The effect of copper on temper embrittlement was investigated using four heats of ASTM A533–B steel. After being quenched and tempered, each specimen was aged at 300, 400, 500 and 600°C for various lengths of time up to 1000 hr. The impact test was carried out and several specimens were observed by means of scanning electron microscopy and Auger electron spectroscopic techniques.
The results obtained are summarized as follows:
(1) The specimens containing 0.37% copper showed temper embrittlement, and the phenomenon of the embrittlement was similar to that caused by phosphorus under the same heat treatment conditions.
(2) The specimens containing copper or phosphorus, the degree of embrittlement was affected by the aging temperature, aging time and prior austenite grain size. For the same time aging, this embrittlement showed a maximum value at about 500°C, and was still progressing after 1000 hr aging.
(3) At the fracture surface of Charpy impact test pieces, intergranular fracture was observed in the copper or phosphorus added specimen after aging treatment.
(4) After prolonged aging, the concentration of copper or phosphorus on the fracture surface was observed by Auger electron spectroscopy.