Refractories used in steel smelting

Blast furnace refractories:

Development of blast furnace ceramic cup increasingly common, but require high corrosion resistance of refractories application to ensure its life extended. In addition to changes in the design of the refractory material respects, great changes have taken place, such as a micro porous carbon brick ordinary charcoal instead of the past in order to reduce the penetration of molten iron. Clay refractory bricks used as raw material can adapt to the requirements stemming mouth of iron. Grouting method using blast furnace repair backing backing can effectively prevent the erosion of hot air, thereby extending the life of the blast furnace lining.

Clay refractory bricks used as raw material can adapt to the requirements stemming mouth of iron. Grouting method using blast furnace repair backing backing can effectively prevent the erosion of hot air, thereby extending the life of the blast furnace lining.

Converter refractories:

In steelmaking, the kind of water-cooled technolovgy and suspension systems are in the upper part and the lower cone barrel parts BOF shell has been applied, thus reducing the converter furnace deformation, extending converter lining life, improve productivity converter. These new technologies have some impact on the use of refractories. So that the converter furnace furnace up to 4000 more than the average, combined with gunning, the application of high lime and dolomite applications and slag splashing technology, furnace over 10,000 times is not a problem. This is the direction of development of refractories producer worth attention.

Submerged nozzle for continuous casting:

Since the development of the system of casting tundish transfer station from the past into the present effects of cast steel quality and increase the productivity

of the metallurgical vessel. Therefore, many functional materials gradually applied in the middle of the package, such as slag dam, impact plates, filters, plugs, etc. argon permeability.

Submerged nozzle as an important function of continuous casting refractories, research carried out mainly focused on two aspects, one is to improve the corrosion resistance of slag line, the second is to reduce the inner wall of Al2O3 attachment. Take the ZrO2 content increased 88%, as well as a good measure of the particle size distribution can reduce the thermal expansion coefficient and porosity of products, improve the density improvement slag resistance.

Advantages of castable in refractory material

General portland cement concrete can not withstand high temperature operating conditions, precipitation of calcium hydroxide in the hydration process, it becomes calcium oxide at high temperatures; As aggregate of limestone under high temperature thermal decomposition, strength destroyed.strength destroyed.

Ordinary concrete can only be used below 300 ℃ low temperature parts of the foundation and chimney stove. The castable temperature up to 900 ℃ or more.

Compared with other refractory castable has some distinctive features:

(1)Castable has almost same refractoriness with the firebrick, but because castable without sintering, the larger contraction when heated first time, so the load is slightly lower than the softening point firebrick. Nevertheless, a measure of overall performance is better than firebrick.

(2) As the effect of low temperature cementation materials, castable has high temperature compressive strength. and because masonry's good integrity, furnace air tightness, not easily deformed, outside the furnace shell plate can be canceled, stoves resistance to mechanical vibration and shock performance is better than brick masonry. For example, the upper sidewall of soaking furnace, where mechanical abrasion and impact are more severe, life expectancy increased by several times than brick.

(3)Good thermal stability, most or all of the aggregate are clinker,;expansion and contraction of cementing material phase offset,

Relatively speaking,the thermal expansion of masonry is smaller than a brick, thermal stress is also small. And there are a variety of mesh, needle and chain crystalline phase structures, a strong resistance to temperature.For example, to pouring soaking furnace mouth and lid. Life expectancy to a year and a half.

(4)The production process is simple, eliminating the complex steps of brick making. Castable can be made into a variety of prefabricated blocks, and to mechanized construction, brickwork greatly accelerate the speed and improve the efficiency of more than ten times higher than bricklaying. Waste bricks can also use as aggregate, waste for profit.

Species and characteristics of clay

Alumino silicate clay is dominated by rocks, such as feldspar pegmatite granite, porphyry, gneiss, etc. The long-term weathering, and often through water transport and deposition are too many fine mineral mixture, its main chemical composition of SiO2, Al2O3, and water of crystallization. With different geological formation conditions, may also contain small amounts of alkali metal oxides, alkaline earth metal oxides and coloring oxides.

Varieties and uses a lot of clay, often according to mineralogical, geological origin, chemical composition, physical properties or industrial uses clay classification.

1. More clay minerals in the main types can be divided kaolin clay series, smectite and illite clay series. 
2. According generation, the clay can be divided into the native clay (Primary clay) and secondary clay (Secondary clay), the native clay is the generation after feldspar weathering of silicate hydrous kaolin and other minerals, quartz, etc., is not completely broken weathered residual debris in situ, and soluble salts were dissolved; secondary raw clay is a former clay transferred under dynamic conditions to the rest of the natural crystalline clay again.
3. According to the plasticity of clay can be divided into soft clay (strong plasticity clay), semi-soft clay (clay plasticity) and hard clay (clay plasticity weak), mostly secondary soft clay clay, because fine particles dispersed degree, so plasticity; hard clay and more by diagenesis ancient community, and the lack of free water is not easy to dip into the bulk, plasticity poor.

Some Western industrialized countries often comes down to the clay six categories, namely: Kaolin (Kaolin), fire clay (Fire clay), ball clay (Ball clay), bentonite (Bentonite), bleaching earth (Fuller, s earth) and the general clay (Common) where bentonite, fuller's earth and ordinary clay mainly composed of montmorillonite, illite and chlorite, etc., poor fire resistance.

Classification and habits at home and abroad, the refractory clay Category: kaolin, ball clay and fire clay. Natural clay minerals according to the above classification is not always a sharp distinction between, and sometimes a clay can contain a variety of clay, but the performance is also superimposed on each other, such as mineral composition and chemical composition of many hard clay and kaolin are very close; many balls soft refractory clay and the clay of the same physical properties. Regardless of how the kind of clay, clay determine its performance properties.

Overview of domestic refractories recycling

Our refractories for reuse after a late start, the relatively low recycling rate. According to reports, after the re-utilization of refractories for about 20%, some even use, but also to reduce the product quality for the price.

In recent years, most of the major domestic steel mills and factories have attached great importance to the refractories  recycling and reuse, ongoing research and application of all aspects of the work.

Baosteel better after Refractory reuse the work performed, the main blast furnace trough castable have been recycled as slag trough castable materials, prepared for the regeneration of MgO-C regenerated after treatment with the antioxidant and MgO-C strong slag resistance, long life advantages.

WISCO will use the aluminum-magnesium carbon debris classification, after removal of impurities, manually eradicate sticky residue and buffer layers, and magnetic separation and hydration treatment, using a jaw crusher crushing the material to 25mm or less, and finally with a hammer crusher processed into the desired particle size to produce renewable alumina magnesia.

Jigang aluminum carbon refractories (later abandoned skateboard brick, brick pedestal, outlet, plug the stick) for iron ditch Ramming expected to replace some high-alumina material. Magnesia chrome brick after as raw material, by a certain percentage added to the RH gunning years, with favorable results. Meanwhile, the better the performance of renewable prepared magnesia-chrome brick, cement kilns in non-critical areas and RH have better prospects.

At present, the domestic researchers also proposed: By adding an appropriate amount

in the refractory oxides useful in improving high-temperature performance to optimize the preparation of high quality modified material; through the reduction reaction of the transition temperature materials such as SiC,-Sialon, Mgalon etc. ; adopted by the brick after brick with a skateboard mullite; adopted by the silica brick, with C as a reducing agent synthesis SiC; using brick with a skateboard after synthesis-Sialon; using bricks with the skateboard, with the MgO-C synthetic oxide and non-oxide Mgalon and other composite materials to make products with high strength, thermal shock and erosion resistance, excellent performance, as a new and efficient high-temperature refractory materials for key parts of the equipment in order to achieve efficient use of resources and energy.

Refractory recyclable become refractory industry development trend. To achieve a breakthrough in the refractory industry, we must follow the needs of the community development.

Use of recarburiser

Carbon additive is an additive used in steel making. It is an essential raw material for the production of high-quality steel. Further, also the production of the electrode paste material.

After pressing graphite powder,

can greatly increase the amount of scrap castings production, reducing the amount of pig iron or no iron in an electric furnace smelting, will increase carbon agent in the middle, (the latter part of the furnace discharge material put Recarburizer) added measure is 1-3% metal content. Recarburizer characterized by carbon absorption in liquid iron in effect, does not return slag, using carbon agent can greatly reduce the casting cost of production.

Advanced refractory and coatings are widely used in metallurgical industry, steel core light industry, electrical industry, carbon brush, electrode in battery industry, fertilizer industry catalyst. Graphite after processing, can produce graphite, graphite paper, graphite sealing materials and other graphite products, has become an important non-metallic mineral raw materials in various industrial sectors.