CONTINUOUS HEAT TREATING FURNACE AND ATMOSPHERE CONTROL METHOD AND COOLING METHOD IN CONTINUOUS HEAT TREATING FURNACE

摘要

A continuous heat treating furnace comprising a quenching zone (11) constituting one of a plurality of furnace zones excluding the first and the last zones and adapted to quench materials by blowing an atmospheric gas and, as atmospheric gas sealing means, a roll seal room (3) disposed at an entrance and partitioned by first and second roll seal devices (4A, 4B) arranged in that order from the upstream side and a third roll seal device (4C) disposed at an exit, wherein the entrance of the first roll seal device is connected to the exit of the third roll seal device and/or roll seal rooms are connected to the upstream-most portion (6) of the quenching zone, an in-furnace hydrogen concentration being controlled to not lower than 10 % in the quenching zone and to not higher than 10 % in zones on the entry side of the quenching zone. The above design can provide a continuous heat treating furnace that can prevent by a simple means mixing of an atmospheric gas in the quenching zone using a gas jet cooling system with an atmospheric gas in zones adjacent to the quenching zone (heating zones and cooling zones), and an in-furnace atmospheric gas control method that can prevent nitriding.