Laser weld distortion control by cryogenic cooling

The use of laser welding as a high quality low distortion welding process is well known. However, as a thermal welding process some distortion is still introduced which can be problematic for high precision welding of critical components. Lwo Stress No Distortion techniques (LSND) have been shown to eliminate buckling distortion in arc welding. In this paper the LSND technique has been extended to laser welding. The thermal tensioning forces are introduced via a cryogenic cooling medium that is sprayed immediately behind the weld pool. This technique has been successfully applied using direct laser diode and CO 2 laser welding to virtually eliminate buckling distortion when welding a wide range of materials including stainless steels and aluminum alloys. The results presented will include an assessment of the control of distortion as well as the effects of this technique on the weld microstructure and residual stresses in the weld zone. In-process thermal imaging of the process has also been used to show the efficiency of the process to control the thermal field in the weld zone.