Several species of castable

   Castable consists of aggregate, binder and admixtures. Depending on the binders can be divided into Portland cement castable, aluminate cement castable, castable sodium silicate, phosphate castable refractory concrete and clay combined with magnesia refractory castable.

   Portland cement castable concrete binder weight accounted for 7% -20%. Portland cement castable cementitious material used, the need to eliminate the role of calcium oxide. When the addition of 50% -100% by weight of cement of clinker fine clay powder as admixture, it combines with calcium oxide and aluminum to form a stable calcium silicate minerals. This refractory concrete stick low cost, available at the following 1000 ℃, temperature fluctuation is not, no acid erosion in places such as basic equipment, flues, chimneys, etc.

Aluminate cement castable based on alumina as binder to bauxite clinker as aggregate and blending material made ​​of hydraulic concrete. The main mineral bauxite is calcium aluminate cement hydration fast. Therefore, this concrete hardening, high early strength.

   Water glass castable is a water glass binder and add the appropriate amount of sodium silicon fluoride gas as hard concrete coagulant made​​. Silicone silicate hydrolysis of the aggregate, admixtures together. This concrete strength is relatively high, but the low refractoriness and load softening point, applies to the following 1000 ℃ require a higher strength, wear resistance, corrosion can antacid site, but not for regular water or water vapor effect place.

   

Phosphate castable based on industrial phosphoric acid binder, sometimes plus the amount of alumina cement as a coagulant and made of hot hard concrete. This is characteristic of concrete cured at room temperature without consolidation, in order to solidify and a certain intensity, to add coagulant. Was heated to 500 ℃ hardened consolidation, and the strength will be improved, but near 800 ℃, low temperature strength of its shortcomings, and strength after the temperature rise. This refractory concrete has excellent fire resistance, abrasion resistance, slag resistance and thermal shock resistance, long-term use under the conditions of 1400-1600 ℃.

   The casting material can be poured directly on the thermal equipment templates, add anchors inside after tamping after a certain curing period can be. Can also be made of prefabricated blocks, such as the vault, ceiling, wall oven, lid, door, etc., than the brick or directly casted, both during construction and replacement much more convenient.

U.S. levy anti-dumping taxes on China Refractories

U.S. Department of Commerce preliminary ruling made ​​by the first half of last year, China's exports to the U.S. decision to impose refractories ~ 91.16% 84.89% anti-dumping duty. The U.S. Commerce Department's announcement that day showed specific products being taxed at least 90% of silica containing silica brick.

This acid refractory is mainly used for masonry coke ovens, blast furnaces, glass kilns and other high-temperature furnaces.

Chinese exports to the U.S. silica brick case began in November 2012. Utah, a refractory company complaint, claiming that Chinese companies of dumping in the United States, asked the U.S. Department of Commerce initiated anti-dumping investigation, the dumping margin was made ​​up 118.47% ~ 290.12%.

U.S. Department of Commerce statistics show that in 2011 Chinese exports to the U.S. totaled about $43,240,000 silica brick, but in 2012 the total value of exports to the U.S. fell to $25.7 million sharply, a decline of nearly 40%.

For the United States frequently waving "trade stick", Chinese Ministry of Commerce has repeatedly stressed that trade protectionism is not only unfair to him, the country, there is no advantage to domestic companies, do not want the United States to measure high-sounding but actually with a strong political background to implementation of trade protectionism, but should abide by its commitment to oppose trade protectionism, with a more rational approach to properly handle trade frictions

Solutions for refractory castable expansion

In the application process of the refractory castable  often appear a certain degree of expansion coefficients, which will affect the quality of the work castable body. So, to the problem of refractory castable how to solve it? Castable refractory is a material made ​​by the granular and powdered materials, and add a certain amount of binder composition and water together.

Luoyang Elon Refractories technical staff tell everyone how to solve the problem of castable expansion:

1.    You can then add refractory castable aluminum dihydrogen phosphate, aluminum dihydrogen phosphate dosage should be controlled at 13% to 15%, but due to the liquid aluminum dihydrogen phosphate refractory generate hydrogen reacts with metallic iron at room temperature, and after pouring the liner body swell, parallel porous loose body.

2.    Since the cement composition contains a certain amount of metallic iron. Therefore, you must add the anti-bulging inhibitors (covert agent), or mixed castable liquid potassium dihydrogen phosphate was added in two hours. The specific method is first added 6% to 7% potassium dihydrogen phosphate in castable mixture , trapped material in the semi-wet state 24h. Before the second plus potassium dihydrogen phosphate, first add 2 to 3% of coagulant, the material mix well, then add the remaining 6-7% potassium dihydrogen phosphate solution, and then mixed evenly pouring. Expansion can be prevented in general.

3.    Porcelain ball mill grinding, or by using a strong acid (such as hydrochloric acid, etc.) washing powder and magnetic separation methods such as using less metal and other impurities into or excluded.

4.   Reduce the amount of cement, mixing inhibitor or improve molding pressure.

Foreign refractory recycling situation

Developed countries attach great importance to the re-use of refractories from resources, environmental protection height to understand, even with the development of laws and regulations strictly limit emissions after the refractory, which greatly promoted the study of the refractory recycling after refractory recycling rate has reached more than 60% and rising.

Japan to scrap steel slabs based raw materials, developed around the bottom of the ladle ramming mixes, ladle castable and styling products, such as: with 85% recycled material and 15% of new material to produce a molten pool area with no burning furnace brick, with 90% recycled material and 10% new material to produce electricity lines slag MgO-C, as well as all recycled materials to produce RH bottom burned magnesia chrome brick. Secondary use of technology Kashima Steel has developed a skateboard brick, using surface grinding, pouring castable recovery method, the Mosaic law makes skateboard ring after the repair has reached a new skateboard using the same effect; scrap iron ditch refractories are repeated use, primarily as A12O3-SiC-C castable aggregate.

Italian company has developed a method for recovering the refractory technology, mainly used for recycling of the furnace , tundish , ladle ingot mold and the refractory lining , and the recovered blowing directly into the furnace refractories to protect the furnace wall . American Refractories previously only a small amount of waste recycled , the rest almost completely buried. 1998 U.S. Department of Energy , Department of Industrial Technology and steel producers jointly developed a three-year plan to extend the life of refractories and refractory waste recycling .Refractory Factory cooperation with users to minimize the amount of the waste refractories . The United States also after dolomite brick as a soil conditioner and slagging agents were studied , and achieved good results.

India conducted the first study of waste refractories can be traced back to 1978, first in the steel company to carry out, the use of Indian steel company (now known as TISCO steel Branch) high alumina brick furnace waste generated (60% to 62% aluminum) production castable (56% alumina), fire clay (50% alumina) and fire-resistant plastic. Developed material which is mainly used for the production of cast burner tiles, dampers, tiles, etc., and can meet the requirements within the industry.

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.