Nodular cast iron wears answer look ball model casts blemish to reach avoid measure

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One, nodular cast iron wears overview answer look the ball is the new product that my factory developed 2000, upgrade with what grind a ball at former low alloy replacement. My factory produces per year this kinds to grind a ball to measure nearly 10 thousand tons, in actual production, as a result of the existence of different and phyletic blemish, make grind a ball to often appear below operating condition condition not wear-resisting, miss the circle adverse factor that affects the service life that grind a ball, be necessary to undertake an analysis to of all kinds blemish for this, make phasing answer prevent a method, use at coaching production is carried out. 2, common flaw and feature 1. The ball is changed undesirable change feature of decline both blemish with the ball identical. (Fracture surface of cast of 1) macroscopical feature is silver grey color to go up stain of black of shape of distributinging sesame seed, its amount much, diameter is big, show degree is serious. If show dark gray thick grain entirely, show the ball is changed not complete. (2) metallographic organization distributings centrally a large number of thick flake graphite, more, area exceeds its amount big, show degree is more serious, the ball does not change full-time to show flake graphite. (Fluid of raw iron of 3) generation reason contains sulfur tall, and excessive is contained to turn over a ball to change an element in the charging of serious oxidation; Magnesium of remain of fluid of the iron after processing and rare earth amount are too small. The dissolved oxygen in iron fluid measures on the high side is the ball changes undesirable main reason. Choose low sulfur coke and metallic charging, undertake desulphurization is handled when necessary. Additional, should undertake steel divides rust abandoning, and dosage of the rare-earth element in increasing a ball to change an agent, strict control ball changes technology. 2. Shrinkage cavity and shrink loose feature and generation reason: Shrinkage cavity generation drops at iron fluid temperature produce contractive level. Be like atmosphere the surface defect of caky thin lamination, present the surface to cave reach local heat section to cave, otherwise separate out of the gas in iron fluid comes the dark shrinkage cavity with the smooth wall that gathers to contain air hole in coping carapace, also be interlinked with the outside sometimes form bright shrinkage cavity, criterion inside although the surface is smooth also, but already was oxidized. Nodular cast iron in all brilliant is caky time is longer than casting pig, the shape that show congee is caky, caky crust is more fragile, when expanding 2 times, make below graphitization expansibility action crust expands, flabby in-house pressure. Because this is in 2 times in contractive process, pressure of caky finally interior of hot item place under atmosphere, be in to make vacuum division by the small bath of branch brilliant space, completely caky epigenesis is hole wall coarse and the loose aperture that discharges Man Shuzhi brilliant, shrink namely loose blemish. Macroscopical shrink loose generation begins at heating up fluid of iron of division division remains many and caky inchoate, included systole of leftover iron fluid and 2 systole, consequently dimension slightly the wall discharges Dajunei Man Zhijing, show gloomy and loose aperture or macula of shape of fly foot mark; Microcosmic shrink loose generation contracts at 2 evening, in all the iron fluid between brilliant group or its group is couldn't get below negative pressure fill shrink caky and contractive and into, section is in common Yu Hou. 3. Hypodermic stoma (3mm of below skin of cast of feature of 1) form appearance 2 ～ is in even or the globose, elliptical shape that beehive shape distributings or pinhole shape wall are smooth hole, diameter 0.

5 ～ 3mm, can mix in heat treatment after casting bolus to clear, be exposed or discover when machine treatment, small in more. (2) forms a reason to embody pulling force of surface of magnesian iron fluid big, easy form oxidation film, gas of block up separate out and invade aeriform eduction, stop at hypodermic and form. Form film temperature follows rudimental magnesium to the quantity increases and rise, aggravate action of its block up. Bao Bi refrigeration is fast, form film is early, easy form this blemish. Aeriform origin basically is to drop in temperature the magnesian vapour of separate out of fluid of the iron in the process, in fill model fluid of the iron in the process rolls hurried its rise. Moisture of the magnesium in iron fluid and molding sand reacts, and water and acetylene of generation of reaction of magnesian, carbide are decomposed all may arise hydric. In addition damp, rustily charging, damp ferrosilicon and master alloy, and blast of cupola high temperature can be taken hydric, minim Al can increase hypodermic stoma significantly, certain binder of arenaceous core colophony contains nitrogen more, afore-mentioned each elements all can promote this blemish to form. Additional, nodular cast iron is mushy and caky the characteristic makes aeriform passageway is jammed earlier, also can promote the formation of hypodermic stoma. 4. Stress is out of shape and crackle (1) forms the contraction stress in reason and process of refrigeration of cast of form appearance feature, thermal stress, photograph to change the algebra of stress and namely casting stress exceeds this section metal to fight rupture ability forms crackle. Fall in high temperature (1150 ℃ of 1000 ～ ) form hot tearing, show dark Brown and rough entire fracture surface; Appear inside limits of 600qC the following flexibility cold cracking, show beige smooth and flat fracture surface; Succumb to be able to produce plasticity to be out of shape in a limited time extremely more than in casting stress of 600 ℃ above. Produce hot tearing not easily when part of nodular cast iron is normal. (Influencing factor increases 2) the element of white mouth tendency, if low, carbide forms carbolic silicon content,the element increases, inadequacy of be pregnant with and refrigeration pass to wait quickly to be able to increase casting stress and cold cracking liability. Phosphor makes cold cracking tendency increases, wp>0.

25 ％ still can cause hot tearing. Additional, cast wall large difference big, form is complex, easy generation is out of shape and crackle. 5. Slag inclusion (feature of 1) form appearance distributings at cast pouring locally the surface, model of core below reach cast blind angle to be in, dark black is shown on section the field trash with lacklustre, differ depth and show intermittent distributing. Metallographic observes field trash of visible strip, lump, adjacent black lead can submit a form or bulbiform. Mark of the magnetism when magnetic particle flaw detection shows strip to distributing, stripe is much and thick, accumulation density shows slag inclusion is serious. Electronic bougie analysis shows slag inclusion contains Mg, Si, O, S, C, Al to wait, be add up to the composition such as content, magnesian pointed spar by vulcanization of siliceous magnesium, oxygen. (Reaction of the O in the Mg when 2) forms process ball to change processing, RE and iron fluid, S forms broken bits. When iron fluid temperature effect of agent of low, rare broken bits not rise of beautiful, broken bits inadequate or gather up broken bits ungodliness and in fluid of rudimental Yu Tie, this is broken bits; Iron fluid is being carried, bag, pouring, fill model film of the oxidation when rolling is broken and by casting mould of be involved in, in model inside adsorptive sulfide gathers at going up in rise process the surface or blind angle place, this is broken bits 2 times. Give priority to with 2 broken bits commonly. 3, avoid measure 1. The ball changes decline reason to reach prevent measure tall sulfur, low temperature and slag inclusion of the sulfide that after the ball of iron fluid classics with serious oxidation changes processing, forms, oxide is not sufficient rise, gather up broken bits is inadequate, iron fluid is enclothed bad, and the oxygen in air passes broken bits layer or enter iron fluid directly, make effective ball changes elemental oxidation, making active oxygen increases is the main reason that the ball turns decline. The sulfur in broken bits also can enter iron fluid afresh and use up among them ball to change an element, iron fluid is being carried, the magnesium in agitate, process pouring a bag collects rise transgression to be oxidized, because this makes effective remain ball changes an element to decrease, cause a ball to turn decline. In addition decline of be pregnant with also makes the ball counts black lead to decrease and bring about aggravation of black lead configuration, afore-mentioned causing the ball changes undesirable element to also can accelerate a ball to turn decline. Turn decline to prevent a ball, answer to reduce content of sulfur of raw iron fluid, oxygen as far as possible, control temperature appropriately. Can add agent of rare broken bits to make broken bits sufficient rise gathers up in time broken bits, gather up careless ash, cryolite pink, black lead pink or other coverture are added after clean broken bits in order to keep apart air; Add packet of lid or use sealed formula pouring bag, use nitrogen or argon gas protection to be able to prevent a ball effectively to turn decline; Should accelerate pouring speed, reduce a bag as far as possible, carry reach retention period; Additional, use yttrium radical to weigh rare earth magnesian ball to change an agent, its decline time can be lengthened 1.

5 ～ 2 times. Magnesian ball of small rare land changes agent decline time to also grow to change an agent at magnesian ball slightly, and also can increase a ball to change an agent to add a capacity appropriately when necessary. The black lead configuration that as a result of be pregnant with decline causes is exasperate, after compensatory be pregnant with attainable improvement. 2. Shrinkage cavity, shrink small conference raises loose influencing factor and equivalent of precautionary measures carbon shrinkage cavity, shrink loose tendency; In addition phosphor in all brilliant can weaken caky crust intensity, 3 yuan of phosphor in all brilliant reduces graphitization to expand, because this contains phosphor to measure Gaoke to increase significantly,shrink loose tendency; Molybdenum increases carbide stability, form carbide easily below tall phosphor condition especially, phosphor in all brilliant is compound content, more increase shrink tendency of loose, shrinkage cavity; Rudimental magnesium quantity is exorbitant, increase shrink tendency of loose, shrinkage cavity, and quantity of rare earth of right amount remain can decrease shrink loose. Because this should raise equivalent of iron fluid carbon, reduce phosphorous content, in make sure the ball changes a condition to fall to reduce remain of rare earth magnesium to measure as far as possible, reasonable use molybdenum. Additional, raise casting mould stiffness, raise equivalent of iron fluid carbon, reduce appropriately pouring temperature, use Bao Erkuan inside runner makes his caky before expanding 2 times close, and use graphitization to expand systole of liquid state of compensation iron fluid and caky systole, can eliminate shrinkage cavity, shrink loose. 3. The precautionary measures of hypodermic stoma is pouring temperature is not gotten under 1300 ℃ . When rudimental magnesium volume is high, should rise accordingly pouring temperature; In make sure the ball changes a condition to fall to reduce rudimental magnesium to measure as far as possible, use rare land appropriately; Use gating system of open mode much flow path, make iron fluid sheds person accent smoothly, avoid to be in model flip through inside antrum; ≤ of moisture of control molding sand 4.

5 ％ , match coal fines 15 ％ of 8 ％ ～ can burn generate CO to restrain hydrosphere and magnesian reaction to form oil of spindle of spray of surface of H2(casting mould to also can remove similar action) ; Casting mould surface removes cryolite pink, with hydrosphere reaction forms HF gas to protect iron fluid below high temperature. Additional, still should control iron fluid to contain aluminous amount low, charging is dry little rust, cupola dehumidify sends wind, reduce the gas in iron fluid, and use little nitrogen or do not have azotic colophony arenaceous etc. 4. Stress is out of shape and crackle prevents measure to raise carbolic equivalent appropriately, reduce the amount that contain phosphor, strengthen be pregnant with, and take step of necessary casting mould craft. 5. The main reason that the influencing factor of slag inclusion and precautionary measures form slag inclusion is sulfur content of raw iron juice tall, oxidation is serious. Precautionary measures is to reduce content of sulfur of raw iron fluid, oxygen, rise pouring temperature. The main reason that builds broken bits 2 times is rudimental magnesium the quantity is exorbitant, raised oxidation film to form temperature. Main measure is to be in make sure the ball changes a condition to fall to reduce rudimental magnesium to measure as far as possible (in small WMg does not exceed 0.

055 ％ ) , join right amount rare earth can drop form film temperature; When the ball changes processing, add 0.

16 ％ cryolite, the surface after processing is scattered into 0 again.

Rare broken bits of in order to of 3 ％ cryolite, generate AlF3 gas and MgF2 film to oxidize in order to decrease 2 times. This kind of method basically is used at preventing big slag inclusion, pouring temperature is not gotten under 1300 ℃ , make pouring temperature of film of form of temperature prep above, can prevent broken bits 2 times to form. Additional, gating system design should assure to fill model smooth, in easy occurrence mix arenaceous place installs cuttings pick-up rising head, screen pack of this peripheral buy can prevent broken bits to enter model antrum. CNC Milling CNC Machining