Welding Rods Welding Rods: Manual Metal Arc Welding (MMA)

Welding Rods | Manual Metal Arc Welding [MMA]
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Manual Metal Arc
Welding (MMA)
Tungsten Inert Gas
Welding (TIG)
Oxy-Acetylene
Welding
Welding Rods
Whilst there are many types of welding rods it is first
necessary to understand the welding processes involved so
that these can be related to the welding materials which fall
under this heading.
There are 3 common processes for the deposition of welding
rods:1. Manual Metal Arc Welding[MMA]
2. Tungsten Inert Gas Welding [TIG]
3. Oxy-Acetylen Welding
Manual Metal Arc Welding [MMA]

In MMA the welding rods are more commonly called
electrodes. An electric arc is formed when an electric arc
passes between two electrodes separated by a short distance
from each other. In MMA welding the electrodes is connected
to the positive + pole and the material to be welded [now
called the base plate] to the negative [please note that this
polarity may be changed based on the welding electrode
manufacturers recommendations. This will be dealt with
additional technical information, on this site, in the future].The
arc is started by momentarily touching electrode onto the
base plate and then withdrawing it to about 3mm from the
plate. When the electrode touches the plate a current flows,
and as it is withdrawn the current continues to flow in the
form of a spark across the gap first formed. This causes the
air gap to become ionized, or made conductive, and as a
result the current is able to flow across the gap, in the form
of an arc. The electrode must always be touched down, or
scratched on the plate before the arc can be started, since
the smallest air gap will not conduct a current unless it is first
ionized.
If a bare wire is used as an electrode it is found that the arc
is difficult to control and the arc stream will wander over the
molten pool formed in the base material. The metal globules
projected across the arc [ionized] gap are exposed to the
atmosphere and the absorption of oxygen and nitrogen takes
place, even when a short arc is held.
The arc can be rendered easy to control and the absorption of
atmospheric gases reduced to a minimum by shielding the
arc. This can be done by extruding a coating onto the
electrode and as a result gases, such as hydrogen and carbon
dioxide are released from the coating as it burns down in
conjunction with the melt rate of the rod[core wire]. This
forms a covering around the arc and molten pool, thus
excluding the detrimental effects from the atmosphere. Under
the heat of the arc chemical compounds in the electrode
covering also react to form a slag which in its liquid form is
lighter than the molten metal. This rises to the surface, cools
and solidifies, forming a protective cover of the welded joint,
as it solidifies and also slow down the cooling rate. Some
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slags are self releasing whilst others my need to be lightly

chipped with a welders chipping hammer.
The electrode coating
normally melts at a
slightly slower rate
than the core wire so
that it extends a little
beyond the core,
concentrating and
directing the arc
stream, making the
arc stable and easier
to control.
[drawing courtesy of TWI]
When an arc is struck between the metal and the plate, the
heat generated forms a molten pool in the plate and at the
same time the electrode begins to melt, this metal being
transferred from the metal to the plate.
Which Electrode?
Welding electrodes are selected based on their compatibility
with the base materials and the more common ones are listed
below:A] Mild & Low Alloy Steels
B] Stainless Steels
C] Cast Iron
D] Metalworking
E] Wear facing [Hardfacing]
F] Aluminium
G] Bronzes
H] Copper
A] Mild and Low Alloys Steels

AWS A5.1: E6013
EN.ISO 2560:E 42 0 RR 12**
Normally a general purpose mild steel electrode for joints in
base materials of similar composition, having Tensile strengths
of around 450 520 N/mm2.
These can be for down hand [flat] welding or for all positional
welding of mild steel, in the vertical and horizontal positions.
AWS A5.1: E7018-1
EN.ISO 2560: E 46 4B 32 H5
These are known as Low Hydrogen, or Hydrogen controlled
electrodes and are normally used in steel construction, where
components are subject to higher degrees of stress and as
such would have a Tensile strength in the range of
530 580 N/mm2
AWS A5.1: E7024
EN.ISO 2560: E 42 0 RR 53
Classed as a High recovery electrode based on the fact that
this type of mild Steel electrode is highly efficient in that by
incorporating metal powder in the electrode coating it will
deposit weld metal equivalent to up to 160% of the electrode

core wire weight. This electrode is very popular in fabrication
shops for rapid welding of sheet steel.
** Electrode Classification [British]
Abridged classification to cover carbon and carbon
manganese steel electrodes for manual arc welding.
BS639 [1986]
This classification is for deposited weld metal having a tensile
strength not greater than 650N/mm2. The classification is
noted by a code consisting of 2 parts: [a] a general code,
followed by [b] an additional code in parentheses, for example
E 43 2 2 RR [21]
[a] General Code
[1] The letter E indicating a covered electrode for
manual arc welding
[2] Two digits indicating the strength [Tensile, yield and
elongation properties]
Of the base material.
[3] One digit for a minimum average impact value of 28
Jules.
[4] One indicating the temperature for a minimum
average value of 47 Jules.
[5] Either one, or two letters indicating the type of
electrode coating e.g.
B basic; BB basic, high efficiency; C cellulosic; R
rutile etc
[b] Additional Code

A digit recommended welding positions for the electrode.
1
2
3
4
5
9
all positions
all positions except vertical down
flat an for fillet welds
flat
flat, vertical down and for fillet welds
any other positions not classified above.
Also a letter H, indicating a hydrogen controlled electrode.
B] Stainless Steels
AWS A5.4 E308L-17
E 19 9 LR 32
For the welding of stainless steels such as Types 304L, 321 &
347. This alloy has maximum carbon content of 0.03% which
increases the resistance to intergranular corrosion.
AWS A 5.4 E316L-17
E 19 12 3 LR 12
Used primarily for welding molybdenum bearing low carbon
austenitic alloys. Also available as ER316H for elevated
temperatures.
AWS A5.4 E307-16 [mod]
E 18.8.Mn LR53
For the joining and overlaying of alloy steels and can also be
used as a buffer layer prior to the depositing of a wear
resistant [hard facing] coating.
AWS A 5.4 E309-17
E 23.12 LR32
For the welding of corrosion and heat resistant stainless
steels. The low carbon content [0.03% maximum] increases
resistance to inter granular corrosion. 309L superior to 309
for the cladding of carbon or low alloy steels.
AWS A 5.4 E310-16
E 25.20. LR26
For joining heat resisting stainless steels up to an operating
temperature of 1200C. High oxidation resistance and strength
at elevated temperatures.
C] Cast Iron
AWS E Ni-BG11
DIN 8573 E Ni-BG11
High nickel content electrode for the welding of grey,
malleable and cast irons. Suitable for contaminated cast iron
components, such as cylinder blocks, pump housings and
electric motor casings.
AWS E Ni Fe -1-BG11
DIN 8573 E Ni Fe C1
A nickel iron electrode for repairs to nodular, spheroidal
graphite and malleable cast iron components. Suitable for
joining cast iron to steel and where an oil tight joint is
required.
D] Metal Working
CUTTING ELECRODES
Cutting electrodes have a special flux coating which produces
a forceful non metal depositing arc. This will cut, or pierce, all
ferrous and non ferrous materials.
GOUGING ELECTRODES
Use for grooving, gouging or otherwise preparing metal prior
to welding. This electrode is particularly suitable for sealing
the oil contaminated surface of cast iron components before
depositing either a Nickel, or Nickel Iron welding material.
E] Wear facing [Hard facing]

Use for protection from components subject to wear whilst in
service, from abrasion, impact and other medium. The alloys
fall into three common groups.
E1] High carbon
E2] Complex carbides
E3] Tungsten carbides
E1] For wear facing components subject to both impact and

abrasion with a hardness of up to 57RC being achieved after 3
passes. Applications include coatings on steels, cast steels and
manganese steels, such as crusher rings, earth moving plant
and screw conveyors.
E2] Depending on the complexity and percentages of carbides
such as chromium and tungsten in these alloys a hardness of
up to 70RC can be achieved. Whilst some of these alloys can
be used for resistance to impact and abrasion the upper
hardness values are for resistance to abrasion with minor
impact. Applications include: wear resistant coatings on
crusher hammers, bucket lips, chutes, liners and screw
conveyors
E3] Consisting of up to 70% Tungsten carbides in a complex
carbide matrix, with an approximate hardness of 70RC. This is
the hardest of the more popular wear resisting coatings and is
used in applications where extreme abrasion is experienced.
Applications include mixer paddles, sinter fan, mineral drilling
tools, ceramic and glass process plant.
F] Aluminium
DIN 1732 EL-Al Si 12
AWS A 5.3 E 4047
Whilst there are a number of alloys suitable for joining
aluminium and most of its weldable alloys the most common
and successful is the aluminium, 12% silicon alloy.
Applications include: engine casings, sumps, aluminium
framework etc.
DIN 1732 EL-Al 99.8
Coated electrode, 99.8% pure aluminium, for welding pure
and cast aluminium alloys.
DIN 1732 EL-Al Si 5
AWS A 5.3 E4043
Coated electrode containing 5% silicon, for the welding of
wrought and cast aluminium alloys.
G] Bronzes
AWS A 5.6 E Cu Al-A2
DIN 1733 EL-Cu A19
For the joining of aluminium bronzes with an aluminium
content of up to 10%
AWS A 5.6 E Cu Sn-C
DIN 1733 EL-Cu Sn 7
A tin bonze alloy for repair and reclamation of tin and
phosphor bronzes.
AWS A 5.6 E Cu Mn Ni Al
DIN 1733 EL-Cu Mn 14 Al
For joining and wear surfacing of brass, bronze and cast steel.
This alloy has a low coefficient of friction which makes it an

ideal alloy for sliding surfaces.
H] Copper
AWS A 5.6 E Cu
DIN 1733 EL-Cu Mn 2
A 97% copper electrode for the joining and coating of copper
and copper alloys.

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Welding Rods | Manual Metal Arc Welding [MMA]

Manual Metal Arc Welding [MMA]

Welding Rods | Manual Metal Arc Welding [MMA]

slags are self releasing whilst others my need to be lightly

A] Mild and Low Alloys Steels

http://weldingrods.co.uk/index.htm[08-Sep-11 11:43:31 AM]

Welding Rods | Manual Metal Arc Welding [MMA]

deposit weld metal equivalent to up to 160% of the electrode

[b] Additional Code

Also a letter H, indicating a hydrogen controlled electrode.

http://weldingrods.co.uk/index.htm[08-Sep-11 11:43:31 AM]

Welding Rods | Manual Metal Arc Welding [MMA]

E] Wear facing [Hard facing]

Welding Rods | Manual Metal Arc Welding [MMA]

E1] For wear facing components subject to both impact and

http://weldingrods.co.uk/index.htm[08-Sep-11 11:43:31 AM]

Welding Rods | Manual Metal Arc Welding [MMA]

This alloy has a low coefficient of friction which makes it an

http://weldingrods.co.uk/index.htm[08-Sep-11 11:43:31 AM]

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