Effects of Different Forging Ratios on Microstructure, Mechanical Properties and Friction and Wear Behavior of Q355D Steel

Abstract

In order to meet the mechanical performance demands of large oil cylinder barrels and piston rods, an investigation into the forging process of Q355D low-alloy high-strength steel was conducted. This study rigorously examined the impact of various forging ratios (2.6, 4.3, and 6.2) on both the microstructural characteristics and mechanical properties (including tensile strength, hardness, elongation, and impact toughness) of Q355D steel through a comprehensive systematic analysis. The findings revealed that an escalation in the forging ratio resulted in a refinement of the grain size in both ferrite and pearlite, concurrently with the fragmentation of MnS inclusions. The augmentation in both hardness and impact toughness correlated proportionally with the increased forging ratio, primarily attributed to the grain size refinement and augmented dislocation density. The yield strength exhibited a corresponding increase with the forging ratio increments: 303.56, 324.32, and 346.69 MPa, while hardness values were recorded as 174.32, 187.31, and 200.95 HV, respectively. Furthermore, grain refinement significantly contributed to enhancing the steel’s ductility and toughness. Additionally, the escalated forging ratio notably reduced the duration required for the steel to reach a stabilized friction coefficient and reduced the stabilized friction coefficient, consequently amplifying the steel’s resistance to frictional wear.