公开(公告)号：US20180216218A1

公开(公告)日：2018-08-02

申请号：US15748262

申请日：2016-07-29

Applicant: ARCELORMITTAL

Inventor： Tiago MACHADO AMORIM ,  Christian ALLELY ,  Grégory LEUILLIER

IPC: C23C2/12 ,  C23C2/28 ,  C23C2/06 ,  C21D8/02

CPC classification number: C23C2/12 ,  C21D1/673 ,  C21D8/0257 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C23C2/06 ,  C23C2/28

Abstract: A method for the manufacture of a hardened part coated with a phosphatable coating is provided. The method includes providing a steel sheet pre-coated with a metallic coating including from 4.0 to 20.0% by weight of zinc, from 1.0 to 3.5% by weight of silicon, optionally from 1.0 to 4.0% by weight of magnesium, 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. The steel sheet is cut to obtain a blank, the blank is thermally treated at a temperature between 840 and 950° C. to obtain a fully austenitic microstructure in the steel, the blank is transferred into a press tool and hot-formed to obtain a part. The part is cooled to obtain a martensitic or martensitic-bainitic microstructure 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%.