cUnshaped refractory materials are a new type of refractory materials that are not calcined. They are developing very fast. The output of Japan, the United States and Germany has accounted for more than 1/3 of the total output of refractory materials. The scope of use has expanded from steel rolling industrial furnaces to high-temperature kilns such as steelmaking and ironmaking, solving some key process equipment lining problems.
01 Definition of unshaped refractory materials
Unshaped refractory materials are refractory materials that are used without forming and firing and are composed of reasonably formulated granular and powdery materials and binders. Usually, the granular materials that constitute such materials are called aggregates; the powdery materials are called admixtures; and the binders are called cementing agents. This type of material has no fixed shape and can be made into slurry, mud paste and loose shapes, so it is also commonly called loose refractory materials. This type of refractory material can be used to form a seamless integral structure, so it is also called an integral refractory material.
The basic composition of unshaped refractory materials is granular and powdery refractory materials. According to its use requirements, it can be made of various materials. In order to combine these refractory materials into a whole, except for very few special cases, appropriate types and quantities of binders are generally added. In order to improve its plasticity, a small amount of appropriate plasticizer can be added. In order to meet other special requirements, a small amount of hardening accelerator, hardening retardant, flux, shrinkage inhibitor and other additives can also be added.
02 Classification of amorphous refractories
There are many types of amorphous refractories, which can be classified according to the material of the refractory material or the type of binder used. Usually, according to its process characteristics, it is divided into cast or pouring refractory materials (referred to as castables or pouring materials), plastic refractory materials (referred to as plastic), ramming refractory materials (referred to as ramming materials), spraying refractory materials (referred to as spraying materials), projection refractory materials (referred to as projection materials) and refractory mud. Refractory coatings can also be considered as a kind of amorphous refractory.
03 Characteristics of amorphous refractories
The chemical and mineral composition of amorphous refractories mainly depends on the granular and powdered refractory materials used. In addition, it is also most closely related to the type and number of binders. The density of structures or products made of amorphous refractory materials is mainly related to the constituent materials and their proportions. At the same time, it depends to a large extent on the construction methods and techniques. Generally speaking, compared with sintered refractory products of the same material, most amorphous refractory materials have a higher porosity before or even after sintering due to the smaller external force applied during molding; some properties of structures or products may also change due to chemical reactions before sintering, such as some medium-temperature strength may be slightly reduced; due to the presence of binders and other non-high-temperature stable materials, its volume stability at high temperature may be slightly lower; due to its high porosity, it may be less corrosive; but its thermal shock resistance is generally higher.
Usually, the production of amorphous refractory materials only goes through the preparation of granular and powdery materials and the mixing of mixed materials. The process is simple, the yield is high, the supply is fast, and the heat energy consumption is low. According to the process characteristics of the mixture, the corresponding construction method can be used to make structures of any shape, which has strong adaptability and is more suitable for use in places where bricks are not suitable. Most amorphous refractory materials can be made into solid integral structures, avoiding weak points caused by joints. When the masonry or integral structure of refractory bricks is partially damaged, it can be repaired cold or hot by spraying, which is both quick and economical. It is particularly necessary to use it as a protective layer and joint material for masonry or lightweight refractory materials. It is also convenient to use it to manufacture large refractory products.
HOME