ZnAlMg-coated metal sheet with improved flexibility and corresponding manufacturing process

Patent metadata

Field	Value
Publication number	US-12116673-B2
Application number	US-202117347868-A
Country	US
Kind code	B2
Filing date	Jun 15, 2021
Priority date	Oct 9, 2013
Publication date	Oct 15, 2024
Grant date	Oct 15, 2024

Abstract

A process for the manufacture of a pre-painted sheet. The process includes supplying a steel substrate, depositing a metallic coating on at least one face by hot-dipping of the substrate in a bath including 4.4% to 5.25% by weight aluminum and 0.3% to 0.56% by weight magnesium. The rest of the bath includes exclusively zinc, unavoidable impurities resulting from the process and optionally one or more additional elements including Si, Ti, Ca, Mn, La, Ce and Bi. The content by weight of each additional element in the metallic coating is less than 0.3% and the presence of nickel is excluded. The process further includes solidifying the metallic coating, surface preparation of the metallic coating and painting of the metallic coating. The present invention further provides a pre-painted sheet.

First claim

What is claimed is:

1. A process for the manufacture of a pre-painted sheet consisting of:
supplying a steel substrate;
depositing a metallic coating on at least one face by hot-dipping the steel substrate in a bath containing:
4.4% to 5.25% by weight aluminum,
0.3% to 0.56% by weight magnesium,
0.0 to less than 0.3% by weight Si,
0.0 to less than 0.3% by weight Ti,
0.0 to less than 0.3% by weight Ca,
0.0 to less than 0.3% by weight Mn,
0.0 to less than 0.3% by weight La,
0.0 to less than 0.3% by weight Ce,
0.0 to less than 0.3% by weight Bi,
a remainder of the bath including zinc and unavoidable impurities resulting from the process, the presence of nickel being excluded;

wiping the substrate with a wiping gas:
solidifying the metallic coating, the solidification of the metallic coating taking place at a cooling rate greater than or equal to 15° C./s between the beginning of solidification and the end of solidification of the metallic coating;
optionally skin-pass treating the steel substrate with the metallic coating to provide a roughness;
surface preparation of the metallic coating;
optionally coiling the surface prepared steel substrate with the metallic coating;
painting the metallic coating with a paint film comprising at least one layer of paint comprising at least one polymer selected from the group consisting of melamine cross-linked polyesters, isocyanate cross-linked polyesters, polyurethanes and halogenated derivatives of vinyl polymers, with the exclusion of cataphoretic paints, thereby providing the pre-painted sheet; and
optionally recoiling the steel sheet with the metallic coating after the painting;
wherein the paint film has a thickness between 1 and 200 μm, and
the metallic coating has a thickness less than or equal to 25 μm.

2. The manufacturing method according to claim 1 , wherein the surface prepared steel substrate with the metallic coating is coiled before the surface preparation and the painting.

3. The manufacturing method according to claim 1 , wherein the surface preparation includes degreasing in an alkaline environment.

4. The manufacturing method according to claim 3 , wherein the pH of the degreasing is between 12 and 13.

5. The manufacturing method according to claim 1 , wherein the degreased steel substrate with the metallic coating is subjected to a conversion treatment.

6. The manufacturing method according to claim 5 , wherein prior to the conversion treatment and after the degreasing, an acid solution is applied to the metallic coating.

7. The manufacturing process according to claim 1 , wherein the metallic coating is free from spangles visible to the naked eye.

8. The manufacturing process according to claim 1 , wherein the bath consists of:
4.4% to 5.25% by weight aluminum,
0.3% to 0.56% by weight magnesium,
0.0 to less than 0.3% by weight Si,
0.0 to less than 0.3% by weight Ti,
0.0 to less than 0.3% by weight Ca,
0.0 to less than 0.3% by weight Mn,
0.0 to less than 0.3% by weight La,
0.0 to less than 0.3% by weight Ce,
0.0 to less than 0.3% by weight Bi,
a remainder of the bath including zinc and unavoidable impurities resulting from the process, the presence of nickel being excluded.

9. The manufacturing process according to claim 1 , wherein the painting is performed by depositing layers of paint by roll coaters.

10. The manufacturing process according to claim 9 , the painting includes curing in a furnace to cross-link the paint and/or to evaporate any solvents and thereby obtain a dry paint film.

11. The manufacturing process according to claim 10 , wherein the process includes skin-passing the steel substrate with the metallic coating and coiling before painting.

12. The manufacturing process according claim 1 , wherein magnesium content of the bath is from 0.3 to 0.55% by weight.

13. The manufacturing process according claim 1 , wherein magnesium content of the bath is from 0.44 to 0.56% by weight.

14. The manufacturing process according claim 1 , wherein the solidifying is by cooling under natural convection.

15. The manufacturing process according claim 1 , wherein paint film is formed by two successive layers of paints.

16. The manufacturing process according claim 15 , wherein the two successive layers of paint consist of a primer layer of the melamine cross-linked polyester containing anti-corrosion pigments, and a finish layer of paint of the melamine cross-linked polyester.

17. The manufacturing process according claim 16 , wherein the paint film has a thickness between 13 and 20 m, the metallic coating has a thickness between 12 and 20 μm.

18. The manufacturing process according to claim 17 , wherein aluminum content of the bath is from 4.6 to 5.1% by weight and magnesium content of the bath is 0.45 to 0.55%.

19. The manufacturing process according to claim 18 , wherein a propensity of the metallic coating to cracking is reduced by the paint film, as determined by a T-bend test as defined in standard EN13523-7 dated April 2001, and the propensity of the metallic coating to cracking includes a reduction in an average crack width in the metallic coating.

20. The manufacturing process according to claim 19 , wherein the cooling rate is from 15° C./see to 30° C./sec.

21. The manufacturing process of claim 1 , wherein the at least one polymer is selected from the group consisting of melamine cross-linked polyesters, isocyanate cross-linked polyesters, and halogenated derivatives of vinyl polymers.

Assignees

• Arcelormittal

Inventors

• Diez Luc
• Filou Clémence
• Föjer Gunhild
• BEN SAAD Manel

Classifications

• C23C22/82

  After-treatment · CPC title

• C23C22/34

  containing fluorides or complex fluorides · CPC title

• C23C2/36

  Elongated material · CPC title

• C23C2/26

  After-treatment (C23C2/14 takes precedence) · CPC title

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title