Common defects in heat treatment of spring steel and preventive and remedial measures

Defect situation

Preventive remedies

Insufficient hardness and low elasticity

1. Quenching temperature is too high, too much retained austenite

2. Decarburization of quenching heating surface

3. Tempering or aging temperature is too high or fluctuates greatly

1. Strictly implement the process and control the quenching temperature and holding time

2. The salt furnace should be deoxidized in time, or adopt protective atmosphere, vacuum heat treatment

3. Appropriately reduce the tempering temperature to improve the tempering or aging temperature control accuracy and control the furnace temperature uniformity


1. Produce temper brittleness

2. Overheating

1. Use rapid cooling to eliminate temper brittleness

2. Strictly control the quenching temperature and holding time

3. Overheating can be rescued by re-normalizing to achieve grain refinement


1. Excessive internal stress, deformation after tempering

2. Too much retained austenite

1. Use special fixtures for shaping and tempering

2. Use the method of extending the tempering time or multiple tempering for tempering treatment

3. Use ice-cold treatment or aging treatment to reduce retained austenite

Quenching cracking

1. Quenching heating temperature is too fast, no preheating or insufficient preheating

2. The cooling rate is too fast and the quenching cooling medium is improper

3. The heating temperature is too high and the holding time is too long

1. Fully preheating or heating in sections

2. Strictly implement the process, strictly control the heating temperature and protection time, and use qualified quenching media

Surface decarburization or element depletion

1. Raw materials are decarbonized or exceed standards

2. Insufficient deoxidation in the salt bath heated by quenching

3. The vacuum heat treatment is too high or too low, the leakage rate is too large; the protective atmosphere is not properly controlled

1. Strict re-inspection of raw materials

2. The salt bath furnace should be fully deoxidized in time

3. Choose appropriate vacuum heat treatment and protective atmosphere process parameters

Surface corrosion

1. Poor deoxidation of salt bath furnace, or nitrate

2. Failure to clean up residual salt in time

3. The surface of the part is not clean

1. The salt bath furnace should be fully deoxidized in time

2. Clean up the residual salt of the parts in time

3. The surface of the parts is cleaned before heat treatment, and dried in time after heat treatment and treated for rust prevention