Study On Strip Surfacing Technologies And Mechanical And Property Of Surfacing Deposit For 2.25Cr1Mo Steel

The 2.25Cr1Mo steel is a pearlitic heat-resistant steel, which belongs to low alloy heat-resistant steel. It has been used for manufacturing some heat and corrosion resistant components in modern petrochemical industry. Moreover, it has been also received a wide application in hydrogenation reactors. Because hydrogenation reactors usually operate under such serious environments as high temperature, high pressure and rich hydrogen, the corrosion-resistant deposit has to be surfaced on the 2.25Cr1Mo steel in order to avoid the corrosion from H₂ and H₂S. In this paper, the experimental study concerning both arc-electroslag and electroslag-electroslag strip surfacing technologies, as well as mechanical property, nondestructive detection, intergranular corrosion and microstructure have been conducted on the 2.25CrlMo heat-resistant steel to provide a technical support for applying corrosion-resistant surfacing deposit in hydrogenation reactors.Through the technological experiments of both arc-electroslag and electroslag-electroslag strip surfacing on the 2.25Cr1Mo heat-resistant steel, the optimal arc-electroslag surfacing parameters are determined as follows. For the arc strip surfacing, the surfacing current is 650-700A, the surfacing voltage 26-32V, the surfacing speed 140-200 mm/min, the wire extension 30 mm, the lap width 3-8 mm, and the pre-heating temperature 200 ℃, while for the electroslag strip surfacing, the surfacing current is 700-750A, the surfacing voltage 25-30V, the surfacing speed 160-200 mm/min, the flux thickness 20-25 mm, the wire extension 30 mm, the lap width 8-10 mm, and the pre-heating temperature 200 ℃. In addition, the optimal electroslag-electroslag strip surfacing parameters are also obtained, that is, the surfacing current is 700-750A, the surfacing voltage 26³2V, the surfacing speed 140-200 mm/min, the flux thickness 20-25 mm, the wire extension 30 mm, the lap width 8-10 mm, and the pre-heating temperature 200 ℃. The experimental results about mechanical property, nondestructive detection, intergranular corrosion and microstructure reveal that the ultimate tensile strength and shear strength of both arc-electroslag and electroslag-electroslag strip surfacing deposits can satisfy the operating requirement of hydrogenation reactors, and there is no appearanceof cracks during bending. Furthermore, the welding defects and intergranular corrosion have also not been observed in both arc-electroslag and electroslag-electroslag strip surfacing deposits. The microstructure of two strip surfacing deposits is composed of austenite and ferrite, and the a phase does not appear. The morphology of the ferrite is net-like or dendritic. It is obvious that the corrosion-resistant surfacing deposit to meet completely the microstructure and property requirement for hydrogenation reactors can be achieved using the above-mentioned optimal arc-electroslag and electroslag-electroslag strip surfacing parameters.