The constituent structure of film of pottery and porcelain of small arc oxidation reachs its influencing factor

Oxidation of foreword small arc is a kind of when the high-pressured discharge action in passing electrolyte forms film of pottery and porcelain in light metal surface new technology, it is current one of research heat of technology of material surface modified. The hole rate of film of small arc oxidation is low, be able to bear or endure corrode sex, wearability is good, velar layer is even, craft of this kind of technology is simple at the same time, small to environmental pollution, capability of processing spare parts is strong, be opposite especially the pottery and porcelain of surface of machinability excel other of different spare parts, hole, welding line changes technology, it is a kind of finishing technology that has development outlook very much. Because the constituent structure of film of small arc oxidation decides velar integral performance directly, because of this article integration analysis the constituent structure of film of small arc oxidation, discussed the factor that affects velar quality, introduced to raise film the way of integral performance. With period to promote the development of technology of small arc combustion, provide certain reference. 2.

The constituent structure of film of small arc oxidation 2.

The process of combustion of basic structure small arc of 1 film can divide apparently for 4 phase: Phase of common and zincous oxidation, scintilla discharge phase, small arc phase, arc discharge phase. In process of small arc combustion, scintilla, small arc all belongs to small area arc discharge phase, discharge area is in plasma condition. Film of small arc oxidation submits melt refrigeration form, the surface has opening, but not be perforative. Think commonly, film of small arc oxidation basically is comprised by compact layer and loose layer, compact layer and matrix union are good with exterior and loose layer interlocking is together. Only simple to compact layer and loose layer definition is numerous document: Compact layer grain is petty, interstitial rate is very minor, without apparent stoma and other blemish, hardness and insulation resistance all very big; Loose layer grain is bulkier, put in a lot of hole and other blemish, coarser and loose, and there are a lot of micro-cracks to expand upcountry again all round hole. But, compact layer and loose layer do not have apparent boundary. Consider to make clear, in initial stage of small arc oxidation, film of pottery and porcelain is relatively compact, do not observe loose layer almost, but lengthen those who reach velar layer to add as what handle time thick, form loose surface layer gradually, place of final and loose layer occupies scale to be able to be as high as the 90 ％ left and right sides of velar layer total ply. Because small arc oxidizes,the reason that forms loose surface layer is later period, spark voltage is opposite taller small arc the repetition of original film layer puncture, make on one hand the combustion process of lining is able to undertake, on the other hand the discharge hole existence of larger size forms loose layer. Small arc contains the element of base metal and its alloy not only in oxidation film, also have the element in coming from electrolyte. Matrix element and oxygen or the oxide of all sorts of structures that build with the ionic reaction in electrolyte are the main body photograph of velar layer, still have the compound between the metal that forms by place of the alloying element in matrix at the same time. Through adjusting matrix alloy composition, the photograph of the film that can win contented function to need is comprised; Change electrolyte class status, also can change the composition of velar layer, but basically be the composition composition that changes loose layer. Because compact layer becomes dispenses alloy part closely related, suffer the effect of electrolyte scarcely. If be in the system of phosphate and silicate, contain in great quantities in loose layer contain phosphor and the compound that contain silicon, and compact layer reachs its compound without phosphor and silicon almost. A large number of document make clear: Direction of deepness of edge film layer is had to pass the law that change in the no matter be the content of chemical element,still is compositive photograph content in film of small arc oxidation. The element that comes from electrolyte is reached by the watch in the content in film of small arc oxidation in it is degressive, and the element in coming from matrix increases by degrees. The direction of deepness of layer of film of edge of stable appearance content in film of small arc oxidation increases by degrees. The α with arc oxidation if aluminium alloy is small medium film - the rutile photograph in film of oxidation of small arc of Al2O3 photograph and titanium alloy. Contrary, direction of deepness of layer of film of edge of content of appearance of the metastable in film of small arc oxidation is degressive, the γ with arc oxidation if aluminium alloy is small medium film - the acute titanium mine in film of oxidation of small arc of Al2O3 and titanium alloy. The transmission rule of the quantity of heat in these rules and process of small arc combustion and quality is consistent. In process of small arc combustion, velar surface and electrolyte are contacted, cooling rate is old, form metastable photograph more easily, appear to be not brilliant photograph in great quantities even; Reach the interfacial point of film and matrix from velar surface, temperature lifts gradually, cooling rate is reduced gradually, the trend that makes stable appearance increases. Normal >2.

2 matrix and contented enamel coating organize relation Normal > aluminium and its alloy is: Outside face γ - Al2O3 photograph, by outside to in decrease stage by stage, α - Al2O3 photograph by outside to in increase gradually, structure of layer of this kind of oxidation and layer of agglomeration pottery and porcelain are similar. Still include in velar layer among them a few α - the organization is not brilliant with AlO(OH) and orderly short distance, as a result of γ - Al2O3, α - AlO(OH) and blame brilliant organization allow to be out of shape, so film of pottery and porcelain has taller hardness not only, and have higher rate be out of shape characteristic. Normal > magnesium and film of aluminous pottery and porcelain of small arc oxidation is: Compact layer place holds proportion in layer of former pottery and porcelain opposite taller, because oxygen compares the cause that diffuses easily to magnesium alloy,the likelihood is. Compact layer basically is comprised by photograph of cubic structure MgO, loose layer is comprised by photograph of cubic structure MgO and pointed spar MgAl2O4, still contain a few amorphous photographs among them. Normal > titanium and its alloy is outer and main it is You Jing voice TiAl2O3 and a few rutile TiO2 photograph and composition of photograph of SiO2 blame brilliant, and lining basically is composition of rutile photograph TiO2, still have a few acute titanium mine TiO2. It is phosphatic system to electrolyte, the roentgen that oxidation film still contains element of Ti, P, O to comprise is not brilliant photograph, this noncrystalline photograph is restrained corrode layer of pottery and porcelain, and hydrogen is osmotic low. Normal >normal >3.

Affect the element Normal >3.

1 electrolyte Normal >3.

1.

1 composition Normal > small arc is the important segment that wins film of superior performance oxidation. Think commonly, the composition of electrolyte of small arc oxidation divides roughly for 5 parts: Namely advocate additive of agent of improvement of conditioning agent of value of the agent that become film, PH, performance, stabilizing agent, other. Among them advocate the agent that become film basically has siliceous natrium, phosphoric acid natrium, 6 slant phosphoric acid natrium, sodium carbonate. Normal > but, also a few consider to make clear, electrolyte composition is chosen to want when applying actually with be cooperated very well by the material of modified, cannot simple basis of electrolyte: The theorematic element such as PH value, conductivity, viscosity, thermal capacity will decide. If differ,electrolyte of phyletic small arc oxidation is opposite the α in film of aluminium alloy pottery and porcelain - Al2O3 is opposite content (P) and compositive element impact are very big. Closely related the sort of the influence that electrolyte chroma is worth to P of film of pottery and porcelain and electrolyte, with the film of pottery and porcelain of Na2SiO3 electrolyte preparation its P value increases to drop somewhat along with pH indicator; The chroma of NaAlO2 electrolyte is worth an influence to the P of pottery and porcelain not quite; And be in (in NaPO3)6 electrolyte, when chroma is 12g/L, the P value of film of pottery and porcelain is the greatest. Normal > also has a few to consider to make clear, join a few like cerium, the rare-earth element such as lanthanum and transfer the metal is like cobaltic, nickel to wait, can raise film of pottery and porcelain of small arc oxidation to send density, improve its wearability thereby. Normal >normal Align=center>normal MARGIN of film of pottery and porcelain of oxidation of 25pt" Align=center> small arc: 0cm 0cm 0pt; LINE-HEIGHT: 25pt">3.

1.

2 temperature Normal > electrolyte temperature is opposite not only the growth of pottery and porcelain rate is influential, some affect the performance of layer of pottery and porcelain even. The experiment makes clear, when temperature is low, of layer of pottery and porcelain grow rate is rapidder, film of pottery and porcelain is more compact, function relatively beautiful. But when temperature is too low, oxidation is weaker, film is deep be worth with hardness inferior. When temperature is exorbitant, alkalescent electrolyte increases to the deliquescent action of oxidation film, cause film thick drop significantly with hardness, and electrolyte Yi Fei is splashed, velar layer is easy also by local scorch or attack correct, so optimal temperature is between 40 ℃ of 20 ～ . Normal >3.

1.

3 electrical conductivity Normal > electrolyte speed and send density influential. Along with the accretion of electrical conductivity, remove arc voltage to be reduced gradually, the ply of layer of pottery and porcelain shows the trend that approximate linear grows; Drop off of number of small hole of surface of film of pottery and porcelain, small Kong Kongjing increases gradually, inside layer of pottery and porcelain microscopical blemish amount is added gradually much; Of layer of pottery and porcelain be able to bear or endure corrode sex shows the metabolic pattern that after be being added first, decreases. Accordingly, in producing a course actually, the electrical conductivity of electrolyte system shoulds not be too big, want control to be in some is appropriate inside limits, such ability obtain tall ply compact be able to bear or endure the layer of pottery and porcelain of corrode. Normal > has a few to consider to point out again, undertake exterior plasticity be out of shape beforehand to aluminium alloy, undertake small arc oxidizes again next, the α that can make velar layer medium - Al2O3 measure increase, what raised velar layer further is microscopical hardness, send what density also gets fixed rate to rise. Normal >3.

Normal > base material reachs function to the ply of film of small arc oxidation, porosity also is apparent. Generally speaking, the impurity in aluminium alloy and content of other alloying element add congress oxidize velar ply is reduced, layer of pottery and porcelain becomes loose, among them the influence of the element such as iron, zinc, copper particularly apparent, can reduce film ply and send density, increase hole rate. Although silicon is not as big as the negative effect of afore-mentioned elements, but after silicon content is worth certainly more than, also meet oxidize film becomes thin and loose. Because contain silicon to measure tall silicon aluminium alloy application is very wide, when using technology of small arc combustion to undertake exterior modified to its, answer to heed the effect of silicon adequately. Normal >3.

Normal > small arc is output tall voltage and big electric current, output weaveform has dc, communication and pulse 3 kinds big, power source structure has type of capacitor type, transformer type, silicon controlled rectifier to wait. Normal > is general and theory, hardness of film of oxidation of dc small arc is low, communication and the hardness that communicate film of oxidation of pulse small arc are taller, the quality of velar layer is better, but what need time longer. The communication here is not the sine wave of common 50Hz, however to as certain as negative Xiangcheng proportional " alternating current. Use modulation electricity, include periodic and retrorse pulse and asymmetry alternating current to wait undertake small arc oxidizes to have clear advantage than using dc and sine alternating current. And weaveform is opposite the deposit of film of pottery and porcelain of small arc oxidation has certain effect. In process of small arc combustion, the growth that the action of pulse is stimulative oxidation film, and negative pulse is to have the effect that prevents film of oxidation of pottery and porcelain to grow however, and can dissolve a few not stable oxide. The pinpoint action with pulse peculiar voltage, still can make the exterior small hole of film of small arc oxidation overlaps each other, velar layer quality is good. When undertaking with pulse alternating current small arc oxidizes so, should optimize adjust, negative pulse extent and width, make the function of film of small arc oxidation is achieved optimal, and can effective managing the sources of energy. Normal > voltage is one of main factors that affect technology of small arc combustion, the velar opening aperture that low pressure generates is small, kong Shu is much, but when voltage is too low, the rate that become film is slow, velar layer is thin, color is light, hardness is low; Aperture of opening of the film when maximum pressure is high is big, kong Shu is little, the rate that become film is rapid, but when voltage is exorbitant, layer of easy occurrence film is local puncture, to velar layer be able to bear or endure corrode sex is adverse. Beijing Normal University is used hold electrolyte part changeless, progressively pressurization and direct pressurization had comparative test. The result makes clear, both thick to film impact is not big, but progressively pressurization law getatable is opposite thicker compact layer. Normal > next time of small arc oxidation also answer reasonable control. Although the addition as oxidation time, oxidation film ply increases gradually, but after amounting to proper time, film is deep add fast decelerate increase no longer even. Oxidation time grows to still can cause certain metal to appear 2 times too loose layer place holds proportion in the velar layer that discharge phenomenon perhaps forms exorbitant. Normal > current density also is an influence film of small arc oxidation is bright and clean degree, film is deep one of crucial parameter of the function that reach film. Current density is smaller, the rate that become film is minorrer, velar layer is thinner, velar color is lighter, hardness is inferior, cannot satisfy wear-resisting and be able to bear or endure the requirement of corrode; Current density is big, on fire time is short, film is deep the growth rate that reachs compact layer is accelerated, the brilliant of velar layer changes rate tall. As the accretion of current density, the amount of exterior small hole of film of pottery and porcelain decreases, bore diameter increases, velar surface roughness and hole rate are elevatory, impedance drops instead; Of film of oxidation of pottery and porcelain be able to bear or endure corrode sex as current density elevatory the abate trend after appearing to increase first. When current density is exorbitant, compact layer place takes velar layer scale is reduced gradually, appear extremely easily the phenomenon that burn caustic. Normal > power source and take the effect that compares pair of oxidation film ply for nothing not quite, but the opposite proportion that can affect loose layer and compact layer. High frequency when, the sample of low frequency of scale far outclass of photograph of condition of brilliant of velar layer Central Africa, small Kong Kongjing is small and distributing even, whole face is compared level off, compact, film grows rate is high, but ultimate ply is thinner. When low frequency, small hole hole is large and deep, and sample is burned easily caustic. Take the effect that compares pair of film layers for nothing apropos as contrary as frequency, occupy sky comparing smaller, velar layer sends density to had been jumped over; When occupying sky comparing higher, bore diameter is big, the surface of oxidation film has the presence of crackle, sample is burned easily caustic. Normal >normal >4.

Last word Normal > is current, because technology of small arc combustion is in,theory and craft respect still are waited for development and perfect, all did not enter large-scale industrial application domestic and internationally consequently. Already the technique that some research works are raising oxidation film ply centrally mostly, and to raising velar layer cause density and spread roughly close layer is in oxidation film proportional research is less. Oxidation film layer has certain ply already only, have again send density higher, ability receives large-scale application in industrial domain. The it is particular to send density to have real significance that considers to raise velar layer so. Basis already some research results, to achieve above at the same time two conditions, answer to explore new technique to optimize parameter further. After small arc oxidation ends, should do further processing to reduce space to lead to the loose layer of oxidation film surface with all sorts of blemish, if with other finishing technology union rises,also be the important way that future studies. Normal > believes to be in before long in the future, technology of small arc combustion will get extensive promotion in the finishing respect of light metal. CNC Milling CNC Machining