Causes of Structural Heterogeneity in High-Strength OCTG Tubes and Minimizing Their Impact on Sulfide Stress Corrosion Cracking Resistance

Abstract

High-strength oil country tubular goods (OCTG) like C110, according to standard API 5CT (yield strength at least 758 MPa), are subject to requirements in terms of mechanical and corrosion properties. In this work, we studied the microstructure of seamless casing tubes made of class C110 high-strength steel with a 194.5 mm diameter and 19.7 mm wall thickness, and its influence on sulfide stress corrosion cracking (SSC). Casing tubes were obtained from continuous billets by screw piercing with preliminary quenching and tempering. It was shown that cracking during the tests always begins from the inner surface of the tube. Rough segregation bands were found on the inner tube surface, which occupies about a third of the thickness of the wall. To increase the resistance of 0.3C-Cr-Mn-Mo + 0.15(V + Nb + Ti) steel to SSC, primary recommendations for adjusting the chemical composition, production technology and heat treatment were developed.

Structural Anisotropy Parameters’ Effect on the Low-Temperature Impact Strength of Alloy Steels in Rolled Products

“…Of course, characteristics of bainite can be determined using modern methods based on the use of scanning electron microscopy and backscattered electron diffraction. However, in this work, with the use of special etching methods based on hydrofluoric acid, characteristics of lath-morphology bainite were evaluated via optical methods [22][23][24].…”

Corrosion Resistance of 13Cr Steels

“…With a decrease in the carbon content, the ductility of the steel increases, the impact resistance increases, and the machinability improves, while the hardness and strength decrease. Additional alloying of steels of the supermartensitic 13Cr type with strong carbide-forming elements in an amount of up to 0.05% contributes to a significant increase in strength properties due to secondary hardening without a negative effect on the ductile and corrosion properties [29][30][31].…”

Microstructure and Hardness of Hollow Tube Shells at Piercing in Two-High Screw Rolling Mill with Different Plugs

“…Regarding the review of two-high screw rolling research publications, it is worth noting articles connected with hollow shell microstructure formation under different deformation regimes [ 20 , 21 , 22 , 23 , 24 ]. Publications [ 25 , 26 ] are about the influence of the shape and dimensions of the plug on the accuracy of the hollow shell dimensions.…”