welding processes Flashcards
brazing v soldering?
brazing: filler material above 450deg. more stable joints made than soldering. higher cost than soldering
two classes of welding
fusion (melting, mixing, filler material) and solid state (heat/pressure but no melting)
butt joint
parts in same plane, joined at edges
corner joint
parts form right angle, joined at corner
tee joint
like letter T, perpendicular
lap joint
two overlapping joints
edge joint
parts parallel with at least one edge in common
fillet weld
‘fill’ edge of plates made by corner, lap, tee, joints
butt/groove welds
requires edge of parts to be shaped into groove for weld penetration (square, bevel, V, U, Y, single/double sided
plug/slot welds
attaching flat plates using 1+ holes or slots in top part
spot/seam weld
small fused section b/w surfaces
types of electrical arc welding
shielded metal arc (SMA). metal inert gas (MIG). submerged arc. tungsten inert gas (TIG).
what is electric arc
discharge of electric current across a gap in circuit.
steps of electrical arc welding
electrode metal melted. droplets carried across arc and mixed with base metal. mixed molten metal pushed to rear. (higher current, faster deposit)
what prevents formation of oxide and nitride
gas forms covering arc and prevents exposure of molten metal to air
what is consumable electrode vs non consumable electrode
shielded metal arc welding is consumable. TIG is non consumable
ac current method?
arc pulsates rapidly.
large diameter electrodes at maximum current
thick section
direct current, straight polarity?
narrow, deep welds. electrode negative, workpiece positive.
direct current, reverse polarity?
shallow, wide welds.
electrode positive, workpiece negative.
what is sma used in
general construction, shipbuilding, pipelines.
what gases does SMA generate
carbon dioxide, water vapour, carbon monoxide, hydrogen
gases from mig welding
argon, helium, co2 for steel
difference between mig and sma
no slag. wire fed continuously from spool through welding gun
submerged arc welding
arc shielded by cover of granular flux, from gopper. no sparks or spatter or radiation
TIG welding?
used with and without filler material. no filler ideal for stainless steel.
oxyfuel gas welding?
base metal melted with welding torch
resistance welding?
fusion welding, combo of heat and pressure. pulsed low voltage, high A current
