LME METHOD FOR THE MANUFACTURE OF A HARDENED PART WHICH DOES NOT HAVE LME ISSUES

摘要

The present invention relates to a method for producing a cured part, the method comprising: A) providing a steel sheet precoated with a metal coating, the metal coating comprising 2.0 to 24.0 wt% zinc, 1.1 to 7.0 wt% silicon Optionally, from 1.1 to 8.0% by weight of magnesium when the amount of silicon is from 1.1 to 4.0%, and optionally additional elements selected from Pb, Ni, Zr, or Hf, wherein the weight content of each additional element is 0.3 Providing a steel sheet pre-coated with the metal coating, the balance being less than% by weight, the remainder being aluminum and inevitable impurities and residual elements, and the ratio Al / Zn being greater than 2.9, B) the steel sheet coated to obtain a blank Cutting the blank, C) heat treating the blank at a temperature of 840 to 950 ° C. to obtain a complete austenite microstructure in the steel, and d) moving the blank into a press tool. E) hot forming the blank to obtain a part, F) martensite or martensiate-bainite, or at least 75% equiaxed ferrite, 5-20% martensite, and up to 10% Cooling said part obtained in step E) to obtain a microstructure of the steel made of bainite.