The selection of the proper joint type and weld type is the essence of good design and engineering. Factors such as base metal preparation, joint access, weld distortion, overall strength, fatigue performance, and corrosion resistance amongst other related factors must meet the safety and service conditions for their given application. Ultimately cost and the ability of the selected joint design to meet in-service requirements dictates what is used.
CJP or a Complete Joint Penetration weld is a weld in which the weld metal extends through the full thickness of the base material being welded.
PJP or Partial Joint Penetration weld is a weld in which the weld metal does not reach the full thickness of the base material being welded but extends only through a portion of it.
Omitting the depth of bevel and groove weld size dimensions from groove welding symbols requires complete joint penetration.
Fillet welds are most commonly used to join Corner, T, and Lap joints. Fillet welds are typically more economical than groove welds due to less edge preparation and easier fit-up in weld sizes smaller than 5/8”.
Single-sided fillet welds should not be used where bending, impact or rotational forces may place leverage or tensile stress at the root, as this condition may allow the notch toughness of the weld to be exceeded and weld failure to result. Smaller double fillet welds are preferred to a large single fillet weld. Fillet welds can be combined with complete and partial penetration groove welds.
Fillet welds may be used in skewed T or corner joints having a dihedral angle between 60 and 135 degrees. Beyond these limits, these welds are considered partial joint penetration groove welds.
Groove welds are most commonly applied to butt joints and consist of the following types