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Investment casting

Inactive Publication Date: 2002-12-26
BUNTROCK IND INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0005] It remains therefore a desirable object to provide an alternative means for reducing the time required to build a shell mould of suitable thickness during the process of investment casting.
[0010] Surprisingly, the present inventors have found that a refractory slurry comprising a quantity of water-insoluble organic fibres is capable of forming significantly thicker coats around dipped objects than are slurries of the types known in the prior art. An increase in coat thickness obviously implies a concomitant decrease in the number of dipping cycles required to build a mould of sufficient thickness, and hence a significant reduction in the rate of refractory mould production. Coats of fibre-modified slurry are subject to a comparable drying time in comparison with the products of the prior art, and have been found to possess a comparable green strength.

Problems solved by technology

However, where an unmodified aqueous silica sol is used, the time taken for this process is disadvantageously long.
Moreover, soluble organic polymers are expensive, and their use in investment casting may significantly increase the cost of this process.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0034] A slurry in accordance with the invention was produced from the following components:

[0035] Silica Sol Binder

[0036] An aqueous silica sol comprising 24% SiO.sub.2, having an specific gravity (relative density) of approximately 1.167 and a nominal particle size of 10 nm at a pH of 10.2, and 0.5% wt / wt antifoam (WEX antifoam A10).

[0037] Refractory

[0038] -200 mesh Molochite.RTM. (calcined aluminosilicate, commercially available from English China Clays).

[0039] Water-Insoluble Organic Fibres

[0040] Nylon.RTM. fibres; 1.8 denier, 1 mm length.

[0041] The slurry was produced as follows. 20g of Nylon.RTM. fibres were added to 1.170 kg of the silica sol binder and mixed to disperse the fibres therein. 1.755 kg of refractory (3:2 wt / wt ratio of refractory:binder) was added to the resulting fibre-modified binder. The resulting mix was stirred thoroughly to produce a slurry (0.68% wt / wt fibre:slurry). Following thorough agitation and dispersion, the viscosity of the slurry was tested using...

example 2

[0049] A slurry in accordance with the invention was produced from the following components:

[0050] Silica Sol Binder

[0051] An aqueous silica sol comprising 24% SiO.sub.2, having an specific gravity (relative density) of approximately 1.167 and a nominal particle size of 10 nm at a pH of 10.2, and 0.5% wt / wt antifoam.

[0052] Refractory

[0053] -200 mesh Molochite.RTM. (calcined aluminosilicate, commercially available from English China Clays).

[0054] Water-Insoluble Organic Fibres

[0055] Polypropylene fibres; 1.8 denier, 1 mm length.

[0056] The slurry was produced as follows. 63g of polypropylene fibres were added to 3.5 liters (4.08 kg) of the silica sol binder (18g fibres / liter of binder) and mixed to disperse the fibres therein. 6.13 kg of refractory (3:2 wt / wt ratio of refractory:binder) was added to the resulting fibre-modified binder. The resulting mix was stirred thoroughly to produce a slurry. Following thorough agitation and dispersion, the viscosity of the slurry was tested using...

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PUM

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Abstract

The present invention relates to improvements in and relating to investment casting. In particular, the invention provides a method of investment casting, comprising the steps of mixing a binder, a refractory material, and a quantity of water-insoluble organic fibers to form a slurry; coating an expendable pattern with a coat of said slurry; and drying said coat or allowing said coat to dry to form a shell. The present invention further provides a refractory slurry for use in the method of the invention, and a kit of ingredients for putting the method of the invention into effect.

Description

[0001] The present invention relates to improvements in and relating to investment casting. In particular, the invention relates to a method of investment casting which involves the successive application of one or more coats of a refractory slurry to an expendable pattern, so as to build up a shell. The present invention further provides a refractory slurry for use in the method of the invention, and a kit of ingredients for putting the method of the invention into effect.BACKGROUND TO THE INVENTION[0002] The process of investment casting, otherwise known as the lost wax process, is well known and widely used. Typically, the process involves dipping a wax model into a slurry comprising a binder and a refractory material, so as to coat the model with a layer of slurry; applying a stucco coating of dry refractory to the surface of the layer; allowing the resulting stuccoed slurry layer to dry; and applying further stuccoed slurry layers as appropriate to create a shell mould around t...

Claims

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Application Information

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IPC IPC(8): B22C1/00B22C1/02B22C1/16B22C9/04
CPCB22C1/00B22C9/04B22C1/165B22C1/02
Inventor SHAW, RICHARD DUDLEYDUFFEY, DANIEL JAMES
Owner BUNTROCK IND INC
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