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Process for fabrication of dense-structure refractories which have resistance to spalling
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Inventors: Fujimoto, Shyoichiro; Ueno, Haruyuki;
Assignee: Kurosaki Refractories Co., Ltd. (Fukuoka, JP)
Primary Examiner: Parrish; John
Assistant Examiner:
Attorney, Agent or Firm: Jordan and Hamburg
A process by which dense structure refractories that have resistance to spalling may be produced which comprises building up secondary particulates from fine and/or ultra-fine particles of primary particulate, separating the thus prepared secondary particulates, reconstituting the batch within a definite range and proportion of particle size composition, molding the thus reconstituted batch under a predetermined pressure and finally firing the above molded material is disclosed. |
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DETAILED DESCRIPTION OF THE INVENTION With the increasingly critical conditions encountered during the service of industrial furnaces, the need for improvement of the properties of refractories is keenly felt.
Broadly speaking, any refractory may be categorized as either an ordinary refractory or a highly dense structure refractory based upon the structure which is defined by the number and sizes of the grains and pores, the manner in which the pores are arranged in the material and the physical strength of the body.
Since ordinary refractories have an apparent porosity of about 10-20% by volume and the porosity of the matrix area is in the range of 30-40% by volume, and since the rate of penetration of slag and molten metal increases rapidly with increasing porosity, these corrosive agents react increasingly with the refractories at high temperatures, accelerating corrosion and errosion and resulting in structural spalling.
On the other hand, highly dense structure refractories which have an apparent porosity of less than 10% by volume and are fabricated by means of the fused casting method or the sintering method, wherein fine and/or ultra-fine particles are used as the raw material, have a characteristic low porosity, high mechanical strength and excellent resistance to corrosion and errosion, but have low spalling resistance.
This factor causes them to be unsuitable for service in locations where sudden temperature changes occur and other locations where this type of refractory is employable are also limited.
The phenomenon of thermal spalling is mainly attributed to a sudden temperature change in the refractories, which causes thermal stresses to develop.
If these stresses exceed the shear or tensile strength of the refractories, cracks will develop throughout the structure and will bring about the collapse of the refractories.
In order to prevent thermal spalling, the employment of a material with either a low expansion coefficient or a high thermal conductivity is advocated.
These materials, however, are used for the purpose of precluding the development of thermal stress and not for arresting the development of the crack
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Electrical and Wave 
