【作者】 杨洋；

【导师】 于宝义；

【作者基本信息】 沈阳工业大学 ， 材料加工工程， 2008， 硕士

【摘要】 随着现代制造技术的迅速发展,越来越多的零件采用热挤压、精锻、压铸等工艺成形,由于铜合金零部件具有良好的耐腐蚀性和再生率高等优点,铜合金零部件应用领域也在不断扩展。针对铜合金以往的离心三铸造方法的缺陷和其压铸模具寿命低等原因,本课题采用压铸技术,对铜合金压铸工艺、压铸模具钢组织性能和模具钢的热疲劳性能方面进行了研究。本文使用HPb59-1铜合金作为压铸材料,通过数值模拟,研究确定大型轴承中球面向心圆柱滚子保持架的压铸工艺:浇注温度1100℃,模具温度200℃,开模时间20s,快速压射速度为2.0m/s。并对铜合金轴承保持架进行了压铸试验。考虑到压铸后铸件容易产生内部气孔等缺陷,加入了真空系统,使得在压铸前模具型腔基本处于真空状态,最终基本解决了产品内部缺陷问题。在H13钢的基础上,通过对合金化学成分设计,配制出一种适合于铜合金压铸模具钢。该钢经过1150℃淬火,650℃回火,保温2小时的热处理工艺后,具有微细的显微组织和较高的强韧性配合。回火组织为细小板条状马氏体,其上分布有细小的碳化物。本文采用盐浴热疲劳试验法为手段,对配制的模具钢试样进行了热疲劳研究试验。通过不同的热处理工艺,比较热疲劳裂纹的生长情况,研究发现,经铜合金液腐蚀试样,其裂纹扩展速度明显加快。在冷热循环的过程中,模具表面的温度交替足以产生一定的压应力导致试样缺口处的塑性变形,是模具表面产生裂纹的主要原因。在相同的热处理条件下,该模具钢试样裂纹生长速度大大低于H13钢,经过400个周期后,裂纹长度为1.16mm。在1100℃淬火,630℃回火,保温2小时后,试样钢的热稳定性优于H13钢,其硬度值为50HRC,比H13钢高6.9HRC。更多还原

【Abstract】 With the high-speed development of mechanical industry, more and more parts are processed by hot extrusion、die casting and finish forging. The copper alloys are wildly used because they have the property of erosion resistance and high rate of reproduction. In order to avoid the defects of the centrifugal casting method and the shortage of casting mould life, the technique of die-casting was used, and the research on the cast craft、structure property and mould thermal fatigue properties were studied in this paper.HPb59-1 copper alloy was prepared by die-casting. through numerical simulation, the best die-casting craft of large-sized sphere centripetal roller holder has been obtained: pouring temperature was 1100℃, mould temperature was 200℃, die sinking time was 20s, the shot velocity was 2.0m/s. Furthermore, the copper alloy retainer was produced by using the parameters above. Considering the defects during the process of die-casting, such as the porosities in the casting, the vacuum system was added to it to ensure the vacuum state in the mould before cast. So the defects in the production of keeper was been solved, in order to obtain good retainer.A new kind of copper alloy die-casting mold steel was developed through optimization of alloy composition on the basis of H13. The steel has fine microstructure and higher strength and toughness. When quenching at 1150℃, tempering at 650℃, soaking for 2hours.The quenching structures of steel consist of lath martensite and a small amount of carbide.The main factor which impacts the die life is the thermal fatigue inactivation. The thermal fatigue experiment on new steel sample has been done through the method of salt bath. The growth condition of thermal fatigue crack was research through different heat processing. The rate of crack growth of the steel sample which has been corroded by copper alloy was much faster. In loop around of cold and hot, the main reason of the thermal fatigue crack was the temperature interchange in mould face which caused compression stress and produced plastic yield in sample steel gap. Under the same condition, the rate of growth of the steel sample was much lower than H13 steel. After 400 period, the length of the crack was 1.16mm. The heat stability of the sample steel was much better than H13 steel, when quenching at 1100℃, tempering at 630℃, soaking for 2hours, and its hardness was 50HRC.It was 6.9HRC higher than H13 steel.更多还原