SAW Applications 335

AC

Alternating current. An electrical current that reverses direction at regularly recurring intervals of time. In the United States, typical AC switches direction 60 times per second, or 60 hertz (Hz).

alternating current

AC. An electrical current that reverses direction at regularly recurring intervals of time. In the United States, typical alternating current switches direction 60 times per second, or 60 hertz (Hz).

American Welding Society

AWS. The non-profit organization that regulates industrial standards for welding. The American Welding Society also promotes the welding industry in the United States.

amperage

The amount of current flowing through a circuit. Amperage is measured in amperes (A), or amps.

arc

The area in which electricity transfers between the electrode and the workpiece. The arc generates the heat that melts the base metals and filler metal during welding.

arc blow

A condition that occurs when the arc does not follow its intended path from the electrode to the workpiece. Arc blow can cause undesirable weld beads and porosity.

arc blow porosity

A discontinuity characterized by the appearance of tiny voids that occurs when arc instability causes gases to be trapped in a weld bead. Arc blow porosity occurs when arc instability introduces nitrogen and contaminants from the atmosphere into the weld.

arc length

The distance that electricity must travel from the tip of the electrode to the weld puddle. Arc length is determined by voltage.

arcing

The flow of electricity through the air from one conductor to another. Arcing can be dangerous, especially when it occurs accidentally.

automatic SAW

A mode of SAW in which mechanical equipment holds the electrode and guides it along the joint with minimal operator involvement. Automatic SAW systems typically use a welding head and travel carriage or a manipulator.

bearings

A friction-reducing device that allows moving parts to glide past one another. Bearings facilitate linear or rotational movement.

burnthrough

A discontinuity that occurs when weld metal from one side of a joint melts through to the other side. Burnthrough can leave an open hole in the joint, which must then be ground down and re-welded.

circuit

A controlled path for electricity. All arc welding processes require a closed electrical circuit that includes a source, path, load, and control.

circumferential welds

A weld produced around the outer or inner surface of a cylindrical or spiral workpiece. Circumferential welds are used to fabricate structural pipes.

codes

A collection of laws or standards that outline practices for a particular application. Welding codes ensure safe welding practices and high-quality welded products.

concave

Curving inward, like the interior of a bowl. Excessively high voltages can lead to concave weld beads.

constant current

CC. A power supply in which the amperage is set at a fixed level and the wire feed speed (WFS) varies to maintain the constant amperage. With constant current power, the voltage is also set at a fixed level and maintained by the varying WFS.

constant voltage

CV. A power supply in which the voltage is set at a fixed level and the amperage varies to maintain the constant voltage. With constant voltage power, the wire feed speed (WFS) is also set at a fixed rate and maintained by the varying amperage.

consumable electrode

An electrode that conducts electricity to the arc and melts into the weld as filler metal. SAW uses a consumable electrode in the form of a wire.

contact tip

The device located inside the welding head or gun that conducts electricity to the electrode. The contact tip is usually made of copper.

contact tip to work distance

CTWD. The distance from the contact tip of the welding head or gun to the workpiece surface. For SAW, contact tip to work distance is generally eight times greater than the electrode diameter.

convex

Curving outward like the exterior surface of a circle or sphere. Fast cooling rates can lead to convex weld beads.

CTWD

Contact tip to work distance. The distance from the contact tip of the welding head or gun to the workpiece surface. For SAW, CTWD is generally eight times greater than the electrode diameter.

current

The flow of electricity through a circuit. Current is measured in amperes (A), or amps, and controls the heat of the arc.

DC

Direct current. An electrical current that flows in one continuous direction. DC does not reverse the direction of flow.

DCEN

Direct current electrode negative. Current that always flows in one continuous direction from the negative electrode to the positive workpiece. DCEN polarity is also known as straight polarity, but this is a nonstandard term.

DCEP

Direct current electrode positive. Current that always flows in one continuous direction from the negative workpiece to the positive electrode. DCEP polarity is also known as reverse polarity, but this is a nonstandard term.

defects

An irregularity in the specified and expected composition of a weld that exceeds the part design's tolerances. A defect is an unacceptable discontinuity.

deposition rate

The rate at which filler metal melts off the electrode and into the weld puddle, which is measured in pounds per hour (lb./hr.) or kilograms per hour (kg/h). In SAW, the deposition rate depends on the amperage, the number of electrodes, and the polarity of the current.

diffusible hydrogen

The maximum amount of hydrogen, given in milliliters (mL), that will be present per 100 grams (g) of weld metal. A flux-electrode classification may include a designation for diffusible hydrogen.

direct current

DC. An electrical current that flows in one continuous direction. Direct current does not reverse the direction of flow.

direct current electrode negative

DCEN. Current that always flows in one continuous direction from the negative electrode to the positive workpiece. Direct current electrode negative polarity is also known as straight polarity, but this is a nonstandard term.

direct current electrode positive

DCEP. Current that always flows in one continuous direction from the negative workpiece to the positive electrode. Direct current electrode positive polarity is also known as reverse polarity, but this is a nonstandard term.

discontinuities

An irregularity in the specified and expected composition of a weld. Discontinuities are not always defects.

electric shock

The flow of electricity through the body. Severe electric shock can be fatal.

fixtures

A device used to hold and secure a workpiece during welding. A welding circuit may connect to the workpiece through the fixture.

flash-through

Unintended exposure of the electrical arc through the flux and slag. Flash-through typically occurs because of insufficient flux.

flux

A nonmetallic material used to protect the weld puddle and arc from atmospheric contamination. SAW uses a blanket of loose, granular flux that covers the arc and weld puddle.

flux dam

A device used to secure loose flux and prevent it from falling off the workpiece during circumferential welding. Flux dams, also known as flux supports, must be insulated to prevent them from conducting electricity.

flux delivery system

A collection of hoses and tubes that transport flux from a storage container to the weld area. Flux delivery systems may transport flux to an SAW gun, a flux hopper, or a flux dispensing nozzle.

flux depth

The height of the flux pile in SAW. The flux depth must be sufficient to fully cover the arc but not prevent gas from escaping.

flux recovery system

A vacuum-powered assembly used to collect used flux material from SAW. Flux recovery systems are most commonly used with automatic SAW.

flux support

A device used to secure loose flux and prevent it from falling off the workpiece during circumferential welding. Flux supports, also known as flux dams, must be insulated to prevent them from conducting electricity.

heat treatment

A controlled heating and cooling process used to change the structure of a material. Heat treatment alters a material's physical and mechanical properties.

humidity

The presence of water vapor or moisture in the air. Excessive humidity can make an area unsuitable for storing flux material for submerged arc welding.

hydrocarbons

A chemical compound that contains only hydrogen and carbon. Hydrocarbons can contaminate SAW fluxes.

hydrogen

A colorless, odorless gas that is the most abundant element on the planet. Hydrogen can cause weld metal to crack.

impact strength

The measure of a material's ability to withstand sudden, sharp blows without fracturing or breaking. The impact strength of a weld can be determined by putting the weld through different types of impact testing.

incomplete fusion

A discontinuity in which the weld metal and base metal or adjoining weld beads are not fully fused. Incomplete fusion significantly weakens the integrity of the weld.

inductance

The generation of or change in an electric current caused by another electric current. Inductance can occur with AC systems but not DC systems.

interpass temperature

The temperature of the base metals around the joint between weld passes. Welders must monitor the interpass temperature during SAW.

lead electrode

The electrode wire located at the front of the weld puddle during tandem arc SAW. The lead electrode can be powered by AC or DC.

manipulator

An SAW machine with a boom and a column that allow the welding head to move in all directions. Manipulators are used for automatic SAW.

melt-off rates

The rate at which metal melts off the electrode. The melt-off rate is measured in pounds per hour (lb./hr.) or grams per minute (g/min).

mill scale

A tough surface contaminant found on metals that is composed mainly of iron oxides. Mill scale can contaminate a weld and cause porosity.

multi-arc SAW

An SAW process that uses two or more electrodes at the same time. Multi-arc SAW methods include twin arc and tandem arc SAW.

nitrogen

A colorless, odorless, tasteless gas that naturally makes up 78% of breathable air. Arc instability can introduce nitrogen into the weld bead, which leads to arc blow porosity.

parallel electrode SAW

A multi-arc SAW process that uses two electrodes connected to the same power source. Parallel electrode SAW, also known as twin arc SAW, uses small electrodes.

penetration

The depth to which the arc heat melts the joint below the surface of the base metals. The amount of amperage directly affects weld penetration.

polarity

Having two oppositely charged poles, one positive and one negative. Polarity determines the direction in which current flows.

porosity

A discontinuity characterized by the appearance of tiny voids in a weld bead, resulting from trapped gases in a material. Excessive porosity can weaken a weld.

power source

The device that provides the electricity needed to perform arc welding. SAW power sources can typically run on AC or DC and in CC or CV mode.

preheat temperature

The temperature of the base metals around the joint immediately before welding begins. Base metals must stay at or above the preheat temperature during welding.

pressure vessels

A closed container designed to hold liquids or gases at high pressures. Pressure vessels include propane tanks.

relative humidity

The amount of water in the air at a given temperature compared to the maximum amount of water the air could hold at that temperature. Flux manufacturers may provide specific relative humidity recommendations for flux storage locations.

rollover

A weld discontinuity that occurs when weld metal spills over the edge of the weld groove or forward ahead of the arc. During SAW, an excessively slow travel speed can result in rollover.

rotary positioners

A welding fixture that rotates the workpiece. Rotary positioners are often used for circumferential welding.

rotary work clamp

A component used to connect the work cable to the workpiece with a rotating mechanism that allows it to move without moving the cable. Rotary work clamps are used when the work cable must be attached to a rotating workpiece.

SAW

Submerged arc welding. An arc welding process that uses a consumable wire electrode and a layer of flux over the weld to shield the arc. SAW, also known as subarc welding, has no visible arc and produces a clean, spatter-free weld.

scavenging elements

A material that cleanses and purifies the weld puddle while it is still in a molten condition. Scavenging elements can help improve the quality of the finished weld.

seam welds

A continuous weld made on or between the surfaces of overlapping parts. Seam welds are often used for tanks and pipes.

semi-automatic SAW

A mode of SAW in which an operator manipulates a welding gun to guide the electrode. Semi-automatic SAW is less popular than automatic SAW because it provides lower deposition rates.

side beam

A horizontal beam that supports the travel carriage and welding head. The welding head moves along the side beam to track the electrode along the joint.

single-arc SAW

An SAW process that uses only one electrode. Single-arc SAW is ideal for seam welds on sheet metal and short welds.

slag

Cooled flux that forms on top of the weld bead. Slag protects the cooling metal and is chipped off after the weld puddle cools.

subarc welding

An arc welding process that uses a consumable wire electrode and a layer of flux over the weld to shield the arc. Subarc welding, also known as submerged arc welding (SAW), has no visible arc and produces a clean, spatter-free weld.

submerged arc welding

SAW. An arc welding process that uses a consumable wire electrode and a layer of flux over the weld to shield the arc. Submerged arc welding, also known as subarc welding, has no visible arc and produces a clean, spatter-free weld.

tandem arc SAW

A multi-arc SAW process that uses two or more electrodes that are connected to separate power sources. With tandem arc SAW, the lead electrode is at the front of the weld puddle and the trail electrode is at the back.

tensile strength

A material's ability to resist forces that attempt to pull it apart or stretch it. Tensile strength is usually expressed in pounds per square inch (psi) or in kilopascals (kPa).

trail electrode

The electrode wire located at the back of the weld puddle during tandem arc SAW. The trail electrode must be powered by AC.

travel carriage

A motor-driven device that moves the welding head along the joint. The travel carriage is mounted to the side beam of an SAW machine.

travel speed

The rate at which the electrode moves along the seam to make a weld. Travel speed affects bead shape and penetration.

twin arc SAW

A multi-arc SAW process that uses two electrodes connected to the same power source. Twin arc SAW, also known as parallel electrode SAW, uses small electrodes.

undercut

An undesired gap left along the edge of a finished weld. Undercut can be caused by excessively high voltages or fast travel speeds.

voltage

The electrical force or pressure that causes current to flow in a circuit. Voltage is measured in volts (V).

weld beads

The end product of a joint that has been welded. Weld beads are formed using a variety of different techniques.

weld puddle

The small area of molten metal that forms during welding. The cooled weld puddle forms the permanent joint.

welding gun

A hand-held welding instrument that conducts electricity and guides the electrode. Welding guns are used in semi-automatic SAW.

welding head

A component with a contact nozzle that holds and positions the electrode during automatic SAW processes. The welding head is attached to a travel carriage that moves it along the joint.

welding procedure specification

WPS. A written document that contains all the necessary and specific information for creating a qualified weld. A welding procedure specification must be approved and tested before welding can begin.

wet-in

The process of a liquid filler metal spreading across and adhering to a solid workpiece surface in a thin, continuous layer. Excessively fast travel speeds can reduce wet-in.

WFS

Wire feed speed. The rate at which the wire electrode is fed through the contact nozzle. WFS is measured in inches per minute or meters per minute.

wind towers

A large vertical structure with turbines used to convert power from moving air into other types of energy. A wind tower's main cylindrical portion is often produced by submerged arc welding.

wire brush

A tool with wire filaments used to clean the surface of a workpiece. Wire brushes can be used to prepare base metals before welding or to clean finished welds.

wire feed speed

WFS. The rate at which the wire electrode is fed through the contact nozzle. Wire feed speed is measured in inches per minute or meters per minute.

wire feeder

A device that delivers a supply of wire electrode to a welding gun or welding head. A wire feeder may be combined with a flux tank for SAW.

wire reel assembly

A set of components used to hold a coil of wire electrode for delivery to the contact nozzle. A wire reel assembly may be mounted on a travel carriage for submerged arc welding.

wire straightener

A component of the welding head through which the electrode passes before passing through the contact tip. The wire straightener ensures that the electrode comes straight out of the contact tip, not at an angle.

work cable

The path used in arc welding to conduct electricity between the power source and the workpiece. The work cable connects to the workpiece via the work clamp.

work clamp

A component that connects the work cable from the power source to the workpiece. The work clamp is used to complete the welding circuit between the workpiece and the electrode.

WPS

Welding procedure specification. A written document that contains all the necessary and specific information for creating a qualified weld. A WPS must be approved and tested before welding can begin.