US 2015/0030382 A1 · HOT-FORMED PREVIOUSLY WELDED STEEL PART WITH VERY HIGH MECHANICAL RESISTANCE AND PRODUCTION METHOD

Abstract

The invention relates principally to a welded steel part with a very high mechanical strength characteristics obtained by heating followed by hot forming, then cooling of at least one welded blank obtained by butt welding of at least one first and one second sheet consisting at least in part of a steel substrate and a pre-coating which is constituted by an intermetallic alloy layer in contact with the steel substrate, topped by a metal alloy layer of aluminum or aluminum-based alloy. This welded steel part claimed by the invention is essentially characterized in that the metal alloy layer (19, 20) has been removed from the edges (36) in direct proximity to the weld metal zone (35), while the intermetallic alloy layer (17, 18) has been left in place, and in that over at least a portion of the length of the weld metal zone (35), the ratio between the carbon content of the weld metal zone (35) and the carbon content of the substrate (25, 26) of either the first or the second sheet (11, 12) having the higher carbon content (Cmax) is between 1.27 and 1.59. The invention likewise relates to a method for the fabrication of a welded steel part as well as the use of this welded steel part for the fabrication of structural or safety parts for automotive vehicles.

Claims34

Dependent claims

1-29. (canceled)

A welded steel part obtained by heating in the austenitic range followed by hot forming, then cooling, of at least one welded blank obtained by a butt welding of at least a first and a second sheet comprising:

a steel substrate;
and
a pre-coating including an intermetallic alloy layer and a metal alloy layer of an aluminum or aluminum-base alloy, the intermetallic alloy layer contacting the steel substrate, the metal alloy layer topping the intermetallic alloy layer;
a weld metal zone resulting from the welding operation and forming a bond between the first and second sheets;
the metal alloy layer being removed from edges peripheral to the weld metal zone while the intermetallic alloy layer remains;
over at least a portion of the weld metal zone, a ratio between a carbon content of the weld metal zone and a carbon content of the steel substrate of the first or second sheet having a higher carbon content Cmax, is between 1.27 and 1.59;
a composition of the steel substrate of at least the first or the second sheet, comprises the following elements, expressed in per cent by weight:
0.10%≦C≦0.5%
0.5%≦Mn≦3%
0.1%≦Si≦1%
0.01%≦Cr≦1%
Ti≦0.2%
Al≦0.1%
S≦0.05%
P≦0.1%
0.0002%≦B≦0.010%,
the balance being iron and unavoidable impurities from processing.

14 more elements

Dependencies are inferred from the claim text.

Facts

Application

14/235,420Filed 23 Jul 2012

Priority

IB PCT/IB2011/00172526 Jul 2011

Published

29 Jan 2015

Term ends

Not estimatedThe source records don’t support an estimate.

Classification29 codes

B23K 31/02
Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by any single one of main groups…:…
B23K 26/32
Bonding: taking account of the properties of the material involved
B23K 26/60
Working by laser beam, e.g. welding, cutting or boring: preliminary treatment
B23K 35/0261
For use in welding: rods, electrodes or wires

Hot-formed previously welded steel part with very high mechanical resistance and production method

Life of this patent

Hot-formed previously welded steel part with very high mechanical resistance and production method

Life of this patent

Abstract

Claims34