Chapter 37

Question 1

Solid state welding

Answer 1

Creates joints without melting of the workpiece of fillers.

Question 2

Resistance welding

Answer 2

Heat and pressure are combined to induce coalescence. Electrodes are placed in contact with the material and electrical current is passed between them.

Question 3

Pressure

Answer 3

Applied by the electrodes

Question 4

Pros?

Answer 4

Rapid and economical. No filler required and no fluxes needed.

Question 5

Heat in resistance welding

Answer 5

Obtained by passing a large electrical current through the workpiece for a short period.

Question 6

Total resistance of electrodes consists of:

Answer 6

1) bull resistance of electrodes and workpieces 2) the contact resistance between the electrodes and workpieces 3) resistance between surfaces to be joined, faying surfaces.

Question 7

Resistance between facing surfaces:

Answer 7

A function of 1) quality of surfaces, 2) the presence of contaminants, 3) pressure, 4) the contact area.

Question 8

Pressure?

Answer 8

Too little causes high resistance and pitting or electrodes. Too high causes molten metal to be expelled. A moderate pressure should be used.

Question 9

Temperature of welding?

Answer 9

Determined by the magnitude and duration of the welding current

Question 10

What conditions are preferred?

Answer 10

High currents and short time intervals

Question 11

Power supply?

Answer 11

High currents are generally required to produce a resistance weld

Question 12

Resistance spot welding

Answer 12

Simplest and most widely used form of resistance welding. Provides a fast and economical means of joining materials.

Question 13

Nugget

Answer 13

A satisfactory spot weld full of coalesced metal between faying surfaces

Question 14

Spot welding equipment

Answer 14

Rocker arm machine

Question 15

Larger spot welders?

Answer 15

Generally press type. Moveable electrodes are controlled by an air cylinder

Question 16

Spot welding guns

Answer 16

For desired products that are too large to be manipulated and positioned on a welding machine.

Question 17

Transguns

Answer 17

Welding transformer has been integrated into the welding gun. Transguns offer reduced power losses and enchanted process efficiency.

Question 18

Electrodes

Answer 18

Electrodes should never melt, and should have a composition that does not allot to the material being welded

Question 19

What metals can be used in spot welds?

Answer 19

Virtually all metals can be used.limit on metal thickness is 3 mm.

Question 20

Resistance seam welding

Answer 20

The seam could be an overlapping series of spot welds.

Question 21

Second type of resistance seam welding

Answer 21

Resistance butt welding. Produced butt welds between thicker metal plates. Used mostly for pipes and tubes.any combination of metal can be welded.

Question 22

Projection welding

Answer 22

Produces many spot welds at once

Question 23

How does projection welding work?

Answer 23

A simple is embossed into the workpieces and then pressure and current are applied. Multiple dimples can be used to enable multiple welds. Spot welding machines can be changed to projection welding machines.

Question 24

Capacitor discharge stud welding

Answer 24

A chest of current from an electrostatic site system melts the projection and the pieces are pushed together.

Question 25

Advantages of resistance

Answer 25

Rapid, equipment automated, conserve materials, minimal distortion, not required skilled operators, dissimilar metals may be joined, reliability.

Question 26

Limitations of resistance?

Answer 26

High cost, lap joints are limited, accès to both sides of joint is required for pressure, skilled maintenance is required to service the machine, clean surfaces are necessary, impose heavy electrical load.