Research On The Welding Of Heat-resistant Alloy HP And Influence Of Its Structure And Performance In High Temperature Aging

Aimed at practice of construction in our country, this article researched weldability of Nickel-based weld metals and heat resistant alloy for ethylene cracking furnace tube. A set of reasonable welding process was drew up through analyzed the weldability of austenitic thermal resistant alloy HP. At last, the dependable and simplified weld technology was commended to ethylene cracking furnace tube construction.First, The hot crack and joint corrosion of the austenitic thermal resistant alloy were discussed in this article. And put forward to method and craft measures about preventing the austenitic thermal resistant alloy from hot crack and joint corrosion.Secondly, The weldability of centrifugally casting heat resistant alloy HP40Nb and HP45NbTi were analysed. The HP40Nb and HP45NbTi furnace tubes with thickness of 11mm and outer diameter of 125mm were butt-welded using a combined process.The HP40Nb root passes were welded by manual TIG with nickel based wire 20.70.Nb and HP45NbTi with NiR82. And the subsequent filling and top passes with wire 25-35Nb(Adavanced Technology & Materials Co.Ltd METRODE company in England). The mechanical properties of welded joint were examined and were up to the mustard. The microstructure of joint were also observed.variety of microscopic structure of the HP40-Nb ageing with high temperature in 1050℃ differ hours were observed. With the high temperature aging in differ hours, the shape and quantity of eutectic carbide also changed. Especially the shape. M7C3 become to M₂₃C₆ with shorter time on the grain boundary. And the shape of eutectic carbide was from frame shape change to massive or chain. The main emergence of eutectic carbide NbC lixiviation are in the middle of prismatical and equiaxed structureN columnar grain and Cr₂₃C₆. Expose in high temperature,The high melting-point NbC will keep with the constant physical volume score in the home position.Finally, The weld butt-joint of HP40Nb and HP45NbTi were investigated in 1050℃ high temperature aging from 72 to 200 hours. Theresults are follows: With differ hours in high temperature aging, mechanical property of two kinds of material are no variety. The eutectic carbide of HP40Nb in 1050℃ high temperature aging 200 hours is Cr₂₃C₆ and NbC, and HP45NbTi is Cr₂₃C₆. High temperature aging in 200 hours,The varieties of yield strength with two joint test samples are all smaller. The main reason is the metal alloy reserved the good heat-durability of single austenitic matrix and the dispersion carbide Cr₂₃C₆ NbC and γ' enhanced. With the high temperature aging, the enhanced phases of lixiviation of carbide and γ'have higher stability.