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The biaxial formability of 22MnB5 boron steel sheet at room and elevated temperature was investigated. The formability performance was experimentally and mumerically studied in Erichsen limit dome height tests. The numerical simulation was conducted by using commercial software Forge-2008 and that results were compared with the experimental ones. In order to describe the forming process properly, the heat transfer effect were considered.
The combination of tailor welded blank (TWB) and hot stamping often offers improved crash-worthiness and reduced mass of stamped parts in the automobile body. To investigate the formability of laser TWB and the reliability of weld line, the present study used 22MnB5 boron steel sheet of the same thickness and used the Erichsen cupping test at elevated temperatures. The effects of laser direction, die temperature, weld line positions and forming speed on formability(the limiting dome height) were studied and the results were compared with the formability of the base material.
For the purpose of improving crashworthiness qualities and maximizing weight saving efficiency, TWB's(tailor welded blanks) of quench-hardenable boron steel sheet formed by hot stamping processes has been used for automotive BIW (body in white) applications. In this work, the flow behaviors of TWB of quench-hardenable boron steel sheet were investigated in uniaxial tension tests at elevated temperature. TWB's having a uniform thickness of 1.4mm were fabricated by laser welding. Specimens with two weld line directions were used to test the mechanical property and reliability of the weld zone. After heating at 950℃ for 5min, the specimens were subjected to tension test at 650, 700 and 800℃ with a strain rate of 0.01 /s and at 700℃ with strain rates of 0.01, 0.1 and 1/s. The ultimate strength of the weld zones was higher than that of the base materials at 650 and 700℃, but was similar to the base metal at 800℃. Fracture occurred at the base material at 650 and 700℃ but at the weld zone at 800℃.
In this paper. weldability and formability of Tailored-Blank (TB) and the structural impact testing of bump beam were investigated to apply TB to automobile bumper beam. The optimal CO₂ laser welding condition for TB of SPEC and SPRC steel plates with different thicknesses was obtained. Before welding, the cross section of butt joint was prepared only by shearing without milling process. Real type bump beam was produced by two kind of forming processes such as roll-forming and press-forming, and the good formability of TB was obtained. Impact test results of bump by using pendulum and barrier were satisfied the impact regulation of bump. Finally, It may be confirmed that laser welded TB is well-balanced material in both weight reduction and production cost of automobile bump.<br/>
The roll forming process is often used to manufacture long, thin-walled products such as a pipe. The final cross-section is a comparatively simple open-channel, a closed tube section or a complex profile with several bends. In recent years, that process is often applied to the bumper beam in the automotive industries. In this study, a optimal Center Floor Cross Member manufacturing technology, model deign and proper roll-pass sequences can be suggested by forming number of roll-pass and bending angle, and also effects of the process parameters on the final shape formed by roll forming defects were evaluated.
In roll forming process, a sheet metal is continuously progressively formed into a product with required cross-section and longitudinal shape, such as a circular tube with required diameter, wall-thickness and straightness, by passing through a series of forming rolls in arranged in tandem. In this process, each pair of forming rolls installed in a forming machine play a particular role in making up the required cross-section and longitudinal shape of the product. In recent years, that process is often applied to the bumper rail in the automotive industries. In this study, a optimal Front Bumper Beam manufacturing technology, model deign and proper roll-pass sequences can be suggested by forming number of roll-pass and bending angle. And also effects of the process parameters on the final shape formed by roll forming defects were evaluated.
The surface hardening treatment such as high-frequency induction hardening method is widely used to increase fatigue life and to prevent failure of materials by increasing locally the surface hardness. This method, specially, brings an improvement of static strength by the compressive residual stress of surface due to the hardening. In this study, mechanical properties of high-frequency induction hardened SCM440 steel were investigated. These results, also, were compared with those of base metal and Q/T (tempering after quenching) treatment specimen. From test results, we showed that the partially high-frequency induction hardened SCM440 steel were more improved at static strength, surface hardness, fatigue limit and anti-wear than base metal and Q/T treatment specimen. Specially, fatigue limit of the high-frequency induction hardened SCM440 steel increased more about 52% than that of base metal and about 25% than that of Q/T specimen.