Effect of Layer-by-Layer Texture Inhomogeneity on the Stress Corrosion of Gas Steel Tubes

Abstract

Based on the data of X-ray texture and structure analysis of the material of main gas pipelines it was shown that the layerwise inhomogeneity of tubes is formed during their manufacturing. The layerwise texture inhomogeneity of steel tubes, obtained by hot rolling at the air, differs depending on variation of technological parameters of their processing in inner and outer layers, i.e. the temperature and deformation gradients, penetration of interstitial impurities into the surface layer from surrounding atmosphere etc. The thickness of the surface layer with modified texture parameters depends on the temperature of rolling and its regime. Under exploitation when stress-corrosion cracks grows and reach the layer with a modified texture, their opening is slowing down or stops because of the high mutual misorientation of grains of different layers and the necessity of changing the plane of moving cracks, what requires additional tensile stresses. Layered textures of different gas tubes were compared. It was shown that character and degree of arising inhomogeneity correlates with the tubes resistance to stress-corrosion cracking.

The Analysis of the Influence of Various Factors on the Development of Stress Corrosion Defects in the Main Gas Pipeline Walls in the Conditions of the European Part of the Russian Federation

“…At the same time, the degree of defects' danger, the depth of which is less than 10-15% of the wall thickness, under condition that access of corrosive medium to them is restricted, is determined by many researchers as insignificant [13][14][15][16]. At the present time, there are methods of repairing the pipelines polymer insulation, which do not allow the cracks to develop and threaten the reliability of pipelines for a long time [17,18]. However, methods for an accurate assessment of the SCC cracks depth are not developed, and the factors that influence the distribution of SCC defects in extended sections are not always considered systematically during major overhauls.…”

Safe operation of gas pipelines based on the control of stress corrosion cracking

“…Measured with authors' participation distributions of residual stresses by X-ray sin2ψ method (Perlovich et al , 2017a, b, 2019) showed the similar tendency. As operational stresses are constant and residual stresses decrease, total circumferential stresses, which cause the crack propagation, decrease as well.…”

“…When etched with soil electrolyte, the tips of these cracks become blunt. This process contributes to completely stopping their propagation (Perlovich et al , 2017b; Leis, 1996).…”

Mechanical Properties of Gas Main Steels after Long-Term Operation and Peculiarities of Their Fracture Surface Morphology

“…It is known that 17MnSi and 17Mn1Si steels were widely used for manufacturing gas mains over the territory of the former Soviet Union [1,2,3]. Conventionally, main gas pipes were insulated with mastic and film protective coatings.…”

“…Conventionally, main gas pipes were insulated with mastic and film protective coatings. Nowadays, the run-time of these gas pipelines exceeds 30 years, while in some cases it reaches even 50 years of operation [3,4,5,6,7,8].…”