Basic Terms and Technologies in Welding
Pressure
welding : Welding in which sufficient outer force is applied to cause
more or less
plastic deformation of both the facing surfaces, generally without the addition
of filler metal. Usually, but
not necessarily, the facing surfaces are heated in order to permit or to facilitate bonding.
Fusion Welding
: Welding without application of outer force in which the
facing surface(s) must be melted. Usually, but not necessarily, molten filler
metal is added.
Surfacing :
Producing a layer of different metal by welding, e.g. with higher corrosion,
abrasion or heat resistance than the parent metal.
Welding
procedure specijication (WPS) : A document specifying the details of the required
variables for a specific application in order to assure repeatability (EN 288).
Deposition
Rate : Amount of metal
supplied to the joint per unit time during welding.
Heat input
: The heat input has great importance for the rate of cooling
of the weld. It can be calculated from the formula:
Efficiency*: MMA: 0.75 , MIGIMAG: 0.90 , TIG: 0.80 , SAW: 0.90
where Q = heat input (kJ1mrn) , U = voltage (V) , I = current
(A) ,V = welding speed (mndmin)
* These eflciencies are close to physical measured values.
Always check ifother values are given in the regulations or standards used by
your company.
Heat
Afected Zone (HAZ) : The heat affected zone, is that area of the base metal
not melted during the welding operation but whose physical properties are altered
by the heat induced from the weld joint.
Throat Thickness
: Fillet welds are calculated by reference to the throat size. The size required
is specified on drawings in terms of throat thickness, t, or the leg length, 1.
Joint types
: Joint types are chosen with regard to the welding method and
plate thickness. The ideal joint provides the required structural strength and
quality without an unnecessarily large joint volume. The weld cost increases
with the size of the joint, and the higher heat input will cause problems with
impact strength and distortion. Joint preparation can also be expensive;
therefore it is preferable to use joint types where the joint faces are parts
of the workpiece. This means that fillet welds are probably the most commonly
used joints.
Welding Positions
: There are essentially four different fundamental welding
positions, namely flat, horizontal-vertical, overhead and vertical position.
Vertical position welding can be carried out as vertical upward or vertical
downward welding. In addition, fillet welds can be made in the
horizontal-vertical position or in the flat position.
