Insufficient hardness and uneven hardness are critical issues in injection mold manufacturing hardness are critical issues in injection mold manufacturing
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Insufficient hardness and uneven hardness are critical issues in injection mold manufacturing123

Insufficient hardness and uneven hardness are critical issues in injection mold manufacturing.

Insufficient or uneven hardness after heat treatment can reduce the wear resistance and fatigue strength of the mold, leading to premature failure and significantly decreasing its lifespan.

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injection mold

Causes:

1) Large mold sections with poor steel hardenability, such as using low-hardenability steel for large molds.

2) Severe carbide segregation or coarse structure in the original steel organization, presence of graphite carbon and carbide segregation and aggregation.

3) Incorrect forging process of the mold, inadequate spheroidizing annealing after forging resulting in poor spheroidized steel structure.

4) Incomplete removal of decarburization layer on the mold surface during annealing or quenching heating.

5) Excessively high quenching temperature leading to excessive retained austenite after quenching; or excessively low quenching temperature with insufficient heating and holding time resulting in incomplete phase transformation of the mold steel.

6) Slow cooling rate after quenching heating, excessively high graded and isothermal temperatures or prolonged time, inappropriate quenching cooling medium selected.

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injection mold manufacturing

7) Inadequate water content in the alkali bath or excessive impurities in the quenching cooling medium, or aging of the quenching cooling medium.

8) Excessive temperature of the quenching cooling medium when the mold is removed after quenching cooling, inadequate cooling.

9) Insufficient tempering or excessively high tempering temperature, etc.

mold
injection mold manufacturing

Countermeasures:

1) Proper selection of mold steel, high-alloy mold steel with high hardenability should be used for large molds.

2) Strengthen material inspection to ensure compliance with standards. Proper forging of defective raw material steel and spheroidizing annealing treatment to obtain a good structure. Carbon tool steel should not be annealed multiple times to prevent graphitization.

3) Strictly follow forging and spheroidizing annealing process, ensuring a good pre-heat treatment structure.

4) Thoroughly remove rust spots and oxides on the mold surface before heat treatment, use vacuum heating quenching or protective atmosphere heating quenching as much as possible, good deoxidation treatment should be carried out during salt bath heating.

5) Develop correct mold quenching heating process parameters to ensure sufficient phase transformation, rapid cooling at a rate higher than the critical cooling rate to obtain a qualified metallographic structure.

6) Proper selection of quenching cooling medium and cooling method, strict control of graded and isothermal temperatures and time.

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injection mold manufacturing
Insufficient hardness and uneven hardness are critical issues in injection mold manufacturing.

7) Strictly control the alkali bath water content, regularly filter and replace long-term used quenching cooling mediums, keep them clean, and periodically check their quenching cooling characteristic curves.

8) For large-sized molds, appropriately extend the immersion time in the quenching cooling medium to prevent excessively high temperature when the mold is removed.

9) Timely and adequate tempering after quenching the mold, and prevent excessive tempering temperature.

10) Deep cryogenic treatment can be applied to molds with high hardness requirements (such as -110 to -196°C).

11) Implement surface strengthening treatment.

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injection mold manufacturing

The article is sourced from a Chinese injection mold manufacturer.

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