First, the coolant will cool the chips too quickly and fuse to the blade, resulting in a reduction in tool life;
Too high a feed rate will cause material accumulation, while too low a feed rate will cause friction between the tool and the workpiece, which will also cause overheating.
In fact, in order to avoid tool tumors, it is necessary to process stainless steel cutting heat. The main cutting speed for processing stainless steel milling cutters should be appropriate, so that the chips have a light brown color.
If the chips turn dark brown, it means that the cutting speed has reached the maximum limit. It is necessary to pay attention to the cutting speed when selecting a milling cutter for processing stainless steel.
The cutting tool should be rigid, advanced, and have the highest possible overload capacity. It is best to cut below 75% of the machine tool load rating.
The workpiece and tool should be firmly clamped, and the tool extension should be as short as possible. Additional support can be used if necessary. Whether it is a high-speed steel tool or a carbide tool, it should be kept sharp at all times. It is best to sharpen it regularly and not sharpen it when it is absolutely necessary.
A good lubricant should be used, such as chlorinated petroleum grease. This lubricant is particularly effective for high-power cutting with a relatively slow feed rate.
For high-speed finishing cutting, it is recommended to dilute this lubricant with kerosene before use. This mixture can keep the workpiece and tool at a low temperature. Special attention should be paid to the cutting of Cr-Ni austenitic stainless steel. When cutting this stainless steel, you should be as careful as possible, and if possible, perform forced cutting to avoid pauses, so as not to cause work hardening and material slippage.
The characteristics of milling stainless steel are:
stainless steel has strong adhesion and melting properties, and chips are easy to adhere to the milling cutter teeth, which worsens the cutting conditions; when reverse milling, the teeth first slide on the hardened surface, increasing the tendency of work hardening; the impact and vibration during milling are large, which makes the milling cutter teeth easy to break and wear.
Except for end mills and some end mills that can use cemented carbide as milling cutter tooth materials, all other types of milling cutters use high-speed steel, especially tungsten-molybdenum and high-vanadium high-speed steel, which have good effects, and their tool durability can be increased by 1 to 2 times compared with W18Cr4V. Carbide grades suitable for making stainless steel milling cutters include YG8, YW2, 813, 798, YS2T, YS30, YS25, etc.
When milling stainless steel, the cutting edge must be sharp and able to withstand impact, and the chip groove must be large. Large helical angle milling cutters (cylindrical milling cutters, end milling cutters) can be used. The helical angle b increases from 20° to 45° (n=5°), and the tool durability can be increased by more than 2 times, because at this time the working front angle g0e of the milling cutter increases from 11° to more than 27°, and milling is light. However, the b value should not be larger, especially for end mills, b≤35° is appropriate to avoid weakening the teeth.
When processing stainless steel pipes or thin-walled parts with corrugated edge end mills, cutting is light, vibration is small, chips are fragile, and workpieces are not deformed. High-speed milling with carbide end mills and milling of stainless steel with indexable end mills can achieve good results.
When milling 1Cr18Ni9Ti with a silver white chip (SWC) end mill, the geometric parameters are gf=5°, gp=15°, af=15°, ap=5°, kr=55°, k′r=35°, g01=-30°, bg=0.4mm, re=6mm. When Vc=50～90 m/min, Vf=630～750mm/min, a′pb can reach 20=2～6mm, the milling power is reduced by 44%, and the efficiency is greatly improved. The principle is to grind a negative chamfer on the main cutting edge, and artificially generate a built-up edge during milling, so that it replaces the cutting edge for cutting. The front angle of the built-up edge is ~~302. Due to the effect of the main deflection angle, the built-up edge is subjected to the thrust generated on the front cutting face parallel to the cutting edge and becomes a secondary chip outflow, thereby taking away the cutting heat and reducing the cutting temperature.
When milling stainless steel, the down milling method should be used as much as possible. The asymmetric down milling method can ensure that the cutting edge is smoothly separated from the metal. The chip bonding contact area is small and is easily thrown off under the action of high-speed centrifugal force, so as to prevent the chip from impacting the front cutting edge and causing peeling and chipping when the cutter teeth re-enter the workpiece, thereby improving the durability of the tool.
The spray cooling method has the most significant effect, which can increase the durability of the milling cutter by more than double; if a general 10% emulsion is used for cooling, the cutting fluid flow should be ensured to achieve sufficient cooling. When a carbide milling cutter is used to mill stainless steel, Vc=70～150 m/min, Vf=37.5～150 mm/min, and appropriate adjustments should be made according to the alloy grade and workpiece material.
Of course, the above content is to introduce the process difficulties in the machining process of stainless steel, and it can also enable our customers to clearly understand how difficult it is to turn metal materials into finished products. In addition, if you need a large number of stainless steel milling processing services, you can choose Mulan Metal. Mulan Metal has 12 years of CNC machining experience and can meet all your metal CNC machining requirements. Fast delivery, low minimum order quantity, and support various certifications.
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