In the field of machining, stainless steel is widely used in industries such as power equipment, petrochemicals, medical devices, and precision instruments due to its excellent corrosion resistance, good mechanical properties, and high comprehensive value. However, the machinability of CNC steel parts is relatively poor, mainly characterized by strong work hardening tendency, high cutting temperature, difficulty in chip breakage, and rapid tool wear. Therefore, the key to achieving efficient and high-quality machining of stainless steel parts lies in the rational selection of tool materials, optimization of tool geometry parameters, and matching of appropriate cutting parameters.
Machining Characteristics and Processing Challenges of Stainless Steel
Under certain conditions, a severe work-hardened layer is formed, with a hardness exceeding 1.5 times that of the base material. This negatively impacts subsequent cutting and accelerates tool wear.
Low Thermal Conductivity: The thermal conductivity of stainless steel is approximately one-third to one-quarter that of ordinary carbon steel. Cutting heat is concentrated near the tool tip, causing a rapid increase in the cutting edge temperature, accelerating tool wear and breakage.
High Chip Toughness: Stainless steel chips have high toughness and are not easily broken. They easily form entangled or ribbon-like chips, affecting the stability and operational safety of the cutting process.
High Adhesion: Under high temperature and pressure, stainless steel easily adheres to the tool material, leading to built-up edge formation and affecting the quality of the machined surface.
Typical Stainless Steel Turning Tools and Their Characteristics
1. 75° Large Circular Cutting Edge Turning Tool
This tool features a large circular cutting edge with a radius of 50mm for stainless steel CNC turning parts. The principal cutting edge angle varies along the cutting edge, reaching a maximum of 75°. The circular cutting edge disperses the cutting force along the cutting edge direction, significantly improving the tool tip strength and impact resistance. The tool for CNC stainless steel parts has a 20° rake angle and a 0.5mm to 0.8mm wide negative chamfer, enhancing cutting edge strength while ensuring cutting sharpness. The inclination angle is -5° to -3°, which helps control chip flow. The clearance angle is 10°, effectively reducing friction between the tool's flank face and the machined surface of the workpiece.
2. 75° Chip-Breaking External Turning Tool
This tool for CNC machining stainless steel parts uses YG6X or YG8 carbide inserts. The rake angle is 18° to 20°, the clearance angle is 6° to 8°, the principal cutting edge angle is 75°, and the secondary cutting edge angle is 6° to 8°. This tool achieves excellent chip breaking even with a large depth of cut, producing blue or dark yellow chips with stable chip breaking, avoiding the problem of long chips entangled for steel CNC machining parts in the workpiece or tool.
3. Stainless Steel Finish Turning Tool
Finish turning processes place high demands on tool sharpness, surface quality, and dimensional accuracy. This tool for stainless steel CNC parts uses YG6X or YA6 carbide inserts with a rake angle increased to 25° to reduce cutting forces and heat; the clearance angle is 6° to 8°, the principal cutting edge angle is 45°, and the secondary cutting edge angle is 8°. The larger rake angle makes the cutting process for CNC machining steel parts smoother and effectively suppresses the formation of built-up edge. In practical applications, this tool can achieve a surface roughness value of Ra 1.8μm, with chips curling into small springs and exiting in a silvery-white color, indicating proper cutting temperature control.
4. Stainless Steel Fading Turning Tool
Face machining places high demands on tool penetration performance and vibration resistance. This tool uses YG8 carbide inserts, with the tool holder made of 45 steel and hardened, possessing good rigidity. Suitable for roughing of end faces with a large depth of cut for stainless steel milling parts.
Tool Material Selection and Geometric Parameter Optimization
In stainless steel milling, the choice of tool material directly affects machining efficiency and tool life. Carbide tools such as YW1, YW2, YG6X, YG8, and YA6 are the mainstream choice for stainless steel turning due to their good red hardness and anti-adhesion properties. Among them, fine-grained carbides containing tantalum or niobium exhibit higher impact resistance under interrupted cutting conditions.
Regarding tool geometry, milling stainless steel typically uses a larger rake angle (15° to 25°) to reduce cutting forces and heat; the clearance angle is 6° to 10° to balance edge strength and friction control; the principal cutting edge angle is selected according to the machining area, with 75° often used for roughing to improve tool strength and 45° for finishing to improve surface quality; the application of negative chamfering or edge blunting can effectively prevent chipping and extend tool life.
Stainless steel CNC milling raw materials hold an important position in industrial manufacturing due to their excellent comprehensive properties. However, the poor machinability of stainless steel rolling mills places high demands on tool selection and process design. By selecting suitable carbide tool materials, optimizing geometric parameters such as rake angle, clearance angle, and principal cutting edge angle, matching reasonable cutting parameters, and combining machining experience to design the tool structure specifically, challenges such as work hardening, cutting heat concentration, and chip control in milling 304 stainless steel can be effectively solved.
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