High strength gradient steels

Patent metadata

Field	Value
Publication number	US-2024191318-A1
Application number	US-202218076693-A
Country	US
Kind code	A1
Filing date	Dec 7, 2022
Priority date	Dec 7, 2022
Publication date	Jun 13, 2024
Grant date	—

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 comprising:
a first layer having a first surface and a second surface parallel with the first surface, the first layer comprising a ferrite phase in a first volume; 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 comprising ferrite phase in a second volume that is greater than the first volume.

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 comprising ferrite phase in a third volume that is greater than the second volume.

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 comprising a ferrite phase in a fourth volume that is greater than the third volume.

4 . The gradient steel of claim 3 , the first volume is less than or equal to about 5 vol. %, the second volume is greater than or equal to about 30 vol. % to less than or equal to about 40 vol. %, the third volume is greater than or equal to about 70 vol. % to less than or equal to about 90 vol. %, and the fourth volume is about 100 vol. %.

5 . The gradient steel of claim 4 , 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.

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

7 . The gradient steel of claim 5 , 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.

8 . The gradient steel of claim 5 , 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.

9 . The gradient steel of claim 4 , 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.

10 . The gradient steel of claim 9 , 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.

11 . The gradient steel of claim 9 , 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.

12 . The gradient steel of claim 4 , 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.

13 . The gradient steel of claim 12 , 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.

14 . The gradient steel of claim 4 , 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.

15 . The gradient steel of claim 4 , 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.

16 . The gradient steel of claim 4 , wherein an overall thickness of the gradient steel is represented by t, the first layer has an average thickness of about 0.6(t), the second and third layers have average thicknesses of about 0.2(t), the fourth and fifth layers have average thicknesses of about 0.15(t), and the sixth and seventh layers have average thicknesses of about 0.05(t).

17 . A gradient steel comprising:
a central high-retained austenite layer having a first surface and a second surface parallel with the first surface, the central high-retained austenite layer comprising a first amount of carbon; a first low-retained austenite layer disposed adjacent to the central high-retained austenite surface of the central high-retained austenite layer; a second low-retained austenite layer disposed adjacent to the second surface of the central high-retained austenite layer, wherein the first and second low-retained austenite layers each comprises a second amount of carbon, the second amount of carbon being less than the first amount of carbon; a first lean-chemistry, low-martensite layer disposed adjacent to a surface of the first low-retained austenite layer that faces away from the central high-retained austenite layer; a second lean-chemistry, low-martensite layer disposed adjacent to a surface of the second low-retained austenite layer that faces away from the central high-retained austenite layer, wherein the first lean-chemistry, low-martensite layer and the second lean-chemistry, low-martensite layer each comprises a third amount of carbon, the third amount of carbon being less than the second amount of carbon; a first ferritic layer disposed adjacent to a surface of the first lean-chemistry, low-martensite layer that faces away from the central high-retained austenite layer; and a second ferritic layer disposed adjacent to a surface of the second lean-chemistry, low-martensite layer that faces away from the central high-retained austenite layer, wherein the first ferritic layer and the second ferritic layer each comprises a fourth amount of carbon, the fourth amount of carbon being less than the third amount of carbon.

18 . The gradient steel of claim 17 , wherein the central high-retained austenite layer comprises a bainite/tempered martensite phase and a retained austenite phase,

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

• B32B33/00

  Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class · CPC title

• B32B15/011

  all layers being formed of iron alloys or steels · CPC title

• C22C38/06 Primary

  containing aluminium · CPC title

• C22C38/04

  containing manganese · CPC title