High hole expansion steel is a specialized type of steel primarily utilized in automobile rear axle suspension and other similar applications where exceptional flanging performance is required. This steel can be classified into two categories based on its structure: low carbon ferritic high hole expansion steel and ferrite + shellfish Fensite (FB) dual-phase high-hole expansion steel. As numerous automotive components require punching and flanging, the steel plate’s structure significantly affects the hole reaming and flanging performance. Studies have demonstrated that a single microstructure offers better hole reaming and flanging performance, and the steel plate’s hole reaming and flanging performance improve with a lower hardness difference between the two phases (such as F+B).

This steel is utilized in various automotive applications, such as swing arms, rim spokes, and chassis components, as well as in components that require reaming or flanging.