Hot dip galvanized ultra-high strength steel sheets with high flatness

Patent metadata

Field	Value
Publication number	US-12344915-B2
Application number	US-202318364840-A
Country	US
Kind code	B2
Filing date	Aug 3, 2023
Priority date	Jan 10, 2023
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

A coated steel sheet includes a steel sheet comprising iron (Fe); carbon (C) in a range from 0.05% to 0.35 wt. %; manganese (Mn) in a range from 0.1% to less than 2 wt. %; chromium (Cr) in a range from 1.2% to 6.0 wt. %; silicon (Si) in a range from 0.01% to less than 0.6 wt. %; aluminum (Al) in a range from 0.5% to 1.3 wt. %; vanadium (V) in a range from 0.01% to 0.5 wt. %; niobium (Nb) in a range from 0.01% to 0.2 wt. %; and titanium (Ti) in a range from 0.01% to 0.3 wt. %. A zinc coating is formed on an outer surface of the steel sheet.

First claim

What is claimed is:

1. A coated steel sheet comprising:
a steel sheet comprising iron (Fe), carbon (C) in a range from 0.05% to 0.35 wt. %, manganese (Mn) in a range from 0.1% to less than 2 wt. %, chromium (Cr) in a range from 1.2% to 6.0 wt. %, silicon (Si) in a range from 0.01% to less than 0.6 wt. %, aluminum (Al) in a range from 0.5% to 1.3 wt. %, vanadium (V) in a range from 0.01% to 0.5 wt. %, niobium (Nb) in a range from 0.01% to 0.2 wt. %, and titanium (Ti) in a range from 0.01% to 0.3 wt. %; and
a zinc coating formed on an outer surface of the steel sheet, and
wherein a microstructure of the steel sheet comprises martensite in a range from 70-99 vol. %, austenite in a range from 3-20 vol. %, bainite in a range from 0-20 vol. %, ferrite in a range from 0-10 vol. %, and Cr-enriched carbide in a range from 0.1% to 10 vol. %, and wherein the Cr-enriched carbide includes Cr in a range from 10% to 51 wt. % and carbon (C) in a range from 49 to 90 wt. %.

2. The coated steel sheet of claim 1 , wherein a sum of a weight of the manganese (Mn) and 3 times a weight of the silicon Si is less than 5 wt. %.

3. The coated steel sheet of claim 1 , wherein a sum of a weight of the aluminum (Al) and the silicon (Si) is greater than 1.0 wt. %.

4. The coated steel sheet of claim 1 , further comprising one or more materials selected from the group consisting of tin (Sn), copper (Cu), molybdenum (Mo), and/or nickel (Ni).

5. The coated steel sheet of claim 4 , wherein the tin (Sn) is less than 0.1 wt. %, the copper (Cu) is less than 0.5 wt. %, the molybdenum (Mo) is less than 0.5 wt. %, and/or the nickel (Ni) is less than 0.5 wt. %.

6. The coated steel sheet of claim 1 , wherein the wt % of the chromium (Cr) is greater than the wt % of the manganese (Mn).

7. A coated steel sheet comprising:
a steel sheet comprising iron (Fe), carbon (C) in a range from 0.05% to 0.35 wt. %, manganese (Mn) in a range from 0.1% to less than 2 wt. %, chromium (Cr) in a range from 1.2% to 6.0 wt. %, silicon (Si) in a range from 0.5% to 1.3 wt. %, aluminum (Al) in a range from 0.01% to less than 0.6 wt. %, vanadium (V) in a range from 0.01% to 0.5 wt. %, niobium (Nb) in a range from 0.01% to 0.2 wt. %, and titanium (Ti) in a range from 0.01% to 0.3 wt. %; and
a zinc coating formed on outer surfaces of the steel sheet, and
wherein a microstructure of the steel sheet comprises martensite in a range from 70-99 vol. %, austenite in a range from 3-20 vol. %, bainite in a range from 0-20 vol. %, ferrite in a range from 0-10 vol. %, and Cr-enriched carbide in a range from 0.1% to 10 vol. %, and wherein the Cr-enriched carbide includes Cr in a range from 10% to 51 wt. % and carbon (C) in a range from 49 to 90 wt. %.

8. The coated steel sheet of claim 7 , wherein a sum of a weight of the manganese (Mn) and 3 times a weight of the silicon Si is less than 5 wt. %.

9. The coated steel sheet of claim 7 , wherein a sum of a weight of the aluminum (Al) and the silicon (Si) is greater than 1.0 wt. %.

10. The coated steel sheet of claim 7 , further comprising one or more materials selected from the group consisting of tin (Sn), copper (Cu), molybdenum (Mo), and/or nickel (Ni).

11. The coated steel sheet of claim 10 , wherein the tin (Sn) is less than 0.1 wt. %, the copper (Cu) is less than 0.5 wt. %, the molybdenum (Mo) is less than 0.5 wt. %, and/or the nickel (Ni) is less than 0.5 wt. %.

12. A method of manufacturing a hot dip galvanized high strength steel sheet, comprising:
heating a steel sheet to a temperature in a predetermined range from 800° C. to 950° C. for a soaking period,
wherein the steel sheet comprises one of
a first composition comprising iron (Fe), carbon (C) in a range from 0.05% to 0.35 wt. %, manganese (Mn) in a range from 0.1% to less than 2 wt. %, chromium (Cr) in a range from 1.2% to 6.0 wt. %, silicon (Si) in a range from 0.01% to less than 0.6 wt. %, aluminum (Al) in a range from 0.5% to 1.3 wt. %, vanadium (V) in a range from 0.01% to 0.5 wt. %, niobium (Nb) in a range from 0.01% to 0.2 wt. %, and titanium (Ti) in a range from 0.01% to 0.3 wt. %; and
a second composition comprising iron (Fe), carbon (C) in a range from 0.05% to 0.35 wt. %, manganese (Mn) in a range from 0.1% to less than 2 wt. %, chromium (Cr) in a range from 1.2% to 6.0 wt. %, silicon (Si) in a range from 0.5% to 1.3 wt. %, aluminum (Al) in a range from 0.01% to less than 0.6 wt. %, vanadium (V) in a range from 0.01% to 0.5 wt. %, niobium (Nb) in a range from 0.01% to 0.2 wt. %, and titanium (Ti) in a range from 0.01% to 0.3 wt. %;

after the soaking period, cooling the steel sheet using gas cooling having a cooling rate in a predetermined range from 2° C./s to 15° C./s to a first predetermined temperature less than or equal to a second predetermined temperature; and
hot dip galvanizing the steel sheet at the second predetermined temperature to form a zinc coating, and
wherein a microstructure of the steel sheet comprises martensite in a range from 70-99 vol. %, austenite in a range from 3-20 vol. %, bainite in a range from 0-20 vol. %, ferrite in a range from 0-10 vol. %, and Cr-enriched carbide in a range from 0.1% to 10 vol. %, and wherein the Cr-enriched carbide includes Cr in a range from 10% to 51 wt. % and carbon (C) in a range from 49 to 90 wt. %.

13. The method of claim 12 , wherein the soaking period is in a range from 1 s to 10 ks.

14. The method of claim 12 , wherein the soaking period is in a range from 200 s to 500 s.

15. The method of claim 12 , wherein heating the steel sheet is performed in an atmosphere selected from a group consisting of: the group consisting of molecular nitrogen (N 2 ), and a mixture of N 2 and molecular hydrogen H 2 .

16. The method of claim 12 , wherein the first predetermined temperature is equal to the second predetermined temperature.

17. The method of claim 12 , wherein the first predetermined temperature is less than the second predetermined temperature.

18. The method of claim 17 , wherein the first predetermined temperature is in a range from 250° C. to 400° C.

19. The method of claim 17 , further comprising, after gas cooling, heating the steel sheet to the second predetermined temperature.

20. The method of claim 12 , wherein:
a sum of a weight of the manganese (Mn) and 3 times a weight of the silicon Si is less than 5 wt. %; and
a sum of a weight of the aluminum (Al) and the silicon (Si) is greater than 1.0 wt. %.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Wang Zhou
• Chai Zhisong
• Xu Wei
• Wang Jianfeng

Classifications

• C22C38/38

  with more than 1.5% by weight of manganese · CPC title

• C21D2211/002

  Bainite · CPC title

• C21D2211/001

  Austenite · CPC title

• C21D2211/008

  Martensite · CPC title

• C23C2/40

  Plates; Strips · CPC title