Patent ID: 8075836

Claim:
Steel-sheet continuous annealing equipment capable of annealing to produce at least mild steel, high-tensile steel and ultrahigh-tensile steel, comprising, in sequence, a plurality of enclosures defining a pre-heating zone, a heating zone, a soaking zone, a cooling zone, a reheating zone, an overaging zone, and a final cooling zone, wherein said pre-heating zone, heating zone, soaking zone, cooling zone, reheating zone, overaging zone, and final cooling zone are capable of temperatures for annealing sheet steel to produce at least mild steel and high-tensile steel, and further comprising a rapid heating region and a rapid cooling region provided in said plurality of enclosures within a range from the reheating zone to the final cooling zone, wherein for annealing to produce ultrahigh-tensile steel, the rapid heating region provides selective rapid heating of a steel sheet at a heating rate of 15° C./s or more and the rapid cooling region provides selective rapid cooling, at a cooling rate of 10° C./s or more, of the steel sheet that has been rapidly heated in the rapid heating region, wherein for providing selective rapid heating, the rapid heating region includes a plurality of heating units whose heating capabilities are independently controllable, and wherein for providing selective rapid cooling, the rapid cooling region includes a plurality of cooling units whose cooling capabilities are independently controllable.