Research On The Influence Of Reheating And Tempering Process On Microstructures And Properties Of K65Weld Metal

The bended pipeline steel is an important component in the long distance transportingpipeline which is widely used in oil and gas transmission. It is also one of the importantstructural parts which is strict by mechanical condition. However, K65bended steel israrely reported in China, especially the research of the weld metal in K65bended steel.Therefore, it is necessary to make a study between microstructures and mechanicalproperties in K65weld metal, so that an optimizing parameter can be achieved.In this paper, in order to research the influence of reheating and tempering process onK65weld metal, a Gleeble-3500simulator is used to simulate actual production process ofK65weld metal. The tempering process is done in a boxing tempering furnace. Two kindsof chemical weld metal are researched by OM, SEM, TEM, EDS and so on. Therelationship between microstructures and mechanical properties in K65weld metal indifferent bending conditions are explored.With the increasing of the reheating temperature, the PF microstructures decrease andthe AF microstructures increase in the weld metal. As the reheating temperature furtherincreases, the BF microstructures increase. The value of hardness is increasing with therising of the reheating temperature. The value of toughness has a peak at1030oC.Compared with that before tempering, degenerate pearlite and some particlesappear in tempered steels. TEM analysis indicates that the particles include Fe3C and NbC.The hardness and toughness of K65bended steel in different tempering temperature is alsoresearched. The results indicate that the value of hardness is increasing before620oC andafter that, the value of hardness decreases with the tempering temperature arising. Thehighest value of hardness is observed in weld metal with a value of620oC. For toughness,the value of it is decreasing with the rising tempering temperature.