This article presents a review of current results of theoretical and experimental studies of the specific features of the structure that is formed in high-strength low-alloy steel in the...

Thermo-mechanical controlled processing (TMCP) is employed to obtain the required level of mechanical properties of contemporary HSLA steel plates utilized for gas and oil pipeline production. The strength and crack resistance of pipeline steels are mainly determined by its microstructure and crystallographic texture. In this study, the influence of the structural and textural states of industrially produced API-5L X70-X80 pipeline steels on tensile mechanical properties was analyzed. TMCP routes with different hot rolling temperatures and cooling rates were employed. The texture of steel was assessed using the Taylor factor, which was calculated based on electron backscatter diffraction (EBSD). The decrease in rolling temperature resulted in the sharper texture characterized by {001} planes banding (cleavage planes in the bcc lattice) parallel to rolling direction. The tensile deformation behavior at the stage of necking was determined by the crystallographic and morphological texture of the material and demonstrated significant anisotropy. Rupture of all investigated samples was accompanied by the development of splitting on the fracture surface. The splitting was localized in the rolling plane similar to the splitting in standard Charpy tests of pipeline steels.

Thermo-mechanical controlled processing (TMCP) is employed to obtain the required level of mechanical properties of contemporary high-strength low-alloy (HSLA) steel plates utilized for gas and oil pipeline production. The strength, deformation behavior and resistance to the formation and propagation of running fractures of the pipeline steel are mainly determined by its microstructure and crystallographic texture. These are formed as a result of austenite deformation and consequent γ→α-transformation. This present study analyses the crystallographic regularities of the structural and textural state formation in a steel plate that has been industrially produced by means of TMCP. The values of the mechanical properties that have been measured in different directions demonstrate the significance of the crystallographic texture in the deformation and failure of steel products. An electron backscatter diffraction (EBSD) method and crystallographic analysis were utilized to establish the connection between the main texture components of the deformed austenite and α-phase orientations. This paper demonstrates that the crystallographic texture that is formed due to a multipath γ→α-transformation results from the α-phase nucleation on the special boundaries between grains with γ-phase orientations. The analysis of the spectra of the α-γ-interface boundary angle deviations from the Kurdjumov–Sachs (K–S), Nishiyama–Wassermann (N–W), and Greninger–Troiano (G–T) orientation relationships (ORs) allows to suggest that the observed austenite particles represent a secondary austenite (not retained) that precipitates at intercrystalline α-phase boundaries and correspond to the ORs with regard to only one adjacent crystallite.

The electron back-scatter diffraction (EBSD) method was used to study the structural and textural states of low-carbon low-alloy steel after thermomechanical controlled processing (TMCP) and...

Thermo-mechanical controlled processing (TMCP) of low-carbon low-alloy pipe steels is used to attain the required level of mechanical properties in rolled plates designed for pipe production, thereby ensuring the operational stability and reliability of trunk pipelines. The TMCP involves the hot deformation of austenite followed by accelerated cooling, during which the γ → α transformation occurs. The technological capabilities of contemporary plate mills permit developing and implementing information systems for the control of steel structure and, consequently, its properties. The reliability and accuracy of such systems can be enhanced by using the correct thermophysical parameters of steels. In the present work the critical temperatures, temperature dependences of heat capacities of main phases, and thermal effects of phase transformations in specimens of 05G2MB (wt % ~ 0.05 C; ≤ 2.0 Mn; ~ 0.2 Mo; ~ 0.05 Nb) high-strength low-alloyed pipe steel have been determined employing differential scanning calorimetry method, dilatometric analysis, and calculations using Thermo-Calc software. It has been demonstrated that the thermal effect of magnetic transformation exhibits a markedly greater value than that of polymorphic phase transformation.