Tempering of hot-formed steel using induction heating
Tempering of hot-formed steel using induction heating
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发表时间：
2011
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通讯作者：
Olof P. Hedegärd;Martin A. T. Åslund
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作者：
Olof P. Hedegärd;Martin A. T. Åslund
热成型马氏体硼钢板具有非常高的强度，因此可用于变形应保持在最低限度的车身区域，如安全笼。然而，在机械加载期间，裂纹可能在点焊周围开始。该问题主要源于热影响区（HAZ）的屈服强度较低，导致应变局部化。在本项目中，研究了点焊前通过感应回火防止裂纹的可能性。这种想法是为了分散应变，避免焊缝周围的局部化。拉伸试验已在炉中回火和感应加热的样品上进行，有和没有点焊。结果表明，回火处理可以消除焊点的弱化效应。此外，高应变率3点落塔试验已进行全尺寸的B柱与回火法兰和不。与完全硬化相比，带回火法兰的B柱显示出良好的效果。根据结果，在裂纹萌生时观察到30%的额外动能吸收。
Hot-formed martensitic boron steel plate offers very high strength and is therefore useful in car bodies in areas where deformation should be kept to a minimum, like the safety cage. However, cracks may initiate around spot welds during mechanical loading. The problem mainly originates from the lower yield strength in the heat-affected zones (HAZ) as compared to the surrounding structure, causing strain localization. In this project the possibility to prevent cracking by induction tempering before spot welding has been investigated. The idea has been to distribute strains and avoid localization around welds. Tensile tests have been performed on samples tempered in furnace and by induction heating, with and without spot welds. The results show that the weakening effect from the spot weld can be eliminated by a tempering operation. Further, high strain rate 3-point drop tower tests have been performed on full scale B-pillars with and without tempered flanges. B-pillars with tempered flanges show promising results compared to fully hardened. According to the results additional kinetic energy absorption of 30% at crack initiation was observed.