FORMING/BENDING
The main tooling problems in bending and forming are wear and deformation of the tools, which result in loss of tolerance of the workpiece. Other problems such as breakage and galling are also encountered.

• To minimize deformation, consider tool steels with high hardness and therefore high compressive yield strength. High hardness is usually the first consideration for bending and forming tooling. However, hardness is not a highly distinguishing factor as most of the tool steels have similar working hardness ranges.

  If you are using A2 or D2 and are experiencing deformation, other grades with higher hardness, such as CPM M4, may be beneficial. The Working Hardness Range table and Hardness vs. Compressive Yield Strength chart can help select an appropriate grade for improving the deformation resistance of tools.

• A broken die is worthless, often beyond repair. To minimize breakage or chipping, consider tool steels with high toughness.

  Where A2 or D2 are prone to breaking or chipping, tool steels such as S7 can offer high toughness, but often at a considerable drop in wear life. Many of the CPM grades offer high toughness, without sacrificing wear life. For instance, 3V may be commonly substituted for D2, and will still offer long wear life. See the Wear Resistance and Toughness chart for more details.

• Abrasion of the tool involves actual metal loss and results in loss of tolerance of the workpiece. To minimize abrasion consider tool steels with high wear resistance.

  The high alloy capabilities of the CPM grades: If you are using A2 or D2 and are experiencing premature wear, try CPM 3V, CPM 10V or CPM M4.

• Galling is not generally easily solved by a change of tooling materials, as most tool steels have similar physical surface properties. Try coatings. Coatings or surface treatments may be helpful.