CN102861871A - Vacuum evaporative mold casting process of dry-type cylinder block - Google Patents

Abstract

The invention relates to the technical field of casting, in particular to a vacuum evaporative mold casting process of a dry-type cylinder block. The vacuum evaporative mold casting process comprises following production steps of (1) producing a foam plastic gasification mold; (2) assembling a casting system; (3) spraying special fireproof paint on the surface of the evaporation mold to be dried; (4) placing a special interlayer sand box onto a vibration working platform; (5) filling bottom sand to be compacted, and scraping the platform; (6) placing the dried gasification mold on the bottom sand to be fulfilled with dry sand, slightly the sand box for an appropriate time, and scraping a box opening; (7) utilizing a plastic film to cover the sand box, placing a pouring cup, utilizing a vacuum system to pump vacuum of the sand box, conducting the casting after the bottom sand is compacted and formed, gasifying the gasification mold to be disappeared, and adopting metal liquid to substitute the position of the gasification mold; and (8) releasing the vacuum, turning the box after a cast piece is condensed, and taking out the cast piece from the bottom sand. The vacuum evaporative mold casting process has advantages of attractive appearance, shorter production period and lower production cost. The machining surplus is small, and the weight of the cast piece is light. Raw materials are saved, the circulating utilization of waste sand can be favored, the noise is low, waste is little, and less pollution exists.

Description

The technique of founding casing with vacuum of dry type cylinder body

Technical field

The present invention relates to casting technology field, refer to especially a kind of technique of founding casing with vacuum of dry type cylinder body.

Background technology

Lost foam casting China claims vacuum-evaporative pattern casting, and people from U.S. claims evaporative pattern or gasified pattern casting, claims in the world EPC technique.Lost foam casting is to replace metal or wooden model with bubbles model, apperance is not taken out after the moulding, be the entity die cavity, namely one is retained in the casting mold with the on all four bubbles model of foundry goods shape, forms " full mold " casting mold, rather than " cavity " casting mold of traditional sand mold, when watering molten metal, bubbles model constantly decomposes gasification under the high temperature metal liquid effect, produce metal---the replacement process of model, is the stowing operation of a metal liquid and do not resemble tradition " casement " casting; Final apperance gasification obtains foundry goods.Lost foam casting is the revolutionary new technology that grows up late 1950s, because it manufactures and designs flexibly, production process is succinct, product Near net shape, Accurate Shaping, casting quality is good, production efficiency height and environmental protection, and can produce very complicated foundry goods, be described as " foundry engieering of 21st century " and " green casting engineering ".

There is more than 20,000 in Foundry Works or workshop in China, and the overwhelming majority adopts traditional sand casting, and labour intensity is large, workman's anthraco-silicosis that is easy to get, and environmental pollution is serious, and useless brilliant rate is high; Its product is fully by producing the area expansion: the product quality quality largely relies on operator's technical merit, cultivates a collection of 5-10 at least of moulder troop more than three grades.The past lost foam casting is at China's slower development always, its main cause is that many outside objective condition are immature, such as producing 100,000/year aluminium alloy sedan air inlet pipe, (casting polystyrene beads) raw material and apparatus for production line all will lean on the import supply from adhesive to foam mould EPS processed, cost is higher, adds lost foam casting and belongs to new things for most enterprises.

The manufacture level of engine cylinder-body, cylinder cap is one of important symbol of weighing a national manufacturing industry level, to a great extent representing the development level of a national auto industry.Improve constantly engine power, reduce fuel oil consumption and minimizing exhaust emissions are the domestic demands of auto industry self-growth, also are the objective requirements of external environment condition.The weight that makes engine and even car load of selecting of aluminum alloy materials has obtained effectively alleviating, and has promoted the development of auto industry.But, the progress of automotive engineering has proposed higher code requirement to saving and the environmental protection of raw material, the energy, make the specific power (kW/ discharge capacity L) of engine increasing, cause the operating temperature of engine cylinder-body, cylinder cap generally to improve, many regional area operating temperatures have surpassed 200 ℃ (normal working temperature is about 105 ℃), on the one hand, the mechanical property of aluminium alloy can descend very fast, and seeming can't bear the heavy load; On the other hand, so high temperature dies down the lubricated and conductive force of machine oil, and cast iron materials still can work and show excellent performance under this temperature.At present, solving aluminium alloy not high measure of mechanical property under high temperature and normal temperature, is to carry out castingin casting pig at gray iron connecting bolt place and cylinder body with bearing cap connecting bolt place, with reinforcing screw element or casting pig connecting plate.Do like this, increased on the one hand the technical difficulty of casting and the weight of parts, manufacturing cost is risen; On the other hand because the coefficient of expansion of aluminium alloy and casting pig has difference, so under the engine operation situation, produce easily the loosening defective of fatigue crack and castingin spare.

Make a general survey of the overall process that cast article is shaped, the power consumption of aluminium alloy is higher than cast iron; And the vibrationproof ability of cast iron products, self-lubricating ability and mechanical behavior under high temperature are much larger than aluminium alloy.Therefore can predict, the auto parts and components of the materials such as common grey iron, high trade mark inoculation cast iron, alloy cast iron, vermicular cast iron and spheroidal graphite cast-iron will be subject to people's attention more and more.Especially pieces of vermicular cast iron, as a kind of engine new material, vermicular cast iron is compared with common grey iron, tensile strength has improved about 75%, elastic modelling quantity increases nearly 40%, fatigue strength almost is 2 times of casting pig, but replaces at least weight reduction 10% of engine cylinder-body that casting pig is produced with vermicular cast iron, greatly reduces simultaneously the pollutant discharge amount of fatigue deformation and diesel engine.On the high-power diesel engine motor piece, generally adopted vermicular graphite iron material abroad, it possesses the intensity near spheroidal graphite cast-iron, vibrationproof, the capacity of heat transmission and casting character that similar common grey iron is arranged, and than common grey iron better plasticity and fatigue performance are arranged again.In a word, from the practical application of present alloy material, the mechanical property of ironcasting and high-temperature behavior can satisfy the requirement of automobile engine future development.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, and a kind of technique of founding casing with vacuum that utilizes Foam Pattern to replace traditional complex model process implementation part to produce is provided.

Technical scheme of the present invention is:

1. make bubble and mould gasified pattern;

2. make up casting system;

3. vaporize the mould surface brush, the spray special fireproof coating and the oven dry;

4. special interlayer sandbox is placed on the shaking table;

5. insert bed load jolt ramming, scrape platform

6. will dry to such an extent that gasified pattern is put on the bed load, and fill up dry sand, little appropriate time that shakes strikes off the case mouth;

7. cover with plastic sheeting, put cup, connect vacuum system and vacuumize, after the fastening moulding of bed load, pour into a mould, the gasified pattern gasification disappears, and metal liquid replaces its position;

8. discharge vacuum, mould turnover after the foundry goods condensation takes out foundry goods from bed load.

Production principle: the vacuum pressing and casting evaporative pattern is made bubble by EPC technique (lost foam casting process) and is moulded model, be coated with handtailor coating, after the drying, place special sandbox, insert dry sand, the three-dimensional vibrating consolidation, vacuumize under the state and cast, the model gasification disappears, and the metal replacement model copies the foundry goods the same with steeping moulding model.

The invention has the advantages that, (1) mulling, coremaking operation have been cancelled, save branch mailbox, molding in the traditional design operation, repaiied the operations such as type, lower core and mould assembling, knockout, casting cleaning and sand treatment process have greatly been simplified, overall appearance is beautiful, shorten the production cycle, reduced production cost.

(2) because large in negative pressure lower mold rigidity, ironcasting is easy to realize from feeding, thereby reduces the required Riser Dimensions of foundry goods; Because the assembling free degree of bubbles model bunch is large, be easy to realize many castables of a type on the other hand, improved product yield, can obtain any surface finish, size accurately and non-trimming, burr without the surplus foundry goods.

(3) the evaporative pattern Roughcast Allowances is little, and surplus is 2.5～3.5mm, and the wall thickness uniformity is high, and the aperture can directly cast out greater than the inside die cavity of 7mm, and casting weight on year-on-year basis common sand-cast alleviates 8%～12%.

(4) need not binding agent and additive in the lost foam modeling dry sand, for example coal dust, bentonite, water), a large amount of raw material had both been saved, being conducive to again old sand recycles, noise is low, refuse is few, pollution is few, can keep foundry's cleaning and low intensive condition of work, alleviate environmental pollution.

The specific embodiment

Be described further of the present invention below in conjunction with embodiment, the present invention includes following production stage:

1. make bubble and mould gasified pattern;

2. make up casting system;

3. vaporize the mould surface brush, the spray special fireproof coating and the oven dry;

4. special interlayer sandbox is placed on the shaking table;

5. insert bed load jolt ramming, scrape platform;

6. will dry to such an extent that gasified pattern is put on the bed load, and fill up dry sand, little appropriate time that shakes strikes off the case mouth;

7. cover with plastic sheeting, put cup, connect vacuum system and vacuumize, after the fastening moulding of bed load, pour into a mould, the gasified pattern gasification disappears, and metal liquid replaces its position;

8. discharge vacuum, mould turnover after the foundry goods condensation takes out foundry goods from bed load.

Embodiment one:

(1) designing and developing of mould, the maximum difficult point of wet cylinder body and dry type cylinder body casting is exactly the leakage problems of water channel, oil duct.Die joint try not too much at water, oil duct place (be die joint unsuitable too many) at first too much can cause this place's glue consumption excessive or do not have bonding putting in place and the phenomenon (particularly the cemented side seam of water channel is not easy to check) that causes oozing coating.The main wall thickness of cylinder body is in 5 millimeter, and the carbide that the coating of infiltration and bonding agent gasification not exclusively stay is easy to just penetrate wall thickness and causes seepage when suppressing.Therefore mould development at first needs to solve is how at water channel with the oil duct place is not bonding or few bonding.Next is dimensional problem, and conventional evaporative pattern product custom removes the limit the wall thickness of foundry goods, and the overall weight of foundry goods is alleviated, and embodies the advantage of lost foam casting with this.But be worthless for the such foundry goods of engine cylinder-body.Once suppress qualification rate for what improve foundry goods, the wall thickness of all water channels and oil duct all should be walked the upper limit, to increase the wall thickness in the above-mentioned scope.

(2) moulding of apperance because the wall thickness of cylinder body is thinner, adopts P-S bead or 4S to expect to come moulding, sends out in advance density and is controlled at 23 to 26g/l.What common evaporative pattern foundry goods was emphasized is more light better in the state lower density of energy moulding, but concerning cylinder body class thin-section casting, the too low meeting of density causes fusion difficulty between the bead, cause matrix that rarefaction defect is arranged, and then when the dip-coating material, can cause to ooze in the coating and form the coating slag, the foundry goods of cast just has suppresses Seepage.Therefore density should not be too low.Show that by suppressing the result after further demonstration and the processing this density range standard can satisfy quality requirement.What forming machine adopted is the semi-automatic liquid die mould, i.e. all the other operations were finished automatically by apparatus control system after hand stock was complete, can guarantee like this uniformity of white mould quality, were very important for producing in enormous quantities.

(3) combination of apperance,

1. white mould must thoroughly be dried, and comprises running gate system, and the oven dry record need be arranged, and checks the tail spare oven dry situation of each batch, and the oven dry of tail spare means the white mould oven dry of this batch, can make up.All to do the record of weighing to each part model before the combination, and write on the place of regulation with oil painting brush.What weight exceeded standard will formulate separately the cast parameter.

2. the control of glue consumption, the harm of the white mould of hazard ratio of glue is much bigger theoretically, and this has also proved this point in practice, therefore should control for the consumption of glue, and is special all the more so at the bonding plane of water channel and oil duct.Integral body is weighed again after white die combination is complete, and the weight that deducts white calligraphy or painting model body with this weight is exactly that glue is heavy, and eye-catching sign on the work of finding to exceed standard is in order to solve by improving pouring temperature or vacuum degree in subsequent handling.

3. the repairing of cemented side seam, Engine Body Castings belong to complexity coefficient larger a class foundry goods, particularly water channel chamber, and this place is the most complicated, are difficult on the mould and should locate one-shot forming out, such as the pump case of cylinder body.Just formed the quite long two-layer bonded seam of place's flow process at this place, bad if the cemented side seam that should locate is processed, in the water pressure test Seepage will appear so.This is unallowed in the quality requirement process.The method that my company adopts is once bondingly evenly to be coated with the evaporative pattern mending paste special that last layer the author prepares voluntarily at all cemented side seam places after complete, and this mending paste can cover cemented side seam fully, at high temperature can be gasified totally.Avoided the infiltration of coating in the dip-coating process to cause the coating slag, seepage occurs in suppressing process and caused product rejection.

4. Design of Runner System, it is main that pouring type is taked the rain type top casting.

(4) coating process, Engine Body Castings also has two point values to get especially attention except general performance requirement to the requirement of coating: 1. coating cracking resistance at normal temperatures will be got well.The water channel chamber of cylinder body is very complicated, and coating is piled up easily at this place, piles up blocked up water based paint and be easy to occur crackle in the process of oven dry.And these crackles are very difficult found.If process badly, will cause water jacket scab during cast, the scab of water channel usually can't be cleared up and be caused foundry goods to be scrapped.2. the stripping performance of coating, cylinder block passage is similar to the container of a sealing, and can't to enter into the water channel chamber inner for shot in the middle of the ball blast process, the dope layer of water channel inner chamber can't be cleared up if the stripping performance of coating is bad.Now take in coating, to add the way of cosolvent, by repeatedly adjusting, finally satisfied instructions for use.

(5) moulding and cast, the cylinder body material belongs to the HT250 low-alloy cast iron, requires Cu:0.2%-0.4%, Cr:0.15%-0.25%.The control range of other five large elements is: C:3.2%-3.35%, Si:1.85%-2.05%, Mn:0.8%-0.95%, P :≤0.08%, S:0.05%-0.07%.Batching: steel scrap 60%, the pig iron 20%, foundry returns 20%, common 75 ferrosilicon breed.Guarantee chemical analysis by the both analysis instrument, it should be noted that Cr should add after the sampling of stokehold, in order to avoid disturb the on-the-spot sample analysis instrument, copper directly adds ladle.Molten iron goes out 1490 ℃ of 1590 ℃ of pouring temperatures of furnace temperature, and negative pressure remains on-0.04MPa is to-0.05MPa, about duration of pouring 30s, at last by strength checking and hardness test.

The key technology that reaches:

(1) manufacturing technology of gasified pattern

Polystyrene foam sheet (EPS), selecting ρ=0.017-0.02g/cm3 is the material of using of 17-20kg/m3; Adopt resistance wire (d=0.5-0.8mm) to cut (voltage is optionally regulated, and is generally 12-25V) with 3KVA pressure regulation power supply; Gasified pattern is bonding: with Beijing just wearing China 500WPH-1 type glue (liquid) or WH-1 glue (solid); Gasified pattern any surface finish and repairing: with fine sandpaper friction, the available nitrocellulose aqueous solution apply, effects on surface gets finedraw and pit can subsidize with the adhesive tape equating, fillet can be bonding with the strip foam board.

(2) equipment of fireproof coating and use

It is that utmost point pass is important that the vacuum expendable pattern moulded steel gets coating, and major requirement has high intensity and higher gas permeability.Coating generally is comprised of solid material, binding agent and carrier three parts, according to alloy is all kinds of various prescriptions is arranged again, and company researchs and develops out unique fireproof coating prescription.

(3) unique running gate system bonding: the bonding cast is a very elaboration during moulding, requires bonding firmly, and the way of available dowel nail is auxiliary in case of necessity solves, as early as possible with the tight sealing-in mouth of oven dry coating.Sprue is generally 25-45, should not be too large, otherwise molten metal waters first the foam at its center of mistake, and be subjected to the too early gasification of the thermal-radiating foam of molten metal, produce the RESEARCH OF PYROCARBON over-emitting black exhaust.Down gate can disposable coating, is suspended from the oven dry of wall type with wood screw, and ingate preferably is bonded on the model in advance, and runner gate is made as straight horizontal stroke.

1. foundry goods one-shot forming, dimensional accuracy is high.Because adopt the foamed plastics of very easily gasification to make model, the dimensional accuracy of product and surface roughness are near precision-investment casting.Simultaneously, because adopt dry moulding, the casting wasted product rate significantly descends.This new technology is less demanding to operator's technical merit in addition, and casting industry is had huge attraction.Although the distortion of bubbles model and the thermal decomposition product of foamed material may bring adverse effect to the quality of foundry goods, but as long as the links such as cast material and mould making process, coating and dry sand consolidation are carried out strict control, can overcome the adverse influence factor fully, obtain the precision casting of high-quality.

2. whole technical process realizes mechanization, automated production easily.Can greatly improve the environmental condition of foundry, realize easily CR production.Polystyrene under the low temperature (EPS) is fully harmless to environment, the organic matter amount of getting rid of during cast few (only account for weight of molten iron 0.3%), and the organic matter discharge capacity when adopting the self-hardening sand casting accounts for more than 5%; It is short that EPS produces the organic time simultaneously, is easy to collect, and can focus on by sandbox is vacuumized the real nuisanceless discharging that belongs to environment.This external application evaporative pattern technique, the cleaning work amount of foundry goods reduces greatly, and noise is few, the harm of carbon monoxide and silica dust is little, and the old sand recovery utilization rate can reach more than 97%.

3. foundry goods shape, structure are unrestricted, for casting design provides the sufficient free degree.By the member of a plurality of parts processing assembling, can by the burst molding then bonding way carry out the integral cast moulding.The hole that upright stone tablet need to be processed, hole can directly cast out, and this has just greatly reduced man-hour and the expense of process and assemble.

4. manufacturing cost is low, and equipment investment is little.Because the cost of manufacture of gasified pattern low (only be wooden model price 1/3), material source is extensive, and required former is few, invests little.Adopt in general this technology, equipment investment can reduce 30%-50%, and the foundry goods manufacturing cost can descend 25%-30%, the yield rate 99% of foundry goods.Therefore, Technology of EPC meets the general trend of cast growth, and widely development prospect is arranged.

Claims (1)

1. the technique of founding casing with vacuum of dry type cylinder body is characterized in that may further comprise the steps:

1. make bubble and mould gasified pattern;

2. make up casting system;

3. vaporize the mould surface brush, the spray special fireproof coating and the oven dry;

4. special interlayer sandbox is placed on the shaking table;

5. insert bed load jolt ramming, scrape platform;

6. will dry to such an extent that gasified pattern is put on the bed load, and fill up dry sand, little appropriate time that shakes strikes off the case mouth;

7. cover with plastic sheeting, put cup, connect vacuum system and vacuumize, after the fastening moulding of bed load, pour into a mould, the gasified pattern gasification disappears, and metal liquid replaces its position;

8. discharge vacuum, mould turnover after the foundry goods condensation takes out foundry goods from bed load.