Easy damaged part and common refractory for steelmaking electric arc furnace

The current commonly used arc furnace, furnace wall and bottom furnace, the hot spot is the weak link of electric arc furnace.

Reasons for damage of the refractory at the top of the one is splashes, furnace dust erosion; second is due to the high around the electrode temperature, top temperature difference larger
caused by melt erosion and thermal shock. Commonly used in the refractory with high aluminum brick, magnesia chrome brick, dolomite brick, silica and other and relevant material of refractory pouring material or ramming material, and some also used prefabricated pieces of the roof of the furnace.

Hot parts of furnace wall lining easy erosion, the reason is high temperature, molten steel and slag erosion, charging the impact.Refractory material is mainly used all kinds of basic refractories, the prevailing magnesia carbon brick.

The damage of the bottom is mainly due to chemical erosion and mechanical Chong, commonly used alkaline refractory ramming material or castable lining, the dry vibration material effect is good.

The overall development trend of the steelmaking electric arc furnace is the large-scale, two is the power unceasing enhancement, and three is the additional enhancement smelting measure. The steelmaking arc furnace of new technology: strengthening smelting enriched pulverized coal injection, bottom blowing stirring, eccentric bottom tapping, DC electric arc furnace.

The new technology adopted, both positive and negative influences to the refractory material, overall negative effect on refractory larger, such as ultra high power, oxygen enriched intensified smelting, bottom blowing stirring the refractory material of the more demanding conditions of use. Eccentric bottom tapping and DC arc furnaces are the conditions for the use of refractory material of furnace wall relative improvement, but conditions of use of certain parts of refractory become demanding, especially for DC arc furnace bottom lining. Therefore, the refractory industry must develop new varieties to meet the need of new technology for steelmaking arc furnace.

Properties of clay refractory

(1) Fire resistance. The low degree of fire resistance of clay refractory products is lower, and the increase of three aluminum oxide content in clay brick is improved… Generally 1580 for ~1750;

(2) Load softening temperature. Fireclay refractory load softening temperature is low; refractoriness under load was usually less than 1300 degrees.

(3) Thermal shock stability. Fireclay refractory thermal shock stability is better, the main reason is mullite crystals are surrounded by glass phase, mullite itself smaller coefficient of expansion, when heated does not produce stress concentration, so the stability of thermal shock resistance is good.

The main factors that affect the thermal shock stability of clay refractory are the physical properties of raw materials and the structure of clay brick… Therefore, the thermal stability of the clay brick can be improved by increasing the proportion of clinker and adopting reasonable brick making process…

(4) Slag resistance. The main chemical constituents of the clay refractory are silica and threealumina, and the former is more than the latter, and the clay brick is obviously weak acidity… Therefore, the ability of acid slag erosion ability than the strong anti alkaline slag.

Increase the density of two aluminum oxide and clay brick, increase the content of clinker, decrease porosity and decrease the impurity content of clay brick, and increase slag resistance of clay brick…

(5) The change of heavy firing line. For the clay refractory, the shrinkage of the residual shrinkage is no more than l%. Increasing tile clinker proportion, an appropriate increase in firing temperature and reasonable insulation, can make clay brick volume stability improvement, that reheating linear change decreases.

Why coke oven must use silica bricks

Silica brick belongs to acidic refractory  material, has good acid resistance erosion ability, its good thermal conductivity, high refractoriness under load, general in 1620 DEG C above, only than the low refractoriness of 70 to 80 DEG C. Brick thermal conductivity increases with theincrease of temperature, no residual shrinkage, in the baking process, the volume of the brick with the increase of temperature increases. Therefore, silica is coke oven ideal refractory products, modern large and medium coke important parts (such as the combustion chamber, ramps and regenerator with brick masonry.

In the baking process, silica brick maximum expansion occurred in the 100 to 300 DEG C, 300 DEG C before the expansion is about 70% to 75% of the total amount of expansion. The reason is SiO2 in baking process appear 117 degrees, 163 DEG, 180 to 270 DEG C and 573 DEG C four crystal transition points, including 180 to 270 DEG C, caused by cristobalite volume maximum swelling.

Thermal stability of silica brick quality is the key to true density and the size of the true density is to determine the important symbol of the transformation of the quartz. The true density ofsilicon is smaller, the lime into more completely and the residual in the oven in the process of expansion is small.

In the brick, tridymite crystal true density minimum and linear expansion rate, good thermal stability such as quartz and quartz, slag corrosion resistance strong, good thermal conductivity, high refractoriness under load is quartz volume is the most stable form. Burnt better silica brick, tridymite content was the highest, accounting for 50% ~ 80%; cristobalite times accounted for only 10% ~ 30%; and quartz and glass phase content fluctuation in 5% ~ 15%.

When the working temperature is lower than 600 DEG C, brick volume changes larger, anti sudden cold and hot performance is poor, the thermal stability is not good. If the coke oven is working at this temperature, the masonry is easily cracked and damaged…

Refractories for heat exchange furnaces

The heat exchanger is an important part of the center of bottom burner furnace, four corners burner soaking pit and one sided upper burner soaking pit for the preheating of the air or gas. The first two stove of heat exchanger is arranged in the stove on both sides of the wall outside, after a set the end wall burner in an external, are located in the flue and the exhaust vent and furnace stare Unicom.

The lining of heat exchanger is made of clay brick, and its brick type has four holes of clay brick, circular or star shaped clay or clay brick, etc… The characteristic is that the preheating temperature of air and gas is high, but the air leakage rate is big, and the service life is about 1 year… When high alumina silicon carbide refractory cast material, the centrifugal method is used to form round pipe brick, the length of 2m is above, and the leakage rate is reduced, the service life is increased by 50%…

Refractory for ordinary boilers

Ordinary boiler boiler tube system, combustion chamber, flue and dust collector and other parts, the work is not high, mainly for industrial and civil heating and other departments. Thereare many types of boilers, the number of large, commonly used coal as fuel; there is heavy oil or gas. Today, we introduce fire resistant materials for ordinary boiler…

Ordinary boiler combustion chamber operating temperature for 1400 to 1600 DEG C, the lining generally use a clay brick masonry, the remaining parts of the lining and flue layer with three level of clay brick, non working layer adopts ordinary red brick masonry. Recently, some of the boiler combustion chamber is lined with refractory of 1710 – 1790 DEG C of the refractory can be plastic ramming or refractory castable watering, flue layer with high alumina cement clay castable refractories production and its application effect is good.

Some of the ordinary boiler front arch temperature of 1300 to 1400 DEG C, using high aluminacements high alumina castable or phosphate clayey castable watering. After the arch parts of the work temperature of about 1000 DEG C, is commonly used in high alumina cement clay refractory castable production, the remaining parts of the lining, the Portland cement or high alumina cement clay castable; coal-fired boiler are generally installed with a dust remover, temperature is not high, but the smoke and dust grinding loss is severe. If a steel plate to produce the dust collector and the inner wall should daub fruit plate making precipitator by silicate or phosphate refractory and the inner wall should be using water glass or refractory phosphate coating material for protection layer, service life can improve the L ~ 3 times.

In order to save energy and low temperature part of the ordinary boiler can use insulation board and light refractory pouring material used for lining, high-temperature parts also added a heat insulation layer, to reduce heat loss of a furnace body and improve boiler potency.

Production technology introduction of high alumina brick

High alumina brick and clay brick of the same way of molding production. The process of crushing, mixing, molding, drying, sintering, and testing, packaging, etc.. Production practice proved that the high Al clinker in front of the broken strictly chosen grading, low temperatureunder the compressive stress bear better but high temperature slightly lower so kiln in piling up less than 1 meter, and siliceous brick can be up to 1.7 meters. There are just some differences in process parameters… And classification of storage using bauxite and clay together with fine grinding method can improve the quality of products.

Raw materials and technology: mineral mainly consists of Mo mullite and corundum phase and blast furnace with corundum mullite brick using artificial electric melting or sintering corundum and Mo mullite raw materials as the main raw material, through high pressure shaping and high temperature sintering, mineral mainly consists of mullite. Features: the products have apparent porosity rate is low; load softening point, high creep resistance and chemical corrosion resistance excellent characteristics. Features: the product has the appearance of pure white, precise size, withexcellent physical properties and chemical erosion resistance of high temperature. Uses: mainly used for blast furnace bottom and hearth, is one of the advanced large blast furnace and ceramic cup material.

High alumina brick and clinker clay brick production process is similar differences. Uses: large blast furnace with advanced ceramic cup “one of the materials and hot blast stove industrial furnace in high-grade refractory material can be used. Raw materials and technology: blast furnace with mullite brick using artificial electric melting or sintering Mo mullite raw materials as the main raw material, through high pressure shaping and high temperature sintering is ingredients in a higher proportion of clinker can be as high as 90% ~ 9% clinker before breaking for classification is chosen, screened in addition to iron firing temperature is higher, such as high alumina brick tunnel kiln firing average 1500 ~ 1600 DEG C.

The main factor of refractory high temperature creep

The factors that affect the high temperature creep of refractory are many, and many factors are interrelated… The main factors that affect the creep deformation of refractory are the following:

1, refractory material, including: chemical composition, mineral composition (single phase or multiphase), microstructure.

2, the outside conditions in effect, including: temperature, load, and time, atmosphere (oxidative or reductive).

3, the chemical mineral composition and microstructure of refractory materials determine the creep resistance of the materials.

4, in phase composition to determine the basic conditions, high bulk density, compressive strength, porosity low refractory products, creep resistance is better, but with the increase of temperature and time increase, refractory material stress will be increased creep deformation will increase.