Interface Metallurgical Behavior Of Submerged Arc Brazing Of Tin-based Babbit

Due to its good anti-wear properties,tin-based babies are widely used in the preparation of wear-resistant layers on the surface of bearing components such as ships,steam turbines and aerospace.Compared with other methods for preparing tin-based Babbitt alloy layers on steel substrates,the preparation of tin-based Babbitt alloy layers by submerged arc brazing has the advantages of green manufacturing,resource saving,and good bonding properties.However,regarding tin-based pasteurization The research on interface metallurgical behavior during the submerged arc brazing of alloys is almost blank.Therefore,studying the interfacial metallurgical behavior of the submerged arc brazing of tin-based Babbitt alloy is of great significance for improving the performance of Fe/Sn dissimilar alloy joints and improving their use value.Firstly,the metallurgical behavior of the arc-gold interface during the submerged arc brazing process is analyzed.Due to the action of the arc thermal field,a cavity is formed around the arc.The cavity is filled with metal vapor and flux decomposition products mixed with flue gas.The CO₂ released by calcium decomposition forms a gas hood on the one hand,which reduces the partial pressure of harmful gases O2 and H2 in the arc zone,avoids reoxidation of the surface of the steel substrate in a high temperature environment,creates a good interface environment,and increases the liquid bar on the other hand.The stirring force of the alloy promotes the slag generated by the metallurgical reaction to float to the metal surface;at the same time,the CaO formed by the decomposition of calcium carbonate and the alkaline fluoride NaF in the flux can adjust the alkalinity of the slag,reduce the content of diffusible hydrogen,and eliminate the cause Welding defects caused by hydrogen.Calcium atoms and sodium atoms have low ionization potential and are prone to lose electrons,which can increase the arc conductivity and thus stabilize the arc.The choice of boric acid and borax as flux remover in the flux can reduce the surface tension of the droplet metal,make the droplet droplets thinner,and make it easier to achieve fine particle transition,which makes the arc more stable and thus obtains good weld formation.Secondly,the metallurgical behavior of the slag-gold interface in the submerged arc brazing process was tested.The XRD phase analysis was carried out on the slag at the interface between the submerged arc brazing flux and the Babbitt alloy layer.It was found that there was Sn?BO₂?in the interfacial layer slag.The 4 and 2Fe₂O₃.3B₂O₃ compounds show that under the action of the arc thermal field,the residual SnO₂ and Fe₂O₃ on the steel substrate and the solder surface are removed by the slag-gold interface metallurgical reaction,realizing the purity of the liquid Babbitt alloy and the steel matrix.Metal contact.The slag coexistence theory is applied to analyze the thermodynamics of the Bainite submerged arc brazing slag-gold interface metallurgical thermochemical reaction.It is found that the addition of SnO₂,Sb₂O₃ and CuO to the slag can reduce the oxidative burning loss of alloying elements and increase the slag in an appropriate amount.The content of SnO₂ is more conducive to the transition of alloying elements.The CuO and Sb₂O₃ in the slag and the Sn in the brazing material undergo interface mass transfer on the surface of the steel substrate to improve the wettability of the babbitt alloy.Then,the metallurgical behavior of the submerged arc brazing joint was studied.It was found that during the metallurgical reaction of the material-gold interface,the Fe atoms in the steel matrix will diffuse to a long distance into the liquid babbitt and form iron at the interface.Tin intermetallic phase.The first step in the growth of intermetallic compounds is determined by its growth thermodynamics.The Gibbs free energy?G of different intermetallic compounds is calculated,and the possibility of various intermetallic compounds at the interface is predicted.The results of kinetic analysis show that the growth behavior of the interface layer is controlled by the dissolution kinetics,and the peak temperature of the interface plays a decisive role in the dissolution process.When the interface temperature reaches 607°C,FeSn precipitates at the interface,and when the interface temperature cools down to The precipitation of FeSn₂ at 513°C has important theoretical guiding significance for controlling the growth of intermetallic compounds at the joint interface.Finally,the influence of the metallurgical reaction of the joint interface on the microstructure and the mechanical properties of the joint was studied.Three interface layers composed of different intermetallic compounds were obtained during the interface metallurgical reaction,which were respectively the interface layer containing FeSn₂ and the stack containing FeSn and FeSn₂.The interfacial layer of the structure and the interfacial layer containing the laminated structure of Fe₃Sn₂,FeSn and FeSn₂.It is found that the intermetallic compound layer with discontinuous pores prevents the crack from expanding.The FeSn and the hard phase compound in the form of needles or short whiskers:the?phase?SbSn?and the?phase?Cu₆Sn₅?are interdigitated in the plastic tin base.In the solid solution,it is firmly bonded to the weld seam,which acts as a“pinning effect”to further prevent crack propagation and improve the joint strength of the joint.Combined with the interface structure and shear strength test under different heat input conditions,the welding current is 180A and the welding time is 2s.The peak temperature of the interface is about1100°C.The wetting-spreading of the brazing material is sufficient,and the well-formed welding is obtained.The joint and the growth of the interface layer are effectively controlled.It consists of two compounds,FeSn₂ and FeSn,and the shear strength reaches 198 MPa.