4130 alloy steel is a chromium-molybdenum steel known for its good strength, weldability, and resistance to abrasion and impact. Square bars made of 4130 alloy steel are commonly used for structural applications such as frames, gears, fasteners, as well as in the automotive, aerospace, bicycling, and firearm industries where high mechanical properties are required. The square bar shape allows for versatile uses in structural components and fabrication projects.