Roller hearth furnace LOI Thermprocess

Steel rods and pipes are mainly heat-treated using roller hearth furnaces. The high temperature consistency and low energy consumption of these furnaces, normally gas-fired, ensure reproducible quality and short treatment times. The processes used for heat treating non-alloyed and alloyed carbon steel pipes at temperatures between 450°C and 1050°C include stress relieving, recrystallizing, normalizing, soft annealing and spheroidizing in indirectly fired continuous roller hearth furnaces. For the spheroidizing of pipes made from high-carbon ball bearing steel, vacuum vestibules to completely isolate the furnace atmosphere from the surrounding air are essential, at least at the furnace entry. Vacuum vestibules are also needed at the entry and exit of continuous roller hearth furnaces for the bright solution annealing of high-alloy austenitic pipes. In the heat treatment of copper alloy bars and pipes, zinc, which can be easily oxidized, is the critical element in the alloy. Rapid cooling is essential to ensure that the zinc is kept in solution. This can be achieved using optional high-convection cooling chambers with a hydrogen atmosphere.

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