The six-stand hot mill complex at the Severstal Columbus mill includes a tunnel furnace that connects
the hot mill to the continuous caster. The in-line tunnel reheat/equalizing furnace has a heating
capacity of 338 tons/hour. The furnace has a recuperative-type roller hearth design with an internal
width of 84.5 inches that accommodates the 40- to 74-inch-wide, 98- to 183-foot-long thin-slab sections.
With an overall length of 855 feet, the furnace consists of a 670-foot stationary furnace, plus a 185-foot shifter car unit.
The individually-driven furnace transfer rollers are internally water-cooled and use heat-resistant alloy metal tires to support the slab as it travels through the furnace. The tires are separated by refractory. With a total heating capacity of approximately 160 million BTU/hour, the furnace has five heating zones and two holding zones. A total of 164 recuperative-type low-NOx burners are located on the upper side of the furnace.
Fired by natural gas, the furnace is designed to heat slabs from approximately 1,000 to 2,000°F for rolling on the direct coupled hot strip mill. Maximum slab delivery speed is 98 feet/minute. Foundations have already been built for a second 670-foot-long stationary tunnel furnace that will feed into the existing shifter car unit.
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