Sulfide Stress Cracking of Steels For API Grade N-80 Tubular Products^★

A laboratory investigation was made of various factors affecting the sulfide stress cracking resistance of a C-Mn-Mo grade of steel commonly used for producing API Standard 5A, Grade N-80 tubular products. It was found that the sensitivity to sulfide stress cracking of this steel in the normalized condition was increased significantly by 1 percent plastic prestrain. Experiments with the same material in the normalized and tempered condition indicated that tempering decreased the effect of subsequent cold work on sulfide stress cracking. Specimens tempered at 1150 F had somewhat greater resistance to failure than those tempered at 1200 F. The corrosion rate of this C-Mn-Mo steel in the acidified sulfide solution used for testing was independent of applied stress and prior thermal or mechanical history. An experimental C-Mn-Mo-V low alloy steel capable of meeting API 5A Grade N-80 requirements was developed for use in sulfide wells. The laboratory results obtained suggest that the sulfide stress cracking resistance of this new steel is superior to that of the normalized and tempered C-Mn-Mo steel. 3.5.8, 6.2.3