Abstract
Pure copper castings are used for water jacket at high temperatures because of their excellent heat conductivity, and so these castings are required to have high strength at elevated temperatures. A study was carried out the effects of alloying elements on the high temperature strength of pure copper castings. Alloying elements were classified into two groups according to their solubility in copper; silver and cadmium have relatively large solubility in copper, while chromium and zirconium have small solubility. By an addition of elements of the former group, we expected an increase in strength of copper as a result of solid-solution formation. In the case of the latter group, increase in strength was expected as a result of of precipitation hardening. Measurement of tensile properties and hardness was made in the range from room temperature to 600°C and that for creep rupture tests in the range from 400°C to 600°C. The experimental results were : 1) the high temperature tensile strength and hardness of pure copper castings were more improved by the addition of chromium and zisconium than by the addition of silver and cadmium, 2) creep rupture strength of copper castings was raised by addition of chromium and zirconium especially, 3) the largest difference in high temperature strength was found with respect to creep rupture strength at 400°C. 4) the type of fracture surfaces of test pieces of creep rupture tests were closely related to degrees of creep rupture strength.
