PURPOSE: To easily attain a dew point below -40°C for inhibiting the decarburization, in annealing a hot-rolled steel piece in an atmosphere of N2 inside the titled atmospheric oven for annealing a hot-rolled steel piece, by coating the surface of a refractory material inside the oven with a metal plate, and providing an exhaust hole at the shell of an outer wall.
CONSTITUTION: Taking into consideration the thermal expansions of a refractory material 3 and a metal plate 4 so as to cover the entire surface 10 of an in-oven refractory material inside the atmospheric oven in a predetermined space, said metal plate 4 is supported by spot welding it with a stud bolt welded to the shell 2 of an outer wall at the ceiling part. The side wall is constituted into a suspended state fixed to a stud bolt at its upper part, while the lower part is constituted into the state that the plate 4 is mounted through a predetermined spacer onto the surface of the refractory material. Although the interior 13 of the oven and the surface 10 are not completely seale from each other by the plate 4, N2 gas is introduced through an agitation fan 5, a radiant tube 6 and the part of a carrier roller 9 into a space between the refractory material 3 and the plate 4 and then withdrawn through an exhaust opening 8 equipped with a valve 11 for regulating the amount of exhaust gas. Hence, a dew point inside the oven can be stably maintained below -40°C, and the ability of annealing, a time for seasoning, etc. can be remarkably improved.
ISHIBASHI YASUSHI
IWASA MASARU
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