| As a widely used wear-resistant bearing material with high load-bearing capacity,copper-lead alloy has been irreplaceable in large ships and racing cars.Since the British scholars invented copper-lead alloys and successfully applied them on railways in the early 20th century,the continuous casting process with high efficiency and low cost has been widely used in Britain,the United States,Germany,Japan and other countries to produce copper-lead bearing shells.This process can produce copper-lead bearing material with excellent performance,which is the most suitable process.At present,there isn't a continuous casting copper-lead bearing material production line with independent property rights in China.There is a lack of research on this process,and the domestically used high-speed heavy-duty copper-lead bearings are imported products.In order to provide experience for the development of the continuous casting process of domestic copper-lead bearing materials,and promote the research of independent intellectual property rights,this paper has carried out a more comprehensive and in-depth research on this process with the support of the project.This paper builds the first continuous casting production line of copper-lead bearing materials in China,and selects CuPb22Sn2 alloy as the standard for the design of the experimental alloy composition.This paper studies the influence of process parameters on the structure and properties of the alloy and the influence on the bonding properties of bimetallic materials,provides some reference for domestic continuous casting process research.The main conclusions of the paper are as follows:The structure of the copper-lead alloy at room temperature is ?-phase+(?+?)eutectoid+Pb elementary phase,Pb and Cu have a large difference on melting point and they are not miscible,so Pb exists on the copper matrix as a single substance,which is good for lubrication.Due to the continuous casting process parameters,Pb will be distributed on the copper substrate with different morphologies.When the Sn content is 1.6%,Pb is mainly distributed on the substrate in spots and blocks.When the Sn content is 2.0%,Pb is mainly distributed in points Shaped,intermittent network or dendritic distribution on the substrate.The lower the preheating temperature of the steel back,the easier the Pb phase is deposited near the bonding interface.At a preheating temperature of 800?,the aggregation of Pb was observed near the interface,and the microstructure of the alloy layer has loose defects.The preheating temperature rises,the deposition phenomenon of Pb is improved;the faster the cooling rate,the more uniform and fine the Pb phase of the alloy layer and the higher the hardness.As the Sn content increases,the smaller the Pb phase size,and the hardness value of the alloy layer increases with the increase of tin content.The copper-lead alloy layer is well combined with the steel back under the macro,and the alloy layer elements and the steel back elements are diffused near the interface under the micro,forming a diffusion layer with a certain thickness.The thickness of the diffusion layer has no significant effect on the bonding performance of the bimetal In the bonding strength test,the bimetallic material with a preheating temperature of 1000? has a good bonding performance,the alloy layer has not peeled off from the steel back;the bimetallic material with a preheating temperature of900? has a poor bonding performance,because the alloy layer has peeled off the steel back.Through the study of continuous casting process,it can be determined that the preheating temperature of the steel back is about 1000?(not less than 900?),and the cooling rate above 350?/min can obtain a copper-lead-steel bimetal with uniform and fine structure and good interface,and within the allowable range of composition,the higher the Sn content,the higher the hardness of the alloy layer. |
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