Welding

Question 1

What are the three catigories of welding?

Answer 1

Fusion welding
brazing and soldering
solid state welding

Question 2

Describe fusion welding

Answer 2

heat is applied to the interfact of two parts felting filler metal and the work pieces to create a connection

Question 3

describe oxyfuel (oxy-aceltylene) gas welding

Answer 3

combusion of gases create high temperatures which melts the filler metal and workpiece interface

Question 4

Describe Arc welding

Answer 4

An eletrode creates a large current and voltage between it and the workpiece. this creates a spark which melts the workpiece and filler metal

Question 5

What is a shielding gas?

Answer 5

An inert gas e.g. Argon which is used to sheild a weld from oxidation during welding

Question 6

how is heat transfer of arc welding cauculated

Answer 6

H/L = e VI/v
H = heat input in joules
l = weld length
V = voltage applied
I = current
v=welding velocity
e = efficiency

Question 7

how is weld velocity determined?

Answer 7

v =e VI/uA
v = weld velocity
e = efficency
V = voltage
I = current
u = specific energy (J/m^3)
A= Area

Question 8

What is Stick welding SMAW?

Answer 8

shielded metal-arc welding
electric arc is created between electrode and workpiece melting both and forming the connection
the sheilding gas is created from the eletrode coating as it melts

Question 9

What is flux?

Answer 9

a Chemical additive which improves metal flow and removed impurties and oxides

Question 10

What is MIG (GMAW) welding

Answer 10

Metal Inert Gas or Gas -Metal Arc Welding

consumable elctrode is melted continously with an electic arc while inert gas (e.g. argon) is pumped over the weld to protect it

Question 11

What is TIG (GTAW) welding

Answer 11

Tungsten inert gas welding (gas-tungsten arc welding)

tungesten electrode creates arc which melts both the workpiece and the seperate filler rod to form the connection. tungestens high melting point means the electrode is not damaged creating a constant stable arc

Question 12

what are the advantages and disadvantages of TIG welding?

Answer 12

ADV: High quality and strong connection, can be done without filler metal
DIS: slow costly and difficult to do

Question 13

what are the advantages and disadvantages of MIG welding?

Answer 13

ADV: easily automated, fast rapid and econmical, stronger than stick welding
DIS: can only do thin materials

Question 14

what are the advantages and disadvantages of Stick welding?

Answer 14

ADV: simple easy and versitle, does not require sheilding gas, very portable
DIS: low strength, high oxidation connection

Question 15

What is Electron beam welding (EBW)?

Answer 15

heat is generated by high- velocity narrowbeam electrons. The kinetic energy of the electrons is converted into heat as
they strike the workpiece fusing the material.
magnetic fields are used to precisly control tthe beam

Question 16

What is laser welding

Answer 16

A high energy laser is used to fuse material together. the laser beam is controlled with a robotic arm and lenses to focus it

Question 17

What is slag?

Answer 17

Waste material which forms a hard layer on top of the weld

Question 18

What is a Heat-affected Zone in a weld?

Answer 18

Heat from the welding process causes changes in the microstructure e.g. recystalization which affects its material properties

Question 19

What factors affect weldablity?

Answer 19

1)fusability of the metal
2)local stress and loading concentrations
3)preparation of the welded edges
4) effect of temperature on the HAZ

Question 20

What is solid state welding ?

Answer 20

welding using heat, pressure relative movement of workpiece to combine them without melting the parts

Question 21

What is friction welding?

Answer 21

one part is rotating the other is stationary. the relative movement creates friction which generates the heat for the weld. then an axial force is applied to form a strong joint

Question 22

what is friction stir welding?

Answer 22

a rotating tool applies rotation to create friction and heat. it also applies high pressure to form the connection. this tool moves along a joint to create the weld

Question 23

What is Resistance Welding ? what is the difference between the spot and seam version of this process?

Answer 23

an electrical current is applied across the material. its natural resistance causes it to heat up creating the connection
can be stationary (spot welding)
or move alone a connection (seam welding)

Question 24

What are the advantages and disadvantages of resitance welding?

Answer 24

ADV: does not require consumable eletrodes shielding gas or flux, is easily automated
DIS: creates a HAZ and requires a uniform smooth interface with no oxide layers

Question 25

What are the advantages and disadvantages of Friction welding?

Answer 25

ADV: generally easy to impliment, does not require flux, sheilding gases or consumable eletrodes
DIS: workpiece needs to be well secured, rotational forces may damage the parts
any tools used (e.g. stir welding) must withstand high wear

Question 26

How does solid state welding work?

Answer 26

High temperature and pressure allows material to diffuse across the interface allowing new crystals to form creating a single homogenous part

Question 27

What is diffusion bonding/ superplastic forming?

Answer 27

thin sheets of metal are stacked and prepared with stop off patterns. internal heat and pressure causes them to expand into the desired shape and solid-state weld

Question 28

What are stop off patterns in diffusion bonding?

Answer 28

Unbonded section of stacked metal sheets whihc expand outwards into the desired shapes

Question 29

What is brazing/soldering? what is the difference between the two?

Answer 29

filler metal different to the base metal is melted into the interface connecting the two parts together mechanically
brazing is higher temperature than soldering and is generally stronger

Question 30

What are the advantages and disadvanatges of brazing/ soldering

Answer 30

ADV: low temperature does not damage workpiece, very easy and low cost, can join dissimmilar metals
DIS: weaker bonds and there is no chemical connection, generally low melting point metals used which are weaker and melt easily