Welding Basics


In this article, we will talk about the ff:

- types of joints

– types of welds,

– how to interpret weld symbols



Welding is the process of joining two or more pieces of metal by applying heat and/or pressure with or without filler metal, to produce a union through localized fusion of the substrates and solidification across the interface



  • Simple joint design
  • Reduce the amount of materials and work sequence
  • Reduce the weight of components
  • High joint efficiency
  • Well air tightening
  • No limitation for joint thickness
  • Less noise during work



  • Distortion due to the local heating/cooling by welding
  • Residual stress
  • Changes in metallurgical or mechanical property of the base metal
  • Propagation of the cracks
  • Difficult to dismantle


Types of Joints

types of joints
















Types of Welds

fillet weldsquare weld

bevel weld V-grooveJ-groove U-grooveflare-bevelflare v-groove




















Other Types of Welds

Plug or Slot Weld – are welds which partially or entirely fill the holes.

plug or slot weld







Side Seam Weld

side seam








Spot Weld – is typically used when welding particular types of sheet metal by application of heat.

spot weld









Stud Weld – is a form of spot welding where a bolt or specially formed nut is welded on to another metal part. The bolts may be automatically fed into the spot welder. Weld nuts generally have a flange with small nubs that melt to form the weld. Studs have a necked down, unthreaded area for the same purpose.

stud weld



Weld Terminology

  • Leg
  • Face
  • Throat
  • Groove radius
  • Root opening (groove weld) is the space between the pieces before welding
  • Root face
  • Groove angle

weld term







weld term






weld term











weld symbols


Significance of Arrow

significance of arrow









Weld Symbols

Fillet Weld Symbol

fillet symbol







Square Groove Weld Symbol

square groove symbol







Bevel Groove Weld Symbol

bevel groove symbol











V-Groove Weld Symbol

v groove symbol











J-Groove Weld Symbol

j groove symbol







U-Groove Weld Symbol

u groove symbol








Flare-Bevel Groove Weld Symbol

flare bevel groove weld symbol











Flare-V Groove Weld Symbol

Flare-V Groove Weld Symbol








Plug or Slot Weld Symbol

Plug or Slot Weld Symbol







Stud Weld Symbol

Stud Weld Symbol







Spot Weld Symbol

Spot Weld Symbol







Basic and Supplementary Weld Symbols

Basic and Supplementary Weld Symbols



Basic and Supplementary Weld Symbols



Back or Backing Weld

Back or backing weld symbols are used to indicate bead-type back or backing welds deposited at the back of single-groove welds to assure complete root penetration.

The back weld is made after the groove weld.

The backing weld is made before the groove weld.

Back or Backing Weld













Surfacing is the deposition of filler metal on a metal surface to obtain desired properties or dimensions.


Field Weld

Field welds are welds not made in the shop or at the place of initial construction.

Small black flag symbol is placed above and at right angles to the reference line.


All Around Weld

Welds extending completely around a joint is indicated by a weld-all-around symbol placed at the intersection of the reference line and the arrow.

It is not required for welds extending around the circumference of a pipe.


Finish Contour

Finish Contour








Additional Information

  • Welding symbols can be combined

Additional Information




  • Multiple reference lines can be used to indicate sequencing

–  Line closest to the arrow is first

Additional Information






  • Cranked arrow line points to the member to be prepared

Additional Information





  • Application of Break in Arrow Symbol

Application of Break in Arrow SymbolApplication of Break in Arrow Symbol

Application of Break in Arrow Symbol




Photo credit to bugphai of freedigitalphotos.net


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