Effect of Varying Levels of Work Hardening and Bake Hardening on the Mechanical Properties of Dual Phase Steels

In most cases, the properties of a metal are evaluated in their as rolled condition, prior to any work hardening or bake hardening. But in the Automotive World, these steels get work hardened during the forming process and bake hardened in the paint shop. The goal of this paper is to evaluate the variations in the performance of Dual Phase (DP) steels and understand the most optimized method of testing and property generation. This method can then be used to extrapolate to real automotive components. Dual Phase Steels or DP Steels contain a mixture of Ferrite & Martensite from which they derive their name. They are a part of the advanced high strength and ultra-high strength steels steel family according to World Auto Steels. The Ferrite phase, with its iron content contributes to the material displaying an increased level of ductility whilst, the martensitic phase provides the steel with increased mechanical strength. These two properties together enable the steel to be highly desirable in the automotive industry with varying uses from being used as Body Panels to Crash critical components. These two critical part sets of the vehicle are often heavily simulated and tested. Over the course of this paper, we will try to understand the effects of work hardening, also referred to as Pre-Straining and bake hardening on two popularly used DP Steels. DP grade steels, ISC590Y and ISC780Y were used for the study. The aim of the study is to understand the effect of bake hardening, effect varying levels of work hardening and bake hardening on these steels and correlate it to the base data which is used in simulations. It is also important to try and understand the optimum degree of work hardening that might be required to gain the most out of these steels.