The Research On Surface Hardening Technology And Self-sharpening Effects Of Hammers In Hammer Mills

The hammer is one of the most important but easy-weared part of the hammer mills, the passivation wear of hammers can not only affect the efficiency of processing but also reduce the quality of feed. In order to enhance the effective working time of hammers and improve the processing quality of feed, obtaining three kinds of self-sharpening hammers whose carburized layer thickness separately were 0.3mm,0.5mm,0.8mm by using local gas carburizing, quenching and tempering heat treatment process for the hammers. And then these self-sharpening hammers were installed in the grinder whose model is SFSP60X60 to start wear test. Analyzing three kinds of hammers'microstructure and hardness variation; the weight wear and size wear variation in the wear process; the surface morphology variation and so on. The main conclusions are as follows:(1) Through the microstructure observation and the hardness determination of samples, analyzed the relationships between the carburized layer thickness and hardness gradient. Data shows: the thicker the carburized layer is, the more gently the hardness gradient is.(2) On the basis of data which obtained from actual production test, analyzed the weight wear and size wear variation of three kinds of carburized layer thickness hammers in each wear stage. Test confirmed: the relationship between wear and time of hammer and soft materials resembles in the relationship between wear and time of metal and metal to some extent.(3) After contrastively analyzed the macro-morphology of wear of three kinds of carburized layer hammers, the results confirmed that the 0.3mm carburized layer hammers have large mount of wear and non-self-sharpening effect; the 0.8mm carburized layer hammers form the self-sharpening, but easy to produce chipping because of the high hardness of the edges and corners; the 0.5mm carburized layer hammers have the relatively best self-sharpening effect .(4) Considering the processing time, production costs, wear resistance self-sharpening effect and so on, the 0.5mm carburized layer hammers have the best self-sharpening effect and wear resistance.