Influence of Metallurgical Variables On Resistance of Steels to Sulfide Corrosion Cracking^*

A statistical study has been made of sulfide corrosion cracking of steel as a function of chemical composition, mechanical properties, and heat treatment. A total of 104 different alloys were studied, of which 79 were commercially-produced API grades J-55, N-80, and P-110 steels. It was possible to derive predictive equations which can be used to rate the cracking susceptibility of a new alloy from its known metallurgical properties. Resistance to cracking is increased most rapidly by increases in ductility and in carbon content. Resistance to cracking is decreased most rapidly by increases in hardness, strength, and manganese and molybdenum content. An additional result of this investigation is the demonstration that resistance to cracking can be markedly improved by tempering N-80 steel for one-half hour at 1100 F. The accompanying loss of yield strength is not excessive. 3.2.2