The quality of refractory bricks can be evaluated from multiple aspects, including physical properties, chemical composition, refractory performance, etc. The following are several commonly used key indicators for judging the quality of refractory bricks:
1. Chemical composition
The main chemical composition of refractory bricks determines its performance and service life. Through chemical composition analysis, the purity of refractory bricks and whether they meet the requirements can be judged.
Alumina content: In high-alumina bricks, the higher the content of alumina (Alz0;), the better the refractoriness and thermal shock resistance are generally. Impurity content: If the content of impurities such as iron oxide and calcium oxide is too high, the refractoriness, erosion resistance and mechanical strength of refractory bricks will be reduced. Therefore, low impurity content is usually a sign of high-quality refractory bricks.
2. Refractoriness
Refractory bricks: By repeatedly heating and cooling bricks quickly, observe whether they crack or peel off. Refractory bricks with good thermal shock resistance are tested in kilns and other frequencies
Refractory test: The softening point temperature of refractory bricks can be tested through the refractory cone test of refractory bricks. Generally speaking, the higher the refractoriness, the better the quality of the brick. The refractoriness of high-alumina bricks is generally above 1770°C, and the refractoriness of ordinary clay bricks is usually between 1580°C and 1730°C.
3. Bulk density
Bulk density is another important parameter to measure the quality of refractory bricks. The higher the bulk density, the better the compactness of the refractory brick, which usually also means that its mechanical strength and wear resistance are stronger.
High-density bricks: generally have good wear and erosion resistance, suitable for high-load and high-wear environments.
Lightweight bricks: suitable for thermal insulation purposes, although the strength and wear resistance are low, but the thermal insulation performance is excellent.
4. Apparent porosity The apparent porosity refers to the proportion of open pores in the refractory brick, which affects the slag resistance and mechanical strength of the refractory brick.
Low apparent porosity: The refractory brick has high density, good mechanical strength and wear resistance, and strong erosion resistance. High apparent porosity: The refractory brick has good thermal insulation performance, but poor strength and erosion resistance. Under high temperature conditions, it is easy to be damaged by the penetration of slag or molten material.
5. Compressive strength
In general, the higher the load softening temperature, the more stable the brick is in a high temperature and high pressure environment, especially when used in a high-load kiln or high-temperature equipment.
Compressive strength test: usually carried out by crushing test. The higher the compressive strength, the less likely the refractory brick is to crack or deform during use, and the longer the service life.
6. Thermal shock resistance
Thermal shock resistance refers to the ability of refractory bricks to resist cracking and spalling when the temperature changes sharply. Refractory bricks with good thermal shock resistance can withstand frequent temperature fluctuations without damage.
Thermal shock resistance test: by repeatedly heating and cooling the bricks quickly, observe whether they crack or peel off. Refractory bricks with good thermal shock resistance are more durable in environments with frequent thermal changes such as kilns.
7. Load softening temperature
The load softening temperature is the temperature at which refractory bricks deform when subjected to load at high temperature. High-quality refractory bricks have a high load softening temperature and can maintain structural stability under high temperature and heavy load.
Load softening temperature test: usually expressed in softening point temperature. Generally speaking, the higher the load softening temperature, the better the stability of the brick under high temperature and high pressure environment
8. Erosion resistance
The erosion resistance of refractory bricks refers to their ability to resist chemical erosion, especially the slag and gas in the kiln will corrode the refractory bricks.
Slag erosion resistance: In a high temperature environment, refractory bricks will react chemically with slag, molten metal, etc. Through the slag erosion test, the chemical corrosion resistance of refractory bricks can be evaluated. High erosion resistance is a characteristic of high-quality refractory bricks.
9. Linear change rate Linear change rate refers to the volume or size change of refractory bricks at high temperature, reflecting the thermal stability of the material
Low linear change rate: means that the refractory bricks expand or contract less at high temperature and have good dimensional stability. Refractory bricks with low linear change rate are not easy to deform or crack during use and have strong durability.
10. Appearance and manufacturing process
The appearance quality of refractory bricks is also a simple and intuitive way to judge their quality. High-quality refractory bricks usually have good manufacturing technology, flat surface, no cracks, no obvious defects, regular shape, and small dimensional error.
Dimensional accuracy: The brick size has high accuracy, can be tightly combined during installation, and reduce kiln heat loss and mechanical stress concentration.
Surface quality: The brick surface is smooth, free of pores and inclusions, indicating that the material has good uniformity and is not prone to local damage during use.
Summary: Judging the quality of refractory bricks requires comprehensive consideration of its chemical composition, refractoriness, bulk density, apparent porosity, compressive strength, thermal shock resistance, load softening temperature, erosion resistance, linear change rate, and appearance. The performance and applicability of refractory bricks can be effectively evaluated through chemical analysis, physical testing, and appearance inspection. Good refractory bricks should have good high temperature resistance, erosion resistance, endurance, and thermal shock resistance, and have a long service life in practical applications.
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