Steel of hard bearing of temper by dipping in water of dry cutting of PCBN cutting tool wears away the research of mechanism

8mm, lose arris to be 26 ° × 0.

The picture of scanning report lens of 1mm(razor blade sees graph 3a) . 4) cutting parameter: Cutting speed Vc=140m/min, back penetration of a cutting tool measures Ap=0.

2mm, feed rate F=0.

1mm/r, use dry type cutting. 5) measures with observation: In cutting experiment, every interval 3min, cutting tool is measured below microscope of 40 times tool advocate hind knife face wear extent observes around knife face wear away configuration; When cutting journey achieves 7800m, with lens of report of HITACHI S-570 scanning (surface of SEM) observation cutting tool wears away take form appearance, measure cutting temperature with thermocouple law, measure exterior surface roughness with YCL surface contourgraph. Observe in the experiment that 2 tests result and analysis are in appearance of razor blade of graph 1 CB20 to do steel of bearing of hard GCr15 of turning temper by dipping in water with PCBN cutting tool: Cut bits to show wine, pour out of along direction of deputy cutting blade. The cutting temperature that measures with thermocouple law amounts to 1000 ℃ above. 1) PCBN cutting tool wears away when steel of bearing of hard GCr15 of temper by dipping in water of turning of diagnostic CB20 razor blade, in face of knife of cutting tool around metropolis generation wears away (if pursue,5a of 3b, graph and graph 5b place show) . In cutting process, place of point of a knife most happen first wear away, face of back-to-back the knife before happening wears away, its are main the feature is to standing by arris face to be in most form crescent moon first depression. As cutting undertake, crescent moon is depression in forward knife face, advocate edge and deputy edge are outspread. The picture of lens of report of crescent moon depression scanning that when cutting journey achieves 7800m, forms is shown like graph 3b place, crescent moon depression width and deepness are evener, but the metallographic photograph that approaching part of point of a knife and outspread the photograph has the metallographic to both sides to differ apparently, there is grain to flake in place of point of a knife with phenomenon of small collapse blade. In cutting initial stage face of the knife after observing very hard wears away, but stand by place of point of a knife wear away relatively apparent. After cutting undertakes 6 ～ 7 minutes, advocate hind knife face stood by place of circular arc of point of a knife to appear to wear away phenomenon. Face of the knife after cutting journey achieves what form when 7800m wears away take picture of scanning report lens to see graph 5b, knife face wears away after of belt and tradition hind knife face wears away contain differ apparently, see by graph 5a, deputy hind of knife face wear away far under advocate hind of knife face wear away, before, hind knife face wears away area is lesser. Wear curve of 2) cutting tool pursues 2 be advocate hind knife face wear curve. See from the graph, as the addition of cutting time, of CB20 razor blade wear away to increase equably gradually, initial stage wears away level and wear away normally level has clear distinction, and wear away normally level and acuteness wear away level does not have apparent divisional end. Razor blade of graph 2 CB20 advocate hind knife face wear curve analysis thinks, in cutting experiment initial stage, because the around knife face of new cutting tool is in microcosmic go up to still existing place of a few coarse cobbly, very as big as the osculatory stress of workpiece surface in cutting treatment, of reason cutting tool wear away faster; As the addition of cutting time, after classics of new cutting tool is adjusted, the osculatory area of cutting tool and workpiece increases, intensity of pressure is reduced, wear curve change tends stable. By the graph 2 visible, when to the experiment journey of end, cutting achieves 7800m, advocate hind knife face wear extent is amounted to 0.

When 35mm, cutting process is smoother still, ra is exterior surface roughness 1.

6. 3) wears away the research of mechanism and discuss A.

Face of the knife before knife face wears away before wears away the phenomenon begins level to be able to happen namely in cutting experiment, basically behave the slight nick that causes for mechanical wear and abrade; As the elapse of cutting time, stand by point of a knife around before knife face wears away submit crescent moon depression form, because the high temperature action of cutting area makes cutting tool surface happened to change,this is wear away, behave thereby for " crescent moon is depression " appear. If proper refrigeration undertakes to PCBN cutting tool in cutting process, use inert gase for instance (it is beautiful with N2) try to protect, OK greatly of face of the knife before slow down cutting tool wear away, improve the service life of cutting tool thereby. The form appearance before A) cutting tool wears away (the form appearance after B) cutting tool wears away pursues 3 before picture of lens of report of knife face scanning (100 × ) use scanning report lens the crescent moon of area of blade of small to standing by collapse observes an analysis further partly depression, undertake contrast with the picture of metallographic of cutting tool surface before wearing away (4b) of 4a seeing a picture, graph. From the graph 4 can see clearly not grain of face of the knife before the CB20 cutting tool of cutting distributings to agree equably, and the exterior structure that the cutting tool after wearing away presents sex of bumpy random law. To the generation of this phenomenon, the temperature that because cutting is machined,the author considers as is as high as 1000 ℃ above, PCBN cutting tool can happen to oxidize and put azotic reaction necessarily, its react equation is: ↑ of 4BN(CBN)+3O2 → 2N2 + the type on 2B2O3 shows classics of surface of PCBN cutting tool is met after oxidation in its the surface forms an oxidation film, but because cut the intense friction of bits and thermal shock action, this oxidation film will be very fast the bits that be cut is taken away, cause farther oxidation to wear away. Wear away to changing, behave not apparently in graph 4b. (A) new cutting tool is microcosmic organization (picture of lens of report of scanning of face of the knife before the cutting tool of 4 PCBN of microcosmic organization chart after B) cutting tool wears away (3000 × ) B.

Knife face wears away to machine initial stage in cutting after, hind of knife face wear away the phenomenon observes very hard, but part of point of a knife wears away more apparent however, this is the Re=0 of circular arc of point of a knife as a result of bit.

8mm, back penetration of a cutting tool measures Ap=0.

2mm, cutting treatment is firm in the begining of cutting tool hind knife face and workpiece are not contacted, after that of knife face wear away to also be mirrorred in only point of a knife and hind the circular arc joint of knife face, undertook 6 ～ 7 minutes or so till cutting, in advocate from the back stood by place of circular arc of point of a knife to appear to wear away phenomenon. If the graph is shown 5 times, knife face wears away to show hemp to order state partly after, cutting tool surface has grain to fall off. Because be below constant pressure and high temperature condition,this is, CBN active increases, increase with treatment material ceaselessly with the tendency in person, brought about felt tatty to happen thereby. The contrast that passes graph 5a and graph 5b still can discover further deputy hind the felt circumstance of knife face is compared advocate hind knife face is close friends. In be being machined as a result of cutting, advocate hind the temperature of knife face comes from the acuteness attrition at cutting tool and workpiece and cut bits to be opposite the thermal shock of cutting tool surface, and deputy hind high temperature cuts bits to had flowed and the temperature of knife face basically is caused, compare apparently advocate hind the cutting temperature of knife face wants low, because this proved felt wears away,suffer the effect of temperature, temperature is higher, felt case is more severe. (A) deputy hind appearance of form of knife face face (100 × ) (B) advocate hind appearance of form of knife face face (100 × ) (C) advocate hind knife face is microcosmic organize (3000 × ) face of the knife after graph 5 CB20 wears away 5c of graph of picture of lens of exterior scanning report explains, the appearance that mentions in A section namely changes wear away. By CB20 advocate hind the metallographic organization of knife face can observe breast dash forward shape Ma Ban, CBN grain is outstanding in the surface, the binder all round already by abrasion. This happens to change just about tatty model feature, namely CBN grain produced CBN → HBN change. Because HBN hardness is very low, lost cutting ability thereby. Area of the knife after as a result of the cutting of face of the knife before thinking normally temperature should be compared is high, knife face has after change wear away generation, criterion before knife range also occurred to change necessarily wear away. C.

Grain flakes and grain of phenomenon of small collapse blade flakes and phenomenon of small collapse blade is to exceed get together forcedly some place of stuff of brilliant diamond cutting tool is special wearing away type. In this experiment, when cutting when 25 minutes are controlled, blade of cutting of CB20 cutting tool and area of contact of treatment workpiece surface (lose arris to approach part of circular arc of point of a knife namely) produced phenomenon of small collapse blade, with scanning report lens observation produces the part of CB20 point of a knife of small collapse, see part of point of a knife already had be short of caustic (6) seeing a picture. Because PCBN cutting tool is made by countless petty CBN grain, crystal boundary handles rich volume " foreign matter group yuan " be equivalent to a kind " careful crackle " , and put in the internal stress with inhomogenous move, reduced crystal boundary intensity greatly consequently. When because this cuts bits when high temperature,shedding cutting tool point of a knife, be pledged by treatment material material inhomogenous or those who be put in the small impact that horniness is nodded and causes and machine tool main shaft is jumpy etc caused CBN grain to flake with small collapse blade. Graph the picture of scanning report lens of small collapse of 6 point of a knife (100 × ) the research that 4) cuts bits configuration change to analyse Yan Qiusheng to teach thinks: In cutting speed material of taller, treatment still is in the circumstance of inferior temperature to fall, position of point of a knife had been satisfied by the condition of clipping of brittleness of excision material generation, generation was formed before satisfying plasticity of cutting area material to cut slippage stress condition consequently zigzag cut the crackle of bits and generate zigzag cut bits. The discovery in the experiment falls in identical cutting dosage, cut bits to there also can be a few changes in different period. In phase of cutting initial stage (7a) seeing a picture, can see by layer shape chip extruding accumulation forms cut bits clearly. Union pursues 8 will try to explain: Cutting initial stage, the interface of cutting tool and workpiece is small, extruding effect is bigger, the eduction that cut bits is difficult; After cutting had period of time, as the occurrence of Rn of cutting tool blunt circle, cutting contacts an area to increase, and the before arising to also make cutting tool actual horn with depression crescent moon of face of the knife before cutting tool increases, what at the same time course of cutting tool surface cuts bits is slippery brush action to also become smooth, cut bits aptly thereby pour out of, the cutting that cuts bits is out of shape and eduction obstruction is reduced somewhat, cut bits surface consequently relatively smooth (7b seeing a picture, 7c) . (The configuration cutting bits when cutting of A) new cutting tool is earlier (100 × ) (the below inferior temperature form cutting bits after B) cutting tool wears away (100 × ) (the below successive cutting, high temperature configuration cutting bits after C) cutting tool wears away (80 × ) pursue: Graph 7b is bit makes wearing away cutting undertakes again after measuring (workpiece temperature is inferior) the first form cutting bits of generation, cut bits flat submit strip form; As the extension of cutting time, after cutting temperature is elevatory, cut bits to turn into the helix of graph 7c is dentate configuration. Because there was cutting temperature to produce change only in the process here, cutting parameter does not have a change, because this author thinks the change of temperature also is having certain effect to cutting bits pattern: As cutting temperature elevatory, the cutting that cuts bits is out of shape increase, dentate the pitch that cuts bits and tooth depth can change somewhat. Concerned temperature element still remains to study deep to cutting the specific influence of bits. Graph 8 cutting tool are different wear away 3 conclusion 1) uses the cutting sketch map below condition hard steel of temper by dipping in water of vehicle of fine of CB20 cutting tool (HRC>60) , cutting process is smoother and cutting tool service life is long, it is the ideal cutting tool of the hard fragile data such as hard steel of finish machining temper by dipping in water. The proposal uses the cutting dosage that be as follows: ≥ of cutting speed Vc 140m/min, back penetration of a cutting tool measures Ap=0.

2mm, feed rate F=0.

1mm/r. Face of knife of around of 2) CB20 cutting tool wears away area is lesser and main concentration is mixed in point of a knife deputy near arris, wear away the reason basically is mechanical wear, oxidation wears away, change wear away with felt, their joint action caused cutting tool wear away. 3) CB20 cutting tool is in wear away area has grain flakes and small collapse blade happens, because this is in treatment must dosage of logical choice cutting, the ability that enhances workpiece material is qualitative, choose the machine tool with good tigidity, notice a machine tool, workpiece, the vibration of cutting tool machining complex. 4) cutting treatment is a dynamic process, below identical cutting parameter, the configuration that cut bits as cutting tool wear away can produce change, the reason that about the influence the configuration that cut bits changes and mechanism remain to study at further development. CNC Milling