E 7018 is best for weld deposit. you can weld with
E 7018 but the root penetration will not be sufficient. for your help
just read the follwoing items. It might be help for you.
saamy
Welding consumables - Part 1
Part 2
Part 3
Part 4
Part 5
The next series of Connect articles will cover welding electrodes and
filler metals, beginning with a brief look at the requirements for a
flux. Whether a flux is in an electrode coating or is in granular
form, as in a submerged arc flux, the requirements are the same.
• The flux must be capable of providing a protective shield to prevent
atmospheric contamination of the electrode tip, the filler metal as it
is transferred across the arc and the molten weld pool. Generally, it
does this by decomposing in the heat of the arc to form a protective
gaseous shield.
• It must be capable of removing any oxide film (failure to do so will
result in lack of fusion defects and oxide entrapment). It does this
by reacting chemically with the oxide.
• It should improve mechanical properties by providing clean, high
quality weld metal and perhaps by transferring alloying elements
across the arc.
• It must be capable of providing the desired weld metal composition,
again by transferring alloying elements across the arc.
• It should aid arc striking and arc stability.
• It should produce a slag that will shape the molten pool and hold
the pool in place during positional welding if required.
• Any slag should be readily removable and preferably self-detaching.
• It should not produce large amounts of fume and any that it does
should not be harmful to the welder.
These requirements have resulted in a multitude of different
consumables, many being apparently identical, and this can make filler
metal selection a difficult and confusing task. This article attempts
to give some insight into the various types of flux coated manual
metal arc (MMA) electrodes before moving on in later articles to look
at other types of welding fluxes.
Most MMA electrodes can be conveniently divided into three groups by
their coating composition. These are cellulosic, rutile and basic
coatings, each of which gives the electrode a distinctive set of
characteristics.
Cellulosic electrodes contain a large proportion of cellulose, over
30% and generally in the form of wood flour. This is mixed with rutile
(titanium dioxide, TiO2 ), manganese oxide and ferro-manganese and is
bonded onto the core wire with sodium or potassium silicate. Moisture
content of these electrodes is quite high, typically 4 to 5%. The
cellulose burns in the arc to form a gas shield of carbon monoxide,
carbon dioxide and, in conjunction with the moisture in the coating,
produces a large amount of hydrogen, typically 30 to 45ml
hydrogen/100gm weld metal.
The hydrogen raises arc voltage and gives the electrodes their
characteristics of deep penetration and high deposition rates. The
high voltage requires a high open circuit voltage of around 70 volts
to allow easy arc striking and to maintain arc stability. The forceful
arc also results in appreciable amounts of weld spatter and this
limits the maximum current that can be used on the larger diameter
electrodes. A thin, friable and easily removed slag is produced,
giving a rather coarsely rippled weld profile. The slag is also fast
freezing so that, unlike most other electrodes, they can be used in
the vertical down position - 'stovepiping'.
Electrodes with a sodium silicate binder can be used only on DC
electrode positive (reverse polarity). Those with a potassium silicate
binder can be used either DC electrode positive or on AC. The
electrodes require some moisture in the coating to aid the running
characteristics and they must never be baked, as may be done on basic
coated electrodes. This has the advantage that the electrodes are
tolerant to site conditions. If they become damp, drying at a
temperature of around 120°C will be sufficient.
Electrode compositions are only available for welding low carbon
non-alloyed steels although nickel additions may be made to improve
notch toughness. Charpy-V values of around 27J at -20°C are possible
in the unalloyed electrodes. The high hydrogen level means that any
steel welded with these electrodes should be selected to have a very
high resistance to hydrogen induced, cold cracking (see Connect
articles numbers 45 and 46). They should not be used without giving
due consideration to the steel composition, restraint and the need for
preheat. The characteristics of deep penetration, high deposition
rates and the ability to be used vertically down means that the main
use for these electrodes is for cross country pipelining although they
are used to a more limited extent for welding storage tanks.
Rutile coatings, as the name suggests, contain a large amount of
rutile, titanium dioxide, typically around 50%, in addition to
cellulose, limestone (calcium carbonate), silica (SiO 2 ) mica
(potassium aluminium silicate), ferro-manganese and some moisture,
around 1 to 2%. Binders are either sodium or potassium silicate. The
cellulose and the limestone decompose in the arc to form a gas shield
containing hydrogen (around 20ml/100gm weld metal) carbon monoxide and
carbon dioxide. The electrodes have medium penetration
characteristics, a soft, quiet but stable arc and very little spatter,
making them a 'welder friendly' electrode. Striking and re-striking is
easy and the electrodes will run on very low open circuit voltages.
The electrodes produce a dense covering of slag that is easily removed
and gives a smooth evenly rippled weld profile.
The presence of cellulose and moisture means that the electrodes
produce relatively high levels of hydrogen, perhaps 20 to 25ml/100gm
weld metal. This restricts their use to mild steels less than 25mm
thickness and thin section low alloy steels of the C/Mo and 1Cr1/2Mo
type. Mechanical properties are good and Charpy-V notch toughnesses of
40J at -20°C are possible. They are probably the most widely used
general purpose electrode. Rutile coated austenitic stainless steel
electrodes can be obtained and can be used in all thicknesses as cold
cracking is not a problem with these alloys.
Rutile electrodes, like cellulosic electrodes, require some moisture
in the coating and they should not be baked. If they become damp,
re-drying at around 120°C should be sufficient. Those electrodes with
a sodium silicate binder can be used on DC electrode negative or AC.
Electrodes with the potassium silicate binder can be used on both
polarities and on AC. The potassium silicate binder electrodes
generally have better arc striking and stability characteristics than
the sodium silicate binder types and a more readily detachable slag.
The next article will look at the basic, low hydrogen electrodes and
some of the other less common types of coatings.
This article was written by Gene Mathers.
Copyright © 2010 TWI Ltd
Information and advice from TWI and its partners are provided in good
faith and based, where appropriate, on the best engineering knowledge
available at the time and incorporated into TWI's website in
accordance with TWI's ISO 9001:2000 accredited status. No warranty
expressed or implied is given regarding the results or effects of
applying information or advice obtained from the website, nor is any
responsibility accepted for any consequential loss or damage.
Part 2
Welding consumables - Part 2
The previous article, Part 1, dealt with the cellulosic and rutile
electrodes. This article will cover the basic, iron powder and acid
electrodes.
The description 'basic' originates from the chemical composition of
the flux coating which contains up to perhaps 50% of limestone,
calcium carbonate (CaCO 3 ). This decomposes in the arc to form a gas
shield of carbon monoxide/dioxide.
In addition to the limestone there may be up to 30% of calcium
fluoride (CaF 2 ) added to lower the melting point of the limestone
and to reduce its oxidising effect. Also deoxidants such as
ferro-manganese, ferro-silicon and ferro-titanium are added to provide
de-oxidation of the weld pool.
Other alloying elements such as ferro-chromium, ferro-molybdenum or
ferro-nickel may be added to provide an alloy steel deposit. Binders
may be sodium silicate, only for use on DC+ve current, or potassium
silicate which enables the electrodes to operate on both direct and
alternating current.
The gas shield from basic electrodes is not as efficient as that from
the rutile or cellulosic types and it is necessary to maintain a
constant short arc if porosity from atmospheric contamination is not
to be a problem. The electrodes are particularly sensitive to start
porosity because of the length of time taken to establish an efficient
protective shield. An essential part of welder training is
familiarisation with the technique of starting the weld ahead of the
required start position and moving back before proceeding in the
direction of welding.
The penetration characteristics of basic electrodes are similar to
those of rutile electrodes although the surface finish is not as good.
The slag cover is heavier than rutile electrodes but is easily
controlled, enabling the electrodes to be used in all positions. High
limestone coatings have been developed that enable a limited range of
electrodes to be used in the vertical-down (PG) position. The weld
pool blends smoothly into the parent metal and undercutting should not
occur.
The slag is not as easily removed as with rutile or cellulosic
electrodes but the low melting point means that slag entrapment is
less likely. The chemical action of the basic slag also provides very
clean, high quality weld metal with mechanical properties,
particularly notch toughness, better than that provided by the other
electrode types. A further feature of these electrodes is that the
welds are more resistant to solidification cracking, tolerating higher
levels of sulphur than a rutile or cellulosic electrode. This makes
them valuable if it becomes necessary to weld free cutting steels.
The basic electrode is also known as a low hydrogen rod ('lo-hi'). The
coating contains no cellulose and little or no moisture provided the
electrodes are correctly handled. When exposed to the atmosphere,
moisture pick-up can be rapid. However, baking the electrodes at the
manufacturers' recommended baking temperature, generally around 400°C,
will drive off any moisture and should provide hydrogen levels of less
than 5ml/100g weld metal. After baking the electrodes need to be
carefully stored in a holding oven at a temperature of some 120°C to
prevent moisture pick-up.
Many manufacturers now provide electrodes in hermetically sealed
vacuum packs with hydrogen levels guaranteed to be less than 5ml/100g
weld metal. These are particularly useful in site applications where
there is a need to maintain very low hydrogen levels and baking and
storage facilities are not available. The electrodes are taken
directly from the pack and can be used for up to 12 hours from opening
before sufficient moisture has been absorbed to require baking.
Basic, low hydrogen electrodes are therefore widely used in a variety
of applications where clean weld metal and good mechanical properties
are required. They can be obtained with alloyed core wires and/or
ferro-alloy additions to the coating to give very wide selection of
weld metal compositions, ranging from conventional carbon steels,
creep resistant and cryogenic steels and duplex and stainless steels.
Where high quality, radiographically or ultrasonically clean weld
metal is a requirement, such as on offshore structures and pressure
vessels, basic electrodes will be used.
Developments over the last 20 or so years have enabled
carbon-manganese steel consumables to give good Charpy-V and CTOD
values at temperatures down to -500C. The low hydrogen capabilities
also mean that basic electrodes would be used for the welding of thick
section carbon steels and high strength, high carbon and low alloy
steels where cold cracking is a risk (see Job knowledge articles Nos.
45 and 46).
In addition to the 'standard' cellulosic, rutile and basic electrodes
discussed above, electrodes may be classified as 'high recovery'.
By adding substantial amounts of iron powder, up to 50% of the weight
of the flux coating, to either basic and rutile electrode coatings it
is possible to deposit a greater weight of weld metal than is
contained in the core wire. These electrodes are described as having
an efficiency above 100% eg 120%, 140% etc and this 3 digit figure is
often included in the electrode classification.
The electrodes have thicker coatings than the 'standard' electrodes
which can make them difficult to use in restricted access conditions.
They are, however, welder friendly with good running characteristics
and a smooth stable arc. The iron powder not only melts in the heat of
the arc to increase deposition rate but also enables the electrode to
carry a higher welding current than a 'standard' electrode.
The iron powder is electrically conducting, so allowing some of the
welding current to pass through the coating. High welding currents can
therefore be used without the risk of the core wire overheating, thus
increasing both the burn-off and the deposition rates. The high
recovery electrodes are ideally suited for fillet welding, giving a
smooth, finely rippled surface with a smooth blend at the weld toes.
They are generally more tolerant to variations in fit-up and their
stability on low open circuit voltages means that they are very good
at bridging wide gaps. However, the large weld pool means that they
are not suited to positional welding and are generally confined to
welding in the flat (PA) and horizontal-vertical (PC) positions.
The last type of electrode covering is described as 'acid'. These
electrodes have large amounts of iron oxides in the flux coating which
would result in a high oxygen content in the weld metal and poor
mechanical properties. It is therefore necessary to incorporate large
amounts of de-oxidants such as ferro-manganese and ferro-silicon in
the flux. Although they produce smooth flat weld beads of good
appearance and can be used on rusty and scaled steel items the
mechanical properties tend to be inferior to the rutile and basic
coated electrodes. They are also more sensitive to solidification
cracking and are therefore little used.
The next articles will cover specification and classification of MMA
(SMAW) electrodes.
Part 3
Part 4
Part 5
This article was written by Gene Mathers.
Copyright © 2006 TWI Ltd
Information and advice from TWI and its partners are provided in good
faith and based, where appropriate, on the best engineering knowledge
available at the time and incorporated into TWI's website in
accordance with TWI's ISO 9001:2000 accredited status. No warranty
expressed or implied is given regarding the results or effects of
applying information or advice obtained from the website, nor is any
responsibility accepted for any consequential loss or damage.
Part 3
Welding consumables - Part 3
Part 1
Part 2
Part 4
Part 5
The last two articles covered the various types of manual metal arc
consumables that are available.
In order to be able to specify the type of flux coating, welding
characteristics and chemical composition of an electrode for a
particular application, there needs to be some standardised method of
unique identification that is universally recognised.
This requirement has led to the writing of a series of consumable
specifications that enable an electrode to be easily and uniquely
identified by assigning a consumable a 'classification'. The two MMA
electrode classification schemes that will be dealt with in this
month's article are the EN (Euronorm) and the AWS (American Welding
Society) specifications. There is insufficient space to cover in
detail the whole range of compositions for MMA electrodes so the
emphasis here will be on the carbon steel filler metals.
The European specification for non-alloy and fine grained steel MMA
electrodes is EN 499. This divides the classification or designation
number into two parts. Part 1 is a compulsory section that requires
symbols for the process, strength and elongation, impact strength, the
chemical composition and the type of flux coating. The second part is
optional and includes that includes symbols for the type of current
and metal recovery, the welding position(s) that the electrode can be
used in and for the maximum hydrogen content of the deposited weld
metal (NOT the electrode).
The designation of a covered electrode begins with the letter 'E'.
This tells us that this is a covered electrode intended for MMA
welding. The next two numbers give the minimum yield strength that may
be expected as shown in Table 1.
Table 1 Strength and elongation symbols
Symbol Min Yield Strength
N/mm Tensile Strength
N/mm Minimum
Elongation %
35 355 440 - 570 22
38 380 470 - 600 20
42 420 500 - 640 20
46 460 530 - 680 20
50 500 560 - 720 18
The next symbol indicates the temperature at which an average impact
value of 47J can be achieved, as shown in Table 2.
Table 2 Impact value symbol
Symbol Temperature for
average of 47J °C
Z No requirement
A +20
0 0
2 -20
3 -30
4 -40
5 -50
6 -60
The third mandatory symbol is for the composition. Although the
specification title (non-alloy and fine grained steels) suggests that
the electrodes have no alloying elements present, up to 3% Ni and NiMo
electrodes are included, see Table 3. (This symbol is only applied
where the electrode contains 0.3Mo or 0.6Ni).
Table 3 Chemical composition symbols
Symbol Chemical composition % max or range
Mn Mo Ni
No symbol 2.0 - -
Mo 1.4 0.3 - 0.6 -
MnMo >1.4 - 2.0 0.3 - 0.6 -
1Ni 1.4 - 0.6 - 1.2
2Ni 1.4 - 1.8 - 2.6
3Ni 1.4 - >2.6 - 3.8
Mn1Ni >1.4 - 2.0 - 0.6 - 1.2
1NiMo 1.4 0.3 - 0.6 0.6 - 1.2
Z Any other agreed composition
The fourth symbol indicates the type of flux coating - basic, rutile
etc as shown in Table 4.
Table 4 Symbol for flux coating
Symbol Coating
A acid
C cellulosic
R rutile
RR thick rutile
RC rutile-cellulosic
RA rutile-acid
RB rutile-basic
B basic
The next three symbols are not compulsory and give additional
information on the percentage weld metal recovery and the type of
welding current on which the electrode can be operated ( Table 5); the
welding position ( Table 6) and the maximum hydrogen content of the
deposited weld metal if the electrodes are dried or baked as
recommended by the manufacturer ( Table 7).
Table 5 Symbol for weld metal recovery and current type
Symbol Weld metal recovery % Current type
1 <= 105 AC or DC+
2 <= 105 DC+ or DC-
3 >105<=125 AC or DC+
4 >105<=125 DC+ or DC-
5 >125<=160 AC or DC+
6 >125<=160 DC+ or DC-
7 >160 AC or DC+
8 >160 DC+ or DC-
Table 6 Symbols for welding position
Symbol Welding position
1 All positions
2 All positions except V-down
3 Flat butt and fillet welds, HV fillet weld
4 Flat
5 V-down, flat butt, flat and HV fillet welds
Table 7 Symbol for hydrogen content in weld metal
Symbol Max Hydrogen
ml/100gms weld metal
H5 5
H10 10
H15 15
A full designation may therefore read E42 2 B32H5. This describes a
basic carbon manganese steel electrode; weld metal yield strength of
420N/mm2, better than 47J at -20°C, a weld metal recovery of over
105%, capable of being used on AC or DC+ current in all positions
except vertical down and providing less than 5mls hydrogen in the weld
metal.
The AWS specification equivalent to EN 499 is AWS A5.1 - Carbon Steel
Electrodes for Shielded Metal Arc Welding. The classification
comprises five characters but in the 2004 edition of the specification
there are two separate schemes. A5.1, based on the US units of tensile
strength in pounds per square inch, Charpy -V values in foot-pounds
and A5.1M, based on the SI system, with strength in MPa, Charpy-V
values in Joules.
It is thus possible to have virtually identical electrodes with
different classifications, one using US units, the other SI units.
There is insufficient space within this brief article to describe
fully all of the 18 types covered by the specification except perhaps
for the most commonly used electrodes. For full details of the AWS
scheme it is necessary to consult the specification.
To illustrate briefly how the electrodes are classified, the following
gives a summary of the key features.
The first character 'E' is common to both classifications and
indicates that the electrode is a flux coated manual metal arc
electrode. The next two digits indicate the tensile strength. In the
A5.1 designation this is either '60', indicating a UTS of 60ksi and a
yield strength of 48ksi, or '70', indicating a UTS of 70ksi and a
yield strength of 58ksi. In the A5.1M designation these are 43 or 49,
indicating a UTS of 430MPa, yield strength of 330MPa or 490MPa UTS,
400MPa yield respectively.
The last two digits give information on flux coating type, welding
position, current type and polarity and Charpy-V impact strength, if
required. Those electrodes suffixed XX10 or XX11 have cellulosic
coatings; those suffixed XX12, XX13, XX14, XX19 or XX24 have rutile
coatings and those suffixed XX15, XX16, XX18, XX28 and XX48 are basic
low hydrogen. XX18, XX28 and XX48 all have iron powder additions and
are therefore high recovery electrodes.
Listed below are those EN and AWS specifications that prescribe the
requirements for ferrous electrodes.
BS EN 499 Non-alloyed and fine grained steel electrodes
BS EN 757 High strength steels
BS EN 1599 Creep resisting steels
BS EN 1600 Stainless and heat resisting steels
AWS A5.1/A5.1M Carbon Steel Electrodes for SMAW
AWS A5.4 Stainless Steel Electrodes for SMAW
AWS A5.5 Low Alloy Steel Electrodes for SMAW
This article was written by Gene Mathers.
Part 4
This article looks at the wire consumables used in the gas shielded
MIG/MAG, metal cored (MC) and flux cored (FC) arc welding processes.
The MIG/MAG processes were first developed using a solid wire but some
25 years ago tubular wires began to be supplied and since then the use
of these wires has grown rapidly and they now form a significant
proportion of the welding wire market - cored wires are now used not
only in the MIG/MAG process but also in TIG, plasma-TIG and submerged
arc welding.
Solid wire for welding of alloy steels is an expensive commodity. The
composition of a ferritic steel welding wire is not the same as that
of the steel that it will be used to weld. The ingot from which the
wire is drawn must contain all the de-oxidation and alloying elements
that can be contained in the flux on an MMA electrode.
Steel is produced most economically in large tonnages whereas a
consumable supplier requires only relatively small amounts and these
requirements have a significant effect on the cost. In addition, it
can be difficult to draw down the wire to the small diameters required
for welding.
Cored wires for welding carbon and alloy steels, however, can be made
from mild steel with the alloying elements added to the flux filling.
This enables small amounts of wire to be economically produced
matching the composition of steels where the usage is limited, eg high
chromium creep resistant steels or hardfacing. Non-ferrous and
austenitic steel wires, aluminium, nickel based, stainless steel etc
however, generally match closely the parent metal composition and
obtaining ingots for drawing into wire is less of a problem.
MIG/MAG welding solid wires are provided in diameters ranging from 0.6
to 2.4mm, the most commonly used diameters being 1.2 and 1.6mm.
As mentioned above, the solid wires are generally formulated to match
the composition of the alloy to be welded. Silicon, 0.5 to 0.9%, and
perhaps aluminium, up to 0.15%, are added to ferritic steel wires to
provide de-oxidation; carbon content is generally below 0.1%.
Alloying elements such as manganese, chromium, nickel and molybdenum
are added to the ingot to provide improved mechanical properties and
corrosion resistance. In addition the carbon and low alloy steel wires
are often copper coated, both to reduce corrosion during storage and
to improve welding current pick-up in the contact tip.
The stainless steel and non-ferrous wires are not copper coated. Poor
control during the drawing operation may form laps on the wire surface
that trap contaminants and give rise to porosity, as can a poor
quality copper coat on ferritic steel wires.
Porosity from drawing defects can be a particular problem with
aluminium alloy wires and where high quality weld metal is required,
then shaving the wire to remove defects on the wire surface is
recommended.
The cored wires are small diameter tubes in which are packed fluxes
and alloying elements. There are two fundamental types, one containing
mostly fluxes, the other containing metal powders. There is a
sub-class of the flux cored wires, the self-shielded wires, that
contain gas-generating compounds that decompose in the arc to provide
enough shielding gas so that additional gas shielding is not required.
In cross-section, the wires may be seamless tubes packed with the flux
and extruded before being drawn into a wire. Alternatively, they may
be or made by rolling a flat strip into a 'U', filling this with the
flux or metal power and then folding this into a tube. The edges of
the tube may be butted together or overlapped.
The seamless and closed butt wires tend to have thicker walls and
therefore less fill than the overlapped wires, perhaps as little as
20% of cross sectional area compared with 50% for the overlapped
wires. This enables the overlapped wires to contain more alloying
elements and they are therefore often used for stainless steel and
hardfacing welding.
Cored wires have a number of advantages over the solid wires. The
reduced current carrying cross-sectional area of the wire results in
greater current density and an increase in burn-off rate with
increased deposition.
The flux also produces a slag that will control weld bead shape
enabling higher welding currents to be used in positional welding than
can be used with MAG. A 7mm throat fillet is possible in the
horizontal-vertical position, for example. The slag will also react
with the weldpool and provide better properties than can be achieved
with MAG. Good Charpy impact properties down to -50°C are achievable
in carbon steels with the correct wire.
Disadvantages with the cored wires are:
• The wire is mechanically weak and over-pressure on the wire drive
rolls may crush the wire preventing it from feeding through the
contact tip.
• The flux cored wires produce a slag that must be removed.
While solid wires often produce islands of a glassy slag that tend to
lie in the finish craters this does not necessarily prevent a
multi-pass weld being made without de-slagging.
This is not possible with flux cored wires, restricting their use in
applications such as robotic welding to single pass welds. Metal cored
wires are less of a problem in this context and are often used in
fully automated, multi-pass applications.
As with MMA electrodes, the flux in the core may be either rutile or
basic, the rutile flux providing a smooth arc, easy slag removal and
'welder appeal', the basic fluxes providing better mechanical
properties and cleaner radiographic quality welds.
Hydrogen control is less of a problem than with MMA electrodes. Both
rutile, basic and metal cored wires all have very low hydrogen
potential levels, allowing lower preheat than might otherwise be the
case and enabling rutile wires to be used in applications such as the
welding of high strength or thick section steels. Hydrogen pick-up on
the shop floor is also less of a problem as the flux/metal powder is
contained within a sealed tube, preventing moisture ingress. Seamless
wires tend to be better in this respect than seamed wires.
There are a number of specifications detailing the requirements for
solid and cored wires for MIG/MAG, FCA and MCA welding and these will
be covered in the next article.
This article was written by Gene Mathers.
Part 5
Welding consumables Part 5 - MIG/MAG and cored carbon steel wires
Part 1
Part 2
Part 3
Part 4
To ensure that there is a consistency in composition and properties
between wires from a variety of manufacturers, specifications have
been produced that enable a wire to be easily and uniquely identified
by assigning the consumable a 'classification', a unique
identification that is universally recognised.
The two schemes that are dealt with in this article are the EN/ISO
method and the AWS scheme. There are such a large number of
specifications covering the whole range of ferrous and non-ferrous
filler metals, both solid wire and cored, that it will not be possible
to describe all of these here. This article therefore reviews just the
carbon steel specifications.
The identification of the solid wires is relatively simple, as the
chemical composition is the major variable although both the EN/ISO
and the AWS specifications detail the strength that may be expected
from an all-weld deposit carried out using parameters given in the
specification. It should be remembered, however, that most welds will
contain some parent metal and that the welding parameters to be used
in production may be different from those used in the test. The result
is that the mechanical properties of a weld can be significantly
different from those quoted by the wire supplier, hence the need to
always perform a procedure qualification test when strength is
important. In addition, the mechanical properties specified in the
full designation include the yield strength. (In the EN/ISO
specifications, the classification may indicate either yield or
ultimate tensile strength).
When selecting a wire remember that the yield and ultimate tensile
strengths are very close together in weld metal but can be widely
separated in parent metal. A filler metal that is selected because its
yield strength matches that of the parent metal may not, therefore,
match the parent metal on ultimate tensile strength. This may cause
the cross joint tensile specimens to fail during procedure
qualification testing or perhaps in service.
The EN/ISO specification for non-alloyed steel solid wires is BS EN
ISO 14341. This specification classifies wire electrodes in the
as-welded condition and in the post weld heat-treated condition, based
on classification system, strength, Charpy-V impact strength,
shielding gas and composition. The classification utilises two systems
based either on the yield strength (System A) or the tensile strength
(System B):
• System A - based on the yield strength and average impact energy of
47J of all-weld metal.
• System B - based on the tensile strength and the average impact
energy of 27J of all-weld metal.
In most cases, a given commercial product can be classified to both
systems. Then either or both classification designations can be used
for the product.
The symbolisation for mechanical properties is summarised in Table 1A
for classification system A and Table 1B for classification system B.
For classification system B, the "X" can be either "A" or "P", where
"A" indicates testing in the as-welded condition and "P" indicates
testing in the post weld heat-treated condition. The symbol for
chemical composition is summarised in Table 3A and 3B of BS EN ISO
14341 based on each classification system. For classification system
A, the standard lists eleven compositions, too many to describe
completely here. Six of the wires are carbon steel with varying
amounts of deoxidants, two wires contain approximately 1% or 2.5%
nickel and an additional two wires contain around 0.5% molybdenum. The
designation of these wires is for example G3Si1, 'G' identifying it as
a solid wire, '3' as containing some 1.5% manganese and Si1 as
containing around 0.8% silicon; G3Ni1 is a wire with approximately
1.5% manganese and 1% nickel.
Table 1A Symbols for mechanical properties based on classification system A
Symbol Min Yield Strength
N/mm 2 UTS
N/mm 2 Min Elongation
% Symbol Charpy-V Test 47 J at Temp °C
35 355 440 to 570 22 Z No requirements
38 380 470 to 600 20 A +20
42 420 500 to 640 20 0 0
46 460 530 to 680 20 2 -20
50 500 560 to 720 18 3 -30
4 -40
5 -50
6 -60
7 -70
8 -80
9 -90
10 -100
Table 1B Symbols for mechanical properties based on classification system B
Symbol Min Yield Strength
N/mm 2 UTS
N/mm 2 Min Elongation
% Symbol Charpy-V Test 27 J at Temp °C
43X 330 430 to 600 20 Z No requirements
49X 390 490 to 670 18 Y +20
55x 460 550 to 740 17 0 0
57x 490 570 to 770 17 2 -20
3 -30
4 -40
5 -50
6 -60
7 -70
8 -80
9 -90
10 -100
A full designation could therefore be ISO 14341-A-G 46 5 M G3Si1 where
the '-A' designates the classification system A, the "-G" designates
solid wire electrode/or deposits, and the 'M' designates a mixed gas.
An example of a System B designation could be ISO 14341-B-G 49A 6 M
G3, where "A" indicates testing in the as-welded condition.
A full designation could therefore be BS EN 440 G46 3 M G3Si1 where
the 'M' designates a mixed gas and 'C' 100% CO 2.
The AWS specification AWS A5.18 covers both solid, composite stranded
and cored wires comprising six carbon steel filler metals for MAG, TIG
and plasma welding in both US and metric units.
The classification commences with the letters 'E' or 'ER'. 'E'
designates an electrode. 'ER' indicates that the filler metal may be
used either as an electrode or a rod. The next two digits designates
the tensile strength in either 1000s of psi.(ksi) or N/mm2 eg ER70
(70ksi UTS) or ER48 (480N/mm 2 UTS). However, note that there is only
one strength level in the specification.
The next two characters identify the composition, essentially small
variations in carbon, manganese and silicon contents, the wire type
(solid wire (S) or metal cored or composite wire (C)) and the Charpy-V
impact values.
With one exception, the solid wires are tested using 100% CO2, the
cored wires with argon/CO2 or as agreed between customer and supplier,
in which case there is a final letter 'C' designating CO2 or 'M', a
mixed gas.
The permutations in these identifiers are too many and too complicated
to be able to describe them all in sufficient detail but as an
illustration, a typical designation would be ER70S-3, a 70ksi filler
metal, CO2 gas shielded and with minimum Charpy-V energy of 27J at
-20°C. E70C-3M identifies the wire as a solid wire 70ksi UTS metal
cored filler metal, 27J at -20°C and tested with an argon/CO2
shielding gas.
The EN/ISO specification for non-alloy steel flux and metal cored
wires is BS EN ISO 17632. This covers gas shielded as well as
self-shielded wires. The standard identifies electrode based on two
systems in a similar way as BS EN ISO 14341, indicating the tensile
properties and the impact properties of the all-weld metal obtained
with a given electrode. Although the specification claims that the
wires are all non-alloy, they can contain molybdenum up to 0.6% and/or
nickel up to 3.85%. The classification commences with the letter 'T',
identifying the consumable as a cored wire.
The classification uses the same symbols for mechanical properties as
shown in Table 1A&B and a somewhat similar method to describe the
composition as BS EN ISO 14341. Thus MnMo contains approximately 1.7%
manganese and 0.5% molybdenum; 1.5Ni contains 1% manganese and 1.5%
nickel. In addition to the symbols for properties and composition,
there are symbols for electrode core composition. Table 2 summarises
the symbols for electrode core type and welding position in accordance
with classification system A. Classification system B uses Usability
Indicators as oppose to a one-letter symbol for electrode core type,
which can be found in Table 5B of BS EN ISO 17632.
Table 2 Symbols for electrode core type and position based on
classification system A
Flux Core Welding Position
Symbol Flux Core Type Shielding Gas Symbol Welding position
R Rutile, slow freezing slag Required 1 All
P Rutile, fast freezing slag Required 2 All except V-down
B Basic Required 3 Flat butt, flat and HV fillet
M Metal powder Required 4 Flat butt and fillet
V Rutile or basic/fluoride Not required 5 V-down and (3)
W Basic/fluoride, slow freezing slag Not required
Y Basic/fluoride, fast freezing slag Not required
Z Other types
In addition, there are symbols for gas type. These are 'M' for mixed
gases, 'C' for 100% CO2 and 'N' for self-shielded wires and 'H' for
hydrogen controlled wires. A full designation may therefore be ISO
17632-A -T46 3 1Ni B M 1 H5 in accordance with classification system
A. For classification system B, an example may be ISO 17632-B -T55 4
T5-1MA-N2-UH5, where "T5" is the usability designator, "A" indicates
test in the as-welded condition, "N2" is the chemical composition
symbol, and "U" is an optional designator.
The American Welding Society classification scheme for carbon steel
flux cored wires is detailed in the specification AWS A5.20. The full
designation is ten characters in length beginning 'E' for an electrode
then designators for strength, welding position, cored wire,
usability, shielding gas, toughness, heat input limits and diffusible
hydrogen, the last four designators being optional.
There are two strength levels - E7 (70ksi UTS) and E6 (60ksi UTS)
followed by a designator for welding position,'0' for flat and
horizontal and '1' for all positions, including vertical-up and
vertical-down.
The next symbol 'T' identifies the wire as being flux cored and this
is followed by either a number between 1 and 14 or the letter 'G' that
identifies the usability. This number refers to the recommended
polarity, requirements for external shielding, and whether the wire
can be used to deposit single or multi-pass welds. 'G' means that the
operating characteristics are not specified. The sixth letter
identifies the shielding gas used for the classification, 'C' being
100% CO2, 'M' for argon/CO2, no letter indicating a self-shielded
wire.
The non-compulsory part of the designation may include the letter 'J',
confirming that the all-weld metal test can give Charpy-V values of
27J at -40°C; the next designator may be either 'D' or 'Q'. These
indicate that the weld metal will achieve supplementary mechanical
properties at various heat inputs and cooling rates. The final two
designators identify the hydrogen potential of the wire.
A full AWS A5.20 designation could therefore be E71T-2M-JQH5. This
identifies the wire as a cored, all positional wire to be used with
argon/CO2 shielding gas on electrode positive polarity. The weld metal
should achieve 70ksi tensile strength, 27J at -40°C, 58 to 80ksi yield
strength at high heat input, a maximum 90ksi at low heat input, and a
diffusible hydrogen content of less than 5ml of H 2 /100g of deposited
weld metal.
This article was written by Gene Mathers, reviewed and modified by Runlin Zhou.
On 3/3/11, manpreet <manpreetsin88@rediffmail.com> wrote:
> Hi Shri,There are some importent information missing like grade of
> material and thickness, E7018 electrode contains iron powder in the
> flux,With the root run a fast cooling electrode is desirable (that is why
> cellulosic electrodes are so commonly used)and the E7018 is not a fast
> cooling electrode.I would suggest to go for E7010 for root runs which can be
> used for higher API grades, having said that you should also know that E7010
> may induce hydrogen into the weld and cause cold cracking if Preheat not
> done. also E6010 is widely used for Pipe root runs.RegardsManpreet Singh
> 2011/3/2 Engineer Mech <mengineer010@gmail.com>>
> Hi All,>>Can I use E 7018 in Pipe root runs? Wats the
> disadvantages?>Can i go E 7018 root run& filler WPS
> qualification?>>Regards>Srinivasan>>-->To post to this
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