Study On The Pre-puffing Process Of Perlite And Development Of Slag Conglomeration Agent With The Perlite Tailings

Since the 1980 s, slag conglomeration agent has been widely used as one of the important supplementary materials in the field of steel casting production. With the increasing of casting production and the improvement requirement for castings property of equipment manufacturing industry in our country, single perlite polyethylene slag agent couldn’t have met the requirements of the casts performance, and over exploitation and processing of perlite caused a lot of pearlite tailings abandoned which have affected the ecological environment seriously.The influences of drying temperature, pre-puffing temperature and holding time on microstructure, expansion, weight loss, density of the pearlite were researched by the experimental methods of the scanning electron microscope(SEM), differential thermal analysis(DTA) et al. Based on the optimization of pre-puffing process, the new kind of compound slag agent formula with pearlite tailings being the main raw materials has been developed through industrial tests.The results showed the water in the pearlite produced in Xinyang has two forms: one is free-water adsorbed on the surface, and the other is structure water wrapped by vitroo. The weight loss rate of pearlite increased with drying temperature increasing, and stabilized at 3.85% when the drying temperature was above 450℃.With the increase of pre-puffing temperature, the weight loss of pearlite decreased gradually, and expansion times rised first and then deceased. On the contrary, the volume-weight falled initially and then increased. The micropores appear on the surface of pearlite after pre-puffing. The fracture surface presents lamellar, and has a few cavities. With the increase of pre-puffing temperature, the amount of micropore increased and the diameter of cavities became bigger. But when the temperature reached to 1050℃, some spindly cracks produced on the surface.The weight loss rate declined as the holding time increased, and became stable when it was above 23 s. The expansion times improved initially and then droped with the prolonging of holding time, however, the volume-weight was decreased initially and then increased. With the extension of holding time, the cracks on the surface disappeared, the amount and diameter of micropore both decreased, and With the holding time prolonged, the surface of perlite had no crack, and smaller micropores which had benng distributed and similar diameter gradually appeared. The diameter of the cavities on the fracture surface increased initially and then decreased. When the holding time was longer than 23 s, some debris was produced by the broken of some cavities. The optimized pro-puffing temperature and holding time were 950℃ and 15 s, the expansion times and volume-weight of pearlite were 2.733 and 912 kg/m3 respectively.Compared with the pearlite with pre-puffed, the pearlite without pre-puffing and the pearlite heated along with the furnace have larger volume-weight and lower expansion times. The pearlite particles heated along with the furnace may shrink in some cases.The industrial experiment results showed that, the compound pearlite tailings slag conglomeration agent have more advantages than the single pearlite slag conglomeration agent, such as better spread ability and conglomeration effect, slagging off easily and so on. This optimized the ingredient of new compound slag conglomeration agent which is 8% activity Si O2, 4% activity Al2O3, 4% sodium silicate and the rest pearlite tailings.