1Cr18Ni9Ti stainless steel has a very low hardness (hardness ≤ 187 HB), high plasticity, good acid and corrosion resistance. Mechanical properties after solution treatment, yield strength s0.2 ≥ 205 MPa, tensile strength sb ≥ 520 MPa, elongation d5 ≥ 40%, shrinkage y ≥ 50%, conventional grade hard alloy cutting tools and conventional methods The processing is very difficult because the material is plastic and tough, it is easy to produce sticking knife phenomenon, it is difficult to break chips, and vibration is generated at the same time, which makes the tool easy to chip and wear. 1 The choice of tool material According to the performance and characteristics of 1Cr18Ni9Ti stainless steel, the carbide cutting insert manufactured by our company is used as the tool, and the grade is YG813. YG813 cemented carbide is equivalent to international standard ISO K10 ~ K20/M20, density is 14.4g/cm3, hardness is 91.5HRA, bending strength is 2100MPa. The hard alloy has good wear resistance, hot hardness, high temperature toughness and anti-adhesion ability and is suitable for processing high-temperature alloys, stainless steels, high manganese steels and other materials. Because YG813 is a kind of WC-Co alloy with a small amount of rare refractory metal carbides, it has fine structure and high strength, so it is suitable for coarse and fine processing. (Note: This product was obtained by the Ministry of Metallurgy and Sichuan Province.) Major Science and Technology Achievement Award. 2 Selection of parameters such as cutting amount, tool angle, etc. Take the flange (Fig. 1) produced by our company as an example to introduce the selection of parameters such as cutting amount and tool angle.
Figure 1 Flange
Choice of cutting amount in finishing In cutting three factors, the depth of cutting ap and the increase of feed f will increase the cutting force, increase the deformation of the workpiece, and may cause vibration, which will reduce the machining accuracy and increase. Surface roughness Ra value. When the cutting speed v increases, the cutting force decreases, and the built-up edge can be reduced or avoided, which is beneficial to the improvement of the processing quality and the surface quality. However, when turning, when the cutting speed v = 30 ~ 70m/min, it is easy to produce vibration, higher or lower than this range, the vibration is weakening trend: when the feed amount f is small, the amplitude is larger, with f As the amplitude increases, the depth of ap increases and the amplitude increases. Based on the above conclusions, the cutting depth ap should be reduced as much as possible, and the feed amount f should be appropriately reduced. Practice shows that the cutting speed v = 15 ~ 25m/min, depth of cut ap = 0.10 ~ 0.15mm, feed rate f = 0.18 ~ 0.25mm / r, the last fine car, the cutting speed v = 80 ~ 100m / Min, cutting depth ap = 0.01 ~ 0.03mm, feed rate f = 0.11 ~ 0.16mm / r, can achieve satisfactory results. The choice of tool angle is appropriate to increase the rake angle of the tool and reduce the feed amount, and increase the cutting speed to obtain the band-shaped chips. The cutting force of the strip chip is relatively smooth and the machining surface is smooth and clean. Because of the low hardness of the workpiece material, the requirements on the solidity of the cutting edge are lower, and the back angle of the tool can be increased appropriately, and the friction between the flank surface and the workpiece surface is reduced, so that the cutting edge is sharp. The choice of tool angle is shown in Figure 2.
Figure 2 Tool Angle Schematic
Choice of cutting fluid The main effect of the cutting fluid is cooling and lubrication to improve the cutting process. When finishing the workpiece, the main purpose is to improve the surface quality and reduce tool wear. Therefore, the cutting oil with small specific heat and poor fluidity is selected. Its main function is lubrication, and it also has a certain cooling effect. The installation of the workpiece is usually carried out by clamping the flange workpiece with a three-jaw chuck. It is difficult to achieve the machining accuracy, especially the flatness and parallelism of the workpiece. Therefore, it is necessary to design a set of disposable jigs. Firstly, the flange blanks are well-turned, and the inner hole is temporarily drilled with a Ø18mm hole, and the remaining 0.5mm margin is left between the end face and the outer circle. When finishing the car, install it first, turn the outer circle of the end face well, and then install the turning inner hole, which can basically meet the technical requirements of the drawing.
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