US3379540A - Additive to sand moulds and cores - Google Patents

Additive to sand moulds and cores Download PDF

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US3379540A
US3379540A US473851A US47385165A US3379540A US 3379540 A US3379540 A US 3379540A US 473851 A US473851 A US 473851A US 47385165 A US47385165 A US 47385165A US 3379540 A US3379540 A US 3379540A
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cores
sand
additive
bonded
resin
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Helliwell Derek Priestley
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Foseco International Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
    • B22C1/04—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives for protection of the casting, e.g. against decarbonisation

Definitions

  • ABSTRACT OF THE DISCLOSURE Pinning or veining produced on metal casting cast in sand moulds or around sand cores may be minimised by the incorporation into the sand mould or core of a proportion of colemanite or unexpanded perlite.
  • This invention relates to said moulds and cores and more particularly to additives for sand moulds and cores which improve the characteristics thereof.
  • the invention may be applied to sand moulds and cores incorporarting any organic binder but it is of greatest practical value in connection with oil-bonded sand cores as hereinafter set forth.
  • the invention is concerned with the production of castings from non-skin-forming metals which are poured at above 750 C.
  • metals are the cast irons (grey or modular) and copper based alloys such as lead-, tinand Phosphor-bronzes.
  • Sand moulds and cores in which the bonding agent is oil, Le. a drying or semi-drying oil such as linseed, tung or oilicica, or mixtures of any of these, the oil being optionally in association with a cereal carbohydrate or the like, which usually include a metal, e.g. cobalt or lead, naphthenate as hardener, and which require stoving before use, show some tendency to finning and veining.
  • Sand moulds and cores in which the binder is an air-drying oil (as above) together with an accelerator, e.g. an inorganic peroxy compound such as sodium perborate, show a slightly greater tendency to finning and veining.
  • the resin-bonded sand moulds and cores generally exhibit the phenomenon to an appreciably greater extent: e.g. in the case of furane bonding resins which are set by heating the problem is very severe and in the case of furane bonding resins which are cold set the problem, though still severe, is not quite so serious.
  • an oil-bonded or resin-bonded natural, synethetic or semisynthetic silica sand mould, or core containing less than 5% of clay, for use in casting non-skin forming metals, having a dry compression strength of more than 14 kg./ sq. cm. which includes as an additive to the composition of the sand mould or core, potassium nitrate, colemanite, unexpanded perlite, barium sulphate, sodium rnetaphosphate or potassium alum, or a mixture of any of said substances.
  • the quantity of said substance or mixture of said substances suitable for addition to the material of the mould or core may be within the range 0.5 to 5% of the total weight of the dry mould or core, although a somewhat higher proportion may be required occasionally.
  • a successful additive should not only prevent finning, but also maintain strength, the knock out properties should not be affected, nor must the bonding properties of the oil or the polymerisation of the resin be inhibited.
  • the gas evolution must not be increased and the surface finish should be improved rather than impaired.
  • the additives of this invention tend to fulfill all these requirements.
  • the binder for the sand is a resin it is preferably a furane resin but other resin binders may be employed, e.g. phenol-formaldehyde or urea-formaldehyde resins. If desired there may be used, with any such resin binder, a diluent liquid which will assist in providing a suitably mouldable sand mix.
  • the diluent liquid if used, should of course not have any deleterious inhibitory effect on the polymerisation or polycondensation of the resin whereby the resin hardens to give a rigid product.
  • Suitable liquids for the purpose are inert mineral oils and the oil product sold commercially under the trademark Dutrex 55.
  • 0.15% of a catalyst for a furane-type hot-box resin was then added and the mixture milled again followed by 2% by weight of a furane-type hot-box resin and the mixture milled again until all the additives were evenly distributed throughout the sand.
  • the mixture was then fed to a conventional foundry core blower for the manufacture of cores, by the hot-box technique. These cores were incorporated in foundry moulds for the manufacture of castings of low phosphorus cast iron which was poured at 1400 C.
  • Cores manufactures from this mixture had a dry compression strength of 57 kg./sq. cm. (this compares with the strength of approximately only 42 kg./sq. cm. when used without the anti-finning additive) and the castings produced were entirely free from veins or fins whereas there had previously been a severe level of scrapped castings because of the incidence of such faults.
  • a mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and having a dry compression strength of more than 14 kg./sq. cm. which includes as an additive to the composition thereof, at least 0.5% by weight of a substance selected from the class consisting of colemanite and unexpanded perlite.
  • a mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying compression strength of more than.
  • a mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and having a dry compression strength of more than 14 kg./sq. cm. which includes, as an additive to the composition thereof, at least 0.5% by weight ofunexpanded perlite.
  • Oil-bonded and resin-bonded natural, synthetic and semi-synthetic silica sand moulds and cores containing less than 5% of clay, for use in casting non-skin forming metals, having a dry compression strength of more than 14 kg./sq. cm. which include as an additive to the composition thereof, a substance selected from the class consisting of colemanite and unexpanded perlite, the said additive being present in a proportion of 0.5 to 5% by weight of the composition.
  • a mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and having a dry compression strength of more than 14 kg./ sq. cm. which includes as an additive to the composition thereof, a substance selected from the class consisting of colemanite and unexpanded perlite, the said additive being present in a proportion of 0.5 to 5% by weight of the composition.
  • a mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and
  • a mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and having a dry compression strength of more than 14 kg./sq. cm. which includes, as an additive to the composition thereof, unexpanded perlite, the said additive being present in a proportion of 0.5 to 5% by weight of the composition.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Mold Materials And Core Materials (AREA)

Description

United States Patent ADDITIVES T0 SAND MOULDS AND CORES Derek Priestley Helliwell, Birmingham, England, assignor to Foseco International Limited, Birmingham, England,
a British company No Drawing. Filed July 21, 1965, Ser. No. 473,851 Claims priority, application Great Britain, Aug. 20, 1964,
34,116/64; Nov. 24, 1964, 47,774/64; Dec. 31, 1964,
8 Claims. (Cl. 106-385) ABSTRACT OF THE DISCLOSURE Pinning or veining produced on metal casting cast in sand moulds or around sand cores may be minimised by the incorporation into the sand mould or core of a proportion of colemanite or unexpanded perlite.
This invention relates to said moulds and cores and more particularly to additives for sand moulds and cores which improve the characteristics thereof. The invention may be applied to sand moulds and cores incorporarting any organic binder but it is of greatest practical value in connection with oil-bonded sand cores as hereinafter set forth.
The invention is concerned with the production of castings from non-skin-forming metals which are poured at above 750 C. Such metals are the cast irons (grey or modular) and copper based alloys such as lead-, tinand Phosphor-bronzes.
In producing castings of such metals using moulds or cores of oilbonded or resin-bonded natural, synthetic or semi-synthetic silica sands (i.e. which contain less than clay), which have a high dry compression strength, a ditiiculty sometimes arises which is known in the art as finning or veining. When such a sand core is heated by the molten metal it may develop surface cracks. The molten metal tends to enter these cracks and in consequence when the casting is stripped away from the core it may have projections corresponding to these cracks, so called fins or veins which of course must, where possible, afterwards be removed from the casting by a machining operation. The phenomenon of finning and veining thus leads to an increase in overall production costs. Moreover in some cases, e.g. where the finning or veining occurs in a narrow passage way of the casting, the removal of the fins or veins may not be a practical possibility.
The incidence of finning or veining appears to vary with the nature of the bonding agent. Sand moulds and cores which have inorganic binders, e.g. which are bonded with silicate, appear to show little tendency towards this phenomenon and such moulds and cores are therefore not included within the scope of this invention.
Sand moulds and cores in which the bonding agent is oil, Le. a drying or semi-drying oil such as linseed, tung or oilicica, or mixtures of any of these, the oil being optionally in association with a cereal carbohydrate or the like, which usually include a metal, e.g. cobalt or lead, naphthenate as hardener, and which require stoving before use, show some tendency to finning and veining. Sand moulds and cores in which the binder is an air-drying oil (as above) together with an accelerator, e.g. an inorganic peroxy compound such as sodium perborate, show a slightly greater tendency to finning and veining. The resin-bonded sand moulds and cores generally exhibit the phenomenon to an appreciably greater extent: e.g. in the case of furane bonding resins which are set by heating the problem is very severe and in the case of furane bonding resins which are cold set the problem, though still severe, is not quite so serious.
It is an object of the present invention to provide oilbonded or resin-bonded synthetic or washed silica sand moulds and cores of high dry compression strength, especially cores which contain certain additives tending to reduce the incidence of finning or veining to be used for casting non-skin forming metals.
According to the present invention, there is provided an oil-bonded or resin-bonded natural, synethetic or semisynthetic silica sand mould, or core containing less than 5% of clay, for use in casting non-skin forming metals, having a dry compression strength of more than 14 kg./ sq. cm. which includes as an additive to the composition of the sand mould or core, potassium nitrate, colemanite, unexpanded perlite, barium sulphate, sodium rnetaphosphate or potassium alum, or a mixture of any of said substances.
The reason why these substances function is not understood, especially since they are inherently dissimilar in chemical and physical properties. Potassium nitrate, barium sulphate, sodium metaphosphate and potassium alum are relatively simple chemical substances the characteristics of which are well known. Colemanite is a commercially available mineral of the approximate formula 2CaO-3B O -5H O. A naturally occurring hydrated calcium tetraborate, which in the anhydrous form melts at nearly 1000 C. and is also known as bore-calcite, and perlite is a mineral which, on heating, exfoliates to reduce its initial density of between 2 and 3 to a value very much below 1. It is believed that each of these substances acts in its own way to facilitate relative movement of the sand grains so that the expansion of the mould or core on heating can be taken up by the material of the mould or core without giving rise to cracking.
Generally speaking the quantity of said substance or mixture of said substances suitable for addition to the material of the mould or core may be within the range 0.5 to 5% of the total weight of the dry mould or core, although a somewhat higher proportion may be required occasionally.
It is to be noted however that a successful additive should not only prevent finning, but also maintain strength, the knock out properties should not be affected, nor must the bonding properties of the oil or the polymerisation of the resin be inhibited. The gas evolution must not be increased and the surface finish should be improved rather than impaired. The additives of this invention tend to fulfill all these requirements.
Where the binder for the sand is a resin it is preferably a furane resin but other resin binders may be employed, e.g. phenol-formaldehyde or urea-formaldehyde resins. If desired there may be used, with any such resin binder, a diluent liquid which will assist in providing a suitably mouldable sand mix. The diluent liquid, if used, should of course not have any deleterious inhibitory effect on the polymerisation or polycondensation of the resin whereby the resin hardens to give a rigid product. Suitable liquids for the purpose are inert mineral oils and the oil product sold commercially under the trademark Dutrex 55.
The use of the special additives of the present invention makes it possible to use a smaller amount of the resin binder While still obtaining a desired strength in the final product. The inclusion of a liquid diluent as just described makes the use of such smaller quantities of resin binder easier to handle in practice.
However, while the additives of the present invention reduce the incidence of finning or veining in such resinbonded sand moulds and cores the additives are not aL ways wholly successful in totally eliminating the phenomenon. On the other hand, applied to oil-bonded sand resins and cores as referred to above, substantially complete elimination of the finning and veining is achieved. The following examples will serve to illustrate the invention EXAMPLE 1 To Kings Lynn 85. sand, at fine washed silica sand, bonded with a hot-box furane resin, was added 0.5% by weight of the dry sand of the additives listed below. This mixture was milled until evenly dispersed. 0.15% of a catalyst for a furane-type hot-box resin was then added and the mixture milled again followed by 2% by weight of a furane-type hot-box resin and the mixture milled again until all the additives were evenly distributed throughout the sand. The mixture was then fed to a conventional foundry core blower for the manufacture of cores, by the hot-box technique. These cores were incorporated in foundry moulds for the manufacture of castings of low phosphorus cast iron which was poured at 1400 C.
The following results show that the three additives of this invention either used singly or in combination all tend to reduce finning on non-skin forming metals.
Percent composition of additive Dry strength, Finning The following sand mix was used for the manufacture of cores, for the manufacture of cast iron castings:
Congleton sand kg 181.6 Dextrin kg 2.72 Core oil c" 1120 Water cc 1680 Anti-finning (50/50 mixture of colemanite and unexpanded perlite) kg 1.82
Cores manufactures from this mixture had a dry compression strength of 57 kg./sq. cm. (this compares with the strength of approximately only 42 kg./sq. cm. when used without the anti-finning additive) and the castings produced were entirely free from veins or fins whereas there had previously been a severe level of scrapped castings because of the incidence of such faults.
I claim as my invention:
1. Oil-bonded and resin-bonded natural, synthetic and semi-synthetic silica sand moulds and cores containing less than 5% of clay, for use in casting non-skin forming metals, having a dry compression strength of more than 14 kg./sq. cm. which include as an additive to the composition thereof, at least 0.5% by weight of a substance selected from the class consisting of colemanite and unexpanded perlite.
2. A mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and having a dry compression strength of more than 14 kg./sq. cm. which includes as an additive to the composition thereof, at least 0.5% by weight of a substance selected from the class consisting of colemanite and unexpanded perlite.
3. A mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying compression strength of more than.
14 kg./sq. cm. which includes, as an additive to the composition thereof, at least 0.5% by weight of colemanite.
4. A mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and having a dry compression strength of more than 14 kg./sq. cm. which includes, as an additive to the composition thereof, at least 0.5% by weight ofunexpanded perlite.
5. Oil-bonded and resin-bonded natural, synthetic and semi-synthetic silica sand moulds and cores containing less than 5% of clay, for use in casting non-skin forming metals, having a dry compression strength of more than 14 kg./sq. cm. which include as an additive to the composition thereof, a substance selected from the class consisting of colemanite and unexpanded perlite, the said additive being present in a proportion of 0.5 to 5% by weight of the composition.
6. A mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and having a dry compression strength of more than 14 kg./ sq. cm. which includes as an additive to the composition thereof, a substance selected from the class consisting of colemanite and unexpanded perlite, the said additive being present in a proportion of 0.5 to 5% by weight of the composition.
7. A mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and
having a dry compression strength of more than 14 r kg./sq. cm. which includes, as an additive to the composition thereof, colemanite, the said additive being present in a proportion of 0.5 to 5% by weight of the composition.
8. A mould or core for use in casting non-skin forming metals which comprises essentially silica sand containing less than 5% by weight of clay and bonded by means of a drying oil and a cereal carbohydrate, and having a dry compression strength of more than 14 kg./sq. cm. which includes, as an additive to the composition thereof, unexpanded perlite, the said additive being present in a proportion of 0.5 to 5% by weight of the composition.
References Cited UNITED STATES PATENTS 2,237,592 4/1941 Dunbeck l06-38.9 2,426,000 8/1947 Cutler 106--38.7 X 2,789,331 4/1957 Dietert 22---l93 2,797,457 7/1957 Kramer 22-493 2,974,050 3/1961 Barlow 10638.5 3,104,230 9/1963 Dewey et al 22193 X ALEXANDER H. BRODMERKEL, Primary Examiner.
DONALD J. ARNOLD, Examiner.
L. B. HAYES, Assistant Examiner.
US473851A 1964-08-20 1965-07-21 Additive to sand moulds and cores Expired - Lifetime US3379540A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003041892A2 (en) * 2001-11-14 2003-05-22 The Hill And Griffith Company Method of reducing veining defects in sand-based foundry shapes
US20100224756A1 (en) * 2006-10-19 2010-09-09 Ashland-Sudchemie-Kernfest Gmbh Moulding material mixture containing carbohydrates
US20110139310A1 (en) * 2009-12-16 2011-06-16 Showman Ralph E Foundry mixes containing sulfate and/or nitrate salts and their uses
WO2012104096A1 (en) * 2011-02-04 2012-08-09 Ask Chemicals L.P. Sand additives for molds/cores for metal casting

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2445185C1 (en) * 2010-12-24 2012-03-20 Государственное образовательное учреждение высшего профессионального образования "Нижегородский государственный технический университет им. Р.Е. Алексеева" (НГТУ) Mix for making casting cores and moulds
RU2456115C1 (en) * 2011-04-08 2012-07-20 Федеральное государственное образовательное учреждение высшего профессионального образования "Уральский федеральный университет имени первого Президента России Б.Н. Ельцина" Moulding mix
DE102012104934A1 (en) * 2012-06-06 2013-12-12 Ask Chemicals Gmbh Forstoffmischungen containing barium sulfate
CN113084080B (en) * 2021-04-19 2022-07-19 河南伟业新材料有限公司 Anti-vein agent for casting production
CN113102692B (en) * 2021-04-19 2022-07-19 河南伟业新材料有限公司 Manufacturing method of vein-proof sand core

Citations (6)

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Publication number Priority date Publication date Assignee Title
US2237592A (en) * 1939-11-27 1941-04-08 Peerpatco Inc Foundry composition and method
US2426000A (en) * 1946-03-15 1947-08-19 J S Mccormick Co Production of mold parts
US2789331A (en) * 1953-03-30 1957-04-23 Harry W Dietert Company Method and apparatus for making molds useful in casting
US2797457A (en) * 1954-06-29 1957-07-02 Mercast Corp Method of joining shell molds
US2974050A (en) * 1958-06-27 1961-03-07 Int Minerals & Chem Corp Core binder
US3104230A (en) * 1959-04-13 1963-09-17 Dow Chemical Co Foundry sand compositions containing polyelectrolytes and salts of the oxy acids of phosphorus and sulfur

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2237592A (en) * 1939-11-27 1941-04-08 Peerpatco Inc Foundry composition and method
US2426000A (en) * 1946-03-15 1947-08-19 J S Mccormick Co Production of mold parts
US2789331A (en) * 1953-03-30 1957-04-23 Harry W Dietert Company Method and apparatus for making molds useful in casting
US2797457A (en) * 1954-06-29 1957-07-02 Mercast Corp Method of joining shell molds
US2974050A (en) * 1958-06-27 1961-03-07 Int Minerals & Chem Corp Core binder
US3104230A (en) * 1959-04-13 1963-09-17 Dow Chemical Co Foundry sand compositions containing polyelectrolytes and salts of the oxy acids of phosphorus and sulfur

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003041892A2 (en) * 2001-11-14 2003-05-22 The Hill And Griffith Company Method of reducing veining defects in sand-based foundry shapes
WO2003041892A3 (en) * 2001-11-14 2005-07-21 Hill And Griffith Company Method of reducing veining defects in sand-based foundry shapes
US20100224756A1 (en) * 2006-10-19 2010-09-09 Ashland-Sudchemie-Kernfest Gmbh Moulding material mixture containing carbohydrates
US20110139310A1 (en) * 2009-12-16 2011-06-16 Showman Ralph E Foundry mixes containing sulfate and/or nitrate salts and their uses
WO2011075221A1 (en) * 2009-12-16 2011-06-23 Ashland Licensing And Intellectual Property Llc Foundry mixes containing sulfate and/or nitrate salts and their uses
CN102762514A (en) * 2009-12-16 2012-10-31 亚世科化学有限公司 Foundry mixes containing sulfate and/or nitrate salts and their uses
US8426493B2 (en) 2009-12-16 2013-04-23 Ask Chemicals L.P. Foundry mixes containing sulfate and/or nitrate salts and their uses
WO2012104096A1 (en) * 2011-02-04 2012-08-09 Ask Chemicals L.P. Sand additives for molds/cores for metal casting

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