to resolve the problem of metal pen- etration. Te melt department would go for weeks and see no penetration, but it then would reappear. Frustrated after several years of try-
Fig. 3-4. An example of a scaler (left) and chipping hammer are shown.
the mechanical deterioration of the furnace bottoms resulted from the daily drainings and the impact of the cold charges. Sharp’s Greg Payleit- ner recommended a different bot- tom material to better handle cold charges, which eliminated the need for premature relines.
Two Furnaces, One Big Problem
Te final challenge for Motor Castings also was the most signifi- cant. Every time employees knocked out either furnace, a significant amount of metal was stuck to the brick behind the lining (Fig. 2). Management began reviewing the weekend repair work, because pen- etration was in the general area of the weekend repairs. Employees used a chipping hammer to remove the slag from refractory, which was concern- ing because the refractory material also could have been chipped away. In addition, cracks may have been created that would not seal during the sinter cycle. To remedy the problem, melt
department employees began using scalers instead of chipping ham- mers to remove the slag (Figs. 3-4). Employees were instructed to chip downward on the slag and not inward toward the coil. After these changes, however, the penetration remained present.
Motor Castings solic-
ited technical support from Sharp Refractories representatives and other individuals familiar with similar lining issues. Several suggestions came from those discussions: 1. Conduct daily spout
maintenance. 2. Look into differ- Fig. 5. A chipped out furnace spout is shown.
ent material as a top cap. (A low sintering alumina material was used because of the difficulty in getting sufficient heat to the top of the linings during sintering.)
3. Change top cap procedures. 4. Review sinter cycle. Te Motor Castings team believed the spouts were maintained appro- priately because the furnaces were drained daily so the spout could be repaired. However, they were open to other material options. Te Motor Castings team adjusted the sinter cycle to ensure a high level of molten iron and instructed operators to turn off dust collection during sintering to generate as much heat as pos- sible around the top of the furnace to ensure proper sintering. Motor Castings also experimented with different top cap material, including silica, alumina and aluminum cast- able. Although a number of different materials were tried, the melt depart- ment determined this was not the source of the problem. Te team continued to monitor the
operation and stayed in contact with suppliers. However, it could not seem
ing different things, the Motor Casting team again met with Sharp Refractories. During the changes to the installations and weekend repair practices, Motor Castings went from relying on its installer for repairs, bricking, grouting and lining installation to doing such operations itself. Te company, however, needed help to resolve the problem and asked the installer to take a second look. Sharp Refractories’ Payleitner first
reviewed how Motor Castings handled weekend repairs. One weekend, after cleaning slag from around the furnace, the installer’s crew began removing lining material underneath the spout, assuming it was the root of the prob- lem. (See Fig. 5.) As with previous cases, metal was
found behind the lining. Te supplier determined metal penetration occurred at the seam between the spout and the lining. With Payleitner’s help, the company began changing procedures for installing new linings and week- end repairs. Te Motor Castings team tried to seal between the lining and the spout with refractory paper or a brick in that location during lining installation. It added more silica in the spout and added mica paper between the brick and the lining material to prevent metal penetration. Still, these repairs led to similarly inconsistent metal penetration. Finally, during
weekend repairs, observers took a closer look at the lining and spout separation. A technical expert deter- mined that a mono- lithic plane needed to be established from the tip of the spout into the furnace. Te company wanted to eliminate the seam’s visibility between the spout and lining. After the first tap of a new lining, the furnace
August 2014 MODERN CASTING | 33
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