Electro slag Welding

Electro slag Welding is a welding process, in which the heat isgenerated by an electric current passing between the consumableelectrode (filler metal) and the work piece through a molten slagcovering the weld surface.

Prior to welding the gap between the two work pieces is filledwith a welding flux. Electro slag Welding is initiated by an arcbetween the electrode and the work piece (or starting plate).Heat, generated by the arc, melts the fluxing powder and formsmolten slag. The slag, having low electric conductivity, ismaintained in liquid state due to heat produced by the electriccurrent.

Electro slag Welding

Electro slag Welding is a welding process, in which the heat isgenerated by an electric current passing between the consumableelectrode (filler metal) and the work piece through a molten slagcovering the weld surface.

Prior to welding the gap between the two work pieces is filledwith a welding flux. Electro slag Welding is initiated by an arcbetween the electrode and the work piece (or starting plate).Heat, generated by the arc, melts the fluxing powder and formsmolten slag. The slag, having low electric conductivity, ismaintained in liquid state due to heat produced by the electriccurrent.

Electro slag welding (ESW) is a highly productive, single pass weldingprocess for thick (greater than 50 mm) materials in a vertical or close tovertical position. An electric arc is initially struck by wire that is fed intothe desired weld location and then flux is added

The slag reaches a temperature of about 3500°F (1930°C). Thistemperature is sufficient for melting the consumable electrode and workpiece edges. Metal droplets fall to the weld pool and join the work pieces.

Electro slag Welding is used mainly for steels.

Electro slag welding (ESW) is a highly productive, single pass weldingprocess for thick (greater than 50 mm) materials in a vertical or close tovertical position. An electric arc is initially struck by wire that is fed intothe desired weld location and then flux is added

The slag reaches a temperature of about 3500°F (1930°C). Thistemperature is sufficient for melting the consumable electrode and workpiece edges. Metal droplets fall to the weld pool and join the work pieces.

Electro slag Welding is used mainly for steels.

Electroslag Welding equipments

Power sourceWire feederElectrode guide tubeRetaining BlocksWelding head and Controls

Power sourceWire feederElectrode guide tubeRetaining BlocksWelding head and Controls

Power source

100 % duty cycle

AC and DC (EP) power source

10,000 Amp

OCV 60V (range is 30 V to 100 V)

Remote controlled

100 % duty cycle

AC and DC (EP) power source

10,000 Amp

OCV 60V (range is 30 V to 100 V)

Remote controlled

Wire feeder

Feed roller

Drive motor

Provide oscillationrack and pinion motioncam and crank arrangement

Feed roller

Drive motor

Provide oscillationrack and pinion motioncam and crank arrangement

Retaining Blocks

Maintain the slag and molten metal with in the cavity

Solid copper and water cooled copper shoe

Travel upward as welding progress

For low melting point graphite or steel can be used

Maintain the slag and molten metal with in the cavity

Solid copper and water cooled copper shoe

Travel upward as welding progress

For low melting point graphite or steel can be used

Welding head and Controls

It Consists :-

wire feeder

Electrode supply

Wire guide tube

Oscillation drive

It Consists :-

wire feeder

Electrode supply

Wire guide tube

Oscillation drive

Consumables

Electrode

Solid and metal-cored

Wire range 1.6 to 4.0 mm diameter.

Electrode

Solid and metal-cored

Wire range 1.6 to 4.0 mm diameter.

Flux

Should sufficient resistance to melt the filler material.

Optimum viscosity.

Melting point should lower then the material to be joined.

5 to 10 Kg for each 100kg of metal deposited.

Two types of fluxesstarting (low melting point, )running

Should sufficient resistance to melt the filler material.

Optimum viscosity.

Melting point should lower then the material to be joined.

5 to 10 Kg for each 100kg of metal deposited.

Two types of fluxesstarting (low melting point, )running

ESW variables Welding Current Welding Voltage Electrode diameter Electrode extension Electrode oscillation Slag Pool depth Number of electrode and their spacing Root gap

Welding Current Welding Voltage Electrode diameter Electrode extension Electrode oscillation Slag Pool depth Number of electrode and their spacing Root gap

Welding current

It depend upon welding voltage and Electrode feed rate. Increases with increase in wire feed rate. Increasing in current means increasing in welding speed. Due to increase in welding speed depth of penetration will

reduce and lack of fusion is likely occur. It may cause cracking Max level of current used bellow 500 A for wire dia 3.2 mm

and bellow 400 A for 2.4 dia.

It depend upon welding voltage and Electrode feed rate. Increases with increase in wire feed rate. Increasing in current means increasing in welding speed. Due to increase in welding speed depth of penetration will

reduce and lack of fusion is likely occur. It may cause cracking Max level of current used bellow 500 A for wire dia 3.2 mm

and bellow 400 A for 2.4 dia.

Welding voltage

Effect the depth of penetration and stability of process. Excessive voltage may cause overheating of metal,

gassing of slag pool and even sparking. With Low voltage electrode may short-circuit to the

pool of molten metal. Selection of voltage is governed by the type of flux

used and is usually 32 to 55 volt per electrode. Higher voltage is used with thicker section.

Effect the depth of penetration and stability of process. Excessive voltage may cause overheating of metal,

gassing of slag pool and even sparking. With Low voltage electrode may short-circuit to the

pool of molten metal. Selection of voltage is governed by the type of flux

used and is usually 32 to 55 volt per electrode. Higher voltage is used with thicker section.

Electrode diameter

Greater the diameter of electrode more the depth ofpenetration and the suitable operation of process. In such cases use is made of electrode plates instead of

large diameter wires.

Greater the diameter of electrode more the depth ofpenetration and the suitable operation of process. In such cases use is made of electrode plates instead of

large diameter wires.

Electrode Extension Distance between contact tube and slag pool surface is

referred to as “dry electrode extension”. And length ofelectrode dipped in slag is called “wet extension”. Electrode extension of 50-75mm are normally used. Bellow 50 mm resulting in overheating of contact tube

and more then 75 mm resulting in overheating ofelectrode because of increasing in electrode resistance. Leads to melt the electrode at the surface of slag pool

instead of inside it.

Distance between contact tube and slag pool surface isreferred to as “dry electrode extension”. And length ofelectrode dipped in slag is called “wet extension”. Electrode extension of 50-75mm are normally used. Bellow 50 mm resulting in overheating of contact tube

and more then 75 mm resulting in overheating ofelectrode because of increasing in electrode resistance. Leads to melt the electrode at the surface of slag pool

instead of inside it.

Electrode Oscillation

Plates upto 75 mm thick can be welded withoutoscillation but with high voltage. To achieve better fusion it is necessary to oscillate the

electrode horizontally across the thickness. Oscillation speed normally varies between 10-40

mm/sec. Increasing in speed result in reduce weld width.

Plates upto 75 mm thick can be welded withoutoscillation but with high voltage. To achieve better fusion it is necessary to oscillate the

electrode horizontally across the thickness. Oscillation speed normally varies between 10-40

mm/sec. Increasing in speed result in reduce weld width.

Slag Pool depth

Excessive pool depth resulting slag inclusion. Lead to reduce weld penetration. Too shallow result arcing on the slag surface. Optimum depth of weld pool is about 40 mm And the range can be used between 25 mm to 60 mm.

Excessive pool depth resulting slag inclusion. Lead to reduce weld penetration. Too shallow result arcing on the slag surface. Optimum depth of weld pool is about 40 mm And the range can be used between 25 mm to 60 mm.

Root gap

It effect the depth of penetration Decrease in root gap result in decrease in penetration

and vice-versa. Narrow gap increase in short-circuit. Large gap required an extra amount of filler metal. Feasible root gap should between 20-35 mm.

It effect the depth of penetration Decrease in root gap result in decrease in penetration

and vice-versa. Narrow gap increase in short-circuit. Large gap required an extra amount of filler metal. Feasible root gap should between 20-35 mm.

Applications of ESW

Welding of structure, machinery, ships, pressure vesseland casting. Applicable to long butt weld.

Welding of structure, machinery, ships, pressure vesseland casting. Applicable to long butt weld.

Advantages of Electroslag Welding:

High deposition rate - up to 45 lbs/h (20 kg/h); Low slag consumption (about 5% of the deposited

metal weight); Low distortion; Unlimited thickness of work piece.

Disadvantages of Electroslag welding:

Coarse grain structure of the weld; Low toughness of the weld; Only vertical position is possible.

Advantages of Electroslag Welding:

High deposition rate - up to 45 lbs/h (20 kg/h); Low slag consumption (about 5% of the deposited

metal weight); Low distortion; Unlimited thickness of work piece.

Disadvantages of Electroslag welding:

Coarse grain structure of the weld; Low toughness of the weld; Only vertical position is possible.

Variants of ESW

Consumable guide ESW ESW with plate electrode Electroslag butt welding

Consumable guide ESW ESW with plate electrode Electroslag butt welding

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