. The gear is preheated to 400-450 ℃ and then transferred to a main furnace for carburizing, so that the gear is favorably and slowly heated to the carburizing temperature, the preheating effect cannot be achieved if the preheating temperature is too low, and the surface of the gear is seriously oxidized if the preheating temperature is too high. The traditional carburizing and quenching mode is that the gear is heated to about 900 ℃ for carburizing and diffusing, then the temperature is reduced to the quenching temperature for heat preservation and then quenching is carried out, the invention adopts the constant temperature carburizing and quenching mode, thereby greatly avoiding the influence of the thermal stress of carburizing and diffusing at high temperature on the gear deformation, and the time for heating to the carburizing temperature and reducing the temperature to the quenching temperature in the heat treatment process is saved, so the whole heat treatment production time is not prolonged although the carburizing efficiency at low temperature is reduced. On the premise of ensuring that the metallographic index is qualified, the quenching oil temperature and the stirring speed of the oil pool are adjusted, the quenching oil temperature is increased within a reasonable range, and the low stirring speed is adopted, so that the thermal deformation problem of the gear is also favorably improved. In addition, for some gears which are easy to deform due to structural reasons, the gears can be prevented from deforming in the heat treatment process through an additional limiting tool, on one hand, the gears can support the easily-deformable area, on the other hand, the gear structure is compensated after the external limiting tool is machined, the sudden change of the size of the gear structure can be reduced, and the problem that the gears deform due to the fact that the gear structure changes and causes different local cooling speeds during quenching is solved. By the embodiment, the qualified rate of the gear tooth direction angle variation amount is greatly improved after the heat treatment process parameters are optimized, and a corresponding additional compensation tool is used for assisting the gear with an easily deformed structure, so that the problem of gear deformation is solved, and the product scrap is reduced.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (7)
1. A heat treatment method for reducing gear tooth direction angle variation is characterized in that a lining ring matched with a gear weight reduction groove is arranged outside an easily deformable area of a gear, and heat treatment is realized by carburizing and quenching after preheating;
the easily deformable area refers to: a weight-reduction slot region;
the shape of the lining ring is matched with the annular weight-reducing groove of the gear, and a gap is arranged on the side edge of the lining ring;
the quenching is to place in an oil pool after carburization and then stir.
2. The method as claimed in claim 1, wherein the one-side clearance between the liner ring and the gear weight-reduction groove is 0.6-1.0 mm.
3. The method as set forth in claim 1, wherein said preheating is at a temperature of 400-450 ℃.
4. The method as claimed in claim 1, wherein the carburizing is carried out in a controlled atmosphere box type multi-purpose furnace using a nitrogen methanol atmosphere and propane as the enriching gas.
5. The method as claimed in claim 1, wherein the carburizing temperature is 830-850 ℃.
6. The method as claimed in claim 1, wherein the quenching is controlled by the quenching oil temperature and the rotation speed of the oil pool stirring motor, wherein the quenching oil temperature is 130-150 ℃, the quenching oil cooling capacity is greater than 70 ℃/s, and the rotation speed of the oil pool stirring motor is 600-900 rpm.
7. The method as claimed in claim 1 or 6, wherein the quenching step is carried out by standing in an oil bath for 10-20s without stirring and then stirring at 900rpm for 580-600 s.
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| CN201910383099.0A CN111910050A (en) | 2019-05-09 | 2019-05-09 | Heat treatment method for reducing gear tooth direction angle variation |
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| CN108486352A (en) * | 2018-07-03 | 2018-09-04 | 平湖市永成齿轮配件厂 | A kind of holder for gear quenching |
| CN109097539A (en) * | 2018-10-17 | 2018-12-28 | 江麓机电集团有限公司 | A kind of thin arc plate spline gear press quenching tooling of carburizing and processing method |
| CN208328118U (en) * | 2018-05-21 | 2019-01-04 | 上海汽车变速器有限公司 | Polymorphic structure gear carburizing and quenching tooling |
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2019
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| CN201873758U (en) * | 2010-11-29 | 2011-06-22 | 大连创新齿轮箱制造有限公司 | Thermal treating and carburizing tooling for furnace charging |
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