5. Cutting of chilled cast iron:
The surface layer of this kind of cast iron is white-mouthed, the hardness can reach about HRC60; the unit cutting force K c can reach 3000MPa, which is 1.5 times that of cutting 45 steel; the cutting force is concentrated near the cutting edge, and the processing has pores, sand, and cutting. It is easy to damage the tool; its brittleness is large, and chipping and slag will occur during cutting.
1 Tool material: 1) Cemented carbide: Hard alloy with high hardness and high flexural strength should be selected. YS2, YS8, YS10, 600, 610, 726. 2) Ceramics: SG4, AT6, SM, FT80, FT85. 3) PCBN: used for finishing vehicles.
2 Tool geometry parameters: 1) Cemented carbide: γ0 = 0 ~ -5 °, α 0 = 5 ~ 10 °, κr ≤ 45 ° (κr = 45 °), λs = -5 ~ 10 °, γ ε = 0.5 ~1 mm;
3 Cutting amount: 1) Carbide tool: rough machining Vc=7～10m/min, α p=5～10mm, f=0.5～1.5mm/r. Finishing: Vc = 15 ~ 20m / min, α p = 0.5 ~ 2mm, f = 0.3 ~ O. 5mm / r. 2) Ceramic cutter: Vc = 40 ~ 50m / min, α p = 0.5 ~ 2mm, f = 0.3 ~ 0.6mm / r. 3) PCBN cutter: Vc=60～70m/min, α p=0.5～2mm, f=0.1～0.3mm/r.
6. Turning of thermal spraying (welding) materials:
Most of the thermal spraying materials are multi-component high-strength alloys, which are sprayed onto the surface of the workpiece at high temperature and high speed to greatly improve the hardness, corrosion resistance, wear resistance and heat resistance of the surface layer of the workpiece, and have been widely used. The hardness of the copper-based and iron-based powder coating layers is easier to cut. The hardness of the cobalt-based and nickel-based powder coating layer is >HRC50, which is difficult to cut. The hardness of the coating of cobalt-coated WC, nickel-coated WC, and nickel-coated Al2O3 is >HRC65, which is the most difficult to cut.
1 Tool material: 1) Cemented carbide: hardness > HRC45, using YG, YW hard alloy; hardness, using 600, 610, 726, 767, YD05, YC12, YS2, YS8: hardness > HRC65, using YG3X, YD05, YC09, YC12, YS8, 600, 610.
2) Ceramic tools: 3) PCBN
2 Tool geometry parameters: γ0 = 0 ~ -5 °, α 0 = 8 ~ 12 °, κr ≤ 45 °.
3 Cutting amount: cemented carbide Vc=6～40m/min; ceramic tool Vc=18～80m/min; PCBN cutter: Vc=24～160m/min. α p = 0.15 to 0.6 mm; f = 0.1 to 1 mm/r.
7, soft rubber cutting:
Soft rubber hardness (Shore A type 30 ~ 35) and strength (σb 20 ~ 25 MPa) is extremely low, thermal conductivity is very poor (0.14W / m? k), plasticity is extremely high (δ = 500 ~ 700), elasticity The modulus is extremely small (2 to 4 MPa). Due to the above properties, it has good elasticity, flexibility and variability, so it is difficult to cut it.
1 Tool material: high speed steel, YG type hard alloy.
2 Tool geometry parameters: γ0=45～55°, α 0=10～15°, β0=20～30°; when scraping, γ0=0°, α 0=70°, also use cutter (β0=5～ 10°), nesting knife.
3 Cutting amount: Vc≤100 m/min. α p = 2 to 5 mm; f = 0.5 to 0.7 mm / r.
4 cutting fluid: use an oil-free aqueous solution.
8. Turning of the grinding wheel:
Generally, the hardness of corundum abrasives is 1800 ~ 2450 HV, the hardness of silicon carbide abrasives is 3100 ~ 3400 HV, and the grinding wheel of these two kinds of abrasives is made by PCD and PCBN cutters, just as easy to cut tofu with a knife.
1 In order to prevent the grinding wheel from collapsing during turning, a machine tool with a circular blade is used.
2 Tool geometry parameters: circular blade γ0 = -8 ~ -10 °, α 0 = 8 ~ 10 °.
3 cutting amount: Vc = 30 ~ 50m / min. α p = 4 to 5 mm; f = 1 to 1.5 mm / r.
9. Turning of cemented carbide:
The hardness of the cemented carbide is high (HRA 85 to 92.5, HV 1300 to 1650, HRC 67 to 81), and the brittleness is large (σb 900 to 2500 MPa). Previously, only grinding and electromachining were used for processing. Due to the emergence of PCD and PCBN superhard tools, conditions for turning are provided.
1 tool material: PCD, PCBN. 2 Tool geometry parameters: γ0 = 0 ~ -5 °, α 0 = 6 ~ 8 °, κr ≤ 30 ~ 45 °.
3 Cutting amount: Vc=20～35m/min, α p=0.1～1.5mm, f=0.05～0.15 mm/r.
4 Note: Prevent chipping: Use kerosene as cutting fluid.
10. Turning of engineering ceramics:
Traditional ceramics are ground with diamond wheels. This is because of its high hardness (1100 to 2250 HV), low bending strength (450 to 1300 MPa), and high modulus of elasticity (315,000 to 400,000 MPa).
1 Tool material: PCD, PCBN; easy-cut ceramics, can also be made of hard alloy, but the tool durability is low.
2 Tool geometry parameters: γ0 = -10 ~ -15 °, α 0 = 8 ~ 12 °, κr = 30 ~ 60 °. In order to make the cut-out smooth, a round blade can also be used.
3 Cutting amount: Carbide cutter with easy-cut ceramic Vc=10～20m/min. Use PCD, PCBN tool Vc = 30 ~ 60m / min, α p = 0.1 ~ 2mm; f = 0.05 ~ 0.1 mm / r.
4 cutting fluid: one use of emulsion. 5 attention to the problem: to prevent chipping.
11. Turning of composite materials:
A composite material is a multi-phase solid material that is artificially made of two or more materials of different physical, chemical, and mechanical properties. Such as FRP is a typical composite material. The composite materials are glass fiber reinforced composite (GFRP), carbon fiber reinforced composite (CFRP), aramid fiber reinforced composite (KFRP), and boron fiber reinforced composite materials, collectively referred to as resin-based fiber reinforced composites (FRP). It has only high specific strength and specific stiffness (3 to 8 times higher than metal), and has good fatigue resistance, shock absorption and fracture safety, and is widely used in aerospace, aviation, chemical and other industries. When the composite material is cut, the thermal conductivity of the material is very low (less than 1/16 of that of ordinary steel), resulting in high cutting temperature, easy to deteriorate and soften, the performance of fiber and resin is very different, and the surface roughness is difficult to reach. The tool wear is severe and the cutting fluid cannot be used in most cases.
1 Tool material: high speed steel and coated high speed steel, YG type hard alloy. In order to improve tool durability from tens to hundreds of times, PCD and PCBN tools should be selected.
2 Tool geometry parameters: γ0=-10～-15°, α 0=10～12°, γε=1～3mm under normal conditions, γt=-15～-25° to prevent disintegration during threading.
3 Cutting amount: high-speed steel tool Vc=1O～15 m/min; cemented carbide tool Vc=40～80m/min; PCD, PCBN tool Vc=80～120m/min, f=0.2～0.5 mm/r,α p has no special requirements.
4 Note: In order to prevent delamination and tearing, protective measures should be taken (supporting the protective plate, reducing the tool's main declination and feed rate, and chamfering at the cut-in and cut-out).
Third, the conclusion:
With the development of science and technology, the emergence and application of high-performance and special-performance materials mostly require cutting, which brings problems to the cutting process. In addition to the above-mentioned types of difficult-to-machine materials, there are many pure metals and alloys, such as pure nickel, pure molybdenum, pure tungsten, pure iron, antimony, etc., among which some of them have extremely poor machinability. To this end, we must understand the performance of the materials being processed, and extensively learn the experience and knowledge of others to successfully solve the processing of difficult-to-cut materials in production.
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