In many areas within the melting department, molten metal will come in contact with refractory material. It is important to pay attention to this, as a number of defects and inclusion occur when refractory material is eroded or surface reactions occur.
The use of carbon based blackings can effectively protect the refractory from attack by the molten metal. Blackings are usually applied to a hot surface, by brushing or spraying. They harden completely, and build a stable and abrasion resistant protective layer on different surfaces.
This layer protects i.e. the refractory lining/furnace border area against adhesions of melt and protects pouring lips and troughs.
Special carbons are the main filler of blackings. Other additives are used to improve the workability are included. Therefore it is important that the mixing instructions are followed, to prevent any loss on performance.
For instance: It is essential to pre mix the Carboform/Carboform ZD in to a paste, the material should be allowed to stand for 24hrs before use to allow the product to reach full performance. This step is time consuming but will greatly improve the performance of the coating.
Also concerning the casting of rolls, blackings are used (eg No.15 Chillroll Blacking), to facilitate removal of the casting from the metallic permanent mould after the casting process.