Refractorie mixes and mortas

Descriptions

♦ According to application method

• Castable mixes for patching and trowelling
• Castable mixes applied by vibration
• Self-levelling castable mixes

♦ According to binder system

Raw Materials

♦Metacast-K95, -K97, -K97af

♦Metacast-K95/MA, -K97/MA, -K97/MAc

• Based on tabular alumina and MA-spinel, 92-97% Al₂O₃
• Suitable for application areas with molten steel contact
• Hot/cold all kinds of repairs
• Low porosity, high strength properties

♦Metacast-B80, -B82, -B82st, -B86c

• Based on high quality bauxite, 80-85% Al₂O₃
• Tundish permanent lining and high temperature furnance areas
• Metacast-B82st includes stainless steel fibers (10-20 kg/m³)

Low Cement

Castable Mixes

♦Low CaO value due to decrease in cement ratio (1.5%>CaO>1.0%)

♦Decrease in water demand for mixing

♦Castable mixed with water remains workable for a longer period

♦Initial setting of castable starts at temperatures over 15°C

♦High strength properties remain the same till working temperatures

♦Well designed particle size distribution, low porosity and high strength due to less CaO and water content

♦Application areas:

• Steel ladle working lining areas
• Tundish permanent lining
• Blast furnance runner
• Linings of reheating furnances

Application

(1) Storing of raw materials

Castable mixes are packed dry in humidity-proof bags of 25kg or 50kg. Shelf-life is approximately 6 months under dry and rost-proof conditions of storing. The best way to store castables is in a ventilated,closed area with room tenperature of approximately 20°C. Unproper storing conditions detoriate performance of castable mix at application area.

(2) Mixing

The castable is preferably mixed in an intensive mixer. Horizontal pan type, with pallets and preferably agitators give best results in mixing. Considering a possible segregation of the grains, mixing should start dry. The whole content of the castable bag is to be poured into the mixer. Only the quantity of castable to be applied at given period should be mixed with water. Minimum and maximum water quantity to be added is mentioned in using instructions.

Water demand and consistency

Water quality for mixing should be drinkable, clear, no odor, co color. Mud, sugar, grease and particles should not be present in water. Ph value for water should be between 7,0-7,5 and never less than 7,0. Hardness should be over 2.0°d. Water temperature of 15-20°C improves consistency and casting properties. Mixing should start with the lowest water addition ratio. Depending on consistency of the castable, water content can be increased till to upper limit value. In order to determine consistency some castable is shaped as a ball in hand. Mixing time is mentioned in using instructions. If mixing time is hold short, a good mixing is not achieved. If mixing is longer than required than the castable may get warm and set early.

(3) casting into mould under vibration

• Castable mixes are shaped in stationary steel or wooden templates or moulds. Mould surface shoud
  be greased before application.

• Immediately after casting the mix it is compacted by vibration with use of external or submerged shakers.

• Submerged vibrators compact the castable by quickly inserting in the castable and slow withdrawal movement.
  In case if the vibrator is withdrawn quickly there may occur gaps in the castable and if it is held for a long time
  than twister may occur.

• Vibrators are driven with electricity or compressed air.

• Choice of vibration frequency may influence coarse/fine grain segregation in the castable. Increasing frequency
  may prevent fine grains moving towards mould surfaces.

Vibration equipment

Submerged vibrators	Exrernal vibrators
Compressed air type external vibrators	Quick connection parts for external vibrators

(4)  Setting of castable and demoulding

Binding time of dense castable mixes is around  2-3 hours depending on environmental conditions, water added and type of raw material. Depending on wall thickness, room temperature and material type, it is possible to remove template or mould after 6 to 12 hours. In contructions like roof this period should at least be doubled. After demoulding the material should be airdried at least for 24 hours. Lining to be cast can be structurally strengthened by suitable anchors. They should be placed with a disance of approximately 30cm to each other and the length to be 2/3 of the lining thickness. Generally, Y-shape anchors are prefered.

(5) Drying

• Water in refractory lining may be present in following states;

• Drying by heat generally consist of two steps;

• Drying curve to e applied is given in using instructions of castable mix.

• Rapid drying may cause explotion due to sudden increase in steam pressure inside the materials.

• Special additives in dense castables for thick linings may help easier escape of water and risk
  of explosion in reduced.

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