Abstract: A valve assembly for insertion into the bottom of a ladle for molten metal comprises refractory upper and lower parts defining a flow passage with an enlarged central region containing a valve head. The valve head is moved by a spindle to control the flow of gas injected through the valve into the metal.

Abstract: The invention relates to reducing the thermal inertia of furnace or oven walls. Insulating modules under compression are secured to the wall and released from compression upon firing of the furnace.

Abstract: Ethyl or other lower alkyl silicate is prepared by the direct reaction of alcohol and silicon thereby avoiding the generation of hydrogen chloride as a by-product. The reaction is carried out at elevated temperature in a catalytic solution of high thermal capacity.

Abstract: The present invention provides a method of rigidizing articles of refractory fibres. This is achieved by impregnating the fibre article with a zirconium salt, a gellation-inducing agent and a gellation-delaying agent.

Abstract: The invention concerns the binding of refractory powders into self-supporting `green` shapes which are fired to provide refractory objects. In accordance with the invention the binders are based on zirconium salts and include a separate gell time delaying agent to ensure satisfactory gelling and to achieve control and to allow complex shapes to be made.

Abstract: The invention relates to the insulating of furnace walls. In accordance with the invention insulating modules are secured to the wall with cement. According to a preferred feature of the invention the modules are contained under elastic compression in a combustible netting envelope.

Abstract: The invention provides a method of producing a usefully gellable cohydrolysate from a normally gellable substance and a substance not normally gellable. The latter substance has an alkoxy group implanted on it and preferably is a hydrous oxide which offers appropriate bridge groups for this implant.

Abstract: The present invention provides a method of producing a shaped object by coating a pattern with a slurry of a refractory powder in a binder. The binder comprises an acidic zirconium salt and also a gellation delaying agent. The slurry is caused to gell by contacting it with ammonia vapor.

Abstract: The invention concerns the binding of refractory powders into self-supporting `green` shapes which are fired to provide refractory objects. In accordance with the invention the binders are based on zirconium salts and include a separate gell time delaying agent to ensure satisfactory gelling and to achieve control and to allow complex shapes to be made.

Abstract: The invention concerns the binding of refractory powders into self-supporting "green" shapes which are fired to provide refractory objects. In accordance with the invention the binders are based on zirconium salts and include a dispersion of calcined magnesia in a mixture of water and a polyhydric alcohol. The magnesia reacts with the zirconium salt to form zirconium oxide/hydroxide which gells hard. In order to control the speed of gelling a separate gell time delaying agent is also optionally included.

Abstract: A gel is prepared through the intermediary of an acid hydrolysate. The hydrolysate is produced by the hydrolysis of an organic silicate with the metal salt whose oxide it is desired to gell.

Abstract: A rigid gel is prepared by treating a solution of an aluminium hydroxyhalide solution of a specified formula and composition with an acetate or lactate accelerator. The invention has particular application to the preparation of refractories.

Abstract: A mould for casting metals by the "lost wax" process is formed by coating an expendable pattern with refractory powder in a binder dispersed in an aluminum hydroxyhalide solution. The coating is hardened by an acetate or lactate.BACKGROUND OF THE INVENTIONThis invention relates to the preparation of moulds for casting metals and alloys, particularly to the preparation of moulds which are used in the investment casting, or "lost wax" process. These moulds are prepared by applying to an expendable pattern made of wax, plastic or a low melting alloy at least one coating of a refractory powder suspended in a suitable binding agent.SUMMARY OF THE INVENTIONAccording to the present invention there is provided a method of preparing a mould suitable for use in the casting of metals or alloys includes the step of coating an expendable pattern with a composition which is a finely divided refractory powder dispersed in an aqueous alcoholic solution of an aluminium hydroxyhalide of the general formula Al.sub.2 (OH).sub.

Abstract: Linings for furnaces or ovens are made by cutting a sheet of refractory fibrous material having fibers extending longitudinally parallel therein into strips that extend laterally, then turning the strips through 90.degree. so the fibers are end-on, compressing the fiber end-on strips together to form a hot-face surface and attaching the strips at their base to a support.