Study On Die-casting Technology Of Copper Alloy

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.