Microstructural optimization of automotive structures

Abstract

A process for hot stamping a steel component is described. The hot stamping process enables the formation of one or more regions of the component to exhibit specific physical properties different than other regions of the component. The various processes are particularly well suited for forming a variety of automobile structural members.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority upon U.S. provisional application Ser. No. 61 / 040,989 filed Mar. 31, 2008.BACKGROUND OF THE INVENTION[0002]The presently disclosed embodiments are directed to the field of automotive components, and particularly, controlling the microstructure of regions within such components by use of particular hot stamping processes.[0003]It is well known in the art to selectively heat treat vehicle components to impart desired characteristics to certain portions or regions of the component. For example, it is known to selectively heat a side intrusion door beam. Select portions of the beam may be heat treated to modify the load characteristics of the beam.[0004]It is also known to selectively cool or quench in order to harden regions of vehicle components such as bumpers. Such components can be formed to exhibit improved strength from selective austenitic-martensitic hardening. Bumpers can be formed by stamping a bump...

AI Technical Summary

Benefits of technology

[0011]In one aspect, the present invention provides a process for forming a steel component with a high strength martensite microstructure in only a portion of the component after stamping in a die, and without removal of the component from the die. The process comprises stamping a steel component in a die, the steel component having a temperature greater than about 850° C. and an austenite microstructure throughout the entire component. The process also comprises cooling a desired portion of the steel component while the component is in the die at a cooling rate of greater than about 27° C. per second, so that the microstructure of the steel component in the desired portion undergoing cooling is transformed into a martensite microstructure. A remainder portion of the steel component is cooled at a rate of less than about 27° C. per second. During the cooling operations, the die contacts the entire surface of the steel component. And, the process comprises, after formation of the martensite microstructure in the desired portion, removing the component from the die.

Problems solved by technology

Although satisfactory in many regards, these prior strategies for forming vehicle components utilize multiple operations which typically require additional manufacturing time, floor space, and capital expenditures.

And so, if it were desired to produce an engineered steel component with different physical characteristics at different regions of the component, it was generally not feasible to use currently known hot stamping processes.

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