不同焊接方法对超高强装甲钢焊接接头力学性能与组织的影响

Influence of different welding methods on mechanical properties and microstructure of laser welded joints of ultra-high strength armored steel

  • 摘要: 装甲钢MAG工艺常采用奥氏体、铁素体不锈钢焊丝,使得焊接接头抗拉强度和硬度会大幅度降低,同时造成热影响区的局部软化,降低了装甲车辆的防护性能。为了满足超高强装甲钢焊接接头强度和硬度防护要求,该文对超高强装甲钢激光焊接工艺进行了研究,分别为MAG、激光自熔焊、激光填丝焊、激光‒电弧复合焊4种焊接方法,研究接头拉伸、弯曲、硬度等性能指标及接头组织。结果表明,激光焊接头的焊缝组织为粗大的板条马氏体,MAG焊缝组织为铁素体和粒状贝氏体;对于激光焊和MAG,淬火粗晶区均为粗针状马氏体,淬火细晶区为细小的针状马氏体,不完全淬火区为马氏体与铁素体的混合组织。激光焊接头的抗拉强度和硬度远高于MAG,激光焊接头的抗拉强度可达到母材的90%以上,硬度约为母材的82%,大大提高了防护型车辆的防护性能。然而,激光焊接头的抗弯强度要低于MAG,无论面弯还是背弯,激光焊弯曲试样通常在弯曲角度10°~30°之间即发生断裂,大大低于MAG弯曲角度90°(不断裂),从而限制了其使用场景。

     

    Abstract: Austenitic and ferritic stainless steel welding wires are often used in MAG process of armored steel, which greatly reduces tensile strength and hardness of welded joints, meanwhile, causes local softening of heat-affected zone, and reduces protective performance of armored vehicles. In order to meet strength and hardness protection requirements of welded joints with ultra-high strength armored steel, laser welding process of ultra-high strength armored steel was studied in this paper, which included four welding methods, MAG, laser self-fusion welding, laser wire filler welding and laser-arc hybrid welding. Performance indicators of tensile, bending and hardness of welded joints and microstructure of welded joints were studied. The result showed that weld of laser welded joints was composed of coarse lath martensite, and microstructure of MAG weld was made up of ferrite and granular bainite. For laser welding and MAG, quenched coarse grain zone was composed of both coarse acicular martensite, quenched fine-grain zone was made up of fine acicular martensite, and incomplete quenched zone consisted of mixed microstructure of martensite and ferrite. Tensile strength and hardness of laser welded joints were much higher than those of MAG joints. Tensile strength of laser welded joints could reach more than 90% of base metal, and hardness was about 82% of base metal, which greatly improved safety of protective vehicle. However, bending strength of laser welded joints was lower than that of MAG joints. Regardless of face bending or back bending, bending samples of laser welding usually were broken when bending angle was between 10°~30°, which was much lower than bending angle 90° (not broken) of bending samples of MAG, thus limited its usage scenarios.

     

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