The Research On Carbon Content Control In Preparation Of Superfine Cemented Carbide

By the rapid development of manufacture industry which is represented by automobile industry, more high requirements for hard alloy tools are proposed. Superfine cemented carbide with high hardness, high strength has been paid much attention in material development nowadays. In view of the close relationship of material performance and material manufacture processing technology, the research on the structure and performance of the material of YG10 cemented carbide changing in different sintering atmospheres has been taken in this paper, and the optimization of the technology parameters is also suggested.In this paper, mixed gases (CHt and Hb) are used as sintering atmosphere .The key technical parameters such as temperature, gas pressure and critical methane concentration have been calculated by thermodynamics theroy. On the basis of the results of thermodynamics theroy, many tests have been carried on. The results of the research indicate that when the carbon content of WC and the atmosphere pressure are certain, the carbon content of sample after sintering is sensitively changed with methane concentration. When the methane concentration is high enough, the graphite could be found in the sample. The time of carbonization and the thickness of sample have heavily influenced the carbon content of sample after sintering.Because of the interference of atmosphere, the factors those influence the carbon content of the alloy in atmosphere sintering are more complicated than those in traditional vacuum sintering. So in this paper the research on the six influence factors such as carbonization time, methane concentration, carbonization temperature, WC general carbon, and sintering temperature, as well as mixed gas flow, on materialperformance such as cobalt magnetism, bending strength, rectify stupid magnetic force and hardness, have been done through the method of correct-cross test. The results of the research show, as methane concentration changing within a specific range, the carbon content of the material changes within the range of two-phase district. In order to make the carbon exchange between the sample and the atmosphere to reach balance, the carbonization time of 2. 5-3. 5 hours is necessary needed. When the carbon exchange reach balance, that increasing carbonization time can't obviously influence on the bending strength of the material. Of all factors, WC general carbon and sintering temperature are the most important factors which have much effects on material performance.The study of the influence of processing on micro-structure and performance of material shows: a certain methane concentration corresponds to a certain value of total carbon of WC. When the real total carbon of WC in the sample is higher than the certain value, the carbon in the sample decrease, otherwise, the carbon in the sample increase, and the lower the carbon content of WC, the more obvious the trend of increasing the carbon. However, the longer the carbonization time, the heaver the methane concentration, and the lower the carbon content of WC, the more obviously the crystalline grain of the sample grows up after sintering. Especially for superfine cemented carbide with low cobalt, crystalline grain unusually grows up through WC neck. In this paper, a possible theory to explain above-mentioned experimental results is proposed.Under the certain condition of sintering atmosphere, through optimizing the technology parameters, the performance of WC-10%Co cemented carbide is greatly improved. The bending strength can averagely reach to 3368 MPa(the highest reach to 3708 MPa), the hardness can reach 92.8-93.4 HRA, the density 14.21-14.32 g.cm"3. This paper established the foundation for the industry application of this technology.Xiao Zhongwen (Major in Materials) Directed by Professor Bai Jiasheng...