Understand the performance, formulation and construction pro
Understand the performance, formulation and construction process of refractory ramming materials
The basic material composition of ordinary refractory ramming material is basically similar to refractory castable and temperable plastic. It is also composed of refractory aggregate, powder and binder, admixture, etc., the difference is that the amount of flour in the ramming material is higher. More, and the amount of binder is small, usually adding soft clay to increase the viscoplasticity and sinterability of the material, and it is applied by beating method, which is called refractory ramming material.
According to the different types of refractory aggregates, it can be divided into clay, high alumina, mullite corundum, siliceous, magnesia and silicon carbide. According to the different types of binders, it can be divided into phosphoric acid and phosphate. Aluminum sulfate, water glass, cement, bonded clay and organic binders.
The composition of the refractory ramming material is generally 60-65% of the refractory aggregate and 35-40% of the refractory powder, so that a large packing density can be obtained, and the density of the lining body after the beating is also large. The critical particle size of refractory aggregate is 10mm, and it is also useful for 5mm. The mass ratio of coarse and fine aggregate is 3:7~4:6. More fine aggregates are easier to beat and dense.
The refractory ramming material is applied on site and can be beaten by mechanical methods such as pneumatic picking. The wind pressure should be no less than 0.5 MPa. The part with less or no material is also available for manual beating. The lining of the refractory ramming material has a low moisture content, such as beating and compacting, and the performance is superior to the refractory castable of the same material. The construction speed of the refractory ramming material is slow and the labor intensity is large.
The high-aluminum ramming material is made of alumina bauxite containing 82% alumina as aggregate and powder, and more fused corundum powder is added to improve the performance of the matrix, and clay is added as a plasticizer.
Magnesium-aluminum-chromium-resistant ramming material is prepared from materials such as fused magnesia-chromium composite and aluminum-magnesium spinel.
The aluminum zirconium ramming material is made of alumina bauxite containing 85% alumina as refractory aggregate and powder, and zirconium oxide containing 64% zirconium dioxide and Jiaozuo mud.
Mixing ratio of magnesia-chrome refractory ramming material: the masonry aggregate and powder containing 91% of magnesia are 55% and 15%, respectively, and the chromite aggregate and powder containing Cr2O347% are 15, respectively. The water glass solution is 4 to 5%.
The high-strength magnesia refractory ramming material uses fused magnesia containing 97% of magnesium oxide as the bone powder. The critical particle size is 5mm, the fourth-grade ingredients, the ratio of bone powder is between 7:3 and 6:4; the phosphate is used as the binder, the dosage is 2~4%, and the composite metal powder is added.
Basic characteristics of refractory ramming
Refractory ramming material has the following basic characteristics:
(1) It has thermosetting property, peeling resistance, abrasion resistance and corrosion resistance; adding tar to dolomite ramming material can enhance hydration resistance; graphite ramming material adding tar as bonding agent has good workability.
(2) It has a high use temperature, generally between 1450 and 1700 °C.
(3) The bulk density of silicon carbide ramming material should not be lower than 2.2t per cubic meter, and the bulk density of dolomite and magnesia ramming material with tar added should not be lower than 2.9t per cubic meter; high aluminum, The bulk density of the magnesium ramming material should not be lower than 2.95t per cubic meter.
(4) The finished ramming material shall be selected from the finished products produced by the special manufacturer. The finished ramming material shall have the factory certificate and the instruction manual.
(5) The particle size of the ramming material should be evenly matched. The ratio of coarse, medium and fine granules is approximately 4:2:4, and the maximum particle size is between 5 and 7 mm.
Quality requirements for the constituent materials
(1) The varieties and grades of finished refractory ramming materials shall meet the design requirements;
(2) The quality of the materials for the preparation of refractory beats on site shall meet the following requirements:
1 Strictly check the quality of each component material and formulate it according to the design mix ratio;
2 High-aluminum ramming material is prepared by high-aluminum aggregate, powder, water glass and sodium fluorosilicate. The materials should meet the requirements;
3 Magnesium ramming material is composed of metallurgical magnesia, clay refractory mud, iron slag, iron oxide powder, brine or coal tar. The composition materials should meet the quality standards of related materials.
4 Dolomite ramming material consists of dolomite and anhydrous tar;
5 Graphite crucible is composed of metallurgical coke powder, dehydrated coal tar and coal bitumen. The composition materials should meet the quality standards of related materials.
Scope of ramming
The applicable scope of commonly used refractory ramming materials is as follows:
(1) High-aluminum ramming material is suitable for electric furnace furnace items and rotary kiln discharge ports;
(2) Magnesium ramming material is suitable for the furnace bottom of electric furnace, open hearth furnace and converter;
(3) Dolomite ramming is suitable for the bottom of converter and ferroalloy electric furnace;
(4) Graphite and silicon carbide ramming materials are suitable for use in blast furnaces and iron water trenches.
Paving and beating
Before beating the ramming material, the paving should be uniform. If it is beaten with a pneumatic hammer, it should be hammered and half hammered, and continuously and layer by layer. The second paving shall be carried out after the surface of the ramming material that has been knotted is smashed, and the working wind pressure of the pneumatic hammer shall not be less than 0.5 MPa.
Carbon ramming can be applied by cold heading or hot smashing. Before the bottom of the furnace is beaten, the furnace base should be dried and cleaned.
The temperature of the cold carbonaceous material when beaten should be about 10 °C higher than the softening temperature of the binder.
For hot carbon materials, it is advisable to use finished materials. Before the beating, the carbon material must be crushed and uniformly heated. The heating temperature should be determined according to the mixing temperature of the finished material. There should be no hard blocks in the heated carbon material. A hot hammer should be used when hitting, and the material temperature should not be lower than 70 °C.
When hitting with a pneumatic hammer, the thickness of each layer should not exceed 100 mm. The tamping density of each layer of carbon ramming material shall be checked according to the specified bulk density or compression ratio. The compression ratio is: the amount of reduction / the thickness of the looseness × 100%, and the value should be 40 to 45%.
When the beating of the carbon ramming material is interrupted and the beating is continued, the solid surface of the crucible should be cleaned, brushed and brushed with coal tar.
Using coal tar and coal tar pitch as binder
Magnesia or dolomite ramming material using coal tar and coal tar pitch as a binder should be beaten with a hot hammer. Coal tar, coal tar pitch and aggregate should be separately dehydrated and heated and mixed, and stirred evenly.
Key points of magnesite ramming with tar pitch as binder
The construction of magnesia ramming material with tar pitch as binder is as follows:
1 The magnesia used should be dried and heated, and the temperature of the material when beaten should be 80~130 °C.
2 The temperature of the masonry surface should be heated to 50~60 °C.
3 The surface of the masonry before beating should be cleaned and brushed with a layer of tar pitch;
4 When layering, it should be layered and laid. The thickness of each layer should be 20~30mm, and the surface will be smooth and feel the wind hammer has a rebounding force and can emit metal sound.
For the construction of the beating, the template shall be set as required. The formwork shall have sufficient strength and rigidity, and the connecting parts and the reinforcing members shall not be disengaged when beaten.
For templates with small areas and complex shapes, wood molds should be used; steel sheets should be used for larger areas and regular surfaces. The wood formwork should be supported by wood, and the steel formwork should be supported by steel. The combination template should be bolted.