Chromium-Driven Microstructural Evolution and Mechanical Property Enhancement in Forged Low-Alloy Steels

To meet the lightweight requirement of large hydraulic cylinder barrels and piston rods, precise control of Cr content in low alloy steel was carried out. Material structure and comprehensive mechanical properties were analyzed using EBSD, XRD, SEM, EDS, etc. The results showed that an increase in Cr content refines the grain size of ferrite and pearlite, reduces the precipitation of inclusions like MnS, increases the precipitation of Cr23C6, induces grain orientation changes, and elevates the proportion of low-angle grain boundaries. The Cr contents of 0.0312, 0.111, and 0.22% correspond to the yield strengths of 303.56, 324.32, and 346.69 MPa, and the tensile strengths are 496.03, 536.993, and 595.238 MPa, with hardness values of 175.32, 186.31, and 201.95 HV, and scratch widths of 531, 518, and 506 µm respectively.