The tubes are heated to a temperature above the transformation range in the austenitizing furnace. This allows hardening or normalization to be carried out. Hardening occurs when the austenitized tube is rapidly cooled in an external water quench. The as-quenched tube has a particular hardness and microstructure. It is now ready for subsequent tempering. The hardened tube is heated in a tempering furnace, held at a specific temperature for a set period of time and air-cooled. This treatment establishes mechanical properties of the tube and is commonly referred to as "hardening and tempering" or "quenching and tempering".
Normalization occurs when the austenized tube is allowed to cool at ambient temperatures in still air. In such cases, the mechanical properties are dictated by the chemical properties of the steel.
|type||Two - Zone walking beam furnance 96 pipes|
|heating||natural gas, combustion air preheated via recuperator|
|load per surface unit||max. 200 kg/m³ (0,3 psi)|
|outside diameter range||40 -200 mm (1.575 - 7.874 inch)|
|length restrictions||max. length 12.800 mm (42 ft)|
|process control||zone temperatures pipe exit temperature|