Tool steel is specified for numerous die components and it may be well to discuss briefly the most commonly used types. they are:
1. Water hardening tool steel.
2. Oil hardening tool steel.
3. Air hardening tool steel.
4. High carbon high chromium tool steel.
5. High speed steel.
6. Shock resisting tool steel.
7. Hot work die steel.
1. Water hardening tool steel
As its name indicates water hardening tool steel is hardened by quenching it in water after it has first been heated to proper hardening temperature. it is employed for parts which can be ground after hardening. water hardening tool steel is subject to distortion in hardening process and it should not be specified for parts with internal contours that must remain accurate and which cannot be ground after hardening.
2. Oil hardening tool steel.
oil hardening tool steel contains chromium and it is quenched in oil in the hardening process.warpage or distortion is much less than for corresponding grades of water hardening steels. when accurate surfaces cannot be ground after hardening, and anticipated production rates are average, oil hardening tool steel should be specified. the abbreviation is O.H.T.S.
3. Air hardening tool steel.
air hardening tool steel need not be quenched in either oil or water for hardening to occur. after heating beyond the critical range, it is simply exposed in air until cool. air hardening tool steels have minimum warpage and this is combined with greater toughness and wear resistance than corresponding grades of oil or water hardening tool steels.
4. High carbon high chromium tool steel.
high carbon high chromium tool steel, have about the same properties as air hardening steels except that they posses a greater degree of resistance to wear. high carbon high chromium tool steel should be specified for die parts when long production runs are anticipated.
5. High speed steel.
The outstanding quality of high speed steel is its toughness, combined with a high degree of wear resistance. it should be specified for weak die parts such as frail inserts, small diameter punches, and the like another excellent application is in dies for cold working, coining and upsetting of metal.
6. Shock resisting tool steel.
shock resisting tool steel contain a smaller amount of carbon and therefore it is tougher than other types. it is employed for heavy cutting and forming operations where steels with higher carbon content would be subject to breakage.
7. Hot work die steel.
These steels are employed in dies
| TYPE OF STEEL | Non deforming properties | Safety in hardening | Toughness | Wear resistance | machinability | Resistance to softening under heat |
| water hardening tool steel | POOR | FAIR | GOOD | FAIR | BEST | POOR |
| oil hardening tool steel | GOOD | GOOD | FAIR | FAIR | GOOD | POOR |
| air hardening tool steel | BEST | BEST | FAIR | GOOD | FAIR | FAIR |
| high carbon high chromium tool steel | BEST | BEST | POOR | GOOD | POOR | FAIR |
| high speed steel | GOOD | BEST | BEST | GOOD | FAIR | GOOD |
| shock resisting tool steel | FAIR | GOOD | BEST | FAIR | FAIR | FAIR |
| hot work die steel | BEST | BEST | BEST | FAIR | FAIR | GOOD |
