激光热丝焊热输入小，填丝效率高，焊缝熔合比小，特别适合于表面堆焊及厚板的窄间隙焊接，如何获得稳定的焊丝过渡是其关键问题。采用高速摄像观察了不同工艺参数下的焊丝过渡行为，将其分为滴状过渡、熔断过渡、连续过渡、顶丝过渡4种类型，连续过渡是稳定的焊丝过渡，是获得良好焊缝成形的前提。不同焊丝过渡行为的区别表现为焊丝熔化位置不同，这是由焊丝获得热量的大小不同所导致的。获得稳定焊丝过渡的工艺控制原则是：电阻热小于焊丝熔化热，且电阻热与熔池传热之和大于焊丝熔化热。通过理论推导对熔池外焊丝温度进行了计算，发现当电阻热将熔池外焊丝加热至接近熔点时，有利于获得稳定的焊丝过渡。

With advantages of low heat input, high feeding efficiency and low penetration ratio, laser hot wire welding is fit for surfacing and joining thick plate. How to obtain the stable wire transfer is the key problem for laser hot wire welding. High speed imaging is used to observe wire transfer behavior under different welding parameters, which are divided into four kinds: drop transfer, fusing transfer, continuous transfer and wire hit transfer. The continuous transfer is the stable wire transfer and it is the assurance of good weld formation. The differences among the four wire transfer kinds show that the different wire fusion positions are decided by the wire heat. Therefore, the control principles to obtain the stable wire transfer are that wire fusion heat is larger than the resistance heat, and smaller than the total of the resistance heat and the conduct heat from the molten pool to the wire. The temperature of the wire outside the molten pool is calculated. It is found that it is beneficial to obtain the stable wire transfer when the wire temperature is close to the wire fusion point.