Patent ID: 8733142

Claim:
A process for making a hot stamped coated steel sheet product, comprising: pre-coating a steel strip or sheet with aluminum or aluminum alloy by hot dipping said steel strip or sheet having a first side and a second side in an aluminum or aluminum alloy bath to provide a pre-coating having a thickness t p of from 20 to 33 micrometers; cutting said pre-coated steel strip or sheet to obtain a pre-coated steel blank; heating said aluminum or aluminum alloy pre-coated steel blank in a furnace; transferring said heated blank to a die; hot stamping said heated blank in said die, to thereby obtain a hot stamped steel product, and cooling said hot stamped steel sheet product at a mean rate Vr during an interval between when said product exits said furnace and when said product reaches 400° C., of at least 30° C./s so as to obtain a hot stamped coated steel sheet product with a coating having a plurality of layers; the plurality of layers including, from the steel strip or sheet outwards, an interdiffusion layer, an intermediate layer, an intermetallic layer and a superficial layer, the superficial layer having a hardness HV50 g from 810 to 1100.