GB1588185A

GB1588185A - Refractory suspension for making foundry moulds

Info

Publication number: GB1588185A
Application number: GB3937177A
Authority: GB
Original assignee: YASINSKY K K GLAZUNOV S G ROSS
Current assignee: YASINSKY K K GLAZUNOV S G ROSS
Priority date: 1977-09-21
Filing date: 1977-09-21
Publication date: 1981-04-15

Description

(54) REFRACTORY SUSPENSION FOR MAKING FOUNDRY MOULDS (71) We, KONSTANTIN KONSTANTINO VICH YASINSKY, of kvartira 52, 18 ulitsa Spartakovskaya, Moscow, SERGEI GEORGIE VICH GLAZUNOV, of kvartira 62, 41 Leninsky prospekt, Moscow, JURY NIKOLAEVICH Ross, of kvartira 36, 74 ulitsa Patrioticheskaya, Zaporozhie, and IGOR DMITRIEVICH BYKOV, of kvartira 6, 44 ulitsa Turgeneva, Zaporozhie, all of the Union of Soviet Socialist Republics, all citizens of the Union of Soviet Socialist Republics, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: The present invention relates to a refractory suspension for making lost wax foundry moulds for casting pieces of chemically active metals.

The present invention provides a refractory suspension for making lost wax foundry moulds for casting chemically-active metals, which comprises the following constituents in the following parts by weight: a coke 10-60; a powdered metal selected from titanium, zirconium and mixtures thereof 0.3-5.0; resol resin (as defined herein) 5-50; a hardener selected from organic and inorganic acids 2-30; and an organic solvent 20-60.

The use of this coke-resin suspension for producing lost wax moulds which uses a powdered coke as parting dust enabled the shell strength of a mould produced therefrom to be increased 1.5 times as against that of moulds made from prior art suspension, i.e. be increased from 12 to 17-18 kgf/ cm2, enables the geometric accuracy spread to be decreased and enables casting accuracy to be enhanced by 2 classes, according to the USSR classification (i.e. by 100 mm + 0.3-0.5 mm instead of + 0.60.8 mm).

The presence of these constituents in the composition of the present invention as well as the use of coke as a parting dust decreases by several times the heat conductivity of the mould. This leads to a higher mouldfilling ability and thus allows the manufacture of thin-section castings of intricate geometry; enhancing at the same time their quality by eliminating cold shuts and other defects The suspension composition incorporates less scarce materials, and is less expensive than prior-art compositions, and so finds extensive application in various branches of industry.

When producing moulds from the suspension of the present invention, filler requirements are decreased by 50-60% compared to known suspensions owing to the possibility of recurrent reclaiming of used moulds after casting.

Used moulds may be reclaimed without impairing the quality of either the reclaimed moulds or casting produced therein and as a result the production cost of the moulding material is reduced by 2530%.

By "resol resin" as used herein, we mean a resin containing substituted or unsubstituted methylol groups (-cH2OH) and which can be hardened by means of an acidic catalyst.

According to a preferred feature of the present invention, it is expedient that the proposed suspension comprise a phenolic resin as the resol resin binder.

However, a furan resin may alternatively be used as said resol resin binder.

It was found that the introduction of resol resins, e.g. phenolic or furan resins, characterized by a high coke yield into the refractory suspension allowed an increase in the strength of the produced foundry moulds to be attained, their geometric stability to be enhanced and the mould collapsibility to be reduced.

For providing a refractory suspension suitable for making foundry moulds, it is preferred that the composition of the suspension incorporate hydrochloric, sulphuric or benzene-sulphonic acids as hardener, said acids featuring the highest reactivity for setting the resin.

It is good practice that the suspension comprise an alcohol or mixture of alcohols as said organic solvent.

The introduction of said alcohols into the suspension of the invention renders possible the long-term storage of a prepared suspension prior to its use.

Further advantages of the invention will become apparent from the following detailed description of a preferred refractory suspension for making foundry moulds and illustrative examples of a preferred embodiment.

The use of 1060 parts by weight of powdered coke derived from oil, pitch, coal, or wood (treated so as to produce a charcoal having properties resembling those of coke) in the proposed suspesnion allowed a foundry mould of requisite strength to be produced, thereby reducing its collapsibility and allowing better filling of the mould with molten metal as a result of the lower heat conductivity of the coke (which amounted to 6.2 W/m.deg as against that of graphite which was equal to 129 W/m.deg.) The reduced heat conductivity enhances the mould-filling ability and so makes it possible to produce thin-section pieces having a wall thickness of 1.5 mm and being up to 30 mm long, eliminates surface defects on the castings, such as cold shuts, and improves the quality of the castings.

As the moulds are cured both the resin and the hardener comprised in the suspension pass into the coke and since the latter is employed as a filler, the linear expansion factor of the two materials thus produced will be the same. This results in stable shrinkage of the mould and a higher accuracy of the castings.

The use of said coke-filled suspension for making coke moulds allows the moulds to be compeltely reclaimed after filling them with metal, to produce the powdered coke required for their recurrent application in said suspension or for dusting use.

We have also found that with a coke content less than 10 parts by weight the produced refractory suspension exhibits a low binding power when making moulds and dusting them with powdered coke, and the mould-making operation also requires much time. With a coke content exceeding 60 parts by weight a thick slurry is obtained, the process of applying the next layers to the mould being complicated thereby and the geometry of the produced mould being disturbed.

As a second constituent of the filler, we use metallic titanium and/or zirconium powders varying in amount from 0.3 to 5.0 parts by weight. Such a filler contributes to the production of foundry moulds which are more inert to molten metal. This is attributable to the formation during curing of carbides of said metals in the mould per se and on its surface in particular. These carbides decrease the molten metal/mould interaction and enhance at the same time the mould strength by 1.5-2.0 kgf/cm2. However a higher content of said metallic powders in excess of 5.0 parts by weight results in lower strength and higher collapsibility of the mould (which is caused in our opinion by the disturbance of the bonds between the binder-resin and the coke filler).

The suspension contains from 5 to 50 parts by weight of the binder-resol resins.

The present invention envisages the possibility of using, any of the following resins as resol resin: phenol-formaldehyde, phendlfurfural, phenol-furfuryl, phenol-furfuralformaldehyde, phenol - cresol - furfural, furfural-acetone furfural-aldehyde, furan resin, carbamide-furan phenolic alcohols, carbamide-formaldehyde, carbamide-furfural, carbamide-formaldehyde-furfural, resorcinol resin, resorcinol-formaldehyde. resorcinolphenol - formaldehyde, resorcinol - phenolfurfural; melamine-formaldehyde, melaminephenol-formaldehyde, amine-formaldehyde (the amine being aniline or urea for example) and amine-phenol-formaldehyde (e.g.

the amine being aniline or urea) resins.

On being introduced into the suspension as a binder said resins or a mixture thereof ensure due to their coking during curing a mould strength in the range of 17-25 kgf/ cm2. It does not affect the minimum scattering of the mould geometric dimensions, and the castings are held within closer tolerances of up to +0.3-0.5 mm per 100 mm diameter.

However when the content of said resin in the suspension drops below 5 parts by weight, the strength of the moulds produced therefrom deteriorates, their collapsibility increases and the moulds fail as they are being filled with molten metal. Where the resin content in the suspension increases in excess of 50 parts by weight, the process of extracting the castings from the moulds produced from said suspension is complicated due to the excessive strength of the moulds; moreover the stability of the mould geometric dimensions is disturbed during baking which adversely affects the accuracy of the castings produced.

As regards the hardener, use may be made of various organic and inorganic acids which are introduced into the suspension composition in amounts ranging from 2 to 30 parts by weight. Suitable acids are:-- hydrochloric, sulphuric, benzenesulphonic, paratoluenesulphonic, orthotoluenesulphonic, orthophosphoric, acetic, boric, oxalic, formic acids, paratoluenesulphochloride and a mix ture- of sulphonaphthenic acids ("Petrov's contact catalyst").

As catalysts said compounds assist in the rapid hardening of the binders contained in the suspension, thus ensuring stable mould shrinkage during moulding. This enables the required shrinkage of the mould and a preset casting accuracy to be attained.

A hardener content of less than 2 parts by weight extends the setting period of the resins in the suspension, whereas with a resin content exceeding 30 parts by weight polymerization of said resins proceeds at an extremely high rate, the making of moulds from such a suspension being thereby unfeasible in practice.

The solvents employed in the suspension vary in amount from 20 to 60 parts by weight and are adapted for diluting the resin and / or their mixtures to the required density and viscosity so as to ensure proper handling properties of the suspension when making a mould. As solvent, use may be made of alcohols such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl alcohols and their isomers; esters such as ethyl, butyl, propyl and amyl acetates; mixtures of aromatic hydrocarbons such as benzene, toluene and xylene with alcohols; glycol ethers and mixtures thereof, such as monomethyl ethylene glycol, mono-ethyl ethylene glycol, monoisopropyl ethylene glycol, monobutyl ethylene glycol ethers and their mixtures with alcohols as well as acetone.

By varying the solvent content within the above-specified range it is possible to create a suspension having a predetermined density and viscosity.

Thus, the above-mentioned combination of coke, resin, hardener and solvent employed for preparing the suspension of the invention allows the production of foundry moulds featuring stable shrinkage and a requisite strength in the range 17 to 25 kgf/cm2.

At the same time the use of the suspension with a preset weight ratio of its constituents for making foundry moulds allows the mould-filling ability to be enhanced and castings having thinner walls and a good surface finish without any cold shuts whatsoever to be obtained; these qualities resulting from the lower heat conductivity of the coke moulds as compared with graphite ones.

Moreover, the suspension comprising said constituents for making coke-based foundry moulds affords the possibility of repeated reclaiming of the mould after filling with molten metal, without -impairing the quality of reclaimed moulds produced from the re clPimed powder.

When emnloyed for making casting moulds said suspension reduces the random varia tins in the geometric dimensions of the moulds and enables cast pieces to be produced with close tolerances that are held within + 0.34.5 mm per 100 mm diameter.

Finally the use of the herein-proposed refractory suspension for making lost wax foundry moulds enables the heat conductivity of said moulds to be reduced. This results in a higher mould-filling ability and allows the production of thin-section castings with a wall thickness of up to 1.5 mm.

The better surface quality of the produced castings is obtained due to the elimination of cold shuts and other defects related to the heat conductivity of the mould. The use of coke, a less scarce material, in said suspension as a filler instead of graphite brings down the cost of the mould and allows the recurrent reclaiming of the used coke moulds for producing parting dusts. The consumption of moulding materials (powdered coke required for producing both the suspension and moulds) decreases thereby by 5060% with an ensuing reduction in the cost of said materials by another 2530%. The recurrent reclaiming of the used moulds for producing powders does not affect the quality of either the reclaimed moulds or the castings produced therefrom.

In view of the reduction in the cost of producing foundry moulds which is rendered possible by using less scarce inexpensive materials and reclaiming the moulds, the herein-proposed suspension may find wide acceptance for making coke moulds in the various branches of industry where a need arises for casting such metals as titanium and zirconium.Given herein-below are Examples of the technique of preparing said suspension and making coke moulds thereof, said technique being similar for all suspensions, Example I For preparing a refractory suspension 26 parts by weight of phenol-formaldehyde resol resin are dissolved in 36 parts by weight of methyl alcohol, whereupon 0.8 parts of powdered zirconium and 28 parts by weight of powdered coal coke are introduced in the produced composition, all components are thoroughly stirred and the last constituent-a hardener which is concentrated hydrochloric acid taken in an amount of 4 parts by weight, is added to the suspension.

After some more stirring the suspension is subjected to holding for 0.5-1.0 hour -for removing air bubbles which may be entrapped therein.

Foundry moulds were produced by dipping wax patterns in the thus prepared suspension, this being followed by dusting them with a coke powder. On applying each next layer to the wax pattern it was subjected to drying in special driers at a temperature varying in the range between 28 and 30"C for 2.5 hours. The pattern was thus coated with 7-8 layers of coke whereupon the wax was melted out in a steam bath, moulding composition or in water acidified by adding 3% hydrochloric acid thereto.

On being released from the wax composi tion the moulds were subjected to curing by heating them to a temperature ranging within 1300--1350"C and holding at this temperature for 4 hours.

The baked moulds are placed in a vacuum skull furnace and filled with molten metal.

Produced castings are discharged from the furnace, extracted out of the moulds and cut off the gate system and heads. All operations completed the cast pieces are subjected to sandblasting and checked for quality and accuracy.

The accuracy of the castings produced by using coke moulds made from said suspension varies within +0.3--0.38 mm per 100 mm diameter and their strength is of the order of 20 kgf/cm2. The castings feature a good surface finish without any cold shuts whatsoever.

Example 2 For preparing a refractory suspension 31 parts by weight of furan resol resin are dis solved in 40 parts by weight of isobutyl alcohol whereupon 1.8 parts by weight of powdered titanium and 36 parts by weight of powdered oil coke are introduced into the produced solution. All components are carefullly stirred, whereas a hardener-3 parts by weight of concentrated sulphuric acids introduced into the thus obtained suspension. This is followed by some more stirring and the suspension is held for 0.5 1.0 hour for removing air bubbles which may be entrapped therein.

The thus produced suspension is employed for making a foundry moulds by using the technique described in Example 1 and then a casting per se. The produced casting mould exhibits a good strength amounting to 22 kgf/cm2 and an accuracy that is held within +0.4-0.45 mm per 100 mm diameter.

Example 3 For preparing a refractory suspension 10 parts by weight of resorcinol resol resin and 25 parts by weight of furfural aldehyde resol resin are dissolved in 38 parts by weight of isopropyl alcohol, whereupon 40 parts by weight of titanium and 42 parts by weight of coal coke powders are introduced into the obtained solution. All components are thoroughly mixed and a hardener-7.0 parts by weight of paratoluenesulphonic acid-is introduced into the thus produced suspension.

The latter is stirred again and held for 0.5-1.0 hour for removing air bubbles which may be entrapped into the suspension.

The thus produced suspension is employed for making (using the technique quoted in Example 1) a foundry mould featuring a strength of 23.5 kgf/cm2. Said high strength inherent in the foundry moulds allows using more thin-walled moulds and producing sound castings accurate within +0.48 mm per 100 mm diameter.

Example 4 To produce a refractory suspension 15 parts by weight of phenol-furan resol resin are dissolved in 57 parts by weight of ethyl alcohol whereupon 0.3 parts by weight of titanium and 60 parts by weight of pitch coke powders are introduced into the obtained solution. All components are thoroughly stirred and a hardener-13 parts by weight of paratoluenesulphochloride-is introduced into the thus produced suspension. After some more stirring the suspension is held for 0.5-1.0 hour for removing air bubbles which may be entrapped therein.

The thus produced suspension is employed for making (using the technique described in Example l) a foundry mould and then a casting featuring an adequate surface finish and an accuracy of rut0.41 mm per 100 mm diameter.

Example 5 For preparing a refractory suspension 42 parts by weight of furfural-aldehyde resol resin are dissolved in 28 parts by by weight of amyl alcohol, whereupon 5.0 parts by weight of zirconium and 18 parts by weight of pitch coke powders are introduced into the obtained solution. All components are carefully stirred and a hardener 19 parts by weight of paratoluenesuphonic acid-is introduced into the thus produced suspension. The latter is subjected to some more stirring and held for 0.5-1.0 hour for removing air bubbles which may be entrapped therein.

The thus produced suspension is employed for making (using the technique described in Example 1) a foundry mould featuring an adequate heat conductivity and an enhanced chemical resistance to molten titanium and other high-melting point metals. The accuracy of the castings produced in said mould does not exceed +0.5 mm per 100 mm diameter.

Example 6 For preparing a refractory suspension 24 parts by weight of furnan resol resin and 8 parts by weight of phenol-furfuryl resol resin are dissolved in 40 parts by weight of butyl alcohol, whereupon 1.2 parts by weight of titanium and 32 parts by weight of pitch coke powders are introduced in the produced solution. All components are thoroughly stirred and a hardener-6 parts by weight of benzenesulphonic acid-is introduced into the thus produced suspension. After some more stirring the suspension is held for 0.5-1.0 hour for removing air bubbles which may get into the suspension.

The thus produced suspension is employed for making a foundry mould by using the technique described in Example 1, - said mould featuring a high strength amount to 23 kgf/cm2 with the castings having an accuracy of + 0.35 mIn per 100 mm diameter.

Example 7 For preparing a refractory suspension 3 parts by weight of resorcinol resol resin and 11 parts by weight of phenol-furfural resol resin are dissolved in 60 parts by weight of isobutyl alcohol whereupon 2.5 parts by weight of zirconium and 36 parts by weight of oil coke powders are introduced into the produced solution. All components are thoroughly stirred and a hardener-3 parts by weight of orthophosphoric acid are introduced into the thus produced suspension. After some more stirring the suspension is held for 0.5-1.0 hour to remove air bubbles that. may be entrapped therein.

The thus produced suspension which can withstand long-term storage without hardening is employed for making a foundry mould, using the technique described in Example 1, said foundry mould exhibiting a strength of 25 kgf/cm2 which makes it possible to produce castings featuring a high accuracy of +0.35 mm per 10 mm diameter.

Example 8 For preparing a refractory suspension 48 parts by weight of carbámide-furan resol resin are dissolved in 26 parts by weight of amyl acetate whereupon 3.2 parts by weight of titanium and 52 parts by weight of coal coke powders are introduced into the obtained solution. All components are thoroughly stirred and a hardener 14 parts by weight of boric acidis introduced into the thus produced suspension. After some more stirring the suspension is held for 0.51.0 hour for removing air bubbles entrapped therein.

The thus produced suspension is employed using the technique described in Example 1 for making a foundry mould.

the suspension hardening rapidly on said mould as it is being produced. The produced casting exhibits a good surface finish, as for the mould strength it is at the level of 20-21 kgf/cm2.

Example 9 For preparing a refractory suspension 40 parts by weight of furfural-acetone resol resin are dissolved in 17 parts by weight of acetone whereupon 1.0 part by weight of titanium and 29 parts by weight of coal coke powders are introduced into the obtained solution. All components are thoroughly stirred and a hardener--15 parts by weight of acetic acid-is introduced into the thus produced suspension. The latter is stirred once more and held for 0.5-1.0 hours to remove bubbles which may be en trapped therein.

The thus produced suspension is em ployed using the technique described in Example 1 for making a foundry mould, said suspension allowing a rapidly-drying mould to be obtained. The strength of the produced casting mould amounts to 17 kgf/ cm2 and casting accuracy is held within + 0.5 mm per 100 mm diameter.

Example 10 For preparing a refractory suspension 28 parts by weight of carbamide-furfural resol resin are dissolved in a mixture of solvents comprising 16 parts by weight of butyl acetate and 7 parts by weight of butyl alcohol, whereupon 4.5 parts by weight of a mixture containing titanium and zirconium powders and 10 parts by weight of an oil coke powder are introduced into the obtained solution. All components are carefully stirred and a hardener-12 parts by weight of -a mixture of sulphonapthenic acids ("Petrov's contact catalyst")-is introduced into the thus produced suspension. After some more stirring the suspension is held for 0.5-1.0 hour for removing air bubbles which may be entrapped therein.

The thus produced suspension is em ployed using the technique described in Example 1 for mák;ing a foundry mould exhibiting a. strength of 18 kgf/cm2, the accuracy of the produced casting being equal to -0.46 mm per 100 mm diameter.

Example 11 For preparaing a refractory suspension 20 parts by weight of melamine-phenol-form aldehyde resol resin and 12 parts by weight of a mixture of phenols are dissolved in 32 parts by weight of monoethyl ethylene glycol ether whereupon 3.2 parts by weight of a titanium powder and 31 parts by weight of a coal coke powder are introduced into the obtained solution. All components are thoroughly stirred and a hardener-7 parts by weight of orthotoluenesulphonic acid is introduced into the thus produced suspen sion. The latter is given some more stirring and held for 0.5-1.0 hour to remove air bubbles which may be entrapped therein.

The thus produced suspension is em ployed using the technique described in Example 1 for making a foundry mould exhibiting a strength of 21 kgf/cm2. As for the produced castings, their accuracy is held within s0.5 mm per 100 mm diameter.

Example 12 For preparing a refractory suspension 18 parts by weight of amine-formaldehyde (where the amine is aniline, melamine or urea) resol resin and 8 parts by weight of epoxy resin are dissolved in a mixture of aromatic hydrocarbons and alcohols (xylene + butyl alcohol) taken in an amount of 32 parts by weight whereupon 2.8 parts by weight of a zirconium and 31 parts by weight of pitch coke powders are introduced into obtained solution. All components are thoroughly stirred and a hardener-il parts by weight of formic acid-is introduced into the thus produced suspension. After some more stirring the suspension is held for 0.51.0 hour for removing air bubbles entrapped therein.

The thus produced suspension is employed using the technique described in Example 1 for making a foundry mould exhibiting a strength of 19 kgf/cm2. The castings have an accuracy of + 0.4 mm per 100 mm diameter WHAT WE CLAIM IS: 1. A refractory suspension for making lost wax foundry moulds for casting chemically-active metals, which comprises the following constituents in the following parts by weight: a coke 10-60; a powdered metal selected from titanium, zirconium and mixtures thereof 0.3-5.0; resol resin (as defined herein) 5-50; a hardener selected from organic and inorganic acids 2-30; and an organic solvent 2060.

2. A refractory suspension according to claim 1, wherein the resol resin is a phenolic resin.

3. A refractory suspension according to claim 1, wherein the resol resin is a furan resin.

4. A refractory suspension according to any preceding claim, wherein the hardener is hydrochloric acid.

5. A refractory suspension according to any one of claims 1-3, wherein the hardener is sulphuric acid.

6. A refractory suspension according to any one of claims 1-3, wherein the hardener is benzenesulphonic acid.

7. A refractory suspension according to claim 1, wherein the organic solvent is an alcohol or mixture of alcohols.

8. A refractory suspension substantially according to any of the exemplified embodiments.

9. A method of making a lost wax foundry mould for casting chemically active metals which comprises at least partially coating a wax pattern with a suspension according to any preceding claim, drying the coating of said suspension, melting out the wax and curing the coating.

10. A method of making a lost wax foundry mould substantially as herein exemplified.

11. A mould produced by the method of claim 9 or claim 10.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the produced castings, their accuracy is held within s0.5 mm per 100 mm diameter. Example 12 For preparing a refractory suspension 18 parts by weight of amine-formaldehyde (where the amine is aniline, melamine or urea) resol resin and 8 parts by weight of epoxy resin are dissolved in a mixture of aromatic hydrocarbons and alcohols (xylene + butyl alcohol) taken in an amount of 32 parts by weight whereupon 2.8 parts by weight of a zirconium and 31 parts by weight of pitch coke powders are introduced into obtained solution. All components are thoroughly stirred and a hardener-il parts by weight of formic acid-is introduced into the thus produced suspension. After some more stirring the suspension is held for 0.51.0 hour for removing air bubbles entrapped therein. The thus produced suspension is employed using the technique described in Example 1 for making a foundry mould exhibiting a strength of 19 kgf/cm2. The castings have an accuracy of + 0.4 mm per 100 mm diameter WHAT WE CLAIM IS:

1. A refractory suspension for making lost wax foundry moulds for casting chemically-active metals, which comprises the following constituents in the following parts by weight: a coke 10-60; a powdered metal selected from titanium, zirconium and mixtures thereof 0.3-5.0; resol resin (as defined herein) 5-50; a hardener selected from organic and inorganic acids 2-30; and an organic solvent 2060.

11. A mould produced by the method of claim 9 or claim 10.