【摘要】：牙掌和牙輪是三牙輪鉆頭的主要結(jié)構(gòu)部件。根據(jù)使用工況,其用鋼需經(jīng)滲碳處理,使之表面獲得較高的硬度、接觸疲勞強(qiáng)度而心部仍保持良好的沖擊韌性。合理的滲碳層碳含量和滲碳后熱處理工藝是滲碳鋼獲得良好性能的必要條件。本文分別以滲碳鋼15CrNiMo、15MnNi4Mo作為牙掌和牙輪試驗(yàn)用鋼,通過金相組織分析、掃描電子顯微鏡分析、電子探針分析、X射線衍射分析、洛氏硬度分析等手段,研究了滲碳層最高碳含量、滲碳后淬火溫度及方式對(duì)滲碳層、心部顯微組織和力學(xué)性能的影響,確定了滲碳層最高碳含量的最佳范圍和滲碳后的熱處理工藝。結(jié)果表明:牙掌用15CrNiMo鋼滲碳層最高碳含量應(yīng)控制在1.00~1.05%為宜,此范圍內(nèi)熱處理后滲層由針狀馬氏體、細(xì)小顆粒碳化物和殘余奧氏體組成,其硬度和耐磨性明顯較好。滲層最高碳含量低于1.00%時(shí),滲層無明顯碳化物,耐磨性大大下降;滲層最高碳含量高于1.05%時(shí),滲層碳化物為塊狀或半網(wǎng)狀,硬度和耐磨性下降。15CrNiMo鋼滲碳后淬火溫度應(yīng)控制在810℃為宜,在180℃回火后,滲層和心部組織配合良好,滲碳層最高碳含量為1.05%試樣的表層、心部硬度和心部沖擊韌性分別為61.0HRC、21.5HRC和97J。淬火溫度為800℃時(shí),心部大塊狀鐵素體較多,不利于心部強(qiáng)度;淬火溫度為820℃時(shí),滲層組織相對(duì)粗大,硬度和耐磨性較差。二次淬火工藝能細(xì)化晶粒,使?jié)B碳層和心部組織配合良好,但存在工藝復(fù)雜,成本較高的問題。牙輪用15MnNi4Mo鋼滲碳層最高碳含量應(yīng)控制在0.85~0.90%為宜,此范圍內(nèi)熱處理后滲層由針狀馬氏體和殘余奧氏體組成,硬度和耐磨性較好。滲層最高碳含量低于0.85%時(shí),滲層硬度較低,耐磨性不足;滲層最高碳含量高于0.90%時(shí),滲層殘余奧氏體量增多,滲層硬度降低。15MnNi4Mo鋼滲碳后淬火溫度應(yīng)控制在805℃為宜,在170℃回火后,滲層和心部組織配合良好,滲碳層最高碳含量為0.85%試樣的表層、心部硬度和心部沖擊韌性分別為59.4HRC、37.5HRC和86J。淬火溫度為800℃時(shí),心部鐵素體相對(duì)較多,不利于心部強(qiáng)度;淬火溫度為810℃時(shí),滲層組織相對(duì)粗大,硬度和耐磨性較差。二次淬火工藝同樣能在一定程度上優(yōu)化15MnNi4Mo鋼滲層和心部性能。
[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，

本文編號(hào)：2458536