Arcelormittal

Thierry Sturel

Pascal Drillet

Raisa Grigorieva

Brahim Nabi

Florin Duminica

Emmanuel Lucas

Alexandre Blaise

Blandine Remy

Gianni Boi

Cédric Georges

Cedric Georges

A press hardening method including the following steps: A. the provision of a steel sheet for heat treatment being optionally coated with a zinc- or aluminum-based pre-coating, B. the flexible rolling of the steel sheet in the rolling direction so as to obtain a steel sheet having a variable thickness, C. the cutting of the rolled steel sheet to obtain a tailored rolled blank, D. the deposition of a hydrogen barrier pre-coating over a thickness from 10 to 550 nm, E. the heat treatment of the tailored rolled blank to obtain a fully austenitic microstructure in the steel, F. the transfer of the tailored rolled blank into a press tool, G. the hot-forming of the tailored rolled blank to obtain a part having a variable thickness,H. the cooling of the part having a variable thickness obtained at step G).

Press hardening method

A press hardening method includes the following steps: A. the provision of a steel sheet for heat treatment, precoated with a zinc- or aluminum-based pre-coating for anti-corrosion purpose, B. the deposition of a hydrogen barrier pre-coating over a thickness from 10 to 550 nm, C. the batch annealing of the precoated steel sheet in an inert atmosphere to obtain a pre-alloyed steel sheet, D. the cutting of the pre-alloyed steel sheet to obtain blank, E. the thermal treatment of the blank to obtain a fully austenitic microstructure in the steel, F. the transfer of the blank into a press tool, G. the hot-forming of the blank to obtain a part, H. the cooling of the part obtained at step G).

press hardening method includes the following steps: A. the provision of a steel sheet for heat-treatment, precoated with a zinc- or aluminum-based pre-coating, B. the deposition of a hydrogen barrier pre-coating over a thickness from 10 to 550 nm, and comprising at least one element chosen from among: nickel, chromium, magnesium, aluminum and yttrium, C. batch annealing of the precoated steel sheet to obtain a pre-alloyed steel sheet, the cooling after the batch annealing being performed at a speed of 29.0° C.hor less, D. the cutting of the pre-alloyed steel sheet to obtain blank, E. thermal treatment of the blank to obtain a fully austenitic microstructure in the steel, F. the transfer of the blank into a press tool, G. the hot-forming of the blank to obtain a part, H. the cooling of the part obtained at step G).

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 press hardening method includes the following steps providing a carbon steel sheet coated with a barrier pre-coating including nickel and chromium wherein the weight ratio Ni/Cr is between 1.5 and 9, cutting the sheet to obtain a blank, thermal treatment of the blank in an atmosphere having an oxidizing power equal or higher than that of an atmosphere consisting of 1% by volume of oxygen and equal or smaller than that of an atmosphere consisting of 50% by volume of oxygen, such atmosphere having a dew point between &#x2212;30 and +30&#xb0; C., transfer of the blank into a press tool, hot-forming of the blank to obtain a part, cooling of the part to obtain a microstructure in steel being martensitic or martensito-bainitic or made of at least 75 wt. % of equiaxed ferrite, from 5 to 20 wt. % of martensite and bainite in amount less than or equal to 10 wt. %.

A press hardened coated steel part with high resistance to delayed fracture, the coating containing (Fe&#x2014;Al) intermetallic compounds resulting from the diffusion of iron into an aluminum or an aluminum-based alloy, or an aluminum alloy of a precoating, wherein the chemical composition of the steel includes, in weight: 0.16%&#x2264;C&#x2264;0.42%, 0.1%&#x2264;Mn&#x2264;3%, 0.07%&#x2264;Si&#x2264;1.60%, 0.002%&#x2264;Al&#x2264;0.070%, 0.02%&#x2264;Cr&#x2264;1.0%, 0.0005&#x2264;B&#x2264;0.005%, 0.002%&#x2264;Mg&#x2264;0.007%, 0.002%&#x2264;Ti&#x2264;0.11%, 0.0008%&#x2264;O&#x2264;0.005%, wherein (Ti)&#xd7;(O)&#xd7;10&#x2264;2, 0.001%&#x2264;N&#x2264;0.007%, 0.001%&#x2264;S&#x2264;0.005%, 0.001%&#x2264;P&#x2264;0.025% and optionally one or more elements selected from the list of: 0.005%&#x2264;Ni&#x2264;0.23%, 0.005%&#x2264;Nb&#x2264;0.060%, the remainder being Fe and unavoidable impurities, and wherein the microstructure includes at least 95% martensite.

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Le Ban Saint Martin, France

Thierry Sturel