Study On Microstructure And Properties Of MIG Welded New Type Cast Hot Work Die Steel Joints

Recently, the study on the cast die materials received rapid development. The cast replacing forge not only reduces the waste of resource and energy, but also reduces the cost of the mould and shortens the produce cycle of the mould. However, it is hard to avoid defects of pore and slag etc. in the casting procedure of the mould, the mishandling of processing oversize etc. in the mould processing and the failure forms of pitting and thermo-mechanical fatigue etc. in the using process. It is worth repairing mould. At present, the regular method of repairing mould is the welding method. MIG has been widely used due to its advantage of easier operation, higher automatization and produce efficiency.This paper takes the welded joint of the new type cast hot work die steel with MIG method and the flux-cored wire which is developed by Jilin University as the research object. Optical microscope (OM), scanning electron microscopy(SEM), hardness tests, tensile property tests and crack sensitivity tests have been carried out to study the microstructural characterization of the welded joint, the effect of welding parameters(welding heat input, welding current, welding speed) on the joint microstructure and hardness and the joint property and crack sensitivity. By analyzing the experimental data, some conclusions have been drawn as follows: (1) The as-welded joint of the new type cast hot work die steel is composed of weld zone, heat affected zone (HAZ) and base metal zone. The microstructure of...