Importance

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Abstract

A process for manufacturing a non-stamped prealloyed steel coil, sheet or blank, comprising the following successive steps of: providing a non-stamped precoated steel coil, sheet or blank composed of a steel substrate covered by a precoating of aluminum, or aluminum-based alloy, or aluminum alloy, wherein the precoating thickness is comprised between 10 and 35 micrometers on each side of the steel coil, sheet or blank, then heating the non-stamped steel coil, sheet or blank in a furnace under an atmosphere containing at least 5% oxygen, up to a temperature θ₁ comprised between 750 and 1000° C., for a duration t₁ comprised between t_1min and t_1max, wherein: t_1min=23500/(θ₁−729.5) and t_1max=4.946×10⁴¹×θ₁^−13.08, t₁ designating the total duration in the furnace, θ₁ being expressed in ° C. and t_1min and t_1max being expressed in seconds, then cooling the non-stamped steel coil, sheet or blank at a cooling rate V_r1 down to a temperature θ_i, then maintaining the non-stamped steel coil, sheet or blank at a temperature θ₂ comprised between 100 and 500° C., for a duration t₂ comprised between 3 and 45 minutes, so to obtain a diffusible hydrogen less than 0.35 ppm.

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First Claim