Preparation And Performance Study Of Cu-Based Electrical Contact Materials Based On Warm Compaction Process

Electrical contact is very important component of electrical switches. So its performancesdirectly determine the switch’s reliability and service life. With the development of electricalcontact preparation process and the increase of variety, people pay important attention to theresearch of saving silver contact materials. Generally speaking, increasing density is the bestway to increase the performance of PM parts. There are some processes that can increasedensity of PM parts, such as double press/double sinter (DP/DS), Cu infiltration, powderforging and warm compaction. It is found that, for improving the same density of parts, warmcompaction is cost effective. Therefore, it has been widely used in the preparation of iron-basedmaterials.In this paper, it is studied that the compacting pressure, compacting temperature andlubricant concentration influenced the physical and mechanical properties of Cu-basedelectrical contact materials by orthogonal experimental method as so on. Then the optimalprocess parameters were identified through analysis of comprehensive performance of contactmaterials. Additionally, at the optimal warm compaction condition, it is researched that effectof added different content RE-Cu on Cu-based electrical contact materials. Finally, the optimalcomprehensive performance of electrical contact material was prepared.Through studying effects of warm compaction process parameters on properties of contactmaterials, it is shown, in a certain temperature range, with increasing temperature, theresistivity and gaining weight decreased, and the minimum values of resistivity and gainingweight were gained at130℃. Hardness first increases and then decreases with increasingtemperature, and the maximum hardness value was obtained at160℃. Through the range anderror analysis of resistivity and hardness, compacting temperature is the main factor, andlubricant concentration is a secondary factor. Finally, the optimal warm compaction parameterswere preliminarily determined: compacting temperature is130℃, and the lubricantconcentration of admixed PS is0.7%.Through the further tests, it is suggested, for admixed lubricant ZS and PS, with theincrease of compacting pressure, the density and hardness gradually increased, while theresistivity and gaining weight decreased. And there was large changes in the sample properties before550MPa, the trend got weaken after550MPa. Secondly, with the increase of compactingtemperature, density and hardness increase within a certain range, and then decreases. Thetrend of resistivity and gaining weight is the opposite. It is indicated that, through the arcerosion of admixed0.4%ZS, the microscopic morphology of sample arc erosion was smootherat120℃compacting temperature. At other compacting temperature, the microstructuremorphology was very rough and there are many porous in welding region, that is to say that arcresistance is poor.By the orthogonal experimental range and variance analysis, it is showed that the degreeof effect of warm compaction conditions on properties is in turn from big to small followed as:the compacting pressure, compacting temperature and lubricant concentration. The optimumparameters of admixed ZS are120℃,0.4%and650MPa; while the optimal parameters ofadmixed PS are140℃,0.7%and650MPa. And the densification mechanism of warmcompaction was investigated in theory.Compared to the performances of warm compation and cold press, it is showed that thesample properties of warm compation are superior to that of cold press. In addition, thecomprehensive performance of admixed PS is better than that of admixed ZS, which is relatedto the characteristics of lubricant itself. For the warm compaction process, types of lubricantare different, the material properties are also different. Because as the temperature rises, thepowder fluidity of admixed PS is better than that of admixed ZS. the better fluidity powderhave, the more densification the sample get.At the optimal warm compaction conditions, effect of RE-Cu content on electricalcontact materials is studied. It is found that, the density and hardness decreased with theincrease of RE-Cu content, but the trend of resistivity is reverse. With the increase ofoxidation days, the gaining weight of sample added RE-Cu of0.6%La-rich increased; whenrespectively added RE-Cu of0.4%La and Ce-rich, the gaining weight is almost constant;while separately added RE-Cu of0.2%La and Ce-rich, the gaining weight of samplegradually decreases. In addition, the arc erosion capacity of contact material graduallyweakened with increase of RE-Cu content. Therefore, as increase of RE-Cu content, thecomprehensive performance of electrical contact material became bad.