Abstract: With the continuous improvement of China's ultra supercritical coal-fired power unit technology,the unit parameters are becoming higher and higher.At present,the 630℃parameter ultra supercritical unit has basically matured,and the new martensitic heat-resistant steel G115 has become the only candidate material for the main steam pipeline of China's 630℃ultra supercritical unit.It will be applied to the header,steam pipeline,heating surface pipe and other components of ultra supercritical boilers.The on-site welding and heat treatment process of this steel is still in the exploratory research stage.This article conducts research on the welding and heat treatment processes of the new martensitic heat-resistant steel G115,systematically analyzes the performance of G115 steel compared to other existing similar steel types,grasps the welding performance of G115 steel,and combines the key welding technologies of high alloy large diameter thick wall pipelines that our company has mastered to develop feasible welding and heat treatment processes.After inspection and testing,the performance meets the requirements,Provide technical reserves for the promotion and application of domestic new martensitic heat-resistant steel G115.