GB2160454A - Improvements in the manufacture of castings - Google Patents

Improvements in the manufacture of castings Download PDF

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Publication number
GB2160454A
GB2160454A GB08415740A GB8415740A GB2160454A GB 2160454 A GB2160454 A GB 2160454A GB 08415740 A GB08415740 A GB 08415740A GB 8415740 A GB8415740 A GB 8415740A GB 2160454 A GB2160454 A GB 2160454A
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GB
United Kingdom
Prior art keywords
alloy
metal
casting
mould
castings
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08415740A
Other versions
GB2160454B (en
GB8415740D0 (en
Inventor
Terence William Davis
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Individual
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Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to GB08415740A priority Critical patent/GB2160454B/en
Publication of GB8415740D0 publication Critical patent/GB8415740D0/en
Publication of GB2160454A publication Critical patent/GB2160454A/en
Application granted granted Critical
Publication of GB2160454B publication Critical patent/GB2160454B/en
Expired legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D19/00Casting in, on, or around objects which form part of the product
    • B22D19/14Casting in, on, or around objects which form part of the product the objects being filamentary or particulate in form
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22CFOUNDRY MOULDING
    • B22C9/00Moulds or cores; Moulding processes
    • B22C9/12Treating moulds or cores, e.g. drying, hardening
    • B22C9/126Hardening by freezing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D18/00Pressure casting; Vacuum casting
    • B22D18/02Pressure casting making use of mechanical pressure devices, e.g. cast-forging

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)

Abstract

Shrinkage in a casting is reduced or modified by introducing the metal or alloy under pressure into a frozen sand mould. Solidification begins quickly which results in more even distribution of porosity in the casting, and because the need is avoided for metal or alloy to be fed to the casting as it solidifies defects and distortion are reduced. The method is particularly advantageous applied to metals or alloys cast in the temperature range 400 DEG -800 DEG ; it may be applied to zinc-aluminium alloys, and to the manufacture of castings having fibre reinforcement.

Description

SPECIFICATION Improvements in the manufacture of castings This invention relates to improvements in the manufacture of castings.
A problem accociated with casting is shrinkage which can result in defects in the castings produced and distortion, as well as dimensional inaccu racies.
The present invention seeks to reduce or modify shrinkage in castings.
According to the present invention there is provided a method of manufacturing a casting from a metal or alloy, comprising the steps of making and freezing a sand mould and introducing the molten metal or alloy into the frozen mould under pressure.
As the metal or alloy is introduced under pressure the mould is quickly filled. The metal or alloy is rapidly cooled by the frozen mould and so solidification begins quickly. This reduces shrinkage in the casting, or at least reduces the occurence of un-even shrinkage in the casting because a more even distribution of porosity throughout the casting can be achieved. Furthermore, introducing the metal or alloy under pressure reduces or avoids the need to feed metal or alloy to the casting as it solidifies, which minimises the occurrence of defects in the casting and the possibility of distortion.
A good quality casting may be obtained, therefore, with dimensions which are contained within close tolerances.
With the additional advantage of a good surface finish on the casting, which results from the use of the frozen mould, it will be appreciated that the need for fettling or other surface finishing treatment of the casting after removal from the mould is reduced.
The pressure at which the metal or alloy is introduced into the mould is dependent upon the metal or alloy to be cast. In general the pressure may be relatively low, for example of the order of 20 p.s.i.
(1.4 kg/cm2) or less, but for some metals or alloys the pressure may have to be higher. It is probable that the lighter the metal or alloy is that is to be cast the higher will be the pressure required. With a relatively low pressure of introduction the inherent strength of the frozen mould may be adequate to withstand such pressures. If reinforcement should be required the mould may be supported externally by a flask or clamp.
The more quickly the metal or alloy solidifies in the frozen mould the more effective may be the control of the shrinkage in the resultant casting.
The temperature of the frozen mould and the temperature at which the metal or alloy is cast are determining factors in this. Accordingly the effectiveness of the present method in controlling the shrinkage of casting may increase the lower the temperature of the mould and the lower the temperature of casting the metal or alloy.
Preferably the mould is frozen to a termperature considerably below the freezing point. It may be frozen by means of liquid nitrogen or other suitable liquid gas.
The mould may be made of a sand which produces a self-supporting mould before it is frozen.
Alternatively the mould may be made to become self-supporting as it is frozen. It may, for example, be made by the known 'Effset Process' developed by W.H. Booth % Co. Limited in which the sand is bonded into the self-supporting state by freezing by the use of liquid nitrogen.
The method is most effective when applied to metals or alloys which are cast at a temperature of 1300"C or less. It is particularly advantageous when applied to the casting of metals and alloys which are cast in the temperature range 400-800"C, or, such as lead, at an even lower temperature. It will be appreciated, therefore that aluminium, zinc and copper and their alloys, and gun and Babbit-metals, for example, may benefit from being cast by the present method.
Zinc-aluminium alloys have low melting points (550-650 C). There are alloys within this group, such as the ZA alloys introduced in recent years, which are readily cast, and the castings produced from them have strengths which are comparable with castings made of mild steel. They have been used increasingly instead of cast iron and brass for the manufacture of air cylinders and small components for general engineering because they are lighter and cheaper. However, a problem has been their tendency to shrink excessively and un-evenly and distort when cast by conventional sand mould ing methods. In order to contain the shrinkage within reasonable limits it has been the general practice hitherto to cast these alloys in permanent moulds. Such moulds are expensive and for their use to be economically acceptable manufacture of castings in high volume is required.The application of the method according to the present invention to these alloys reduces the problem of shrinkage and distortion. In addition, because the frozen mould can be made relatively cheaply, the use of the method makes the manufacture of small numbers of castings, and even one-off castings, of the alloys a viable proposition.
Because the metal or alloy is introduced into the mould under pressure the method may be applied to the manufacture of a casting which has fibre-reinforcement. The pressure of the metal or alloy assists its passage between the fibres so that a satisfactory dispersion of the fibres in the casting can be obtained. A reinforcing fibre which may be used is, for example, the alumina fibre made by Imperial Chemical Industries PLC sold under the Trade Mark "Saffil". This may be used with a range of metals and alloys. In light metal alloys of aluminium and zinc, for example, the inclusion of this fibre singnificantly improves the strength of the casting at operating temperatures above room temperature and so the temperature range in which the casting may be satisfactorily employed is extended. The inclusion of the fibre can also assist in reducing creep. A zinc-aluminium alloy with fibre reinforcement may be introduced at a pressure of about 20 p.s.i. (1.4 kgicms) into the mould when frozen by liquid nitrogen.
It will be appreciated from the foregoing that not only does the present invention enable shrinkage in castings to be controlled so that the accurec r the castings is improved, but also it can extend :ne usefulness of some metals and alloys and enable castings to be manufactured at reasonable cost.
After a casting has been made the sand of the mould can be knocked out and made ready for r & use with minimal preparation.

Claims (7)

1. A method of manufacturing a casting from a metal or alloy comprising the steps of making and freezing a sand mould and introducing the molten metal or alloy into the frozen mould under pressure.
2. A method according to claim 1 in which the metal or alloy is molten at a temperature of 1300 C or less.
3. A method according to claim 2 in which the metal or alloy is molten in the temperature range 400-800 C.
4. A method according to claim 1 in which the molten metal or alloy is introduced into the mould under a pressure of up to 20 p.s.i. (1.4 kgtcm2).
5. A method according to any preceding claim in which the metal or alloy has fibre reinforcement.
6. A method according to claim 4 in which the mould is frozen by means of liquid nitrogen and molten zinc- aluminium alloy is introduced into the mould under a pressure of 20 p.s.i. (1.4 kg/cm2).
New claim filed on 18 June 1985
7. A method of manufacturing a casting from a metal or alloy substantially as described herein.
GB08415740A 1984-06-20 1984-06-20 Improvements in the manufacture of castings Expired GB2160454B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08415740A GB2160454B (en) 1984-06-20 1984-06-20 Improvements in the manufacture of castings

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08415740A GB2160454B (en) 1984-06-20 1984-06-20 Improvements in the manufacture of castings

Publications (3)

Publication Number Publication Date
GB8415740D0 GB8415740D0 (en) 1984-07-25
GB2160454A true GB2160454A (en) 1985-12-24
GB2160454B GB2160454B (en) 1987-12-02

Family

ID=10562715

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08415740A Expired GB2160454B (en) 1984-06-20 1984-06-20 Improvements in the manufacture of castings

Country Status (1)

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GB (1) GB2160454B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7299163B2 (en) * 2002-08-05 2007-11-20 Denso Corporation Device, method, and program for design-aiding of casting product

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1537471A (en) * 1975-08-14 1978-12-29 Booth & Co Ltd W H Foundry mould production
GB1537743A (en) * 1977-01-17 1979-01-04 Booth & Co Ltd W H Methods of casting and sand moulds therefor
GB2043508A (en) * 1979-02-16 1980-10-08 Inst Odelwnictwa Methods of making foundry moulds and cores
GB2098898A (en) * 1981-05-20 1982-12-01 Booth W H & Co Ltd Foundry mould production

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1537471A (en) * 1975-08-14 1978-12-29 Booth & Co Ltd W H Foundry mould production
GB1537743A (en) * 1977-01-17 1979-01-04 Booth & Co Ltd W H Methods of casting and sand moulds therefor
GB2043508A (en) * 1979-02-16 1980-10-08 Inst Odelwnictwa Methods of making foundry moulds and cores
GB2098898A (en) * 1981-05-20 1982-12-01 Booth W H & Co Ltd Foundry mould production

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7299163B2 (en) * 2002-08-05 2007-11-20 Denso Corporation Device, method, and program for design-aiding of casting product

Also Published As

Publication number Publication date
GB2160454B (en) 1987-12-02
GB8415740D0 (en) 1984-07-25

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