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Fusion-welding Process
Oxyfuel-gas welding
Electrodes arc weldingElectron beam welding
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General characteristic of fusion-
welding Process
Joining
ProcessOperation Advantage
Skill level
required
Welding
position
Current
type
Distortion
*
Typical
cost of
equipmen
t ($)
Oxyfuel ManualPortable
and flexibleHigh All - 2-4
Low
(500+)
*1=highest; 5=lowest
Source: Serope Kalpakjian, Manufacturing Engineering and
Technology
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Oxyfuel-gas welding
Abbreviation OFG
It uses a fuel gas combined with oxygen to
produce a flame at high temperature to melt
the metals at joint.
The most popular welding process is
acetylene, also known as oxyacetylene-gas
welding (OAW)
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C2H2 + O2 -> 2CO + H2+ Heat
Primary combustion process
2CO + H2+ 1.5O2 -> 2CO2+ H2O + Heat
Secondary combustion process
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Types of flame
The proportional of acetylene and oxygen in the gasmixture is an important factor in oxyfuel-gas welding.
(a) At neutral flame, the ratio of oxyfuel-gas welding is
1:1.(b) When higher oxygen supply, the flame can be harmful
for steel because it oxidizes the metal. Known asoxidizing flame
(c) If oxygenis insufficient, the flame is known asreducing, or carburizing flame. Suitable for lowmelting welding material.
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TYPES OF FLAME
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The principle of the OGW
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Filler metals used to supply additional metal
to the weld zone during welding, and may be
coated with flux.
The purpose of the flux is to retard oxidation
of the surfaces of the parts being welded.
The slag development protects the molten
puddle of metal against oxidation as the weld
cools.
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Welding Practice and Equipment
OGW can be used with most ferrous and non-
ferrous metals for almost any workpiece
thickness, limit to 6mm less.
The equipment for OGW consists of a welding
torch, proper goggle, face shields for safety
measures.
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General view and cross sectional of a
torch
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Other type of gas welding
Pressure gas welding
Termit welding
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Thermit welding
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Also known as thermite or exothermic welding
Involves mixing a metal powder with a metal
oxide and apply a high temperature ignition
source to cause an oxidation-reduction
reaction. The temperature can reach up to
2500oC.
Also combined with aluminum powder
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Application of thermit welding
1 2 3
4
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Electrodes for Arc Welding
Electrodes for consumable arc-welding process
are classified according to following properties:
Strength of the deposited weld metal
Current (AC or DC)
Type of coating
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Specifications for electrodes and filler metals(including dimensional tolerances, quality controlprocedures, and processes) are published by the
American Welding Society (AWS) and theAmerican National Standards Institute (ANSI).
Some specifications appear in the AerospaceMaterials Specifications (AMS) by the Society of
Automotive Engineers (SAE). Electrodes are sold by weight and are available in
a wide variety of sizes and specifications.
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Example of mild steel coated electrode
table
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Functions of electrode coating
Stabilizethe arc.
Generate gases as a shield against thesurrounding atmosphere.
Controlthe rate at which the electrode melts
Act as a flux to protect the weld against theformation of oxides, nitrides and other
inclusions. Add alloying elements to enhance the
properties of the joint.
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Electron-beam welding
Or called (EBW), developed in the 1960s.
Heat is generated by high velocity, narrow-beam
electrons.
Requires special equipment in order to focus the
beam on the workpiece, typically in a vacuum.
The higher the vacuum, the deeper the beam
penetrates, the greater the depth-to-width ratio
There are 3 methods; EBW-HV, EBW-MV, EBW-NV
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Almost any metal can be welded andworkpiece thickness range from foil to plate.
Capacities of electron beam guns range up to
100kW. This process has a capability of making high-
quality welds that are almost parallel sided,
are deep and narrow. It can process any metal (butt and lap) with
thickness up to 150 mm.
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Application of EBW
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Results of EBW work
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References
Serope Kalpakjian, Manufacturing Engineering
and Technology, 7thedition.
Some pictures are taken from the Google
Images.