ARC-WELDING-FITTER ONLINE NOTE

• Introduction:-

i)- Two similar or dissimilar metals are joining together by the help of electrode, filler rod or pressure type of joining that is called welding.

ii)- Welding are two types Fusion Welding and Non-Fusion Welding.

Fusion Welding:- 

i)- In this type of welding the edge are melted by heating and filler rod is filled after melting in these edge.

ii)- Thus the weld metal and filler metal are joint together by mixing of filler rod.

iii)- When this filler metal cooled down then made strong joint.

Types of Fusion Welding:-

1- Arc Welding, 2- Gas Welding, 3- Thermit Welding, 4- Electron Beam Welding.

1- Arc Welding:-

i)- In this method of welding an arc is produced by an electricity and get this either generator or transformer is used.

ii)- Arc welding further divided in to many types. a)- Metal arc welding, b)- Carbon arc welding,  c)- Tig welding, d)- Arc stud welding, e)- Electro-Gas welding, f)- Atomic Hydrogen welding, g)- Plasma arc welding.

Equipment used in arc welding:-

There are following equipment used in arc welding.

1- Welding Machine, 2- Welding cable and lead, 3- Cable connector, 4- Electrode holder, 5- Earth clamp, 6- Welding Table, 7- Welding goggles, 8- Helmet, 9- Gloves, 10- Apron and leg guard, 11- Chipping hammer and wire brush, 12- Electrode.

1- Welding Machine:-

i)- There are two types of welding machine. a)- A.C Welding Machine, b)- D.C welding machine.

a)- Alternative Current (A.C.)  Machine:-

i)- In this machine A.C. transformer is used.

ii)- Its function is to convert A.C. main supply in to A.C welding supply.

iii)- It should be remembered that A.C. main supply has high voltage and low ampere but A.C. welding supply has low voltages and high ampere.

iv)- A.C machine is like a step down transformer which change A.C. main supply of 220 volts 440 volts to 40 v or 100 v welding supply.

v)- It changes low current in to 100 or 1000 amperes of high current A.C. main supply can be used without A.C. welding machine.

Advantages - 

1- Less initial cost.

2 - Less maintenance cost .

3- Freedom from arc blow. 

4- Magnetic effect which disturbs the arc is called the arc blow. 

Disadvantages :- 

1- Not suitable for the welding of non-ferrous metals, light coated and special electrodes. 

2- The A.C. cannot be used without special safety precautions.

b)- D.C welding machine:-

i)- There are two types of D.C. welding machine:- 1)- Welding generator set, 2)- Welding Rectifier set.

1)- Welding generator set:- 

There are further divided in two groups a)- Motor Generator set, b)- Engine Generator set.

a)- Motor Generator set:-

i)- It is used to generate D.C. for arc-welding. 

ii)- The generator is driven by an A.C. or D.C. motor.

iii)- Main supply is a must to run the machine.

Motor Generator set

b)- Engine generator set:-

i)- Its Equipment is similar to the motor generator set But its generator is driven by a pertrol or diesel engine. 

ii)-Its running and maintenance charges are higher. 

iii)- It can be used anywhere in field work, away from electric lines. 

Rectifier set:-

i)- It is used to convert A.C.  into D.C. welding supply.

ii)- Basically it is an A.C. welding transformer. 

iii)- The output of the transformer is connected with a rectifier to change the A.C. into D.C.

iv)-  It may be designed to supply both A.C. and D.C. currents for welding (called A.C.-D.C. rectifier set). 

 rectifier set). 

Advantages:-

i)- It is Suitable for welding all ferrous and non-ferrous metals using all types of electrodes .

ii)- Better heat distribution in  the electrode and job due to polarity  in the welding current supplies.

iii)- It is constant main load and accurate current setting. 

iv)- It ensures safe working. 

Disadvantages :-

i)- Initial cost is higher .

ii)- Maintenance cost is more .

iii)- Arc-blow trouble faced at certain times.

Polarity in arc welding:-

i)- The meaning of polarity is direction of current.

ii)- It is required in D.C. supply only.

iii)- Polarity may be two types straight polarity or reverse polarity.

Straight polarity:- 

When the electrode cable is connected to the negative terminal as it is called negative polarity or straight polarity.

Reverse polarity:- 

When the electrode cable is connected to the positive terminal, it is called positive polarity or reverse polarity.

Welding Cable and Lead:-

i)- Cable and lead are the main wires of electricity which connect electrode holder to transformer and to job of work.

ii)- Selection of cable depends upon thickness of electrodes and the distance of job from the 

machine.

Welding cable

Cable Connector:-

i)- Cable has copper conductor and when high ampere is passed through the cable then there is change of sparking on its joint.

ii)- To remove this error(defect) cable connectors are used on its joint.

Electrode holder:-

i)- Holder is a device like a plier.

ii)- It is used to hold the electrode and to connect it with welding set through cable.

iii)- Its jaws are made of copper.

iv)- It has grooves for holding the electrode in it.

Electrode Holder

Earth Clamp:-

i)- Earth clamp is used to connect job of work with earth to get good and find welding work of job or cable surface should be properly earthed.

Earth Clamp

Helmet and Hand shield:-

i)- These are used to protect the eyes and face of a welder from arc radiation and sparks during arc welding. 

ii)- A hand screen is designed to hold in hand.

iii)- A helmet screen is designed to wear on the head.

Helmet and Hand shield

Googles:- 

i)- Plain goggles are used to protect the eyes while chipping the slag or grinding the job.

Chipping Hammer and Wire brush:-

i)- The chipping hammer is used to remove the slag which covers the deposited weld bead.

ii)- It is made of medium carbon steel with a mild steel handle.

iii)- It is provided with a chisel edge on one end and a point on the other end for chipping off slag in any position.

iv)- Wire brush is used cleaning the work surface from rust, oxide and other dirt etc. prior to welding. 

v)- Cleaning the interbead weld deposits after chipping off the slag.

Chipping Hammer

 Tongs:-

i)- Tongs is used to hold hot work pieces and to hold the job in position.

 Tong

Apron:-

i)- An apron is used to protect the body. 

ii)- It should be made of leather and worn. 

iii)- It must be worn for protection from the radiation of the heat rays and hot spatters.

Apron

 Hand gloves:-

i)- Hand gloves are  used to protect the hands from electrical shock, arc radiation, heat, and hot spatters. 

ii)- The gloves are also made of leather.

gloves

Arc Length:-

i)- It is the straight distance between the electrode tip and the job surface when an arc is formed. 

ii)- There are three types of arc length. - Normal - Long - Short

iii)- Normal arc length is the correct arc length or normal arc length is approximately equal to the diameter of the core wire of the electrode.

iv)- Long arc length is If the distance between the tip of the electrode and the base metal is more than the diameter of the core wire, it is called ‘long arc’.

v)- Short arc length is If the distance between the tip of the electrode and the base metal is less than the dia. of the core wire, it is called a ‘short arc’.

Arc Length

Effects of arc length:- 

i)- A long arc makes a humming sound.

ii)- The arc is unstable ,

iii)- Causes oxidation of the weld metal.

iv)- Fusion and penetration are poor.

v) - Poor control of the molten metal. 

vi)- Creates more spatters resulting in wastage of the electrode metal. 

Short arc:- 

i)- It makes a popping sound. 

ii)- The electrode to melt slowly and try to freeze the job. 

iii)- Higher metal deposition with  narrow width bead. 

iv)- Less spatters. 

v)- Fusion and penetration is less.

Normal arc -

i)-  A stable arc produces a steady sharp crackling sound.

ii) - Electrode burns evenly. 

iii)- Less spatters.

iv)- Correct fusion and penetration. 

v)- The size of  metal deposition is correct.

Faults in arc welding:-

Weld faults are classified as two types: - 

Visible faults:-These are visible  to the naked eye on the weld surface.  Invisible faults:- These faults are inside the weld metal and cannot be seen by the naked eye.

comming shoon