Numerical Simulation Of The Dynamic Behavior Of CMT Welding Pool And Its Application In Large Metal Components Of Power Plant

CMT (Cold Metal Transfer) technology is a novel short circuit transfer technology toachieve metal droplet transfer under no-current condition, this approach has a smaller amountof heat input during welding than the traditional MIG/MAG. This work is sponsored by theproject“Research on new welding technology of large metal components in power plants”.For the problems of repair welding, it is significant to apply the low heat input characteristicsof CMT technology to large metal components in power plants to obtain a low dilution rate ofthe cladding layer.This work intends to simulate the CMT welding temperature field based on the finiteelement software ANSYS13.0. An appropriate geometric model is established usingsecondary development function of APDL language. A computing program based on doubleellipsoidal moving heat source model is written. The dynamic behavior of the CMT weld poolis simulated, the materials are mainly Q235and16Mn steels which are used widely in powerplants. Using the distribution of welding temperature field, the effects of welding current,welding voltage, welding speed and wire feed speed on the CMT welding heat input areanalyzed. The weld thermal cycle curves, shapes and sizes of the welds are verified byexperiments.In this work, the mechanical properties of CMT welded joints of Q235steel are studied.The organizations of the weld zone, the transition zone and the zone far away from weld areinvestigated by metallographic analysis. The high temperature tensile tests of CMT weldingjoints were further analyzed. The fracture sections of CMT welded joints are investigated bySEM.This work is for the welding process to repair large metal components in the powerplant, applies CMT technology to achieve cladding welding process on the surfaces, andadopts ASME standards to assess the welding process qualification. The welding processunder low preheated temperature and low interlayer temperature is achieved to improve thereliability of the joints. The work has great effect to guarantee the safe operation of the units,to reduce the failure outage impact on the grid security, to improve power grid to withstandthe uncertainty of applying high-parameter and large capacity units.