Abstract
The weld seam characteristics of continuously roll formed and induction seam welded TRIP690 tubes were examined in this work. These tube are subsequently used in automotive hydroforming applications, where the weld seam characteristics are critical. The induction seam welds are created through a solid-state welding process and it was shown that by increasing the induction frequency by 26%, the weld seam width within the heat affected zone (HAZ) reduced due to a plateau in the hardness distribution which was a result of a delay in the transformation of martensite. 2D hardness distribution contours were also created to show that some of the weld conditions examined in this work resulted in a strong asymmetric hardness distribution throughout the weld, which may be undesirable from a performance perspective. An increase in the pressure roll force was also examined and revealed that a wider total weld seam width was produced likely due to an increase in temperature which resulted in more austenitization of the sheet edge prior to welding. The ring hoop tension test (RHTT) was applied to the tube sections created in this work. A Tensile and Notch style ring specimen were tested and revealed excellent performance for these welds due to high peak loads (~17.2 kN) for the Notch specimens (force deformation within weld) and lower peak loads (~15.2 kN) for the Tensile specimens for which fracture occurred in the base metal.
Highlights
In order to combat the effects of vehicle greenhouse gas emissions on global warming, the CorporateAverage Fuel Economy (CAFÉ) standards [1] were enacted by the United States administration and research activity into vehicle lightweighting of body-in-weight (BIW) structures has been targeted by automakers
As a result of the experimental investigation into the effect of induction seam welding parameters in roll formed TRIP690 tubes, a more thorough understanding has been gained on the impact that induction welding frequency has on the resultant weld seam characteristics, microstructure and fracture performance
Based on the measured centerline hardness distributions, the LOW and MED weld frequency cases resulted in similar hardness distributions, while the HIGH weld frequency resulted in a narrower total weld width within the heat affected zone (HAZ) due to a plateau in hardness at approximately
Summary
In order to combat the effects of vehicle greenhouse gas emissions on global warming, the CorporateAverage Fuel Economy (CAFÉ) standards [1] were enacted by the United States administration and research activity into vehicle lightweighting of body-in-weight (BIW) structures has been targeted by automakers. One of the methods used to reduce BIW weight has been the development and implementation of Advanced High Strength Steel (AHSS), which allows for down gauging of sheet metal thickness while maintaining high crash performance standards [2]. AHSS steels include Dual-Phase (DP), Complex Phase (CP), Transformation Induced Plasticity (TRIP) and Quench and Partitioned (Q&P) steels. Another approach to BIW lightweighting is through the implementation of innovative metal forming manufacturing processes such as: (1) press hardening of steel [3] and high strength aluminum alloys [4]; (2) warm forming of aluminum [5] and magnesium [6]; and (3) hydroforming of tubular steel [7]. The effect of the induction weld frequency on the resultant weld microstructure
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