Method and system for enhancing rivetability

Abstract

A joined sheet stack and a method and system for forming the stack are disclosed. The stack may include a steel sheet and a second sheet. The steel sheet may include a bulk portion having a first tensile strength and one or more fastener regions having a second tensile strength that is lower than the first tensile strength and a microstructure that includes tempered martensite. A fastener may extend through each fastener region joining the steel sheet to the second sheet. The method may include heat treating one or more regions of a steel sheet to form one or more fastener regions having a tensile strength that is lower than a bulk tensile strength of the steel sheet and a microstructure that includes tempered martensite. A fastener may then be inserted into the one or more fastener regions to join the steel sheet to a second sheet.

Dependencies are inferred from the claim text.