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Causes and preventive measures of quenching crack in die

Categories: ZCMIM NewsStars: 3StarsVisit: -Release time: 2019-07-05 10:23:00
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Metal injection dieing products are inseparable from the die, and the quality of the die directly affects the quality of products. Therefore, before metal injection products are produced, dies must be made. Many problems often occur in the process of die making, for example, cracks will appear in die quenching, regarding the reasons and prevention measures are as follows: 

Causes:

1) serious net carbide segregation in die material.

2) mechanical process or cold plastic deformation stress.

3) improper operation of heat treatment (heating or cooling too fast, improper choice of quenching or cooling medium, too low cooling temperature, too long cooling time, etc.).

4) the die has complicated shape, uneven thickness, sharp Angle and threaded hole, etc., which leads to excessive thermal stress and tissue stress.

5) excessive quenching temperature lead to overheating or overburning.

6) delay in tempering after quenching or insufficient tempering time for insulation

7) When the mould is reheated, it is reheated without intermediate annealing. 

8) improper grinding for die heat treatment.

9) there are high tensile stress and micro cracks in the hardened layer during EDM after heat treatment.

Preventive measures:

1) strictly control the internal quality of die raw materials

2) improve forging and spheroidizing annealing process, eliminate network, band and chain carbides, and improve the uniformity of spheroidizing structure.

3) The die shall be subjected to stress relief annealing (>600℃) before heating and quenching after mechanical processing or cold plastic deformation.

4) for moulds with complex shapes, asbestos shall be used to plug the threaded holes, wrap up the dangerous sections and thin walls, and adopt graded quenching or isothermal quenching.

5) annealing or high temperature tempering shall be carried out when the die is repaired or renovated.

6) the die shall be preheated when quenching and precooled when cooling, and select  appropriate quenching medium.

7) quenching temperature and time should be strictly controlled to prevent overheating and overburning of dies.

8) the die should be tempered in time after quenching, and the insulation time should be sufficient. The high-alloy complex die should be tempered for 2-3 times.

9) select correct grinding process and appropriate grinding wheel.

10) Improve the die EDM process, and carry out stress reduction and tempering.


Keywords in the article: Metal injection dieing
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