Effect of Heat Treatment Method in Minimizing the Residual Stress Level in Cold Drawn Welded Tubes (Cdw/Dom)
Abstract:
Conventionally cold drawn welded tubes are stress relieved in a roller hearth furnace. In this study, induction stress relieving is compared with the conventional method for plain carbon steels. Technical comparison between the two methods is conducted by mechanical properties measurement and residual stress analysis by X-ray diffraction method.
Introduction:
Residual stress is a macroscopic stress that is set up within a metal during non-uniform plastic deformation, as in cold drawing or thermal gradients, as in quenching or welding. Up to 45% area reduction is employed in the manufacturing process of CDW tubes resulting in residual stresses in the tube. These can be tensile or compressive based on the type of cold work. Residual stress can affect the fatigue strength and fracture toughness of the material and can cause stress corrosion cracking and dimensional instability during further machining, welding and forming operations. Hence minimizing the unfavorable residual stress is an important process requirement for tubes involving critical applications. Residual stress is usually relieved by Stress Relieve Annealing (SRA), a low temperature annealing (350oC-600oC) in a roller hearth furnace.
Induction Heating System and Continuous Roller Hearth Furnace
Induction heating is a non-contact heating process, in which intense electromagnetic field generated by an AC current is used to heat the job. The shorter and higher temperature cycle in Induction heating yields the same mechanical properties as obtained in a conventional roller furnace where the tempering cycle time is higher. The high frequency induced generates skin effect, which ensures that the current will flow in a thin layer in the surface of the work-piece. This increases the effective resistance of the metal and enhances the heating effect.
In a continuous roller hearth furnace, CDW tubes are annealed, normalized, stress relieved or tempered with a protective
Conventionally cold drawn welded tubes are stress relieved in a roller hearth furnace. In this study, induction stress relieving is compared with the conventional method for plain carbon steels. Technical comparison between the two methods is conducted by mechanical properties measurement and residual stress analysis by X-ray diffraction method.
Introduction:
Residual stress is a macroscopic stress that is set up within a metal during non-uniform plastic deformation, as in cold drawing or thermal gradients, as in quenching or welding. Up to 45% area reduction is employed in the manufacturing process of CDW tubes resulting in residual stresses in the tube. These can be tensile or compressive based on the type of cold work. Residual stress can affect the fatigue strength and fracture toughness of the material and can cause stress corrosion cracking and dimensional instability during further machining, welding and forming operations. Hence minimizing the unfavorable residual stress is an important process requirement for tubes involving critical applications. Residual stress is usually relieved by Stress Relieve Annealing (SRA), a low temperature annealing (350oC-600oC) in a roller hearth furnace.
Induction Heating System and Continuous Roller Hearth Furnace
Induction heating is a non-contact heating process, in which intense electromagnetic field generated by an AC current is used to heat the job. The shorter and higher temperature cycle in Induction heating yields the same mechanical properties as obtained in a conventional roller furnace where the tempering cycle time is higher. The high frequency induced generates skin effect, which ensures that the current will flow in a thin layer in the surface of the work-piece. This increases the effective resistance of the metal and enhances the heating effect.
In a continuous roller hearth furnace, CDW tubes are annealed, normalized, stress relieved or tempered with a protective