Creep crack growth in 2¼CrMo weld metals: the suppression of trace element embrittlement by creep strength effects

Abstract
It has been shown previously (Gooch et al . 1977) that bainitic steels of the 1/2 Cr 1/2 Mo 1/4 V type are severely embrittled in the creep range by the presence of trace amounts of phosphorus, arsenic, tin and antimony. These steels are commonly welded by using 2 1/4Cr1Mo electrodes and problems of weld metal cracking transverse to the welding direction have been experienced both after post-weld heat treatment and during subsequent service. It has been suggested (Bruscato 1970) that trace element embrittlement also may be operative in 2 1/4Cr1Mo weld metal. In the present work, creep crack growth tests were performed in vacuum at 565 °C on single edge notched tension specimens of four commercial manual metal arc weld metals with varying carbon (0.02-0.06%), phosphorus (0.012-0.031%) and arsenic (0.019-0.050%) levels. Specimens were tested either after tempering at 650 or 700 °C, or after stress relaxation (before notching) at the same temperatures. Complementary creep rupture tests were performed on tempered material.

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