(1) Tool geometry parameter design
Most of the reaming of stainless steel materials uses carbide reamer. The structure and geometric parameters of the reamer are different from those of a normal reamer. In order to enhance the strength of the teeth and prevent chip clogging during reaming, the number of reamer teeth is generally small. The rake angle of the reamer is generally 8 ° ~ 12 °, but in some specific cases, in order to achieve high-speed reaming, the 0 ° ~ 5 ° rake angle can also be used; the back angle is generally 8 ° ~ 12 °; the main declination Selecting the hole varies from hole to hole. Generally, the through hole is 15° to 30°, and the through hole is 45°. When the hole is reamed, the blade inclination angle can be appropriately increased. The blade inclination angle is generally 10 °～20°; the width of the land is 0.1～0.15mm; the inverted cone on the reamer should be larger than the ordinary reamer, the hard alloy reamer is generally 0.25~0.5mm/100mm, and the high speed steel reamer is 0.1~0.25mm/ 100mm; the length of the reamer correction part is generally 65% to 80% of the ordinary reamer, and the length of the cylindrical part is 40% to 50% of the ordinary reamer.
(2) Cutting amount selection
When the reaming is performed, the feed amount is 0.08 to 0.4 mm/r, the cutting speed is 10 to 20 m/min, the coarse hinge allowance is generally 0.2 to 0.3 mm, and the fine hinge allowance is 0.1 to 0.2 mm. Carbide tools should be used for rough hinges and high speed steel tools for fine hinges.
(3) Cutting fluid selection
When the stainless steel material is reamed, the full loss system oil or molybdenum disulfide can be used as the cooling medium.
3. Boring processing
(1) Tool material selection
Due to the high cutting force and high cutting temperature when processing stainless steel parts, the tool material should be selected as high-quality, high thermal conductivity YW or YG type hard alloy. YT14 and YT15 carbide inserts are also available for finishing. When processing the above-mentioned material parts in batches, ceramic materials can be used. Since the characteristics of such materials are mainly toughness and severe work hardening, the chips cutting these materials are generated in the form of unit chips, which will cause the tool to vibrate and easily cause the blade to be slightly generated. The phenomenon of collapse, so the choice of ceramic tools to cut such material parts should first consider the micro toughness. At present, Sialon is a good choice, especially α/βSialon material, which is attracting attention due to its excellent resistance to high temperature deformation and diffusion wear. It has been successfully used in cutting nickel-based alloys, and its life span far exceeds Al2O3-based ceramics. In addition, SiC whisker reinforced ceramics are also a very effective tool material for cutting stainless steel or nickel based alloys.
For the processing of quenched parts of such materials, CBN (cubic boron nitride) inserts can be used. The hardness of CBN is second only to diamond, and the hardness can reach 7000-8000 HV. Therefore, the wear resistance is very high. Compared with diamond, the outstanding advantage of CBN is Heat resistance is much higher than diamond, up to 1200 ° C, can withstand high cutting temperatures. In addition, its chemical inertness is very large, and it does not play a chemical role with iron-group metals at 1200-1300 °C, so it is very suitable for processing stainless steel materials. Its tool life is dozens of times that of cemented carbide or ceramic tools.
(2) Tool geometry parameter design
The geometrical parameters of the tool play an important role in the cutting performance. In order to make the cutting light and smooth, the carbide tool should adopt a larger rake angle to improve the tool life. Generally, when roughing, the front angle is 10°-20°, 15°-20° for semi-finishing, and 20°-30° for finishing. The main declination is selected based on the fact that when the process system is rigid, it can be taken from 30° to 45°; if the process system is poor in rigidity, it is taken from 60 to 75°. When the ratio of the length to the diameter of the workpiece exceeds 10 times, 90 can be taken. °.
When boring stainless steel with ceramic tools, in most cases, ceramic tools are cut with a negative rake angle. The size of the rake angle should generally be -5 ° ~ -12 °. This is conducive to strengthening the blade and giving full play to the superiority of the ceramic tool with high compressive strength. The size of the back angle directly affects the tool wear and has an effect on the edge strength. It is generally selected from 5° to 12°. The change in the lead angle affects the variation of the radial and component cutting forces as well as the cutting width and the thickness of the cutting. Because the vibration of the process system is extremely unfavorable to the ceramic tool, the choice of the lead angle is beneficial to reduce this vibration, generally 30 ° ~ 75 °. When CBN is selected as the tool material, the tool geometry parameters are 0°~10° for the rake angle, 12°～20° for the back angle, and 45°～90° for the main angle.
(3) The roughness value of the rake face is small when sharpening
In order to avoid chip sticking, the front and back flank of the tool should be carefully sharpened to ensure a small roughness value, thus reducing chip outflow resistance and avoiding chip sticking.
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