Refractory plastic is a refractory material prepared from 70%~80% granular and powdery materials, 10%~25% plastic clay and other binders, and an appropriate amount of plasticizer. It is mainly used in various heating furnaces that are not in direct contact with the molten material. The materials are mostly clay and high alumina, and there are also silicon, magnesium, chromium, zircon and silicon carbide, etc.; it is also used in steel The lining body of various heating furnaces, soaking furnaces, annealing furnaces, sintering furnaces and electric furnace roofs in the industry.
Refractory plastic is in the form of hard mud paste, and maintains high plasticity for a long time, contains more plastic clay components, and has more moisture than ramming material. It has good plasticity before hardening; it has certain strength after hardening. It has good sinterability, certain volume stability and other high temperature properties at high temperature. It can be made into flakes and blocks. Certain binders can also be added during construction. When used, the mixture is compacted or pounded, and after baking, it can form a dense inner lining and structure.
As one of the main categories of unshaped refractories, refractory plastics are widely used in the iron and steel industry due to their high plasticity, good thermal shock resistance, hard sintering strength, no need to add water during construction, and immediate demoulding. be widely used. Because plastic refractory materials are mostly used in heating furnaces. After the refractory material is damaged, if it is not repaired and maintained in time, it will further deteriorate, and in severe cases, production will be affected. The gunning method can effectively solve the above problems. The following describes the 5-step construction steps for repairing and maintaining refractory plastics after damage:
1. Remove the damaged part
Completely remove the plastic that has caused problems, including the inner lining, anchor bricks, and anchors. If the furnace skin is severely oxidized or deformed, it also needs to be cut off.
2. Re-weld the anchor
Before welding the anchors, the original furnace skin lining is firstly polished to remove the refractory material residue on the inner surface of the furnace skin to ensure the sealing of the new refractory lining and the furnace skin. In addition, the repaired parts can be compared with the original furnace skin according to the actual situation Design the number and manner of placement of appropriate encryption anchors.
3. Lay the backing layer
The main function of the backing layer is to insulate heat and reduce heat loss. Fiberboards and lightweight refractory bricks with low thermal conductivity are usually used. This link requires: first, to ensure the sealing of the backing layer and the contact parts of the furnace skin and anchor bricks The second is that the layer of the backing layer closest to the furnace cavity should be coated with a layer of light castable to ensure the spraying effect.
4. Spraying
Spraying can be started after the required tools and machines are ready. The personnel are divided into two batches. The first batch is feeding materials. This batch is mainly to feed the blowing machine outside the furnace and operate the blowing machine. Control the size of the damper to obtain the ideal blowing Effect; the second batch is spraying, which is mainly for the operation layer in the furnace, and the hand-held spray gun controls the appropriate angle and spraying speed to obtain better spraying effect.
It should be noted that during the spraying process, it is necessary to constantly correct the sprayed surface, scrape off the floating material on the surface, and at the same time trim the desired shape and angle, and cut out the reserved expansion seam and shave it, otherwise it will be slightly air-dried The rear surface will be hard and difficult to apply.
5. Heating, baking and sintering
This link is mainly based on the performance of the refractory material and adopts a suitable heating curve to bake and sinter the refractory material to finally meet the use requirements.