Transfer and Casting Ladle
In stainless steel melting shops the refractories are most commonly, and in many cases exclusively, exposed to silicate slags. Since the solubility of MgO in silicate slags can be relatively high (up to 17 % at dual saturation), this favours the use of dolomite bricks, as silicate slags in contact with magnesia-carbon refractories will require significant additions of MgO. The solubility of MgO in silicate slags also increases rapidly with decreasing basicity (from 17 % up to 30 %). In the transfer ladle this is likely to be significant, since the basicity of the carryover slag from the furnace is often relatively low.
Lining design
Proper refractory selection is critical since different areas of the ladle are subjected to different wear mechanisms.
Slag Line
- Transfer ladles: linings often comprise carbon-bonded dolomite throughout (i.e. barrel and slagline) since the ladle is not used for any major steel-refining activities, although some plants prefer to install fired doloma slaglines, when carbon pick-up is a concern.
- Casting ladles: the most common slagline refractories used are fired doloma or magnesia-carbon. The refractory should match the type of slag (predominately) encountered.
Typically, dolomite refractories are selected for silicate slags (Si-killed steels) and magnesia-carbon for aluminate slags (aluminium-killed steels). On casting ladles lined with dolomite barrel bricks it is common to undertake a mid-campaign repair of the slagline because of the exceptionally low wear rates of the refractory barrel.
Barrel/Sidewalls
- Casting and transfer ladles: in Si-killed steel operation with good slags and good thermal discipline, carbon-bonded dolomite refractories cannot be matched in terms of performance and cost. The slags normally form a coating on the dolomite brick while in service which effectively becomes the working lining.
Typically, only 20–35 % of the doloma barrel bricks is consumed after an extended ladle campaign, hence the widespread use of doloma in all types of ladles used in the making of stainless steel.
Floor
An impact panel is typically installed in the floor (and adjoining section of the lower sidewall) constructed from longer bricks. Either carbon-bonded dolomite or AMC bricks can be used in the impact panel as both exhibit high strength. The brick quality surrounding the impact panel, i.e. in the remainder of the floor, usually matches the quality used in the barrel.
