(1. 國核電站運行服務技術有限公司，上海 200233；
2. 湖南大學 材料科學與工程學院，長沙 410082)
摘 要: 采用CO2激光對高熱裂傾向的ZK60高強鎂合金擠壓板材進行焊接，研究焊接工藝參數(shù)對焊縫成形特征及裂紋傾向的影響規(guī)律。結(jié)果表明：激光焦點位置設定在板材上表面時，焊縫可以獲得最大的熔深和深寬比；焊接速度過高或過低均會導致焊縫深寬比的減小和熱裂紋的產(chǎn)生，采用優(yōu)化的焊接速度可得到成形形狀良好且無裂紋的焊縫；激光深熔焊匙孔形成所需的功率密度閾值在0.99×105~1.23×105W/cm2之間，為了保證深熔匙孔的穩(wěn)定，激光功率選擇的下限應不低于750 W；而功率增大到一定值以后，焊縫的熔深不再增大，功率選擇的上限應不高于750 W。高速焊接條件下，隨著焊接速度的增大，焊縫熱裂傾向增大，且開裂形式逐漸由橫向裂紋向縱向裂紋轉(zhuǎn)變。
關鍵字: ZK60鎂合金；工藝參數(shù)；焊縫成形；熱裂紋；激光焊接
（1. State Nuclear Power Plant Service Company, Shanghai 200233, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:The high cracking susceptible ZK60 magnesium alloy plates were welded by CO2 laser beam. The effects of welding parameters on the appearance and cracking tendency of the welds were studied. The results show that weld with maximum penetration and aspect ratio can be obtained when the position of focal point is adjusted on the top surface of the plate. Too higher or too lower welding speed deteriorates aspect ratio and leads to the occurrence of hot cracking. Under optimum welding speed range, the weld with high aspect ratio and free of cracking can be manufactured successfully. The threshold power density for deep penetration mode welding of ZK60 alloy is approximately between 0.99×105 and 1.23×105 W/cm2, thus the minimum laser power to sustain is about 750W, and the upper limit of recommend laser power for welding should be lower than that results in maximum penetration deep. Under the condition of higher welding speed, ZK60 alloy presents stronger cracking tendency and morphologies of cracks evolve from transverse to longitudinal with the welding speed increasing further.
Key words: ZK60 magnesium alloy; welding parameter; weld appearance; hot cracking; laser beam welding
