Industrial heat treating furnace that uses a protective gas

An industrial furnace into which a protective gas is admitted for the heat treatment of batches of metal workpieces, comprising:

• a) a heat treatment chamber that is dimensioned to hold a plurality of batches of metal workpieces, said heat treatment chamber having an entrance end and an exit end;
• b) an entrance air lock connected to the entrance end of said heat treatment chamber for receiving one of the batches of metal workpieces from outside the industrial furnace, said entrance air lock having a first gas-tight door located for sealing the interior of said entrance air lock from an environment surrounding the industrial furnace, and
• c) a third gas-tight door disposed at the exit end of said heat treatment chamber,
• whereby a pressure of the protective gas admitted into the heat treatment chamber can be maintained during loading and unloading of each of the batches of metal workpieces;
• said industrial furnace further comprising:
• a gas supply connection disposed in a wall of the heat treatment chamber for admitting the protective gas to said heat treatment chamber and to said entrance air lock;
• a used-gas conveying line connected to said entrance air lock for conveying used protective gas from said entrance air lock;
• and
• a protective gas extraction system connected to said entrance air lock for removing protective gas from the entrance air lock and transferring the protective gas, wherein said protective gas extraction system includes a programmable controller that is programmed with a heat treatment program having a process step of protective gas extraction for the downstream use of the protective gas or for reuse in the industrial furnace itself.