OTAI SPECIAL STEEL is O1 steel stockholders and suppliers from china. more 16 years experience in AISI O1 tool steel round bar, flat bar and plate supply. AISI O1 Steel is a high quality Cold work tool steel, It belong to the high quality high carbon alloy tool steel. Oil AISI O1 Steel - DIN 1.2510 - JIS SKS3 - Songshun SteelO1 steel also is called DIN 1.2510 and JIS SKS3 steel. High content for manganese, chromium and tungsten in 1.2510 steel composition, that could increase the hardening ability. Then the steel does not need to undergo water quenching. After oil cooling and quenching, the hardness could reach 62HRC. O1 tool steel round bar sheet plate was used widely as a cold work mold steel.