Multilayer steel and method of reducing liquid metal embrittlement

Patent metadata

Field	Value
Publication number	US-10329639-B2
Application number	US-201715668751-A
Country	US
Kind code	B2
Filing date	Aug 4, 2017
Priority date	Aug 4, 2017
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

A multilayer steel includes a core formed of transformation-induced plasticity (TRIP) steel. A decarburized layer is exterior to the core on at least one side thereof. The decarburized layer has reduced carbon content relative to the core. A zinc-based layer is exterior to the decarburized layer. The decarburized layer may have a composition of at least 80 percent ferrite, such that LME is reduced or mitigated. In some configurations, the decarburized layer is between 10-50 microns thick. A method of creating a coated advanced high-strength steel component is also provided. An apparatus for forming a coated advanced high-strength steel is also provided. The core of the multilayer steel may have a carbon weight-percent of less than or equal to 0.4. The decarburized layer of the multilayer steel may have a carbon weight-percent of less than or equal to 50 percent of the carbon weight-percent of the core.

First claim

The invention claimed is:

1. A multilayer steel, comprising:
a core formed of transformation-induced plasticity (TRIP) steel;
a decarburized layer exterior to the core, wherein the decarburized layer has a carbon weight-percent of less than or equal to 50 percent of the carbon weight-percent of the core, and has at least 80 percent ferrite; and
a zinc-based layer exterior to the decarburized layer.

2. The multilayer steel of claim 1 , wherein the decarburized layer is between 10-50 microns thick.

3. The multilayer steel of claim 1 , wherein the core includes a carbon weight-percent of less than or equal to 0.4.

4. The multilayer steel of claim 3 , wherein the decarburized layer has a carbon weight-percent of less than or equal to 20 percent of the carbon weight-percent of the core.

5. The multilayer steel of claim 3 , wherein the core has a first side and a second side, opposite the first side, and the decarburized layer is a first decarburized layer located on the first side of the core, and further comprising:
a second decarburized layer exterior to the core on the second side of the core, wherein the second decarburized layer has carbon weight-percent of less than or equal to 50 percent of the carbon weight-percent of the core, and has at least 80 percent ferrite.

6. A multilayer steel, comprising:
a core formed of transformation-induced plasticity (TRIP) steel, wherein the core has a first side and a second side, opposite the first side, and includes a carbon weight-percent of less than or equal to 0.4;
a first decarburized layer exterior to the core on the first side of the core, wherein the first decarburized layer has reduced carbon content relative to the core;
a second decarburized layer exterior to the core on the second side of the core, wherein the second decarburized layer has reduced carbon content relative to the core;
wherein the first decarburized layer and the second decarburized layer both have a composition of at least 90 percent ferrite; and
a zinc-based layer exterior to both the first decarburized layer and the second decarburized layer.

7. The multilayer steel of claim 6 , wherein the decarburized layer has a carbon weight-percent of less than or equal to 50 percent of the carbon weight-percent of the core.

8. The multilayer steel of claim 7 , wherein the decarburized layer is between 10-50 microns thick.

9. A method of creating a coated advanced high-strength steel component, the method comprising:
cold-rolling a core from transformation-induced plasticity (TRIP) steel;
annealing the TRIP steel core;
decarburizing an exposed surface of the TRIP steel core to form a decarburized layer, wherein the decarburized layer is composed of equal to or greater than 80 percent ferrite and has a carbon weight-percent of less than or equal to 50 percent of the carbon weight-percent of the core;
applying a zinc-based coating to an exterior surface of the decarburized layer to form a coated blank; and
welding the coated blank having the decarburized layer.

10. The method of claim 9 , wherein annealing the TRIP steel core and decarburizing the exposed surface of the TRIP steel core occurs in a single process, within the same apparatus.

11. The method of claim 10 , wherein decarburizing the exposed surface of the TRIP steel core includes oxidizing carbon into one of carbon monoxide and carbon dioxide.

12. The method of claim 11 , wherein decarburizing the exposed surface of the TRIP steel core occurs at a temperature of greater than or equal to about 500° C. in an environment comprising nitrogen and water.

13. The method of claim 12 , wherein decarburizing the exposed surface of the TRIP steel core occurs in an environment that is non-oxidizing to iron.

14. The method of claim 9 , wherein decarburizing the exposed surface of the TRIP steel core occurs in an environment with a dew point of greater than −5° C., such that the internal oxidation of silicon and manganese occurs within the decarburized layer.

15. The method of claim 9 , wherein decarburizing the exposed surface of the TRIP steel core occurs in an environment with a dew point of less than −5° C., such that the external oxidation of silicon and manganese occurs at the exposed surface of the decarburized layer.

16. The method of claim 9 ,
wherein decarburizing the exposed surface of the TRIP steel core forms the decarburized layer at a thickness of between 10-50 micrometers, and
wherein welding the decarburized layer of the coated blank includes resistance spot welding.

17. The method of claim 9 ,
wherein decarburizing the exposed surface of the TRIP steel core forms the decarburized layer at a thickness of between 10-50 micrometers, and
wherein welding the decarburized layer of the coated blank includes laser spot welding.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Enloe Charles
• Horvath Curt D
• Yang David
• Lu Qi
• Tao Wu

Classifications

• C21D8/02

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

• C23C2/28

  Thermal after-treatment, e.g. treatment in oil bath · CPC title

• Y10T428/24967

  Absolute thicknesses specified · CPC title

• B32B15/013

  one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium · CPC title

• B23K26/322

  involving coated metal parts (using absorbing layers on the workpiece B23K26/18) · CPC title