Method of producing press-hardened and coated steel parts at a high productivity rate

Patent metadata

Field	Value
Publication number	US-10619224-B2
Application number	US-201916281748-A
Country	US
Kind code	B2
Filing date	Feb 21, 2019
Priority date	Mar 31, 2014
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

A part obtained by austenitization followed by hot stamping and hardening by holding in the stamping tool a sheet or blank is provided, including, a steel substrate, a precoating having at least one layer of aluminum or aluminum alloy, a microstructure of a steel substrate including martensite and/or bainite, a coating on at least one face of the steel substrate resulting from the interdiffusion between the steel substrate and the pre-coating and an oxide layer overlying the coating, an average content by weight of oxygen between 0 and 0.01 μm below a surface of the part being less than 25%, and the average percent by weight of oxygen between 0.1 and 0.2 μm below the surface being less than 10%.

First claim

What is claimed is:

1. A part obtained by austenitization followed by hot stamping and hardening by holding in the stamping tool a sheet or blank comprising:
a steel substrate;
a precoating having at least one layer of aluminum or aluminum alloy; a microstructure of a steel substrate including martensite and/or bainite; a coating on at least one face of the steel substrate resulting from the interdiffusion between the steel substrate and the pre-coating; and an oxide layer overlying the coating;
an average content by weight of oxygen between 0 and 0.01 μm below a surface of the part being less than 25%, and the average percent by weight of oxygen between 0.1 and 0.2 μm below the surface being less than 10%;
wherein, prior to austenitization, a polymerized layer is provided on at least a part of the pre-coating, the polymerized layer having a thickness from 2 μm to 30 μm and comprising a polymer that does not contain silicon, a nitrogen content of less than 1% by weight and carbon pigments in a quantity from 3 to 30% by weight.

2. The part of claim 1 , wherein the average content by weight of oxygen between 0 and 0.01 μm below a surface of the part being 17.5% or less, and the average percent by weight of oxygen between 0.1 and 0.2 μm below the surface being 4.8% or less.

3. The part of claim 1 , wherein the polymer consists of C, H, O, or N.

4. The part of claim 1 , wherein the polymerized layer is obtained from a resin in a form of a dispersion or emulsion in aqueous phase.

5. The part of claim 1 , wherein the polymerized layer is obtained from a resin in the form of solution in a non-aqueous solvent.

6. The part of claim 1 , wherein the polymerized layer is a film roll bonded to the substrate.

7. The part of claim 4 , wherein the polymerized layer is obtained from an acrylic type resin.

8. The part of claim 5 , wherein the polymerized layer is obtained from an epoxy or acrylic type resin.

9. The part of claim 6 , wherein the polymerized layer is a film of polyethylene-terephthalate or polyethylene or polybutylene-terephthalate or polypropylene.

10. The part of claim 1 , wherein the carbon pigments include activated carbon.

11. The part of claim 1 , wherein the carbon pigments include graphite.

12. The part of claim 10 , wherein a quantity of activated carbon in the polymerized layer is less than 5% by weight.

13. The part according to claim 1 , wherein the layer of aluminum or aluminum alloy is more than 50% of a thickness of the pre-coating.

14. The part according to claim 1 , wherein the pre-coating is applied by a continuous hot dip process, and wherein the pre-coating is an aluminum-silicon alloy comprising 7-15% silicon by weight, 2 to 4% iron by weight, optionally between 15 and 30 ppm calcium, the remainder consisting of aluminum and unavoidable impurities resulting from processing.

15. The part according to claim 1 , wherein the pre-coating is an aluminum alloy containing 40-45% Zn, 3-10% Fe, 1-3% Si, the balance consisting of aluminum and the unavoidable impurities resulting from processing.

16. The part according to claim 1 , wherein the austenitization includes heating to an austenitization temperature T γ and wherein the heating includes heating at a heating rate between 15 and 40° C. between 50 and 500° C.

17. The part according to claim 16 , wherein the austenitization temperature is at least 900° C.

18. The part according to claim 1 , wherein the austenitization includes heating to an austenitization temperature T γ and wherein the carbon in the carbon pigment gradually combines with atmospheric oxygen during said heating.

19. The part according to claim 18 , wherein the heating includes heating at a heating rate between 15 and 40° C. between 50 and 500° C.

20. The part according to claim 19 , wherein the carbon in the carbon pigment remains present during a larger part of said heating and substantially disappears when the austenitization temperature T γ is reached.

Assignees

• Arcelormittal

Inventors

• Sanadres Michel
• Dessain Christine

Classifications

• B21D22/022

  by heating the blank or stamping associated with heat treatment (C21D takes precedence) · CPC title

• C22C38/02

  containing silicon · CPC title

• C09D5/00

  Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced {(electrically insulating plastics, resins or waxes H01B3/30)}; Filling pastes · CPC title

• C09D5/32

  Radiation-absorbing paints {(protection against X-, gamma- or corpuscular radiation G21F)} · CPC title

• C22C38/32

  with boron · CPC title