Technical Study On Brazing Of Mn-Cu Alloy To Stainless Steel

It is well known that the noise and vibration are harmful in industry.Hence,the high damping Mn-Cu alloys have attracted much attention.However,a major problem with their applications is their joining with other general metals,such as stainless steel.The main reason is attributed to the large difference on their physical and mechanical properties.In this paper,the ways of vacuum brazing and induction brazing were induced to bond a Mn-Cu alloy and a stainless steel by using the Cu-Mn-Zn-Ni-Si based filler.The microstructure and the mechanical properties of the joint were analyzed with SEM and XRD etc.Meanwhile,the forming mechanism of brazing interface was also discussed.It is found that there are two phases,the a?Cu,Mn,Zn?phase and?Mn,Cu?₃Ni₂Si phase,forming in the melted Cu-Mn-Zn-Ni-Si brazing alloy,whose melting range are from 837 to 861 ?.The joint of Mn-Cu alloy/Cu-Mn-Zn-Ni-Si/stainless steel contains four regions as followed:Mn-Cu alloy/a?Cu,Mn,Zn?phase + MnO/Mn?Fe?phase/stainless steel.The highest shear strength of the joint were achieved at about135MPa.And the fracture happened between the Mn?Fe?reaction layer and brazing alloy.The effect of the brazing parameters on interfacial microstructure and shear strength of the brazed joint was also discussed.With the higher brazing temperature,the thicker Mn?Fe?reaction layer was observed in the joint.As to the specimen with the electroplated Cu coating on the surface of stainless steel,the Mn?Fe?phase was formed in the reaction layer.On the other hand,the interfacial reaction layer was composed of MnCuNi solid solution and NiFe solid solution phase due to the electroplated Ni coating on the surface of stainless steel.The interfacial microstructure of the induction brazing joint was similar to that of the vacuum brazing one,but its shearing strength reaches at about 195 MPa,much higher than that of the vacuum brazing joint.The main reason is that the heating rate is so faster that the oxide film of the stainless steel can not formed in time.As a result,the filler metal have a higher wettability to the stainless steel,the sufficient reaction between the brazing alloy and base metals happens with the MnO inclusions lessened.