公开(公告)号：US20180223386A1

公开(公告)日：2018-08-09

申请号：US15748395

申请日：2016-07-11

Applicant: ARCELORMITTAL

Inventor： Tiago MACHADO AMORIM ,  Christian ALLELY ,  Raisa GRIGORIEVA ,  David DUSSAUSSOIS

IPC: C21D9/46 ,  C22C21/10 ,  C23C2/12 ,  C23C2/28 ,  C23C2/40 ,  B32B15/01 ,  C21D8/00 ,  C21D6/00 ,  B21D22/02

CPC classification number: C21D9/46 ,  B21D22/022 ,  B32B15/012 ,  C21D1/673 ,  C21D6/004 ,  C21D6/005 ,  C21D6/008 ,  C21D8/005 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C22C21/02 ,  C22C21/10 ,  C23C2/12 ,  C23C2/26 ,  C23C2/28 ,  C23C2/40

Abstract: The present invention provides a method for the manufacture of a hardened part. The method includes the provision of a steel sheet pre-coated with a metallic coating including from 2.0 to 24.0% by weight of zinc, from 1.1 to 7.0% by weight of silicon, optionally from 1.1 to 8.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%, and optionally additional elements chosen from Pb, Ni, Zr, or Hf, the content by weight of each additional element being less than 0.3% by weight, the balance being aluminum and unavoidable impurities and residuals elements, wherein the ratio Al/Zn is above 2.9. The method further includes the cutting of the coated steel sheet to obtain a blank, the thermal treatment of the blank at a temperature between 840 and 950° C. to obtain a fully austenitic microstructure in the steel, the transfer of the blank into a press tool, the hot-forming of the blank to obtain a part, the cooling of the part in order to obtain a microstructure in steel being martensitic or martensitic-bainitic or made of at least 75% of equiaxed ferrite, from 5 to 20% of martensite and bainite in amount less than or equal to 10%.