Microstructure and Mechanical Property Analysis of Small Diameter G115 New Martensitic Heat Resistant Steel Tube Welded Joint
Using self-developed welding material,the welding procedure test was performed for small dimameter tube of new martensitic heat resistant steel G115 developed in China.The microstructure of the G115 welded joint was observed and its mechanical properties were tested.The results show that the welding process of the G115 small dimameter tube is good and the joint without defects can be obtained by conventional GTAW process.The room temperature tensile and bending properties of the joint meet the relevant requirements.The toughness of the weld seam in welded state is very low.After the postweld heat treatment(PWHT)at 760℃ for 1.5 h,its impact absorption energy increases from 6 J to more than 80 J.After PWHT,the fracture mode of the crack initiation area changes from cleavage to dimple,which increases the crack propagation energy.There are still fine grain heat-affected zone and softening zone in the joint,softening occurs in the intercritical heat-affected zone near the base metal.
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