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Welding Vocabulary
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Welding Porosity- holes in the weld
Weld cracks- cracks on the top or inside the weld bead
Weld distortion- uneven weld bead
Weld spatter- drops of electrode on and around weld bead
Weld undercut- groove melted along either side of the weld and left unfilled
Weld overlap- excess weld metal mounted on top and either side of the weld bead
Too little weld penetration- weld bead sitting on top of the base metal
Too much weld penetration- burn- through beneath the lower base metal
The distance between the contact tip and the weld- 5/16-9/16 inch
Welding wire must carry a minimum specification of- AWS-ER-70-6
MIG welding- produces 100% fusion in the parent metals MIG welding wire- common size .023
MIG/GMAW- metal inert gas/ gas metal arc welding
WELD ROOT: is the part of the joint where the wire electrode is directed
WELD FACE: is the exposed surface of the weld on the side that has been welded
WELD PENETRATION: is indicated by the height of the exposed surface of the weld on the back
side
BURN MARK: is on the back of a weld is an indication of good weld penetration
BURN-THROUGH: results from penetrating too much into the lower base metal, which burns a
hole through the back side of the metal
WELD LEGS: are the width and height of the weld bead
WELD THROUAT: the depth of the triangular cross section of the weld
WELD FIT-UP: refers to holding work pieces tightly together (in alignment)
Chapter 8 outline
Welding
Chapter 8 part 2 welding
TIG Welding
Uses nozzle-fed shielding gas and hand-held filler rod
Limited use in body shop repair applications
Valuable tool in general auto repair and engine rebuilding
Slower speed allows for much more control, resulting in best-looking weld obtainable
Resistance Spot Welding
Used to make many OEM welds on unibody cars
Ideal for welding thin-gauge sections that require good weld strength and no distortion
Relies on resistance heat generated by low-voltage electric current flowing through two pieces of metal
held together, under pressure, by squeeze force of welding electrodes
Resistance Spot Welding (continued)
Resistance spot welding components
Welding transformer, welder control, and welding gun with interchangeable arm sets
Spot welder adjustments
Arm selection, adjustment of arm, alignment of electrode tips, diameter of electrode tip, and electrical
current flow time
Resistance Spot Welding (continued)
Operational considerations when using squeeze-type resistance spot welder
Clearance between welding surfaces
Metal surface to be welded
Corrosion
Performance of spot welding operations
Number of points of spot welding
Minimum welding pitch
Position of welding spot from edge and end of panel
Resistance Spot Welding (continued)
Operational considerations when using squeeze-type resistance spot welder (continued)
Spotting sequence
Welding corners
Inspection of spot welds
Appearance inspection
Destructive testing
Destructive test
Nondestructive test
Other Spot Welding Functions
With proper gun attachment, spot welder can be used as:
Panel spotter
Stud welder
Spot shrinker
Mold rivet welder
Stud Spot Welding for Dent Removal
Studs used in dent removal can be resistance welded with special stud welder
To remove dent properly with either a stud or stud spot welder, a good quality stud is necessary
Stud should have necessary combination of pull strength and tensile strength, while remaining
extremely flexible
Oxyacetylene Welding
Fusion welding
Acetylene and oxygen are mixed in a chamber, ignited at the tip, and used as high-temperature heat
source to melt and join welding rod and base metal together
Welding and cutting equipment
Steel tanks filled with oxygen and acetylene
Regulators
Hoses
Torch
Oxyacetylene Welding (continued)
Types of flame
Neutral flame, carburizing flame, and oxidizing flame
Welding torch flame adjustment
Attach appropriate tip to the end of the torch
Set oxygen and acetylene regulators at proper pressure
Mix acetylene and oxygen as required to obtain neutral flame, carburizing flame, or oxidizing flame
Oxyacetylene Welding (continued)
Gas cutting torch flame adjustment
Adjust oxygen and acetylene valves for preheating neutral flame
Open preheating oxygen valve slowly until oxidizing flame appears
Thick panel cutting method
Heat portion of base metal until it is red hot
Just before it melts, open high-pressure oxygen valve and cut panel
Oxyacetylene Welding (continued)
Gas cutting torch flame adjustment (continued)
Thin panel cutting method
Heat small spot on base metal until it is red hot
Just before it melts, open high-pressure oxygen valve and incline torch to cut panel
Cutting HSS for salvage purposes
Cut metal structure at least 2 inches (51 mm) away from desired cut line
Use grinding wheel disc, air chisel, or metal saw to make final cut at desired cut line
Oxyacetylene Welding (continued)
Cleaning with a torch
Use scraper followed by oxyacetylene torch
If needed, follow with wire brush and torch, using carburizing flame
Keep torch at very low, controlled heat to prevent part damage
Flame abnormalities
Overheating of flame outlet, adhesion of spatter, or fluctuations in gas adjustment pressure will result in
variations in flame and weld
Brazing
Method of welding in which a nonferrous metal with lower melting point than that of base metal is
melted without melting base metal
Interaction of flux and brazing rods
Flux removes oxidized film that covers metal surfaces exposed to atmosphere and prevents reoxidizing
Increases bond between base metal and brazing material
Brazing (continued)
Brazing joint strength
Dependent on surface area of pieces to be joined
Make joint overlap as wide as possible
Brazing operations
Cleaning base metal
Flux application
Base metal heating
Base metal brazing operation
Brazing (continued)
Treatment after brazing
Once brazed portion has cooled down, rinse off remaining flux sediment with water
Scrub surface with stiff wire brush
Baked and blackened flux can be removed with sander or sharp-pointed tool
Soldering (Soft Brazing)
Used only for final finishing, such as in leveling panel surface and correcting surface of welded joints
Soldering procedure
Heat the portion to be soldered. Wipe with cloth after heating
Stir solder paste well. Apply it to an area 1 to 1½ inches (25.4 to 38 mm) larger than built-up area
Soldering (Soft Brazing) (continued)
Soldering procedure (continued)
Heat it from a distance
Wipe solder paste from center to outside
Make sure soldered portion is silver gray
Plasma Arc Cutting
Creates intensely hot air stream which melts and removes metal over a very small area
Operating a plasma arc cutter
Connect unit to a clean, dry source of compressed air with minimum line pressure of 60 psi (413 kPa) at
the air connection
Connect torch and ground clamp to unit. After plugging machine in, connect ground clamp to a clean
metal surface on vehicle. Clamp should be as close as possible to the area to be cut
Plasma Arc Cutting (continued)
Operating a plasma arc cutter (continued)
Move cutting nozzle into contact with an electrically conductive part of the work
Hold plasma torch so that cutting nozzle is perpendicular to work surface. Push plasma torch down,
forcing cutting nozzle down until it comes in contact with the electrode. Then the plasma arc will start.
Keeping cutting nozzle in light contact with the work, drag gun lightly across the work surface
Move plasma torch in the direction metal is to be cut
Plasma Arc Cutting (continued)
Plasma air cutter
Some equipment has built-in safety protection system to protect operator
Cuts output power automatically if:
Safety cup is removed from torch
Tip and electrode are accidentally short-circuited
Duty cycle is exceeded
Some units have a switch to alter current mode when cutting bare or painted metal
Continue with welding ASE style assessment
Practice and prepare for lab exam
Objectives
Objectives for welding (MIG)
Identify the three classes of welding
Explain how to use a MIG welding machine
Name the six basic welding techniques employed with MIG equipment
Describe differences between MIG electrode wires
Determine where and how to use resistance spot welding
Identify oxyacetylene welding equipment and techniques
Objectives (continued)
Explain general brazing and soldering techniques used in a body shop
Describe plasma arc cutting of body panels
Explain plasma cutting techniques
List safety procedures important in each welding operation
Answer ASE-style review questions relating to welding equipment
Introduction
With major collision repair, many of the panels on a vehicle must be replaced and welded into place
Structural integrity of vehicle is dependent on how well repair panels are welded and installed