DEFINITIONS AND TERMS (cont) - TM-750-245-40097

TM 750-245-4

PERCUSSIVE WELDING: A resistance welding process in

PRE WELD INTERVAL: In spot, projection, and upset

which a discharge of electrical energy and the application

welding, the time between the end of squeeze time and the

of high pressure occurs simultaneously or with the electrical

start of weld time or weld interval during which the material

discharge occurring slightly before the application of

is preheated. In flash welding, it is time during which the

pressure.

material is preheated.

PERMANENT MAGNET: usually an iron alloy having a

PROJECTION WELDING: A resistance welding process

high value of coercive force; that is, the magnetic domains

between two or more surfaces or between the ends of one

are not easily rotated. Thus, after the alloy has been

member and the surface of another. The welds are

saturated by the application of a sufficiently large

localized or predetermined points or projections.

magnetizing force, the domains tend to remain aligned

indefinitely, even after the magnetizing force has been

PULSATION WELDING: A spot, projection, or seam

removed.

welding process in which the welding current is interrupted

one or more times without the release of pressure or

PIT: A small circular indentation in a surface resulting from change of location of electrodes.

chemical action or corrosion.

PUNCTURE: A complete surface penetration, usually from

PITCH: Center to center spacing of welds.

a sharp object.

PLUG WELD: A weld is made in a hole in one member of a

PUSH WELDING: The making of a spot of projection weld

lap joint, joining that member to that portion of the surface

in which the force is applied manually to one electrode and

of the other member which is exposed through the hole.

the work or a backing bar takes the place of the other

The walls of the hole may or may not be parallel, and the

electrode.

hole may be partially or completely filled with the weld

metal.

QUENCHING: The sudden cooling of heated metal with oil,

POKE WELDING: A spot welding process in which water, or compressed air.

pressure is applied manually to one electrode. The other

electrode is clamped to any part of the metal much in the

same manner that arc welding is grounded.

REACTION STRESS: The residual stress which could not

otherwise exist if the members or parts being welded were

POROSITY: The presence of gas pockets or inclusions in isolated as free bodies without connection to other parts of

welding.

the structure.

POSITIONS OF WELDING: All welding is accomplished in REDUCING FLAME: See carburizing flame.

one of four positions: flat; horizontal; overhead or vertical.

The limiting angles of the various positions depend REGULATOR: A device used to reduce cylinder pressure

somewhat as to whether the weld is of a fillet or groove to a suitable torch working pressure.

type.

REINFORCED WELD: The weld metal is built up above

POSTWELD INTERVAL: In resistance welding, the heat the general surface of the two abutting sheets or plates in

time between the end of weld time, or weld interval, and excess of that required for the size of the weld specified.

the start of hold time. During this interval, the weld is

subjected to mechanical and heat treatment.

RESIDUAL STRESS: Stress remaining in a structure or

member as a result of thermal and / or mechanical

POUR POINT: The temperature at which an oil just ceases treatment.

to flow or pour.

RESISTANCE BRAZING: A brazing process in which

PREHEATING: The application of heat to a base metal fusion is produced by the heat obtained from resistance to

prior to a welding or cutting operation.

the flow of electric current in a circuit of which the work is a

part and by using a nonferrous filler metal having a melting

PRESSURE CONTROLLED WELDING: The making of a point above 800 degrees F, but below that of the base

number of spot or projection welds in which several metals. The filler metal is distributed in the joint by

electrodes function progressively under the control of a capillary attraction.

pressure sequencing device.

RESISTANCE BUTT WELDING: A group 'f resistance

PRESSURE WELDING: Any welding process or method in welding processes in which the weld occurs simultaneously

which pressure is used to complete the weld.

over the entire contact area of the parts being joined.

B-11