Manufacturing and Performance Analysis of Q390A High-Strength Steel V-Shaped Stiffeners via Warm Drawing Process
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JMEPEG (2020) 29:5088–5103 https://doi.org/10.1007/s11665-020-04918-3
Manufacturing and Performance Analysis of Q390A High-Strength Steel V-Shaped Stiffeners via Warm Drawing Process Yushi Qi, Kefeng Li, Lili Chen, Gang Chen, Changan Shao, and Zhiming Du (Submitted April 11, 2020; in revised form May 25, 2020; published online August 20, 2020) Herein, warm drawing technology assisted by an electric current heating system is proposed to minimize the formation of wrinkles and cracks on the surface of Q390A high-strength steel V-shaped stiffeners during cold forming. V-shaped stiffeners with excellent properties were obtained by elevating the forming temperature and improving the material plasticity. The influence of temperature and tensile rate on the mechanical properties of the Q390A high-strength steel at 400-800°C was investigated. The effects of blankholder force and friction coefficient on the formed parts were simulated and analyzed by the finite element simulation software DYNAFORM. The law of heating and cooling for the formed parts during the forming process was studied through the electric current heating experiments. The forming temperature was controlled from 530 to 720 °C as the current density was maintained in the range from 7.3 to 8.5 A/ mm2. Surface oxidation, cracks, sheet warping degree, sectional thickness distribution, mechanical properties, and microstructure of the V-shaped stiffeners formed at 400 to 700 °C were analyzed. The results show that the V-shaped stiffeners formed at 600 °C possess excellent overall properties. Keywords
draw forming, electric current heating system, numerical simulation, Q390A high-strength steel, V-shaped stiffener
1. Introduction Compared with composite and alloy materials, high-strength steel has been widely used in the transportation and construction industries due to its advantages of high strength and simple preparation process (Ref 1-6). The application of high-strength steel for vehicle structural parts is a current research focus, e.g., high-strength steel can be used to satisfy the requirements of weight reduction and vehicle safety (Ref 7-11). Most military vehicles adopt high-strength steel parts with particular stiffeners, which not only guarantee strength but also satisfy the requirement of lightweight, improving on vehicle mobility and flexibility (Ref 12-16). However, the poor plasticity and forming ability of high-strength steel limit its application. In particular, the formed parts are prone to wrinkling and partial cracking (Ref 17, 18). The high tensile strength of high-strength steel is responsible for its poor plasticity at room temperature. During the forming process, high-strength steel requires an extremely large Yushi Qi, Lili Chen, and Zhiming Du, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, PeopleÕs Republic of China; Kefeng Li, Harbin First Machinery Group Co., Ltd., Harbin 150056, PeopleÕs Republic of China; Gang Chen, School of Materials Science and Engineering, Harbin Institute of Technolog
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