| 摘要 |
PURPOSE:To prevent the deformation, etc., of nozzles owing to the thermal stress thereof by changing the combustion rate of radiant tubes and changing at the same time the gas flow rate from the nozzle prior to the change of a strip thickness. CONSTITUTION:The fuel supply rate from the combustion burners of the radiant tubes 4 is decreased before the stage of changing conditions in the stage of decreasing a heating rate when the thickness of the strip 1 decreases. On the other hand, the supply of a high temp. gas to a pebble heater 11 is stopped and gaseous NH is supplied from the bottom of the heater 11. The gaseous NH is increased in temp. by contacting with pebbles 10 up to the max. temp. in a short period and such high-temp.l gas is supplied to a plenum chamber 2. The gas heater to the high temp. is supplied gradually by as much as the quantity corresponding to the quantity of heat deficient for heating. As a result, the thermal deformation and breakdown of gas jet nozzles 3 by the effect of high temp. are prevented.
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