Effect of Quenching and Tempering Processes on Sharpness of Knives Made from 6Cr13 High-Carbon Martensitic Stainless Steel

In the present work, the effect of quenching and tempering processes on the sharpness performance of 6Cr13 high-carbon martensitic stainless steel knives was investigated. The results show that the sharp persistence of the knife increases as the quenching temperature increases from 975 to 1125 °C. The initial sharpness first increases and then decreases, reaching a maximum of 95.9 mm at 1075 °C. When the tempering temperature is below 300 °C, the initial sharpness and sharp persistence of the knife both decrease with the increase of tempering temperature. The secondary carbide in the steel dissolved and the carbide content decrease continuously with the increase of quenching temperature. After the quenching temperature exceeds 1050 °C, a large amount of secondary carbide solid solution is formed into the austenite. The carbides precipitate from steel matrix after the tempering temperature exceeds 400 °C. The refinement and dissolution of secondary carbides are the main reasons for the good sharpness performance of 6Cr13 steel knives. The variation of hardness has little effect on the sharpness performance. However, the cutting capacity of knives fluctuates more sharply as the hardness decreases. Quenching at 1050–1075 °C and tempering at 180–220 °C can obtain 6Cr13 steel knives with optimal sharpness, hardness and fine grain size combination.