Studies On Mechanical Properties Of HP40 Alloy With High Al And Low Ni

HP40 alloy has been extensively used for high temperature tubes such as ethylene cracking furnace tubes.During running the material is often destroied by high temperature oxidation,squirm invalidation and so on.Therefore we attempt to develop the HP40 steel with Al element in displacement of Ni to improve elevated temperature mechanical properties,oxidation resistance as well as decrease cost of the steel in this thesis.Five,10,15,20%content of Al in displacement of Ni in the HP40 alloy, respectively.Microstructures and mechanical properties of the steels were investigated via melting in vacuum arc furnace and solidifing in water-cooling-molds.The results showed that the strength and hardness of the alloys increased with increasing Al content, but the plastic property decreased at the same time.Then,HP40 based steels with 5～15%Al content in displacement of Ni were prepared by frequency inductive furnace melting at air atomosphere.Mechanical properties at room temperature of the alloys were also investigated.The results showed that theσ_b andσ_0.2of the alloys increased at first and then decreased with increasing Al content.Hardness of alloys obviously increased with increasing Al content.The elongation of the alloys with 5%Al alloy did not changed has not change,but then the elongation of the alloys decreased with increasing Al mass contents.With increasing Al mass fractional,the microstructure of alloys also has changed from meshy structure to ramiform and plumose structure due to precipitation of(Ni,Fe)Al.Theσ_b andσ_0.2at 900℃of the alloy with the content of 5%Al are higher than that of the other alloys and the instantaneous strength of the alloy at 900℃is great higher than that of the other alloys,but the elongation is low.The creep resistance of the alloy with 5%Al is highest.The results of the welding performance indicated that the alloy with 5%Al exhibited good joining properties.