High strength gradient steels

Patent metadata

Field	Value
Publication number	US-12553100-B2
Application number	US-202218076693-A
Country	US
Kind code	B2
Filing date	Dec 7, 2022
Priority date	Dec 7, 2022
Publication date	Feb 17, 2026
Grant date	Feb 17, 2026

Abstract

A gradient steel includes a first layer, a second layer near a first surface of the first layer, and a third layer near a second surface of the first layer. The first layer includes a first ferrite phase volume. The second and third layers include a second ferrite phase volume greater than the first ferrite phase volume. The gradient steel may also include a fourth layer near the second layer and a fifth layer near the third layer. The fourth and fifth layers may each include a third ferrite phase volume greater than the second ferrite phase volume. The gradient steel may also include a sixth layer near the fourth layer and a seventh layer near the fifth layer. The sixth and seventh layers may each include a fourth ferrite phase volume greater than the third ferrite phase volume.

First claim

What is claimed is:

1 . A gradient steel having an overall thickness represented by t and comprising:
a first layer having a first surface and a second surface parallel with the first surface, the first layer being a continuous layer comprising ferrite phase in a first volume less than or equal to about 5 vol. % and having a thickness of about 0.6(t); a second layer disposed adjacent to the first surface of the first layer; and a third layer disposed adjacent to the second surface of the first layer, the second and third layers each being a continuous layer comprising ferrite phase in a second volume greater than or equal to about 30 vol. % to less than or equal to about 40 vol. % and having a thickness of about 0.2(t).

2 . The gradient steel of claim 1 , wherein the gradient steel further comprises:
a fourth layer disposed adjacent to a surface of the second layer that faces away from the first layer; and a fifth layer disposed adjacent to a surface of the third layer that faces away from the first layer, the fourth and fifth layers each being a continuous layer comprising ferrite phase in a third volume greater than or equal to about 70 vol. % to less than or equal to about 90 vol. % and having a thickness of about 0.15(t).

3 . The gradient steel of claim 2 , wherein the gradient steel further comprises:
a sixth layer disposed adjacent to a surface of the fourth layer that faces away from the first layer; and a seventh layer disposed adjacent to a surface of the fifth layer that faces away from the first layer, the sixth and seventh layers each being a continuous layer comprising ferrite phase in a fourth volume that is about 100 vol. % and having a thickness of about 0.05(t).

4 . The gradient steel of claim 3 , wherein the first layer further comprises a bainite/tempered martensite phase and a retained austenite phase, the first layer comprising greater than or equal to about 50 vol. % to less than or equal to about 70 vol. % of the bainite/tempered martensite phase and greater than or equal to about 15 vol. % to less than or equal to about 30 vol. % of the retained austenite phase.

5 . The gradient steel of claim 4 , wherein the first layer further comprises a martensite phase, the first layer comprising greater than 0 vol. % to less than or equal to about 5 vol. % of the martensite phase.

6 . The gradient steel of claim 4 , wherein the first layer has an ultimate tensile strength that is greater than an ultimate tensile strength of the second, third, fourth, fifth, sixth, and seventh layers.

7 . The gradient steel of claim 4 , wherein the first layer comprises:
greater than or equal to about 0.2 weight percent to less than or equal to about 0.5 wt. % of carbon; greater than or equal to about 1.5 wt. % to less than or equal to about 5 wt. % of manganese; greater than or equal to about 1 wt. % to less than or equal to about 3 wt. % of silicon; greater than or equal to about 0.1 wt. % to less than or equal to about 1.5 wt. % of aluminum; and a balance of iron.

8 . The gradient steel of claim 3 , wherein the second and third layers further comprise a martensite phase, the second and third layers each comprising greater than or equal to about 30 vol. % to less than or equal to about 40 vol. % of the martensite phase.

9 . The gradient steel of claim 8 , wherein the second and third layers further comprise a bainite/tempered martensite phase and a retained austenite phase, the second and third layers each comprising less than or equal to about 20 vol. % of the bainite/tempered martensite phase and less than or equal to about 5 vol. % of the retained austenite phase.

10 . The gradient steel of claim 8 , wherein the second and third layers each comprise:
less than or equal to about 0.15 wt. % of carbon; greater than or equal to about 1 wt. % to less than or equal to about 2 wt. % of manganese; greater than or equal to about 0.2 wt. % to less than or equal to about 1 wt. % of silicon; greater than or equal to about 0.1 wt. % to less than or equal to about 0.5 wt. % of aluminum; and a balance of iron.

11 . The gradient steel of claim 3 , wherein the fourth and fifth layers further comprise a martensite phase, the fourth and fifth layers comprising greater than or equal to about 10 vol. % to less than or equal to about 30 vol. % of the martensite phase.

12 . The gradient steel of claim 11 , wherein the fourth and fifth layers each comprise:
less than or equal to about 0.1 wt. % of carbon; greater than or equal to about 0.5 wt. % to less than or equal to about 1.5 wt. % of manganese; greater than or equal to about 0.1 wt. % to less than or equal to about 0.5 wt. % of silicon; greater than or equal to about 0.1 wt. % to less than or equal to about 0.5 wt. % of aluminum; and a balance of iron.

13 . The gradient steel of claim 3 , wherein the sixth and seventh layers each have a total elongation that is larger than the total elongation of the first, second, third, fourth, and fifth layers.

14 . The gradient steel of claim 3 , wherein the sixth and seventh layers comprise:
less than or equal to about 0.02 wt. % of carbon; less than or equal to about 0.5 wt. % of manganese; less than or equal to about 0.1 wt. % of silicon; less than or equal to about 0.1 wt. % of aluminum; and a balance of iron.

15 . A gradient steel having an overall thickness represented by t and comprising:
a first layer having a first surface and a second surface parallel with the first surface, the first layer being a continuous layer comprising a first amount of carbon and a first ferrite volume less than or equal to about 5 vol. % and having a thickness of about 0.6(t); a second layer disposed adjacent to the first surface of the first layer; a third layer disposed adjacent to the second surface of the first layer, wherein the second and third layers each being a continuous layer comprising a second ferrite volume greater than or equal to about 30 vol. % to less than or equal to about 40 vol. %, a second amount of carbon being less than the first amount of carbon and having a thickness of about 0.2(t); a fourth layer disposed adjacent to a surface of the second layer that faces away from the first layer; a fifth layer disposed adjacent to a surface of the third layer that faces away from the first layer, the fourth and fifth layers each being a continuous layer comprising ferrite phase in a third volume greater than or equal to about 70 vol. % to less than or equal to about 90 vol. %, a third amount of carbon being less than the second amount of carbon and having a thickness of about 0.15(t); a sixth layer disposed adjacent to a surface of the fourth layer that faces away from the first layer; and a seventh layer disposed adjacent to a surface of the fifth layer that faces away from the first layer, the sixth and seventh layers each being a continuous layer comprising ferrite phase in a fourth volume that is about 100 vol. %, a fourth amount of carbon being less than the third amount of carbon and having a thickness of about 0.05(t).

16 . The gradient steel of claim 15 , wherein the first layer comprises a bainite/tempered martensite phase and a retained austenite phase, the first layer comprising greater than or equal to about 50 vol. % to less than or equal to about 70 vol. % of the bainite/tempered martensite phase and greater than or equal to about 15 vol. % to less than or equal to about 30 vol. % of the retained austenite phase.

17 . A gradient steel having an overall thickness represented by t and comprising:
a first layer h

Assignees

• Gm Global Tech Operations Llc

Inventors

• Bhattacharya Diptak
• Ghassemi-Armaki Hassan
• Bobel Andrew Clay
• Sachdev Anil K

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C21D2211/005

  Ferrite · CPC title

• C21D2211/008

  Martensite · CPC title

• C21D2211/001

  Austenite · CPC title

• C21D8/0236

  Cold rolling · CPC title