Paying attention to draft, chemistry, and steel melt source processes can help you minimize the potential for cracks at your customer after cold work operations.
After a crimping, staking or swaging operation, cracks can develop. This is because the cold work needed to swage, stake, crimp, etc. was greater than the material’s available elasticity. This is the case in the part photographed here.
In order to minimize cracking during or after crimping, or thread rolling, or other substantial cold work, take the following steps:
- Specify non-renitrogenized material;
- Inform your supplier of your cold work application. They can consider reducing cold draft, or changing suppliers of the hot roll to get basic oxygen process, low residual, low nitrogen steel;
- Ask the customer to consider changing the grade. Resulfurized steels are capable of being somewhat cold worked, but their high volume fraction and weight percent of nonmetallic inclusions (What makes them cut so well!) is also what works against successful cold work.
To minimize the occurrence of cracks that are not a result of cold work, try this:
- Assure that adequate stock removal is taken in machining;
- Buying from reputable sources whose quality systems employ rototesting and eddy current testing;
When cracks are discovered in your shop, what actions do you take?