The definition of the fire resistance of refractory material

Refractoriness refractory contend in no load temperature when the utility without melting softening function. Significance and melting refractory degree is not the same. The melting point is a crystallization of pure object phase and liquid phase in the flat static temperature. While the ordinary refractory material is composed of a variety of mineral synthesis of multi solid mixture, non congruent melting, but under certain temperatures have liquid, liquid on the proportion unceasingly increases with the temperature rising, to a fixed temperature solid phase can completely melted into a liquid, in a temperature range the two fixed temperatures during the in both liquid and solid, two also exist.

The fundamental decision conditions refractoriness of the material chemical mineral synthesis and distribution. Variety magazine, especially magazine ingredients with strong flux utility, will seriously decrease products refractoriness. Component is not evenly distributed, high melting point of mineral and cannot constitute an ideal, will make the products refractoriness decreased. Note the, refractoriness does not represent the product using the temperature, because the refractory material in the process often subjected to high temperatures utility at the same time, also with load and material flux effect, so the temperature often are much lower than the refractoriness.

Refractoriness are usually made of cone, pyrometric cone scale representation. Measure refractory refractory experimental approach is: will the tested refractory raw materials or made of refractory fiber products test cone with known refractoriness scale cases in cone, in under the premise of gun and compare test cone and scale of smelting temperature cone bend down, until the test cone top bent the pilot scale contact chassis, and on behalf of the cone bend down the temperature for the test cone refractoriness.

Three classification of refractory material according to temperature

Refractory material is a class of inorganic non metallic materials which the fire degree not lower than 1580 ℃. Refractoriness is refractory cone specimen under no load condition, resistance to high temperature without melting temperature in Celsius. Here we introduce three classification index of refractory material:

Can be divided into the ordinary refractory material: 1580 ~ 1770 ℃ refractoriness, refractoriness 1580 ~ 1770 ℃ is equivalent to Al2O315% ~ SiO2-Al2O3 two yuan in 45% refractory products, the main mineral composition of raw materials are the kaolinite.

Can be divided into high-grade  refractory materials:refractoriness 1770 ~ 2000 ℃, high aluminum bricks, magnesia brick, Mo to ordinary products, magnesia brick, of common magnesia chrome brick, brick belongs to this class of olive.

Can be divided into super refractory material: Refractory degree is higher than 2000 ℃, pure oxide products, casting products, high purity magnesia chrome brick, magnesia spinel brick, non oxide products belonging to this class.

Application of unshaped refractory materials

Unshaped refractory material is composed of reasonable distribution in the granular and powder and binder not forming and firing directly use of the refractories. Then what is the different unshaped refractory material application area, let us see it.

1. Ironmaking system.

• Alumina silicon carbide carbon refractory castable for blast furnace trough.
• As with hot-air burner refractory pouring castable lining.
• Torpedo type iron waterwheel partial or full using refractory castable, can also use refractory coating to repair.

2. Rolling system.

• All available unshaped refractory lining, steel forging heating furnace.

3. The steelmaking system.

• The cement rotary kiln.
• Glass tank furnace.
• Ceramic kiln.

4. Other industrial system.

• Petrochemical industry, ferrous metallurgy, fluidized bed boiler.

5. Building system.

• Refractory coating repair of BOF and eaf.
• Slag splashing.
• Alumina magnesia castable making converter lining.

Above is the simple introduction application of unshaped refractory materials, thank you for reading, more detailed information can contact us, we will try our best to answer your questions.

Scientific analysis of castable “appears white hair” phenomenon and effective solution

Castable material in using process often can see high alumina cement castable appeared on the surface of hanging “frost”, “long hair” “powder” “powder” phenomenon. In the common refractory castable surface and water to have loose gelatinous precipitate. These “frost” is because the cement particle surface castable not hydrated in water, forming supersaturated solution, then precipitated alumina sol and hydrated calcium aluminate induced. In fact, “white box” is not affect castables performance, but too much can cause rough skin on the construction, affecting the appearance.

Reason of castable long white: containing alkali refractory raw material, such as calcined alum refractory aggregate in, calcination sticky superior, as calcium aluminates cement castable. All kinds of powder, such as a variety of fine powder, silicon powder and kyanite; there are also contains alkali additives, such as reducing agent, coagulant, explosion-proof toughness. These materials often contain a small amount of alkali, the alkali, some can be dissolved in water, especially the dispersing agent of alkali, almost all into the wood. These “base” by capillary hole to the hardening decent migration, arrives at the table and then, the formation of carbonate and C02 reaction in the air.

Solution for casting material surface “frost” phenomenon:

1. Choosing low alkali content of refractory materials;
2. As soon as possible out of the water, drying, carrier to eliminate sodium alkali, stranded in the construction of the body, not to migrate to the surface.
3. The castable airtight, covered with plastic film, thereby preventing the moisture with alkali to migrate to the surface.
4. Improve the refractory castable viscosity and rapid hardening (reduce sodium migration velocity).
5. Strengthen quality control, strict control of water, to prevent too much water.

Application of refractory aggregate and powder in castable.

The unshaped refractory castable, refractory aggregate amount is generally 63%~73%, acting as a framework, can significantly affect the performance. Refractory powder dosage is 17%~37%, filling aggregate porosity and improve the construction resistance and so on. Some refractory powder, such as clay and ultra – fine powder, or a good bond. The ideal particle gradation is the gap caused by the coarse aggregate is just fine aggregate void filling, between the two has been refractory powder filled, no no surplus, to achieve the greatest packing density, in order to get the best performance.

Refractory aggregate divided into coarse and fine aggregate. Average particle size greater than 5mm is referred to as the coarse aggregate; 5mm and 5mm to 0.09mm is referred to as the fine aggregate. Habit will 5~0.15mm particles known as fine aggregate. Aggregate critical particle size depends on the thickness of the lining of the body, as shown in the following table. At present, the refractory critical particle size is reduced tendency, generally use 8mm or 5mm, pump feeding with 3mm. It should be noted that, in the preparation of unshaped refractory materials, the refractory aggregate gradation shall request the composite table technology.

In the production of unshaped refractory materials used as refractory materials, refractory aggregate and powder: bauxite, clay material, semi silica raw material, silicon material, magnesium material, kyanite group mineral raw materials, mullite, alumina, corundum, spinel raw material, silicon carbide, silicon nitride, chromium iron, zircon etc..

After the destruction of these refractory raw material, crushing, unshaped refractory materials to prepare the composite requirements of raw materials, to ensure the quality of the product, before use must be tested raw materials.

Commonly used ladle castable varieties

1. Clay brick, clay brick and A12O3 content in ordinary during 30%-50%, low price. It is important for ladle backing layer and ladle bottom.
2. High alumina brick. The content of A12O3 brick during 50%-80%, it is important for the working layer of ladle.
3. Wax brick. The brick is characteristic of high content of SiO2. In general more than 80%, than the corrosion resistance and the mass of clay bricks, and without residue. Used in ladle wall and the bottom of the bag.
4. Zircon brick. The brick mainly for ladle slag line. The content of ZrO2 in ordinary brick during 60%-65%.
5. Magnesia carbon brick. The brick for ladle slag line, special apply to multiple ladle continuous casting sessions. The content of MgO in ordinary brick in 76% and, in the meantime the carbon content of 15%-20%. Its characteristic is to slag corrosion, corrosion resistance, good peeling property.
6. Alumina magnesia castable. The castable for ladle body, its characteristic is the utility in molten steel, casting material of MgO and A12O3 and Al ovate spinel, improved the lining slag resistance and thermal shock resistance.
7. Alumina magnesia carbon brick. This brick is on aluminum magnesium casting material basically developed ladle lining, has a long service life.
8. Unfired brick. Now the ladle for fire brick materials, almost all can be made compared to unburned brick. Its characteristic is compared with the producer process simple, low unit price. The brick itself has certain machine intensity and corrosion resistance, easy construction and masonry

If ladle for refining itself, you can also choose the MgO-Cr2O3-A12O3 series and MgO-CaO-C series refractory castable, important: magnesia chrome brick, magnesia chrome brick, aluminum dolomite brick. As in the brick of ladle lining containing graphite material, preferably coated with a layer of chemical synthetic coating at the surface, the dike in siopao, lining surface compound loose, affect the using life.