Abstract: the combination of refractory materials never finalized, on the one hand, its development trend is bound to hydrate chemically bound to the hydration combined with coagulation with condensationbondingare, in fact it is by will bring high impurity to bond and low impurity impurity free bond direction, to improve the purity of the direction of unshaped refractory materials the development of. On the other hand, the development trend is high water to low water to no water, in fact, it is from low density to high density direction.

First, introduction

The structural strength of amorphous refractories depends on three binding forces: (A) combined with the binding force of the phase itself; (B) combining the binding force between phase and aggregate phase; (C) the binding force of aggregate phase particles (crystalline phase to crystalline phase, crystalline phase to amorphous phase). In more than material can withstand the maximum stress, if < (A) (B) and (C), the material through combination of fracture: if (B) "(A) and (C), and combined with the material along the aggregate phase is broken; if < ((C) A) and (B), the material must through the aggregate particles fracture.

The amorphous refractory is usually composed of continuous binding phase and discontinuous aggregate phase. But generally speaking, the strength of aggregate phase is larger than that of the binding phase. Therefore, the structural strength of the amorphous refractory is controlled by the binding phase, that is to say, the binder is the main component to decide the strength of the amorphous refractory.

Two, combination mode and mechanism

The binder used for unshaped refractory materials can be divided into the following combinations: hydration, chemical bonding, ceramic bonding, adhesion and condensation.

(1) hydration. The binder used is calcium aluminate cement, Portland cement and beta A2lO3. Hydration is combined with the hydration product at normal temperature, which reflects hydration products.

The hydration reaction of water binding cementing material at room temperature needs a certain time, so it has certain time of setting and hardening. These materials are mainly used as binding agents for refractory castables.

(2) chemical bonding: the binder used is phosphoric acid or phosphate (with or without hardener), sodium silicate or potassium silicate (plus or without hardener), phenolic resin and hardeners. They are with the help of binder and refractory materials (oxides aggregate), chemical reaction or binder and hardener between chemical reactions occur at room temperature or heating to generate new compounds or polymerization (condensation) combination of crosslinking, so some polymerization also contain binding.

Chemical binder and sclerosing agent are used mainly as binder for refractory castables, but used as tamper without hardened agents and binder for plastics and coatings.

(3): low temperature sintering ceramic combination or combined in unshaped refractory materials can reduce adding additives or metal powder sintering temperature, to greatly reduce the liquid phase temperature, promoting low temperature solid liquid reaction and the formation of low temperature sintering with low temperature sintering aid for some borate, boron, and fluoride sodium glass, metal powder and SiAAlMMg powder.

The use of additives by 500-1000 degrees in the low temperature of liquid viscosity will first generate aggregate particles are bonded together, then with the increase in temperature by liquid - temperature chemical reaction between solid, combined with the generated with higher melting temperature is generated as in boron oxide corundum material with a small amount of dry vibration with strong the boron anhydride melt generated viscous liquid at 577 DEG C to smell, followed by liquid - solid reaction has higher melting temperature of the compound 2A2lO3 - 2B2O3 and a-A2lO3 (incongruent melting temperature of 1035 DEG C), 9A2lO3 2B2O3 (incongruent melting temperature of 1950 DEG C) and corundum aggregate with consolidation.

This kind of binder is mainly used as binder dry vibration material, dry vibration material can be used as lining of induction furnace and high temperature melting groove, container liner.

(4): adhesive bond can be formed with adhesive (adhesion) most bond organic binder, such as synthetic resin dextrin, molasses, Arabia gum, waste paper pulp, methyl cellulose, polyethylene polymer asphalt and phenolic resin, some temporary bonding agent, after high temperature treatment will burn off some permanent bonded, after high temperature treatment will be formed with carbide carbon, there are also some inorganic binder with adhesive binding, such as aluminum, two hydrogen phosphate water glass etc..

Adhesively bonded binder is mostly used as binder for refractory slurry, paint, spray coating and ramming material, and carbon and silicon carbide amorphous refractories are mostly used.

(5) condensationbondingare: can produce condensationbondingare materials with clay powder, ultrafine oxide (SiO2, A2lO3, TiO2, Cr2O3 etc.), silica sol and alumina sol and alumina sol condensationbondingare brick, which is on the particle (colloidal particles) attraction in close contact with van Edward force together but, the use must be adding coagulant to make colloidal particles agglomerate and combination.

The material produced by coagulation is mainly used as a binder for refractory castables, or as a binder for refractory ramming materials, coatings and so on.

Three, the evolution of the mode of combination

In unshaped refractory, mechanized construction is castable and gunning (spray), so it is always able to get stable development is castable and gunning (spraying) material, such as varieties in Japan and unshaped refractory materials for example [3], from 1955 to 1986 the casting material and coating the increase in yield, while other unshaped refractory materials is on the decline. By 85 years, the castable has accounted for 40% of the amorphous refractory. The development of other countries is also roughly similar, so it is focused on the evolution of the casting process.

Castable is the first aluminum silicate castable with aluminous cement, due to the high CaO content of alumina cement, A2lO3 and SiO2 reaction of C2AS or CAS2 low melting it ash and aluminum silicate castable aggregate, greatly reduce the aluminum silicate castable refractory and high temperature performance, can only be used in general 1300 degrees below. Therefore, after 60s the development of low calcium aluminate cement and calcium aluminate cement, the mineral is CaO - 2A2lO3, the CaO content of calcium aluminate cement in the 33 - 35% down to 21-25%, it will use the high temperature aluminum and corundum castable aggregate set made of composite material and 1350 to 1450 DEG -1600 DEG C.

However, the low calcium aluminate cement and calcium aluminate cement, there is a certain amount of CaO into the refractory castable, affect the high-temperature structural strength and other properties at high temperature, so in the past ten years, the foreign research is dedicated to the development of low and ultra-low cement refractory castable (4) (5) so, no cement castable to calcium aluminate cement pouring amount decreased from 15-20% to 5-7% (low cement castable), 1-3% (ultra low cement) and 0% (chemical bond, condensationbondingare castable). This series of evolution processes greatly improved the high temperature application technology of the refractory castable. Thus, the effect of the application is greatly improved.

But in the absence of cement castable castable, chemical combination also has some shortcomings, as binders for chemical combination with phosphate, sulfate, silicate is not large, the bond will not decompose volatile harmful gases in use (P205, SO2), equipment corrosion and pollution. The environment is not convenient to use (most before using tyingor material), impurities or how much will bring into the other live resistant castable Cyperus malaccensis high temperature properties (such as silicate binder in Na2O, K2O, etc.) and condensed with castable, because condensation combined with materials used can be pouring material of the same composition with a small amount of available ultrafine coagulant or component sol with minimal speed coagulant, so you can not Cyperus malaccensis refractoriness and temperature, but also may be in use A self bonding or direct combination structure is formed to improve the high temperature structural strength of the material. Meanwhile, the castable with superfine powder can also greatly reduce the water consumption during forming, reduce the porosity and improve the permeability and corrosion resistance of the high temperature melt.

Four. Conclusion

Unshaped refractory material combination, on the one hand, the development trends of hydration combined with chemical combination combined with coagulation combined with hydration condensation, in fact it is by will bring high impurity to bond low impurity, and no impurity bond direction, to improve the purity of unshaped refractory materials development. On the other hand, the trend of development is the high water and low water content, which is actually developed from low density to high density. It is worth pointing out that this trend is to develop new materials, new varieties of unshaped refractory materials in order to adapt to the harsh conditions of use, expand the scope of use, but can not be completely eliminated in the past some of the traditional products, because the product of those traditional still have their advantages, such as abundant raw materials, cheap price, so in some very harsh conditions do not use their site is still useless