Through high pressure refrigeration improves the cutting efficiency of titanium alloy

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  • source:LENA CNC Machining
Titanium and titanium alloy have good physics and mechanical property. By the component part that this kind of material makes, with especially high strenth, firm, weight light, anti-corrosive and high temperature resistant wait for character to wear say. This makes titanium material applies in aviation industry more and more. The physics with titanium good alloy and mechanical function, great to meaning of plane component part -- taller comparing intensity, have the strength that is similar to steel, have the weight of steel half only however; Inferior thermal conductance, make component part also won't become fragile below particularly low temperature, also won't have below higher temperature expand apparently; Higher high temperature intensity, can bear the temperature that is as high as 550 ℃ , also do not send produce material performance change; Better corrosion resistance can, comfortable at making the connection with component of carbon fiber material; And inferior stretch model quantity, make component part is had fight plasticity metabolic ability to wait. The material that titanium alloy is very difficult cutting however, these advantages of titanium alloy material became the difficult point when cutting is machined however. Be hard to the main reason of cutting titanium alloy depends on its very poor thermal conductance and higher specific heat capacity, block up the process that goes out through cutting bits and workpiece to convey heat in metal cutting from cutting area. Major heat (about 75% ) passed cutting edge, in edge apparently happen diffuse and felt, form the tumour that accumulate bits. At the same time the high strenth as a result of titanium alloy material, the meeting when cutting produces greater cutting power. Accordingly, cutting tool must bear in machining a process very high hot load and mechanical load. The stretch model amount of titanium alloy is small, can arise in the component below cutting strength effect be out of shape, spring back happens again after, also can affect the treatment precision of component part. So, the big question that must want to handle when cutting titanium alloy is: The heat in metal cutting that absorbs as a result of cutting tool is too much, accelerated cutting tool wear away, be forced to use inferior cutting rate so, but this can reduce treatment apparently efficiency and increase sheet cost. For example, the impeller of compressor of turbine pressure boost with qualitative material of a Ti6Al4V, of production charge 50% be used at cutting to machine namely. In last few years, it is especially in aircraft manufacturing industry, titanium alloy component and titanium alloy / the addition with ceaseless portion of component of carbon fiber join, accordingly, the manufacturing efficiency that improves cutting to process titanium alloy data has important sense more and more. See not hard, the cutting problem that solves titanium alloy material depends on using high temperature resistant hard metal cutting tool and to cutting process medium cutting tool undertakes cooling effectively. To raise the cutting efficiency of titanium alloy material and treatment dependability, many cutting tool produced manufacturer and institution of higher learing to begin fruitful research experiment to work. Be in Germany, especially university of industry of such as Darmstadt, inferior the school such as treasure industry university, Braunschweig industry university and Dortmund industry university, in titanium alloy cutting mechanism, finite yuan of model analysis, emulate, cutting experiments and used the respect such as different and cooling means to all begin a series of research, among them, inferior the machine tool lab of treasure industry university (WZL) still with Yisika (Iscar) , kennajin is belonged to (Kennametal) , hill tall cutting tool (Seco Tools) with Shanteweike (Sandvik) wait for tool works, clasp began the research that includes the technology such as high-pressured refrigeration. High-pressured refrigeration is a kind solve method effectively to consider to make clear, cooling cutting tool is a kind of when solve difficult problem of titanium alloy cutting efficient way. Current, the technology of efficient and cooling cutting tool is developed, basically have way of two kinds of development. One kind is to use high-pressured refrigeration to lubricate; Another kind is to use air conditioning to undertake cooling, use liquid state nitrogen or liquid state carbon dioxide namely (CO2) undertake cooling, especially liquid nitrogen (- 196 ℃ ) , this to cooling milling cutter it is the cooling kind that has applied outlook one kind very much (graph 1) . Graph 1 when machining titanium alloy, use what liquid nitrogen undertakes cooling can reducing cutting tool apparently to wear away. (data sources: WZL) be in at present, the good and cooling effect that cools considering high pressure, existing machining center and turning center deserve to have a lot of cooling and lubricant equipment, cutting tool manufacturer can provide the cutting tool that is used at refrigeration of this kind of high pressure, accumulated a lot of use experience actually (no matter be turning or milling) wait for an element, using the high-pressured refrigeration lubricating fluid that passes main shaft is a kind of first selection undoubtedly. Use method of groovy large flow refrigeration, cooling lubricating fluid cannot arrive cutting edge and cut the cutting area between bits (graph 2) , cannot cool effectively cutting edge. To realize effective cooling cutting tool, the supply of cooling lubricating fluid should be mixed with higher pressure sufficient flow, accurately alignment cutting edge and cut the osculatory area between bits (graph 3) . In this osculatory area forms a high energy to pound nail, shorten from this cut the osculatory time between bits and edge, drop cutting area temperature, make cut bits to become fragile at the same time, pass refrigeration and mechanical wallop the overlay of these two effect, make cut bits to break off very quickly to go out side by side, raise the dependability of treatment greatly thereby, this also is helpful for implementing the automation of cutting process. High-pressured refrigeration conduces to raise practice of manufacturing efficiency Nextpage to make clear, through high pressure refrigeration can raise the cutting tool durability of 50% . Through adjusting the pressure size of cooling lubricating fluid can affect the figure that cuts bits, improvement breaks bits. The pressure that can understand different and cooling lubricating fluid through the data of Iscar company leaves the case of the figuration that cut bits. When the pressure that uses 2MPa makes cool outside large flow, cut bits to be twined into strip of form cut bits (pursue 4) ; Should use 8MPa pressure inside when refrigeration, cut bits to be broken off to cut bits into small arc below high-pressured concussion (graph 5) , if use 30MPa superhigh pressure to undertake inside cooling, became at this moment acicular form cut bits (graph 6) . See not hard from these 3 example, through high pressure refrigeration can control the figuration that cuts bits, raise the dependability of cutting process, increase the cutting dosage that titanium alloy machines. Graph the 4 cooling lubricating fluid that use 2MPa pressure undertake exterior refrigeration. Right now, cut bits to be twined into strip of form cut bits. Graph 5 use lubricating fluid of refrigeration of 8MPa high pressure to undertake in-house refrigeration. What appear right now is small arc cuts bits. Graph 6 use lubricating fluid of refrigeration of 30MPa high pressure to undertake in-house refrigeration. What appear right now is acicular form cut bits. Those who need an attention is: The pressure in cooling lubricating fluid under 7MPa when, cooling fluid can be before cutting edge vaporization forms blister, thereby block up heat is conducted. When using the cooling fluid pressure that is more than 7MPa, can eliminate this kind of blister, direct gush goes to refrigerative fluid cutting position. When titanium alloy is machined, basically use mechanical clip to originally but dislocation piece cutting tool and cutting tool of integral hard alloy. Press convention, the cutting speed when rough machining is 50m/min left and right sides commonly, the cutting speed of finish machining is 200~300m/min, after using high pressure to cool, cutting rate can rise 20% , won't rise because of cutting speed right now and bring about temperature to lift. If use extrahigh voltage refrigeration, use CBN cutting tool at the same time, cutting rate still can rise further. But, need of cooling and lubricant plant has uses superhigh pressure special equipment. Because center of machining center, turning is mixed muti_function the pressure of the cooling and lubricant unit that place of compound machine tool provides has 7~10MPa only commonly. High-pressured refrigeration offerred a condition to raise cutting parameter. Use tall cutting parameter to be able to be shown improve manufacturing efficiency, reduce sheet substantially charge. Need is attentively, although pass high pressure,durability of cooling cutting tool can rise 50% , 3% what take production charge only commonly as a result of cutting tool charge, so this one pace can make only odd charge decreases 1.

5% . Use high-pressured refrigeration, want to note the concern between accurate harmonious pressure, discharge and opening diameter of nozzle. According to the data of Sandvik company, the spray head of 1mm aperture is used on cutting tool, to maintain pressure, need has the flow of cooling lubricating fluid of 5 L/min. Accordingly, should choose to be able to generate highest pressure and OK and optimal the measurement of opening diameter of nozzle that uses flow of cooling lubricating fluid. To milling treatment, use the spray head that many measures provided necessarily when many razor blade, need flow of larger cooling lubricating fluid so. The meeting is right if lubricant system flow rate is insufficient nozzle outlet pressure produces an effect. Right now, can consider to use the spray head with spout small diameter, in order to reduce the spraying pressure that discharge maintains cooling lubricating fluid. The advantage of technology of refrigeration of epilogue high pressure, basically cutting bits figuration at extending cutting tool life, control, raise cutting speed and improve workpiece surface quality, improve manufacturing efficiency from this. High-pressured refrigeration technology, solve the treatment difficult problem of cutting titanium alloy effectively not only, and also can apply effectively at nickel base alloy (for example Inconel 718, chromic ferronickel alloy 718) , stainless steel and the treatment that contain carbon to measure the difficult cutting material such as very low steel. CNC Milling