CN1226470A - Method of producing metal casting - Google Patents

Abstract

A method for manufacturing metal castings features the use of a thermoplastic foam mould which is formed by moulding foamable resin composition that is a copolymer with 150000-350000 of average molecular weight. Said copolymer is prepared from styrene monomer (55-85 wt.%) and methylacrylate monomer (15-45 wt.%) through copolymerization.

Description

Produce the method for metal casting

Present patent application is a Chinese patent application number: 92112468.6, the applying date: on September 19th, 1992, denomination of invention: the dividing an application of the Chinese patent application of " apperance of be used for making the resin combination of foam thermal mold, being made by this resin combination and they are in the application of metal casting ".

The present invention relates to a kind of resin combination that is used to make the foamed thermoplastic metal mold, by apperance and their application in metal casting of this resin combination manufacturing.

The apperance of foam thermal moulding material, as foamed polystyrene, the full mould casting of the deposite metal that is used to cast or lose in the foam casting.Scribble refractory coating with the metal casting that will produce and the corresponding one or more apperances of cast gate and casting mold runner system, and in molding box, surrounded to form a casting mold by NAG molding sand.When motlten metal poured into casting mold, the apperance combustion decomposition was substituted by metal, metal-cured then formation and the identical shaped foundry goods of apperance.

The expanded polystyrene pattern that above-mentioned technology is used is usually by following process production: under heat effect, the polystyrene sphere grain partial foaming that will contain volatile foaming agent such as pentane, and with the pellet slaking, the pellet of partial foamingization is charged in the mould, this mould is generally made by metal such as aluminium, then under heat effect in mould further this pellet of foamingization, thereby make pellet be melted in formation apperance together.Inject steam by pellet material and come heating mould inside to partial foamingization.

As everyone knows, when expanded polystyrene pattern is used for full mold or similar casting, in casting, because defective will appear in the incomplete volatilization of apperance or decomposition, these defectives are called as carbon defects, the most prominent in iron casting, it shows as, and wrinkle, cooling scab, surface depression and subsurface slag inclusion, are commonly referred to be because the existence of the pitch shape thing of the polystyrene thermal decomposition of apperance causes.

Existing many schemes adopt uses additive in order to solve carbon defects this difficult problem relevant with expanded polystyrene pattern to apperance.Adopt a kind of additive of ammonium perchlorate among the Japanese patent application publication No. 40-24146 as apperance, adopt among the Japanese patent application publication No. 41-16925 among the depolymerization catalyst GB Patent Application No. 2193666A and adopt oxidant such as iron oxide or manganese dioxide, making oxidation of coal is carbon dioxide or carbon monoxide.

Yet all have deficiency in these applications, they make the manufacturing of mould more difficult, and its effect can not overcome a carbon defects difficult problem preferably.

Also there is other scheme in foam mould, to adopt other polymer rather than polystyrene.Utilize acrylic acid alkyl ester polymer such as polymethyl methacrylate to make apperance in the United States Patent (USP) 4790367 and 4983640.But when adopting methylmethacrylate polymer, can not make the blowing agent thorough impregnation effectively, thereby cause foamingization grain foamingization degree low.Also have mouldability not good, the shortcoming of the mechanical strength of mold product and surface quality difference.

In casting polymethyl methacrylate process, can emit a large amount of gases fast, and cause splash, thus the poor surface smoothness of the product that causes casting.

The mixture of the polystyrene of used part foamingization and the polymethyl methacrylate of partial foamingization is made apperance and is attempted, but many difficult problems occurred in the manufacturing of this mould with in using.These two kinds of materials difference prefoamization in it is mixed, must be difficult to produce uniform mixture,, need trade off these conditions because the optimum condition of the pressure and temperature of moulding polystyrene is different from polymethyl methacrylate.The apperance of making has uneven density, because polystyrene sphere grain and polymethyl methacrylate pellet are fusing rather than fusing separately mutually respectively, thereby make apperance easily broken, and the surface smoothness of apperance is also poor.

Adopting with the methacrylic acid isobutyl with good thermal decomposition characteristic among the Japanese patent application publication No. 49-23458 is Main Ingredients and Appearance, with methyl methacrylate is that the composition of copolymerisation is made the foam mould, and employing is also arranged is the scheme that Main Ingredients and Appearance is made the foam mould with the methyl methacrylate.

Above-mentionedly be Main Ingredients and Appearance and be that the foam mould of the composition of copolymerisation also has shortcoming with methyl methacrylate with the methacrylic acid isobutyl, its glass transition temperature is more much lower than the temperature of polystyrene foam mould, if be used for the prefoamization and the mould of foamed polystyrene thing, to cause that the foam mould produces suitable contraction, thereby cause the scale error of foundry goods.Be necessary to adopt different moulds, and conversion such as temperature, these conditions of molding of pressure.

In Japanese patent application publication No. 51-24307, disclosed with the methyl methacrylate of 80-95% and the styrene copolymerized method of 5-20% weight and improved the foamingization characteristic.Having adopted in Japanese patent application publication No. 50-40160 when methyl methacrylate polymerization influences combined polymerization with the AMS additive for replenishing composition, and having disclosed employing methyl methacrylate and AMS in Japanese patent application publication No. 60-184447 is co-polymer foamedization thing.

With the methyl methacrylate is main component, with styrene or AMS is that the foam mould that polymeric composition comprising body is made also has prefoam pellet and the remarkable similar shortcoming of shrinking of moulding apperance, and is difficult to accomplish not only to increase the degree while of prefoamization but also reduce to shrink in moulding.This apperance produces the trend of too much gas in addition and causes surface smoothness not good.

The present invention has solved these difficult problems by a kind of foaming resin combination is provided, this resin combination can be a condensate from monomer promptly, have good prefoamization and processability, and have only the carbon trash of trace to produce in casting cycle, and foundry goods has good surface smoothness.

Foaming resin combination of the present invention floods a kind of volatile blowing agent with a kind of copolymer and makes.This copolymer weight average molecular weight is 150,000 to 350,000, is that styrene monomer and the heavy general formula of 15-45% that is weighed by 55-85% is CH ₂=C (CH ₃) the methacrylate monomers co-polymerization of COOR (R represents the alkyl of a 1-4 carbon atom herein) produces, the ratio that volatilization blowing agent weight accounts for total monomer weight can reach 10%.

Another characteristics of the present invention have provided a kind of foam thermal mold that is used for metal casting, and this mould is to make required shape by above-mentioned resin combination by foamingization and moulding.

The manufacturing of apperance be by pellet that can the foaming resin combination is carried out prefoamization and allow its slaking then the pellet of prefoamization draw and inject among the mould that has with the corresponding interior shape of apperance of the moulding of wanting, be filled full up to mould, heat these mixtures, make these pellets further foaming and fusing, and form apperance.

Another feature of this invention also is to provide a kind of method of producing metal casting, the structure of the parcel foaming heat-transmission mold of making by above-mentioned foaming resin combination and graininess refractory material, when the casting of metals that will melt is on mould, apperance is decomposed, and metal-cured back forms and the equiform foundry goods of apperance.

Preferable is to scribble refractory coating on the mould.

The composition of R can be methyl, ethyl, n-pro-pyl, isopropyl, normal-butyl sec-butyl, the tert-butyl group or isobutyl group in the methacrylate resin of copolymer.

In the present invention, what constitute the copolymer Main Ingredients and Appearance in can the foaming resin combination is to account for 55-85% by weight, and preferably the styrene of 60-80% and weight account for 15-45%, preferably 20-40%'s by general formula CH ₂=C (CH ₃) copolymer that produces by combined polymerization of the methacrylate resin represented of COOR.Surpass 85% material and be used for the foam mould if contain the styrene weight ratio, the resolution of this resin combination when casting will descend, can produce carbon residue, make the cast(ing) surface contamination.On the other hand,, will cause the prefoam degree to descend, when molding, can produce significantly and shrink if methacrylate content surpasses 45%.

In the present invention, the weight average molecular weight of copolymer (Mw) is controlled at 150,000-350,000.If weight average molecular weight surpasses 350,000,, under the Steam Heating condition of common foamingization and moulding, can not reach gratifying foamingization although improve as the copolymer intensity of the matrix of mould.Weight average molecular weight is lower than at 150,000 o'clock, occurs obstruction in the time of may causing moulding when the high-temperature region partial foamingization of mould and epidermis fusing (cutin shapings).

Above-mentioned co-polymer can be by the polymerisation in solution effect, and arbitrary mode of emulsion polymerization effect or suspension polymerisation effect makes.

Being used for the polymerization initiator that copolymer plays polymerization can be a kind of peroxidating organic matter, as: lauroyl peroxide, benzoyl peroxide, tert-butyl peroxide (2 ethyl hexanoic acid ester).The t-butyl peroxy benzoic ether, t-butyl peroxy pivalate or similar simple function group organic peroxide, or 1,1-di-tert-butyl peroxide-3,3,5-trimethyl thiacyclohexane, di-tert-butyl peroxide hexahydro terephthalate, di-t-butyl peroxide isophthalate, di-t-butyl peroxide trimethyladipic acid or similar difunctional organic peroxide, or a kind of azo-compound, as azodiisobutyronitrile or the two methyl pentane nitriles of azo.

Being added in of above-mentioned polymerization initiator carried out before monomer is added into polymer reactor, still carry out after monomer is added into polymer reactor, or it all is feasible together joining polymer reactor with monomer.If it is 150,000～350,000 co-polymer that polymerization initiator can produce weight average molecular weight in right amount well, preferably account for 0.1～2% of total monomer weight.

In order to regulate the molecular weight of copolymer, can use n-dodecyl mercaptan, n-octyl mercaptan, normal-butyl mercaptan or tert-butyl mercaptan, these amount of substances preferably account for for monomer≤1mol%.

Polymerization temperature should be chosen in 0～200 ℃ of scope.

Pentane can be applied in volatilization blowing agent that can the foaming resin combination in the present invention, and it is liquid under the normal temperature at normal pressure, can not dissolve above-mentioned copolymer, it is a kind of organic compound that can volatilize fast, and used pentane can be a pentane, isopentane, neopentane or pentamethylene.Preferably use isopentane from performance and economy.The pentane amount reaches with respect to 10% of monomer total amount, preferably accounts for 1～10%, exceeds the foaming mould that this scope can not be produced.

In this invention, except pentane, also can be used in combination the organic compound of quick volatilization, these organic compounds are in a liquid state or gaseous state under normal pressure, normal temperature, can't dissolve copolymer.These compounds comprise: aliphatic hydrocarbon, as propane, butane, hexane and benzinum; Alicyclic, as cyclohexane, aliphatic halide, as carrene, trichorotrifluoroethane and dichloro Difluoroethane.The consumption of other blowing agent except that pentane be the weight of blowing agent be no more than total monomer weight 10%.

If adopt the manufacture of suspension polymerisation as polymer, can add blowing agent and make polymer soak blowing agent, preferably be added with under the certain pressure blowing agent is being added in the second half of polymerization.Be meant in conversion weight percent 〉=50% of polymerization, preferably 〉=70% in this " the second half of polymerization ".Copolymer with spherical or little particle shape can suspend in aqueous medium, and be added with blowing agent in this medium, dipping when being preferably in 20～130 ℃, and in other mode of production, can and mix copolymer and blowing agent fusing, can the foaming resin combination by extruding formation.

When copolymer dipping blowing agent, can add plasticizer, can use a kind of organic solvent that can dissolve co-polymer or cause its expansion as plasticizer, the best boiling point of this material≤150 ℃, preferably the softening point than co-polymer hangs down about 10 ℃ or lower.Plasticizer comprises: aromatic hydrocarbons is as ethylbenzene, toluene, styrene and dimethylbenzene, hydrocarbon halide as: 1,2-dichloropropane, trichloro-ethylene and perchloroethylene.The plasticizer that adds is compared with copolymer weight and preferably is no more than 5%.

In foaming resin combination of the present invention, can use some other known additives such as antistatic additive.

In the present invention, prefoamization that can foaming resin compound and styrene resin prefoamization and the moulding process that moulding can be adopted industrial extensive use, and need not make amendment, by at normal pressure or pressure or under reduced pressure can reach prefoamization effectively by steam or gas heating.For example:, can in mould, inject further foaming of steam, thereby make foam molded articles if resin is the bead particle shape.Change, also available extruding foaming machine is made foam molded articles.

In the present invention, prefoam degree that can the foaming resin combination can be selected arbitrarily to the scope of height ratio from low ratio.Adopt above-mentioned mode, can make the foam mould by above-mentioned foaming resin combination, this foam mould is used in the casting of foam mould, in the step therein, this mould preferably scribbles one deck heat-resisting paint, and surrounds with sand grains, when being molded into the metal that is melted, the heat that is melted metal makes and can decompose and cancellation by the foaming mould, and the deposite metal replaces the mould of cancellation, thereby forms foundry goods.

Can heat-resisting paint be coated on the mould by mould being dipped in the heat-resistant coating compositions or heat-resistant coating compositions sprayed or watering on mould.

Following branded goods STY-ROMOL that sells on heat-resistant coating compositions that is suitable for such as the market and HOLCOTE (making) by Foseco company, EPICO K-124, EPICO K-125 and EPICO K-127 (making) by KOBE Rikagakukogyo KK, OK A SUPER 2500, OK A SUPER 2510, OKA SUPER2700, OK A SUPER 2600, OK A SUPER2600S, OKA PAINT 319, OKA PAINT 210 and OKA PAINT101 (making) by OKazakiSangyo KK, STYROKOTE 270 and STYROKOTE 380 PM (producing) and HARD MIX VF20 (producing) by TSUCHIYOSHI KK by KUROSUKK.

But be used to surround sand silica sand, inscription iron ore, zircon sand or the alumina of mould.

The casting program that in casting, adopts common use foam mould to be adopted.

Below several examples are several embodiment about this invention.In all examples, " partly " and " % " is based on weight.

Example 1-7 and reference examples 1-8

Lauroyl peroxide, benzoyl peroxide, tert butyl peroxy benzoate and by the molecular weight regulator that n-octyl mercaptan is formed be dissolved in the monomer with the ratio described in table 1 and the table 2 and the mixed solution of monomer in, every kind of solution adds in the aqueous solution with the 270rpm stir speed (S.S.), this aqueous solution is to be that the sodium sulphate of 0.5% sodium dodecyl benzene sulfonate aqueous solution and 0.5 gram is dissolved in 3 liters autoclave in the water of 1500 grams and makes by the tricalcium phosphates of 5 grams, 6 gram concentration, and the atmosphere in this autoclave is nitrogen.After temperature rises to 80 ℃, these materials were stirred 5 hours under this temperature subsequently.After this this material is cooled off, and take out the fluidized polymer particle that to foam, use earlier the salt acid elution.After wash with water then and dehydrate.

Be the average diameter of particles of foamed fluidized polymer particle of gained and the total amount of volatilizer component shown in table 1, the table 2.With the prepared particle screening of polymerization particle diameter extremely separately, from small diameter particles to the major diameter particle, have and describe to change curve, and provide weight median particle diameter, as the particle diameter of cumulant 50% particle with respect to the accumulating weight of particle about the particle diameter of screened particle.Accounting for the percentage of total amount for the total amount of volatile matter, is that the samples of 2 grams are put into the aluminium dish, 180 ℃ of heating 10 minutes down, determines its weight then, and calculates its percentage composition that accounts for gross weight (X) according to following formula:

Immerse the polymer beads of the foamed change that obtains in the boiling water and according to the time heating that is provided in table 1, the table 2, can make the prefoam particle, shown in table 1, the table 2 is the specific volume of measured prefoam particle, trying to achieve of specific volume, be that the prefoam particle is contained in the pipe of 1000ml capacity, determine its weight, specific volume is shown by volume/weight.

The shrinkage factor of prefoam particle (Y) is determined by following formula in percentage: $Y=\frac{a-b}{a}\×100$

Here the volume after a represents to recover (after the prefoamization 24 hours), b represent to measure immediately after the prefoamization volume.Data as shown in table 1, table 2.

With the prefoam particle in air, under 25 ℃ of temperature conditions, slaking 24 hours, put into the metal pattern of the slab that is used to pour into a mould 190mm * 120mm * 10mm, in the bench-type thermal compressor with the steam of 98.0665kPa gauge pressure (120 ℃), and, make mold according to the heating of the time shown in table 1, the table 2.

The generation rate of the surface smoothness of obtained foam mold and contraction or non-generation rate are carried out after macroscopic view estimates,, and estimate the black smoke and the ash that are produced the mould burning.Can find these data estimators in table 1, the table 2.

In order to determine the shrinkage factor of mould, the fluidized polymer particle independent prefoamization in atmospheric steam batch (-type) foamingization device that can foam arrives 0.020-0.021/cm ³Density.Use decompression cooled injection machine (Daiya VS-300, make by Daisen Kogyo KK), under 25 ℃ of temperature in air with prefoam particle slaking 24 hours, be shaped to the thick wall of 50mm, be of a size of 552mm length * 335mm wide * box-shaped mechanograph that 150mm is high, condition of molding is the VS preheating: 3 seconds, heat 1:3 second, heat 2:7 second, water cooling: 10 seconds, freely cool off: 300 seconds, steam pressure was 78.4528kPa.Measure the thickness of goods wall after the moulding immediately, relatively the error of mould size (50mm) be+2-0% (51-50mm), and for not surpassing the not enough mechanograph of cooling condition or cooling drying 24 hours under 40 ℃ of temperature.

Calculate by following formula with the shrinkage factor that percentage is represented: $Y^{\′}=\frac{a^{\′}-b^{\′}}{a^{\′}}\×100$

At this a ' is mould size (length 552mm), and b ＇ is the size of mould after 24 hours, sees in the data shown in table 1, the table 2.

Table 1

	Example
									????1	?2	???3	????4	???5	????6	????7
Composition (gram) styrene methyl methacrylate EMA butyl methacrylate lauroyl peroxide benzoyl peroxide tert butyl peroxy benzoate n-octyl mercaptan pentane toluene butane	????750 ????250 ????- ????- ????2 ????2 ????1 ????1 ????100 ????- ????-	?600 ?400 ?- ?- ?2 ?2 ?1 ?1.5 ?80 ?- ?-	??800 ??- ??200 ??- ??2 ??2.5 ??1 ??0.5 ??20 ??- ??80	????800 ????- ????- ????200 ????2 ????2.5 ????1 ????0.5 ????40 ????- ????60	??600 ??400 ??- ??- ??5 ??3 ??2 ??3 ??90 ??- ??-	????700 ????300 ????- ????- ????2 ????2 ????1 ????0.5 ????60 ????5 ????30	???650 ???100 ???250 ???- ???3 ???4 ???1.5 ???2 ???100 ???- ???-
								Characteristic can foaming molecular resin amount (* 10 4) average diameter of particles (mm) volatilizer content (%) pentane content (%) prefoam heat time heating time (branch) specific volume (ml/g) macroscopical degree of shrinkage foamingization particle shrinkage factor (%)	????29.6 ????0.61 ????8.1 ????7.7 ????1 ????47 ????A ????1.5	?26.5 ?0.54 ?6.7 ?6.4 ?2 ?41 ?A ?2.2	??34.1 ??0.47 ??6.2 ??1.6 ??2 ??45 ??A ??1.7	????32.6 ????0.65 ????6.9 ????3.6 ????1 ????45 ????A ????2.6	??17.2 ??0.44 ??6.5 ??5.9 ??1 ??46 ??A ??2.7	????25.4 ????0.41 ????6.2 ????5.6 ????2 ????50 ????A ????0.9	???20.7 ???0.62 ???7.1 ???6.7 ???1 ???49 ???A ???2.5

Shaping apperance heat time heating time, (branch) specific volume, (ml/g) macroscopical degree of shrinkage mould shrinkage factor surface smoothness black smoke/grey generation

????1 ????61 ????A ????0.3 ????D ????A

??2 ??54 ??A ??0.3 ??D ??A

??2 ??58 ??A ??0.4 ??D ??A

??2 ??58 ??A ??0.4 ??D ??A

??1 ??60 ??A ??0.3 ??D ??A

??2 ??64 ??A ??0.3 ??D ??A

??1 ??62 ??A ??0.4 ??D ??A

Table 2

	Comparative example
										????1	????2	?3	??4	??5	??6	???7	????8
Composition (gram) styrene methyl methacrylate EMA butyl methacrylate lauroyl peroxide benzoyl peroxide tert butyl peroxy benzoate n-octyl mercaptan pentane toluene butane	?1000 ?- ?- ?- ?- ?2.5 ?1 ?- ?80 ?- ?-	- 1000 - - 5 - 0.5 2 90 - -	?700 ?300 ?- ?- ?1.5 ?2 ? ?1 ?1 ?100 ?10 ?-	700 300 - - - 3 1 4 80 - -	?700 ?300 ?- ?- ?2 ?2 ?1 ?1.5 ?150 ?- ?-	?700 ?300 ?- ?- ?2 ?2 ?1 ?1.5 ?5 ?- ?100	???900 ???100 ???- ???- ???2 ???2 ???1 ???- ???100 ???- ???-	???500 ???500 ???- ???- ???2 ???2 ???1 ???1 ???100 ???- ???-
									Characteristic can foaming molecular resin amount (* 10 4) average diameter of particles (mm) volatilizer content (%) pentane content (%)	?24.2 ?0.51 ?6.9 ?6.6	16.2 0.57 7.6 7.2	?36.7 ?0.62 ?8.2 ?6.8	14.1 0.52 7.2 6.7	?28.2 ?0.49 ?11.4 ?11.4	?28.5 ?0.53 ?7.4 ?0.4	???27.4 ???0.57 ???7.9 ???7.5	???26.2 ???0.55 ???8.0 ???7.6
Prefoam heat time heating time (branch)	?1	1	?3	0.5	?0.5	?3	???1	???1

Specific volume (ml/g) macroscopical degree of shrinkage foamingization particle shrinkage factor (%)	????52 ????A ????1.2	?47 ?B ?1.7	?36 ?A ?1.5	?51 ?B ?6.2	?47 ?B ?5.7	?46 ?A ?1.4	?50 ?A ?1.1	?44 ?C ?4.1
									Moulding apperance heat time heating time, (branch) specific volume, (ml/g) macroscopical degree of shrinkage mould shrinkage factor, (%) surface smoothness black smoke/grey generation	????1 ????68 ????A ????0.6 ????D ????G	?1 ?57 ?B ?1.9 ?E ?A	?3 ?58 ?A ?0.3 ?F ?A	?1 ?66 ?B ?1.8 ?E ?A	?1 ?57 ?B ?1.6 ?E ?A	?3 ?55 ?A ?0.3 ?F ?A	?1 ?64 ?A ?0.3 ?D ?G	?1 ?57 ?C ?0.5 ?E ?G

In table 1, table 2, molecular weight is a weight average molecular weight, is determined by the gel permeation chromatography that with the polystyrene is standard.

Alphabetical A is as follows to the G representative meaning among the result in the table:

A-does not have

B-is remarkable

C-is little

D-is good

The many wrinkles of E-

The big shrinkage depression of F-

G-is a large amount of

The foamed change of routine 1-7 resin particle is used for and can the casting of foaming mould tests in the table 1, and it the results are shown in down described.

Foamed polystyrene (High Beads, HCF-5000 is made by Hitachi KaseiKogyo KK) is used for contrast.

The screening scope of can the foaming resin particle being given among the example 1-7 is 26 orders (0.60mm), and is arrived 45ml/g by prefoamization.After 24 hours, pour into foamed change mould (168mm * 168mm, the volume 520cm of the valve gap that is used for the feed pipe connecting portion as shown in accompanying drawing 1 temperature 20-25 ℃ of following slaking ³) this can the foaming mould be used to make foundry goods and does contrast.

Cast under the 1450-1470 ℃ of temperature, use spheroidal graphite cast-iron (carbon containing 3.55%, silicon 2.4%, magnesium 0.04%, manganese 0.2%) to finish.Foundry goods to example 1 and foamed polystyrene (HFC-50000) has carried out three casting respectively.

When using foamed polyethylene (HFC-5000) mould to be used for the iron casting, found all that on three casted article surfaces carbon adheres to, and found that carbon is penetrated into foundry goods inside.In contrast, do not find that carbon is attached to the casting surface in the iron castings that uses the foamed change mould can the foaming resin particle made to cast among the routine 1-7.Do not find that carbon is penetrated into foundry goods inside yet.And then, the surface of watering foundry goods compared demonstrate, use the cast(ing) surface of expanded polystyrene pattern (HFC-5000) casting very coarse, and that routine 1-7 makes the casting surface is more smooth, do not have concavo-convex, the shaggy generation of foundry goods may be because remaining resin decomposes the induced gas that is produced, and may be since the molten iron cast inappropriate due to.May be because foamed the changes resin particle of routine 1-7 have than can the better thermal decomposition performance of foaming polystyrene, and it is easier to volatilize, thus the thermal decomposition of resin is carried out completely in the casting of metals that has melted, and it is concavo-convex to make that cast(ing) surface can not produce.And then, when using the foam polymethacrylates can the foaming mould time, there not be the blowback phenomenon of the deposite metal that generation causes owing to thermal decomposition gas.

Example 8

A kind of foam thermal mold that is used for valve gap casting, heavy 3.7kg has size: 168 * 168 * 80mm, averga cross section thickness are that to be molded as density with foamed polystyrene (HFC-5000) be 0.020～0.021g/cm to 15mm ³Apperance.The second kind of mould that is used for same foundry goods is to be become by the foamingization copolymer molding, and this copolymer is to be made by methyl methacrylate that occupies 30% weight and 70% heavy cinnamic monomer mixture.Two moulds all are to be connected with the cast gate of cross section 8 * 40mm with high 15mm with a kind of special-purpose hot-melt adhesive (CORFI * 600), and it is connected with the horizontal other end that waters rod that is of a size of 140 * 40 * 40mm again conversely.Cast gate and the horizontal rod that waters are to be 0.020g/cm from the density of being made by the granules of polystyrene of special use ³The molding piece on cut down, this special use granules of polystyrene is BASF455 (being made by BASF).

Assembly scribbles one deck and has special-purpose water-based, not heat insulation, the permeable refractory coating of medium (STYROMOL 142.06), and dry under 45 ℃ of temperature.The down gate of whole heat resistance fiber base cup and high 600mm is connected with the horizontal rod that waters, and whole assembly places in the sandbox, is surrounded by NAG silica sand, makes silica sand closely knit by vibration.Under 1472 ℃ of temperature, the carbon by 3.74%, 0.01% sulphur, 2.20% silicon, the fusing magnesium iron that 0.19% manganese and 0.039% magnesium are formed is poured in the cup.Allow the foundry goods of casting cool off, from sand it is taken out, slight bullet grain sandblast is to check its defective.

In by front view Fig. 2 of the foundry goods of expanded polystyrene pattern casting and rearview Fig. 3, its result has been described with respective markers.Mark 1 is the cast gate that is positioned on the foundry goods, 2 the expression be the top of foundry goods, 3 the expression shadow regions be have coarse, the surface of defective, 4 the expression be the foundry goods front, 5 expressions be the reverse side of foundry goods, the mould that the copolymer that methymethacrylate by heavy 30% and heavy 70% styrene polymerization produce is made is watered the foundry goods that casts out does not then have blemish fully.

Said process is through repeated test, and that obtain is identical result.

Claims (14)

1. method of producing metal casting, the foam thermal mold of Shi Yonging is surrounded by special heat proof material in the method, the casting of metals that has melted is gone on this mould, this mould is decomposed, metal-cured back forms and the equiform foundry goods of this mould, the method is characterized in that this foam thermal mold is by making by foamingization with according to required form is molded by the foaming resin combination, and this can the foaming resin combination be a kind of foamed change resin combination of being made by the copolymer of volatile foaming agent dipping, this copolymer has 150,000 to 350,000 weight average molecular weight, be to be produced by the co-polymerization that accounts for the heavy styrene monomer of 55-85% and account for the heavy methacrylate monomers of 15-45%, its general formula of the latter is that wherein R represents the CH of the alkyl of 1-4 carbon atom ₂=C (CH ₃) COOR, and the volatilization foaming agents content is up to 10% of total monomer weight.

2. a kind of method according to claim 1 is characterized in that this foam thermal mold scribbles one deck refractory coating.

3. method according to claim 1, wherein applied a kind of foaming resin combination is characterised in that copolymer wherein is the copolymer that is produced by the co-polymerization that accounts for the heavy methacrylate monomers of heavy styrene monomer of 60-80% and 20-40%.

4. method according to claim 1, wherein applied a kind of foaming resin combination is characterised in that CH therein ₂=C (CH ₃) R is methyl, ethyl, n-pro-pyl, isopropyl, normal-butyl, sec-butyl, the tert-butyl group or isobutyl group among the COOR.

5. according to the method for each claim in the claim 1 to 4, wherein applied foaming resin combination is characterised in that, makes the polymerization of monomer be accomplished under the situation that has organic peroxide as polymerization initiator.

6. method according to claim 5, wherein using a kind of foaming resin combination is characterised in that, described organic peroxide is: lauroyl peroxide, benzoyl peroxide, tert-butyl peroxide (2 ethyl hexanoic acid ester), tert butyl peroxy benzoate, t-butylperoxy pivarate, 1,1-di-tert-butyl peroxide-3,3,5-trimethyl-cyclohexane, di-tert-butyl peroxide hexahydro terephthalic acid ester, di-tert-butyl peroxide isophthalic acid ester, di-tert-butyl peroxide trimethyladipic acid ester.

7. according to the described method of each claim in the claim 1 to 4, wherein use a kind of foaming resin combination and be characterised in that, under the situation that has n-dodecyl mercaptan, n-octyl mercaptan, normal-butyl mercaptan or tert-butyl mercaptan to exist, make polymer of monomers with being accomplished.

8. method according to claim 7 is wherein used the amount that a kind of foaming resin combination is characterised in that described mercaptan and be no more than 1mol% for monomer.

9. according to the described method of each claim in the claim 1 to 4, wherein applied a kind of foaming resin combination is characterised in that its volatile foaming agent is a pentane.

10. method according to claim 9, wherein applied a kind of foaming resin combination are characterised in that a kind of auxiliary volatile foaming agent exists, and this blowing agent is selected from the fat chain hydrocarbon.Alicyclic and aliphatic hydrocarbon halide.

11. method according to claim 10, wherein said auxiliary volatile foaming agent are propane, butane, hexane, benzinum, cyclohexane, carrene, trichorotrifluoroethane or dichloro Difluoroethane.

12. method according to claim 1, wherein applied a kind of foaming resin combination is characterised in that and has plasticizer.

13. method according to claim 12, wherein said plasticizer are second benzene,toluene,xylene, 1,2-dichloropropane, trichloro-ethylene or perchloroethylene.

14. according to claim 12 or 13 described methods, wherein applied a kind of foaming resin combination is characterised in that the amount of described plasticizer is to be no more than 5% of copolymer weight.

Images