POSCO Holdings Inc.
Aluminum-iron alloy-coated steel sheet for hot press forming, having excellent hydrogen delayed fracture resistance, peeling resistance, and weldability and hot-formed member using same

Abstract:

An Al--Fe alloy coated steel sheet includes a base steel sheet and an alloy coating layer, wherein the base steel sheet includes, by wt %, C: 0.1%.about.0.5%, Si: 0.01%.about.2%, Mn: 0.01%.about.10%, P: 0.001%.about.0.05%, S: 0.0001%.about.0.02%, Al: 0.001%.about.1.0%, N: 0.001%.about.0.02%, and the balance of Fe and other impurities, wherein the alloy coating layer includes: an Al--Fe alloy layer I formed on the base steel sheet and having a Vickers hardness of 200.about.800 Hv; an Al--Fe alloy layer III formed on the Al--Fe alloy layer I and having a Vickers hardness of 700.about.1200 Hv; and an Al--Fe alloy layer II formed in the Al--Fe alloy layer III continuously or discontinuously in a length direction of the steel sheet, and having a Vickers hardness of 400.about.900 Hv, wherein an average oxygen content at a depth of 0.1 .mu.m from a surface of the oxide layer is 20% or less by weight.