Method of thermomechanical shaping a final product with very high strength and a product produced thereby

Patent metadata

Field	Value
Publication number	US-9481916-B2
Application number	US-201414231174-A
Country	US
Kind code	B2
Filing date	Mar 31, 2014
Priority date	Feb 23, 2007
Publication date	Nov 1, 2016
Grant date	Nov 1, 2016

Abstract

A method of thermomechanical shaping a final product with very high strength including the steps of: providing a coated hot-rolled and/or cold-rolled steel strip or sheet including (all percentages in wt. %): 0.04%<carbon<0.5%, 0.5%<manganese<3.5%, silicon<1.0%, 0.01%<chromium<1%, titanium<0.2%, aluminum<0.2%, phosphorus<0.1%, nitrogen<0.015% N, sulphur<0.05%, boron<0.015%, unavoidable impurities, balance iron, the steel being coated with a zinc alloy coating layer, wherein the zinc alloy includes 0.3-4.0% Mg and 0.05-6.0% Al; optionally at most 0.2% of one or more additional elements; unavoidable impurities; the remainder being zinc; cutting the steel sheet to obtain a steel sheet blank; thermomechanical shaping of the steel sheet blank to a final product with its final properties.

First claim

The invention claimed is:

1. Method of thermomechanical shaping a final product with very high strength comprising the steps of:
providing a coated hot-rolled and/or cold-rolled steel strip or sheet comprising (all percentages in wt. %):
0.04%<carbon<0.5%
0.5%<manganese<3.5%
silicon<1.0%
0.01%<chromium<1%
titanium<0.2%
aluminium<2.0%
phosphorus<0.1%
nitrogen<0.015%
sulphur<0.05%
boron<0.015%
unavoidable impurities,
balance iron,
the steel being coated with a zinc alloy coating layer, wherein the zinc alloy consists of 1.6-2.3% Mg and 1.6-2.3% Al; optionally at most 0.2% of one or more additional elements; unavoidable impurities; the remainder being zinc;

cutting the coated steel strip or sheet to obtain a steel sheet blank;
shaping the blank at ambient temperature in a first deformation step to form an ambient shaped coated steel sheet blank;
thermomechanical shaping of the ambient shaped steel sheet blank to a final product with its final properties;
wherein the thermomechanical shaping comprises heating the ambient shaped blank to a temperature above Ac1 to at least partially austenitise the ambient shaped blank, shaping the heated blank into a product at elevated temperature in a second deformation step and rapid cooling the shaped heated product to obtain the final product with its final properties.

2. Method according to claim 1 , wherein the coated hot-rolled and/or cold-rolled steel strip or sheet consists of:
0.15%<carbon<0.5%
0.5%<manganese<3.5%
silicon<1.0%
0.01%<chromium<1%
titanium<0.2%
aluminium<2.0%
phosphorus<0.1%
nitrogen<0.015%
sulphur<0.05%
boron<0.015%
Nb<0.05%
unavoidable impurities,
balance iron.

3. Method according to claim 1 , wherein the steel comprises:
0.15%<carbon<0.5%
0.5%<manganese<3%
0.1%<silicon<0.5%
0.01%<chromium<1%
titanium<0.2%
aluminium<0.1%
phosphorus<0.1%
nitrogen 0-0.01%
sulphur<0.05%
0.0005%<boron<0.015%
unavoidable impurities,
balance iron.

4. Method according to claim 1 , wherein the steel comprises:
0.15%<carbon<0.40%
0.8%<manganese<1.5%
0.1% silicon<0.35%
0.01%<chromium<1%
nitrogen 0-0.01%
titanium<0.1%
aluminium<0.1%
phosphorus<0.05%
sulphur<0.03%
0.0005%<boron<0.01%,
unavoidable impurities,
balance iron,
wherein Ti>3.4N.

5. Method according to claim 1 , wherein the steel comprises:
0.15-0.25% C
1.0-1.5% Mn
0.1-0.35% Si
max 0.8% Cr
max 0.1% Al
0-0.05% Nb
0-0.01% N
0.01-0.07% Ti
phosphorus<0.05%
sulphur<0.03%
0.0005%<boron<0.008%
unavoidable impurities,
balance iron.

6. Method according to claim 1 , wherein the steel comprises at least 0.0015% B.

7. Method according to claim 1 , wherein the steel comprises:
0.15-0.25% C
1.0-1.5% Mn
0.1-0.35% Si
max 0.8% Cr
max 0.1% Al
0-0.05% Nb
0-0.01% N
0.0015-0.008% B
0.01-0.07% Ti wherein Ti>3.4N
unavoidable impurities
balance iron.

8. Method according to claim 1 , wherein the steel comprises Ti-3.4N<0.05%.

9. Method according to claim 1 , wherein the final product is an automotive part.

10. Structural and/or anti-intrusion or substructure parts for a land motor vehicle selected from the group consisting of a bumper beam of a car, a door reinforcement or a B-pillar reinforcement produced according to claim 1 .

11. Method according to claim 1 , wherein the steel comprises Ti-3.4N<0.02%.

12. The method of claim 1 , wherein the cooling is at a rate higher than the critical cooling rate.

13. The method of claim 1 , wherein the cooling is at a rate higher than the critical cooling rate and the forming at elevated temperature and the cooling are performed within the forming press.

14. The method of claim 1 , wherein any excess material is trimmed from the ambient shaped blank after the first deformation step prior to heating.

15. Method of thermomechanical shaping a final product with very high strength comprising the steps of:
providing a coated hot-rolled and/or cold-rolled steel sheet blank, the steel comprising (all percentages in wt. %):
0.04%<carbon<0.5%
0.5%<manganese<3.5%
silicon<1.0%
0.01%<chromium<1%
titanium<0.2%
aluminium<2.0%
phosphorus<0.1%
nitrogen<0.015%
sulphur<0.05%
<boron<0.015%
unavoidable impurities,
balance iron,
the steel being coated with a zinc alloy coating layer, wherein the zinc alloy consists of 1.6-2.3% Mg and 1.6-2.3% Al; optionally at most 0.2% of one or more additional elements; unavoidable impurities; the remainder being zinc;
thermomechanical shaping of the steel sheet blank to a final product with its final properties;
wherein the thermomechanical shaping comprises heating the blank to a temperature above Ac1 to at least partially austenitise the blank, shaping the blank into a product at elevated temperature and rapid cooling the product to obtain the final product with its final properties.

16. The method of claim 15 , further comprising shaping the blank at ambient temperature in a first deformation step to form an ambient shaped coated steel sheet blank prior to said thermomechanical shaping.

17. Method according to claim 15 , wherein the steel comprises:
0.15%<carbon<0.5%
0.5%<manganese<3%
0.1%<silicon<0.5%
0.01%<chromium<1%
titanium<0.2%
aluminium<0.1%
phosphorus<0.1%
nitrogen 0-0.01%
sulphur<0.05%
0.0005%<boron<0.015%
unavoidable impurities,
balance iron.

18. Method according to claim 15 , wherein the steel comprises:
0.15-0.25% C
1.0-1.5% Mn
0.1-0.35% Si
max 0.8% Cr
max 0.1% Al
0-0.05% Nb
0-0.01% N
0.0015-0.008% B
0.01-0.07% Ti wherein Ti>3.4N
unavoidable impurities
balance iron.

19. Method according to claim 15 , wherein the steel comprises Ti-3.4N<0.05%.

20. Method according to claim 15 , wherein the final product is an automotive part.

21. Structural and/or anti-intrusion or substructure parts for a land motor vehicle selected from the group consisting of a bumper beam of a car, a door reinforcement or a B-pillar reinforcement produced according to claim 15 .

22. Method according to claim 15 , wherein the steel comprises Ti-3.4N<0.02%.

23. The method of claim 15 , wherein the cooling is at a rate higher than the critical cooling rate.

24. The method of claim 15 , wherein the cooling is at a rate higher than the critical cooling rate and the forming at elevated temperature and the cooling are performed within the forming press.

Assignees

• Tata Steel Ijmuiden Bv

Inventors

• Vlot Margot Julia
• Van Tol Ronald Theodoor

Classifications

• C21D8/00 Primary

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/18

  containing chromium · CPC title

• C23C2/26

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

• C21D2211/005

  Ferrite · CPC title

• C21D1/18 Primary

  Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62) · CPC title