TIGBook_Chpt12.pdf

XII. Glossary

Balanced Wave: An alternating current waveform that has

equal negative and positive polarity current values.

Advanced Squarewave: The advanced AC output available

from certain types of power sources. The wave is much more

square than the conventional Squarewave power source. It also

has expanded balance control to 90% electrode negative

(max penetration) and the ability to control arc frequency

(arc direction). Some have the additional ability to adjust the

amount of current in the electrode negative and electrode

positive cycles independently.

Bevel Angle: An angle formed between a plane, perpendicular

to the surface of the base metal and the prepared edge of the

base metal. This angle refers to the metal that has been removed.

Butt Joint: A weldment where the material surfaces and

joining edges are in or near the same plane.

Carbide Precipitation: Occurs when austenitic stainless steel is

heated within a temperature range of 800˚–1600˚ F, 427˚– 870˚ C

for a critical period of time. Carbon moves from a solid

solution to grain boundaries and combines with chromium.

The metal adjacent to the grain boundaries is left with less

chromium and is said to be sensitized. Corrosion resistance is

therefore reduced in the grain boundary region. See Figure 12.1.

Carbon Arc Gouging: A cutting process by which metals are

melted by the heat of an arc using a carbon electrode. Molten

metal is forced away from the cut by a blast of forced air.

Air Carbon Arc Cutting: A cutting process by which metals are

melted by the heat of an arc using a carbon electrode. Molten

metal is forced away from the cut by a blast of forced air.

Alternating Current (AC): An electrical current that reverses

its direction at regular intervals, such as 60 cycles alternating

current (AC), or 60 hertz (Hz).

Amperage: The measurement of the amount of electricity

flowing past a given point in a conductor per second. Current

is another name for amperage.

Cerium Tungsten: GTAW tungsten electrode with small amount

of the rare earth and nonradioactive ceria added. Improves

arc starting and provides for use of wider current range.

Annealing: The opposite of hardening. A heat treating

process used to soften a metal and relieve internal stresses.

Characteristics: Special qualities or properties. For instance,

some welding machines have certain internal characteristics

which allow a welder to perform more welding applications

than with other welding machines.

Anodize: To anodize aluminum is to coat the metal by either

chemical or electrical means. The coating provides improved

corrosion and wear resistance. The thickness of this coating

depends upon the length of the treatment. This coating is

often removed from the area to be welded. This coating can

be reapplied after welding.

Arc: The physical gap between the end of the electrode and

the base metal. The physical gap causes heat due to resistance

of current flow and arc rays.

Circuit: The complete path or route traveled by the electrical

current. A circuit for GTAW can include the welding machine,

weld cables, torch assembly, arc, base metal and work clamp

with cable.

Cold Lap: See preferred term Incomplete Fusion.

Conductor: An electrical path where current will flow with

the least amount of resistance. Most metals are good

electrical conductors.

Arc Length: Distance or air space between the tip of the

electrode and the work.

Arc Voltage: Measured across the welding arc between the

electrode tip and the surface of the weld pool.

Constant Current (CC) Welding Machine: These welding

machines have limited maximum short circuit current. They

have a negative volt-amp curve and are often referred to as

“droopers”. The voltage will change with different arc lengths

while only slightly varying the amperage, thus the name constant

current or variable voltage.

Asymmetric Waveform: The output waveform of a welding

power source that has the ability to modify both the amplitude

and duration of the positive and negative half cycles of

alternating current.

Autogenous Weld: When a TIG weld is made without the

addition of filler metal.

Chromium-Depleted Zone

Automatic Welding (AU): Uses equipment which welds without

the constant adjusting of controls by the welder or operator.

Equipment controls joint alignment by using an automatic

sensing device.

Grain

Boundaries

Axis of Weld: Can be thought of as an imaginary line through

the center of a weld, lengthwise.

Back Gouging: The removal of weld metal and base metal

from the other side (root side) of a weld joint. When this

gouged area is welded, complete penetration of the weld

joint is assured.

Chromium

Carbides

Figure 12.1 Carbide precipitation.

Constant Voltage (CV), Constant Potential (CP) Welding

Machine: “Potential” and “voltage” are basically the same in

meaning. This type of welding machine output maintains a

relatively stable, consistent voltage regardless of the amperage

output. It results in a relatively flat volt-amp curve as opposed

to the drooping volt-amp curve of a typical GTAW (TIG)

welding machine.

Distortion: The warpage of a metal due to the internal residual

stresses remaining after welding from metal expansion (during

heating), and contraction (during cooling).

Duty Cycle: The number of minutes out of a 10-minute time

period an arc welding machine can be operated at maximum

rated output. An example would be 60% duty cycle at 300

amps. This would mean that at 300 amps the welding machine

can be used for 6 minutes and then must be allowed to cool

with the fan motor running for 4 minutes. (Some imported

welding machines are based on a 5-minute cycle).

Consumable Insert: Preplaced filler metal that is completely

fused into the joint root and becomes part of the weld.

Contactor: An electrical switch that is used to energize or

de-energize output terminals of a welding machine. In some

types of welding machines they can be of solid state design,

with no moving parts and thus no arcing of contact points.

Edge Joint: A joint that occurs when the surfaces of the two

pieces of metal to be joined are parallel or nearly parallel, and

the weld is made along their edges.

Corner Joint: Produced when the weld members meet at

approximately 90˚ to each other in the shape of an “L”.

Crater: A depression at the end of a weld bead.

Electrode Extension: While welding, the length of electrode

extending beyond the end of the gas cup. Also referred to as

electrical stickout.

Electron: A very small atomic particle which carries a negative

electrical charge. Electrons can move from one place to

another in atomic structures. It is electrons that move when

electrical current flows in an electrical conductor.

Current: Another name for amperage. The amount of electricity

flowing past a point in a conductor every second.

Current Density: The amount of current per square inch of

cross-sectional area in an electrode. For any electrode diameter,

find the current density by dividing the current value by the

electrode cross-sectional area in square inches.

Etching: When a weld specimen is cut through a weld, an

acid or similar solution can be applied to the weld area to

bring out the features of the weld. These include the deposited

weld metal, heat affected zone, penetration and weld profile.

Many different etching solutions and techniques exist for the

various kinds of metals.

Cycle: One cycle equals 360 electrical degrees. For alternating

current, current flow is in one direction through a circuit for

180˚ and in the opposite direction for the other 180˚. For 60

cycle power, a cycle is repeated 60 times per second. Some

welding machines, especially outside the United States, require

50 cycle (hertz) power. Hertz stands for cycles per second.

Defect: One or more discontinuities that exceed the acceptance

criteria as specified for a weld.

Excessive Melt-Through: A weld defect occurring in a weld

joint when weld metal no longer fuses the base metals being

joined. Rather, the weld metal falls through the weld joint or

“burns through”. Also referred to as excess penetration.

Face: The surface of the weld as seen from the side of the

joint on which the weld was made.

Face Rotation: Can be thought of as an imaginary line from

the axis of the weld through the center of the welds face.

This face rotation angle along with the axis angle determine

the actual welding position. Face rotation is measured in a

clockwise direction starting from the 6 o’clock position.

A weld with the face rotation at 12 o’clock would have the

face rotation at 1800.

Depth of Fusion: The depth or distance that deposited weld

metal extends into the base metal or the previous pass.

Direct Current: Flows in one direction and does not reverse

its direction of flow as does alternating current.

Direct Current Electrode Negative (DCEN): The specific direction

of current flow through a welding circuit when the electrode

lead is connected to the negative terminal and the work lead

is connected to the positive terminal of a DC welding machine.

Direct Current Electrode Positive (DCEP): The specific direction

of current flow through a welding circuit when the electrode

lead is connected to a positive terminal and the work lead is

connected to a negative terminal to a DC welding machine.

Ferrous: Refers to a metal that contains primarily iron, such

as steel, stainless steel and cast iron.

Filler Metal: The metal added when making a welded,

brazed, or soldered joint.

Discontinuity: Any change in a metal’s typical structure. It is

the lack of consistence in mechanical, metallurgical or physical

characteristics. Discontinuities are found in all metals and

welds because they have some degree of inconsistency in

them. However, this is acceptable as long as the discontinuities

do not exceed the acceptance criteria of the weld or metal in

question. If a discontinuity exceeds the acceptance criteria,

they are defects and must be repaired.

Fillet Weld: A weld that is used to join base metal surfaces

that are approximately 90˚ to each other, as used on T-joint,

corner joint or lap joint. The cross sectional shape of a fillet

weld is approximately triangular.

Fit-Up: Often used to refer to the manner in which two mem-

bers are brought together to be welded, such as the actual

space or any clearance or alignment between two members

to be welded. Proper fit-up is important if a good weld is to

be made. Tacking, clamping or fixturing is often done to

ensure proper fit-up. Where it applies, base metal must be

beveled correctly and consistently. Also, any root openings or

joint angles must be consistent for the entire length of a joint.

An example of poor fit-up can be too large of a root opening

in a V-groove butt weld.

Ground Connection: A safety connection from a welding

machine frame to the earth. Often used for grounding an

engine driven welding machine where a cable is connected

from a ground stud on the welding machine to a metal stake

placed in the ground. See Work Connection for the difference

between work connection and ground connection.

Ground Lead: When referring to the connection from the

welding machine to the work, see preferred term Work Lead.

Heat Affected Zone (HAZ): The portion of a weldment that

has not melted, but has changed due to the heat of welding.

The HAZ is between the weld deposit and the unaffected base

metal. The physical makeup or mechanical properties of this

zone are different after welding.

Flat Position: When welding is done from the top side of a

joint, it is in the flat position if the face of the weld is approxi-

mately horizontal. Sometimes referred to as downhand welding.

The axis angle can be from 0˚ – 15˚ in either direction from a

horizontal surface. Face rotation can be from 150˚ – 210˚.

Heat Sink: A good weld needs a certain amount of base

metal to absorb the high heat input from the welding arc area.

The more base metal, or the thicker the base metal, the better

heat sink effect. If this heat sink is not present, too much heat

will stay in the weld area, and defects can occur.

High Frequency: Covers the entire frequency spectrum

above 50,000 Hz. Used in GTAW welding for arc ignition

and stabilization.

Flux Cored Arc Welding (FCAW): An arc welding process

which melts and joins metals by heating them with an arc

between a continuous, consumable tubular electrode wire

(consumable) and the workpiece. Shielding is obtained from

a flux contained within the electrode’s tubular core. Depending

upon the type of flux-cored wire, added shielding may or may

not be provided from externally supplied gas or gas mixture.

Horizontal Position: Occurs when the axis of the weld is

from 0˚ – 15˚ from the horizontal, and the face rotation is

from either 80˚ – 150˚ or 210˚ – 280˚ for groove welds, or

from either 125˚ – 150˚ or 210˚ – 235˚ for fillet welds.

Freeze Lines: The lines formed across a weld bead. They are the

result of the weld pool freezing. In appearance they sometimes

look as if one tiny weld was continuously laid upon another.

Frequency: The number of double directional changes made

by an alternating current in one second. Usually referred to

as “hertz per second” or “cycles per second”. In the United

States, the frequency or directional change of alternating

current is usually 60 hertz. Some Advanced Squarewave

power sources allow the arc frequency to be adjusted. As arc

frequency is increased the arc becomes more directional.

Impedance: In electricity, impedance will slow down, but not

stop, amperage flowing in a circuit. It is the resistance in an

alternating current circuit. Impedance is the combination of

the natural resistance to current flow in any conductor and

the inductive or capacitive reactance in an electric circuit. It is

brought about by the building and collapsing field of alternating

current. This building and collapsing induces a counter electro

motive force (CEMF) (voltage) that holds back, but does not

stop, current flow.

Gas Metal Arc Welding (GMAW): An arc welding process

which joins metals by heating them with an arc. The arc is

between a continuously fed solid filler wire (consumable)

electrode and the workpiece. Externally supplied gas or gas

mixtures provide shielding for GMAW. Sometimes called MIG

welding (Metal Inert Gas) or MAG welding (Metal Active Gas).

Included Groove Angle: See preferred term Groove Angle.

Incomplete Fusion: Molten filler metal rolling over a weld edge

but failing to fuse to the base metal. Also referred to as cold lap.

Gas Nozzle: That part of the GTAW torch that directs the

shielding gas flow over the weld area. Made of ceramic,

glass, or metal in various styles.

Inductance: Inductance (an inductor) will slow down the

changes in current, as if the electrons were sluggish.

Inert Gas: A gas that will not combine with any known element.

At present 6 are known; argon, helium, xenon, radon, neon,

and krypton. Only argon and helium are used as shielding

gases for welding.

Gas Tungsten Arc Welding (GTAW): Sometimes called TIG

welding (Tungsten Inert Gas), it is a welding process which

joins metals by heating them with a tungsten electrode which

should not become part of the completed weld. Filler metal is

sometimes used and argon inert gas or inert gas mixtures are

used for shielding.

Groove Angle: When a groove is made between two materials

to be joined together, the groove angle represents the total

size of the angle between the two beveled edges and denotes

the amount of material that is to be removed.

Inverter: Power source which increases the frequency of the

incoming primary power, thus providing for a smaller size

machine and improved electrical characteristics for welding,

such as faster response time and more control for waveshaping

and pulse welding.

Joint Design: A cross-sectional design and the given meas-

urements for a particular weld. Generally includes included

angles, root opening, root face, etc.

Penetration: The nonstandard term used to describe

the following:

Depth of Fusion: The distance from the surface melted

during welding to the extent of the fusion into the base

metal or previous weld bead.

Joint Penetration: The depth that a weld extends from the

weld face into the joint, minus reinforcement. Joint pene-

tration may include root penetration.

Root Penetration: The depth that a weld extends into the

root of a joint.

Complete Joint Penetration: Occurs when the “filler”

metal completely fills the groove, and good fusion to the

base metal is present.

Incomplete Joint Penetration: A condition in the root of a

groove weld when the weld metal does not extend through

the joint thickness. This is generally considered a defect when

the joint by design was to have complete joint penetration.

Partial Joint Penetration: A condition in the root of a groove

weld when the weld metal does not extend through the

joint thickness. By design this is acceptable and not a defect,

because it will carry the load for which it was intended.

Plasma: The electrically charged, heated ionized gas which

conducts welding current in a welding arc.

Joint Root: That part of a joint that comes closes together

where the weld is to be made. This maybe an area of the joint

or just a line or point of that joint.

Lanthanum Tungsten: GTAW tungsten electrode with

small amount of the rare earth and nonradioactive lanthana

added. Improves arc starting and provides for use of wider

current range.

Lap Joint: A joint that is produced when two or more members

of a weldment overlap one another.

Lift Arc: An arc starting method built into the GTAW power

source to allow contact type starts. Tungsten contamination is

virtually eliminated.

Load Voltage: Measured at the output terminals of a welding

machine while a welder is welding. It includes the arc voltage

(measured while welding), and the voltage drop through

connections and weld cables.

Machine Welding (ME): Uses equipment which welds with

the constant adjusting and setting of controls by a welder

or operator.

Microprocessor: One or more integrated circuits that can be

programmed with stored instructions to perform a variety

of functions.

Nonferrous: Refers to a metal that contains no iron, such as

aluminum, copper, bronze, brass, tin, lead, gold, silver, etc.

Plug Welding: A weld made by filling (or partially filling) a hole

in one member of a joint, fusing that member to another member.

Pool: The weld pool is the liquid state of a weld prior to its

becoming solid weld metal. It indicates no limit to depth as

the nonstandard term puddle tends to note a shallower depth.

Open Circuit Voltage (OCV): As the name implies, no current

is flowing in the circuit because the circuit is open. The voltage

is impressed upon the circuit, however, so that when the circuit

is completed, the current will flow immediately. For example,

a welding machine that is turned on but not being used for

welding at the moment will have an open circuit voltage

applied to the cables attached to the output terminals of the

welding machine.

Porosity: A cavity type discontinuity formed by gas entrapment

during solidification.

Positioner: A device which moves the weldment when a

stationary arc is used. Positioners include turning rolls,

head and tail stocks and turntables.

Pounds Per Square Inch (psi): A measurement equal to a

mass or weight applied to one square inch of surface area.

Output Control: An electrical switch that is used to energize

or de-energize output terminals of a welding machine. In some

types of welding machines they can be of solid state design,

with no moving parts and thus no arcing of contact points.

Primary Power: Often referred to as the input line voltage and

amperage available to the welding machine from the shop’s

main power line. Often expressed in watts or kilowatts (kw),

primary input power is AC and may be single- or three-phase.

Welding machines with the capability of accepting more than

one primary input voltage and amperage must be properly

connected for the incoming primary power being used.

Overhead Position: When the axis angle is from 0˚ – 80˚ and

the face rotation is from 0˚ – 80˚ or 280˚ – 360˚ for groove

welds or from 0˚ – 125˚ or 235˚ – 360˚ for fillet welds, the

weld position is considered to be in the overhead position.

Parameters : The welding settings on a welding machine such

as voltage and amperage, normally read on a volt meter and

an amp meter. It may also include things as travel speed,

electrode size, torch angle, electrode extension and weld joint

position and preparation.

Puddle: More properly referred to as molten weld pool, the

weld puddle is the liquid state of a weld prior to its becoming

solid weld metal.

Pulsing: Varying the current from a high peak amperage level

to a lower background amperage level at regular intervals.

Pulse controls also adjust for the number of pulses per second

and the percent of time spent at the peak amperage level.

Pulsing is used to control heat input and allow for improved

weld profile.

Purging: Cleaning, purifying or removing something from a

container. Such as applying shielding gas to the inside of a

piping structure prior to welding it with the GTAW process.

Shielding Gas: Protective gas used to prevent atmospheric

contamination of the weld pool.

Single-Phase: When an electrical circuit produces only

one alternating cycle within a 360˚ time span, it is a

single-phase circuit.

Quenching: The dipping of a heated metal into water, oil or

other liquid to obtain necessary hardness.

Rectifier: An electrical device that allows the flow of electricity

in basically only one direction. Its purpose is to change

alternating current (AC) to direct current (DC).

Slot Welding: A weld made by filling (or partially filling) an

external hole (slot) in one member of a joint, fusing that

member to another member. The hole (slot) may be com-

pletely enclosed, or it may be open at one end of the metal.

Residual Stress: The stress remaining in a metal resulting

from thermal or mechanical treatment or both. When welding,

stress results when the melted material expands and then

cools and contracts. Residual stresses can cause distortion

as well as premature weld failures.

Resistance: The opposition to the flow of electrical current in

a conductor. This opposition to current flow changes electric

energy into heat energy. Resistance is measured in ohms

with an ohm meter.

Solenoid: An electrical device which either stops or permits

the flow of gas used to shield the weld pool and arc or the

flow of water used to cool a welding torch.

Spatter: Metal particles blown away from the welding arc.

These particles do not become part of the completed weld.

Squarewave: The AC output of a power source that has the

ability to rapidly switch between the positive and negative

half cycles of alternating current. Advanced Squarewave is

an enhanced version of this output waveform.

Resistance Spot Welding (RSW): A process in which two

pieces of metal are joined by passing current between elec-

trodes positioned on opposite sides of the pieces to be welded.

There is no arc with this process, and it is the resistance of

the metal to the current flow that causes the fusion.

Stabilizer: A device used in AC welding to assist re-ignition of

the arc as current passes through the sine wave zero point.

Straight Polarity: An old nonstandard term denoting electron

flow from the electrode to the workpiece.

Submerged Arc Welding (SAW): A process by which metals

are joined by an arc or arcs between a bare solid metal

electrode or electrodes and the work. Shielding is supplied

by a granular, fusible material usually brought to the work

from a flux hopper. Filler metal comes from the electrode and

sometimes from a second filler wire or strip.

Reverse Polarity: An old nonstandard term denoting electron

flow from the workpiece to the electrode.

Root: A nonstandard term to denote joint root or weld root.

Root Opening: The separation of the members to be welded

together at the root of the joint.

SCR: Silicon Controlled Rectifier. Used to change AC current

to DC. Functions as an output control device for regulating

the current/voltage and arc off-on ability.

T-Joint: A joint produced when two members are located

approximately 90˚ to each other in the shape of a “T”.

Secondary Power: Refers to the actual power output of

a welding machine. This includes the load voltage while

welding, measured at the output terminals and the current

(amperage) flowing in the circuit outside the welding machine.

Secondary amperage can be measured at any point along the

secondary circuit.

Thoriated Tungsten: GTAW tungsten electrode with small

amount of thorium added. Improves arc starting and provides

for use of wider current range.

Three-Phase: When an electrical circuit delivers three cycles

within a 360˚ time span, and the cycles are 120 electrical

degrees apart, it is a three-phase circuit.

TIG: The abbreviation for Tungsten Inert Gas. A shop term for

the Gas Tungsten Arc Welding process.

Sensitization: The changing of a stainless steel’s physical

properties when being exposed to a temperature range of

800˚ – 1600˚ F, 427˚ – 870˚ C for a critical period of time.

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