Variety of furnaces
Furnaces are necessary to give steel the desired properties by heating to particular temperatures and profiles thereby determining the grain structure within the metal, and to prepare for further processing such as galvanizing.
In the heating furnace, the cold strip is heated to the highest temperature of the annealing profile. Because of the danger of oxygen contamination and flame length hotspots, the heat is radiated to the strip using ceramic radiant tubes, themselves fired by gas.
The soaking furnace is required to maintain strip temperature and is electrically heated.
The first of the primary cooling sections is the slow cooling chamber, where two variable speed blowers circulate the atmosphere gas through two water-cooled heat exchangers. The second of the primary cooling sections is the fast cooling chamber, where the strip is cooled by a variable speed fan and the cooling length is determined by the positions of three dampers along its vertical length. This chamber is also split vertically for temperature profile control across the width of the strip using a scanning pyrometer.
The overaging chamber provides electrical heating to maintain the strip at an intermediate temperature.
The secondary cooling section cools the strip by variable speed cascaded fans blowing recirculation atmosphere gas cooled by water-cooled heat exchangers.
Final cooling is achieved by spraying and immersion in water.
