Full Penetration Welding of Thick Steel Plates Using 20 kW CO2 Laser
作者单位：Steel Research Center National Institute for Materials Science Tsukuba Ibaraki Japan
会议名称：《第二届先进钢铁结构材料国际会议》
会议日期：2004年
学科分类：080503[工学-材料加工工程] 08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0802[工学-机械工程] 080201[工学-机械制造及其自动化]
关 键 词：Laser Welding Porosity Hot Cracking Keyhole Denitrification
摘 要：Full penetration laser welding of thick steel plates has been carried out using a 20 kW CO laser facility. Dynamic keyhole behaviour has been observed using an x-ray transmission imaging system to elucidate the formation mechanism of the weld defects. Relatively wide optimum power range to prevent the porosity can be attained when the back surface is shielded by inert gas. However, hot cracking susceptible weld sections are formed due to significant perturbation of the keyhole caused by indissoluble back shielding gas. The keyhole is stabilised if the back surface is not shielded by inert gas. However, large porosities are easily formed near the bottom due to super saturation of nitrogen, which is supplied from the plasma formed on the back surface. A small amount of aluminium addition in the base metal is effective to prevent the porosity due to denitrification effect of aluminium, even if the back surface is not shielded.