Arcelormittal

Alexandre Blaise

Pascal Drillet

Thierry Sturel

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 θcomprised between 750 and 1000° C., for a duration tcomprised between tand t, wherein: t=23500/(θ−729.5) and t=4.946×10×θ, tdesignating the total duration in the furnace, θbeing expressed in ° C. and tand tbeing expressed in seconds, then cooling the non-stamped steel coil, sheet or blank at a cooling rate Vdown to a temperature θ, then maintaining the non-stamped steel coil, sheet or blank at a temperature θcomprised between 100 and 500° C., for a duration tcomprised between 3 and 45 minutes, so to obtain a diffusible hydrogen less than 0.35 ppm.

Manufacturing process of press hardened parts with high productivity

A manufacturing process of a press hardened coated part including providing a furnace containing N zones, each furnace zone being respectively heated at a setting temperature &#x398;, &#x398;, . . . &#x398;, . . . , &#x398;, including: providing a steel sheet with thickness th between 0.5 and 5 mm, the steel sheet covered by an aluminium alloy precoating with a thickness between 15 and 50 &#x3bc;m, the emissivity coefficient being equal to 0.15(1+&#x3b1;), &#x3b1; being between 0 and 2.4, then cutting the steel sheet to obtain a precoated steel blank, then placing the precoated steel blank in furnace zone 1 for a duration tbetween 5 and 600 s, wherein &#x398;and tare such that: &#x398;&#x3e;&#x398;&#x3e;&#x398;then transferring the precoated steel blank in the furnace zone 2 heated at a setting temperature &#x398;=&#x398;and maintaining isothermally the precoated steel blank for a duration t, then transferring the precoated steel blank in further zones (3, . . . i, . . . , N) of the furnace, so to reach a maximum blank temperature &#x398;between 850&#xb0; C. and 950&#xb0; C., the average heating rate Vof the blank between &#x398;and &#x398;being between 5 and 500&#xb0; C./s, then hot forming the heated steel blank so as to obtain a part, then cooling the part to obtain martensite or bainite.

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Montataire, France

Alexandre Blaise