Mix for surfacing and joining chamotte and dinas

 

(57) Abstract:

The invention relates to compositions for hot repair of masonry ovens by the method of self-propagating high temperature synthesis and can be used in metallurgical, coke and other industries. The task of the invention is a mixture for surfacing and joining chamotte and Dinas obtaining ceramic bond high fire resistance and low porosity. The proposed mixture contains the following components, wt. %: powder iron oxide 60-70; aluminium powder 10-20; powder of silicon 1-15; welding flux 3-19. table 1.

The invention relates to compositions for hot repair of masonry stoves method of propagating high-temperature synthesis (SHS) and can be used in metallurgical, coke and other industries.

Known mixture for welding, comprising, by weight. refractory powder (silica mortars) 50-70, powder aluminium 2-5, the powder of silicon 8-15, diabase flour 10-30 [1]

The disadvantage of this mixture for welding is its low terminate and weak resistance obtained after the reactions, the SAF product, due to the absence of the required number of OII", in the current air-powder stream (flow rate of the substance of 0.8-1.0 kg/min, oxygen flow rate of 0.2-0.25 m3/min) when the temperature of the furnace lining 800-900oC.

The closest in technical essence and the achieved result of the claimed invention is exothermic composition [2] containing the following components, wt.

the silicon oxide 25,6-42,0

aluminum 14.4V-16,0

1-3% aqueous solution of liquid glass the rest

The disadvantage of this material is low terminate composition, weak resistance, caused by the use of a solution of liquid glass.

The objective of the proposed invention is a mixture for surfacing and joining chamotte and Dinas obtaining ceramic bond high fire resistance and low porosity resulting from reactions SHS.

This task is solved in that the mixture of fusing and welding chamotte and Dinas, including powder silicon-containing substance, the aluminum powder and the additive according to the invention contains as a powder silicon-containing substance powder of silicon as an additive welding flux, and optionally, a powder of iron oxide in the following ratio, wt.


The invention consists in the following.

We offer a mixture of metal-reducing agents (silicon and aluminum) and metal oxide (iron oxide), obtained from powder materials by simple mixing with welding flux, crushed together with silicon to a particle size of less than 0.08 mm

Air-dry the mixture at a temperature of 900oC chamotte or Dinas refractories, then spend the initiation of SHS processes and sintering the mixture to obtain ceramic bond.

The use of two metals, reducing agents leads to the fact that for the synthesis of all cases from the standpoint of thermodynami initially occurs aluminothermy iron oxides:

Fe2O3+2Al= 2Fe+Al2O3(1)

or:

3Fe3O4+8Al=9Fe+4Al2O3(II)

If surplus remains Al, the reaction will be:

3SiO2+4Al=3Si+2Al2O3(III)

With an excess of Fe2O3is it the restoration of silicon:

2Fe2O3+3Si=4Fe+3SiO2(IV)

When the silicon content in the mixture is less than 1% of primary development get reactions I, II and III, i.e., due to small amounts of silicon, i.e., almost in pure form is "aluminothermy and abundance of iron oxides. In the case of stoichiometric ratios of the reactants and the proposed limits of the increased content of silicon > 15% ineffective.

When the content of aluminum in a mixture of more than 20% will come into effect on the reaction (III) and terminate mixture exceeds the optimal level of 2800-3200 kJ/kg, ensuring a good resistance and low porosity ceramic bond.

When the content of aluminum in the mixture is less than 10% of the synthesis of new substances occurs by the reaction of (IV), and the optimal level of terminate provided the total heat dissipation from oxidation as aluminum, and silicon. The downside of aluminum with the joint use of two metals reducing agents lowers heat dissipation, because the combustion of silicon emits significantly less heat, which reduces fire resistance ceramic bond formed during reactions SHS.

When excess iron oxide Fe2O3in the mixture (over 70%) is very rapid aluminothermic recovery according to reaction (I). Ceramic bond has a high porosity, which dramatically reduces its strength.

With the reduction in the content of iron oxide Fe2O3in a mixture of less than 60% increases respectively to the of iliceto manganese:

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Since this decomposition is accompanied by additional heat consumption, mixtures of such compounds is reduced terminate for SHS processes and the resistance of the obtained product.

When the content in the mixture for surfacing welding flux more than 19% as in the previous case, the role of reaction (V), which leads to the cost of heat for the decomposition of silicates and the corresponding decrease in terminate mixture and fire resistance is obtained in the reactions of the SAF product.

The use of compounds of welding flux in the amount of less than 3% is impractical, as formed during the SHS reaction liquid is very small, due to the fact that these reactions are mainly in the solid phase and the resulting thermal link does not have sufficient recordvideo. This makes it difficult for hot repair when sealing defects hearth coke ovens.

A new technical result of the claimed mixture is that when the joint grinding of welding flux containing flux CaF2and silicon metal to a particle size of 0.08 mm, and further mixing with thermite component, comprising iron oxide Fe2O3and aluminum, as well as joint participation aluminum is a material predetermined ceramic bond, with high resistance and low porosity.

When the joint oxidation of silicon metal and aluminum are the most easily oxidized aluminum, in addition, the stability of the oxide above. Due to the lack of a dense oxide film on the silicon oxide, which is abundant in welding flux, in the presence of gaseous oxides increases the rate of oxidation of the particles of silicon metal, which promotes the formation of a ceramic bond mullite-type reactions SHS.

Mix for surfacing and joining fireclay and silica was prepared as follows.

The mixture consisting of the following components, wt.

powder iron oxide 70

powder aluminum 15

the powder of silicon 10

welding flux 5

the moisture content of 2.3% and terminally 3253 kJ/kg were placed in an empty preheated to a temperature of 900oC camera coking on the cameras.

After heating the mixture until a specified temperature due to the physical heat chamber coking spontaneously occurred initiation of SHS processes and sintering the mixture with the formation of a ceramic bond. Ligament, spreading on a horizontal surface baking camera, fills the defect is in the course of SHS reactions for this example implementation,

the silicon oxide 40,3

aluminum oxide 59,7

The resistance is 1710oC, the porosity of 14%

The test results of the proposed mixes for surfacing and joining chamotte and Dinas at the optimum, the boundary parameters of the distinctive features of the claims given in the table.

The table shows that in the examples of terminate of SHS processes for the proposed mixtures was 2655-3286 kJ/kg, a moisture content of 2.0-2.5% of the Refractory ceramic bond formed during reactions SHS was 1450-1730oC and porosity 14-24%

The proposed mixture for welding chamotte and Dinas industrially applicable, as confirmed by the test report.

Mix for surfacing and joining chamotte and Dinas, including powder silicon-containing substance, the aluminum powder and an additive, characterized in that it contains as a powder silicon-containing substance powder of silicon as an additive welding flux, and optionally, a powder of iron oxide in the following ratio, wt.

The silicon powder 1 15

Powder aluminum 10 20

Welding flux 3 19

Powder iron oxide 60 70

 

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