The Structure of the Surface Layer of 0.4C-1Cr Structural Steel after Finishing Stages of Machining by Cutting

The microstructure and local fields of internal stresses arising in the surface layer of 0.4C-1Cr structural alloy steel (type 40X) samples after machining by cutting are investigated. Before treatment, the samples were subjected to recrystallization annealing at a temperature of 600 degrees C for 60 min. Sample processing was carried out in three modes: finishing (mode 1); sequential combination of roughing and semifinishing (mode 2); sequential combination of roughing, semifinishing, and finishing (mode 3). In processing modes 1, 2, and 3, chips were removed to a depth of 0.25, 1.5, and 1.75 mm, respectively. Transmission electron microscopy was used to determine the amplitude of the curvature-torsion of the crystal lattice of the phases formed, the excess dislocation density, and the amplitude of internal stresses. It was found that the main phase components in steel 40X after cutting are represented by lamellar pearlite with different morphology and fragmented and unfragmented ferrite.