Tailored Properties By Post Hot Forming Processing

Abstract

A method of forming a product from an initial blank comprises subjecting the initial blank to a hot forming and press hardening operation to form the product with substantially a uniform first tensile strength. Subsequently, the product is subjected to post hot-forming processing in which a first region of the product is heated selectively to above a known temperature, using one of conduction heating, resistance heating, and induction heating. The first region is then cooled, such that the first region attains a second tensile strength that is substantially less than the first tensile strength.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. provisional application Ser. No. 61 / 358,174 filed Jun. 24, 2010, the entire disclosure of the application being considered part of the disclosure of this application, and hereby incorporated by reference.FIELD OF THE INVENTION[0002]The instant invention relates generally to metallic products having tailored properties, and more particularly to a method of producing regions of reduced hardness and reduced strength in products via post hot-forming processing.BACKGROUND OF THE INVENTION[0003]In the field of vehicle construction, more and more vehicle parts that are made of high-strength and ultra-high-strength steel are being employed in order to satisfy criteria for lightweight construction. This applies to car body construction where, in order to meet weight goals and safety requirements, for instance structural and / or safety elements such as door intrusion beams, A and B columns, bumpers, side ra...

AI Technical Summary

Benefits of technology

[0008]According to at least one embodiment of the instant invention, a method of forming a product from an initial blank is provided in which the initial blank is subjected firstly to a hot forming and press hardening operation, so as to form the product with substantially a uniform first tensile strength. In particular, the initial blank is heated to a temperature above its transition temperature Ac3, which is defined as the temperature at which transformation of ferrite into austenite is completed upon heating. By way of a specific and non-limiting example, the initial blank is heated to approximately 950° C. The heated initial blank is inserted into a cooled press having a pair of die halves, which is used for both hot forming and hardening the product. The press is subsequently closed, thereby deforming the initial blank such that it conforms to contours that are defined along facing surfaces of the die halves. Deformation and concomitant rapid cooling of the initial blank within the die halves produces the product, in which the austenite structure has been transformed into martensite structure. The tensile strength and hardness of the product is substantially uniform throughout. Optionally, the die halves are not cooled, provided that a suitably rapid cooling rate of the product can still be achieved to form the martensite structure.

Problems solved by technology

Unfortunately, the die halves must be specially made for each part, which is both laborious and costly.

In addition, special effort is required in order to minimize the extent of formation of transition regions between the different portions, since typically these transition regions exhibit properties that are less well defined than the properties of the rest of the finished product.

Unfortunately, the use of highly specialized laser equipment adds to the cost and complexity of manufacturing the component.

In addition, this approach is not well suited either to batch processing or to applications requiring the formation of substantial regions having reduced tensile strength within the component.

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