CN103132086A - Novel carburizing-constant temperature-quenching process for heavy-duty gears - Google Patents

Abstract

The invention discloses a novel carburizing-constant temperature-quenching process for heavy-duty gears. The process comprises the steps of: (a) after carburizing treatment, cooling down to a temperature range (600-650 DEG C) below Ar1, and carrying out constant temperature for a period of time until the temperature of workpieces is equalized; (b) heating up to quenching temperature, and quenching after carrying out heat insulation for a period of time according to the requirements of the process; and (c) carrying out low-temperature tempering. According to the process, after the carburizing stage for the gears is completed, the gears are cooled down to some temperature below the Ar1 through furnace cooling, and the constant-temperature retention is carried out, so that the first-time phase conversion is realized; the gears are directly heated up to the quenching temperature after the temperature of the gears is equalized at the temperature, so that the second-time phase conversion is realized; and the quenching treatment is carried out, so that the third-time phase conversion is realized. Proved by production practices, the process disclosed by the invention has the advantages that the energy source consumption is remarkably reduced, the oxidation and decarburization of the gears are reduced, the distortion amount is reduced, the heat treatment process flow is shortened, and the efficiency of labor productivity is increased.

Description

A kind of Carburizing in Heavy-duty Gears-isothermal-Fresh Quenching Process

Technical field

The present invention relates to a kind of metal heating processing technology, relate in particular to a kind of gear thermal treatment process.

Background technology

Gear is a kind of mechanical transmission part of widespread use, plays the vital role of transferring power, change rotating speed and sense of rotation at the mechanized equipment middle gear.Generally the type of belt drive by gear is divided three classes it: cylindrical gear is used for the transmission between parallel diaxon; Cone gear is used for intersecting the transmission between diaxon; Worm gear and worm screw are used for intersecting the transmission between diaxon.Compare the advantage such as that geartransmission has is simple in structure, transmitting ratio is relatively fixing, transmitting ratio is accurate, transfer charge is large with the chain drive of transmitting motion with transmission, by chain and sprocket engagement that relies on the frictional force transferring power.

The method manufacturing that hardened face gear mainly hardens with the low-carbon alloy structural steel carburizing also can select medium carbon structural alloy steel to carry out hard surfacing (induction quenching, flame quenching, laser quenching etc.) or nitriding treatment after modifier treatment.For there being high-strong toughness can require, operate in the heavy-duty gear of vibration environment, mainly adopt the method for carburizing-harden.The carburizing of heavy-duty gear-quenching is that a specification of quality is high, the tired lock of technical process, the technique that tooling is strict, energy consumption is high.

At present, cooling and processing method that harden after gear wheel carburization has several, wherein conclude the most comprehensively with " thermo-chemical treatment of steel " (Liaoning science tech publishing house in March, 2009 publish) of Tang Dianfu, fourth of the twelve Earthly Branches Shi Gang chief editor, 20 kinds of the processing methodes (containing induction quenching) of listing altogether cooling after carburizing and hardening.

One, the heat-treatment technology method after existing various carburizing

1, the method for cooling of (before quenching) after eight kinds of carburizings

1.1 direct quenching after carburizing.Be applicable to the inherent fine grain steel of the types such as 20CrMnTi, after carburizing, be chilled in advance quenching temperature direct quenching;

The air cooling 1.2 directly come out of the stove after carburizing;

1.3 enter after carburizing and slowly cool to room temperature in burial pit;

1.4 cooling in logical water-cooled cooling shaft after carburizing, cooling rate is faster than the 1.3rd method;

1.5 after carburizing in cementing furnace with the stove Slow cooling;

1.6 after carburizing, workpiece is cooled to 660 ℃ of isothermal holdings with stove in cementing furnace, then is cooled to 260 ℃ of air coolings of coming out of the stove with stove;

1.7 be applicable to the steel solid carburizing such as 20Cr2Ni4, after carburizing, workpiece is cooling with tank, at 500 ℃ of left and right can opening air coolings, needs timely tempering, prevents the workpiece surface cracking;

1.8 be applicable to salt bath carburizing, be cooled to 700 ℃ of left and right with salt bath after workpiece carbonization, then the air cooling of coming out of the stove.

2, the heat treating method after 12 kinds of carburizings commonly used, see the following form 1.

Table 1:

。

Carburizing in Heavy-duty Gears is because infiltration layer is darker, and carburizing time is longer, and effective hardened layer and core structure and aberration control after carburizing are had strict demand.The normal adopting process of heavy-duty gear is at present: the carburizing-cooling-air cooling of coming out of the stove (realizing changing mutually for the first time)-high tempering makes carbide spheroidization and crystal grain thinning.And then cold charge stove intensification again (realizing changing mutually for the second time)-quench (realizing for the third time transformation mutually).It is long that this technique exists process, and energy consumption is high, gear surface oxidation, decarburization, the deficiency such as amount of distortion is large, the hot operational difficulty of coming out of the stove of heavy-duty gear, and labour intensity is large, productivity is low.

Summary of the invention

Technical problem to be solved by this invention is that a kind of more reasonably Carburizing in Heavy-duty Gears-isothermal-Fresh Quenching Process will be provided, under the prerequisite of guaranteeing product carburizing and quenching quality, the efficient of reduce energy consumption, shortening heat processing technological flow, raising labour productivity.

For solving the problems of the technologies described above, technical scheme of the present invention is as follows:

A kind of Carburizing in Heavy-duty Gears-isothermal-Fresh Quenching Process, its processing step comprises:

After a, carburizing treatment, be cooled to the following warm area of Ar1 (600-650 ℃), isothermal for some time is treated the workpiece samming;

B then be warming up to quenching temperature quenches after insulation for some time by processing requirement;

C, low-temperaturetempering.

Wherein, when Ar1 was cooling after the steel influence of high austenizing temp, austenite decomposition was the temperature of ferrite and pearlite.

After the present invention completed in the gear wheel carburization stage, be cooled to a certain temperature below Ar1 with stove and make isothermal holding (realizing changing mutually for the first time), treat gear at this temperature samming, directly be warming up to quenching temperature (realizing changing mutually for the second time), carry out quench treatment (realizing changing mutually for the third time).Production practice prove, this processing method under the prerequisite of guaranteeing product carburizing and quenching quality, significantly reduces energy consumption, reduces the gear oxidation and decarbonization, reduces amount of distortion, shortening heat processing technological flow, the efficient of raising labour productivity.

The characteristics of this processing method:

1, after carburizing, workpiece is not come out of the stove, and has avoided the workpiece oxidation, decarburization and the distortion degree that cause because coming out of the stove.

2, be cooled to the following a certain warm area isothermal (as 600～650 ℃) of Ar1 after carburizing, make high temperature austenite change perlite+ferrite+a small amount of carbide into, completed once transformation mutually, adjustment is grown up because of crystal grain in long-time high temperature carburizing process, prepares for quenching performs tissue.

3, " accumulation of heat " of work piece isothermal state make and be warming up to subsequently quenching temperature and faster carried out, significantly reduced unnecessary energy consumption.

4, the thermal treatment process operation is greatly simplified, and has reduced turnover heat number, has reduced the labour intensity of high temperature turnover stove, has improved the utilization ratio of large-scale cementing furnace.

5, reduced the loss of the special-purpose large-scale high temperature steel suspender of carburizing, and the consumption of thermal treatment auxiliary material (oil product, penetration enhancer, neutral gas etc.).

6, reduce turnover heat number, avoided the frequent high-low temperature cycle index of burner hearth, be conducive to extend the work-ing life of burner hearth electric heating element and refractory materials.

This technique is applicable to the carburizing and quenching of various periodic cementing furnaces, need not to increase any auxiliary equipment, only needs the adjusting process method, can in conjunction with product separately, implement carburizing → isothermal → Fresh Quenching Process.

Processing method of the present invention is based on traditional carburizing quenching process basis, heat-treatment technology method after carburizing has been done a kind of combination of innovation, in heavy-duty gear Deep Carburization Process-quenching, stood the check of technique circulation ratio, quality stability, product reliability.Heat-treatment technology method of the present invention all can adopt in existing various periodic cementing furnaces, can receive the effect of getting instant result.

Description of drawings

Fig. 1-12 are the process curve schematic diagram of the heat treating method after 12 kinds of carburizings commonly using;

Figure 13 is the process curve schematic diagram of Carburizing in Heavy-duty Gears-isothermal of the present invention-Fresh Quenching Process.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described.

Figure 13 shows a kind of Carburizing in Heavy-duty Gears-isothermal-Fresh Quenching Process, and its processing step comprises:

After a, carburizing treatment, be cooled to the following warm area 600-650 of Ar1 ℃, isothermal for some time (about 2 hours) is treated the workpiece samming;

B then be warming up to quenching temperature quenched after insulation for some time;

C, low-temperaturetempering;

Wherein, when Ar1 was cooling after the steel influence of high austenizing temp, austenite decomposition was the temperature of ferrite and pearlite.

Following examples are take the 17Cr2Ni2Mo steel as example,

Embodiment 1:930 ℃ carburizing (10h)-be chilled to 600 ℃ of tempering (2h)-820 ℃ cold-200 ℃ of tempering of (2h) oil quenching (4h)-air cooling with stove.

Embodiment 2:930 ℃ carburizing (10h)-be chilled to 630 ℃ of tempering (2h)-820 ℃ cold-200 ℃ of tempering of (2h) oil quenching (4h)-air cooling with stove.

Embodiment 3:930 ℃ carburizing (10h)-be chilled to 650 ℃ of tempering (2h)-820 ℃ cold-200 ℃ of tempering of (2h) oil quenching (4h)-air cooling with stove.

Along with the difference of workpiece material, shape, quenching and the tempering process parameters of the temperature and time of carburizing-cooling isothermal-routine can be done accommodation.

We be A, B contrast technique and embodiment 1 do after thermal treatment Performance Ratio:

Technique A:930 ℃ of carburizing (10h)-in advance is chilled to cold-200 ℃ of tempering of 870 ℃-oil quenching (4h)-air cooling.

Technique B:930 ℃ of carburizing (10h)-in advance is chilled to the 870 ℃-air cooling of coming out of the stove-650 ℃ tempering (2h)-820 ℃ cold-200 ℃ of tempering of (2h) oil quenching (4h)-air cooling.

Embodiment 1:930 ℃ carburizing (10h)-be chilled to 600 ℃ of tempering (2h)-820 ℃ cold-200 ℃ of tempering of (2h) oil quenching (4h)-air cooling with stove.

Performance comparison such as the following table of contrast technique and embodiment 1:

。

As seen embodiment 1 compares than A, two kinds of the most frequently used techniques of B, all meet under the prerequisite of lattice technical requirements in elongation after fracture (A5), hardness (HB), yield strength (Rp0.2), tensile strength (Rm), the shrinking percentage of having no progeny (Z) all have raising in various degree.Metallographic structure meets the relevant criterion requirement.

Simultaneously " accumulation of heat " of technique Isothermal Condition of the present invention make and be warming up to subsequently quenching temperature and faster carried out, significantly reduced unnecessary energy consumption.Take the Available Hardened Depth 3mm as example, embodiment 1 technique contrasts technique A, B technique and saves respectively about 4h of quenching heating-up time after carburizing; More save about 10h of high tempering time than B technique.

The above; be only the specific embodiment of the present invention, but protection scope of the present invention is not limited to this, anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; can expect easily changing or replacing, within all should being encompassed in protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion by described protection domain with claim.

Claims (1)

1. Carburizing in Heavy-duty Gears-isothermal-Fresh Quenching Process is characterized in that processing step comprises:

After a, carburizing treatment, be cooled to the following warm area of Ar1 (600-650 ℃), isothermal for some time is treated the workpiece samming;

B then be warming up to quenching temperature quenches after insulation for some time by processing requirement;

C, low-temperaturetempering;

Wherein, when Ar1 was cooling after the steel influence of high austenizing temp, austenite decomposition was the temperature of ferrite and pearlite.

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