Cracks in a weld usually indicate the possibility of weld failure. All types of cracks should be considered as points of weakness. Take steps taken to eliminate their cause and occurrence.

The most common cracks in and about a weld joint are crater cracks, underbead cracks and longitudinal cracks. Cracks along the edge of the weld are sometimes referred to as toe cracks. Then there are also hairline cracks across the weld and micro-cracks.

While these various cracks appear in different parts of the weld and result from different causes, identification and elimination of the basic fault leading to such structural defects will result in crack-free welds.

1. The base metal is not of a weldable grade material.



2. Improper preparation of the weld joints.



3. Wrong welding procedure.



4. The weld joint is too rigid.



5. Welds are too small for the size of the parts being joined in the structure.

1. Use only weldable aluminum, series 4XXX, 5XXX and 6XXX.



2. In preparing joints for welding, space the members uniformly so the gap is even. This may mean there is a gap in the welding groove while in other instances the parts may be welded closely together. The size of the weldment and the welding problem will determine the gap spacing. Clean surfaces to be welded of dirt, oil, moisture or other contamination.



3. Be sure the welding procedure will provide sound welds of good fusion. The welding sequence should allow the open ends of the weldment to move as long as possible. Avoid stringer bead welding if cracking is a problem; use a weaving technique to make a full size weld, doing the job by sections 8 or 10 inches long. Crater cracks may be eliminated by filling the weld crater at the end of each bead. Preheating the parts to be welded is often helpful in avoiding cracked welds.



4. Be sure the structure to be welded has been designed properly and a welding procedure developed to eliminate rigid joints.



5. Always be sure the weld bead is of sufficient strength to withstand the stresses that might develop from the heat of welding. Do not use too small a weld bead between heavy plates. Be sure to use welds of sufficient size on all joints.