For use in refractory mixtures coarser than mortars, where the degree of plasticity is desired for proper emplacement, similarly the magnesian silicate introduces particular advantages.<a href="http://www.coalgrinding.com/project/250-300th-hard-rock-crushing-plant.html">250-300t/h hard rock crushing plant</a> For instance, it can be used in mixtures which are tempered with water and packed about hollow metal forms to fashion the tap holes of metallurgical furnaces. Such applications require a greater degree of volume stability and strength than is usually necessary for mortars. The volume stability can be obtained by suitable proportioning of coarse magnesite clinker with intermediate and fine sized clinker. Thus, excellent results are found to occur with 40 per cent of -6+30 mesh size, 20 per cent of -30+60 mesh size, and 40 per cent of -150 mesh size. About 5 per cent of sodium silicate is desirably included, and hectorite 0.5 to 2 per cent by weight. This composition has excellent working plasticity and cohesiveness, and is not subject to segregation of coarse matter during difficult forming operations.
Illustrative examples of plastic bonding compositions in accordance with the invention are as follows: I. Mortar for laying up magnesite or chrome brick.-Clinker formed from dolomite, magnesite and chrome ore,<a href="http://www.coalgrinding.com/project/250-300th-stone-crusher-plant.html">250-300t/h stone crusher plant</a> by burning the pulverized batch at 3000° F. or higher in a rotary-kiln, and for instance having a composition such as MgO 81 per cent, CaO 8 per cent, Si02 4 per cent, Fe203 4r 3 per cent, Cr203 2 per cent, A1203 2 per cent, and B203 0.05 per cent, 94 per cent -100 mesh, with 3 per cent -100 mesh mill scale, 2 per cent -100 mesh sodium nitrate, and 1 per cent -200 mesh hectorite.
II. Plastic basic refractory for tap-holes.Clinkers, such as the foregoing, are sized and mixed with the other materials, in amount of 40 per cent -4+15 mesh clinker, 20 per cent -15+100 mesh clinker,<a href="http://www.coalgrinding.com/project/30tph-granite-crushing-plant-in-russia.html">30TPH granite crushing plant in Russia</a> 31.5 per cent -200 mesh clinker, 5 per cent water soluble sodium silicate, 2 per cent -200 mesh sodium carbonate, 1.0 per cent trisodium phosphate, and 1.5 per cent -200 mesh hectorite. This is tempered with about 7.5 per cent of water, mixed thoroughly, and tamped about a hollow metal form to make a furnace taphole.