The difficulty of processing of stainless steel material has the following aspects:
1. Cutting force, high cutting temperature
This type of material is high, When cutting, the tangential stress is large, and the plastic deformation is large, and the cutting force is large. Furthermore, the material is extremely poor, resulting in elevated cutting temperature, and high temperature tends to be concentrated in the long area near the cutter cut, thereby accelerating the wear of the tool.
2. Processing hardening
Austenitic stainless steel and some high-temperature alloy stainless steels are austenite tissue, and the process hardening tendency to process during cutting, usually several times the ordinary carbon steel, The tool is cut into the hardening area to shorten the tool life.
3. Easy to stick knife
Whether it is austenite stainless steel or martensite stainless steel, the chip is strong, and the cutting temperature is high. When the tough chip flows through the front knife surface, a phenomenon of sticky knives such as bonding, welding, affecting the surface roughness of the machining parts.
4. Tool wear speed
The above materials generally contain high melting point elements, large plasticity, high cutting temperature, so that the tool wear is accelerated, the knife, the tool change, thereby affects production efficiency, Improve the cost of the tool.
It is mainly to reduce the cutting line speed, feed. It is best to take a tool for a tool for stainless steel or high-temperature alloy.
Stainless steel parts processing process
Through the above processing difficulty analysis, the processing of stainless steel and related tool parameters should have a large difference, and the specific processing technology is as follows: [ 123]
1. During drilling processing, due to poor thermal conductivity in stainless steel, the elastic modulus is small, and the holes are difficult. The pore processing challenge of this type of material is mainly used to select the appropriate tool material to determine the geometric parameters of the reasonable tool and the cutting amount of the tool. When drilling the above materials, the drill should generally use the drill bit of W6MO5CR4V2Al, W2MO9CR4CO8 and other materials, and the disadvantages of these materials are expensive, and it is difficult to purchase. When the commonly used W18CR4V ordinary standard high-speed steel drill bit is drilled, due to the smallest angle, the chips is too wide without timely discharging the hole, the cutting fluid cannot cool the drill bit in time, and the stainless steel material is poor, resulting in a concentrated The cutting temperature on the blade rises, which is easy to cause two rear knife and main blade burn and the strapping, which reduces the life of the drill bit.
1) When the tool geometric parameter is designed to drill through the W18CR4V ordinary high-speed steel drill bit, the cutting force and the cutting temperature are concentrated on the tip of the drill, in order to improve the durability of the drill cutting site, it can increase the top corner Angle, the top corner is generally selected 135 ° ~ 140 °, the top angle will also make the front angle of the outer edge reduction, the drillings are narrowed,It is conducive to tick. However, after the increase of the top angle, the cross blade of the drill should be widened, resulting in increased cutting resistance, thus must grind the drill bit horizontal blade, the oblique angle of the grinding edge of the surface is 47 ° ~ 55 °, the front corner of the horizontal blade is At 3 ° ~ 5 °, when grinding the horizontal blade, the cutting edge should be grinded into a rounded corner to increase the horizontal edge strength. Due to the small elastic modulus of stainless steel, the metal elasticity under the chip layer is large, and the processing is hardened during the processing, the rear angle will speed up the wear of the knife surface after the drill bit, and increase the cutting temperature and reduce the life of the drill bit. Therefore, it is necessary to increase the rear angle, but the back angle is too large, which will make the main edge of the drill bit thinner, reducing the rigidity of the main blade, so the back angle should be 12 ° to 15 °. In order to narrow the drill, it is also necessary to disconnect the divided chip slut in the drill bits.
2) When the cutting amount selects drilling, the choice of cutting should be departed from the basic point to reduce the cutting temperature, because the high-speed cutting will increase the cutting temperature, while the high cutting temperature will exacerbate the tool wear, so The most important thing in the cutting amount is to select the cutting speed. In general, the cutting speed is preferably 12 to 15 m / min. The amount of feed is less affected by the tool life, but the amount of feedback selection is too small to cut the tool in the hardened layer, exacerbate wear; and the amount of feed is too large, and the surface roughness will deteriorate. Comprehensive two factors, the amount of feed is selected from 0.32 to 0.50 mm / r.
3) When the cutting fluid selects drilling, in order to reduce the cutting temperature, an emulsion can be used as a cooling medium.
2. Hinge machining
1) Tool geometric parameters design stainless steel material hinge machining uses a hard alloy reamer. The structure and geometric parameters of the reamer are different from the ordinary reamers. In order to enhance the knife teeth strength and prevent the cutting phenomenon, the number of reams is generally less. The front angle of the reamer is generally 8 ° to 12 °, but in some specific cases, in order to achieve high speed hinge, an angle of 0 ° to 5 ° can also be employed, and the rear angle is generally 8 ° to 12 °; the main corner The difference in the visual hole varies from, in general, the through hole is 15 ° ~ 30 °, no through holes are 45 °; the hinge is in order to make the chips forward, and the edge angle angle can be appropriately increased, and the edge tilt angle is generally 10. ° ~ 20 °; the width of the blade is 0.1 ~ 0.15mm; the reamer is inverted cone, and the hard alloy reamer is generally 0.25 ~ 0.5mm / 100mm, the high speed steel reamer is 0.1 ~ 0.25mm / 100mm; the length of the reamer correction portion is generally 65% \u200b\u200bto 80% of the ordinary reamer, wherein the length of the cylindrical portion is 40% to 50% of the ordinary reamer.
2) When the cutting amount is selected to select the hinge, the feed is 0.08 to 0.4 mm / r, the cutting speed is 10 ~ 20 m / min, the crude hingement is generally 0.2 to 0.3mm, and the hinge amount is 0.1 ~ 0.2mm. Carbide tools should be used when crude hinges.High-speed steel tools can be used when centered.
3) When the cutting fluid selects a stainless steel hinge, a full loss system can be used as a cooling medium.
1) Tool material selection due to processing stainless steel parts, the cutting temperature is high, the cutting temperature should be as high as YW or YG, good strength and good thermal conductivity. Class carbide. YT14 and YT15 cemented carbide blade can also be used when finishing. When the above material parts can be used, a ceramic material tool can be used. Since such materials are mainly tough, the toughness is severe, the chips of the cutting these materials are generated in unit chip, which will cause the tool to generate vibration, which is easy to cause the blade to produce micro The collapse, thus first considering the microsure toughness when choosing a ceramic tool cuts such material parts. At present, Sialon is a better choice, particularly α / βSialon material, which is eye-catching due to its performance of its excellent anti-high temperature deformation and the performance of diffusion wear, and successfully applied to cutting nickel-based alloys, and its life is far more than Al2O3 base ceramic. In addition, SiC whiskers reinforced ceramics are also a very effective tool material for cutting stainless steel or nickel-based alloys.
For the processing of such material quenching parts, CBN (cube boron nitride) blade can be used, the CBN hardness is second only to diamond, the hardness can reach 7000 ~ 8000HV, so wear resistance is high, with diamond phase For the ratio, the highlight of the CBN is that heat resistance is much higher than diamond, up to 1200 ° C, which can withstand high cutting temperatures. In addition, its chemical inert is very small, and the ferrous metal does not work in 1200 to 1300 ° C, so it is very suitable for processing stainless steel materials. Its tool life is a hard alloy or a ceramic tool for dozens of times.
2) The tool geometric parameters design tool geometric parameters have an important role in their cutting performance, in order to make the cutting light, smooth and hard alloy tools, to improve the life of the tool. Generally, when roughly processed, 10 ° ~ 20 °, 5 ° ~ 20 °, half-finishing; 20 ° ~ 30 ° when finishing. The selection of the main gase is based on the rigidity of the process system, and when the process system is rigid, it takes 60 to 75 °, and when the length of the workpiece is more than 10 times, 90 can be obtained. °.
When using ceramic tool boring stainless steel material, in most cases, ceramic tools are cut into cutting angles. The front angle size is generally -5 ° ~ -12 °. This facilitates the reinforcing blade and gives full play to the superiority of ceramic tool compressive strength. The rear size directly affects the tool wear, which also affects the strength of the blade, and is generally 5 ° ~ 12 °. The change in the main regeneration affects the change in radial cutting force and axial cutting force and the size of the cutting width and the cutting thickness. Because the vibration of the process system is extremely unfavorable to ceramic tools, the choice of main offering is beneficial to reduce this vibration, generallyTake 30 ° ~ 75 °. When the CBN is used as the tool material, the tool geometric parameter is 0 ° ~ 10 ° in front corner, the rear angle 12 ° ~ 20 °, the main offset 45 ° ~ 90 °.
3) The roughness value of the front knife surface is small to avoid the phenomenon of chip sticky knife. Before the tool, the rear knife surface should be carefully shardde to ensure a smaller roughness value, thereby reducing The chip effluent resistance is avoided to avoid chip punching knives.
4) The cutter cutting edge should be kept sharp to reduce machining hardening, the amount of feed, and the amount of back-to-knife should not be too small to prevent cutting from cutting in the hardened layer, affecting the tool use. life.
5) Pay attention to the grinding of the chip tank due to the tough characteristics of stainless steel chips, the cutting surface of the cutter should be appropriate, so that the cutting process is cut, accommodating, and the chips are convenient .
6) The choice of cutting amount is preferably cut with low speed and larger input when processing the stainless steel material.
When using a ceramic tool for boring, the reasonable choice of cutting amount is one of the key to the performance of ceramic tool performance. When the ceramic tool is continuously cut, the cutting amount can be selected according to the relationship between wear durability and the cutting amount; the intermittent cut should be determined according to the rules of the tool to determine the reasonable cutting amount. Since the ceramic knife has superior heat resistance and abrasion resistance, the impact of cutting amount on tool wear is smaller than the hard alloy tool. Under normal circumstances, when processing with ceramic tools, the feed amount is most sensitive to the damage of the tool. Therefore, according to the nature of the workpiece material, under the premise of the machine power, process system stiffness and blade intensity, when boring stainless steel parts, as much as possible, the high cutting speed is selected, and the larger back knife and relatively small progress Give the amount.
7) Cutting liquid selection should be suitable for the characteristics of the stainless steel to have poor bonding and heat dissipation, and thus the cutting fluid of the anti-bonding and heat dissipation in boring is quite important, such as chlorine Higher cutting fluids, as well as non-mineral oils that have good cooling, cleaning, rust rust and lubrication, without aqueous solution, such as H1L-2 synthesis cutting fluid.
Using the above process method, it is possible to overcome the processing difficulties of stainless steel, so that stainless steel is greatly improved when drilling, hinge, and boring, reducing the tool in operation, change the number of times, increasing production Efficiency and hole processing quality, reduce workers’ labor intensity and production costs, can achieve satisfactory results.