The physical phenomenon in metallic cutting and basic rule (2)

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2, 　 of the tumour that accumulate bits (1) when the plasticity metal such as steel of the cutting below the condition with accumulate the reason 　 of bits tumour phenomenon and generation to be in certain, brass, aluminium alloy, as a result of before knife face extruding and grinding action, the backwater of one part metal in making cut bits ground floor and accumulation are near cutting point, form nugget, can replace cutting blade to undertake cutting, this nugget calls the tumour that cut bits. If pursue,2-8 place is shown. The place before be like is narrated, because cut bits underside,be the new face that just formed, and face of the knife before the attrition with violent side of the knife before it is right makes again becomes very clean, when both interface achieves constant temperature and pressure, the appearance of felt of new face easy generation that has chemical endophilicity. The ground floor that cuts bits to go up in knife face from felt at this moment is genteel over- (cut slippage) , because of inside attrition is out of shape and generation machines sclerosis, easy be attracted by akin metal and block sluggish is on the ground floor of felt. Such, an accumulation and felt is together, form the tumour that accumulate bits, till till the temperature of the place is mixed,pressure can't cause felt. This shows, the ground floor that cut bits and before the requirement that knife range occurs felt and treatment sclerosis is generation of the tumour that accumulate bits. Say commonly, temperature and pressure are too low, won't produce felt; And temperature is too high, also won't produce the tumor that accumulate bits. Accordingly, cutting temperature is the payoff that the tumour that accumulate bits produces. (2) the 　 of influence graph 2-8 of the tumour that accumulate bits accumulates the one side with bits advantageous tumour is it bag Fu replaces cutting blade to work on cutting blade, rise to protect cutting blade action, the horn before still making cutting tool actual at the same time increases, cutting deformation is reduced, cutting force is reduced; But also have adverse one side, extend cutting blade as a result of its front besides, affect dimension precision, its appearance is irregular also at the same time, in cutting apparently the channel grain with quarter differ depth, affect exterior quality. In addition, it is not stable also, grow, fall off to undertake alternately, cutting Li Yibo is moved, broken face of knife of cut of the meeting when falling off, if stay,already machining apparently, can form wool to perverse etc, increase exterior surface roughness to be worth. Because this is when rough machining, be patient of accumulates bits tumour to exist, but when finish machining, must try to avoid. (3) the controls 　 to control the tumour that cut bits method of the tumour that accumulate bits basically has the following kinds: Raise the hardness of workpiece material, reduce plasticity and treatment sclerosis liability. Control cutting rate, in order to control cutting temperature. Graph 2-9 is the sketch map that speed of cutting of height of the tumour that accumulate bits concerns. Because cutting speed is the factor with the biggest temperature of cutting of the influence in cutting dosage, so this graph reflected the concern of height of the tumour that accumulate bits and cutting temperature. The low temperature when low speed, the high temperature when high speed, do not produce the tumor that accumulate bits. Grow in the tumour that accumulate bits level, its follow Vc heighten highly and increase; Disappearing level increases along with Vc and reduce. Because this control accumulates bits,tumour can choose low speed or high speed cutting. Use the cutting liquid with lubricant good performance, reduce attrition. The horn before increasing, reduce cutting thickness, can make cutting tool cuts bits to contact length to reduce, height of the tumour that accumulate bits is reduced. (4) Ⅲ is out of shape 1 of area 　 　 . Be out of shape characteristic 　 workpiece already machined the osculatory area of face of the knife after the surface and cutting tool, call the 3rd be out of shape area. If graph 2-10 place is shown, point of cutting cutting tool is not very sharp, and R N of radius of existence point circular arc, cut is in the stress state of affairs with intricate existence in O of part of point blunt circle. Cut metal is become via cutting face of the knife before the edge after slippage to pour out of cut bits, the H D of △ of one thin metal under O dot cannot cut slippage along OM direction, by point forward thrust or be pressed to already machined the surface, this part metal is pressed stress above all. In addition, because point wears away,the horn after generation is the small arris face of 0 (BE) reach the flexibility that already machined the surface to restore EF (△ H) , the drawing attrition action of face of the knife after making the layer of △ H D that is squashed gets again, farther generation plasticity is out of shape. Because this already machined the surface,be to pass what be out of shape and form complexly for many times. It is existing exterior treatment sclerosis and exterior remains stress. 2. Exterior treatment sclerosis and 　 of leftover stress 　 (1) the phenomenon that exterior layer hardness already machined to rise after machining sclerotic 　 calls treatment sclerosis. Forming when cutting in already machining exterior process, because surface layer metal passes complex plasticity for many times to be out of shape, hardness rises significantly; On the other hand, cutting temperature makes treatment sclerotic and abate again -- change infirmly; Temperature will cause taller cutting to change. The treatment sclerosis that already machined the surface is this kind of aggrandizement, weak change, change the integrated result of action. The deformation in treatment heals big, sclerotic degree heals tall, sclerotic layer deepness also heals deep. The treatment sclerosis of workpiece surface will give treatment of cutting of follow-up working procedure to increase difficulty. If cutting force increases, cutting tool wears away accelerate, affected exterior quality. While treatment sclerosis is raising workpiece wearability, also increased exterior brittleness, dropped work thereby fight concussion ability. (2) leftover stress of leftover stress 　 is to show in what do not have outside force action the circumstance falls, the stress that exists inside the object. Because cutting force, cutting is out of shape, heat in metal cutting and the action that change, already machined the surface to often be put in leftover stress, remains pulls what stress and remains press stress to fasten. Leftover stress can make already machined the surface to produce crackle, reduce the fatigue intensity of the spare parts, stress of workpiece surface remains distributings inhomogenous also can make workpiece generation is out of shape, affect the appearance of workpiece and measure. It is very adverse to the treatment of nice spare parts. (5) influence cutting metabolic is main element 　 　 1, workpiece material 　 falls in the situation with cutting same condition, the strength of the material that be cut is greater, the friction of material coefficient is reduced, be out of shape coefficient ξ is reduced, because this cutting is out of shape,reduce; If be cut,the plasticity of material heals big, produce plasticity easily more slippage and cut wind shear contrast, because this is out of shape,coefficient ξ heals big. So when the plasticity material such as cutting mild steel, plasticity is out of shape more serious, if pursue 2, 11 are shown. 2, cutting dosage when material of plasticity of cutting rate cutting, cutting speed Vc shows waviness to change to cutting metabolic influence, if pursue 2, 12 are shown. In low speed phase, namely when speed is less than 5m /min, as a result of before knife face grinds with the ground floor that cut bits coefficient is lesser, reason does not form the tumour that accumulate bits. Achieve when cutting speed when making an appointment with Vc 1, begin to produce the tumor that accumulate bits. When cutting speed achieves Vc 2 (make an appointment with for 20m /min) , height of the tumour that accumulate bits reachs maximum, right now before of knife face actual before horn also reachs maximum. When cutting speed enters Vc 3 by Vc 2, cut bits tumour height to be reduced again right now, actual before horn is reduced, cut bits to be out of shape also increase subsequently. When should accumulating bits tumour to disappear completely (cutting speed is 40 ～ 75m/min about) be out of shape coefficient reachs a peak, if increase cutting speed Vc again, so before the coefficient of friction on knife face continues to reduce. On the other hand, as a result of cutting lukewarm heighten, the ground floor that cut bits is in small frit condition, form lubricating film, because this cutting is out of shape,reduce again, be out of shape coefficient also is reduced. Accordingly, can be out of shape through controlling cutting speed to reduce, reduce cutting force and obtain lesser exterior surface roughness to be worth. Aborning, often use energy of low speed of high-speed steel knife car or exceed material of strong cutting tool to undertake high speed essence cut with hard alloy and other, obtain lesser surface surface roughness to be worth thereby. (2) feed times when R of κ of tool cutting edge angle, increase feed, the ply that cut bits also increases, cutting is out of shape is reduced normally, if pursue,2-13 place is shown. Because, increase as cutting ply, sluggish sheds the ply of the layer to increase Debuduo. That is to say, the metallic layer with serious deformation, what its occupy the per cent of the bulk that cut bits to increase and drop as cutting ply. Look from cut whole accordingly, those who cut bits is average be out of shape reduce, be out of shape coefficient ξ is reduced. Knife of the puissant cutting lathe tool that uses in production, puissant Duan Xi and annulus the cutting tool such as the broach that cut pattern is make according to this principle come out. 3, the horn before 　 of angle of cutting tool geometry heals big, cutting is out of shape more small, if pursue,2-14 place is shown. Because before when horn increases, cut horn to increase subsequently, the obstruction when cutting bits to pour out of is reduced, cutting is out of shape reduce, be out of shape coefficient ξ is reduced. Fall in the premise that assures cutting blade intensity it is thus clear that, the horn before increasing cutting tool is advantageous to improving cutting process. 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