Microstructure and properties of ST14 laser tailor-welded blanks

Two types of ST14 laser tailor-welded blanks with equal thickness of 1.5 mm and 0.8 mm were measured by cupping test.The cupping test values were compared between weld and parent metal.Then,the tailor-welded blanks with unequal thickness were examined in tensile test.The fracture appearanse was inspected after tensile test.The microstructure of weld and the changes of its hardness were analysed.The tailor-welded blanks formability was investigated for the different laser welding parameter.The studied results showed,for laser tailor-welded lanks with unequal thickness,the deep-drawing properties of weld is lower than parent metal;the cupping test values of tailor-welded blanks were influenced by the welding speed,and the values were raised when the welding speed grew up.But the tensile strength of weld is better than that of parent metal.For 1.5 mm tailor-welded blanks,the laser tailor-welded blanks formability will be improved because the spiculate ferrite is yielded when the welding speed and the cooling speed raised.The small bainite will be found easily in the weld by laser welding for 0.8 mm tailor-welded blanks,and the formability of weld will be similar with the parent metal.The hardness of the weld and the heat-affected zone are higher than parent metal.