Manufacturing Processes
Welding & Mechanical Fastening
(용접과 조립)
Associate Professor Su-Jin Kim
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
School of Mechanical Engineering
Gyeongsang National University
Welding
•
Welding(용접) joins metals by melting it and adding a
filler metals to form a pool of molten metal that cools
to become a strong joint.
• Energy sources:
gas flame, electric arc,
laser, friction.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Fusion Welding (Liquid State Welding)
1.
2.
3.
4.
Oxyfuel Gas Welding
Arc Welding
Laser Beam Welding
Resistance Welding
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Fusion Welding
•
•
•
•
Heat source: Oxyfuel fire, Arc, Laser
Filler: Additional metals are supplied to the weld zone.
Retarding Oxidization: Flux, shielding Gas
Slag protects molten puddle from oxygen and spatter
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Oxyfuel Gas Welding
•
•
Oxyfuel gas welding (산소용접) uses acetylene(C2H2)
gas combined with oxygen to produce a flame.
The flame melts the metals to be joined.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Oxyfuel Gas Welding
Flame types
(a) NeutralWelding
(b) OxidizingCutting
(c) CarburizingHeating
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://www.youtube.com/watch?v=y3E_MWG9Q0M
Pressure Gas Welding
2 components welded by heating at their interface using a
torch with oxyacetylene gas mixture and pressure.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Rail : http://www.youtube.com/watch?v=B8XLVBYFxyk
Arc Welding
Arc Welding (아크용접) : Electric discharge is heat sorce.
Shield metal AW
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Gas metal AW
(MIG)
Gas tungsten AW
(TIG)
Heat transfer in arc welding
•
Welding speed is
VI
ve
uA
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
e = efficiency
V = voltage applied
I = current
u = specific energy
A=weld section area
Shielded metal arc welding
• SMAW (피복금속AW) is the simplest and most versatile
joining process.
• It uses a consumable electrode coated in flux giving off
a shielding gas.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://www.youtube.com/watch?v=TeBX6cKKHWY&feature=related
Submerged arc welding
•
•
Weld arc is covered by a flux powder which is fed into
the weld zone by gravity through a nozzle.
Flux completely covers the molten metal and prevents
weld from oxidization and spatter.
Welding & Joining
Manufacturing Processes
http://www.youtube.com/watch?v=Uns93e4HaNU&feature=related
© Pearson & GNU Su-Jin Kim
Gas metal arc welding
•
•
GMAW(가스방호AW)= MIG (metal inert-gas welding)
Weld area is shielded by gas (Ar, He, CO2) to prevent
oxidation.
Welding & Joining
MIG:
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://ma.gnu.ac.kr/vod/Joining/Metal_Inert_Gas_Welding.MP4
Flux-cored arc welding
•
•
FCAW (유심용제AW) is similar to MIG but electrode is
tubular and filled with flux.
Continuous and automatic electrode feeding.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
FCAW vs. MIG: http://www.youtube.com/watch?v=chE6RPhM3xE
Electrogas welding
•
EGW welds thick vertical edges in one pass with special
equipment. A shielding gas is sometimes used. Used in
shipbuilding and storage tanks.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://www.youtube.com/watch?v=8nwP0JYQIdg
Electroslag welding
•
•
ESW is for thick (25~300mm) vertical edges.
Flux is added. After the molten slag reaches the tip of
the electrode, arc is extinguishes and energy is supplied
through the electrical resistant of the molten zone.
Welding & Joining
Manufacturing Processes
http://www.youtube.com/watch?v=rCL8NCy2eg8
© Pearson & GNU Su-Jin Kim
Gas tungsten arc welding
•
•
GTAW(텅스텐AW)=TIG(Tungsten inert gas)
A filler metal is supplied from a filler wire.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://www.youtube.com/watch?v=VEEpikDY058
Plasma arc welding
•
•
A concentrated plasma arc is produced and directed
toward the weld area.
Higher quality and speed than the TIG.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Plasma AW
http://www.youtube.com/watch?v=jo376zPns8I
Plasma cutting
• Plasma: gas -(heat)> plasma ( +ions + -electrons )
• Focused stream of plasma cut sheet metal.
• Cutting speed ≈ efficiency, power / thickness, specific
heat, melting point : v ≈ η P / (t w c Tm)
-
Negative
electrode
Cutting gas
Shielding gas
Plasma channel
Positive metal
Weldinghttp://www.youtube.com/watch?v=mJJydOxHwZU&feature=results_main&pla
& Joining
+
Manufacturing
Processes
ynext=1&list=PL8EE6E5350B31D89B
© Pearson & GNU Su-Jin Kim
Electron-beam Welding
•
•
Kinetic energy of high-velocity electrons is converted
into heat to strike the workpiece.
The higher the vacuum the more the beam will be able
to penetrate the part and the greater depth-to-width
ratio.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://www.youtube.com/watch?v=NONurFigP5I
Laser-beam welding
•
•
Uses a high-power laser beam as a heat source to
produce a fusion weld.
Has a high energy density and a deep penetrating
capability.
Welding & Joining
Manufacturing Processes
http://www.youtube.com/watch?v=51d6gQxg1KI
© Pearson & GNU Su-Jin Kim
Laser-beam welding
• Laser welding of diff-case.
Laser welded
Section
Bolted
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Press 10 ton + Laser welding
Laser-beam Cutting
•
High power (kW) laser melts and evaporates material.
• CO2 & Nd:YAG lasers are used for industrial cutting.
Mirror
Nd:YAG
crystal
Xenon
Flashlamp
Mirror
Laser
Welding & Joining
http://ma.gnu.ac.kr/vod/Machining/Laser_beam_machining.MP4
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Laser Welding Machine
• Multi axis machine used for laser cutting, welding,
marking.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://ma.gnu.ac.kr/vod/Joining/Laser_Welding.wmv Machine
Laser-beam Cutting
• Standard roughness ∝ material thickness / laser power,
cutting speed : r ∝ t0.5 / (P0.5 v0.3)
• Cutting rate ≈ laser power / evaporation energy per
volume, thickness, width of laser: v ≈ P / (e t w)
Laser
beam
Focusing
lens
Gas
Material
t
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
w
Laser drill
• Non-contact, a wide range of materials, accuracy and
consistency, as small as 10 – 20 microns.
Aerospace part: http://www.youtube.com/watch?v=83OQTZZ4ML8
Welding & Joining
Manufacturing Processes Glass: http://www.youtube.com/watch?v=CS60VzAkhxk
© Pearson & GNU Su-Jin Kim
Resistance Welding(전기저항용접)
•
•
Welding is produced by means of electrical resistance
between 2 joined members.
Heat generated is H  I 2 Rt
H = heat generated (J)
I = current (A)
R = resistance in ohms
t = time (s)
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Resistance Welding
• Contact resistance of electrode-workpiece < Faying
surface resistance of workpiece surface
• Pressure reduces contact resistance and is increased
after solidification for forging
• Rapid, small heat affected zone, no filler, high reliability,
automation possible
• Mostly lap joint, thickness is limited<12mm, clean
interface is needed
• Difficult to weld high conductivity material (Al, Cu)
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Resistance spot welding
•
•
•
Tips of the 2 opposing electrodes contact surfaces of lap
joint and resistance heating produces a spot weld.
Good bond in the weld nugget is obtained by having
pressure continually applied till current is turned off.
Strength of weld depends on surface roughness and
cleanliness of mating surfaces.
Welding & Joining
http://www.youtube.com/watch?v=AwL1CAg43PU&p=9B6D9EAE75875D9D
Manufacturing Processes
http://ma.gnu.ac.kr/vod/Joining/Resistance_spot_welding_aluminume.MP4
© Pearson & GNU Su-Jin Kim
Resistance Welding
Resistance Seam Welding
Plates
• Current and pressure is continuous or
on-off through rolls
Rolls
Resistance Projection Welding
• Many welds simultaneously
Electrode
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
High frequency welding (고주파용접)
• High frequency current up to 450 kHz  Localize heat 
Forge the joint
• Used for pipe and structural beam welding
• Small heat affected zone
• Highly conductive material can be easily joined (up to 20
mm)
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
The Fusion Welded Joint
3 distinct zones of weld are:
• base metal
• heat-affected zone (HAZ)
• fusion zone
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Weld quality
• Discontinuities that affect weld quality are:
1. Porosity
• trapped gases, chemical reactions, contaminants
2. Slag inclusions
• Slag is trapped in the weld zone.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Weld quality
3. Incomplete fusion and incomplete penetration
4. Weld profile
• Affects the strength and appearance of the weld.
5. Cracks
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Design for Welding
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://www.youtube.com/watch?v=pVyYvcEqkcQ&feature=related
Ex) Design frame for welding
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Ex) Welding
Gas metal arc welding
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Problem of Fusion Welding
•
•
•
•
Composition change
Cavity, inclusion
Grain growth, phase transformation
Residual stress, crack
• Most failures start at heat affected zone
• Sharpness of variation of heat affected zone may be
reduced by preheating
• When C is more than 0.3%, Martensite may form
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Solid State Welding
1.
2.
3.
4.
Cold Welding (냉간압점)
Ultrasonic Welding (초음파용접)
Friction Welding (마찰용접)
Diffusion Bonding (확산접합)
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Cold Welding (냉간압접)
•
Localized pressure is applied to mating faces of parts
through dies or rolls.
• Used to join small workpieces made of soft and ductile
metals.
Roll welding
• Pressure for long pieces or continuous strips is applied
through a pair of rolls.
Separating agent
(graphite)
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Rolls
Ultrasonic Welding (초음파용접)
•
•
Ultrasonic vibration of transducer & Pressure 
Temperature rise to 0.3~0.5 melting point.
Restricted to thin, small, delicate parts like electric
components.
Force
Transducer
Mass
Toolholder
Transducer
Coupling
system
Tip
Workpiece
Anvil
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Direction of
vibration
Roller
DC
polarization
supply
AC
Power
supply
Workpieces
Support
Roller
Workpieces
Support
©정하림 GNU
Vibration Welding
• Vibrate two plastic parts to be joined by friction heat
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
http://ma.gnu.ac.kr/vod/Joining/Vibration_welding_plastic.MP4
Friction Welding (마찰용접)
•
Heat required is generated from friction at the interface
of the 2 members being joined.
Welding &http://www.youtube.com/watch?v=-aEuAK8bsQg&p=9B6D9EAE75875D9D
Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Friction Welding
http://ma.gnu.ac.kr/vod/Joining/Friction_Welding.WMV Friction Welding
Diffusion Bonding (확산접합)
•
•
•
Diffusion bonds two different materials in high pressure,
elevated temperature, long time.
High bond strength, slow process.
Good for Ti, superalloy (Aircraft components)
Copper - Stainless
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Aluminum - Stainless
Brazing (경납접) & Soldering (연납접)
• Solid base, liquid filler
• Filler material: different composition, low melting point,
lower strength
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Brazing (경납접)
•
•
•
Filler metal is placed between faying surfaces where the
temperature is raised to melt the filler metal.
Workpieces must melt in the weld area for fusion.
Clearance is important as it affects the strength of the
brazed joint.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Soldering (연납접)
•
•
•
•
Filler metal (solder) fills the joint by capillary action.
Can be used to join various metals and to thicken parts.
Temperatures are low and have a low strength as they
are for load-bearing structural members.
Solders are tin-lead alloys.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Soldering
•
Soldering robot vs. labor
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Design for Brazing
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Adhesive Bonding
•
•
Numerous components and products can be joined and
assembled.
Adhesive are required to be strong and tough,
resistance to fluids, chemicals and environmental
degradation.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Design for adhesive bonding
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Mechanical Fastening (기계적 죔)
1.
2.
3.
4.
Bolt, Nut, Thread
Rivet, Staple
Snap fit, Shrink fit
Spring clip, Seaming
•
•
Ease of assembly, disassembly.
Ease of parts replacement, maintenance and repair.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Fastening
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Bolt, Nut, Thread
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Rivet, Staple
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Snap-in, Thermal shrink
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Spring clip, Seaming
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Design for Assembly
• Design for assembly (DFA) is to simplify the product so
that the cost of assembly is reduced.
• Comparison of Assembly Methods: Manual assembly /
Fixed or hard automation / Soft automation or robotic
assembly.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Design Guidelines for Manual
Assembly
• eliminate the need for workers to make decisions or adjustments.
• ensure accessibility and visibility.
• eliminate the need for assembly tools and gauges (i.e. prefer selflocating parts).
• minimise the number of different parts - use "standard" parts.
• minimise the number of parts.
• avoid or minimise part orientation during assembly (i.e. prefer
symmetrical parts).
• prefer easily handled parts that do not tangle or nest within one
another.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Design Guidelines for Hard
Automation
• reduce the number of different components by considering
– does the part move relative to other parts?
– must the part be isolated from other parts (electrical, vibration, etc.)?
– must the part be separate to allow assembly (cover plates, etc.)?
• use self-aligning and self-locating features
• avoid screws/bolts
• use the largest and most rigid part as the assembly base and fixture.
Assembly should be performed in a layered, bottom-up manner.
• use standard components and materials.
• avoid tangling or nesting parts.
• avoid flexible and fragile parts.
• avoid parts that require orientation.
• use parts that can be fed automatically.
• design parts with a low centre of gravity.
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim
Design for Assembly
Welding & Joining
Manufacturing Processes
© Pearson & GNU Su-Jin Kim