【作者】 李羽；

【导师】 于宝义；

【作者基本信息】 沈阳工业大学 ， 材料加工工程， 2007， 硕士

【摘要】 21世纪工业正向着节能化和高效率方向发展，在追求降低零部件生产成本和提高效率的过程中，人们对材料的成型方法有着更深的重视。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铸造方法的缺陷和铜合金压铸模具寿命低等原因，本课题采用压铸技术，对铜合金压铸工艺和模具的热疲劳性能进行了研究。本文首先对HPb59-1铜合金试棒进行了压铸试验，研究了压铸工艺对铜合金力学性能的影响，并且得到一组最佳的压铸工艺：浇注温度为970±5℃，模具温度为240～280℃，快压射速度为5.5m／s，增压比压为50MPa。在此基础上，对铜合金轴承保持器进行了生产试验，采用上述工艺参数压铸试件，保证了铸件的力学性能，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，使得在压铸前模具形腔基本处于真空状态，最终基本解决了产品内部缺陷问题，得到良好的保持器件。重点研究了铜合金压铸模具的热疲劳失效问题，以影响模具寿命的最主要因素-热疲劳性能为出发点，采用盐浴热疲劳试验法为手段，对标准的H13模具钢梅氏试样进行了热疲劳研究试验。通过对不同前处理的试样失效裂纹的比较分析确定了H13模具钢的最佳前期热处理工艺：淬火1020℃、回火640℃。在对试验过程中经铜合金液腐蚀试样的结果分析中，发现铜元素对裂纹扩展有着很深的影响。一方面表现在铜与模具钢表面的其他元素形成不稳定相，该相在高温下脆化并且破裂，以促进裂纹扩展，另一方面，由于铜元素比较活泼，高温下很容易被氧化，使得模具钢表面孕育很多裂纹源。而在研究Pb的影响中，我们发现Pb在高温下熔化并富集在裂纹前端，进而加速裂纹的扩展。合金元素的加入在一定程度上能改善模具钢的热疲劳性能，其中本试验加入的铬元素就很大程度的提高了模具的寿命，推迟了热裂纹的扩展，主要表现在铬的含量的增加后，铬元素与钢中其他元素在高温下形成了硬质相，该相具有固溶强化的作用，进而推迟裂纹的扩展。更多还原

【Abstract】 In the 21st century, industry develops toward energy conservation and high efficiency, for pursuing the reduction on the productive cost and increase of efficiency, so the materials’ formation methods are more important than ever before. The copper alloys are wildly used because they have the property of erosion resistance and high rate of reproduction. In the light of the defects of the centrifugal casting method and the shortage of casting mould life, in the test, the technique of die-casting was adopted, and the research on the cast craft and mould thermal fatigue properties were studied.To begin with, the specimen of HPb59-1 copper alloy was prepared for die-casting, and the effect of die-casting craft on the mechanical properties of copper alloys was studied. In the result, the best die-casting craft has been obtained: pouring temperature was 970±5℃, mould temperature was 240～280℃, the shot velocity was 5.5m/s, pressure ratio was 50MPa. Furthermore, the copper alloy retainer was produced by using the parameters above. The mechanical properties have been achieved. Considering about the shortages during the process of die-casting, such as the porosities in the casting, the vaccum system was added to it to ensure the vaccum state in the mould before cast. So the shortage in the production of keeper was been solved, in order to obtain good retainer.Finally, the research on the thermal fatigue of die-casting mould of copper alloys was studied. In this problem, the most important factor was the thermal fatigue property. The thermal fatigue experiment on standard H13 steel specimen has been done through the method of salt bath. The best pre-heating treatrent craft of H13 mould steel was defined through the analysis of the contrast between specimen cracks due to different preheating treatment after the experiment: quenching temperature was 1020℃, tempering temperature was 640℃. The result also indicated that Cu element has great effect on the crack propagation. There are two aspects to cause this phenomenon. First, the unstable phases between surface of the copper alloy and the mould steel were formed. At the high temperature, the phases began to be embrittled and fractured to stimulate the crack propagation. On the other hand, Cu element can be easily oxidized at high temperature, then the surface of mould steel can be rich in cracks. During the research on the effect of element Pb to the crack propagation, the main behavior was that Pb element melted and gathered in front of the cracks at high temperature. Then the crack propagation is stimulated.It can be seen that the addition of alloy elements can improve the thermal fatigue properties of mould steel for some extent. In the experiment, the Cr element can obviously increase the mould life, and postpone the thermal crack propagation. Because the hard phases were formed between Cr element and other elements in the steel at high temperature with the content of Cr increased. The phases have the function of solution strengthening to postpone the crack propagation.更多还原