Welding Technology Fundamentals
362
In friction welding (FRW), one part is held stationary, while the other part is held in a chuck and rotated
rapidly. The parts are pressed tightly together. Friction heats the two parts to their welding temperature.
When the welding temperature is reached, the rotation is stopped. The parts are then suddenly forced
together under heavy pressure. After the heavy pressure is applied, the parts are held firmly until they cool.
In friction stir welding, a rotating tool under high pressure develops heat in the base metals. The
spinning tool mixes the softened base metals.
In ultrasonic welding (USW), a very high-pitched sound is used to vibrate the surfaces of the metals to be
welded. An ultrasonic transducer causes either a wedge-reed or a lateral drive to vibrate extremely fast.
This, in turn, causes a sonotrode (sound electrode) to vibrate. A slight force is applied to the parts through
the sonotrode. The vibrations break up surface films, causing the parts to bond together without heat.
In a laser beam welding (LBW) machine, electrical energy is used to excite a lasing material in the laser
source, releasing photons. Photon energy is released as a laser beam. The photons in the laser beam
produce heat by striking, and having their energy absorbed by, the base metal, fusing the joint.
In an electron beam welding (EBW) machine, electrons are emitted from the electron gun. They are then
focused and directed at the weld joint. The kinetic energy of the electrons creates the heat for welding.
Oxyfuel gas cutting (OFC) is a process that can be done underwater, using a special torch. The torch
has an air jacket installed around the cutting tip. Also, a tube is added to carry compressed air to the
air jacket. The compressed air in the air jacket keeps water away from the cutting tip.
Oxygen arc cutting (OAC) uses an electrode and electrode holder. The electrode holder is equipped
with an oxygen passage. Preheating is done by striking an arc between the hollow electrode and the
metal to be cut. Once the arc is struck, the cutting oxygen lever is depressed, oxygen flows through the
hollow electrode, and the cutting begins. Oxygen arc cutting may be done above or below water.
Air carbon arc cutting (CAC-A) and gouging use an arc to melt the base metal. High pressure air
blowing through holes in the electrode holder removes molten metal from the cutting area.
Exothermic cutting uses an electrode filled with small fuel wires and high volume oxygen to burn
continually without a fuel gas or an arc. The high pressure oxygen blows the molten metal out of the
cutting area. Cutting rods or burning bars are used to cut or gouge any metal or nonmetal.
Lasers (particularly the CO2 laser) can cut mild steel, stainless steel, and even titanium cheaply and
quickly. Laser beam cutting (LBC) produces clean-cut edges.
Write your answers on a separate sheet of paper. Please do not write in this book.
1. How many welding and cutting processes are listed by the AWS?
2. How does EGW differ from ESW?
3. List three gases that may be used to form the plasma for PAW.
4. What process is used to rapidly weld nails, bolts, and location pins to metal plates?
5. List at least four advantages of SAW.
6. List three or more processes used to weld or cut underwater.
7. How is the oxygen delivered to the kerf area in OAC?
8. Which special welding process presses a rotating part against a stationary part?
9. In LBW, the metal is heated by a(n) _____ with high energy density. In EBW, the metal is heated by
_____ energy.
10. What temperature does the exothermic cutting process achieve?
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