薄板TC4钛合金脉冲电子束焊接技术研究

Reaserch on TC4 Titanium Alloy Sheet Welded by Pulsed Electron Beam Welding

摘要:

脉冲电子束焊接是指将电子束流调制成脉冲方波的形式进行焊接的一种先进技术。脉冲束流能提高被焊金属蒸发率，从而提高焊接效率、增加焊缝深宽比。本文采用常规直流电子束和不同频率脉冲电子束对1.2 mm薄板TC4钛合金进行了焊接工艺试验，并对接头进行了微观组织与力学性能检测。结果表明：脉冲电子束焊接能够形成无熔合缺陷的焊缝，随着频率的增加，焊缝咬边和背面余高减小，表面成形得到改善；由于焊接热循环变化，脉冲束流可加快熔池冷却速度，细化组织晶粒；直流和脉冲电子束焊接接头拉伸时均断裂在母材区，拉伸强度不低于母材；高频脉冲电子束可提升焊接接头塑性和焊缝区、热影响区的显微硬度，频率为10 kHz时，焊接接头的断后伸长率可达14.9%，约为母材的80%，焊缝区和热影响区的显微硬度分别为375 HV和368 HV。

Abstract:

Pulsed electron beam welding is an advanced welding technique in which the beam current is modulated into a pulsed square wave. Compared with the conventional continuous electron beam welding, pulsed electron beam welding can increase the evaporation rate of the welded metal, thereby improving the welding efficiency and increasing the weld depth-to-width ratio. In this paper, the welding experiment of 1.2 mm TC4 titanium alloy sheets were carried out by conventional continuous electron beam welding and pulsed electron beam welding with different frequency. Then, the microstructure and mechanical properties of the welded joint were tested. Results show that pulsed electron beam welding can form welds without fusion defects. As the frequency increases, the weld undercut and backside weld?reinforcement decrease and the surface formation is improved. Due to the change of welding thermal cycle, the pulsed beam flow can accelerate the cooling rate of the molten pool and refine the microstructure grains. Both continious and pulsed electron beam welded joints are broken in the base metal zone during tensile process, so the tensile strength is higher than that of the base metal. The high-frequency pulsed electron beam can improve the plasticity of the welded joint and the micro-hardness of the weld zone and the heat-affected zone. When the frequency is 10 kHz, the elongation after fracture of the welded joint can reach 14.9%, which is about 80% of the base metal, and the microhardness of the welding and heat affected zone are 375 HV and 368 HV, respectively.