Process of reducing the consumption of protective gas and the edge oxidation of structural members to be treated in sluice pusher plants with combustible protective gas

摘要

A process is described for reducing the consumption of protective gas and the edge oxidation of structural members to be treated in sluice pusher plants with combustible protective gas. The sluices are now no longer constantly flushed by an excess of protective gas fed into the furnace but the amount of protective gas fed into the furnace is reduced to the amount necessary in order to cover the leakage losses and obtain a minimum pressure of 0.5 mbar gauge, and the sluices are flushed merely during the opening cycle up to 5 to 10 seconds after the closing of the outer sluice doors by a stream of nitrogen which corresponds to 1 to 2.5 times the stream of protective gas. By the flushing with nitrogen, smaller variations of the carbon potential established in the furnace are obtained as well as a reduction in the edge oxidation or edge decarburisation as a result of the avoidance of stronger vacuum phases in the furnace. The total gas consumption of the plant decreases.