ST14钢激光拼焊板焊缝组织及成形性能分析

对1.5mm和0.8mm两种规格的ST14钢等厚激光拼焊板焊缝部位进行杯突试验,比较焊缝与母材杯突值;再对由这两种规格组合拼焊的不等厚激光拼焊板进行单向拉伸试验,检验拼焊板经拉伸后的断裂部位;分析焊缝区组织及其硬度变化,研究激光焊接参数变化对ST14钢拼焊板成形性能的影响.结果表明,焊缝深冲性能低于母材,焊缝杯突值受焊接速度影响,随焊接速度增加而增加;激光焊缝抗拉强度高于母材;对于1.5 mm拼焊板,提高焊接速度,加快焊缝冷却,有利于生成细小的针状铁素体,可提高激光拼焊板的成形性能;而0.8 mm板焊缝生成晶粒细小的粒状贝氏体组织,可使焊缝区材料成形性能接近母材;焊缝及其热影响区的硬度高于母材硬度.

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.