Study On Electro-slag Metallurgy Of Mn-Cu Alloys

As an important part of ship propulsion system,the noise of propeller not only interferes with the normal operation of the underwater acoustic equipment of the ship,but also is the clue of the discovery of the underwater acoustic equipment of the enemy ship.Reducing the noise of propeller is an important task in the modernization of our navy.At present,the most effective method is to use high damping alloy.Mn-Cu damping alloy is the only high damping alloy that can be used as marine propeller material at present.It not only has the high strength of metal material,but also has the high damping performance of non-metal material,and has outstanding performance in vibration reduction and noise reduction.The traditional high damping alloy is basically made by casting process.Although it has good mechanical properties and damping properties,its corrosion resistance in the marine environment is poor due to the serious problem of Mn segregation.Electroslag remelting technology has been used to prepare high-end alloys.Its products are famous for their high purity and uniform structure.In this paper,the electroslag remelting process of high damping alloy is mainly studied.Taking Cu Mn50 alloy as an example,the slag system proportion suitable for the electroslag remelting of Mn-Cu damping alloy is sought.The process parameters of electroslag remelting are designed and optimized.Through ZEISS metallographic microscope,scanning electron microscope,MFDL-100 slow strain rate stress corrosion testing machine and elastic modulus measuring device,the electroslag remelting before and after is carried out The microstructure and properties of the alloy were tested.After testing and calculating the melting point,basicity,viscosity,density,conductivity and other physical and chemical properties of different slag systems,Na F-Ca F₂-Na₃Al F₆ternary slag system is finally adopted.The distribution ratio of each slag system is w?Na F?:w?Ca F₂?:w?Na₃Al F₆?=50:45:5.The electrode rod size is?60 mm×1250 mm,the crystallizer size is?120 mm×4600 mm,the secondary voltage at the furnace mouth is about40V,and the slag content is about 2.8 kg.In order to explore the influence of current on the metallurgical effect of ESR,two ESR experiments were carried out with different current systems.The first one is about 2.5 k A in the stable period of ESR,and the second one is about 2.0ka in the stable period of ESR.The properties of Cu Mn50 alloy before and after electroslag remelting were characterized and analyzed.The results show that the properties of the electroslag ingot obtained under different current systems are slightly different,but the properties of the alloy are improved.In this test,the composition of the alloy basically remains unchanged after electroslag remelting.In the first furnace,the tensile strength and yield strength of the alloy are increased by 150 MPa and 120 MPa respectively,the elongation after fracture is almost doubled,the impact toughness is increased by 30%,the corrosion rate of the alloy in seawater is reduced by 50%,the maximum pitting depth is reduced by 2/3,and the stress corrosion resistance of the alloy is also greatly improved.In dry air,the fracture strength is increased by 246 MPa,and in artificial seawater,the fracture strength is increased by 246MPa Increase about 30 MPa.The properties of the second furnace alloy are slightly lower than that of the first furnace.After electroslag remelting,the phase of the alloy changed,bcc-?-Mn phase disappeared,fcc-Mn Cu phase increased and Mn rich area increased.However,due to the large refinement of the alloy grain,the transformation point Ms of fcc?fct martensite decreased,and martensite was not easy to form,which led to the decrease of the damping property of the alloy,but the alloy still had high damping property.