Q. How can you measure the refractories and refractoriness under load of a refractory material?
Explain segercone test and RUL test of refractory material.
Ans. Segercone test: Refractories is a measure of fusibility of refractory materials. It represents the softening temperatures of the Refractories. This temperature is observed either with the pyrometers or in terms of parametric cone equivalent (PCE) value. In PCE value, refractoriness can be determined on a sample in the form of a cone which is either cut from the material or prepared from the ground sample. The softening of the cone is indicated by the top bending over and the tip touching the plaque on which cone is placed. The PCE is reported in terms of the standard cone and is equivalent to that corresponding in time of softening with test cone. If the test cone softens earlier that one cone and later than other, then the PCE value will be approximately between two cones. The test refractory in the form of cone generally is 38mm height and 19mm base side is kept alongside the similar sized standard cones and all are heated uniformly at 10 degree centigrade per minute. Each standard cone is made of a particular refractory material of a definite softening temperature are assigned serial number with increasing softening temperature. When the test cones softens temperature are losses its shape, at the same time one the standard cones whose refractoriness is near to that of the test cone will also soften, the serial number of the standard cone is noted. For example, the silica brick has a PCE of 33 with a softening temperature range 1700-17500C. It indicates that this refractory can be used in furnace with operating temperature.
Refractoriness under load (RUL): This represents the resistance of a refractory material to the combined efforts of heat and load. RUL is the temperature at which the deformation begins and at which at least 10% deformation takes place. It is necessary that refractory material must also possess very high mechanical strength even at operating temperature to bear the maximum possible load without damage.
Strength of refractory (Refractoriness under load): The high temperature load: bearing characteristics of a refractory material is determined by refractory under test or R.U.L. test. In R.U.L. test, the specimen of refractory of size 5Cm2 and height 75cm. Under a load of 1.75Kg/cm2 is heated in a carbon resistant furnace. The heating rate is maintained at 100C/minute. The temperature at which 10% deformation occurs on test specimen is reported as R.U.L. The determination of deformation is done by recording the height of the height of the specimen at difference temperature. On the basis of R.U.L. test, the refractory materials are classified as:
High heat duty brick
Intermediate heat duty brick
Moderate heat duty brick