The cutting of titanium alloy is machined (on)
- source:PHAUP CNC Machining
1 ％ , dan Jijiang spends low, plasticity tall. 99.
The function of pure titanium of 5 ％ industry is: Density ρ =4.
5g/cm3, melting point is 1800 ℃ , =15 of λ of coefficient of thermal conductivity.
K) , tensile strength σ B=539MPa, ％ of =25 of percentage elongation δ , section shrinkage ψ =25 ％ , stretch model measures E=1.
078 × 105MPa, hardness HB195. (1) is taller than intensity: The density of titanium alloy is in commonly 4.
5g/cm3 left and right sides, it is the 60 ％ of steel only, the intensity of pure titanium is close to the intensity of common steel, alloy of a few high strenth titanium exceeded the intensity of a lot of alloy structure steel. Because of this titanium alloy than intensity (intensity / density) ambitious at material of other metal construction, see watch 7-1, can make an unit intensity tall, tigidity is good, qualitative light 0, component. Use titanium alloy the motor component of the plane, framework, envelope, fastener and landing gear at present. (2) hot intensity is high: To α titanium alloy, when 350 ℃ the σ B of the Gong Da 422MPa of TA6, TA7 amounts to 491MPa, when 500 ℃ the σ B of TA8 amounts to 687MPa; To α + β titanium alloy, the σ B that amounts to 618MPa, TC10 in the σ B of the TC4 when 400 ℃ amounts to 834 MPa, the σ B that all amounts to 589MPa, TC8 in the σ B of the TC6 when 450 ℃ and TC7 amounts to 706MPa, when 500 ℃ the σ B of TC9 amounts to 785MPa. Alloy of these two kinds of titanium is in 150 ℃ ～ still has inside 500 ℃ limits very tall than intensity, and aluminium alloy drops apparently than intensity when 150 ℃ . The working temperature of titanium alloy can amount to 500 ℃ , aluminium alloy is under 200 ℃ . (It is good that 3) fights corrode sex: Titanium alloy works in humid air and briny medium, its fight stainless steel of corrode sex far excel; The resistance that corrodes to nodding corrode, acid etching, stress is particularly strong; Right alkaline, chloride, chloric organic article, nitric acid, vitriolic etc have fight admirably corrode ability. But the sex fighting corrode that titanium reachs chromic salt medium to having reproducibility oxygen is poor. (Performance of 4) low temperature is good: Titanium alloy falls in microtherm and ultralow temperature, still can maintain its mechanical function. In - 100 ℃ and - the σ B of the TA4 when 196 ℃ is 893MPa and 1207MPa respectively, in - 196 ℃ and - the σ B that the σ B of the TA7 when 253 ℃ is the σ B of 1216MPa and 1543MPa, TC1 to be 1133MPa and 1354MPa, TC4 respectively respectively is 1511MPa and 1785MPa respectively. Accordingly, titanium alloy also is a kind of important microtherm construction material. (5) chemical active is big: The chemical active of titanium is big, wait for the chemical reaction with strong generation with gas of the O in atmosphere, N, H, CO, CO2, vapor, ammonia. The quantity that contain carbon is more than 0.
When 2 ％ , horniness TiC can be formed in titanium alloy; When temperature is higher, with N action also can form TiN horniness surface layer; When 600 ℃ above, titanium absorbs oxygen to form the sclerotic layer with very tall hardness; Hydrogenous content rises, also can form fragile change a layer. The deepness of hard fragile surface layer that absorb gas and arises can be amounted to 0.
1 ～ 0.
15 Mm, sclerotic degree is 20 ％ ～ 30 ％ . The chemical endophilicity of titanium is big also, easy produce conglutinate phenomenon with attrition surface. (6) small, stretch model measures coefficient of thermal conductivity small: The =15 of λ of coefficient of thermal conductivity of titanium.
24W ／ (M.
K) , it is the 1/4 of nickel about, the 1/5 of iron, aluminous 1/14, and the coefficient of thermal conductivity of all sorts of titanium alloy drops about than the coefficient of thermal conductivity of titanium 50 ％ . The stretch model of titanium alloy measures the 1/2 that is steel about, reason is out of shape its tigidity difference, easily, lever of the unfavorable slightness that make and thin wall, the spring back amount that the surface processes when cutting is very large, the 2 ～ that are stainless steel about 3 times, the acuteness attrition of face of the knife after causing cutting tool, conglutinate, felt wears away. Visibility of the brand of titanium alloy, sex expresses 7-2. Normal > 3. What cutting characteristic does titanium alloy have? Normal > titanium alloy is more than HB350 machines special difficulty, when be less than HB300 appear easily phenomenon sticking a knife, also be hard to cutting. But the hardness of titanium alloy is only be hard to a respect that cutting machines, the key depends on chemistry of titanium alloy itself, physics, mechanical function between be opposite integratedly the influence of its cutting processability. Titanium alloy is like next cutting characteristics: Normal > (1) is out of shape coefficient is small: This is the marked characteristic that titanium alloy cutting machines, be out of shape coefficient is less than or be close to at 1. Cut bits the distance of the sliding friction on advanced knife face increases greatly, quicken cutting tool to wear away. Normal > (2) cutting is high: Because the coefficient of thermal conductivity of titanium alloy is very small (the 1/5 ～ 1/7) that is equivalent to 45 steel only, cut bits and before the osculatory length of knife face is extremely short, the heat of the generation when cutting comes out not easily, inside the lesser limits that is centered around cutting area and cutting blade, cutting temperature is very high. Below same cutting condition, cutting temperature can compare cutting the tower above when 45 steel one times above. Normal > (3) unit: Advocate cutting force is compared when cutting steel, make an appointment with small 20 ％ , because cut bits and before the osculatory length of knife face is extremely short, unit interface accumulates the cutting muscularity that go up to increase greatly, cause collapse blade easily. In the meantime, because the stretch model amount of titanium alloy is small, easy generation falls to bend in radial load action when treatment be out of shape, cause vibration, increase the precision that cutting tool wears away and affects a part. Accordingly, requirement machining complex should have better tigidity. Normal >(4) is cold good appearance is serious: Because the chemistry of titanium is active big, below high cutting temperature, the oxygen in absorbing air very easily and nitrogen are formed hard and fragile cortical; At the same time the plasticity in cutting process is out of shape also can cause case hardening. Cold good appearance can reduce the fatigue intensity of the spare parts not only, and can aggravate cutting tool wears away, it is a when cutting titanium alloy very important characteristic. Normal > (5) cutting tool is easy wear away: Punch of semifinished product course, forging, after the method such as hot-rolling is machined, form hard and fragile inhomogenous cortical, create collapse blade appearance extremely easily, the it is the most difficult to make excision crustaceous process in becoming titanium alloy to machine. Additional, because titanium alloy is right the chemical endophilicity of cutting tool material is strong, go up high with unit area in cutting temperature below the condition of cutting muscularity, cutting tool produces felt very easily to wear away. When turning titanium alloy, sometimes before the side of the knife after wearing away to be compared even of knife face is more serious; Feed F<0.
When 1 Mm/r, wear away to basically happen after on knife face; When F>0.
When 2 Mm/r, knife face will appear before wear away; When using vehicle of fine of hard alloy cutting tool and half essence car, hind of knife face wear away with VBmax<0.
4 Mm is more appropriate. Normal >normal >4. When cutting titanium alloy how to choose cutting tool material? Normal > cutting machines titanium alloy to answer from reduce cutting temperature and reduce felt two respects set out, choose red rigid good, bending strength the cutting tool material with as good, poor as titanium alloy endophilicity performance of tall, heat conduction, YG kind hard alloy is more appropriate. Because the hear resistance of high-speed steel is poor, because this answers,use the cutting tool that hard alloy makes as far as possible. Material of commonly used hard alloy cutting tool has YG8, YG3, YG6X, YG6A, 813, 643, YS2T and YD15. Normal > coating razor blade and YT kind meeting and titanium alloy generation kiss hard alloy acutenessly and action, the felt of aggravate cutting tool wears away, unfavorable use cutting titanium alloy; To complex, multiple-cutting-edge tool, can choose tall vanadium high-speed steel (like W12Cr4V4Mo) , tall cobaltic high-speed steel (like W2Mo9Cr4VCo8) or aluminous high-speed steel (wait for cutting tool material like W6Mo5Cr4V2Al, M10Mo4Cr4V3Al) , comfortable at making the broach of cutting titanium alloy, reamer, establish the cutting tool such as milling cutter, broach, tap. Normal > uses diamond and cubic nitrogen to change boron to make alloy of titanium of cutting tool cutting, can obtain remarkable result. If use the condition that natural diamond cutting tool cools in emulsion, cutting speed can amount to 200 M/min; If need not cutting fluid, when coequal wear extent, permission cutting rate is 100m/min only. Normal > 5. When cutting titanium alloy how to choose parameter of cutting tool geometry? Normal > (1) 0: Titanium alloy is cut bits and before the osculatory length of knife face is short, before the osculatory area that knife bit can add already when role is minor, it is beyond the mark to make heat in metal cutting and cutting force unapt concentration is near cutting blade, improvement comes loose hot condition, can strengthen cutting blade again, reduce the possibility of collapse caustic. 15 ° of ～ of ° of general 0=5 extraction γ . Normal > (2) 0: Titanium alloy already machined exterior flexibility to restore big, cold good appearance serious, use big hind the attrition that horn can reduce face of the knife after be opposite to cause, conglutinate, felt, tear off wait for a phenomenon, in order to reduce hind of knife face wear away. Of cutting tool of all sorts of cutting titanium alloy hind horn basically is more than be equal to 15 ° . Normal MARGIN: 0cm 0cm 0pt; LINE-HEIGHT: S of λ of dip of 32pt"> (4) blade: Organize with surface layer crustily as a result of semifinished product inhomogenous, blade of the cutting when thick car dies easily caustic, to raise the intensity of cutting blade and sharp rate, should increase the sliding velocity that cuts bits, ～ of ° of general S =-3 extraction λ - 5 ° , ° of S =O of the λ when fine vehicle. Normal > (5) point of a knife: The point of a knife when cutting titanium alloy is the weakest part, easy collapse is dropped and wear away, need to grind a circular arc of point of a knife, =0 of general R ε .
5 ～ 1.
5mm. Normal > turning lose edge (B γ =0.
03 ～ 0.
05 Mm, 0 ° of ～ of γ 01=-10 ° ) , break (roll) the 8 Mm of ～ of Rn=6 of radius of bottom land circular arc of bits chamfer. Normal > is additional, it is very important also to raising its durability that cutting tool blade grinds quality. Appropriate of hard alloy cutting tool is ground with blade of diamond emery wheel, the point when cutting must sharp, ra value should be less than the exterior surface roughness of around knife face 0.
4um, point part not the gap with little be patient of. After cutting tool blade is ground, undertake abrade, its durability can raise 30 ％ . Normal > 6. When cutting titanium alloy how to choose cutting dosage? Normal > cutting titanium, cutting temperature durability of tall, cutting tool is low, rate of the cutting in cutting dosage is the oldest to the influence of cutting temperature, the cutting temperature of the generation below the cutting speed that because this answers,do one's best makes choose approachs optimal range. The optimal cutting temperature when alloy of titanium of cutting of high-speed steel cutting tool is 480 ℃ ～ about 540 ℃ , hard alloy cutting tool is 650 ℃ ～ about 750 ℃ . Cutting titanium alloy uses inferior cutting speed, bigger cutting deepness and feed commonly. Normal > (1) cutting: Cutting rate is the oldest to influence of cutting tool durability, best can make cutting tool is in wear away relatively the job below the minorrest optimal cutting rate. Cutting is different the titanium alloy of the brand, because intensity difference is bigger, cutting speed should be adjusted appropriately. Cutting deepness also has certain effect to cutting speed, answer to determine the size of cutting speed according to different cutting deepness, nucleus coefficient sees watch 7-3 and watch 7-4. Normal Align=center>normal Align=center>normal Align=center>normal >normal > (2) feed: Feed is lesser to the durability influence of cutting tool, below the condition that assures to machine exterior surface roughness, optional bigger feed, take F=0 commonly.
1 ～ 0.
3 Mm/r. Feed is too small, make cutting tool is inside sclerotic layer cutting, increase cutting tool to wear away, cut bits paper-thinly to issue easy spontaneous combustion in high cutting temperature at the same time, because this does not allow F<0.
05 Mm/r. Normal > (3) cutting: Cutting deepness is the smallest to the influence of cutting tool durability, choose bigger cutting deepness commonly, can avoid point of a knife to be inside sclerotic layer not only so cutting, reduce cutting tool to wear away, still can increase edge job length, be helpful for coming loose hot, take 5 Mm of α P=1 ～ commonly. Normal > turning titanium sees watch 7-5. 7. When cutting titanium alloy how to choose cutting fluid? When cutting titanium alloy, to drop cutting temperature, ought to to the gives priority to with cooling action cutting juice with cutting pouring and much area. Have coefficient of thermal conductivity to the requirement of cutting fluid big, specific heat big, vaporization heats up big, thermal capacity speed of big, vaporization fast, discharge big, velocity of flow is rapid. Say commonly, water is bigger than oily coefficient of thermal conductivity 3 ～ 5 times, specific heat is 1 times bigger, vaporization heat is almost 10 times bigger the left and right sides, reason uses water-solubility cutting liquid relatively appropriate. When alloy of titanium of car, milling, often use emulsion, or use have extremely the water-solubility cutting fluid that presses additive. Extremely the recipe that approachs emulsifying agent is: Oil sulphur acerbity natrium 10 ％ oleic acid acerbity lead of sulphur of 3 ％ oil 3 alcohol of 6 ％ amine 3.
Olefin of chloridize of 5 ％ 4 ％ 20 engine oil 70.
Tristearin of 5 ％ chloridize is acerbity 3 ％ extremely the recipe of the water-solubility cutting fluid that presses additive is: Chloridize fatty acid, pvc 0.
5 ％ ～ 0.
8 ％ phosphoric acid 3 natrium 0.
3 alcohol of 59 ％ amine 2 ％ of 1 ％ ～ inferior sodium nitrate 1.
The others of 2 ％ water wait for working procedure to aperture of bore, reaming, bore with a reamer, broaching, tap, should use lubricant function bigger extremely press solubility oil to make cutting juice, if castor oil, oleic acid, sulfurized oil, chloridize is oily,wait. Cooling and lubricant method had better use high-pressured spray law of cooling law, the refrigeration inside high pressure, such ability can have good refrigeration, lubricant effect. Cutting current measures Min of not less than ／ of 15 ～ 20 L. 8. What problem should cutting note when titanium alloy? In the process of cutting titanium alloy, the item that should notice has: (The 1) stretch model amount as a result of titanium alloy is small, workpiece is out of shape in the clamp in treatment and suffer force to be out of shape big, can reduce the treatment precision of workpiece; The clamping force when workpiece is installed shoulds not be too big, can increase auxiliary bearing when necessary. (If 2) uses chloric cutting liquid, the explanation will be divided to give off below high temperature in cutting process hydric, be absorbed to cause hydrogen by titanium fragile; Cause stress of titanium alloy high temperature possibly also to corrode craze. (When the chloride in 3) cutting fluid is used, still may be decomposed or volatilize toxic gas, use what is appropriate to the occasion adopts safe preventive measure, should not use otherwise; Cutting hind should be used in time not chloric clear lotion cleans a spare parts thoroughly, cleared contain chloric hangover. (4) taboo lead or zinc base the work that alloy makes, clamping apparatus and titanium alloy contact, copper, stannum, cadmium and its alloy as much taboo. (5) and all labour that titanium alloy contacts, clamping apparatus or other unit must clean; Via cleaning the titanium alloy part that spend, want to prevent grease or finger mark pollution, may cause salt later otherwise (sodium chloride) stress is corroded. (Usually cutting machines 6) when titanium alloy, dangerous without draw well, it is only when minim cutting, those who cut is petty the ability that cut bits has appearance of draw well combustion. To prevent fire, divide many and pouring besides cutting fluid, still should prevent to cut bits to pile up on the machine tool, cutting tool is used blunt hind undertake changing instantly, or lower cutting rate, increase feed to cut bits ply in order to increase. Once catch fire,be like, should use French chalk, limestone pulverous, dry arenaceous wait for fire extinguisher material to undertake putting out, forbidden use fire extinguisher of 4 chloridize carbon, carbon dioxide, also cannot water, because water can quicken combustion, cause hydrogenous explosion even. 9. How to undertake milling to titanium alloy? Titanium alloy is in in inert gase medium when low speed milling, cut bits to be out of shape coefficient is more than 1.
0; But in atmosphere, when milling rate Vc=30 M/min, cut bits to be out of shape coefficient is less than 1.
0, because titanium alloy is when high temperature milling,this is, very big to the endophilicity of the oxygen in atmosphere and nitrogen, below condition of 800 ℃ high temperature, of titanium alloy cut bits drastically from all round these gas are absorbed in atmosphere, the mill bits that generation changes and makes shorten is new and stretchy. The temperature when titanium alloy milling is very high, wallop is big, should choose can bear well hand in change the material of milling cutter tooth of load and thermal shock. Choose YG normally kind hard alloy, usable also cobalt, aluminium exceeds hard high-speed steel. The geometrical parameter of titanium alloy milling cutter and milling dosage see watch 7-6 and watch 7-7. When milling titanium alloy, appropriate uses asymmetry to obey mill law, part of point of a knife is far from to contact workpiece above all before such tooth, tooth is cut when leaving cut bits very thin, not easy felt is on cutting blade. And when going against mill antipodal, stick bits easily, cut again when tooth fashionable cut bits to be touched, cause cutting tool material to flake collapse blade. The optimal position that the deflection quantity E that carries milling cutter and workpiece axis space can decide to milling cutter tooth and workpiece are contacted above all, arrange mill or go against mill to reach cut the size that bits ply cuts when leaving, measure E=(0 with deflection commonly.
04 ～ 0.
1) Do is advisable (Do is) of diameter of upright milling cutter. Because the stretch model amount of titanium alloy is small, suitable mill creates appearance letting a knife, requirement machine tool and cutting tool have bigger tigidity. The cutting tool when milling and the osculatory length that cut bits are short, coil not easily bits, requirement cutting tool has better tooth strength and larger look bits space, cut bits to jam otherwise can cause cutting tool acuteness wear away. Normal > 10. How to undertake bore to titanium alloy? Normal > bore is half enclosed cutting, very tall to temperature of the cutting in process of titanium alloy bore, the spring back after bore is big, get bits to grow and thin, easy felt and not easy eduction, often cause broach to be waited for by bite into, twist off malign accident. Because this asks broach has the tigidity of tall intensity become reconciled, the chemical endophilicity of broach and titanium alloy wants small, had better use hard alloy bit, but at present the most commonly used still is twist drill, after be being improved through taking a few step, also can obtain better result. Normal > (1) improves bit: To satisfy the need of pair of titanium alloy bore, should adopt to twist drill improve measure below: Normal > increases broach vertex angle, 140 ° of ～ of ° of 2 Ф =135; Increase the role after the predestined relationship outside broach is in, take 12 ° ～ 15 ° ; Increase helix angle, 40 ° of P=35 ° ～ ; Increase the ply that get a heart, take (0.
22 ～ 0.
4)do(do is broach diameter) . Normal > is used " S " form or " X " form long grind broach horizontal blade, b=(0 of horizontal blade length.
08 ～ 0.
1)do, the symmetry ≤ that assures horizontal blade at the same time 0.
06 Mm. The horizontal blade of two kinds of forms all can form blade of the 2nd cutting, the action that divide bits and the axial power when reducing bore reach since. Normal > is the most commonly used is grind on twist drill piece comfortable at the cutting blade form to titanium alloy bore, namely titanium alloy group auger, the appearance of its cutting part sees graph 7-1. 2 φ and 2 φ ′ are in vertex angle of the blade inside graph China and foreign countries 130 ° ～ all is when 10mm of ～ of broach diameter Do>3 140 ° , 125 ° ～ is when Do>10 ～ 30 Mm 140 ° ; α of the horn after blade is outside when Do>3 ～ 10 Mm for 12 ° ～ 18 ° , 10 ° ～ is when Do>10 ～ 30 Mm 15 ° ; ° of =45 of ψ of horizontal blade bevel; Inside ～ of ° of =-10 of τ of γ of the horn before blade - 15 ° ; Inside 15 ° of ～ of ° of =10 of blade bevel τ ; 20 ° of ～ of ° of AR=18 of the horn after circular arc blade. Normal > titanium alloy group the concerned parameter that get and auger cut dosage to see watch 7-8 and watch 7-9. CNC Milling CNC Machining