Study On Welding Proces Of P92/T92Steel In The Frigid Districts Of Ningxia

Now ultra supercritical technology is becoming an important direction in Chinathermal power industry. The development of high performance heat resistant steel and itswelding technology is without doubt hindering the development of high power thermalpower unit. The fine-grain high strength P92/T92steel has been well known because ofits excellent high temperature performance. There are various alloy elements in P92/T92steel, which may cause different types of welding defects. Moreover, welding procesitself is a type of processing technology which are easily influenced to climaticenvironment and artificial factor. This subsequently limits the requirements to introducethe on-hand researching results directly all over the country. Thus, it is valuable to studythe welding proces of fine-grain high strength P92/T92steel in frigid districts such asNingxia. This branch of knowledge could be used to motivate the development of thethermal power in Ningxia.Taking P92/T92steel as the research object，this paper studied the influence of themain welding process parameters on the welding quality. And get the accurate weldingprocess parameters of P92/T92steel in Ningxia. Welding line energy has a veryimportant influence on the properties of welded joints. Thickness of Welding layerreflects directly the welding line energy. Therefore，taking P92steel as the researchobject，the mechanical properties of P92welded joint was studied，which prepared bydifferent welding layer thichness. The results showed that，when the welding layerthickness is3mm，the mechanical properties of the welded joints meets the standardrequirements，but when it is4mm，the welding joint does not meet the requirementsbecause of its lower impact toughness and higher hardness. Microstructure analysisshowed that，when the welding layer thickness is3mm，the microstructure of the weldline is tempered martensite. When the welding layer thickness is4mm， ferriteprecipitates in microstructure because of the higher welding line energy，which Seriouslyaffect the mechanical properties of welding joint.Post weld heat treatment is an essential step in the welding process of P92/T92steel.Taking T92welding joint welded by TIG as the research object，this paper studies theinfluence of Post weld heat treatment temperature on the welding quality. The resultsshowed that，with the decrease of temperature of the post weld heat treatment，thehardness of T92increased. When the temperature is720℃，hardness of the welded jointsfar exceeds the standard requirements. Metallographic results showed that，with theincrease of post weld heat treatment temperature，the number of carbide precipitines in weld line gradually increased，hardness of the welded joints also decreased. When thetemperature of post weld heat treatment is760℃，carbide precipitation enough，mechanics Performance meet the requirements.In this paper, the welding proces and paraments such as weld depth, weld current,weld voltage, heat-treatment temperature，etc., have been studied in detail, which offerguidance to the welding and heat treatment processes specification of fine-grained highstrength P92/T92steel using in1000MW ultra supercritical plants in the frigid districtsof Ningxia.