When recycling scrap metal and when fixing broken metallic parts, technicians and fabricators sometimes need to straighten out metal. Various mechanical forces can straighten the metal back into the proper shape. To make the metal-straightening process easier, fabricators often apply heat. However, too much heat can damage the metal.
Fabricators straighten metal using many methods, including heat straightening. Heat straightening involves applying controlled heat to a deformed part of steel in heating and cooling cycles until the metal gradually straightens. Heat straightening does not symmetrically straighten the metal and is a gradual process. The fabricator does not heat this metal to the point where the metal undergoes molecular changes. In addition, the stresses added to this metal do not surpass the yield stress of the metal in the heated condition, which is the point at which the metal deforms into an undesirable shape. The fabricators do not heat the metal in any location other than that which is being shaped. Welding torches are common sources of heat for heat straightening.
Hot Mechanical Straightening
Hot mechanical straightening is similar to heat straightening, but it straightens the metal beyond the yield stress. This will straighten the metal very quickly, but can lead to unpredictable results, including fractures, changes in material properties, cramps, buckles and wrinkles. The metal may become damaged or degraded.
Hot working is like hot mechanical straightening, except the fabricator heats the metal to the point where the metal might undergo molecular changes. The metal will glow cherry red. This method of metal straightening is even faster, but also more unpredictable. It can cause fractures, changes in molecular structure, increased brittleness, cramps, buckles and wrinkles.
Fabricators use hand-screw presses and hydraulic presses to straighten bent sections and to remove dents from metal sheets. Hand screw presses are devices that drive a ram into the bent metal through force generated by a screw. The screw press has weights attached to the handle that helps the press maintain momentum during operation.
Fabricators heat metal so it does not have as much tension when the fabricator uses force to straighten out the metal. Fabricators generally use locksmith hammers, light metal hammers, mallets, streaming hammers and rubber hammers to straighten the metal. They place the metal on either an anvil or a straightening plate. Other tools used to straighten metal include tongs, vices and clamps, which hold the metal in place so the fabricator can move a part of the metal until it straightens.
When straightening pipes, fabricators sometimes fill the pipes with fine-grained sand and close the ends of the pipes. Then the fabricators heat the pipe and straighten it. The fine-grained sand prevents the pipe section from developing more deformations.