When welding on precise work, one of the greatest difficulties is avoiding distortion. In some instances, a distortion leaves the weldment valueless. In others, it means that considerable work must be done to return it to the desired shape. Such problems may be avoided through proper designing.

1. Improper welding sequence.



2. Insufficient control of the welding heat.



3. Shrinkage of deposited weld metal, pulling parts together and changing their relative positions.



4. Failure to maintain proper dimensions by welding parts in a distorted position.

1. Before attempting to weld a new and difficult weldment, study the structure and develop a definite welding sequence.
   
   
2. Exercise care in distributing the welding heat by skip sequence, back stepping, etc., to prevent excessive local heating. Preheat is sometimes desirable to avoid an excess heat condition, particularly on heavy structures.



3. The effects of weld metal shrinkage can be minimized by pre-forming the parts sufficiently to compensate for weld shrinkage. Clamping or tack welding the parts will also help resist shrinkage. The higher welding currents and speed available with submerged-arc and vapor-shielded arc welding result in minimum weld shrinkage and distortion.
   
   
4. Be sure the various parts of the weldment are properly aligned prior to starting welding. Preheating may be helpful prior to welding since it will tend to relieve stresses brought about by rolling or forming.