When purchasing white fused alumina, you often encounter various products with different prices, models, and processes. Therefore, it is essential to understand the characteristics of white corundum that require attention.
1. Particle Size of White aluminum oxide:
The particle size requirements for white fused alumina used in refractory materials are generally relatively simple. However, with advancements in refractory processing, many companies now require more precise particle size distribution within the specified particle size range.
When Purchasing White corundum for Abrasive Applications: While the national standard model is commonly considered, greater attention should be paid to the particle size distribution within the specific range. If the same model feels too coarse or too fine in actual use, it's related to the particle size distribution control by different factories.
2. Alumina Content of White aluminum oxide:
Alumina (α-Al₂O₃) in white fused alumina is the main component responsible for its high-temperature resistance, wear resistance, and hardness. Therefore, alumina content is arguably the most important indicator. Alumina content is primarily related to the quality of the raw alumina powder and the smelting time.
3. Sodium Content of White aluminum oxide:
As mentioned above, α-Al₂O₃ is the main component responsible for its high-temperature resistance, wear resistance, and hardness. Sodium oxide, during smelting, will react with sodium peraluminate, reducing the formation of α-Al₂O₃ in white corundum and affecting its properties. Controlling sodium content requires increased smelting time, higher electricity consumption, and the use of low-sodium alumina, thus increasing costs.
4. Smelting Process of White aluminum oxide:
There are two main smelting methods: tilting furnace smelting and stationary furnace smelting. Both methods essentially involve the electro-melting and recrystallization of white fused alumina, but different processes result in different characteristics. Tilting furnaces produce large, industrially produced white corundum with a high degree of uniformity in quality; stationary furnaces produce white corundum with good central quality but unstable external quality, but the longer cooling time results in higher density in the center. In some special applications, stationary furnaces are specifically used.
5. Bulk Density of White aluminum oxide:
Bulk density reflects, to a certain extent, particle volume density, porosity, particle shape, and particle size distribution. Simply put, white fused alumina with high bulk density has high volume density, low porosity, rounded particle shape, and dispersed particle size distribution; conversely, white corundum with low bulk density has low volume density, high porosity, sharp particle shape, and concentrated particle size distribution.
6. Whiteness of White aluminum oxide:
Whiteness is measured using a specialized whiteness meter. However, for applications requiring high color and gloss, specific measurements can be taken. Ordinary white fused alumina has a whiteness of around 90.
7. Cleanliness of White aluminum oxide:
Cleanliness corresponds to the turbidity of white fused alumina, measured using a specialized turbidity meter. It mainly reflects the amount of fine dust adhering to the particles. A simple visual assessment can be made by pouring pure water into the white corundum, stirring, and observing the turbidity of the water. Water washing and acid washing processes can improve cleanliness.
8. Hardness of White aluminum oxide:
Hardness indicators include Mohs hardness (scratch test) and microhardness (indentation test). The Mohs hardness is around 9, and the microhardness range is 2200-2400 kg/mm².
9. Melting Point of White aluminum oxide:
The melting point of white fused alumina is 2250℃, and the maximum operating temperature is 1900℃. Generally, higher alumina content and lower sodium content correspond to a higher melting point. It's worth noting that some factories add aluminum fluoride (AlF3) to lower the melting point of alumina during the smelting of white corundum in order to save on electricity costs. This will lower the melting point and other properties of the product.
10. White aluminum oxide Particle Shape:
Different applications require sharp, rounded, or flat particle shapes, depending on the crushing process. Crushing processes include: roller crushing, jaw crushing, Barmac crushing, iron ball tube mill crushing, ceramic ball tube mill crushing, and air jet mill crushing. Generally, coated abrasives require sharp particles, while sandblasting and bonded dies require rounded particles.
Upon closer inspection, you'll realize that focusing solely on price during procurement is incorrect. Due to the presence of recycled waste and substandard secondary materials from production, some factories will quote very low prices. To understand a factory's costs, the price of raw material industrial alumina powder and electricity consumption are essentially the main costs of white fused alumina. If the price is lower than these costs, it's impossible to buy genuine white corundum.
