GB1559471A

GB1559471A - Refractory material

Info

Publication number: GB1559471A
Application number: GB1910475A
Authority: GB
Original assignee: Stein R C
Current assignee: Stein R C
Priority date: 1976-08-09
Filing date: 1976-08-09
Publication date: 1980-01-16

Description

(54) REFRACTORY MATERIAL (71) 1, RONALD CAMPBELL STEIN, a British subject of 11 Grosvener Crescent, Edinburgh EH12 5EL, Scotland do hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement :- This invention relates to refractory material.

Refractory minerals occur in nature and are characterised by their high melting points. Refractory minerals singly or in combination react under the influence of high temperature to form solid masses. The properties of the refractory masses produced are of course determined by the individual minerals selected. In making the selection due consideration is given to the crystal structure of the mineral and how that crystal structure is altered durit temperature calcination. Consideration is also given to the interaction between combinations of minerals.

The mineral or combination of minerals may be pre-shaped, for example into a brick which is calcine before being used as a component in the construction of a furnace or similar device for use at high temperature. Sometimes the brick may be used in the un-calcined condition in which case the firing or calcination occurs in situ by the heat of the furnace device in which it is applied. Furthermore the mineral or mixture of minerals brought to a suitable consistency may be applied to a furnace structure in an unshaped form and then moulded in situ to form a furnace wall ; in this case the calcination would also be carried out in situ by the heat of the furnace.

Generally speaking a mixture of minerals for making a refractory mass has a component of relatively large particles and a component of relatively small particles which pack together to give a denser structure than would be the case if particles all of similar sizes were to be used.

Sometimes other components, for example clay or organic bond or inorganic bonds are added to aid the shaping process and to promote rection and bonding between the main constituents when the article is precalcine or calcine in situ.

A material used with avantage in the manufacture of certain refractory articles is zircon, that is zirconium silicate which is available in its natural state as fine sand grains generally of the order of BS52 mesh (300 microns) and fine. However, whereas a refractory article manufactured wholly from zircon has good refractory properties, particularly its resistance to corrosion by slag when used, for example, in the form of a brick in a ladle for containing molten steel, due to the generally uniform small grain size, difficulty is encountered in manufacture due to a tendency to laminate in shaping. Furthermore such fine texture bricks as are made from zircon are prone to cracking under conditions of fluctuating temperature.

Alternatively other refractory minerals used for producing refractory articles are generally available in larger grain sizes and in a wider range of grain sizes and are frequently produced by a process of crushing and sieving from relatively large mineral aggregates.

According to the present invention there is provided a mineral mixture for use in manufacturing a refractory material comprising an admixture of zircon and andalusite. Andalusite is an alumino-silicate mineral found in nature in particle sizes from about 10 mm and less and frequently 3 mm and lests. Thus andalusite as occurring in nature frequently contains a high proportion of particles of a size which are immediately suitable for producing a well balance packing without the need for further crushing and screening. Typically andalusite contains 50-60% alumina, the remainder being substantially silica and some minor impurities which are fusible at calcination temperatures and thus can act as a flux. Andalusite has the avantage that its natural grain has a low porosity and when calcine its crystal form is changed but it does not suffer from undesirable change in volume.

The present invention also provides a method of manufacturing refractory material comprising mixing together zircon and andalusite and bonding the mixture.

The mixture may be bonded into refractory objectes such as bricks by calcining with or without the addition of a chemical bonding agent. The calcining of the objectes may be effected during manufacture or in situ after installation.

The mixture may be bonded chemically by addition of a bonding agent such as phosphoric acid or other conventional bonding agents.

On calcination of the mixture the fusible components ouf té mixture act as a flux to bind intimately the components of the mixture. The andulisite is converted to crystobalite and to needle-like crystals of mullite, the present of which is particularly advantageous in refractory material.

A particular avantage of this invention is that the preferred materials, zircon and andalusite, are"volume-stable", that is subsequent dring of the preformed object does not substantially alter its dimensions.

With previously used mineral mixtures it was necessary to predetermine explicitly the degree of change in dimensions to be expected during firing and to compensate for that change when designing the objectes.

On the other hand the mixture of the present invention being volume-stable can be used in situ, for example as furnace lining, and subsequently fired without any significant alteration in dimensions.

The mixture of this invention may contain further components conventional in refractory technology for improving the quality of the product or for imparting thereto specifically desired properties.

Claims

WHAT I CLAIM IS :- 1. A mineral mixture for use in manufacturing a refractory material comprising an admixture of zircon and andalusite.
2. A method of manufacturing refractory material comprising mixing together zircon and andalusite and bonding the mixture.
3. A method of fabricating refractory objects comprising moulding into shape a mineral mixture of zircon and andalusite, with or without the addition of a chemical bonding agent and firing the moulded sape.
4. A refractory ob. ject shaving the form of a brick or monolith and comprising a calcine mixture of zircon and andalusite.
5. Refractory objects whenever produced by the method claimed in claim 3.
6. A mineral mixture for use in manufacturing refractory objects substantially as hereinbefore described.