Influence of Sulfur on the Splitting Fracture and Machining Performance of Microalloyed Medium-Carbon Steel 36MnVS4 Connecting Rods

The differences of 0.032% and 0.066% sulfur content on the splitting fracture and machining properties of microalloyed medium-carbon steel 36MnVS4 were studied. The splitting fracture and machining properties were examined by the analysis of MnS inclusions and microstructure, the test of mechanical properties and cutting properties. The results showed that as the number of MnS inclusions increased from 127.3 to 349.8 piece/mm 2 , the product of strength and elongation of 0.066%S steel increased by 12.3%. The functions of MnS as the core of the intragranular ferritic and refining of the austenite grains resulted in the increase in ferrite content by 2.0%, the decrease in ferrite size by 0.5 μm and the decrease in proto-austenite size by 6.0 μm. A higher ferrite content and lower ferrite and proto-austenite size enhanced the plasticity and toughness, which decreased the splitting fracture performance. The tool back surface wear width of 0.066%S steel decreased by 21.0% for 0.032% S steel. The roughness of 0.066%S steel decreased by 10.4% for 0.032%S steel. More and longer MnS inclusions broke the continuity of the matrix and improved the machining performance. For connecting rod manufacturing, to ensure the splitting fracture performance and enhance the machining performance, the sulfur content should be increased.