Chapter 29

Question 1

Define: Arc Welding

Answer 1

A Fusion-Welding process in which coalescence of the metals is achieved by the heat of an electric arc between an electrode and the work.

Question 2

Define: Consumable vs. Non-consumable Electrode

Answer 2

Consumable: Provide the source of filler metal in arc welding; usually come in rods and wire.

Non-Consumable: made of tungsten which resists melting by the arc. Filler metal added by means of separate wire.

Question 3

Define: Shielding

Answer 3

The process of covering up the electrode tip, arc, and molten weld pool with a blanket of gas or flux, or both, which inhibit exposure of the weld metal to the air.

Question 4

Define: Flux

Answer 4

Substance used to prevent the formation of oxides and other unwanted contaminants, or to dissolve them and facilitate removal.

Question 5

Define: SMAW/Stick Welding

Answer 5

(Shielded Metal Arc Welding) AW process that uses a consumable electrode consisting of a filler metal rod coated with chemicals that provide flux and shielding. Usually performed manually.

Question 6

Define: GMAW/Mig Welding

Answer 6

(Gas Metal Arc Welding) An AW process in which the electrode is a consumable bare metal wire and shielding is accomplished by flooding the arc with gas.

Question 7

Define: FCAW

Answer 7

(Flux-Cored Arc Welding) Arc welding process in which the electrode is a continuous consumable tubing that contains flux and other ingredients in its core. Wire is flexible and therefore, can be supplied int he form of coils. (self-shielded and gas shielded)

Question 8

Define: SAW

Answer 8

(Submerged Arc Welding) AW process that uses a continuous, consumable bare wire electrode and arc shielding is provided by a cover of granular flux

Question 9

Define: GTAW/Tig Welding

Answer 9

(Gas Tungsten Arc Welding) AW process that uses non-consumable tungsten electrode an an inert gas for arc shielding. Implemented with or without a filler metal.

Question 10

Define: Plasma Arc Welding

Answer 10

Special form of gas tungsten arc welding in which a constricted plasma arc is directed at the weld area. Tungsten electrode is contained in a specialized nozzle that focuses a high velocity stream of inert gas into the region of the arc to form a high-velocity and intensity arc stream

Question 11

Define: Resistance Welding

Answer 11

A group of fusion-welding processes that uses a combination of heat and pressure to accomplish coalescence, the heat being generated by electrical resistance to current flow at the junction to be welded

Question 12

Define: Electrode

Answer 12

The metal rod which directs the current into the weld point.

Question 13

Define: Weld Nugget

Answer 13

The fused zone between the two parts during resistance Spot welding

Question 14

Define: Spot vs. Seam Welding

Answer 14

Spot: RW Process in which fusion of the two surfaces of a lap joint is achieved at one location by opposing electrodes. Done with stick-shaped electrode.

Seam: Stick electrodes replaced by rotating wheels and a series of overlapping spot welds are made along the lap joint, producing air-tight joints.

Question 15

Define: Projection Welding

Answer 15

RW process in which coalescence occurs at one or more relatively small contact points on the part. These contact points are determined by the design of the parts to be joined and may consist of projects, embossments, or localized intersections of the part

Question 16

Define: Oxyacetylene Welding

Answer 16

A fusion-welding process performed by a high temperature flame from combustion of acetylene and oxygen. Flame is directed by welding torch and filler metal is sometimes added and pressure sometimes applied.

Question 17

Define: Neutral Flame

Answer 17

The flame from an oxygacetylene torch which has three temperature zones:

1) Inner cone - 3480 C
2) Acetylene feather - 2090 C
3) Outer Envelope - 1260 C

Question 18

Define: Electron Beam Welding

Answer 18

A fusion welding process in which the heat for welding is produced by a highly focused, high-intensity stream of electrons impinging against the work surface. Voltages are very high while currents are very low.

Question 19

Define: Laser-Beam Welding

Answer 19

A fusion-welding process in which coalescence is achieved by the energy of a highly concentrated coherent light beam focused on the joint to be welded.

Question 20

Define: Solid-State Welding

Answer 20

Coalescence of the part surfaces is achieved by pressure alone or a combination of heat and pressure. No filler material.

Question 21

Define: Friction Welding

Answer 21

Solid-state welding process in which coalescence is achieved by frictional heat combined with pressure. The friction is induced by mechanical rubbing between two surfaces.

Question 22

Define: Ultrasonic Welding

Answer 22

Solid-state welding process in which two components are held together under modest clamping force and oscillatory shear stresses of ultrasonic frequency are applied to the interface to cause coalescence.

Question 23

Define: Welding Defects

Answer 23

• Cracks: embrittlement or low ductility of weld
• Cavities: Inclusion of atmospheric gases in the weld metal
• Solid Inclusions:nonmetallic solid materials trapped in weld
• Incomplete Fusion: Fusion hasn’t come over entire x-section
• Imperfect Shape or Contour: Wrong profile for high strength
• Miscellaneous Defects: arc strikes and excess spatter