Tangshan Tangbao Refractories Co., Ltd.
Address：Beijiadian Third Street, Guye District, Tangshan
Shortening and swelling of refractory castables
When the refractory castables are subheated, the volume of the castables will decrease twice during dehydration from 50 degrees to 200 degrees and sintering from 9000 degrees to 1000 degrees. In other temperature ranges, heating will swell the castable. After secondary heating, castables are generally no longer shortened. In order to prevent the stress caused by volume change from destroying the castable, it is necessary to divide the lining into zones with diagonal dimension less than 1.5 meters, and to pour the lining in zones and leave gaps of expansion and shortening at the boundary of each casting zone. The size of the gap in the influence area of the expansion joint should ensure that the castables in each district expand freely, and the expansion joint with proper orientation can also become the control joint. In high temperature zone (greater than six Baidu), the width of expansion joint should be controlled at 3-4 mm according to the interval of expansion joint. The expansion joints and control joints are arranged on the plane above and below the protrusion angle 200 mm, while the pavilion is arranged in the protrusion angle and the cone. The cracking tendency of castables on both sides of expansion joint and control joint is larger, and the density of scraping nails can be increased appropriately. The width of the expansion joint is related to the working temperature and the length of the line. The temperature is higher, the length of the control is longer, and the expansion joint can be widened appropriately. In the relatively low temperature area (less than Sibaidu), castables can be directly applied to the equipment shell, and no thermal insulation layer is allowed. Under such conditions, every 1.5 meters into 2 mm thick cardboard or plastic film, can meet the requirements of expansion space.
When determining the orientation of expansion joint, the reasonable arrangement of vibrating process should be taken into account. The vibrating of castables on one side of the gap should not affect the castables that have been poured after vibrating and begin to harden. The direction of the expansion joint avoids the stress position, the furnace skeleton and the holes in the lining. In areas with disorderly shapes, such as edges and protrusions, expansion joints corresponding to their appearance should be set at the surface with small protrusion angle and curvature radius. When the two casting surfaces intersect into concave angles, a expansion joint should be set at the concave angle. The lining diagram should show the orientation and scale of the expansion joint at the primary position. If the working temperature of the castable exceeds 12 Baidu, the expansion joint with a width of more than 3 millimetres should be set up and the fiber felt inserted therein. The setting of refractory castables for control joints needs to set control joints at the convex corners of about 200 mm, because shortening will cause cracks, so that the shortened cracks can occur in the predetermined and safer parts. The control seam can be set up by inserting paper, white wax or veneer into the reserved slot and pouring the flammable or missing material at high temperature. When these flammable materials are burnt or lost, the control seam will be left behind. It is necessary to set the control joint in the adjacent scraping center, which is roughly equal to the scraping nails on both sides. Settings on continuous surfaces, conical surfaces and pipes should be placed on planes and surfaces that cannot be controlled to shorten the danger. It should be prevented to set up expansion joints in areas where expansion joints can not be set up, such as in small pouring surfaces and convex corners.