Post on 05-Apr-2018
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MP-IICode-151901
Metal Joining Process
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Welding Classification
Welding
GasWelding
ArcWelding
ResistanceWelding
RadiantEnergy
Solid StateWelding
ThermoChemical
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Welding Class. Cont.
Gas Welding
Oxy Acetylene
Air Acetylene
Oxy Hydrogen
Pressure Gas
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Welding Class. Cont.
Arc WeldingCarbon Arc
Shilded Metal Arc
Submerged Arc
TIG
Flux Cored Arc
MIGPlasma Arc
Electro Slug
Stud Arc
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Welding Class. Cont.
Solid State Welding
Cold
Diffusion
Forge
Friction
Explosive
Hot PressureRoll
Ultrasonic
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Welding Class. Cont.
Thermo Chemical Welding
Thermit
Atomic Hydrogen
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Oxyacetylene Welding (OAW)
OAW is a manual process in which the welder mustpersonally control the the torch movement and
filler rod application
Cylinders contain oxygen and acetylene gas atextremely high pressure.
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Typical Oxyacetylene Welding(OAW) Station
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Cylinder Transportation
Never transport cylinders without the safety caps inplace
Never transport with the regulators in place
Never allow bottles to stand freely. Always chainthem to a secure cart or some other object thatcannot be toppled easily.
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Pressure Regulators for Cylinders
Reduce high storage cylinder pressure tolower working pressure.
Most regulators have a gauge for cylinderpressure and working pressure.
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Pressure Regulators for Cylinders
Regulators are shut offwhen the adjusting screw
is turn out completely. Regulators maintain a
constant torch pressurealthough cylinder pressuremay vary
Regulator diaphragms aremade of stainless steel
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Pressure Regulators GaugesUsing a Bourdon movement
Gas entering the gauge fills aBourdon tube
As pressure in the semicircularend increases it causes the freeend of the tube to moveoutward.
This movement is transmitted
through to a curved rack whichengages a pinion gear on the
pointer shaft ultimately showingpressure.
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Regulator Hoses
Hoses are fabricated fromrubber
Oxygen hoses are green in
color and have right handthread.
Acetylene hoses are red incolor with left hand thread.
Left hand threads can beidentified by a grove in the
body of the nut and it may haveACET stamped on it
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Check Valves &Flashback Arrestors
Check valves allow gas flow in one direction only
Flashback arrestors are designed to eliminate the possibilityof an explosion at the cylinder.
Combination Check/ Flashback Valves can be placed at the
torch or regulator.
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Acetylene Gas
Virtually all the acetylene distributed for welding and cutting useis created by allowing calcium carbide (a man made product) toreact with water.
The nice thing about the calcium carbide method of producingacetylene is that it can be done on almost any scale desired.Placed in tightly-sealed cans, calcium carbide keeps indefinitely.For years, miners lamps produced acetylene by adding water, adrop at a time, to lumps of carbide.
Before acetylene in cylinders became available in almost everycommunity of appreciable size produced their own gas fromcalcium carbide.
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Acetylene Cylinders
Acetylene is stored in cylinders specially designedfor this purpose only.
Acetylene is extremely unstable in its pure form atpressure above 15 PSI (Pounds per Square Inch)
Acetone is also present within the cylinder tostabilize the acetylene.
Acetylene cylinders should always be stored in theupright position to prevent the acetone formescaping thus causing the acetylene to becomeunstable.
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Acetylene Cylinders
Cylinders are filled with a very porous substancemonolithic filler to help prevent large pockets of pureacetylene form forming
Cylinders have safety (Fuse) plugs in the top and bottomdesigned to melt at 212 F (100 C)
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Acetylene Valves
Acetylene cylindershut off valves should
only be opened 1/4 to1/2 turn
This will allow the
cylinder to be closedquickly in case of fire. Cylinder valve
wrenches should be
left in place on
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Oxygen and Acetylene RegulatorPressure Settings
Regulator pressure may vary with different torch styles andtip sizes.
PSI (pounds per square inch) is sometimes shown as PSIG
(pounds per square inch -gauge) Common gauge settings for cutting
1/4 material Oxy 30-35psi Acet 3-9 psi
1/2 material Oxy 55-85psi Acet 6-12 psi
1 material Oxy 110-160psi Acet 7-15 psi Check the torch manufactures data for optimum pressure
settings
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Regulator Pressure Settings
The maximum safe working pressure foracetylene is 15 PSI !
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Typical startup procedures
Verify that equipment visually appears safe. Clean torch orifices with a tip cleaners (a small wire
gauge file set used to clean slag and dirt form the torchtip)
Open cylinder valves slightly allowing pressure to enterthe regulators slowly
Opening the cylinder valve quickly will Slam theregulator and will cause failure.
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Typical startup procedures
Never stand directly in the path of a regulator whenopening the cylinder
Check for leaks using by listening for Hissing orby using a soapy Bubble solution
Adjust the regulators to the correct operatingpressure
Slightly open and close the Oxygen and Acetylenevalves at the torch head to purge any atmospherefrom the system.
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Flame Settings
There are three distinct types of oxy-acetyleneflames, usually termed:
Neutral Reducing Carburizing (or excess acetylene) Oxidizing (or excess oxygen )
The type of flame produced depends upon the ratio
of oxygen to acetylene in the gas mixture whichleaves the torch tip.
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Neutral Flame
The neutral flame (Fig. 4-1) isproduced when the ratio ofoxygen to acetylene, in themixture leaving the torch, isalmost exactly one-to-one. Itstermed neutral because it willusually have no chemical effecton the metal being welded. Itwill not oxidize the weld metal;
it will not cause an increase inthe carbon content of the weldmetal.
Inner Cone
Outer Cone
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Neutral Flame
O2 = C2H2
Inner cone must be remain 1.5-3 mm above the weld puddle
Equation of flame No chemical reaction take place
3260* C temp. can be archived
Suitable for
- Mild Steel,
- Cast Iron
- Stainless Steel
- Copper
- Aluminium
Inner Cone
Outer Cone
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Reducing Flame(Carburizing)
The excess acetylene flame (Fig.Beside), as its name implies, iscreated when the proportion ofacetylene in the mixture ishigher than that required to
produce the neutral flame.
Increased the Carbon Contain tothe Weld
Outer cone is Longer than
Neutral flame Low Temp. 3038o C (5500o F)
http://ronreil.abana.org/design1.shtml
Reducing Flame
Inner Cone
Outer Cone Acetelyne Feature
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Reducing Flame(Carburizing)
It produced very hard and brittlesubstances Iron Carbide
This chemical change makes
metal unfit for application Its used forLead & Carburizing
purpose.
Suitable for
- Low Alloy Steel.
- Non Ferrous. ( They dontabsorbed carbon )
- High Carbon Steel
http://ronreil.abana.org/design1.shtml
Reducing Flame
Inner Cone
Outer Cone
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Oxidizing Flame
Excess Oxygen ratio 1.5:1
Hotter than Neutral
3480o C
Excess O2 causes the weld beddurty
Suitable for
- Cooper Based
- Zinc
- Ferrus ( Manganese )
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Welding Techniques
Welding Techniques
RightwardLeftward
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