Study On The Process And Defects Of TP2Copper Tubes

In this paper, the manufacturing process of the TP2copper tubes and thedevelopment status were studied first, and then the horizontal continuous casting wereresearched especially according to the demand of the production process and thetechnology improvement. The defects of the TP2casting billets such as cracks andblowholes that lowered the product quality greatly were studied by means of directreading spectrometer, optical microscope (OM) and scanning electrical microscope(SEM). The formation principle of the defects was analyzed by contrasting the OM andSEM results. At last, the influence of different withdraw speeds on the crystalline grainswas tested in order to study its effect on the qualities of casting billets.The results showed that: the hot cracks were distributed on the surfaces of thecasting billets randomly with irregular feature and they could grow into20mm in lengthand5mm in depth. The cracks cracked along to the grain boundaries of the columnarcrystalline grains and the cracks were oxidized seriously. So, the cracks studied belongedto the hot cracks. This kind crack occurred when the casting billet got uneven heating anduneven contraction due to primary cooling shortage during the process of the castingbillet. And then it got worse influenced by the traction resistance and secondary cooling.The blowholes were usually found on the top of the casting billet with casting “skin”over it. The blowhole emerged when the gas in the molten copper rose and gathered butwithout escaping from the liquid copper with fast solidification. Results showed that thegas from blowhole could change the solidification direction of the liquid copper and theblowhole could be prevented by weakening the primary and secondary cooling to reducethe solidification rate and increasing the time before withdrawing the casting billet. Thecrystalline grains from program5with low withdraw speed (260mm/min) were analyzedin contrast to those from program10with high withdraw speed (350mm/min). The graindistribution is not consistent with each other even under the same program which mightbe in connection with the differences from cooling system between the three casting billet,let alone under different program.The product quality was greatly improved by taking on reasonable processparameters according to the generation mechanism of the defects.