The research of steel of hard bearing of temper by dipping in water of GCr15 of cutting of PCBN cutting tool

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1 experiment of 1-25 ° conditional experiment is to be on the CA6140 lathe that contains infinitely variable speeds undertake, the measurement of cutting force uses turning of type of meet an emergency to measure power instrument, cutting temperature uses natural thermocouple the law is measured, workpiece material chooses GCr15 bearing steel, get through heat treatment craft 30HRC, 40HRC, 50HRC, 60HRC and 64HRC add up to the test specimen of 5 kinds of hardness. Round lathe tool is to use Japan to live outside the PCBN that the experiment uses the BN500 of friendly electric company limited is compound piece abstain and become, its geometry parameter is shown like subordinate list place. 2 cutting force and the form that cut bits because the brittleness of material of PCBN cutting tool, big blunt circle should have commonly before using (400µm) of about 200 ～ and processing pouring arris, in cutting process, because cutting deepness and feed are very small, blunt circle and the position that lose edge are the part that basically shares cutting. Suffer the effect of cutting area appearance, PCBN cutting tool is when steel of bearing of hard GC15 of cutting temper by dipping in water, discover radial load Fy normally the biggest, it is next advocate cutting force Fz and axial force Fx. Cutting force experiment still discovers cutting force and workpiece hardness are shown in the analysis as a result nonlinear relation, put in the critical hardness concept of cutting of a strong voice namely, around critical hardness cutting force is the smallest, to steel of hard bearing of GC15 temper by dipping in water, this critical hardness is 50HRC roughly. When cutting rate increases, cutting force drops a little, because raising cutting rate,this basically is while cutting temperature lifts somewhat and make the plasticity of workpiece increases, but the change of this kind of property also says for metallic bate effect, it makes the hardness between cutting tool and workpiece poor increase, reduce cutting tool effectively wear away. Process of strong voice cutting is easy generate zigzag cut bits, in the discovery when the bearing steel cutting to different hardness is machined, workpiece hardness is right zigzag the impact that cuts bits is the biggest, when hardness under 50HRC when, even if big feed and high speed cutting also can be generated only cut bits continuously, after hardness exceeds 50HRC, can observe apparently the configuration that cut bits by cut bits continuously to zigzag cut bits to transfer. Form zigzag the material cutting bits that forward cutting makes get great pressure produces cutting tool to rupture suddenly and the account that cuts bits basically is brought about. 3 wear away when steel of hard bearing of temper by dipping in water of cutting of diagnostic PCBN cutting tool, before of knife face wear away the form basically is crescent moon wears away depression. As a result of PCBN cutting tool high temperature resistant, hardness is tall, after achieving constant temperature and pressure only, ability makes its generation wears away, because this crescent moon wears away to arise only depression,be in the place with distance very close edge, and width is very narrow, this have not at hard alloy cutting tool, the point that at the same time this also reflected PCBN cutting tool retains ability strong, be helpful for realizing the accurate cutting of hard steel of temper by dipping in water. When GCr15 of steel of hard bearing of temper by dipping in water of cutting of PCBN cutting tool hind knife face wears away form appearance, look from the exterior, its wear away the form is wear away with what mechanical wear gives priority to belt, stick at the same time have stuff of a few workpiece, but look not to have clear distinction with hard alloy cutting tool from formally, just wear extent is very small. 4 already machined exterior integrality wallop of susceptive of place of cutting tool of the PCBN in strong voice cutting is work of cutting weak condition of 3 times, mix when feed especially cutting deepness very hour, radial load often is more than advocate cutting force and tangential force, cutting precision is controlled not easily. Replace grinding treatment with strong voice cutting, its are main precision of the treatment surface surface roughness that how problem concentration body assures to obtain ideal now, appearance and treatment surface condition. When discovering workpiece hardness exceeds 50HRC when the experiment, workpiece hardness is taller its surface surface roughness is smaller, because be more than 50HRC when workpiece hardness,this is when, cutting force and heat in metal cutting drop somewhat, make cutting process medium the heat of workpiece expands action is reduced, be helpful for raising treatment precision. Already machined the surface the effect that microcosmic hardness suffers wear extent of face of the knife after feed is mixed is bigger, namely feed is smaller wear extent is bigger, exterior hardness is taller. In addition, already machined exterior hardness to rise and increase of speed along with cutting, mix along with feed cut deep accretion and reduce, and already machined exterior hardness taller 3 sclerotic layer deepness are deeper. The matrix that passes pair of test specimen is organized and contrast analyses the photograph of scanning report lens of surface layer organization, although rise somewhat,strong voice already machined exterior hardness in cutting process, produce certain sclerotic deepness, but to the metallographic of surface layer the organization is not had destroy effect. Use the discovery when steel of bearing of hard GCr152 of temper by dipping in water of cutting of PCBN cutting tool, workpiece surface layer and inferior the constituent position of surface layer changes somewhat, its are microcosmic the organization is by white not of temper layer and black cross temper layer composition, and white layer ply is less than 2µm. Hardness of work of department of 20 ～ 40µm is highest under workpiece surface layer can amount to 900HV. Surface of the workpiece after experimental result shows strong voice cutting is not remains to press stress entirely certainly, if the choice of cutting condition is unreasonable, also can appear remains pulls stress, the stress after strong voice cutting distributings have certain gradient, because this is helpful for improving the working life of bearing steel material, and of the workpiece after grinding the biggest press stress to basically be centered in workpiece surface. The radial load when steel of bearing of hard GCr15 of temper by dipping in water of cutting of cutting tool of 5 conclusion PCBN Fy is the biggest, it is next advocate cutting force Fz and axial force Fx, the 6 ～ that force of the cutting in rough machining is finish machining roughly 9 times. Process of strong voice cutting is easy form zigzag cut bits, its action mechanism is in for workpiece material what press stress action tremendously to fall is macroscopical and microcosmic rupture, generate zigzag the critical hardness that cuts bits is 50HRC. Of PCBN cutting tool before face of the knife after knife face is mixed wears away the ability that the form shows cutting tool to carry point is very strong, be helpful for what PCBN cutting tool realizes hard steel of temper by dipping in water be being ground with car generation. The surface already was machined to press stress for remains after strong voice cutting, the shape of a distribution of leftover stress can improve the life of workpiece greatly, surface roughness of surface of strong voice cutting can achieve the precision of kibble, its surface layer machines sclerosis not to have apparent effect to the organization, the scroll exhaustion of spare parts of strong voice cutting checks a result to show life of its spare parts is taller, use exceed cutting tool of hard data PCBN the accurate cutting treatment of steel of hard to temper by dipping in water bearing is feasible. CNC Milling CNC Machining