Research On Friction Characteristics Of 304, 20Cr Steels And Dry Cutting Performances Of Coated Tools

In recent years, dry cutting is widely used in all kinds of mechanical processing as a green manufacturing technology. With the rapid development of surface engineering technology, a typical representative of TiN coating tools has accelerated the development of dry cutting. Coating tools would not change the geometric size and shape of the substrate, and they have some advantages of the high hardness and wear resistance, so increasingly importance has been attached to coating tools for processing. Aiming at materials which are difficult to machine, research on dry cutting experiments using coating tools has been a hotspot in the field of machining.In this paper, TiN coated tools were used to conduct the dry cutting experiments for 304 stainless steel and 20Cr steel, respectively. Including:(1) The test specimens of 304 stainless steel and 20Cr steel were gained through processing. Employing silicon nitride ceramic balls as friction pair, the influence of friction coefficients and wear volumes were followed by reciprocating sliding test method. The wear mechanisms have been analyzed under corresponding test conditions. (2) The dry turning tests of 304 stainless steel were conducted with TiN coated and uncoated tools, which include the study of cutting force and cutting temperature. Each objective functions were followed with cutting parameters through single factor experiment method. The optimal cutting parameters of cutting force and cutting temperature were obtained through the orthogonal experiment method, which were validated by tests. (3) The dry turning tests of 20Cr steel were conducted with TiN coated tools. Through the single factor experiment method, cutting force and cutting temperature were influenced with changing cutting parameters. The forecasting models of cutting force and cutting temperature were obtained by the response surface method, which were validated by tests. (4) The turning process was simulated by finite element software. It mainly included the formation process and temperature distribution of the chip, dynamic tracking of the cutting force. The mechanisms and change rules were analyzed. The cutting force and cutting temperature were validated by tests. Main conclusions are as follows:(1) By reciprocating sliding friction test, the friction coefficients and wear volumes of 304 stainless steel and 20Cr steel are followed with increasing of the norm load. The friction coefficient of 304 stainless steel is more than 20Cr steel under the same norm load.(2) After cutting force and cutting temperature tests of 304 stainless steel, TiN coated tools are more suitable than those of uncoated tools. With the increase of cutting speed, the three axis forces show a trend of decrease after the first increase. Tangential force and radial force increase with increasing of feed rate. The three axis forces are particularly evident to the depth of cut, which is the quantity of approximate multiplication. Cutting temperature is generally increased with the increase of cutting speed and feed rate. The depth of cut is not obvious on the influence of cutting temperature. Using coating tools to test of stainless steel, the optimal parameters of the cutting force or cutting temperature are obtained by orthogonal experiment, which is A2B1C1, A1B1C3 respectively.(3) After turning tests of 20Cr steel, Tangential force decreases with the increase of cutting speed. The three axis forces increase with increased the feed rate and the depth of cut, but the depth of cut is better influenced than that of feed rate. Cutting temperature is evident along with the change of cutting parameters, and cutting temperature overall increase with the increase of cutting parameters. The prediction models of cutting force or cutting temperature are obtained by the response surface. The prediction error is 2.96%,5.06% respectively.(4) The turning process of 304 stainless steel with TiN coated tool are simulated by DEFORM-3D software. The deformation of the chip is mainly from the shear and squeeze of the tip of the tool. The highest temperature appears on the second deformation area. The simulation of cutting temperature prediction has a good consistency with the test results. Cutting temperature error is between 4.5%-8.14%.