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42. WELDING/SOLDERING/BRAZING
•Welding is the process of joining two or more objects together. In general this is done by melting the adjacent surfaces, or by melting a third material that acts as a ‘glue’
•We can categorize welding by processes,
Arc |
Carbon Electrode |
Shielded |
Shielded |
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Inert Gas |
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UnShielded |
Carbon Arc |
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Twin Carbon Arc |
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Metal Electrode |
Shielded |
CO2 Mig |
CO2 |
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Flux |
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Arc-Spot |
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Coated Electrode |
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Electro Slag |
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Imp. Tape |
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Inert Gas |
Mig |
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Tig |
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Arc-Spot |
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Plasma |
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Stud |
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Submerged |
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Unshielded |
Bare Electrode |
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Stud |
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Brazing |
Block |
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Dip |
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Flow |
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Furnace |
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Induction |
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Resistance |
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Torch |
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Twin Carbon Arc |
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Electron Beam |
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Explosive |
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Flow |
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Forge |
Die |
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Friction |
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Hammer |
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Roll |
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Gas |
Air Acetylene |
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Oxy Acetelene |
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Oxy Hydrogen |
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Pressure |
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Induction |
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Ion Beam |
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Laser Beam |
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Resistance |
Flash |
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Percussion |
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Projection |
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Spot |
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Seam |
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Upset |
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Thermit |
Nonpressure |
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Pressure |
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Ultrasonic |
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page 217
42.1 ADHESIVE BONDING
42.2 ARC WELDING
•Basically, an electric arc is used to heat base metals and a consumable filler rod.
•This is the most common form of welding and is used in about half of all applications.
•A power supply is used to create a high potential between an electrode (guided by the welder) and a metal work piece. When moved close enough electrodes break down the air and start to flow. The local current of the flow is so high that it heats metals up to 30000C or 54000F.
welding stick
electric arc
work piece
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metal welding table |
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•Material is added during this welding process.This material can come from a consumable electrode, or from a rod of material that is fed separately.
•The electrodes/rods are often coated. This coating serves a number of functions,
-it protects the welder from contact
-it deoxidizes and provides a gas shield
•Problems that arise in this form of welding is contamination of the metal with elements in the atmosphere (O, H, N, etc.). There can also be problems with surfaces that are not clean. Solutions to this include,
Gas shields - an inert gas is blown into the weld zone to drive away other atmospheric gases.
page 218
Flux - a material that is added to clean the surface, this may also give off a gas to drive away unwanted gases.
• Common types of processes include,
SMAW (Shielded Metal Arc Welding)/Stick Welding - A consumable electrode with a coating that will act as a flux to clean the metal, and to create a gas shield.
work |
coating sets up gas shield |
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coating
filler material
coating
MIG (Metal Inert Gas) - A consumable electrode in a gas shield. In addition to simple materials, this can handle aluminum, magnesium, titanium, stainless steel, copper, etc. This torch is normally water or air cooled.
gas to shield the arc
work
electrode and feed rod
rod is fed into work
TIG (Tungsten Inert Gas) - A nonconsumable tungsten electrode is used with a filler rods and a gas shield. This can handle aluminum, titanium, stainless steel, copper, etc. This torch is normally water or air cooled.
page 219
gas to shield the arc
work 
tungsten electrode
rod is fed into work
SAW (Submerged Arc Welding) - A normal wire is used as a consumable electrode, and the flux is applied generously around the weld. The weld occurs within the flux, and is protected from the air.
flux covers weld
work
electrode and feed rod
rod is fed into work
•Process variables include,
-electrode current 50-300A is common
-voltage
-polarity
-arc length
-speed
-materials
-flux
-workpiece thickness