7.

WELDING CONSUMABLES

7.1 WELDING CONSUMABLES

Welding consumables are materials used up during welding such as electrodes, filler rods, fluxes
and externally applied shielding gases.
In almost all the developed countries, national codes and standards have been developed to clearly
identify the specifications for various uses. However, in the preceding paragraphs, division will
cover, the most common codes amongst all, i.e. the specification outlined by the American
Welding Society.
The first specification for mild steel covered electrodes “A4.1 specifications for carbon steel
electrodes for shielded metal arc welding” by American Welding Society. As the welding industry
expanded and number of types of electrodes for welding steel increased, it became necessary to
devise a system of electrode classification to avoid confusions.
The process like gas tungsten arc welding consume the electrodes at considerably low rate, hence
it is not common to include such electrodes as consumables. However, the filler wire, if used,
with these, so called, non-consumable electrodes is obviously a consumable item. The welding
consumables can be grouped under will include four major categories, i.e.
i) Coated electrodes
ii) Fluxes
iii) Filler wires/filler rods
iv) Shielding gases
See Table 7.1 for AWS Filler Metal Specifications.
7.2 FACTORS TO BE CONSIDERED FOR SELECTION OF ELECTRODES
7.2.1 Base Metal Strength Properties
Know and match mechanical properties
It is essential to know not only the kind of metal being welded (e.g. mild steel or cast iron etc) but
also its mechanical properties.
Mild steel ----------- generally E60XX or E70XX electrodes match base metal.
Low alloy steel ----- select electrodes that match base metal properties.
7.2.2 Base Metal Composition
Know and match composition
Mild Steel- Any E60XX or E70XX electrode is satisfactory. Low alloy steel - select electrode that
most closely match base metal composition.
7.2.3 Welding Position
Match electrode to welding position encountered

Not all electrodes are designed for use in every position. Electrode must match the welding
position being used.
7-1
 7.2.4 Welding Current

Match power supply available

The electrode selected should be one that closely matches the type of power source being used.
The type of welding current to be used with the particular electrode is indicated by AWS
electrode classification.

Some electrodes are designed for D.C. others A.C, ; some either. Observe correct polarity.

Table 7.1: AWS filler metal specifications.

AWS AWS
DESIGNATI TITLE OF SPECIFICATION DESIGNAT TITLE OF SPECIFICATION
ON ION
A5.01 Filler Metal Procurement Guidelines A5.16 Specification for Titanium and Titanium
Alloy Welding Electrodes and Rods
A5.1 Specification for Carbon Steel A5.17 Specification for Carbon Steel Electrodes
Electrodes for Shielded Metal Arc and Fluxes for Submerged Arc Welding
Welding
A5.2 Specification for Carbon and Low A5.18 Specification for Carbon Steel Electrodes
Alloy Steel Rods for Oxyfuel Gas and Rods for Gas Shielded Arc Welding
Welding
A5.3 Specification for Aluminum and A.519 Specification for Magnesium Alloy Welding
Aluminum Alloy Electrodes for Electrodes and Rods
Shielded Metal Arc Welding
A5.4 Specification for Stainless Steel A5.20 Specification for Carbon Steel Electrodes for
Electrodes for Shielded Metal Arc Flux Cored Arc Welding
Welding
A5.5 Specification for Low Alloy Steel A5.21 Specification for Bare Electrodes and Rods
Electrodes for Shielded Metal Arc for Surfacing
Welding.
A5.6 Specification for Copper and Copper A5.22 Specification for Stainless Steel Electrodes
Alloy Electrodes for Shielded Metal for Flux Cored Arc Welding
Arc Welding
A5.7 Specification for Bare Copper and A5.23 Specification for Low Alloy Steel Electrodes
Copper Alloy Electrodes and Rods and Fluxes for Submerged Arc Welding
A5.8 Specification for Brazing Filler Metals A5.24 Specification for Zirconium and Zirconium
Alloy Welding Electrodes and Rods
A5.9 Specification for Bare Stainless Steel A5.25 Specification for Carbon and Low Alloy
Welding Electrodes and Rods Steel Electrodes and Fluxes for Electroslag
Welding
A5.10 Specification for Bare Aluminum and A5.26 Specification for Carbon and Low Alloy
Aluminum Alloy Welding Electrodes Steel Electrodes for Electrogas Welding
and Rods
A5.11 Specification for Nickel and Nickel A5.27 Specification for Copper and Copper Alloy
Alloy Electrodes for Shielded Metal Rods for Oxyfuel Gas Welding.
Arc Welding
A5.12 Specification for Tungsten Electrodes A5.28 Specification for Low Alloy Steel Electrodes
for Arc Welding and Cutting and Rods for Gas Shielded Arc Welding
A5.13 Specification for Surfacing Electrodes A5.29 Specification for Low Alloy Steel Electrodes
for Shielded Metal Arc Welding. for Flux Cored Arc Welding.
A5.14 Specification for Bare Nickel and A5.30 Specification for Consumable Inserts.
Nickel Alloy Welding Electrodes and
Rods
A5.15 Specification for Welding Rods and
Shielded Metal Arc Electrodes for
Cast Iron

7-2
7.2.5 Joint Design and Fit-Up

Select for penetration characteristic - digging, medium or light.

The design of joint and fitup determines the degree of arc penetration.

No beveling or tight fit up - use digging. Thin materials or wide root opening - light soft arc.
Electrode that gives the required penetration should be selected.

The number of passes is also determined by the type of electrode selected. Multiple passes require
more current than a single pass.

7.2.6 Thickness and Shape of Base Metal

To avoid weld cracking on thick and heavy material of complicated design, select electrode with
max. ductility. Low hydrogen process of electrodes are recommended. The thicker the metal, the
greater the current i.e. required to produce a suitable weld. An increase in the amount of current
requires a corresponding increase in electrode diameter size.

7.2.7 Service Condition and Specifications

Determine service conditions - low temp., High temp. Shock loading - match base metal
composition, ductility and impact resistance. Use low hydrogen process also, check welding
procedure or specification of electrode type.

7.2.8 Production Efficiency and Job Conditions

For high deposition and most efficient production under flat position requirements, select a high
iron powder type of large diameter wires. For other conditions, you may need to experiment with
various electrodes and sizes.

7.3 ELECTRODES STANDARDS

In the world industry countries make their national welding standards e.g.

AWS is the standard which is prepared by American Welding Society.

DIN is the German Industry Standard.

JIS is the Japan Industry Standard.

7.4 SMAW ELECTRODES

About half of all filler metals used as stick electrodes. Stick - electrode welding is the single most
frequently used welding process.

The amount of stick electrodes welding done drops a little each year relative to other processes, as
the cost of welding labor goes up and manufacturer move to one or more of the semi automatic or
automatic processes to increase productivity. Nevertheless, SMAW still holds a large share of
total welding filler metal business. Here we shall give more concentration on the SMAW
electrodes.

7-3
7.4.1 Anatomy of a SMAW Electrode

An electrode for welding steel or cast iron will have a mild-steel core wire. An aluminum
electrode would have an aluminum core wire. An SMAW electrode for welding copper or copper
alloys will have a copper core wire.

Similarly, an electrode for welding any other metal probably would have a relatively pure (as
opposed to an alloy) core wire made out of that metal. There are several reasons why?

A high alloy core wire would be very expensive to make. Many alloys can’t even be made into
wire; they are not ductile enough. In addition, there’s no need to buy small quantities of many
different kinds of alloy-steel, alloy-aluminum, or bronze wires when the SMAW flux coating can
be used to add the alloying elements.

When the welding arc forms between the electrode and the base metal, part of the flux on the hot
working end of the electrode is vaporized, making a protective shielding gas that surrounds the
hot weld metal, the heat-affected zone of the base metal next to the weld, and the molten end of
the electrode wire. Other elements in the flux join with the molten core wire to make weld metal
with the desired final properties.

For example, an austenitic stainless steel electrode will use a mild-steel core wire, but the
chromium and other elements like nickel that make stainless steel, austenitic, will be added to the
weld metal from the flux.

7.5 FLUXES

7.5.1 Definition of Flux

According to British standard 499, the definition of flux is a material used during welding,
brazing or braze welding to clean the surfaces, the joint chemically, to prevent atmospheric
oxidation and reduce impurities or float them to the surface. In arc welding, many other
substances which perform special functions are added to the flux mixture.

7.5.2 Fluxes are Used in Four Main Welding Process

a) Manual metal - arc-welding electrode; the flux is coated to the outside of a filler metal rod.
b) Submerged arc welding fluxes: added separately in the weld pool.
c) Flux cored are welding; the flux is wrapped inside a continuous wire sheath.
d) Electro-slag welding: the fairly large granules of flux are again entirely separate from the
wire.

All these processes require different physical and chemical properties, from the flux; however
many minerals used in flux formulations are common to all four flux processes and have the same
or a similar role to play in all of them.

7.5.3 The Constituents of Flux

The majority of welding fluxes for steel are made from minerals, with as little purification and
treatment as possible; this keep down the cost of manufacture and therefore the price of the flux.

Certain undesirable impurities such as phosphorus, and sulphur etc are however kept to a
minimum.
7-4
Using natural minerals in flux formulations does add to the problems of the manufacturer, as
different mines produce ores with different impurities, which can seriously, effect flux
performance.

7.6 SMAW FLUX COATING

7.6.1 Addition of Elements Which Produce Slag

The molten puddle under the electrode has to be protected from the oxygen and nitrogen in the
air.

The gases produced by vaporizing flux coating would not last long enough to protect the weld
metal until it is fully solidified and cooled below a point where air would not hurt it. Therefore
other elements are put into the flux coating to produce protective slag to keep the hot weld metal
covered until it can expose to the air.

The molten slag is lighter in weight than the molten weld metal. It floats to the top of the weld
puddle and hardens to protect the weld until it is cool. The slag also removes certain unwanted
elements and impurities from the molten weld metal and base metal. When the weld is cool, the
slag is removed and a bright, shiny weld will be found underneath.

7.6.2 Addition of Elements for the Stability of the Arc

Still other elements are put into the flux coating to help control the stability of arc under different
conditions. Some flux additives are best for electrodes that operate with D.C. Other additives are
best for electrodes that operate with A.C. still other additive make electrodes that can operate on
either A.C., DCSP OR DCRP.

7.6.3 Addition of Deoxidizers

Some arc deoxidizers that help remove any excess oxygen in the weld metal created by rust or
scale on the steel (the oxide residue floats out of the weld metal into slag). If these additives are
present, the catalog description of the electrodes will tell you that it is “good for welding rusty or
heavily scaled steel”.

7.6.4 Addition of Elements in the Flux for Fluidity

There are flux coating additives that help keep the molten weld metal from becoming too fluid.
These are put into the flux to make the electrode work better for out of position welding.

7.6.5 Addition of Elements for High Deposition

Even more elements can be added to the flux to increase the deposition rate of finished weld
metal. These additives are excellent for making high deposition rate SMAW electrodes that are
only used in the flat position.

Iron powder in the coating improves arc behaviour, bead appearance, helps increase metal
deposition rate and arc travel speed.

7.6.6 Addition of Elements for Reducing the Moisture Contents

Some electrodes even have additives in the flux coating that reduce the amount of moisture that
the coating can pick up from humid air. These extra duty, moisture resistance electrodes are
specially valuable for welding high strength low alloy steel and full alloy steel that are subject to
7-5
hydrogen embrittlement. Even a tiny amount of moisture in your electrode flux can pass through
the welding arc and become oxygen and hydrogen atoms and ions. The hydrogen will make high
strength steel brittle.

7.6.7 Addition of Alloying Elements

Alloying elements like Ferro-alloys of manganese, molybdenum etc may be added to impart
suitable properties and strength to the weld metal and to make good the loss of some of the
elements, which vaporize while welding.

7.6.8 Binders

Binders are needed to hold the additives together, so that the flux would not chip off the electrode,
and other chemical additives are needed to make it easy to extrude the flux coating on to the
electrode wire.

7.7 MAIN CLASSES OF COVERINGS FOR SMAW ELECTRODES

7.7.1 Acid

The acid covering contain the largest amount of iron and manganese ores and alumina - silicates
(high oxygen contents). This means that the covering is very active, because it contains both
oxygen and hydrogen. The electrode can therefore be used for positional welding.

Welds made with acid electrodes usually have an excellent appearance, but poor mechanical
properties. The welds-tends to be low in strength and for this reason acid electrodes are not widely
used.

7.7.2 Rutile

The Rutile electrodes coverings, mainly contain TiO2 (Rutile). The transferred droplets are larger
than the electrodes having acid coverings.

The arc is more stable but other differences from the acid electrodes type are small. Rutile
electrodes are easy to operate and considered as good general purpose electrodes.

7.7.3 Cellulose

This type of electrode contain organic matter (usually cellulose) which often comprise about 30%
by wt of total flux.

Zirconium silicate is often found in electrodes as both an arc stabilizer and an aid to slag
detachability. With the oxygen and hydrogen contained in the covering, spray transfer occurs and
the hydrogen aids good penetration which is of advantage in applications such as pipe welding.

7.7.4 Basic

The metal transfer observed when welding with basic covered electrode is by droplet, sometime
large droplets and deoxidized low hydrogen metal is deposited.

Basic electrodes can be dried to sufficiently low moisture levels to give the low weld hydrogen
contents which are required to minimise the risk of hydrogen cracking.

7-6
Compared with the acid electrodes, partial pressure of hydrogen in the arc column gas is lower
and hydrogen content of the weld joint will decrease because calcium fluoride combines with
hydrogen at high temperature to produce hydrogen fluoride (HF). So basic electrodes are called
low hydrogen type electrodes. They are capable of giving the low weld oxygen contents needed
for the best weld toughness.

TABLE NO. 7.2: ROUGH COMPOSITIONAL RANGES FOR THE FOUR MAIN MMA
COVERING TYPES WEIGHT %

Compound Acid Rutile Cellulose Basic

TiO2 Trace-10 30 – 50 Trace - 5 Trace - 5
SiO2 10 - 20 5 – 15 5 - 15 5 - 15
ZrSiO4 Trace - 5 Trace – 5 Trace - 10 -
CaCO3 5 - 15 15 – 25 5 - 15 25 - 40
CaF2 - - - 30 - 40
MnO 10 - 20 5 – 10 0 - 10 -
MnO2 10-20 - - -
FeO 10 - 20 5 – 10 0 - 10 -
FeSi - - - 5 - 10
Mica - 10 – 20 - -
Ferro alloys - 0–5 - -
Cellulose - - 25 - 40 -

7.8 AWS CLASSIFICATION

The welding material covered by the specification “A 5.1” “Specification for Carbon steel
electrodes for Shielded Metal Arc Welding” are classified according to the following criteria.

1) Type of the current

2) Type of covering
3) Welding position of the electrode
4) Chemical composition of the weld metal
5) Mechanical properties of the weld metal in as welded condition

7.8.1 Prefix Letters

E = indicates an arc welding electrode, which, by definition, carries the arc welding
current.
R = indicates a welding rod which is heated by means other then by carrying the arc
welding current.
ER = indicates a filler metal, which may be used either as an arc welding electrode or as
a welding rod.
EW = indicates a (non consumable) tungsten electrode
B = indicates a brazing filler metal
F = indicates a flux for use in submerged arc welding etc.

7-7
AWS DESIGNATION TITLE OF SPECIFICATION
A5.1 SPECIFICATION FOR CARBON
STEEL ELECTRODES FOR SHIELDED
METAL ARC WELDING
AWS EXXXX
  
American Welding Society Electrode

 
First two digits of four digit numbers and Next to last digit indicates
position e.g.
first three digits of five digit numbers EXX1X All Positions
indicates minimum tensile strength. EXX2X Flat & Horizontal Fillets
e.g. EXX4X F, OH, H, V-Down
E60XX 60000 psi Minimum Tensile strength
E110XX 110,000 psi Minimum Tensile Strength

Flux Coating
(See table “7.3”) Electrode
classification.

Table no. 7.3: Electrode classification.

Capable of producing
AWS
Type of covering satisfactory welds in Type of current b
classification
position shown a
E60 SERIES ELECTRODES
E6010 High cellulose sodium F, V, OH, H DCEP
E6011 High cellulose potassium F, V, OH, H AC or DCEP
E6012 High titania sodium F, V, OH, H AC or DCEN
E6013 High titania potassium F, V, OH, H AC or DC, either polarity
E6020 High iron oxide H-fillets, F AC or DCEN
E6022c High iron oxide F, H AC or DC, either polarity
E6027 High iron oxide, iron powder H-fillets, F AC or DCEN
E70 SERIES ELECTRODES
E7014 Iron powder, titania F, V, OH, H AC or DC, either polarity
E7015 Low hydrogen sodium F, V, OH, H DCEP
E7016 Low hydrogen potassium F, V, OH, H AC or DCEP
E7018 Low hydrogen potassium, iron F, V, OH, H AC or DCEP
powder
E7024 Iron powder, titania H-fillets, F AC or DC, either polarity
E7027 High iron oxide, iron powder H-fillets, F AC or DCEN
E7028 Low hydrogen potassium, iron H-fillets, F AC or DCEP
powder
E7048 Low hydrogen potassium, iron F, OH, H, V-down AC or DCEP
powder
a. The abbreviations, F, V, V-down, OH, H, and H-fillets indicate the welding positions as follows : F =Flat, H = Horizontal, H-fillet
=Horizontal fillets, V-down =Vertical down, V = Vertical
b. The term DCEP refers to direct current, electrode positive (DC reverse polarity). The term DCEN refers to direct current, electrode
negative (DC straight polarity).

7-8
7.8.2 AWS E6010
All position AWS E6010 electrodes are used for DCRP (electrode-positive) welding. They are
best suited for making vertical and overhead welds.
The molten weld metal sprays through the welding arc something like a miniature paint gun. This
spray transfer helps you weld in the vertical and overhead positions.
AWS E6010 electrodes give you deep weld penetration, which means that you have to be careful
in handling the electrode to minimize spatter.
The thickness of the flux coating on AWS E6010 electrodes is held to a minimum to make it
easier to weld in the vertical and overhead positions, but the coating will give you enough
shielding for high-quality weld deposits. the electrode flux coating is high in cellulose, usually
exceeding 30% cellulose by weight.
Some AWS E6010 electrode flux coatings have a small amount (less than 10 percent by weight)
of iron powder in them to improve their arc characteristics. Because of the coating composition,
these are generally classified as high cellulose sodium type electrodes.
7.8.3 AWS E6011
AWS E6011 electrodes are almost identical to AWS E6010 electrodes except that they operate on
AC as well as DC. Their performance is very similar.
However, AWS E6011 electrodes perform equally well with either AC or DCRP (electrode-
positive) power settings. These electrodes have a forceful digging arc action that results in deep
base-metal penetration.
While the flux coating is slightly heavier than that of AWS E6010 electrodes, the resulting slag
and weld profiles of AWS E6011 stick electrodes are quite similar to those of E6010 electrodes.
The coating is high in cellulose and is designated as the high-cellulose potassium type. (potassium
rather than sodium makes these electrodes work well with AC).
7.8.4 AWS E6012
The flux coating of AWS E6012 electrodes usually is high in titanium dioxide, exceeding 35
percent by weight, which is why these electrodes are often called titania or rutile coated grades.
AWS E6012 elelctrodes are characterized by medium penetration and dense slag which
completely covers the bead.
AWS E6012 stick electrodes are used for all-purpose welding in all positions.
It is used much more frequently in flat and horizontal positions than in vertical or overhead
welding.
They are especially recommended for single-pass, high-speed, high-current, horizontal fillet
welds.
AWS E6012 electrodes have a rather quiet arc. This means that although you get medium base
metal penetration, you also get a lot less spatter.
7.8.5 Low Hydrogen Electrodes
All low-hydrogen electrodes have a lot of calcium carbonate (the mineral in limestone) or calcium
fluoride (a mineral called fluorite) in them. They sometimes are called lime-ferritic, or basic type
electrodes. Materials such as cellulose, clays, asbestos, and other minerals that contain water in
7-9
the crystal lattice are not used, to ensure that the electrode flux coating has a very low hydrogen
content. (Because water is made of hydrogen and oxygen).
In addition, low-hydrogen electrodes are baked at higher temperatures after the flux has been
extruded onto them to ensure that all the water possible has been driven out of the coating.
There must be no moisture, no organic materials and nothing else that might have hydrogen atoms
in it, to prevent hydrogen embrittlement.
For the same reason you have to keep your electrode as dry as possible at all times.
When you use low hydrogen electrode, keep your arc to weld metal distance as short as possible
to reduce the tendency for under bead cracking. Using a “short arc technique also will improve the
quality of your as-welded deposit and will some what reduce the need for preheating and post-
heating of difficult to weld steels.
7.8.6 Hydrogen Embrittlement
The hydrogen molecules when absorbed in steel produce very high stresses in the surface of the
base metal. If the base metal is not very ductile, as in the case of most high strength steels, the
metal acts like it has suddenly becomes very brittle. The result is a crack under the weld bead and
is caused by hydrogen molecules being absorbed from the welding arc atmosphere into the weld
metal and from there into the base metal.
“If you were told that you could only carry around two kinds of steel electrodes, your best choices
would be AWS E6010 AND AWS E7018”.
7.8.7 AWS E7015
AWS E7015 electrodes are low hydrogen electrodes to be used with DCEP (electrode positive).
The slag is chemically basic. The arc of E7015 electrodes is moderately penetrating. The slag is
heavy, friable, and easy to remove. The shortest possible arc should be maintained for best results
with E7015.
7.8.8 AWS E7016
AWS E7016 electrodes have all the characteristics of E7015 electrodes, plus the ability to operate
on AC.
The core wire and coverings are very similar to those of E7015, except for the use of a potassium
silicate binder or other potassium salts in the coverings to facilitate their use with AC.
7.8.9 AWS E7018
AWS E7018 electrode coverings are similar to E7015 coverings, except for the addition of a high
percentage of iron powder. The coverings on these electrodes are slightly thicker than those of the
E7015 and E7016 electrodes. The iron powder in the coverings usually amounts to between 25
and 40 percent of the covering by weight.
7.9 ALLOY STEELS
Alloy steel may be defined as one whose characteristics properties are due to some elements other
than carbon. Although all plain carbon steels contain moderate amount of manganese (up to about
0.90 % ) and silicon (up to about 0.30 %), they are not considered alloy steels because the
principal function of the manganese and silicon is to act as deoxidizers. They combine with O 2
and S to reduce the harmful effect of those elements.

7-10
AWS DESIGNATION TITLE OF SPECIFICATIONS
A5.5 SPECIFICATIONS OF LOW ALLOY STEEL
ELECTRODES FOR SHIELDED METAL
ARC WELDING
Group of letters & numbers
provides a clue to chemical
composition of weld metal or
may indicate a military or
proprietary electrodes.
Often a clue to impact strength or
special heat treatment.

AWS EXXXX-X
  
American Welding Society Electrode

 
First two digits of four digit numbers and Next to last digit indicates
position e.g.
first three digits of five digit numbers EXX1X All Positions
indicates minimum tensile strength. EXX2X Flat &
e.g. Horizontal Fillets
E70XX 70000 psi Minimum Tensile strength EXX4X F, OH, H, V-Down

E110XX 110,000 psi Minimum Tensile Strength

Flux Coating
(See Table “4.3”) Electrode
classification.
AWS A 5.5 includes more than 40 different classifications of low alloy steel electrodes for
example:
AWS EXXXX - A1 ---------- CARBON MOLYBDENUM – STEEL
ELECTRODES WITH Mo FROM 0.40 TO 0.65 %
AWS EXXXX - B1 ------------- CHROMIUM - MOLYBDENUM STEEL
ELECTRODES WITH Cr. AND Mo
FROM 0.4 TO 0.65 %
-------------------------
------------------- etc.
The suffix (Example: EXXXX-A) indicates the approximate alloy in the weld deposit:
-A1 0.5 % Mo
-B1 0.5 % Cr, 0.5% Mo
-B2 1.25 % Cr, 0.5 % Mo
-B3 2.25 % Cr, 1 % Mo
-B4 2% Cr, 0.5 % Mo
-B5 0.5% Cr, 1 % Mo
-C1 2.5% Ni
-C2 3.25% Ni
-C3 1% Ni, 0.35 % Mo, 0.15% Cr
-D1 and D2 0.25 - 0.45 % Mo, 1.75 % Mn
-G 0.5% min. Ni, or 0.3% min. Cr,
or 0.2% min. Mo,
or 0.1% min. V, or 1% min. Mn
(only one element required)
7-11
AWS E 10018-M or AWS E 12018-M are a special military grade for welding sub marine hulls
and test turrets.

7.10 ELECTRODES FOR GAS METAL ARC WELDING PROCESS (GMAW)

In Gas Metal Arc Welding (GMAW) an externally supplied shielded gas is used to protect the arc
and molten weld metal from air. The filler metal is a continuous bare electrode wire fed through a
wire feeder and a welding gun. The gun delivers both, the shielding gas and the electrode filler
wire to the weld.

You can work continuously without stopping to change electrodes or pick up a new welding rod.
The electrodes (filler metals) for gas metal arc welding are covered by various AWS filler metal
specifications.

Generally for joining applications, the composition of the electrode (a filler metal) is similar to
that of the base metal. The filler metal composition may be altered slightly to compensate for
losses that occur in the welding arc, or to provide for deoxidation of the weld pool. In some cases,
this involves very little modifications from the base metal composition.

AWS specification AWS A 5.18 “Carbon Steel Electrode and rods for Gas Shielded Arc
Welding” on the basis of chemical composition of the wire and mechanical properties of the weld
metal.
AWS DESIGNATION TITLE OF SPECIFICATION

A 5.18 SPECIFICATIONS FOR CARBON

STEEL ELECTRODES
AND RODS FOR GAS SHIELDED
ARC WEDLING

SCOPE : This specifications prescribes requirements for bare carbon steel electrodes and rods
for use with the GMAW, GTAW and PAW (Plasma Arc) welding processes.

CLASSIFICATION SYSTEM

(I) The classifications system used in this specifications follows as closely as possible the
standard pattern used in other AWS filler metal specifications.

(II) As an example consider

ER70S-2
ER  Bare filler metal may be used as an electrode or welding rod.
70  Indicates the required minimum Tensile Strength of the weld metal i.e. 70,000 Psi.
S  designates, a bare, solid electrode or Rod.
2  relates to the specific chemical composition for the filler metal.
G  For suffix G, (as in case of ER70S-G), no chemical requirements, with the exception that
there will be no international addition of Ni, Cr, Mo or V. Subject to agreement between supplier
and purchaser.

7.10.1 CHEMICAL COMPOSITION REQUIREMENTS

The chemical composition requirements for bare solid electrodes and welding rods are given in
the following table.

7-12
AWS C Mn Si P S Ni Cr Mo V Cu Ti Zr Al
Classification
0.90 0.40 0.05 0.02 0.05
ER 70S-2 0.07 to to 0.025 0.035 c c c c 0.50 to to to
1.40 0.70 0.15 0.12 0.15
0.06 0.90 0.45
ER 70S-3 to to to -do- -do- -do- -do- -do- -do- -do- ---- ---- ----
0.15 1.40 0.70
0.07 1.00 0.65
ER 70S-4 to to to -do- -do- -do- -do- -do- -do- -do- ---- ---- ----
0.15 1.50 0.85
0.07 0.90 0.30 0.50
ER 70S-5 to to to -do- -do- -do- -do- -do- -do- -do- ---- ---- to
0.19 1.40 0.60 0.90
0.07 1.40 0.80
ER 70S-6 to to to -do- -do- -do- -do- -do- -do- -do- ---- ---- ----
0.15 1.85 1.15
0.07 1.50 0.50
ER 70S-7 to to to -do- -do- -do- -do- -do- -do- -do- ---- ---- ----
0.15 2.00 0.80

ER 70S-G No chemical requirements

7.11 STAINLESS STEEL ELECTRODES/RODS FOR GAS TUNGSTEN ARC

WELDING (GTAW)
GTAW process is the most flexible of all fusion welding processes in terms of large variety of
metals it can join.
Gas tungsten arc welding is not widely used in mass production for welding carbon and low alloy
steel. The quality of gas tungsten arc welds in Carbon and alloy steels is more influenced by
the base metal impurity content (i.e. sulphur, phosphorous, oxygen) than are welds made with
SMAW or SAW. This is because fluxes are not present in GTAW to remove or tie up these
impurities.
Stainless Steel :- Chromium is the major alloying element that makes stainless steels stainless or
corrosion resistant.
Stainless steel and other alloys are extensively welded with the GTAW process because they are
protected from the atmosphere by the inert gas.
Generally, the filler metal composition is adjusted to match the properties of the base metal in its
welded condition.
AWS A 5.9 gives “specifications for base stainless steel welding electrodes and rods” as an
example
AWS DESIGNATION TITLE OF SPECIFICATION
A 5.9 SPECIFICATIONS FOR BARE STAINLESS STEEL
WELDING ELECTRODES AND RODS
The system of classification numbers used in this specification follows the standard pattern used
in other filler metal specifications.
For example consider
AWS ER 308-L
Where AWS ----------- American Welding Society
ER -------------- bare filler metal may be used as an electrode or welding rod.
308 ------------ indicates the chemical composition of filler metal.
L --------------- indicates low carbon.

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7.12 WELDING OF ALUMINUM AND ALUMINUM ALLOYS

Aluminum and Aluminum alloys can be welded by GMAW or GTAW process.

But GTAW is ideally suited for welding of Aluminum alloys. Aluminum alloys form refractory
surface Oxides which make joining more difficult. For this reason most welding of Aluminum is
performed with alternating current, because it provide surface cleaning action.

Argon Shielding Gas is generally used for welding of Aluminum with alternating current because
it provides better arc starting, better cleaning action.

7.13 ALUMINUM AND ALUMINUM ALLOY WELDING RODS AND BARE

ELECTRODES AWS “A 5.10”

This specification prescribes Aluminum and Aluminum alloys welding rods for use with TIG
welding.

Rods and electrodes are classified on the basis of chemical composition of the as manufactured
filler metal.

The letter system for identifying the filler metal classifications in this specification follows the
standard pattern used in other AWS filler metal specifications.

ER Bare filler metal may be used as an electrode or welding rod

The Aluminum association alloy designation nomenclature is used for the numerical portion to
identify the alloy.

e.g.

Aluminum of 99 % minimum purity 1XXX

Copper 2XXX
Manganese 3XXX
Silicon 4XXX
Magnesium 5XXX
Magnesium & Silicon 6XXX
Zinc 7XXX
Other element 8XXX
Unused series 9XXX

7.14 SHIELDING GASES

7.14.1 General

The primary function of the shielding gas is to exclude the atmosphere from contact with the
molten weld metal. This is necessary because most metals, when heated to their melting point in
air, exhibit a strong tendency to form oxides and, to a lesser extent nitrides. Oxygen will also react
with Carbon in molten steel to form Carbon monoxide and Carbon dioxide. These varied reaction
products may result in weld deficiencies, such as trapped slag, porosity and weld metal
embrittlement. Reaction products are easily formed in the atmosphere unless precautions are taken
to exclude Nitrogen and Oxygen.

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In addition to provide a protective environment, the shielding gas and their flow rate also have a
pronounced effect on the following.

1. Arc characteristics.
2. Mode of metal transfer.
3. Penetration and weld bead profile.
4. Speed of welding.
5. Under cutting tendency.
6. Cleaning action.
7. Weld metal mechanical properties.

7.14.2 Argon

Commercial grade purity 99.996 % is obtained by fractional distillation of liquid air from the
atmosphere, in which it is present to about 1 % (0.932 %) by volume. It is supplied in blue-
painted cylinders. Argon is the most common shielding gas used for both GMAW and GTAW to
joint Aluminum and Stainless steel.

The reasons for its popularity, its cost is less than Helium and it makes welding easy. Argon has
low ionization potential. Argon freely, given up electrons, which produce a more stable and quite
arc during welding, such arc stability means less spatter.

The lower ionization potential reduces the arc voltage, creating the lower power in the arc, and
therefore lower joint penetration, and poor bead contour.

When welding heavier steel plates Argon is generally mixed with other gases to produce a more
effective shield, which improves bead contour, appearance and penetration.

High density of Argon reduce flow rates. More shielding gas flow is needed for lighter Helium
than heavier Argon gas when working down hand.

For working over head, less Helium than Argon gas may be needed because Helium is so light it
rises up against over head weld metal.

Argon also produces spray transfer and that is a big factor in its use in GMAW. Not a high energy
input gas, Argon makes a weld that freezes quickly. If the metal is not molten long enough to wet
out to the weld toe, under cutting results. For Ferrous materials, additions of 1 to 5 % Oxygen,
which super heat the metal allows the molten weld metal shielded by Argon to flow out to the toes
of the weld and help avoid undercutting.

7.14.3 Helium

Helium, the next most abundant inert gas, available for shielding welds. Arc stability depends on
shielding gas’s ionization potential. The low ionization potential of Argon turns atoms into ions
easily which helps to sustain a smooth, even arc.

Whereas, Helium has a higher ionization potential than Argon. Therefore Helium shielded
welding produces a less stable arc.

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Arc and puddle control are difficult when using pure Helium shielding gas compared with Argon
or an Argon-Helium Argon- CO2 or Argon-O2 gas mixture. Helium can also present problems in
arc initiation.

Arcs shielded only by Helium do not exhibit true axial spray transfer at any current level. The
result is that Helium-shielded arcs produce a more spatter and have rougher bead surfaces than
Argon-shielded arc.

Helium costs more per unit volume than does Argon or CO 2, but it allows fast welding with
narrow gaps.

7.14.4 Carbon Dioxide

Carbon Dioxide (CO2) is a reactive gas, widely used in its pure form for GMAW of carbon and
low alloy steel. It is the only reactive gas suitable for use alone as a shield in the GMAW process.
Higher welding speed, greater joint penetration, and lower cost are general characteristics which
have encouraged extensive use of CO2 shielding gas.

Major disadvantage of the use of CO2 is its extreme resistance to current flow. Because of this
resistance, the arc length is sensitive. When the arc length is too long, it will extinguish more
readily than when an inert gas, like Argon or Helium is used.

7.15 CARE AND STORAGE OF ELECTRODES

Utmost care is required in handling and storage of electrodes. Electrodes coating should neither
get damped nor be damaged or broken.

Electrodes with damped coating will produce a violent arc, porosity and cracks in the joint.
Electrodes with damaged coating will produce joints of poor mechanical properties.

To avoid damage to coating (a) electrodes during storage should neither bend nor deflect, (b)
Electrode packets should not be thrown are piled over each other.

Electrodes should be stored in a dry and well ventilated store rooms.

Storage temperature of air should be about 20 °C and relative humidity 50% maximum.
Cellulose electrodes are not so critical but they should be protected against condensation.

Before use the electrodes may be dried as per manufacturer's recommendations.

Electrodes should preferably be retained in original (manufacturer's) packing for identification.

Loss of identity of electrodes can waste a lot of time in recognizing them correctly.

7.16 TUNGSTEN ELECTRODES

AWS CLASSIFICATION OF TUNGSTEN ARC WELDING ELECTRODES (AWS A5.12)

7.16.1 Introduction

Tungsten electrodes are non consumable in that, they do not intentionally become part of a
welded joint as do other electrodes used as filler metals.

The function of a tungsten electrode is to serve as one of the terminals of an arc, which supplies
the heat required for welding.

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7.16.2 Classification

The Tungsten Electrodes are classified on the basis of their chemical composition.

They are classified into different groups i.e.

1. EWP
2. EWTh
3. EWCe
4. EWLa
5. EWZr

A classification designation used for Tungsten Electrodes are similar to those used for AWS filler
metals in general i.e.

AWS EWP

AWS = American Welding Society

E = Stands for Electrode
W = Stands for Tungsten
P = Stands for pure Tungsten
Th = Thoriated Tungsten
Zr = Zirconiated Tungsten etc.

7.16.3 Operation and Usability

The choice of an Electrode Classification, size and welding current is influenced by the type &
thickness of the base metals to be welded. The capacity of Tungsten Electrode to carry current is
dependent upon numerous other factors, including i.e.

 Type & polarity of the current

 Shielding gas used
 Type of equipment used (air or water cooled)
 The extension of the electrode beyond the collet & welding position

1. An electrode of given size will have its greatest current capacity with direct current
(straight polarity) (DCSP), less with alternating current and still less with direct
current reverse polarity (DCRP).
2. Tungsten has a very low electrical conductivity and therefore, heats up when
current is passed through it. When welding with tungsten electrodes, the arc tips
should be only hot part of the electrode, the remainder should be kept as cool as
possible.
3. One method of preventing electrode overheating is to keep the extension of the
electrode from the collet short. If the extension is too large, even or relatively low
current can cause the electrode to overheat.
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7.16.4 Colour Code and Alloying Elements for Various Tungsten Electrode Alloys

Nominal weight of
AWS Alloying
Colour a Alloying oxide alloying oxide
classification element
percent
EWP Green - - -
EWCe-2 Orange Cerium CeO2 2
EWLa-1 Black Lanthanum La2O3 1
EWTh-1 Yellow Thorium ThO2 1
EWTh-2 Red Thorium ThO2 2
EWZr-1 Brown Zirconium ZrO2 .25
a) Colour may be applied in the form of bands, dots, etc., at any point on the surface of the electrode.

7.16.5 EWP Electrode Classification (Pure Tungsten)

Pure tungsten electrodes (EWP) contain a minimum of 99.5 percent tungsten, with no intentional
alloying elements. The current carrying capacity of pure tungsten electrodes is lower than that of
the alloyed electrodes. Pure tungsten electrodes are used mainly with ac for welding aluminum
and magnesium alloys. The tip of the EWP electrode maintains a clean, balled end, which
provides good arc stability. They may also be used with dc, but they do not provide the arc
initiation and arc stability characteristics of thoriated, ceriated, or lanthanated electrodes.

7.16.6 Tungsten - Thorium Alloys (Ewth Electrode Classification)

The thermionic emission of tungsten can be improved by alloying it with metal oxides that have
very low work functions. As a result, the electrodes are able to handle higher welding currents
without failing. Thorium oxide (ThO2) is one such addition. Two types of thoriated tungsten
electrodes are available. The EWTh-1 and EWTh-2 electrodes contain 1 % and 2% thorium oxide
(ThO2) called thoria respectively, which is evenly dispersed through their entire lengths. A
discontinued classification of tungsten electrodes is EWTh-3 class.

i. Thoriated tungsten electrodes are superior to pure tungsten electrodes in several

respects i.e.
ii. The thoria provides about 20 % higher current carrying capacity.
iii. Generally longer life.
iv. Greater resistance to contamination of the weld.
v. Arc starting is easier and the arc is more stable than pure tungsten or zirconiated
tungsten electrodes.
vi. The EWTh-1 & EWTh-2 electrodes were designed for DCSP applications. They
maintain a sharpened tip configuration during welding, which is desirable for
welding steel.
vii. They are not often used with AC because it is difficult to maintain the balled end,
which is necessary with AC welding, without splitting electrode.
viii. Thorium is a very low-level radioactive material. The level of radiation has not
been found to represent a health hazard. However, if welding is to be performed in
confined spaces for prolonged periods of time, or if electrode-grinding dust might
be ingested, special precautions relative to ventilation should be considered. The
user should consult the appropriate safety personnel.

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7.16.7 EWCe Electrodes Classification

Ceriated tungsten electrodes were first introduced into the united state market in the early 1980’s.

These electrodes were developed as possible replacements for thoriated electrodes because
cerium, unlike thorium, is not a radioactive element. The EWCe-2 electrodes are tungsten
electrodes containing 2 % cerium oxide (CeO 2) referred to as ceria. EWCe-2 electrodes will
operate successfully with AC or DC.

7.16.8 EWLa Electrode Classification

The EWLa-1 electrodes were developed around the same time as the ceriated electrodes and for
the same reason, that lanthanum is not radioactive. These electrodes contain 1 percent lanthanum
oxide (La2O3), referred to as lanthana. The advantages and operating characteristics of these
electrodes are very similar to the ceriated tungsten electrodes.

7.16.9 EWZr Electrode Classification

Zirconiated tungsten electrodes (EWZr) contain a small amount of zirconium oxide (ZrO 2), as
listed in Table. Zirconiated tungsten electrodes have welding characteristics that generally fall
between those of pure and thoriated tungsten. They are the electrode of choice for ac welding
because they combine the desirable arc stability characteristics and balled end typical of pure
tungsten with the current capacity and starting characteristics of thoriated tungsten. They have
higher resistance to contamination than pure tungsten, and are preferred for radiographic-quality
welding applications where tungsten contamination of the weld must be minimized.

7.16.10 Electrode Tip Configurations

The shape of the tungsten electrode tip is an important process variable in GTAW. Tungsten
electrodes may be used with a variety of tip preparations. With ac welding, pure or zirconiated
tungsten electrodes form a hemispherical balled end. For dc welding, thoriated, ceriated, or
lanthanated tungsten electrodes are usually used. For the latter, the end is typically ground to a
specific included angle, often with a truncated end.

In general as the included angle increases, the weld penetration increases and the width of the
weld bead decreases.

Regardless of the electrode tip geometry selected, it is important that consistent electrode
geometry be used once a welding procedure is established.

7.16.11 Electrode Contamination

Contamination of the tungsten electrode is most likely to occur when a welder accidentally dips
the tungsten into the molten weld pool or touches the tungsten with the filler metal. The tungsten
electrode may also become oxidized by an improper shielding gas or insufficient gas flow, during
welding or after the arc has been extinguished.

The contaminated end of the tungsten electrode will adversely affect the arc characteristics and
may cause tungsten inclusions in the weld metal. If this occurs, the welding operation should be
stopped and the contaminated portion of the electrode removed.

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