November 11th, 2022

...to withstand corrosion by the slag and flame impingement from O2 lances and oxy-fuel burners. Mag-C bricks having C content of 5 % to 20 % are suitable for the lining of the upper side wall. Various qualities and purities of magnesite, graphite and metal powders are used. In the AC EAF, which has hot spots in the upper side wall, bricks of higher quality are needed. These higher quality bricks are to be based on fused magnesia grains compared to the sintered magnesia grains used for the standard quality bricks. The fused magnesia bricks have improved high temperature resistance but they cost considerably higher.

Taphole refractories – Taphole refractories are needed for both the side tapping EAFs and the bottom tapping EAFs. Operating conditions in both these types of the furnaces are similar consisting of flowing at high velocity of liquid steel and to a lesser extent liquid slag through a 125 mm to 200 mm diameter taphole. High velocity flow erodes the taphole refractories. In the side tapping furnace, the taphole refractories have many alternative designs. The alternative having the simplest design consists of leaving an opening in the side wall while installing the initial lining and when the brickwork is completed, either a refractory taphole sleeve or a steel pipe is positioned in the taphole opening. Then the MgO based guniting mix is used to fill in the voids between the sleeve or pipe and the adjacent brickwork. The second alternative consists of using a large taphole assembly with a pre-formed taphole. This assembly is set in place in the EAF prior to the laying of the side wall brickwork. Once the taphole assembly is properly positioned,, the adjacent brickwork is completed, creating a tight fit between the taphole assembly and the side wall brickwork.

Taphole refractories need to be of high quality. If the taphole is made with guniting mix sprayed around the steel pipe mandrel, the guniting mix is of the highest quality. The guniting mix is to have maximum strength and erosion resistance for minimizing the erosive action of the flowing liquid steel. In case of the taphole assembly where a refractory sleeve is used, the sleeve is also to be of high quality MgO brick with C and metal powders. Metallic additions to Mag-C taphole brick assemblies provide added strength and oxidation resistance to the brick in this critical application.

The side tapping furnace has a spout extending from the taphole to enable the liquid steel to flow into the ladle. The spout is a precast monolithic runner shape placed in the runner steel shell during the process of the lining. The precast runner shape is made of MgO based castable if furnace operating practices result in slag entering the taphole and the furnace runner. The slag resistance of the MgO is needed for counteracting the slag attack. On the other hand, ... (To be followed)

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