The conclusions are the following. The cracking limit curve can be proposed as a function of the axial and the circumferential strain, and the hardness of the material. In the case of the material which was worked in two or more processes, the cracking limit was defined by the hardness of the material before cold working, the axial and the circumferential strain imposed during the cold working processes. To suppress cracking, it is effective to reduce the wiredrawing reduction in area before cold forging as much as possible when the material diameter and the final part geometry are constant. The proposed prediction equation can be applied as the indicator of material design and process design for suppressing cracking at cold working.
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