The characteristics of stainless steel milling are as follows:
The adhesion and fusion force of stainless steel are strong, and the chips are easy to adhere to the teeth of the tool, which deteriorates the cutting conditions. In reverse milling, the teeth first slide on the hardened surface, increasing the tendency for work hardening. When milling, the impact and vibration are great, and the cutter teeth are easily crushed and worn. Milling stainless steel end mills and some end mills can use cemented carbide as the tooth material. Other types of milling cutters are made of high-speed steel, especially tungsten-molybdenum and high-vanadium high-speed steel. The tool durability is 1-2 times higher than that of W18Cr4V. Cemented carbide grades suitable for making stainless steel milling cutters are YG8, YW2, 813, 798, YS2T, YS30, YS25, etc.
When milling stainless steel, the cutting edge must be sharp and impact resistant, and the chip pocket must be large. Large helix angle milling cutters (cylindrical milling cutters, end milling cutters) can be used. The thread angle b is increased from 20° to 45° (gn=5°), which more than doubles the durability of the tool. At this time, the working rake angle g0e of the milling cutter is increased from 11° to 27°, making the milling lighter. However, do not increase the value of b, so as not to weaken the number of teeth of the tool, especially when the end mill is B or less than 35 degrees.
Stainless steel pipes or thin-walled parts are processed with corrugated end mills, with light cutting, low vibration, brittle chips, and no deformation of the workpiece. High-speed milling with cemented carbide end mills and stainless steel milling with indexable end mills have achieved good results.
Use a silver tip (SWC) end mill to mill 1Cr18Ni9Ti. The geometric parameters are gf = 5°, gp = 15°, af = 15°, ap = 5°, kr = 55°, k’r = 35°, g01 = -30°, bg = 0.4 mm, re = 6 mm . Vc=50-90m/min, Vf=630-750mm/min, a’p=2-6mm, the feed per tooth reaches 0.4-0.8mm. The cutting force is reduced by 10% to 15%, the cutting force is reduced by 44%, and the efficiency is greatly improved. The principle is to grind the negative chamfer of the main cutting edge and form a chip edge during the milling process. Instead of cutting edge for cutting, the rake angle GB of the built-in cutting edge can reach 20-302°. Due to the influence of the entering angle, the thrust generated on the rake face parallel to the cutting edge makes the chip-accumulating edge become an auxiliary chip, which takes away the cutting heat and reduces the cutting temperature.
When milling stainless steel, try to use the down-cut milling method. The asymmetrical smooth milling method ensures smooth separation of the cutting edge from the metal. The chip bonding has a small contact area and is easy to discard under the action of high-speed centrifugal force. Chips impact the rake face, improve the durability of the tool, and avoid spalling and spalling when the teeth re-cut into the workpiece.
The spray cooling method is the most effective, which can double the durability of the milling cutter. When cooling a typical 10% emulsion, it must be ensured that the cutting fluid flows to completely cool down. When milling cemented carbide with cemented carbide milling cutter, adjust Vc=70～150m/min and Vf=37.5～150mm/min according to the alloy brand and the processed material.
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