Strictly control the intrinsic quality of structural foam mold raw materials

The cracks that occur after quenching in large injection molds are among the most critical defects in the heat treatment process. These cracks can lead to the complete failure of the mold, resulting in significant financial losses for manufacturers. Understanding the root causes of quench cracking is essential for improving the quality and longevity of injection molds. So, what leads to quench cracking in injection molds? Here are the main reasons: 1) The material used in the injection mold may contain severe network carbide segregation, which weakens the structure and makes it more prone to cracking during quenching. 2) Residual stresses from machining or cold deformation can accumulate within the mold, increasing the likelihood of cracks forming during heat treatment. 3) Improper heat treatment practices, such as rapid heating or cooling, incorrect selection of quenching media, or improper cooling temperature and duration, can all contribute to cracking. 4) Molds with complex shapes, uneven thicknesses, sharp corners, or threaded holes are more susceptible to thermal and structural stress, leading to potential cracks. 5) In foam injection molds, an excessively high quenching temperature can cause overheating, which weakens the material and increases the risk of cracking. 6) Insufficient tempering after quenching, or not allowing enough time for tempering, can leave the mold in a brittle state, making it more vulnerable to cracks. 7) Re-working and re-quenching without intermediate annealing can introduce additional stress into the mold, increasing the risk of cracking. 8) Heat treatment processes that are not compatible with subsequent grinding operations can also lead to internal stresses and cracks. 9) If EDM (Electrical Discharge Machining) is performed after heat treatment, the hardened layer may develop tensile stress and micro-cracks, which can propagate during quenching. To prevent these issues, several measures should be taken: 1) Ensure the raw materials used in structural foam molding meet strict quality standards. 2) Optimize forging and spheroidizing annealing processes to eliminate harmful carbide structures and improve material uniformity. 3) After mechanical processing or cold working, perform stress-relief annealing at temperatures above 600°C before proceeding with quenching. 4) For molds with complex geometries, use asbestos plugs in Screw holes and thin sections, and apply graded or isothermal quenching techniques to reduce stress. 5) When reworking or refurbishing molds, ensure proper annealing or high-temperature tempering is carried out first. 6) Preheat the mold before quenching and implement precooling measures to control the cooling rate. Choose the appropriate quenching medium based on the mold’s design. 7) Carefully control the quenching temperature and time to avoid overheating or over-hardening. 8) Immediately temper the mold after quenching, ensuring sufficient holding time. For high-alloy molds, tempering should be done 2–3 times. 9) Select the correct grinding process and suitable grinding wheels to minimize surface damage and residual stress. 10) Improve the EDM process by incorporating stress relief and tempering steps to prevent micro-cracks and residual stresses. By addressing these factors, manufacturers can significantly reduce the occurrence of quench cracking and improve the overall performance and lifespan of their injection molds.

Self Drilling Screw

Self Drilling Screw,Self Drilling Anchor Screws,Modified Truss Head Screws,Pan Head Tek Screws

Suzhou Guangxuan Fasteners Co.,Ltd. , https://www.beinuofastener.com