AWS C4.4/C4.4M PDF

This publication describes some causes of distortion and corrective actions through the use of heat. It also describes some heat shaping techniques and the direction of movement expected in the heated metal. Equations are provided to aid in estimating the amount of movement for a given heating technique. The methods discussed are specifically applicable to ferrous metals, but many of the methods can be applied to nonferrous metals as well. For a more comprehensive description of specific applications, see the attached supplementary reading list.

Heat has been used to shape and straighten structural elements in bridges, buildings and marine constructions for over a hundred years. Since the late 1930s, the use of oxyfuel gas torches to do this work has become more and more prevalent. This publication is a recommended practice for using the torch process for work on bridges and buildings, and to some extent shipbuilding.

Mechanical forces in fabrication and erection, forces occurring in service, accidental impacts from external forces, fire, and explosion, all cause stress in a structural member or a part of a member. If that stress exceeds the elastic limit of the material, distortion will occur, and the member will not conform to its desired shape. Heat shaping and straightening is an economical method to produce the desired movement to bring the member into conformance.

The shipbuilding industry throughout the world has taken heat shaping to new heights in shaping technology. Particularly, the use of line heating to shape complex curves in hull structures has become an integral part of a group technology in shipbuilding which also includes product work packages and accuracy control.

Basically, straightening and shaping involves controlled thermal expansion and contraction of a structural element. The method, location, and shape of the heat application are covered briefly in this publication. This recommended practice is limited to fundamentals and simple applications. (See Annex A for additional information.)