Titanium alloy but the research of cutting sex and design of treatment cutting tool
- source:FANYA CNC Machining
Foreword titanium and titanium alloy are the important construction material of the spacecraft such as production plane, missile, rocket not only, and chemical project is reached in mechanical engineering, marine project, biology project medium application is increasingly wide also. If be made in valve in, make stainless steel valve and titanium valve be used in acidity medium at the same time, titanium makes valve have better service life. Alloying element is joined to form titanium alloy in titanium, its intensity rises significantly, σ B can raise 1200MPa from 350 ～ 700MPa, because this is on industry,the meaning of applied titanium alloy has value more. The organization that leaves by use condition normally is titanium alloy cent α titanium alloy (express with TA) , β titanium alloy and (α + β ) titanium alloy (express with TC) 3 kinds, the most commonly used in alloy of 3 kinds of titanium is α titanium alloy is mixed (α + β ) titanium alloy. As a result of titanium alloy but cutting sex extreme difference, because this gives actual application,bring a lot of difficulty. The author from titanium alloy opposite but cutting sex considers to set out, put forward more economic cutting tool according to producing experience for years, offer the reference when reader application. 2.
Titanium alloy but the research of cutting sex if with 45 steel but cutting sex is 100% , criterion of titanium alloy but cutting sex is 20 ～ about 40% , its but cutting sex is poorer than stainless steel, but a bit better than high temperature alloy. Press β titanium alloy, α again in titanium alloy + β titanium alloy, α titanium alloy is foreword its but cutting sex is improved stage by stage, and of pure titanium but cutting sex is best. Be in namely usually, material hardness heals tall, add alloying element more, of material but cutting sex is poorer. When machining titanium alloy, if material hardness is less than HB 300 to will appear to stick knife phenomenon strongly, and when hardness is more than HB370, machine extremely difficult, because this had better make,the hardness of titanium alloy material is in HB300 ～ 370 between. 2.
The research of mechanism of cutting of 1 titanium alloy (the influence of 1) gas impurity all sorts of gas impurity to titanium alloy but cutting sex has very big effect, among them the most remarkable is oxygen, hydrogen and nitrogen; Of titanium alloy cutting sex increases in the content in titanium alloy as gas and can worsen. The chemical and lively sex of titanium element is tall, have very strong affinity, very easy the foreign matter chemical combination with the contact, titanium can act well with the oxygen in atmosphere in 600 ℃ above, when more than 650 ℃ , those who follow temperature rise and action increases. In skin of exterior occurrence oxidation while, oxygen still diffuses to the middle of titanium; In temperature of transition of compose of the different that be the same as element (882.
5 ℃ ) above, oxygen diffuses in titanium particularly intense, down to is formed fragile change a layer, and its are fragile increase and increase what change a ply to let time, arise namely alleged " constituent α changes a layer " . This is the additional sclerosis that titanium is profaned by oxygen and causes, oxygen quantity is contained to heal in titanium much, sclerosis heals very. The oxidation ability that hydrogen follows the addition of temperature in titanium and appears, its diffuse extremely intense, fashion clearance solid solution, produce hydrogenous brittleness. Below room temperature nitrogen does not have an influence to titanium, the nitrogen when high temperature and titanium are intense chemical combination, form hard and fragile nitrogen to change titanium (TiN) . Can see, in titanium alloy, aeriform impurity oxygen, hydrogen, nitrogen can make titanium alloy fragile change, these impurity still have abrasive quality, wear away in what cutting tool can quicken when machining titanium alloy; Still can form after v and punch get higher than original material hardness much crustaceous with oxidation skin. All these, worsened greatly of titanium and titanium alloy but cutting sex. (The influence of 2) material function from but the viewpoint of cutting sex sets out, all sorts of physics of titanium -- mechanical function is very the combination that goes against cutting, because the existence of function of avery kind of is aggravating another kind of cutting that function place causes is difficult. Titanium alloy plasticity is small, the plasticity when affecting its cutting significantly extremely consequently is out of shape. If use the systole that cuts bits to express by cut be out of shape, criterion the contractive coefficient that titanium alloy cuts bits is equal to 1(to be less than 1) even, and the contractive coefficient ψ that common carbon steel cuts bits is approximated 3, the ψ value with titanium lesser alloy makes cut bits classics advocate cutting blade is cut after leaving, break up up instantly roll, between face of the knife before making cut bits and cutting tool only the interface of one minimum is accumulated (the 1/3) that is rolled steel about, the pressure that makes action contacts an area to go up in lathe tool thereby and local temperature heighten; Because titanium alloy has very tall intensity limit, reason causes a contact the pressure that gets on the area and local temperature are higher; The thermal conductance plus titanium alloy is very low (the 1/5 that is iron only, aluminous 1/10, =7 of TC8 thermal conductance λ .
955W/mk) , limitted the cooling condition of point of a knife greatly; In addition, the metallic titanium with lively height arises easily still to solder and be stuck with cutting tool chemical combination pare. As a result of afore-mentioned function integrated, below same cutting dosage, when force of cutting of susceptive of place of area of unit of the cutting tool when machining titanium alloy wants more general than treatment steel products, get greatly much, cutting temperature is gotten high also much, because this makes cutting tool wears away very fast, of material but cutting sex is exasperate. (Of the influence titanium alloy that 3) contains carbon to measure but cutting sex and the quantity that contain carbon is concerned. Be more than when the quantity that contain carbon 0.
20% when, the meeting in alloy forms hard carbide, make but cutting sex drops; And the quantity that contain carbon is less than 0.
20% when, but cutting sex gets ameliorative. (The influence treatment sclerosis with 4) sclerotic treatment is considered as titanium alloy to process one of difficult accounts. To determine its influence rate, we had a test, the result shows in any treatment the circumstance falls, the treatment sclerosis degree of titanium is far be less than stainless steel, also be less than the steel with other easy and sclerotic sort. The sclerosis with titanium serious alloy is the local high temperature that produces in cutting treatment makes titanium absorbs the oxygen in atmosphere and nitrogen very easily to form hard fragile cortical and cause. Below normal cutting condition, its sclerosis deepness is 0.
1 ～ 0.
15mm, sclerotic degree is 20% ～ 30% . 2.
2 titanium alloy is opposite but the research of condition of cutting sex cutting (when material of 1) cutting tool machines titanium alloy, unfavorable use YT kind hard alloy razor blade. Because: ① YT kind titanium is contained in hard alloy razor blade, alloy happening kisses its meeting and the titanium that are machined and action, stick point of a knife. When alloy of ② turning titanium, lathe tool and the contact that cut bits are far when comparing treatment steel small much, the unit cutting knife that action contacts an area to go up in lathe tool is bigger, as a result of YT kind hard alloy razor blade is more fragile, because of this easy collapse blade. YG is used in average production kind alloy of bit treatment titanium, although its wearability is poorer. Mix in thick car normally intermittent YG8 bit is used when turning, YG3 bit is used when fine vehicle and successive turning, common treatment uses YG6X bit. Carry out a proof, the hard alloy YA6(that contains tantalum belongs to cobalt of fine grained tungsten kind hard alloy) the effect is better, because was joined a few rare element, raised bit wearability, replaced original YG6X, its bending strength, hardness is taller than YG6X also. In low speed cutting or cutting complex model when the face, can use tall vanadium high-speed steel (W12Cr4V4Mo) and tall cobaltic high-speed steel (W2Mo9Cr4VCo8) cutting tool, they are the cutting tool material with treatment titanium best alloy, but because cobaltic resource is little and the price is high, because this answers to be used less as far as possible, reduce cost in order to protect rare resource. (When alloy of titanium of cutting of angle of geometry of 2) cutting tool, α of the horn after lathe tool 0 it is the most sensitive in parameter of all cutting tool, because the metallic flexibility below cut restores to be mixed greatly,machine hardness big, use commonly big hind horn can make point cuts metallic layer easily, of face of the knife after reducing wear away, but hind part is too small (be less than 15 ° ) the conglutinate phenomenon of meeting occurrence metal; After that part is too large, cutting tool will be weakened, edge dies easily broken. Accordingly, the lathe tool of alloy of most cutting titanium uses the part after 15 ° . From the point of cutting tool durability, α 0 be less than or be more than 15 ° , can reduce the durability of lathe tool. In addition, the 0 lathe tool edge that are 15 ° compare α sharp, can drop cutting temperature. Because titanium alloy is in cutting process, the oxygen in meeting and air, hydrogen, nitrogen form hard fragile compound, cause cutting tool to wear away (the) on face of the knife before basically happening in lathe tool, because this should use the part before little value; In addition, the plasticity of titanium alloy is low, cut bits and before the osculatory area of knife face is small, for the horn before this also should choose little value, such doing can increase cut bits and before the osculatory area of knife face, it is beyond the mark to make heat in metal cutting and cutting pressure unapt center at point around, be helpful for coming loose already hot, reinforce point again, avoid to be centered because of cutting force and produce collapse blade. Accordingly, machine with hard alloy cutting tool (α + β ) when titanium alloy, ° of 0=5 of γ of the horn before taking is controlled and grind a width of F(pouring arris for 0.
05 ～ 0.
1mm) , 10 ° of ～ of γ F=0 ° , r=0 of wear of point of a knife.
Circular arc of 5mm little value, ° of =+3 of blade dip λ . But study the job makes clear, the horn before lathe tool is in 30 ° of 28 ° ～ inside limits when the durability of cutting tool is best; Radius of circular arc of point of a knife increases to also can reduce the avalanche phenomenon of cutting tool. The geometrical parameter of round lathe tool outside alloy of general turning titanium: Pour arris F=0.
3 ～ 0.
7mm, γ F=0 ° , 10 ° of ～ of γ 0=8 ° , α 0=15 ° , r=0.
5mm, λ =0 ° , κ R=45 ° , ° of κ ′ R=15. (When 3) cutting dosage uses TA2 of alloy of titanium of turning of YG8 razor blade to the influence of cutting temperature, the relation that changes by the change of cutting parameter and cutting temperature is knowable, t of temperature of the cutting when treatment as cutting speed V rise and rise quickly, increase feed F to also make heighten of cutting temperature T, but the impact that its affect higher than carrying rate is little. The change of cutting deepness is minor to the influence of cutting speed. The high cutting rate when treatment makes acutely of cutting cutting tool wears away, and make titanium alloy is had from all round the ability that oxygen and hydrogen absorb in atmosphere, generation is alleged " constituent α is changed " , make machine exterior aggrandizement. Be in normally when choosing cutting speed and feed, maintain cutting temperature to be controlled in 800 ℃ , become namely feed F=0.
11 ～ 0.
When 35mm/r, take 60m/min of ～ of cutting speed V=40. (The influence of 4) cutting dosage to exterior surface roughness because concentration of force of titanium alloy correspondence is very sensitive, in the fatigue intensity that have scratch or it can reduce severely when dent, the treatment demand of quality of surface of titanium alloy spare parts is very accordingly high. Feed is very big to exterior quality influence. By treatment when titanium alloy TC6 (speed V=40m/min, cutting deepness Ap=1mm, knife face wears away after the ≤ after H 0.
1mm) feed and the relation that already machined exterior face surface roughness are knowable, to want to obtain Ra1 of exterior surface roughness.
6 μ M, must choose feed F=0.
16mm/r; If increase work time,do not use feed F=0.
35mm/r and 0.
45mm/r, the treatment surface surface roughness that obtains accordingly is Ra3.
2 μ M, Ra6.
3 μ M and Ra12.
5 μ M. When cutting titanium alloy, exterior surface roughness and cutting speed have nothing to do, the impact of cutting deepness is very little also, exterior quality changes inside same appearance surface roughness. When alloy of finish machining titanium, to get Ra1.
The exterior surface roughness of 6 μ M, should use YG kind hard alloy razor blade, the working surface of abrade lathe tool, take parameter of lathe tool geometry to be: γ F=0 ° , γ 0=10 ° , α 0=15 ° , r=0.
5mm; Choice cutting dosage is: V=50 ～ 70mm/min, f=0.
1 ～ 0.
3 ～ 1.
0mm; The ≤ after H wearing away at the back of cutting tool 0.
3mm. Through increasing R of radius of circular arc of point of a knife, reduce feed F, reduce cutting tool to wear away after H 0.
15mm, alloy of successive turning titanium, can obtain Ra=1.
25 ～ 0.
The exterior surface roughness of 8 μ M. 3.
The cutting treatment of titanium alloy and cutting tool are designed 3.
The modulus of elasticity of alloy of titanium of 1 turning treatment is small, if the stretch model of TC4 measures E=110GPa, it is the half of steel about, the flexibility of the workpiece that be added that causes by cutting force place consequently is out of shape big, will reduce workpiece precision, want to improve the tigidity that processes a system for this. Workpiece must hold clip very firmly, the knife moment that cutting tool chooses to workpiece bearing is decreased the smallest. Cutting tool must sharp, will produce vibration otherwise, grind, make cutting tool durability shortens, workpiece precision drops. When cutting titanium alloy, be in only cutting speed inside the limits of 1 ～ 5mm/min, just the tumour that accumulate bits is formed. Because this is in below average production condition when cutting titanium alloy, won't produce the tumor that accumulate bits. The friction between workpiece and cutting tool coefficient not very big, get good exterior quality easily. Use cooling lubricating fluid appearance of microcosmic to improving titanium alloy appearance geometry does not have the effect, exterior surface roughness already was machined when cutting titanium alloy inferior because the cause of bits tumour was not accumulated on cutting tool,be. But, to improve cutting condition, drop cutting temperature, improve cutting tool life, at the same time the danger to remove fire, adding man-hour to use many dissolubility refrigerant also is necessary. Normally titanium alloy does not have phenomenon of draw well flaming when spare parts treatment, but be in below small cutting position when treatment,have appearance of draw well combustion, to avoid this kind of dangerous sex, should: ① uses cooling fluid in great quantities; ② cuts bits in time from the broom on the machine tool; Equipment of ③ stock put out a fire; ④ changes in time with blunt cutting tool; When ⑤ workpiece surface is polluted bring on fire easily to spend, must lower cutting rate right now; ⑥ is compared than the thin photograph that cut bits, thick cut bits to produce scintilla not easily, because this wants to increase feed, increase feed to won't be resembled increase cutting speed to make temperature lifts quickly in that way. Machine dosage of titanium alloy cutting choose criterion: Answer to set out from the viewpoint that drops cutting temperature, use inferior cutting speed and bigger feed. Because high cutting temperature makes titanium alloy absorbs oxygen and hydrogen from inside atmosphere,create workpiece appearance hard fragile, make cutting tool acuteness wear away, because this is in treatment process, must make temperature of point of a knife maintains in proper temperature, avoid temperature exorbitant. When crustaceous titanium alloy work is being taken with turning of YG8 lathe tool below the condition of interrupted cutting, commendatory cutting dosage is: V=15 ～ 28m/min, f=0.
25 ～ 0.
35mm/r, ap=1 ～ 3mm. When work of alloy of titanium of vehicle of fine of YG3 lathe tool is being used below the condition in successive cutting, commendatory cutting dosage is: V=50 ～ 70m/min, f=0.
1 ～ 0.
3 ～ 1mm. Express the 2 cutting dosage that choose to when turning machines titanium alloy, can be offerred. Express 2.
The cutting dosage when turning titanium alloy working procedure property - titanium alloy material - hardness - cutting surplus (Mm) - cutting speed (Mm/min) - feed (Mm/r) barren car - TA1 ～ 7, TC1 ～ 2 - soft - ply of ＞ oxidation skin - 18 ～ 36 - 0.
1 ～ 0.
25 barren car - TA8, TC3 ～ 8 - in - ply of ＞ oxidation skin - 12 ～ 27 - 0.
08 ～ 0.
15 barren car - TC9 ～ 10, TB1 ～ 2 - hard - ply of ＞ oxidation skin - 7.
2 ～ 18 - 0.
06 ～ 0.
12 thick cars - TA1 ～ 7, TC1 ～ 2 - soft - ＞ 2 - 30 ～ 54 - 0.
2 ～ 0.
4 thick cars - TA8, TC3 ～ 8 - in - ＞ 2 - 24 ～ 54 - 0.
15 ～ 0.
3 thick cars - TC9 ～ 10, TB1 ～ 2 - hard - ＞ 2 - 15 ～ 30 - 0.
1 ～ 0.
2 fine vehicle - TA1 ～ 7, TC1 ～ 2 - soft - 0.
07 ～ 0.
75 - 37.
5 ～ 60 - 0.
07 ～ 0.
15 fine vehicle - TA8, TC3 ～ 8 - in - 0.
07 ～ 0.
75 - 30 ～ 48 - 0.
07 ～ 0.
12 fine vehicle - TC9 ～ 10, TB1 ～ 2 - hard - 0.
07 ～ 0.
75 - 18 ～ 36 - 0.
05 ～ 0.
12 it is HB320 ～ 360) with hardness of TC4(of turning of YG6X lathe tool, ap=1mm, F=0.
The optimal cutting speed when 1mm/r is 60mm/min. The cutting speed below different on this foundation feed and cutting deepness sees a table 3. Express 3.
The cutting speed Ap of TC4 of turning titanium alloy - 1mm - 2mm - 3mm F(mm/r) - 0.
3 - 0.
3 - 0.
3V(mm/min) - 60, 52, 43, 36 - 49, 40, 34, 28 - 44, 30, the typical lathe tool of alloy of 26 treatment titanium has following characteristics: Material of ① razor blade is YG6X, YG10HT; The role before ② is minor, 6 ° of ～ of ° of general γ 0=4, enhance knife head strength; ③ has F=0.
05 ～ 0.
Of 1mm lose edge, in order to enhance the strength of edge; The part after ④ is larger, 16 ° of ～ of ° of general α 0=14, in order to reduce the friction from the back, raise cutting tool durability; ⑤ does not allow to grind horn giving a tip or transfer commonly blade, and grind a R=0 of round horn of point of a knife.
5mm left and right sides, r=1 ～ 2mm can be amounted to when thick car, in order to enhance strength of point of a knife; ⑥ fine vehicle or turning thin wall when, cutting tool tool cutting edge angle wants big, it is 75 ° ～ commonly 90 ° . Cutting dosage: Thick car: V=40 ～ 50m/min, f=0.
2 ～ 0.
3mm/r, ap=3 ～ 5mm. Half fine vehicle: V=40 ～ 45m/min, f=0.
2 ～ 0.
3mm/r, ap=1 ～ 2mm. Fine vehicle: V=50 ～ 55m/min, f=0.
1 ～ 0.
2 ～ 0.
5mm. Use emulsion is cooling, can raise cutting tool durability effectively. Making below the premise that assures knife head intensity knife head has tall wearability and hardness is the crux of alloy of reasonable treatment titanium. The YG6X razor blade that chooses accordingly ought to use diamond after blade is ground or stone of carbonization silicone oil carries a knife on the back (the back gives arris) , achieve eliminate blade to grind curium the mouth, purpose that enhances edge strength. Thick car is irregular when black skin workpiece, worry bit a 3 ° ～ commonly + 5 ° blade is obliquitous; When fine vehicle, do not have blade dip commonly, conglutinate of face of the knife before right now cutting tool wears away to basically be (felt) wear away. This kind of typical lathe tool can relatively active of the material when solving treatment titanium alloy reasonably lifts along with temperature and raise the question that reachs thermal conductivity difference, consequently cutting tool durability rises greatly. 3.
2 get those who cut titanium alloy it is more difficult to cut treatment, often appear in machining a process burn the knife is mixed get a phenomenon, its are main the reason is broach blade worries bit of undesirable, platoon not seasonable, cooling not beautiful and difference of machining complex tigidity. (The choice of 1) broach: The diameter is more than the broach of 5mm, had better choose hard alloy YG8 to regard cutting tool as material; Treatment is less than the Kong Shi of 5mm, the high-speed steel broach that can be more than 63HRC with hardness (be like M42 or B201) ; Be less than a diameter when hole depth double when, use inclined chamfer (short model) broach; Be more than a diameter when hole depth double when, use twist drill head. The geometrical parameter of broach: 3 ° of ～ of λ =0 ° , 15 ° of ～ of α C=13 ° , 130 ° of ～ of ° of 2 φ =120. Cut the bits, cutting capacity that reduces to grind and improve bit to be formed easily, the width that can reduce oriented first flank according to broach diameter comes 0.
1 ～ 0.
3mm, repair the blade that grind a horizontal stroke to arrive 0.
1D, double blade grinds vertex angle 140 ° of ～ of ° of 2 φ =130, 80 ° of ～ of ° of 2 φ =70. Watch 4 listed the geometrical parameter of broach of type of double sharp angle. Express 4.
Diameter of broach of parameter of geometry of broach of type of double sharp angle (Mm) - vertex angle 2 φ - the 2nd vertex angle 2 φ 0 - α of the horn after the 2nd sharp edge blade - B(mm) - C(mm) >3 ～ 6 - 140 ° of 130 ° ～ - 140 ° of 80 ° ～ - 12 ° ～ 18 ° .
5 - 0.
4 ～ 0.
8 >6 ～ 10 - 140 ° of 130 ° ～ - 140 ° of 80 ° ～ - 18 ° of 12 ° ～ - 1.
5 ～ 2.
5 - 0.
～ of 6 ～ 1 >10 18 - 140 ° of 125 ° ～ - 140 ° of 80 ° ～ - 18 ° of 12 ° ～ - 2.
5 ～ 4 - 0.
～ of 8 ～ 1 >18 30 - 140 ° of 125 ° ～ - 140 ° of 80 ° ～ - 18 ° of 12 ° ～ - 4 ～ 6 - 1 ～ 1.
Dosage of 5 (2) cutting hard alloy broach: V=9 ～ 15m/min, f=0.
05 ～ 0.
2mm/r; 5m/min of ～ of V=4 of high-speed steel broach, f=0.
05 ～ 0.
3mm/r. (When 3) getting cuts deep aperture or small diameter hole, can adopt a hand to move feed. Broach must be exited periodicly from Kong Zhong when bore, so that keep clear of,cut bits. Wear away strongly to avoid bit, in cannot letting broach stay in aperture, do not enter do not retreat, get blade to be able to chafe otherwise treatment surface, cause treatment sclerosis, make broach becomes blunt. Cooling lubricating fluid must furnish abundantly when bore. Use soya-bean oil commonly, can add tap of French OLTIP bore when necessary special oil. Raise machining complex tigidity as far as possible, secure jig go up in workbench, jig appropriate press close to machines the surface, make broach shortens as far as possible. Take what corner is in at the back of broach to wear away the =0 after H.
4 ～ 0.
5mm grinds blunt standard as broach. (4) getting cuts example: Broach of the high-speed steel that use molybdenum is in α + undertake getting cutting machining on workpiece of alloy of β TC4 titanium, broach diameter D=6.
35mm, hole depth H=12.
7mm. Choose cutting parameter V=11.
127mm/r, use emulsion is cooling. T of cutting tool durability in order to wear away the =0 after width H.