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感应钎涂粉末熔融及传热机制

Melting and heat transfer mechanism of powder by induction brazing coating

  • 摘要: 感应钎涂技术是材料表面修型提性的重要技术手段,分别选用碳钢和陶瓷作为基板进行感应钎涂试验,系统研究了粉状和膏状钎涂层温度变化规律,分析了钎涂过程热量传递方式和路径. 结果表明,感应钎涂时涂层材料不能被直接感应加热,钎涂层升温的热源几乎全部来自于钢基体的热传导,液固界面剧烈传热并梯次推进,促进了金属钎料的熔融铺展;当基材由导电且能够被感应加热的碳钢替换为陶瓷时,涂层材料升温只能依靠自身生热. 粉状钎涂料呈游离态,粉末颗粒之间及粉末颗粒与金刚石之间充满气体,基体的热量难以传导至上部,粉末难以充分熔融,而添加粘结剂的膏状钎涂料在感应过程中能快速熔化,粘结剂兼有导热、助熔和保护等多重作用.

     

    Abstract: Induction brazing coating is an important method to improve the surface quality and the performances of materials. In this study, the carbon steel and ceramic were selected as basal plates to perform the induction brazing coating tests. Then the change law of powder and paste temperatures was studied systematically, and the mode and path of heat transfer were analyzed. The results showed that the coating materials could not be heated directly by induction brazing, and the heat source of the temperature rise of the brazing coating was almost all from the heat conduction of the steel matrix. During this process, intense heat transfer occurred at liquid-solid interface, promoting the melting and spreading of powder successively. When the substrate was replaced by carbon steel, which was conductive and heated by induction, the coating material could only be heated up by itself. Powder brazing coating particles presented free state, and were filled of gas between them. As a result, the heat of the matrix was difficult to conduct the upper part, and the powder was difficult to melt fully. However, the paste brazing coating added with adhesive could melt quickly in the induction process, and the binder played the roles of heat transfer, melting promoting and protection, and so on.

     

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