Smaw

Electrode oven

(Up to 350 °C)

Power return

cable

Safety visor

(With dark lens) *

Power source.

Transformer/

Rectifier

Holding Oven

(Up to 200 °C)

Inverter power

source

Electrode holder

Power cable

Power control

panel

Electrodes

Welding of pipes

Welding of structure

AC

DC+

DC-

2- Direct current reverse polarity(DCEP)

3-Direct current straight polarity(DCEN)

1- Stringer Bead −

Steady MovementAlong Seam

2- Weave Bead −

Side To Side MovementAlong Seam

Electrode Angle

Arc Length

Travel Speed

1. Large Spatter Deposits

2. Rough, Uneven Bead

3. Slight Crater During Welding

4. Bad Overlap

5. Poor Penetration

1. Fine Spatter

2. Uniform Bead

3. Moderate Crater During

Welding

4. No Overlap

5. Good Penetration Into

Base Metal

Flux type

Cellulosic Rutile Basic

Cellulosic

Properties 1-covering contains low parentage from cellulose (thin coating from slag).

2-covering contains high parentage from hydrogen (fumes which make gas shield)

3-covering contains silicon (deoxidizer ,fluidity ,high penetration)

4-relative high cooling rate

5-risk hydrogen induced crack

6- not suitable for very thick sections (may not be used on thicknesses > ~ 35mm)

Rutile

Properties1-covering contains high percentage from TiO2 (thick coating from slag )

2-covering contains medium parentage from hydrogen (fumes which

make gas shield)

3- easy to strike arc

4- electrodes can be dried to lower H2 content but cannot be baked as it

will destroy the coating

5- less fluidity and low penetration

Basic

Properties 1- covering contains low parentage from cellulose (thin coating from

slag).

2- covering contains high parentage from hydrogen

3-Prior to use electrodes should be baked, typically 350°C for 2 hour plus

to reduce moisture to very low levels and achieve low hydrogen

potential status.

4-high cooling rate

5- low risk hydrogen induced crack

6- coatings containing calcium carbonate / calcium fluoride.

Provided to perform some of the following objectives:

To increase the arc stability with the help of low ionization

potential elements like Na, K.

To provide protective shielding gas environment to the arc zone and weld pool with the help of inactive gases (like carbon dioxide) generated by thermal decomposition of constituents present in coatings such as hydrocarbon, cellulose.

To remove impurities from the weld pool by forming slag

as constituents present in coatings such as titania,

fluorspar, china-clay react with impurities and oxides in

present weld pool (slag being lighter than weld metal

floats over the surface of weld pool which is removed after

solidification of weld)

Controlled alloying of the weld metal (to achieve specific

properties) can be done by incorporating required alloying

elements in electrode coatings and during welding these

elements get transferred from coating to the weld pool.

However, element transfer efficiency from coating to weld

pool is influenced by the welding parameter and process

itself especially in respect of shielding of molten weld

pool.

To deoxidize weld metal and clean the weld metal:

Elements oxidized in the weld pool may act as inclusions

and deteriorate the performance of the weld joint.

Therefore, metal oxides and other impurities present in

weld metal are removed by de-oxidation and slag

formation. For this purpose, deoxidizers like Ferro-Mn,

silicates of Mg and Al are frequently incorporated in the

coating material.

To increase viscosity of the molten metal and slag so as to

reduce tendency of falling down of molten weld metal in

horizontal, overhead and vertical welding. This is done by

adding constituents like TiO2 and CaF2 in the coating

material. These constituents increase the viscosity of the

slag.

Role on welding arc featuresConstituent in flux

Increases current-carrying capacityQuartz (SiO2)

Increases slag viscosity, good re-strikingRutile (TiO2)

Refines transfer of droplets through the arcMagnetite (Fe3O4)

Reduces arc voltage, produces inactiveshielding gas, slag formation

Calcareous spar (CaCO3)

Increases slag viscosity of basicelectrodes, decreases ionization

Fluorspar (CaF2)

Improves arc stability by easy ionizationCalcareous- fluorspar (K2O Al2O36SiO2)

Acts as deoxidantFerro-manganese and Ferro-silicon

Produces inactive shielding gasCellulose

Acts as a bonding agentPotassium Sodium Silicate(K2SiO3 / Na2SiO3)

SMAW Electrode Identification System

Electrode

SMAW Electrode Identification System

Strength

SMAW Electrode Identification System

Position

1 - used in all positions 2 - used in flat or horizontal fillets only 3 - not used at present time 4 - used for ‘downhill’ progression

SMAW Electrode Identification SystemCoating/Operating

Characteristics

Types end in a ‘5’, ‘6’, or ‘8’ Purchase in sealed, metal containers Store after opening in heated, oven Limit atmospheric exposure

Electrode

Tensile strength

(PSI x 1000)

Positional capabilities

Flux coating &

electrical characteristics

Example:-

- A1 0.5% Mo

- B1 0.5% Mo 0.5% Cr

- B2 0.5% Mo 1.25% Cr

- B3 1.0% Mo 2.25% Cr

- B4 0.5% Mo 2.0% Cr

- C1 2.5% Ni

- C2 3.5% Ni

- C3 1.0% Ni

- D1 0.3% Mo 1.5% Mn

- D2 0.3% Mo 1.75% Mn

- G 0.2% Mo 0.3% Cr 0.5% Ni 1% Mn 0.1% V

As arc voltage, V, drops, arc current, A, rises Arc V related to distance from electrode to work Electrode moved closer, Arc V falls, Arc A rises Electrode moved away, Arc V rises, Arc A drops Arc current directly related to heat input Welder controls heat input to work

Simple equipment Inexpensive Very portable Welds most alloys

Relatively slow Slag removal Electrode storage considerations

Porosity Slag inclusions Spatter Incomplete joint penetration Incomplete fusion