Lecture 7 Flashcards
What are the three types of resistance welding?
- Resistance spot welding
- Resistance seam welding
- Resistance projection welding (dimples)
Which metal is the most common to be spot welded?
Steel
What are the two types of resistance seam welding?
Overlapping spot welds (electrodes are rotating discs) and resistance butt welding
Resistance welding is used mostly for XXX.
Lap joints
In resistance, XXX and XXX are combined to induce XXX.
Heat, pressure, coalescence
Does melting of base metal occur in resistance welding?
Rarely
Where is the resistance coming from in resistance welding?
- Bulk resistance of the electrodes (small)
- Contact resistance between the electrodes and the workpiece (small)
- Contact resistance between the faying surfaces (large!)
What factors must be controlled to produce uniform resistance welds?
- Quality of surfaces (surface roughness, finish)
- Presence of non-conductive contaminants
- Pressure
- Contact area
What happens if too little or too much pressure is applied?
Too little: High contact resistance, electrode burning and pitting
Too high: Electrode indent in workpiece or molten metal expulsed from faying surfaces
How do you know the metal reached the right temperature in forge welding?
By color.
What machine is used in roll welding or roll bonding?
A rolling mill.
For what type of joints is friction stir welding used?
Butt joints
What type of vibrations is used in ultrasonic welding?
Shear vibrations
What temperature is reached during ultrasonic welding?
The temperature at the interface rarely exceeds one-half of the melting point of the material.
Ultrasonic welding is restricted to?
Lap joint welding of thin materials.
