Examination of hydrogen interaction in carbon steel by means of quantitative microstructural and fracture descriptions

The relations between the quantitative microstructural characteristics and the resistance of carbon steels to hydrogen- induced cracking (HIC) were st udied for plates used in the oil and refinery industry. The width of the pe arlitic bands and the degree of banding were considered if the testing of t he resistance to HIC was performed in accordance with the NACE TM 0284 stan dard. The role of the degree of banding was important while that of the wid th of pearlitic bands was negligible, Additional hydrogen embrittlement tes ting of tensile specimens oriented in longitudinal and through-thickness di rections revealed that hydrogen strongly increased the anisotropy of mechan ical properties. These changes could be correlated with the geometric chara cteristics of nonmetallic inclusions (MnS) and the pearlitic bands in diffe rent metallographic sections. A quantitative description of fracture surfac es has been made by means of a profilometric method. (C) 2001 Elsevier Scie nce Inc. All rights reserved.