Research On High-performance Wear-resistant Tin Bronze Alloy And Its Advanced Processing Technology

The wear-resistant tin bronze is mainly used to produce the wear parts such asbearings, impellers, bushes and gears due to its good wear&corrosion resistance,magnetic resistance and low temperature toughness. With the increasing of tin contentin industrial tin bronze alloy (3-14wt.%Sn), the wear resistance of alloy will beimproved while its density and plasticity decreased. For the tin bronze with tin contentmore than8%, the serious problems such as lower density, more as-cast defects andobvious segregation will be caused by using the traditional melting&casting processfor alloy preparation. Furthermore, due to the higher tin content, the plasticity of alloyis extremely inferior and its performance and microstructure are difficult to improvethrough plastic forming process. Therefore, according to the high tin wear-resistant tinbronze alloy with tin content greater than8%, it is urgently necessary to seek anadvanced processing technology, which can improve the density and segregationsimultaneously of alloy.The Cu-10Sn-4Ni-3Pb tin bronze alloy that the range of tin content is8-12%wastaken as the research object in this paper. The experiments on traditional melting&casting technology and solidification&crystallization under different pressuresprocesses were investigated respectively, and then the different homogenizationannealing tests of tin bronze alloy prepared by solidification&crystallization under680MPa pressure were also studied,which attemptted to study the improvement ofannealing process on the dendritic segregation degree. The main properties such asdensity, hardness, tensile strength and elongation of as-cast, as-extruded and as-annealed Cu-10Sn-4Ni-3Pb tin bronze alloy prepared by different processes weretested, and then their microstructures were observed and analyzed by using theOLYMPUSPMG3optical microscope (OM), JSM-5610LV scanning electronmicroscopy (SEM) and energy dispersive X-ray spectrum (EDS) and JEM-2100transmission electron microscope (TEM). As the whole, the following points are considered as the main ideas:The properties of Cu-10Sn-4Ni-3Pb tin bronze alloy prepared by solidification&crystallization under pressure process are superior to that of prepared by traditionalmelting&casting technology, and their properities have been improved with theincreasing of pressures. In Comparison with the remarkably dendrite microstructureand the severe dendritic segregation of as-cast alloy which is mainly consist of α solidsolution,(α+δ) eutectoid and lead simple substance phase, the dendrite has beengradually disappeared with the unit extrusion pressure increasing. Within the range ofexperiments, the properties of Cu-10Sn-4Ni-3Pb tin bronze alloy prepared bysolidification&crystallization under680MPa pressure have been improvedremarkably and its grain refined obviously, the density and hardness have beenincreased by3.4%and29.3%respectively, and the tensile strength and elongationimproved by53%and42.9%separately, compared with that of as-cast alloy preparedby traditional process. The dendritic segregation has been alleviated ulteriorly after thehomogenization annealing, especially after750℃×8h annealed. A large number ofannealing twins have been occurred in alloy and the distribution of lead simplesubstance phase has been more dispersed among the grain and grain boundary.Based on the experimental study, the solidification&crystallization underpressure process has been prepared the Cu-10Sn-4Ni-3Pb tin bronze alloys, whichhave higher density and exceptional mechanical properties and its segregation beenimproved significantly. Within the range of experiments, it is suggested that theprocessing technology parameters of Cu-10Sn-4Ni-3Pb tin bronze alloy is thesolidification&crystallization under680MPa pressure, and the subsequenthomogenization annealing process is heated to750℃and then air-cooled after thermalinsulation8hours.