Roller Hearth Furnace for Stainless Steel Tubes and Bars

Bright annealing combined with solution annealing is the most important heat treatment procedure for stainless steel tubes in roller hearth furnaces.

The heat treatment usually takes place at temperatures of max. 1.250 °C. To achieve the bright annealing effect, an atmosphere of 100 % hydrogen is used as reaction gas during the heat treatment.

Moreover, the furnaces are suitable for 

• stress relieving annealing,
• recrystallization annealing,
• normalizing, and 
• soft annealing.

During the annealing of stainless steel, hydrogen mostly is the active or reactive component of the process gas. Nitrogen, in special cases argon or helium, is used for the furnace purging and forming. The selected instrumentation and used purging gases ensure a furnace operation at the highest safety level. A sophisticated safety logic guarantees safety for the personnel, machines and material at all times of operation.

Since a rapid material cooling is crucial for stainless steel, our furnaces distinguish themselves with a particularly short design of the physical separation between the heating and cooling zone. Due to jet coolers immediately downstream the furnace chamber, we achieve temperature gradients of more than 5 K/second at the latest in the range of 900 to 400 °C. Moreover, the recirculation fan speed can have an impact on the cooling gradient.

LOI’s roller hearth furnaces also suit duplex and super duplex steels that require a precisely adapted atmosphere. In our furnaces, the proper setting of the dew point avoids the individual annealing materials "sticking" together“.

In LOI’s roller hearth furnaces for stainless steel, currently up to two t/h of annealing good with a component length of max. 38 m are heat-treated in top quality. Leading manufacturers of stainless steel pipes apply our furnace plant technology throughout the world.

We design furnaces for longer products or higher throughput according to our customers’ requirements.