Research Of Re-crystallization Silicon Carbide Heating Element By Extrusion Molding

Silicon carbide rod as a conventional electro-heating materials has some disadvantages of big resistance discreteness, bad density, low usage temperature and short operating life. These problems restrict the technology development of silicon carbide electro-heating element industry. So it is necessary to grope new preparation technology and probe into crystal property for improving application properties and increasing operating life and developing new style electro-heating element. Currently, with the development of Chinese industry furnace and high temperature technology, the requirement of silicon carbide rod is increased, at the same time the usage temperature, operating life and property need to be heightened.This paper prepared high density SiC body for high performance SiC electro-heating element using the high pure SiC and efficient lubricate and plasticizer. The article mainly researching content including:(1)The effect of grain composition on the extrusion of SiC was studied. The optimal grain composition of SiC was obtained;(2) The effect of efficient lubricates and plasticizer on the molding pressure and body' density of extrusion was studied. The appropriate dosage of the plasticizer and lubricate was obtained.(3)The effect of the die's structure on extrusion was studies. The appropriate die's parameter which was suitable for extrusion was found.(4) Applying vacuum furnace to sinter SiC body, the optimal sintering temperature was found.(5)The cross-section pattern was analyzed through SEM. Crystallization of the fine particle and crystal structure was observed.The better extrusion effect was achieved by using 0.6wt% of polyscrylamide, 1.8wt% of oxidized polyethylene wax 6wt% moisture content of SiC pug. The highest body density (2.565g/cm3) was obtained by applying particle of 800μm,100μm,5μm. And the proportion of the particle was 7.2:1:1.8 respectively.The suitable sintering parameters were: 2×10(-2) Pa of vacuum degree, 2400°C of sintering temperature and (?)hour of sintering time; under above parameters, its sintering density, conductivity, bending strength was 2.486g/cm~3, 0.3140.cm, 39MPa respectively. Through the SEM picture, it was found that the fine particle was boiled off entirely and coarse particle was uniform distribution.These researches showed that grain composition had a great effect on extrusion. The higher body density was obtained when the coarse particle have bigger particle diameter and more content. But the body's density would become lower when the coarse particle diameter exceeded a fixed value. PX was a efficient plasticizer and oxidized polyethylene wax was a efficient lubricate. These two additives can improve internal-external lubricating of extrusion.