In CNC milling of stainless steel flanges, the selection of tool material is crucial for meeting the challenges of high-hardness cutting. Due to its high plasticity and toughness, stainless steel is prone to work hardening during cutting, with the hardened layer reaching depths several times the thickness of the substrate, leading to a significant increase in cutting forces. Simultaneously, stainless steel has a low thermal conductivity, making it difficult to dissipate heat quickly during cutting, causing a rapid rise in temperature in the cutting zone and accelerating tool wear. Therefore, the tool material must possess high hardness, wear resistance, heat resistance, and good impact resistance to withstand the harsh conditions of stainless steel flange machining.
Carbide is one of the commonly used tool materials for CNC milling of stainless steel flanges. It uses tungsten carbide as a matrix and is sintered through powder metallurgy, possessing extremely high room-temperature hardness and good red hardness, maintaining cutting performance even at high temperatures. For CNC milling of stainless steel flanges, fine-grained or ultra-fine-grained cemented carbides with added titanium carbide or niobium carbide, such as YG or YM grades, are recommended. These materials, through refined grain structure, enhance toughness and impact resistance while maintaining high hardness, effectively resisting wear and chipping risks during stainless steel cutting. Furthermore, carbide tools have better thermal conductivity than high-speed steel, aiding in heat dissipation, reducing tool temperature, and extending service life.
Coated carbide tools further enhance tool performance by depositing one or more wear-resistant coatings on the substrate surface. Common coating materials include TiN, TiAlN, and AlTiN, with TiAlN coatings being the preferred choice for stainless steel machining due to their excellent heat resistance and oxidation resistance. The coating effectively reduces friction and adhesion during cutting, lowers cutting forces, and isolates the cutting heat from the tool substrate, slowing down wear. For CNC milling of stainless steel flanges, coated carbide tools significantly improve machining efficiency and surface quality while reducing tool change frequency and increasing production efficiency.
Under specific working conditions, cermet tools also exhibit good applicability. Cermet tools use titanium carbide as a matrix, adding metal binders such as nickel and molybdenum, and are manufactured using powder metallurgy processes. Its hardness is higher than that of cemented carbide, and its coefficient of friction is lower, resulting in less heat generation during cutting. Cermet tools exhibit excellent wear resistance, making them particularly suitable for the finishing of stainless steel flanges, achieving high surface finish and dimensional accuracy. However, cermets have relatively weak impact resistance, requiring caution in intermittent cutting or high-vibration conditions.
For high-hardness stainless steel flanges or stainless steel materials containing many impurities, cubic boron nitride (CBN) tools are an ideal choice. CBN's hardness is second only to diamond, and it possesses extremely high chemical stability, not reacting with iron group elements at high temperatures. Its heat resistance can reach 1400℃, far exceeding that of cemented carbide and cermets, maintaining stability at extremely high cutting speeds. CBN tools are particularly suitable for the finishing of hardened stainless steel flanges, enabling a highly efficient machining method that replaces grinding with turning, significantly improving production efficiency.
The design of tool geometry parameters also has a significant impact on cutting performance. For CNC milling of stainless steel flanges, a large helix angle design is recommended to increase the actual working rake angle, making cutting smoother and reducing cutting forces. Meanwhile, the cutting edges of CNC milling stainless steel flanges need to be chamfered to enhance edge strength and prevent chipping. The chip flutes must be large enough to ensure smooth chip removal and prevent chip blockage that could damage the tool.
In actual machining, cutting parameters must be flexibly adjusted according to specific working conditions and the characteristics of the stainless steel. For example, in the roughing stage, the cutting speed can be appropriately reduced and the feed rate increased to improve material removal rate; in the finishing stage, the cutting speed needs to be increased and the feed rate reduced to obtain better surface quality. Simultaneously, the full use of cutting fluid for cooling and lubrication can effectively reduce cutting temperature, decrease tool wear, and improve machining stability.
