123/4 BLUE RING
1. Cr-Ni stainless steels austenitic
2. Cr stainless steels ferritic and martensitic
3. nitriding steels
4. heat resisting steels
5. alloy of nickel,
6. Cr stainless steels sulphured
7. structural steels
8. case hardening steels
9. heat treatable steels from 900 N/mm2