A press hardening method

Patent metadata

Field	Value
Publication number	US-2019144963-A1
Application number	US-201716097466-A
Country	US
Kind code	A1
Filing date	Apr 26, 2017
Priority date	Apr 29, 2016
Publication date	May 16, 2019
Grant date	—

Abstract

A carbon steel sheet coated with a barrier pre-coating containing nickel and chromium in a weight ratio between 1.5 and 9, and a press hardening method for providing the carbon steel sheet coated with a barrier pre-coating comprising nickel and chromium are described.

First claim

1 - 28 . (canceled)

29 . A press hardening method comprises the following steps:
a) provision of a carbon steel sheet coated with a barrier pre-coating comprising nickel and chromium, wherein the weight ratio Ni/Cr is between 1.5 and 9, b) cutting of the coated carbon steel sheet to obtain a blank, c) thermal treatment of the blank, d) transfer of the blank into a press tool, e) hot-forming of the blank to obtain a part, f) cooling of the part obtained at step e) in order to obtain a microstructure in steel that is martensitic or martensito-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%.

30 . A press hardening method according to claim 29 , wherein the barrier pre-coating is such that the weight ratio Ni/Cr is between 2.3 and 9.

31 . A press hardening method according to claim 30 , wherein the weight ratio Ni/Cr is between 3 and 5.6.

32 . A press hardening method according to claim 29 , wherein the barrier pre-coating comprises from 55 to 90% by weight of nickel.

33 . A press hardening method according to claim 32 , wherein the barrier pre-coating comprises from 70 to 90% by weight of nickel.

34 . A press hardening method according to claim 33 , wherein the barrier pre-coating comprises from 75 to 85% by weight of nickel.

35 . A press hardening method according to claim 29 , wherein the barrier pre-coating comprises from 10 to 40% of chromium.

36 . A press hardening method according to claim 35 , wherein the barrier pre-coating comprises from 10 to 30% of chromium.

37 . A press hardening method according to claim 36 , wherein the barrier pre-coating comprises from 15 to 25% of chromium.

38 . A press hardening method according to claim 29 , wherein the barrier pre-coating does not comprise at least one of the element chosen from the group consisting of Zn, Al, B, N and Mo.

39 . A press hardening method according to claim 29 , wherein the barrier pre-coating consists of Cr and Ni.

40 . A press hardening method according to claim 39 , wherein the barrier pre-coating has a thickness between 10 nm and 550 nm.

41 . A press hardening method according to claim 40 , wherein the thickness of the barrier pre-coating is between 10 nm and 90 nm.

42 . A press hardening method according to claim 40 , wherein the thickness of the barrier pre-coating is between 150 nm and 250 nm.

43 . A press hardening method according to claim 29 , wherein the carbon steel sheet is directly topped by an anticorrosion pre-coating, this anticorrosion pre-coating layer being directly topped by the barrier pre-coating.

44 . A press hardening method according to claim 43 , wherein the anticorrosion pre-coating comprises at least one of metal selected from the group comprising zinc, aluminum, copper, magnesium, titanium, nickel, chromium, manganese and their alloys.

45 . A press hardening method according to claim 43 , wherein the anticorrosion pre-coating is based on aluminum or based on zinc.

46 . A press hardening method according to claim 43 , wherein the anticorrosion pre-coating is based on aluminum and comprises less than 15% Si, less than 5.0% Fe, optionally 0.1 to 8.0% Mg and optionally 0.1 to 30.0% Zn, the remainder being Al.

47 . A press hardening method according to claim 43 , wherein the anticorrosion pre-coating is based on zinc and comprises from up to 0.3% Al, the remainder being Zn.

48 . A press hardening method according to claim 29 , wherein the barrier pre-coating is deposited by physical vapor deposition, by electro-galvanization, hot-dip galvanization or roll-coating.

49 . A press hardening method according to claim 29 , wherein the thermal treatment is performed at a temperature between 800 and 950° C.

50 . A press hardening method according to claim 29 , wherein the thermal treatment is performed at a temperature between 840 and 950° C., and a fully austenitic microstructure in the steel is obtained.

51 . A press hardening method according to claim 29 , wherein the thermal treatment is performed during a dwell time between 1 to 12 minutes in an inert atmosphere or an atmosphere comprising air.

52 . A press-hardening method according to claim 29 , wherein the hot-forming of the blank is at a temperature between 600 and 830° C.

53 . A part manufactured by the method of claim 29 .

54 . A part according to claim 53 , comprising a carbon steel sheet coated with a barrier pre-coating comprising nickel and chromium, such barrier coating being alloyed through diffusion with the carbon steel sheet.

55 . A part according to claim 53 , comprising the carbon steel sheet directly topped by an anticorrosion pre-coating, this anticorrosion pre-coating layer being directly topped by the barrier pre-coating, such barrier coating being alloyed through diffusion with the anticorrosion coating, the anticorrosion coating being alloyed with the carbon steel sheet.

56 . A method for manufacturing an automotive vehicle comprising manufacturing an automotive vehicle comprising a part according to claim 53 .

Assignees

• Arcelormittal

Inventors

• Georges Cédric
• Duminica Florin
• Sturel Thierry
• Drillet Pascal

Classifications

• C21D8/04 Primary

  to produce plates or strips for drawing, e.g. for deep-drawing · CPC title

• C21D1/673 Primary

  for die quenching · CPC title

• C23C30/00 Primary

  Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process (C23C26/00, C23C28/00 take precedence) · CPC title

• C21D6/005

  containing Mn · CPC title

• B32B15/015

  the said other metal being copper or nickel or an alloy thereof · CPC title