Steel Mart Is An Iso 9001:2008 Certified Company & Is Specializing In The Supply Of A2 Steel Round Bars In All The Standard Sizes In Small, Medium & Large Quantity. We offer trading A2 Steel Round Bars. Air-hardening tool steel containing five percent chromium. Replaces the oil hardening (O1 type) when safer hardening, less distortion and increased wear resistance are required. Provides an intermediate grade between the oil hardening and the high carbon, high chromium (D2) types.