METHOD OF MANUFACTURING A GALVANNEALED STEEL STRIP PRODUCT FOR HOT PRESS FORMING, METHOD OF MANUFACTURING A HOT-PRESSED STEEL COMPONENT, AND GALVANNEALED STEEL STRIP PRODUCT

摘要

There is disclosed a galvannealed steel strip product for hot press forming, comprising a strip of steel (1) made of hardenable steel alloy and plated with a galvannealed overlay coating (2) comprising an iron-zinc solid solution phase having a crystal structure in which zinc is incorporated into a lattice of iron, and wherein the microstructure (3) of the steel (1) has an iron carbide structure consisting of spheroidized iron carbides (5, 6). The galvannealed steel strip product is manufactured by galvanizing a strip of steel (1) made of hardenable steel alloy with a zinc- based coating (2), coiling the galvanized steel strip, and annealing the coiled steel strip having the zinc or zinc alloy overlay in a batch furnace. The annealing time and temperature are set such that an average iron content of the annealed zinc-based coating is more than 15 wt-%, preferably more than 20 wt-%, most preferably more than 54 wt-%. The coiled steel strip may be annealed in an inert or reducing atmosphere to minimize the amount of oxides formed on the surface of the coating. There is also disclosed a method of manufacturing a hot-pressed steel component from the galvannealed steel strip product.