What Is Boron Steel?
Boron steel (B steel) is a type of carbon steel enhanced with boron and chromium. Boron, typically added in about 0.0008%, is effective in improving the steel’s hardenability, while chromium is added in the range of 0.10 to 0.20%. This steel also includes adjustments of other elements such as copper and nickel. In alloy boron steel, the chromium content is higher.
Uses of Boron Steel
Boron steel is commonly used in automotive parts, especially in bolts and nuts, and serves as a general-purpose alternative to alloy steel for applications where extreme strength isn’t necessary. It is suitable for bolt strength classifications up to 10.9. The inclusion of boron allows for the omission of the heat treatment process in wire rod processing, simplifying manufacturing steps like cold forging.
Types of Boron Steel
Boron steel comes in various forms, including carbon boron steel, manganese boron steel, and alloy boron steel, as specified by the SAE (U.S.) standard. For instance, 1021B indicates boron steel with the ‘B’ signifying boron addition.
Different types of boron steel are used to eliminate or reduce heat treatment requirements in parts manufacturing. Examples include hardened boron steel for gear parts, bolt boron steel for bolts, and low-Mo tough boron steel for knuckle parts. High-strength, high-toughness boron steel is used in link applications. When used in high-strength bolts, it’s important to choose a type designed for delayed fracture resistance to prevent brittle fracture from hydrogen embrittlement.