Influences of total reduction of area on drawing stress and tube dimension in inner spiral ribbed copper tube sinking

Abstract

This research was about the development of ultra-small inner spiral ribbed copper tube (ISRCT) with high-quality heat transfer. The production of ISRCT involved various features, such as small size and high functionality which lowered manufacturing cost. Experimental results revealed the significant parameters and the cross-sectional profile of the ISRCT after tube sinking. These were used to indicate and predict the total reduction of area as a percentage (Rt%) and determine the success of the manufacturing process. This analysis determined the optimal process parameters for the ISRCT using the tube sinking method and the effects of the ribbed dimension to attain the maximum Rt% such as the ratio of drawing stress to yield stress (σ/σy), the ratio of the wall thickness and the ribbed height to the diameter [(tw + hr)/D], the ratio of the ribbed base width and the ratio of the ribbed base circumference to the total number of ribs inside the tube [wrb/(πdrb/n)], the ratio of the ribbed tip width and the ratio of ribbed tip circumference to the total number of tube ribs [wrt/(πdrt/n)] and the ribbed spiral angle (ψo). The optimal Rt% of these five parameters was compared. From the results, the optimum Rt% on the method of the tube sinking process with ISRCT must not exceed 57 %, and the size of the ISRCT has to be precise with a gap between the ribbed base and the ribbed tip; the angle of the ribbed spiral must not be zero. The conclusions are that the optimal Rt% used in the manufacture of ISRCT is suggested to be lower than 57 %.