Stainless steel is a widely used difficult-to-machine material in mechanical processing. Austenitic, martensitic, and duplex stainless steels are extensively used in fields such as chemical engineering, aviation, and medicine due to their corrosion resistance and high strength. However, these materials have high plasticity and toughness, and their thermal conductivity is only about 1/3 of 45 steel. During cutting, they are prone to severe work hardening, chip formation, and tool bonding wear. Reasonable selection of TS-30 dual spindle CNC lathe is the core for ensuring processing quality and improving efficiency.
The selection of tool material is the foundation. For rough machining of stainless steel, the cutting load is high and the impact load is numerous. It is advisable to use WC-Co type hard alloy tools with balanced toughness and wear resistance, such as YG8 and YG6 grades with cobalt content of 8%-12%. These tools have strong impact resistance and are suitable for intermittent cutting during rough turning, capable of withstanding the heavy load of austenitic and martensitic stainless steel. If machining harder martensitic stainless steel (HRC40 or above), fine-grained or ultra-fine-grained hard alloys can be selected, such as YG6X. After grain refinement, the wear resistance is improved, effectively reducing tool wear. In the finishing stage, coated hard alloy tools should be used first, as the TiAlN coating has high temperature stability and low friction characteristics, which can form a heat-insulating lubricating layer during high-speed cutting, reducing chip formation and suitable for most stainless steel finishing. It should be noted that hard alloys containing titanium (such as YT types) are prone to chemical affinity with nickel and chromium elements in stainless steel, intensifying adhesion and wear. Generally, they are not used for austenitic stainless steel processing. For high hardness (HRC55 or above) stainless steel finishing, cubic boron nitride (CBN) tools can be selected. They have high hardness, good thermal stability, and weak affinity with iron elements, enabling high-speed hard turning and replacing the high-cost grinding process. However, the cutting allowance needs to be controlled to prevent chipping.
The optimization of tool geometric parameters is also crucial. The selection of the rake angle should take into account both cutting deformation and tool strength: for rough machining, a larger rake angle of 10°-15° is chosen to reduce chip deformation and lower cutting force; for finishing, the rake angle is further increased to 15°-20° to suppress sticking and improve surface quality. The clearance angle is generally set at 6°-10°. A too small clearance angle will intensify the friction between the tool and the workpiece, while a too large one will reduce the strength of the tool tip. The tool tip radius arc affects surface quality and life: for finishing, a small radius of 0.2-0.4mm is selected to reduce residual height and reduce roughness; for rough machining, a large radius of 0.8-1.2mm is selected to increase tool tip strength and adapt to heavy cutting. In terms of the main included angle, when machining thin-walled stainless steel parts, a large main included angle of 75°-90° is selected to reduce radial cutting force, avoid workpiece deformation, and improve the chip flow direction, reducing the impact on the tool.
The selection of tools also needs to be combined with the cutting process: during rough machining of stainless steel, low rotational speed (500-800r/min) and large feed rate (0.2-0.3mm/r) are used, combined with extreme pressure cutting fluid for cooling, to reduce the accumulation of cutting heat; during finishing, the rotational speed is increased to 1500-3000r/min, with a small feed rate (0.05-0.1mm/r), to ensure processing accuracy. During the machining process, chip breaking should be timely to avoid long chips entangling the tool, which can be optimized by adjusting the main included angle and edge inclination angle to further improve the chip-breaking effect and extend tool life.
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