Methods to overcome the difficulties in processing stainless steel materials:
1. The cutting edge of the tool should be kept sharp: the cutting edge of the tool should be kept sharp to reduce work hardening, and the feed rate and the amount of back bite should not be too small to prevent the tool from cutting in the hardened layer and affect the service life of the tool.
2. The roughness value should be small when the rake face is sharpened: in order to avoid the phenomenon of chip sticking to the knife, the front and flank faces of the tool should be carefully sharpened to ensure a small roughness value, thereby reducing the chip flow resistance and avoiding Chips stick to the knife.
3. Selection of tool material: Due to the large cutting force and high cutting temperature when machining stainless steel parts, the tool material should be selected as high strength and good thermal conductivity as possible.
For the processing of quenched parts of such materials, CBN (cubic boron nitride) inserts can be used. CBN hardness is second only to diamond, and its hardness can reach 7000-8000HV, so the wear resistance is very high. Compared with diamond, CBN has outstanding advantages. The heat resistance is much higher than that of diamond, up to 1200 ° C, and can withstand very high cutting temperatures. In addition, its chemical inertness is very large, and it has no chemical effect 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 carbide or ceramic tools.
4. The selection of cutting fluid should be appropriate: because stainless steel is easy to produce adhesion and has poor heat dissipation, it is very important to choose cutting fluid with good anti-adhesion and heat dissipation in boring, such as using cutting fluid with high chlorine content , and a mineral oil-free, sulfite-free aqueous solution with good cooling, cleaning, rust-proof and lubricating effects, such as H1L-2 synthetic cutting fluid.
5. Selection of cutting amount: According to the characteristics of stainless steel materials, low speed and large feed rate should be used for cutting.
6. Tool geometric parameters: The tool geometric parameters play an important role in its cutting performance. In order to make the cutting light and smooth, a larger rake angle should be used for the carbide tool to improve the tool life. In general, the rake angle is 10° to 20° for rough machining, 15° to 20° for semi-finishing, and 20° to 30° for finishing. The selection basis of the main declination angle is that when the rigidity of the process system is good, it can take 30° to 45°; if the rigidity of the process system is poor, it can take 60 to 75°. When the ratio of the length to the diameter of the workpiece exceeds 10 times, it can take 90°. °.
When boring stainless steel materials with ceramic tools, in most cases, ceramic tools use negative rake angle for cutting. The size of the front angle should generally be selected from -5° to -12°. This is beneficial to strengthen the blade and give full play to the superiority of the high compressive strength of the ceramic tool. The size of the relief angle directly affects the wear of the tool and also affects the strength of the blade, generally 5° to 12°. The change of the entering angle will affect the radial cutting force and the axial cutting force, as well as the cutting width and cutting thickness. Because the vibration of the process system is extremely unfavorable to the ceramic tool, the choice of the main declination angle should be conducive to reducing this vibration, generally 30° to 75°. When CBN is selected as the tool material, the geometric parameters of the tool are 0°~10° for the rake angle, 12°~20° for the clearance angle, and 45°~90° for the main declination angle.
7. Pay attention to the grinding of the chip breaker: Due to the strong and tough characteristics of stainless steel chips, the grinding of the chip breaker on the rake face of the tool should be appropriate, so that the chip breaking, chip holding and chip removal are convenient during the cutting process.