Effect of welding heat input on microstructure and properties of P91 steel in welding repair
To further reveal the influence law of heat input in repair welding on the microstructure and properties of the weld zone of the repair welding joint,a comparative study of the influence of heat input in welding on the welding defects,microstructure and mechanical properties of P91 steel welded joint are conducted by microstructure characterization,microhardness test,tensile test and impact test.Results show that when the heat input is 10 kJ/cm,the weld metal microstructure in the repair welding zone are parallel dendrites.When the heat input increase to 15 kJ/cm,the weld metal microstructure in the repair welding zone shows a dovetail lap shape of cross interlocking.When the heat input is further increased to 20 kJ/cm,the weld metal microstructure in the repair zone is mainly composed of parallel dendrites and a few dovetail lap dendrites interlocked.The precipitated phase in the repair welding zoneis mainly composed of NbC,Cr23 C6 and Fe2Nb(Laves phase),and the precipitated phase grows with the increase of heat input.The mechanical property analysis reveals that the strength and impact toughness of the weld metal in the repair zone increase first and then decrease with the increase of heat input.When the heat input is 15 kJ/cm,the"synergistic effect"caused by the dendrite morphology and precipitate morphology of the weld metal in the repair welding zone make the energy threshold required for the nucleation,development and expansion of the micro-crack different,and then the weld metal in the repair welding zone can maintain relatively high toughness.When the heat input is 15 kJ/cm,the strength and toughness matching of weld structure in the repair welding zone proves to bethe best.However,the impact toughness of the welding heat affected zone under three kinds of heat input is the worst due to the coarse grain size and the high constraint stress in the welding process.
万方数据
维普
