Welding-General Outline and Terms

Welding Classification
 Weld Type (By shape of weld pool)
Welds are classified according to their shape when shown in cross-section and on the basis
of joint type for which they are used.

The Fillet Weld

 The fillet is defined as "a weld of approximately triangular cross-section joining two
surfaces approximately at right angles to each other.
 This is the most commonly used type of weld and is so named because of its cross-sectional
shape.
The Plug or Slot Welds
They are considered together since the welding symbol to specify them is the same. Plug or
slot weld has holes prepared in one member so that welding can be done through the hole
into the other member. If the hole is round, it is considered a plug weld; if it is elongated, it
is considered a slot weld. Plug welds were made in early design transition from riveted
structures. As designs improved, the plug welds have been discontinued. They are now
however used for certain blind applications in which the other side of the weld joint may be
inaccessible.
The Spot or Projection Weld:
The spot weld differs from the plug weld in that it does not require a hole in either member.
The weld cross-section is approximately circular. The geometry of the weld is influenced by
the welding process employed. For example, when the resistance welding process is used,
the' weld is at the interface of the members being joined, If the electron beam, laser or an arc
welding process is used the weld melts through one member (usually the top member) into
the second member.
Seam Weld:
This weld in cross section looks similar to a spot weld. The weld geometry is influenced by
the welding process employed. With resistance welding, the weld is at the interface between
members being joined, but with an electron beam, laser, or arc welding process, the weld
melts through the one member to join it to the second member. There are no prepared holes
in the seam weld.
Groove Weld:
This is the second most popular weld type employed. It is defined as a weld made in the
groove between two members to be joined (Fig. 4.3). There are seven basic groove weld
designs, and they can be used as single or double welds.
Back or Backing Weld:
This is a special type of weld made on the back side or root side of a previously made weld.
The root of the original weld is gouged. chipped, or ground to sound metal before the back or
backing weld is made. This improves the quality of the weld joint by assuring complete
penetration.
Surfacing Weld:
This is a type of weld composed of one or more stringer or weave beads deposited on base
metal as an unbroken surface. It is used to build up surface dimensions, to provide metals of
different properties, or to provide protection of the base metal from hostile environment. The
most sought after properties are resistance to frictional wear, impact. abrasion, erosion,
oxidation and corrosion. It is not used for joining. Surfacing filler metals cover an extremely
wide range and can be in the form of bare rods and coated electrodes.
Flange Weld:
The flange weld is extensively used in sheet metal work, particularly on metals lighter than 1
mm in thickness. The edges are prepared for welding by turning up a flange, and the weld is
then made by melting down this flange, usually without the addition of any welding rod. The
upstanding portion of the flange should extend above the surface of the sheet a distance
approximately equal to the thickness of the metal. It is important that the operator make
certain that he is obtaining a weld penetration to the bottom of the joint.
 A joint refers → "the location where two or more members are to be permanently joined
by welding".
 Weld joints are designated according to the location and/or position of the members in
relation to each other. There are five basic types of joints for bringing two members
together for welding
 Welding Position

Edge Preparation for Different Types of Joints

 Welding Symbols
 All welding symbols have a minimum of three basic parts:
(1) a reference line,
(2) an arrowhead, and
(3) a feathery tail.
A welding symbol also can have four more parts:
 Dimensions,
 Finishing symbol,
 Supplementary symbols, and
 Other data
However, a complete welding symbol might contain eight different kinds of information. We
shall, however, restrict ourselves to the mandatory elements of the welding symbol.
 The purpose of welding symbols is to provide complete welding information on
engineering drawings.
The welding symbol consists of eight elements that may or may not all be used in each
symbol.
1. Reference line
2. Arrow
3. Basic weld symbol
4. Dimension and other data
5. Supplementary symbol
6. Finish symbol
7. Tail
8. Specification, process, or reference

The first (Reference line) and second (Arrow) elements and either the third (Basic weld
symbol) or seventh (Tail) must be used to make an intelligible welding symbol.
 The reference line
 Always shown in the horizontal position
 Other parts of the welding symbol are constructed on the reference line

 The main foundation of the weld symbol is a reference line with an arrow at one end.
The reference line is always shown in
 the horizontal position (can be extend upward or downward).
 The arrowhead is directed to the joint location. (The direction of the arrow is not
important)
 All of the necessary data is indicated by geometric figures, numerical values, and
abbreviations and have a standard location

 The arrow
 Line from one end of the reference line to an arrowhead to the arrow side or arrow side
member of the weld joint.

 The tail
 The other end of the reference line carries the tail of the arrow.
 The area in the tail can be used to provide references to specifications, processes, or
other specific information.
 When there is no such references, the tail is omitted.
 Type and location of weld
 Fig. shows the arrow side and other side of the joint.
 If the weld is to be made on the arrow side, the appropriate weld symbol is placed below
the reference line [Fig. 4.8(B)].
 If the weld is to be made on the other side of the joint, the weld symbol is placed above the
reference line [Fig. 4.8(C)].
 When the symbol is placed on both sides, it would indicate that the weld is to be made on
both sides of the joint [Fig. 4.8(D)].