Weld Seam Optimization of Roll Formed TRIP690********

点击翻译按钮获取中文摘要

Nova Steel manufactures high quality roll formed steel tubular products, primarily for the automotive industry. The straight tubes that Nova Steel produces are typically followed by bending and then hydroforming operations by a tier-1 automotive parts supplier. Currently, 75% of the automotive tubes manufactured by Nova Steel utilize conventional steel with relatively low yield strengths, while only 25% of the tubes manufactured by Nova Steel are produced from Advance-High-Strength-Steel (AHSS) where yield strengths can reach up to 900 MPa. Carmakers are implementing AHSS materials in an effort to lightweight their vehicles for improved fuel economy and reduced greenhouse gas emissions, hence, Nova Steel hopes to increase AHSS tube production to 85% by 2020. A current 5-year ($50 million) program requires Nova Steel to produce 15 different products using TRIP690, which is a novel multi-phase AHSS consisting of ferrite/retained austenite/bainite/martensite. Initial tubing trials resulted in premature burst failures at the weld seam during hydroforming, resulting in a significant scrap rate of ~15%. Due to the complex welding response of TRIP690, Nova Steel does not have the expertise to identify the effect of roll forming process parameters (Mill Speed, Weld Temperature, Weld Frequency and Contact Pressure) on the weld seam microstructure/mechanical properties. Understanding the effect of these roll forming parameters on the weld properties is the motivation behind the proposed project between Nova Steel and the University of Guelph. Large scale roll forming trials will be conducted, in-depth characterization of the welds will be completed and weld performance tests will aid to identify optimal roll forming parameters for this class of tubular material.