Preamble

In steelmaking, refractory materials are used in converter, electric furnace, ladle, tundish, and reheating furnaces. In converter, electric furnace, ladle and tundish, molten steel is in contact with slag, whereas in reheating furnaces steel in the solid form is reheated for deformation processing, heat treatment and surface hardening methods.

BOF Refractories

Converter is lined with a permanent lining and above it there is a wear lining. Permanent lining thickness may vary from 100mm to 120mm and is made of chrome-magnesite permanent lining which is given on the full height of the converter.

Above the permanent lining, wear lining is constructed. The cylindrical portion of the converter (barrel) is lined with the ramming mass of tar dolomite and tar dolomite bricks. The detachable bottom is constructed by using mica, fireclay, chrome-magnesite and Mag-chrome bricks.

 refractory materials with 15% high purity graphite have been found to provide increased corrosion resistance.

In duplex blowing (hybrid blowing or combined blowing)  bricks are commonly employed for the bottom tuyeres and around them, since these areas severely worn.

The slag and metal penetration between the refractory grains, chemical attack by slag, mechanical erosion by molten steel movement contribute to the wear of the lining materials.
Some developments to counteract this lining wear are

              i)    Dolomite   is added to create a slag of about  which is close to                      saturation level of slag.

             ii)   Critical wear zones (impact and top pads, slag tapping and trunion areas) are lined in                     furnaces with high quality bricks.

            iii)   Slag splashing in which the residual slag is splashed by high speed  has resulted into                     high lining life (refer lecture 14)

           iv)   Lowering  levels in slag and shorter oxygen-off to charge intervals have reduced                    refractory wear.