Abstract
Herein, the effects of height-diameter ratios (H/D) on the microstructure evolution and mechanical properties of 0.4C-Si-Mn-Cr steel during high temperature deformation are reported. The compression experiments were performed on steel samples using Gleeble to obtain a reasonable deformation temperature, and the degree of deformation was assessed in the range of 1.5 to 2.0 H/D via forging. The forged specimens were quenched using the same heat treatment process. The hardness and impact toughness of the steel samples were tested before and after heat treatment. Grain sizes gradually increased with an increase in the compression temperature from 950 °C to 1150 °C, and the grain sizes decreased with an increase in H/D. The microstructure of the steel samples contained pearlite, bainite, martensite, and retained austenite phase. The microstructure after forging was more uniform and finer as compared to that of as-cast steel samples. The hardness and impact toughness of the steel samples were evaluated after forging; hardness first increased and then decreased with an increase in H/D, while the impact toughness continuously increased with an increase in H/D. Hence, the microstructure and properties of steel could be improved via high temperature deformation, and this was primarily related to grain refinement.
Highlights
Owing to their excellent comprehensive performance, medium carbon steels have been widely used in essential fields such as energy development, machine manufacturing, and rail traffic [1,2,3,4].In recent years, there has been an intense focus on the improvement of material properties through deformation technologies such as hot rolling, cold rolling, and forging [5,6,7,8]
Compression tests were conducted at temperatures of 950 ◦ C, 1050 ◦ C, and 1150 ◦ C and maintained at the specified temperatures for 5 min followed by water quenching to cool the sample to room temperature (Figure 1a,b)
When the temperature increased from 950 to 1150 °C, the maximum flow stress and the average was counted as the grain size
Summary
Owing to their excellent comprehensive performance, medium carbon steels have been widely used in essential fields such as energy development, machine manufacturing, and rail traffic [1,2,3,4].In recent years, there has been an intense focus on the improvement of material properties through deformation technologies such as hot rolling, cold rolling, and forging [5,6,7,8]. Forging is a method for refining the grain size of steel via severe plastic deformation to enhance the strength and toughness. Grain refinement during deformation has a positive effect on the microstructure and properties of steel. G.P. Chaudhari et al [11,12,13,14] found that the grain was clearly refined after multidirectional forging of steel, which induced fine austenite grains because of continuous dynamic recrystallization and dynamic recovery. The formation of fine grains is beneficial for enhancement of tensile strength and hardness. Crystal slips are the primary mode of deformation, and the mechanism of ferrite refinement is comprised grain segmentation and recovery. Sumit et al [15] found that when the steel was forged in pure ferrite regions, the mechanical properties of steel had the best combination of yield
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