Carbon lining stands as the preferred material for most ferroalloy linings. However, with the continuous escalation in the capacity of submerged arc furnaces, the premature failure of the lining has emerged as a significant and persistent issue. This technology introduces a relatively straightforward method to address a long-standing problem that has plagued the industry.
Currently, there are three primary methods employed for constructing carbon furnace linings: the carbon brick seamless method, the carbon brick wide seam method, and the cold ramming and paste integral ramming method.
Each of these methods presents its own set of drawbacks and limitations. The carbon brick seamless method, despite its name, fails to achieve true seamlessness. Molten iron can infiltrate the base of the carbon bricks along the cracks, causing the bricks to float and ultimately leading to the entire lining being scrapped. The carbon brick wide seam method involves shaping the sides of the carbon bricks into ring-shaped grooves, leaving a gap of approximately 50mm during furnace construction, which is then filled with cold ramming material. However, the structure of the wide seam section is relatively loose compared to the dense structure of carbon bricks formed under high pressure by a press, making it susceptible to early erosion by hot metal. Consequently, the molten iron rapidly reaches the bottom of the carbon bricks, causing them to float and resulting in failure. The cold ramming and paste ramming method, due to the loose lining structure it forms, exhibits inferior performance compared to carbon bricks and has a very short service life.
After extensive exploration and research, the author has ingeniously combined the advantages of these three furnace construction methods, leveraging the hot-melt property of carbon paste—remaining solid at room temperature, melting at high temperatures, fusing, and ultimately becoming graphitized. This led to the invention of a furnace construction method aimed at preventing early lining failure, thereby extending the lining's lifespan and overcoming long-standing industry challenges. This method has been granted national utility model patent authorization.
This innovative approach is based on the seamless method of carbon bricks but incorporates special treatment for the weak part of the furnace lining—brick joints. Brick seams are categorized into vertical seams and flat seams, each receiving distinct treatment.
The vertical seam treatment involves cutting two inverted dovetail seal grooves around the carbon bricks, which are then filled with a special low-expansion coarse seam paste. This transforms the carbon bricks into a composite structure consisting of a pre-baked matrix and a self-baked paste, forming an endless belt of material.
After constructing the submerged arc furnace lining using the seamless masonry method, the electric furnace is put into operation. As the temperature rises, the self-baking paste preinstalled in the inverted dovetail grooves of the carbon bricks melts, fuses, roasts, and solidifies, sealing the vertical seams of adjacent carbon bricks together. This is analogous to a sealing ring in a mechanical part, preventing the penetration of molten iron. Since the paste is embedded within the carbon brick, it is not washed away by the molten iron, and the loose structure formed by the paste can still meet actual needs. The connection diagram between the self-baking carbon calcined body and the carbon brick is illustrated in the relevant figure.
The general furnace lining design consists of three layers of carbon bricks, resulting in two flat seams. The arrangement of each layer of carbon bricks is staggered by 45° from the layer below. Inverted dovetail grooves, wider and shallower than the side grooves, are processed on the joint surfaces of the upper and lower carbon bricks. These grooves, along with the side grooves, are filled with self-baking paste, tamped, and ground.
After masonry completion and the electric furnace is put into production, these flat grooves form a flat prismatic mesh. The intersections of the upper and lower grooves fuse together, joining the upper and lower layers of carbon bricks through this prismatic mesh. In the future, even if molten iron penetrates to the bottom of the carbon brick, it will not cause the brick to float. The three-dimensional view of the self-baked paste after sintering is shown in Figure 2, and the three-dimensional schematic diagram of the upper and lower carbon bricks is depicted in the relevant figure.
Through distinct treatments for vertical and flat seams, the carbon bricks used to form the furnace lining, including wall bricks and tap hole bricks, are tightly connected into a cohesive whole, effectively preventing iron penetration and perfectly resolving the industry's problem.
This method is remarkably simple to implement and highly effective, deserving attention and adoption by industry colleagues. I believe that the promotion and application of this method will significantly extend the lifespan of furnace linings, substantially reduce production costs, and elevate lining technology to a new level.
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