What are the characteristics of stainless steel milling cutters?
What are the problems in stainless steel milling?
First of all, the coolant will make the chips cool too fast and fuse on the blade, which will reduce the tool life.
Too high feed rate will cause the accumulation of materials, and too low feed rate will cause friction between the tool and the workpiece, which will also lead to overheating.
In fact, in order to avoid tool bumps, machining stainless steel cutting heat is necessary. When machining stainless steel milling cutter, proper cutting speed should be selected to make the chip light brown.
If the chip turns dark brown, the cutting speed has reached the maximum. It is necessary to pay attention to the cutting speed of the milling cutter when machining stainless steel.
What should be paid attention to when milling stainless steel?
Cutting tools should be rigid, advanced, and have as high overload capacity as possible. It is better to cut under 75% of the load calibration capacity of the machine tool.
The workpiece and cutter should be clamped firmly, the extension of the cutter should be as short as possible, and additional support can be used when necessary. Whether it is high-speed steel tools or cemented carbide tools, they should be kept sharp at all times. It is better to sharpen them regularly, and do not sharpen them when they have to.
Good performance lubricants, such as chlorinated petroleum grease, should be used. This lubricant is particularly effective for heavy cutting where the feed rate is rather slow.
For high-speed finishing cutting, kerosene is recommended to dilute the lubricant 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 kind of stainless steel, we should be careful as far as possible and may carry out compulsory cutting to avoid a pause, so as not to cause work hardening and material slipping.
How to choose the milling cutter for stainless steel milling?
The characteristics of milling stainless steel are: the adhesion and fusibility of stainless steel are strong, and the chips are easy to adhere to the cutter teeth, which worsens the cutting conditions; In reverse milling, the cutter teeth slide on the hardened surface first, which increases the trend of work hardening; When milling, the impact and vibration are large, which makes the cutter teeth easy to crack and wear.
In addition to the end milling cutter and some end milling cutters which can be made of cemented carbide, other kinds of milling cutters are made of high-speed steel, especially tungsten molybdenum series and high vanadium high-speed steel, which have a good effect. The tool life can be 1-2 times higher than that of W18Cr4V. Cemented carbide grades suitable for stainless steel milling cutters are YG8, YW2, 813, 798, YS2T, YS30, YS25, etc.
When milling stainless steel, the cutting edge should be sharp and able to withstand impact, and the chip groove should be large. Large helix angle milling cutter (cylindrical milling cutter, end milling cutter) can be used, and helix angle B is from 20 ° Increase to 45 °（ n=5 °）， The tool life can be increased by more than 2 times, because the working rake angle G0e of the milling cutter is changed from 11 ° Increased to 27 ° Above, milling is light and fast. But b value should not be larger, especially when B ≤ 35 ° To avoid weakening the cutter teeth.
When machining stainless steel pipe or thin-walled parts with wave edge end mill, the cutting speed is light, the vibration is small, the chip is fragile and the workpiece is not deformed. High-speed milling with carbide end milling cutter and indexable end milling cutter can achieve good results in stainless steel milling.
Milling parameter cases
SWC end mill milling 1Cr18Ni9Ti, its geometric parameter is GF = 5 °、 gp=15 °、 af=15 °、 ap=5 °、 kr=55 °、 k′r=35 °、 g01=-30 °、 4 mm, re = 6 mm, when VC = 50 ~ 90 m / min, VF = 630 ~ 750 mm / min, a ′ Pb can reach 20 = 2 ~ 6 mm, milling power is reduced by 44%, efficiency is also greatly improved. The principle is to grind the negative chamfering on the main cutting edge. During milling, the chip build-up is artificially generated to replace the cutting edge for cutting. The rake angle of the chip build-up is ~ 302. Due to the effect of the main deflection angle, the chip build-up is caused by the thrust parallel to the cutting edge generated on a rake face and becomes the secondary chip outflow, which takes away the cutting heat and reduces the cutting temperature.
When milling stainless steel, it is necessary to use the parallel milling method as far as possible. Asymmetric milling method can ensure that the cutting edge smoothly cuts away from the metal, the chip bonding contact area is small, and it is easy to be thrown off under the action of high-speed centrifugal force, so as to avoid the phenomenon of chip spalling and edge collapse when the cutter teeth re cut into the workpiece, and improve the tool durability.
The effect of spray cooling is the most significant, which can increase the durability of milling cutter more than one time. If the general 10% emulsion is used for cooling, the cutting fluid flow should be ensured to achieve sufficient cooling. When milling stainless steel with carbide milling cutter, VC = 70-150 M / min and VF = 37.5-150 mm / min should be selected. At the same time, appropriate adjustment should be made according to different alloy grades and workpiece materials.
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