Study on Production Process, Microstructure, Properties of 15MnNbR Pressure Vessel Steel

The production process, microstructure, and mechanical properties of 15MnNbR pressure vessel steel were studied by optical microscopy, universal tensile testing, and low-temperature impact toughness testing. It was found that the microstructure obtained after controlled rolling and cooling (known as thermo-mechanical control processing) consisted of ferrite and pearlite with non-uniform grain size. The banded microstructure was prominent, the strength was high, and the toughness was poor. After normalizing, the grain size was refined, both the microstructural uniformity and the banded microstructure were improved, and the strength and toughness of the steel were enhanced. After normalizing and water cooling, the grain was further refined, the microstructure was homogenized, the banded microstructure disappeared, and the strength and toughness of the test steel were improved simultaneously, resulting in excellent comprehensive mechanical properties.

Effects of Heat Treatment on Microstructure Parameters, Mechanical Properties and Cold Resistance of Sparingly Alloyed High-Strength Steel

This study considers the influence of various heat treatment conditions on the change of steel microstructure parameters, mechanical properties and cold resistance at a temperature of-60 °C. The common behavior of these properties is considered depending on the heating temperature used for quenching and subsequent tempering. Based on the obtained results, heat treatment conditions are proposed that provide a combination of a guaranteed yield point σ0.2 ≥600 N/mm2 with a low-temperature impact toughness KCV-60 ≥50 J/cm2 and plasticity δ5 ≥17%. The obtained research results are intended for industrial use at the mill "5000" site of MMK PJSC.

Mechanical Properties and Microstructure Comparative Analysis of 500MPa Hot Rolled H-Section Different Positions for Ultra-Deep well Platform

With the increase of drilling depth, the mechanical properties of H-section steel used in drilling platform are more and more demanding. In this paper, the strength, low temperature impact toughness, plasticity, micro-hardness and microstructure of 500MPa hot rolled H-section steel produced by TMCP process were analyzed, and the strengthening mechanism was also studied. The results show that flanges of TMCP hot rolled H-section steel had the best strength and toughness, while the yield strength at web and R Angle was reduced to 91% and 78% of the flange, respectively. The impact toughness at -40°C of web and R Angle was reduced to 86% and 38% of the flange , and the micro-hardness reduced to 91% and 85% of the flange, respectively. The main strengthening mechanism of the TMCP hot rolled H-section steel is fine-grain strengthening, the carbonitride of V precipitation strengthening and surface bainite transformation strengthening.

Increasing Low-Temperature Toughness of 09Mn2Si Steel through Lamellar Structuring by Helical Rolling

The aim of the paper was to investigate the helical rolling parameters (a number of passes) for the microstructural modification and the low-temperature impact toughness improvement of the 09Mn2Si High Strength Low-Alloyed (HSLA) steel. In order to achieve this purpose, work spent to crack initiation and propagation was analyzed and compared with patterns of fracture surfaces. The microstructure and impact toughness values were presented in the temperature range from +20 to –70°C. Also, the fracture mechanisms in individual regions on the fracture surfaces were discussed. In addition, a methodology for computer simulation of the process was developed and implemented within the framework of the excitable cellular automata method and its integration with the kinetic theory of fracture. Finally, a theoretical analysis of the effect of grain shapes and orientations on the strain response patterns of a certain meso-volume simulating the material after the helical rolling was carried out.