Musings from a Military Welding Manual Part 3

Now most people know that joint design is critical to a good weld, but even before any technical information is given to welding the the old Military welding manual I found, it covers basic joint designs and weld joint terminology.  Of course, it covers basic designs that were still in use today.  Perhaps a few of them are not as relevant and some new ones have been added, with advancements being made in engineering and  the adaptation of welding processes like MIG welding and TIG welding.   But one thing I found remarkably fresh and plainly simple was the discussion of the parts of a weld and a clear demonstration in a drawing.  Terms  like these really should be the first course of study for any welder, whether formally trained or not.  Terms like  toe, leg, throat, and face may sound like body parts, but they are indeed the parts of a weld that one should become familiar with.  This will help you to be able to study and improve your welds as each part has an objective measurement or appearance to be considered “correct”.   The toe of the weld is the small marginal area at the edge of the weld where the filler metal merges into the metal being worked.  This area is critical and can indicate a cold, poorly fused weld, or a weld with a lack of filling by an undercut which can lead to cracking and failure of the weld at that point.   The leg of the weld  is the length of the weld from the toe to the center of the original unwelded root.  This length should be uniform and even for most purposes.  An uneven leg can cause weakness on one side or the other of the weld.  The throat of the weld is divided in to the actual throat, and the theoretical throat.  The theoretical throat is the thickness of the weld from the original root to the midpoint of a line drawn between the two toes of the weld.  The actual throat is the measurement  of the thickness of the distance measured from the top of the weld midway between the two toes down to the bottom of the penetration zone.   The face of the weld is the total width of the weld on top.  This area should represent no more than 2-3 times the electrode width, particularly in the root pass.  The fusion zone is another term which is the measurement of the  “side area” of the weld, where the weld penetrates the base metal. The penetration zone is similar, but it represents the area directly under the root, and the depth to which the arc penetrated the weld.  The last significant term is “weld reinforcement”.  This term is the amount weld that sits above the two toes of the weld.  The height of this reinforcement is measured at the center of the weld to the imaginary line drawn between the two toes of the weld.   Studying these terms will  greatly help you converse with other welders, and describe problems intelligently and help you to be able to analyze each part independently to learn how to diagnose and improve your weld.  

Look for part 4 of musings from a military welding manual.