What happens when ceramic products are fired in a kiln?
Generally requires less than 0.5% moisture into the kiln, kiln temperature is lower than 200 degrees. In the furnace operation, we can adjust the opening of the exhaust exhaust valve, and adjust the small set of first, second burner to solve. The diurnal temperature variation in some areas, the temperature dropped, will crack, because the cold slab kiln, and the internal temperature of the surface to reach consensus, to a certain time, if the kiln head temperature is too high, so that the body of the inner and surface temperature difference is too large, resulting in the surface of the billet body out of the water too fast, too fast to make the surface shrinkage. The internal water body is not easy to diffuse exudation, resulting in large internal stress, make the body burst, so in a timely manner to adjust the kiln head pumping power, or in the glaze line and heating device.
2. cracking caused by burningThere are two cases in the process of furnace firing, one is thermal cracking, the other is cold cracking, and the other is cold cracking.A crack in a tropical zone (hot blast)Its characteristic is the crack from the edge to the center of irregular development, the crack is easily mistaken for transport collision cracking. The crack is generally smaller than the mechanical rupture, and mainly in the edge crack, mostly in the outer side, it usually appears in the pre tropical section. The main causes of the defects is blank in the kiln kiln and the water temperature is too high, the kiln head temperature rising speed too fast, or blank material content free quartz and dry sensitive high index is too high, it is worth noting that sometimes adjust kiln in order to avoid black, often lead to cracking.The pre tropical crack can be solved by reducing the water entering the kiln, the temperature of the kiln head and the heating rate of the preheating zone.
There are many kinds of crack defects, such as side crack, surface crack and layer crack. When cracks occur generally, each link should be inspected. After forming, the available clean natural oil method to check, be careful from Adobe press and dryer outlet, rub on the natural oil, to find out whether there are cracks. The cracks can be determined according to the shape of the cracks. The cracks in the quench zone are smooth, sharp and sharp, the cracks in the pre tropical section are rough, the cracks are jagged, the edges of cracks are smooth, and the cracks are often flowing glaze.1. drying and crackingIt refers to the body from the dryer out of the cracks, cracks appeared in the brick side. The main causes of dry cracking are:1) the flowability of the powder is poor or the packing is uneven;2) the powder moisture is too high;3) the drying temperature is too high or the drying speed is too fast, that is, the drying system is unreasonable, and the opening of each damper is not reasonable.4) dry sensitive index of raw materials (such as bentonite) excessive use.- solution1) control the amount of raw material with high drying sensitivity index, stabilize the powder moisture, improve the flowability of powder and the uniformity of filler.2) strict establishment of drying system, the opening of the throttle is particularly important.
