EFFECTS OF COPPER AND PHOSPHORUS ON TEMPER EMBRITTLEMENT OF MN-MO-NI LOW-ALLOY STEEL (ASTM A533-B)

Four heats of ASTM A533-B steel, one of them containing 0. 37% Cu (instead of the usual 0. 15%) and one containing 0. 060% P (instead of 0. 010%) were investigated. Quenched and tempered specimens were aged at 300, 400, 500, and 600 C for up to 1000 hr and then tested for impact resistance and examined by scanning electron microscopy and Auger electron spectroscopic techniques. Temper embrittlement, and the effect of aging on embrittlement, of the steels with the higher Cu or P were the same. Intergranular fracture was observed after aging in the fracture surface of Charpy impact test specimens of both steels. After prolonged aging, concentration of copper or phosphorus on the fracture surface was observed by Auger electron spectroscopy.