FRACTURE ANALYSIS OF THE SCREWED COPPER PIPE FOR HEAT EXCHANGER

FRACTURE ANALYSIS OF THE SCREWED COPPER PIPE FOR HEAT EXCHANGER WU Chaoqun LIU Yingkun Tang Weixue £¨Guangzhou Research Institute of Non-ferrous Metals, Guangzhou, 510650) ¡¡¡¡Abstract: The cracks were appeared on the screwed copper pipe for heat exchanger produced by a company after machine shaping during the installation and use. The crazing reason was investigated by macro examination, chemical analysis, metallography inspection, and electron microscope analysis. The results showed that the chemical compositions of the screwed copper pipe stress were conforming to product requirement. The machining stress wasn¡¯t completely eliminated during later heat treatment. Stress relief annealing of screwed copper pipe was incorrect and a part of acid pickling liquor was residual in the screwed copper pipe during acid cleaning. In the combined action of stress and corrosion mediem, the intergranular brittle cracking of screwed copper pipe for heat exchanger took place. Key Words: microstructure residual stress intergranular brittle cracking screwed copper pipe