Because of its low price and strong thermal stability, cordierite baking slate has seen explosive growth in recent years, which has defeated competitors such as ceramic slate and volcanic slate and become the first choice for home and commercial pizza and bread baking.
"Slate" has been passed on from mouth to mouth among baking lovers, but they don't know how to distinguish. Some of them are much cheaper, but they are still very heavy, and they think the quality is good. In fact, as long as you look at the appearance a little more carefully, you can see many differences.
Cordierite board manufacturing has certain processes, from raw material processing, mixing, to pressing, drying, firing, and later polishing, packaging and other processing, the treatment differences of different manufacturers in these aspects determine the cost.
Difference of raw material quality and mix proportion
Of course, the main content of cordierite board is cordierite, and some clay minerals and soils will be mixed to form and improve the properties. Cordierite with low thermal expansion coefficient plays a crucial role in the thermal stability of the board. Therefore, the quality and quantity of cordierite largely determine the fire resistance of the board.
The raw material cordierite needs to be sintered, so the sintering temperature is high, the cost is high, and the sintering will look cleaner.
But after mixing with other materials, pressing and sintering, it can no longer be distinguished, and the effect on the refractoriness is not as obvious as reducing the content of cordierite.
Generally, the use temperature of home users is limited and the use frequency is not high. Therefore, some manufacturers will "feel relieved" to reduce the cost by reducing the consumption of relatively expensive cordierite, which will directly lead to the decrease of fire resistance, easy to crack in the case of rapid cooling and heating, and the aging of stone slab will be faster.
2. Raw material processing procedure
Before mixing various raw materials, some treatment should be carried out, such as a step that has a great impact on the appearance of the finished product, which is to remove the iron impurities with large particles in the raw materials. Although this process is simple, it has a great impact on the appearance of the finished product, so it is difficult to completely remove it. Generally, the larger particles are isolated.
The product surface with relatively clean iron removal, however, is generally difficult to completely remove, and there are inevitably some black spots after high-temperature firing.
If you can save some time and labor by omitting this process, dense iron particles will appear on the surface of the product after firing.
Some products are not treated with iron removal, and the surface iron is dense.
3. Firing temperature and time
Firing is a very important process of slate manufacturing, which has a great impact on the quality of products. Only with sufficient firing time and proper firing temperature (generally 1200 ℃), can the slate be fully sintered, harder and more fire resistant.
Fully sintered slate surface, solid and flat
The powder on the surface of the unburned slate will fall, and the particles on the surface will look shaky. The powder falling here is not the external dust gathered on the surface area. This kind of dust will not exist again after washing. The unsintered powder falling refers to the material falling off.
For some unsintered products, the powder loss is particularly serious.
Shortening the firing time and reducing the temperature can reduce the fuel consumption. In the same time, more finished products can be fired, which can naturally reduce the cost. Therefore, some slate can be sold at such a low price.
4. Subsequent grinding and packaging
The mineral powder is very soft and needs to be pressed by a large tonnage press. Different shapes and sizes require different molds. The mold consists of several parts. The upper and lower mold cores and the frame form a closed shape. There is a certain gap between the frame and the core. Therefore, the edge of the pressed embryo will be rough, and the embryo is very soft and inconvenient to be polished before firing, so it can only be used. After sintering and forming with hardness. Whether it is semi-automatic machine grinding or manual grinding, it is a time-consuming and labor-consuming process.
Machine grinding production line
Of course, not grinding can also save part of the cost.
Some manufacturers will not polish at all to save labor cost
To sum up, it's easy to distinguish the quality difference of cordierite slate without knowing the deep doorway, as long as you look carefully. It's hard to divide the goods by one penny.