How To Choose Brown Fused Alumina

Introduction of brown fused alumina:

Brown fused alumina, also known as emery, is a brown artificial corundum made by melting and reducing bauxite, carbon material and iron filings in electric arc furnace, so it is named. The main chemical composition of brown corundum is Al2O3, with the content of 95.00% - 97.00%, and a small amount of Fe, Si, Ti, etc. 

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The abrasives made of brown fused alumina are suitable for grinding metals with high tensile strength, such as various general steels, malleable cast iron, hard bronze, etc., and can also be used to manufacture high-grade refractory materials. In particular, its cost performance is much higher than that of traditional brown aluminium oxide, which makes it the best aggregate and filler for brown corundum refractory.

Brown fused alumina is made of bauxite and coke (anthracite) as the main raw materials by high temperature smelting in electric arc furnace. Brown aluminum oxide has the characteristics of high purity, good crystallization, strong fluidity, low coefficient of linear expansion and corrosion resistance. 

Two smelting methods of brown fused alumina:

The smelting of brown fused alumina belongs to the submerged electric furnace smelting method. At present, there are three main smelting methods: fixed furnace smelting method, dumping furnace smelting method, and exile smelting method. Because the third type has a larger investment scale and higher costs, it is now The first two methods are commonly used.

1.The brown aluminum oxide produced by the dumping furnace (method) has many crystal aggregates, small crystal size, high glass phase and distributed on the grain boundary, so the toughness is poor, the brittleness is large, the brown fused alumina abrasive grains are easy to fall off, the self-sharpness is good, and the compactness is good , More suitable for consolidation of abrasive tools and refractory materials.

2.The corundum produced by the frit furnace (method) has less crystal aggregates, large crystal size, and less glass, so it has poor brittleness, high toughness and good wear resistance. Due to the large crystal size, toughness and brittleness, the brown fused alumina produced by this smelting method is more suitable for the manufacture of coated abrasives. Therefore, it is still the most used abrasive in abrasive belt production.

Process steps of producing brown fused alumina:

Brown fused alumina is a kind of brown artificial corundum made of bauxite, carbon material and iron filings after melting and reduction in electric arc furnace. Its main component is Al2O3. What are its specific production process steps? Brown aluminum oxide production process is mainly divided into the following steps:

1. Mix bauxite, scrap iron and anthracite in proportion.

2. Prepare graphite electrode (generate high temperature and high pressure arc).

3. The raw material is added into the electric arc furnace, and the raw material is refined at a high temperature above 2250 ℃ in the electric arc furnace to produce brown fused alumina.

4. After several hours of high temperature smelting, brown aluminum oxide is poured out.

5. Cool the brown aluminum oxide in the container.

6. Brown fused alumina block is put into sand making machine to produce brown corundum sand.

In the production process of brown aluminum oxide, we need to grasp several important factors, that is, temperature, time, raw material ratio, etc., which are related to the quality and performance of the brown fused alumina product, so we must strictly control the production.

Distinguish the quality of brown fused alumina:

Brown fused alumina abrasive is the most popular abrasive so far. It is an artificial emery abrasive produced by processing bauxite, anthracite, etc. as raw materials. The hardness is moderate and the application range is wider, so it has a higher market share. But now the market is mixed, how to distinguish the quality of brown fused alumina abrasive?

1.Judge the quality of brown corundum abrasive by appearance. First, look at the particle size. The brown fused alumina abrasive particles of good quality are uniform and regular, with a hexagonal shape. Secondly, look at the color. People in the industry know that there are two smelting methods for brown aluminum oxide abrasives: fixed furnace and dumping furnace. Fixed furnace brown fused alumina is reddish brown and can be translucent when placed in the sun, while dumping furnace brown aluminium oxide has a black color. Black and red.

2. Judge the magnetic content of brown aluminum oxide abrasive by iron absorption stone. Good-quality brown fused alumina abrasives contain a small amount of magnetic materials. This can be done with magnets. If there are more magnetics attached to the magnets, it means that there are more magnetics in the brown fused alumina. Excessive impurities will seriously affect its hardness. There are fewer magnetic substances, which means that the brown aluminum oxide has less impurities, the content of alumina will be relatively higher and the quality will be better.

3. Judge the ash content of brown fused alumina by clear water. We all know that there is water washing in the production process of brown aluminum oxide. Many brown fused alumina manufacturers ignore this technology in order to reduce costs. This not only causes a large amount of dust in use, and seriously affects the sandblasting effect. 

Users can take some brown fused alumina samples when purchasing and place them in clear water. If a layer of white substance is attached to the surface of the water layer, it means that the product contains a lot of ash. If the water is clear and not polluted, it means that the brown aluminium oxide does not contain ash and is of good quality.

4. Judge the hardness of brown aluminum oxide by rubbing and pressing. Good-quality brown fused alumina will also have a high hardness. Take a handful of brown fused alumina grit and place it on white paper, wipe and press with your bare hands to see if there are any crushed particles. If there is, the hardness is not high enough and the quality is not good enough. If it is intact, the hardness is better and more wear-resistant.

F sand, P sand and W sand of brown fused alumina:

The specifications of brown aluminum oxide grinding products include f sand, P sand and W sand, as well as molding sand and coarse sand (granular sand). Products with different specifications and quality differ greatly. So, like many varieties, what is the identification of brown fused alumina genius products?

Start talking about brown fused alumina F grains. This type of product is a common brown aluminum oxide abrasive product. The important particle sizes are 4 to 240 mesh. It is mainly used for grinding and polishing of various castings and workpieces. It can also be used to consume and manufacture various grinding wheels.

Brown fused alumina P sand is better than f sand. It needs to be processed by pickling, water washing, air selection and other processing methods. The particle size is usually 8 to 220 mesh. It is more used in the grinding process of high precision workpiece. W sand of brown aluminum oxide is a fine powder series of brown fused alumina genius, No. W1-W63, with extremely fine particle size.

In a word, the brown aluminum oxide P sand, f sand and W sand mentioned above belong to brown fused alumina No. sand, because they all have fixed size, also known as sand. However, brown sandstone is not common. For example, the commonly used 1-3mm, 3-5mm and 325-0 are sand, because the size of this brown fused alumina is between two values. It is mainly used to make refractories.

First grade and second grade brown fused alumina:

The main component of brown fused alumina is the same as that of white fused alumina, and the grades are also distinguished by aluminum content. The lower the aluminum content, the lower the hardness. The general particle size is F4~F320, and its chemical composition varies depending on the size of the particle size. The outstanding feature is that the brown fused alumina crystal size is small and impact resistant.

Because it is processed and broken by a self-grinding machine, the particles are mostly spherical particles, and the surface is dry and clean, which is easy to bond with the binder; here is the first to make a difference between the first-grade brown fused alumina and the second-grade brown fused alumina Cf.

First-grade brown fused alumina The main chemical component of brown aluminum oxide is AL2O3, with a content of 94.5%-97%, a brown appearance, and a small amount of Fe, Si, Ti, etc. The primary chemical composition of secondary brown fused alumina is also AL2O3, the alumina content is 85-90%, and the appearance is brown-black. The first-grade brown fused alumina is mainly used for sandblasting abrasives, water filtration, etc.

The secondary brown fused alumina sand is mainly used for sandblasting, polishing, grinding, anti-corrosion and rust removal, stone carving, emery cloth materials and other purposes. It has moderate hardness, high toughness, good self-sharpening, low sand consumption and can be recycled and used, and the brown fused alumina powder abrasive parts have good finish; and the chemical composition is stable, abrasion resistance, acid and alkali resistance.

It can also be processed by washing and pickling according to customer requirements, which can meet the different needs of customers. Sandblasted brown fused alumina has shell-like fractures and sharp corners, which can form new corners and edges in the continuous destruction and classification, so that its grinding can be better than other abrasives. The grain size of brown fused alumina can be processed from 4 mesh to 325 mesh.