Welding Flashcards
DMM1: Manufacturing Deck 3
What are the three catigories of welding?
Fusion welding
brazing and soldering
solid state welding
Describe fusion welding
heat is applied to the interfact of two parts felting filler metal and the work pieces to create a connection
describe oxyfuel (oxy-aceltylene) gas welding
combusion of gases create high temperatures which melts the filler metal and workpiece interface
Describe Arc welding
An eletrode creates a large current and voltage between it and the workpiece. this creates a spark which melts the workpiece and filler metal
What is a shielding gas?
An inert gas e.g. Argon which is used to sheild a weld from oxidation during welding
how is heat transfer of arc welding cauculated
H/L = e VI/v
H = heat input in joules
l = weld length
V = voltage applied
I = current
v=welding velocity
e = efficiency
how is weld velocity determined?
v =e VI/uA
v = weld velocity
e = efficency
V = voltage
I = current
u = specific energy (J/m^3)
A= Area
What is Stick welding SMAW?
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
What is flux?
a Chemical additive which improves metal flow and removed impurties and oxides
What is MIG (GMAW) welding
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
What is TIG (GTAW) welding
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
what are the advantages and disadvantages of TIG welding?
ADV: High quality and strong connection, can be done without filler metal
DIS: slow costly and difficult to do
what are the advantages and disadvantages of MIG welding?
ADV: easily automated, fast rapid and econmical, stronger than stick welding
DIS: can only do thin materials
what are the advantages and disadvantages of Stick welding?
ADV: simple easy and versitle, does not require sheilding gas, very portable
DIS: low strength, high oxidation connection
What is Electron beam welding (EBW)?
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
What is laser welding
A high energy laser is used to fuse material together. the laser beam is controlled with a robotic arm and lenses to focus it
What is slag?
Waste material which forms a hard layer on top of the weld
What is a Heat-affected Zone in a weld?
Heat from the welding process causes changes in the microstructure e.g. recystalization which affects its material properties
What factors affect weldablity?
1)fusability of the metal
2)local stress and loading concentrations
3)preparation of the welded edges
4) effect of temperature on the HAZ
What is solid state welding ?
welding using heat, pressure relative movement of workpiece to combine them without melting the parts
What is friction welding?
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
what is friction stir welding?
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
What is Resistance Welding ? what is the difference between the spot and seam version of this process?
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)
What are the advantages and disadvantages of resitance welding?
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
What are the advantages and disadvantages of Friction welding?
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
How does solid state welding work?
High temperature and pressure allows material to diffuse across the interface allowing new crystals to form creating a single homogenous part
What is diffusion bonding/ superplastic forming?
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
What are stop off patterns in diffusion bonding?
Unbonded section of stacked metal sheets whihc expand outwards into the desired shapes
What is brazing/soldering? what is the difference between the two?
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
What are the advantages and disadvanatges of brazing/ soldering
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
