Friction stir spot welding was successfully applied to the 1.2-mm-thick DH590 dual-phase steel plates by using a polycrystalline cubic boron nitride rotating tool. During welding, the rotation speed ranged from 600 to 1000 r/min and the penetration depth ranged from 0.1 to 0.3 mm. In the spot joints, the size of the stir zone increased with the increase in rotation speed as well as the penetration depth of the tool. Comparing with the banded ferrite and martensite structure of the base metal, a mixed microstructure of ferrite and tempered martensite, refined bainite structure and coarse martensite structure were found in the heat-affected zone, thermomechanically affected zone and stir zone of the joints, respectively. Two kinds of interfacial shapes were formed between the upper and lower steel plates, and the formation of the bonded interface was dominated mainly by the penetration depth of the rotating tool rather than the rotation speed. It was revealed that the joints with straight interfaces showed higher shear tensile loads comparing with those with hook-like interfaces. Shear tensile tests showed that the maximum shear tensile load reached about 15.56 kN when the rotation speed and penetration depth were set as 800 r/min and 0.3 mm, respectively. The specimen was fractured through plug failure mode with a total elongation of about 5.6 mm.

使用多晶立方氮化硼旋转工具，将搅拌摩擦点焊成功应用于1.2毫米厚的DH590双相钢板。在焊接过程中，转速范围为600至1000 r / min，熔深为0.1至0.3 mm。在点接合处，搅拌区域的大小随转速以及工具的穿透深度的增加而增加。与母材的带状铁素体和马氏体组织相比，在接头的热影响区，热机械影响区和搅拌区分别发现了铁素体和回火马氏体的混合显微组织，细化贝氏体组织和粗马氏体组织。上下钢板之间形成两种界面形状，结合界面的形成主要取决于旋转工具的穿透深度而不是旋转速度。结果表明，与具有钩状界面的接头相比，具有直界面的接头具有更高的剪切拉伸载荷。剪切拉伸试验表明，当转速和穿透深度分别设为800 r / min和0.3 mm时，最大剪切拉伸载荷达到约15.56 kN。通过塞破坏模式使样品断裂，总伸长约为5.6mm。剪切拉伸试验表明，当转速和穿透深度分别设为800 r / min和0.3 mm时，最大剪切拉伸载荷达到约15.56 kN。通过塞破坏模式使样品断裂，总伸长约为5.6mm。剪切拉伸试验表明，当转速和穿透深度分别设为800 r / min和0.3 mm时，最大剪切拉伸载荷达到约15.56 kN。通过塞破坏模式使样品断裂，总伸长约为5.6mm。