Identifying the Cause of Tool and Die Failure

Steels used for tools and dies differ from most other steels in several aspects. First, they are used in the manufacture of other products by a variety of forming processes. Second, tools and dies are generally used at a higher hardness than most other steel products; 58 to 68 Rockwell C is a typical range. Dies for plastic molding or hot working are usually used at a lower hardness, typically from 30 to 55 Rockwell C.

These high hardness values are required to resist anticipated service stresses and to provide wear resistance. However, the steels must also be tough enough to accommodate service stresses and strains without cracking. Premature failure caused by cracking must be avoided, or at least minimized, to maintain minimum manufacturing costs. Unexpected tool and die failure can shut down a manufacturing line and disrupt production scheduling.

Tool and die failures caused by breakage, which are generally catastrophic, are the most spectacular and draw the most attention from the failure analyst. Such failures are usually the easiest to diagnose, but the analyst should not halt the investigation when one obvious problem is identified. Several factors can contribute to a failure in varying degrees. The goal of any failure analysis should be to provide a total picture of all problems present so that complete corrective action can be taken on future parts.