Heat treatment process of the spring

The main characteristics of spring steel spring under dynamic load, namely in the impact,vibration conditions, or under the action of alternating stress at

For, using elastic deformation to absorb impact energy, play a buffer role.

Because the spring are often subjected to vibration and stress under the action of longenjoy the work, is the main fatigue failure, therefore, must have high spring steel

High elastic limit and fatigue limit. In addition, also should have enough toughness andplasticity, in order to prevent the sudden brittle fracture under impact loading.

In the process of spring steel, has good hardenability decarburization sensitivity and lowheat. To reduce the surface roughness of the spring

Can increase the fatigue life.

In order to obtain the required performance, carbon spring steel must be high. The carbon content in the carbon spring steel 0.6-0.9%

, due to carbon spring steel hardenability is poor, it is used only for spring manufacturingsection size does not exceed 10-15mm. For the section size is

In the spring, must use the alloy spring steel. Carbon spring steel alloy is between 0.45-0.75%, the alloy elements Mn

Si, W, V, Mo, etc.. Their main purpose is to improve the hardenability and tempering stability, strengthening of ferrite and grain refinement, effectively.

To improve the mechanical properties of spring steel, Cr, W, Mo can improve the high temperature strength of steel.

Spring forming in the hot state (the diameter or thickness is more than 10mm)

Spring forming in cold condition (diameter or thickness below 10mm)

- heat treatment process for the hot spring forming in this way is the most hot spring forming molding and heat treatment together

The spiral spring, and most are heat treated in hot forming. Heat treatment is the spring steel quenching + middle temperature back

The fire, after heat treatment, the microstructure is tempered troostite. The elastic limit of this organization and the yield limit is high, and has a certain toughness.

Cold forming spring heat treatment process for cold rolled steel strip for spring, or cold drawn steel wire made of, because the cold plastic deformation

The material hardening, has reached the required performance of spring. The spring forming only about 250C in the range of about 30min, thermal insulation

Stress, in order to eliminate the stress of cold forming spring door, and the spring type.

Valve spring of engine heat treatment - resistant steel springs are working at high temperature, there are still some corrosive atmosphere, so

Must use special spring steel and suitable heat treatment specification.

The common defects of spring when quenching and prevention measures:

(1) the decarburization (decrease) of --1, using the salt bath furnace or control atmosphere furnace heating. 2, the rapid heating process.

(2) after quenching hardness is insufficient, a large number of non martensite, ferrite coreappears (all residual deformation, reduce the service life of --1)

Selection of materials, good hardenability. 2, improve the quenching cooling capacity of the coolant. 3, spring into the coolant temperature should be controlled at

More than Ar3. 4, improve the quenching temperature.

(3), --1 (hot brittleness increases) to strictly control the temperature of forming andquenching. 2, strengthen the metallographic examination of the quenching.

(4) cracking (fragility, severely reducing the service life of --1), the control of quenching temperature. 2, cold quenching to 250-300C

When removed, air cooling. 3, timely tempering

Improve the spring quality measures:

(1) deformation and heat treatment, steel deformation strengthening combined with heat treatment, in order to further improve the strength and toughness of steel

. Thermomechanical treatment, low temperature, high in the. High temperaturethermomechanical treatment is immediate quenching deformation in the austenite stabilityis far under the

Fire, can also be combined with a forged or rolled, hot forming immediately afterquenching. Deformation heat treatment has been used in the production of automobile leaf spring.

(60Si2Mn)

(2) the isothermal quenching spring for small diameter or through enough spring usingisothermal quenching, it can not only reduce the

The shape, but also can improve the strength and toughness, preferably in a temperingafter isothermal quenching treatment, can improve the elastic limit, the tempering temperature and isothermal quenching

Fire temperature.

(3) spring relaxation spring long time working under the action of external force, due to the stress relaxation can result in the permanent trace

(plastic) deformation, especially spring high temperature, under high temperature stress relaxation phenomenon is more serious, which reduces the accuracy of the spring,

General precision springs is not allowed. Therefore, this kind of spring in the quenching,tempering should be carried out after the relaxation of the spring pre load,

The deformation amount exceeds the spring when possible. And then heated at higher temperature under the condition of 20C, thermal insulation 8-

24h.

(4) low temperature nitrocarburizing by tempering and cryogenic carbonitriding (soft nitriding process) combination, can significantly improve the spring fatigue

Life and corrosion resistance, the process used for coil spring.

(5) the shot peening, scratches, folding, surface defects such as decarburization oftenconcentrated stress at work place and a spring

Fatigue fracture source. If the shot speed of spraying surface fine spring, spring not onlyimprove surface quality, improve the surface hardness, and make the table

Face in a compressive stress state, so as to improve the strength and fatigue life of spring.