The composition of refractory ramming material is generally 60-65% of refractory aggregate and 35-40% of refractory powder, which can obtain larger bulk density and larger density of lining after ramming. The critical particle size of refractory aggregate is 10 mm, which is also useful for 5 mm. The mass ratio of coarse aggregate to fine aggregate is 3:7~4:6. More fine aggregate is easier to tamp and compact.
Fire-resistant tamping material can be tampered with mechanical methods such as air pick in site construction. Its wind pressure should not be less than 0.5 MPa. Less or unimportant parts of the material can also be tampered by hand. The lining of refractory ramming material has low moisture content. If ramming is compact, its performance is better than that of refractory castables of the same material. The construction speed of refractory ramming material is slow and the labor intensity is high.
High alumina ramming material uses bauxite clinker containing 82% aluminium trioxide as aggregate and powder, and adds more fused corundum powder to improve the performance of matrix, at the same time adds clay as plasticizer.
Magnesium-aluminium-chromium ramming material is made of fused magnesia-chromium compound and aluminium-magnesium spinel.
The aluminium zirconium ramming material is made of bauxite clinker containing 85% aluminium trioxide as refractory aggregate and powder, adding zircon powder containing 64% zirconium dioxide and coke mud.
The mix ratio of magnesia-chromium refractory ramming material: magnesia aggregate and powder containing 91% magnesia are 55% and 15%, chromite aggregate and powder containing 34.7% Cr2O are 15% and sodium silicate solution is 4-5%.
High strength magnesia refractory ramming material is made of fused magnesia containing 97% magnesia as aggregate powder. The critical particle size is 5 mm, the ratio of aggregate to powder is 7:3-6:4, and the amount of phosphate as binder is 2-4% with compound metal powder.
Fire-resistant ramming material has the following basic characteristics:
(1) It has heat hardness, spalling resistance, abrasion resistance and erosion resistance; dolomite ramming material added tar can enhance hydration resistance; graphite ramming material added tar as binder, has good construction performance.
(2) It has a high operating temperature, generally between 1450 and 1700 C.
(3) The bulk density of SiC ramming material should not be less than 2.2t/cubic meter, and the bulk density of dolomitic and magnesian ramming material with tar should not be less than 2.9t/cubic meter; the bulk density of high alumina and magnesian ramming material should not be less than 2.95t/cubic meter.
(4) Construction ramming materials shall be manufactured by specialized manufacturers, and finished ramming materials shall have factory certificates and instructions.
(5) The granularity of ramming material should be matched evenly. The proportion of coarse, medium and fine grains is about 4:2:4, and the maximum particle size is between 5 and 7 mm.
The application scope of common refractory ramming materials is as follows:
(1) High alumina ramming material is suitable for electric furnace items and rotary kiln outlets, etc.
(2) Magnesium ramming material is suitable for bottom of electric furnace, open hearth and converter.
(3) Dolomite ramming material is suitable for the bottom of converter and ferroalloy electric furnace.
(4) Graphite and silicon carbide ramming materials are suitable for blast furnaces and hot metal ditches.
Laying Material and Tamping
Before tamping, the paving should be uniform. If tamping with pneumatic hammer, one hammer and half hammer should be used to tamp continuously and evenly layer by layer. The second laying should be done after the knotted ramming surface is rough. The working wind pressure of the pneumatic hammer should not be less than 0.5 MPa.