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7/27/2019 7thlec-welding-120307045613-phpapp02

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Welding is a materials joining process which produces

coalescence of materials by heating them to suitabletemperatures with or without the application of

pressure or by the application of pressure alone, and

with or without the use of filler material.

Welding is used for making permanent joints.

It is used in the manufacture of automobile bodies, aircraft

frames, railway wagons, machine frames, structural works,

tanks, furniture, boilers, general repair work and ship

building.
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Plastic Welding or Pressure WeldingThe piece of metal to be joined are heated to aplastic state and forced together by externalpressure

(Ex) Resistance welding Fusion Welding or Non-Pressure Welding

The material at the joint is heated to a molten state and allowedto solidify

(Ex) Gas welding, Arc welding


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(i). Arc welding Carbon arc Metal arc Metal inert gas Tungsten inert gas Plasma arc

Submerged arc Electro-slag(ii). Gas Welding Oxy-acetylene Air-acetylene Oxy-hydrogen

(iii). Resistance Welding Butt Spot Seam Projection

Percussion

(iv)Thermit Welding(v)Solid State Welding

FrictionUltrasonicDiffusion

Explosive(vi)Newer Welding

Electron-beamLaser

(vii)Related ProcessOxy-acetylene cutting

Arc cuttingHard facingBrazingSoldering


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What is fusion welding..?

A process in which parts are melted andfused or joint together is called fusion welding.

or

Fusion welding is a group of processes that bond metaltogether by heating a portion of each piece above themelting point and causing them to join together.


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Types of fusion welding include:

Arc welding.

Oxy-fuel welding.

Metal Inert Gas (MIG).

Tungsten Inert Gas (TIG).


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Heat is supplied by various means

o Oxyacetylene gas

o Electric Arc

o Plasma Arco Laser

Filler metal may be added


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What is Arc Welding?

Arc welding is a type of welding that uses a welding power

supply to create an electric arc between an electrode and

the base material to melt the metals at the welding point.

They can use either direct (DC) or alternating (AC)current, and consumable or non-consumable electrodes.


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Equipments: A welding generator (D.C.) or Transformer (A.C.)

Two cables- one for work and one for electrode

Electrode holder

Electrode Protective shield

Gloves

Wire brush

Chipping hammer

Goggles


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Transformer:A welding transformer is an

electrical transformer used in

welding power supply.

It pulls relatively low currentdrawn from the mains power

typically limited to 15 A and

converts it to the typical 50 A

to 500 A used in arc welding

and higher currents used in

spot welding.


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Electrode holder:

The insulated handle that clamps

onto the electrode. The welderholds this during welding to

control the arc

Electrode:

Filler metal coated with flux in theform of a rod or heavy wire

Electric cables:

Cables are used in welding toconnect work piece with

electric supply.


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Welding shield (hood):

This is the mask which is worn to protect the

person welding from the bright flash of the

arc.

Welding gloves:

These are special, insulated leather gloves

that reach about 6 inches above the wrists,

and protect the hands and lower arms of thewelder (the person welding).

Welding leathers:

This is an apron like leather jacket that

covers the shoulders and chest of the welder,used for overhead work where sparks might

ignite the welder's clothing, or cause burns.


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Gather the tools and materials you will need to beginwelding.

Set up a safe work area, preferably with a table constructed

of steel or other non-flammable material.

Prepare the metal to be welded. Attach clamps to hold your metal pieces together.

Attach the ground clamp to the larger piece of stock that is

being welded.

Select the correct rod and ampare range for the work you

are attempting.


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Turn on your welding machine.

Hold the stinger in your dominant hand by the insulated

handle.

Select the point where you wish to begin your weld. Strike the electrode against the surface of the metal, pulling

it back slightly when you see an electric arc occur.

Practice traveling across the path of your weld with the

electrode until you can keep a consistent arc, moving at aconsistent speed.

Complete Your weld.

Clean your finished weld.

Paint your weld with a suitable rust-preventative primer to

protect it from corrosion.


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Advantages Most efficient way to join

metals

Lowest-cost joining

method Affords lighter weight

through better utilizationof materials

Joins all commercial

metals Provides design flexibility

Limitations Manually applied, therefore

high labor cost.

Need high energy causing

danger Not convenient for

disassembly.

Defects are hard to detect at

joints.


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Types Of Flames:

1. Neutral Flame.(5600 to 5900 F)In neutral flame both gases are in equal proportions.

2. Oxidizing Flame (Excess of oxygen)(6000 to 6300F)

An oxidizing flame is caused by increasing the oxygen from aneutral flame.

3. Reducing Flame (Excess of acetylene)(5400 to 5500F)

If the oxygen is reduced, a carbonizing flame is created from a

neutral flame.


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Three basic types of oxyacetylene flames used in oxyfuel-gas welding andcutting operations:(a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing flame.

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