CN105586599A - Thermal treatment method for carburizing and quenching of gearbox gears - Google Patents

Abstract

The invention discloses a thermal treatment method for carburizing and quenching of gearbox gears. The thermal treatment method includes the steps of A, carburizing, B, quenching and C tempering. In the step of A, carburizing, the gears are placed in a heating furnace, the temperature of the heating furnace is increased from the room temperature to the temperature of 850-900 DEG C for carburizing, and carburizing time is 2-5 h; the carburizing process includes a beginning stage, a strong carburizing stage and a diffusion stage; the carbon potential (CP) of the beginning stage is 0.9-1 C%, the CP of the strong carburizing stage is 1-1.1 C%, and the CP of the diffusion stage is 0.8-0.9 C%; the time of the beginning stage is 12-15 min, the time of the strong carburizing stage is 200-220 min, and the time of the diffusion stage is 20-40 min. In the step of B, quenching, the carburized gears are cooled to 810-850 DEG C, then temperature equilibrium is carried out for 20-40 min, and then the gears are quenched in quenching oil with the temperature being 85-95 DEG C. In the step C, tempering, the quenched gears are subjected to tempering at the temperature of 155-170 DEG C for 1-2 h.

Description

A kind of heat treatment method of gearbox gear carburizing and quenching

Technical field

The present invention relates to a kind of heat treatment method of gearbox gear carburizing and quenching.

Background technology

Automobile gearbox gear is one of parts that technical requirement is the highest, gear is in operation process, between the intermeshing flank of tooth, existing rolling has again slip, gear is also subject to the effect of pulse stress and alternating bending stress simultaneously, therefore require the gear need be through Overheating Treatment to there is good hardness, wearability, anti-fatigue performance, high dimensional accuracy, the performance of the low noise in running.

Carburizing and quenching, carbo-nitriding are the topmost heat treatment methods of gearbox gear surface peening. In existing carburizing and quenching, carburizing temperature is generally 920-940 DEG C, and carburizing carbon potential CP is generally 1.0-1.2C%, and to obtaining high-quality carburizing top layer, but it has following deficiency: 1, carburizing temperature is high, and the time is long, and energy consumption is large; 2, distortion is large; 3, there is black tissue, cause lower hardness, reduce antifatigue, reduce wearability, reduction of service life.

Summary of the invention

The invention provides a kind of heat treatment method of gearbox gear carburizing and quenching, it has overcome a kind of existing deficiency of heat treatment method of gearbox gear carburizing and quenching in background technology.

The technical scheme adopting that the present invention solves its technical problem is:

A heat treatment method for gearbox gear carburizing and quenching, is characterized in that: comprise the steps:

A. carburization step, is placed in gear in heating furnace, and heating furnace is raised to 850-900 DEG C with carburizing from room temperature, carburizing time 2～5 hours, and in this carburization step, carburizing is divided into initial period, oozes stage and diffusion phase by force; The carbon potential CP of this initial period is 0.9-1C%; The carbon potential CP that oozes by force the stage is 1-1.1C%; The carbon potential 0.8-0.9C% of diffusion phase, the time of initial period is 12-15 minute, oozes by force the time 200-220 minute in stage, the time of diffusion phase is 20-40 minute.

B. the step of quenching, is cooled to 810-850 DEG C by the gear after carburizing, and then samming 20～40 minutes, then at 85-95 DEG C of quenching oil quenching;

C. tempering step, the gear after quenching carries out tempering in 1～2 hour in 155-170 DEG C.

Further, in this carburization step, in heating furnace, pass into methyl alcohol and propane.

The technical program is compared with background technology, its tool has the following advantages: ensureing under the prerequisite of quality of carburized layer, suitably reduce carburizing temperature and hardening heat, improve quenching oil temperature, suitably improve carburizing carbon potential, to produce following technique effect: a, to reduce carburizing temperature and hardening heat, do not extend carburizing time, reduce energy consumption; B, can prevent black tissue produce, obtain uniform carburized layer, improve the carburized layer microscopic structure after carburizing and quenching, obtain best microstructure, obviously to improve gear surface hardness, wearability and fatigue resistance; C, Reducing distortion, improve Gear Processing and fitted position precision, improves gear drive balance, reduces noise, improves service life of gear. Pass into methyl alcohol and propane and can adjust the carbon potential of optimizing in furnace atmosphere.

Detailed description of the invention

Below in conjunction with embodiment, the invention will be further described:

A heat treatment method for gearbox gear carburizing and quenching, comprising:

A. carburization step, packs gear into charging basket, then inserts in the multiplex heating furnace of sealed-box type, and heating furnace is raised to 850-900 DEG C with carburizing from room temperature, carburizing time 2-5 hour; Among the present embodiment, this heating furnace is raised to 900 DEG C from room temperature, carburizing time 2 hours 40 minutes. Pass into methyl alcohol and propane and start carburizing to heating furnace being warmed up to after 850-900 DEG C, this carburizing is divided into initial period, oozes stage and diffusion phase by force; Wherein: the carbon potential CP of the initial period of carburizing is 0.9-1C%, 12-15 minute; The carbon potential CP in the stage of oozing by force of carburizing is 1-1.1C%, 200-220 minute; The carbon potential CP of the diffusion phase of carburizing is 0.8-0.9C%, 20-40 minute; Among the present embodiment, the carbon potential CP of initial period is 0.96C%, 13 minutes; The carbon potential CP that oozes by force the stage is 1.05C%, 210 minutes; The carbon potential CP of diffusion phase is 0.85C%, 30 minutes;

B. the step of quenching, is cooled to 810-850 DEG C by the gear after carburizing, and then samming 20～40 minutes, then at 85-95 DEG C of quenching oil quenching; Among the present embodiment, the gear after carburizing is cooled to 830 DEG C, then samming 30 minutes, then at 85-95 DEG C of quenching oil quenching, and stirring at low speed;

C. tempering step, the gear after quenching carries out tempering in 1-2 hour in 165 DEG C.

For example, among the present embodiment: this gear material is mild steel, selects 20CrMnTi.

Among the present embodiment, the additional proportion of this methyl alcohol and propane: 10:3-4. The addition of this methyl alcohol is 60-76ml/min/ cubic meter 3(heated furnace volume for example). Adopt above-mentioned processing method can produce following technique effect: 1, the gear after heat treatment, effective case depth is 0.5-0.8mm, and case hardness is HRC59-63, and sclerosis rank is 1 grade; 2, prevent from, because interior oxidation produces black tissue, obtaining best microstructure; 3, distortion reduces 1/2, and precision improves 2-3 level, and carbide rank is 1 grade, reduces noise; 4, economize on electricity 5%.

More than describe preferred embodiment of the present invention in detail. Should be appreciated that those of ordinary skill in the art just can design according to the present invention make many modifications and variations without creative work. Therefore, all technical staff in the art, all should be in by the determined protection domain of claims under this invention's idea on the basis of existing technology by the available technical scheme of logical analysis, reasoning, or a limited experiment.

Claims (2)

1. a heat treatment method for gearbox gear carburizing and quenching, is characterized in that: comprising:

A. carburization step, is placed in gear in heating furnace, and heating furnace is raised to 850-900 DEG C with carburizing from room temperature, carburizing time 2～5 hours, and in this carburization step, carburizing is divided into initial period, oozes stage and diffusion phase by force; The carbon potential CP of this initial period is 0.9-1C%; The carbon potential CP that oozes by force the stage is 1-1.1C%; The carbon potential 0.8-0.9C% of diffusion phase, the time of initial period is 12-15 minute, oozes by force the time 200-220 minute in stage, the time of diffusion phase is 20-40 minute,

B. the step of quenching, is cooled to 810-850 DEG C by the gear after carburizing, and then samming 20～40 minutes, then at 85-95 DEG C of quenching oil quenching;

C. tempering step, the gear after quenching carries out tempering in 1～2 hour in 155-170 DEG C.

2. the heat treatment method of a kind of gearbox gear carburizing and quenching according to claim 1, is characterized in that: in steps A, in heating furnace, pass into methyl alcohol and propane.