Preventing Natural Aging Cracks in Deep-Drawing Mold Products

Deep-drawing products often experience longitudinal cracking when they are left unused after undergoing intense forming operations. This phenomenon is mainly caused by residual stress remaining in the material after deformation. For certain metals, the risk varies significantly depending on alloy composition and environmental conditions.

For example, austenitic stainless steel sheets with high nickel content—such as SUS304 and above—typically do not develop natural aging cracks even after severe deep-drawing operations. In contrast, brass and other copper alloys are prone to cracking when stored after heavy forming. Their cracking behavior is closely related to residual internal stress and specific surrounding atmospheres.

Technical Solution: Reduce Residual Stress to Prevent Cracking

Based on extensive testing and process verification, our engineering team has identified that the primary method to prevent natural aging cracks is to minimize residual stress as much as possible. Performing annealing immediately after forming is highly effective in eliminating internal stress and preventing delayed cracking.

To further reduce residual stress during deep-drawing operations, the following technical measures are recommended:

1. Minimize the die fillet radius of the drawing mold.

A properly reduced radius helps control material flow and lowers stress concentration.

2. Retain the flange area when increasing drawing depth through multiple drawing stages.

This allows stress to distribute more evenly during step-by-step deep drawing.

3. Avoid improper or unreasonable process design.

Optimizing the drawing sequence, blank holder force, and lubrication reduces deformation resistance and stress buildup.

4. Regularly polish the blank-holder ring.

Maintaining a smooth surface enhances blank-holding force and prevents wrinkling, which reduces uneven stress development.

Conclusion

The above methods provide a comprehensive solution to prevent natural aging cracks in deep-drawn products. By controlling residual stress through proper mold design, forming process optimization, and immediate post-forming annealing, manufacturers can greatly improve product reliability and durability.

About Qingdao Ronghai Mould Co., Ltd.

Qingdao Ronghai Mould specializes in deep drawing molds, progressive dies, precision stamping tooling, and advanced metal-forming solutions. With state-of-the-art machining equipment, complete inspection systems, and integrated CAE/CAD/CAM engineering, we deliver high-precision, high-stability mold solutions for global customers.

We welcome your inquiries—feel free to contact us or click the online service button to speak with our engineering team.rhmould.com