The thermal expansion property of AZS brick and kiln of glass kiln.

Glass kiln ignition baking oven is according to the furnace refractories used in physical and chemical properties, that is, the thermal expansion of refractory material, after heated baking make refractory after completing internal crystal structure transformation and volume change, can use normally under high temperature in order to achieve process.

AZS bricks used to be expensive. Therefore, kilns are not used or are only used in small quantities in key parts. In the past two decades, with the development of high efficiency and energy-saving technology of kiln, AZS bricks have been widely used, not only to the wall of glass liquid, but also to the fire space with AZS. Due to the influence of traditional inertia thinking, most glass factories still only consider the thermal expansion of silica brick in the kiln, while the thermal expansion of AZS bricks is not paid attention to. Therefore, the fracture problems of AZS bricks before and after the production of the kiln have occurred, which directly affect the life of the kiln.

1. The thermal expansion characteristics of AZS bricks.

AZS brick contains a certain amount of ZrO2, which belongs to homogeneous polycrystal, which is the same chemical composition. Due to different temperature conditions,

There are three crystals of different structures and properties. They are ZrO2, ZrO2, and ZrO2.

Material is 1200 ℃ 2370 ℃ material

The monoclinal crystal system ZrO2 - - - - - - - - - - - - - - - - - - - cubic - crystal ZrO2.

Changes in crystals are often accompanied by changes in volume. 33 # AZS, for example, through the experiment found that when the temperature range in the 0-1100 ℃, the temperature rise is gradually expanding brick; When the temperature range in 1100-1200 ℃, the temperature rise is the sharp contraction of brick, linear expansion rate by about 0.8% to around 0.6%, the usually says the abnormal phenomenon, this is because the ZrO2 monoclinic system into ZrO2 tetragonal crystal system caused; When the temperature is higher than 1200, the brick will start to expand again with the temperature rise.

From laboratory test data shows that about 1600 ℃ below the overall expansion is not large, the average coefficient of expansion of about 10-70 * 7 / ℃.

2. Precautions for baking kiln.

Baking kiln has a link in the fire, hot air roasting kiln put a fire in 900-900 ℃, practice shows that the fracture of AZS brick mostly appear after put the fire, the reason is monoclinic system ZrO2 to tetragonal crystal system ZrO2 changes caused by heat up too fast during 1100-1200 ℃. General requirements, therefore, speed is not more than 15 ℃ / hour, many manufacturers control in 5 ℃ / hour, on the other temperature speed is not more than 15 ℃ / hour, so AZS brick will have sufficient time to crystal shape transformation, can avoid the fracture.

Contact with the flame surface and the contact surface in the process of roasting kiln several baidu temperature difference, to make the outer edge of the brick can safely to the crystal transformation, must be in a large temperature range with low speed. So, usually temperature range by the theory of 1100-1200 ℃ expanded to about 1100-1350 ℃.

The location of the upper wall brick, 300-400 - mm, normal production without heat preservation, need to cooling, roast furnace in order to reduce the inside and outside temperature difference, should use the temporary heat preservation heat preservation materials such as aluminum silicate fiber, prevent rupture of brick, when the temperature is above 1500 ℃ can remove insulation fibre.

When the wall brick is cooled, the cooling air intake should be gradually opened, usually starting at 5 times and starting at 20% per hour.

3. Conclusion.

The work of the kiln is related to the life of the kiln. Therefore, correctly grasp the expansion properties of zirconium fused corundum brick, in the baking furnace heating curves of specification and earnest implementation is very important, our company relevant personnel should be on the issue more communication with users, when good staff, make the supply and demand both sides mutual development.