Chapter 3 Flashcards
Coalescence
Joining together of two or more metals
SMAW - Other Name?
Currents ?
pros ?
Cons?
Shielded Metal Arc Welding (SMAW) AKA - Stick welding
Currents (AC / DCEP / DCEN)
Flux
- Shielding from electrode coating
- Deoxidation, alloy properties
- Insulation for weld metal for slower cooling
- Globular transfered electrode
PROS: Simple / inexpensive /portable / small / lightweight / can weld underwater / weld most alloys /flexible / good for hard to reach areas
CONS: Slow speed / Arc blow / discontinuities / clean up of slag / manual only / not good for low temp welding
Slag
Floats on the outside of the melted weld material
solidifies after the molten metal does, so it slows down the cooling of the weld and also has a less likelihood that it will be trapped inside the weld resulting in slag inclusion
Electrode coating characteristics in SMAW
Shielding - some shielding decomposes to form a gaseous shield for the molten metal
DEIXIDATION - Flux action to remove impurities and oxygen and other gases
ALLOYING - Adds alloying elements to the weld
IONIZING - when flux becomes molten it improves electrical characteristics to increase arc stability
INSULATING - Slag is a insulating blanket that slows down the weld metal cooling rate - The thinkers the slag the better weld appearance you will have
Electrode Identification E XX X X E xx x x
E - Electrode
xx - Strength
x - Position (1=any pos / 2 = flat / 4 = downhill) 3 not used
x - other characteristics determined by the composition
SMAW - Electrode Identification of the X’s
- E XX X X
/\
1 = use in any Position 2 = flat of horizontal for fillet welds 3 = Not used anymore 4 = downhill progression
GMAW - Other Name? Currents ? Metal transfer modes pros ? Cons?
Gas Metal Arc Welding - MIG welding
usually used in DCEP
Metal transfer modes
- Spray, globular, pulsed arc & short circuiting
PROS
Can be automated / little to no clean up during welding
no slag or flux / increased productivity /
CONS
not well suited for field welding / very sensitive to wind & drafts / more complex equipment / mechanical problem can arise / incomplete fusion happens often
- Porosity doe to contamination of loss os shielding
- Incomplete fusion due to use os short circuiting transfers on heavy sections
- Worn liners can cause instability
GMAW - Electrode Identification ER XX S X
ER = Electrode & Rod XX = Strength S = Solid wire X = Chemical composition
Flux Cored Arc Welding
- Similar to GMAW
- FCAW-G - Gas shielded
- FCAW-S - Self shielded
- Electrode is tubular and contains a granular flux instead of a solid wire used in GMAW
- There may or may not be an externally-supplied shielding depending on the electrode used
- shelf shielding
- Gas used are - CO2 or 75%argon & 25%CO2
- G & GS refer to multi pass or single pass
- DCEP (1,2,3,4,6,9,12) or DCEN (7,8,10,11,13,14) or 5 =both
PROS High (most) productivity / Deep penetrating arc / Can handle more metal contamination the GMAW / lack of maintenance can cause issues
CONS
Has slag that must be produced / smoke during welding
/more complex than SMAW
FCAW - Electrode Identification ER XX T X
E = Electrode
X = Strength
X = Position* (0=flat or horizontal / 1=any position)
T = Tubular
X = Chemical / operating composition
(1,2,5,9,12 suffix Electrode require external shielding)
GTAW Electrode type? Filler material? Gas? Best used for ? Currents? Details? Pros? Cons?
Gas Tungsten Arc Welding
- Electrode is not consumable (arc created between the tungsten electrode and the work
- Filler metal must be added externally
(same designation for filler as GMAW) - gas shielding (Aragon and helium
(inert gas won’t combine with metal) - Used on a lot of aluminum because of the BALL TIP
(less concentration of current unlike the pointy electrodes) - DCEP = more heating of electrode (common for steel)
- DCEN = heat base metal more
- AC - heats both - (good for aluminum)
PRO - can weld all metals because electrode is not consumed during welding
- good for aluminum
- can weld at extremely low currents
- can weld the thinest of metals
- good 4 aerospace, food & drug processing, petrochemical
- High quality and visually appealing welds
- NO SLAG due to no FLUX
- don’t need filler material in all cases - cane use a small piece of base metal and feed by hand for filler
CON - Slowest of weld processes - Low tolerance for contamination - req. high skill level - higher cost - Tungsten inclusions - caused by... (contact of electrode tip to base metal of filler material spatter on the electrode tip / exceeding current limit for electrode diameter / over heating of electrode / improper gas / Defects on electrode)
GTAW - Electrode Identification
EWP
EWCe-2
EWLa-1
E = Electrode
W = stand for tungsten
the color coded based on allow chosen
SAW Electrode type? Filler material? shielding? Best used for ? Currents? Pros? Cons?
Submerged Arc Welding SAW - “SUBMERGED ARC”
Continuously fed SOLID WIRE electrode (Like GMAW)
with an ace totally covered with GRANULAR FLUX distributed ahead of or around the wire
Seperat electrode & Flux so many combinations
- Alloy electrode with neutral flux
- Mild steel electrode with alloy flux
DC - constant voltage power source
Pro
- Most efficient - High weld deposition
- No need for protective clothing and eye shielding
- Not a lot of smoke
- Granular flux can be reused if not consumed already
- Can be mechanized
- Can be used on numerous metals
- Deep penetration
CONS
- Slag and clean up
- Cant see the arc for alignment purposes
- has to be used in flat or Horizontal position to a device will need to be used to hold flux
- Need protection from moisture
- Solidification cracking - extreme width to depth ratio
SAW - Electrode Identification
FXXX-EXXX
F = FLUX X = Strength X = A (as welded) or P (post weld heat) X = Lowest temp with impact strength
E = Solid electrode X = L (low) M, H (High) Manganese content / c= composite E X = ? X= ?
PAW
Plasma Arc Welding
- Very similar to GTAW (water hose analogy)
- DC - constant voltage power source
- Tungsten electrode (recessed) to create arc
- Uses plasma gas forced through office resulting in constriction of arc - More force
- more localized heat source (full penetration up to 1.2 in thick
TWO TYPES OF OPERATION
- TRANSFERED - arc between tungsten electrode and workpiece (conductive materials welding/cutting due to greater amount of heating of the workpiece)
- NONTRANSFERED - arc between tungsten electrode and copper orifice (nonconductive materials welding/cutting)
TWO GASES REQ. - Shield gas & orifice (plasma) gas
PROS-
- Deep penetration
- Can use “Key Hole” welding
- Localized heat source
- Faster speeds than GTAW - less distortion
- better visibly for welder due to longer standoff
- Tungsten electrode is recessed - not as likely for inclusion
CONS
- limited to welding 1in thickness or less
- Cost of equipment is slightly greater than that for GTAW
- Greater operator skill needed
- Complex equipment
- Inclusion caused by too high of current
- Tungsten
- Copper orifice melting - Tunneling - Keyhole is not complete filled
“Key Hole” Welding
performed on square butt joints with NO root opening
positive indication of complet penetration and weld unifomity
the concentration of heat penetrates through the material and forms a small key hole then as you move along the join is melts back together
no elaborate joint preparation needed
Fast travel speeds
ESW common use? process ARC? used for PROS CONS
Electroslag Welding
- not as common for use
- used for think metals placed edge to edge (vertical joints)
- water cooled copper shoes used to cool welds
- Welds in a single pass (bottom to top) position is considered flat sue to electrode location
- NOT considered ARC welding
(there is an initial arc then it goes out and the heat from the flux melts joints together - RESISTANCE heating of slag
- used for CARBON STEEL
PROS
- Can weld heavy sections
- High (highest) disposition rate
- Can use multiple electrodes
- No special joint preparation
- alignment easily maintained - no angular distortion
CONS
- can only weld thinker materials 3/4” of thicker
- extensive set up time
- not good for thin metals
- gross porosity can occur due to wet flux or pressure leak -form copper shoes
- Gain growth due to extensive heat
OAW
Current / Energy
Process
Shielding
Oxyacetylene Welding “oxyfuel weldings”
- Energy for weld is created by FLAME
- CHEMICAL welding method
- Shielding is accomplished by the flame as well
(no flux or external shielding needed) - Equipment - (oxygen tank / acetylene Tank, Pressure regulators / torch )variety of tip SZ / connecting hose)
- acetylene dissolved in liquid acetone
- unstable at pressures over 15 PSI
- Cylinder must remain upright
- Fuel adjusted to produce a natural flame
- More oxygen = oxidizing flame
- More acetylene = carburizing Flame - Welding of thin metals - best for thin sections
PROS
- Simple / Portable / small / inexpensive
- No electricity needed
CONs
- Dangerous
- flame does not provide concentrated heat
(edge should have thin feather edge)
- Therefore assure adequate fusion
- Degraded weld properties if flame is oxidized/carburized
- Slow process
- Requires HAND FED FILLER material
- High skill lever required
OAW - Electrode Identification RGXX (RG45)
R = ROD G = GAS XX = Strength
SW Process power source Equipment pros cons Shielding?
Stud Welding
- ARC process - between stud and base metal
- Used to weld studs / attachments
- Used on many metals & many industries (bridge/building)
- DC power source
- Can be automated
- Can use gas shielding for aluminum
- Equipment - mechanical gun / power supply / control unit
(4 cycles)
PROS
- little skill needed
- economical and effective
- eliminated need for hole drilling, tapping or other welding
- Easy to inspect (need to be flush and 360d fusion
(inspect with a hammer, pulled or torque)
CONS
- Malfunction can produce poor welds
- TWO possible discontinuities (caused by improper settings or water, heavy rust, or mill scale on the base metal)
- Lack of 360deg flash
- Incomplete fusion at interface
LBW? Process? Contact ? Shielding? Filler? Details? Energy usage? PROS? CONS?
Laser Beam Welding
- Fusion Joining process
- Non-contact process - no pressure required
- Shielding can be used and filler is sometimes needed
- High energy laser beam causes some of the metal at the joint to vaporize
- LASER (light amplification by stimulated emission of radiation
- Key hole welding is used
- used for welding and cutting
- Small cross section / small spot size at workplace though the use of reflective type focusing / very narrow and deep weld bead
- Power level = 25 kW
PROS
- Can be used over long distances through fiber optics and mirrors
- Full penetration / single pass welds (up to 1 1/4in thick / 32mm)
- Low heat input
- 10:1 depth to width ratio (when in key hole more)
- Focused on small areas / close components
- Variety of metals
- Not influenced by magnetic field
- No vacuum / X-ray shielding required (like Electron beam)
CONS
- Complex / expensive (100K)
- Square butt joints required
- work pieces often faced together
- Fast calling rate produced cracks / traps porosity / & caused embrittlement in HAZ
- Plume of vapors is produced - can be controlled with plasma
EBW? Process? Contact ? Shielding? Filler? Details? Energy usage? PROS? CONS?
Electron Beam Welding
- Fusion Joining process
- Beam of high energy electrons
- FOUR BASIC VARIABLES
( beam accelerating voltage / beam current / beam focal spot size / weld travel speed - Key hole welding is used
- used for welding and cutting
- Small cross section / small spot size at workplace though the use of reflective type focusing / very narrow and deep weld bead
- Power level = 50mA-100Ma (much more than LBW
PROS
- Full penetration / single pass welds
- Can be moved around and in diff shapes
- Fast travel speed
- Low heat input
- 10:1 or more - depth to width ratio (when in key hole more)
- Focused on small areas / close components
- Variety of metals
CONS
- Complex / expensive
- vacuum / X-ray shielding required
- Square butt joints required
- work pieces often faced together
- Fast calling rate produced cracks / traps porosity / & caused embrittlement in HAZ
- Need to be vacuumed and are evacuated
- Takes more time to evacuate
- Influenced by magnetic field
RW Types
RSW = Resistance spot welding
RSEM = Resistance seam welding
PW = Projection welding
RW
Process Used for Filler / Flux? Types? Variables?
Resistance welding (RW)
two electrodes apply force and hold metal in intimate contact. Current is then passed through electrodes and the workpiece
- Heat obtained from RESISTANCE of the workpiece
- Application of PRESSURE
- SHEET METAL applications (1/8in thick)
- No Filler of Flux used
- 3 TYPES
- RSW = Resistance spot welding (most common)
- RSEM = Resistance seam welding
(series of overlapping spot welds)
- PW = Projection welding
(dimples / projections formed / multi welds at a time) - Workpiece must be clean
- Semi-automatic / fully automatic
- Extensive use in automotive industry
VARIABLES (Welding current, welding time, electrode force, and electrode material and design)
what is the difference between Brazing / Soldering ?
Brazing
- Filler Materials Mealting above 840f [450c] degrees
Soldering
- Filler Materials Mealting below 840f [450c] degrees
Brazing / Soldering
Joining of metals without melting base metal
just melting filler material creates the bond that can be as strong as the base metal. This bond his due to 2 reasons
1) must have LARGE SURFACE area
2) The gap distance between the 2 metals in minimal
(max 0.010 in [0.25mm]
- Joints must be really clean
- Heat is applied using one of several heating operations
- after filler reaches melting point CAPILLARY ACTION pulls the filler into the tight spaces
- many diff. Brazing filler types
PROS
- Can join all types of metals and some NON METAL items
- and those that can’t be welded
- inexpensive
- no melt through or distortion
CONS
- parts must be extremely clean
- design must have sufficient surface area
- Can have voids and unbound areas is not
- Localized heat can cause problems like melting or erosion of BM
CAPILLARY ACTION
Phenomenon which causes a liquid to be pulled into a tight space between two surfaces
Brazing filler types
wires, strips, foil, paste & Preforms
Brazing filler metal classifications
B = Braze
followed by the abbreviation of the most prominent chemical element included
BAg = Silver BAu = Gold
“R” before the B means chemistry is identical to with copper and copper alloy gas welding rods
Brazing Methods
TB = Torch brazing / oxyfuel flame (manual or semi auto)
FB = Furnace brazing / Controlled , many at once
IB = Induction B / placed inside induction coil to heat metal
DB = Dip brazing immersed in molten bath
IRB Infrared B = high intense infrared light source
OFC Process similar to? fuels PROS CONS
Oxyfuel Gas Cutting
oxyfuel flame to heat metal to it KINDLING temperature (Steel = 1700f) then it will oxidize and burn
CHEMICAL cutting process
Almost the same as OAW - instead of welding - cutting
Fuels that can be used (Mathane (natural gas) / acetylene / propane / gasoline / methyl acetylene-propadiene (MPS)
- consider - cost , availability, safety, cutting speed, amount of oxygen needed to burn, preheating
PROS
- inexpensive / portable
- shop and field application
- cuts can be thin or thick
- reasonably accurate
- can cut several layers at a time with stack cutting system
Cons
- Limited to cutting carbon and alloy steel
- Additional cleaning after cut to pre edge
- HAZ - additional hardness for machining after cut
(Adding pre / post heat will help this problem)
- safety hazards
Kerf
Width of the cut produced by a cutting process
Drag
offset between the cut entry and the exit point, measured along the cutting edge
CAC-A Process fuels PROS CONS
Air Carbon Arc Cutting
Uses carbon electrode to create an arc for heating
then with high pressure steam of comprised air it mechanically removes the molten metal
- CONSTANT current source / and compressed air
- Uses copper jaws with holes for air to pass through
- arc melts metal
- Can produce gouge or cut (Uniform U groove prep)
- Any nonflammable compressed gas can be used
- Compressed air is the best and cheapest
Pros
- Efficient
Cons
- Need copper electrode holder
- Safety related
- noisy / dirty - need PPE
- need fire watch
- Clean up before welding
PAC Process similar to? fuels PROS CONS
Plasma Arc Cutting
- Similar to PAW - but uses much more power
- uses TRANSFERRED ARC due to increased heating
- 8k-10k degrees
Pros
- Cuts what OFC won’t
- high quality cuts
- increased cutting speed for carbon steel
Cons
- Kerf is large - edges may not come out square
- higher cost the OFC
Mechanical Cutting
use of grinders, saws, shearing, turning, drilling, planning, chipping & milling
AC
Alternating current
the polarity alternates at 60 cycles per second
Alphanumeric
combo of letters and #’s used as designations
DCEN
Straight polarity
Direct curent electrode Negative
DCEP
reverse polarity
Direct curent electrode Positive
Plasma
Ionized gas stream
ferrous
Metals that are primarily iron based such as steel
Flux
Material used to hinder the formation of oxides and other undesirable substances in molten metal and on solid metal surfaces - to resolve or remove these substances
Reactive gas
gas that will combine chemical with other materials
Slag
non metallic product produced from the mutual dissolution of flux and nonmetallic impurities in some welding and brazing processes
Solid solution
for metals, one solid dissolving into another solid
Tensile strength
LBS per Sq In (PSI)
Calculated by dividing the maximum load by the cross- section area
SI units are megapascal (MPa)
Weld
Localized coalescence of metal or nonmetals
heating material to welding material
with or without use of filler metal
SMAW ELECTRODE F GROUPS F1 F2 F3 F4
EXX20, EXX24, EXX27
EXXX2, EXXX3, EXXX4
EXX10 , EXXX1
EXXX5, EXXX6, EXXX8 (LOW HYDROGEN / PROPER STORAGE AT 250 DEG
SMAW ELECTRODE SUFFIXES (BE FAMILIAR) A1 B1 B2 B3 B4 W
.5% MO .5% MO ; . 5% CR .5% MO; 1.25% CR 1.0% MO; 2.25% CR .5% MO; 2.0% CR WEATHERING
Arc blow
CAN BE FIXED BU AC CURRENT
CAUSE BY MAGNETIC FIELD
