Alloy steel 4130 (UNS G41300) is a chromium-molybdenum alloy steel with good strength, weldability, and abrasion/impact resistance. Rectangle bars made of 4130 are versatile and commonly used for structural applications like frames, gears, fasteners, tools, machinery components, and automotive/aerospace parts due to their high tensile strength. This low alloy steel is easy to machine and offers a good balance of strength, toughness and ductility.