PROBLEM TO BE SOLVED: To restrain the surface oxidation of a steel slab as much as possible and to make a perfect combustion of unburning gas produced in a furnace, in the case of heating the steel slab by applying a continuous multi-zone type heating system. ;SOLUTION: When a steel slab is heated to a target temp. by continuously passing it through plural space zones, in the space zone 1 at a temp. of ≥600°C, the air ratio in burners 4 for heating is adjusted into the range of 0.2-1.2 and also, this zone is adjusted to reducing atmosphere, and in the space zone 2, in which the temp. is lower than that in the above zone and the unburning gas remains, a high temp. air of ≥1000°C is blown.;COPYRIGHT: (C)2000,JPO
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