矿用钻头牙轮牙掌渗碳及热处理工艺研究

发布时间：2019-04-15 22:16

【摘要】：牙掌和牙轮是三牙轮钻头的主要结构部件。根据使用工况,其用钢需经渗碳处理,使之表面获得较高的硬度、接触疲劳强度而心部仍保持良好的冲击韧性。合理的渗碳层碳含量和渗碳后热处理工艺是渗碳钢获得良好性能的必要条件。本文分别以渗碳钢15CrNiMo、15MnNi4Mo作为牙掌和牙轮试验用钢,通过金相组织分析、扫描电子显微镜分析、电子探针分析、X射线衍射分析、洛氏硬度分析等手段,研究了渗碳层最高碳含量、渗碳后淬火温度及方式对渗碳层、心部显微组织和力学性能的影响,确定了渗碳层最高碳含量的最佳范围和渗碳后的热处理工艺。结果表明:牙掌用15CrNiMo钢渗碳层最高碳含量应控制在1.00~1.05%为宜,此范围内热处理后渗层由针状马氏体、细小颗粒碳化物和残余奥氏体组成,其硬度和耐磨性明显较好。渗层最高碳含量低于1.00%时,渗层无明显碳化物,耐磨性大大下降;渗层最高碳含量高于1.05%时,渗层碳化物为块状或半网状,硬度和耐磨性下降。15CrNiMo钢渗碳后淬火温度应控制在810℃为宜,在180℃回火后,渗层和心部组织配合良好,渗碳层最高碳含量为1.05%试样的表层、心部硬度和心部冲击韧性分别为61.0HRC、21.5HRC和97J。淬火温度为800℃时,心部大块状铁素体较多,不利于心部强度;淬火温度为820℃时,渗层组织相对粗大,硬度和耐磨性较差。二次淬火工艺能细化晶粒,使渗碳层和心部组织配合良好,但存在工艺复杂,成本较高的问题。牙轮用15MnNi4Mo钢渗碳层最高碳含量应控制在0.85~0.90%为宜,此范围内热处理后渗层由针状马氏体和残余奥氏体组成,硬度和耐磨性较好。渗层最高碳含量低于0.85%时,渗层硬度较低,耐磨性不足;渗层最高碳含量高于0.90%时,渗层残余奥氏体量增多,渗层硬度降低。15MnNi4Mo钢渗碳后淬火温度应控制在805℃为宜,在170℃回火后,渗层和心部组织配合良好,渗碳层最高碳含量为0.85%试样的表层、心部硬度和心部冲击韧性分别为59.4HRC、37.5HRC和86J。淬火温度为800℃时,心部铁素体相对较多,不利于心部强度;淬火温度为810℃时,渗层组织相对粗大,硬度和耐磨性较差。二次淬火工艺同样能在一定程度上优化15MnNi4Mo钢渗层和心部性能。
[Abstract]:The palms and rollers are the main structural components of the three-cone bit. According to the working condition, the steel should be carburized to obtain high hardness, contact fatigue strength and good impact toughness at the center. Reasonable Carburizing layer carbon content and post-carburizing heat treatment process are the necessary conditions for Carburizing carbon steel to obtain good properties. In this paper, Carburized carbon steel 15CrNiMo and 15MnNi4Mo were used as the test steel for dental palms and pulleys respectively. By means of metallographic analysis, scanning electron microscopy, electron probe analysis, X-ray diffraction analysis, Rockwell hardness analysis, etc. The effects of the maximum carbon content of the carburized layer, the quenching temperature and the way of quenching after carburizing on the microstructure and mechanical properties of the carburized layer and the core were studied. The optimum range of the maximum carbon content of the carburized layer and the heat treatment process after carburizing were determined. The results show that the maximum carbon content of the cementitious layer of 15CrNiMo steel for dental palms should be controlled to 1.00x1.05%. After heat treatment, the cementitious layer is composed of acicular martensite, fine carbide and retained austenite. The hardness and wear resistance of the layer are obviously better. When the maximum carbon content of the layer is less than 1.0%, there is no obvious carbides in the layer, and the wear resistance of the layer decreases greatly. When the maximum carbon content of the carburized layer is higher than 1.05%, the carbides of the carburized layer are block or semi-reticulated, and the hardness and wear resistance decrease. The quenching temperature of 15CrNiMo steel after Carburizing should be controlled at 810 鈩，

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