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Flame straightening
Welding and other manufacturing processes where heat is introduced will leave stresses in the metal during the subsequent cooling, causing distortion or warping. Flame straightening is an efficient and long-established method of correcting the distorted parts.
Flame straightening is based on the physical principle that metals expand when heated and contract when cooled. If expansion is limited, compressive stresses build up and result in plastic deformations if the temperatures are high enough. Upon cooling, the plastic deformations remain.
In practice, an oxy-fuel flame is used to rapidly heat a well defined section of the workpiece. Upon cooling, the metal contracts more than it could expand when heated and any resulting distortions can thus be straightened out. Suitable materials include steel, nickel, copper, brass, aluminium and titanium.
Although various fuel gases can be used, the highest flame temperatures and intensities for rapid heating are achieved with acetylene and oxygen.
The choice of appropriate equipment depends on the type and thickness of material. In principle, thin sheet and plate in thicknesses of up to 15 mm can be straightened with a standard torch available in most workshops. For straightening of large plates, such as decks and deck houses on ships, adjustable attachments with three or more single-flame nozzles are available, mounted on a small wheel car for easy movement across large surfaces. For thicker material use our LINDOFLAMM® special torches. |
