Unshaped Refractory Lining Materials for Cupola Linings

Different from the traditional cupola ladle lining, the two types of ladles built with refractory ramming material or refractory castable material can greatly increase the working life of the ladle lining and reduce the number of spare ladles. What are the specific material choices for the two new types of ladle linings?

High-Alumina Refractory Ramming Materials

Refractory Ramming Material Lining

Ramming material is a general term for plastic refractory materials composed of refractory aggregate, binder, and moisture. The mineral composition of refractory aggregate coated with ramming material is generally bauxite, corundum, quartz sand, and quartz powder. The chemical composition is mainly composed of alumina (Al2O3) and silicon oxide (SiO2) two parts. Due to the different mineral compositions and particle sizes, various suppliers have developed a variety of packaging ramming material specifications. At present, the chemical composition of the lining ramming material, among which the higher the alumina content, the higher the use temperature, the greater the drying density, the stronger the thermal conductivity of the lining, and the longer the life of the lining.

Bauxite, corundum, quartz sand, and quartz powder in the lining ramming material are materials with high thermal conductivity. In addition, due to the size grading of refractory materials, the compaction density of ramming materials is larger. Therefore, the thermal conductivity of the lining ramming material is higher. If the ramming material is used completely to build the lining, the heat conduction of the lining causes the temperature of the iron liquid to drop more. Therefore, before using the lining ramming material to build the lining, a heat insulation layer of a certain thickness should be designed inside the cladding.

The ramming die must be prepared in advance to build the packing lining with ramming material. The ramming die is specially designed according to the ladle structure and lining to be located, and either has a certain inclination or has the performance of split disassembly. When building the lining, first use the ramming material layer by layer, ramming the bottom to a certain thickness. Then, the ramming mold is placed in the shell, and the ramming material is filled layer by layer to the mouth of the bag. Finally, pull out or remove the ramming die, and brush the surface of the lining with graphite powder coating.

The construction quality of ramming material lining has a decisive influence on the life of the lining, and the difference in construction quality may make the same material have different life. When building the lining with ramming material, it should be rammed tightly. The ramming compactness must conform to the drying compactness range of the lining material. The drying and roasting temperature and time of the packaging should also meet the technical requirements of the relevant products.

SiC Refractory Castable Lining

Refractory Castable Lining

Refractory castable is a class of amorphous refractory materials with cement as binder. The mineral composition of the refractory aggregate is the same as that of the refractory aggregate used for lining ramming. Calcium oxide (CaO) is an essential component of cement as the binder lining cement castable is high alumina cement. Therefore, the calcium oxide content can indirectly represent the cement content in the castable. Cement-lined castable can be divided into general cement castable, low cement castable and ultra-low cement castable. The lower the cement content, the higher the refractoriness of the material. Chemical composition range of coated low cement and ultra low cement castables. Among them, the higher the Al2O3 and the lower the CaO, the higher the refractoriness and the longer the life of the lining.

Before building the lining with refractory castable, it is necessary to make the casting mold with thin steel plate in advance, and the casting mold needs a certain taper to facilitate smooth pulling out after pouring. A certain thickness of heat insulation layer is set in the interior of the cladding to improve the heat preservation property of the ladle before constructing the cladding with cement castable. During construction, the bottom is covered with castable to the required thickness. After vibrating with a vibrator commonly used in concrete construction, the casting mold is fixed in the cladding. The castable is then filled layer by layer between the insulation layer and the casting mold. At the same time, vibrator is used to vibrate to the envelope, and the casting mold is pulled out in time after the initial solidification of the castable. Finally, the coating surface is coated with graphite powder.

Using low cement or ultra-low cement castable to build the lining is short in construction time, less in physical exertion, and easy to ensure the construction quality. At the same time, the lining can be repaired after partial damage. Therefore, the lining life is long and the consumption of tons of liquid iron refractory is low.

Unshaped Refractory Lining Materials for Cupola

Selection of Amorphous Refractory Castable for Cupola Lining

Cupola is subjected to high temperature and chemical erosion during melting. The melting time of cupola is 6~10 hours, the furnace lining erosion is large, and the furnace condition is unstable.

The corrosive atmosphere of furnace lining has a high requirement on the selection of refractory castable. It is better to use refractory castable with 70%~80% aluminum content in the feeding area and flow channel. Because of the high aluminum content, the high temperature strength and wear resistance and thermal shock performance are good, and the resistance to alternating hot and cold shock is strong.

The main parts of the cupola are hearth, bridge and slag separator. These parts have slag contact, chemical erosion is serious. Refractory castables with high aluminum content, due to the purity of the substrate itself, less impurities, strong resistance to iron wash, and very good oxidation resistance.

When selecting castable material for cupola lining, the slag composition should be considered, because there is a certain proportion of limestone in the burned material. Limestone has an alkaline composition, so the refractory castable used should have the ability to resist alkali erosion. That is, there should be a silicon carbide component in the castable, silicon carbide wear resistance and slag erosion resistance.

If it is alkaline erosion, magnesium or spinel are good choices. If spinel and silicon carbide are added to the castable, then this composite material is the most ideal material. However, silicon carbide and spinel should be added in different proportions according to the different slag composition.

If the top of the furnace lining can also be selected plastic, so easy to construction. Plastic should also consider the composition of ceramic combination, it is best to use phosphoric acid combination of plastic, do not use water glass combination. Because phosphate bonded plastic, strength and high temperature resistance are good. If castable is selected, plastic is still used for daily repair, which can shorten the maintenance time.

It should also be noted that in the furnace production process if the coke does this cupola melting heat source. It is necessary to control the quality of coke to stabilize the use of furnace lining.

In the final analysis, the refractory castable selected for the lining is still a refractory castable with high aluminum content. Because the pure castable has good wear resistance, the castable with silicon carbide or spinel composition has better corrosion resistance.