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Difficult to cut materials processing

Time:2012.05.23 News sources:Yangzhong Hongtu Grinding Tools Co.,Ltd. Browse the number:

First, the Introduction:
What difficult to cut materials?

Cutting poor materials. Greater than or less than this indicator of general material properties (HB> 250, b> 1000 MPa, and > 30%, alpha k> 100 MPa, K <41.8 the W / m? K) The one above all are difficult to cut materials. You can also use the phenomenon of the cutting process (cutting force, cutting heat, tool wear and tool durability, machined surface quality, chip control, etc.) to measure.

2, material cutting factors:

physical properties:

1) The thermal conductivity K: thermal conductivity Gaoyang material allows Vc will be high. The following materials such as carbide cutting tool Vc:

Carbon steel K = 48.2 ~ 50.2 the W / m? K Vc = 100 to 150 m / min.

High-temperature alloy K = 8.4 ~ 16.7 of W / m? K Vc = 7 of 60 m / min.

Titanium K, = 6.3 9.6 the W / m? K Vc = 15 ~~ of 50 m / min.

2) The coefficient of linear expansion : affect the degree of material expansion and contraction affect the machining accuracy.

chemical composition: the ratio of chemical composition affect the mechanical properties, physical properties, heat treatment performance, the microstructure of materials, machining fundamental factors. Such as:

C: The material carbon content increases, the increase of its hardness and strength.

Ni: Ni can improve the material heat resistance, but the material thermal conductivity decreased significantly; when Ni> 8%, the formation of the austenitic steel, so that serious work hardening.

V: As it is content, material grinding performance to deteriorate.

Mo: to improve the strength of the material toughness, but the material thermal conductivity is decreased.

W: material heat resistance temperature strength and room temperature hardness and strength. However, the material thermal conductivity decreased significantly.

Mn: to improve the hardness strength, toughness decreased. When Mn> 1.5%, materials machinability worse.

Si: make the material thermal conductivity decreased.

Ti: Ti is easy to form carbide elements, its workability is poor.

There are Cr, O, S, P, N, Pb, Cu, Al and other elements affect the machinability of materials.

The mechanical properties: 1) hardness strength: material hardness and strength fitness, better machinability, the higher the hardness and strength, machinability worse. Such as normalized 45 steel: HB200, b 640 MPa; quenching 45 Steel: HRC45, the b 2100 to ~ 2600 MPa. Material cutting a metallic material organization, fine debris, such as A1203, Si02, Titania and microhardness of high mechanical wear on the tool; its machinability deterioration. 2) toughness k plasticity of : the toughness plastic materials, cutting resistance, the deformation of the heat on its machinability. 3) elastic modulus E: it represents the material stiffness index, elastic modulus, indicating that difficult to produce elastic deformation of materials under loads. The elastic modulus of the material removal process, the elastic recovery large and tool friction cutting difficult. E, such as soft rubber == 2 ~ 4MP; 45 steel of E = 200000 MPa,: Mo materials of E = 500 000 MPa,

Ferrite the microstructure: 1): it is very low hardness and strength (HB50-90 b = 190 250 MPa) and high ( = 40 ~~ 50%) of plastic toughness, cutting is easy to produce BUE. Poor machinability. 2) pearlite: spherical pearlite cutting and (45 steel) 3) cementite such as: high hardness (HRC66-70), but very brittle ( k = 30-35 MPa), Fc increases the easy chipping and make cutting difficult. 4) Austenitic: hardness is not high (HB200 or so), but the plastic toughness high processing surface hardening of the chip serious with the tool cold welding, cutting poor. 1Cr18Ni9Ti, high temperature alloys. 5) martensite: quenched steel belong to this type of microstructure. High hardness, brittleness, and the relative machinability of 45 steel 1/3 to 1/10.

3, the cutting characteristics of hard cutting materials:

cutting force: In order to cut the 45 steel 1.5 to 2.5 times

cutting temperature: when Vc = 75m/min, cutting the following materials than cutting 45 steel cutting temperature:

TC-4 435 GH132 320 GH36 270 1Cr18Ni9Ti 195

hardening tendency: some hard cutting material toughness, high plasticity, the enhancement factor; combined with cutting heat absorbed by the surrounding medium H, O and N atoms, so that the cutting surface of the machined surface to the formation of hard and brittle layer, the degree of hardening of 50 to 200 percent higher than the matrix. Depth greater than 0.1mm, cutting 45 steel several times.

4, to improve the sexual transmission of difficult to cut materials:

selection of fine tool material. use reasonable tool geometry. The reasonable selection of cutting parameters. The cutting fluid the selection performance. Improvement fixture structure. appropriate heat treatment of the material being processed. other process

Second, the turning of hard cutting materials:

1, the turning of hardened steel:

hardened steel cutting Features: 1) high hardness: HRC45-70. 2) brittleness. 3) high strength: b = 2100 ~ 2600 MPa, 45 steel is about 4 times. 4) The cutting force: unit cutting force Kc is 4500MPa, cut 45 steel 2.5 times. 5) cutting temperature: the thermal conductivity of 45 steel 1/7.

Tool and cutting parameters: 1) cutting tool material: of PCBN, ceramic, tungsten carbide (600,610, YS8, YT05, 758,813) and so on. 2) The tool geometry: 0 = 0 ~~ -10 , the hardness for cutting 0 = -10 to -30 , 0 = 8 to 10 r = 30 to 60 , s = 0 to -3 . 3) the amount of cutting: Carbide Vc = 30 to 50m/min; ceramic tool Vc = 60 to 120m/min; of PCBN tool Vc = 100 ~~ of 200 m / min. Interrupted cutting Vc is above 1/2 and p , f is the cutting of general steel 1/2.

Note: the surge of hardened steel, heat resistance of 200 ~ 400 , the hardness with the temperature increased, decreased. Tool material (carbide, ceramics, PCBN) heat resistance of 800 to 1000 , 1200 , 1400 to 1500 , the use of this feature, continuous cutting, Vc can not choose too low; drilling, Vc reasonable ground retraction; interrupted cutting f smaller r properly reduced æ the increase, s is negative.

3, high temperature alloy turning

High temperature alloys containing many high melting point alloying elements Fe, Ti, Cr, Ni, V, W, Mo, etc., this element with other alloying elements constitute a high purity, compact structure austenitic alloy. Has elements with non-metallic elements C, B, N constitute a high hardness, specific gravity, high melting point metal and nonmetal sets of objects. Cutting becomes poor. It is only the relative machinability of 45 steel 5 to 20 percent.

cutting Features: 1) cutting force: 2 to 3 times larger than the cutting general steel. 2) Cutting temperature: 50% higher than the cut 45 steel. 3) serious: hardening the cutting surface of the machined surface hardness than the matrix of high 50-100%. 4) The tool wear and easy: easy to produce bonding, diffusion, oxidation, the grooves wear.

tool materials: 1) high-speed steel: high vanadium, high carbon, aluminum high-speed steel. 2) carbide: thin ultrafine particles YG

tool geometry parameters: Wrought Superalloys: 0 = 10 , cast superalloy: 0 = 0 , generally do not take the negative chamfer. 0 = 10 to 15 the Rough s = -10 , fine cars s = 0 to 3 r = 45 to 75 .

cutting parameters: 1) high-speed steel cutting tools: Vc = 3 8m/min. 2) carbide cutting tools: Vc = of at 10 ~~ 60 m / min. Wrought Superalloys: Vc = 40 ~ 60m/min. Cast Superalloys: Vc = 7 ~ 10m/min. pf> 0.1mm.

(5) cutting fluid: with stainless steel.

high temperature alloy drill: should maximize the use of carbide drill bits, or S-shaped shallow hole drilling; such as when using high-speed steel drill bit, increase the towel, grinding alpha 0b, Vc of 3 m / min, f 0.2 ~ 0.3mm / r; drill bit sharp, blunt standard for steel 1/2 ~ 1/3, it is best to use the automatic feed not cutting table and stay.

4, titanium turning:

Titanium in recent decades developed a new metal, because of its strength (b / = 1680/4.5 = 373,45 steel 4.5 times), high hot strength (500 C long-term work), good corrosion resistance, excellent low temperature performance, while for the aerospace, chemical, medical and other.

cutting Features: 1) cutting temperatures are high: the same cutting conditions, 1-fold higher than the cut 45 steel. 2) the role of pro-serious bonding, high temperature bonding phenomenon. 3) chemical activity: high temperature cutting conditions, with air, O, N, H, C, reaction to generate the hard cortex of TiO2, TiN, TiH, difficult to cut.

tool materials: 1) high-speed steel: In addition to the ordinary high-speed steel, the best selection of high-vanadium, cobalt, aluminum, high-speed steel. 2) carbide: of YG8 YG6X, YG6A 813,643, YS27, YD15.3) PCD, PCBN natural diamond.

(3) tool geometry parameters: 0 = 5 ~~ 15 , alpha 0 15 .

cutting parameters: 1) high-speed steel cutting tools: Vc = 8 ~~ of 12 m / min. 2) carbide cutting tools: Vc = of at 15 ~~ 60 m / min. 3) PCD, PCBN natural diamond tools: wet cutting Vc = 200 m / min.: Dry cut Vc = of 100 m / min, and alpha p> 0.05mm, f> 0.05mm / r.

cutting fluid: an emulsion, extreme pressure emulsions. Extreme pressure cutting oil used in the finishing.

Note: turning slender shaft (pole) should be used when live top nylon heart with the turret frame claw care; reaming, the application of castor oil 60% + 40% of kerosene for cutting fluid; tapping, due to increase bottom diameter.


Chilled cast iron cutting:

The type of cast iron surface white, hardness up to HRC60 or so; unit cutting force K c up to 3000MPa, cutting 45 steel 1.5 times; near the blade of the cutting force set, processing pores, coarse, easy to damage the tool cutting; It is brittle, cutting, chipping, dregs and other phenomena will happen.

tool materials: 1) carbide: high carbide hardness bending strength should be selected. YS2, YS8, YS10, 600,610,726. 2) ceramics: SG4, AT6, SM FT80, FT85. 3) of PCBN: for fine cars.

tool geometry parameters: 1) Carbide: 0 = 0 ~~ -5 , 0 = 5 to 10 , r 45 (r = 45 ), s = -5 to 10 æ = 0.5 ~ 1 mm;

cutting the amount of carbide cutting tools: 1): roughing of Vc = 7 10m/min, alpha p = 5 ~~ 10mm, f = 0.5 ~~ 1.5mm / r. Finishing: Vc = 15 to 20m/min, alpha p = 0.5 ~~ 2mm, f = 0.3 ~ O.5mm / r. 2) Ceramic cutting tools: Vc = 40 ~ 50m/min, alpha = 0.5 to 2mm, f = 0.3 ~~ 0.6mm / r. 3) of PCBN cutting tools: Vc = 60 ~ 70m/min, alpha = 0.5 to 2mm, f = 0.1 ~~ 0.3mm / r.

6, thermal spraying (welding) material turning:

Thermal spray materials a lot of groups of high strength alloy, high temperature, high-speed jet on the workpiece surface, so that the workpiece surface hardness, corrosion resistance, wear resistance, heat resistance is greatly improved, and widely used. Copper, iron-based powder coating layer hardness, easier cutting. Cobalt base, nickel-based powder coating layer hardness> HRC50, difficult to cut. Cobalt package WC, nickel package WC, nickel package Al2O3 coating layer hardness> HRC65, the most difficult cutting.

tool materials: 1) carbide: hardness> HRC45, using of YG, YW carbide; hardness, 600,610,726,767, YD05, YC12, YS2, YS8: hardness> HRC65 YG3X, YD05 YC09, YC12, YS8, 600,610.

2) Ceramic cutting tools: 3) PCBN

The tool geometry parameters: 0 = 0 ~~ -5 , 0 = 8 to 12 r 45 .

of Cutting: Carbide of Vc = 6 ~ 40m/min; ceramic tool Vc = 18 ~ 80m/min; of PCBN tool: Vc = 24 to 160m/min. p = 0.15 ~ 0.6mm; f = 0.1 ~ 1mm / r.

Soft rubber cutting:

Soft rubber hardness (Shore A 30 to 35), strength (the b 20 to 25 MPa) is very low, poor thermal conductivity (0.14W / m? K), plastic high ( = 500 to 700), the modulus of elasticity very small (2 to 4 MPa). Because of these properties, it has good flexibility, submissive sex variability, it is difficult to cutting it.

tool materials: high-speed steel, YG carbide.

tool geometry parameters: 0 = 45 ~~ 55 , 0 = 10 to 15 , 0 = 20 to 30 ; scraping when 0 = 0 , 0 = 70 , with cutter (0 is ~~ 10 ), nesting knife.

cutting parameters: Vc 100 m / min. p = 2 ~ 5mm; f = 0.5 ~ 0.7 mm / r.

cutting fluid: aqueous solution with no oil.

8, the wheel is turning:

Generally the abrasive hardness of the corundum class of 1800 ~ 2450HV, silicon carbide abrasive hardness of 3100 ~ 3400HV PCDPCBN tool to turning the two grinding wheels as easy as a knife tofu.

In order to prevent the wheel turning, chipping, circular blade clamp tool.

tool geometry: circular blade 0 -8 ~ -10 , 0 = 10 .

cutting parameters: Vc = 30 ~ 50m/min. p = 4 ~ 5mm; f = 1 ~ 1.5 mm / r.

9, carbide turning:

Carbide hardness (HRA85 ~ 92.5, HV1300 ~ 1650, HRC67 ~ 81), brittleness (the b 900 to 2500 MPa). Previously only Grinding EDM processing. PCD, PCBN super-hard tool, provided the conditions for turning operations.

tool material: PCD, PCBN. tool geometry parameters: 0 ~~ -5 , 0 = 6 to 8 r 30 to 45 .

cutting parameters: Vc = 20 ~~ 35m/min, alpha p = 0.1 ~~ 1.5mm, f = 0.05 to 0.15 mm / r.

Note: to prevent chipping: kerosene as a cutting fluid.

10, turning Engineering Ceramics:

The traditional ceramic grinding with diamond wheel. This is due to its high hardness (1100 ~ 2250HV), low flexural strength (450 to 1300MPa) and elastic modulus (315000 ~ 400000MPa).

tool material: PCD, PCBN; easy to cut ceramic can also be used carbide, tool life is low.

The tool geometry parameters: 0 = -10 ~~ -15 , 0 = 8 to 12 r = 30 to 60 . Can be applied in order to cut out cut into the smooth, circular blade.

cutting parameters: the car of carbide cutting tools, easy to cut ceramic Vc = 10 to 20m/min. Using the PCD, PCBN tool Vc = 30 ~~ 60m/min, alpha p = 0.1 ~~ 2mm; f = 0.05 to 0.1 mm / r.

cutting fluid: an emulsion. (5) pay attention to the problem: to prevent chipping.

11 composites turning:

By two or more different physical, chemical, and mechanical properties of material, the composite made of artificial multi-phase composition of solid materials. Typical composite materials such as fiberglass. Types of composite glass fiber reinforced composite materials (GFRP), carbon fiber reinforced composite materials (CFRP), aramid fiber reinforced composite (KFRP), and boron fiber reinforced composite materials, collectively referred to as the resin matrix fiber reinforced composites (FRP). It only has a high specific strength and specific stiffness (higher than that of metal 3 to 8 times), and fatigue resistance, shock absorption, breaking security, and is widely used in aerospace, aviation, chemical and other industries. The machining of composite materials, due to the material thermal conductivity is very low (less than general steel 1/16), resulting in high cutting temperature, easy to produce deterioration softening fiber resin properties vary greatly, the surface roughness is difficult to achieve, and serious tool wear, In most cases you can not use the cutting fluid.

tool materials: high-speed steel coated high speed steel, YG carbide. Tens to hundreds of times to improve tool life, to be elected to the PCD, PCBN cutting tools.

tool geometry parameters: general under 0 = -10 to -15 , 0 = 10 to 12 æ = 1 ~~ 3mm threading in order to prevent the collapse of teeth t = -15 to -25 .

cutting parameters: high-speed steel cutting tools of Vc = 1O to of 15 m / min.; Carbide cutting tools Vc = 40 to 80m/min; the PCD of PCBN tool Vc = 80 ~ 120m/min, f = 0.2 of 0.5 mm / r, p no special re, quirements.

Note: To prevent stratification, tear, and should adopt protective measures (bearing protection pull reduce the tool angle into the the Qie Ruqie source of to the amount of the first chamfer).

       Third, the Conclusion:

With the development of science and technology, high-performance materials of special properties, applications, most still require cutting to cutting problems. 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 and pure tungsten, iron, tantalum, etc., they are cutting is very bad. To this end, we have to understand the performance of the material being processed, the wide range of learning experiences of others and cut knowledge, in order to successfully solve the production of difficult to cut materials.

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