Lec16

Question 1

Brazing is

Answer 1

process in which filler metal is placed between surfaces to be joined - used as glue

Question 2

Brazing filler metal

Answer 2

melts about 450 C BELOW the melting temp of metals to be joined

Question 3

Strength of brazed joint depends on

Answer 3

joint design
adhesion at the interface
filler metal

Question 4

Preparing of brazing surfaecs

Answer 4

chemically or mechanically cleaned to ensure full capillary action

Question 5

Brazing

Answer 5

temp raised enough to melt the filler metal but not the workpiece
molten metal fills the closely fitted space by capillary action

Question 6

Braze welding

Answer 6

filler metal is deposited at the joint with technique similar to oxyfuel gas welding

Question 7

Brazing vs welding process

Answer 7

1 composition of brazing alloy is different from base metal
2 strength of brazing alloy is lower than base metal
3 melting point of brazing alloy lower than base metal
4 bonding requires capillary action

Question 8

Braze joints of desired strength must

Answer 8

have sufficient area of joint to form bond

Question 9

Adv of brazing

Answer 9

virtually all metals can be joined
ideal for dissimilar metals (ferrous to non ferrour different melting points)
less heating is required compared to welding (quicker and more eonomical small HAZ)

Question 10

Shapes brazing is good for

Answer 10

thinner and more complex assemblies wont melt through materal

Question 11

disadv of brazing

Answer 11

subsequent heating of the assembly can cause inadvertent melting of the braze metal (weaken or destroying joint)
brazed joints fail when workers apply hear in an attempt to straighten or repair damaged assemblies

Question 12

Brazing vs welding

Answer 12

brazing is fast parent metal doesnt metal like to unlike

welding stronger joint higher temp needed join zone at temp for longer

Question 13

differences between welding and brazing

Answer 13

brazing always uses filler different to parents welding sometimes uses filler metal
welding does always need a flame
brazing is quicker and cheaper
welding typically temp hot enough to melt parents
brazing never melt parents

Question 14

Soldering

Answer 14

filler metal called solder relatively low temps 450C
solder fills joint by capillary action
high wetting capability and low surface tension

Question 15

soldering heat source

Answer 15

soldering irons torches ovens

Question 16

Brazing vs soldering

Answer 16

solder temps relaively low - limited use at elevated temps - solder filler metals at less than 450 C

Question 17

Adv of soldering

Answer 17

solder metals are cheap and have acceptable mech prop

can be used to join a wide variety of sizes shapes and thickness

Question 18

applications of soldering

Answer 18

electronis industry
electrial coupling
gas/airtight seals
aluminium radiators in automotive industry

Question 19

Mechanical fastening

Answer 19

no fusion or adhesion of surface

mechanical interlocking and interference of surfaces brought about by clamping forces

Question 20

Selection of type of fastener depends on

Answer 20

materials to be joined
function of joint
strength and reliability required
weight limitations
dimensions of components
environmental condition

Question 21

Choose mechanical fastening based on

Answer 21

cost - cheap
appearance - is it gonna be okay with additional fixing
need for future disassembly - quickly and easily

Question 22

When using mechanical fastenings you should

Answer 22

use fewer but larger faseners less coslty
minimum number of fasteners req
use standardised fasteners
holes should be far from edges or corners

Question 23

Adv of mechanical fastening

Answer 23

ease of manufacture
ease of assembly and transportation
easy of disassembly maintenance repair
ease of design - movable joints
low cost

Question 24

Mechanical fastening types

Answer 24

metal stitching or stapling
seaming
crimping
snap in fasteners

Question 25

metal stitching

Answer 25

joining thin metallic and non metallic materials eg staples in carboard

Question 26

seaming

Answer 26

folded two thin pieces of materials (coke can)

Question 27

crimping

Answer 27

caps are fastened to bottles tubular or flat parts - forcing two parts together

Question 28

snap fasteners

Answer 28

classic mechanical fastening

automotive bodies and household appliances