A36 is a carbon structural steel whose chemical composition and mechanical properties strictly conform to American ASTM standards. A36 steel bar mainly consists of iron, carbon, silicon, manganese, phosphorus, sulfur and other elements.

316L stainless steel bar just has a lower carbon content than 316 stainless steel bar and it is used mostly for welding purposes. The lower carbon content greatly lowers the precipitation of carbides in the heat-affected zone close to the weld, and such precipitation is likely to lead to intergranular corrosion of stainless steel in certain settings.

AISI 1045 steel is characterized by good weldability, good machinability and high strength and impact properties in the normalized or hot-rolled condition. So AISI 1045 steel bar is a medium carbon steel designed to be able to function in areas requiring greater strength and hardness.