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Welding Equipment Required for Arc Welding

Updated on August 11, 2013
Source
  1. AC or DC arc welding machine (Power Source)
  2. Electrode with electrode holder
  3. Welding leads
  4. Earthling clamp
  5. Connector
  6. Face shield
  7. Chipping hammer

Mostly AC power source is used for welding. Welding machine transformer may be single phase, two phases, or three phases. For low current supply single phase transformer is used therefore they are used for thinner section welding with minor diameter electrode. For high current two phase and three phase supply transformers are used. They are used for thicker welding plates.

Transformer may be oil cooled or air cooled. Big transformers are always oil cooled. Transformer may be AC or DC generated and generator may be oil/gas operated.

Current range (ac welding transformer) – 600 A

Open circuit voltage-70 to 100 V

Basically two type of the power source can be used for arc welding machine purpose, i.e. AC transformer and DC generator rectifier. Power source consist the two cables, electrode cables and earthing clamp; electrode holder stringer and electrode or rod.

Advantage of Arc Welding Machine

I. Flux shielded manual metal arc welding is very simple as compared to all arc welding process.

II. Cost of equipment is very low.

III. Portable welding machine is available.

IV. Various types of metal and their alloys can be welded.

V. Welding can be carried out in any position, i.e. horizontal, vertical, over head, flat or inclined.

VI. High deposition of penetration can be achieved.

Limitations of Arc Welding Machine

I. FSMMA welding is slow process as compared to MIG Welding Machine.

II. Different material cannot be welded together.

III. Due to flux coated electrode, chance of slag entrapment and other defects are more as compared to TIG Welding Machine and MIG Welding Machine.

IV. Metal transfer is not so clear as compared to MIG Welding Machine.

Application of Arc Welding Machine

I. Shipbuilding industries

II. Pipes and penstocks joining

III. Construction work

IV. Building industries

V. Automobile and aircraft industries

VI. Boiler, chemical, fertilizer industries, etc.

Arc Initiation

Arc initiation refers to the phenomenon of generating or starting an arc between the electrode and the work piece. During welding operation electrode is kept a little away from the work pieces maintaining more or less a constant gap; arc can only be ignited or initiated by first providing a conducting (or ionized) media in the air gap between the electrode and the work piece. Initial conducting media (i.e. the ionized air gap in the beginning) for arc initiation is obtained by following methods:

(a) Touch start arc initiation

(b) High voltage discharge for arc initiation.

(a) Touch Start Arc Initiation

In touch arc electrode is first touched with the work piece and later immediately drawn apart the electrode is touched with the work piece for a very short time, creating short-circuiting conditions, i.e. resistance becoming zero and thus the current increasing to a very high order with raise of exceedingly high current, temperature increase at the point of contact of the electrode and the work piece causing local melting and vaporization of the electrode and the work piece metal besides emission of electrons from the cathode (negative electrode).


Different method of initiating arc

i. Touch start or short circuiting method

ii. Starting by scratching the job with electrode

iii. Using steel wool between the work piece and electrode.

High Voltage Discharge for Arc Initiation

Touch start method of arc generation may contaminate the electrode (When non-consumable electrode is apply, as in TIG Welding) and hence under such condition arc initiated by incorporating a high frequency unit that superimposes a high frequency voltage in the welding circuit these by producing an electric field of very high strength of the order 106 – 107 volts/cm (to air gap), high frequency, high voltage oscillators. Supply a pulse high voltage to generate the arc.

Arc Stability

A stable arc is uniform and steady and given good weld bead and defect free weld nugget. An unstable arc results in slag entrapment, porosity, blow holes and lack of fusion of the weld. For stable arc, the welding unit should be such type that a little variation in arc length (i.e. voltage) should not extinguish the arc. Continues and proper emission of electron from the cathode (electrode) and the thermal ionization in the arc column should be ensured. Proper flux coating on the electrode with the arc stabilising elements can help stabilizing the stable arc.

Arc Blow

Arc blow is a phenomenon in which a strong magnetic field produced (set up) around the electrode and tends to deflect the arc as through a strong wind were blowing. Therefore termed as ‘arc blow’. Arc may be deflected to the side but it is usually deflected either forward or backward along the direction of travel. Arc blow is noted specially when the electrode is used in a corner or towards the joint end. Arc blow is encountered in DC Welding Machine as AC prevents formation of strong magnetic field. In arc blow arc may distort, deflect or rotate.

Several factors are responsible for affecting the arc blow:

Such as:

(a) Magnetic field produced in the work piece adjacent to welding are due to current flow through arc, presence of bus bars in the neigh hood of welding place.

(b) Operating multiple welding heads affecting each other.

(c) Magnetic field produced in the work piece around the earth connection.

Increased Arc blow results in:

i. Unstable arc,

ii. Poor weld bead

iii. Lot of undercuts,

iv. Erratic weld deposition,

v. Spattering,

vi. Slag entrapment and porosity of weld.

Arc blow can be decreased or eliminated by:

i. Changing the position of earthing clamp,

ii. Eliminating presence of magnetic material so arounding the work piece,

iii. By decreasing arc current,

iv. Putting earthing clamp,

v. Away from the point to be welded using short arc,

vi. Decreasing arc travel speed or pre-heating the work piece before welding.

Summery:

Mostly AC power source is used for welding. Welding machine transformer may be single phase, two phases, or three phases. For low current supply single phase transformer is used therefore they are used for thinner section welding with minor diameter electrode. For high current two phase and three phase supply transformers are used. They are used for thicker welding plates.

Basically two type of the power source can be used for arc welding machine purpose, i.e. AC transformer and DC generator rectifier. Power source consist the two cables, electrode cables and earthing clamp; electrode holder stringer and electrode or rod.

Arc initiation refers to the phenomenon of generating or starting an arc between the electrode and the work piece. During welding operation electrode is kept a little away from the work pieces maintaining more or less a constant gap; arc can only be ignited or initiated by first providing a conducting (or ionized) media in the air gap between the electrode and the work piece.

Touch start method of arc generation may contaminate the electrode (When non-consumable electrode is apply, as in TIG Welding) and hence under such condition arc initiated by incorporating a high frequency unit that superimposes a high frequency voltage in the welding circuit these by producing an electric field of very high strength of the order 106 – 107 volts/cm (to air gap), high frequency, high voltage oscillators. Supply a pulse high voltage to generate the arc.

A stable arc is uniform and steady and given good weld bead and defect free weld nugget. An unstable arc results in slag entrapment, porosity, blow holes and lack of fusion of the weld. Continues and proper emission of electron from the cathode (electrode) and the thermal ionization in the arc column should be ensured. Proper flux coating on the electrode with the arc stabilising elements can help stabilizing the stable arc.

Arc blow is a phenomenon in which a strong magnetic field produced (set up) around the electrode and tends to deflect the arc as through a strong wind were blowing. Arc may be deflected to the side but it is usually deflected either forward or backward along the direction of travel. Arc blow is noted specially when the electrode is used in a corner or towards the joint end. Arc blow is encountered in DC Welding Machine as AC prevents formation of strong magnetic field. In arc blow arc may distort, deflect or rotate.

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      caleb n doma 2 years ago

      i respect the department due to arangement of work

    • profile image

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      Raza Vakil

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      cruxweld 3 years ago

      They make quality welding machine and supply machines all over India and abroad