Effects of Finish Rolling Temperature and Deformation on Microstructural Evolution and Precipitation Behavior of Non‐quenched and Tempered Carbide‐Free Bainitic Steel

Abstract

Double compression tests are carried out to investigate the microstructural evolution and precipitation behavior of Nb–Ti microalloyed carbide‐free bainitic steel under different finish rolling conditions. With decreasing finish rolling temperature and increasing finish rolling deformation, the area fraction of lath bainite (LB) and martensite (M) was increased, the width of bainitic ferrite lath was decreased, the dislocation density and the number fraction of high‐angle grain boundaries are raised. Meanwhile, the larger deformation and lower temperature reduce the amount of retained austenite (RA) and refine the precipitated particles, which benefit the performance further. Hence, the phase transformation strengthening, refinement strengthening, dislocation strengthening, and precipitation strengthening synergistically contribute to the increase in hardness with increasing deformation and decreasing temperature.

Effects of rolling process and microstructure on the brittle crack initiation and arrest of a marine steel under low‐temperature

“…Besides, lowering the finish rolling temperature can offer more nucleation driving force for ferrite formation. At the same time, it can retain the dislocations generated during austenite deformation 44 . Both the rolling temperatures of Steel 1 were higher than the rolling temperatures of Steel 2.…”

“…At the same time, it can retain the dislocations generated during austenite deformation. 44 Both the rolling temperatures of Steel 1 were higher than the rolling temperatures of Steel 2. Thus, the prior austenite grain of Steel 2 was bound to be more petite and more uniform than those of Steel 1 at both the surface and central location.…”

Effect of cooling system and forming structure on grain sizes and mechanical properties of S43CMnV for non‐quenched and tempered steel crankshaft

“…Some samples are intercepted from the core of raw materials of the supplier and analysed by direct reading spectrometer for the chemical composition of the material, Table 1. In addition, combined with the continuous cooling curve of the S43CMV steel, the Ac1 temperature of 729 °C, the Ac3 temperature of 811 °C and the austenitising temperature of 870 °C are obtained, which means that the chemical compositions and heat treatment processes of the experimental bars meet the actual production process requirements [2].…”

“…The points P1, P2 and P3 of the numerical simulation results are taken in the sampling area of the actual process to be used for the average grain sizes analysis [2,17]. Whereas, points P1 and P3 are taken as points at 5 mm radial interval from P2, while P2 is 10 mm away from the left surface of the section, and the average grain sizes are taken at three points compared to the experimental results of the cut-point method, Figure 9.…”

“…Compared with the quenched steel crankshaft, the advantages of the non-quenched and tempered steel crankshaft possess the simple process, short production cycle and low cost. However, there are also some defects, such as the insufficient toughness and coarse grain sizes, in the non-quenched and tempered steel crankshaft, which also lead to the fatigue damage of crankshaft and the fracture of pin bearing [2,3]. Currently, there are only few studies on the austenite grain coarsening behaviors of the non-quenched and tempered steel crankshaft, compared with the effect in actual industrial production.…”