| Fe-11Cr-2.5Mo-1Ni dual phase damping alloy has excellent mechanical properties and good damping properties.Compared with the traditional single-phase Fe-Cr damping alloy,It solves the problem that the damping performance of the latter decays rapidly under large stress,and has a broad engineering application prospect.However,as a material with integrated structure and function,it will definitely encounter connection problems in practical engineering application,such as the connection of gas transmission pipeline and bridge support frame.The performance of welding seam will directly affect the reliability of connection and the effect of vibration and noise reduction.In this paper,the damping steel plate is welded by TIG welding and 316 L welding;Then the fatigue properties,damping properties and mechanical properties of the damping steel plate after welding were studied by WDW-RD100 fatigue testing machine、Dynamic mechanical analyzer(DMA),universal tensile testing machine(RGM-4300),salt spray testing machine,Charpy impact testing machine(JB-300b),HV-50 A hardness tester.The microstructure of the weld was observed by optical microscope(Olympus GX51)and scanning electron microscope(SEM),and its composition was analyzed by energy dispersive spectroscopy(EDS),The main conclusions are as follows:(1)The microstructure of Fe-11Cr-2.5Mo-1Ni damping steel plate weld after heat treatment at different temperatures shows obvious differences.The microstructure of the weld after heat treatment at 800 ℃ for 1 hour is single-phase ferrite.The microstructure of the weld after heat treatment at 900 ℃ is martensite and ferrite.Martensite is mainly distributed in the weld fusion line and exists in the form of clusters and strips,After heat treatment at 1000 ℃,the martensite content in the weld is the most,which is widely distributed on the grain boundary and inside the grain.(2)With the increase of post weld heat treatment temperature(800 ℃,900 ℃,1000 ℃),the yield strength Rp0.2 and tensile strength rm of welded tensile specimens increase.The change rule of elongation after fracture is opposite to that.The higher the heat treatment temperature is,the lower the elongation is.The yield strength(Rp0.2)and tensile strength(Rm)of welded tensile specimens after 800 ℃-holding for 1 hour-cooling in furnace are the lowest,only 264 MPa and 395 MPa,but the elongation is the highest,39.6%.The yield strength(Rp0.2)and tensile strength(Rm)of welded tensile specimens after 1000 ℃ heat treatment are the highest,Rp0.2 is282 MPa,Rm is 413 MPa,but the elongation is the lowest,33.3%;In addition,in the tensile test,the fracture position of the sample is located in the base metal,which indicates that the strength of the weld is higher than that of the steel plate.(3)With the increase of heat treatment temperature,the Vickers hardness of the weld increases.The weld with 1000 ℃ heat treatment for 1 hour contains more martensite,so the hardness value is the highest,with 163 HV.Because the microstructure of base metal and weld with 800 ℃ heat treatment is ferrite,the hardness of the two areas is almost the same,about 143 HV.The weld samples with900 ℃ holding for 1 hour and furnace cooling heat treatment have the best impact property,236 J.The weld samples with 1000 ℃ heat treatment have more martensite,so the impact property is lower,only 190 J.(4)With the increase of heat treatment temperature(800 ℃ ~ 1000℃),the internal friction value of steel plate weld first increases and then decreases.The results show that the damping property of the steel plate weld is the best when the prestress is 24 MPa and the strain amplitude is 9.6 × 10-5 The results show that the internal friction Q-1can reach 0.056,and the attenuation of internal friction is small with the increase of prestress,which is mainly due to the activation of dislocation damping due to the increase of parallel dislocations after the introduction of martensite phase,which makes up for the decrease of magnetomechanical hysteresis damping due to the increase of applied stress to a certain extent;In addition,there is no significant difference in the damping properties between the transverse weld and the longitudinal weld after heat treatment at different temperatures,which indicates that the directivity of the weld does not have much influence on the internal friction value of the damping steel plate after welding.(5)The fatigue test of welded damping steel plate was carried out at 900 ℃-holding for 1 hour-furnace cooling heat treatment.Under the condition of stress peak of 0.6Rp0.2(3.86KN),stress ratio R of 0.1,lower peak of 0.386 KN and frequency of 10 Hz,the sample did not fracture for 2 million times of fatigue.When the stress peak of 0.8Rp0.2(5.15KN)and lower peak of 0.515 KN,the alloy fractured at the weld for 1.97 million times of fatigue,Obvious fatigue bands and striations were observed on the fracture surface by SEM. |
