Alloy Steel 4340 Sheet/Plate is normally used for aerospace, heavy-duty industrial, and automotive applications. 4340 steel stock has high strength, toughness, wear resistance, and fatigue strength. It can be machined in all states other than hardened and it is easily welded. 4340 steel sheet/plate stock is available in full size and custom cut lengths. This material meets the following specifications: AMS 6359 and ASTM A829.