Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to flux cored welding electrodes
for use in gas-shieldecl electric arc welcling and hard surfacing.
In open-arc welding of steel it is known to use a
tubular welding electrode filled uniformly throughout its length
with a powdery mixture of slag~forming, deoxidising ancl arc
stabilising substances and, on occasion, metal powders. The
nature and proportions of the respective ingredients used depend
upon the desired conditions of use; for most welding applications
it is customary to employ a core having at least 20% by weight
of the core material ingredients other than metal powders, whereas
in hard surfacing applications more metal powder is normally used.
The inclusion of iron powder in the core is advantageous in that
it helps to increase the rage at which weld metal is able to ~e
deposited from the electrode. In general, it is found that com~
mercial flux-cored welding electrodes of the high metallic hard-
Eacing types have the disadvantages of producing a great deal of
spatter during use and of forming a scaly slag which is difficult
to remove. In addition they frequently produce welds of poor
shape. Electrodes having a higher flux content often suffer from
the disadvantage that they deposit weld metal at a rate which is
less than ideal.
It has always been believed that in order to obtain a
satisfactory surface, it is necessary to use more than a minimum
amount of flux forming materials in the core, and that the type
and quantities of these materials must be within certain limits.
We hav~ now devised a novel Eormulation for the core
of a welding electrode suitable for the generality of welding
applications as well as for hard Eacing applications wllich makes
possible a reduction in the difficulties associated with the gen-
erality of welding electrodes previously used for this purpose.
Accordingly the present invention provides a flux-
cored welding or hard surfacing electrode in the form oE a
flux-cored wire having a tubular casing of which the main
constituent is iron; which casing is filled with dry core
material including from 70 to 92.5% by weight of the core of
one or more powdered metals, and from 0.25 to 4% by weight of
flux-forming material intimately distributed throughout the core
material, the remainder of the core being substantially metallic
deoxidants and the core constituting from 22 to 45% of the total
weight of the electrode.
The core will generally comprise from 22 to 45% by
weight of the total weight of the electrode, and preferably
from 22 to 30% by weight of the total weight of the electrode.
The flux-forming material may comprise compounds
termed in the art as being acidic, compounds termed in the art
as being basic, or a mixture of both acidic and basic compounds.
The flux-forming material may alternatively or in addi-tion
comprise amphoteric compounds.
A preferred acidic flux-forming material for use in
the present invention is a silicate or a titanate. The
silicate or titanate may advantageously be the sole flux-
forming material in the electrode according to the present
invention. An alkali metal silicate or an alkali metal titanate
is preferred if the flux-forming material is required to
comprise a silicate or a titanate.
We have found that if the flux-forming material com-
prises at least one silicate or titanate the electrode
according to the present invention when used in open-arc
gas-shielded welding processes gives less spatter and produces
welds of better shape than do conventional commercial flux-
cored arc-welding electrodes whilst giving in comparison
to cored welding electrodes containing no. . . . . . . . . .
- 2 -
,
~0~
-flux-Eorming material a more stable arc and a weld metal having
better metallurgical properties. sodium silicate, sodium titanate,
potassium silicate and potassiurn titanate in particular all have
good arc--stabilising properties. I,ithium silicate, lithium
titanate, aluminium silicate, manganese silicate, zirconium
silicate or calcium silicate may alternatively or in addition to
the potassium salts be incorporated in the core of an el~ec-trode
according to the present invention.
It is to be appreciated that if an acidic flux-forming
material is chosen for incorporation into an electrode according
to the present invention it need not be a silicate or a titanate.
Indeed, the flux forming material may in general without disad-
vantage comprise one or more oxides. Basic or ampho~eric oxides
may be used instead of acidic oxides~ suitable oxides are silica,
titanium dioxide, manganese oxide, aluminium oxide, oxides oE
transition metals such as nickel, zirconium, molybdenum, iron,
: and chromium, and oxides of rare earths such as yttrium, cerium
and lanthanium.
Although not preferred, both tit~nium dioxide and silicon
dioxide may comprise the flux-forming material. I-f they do, how-
ever, the relative proportions of the two are preferably not
graater than 0.5 parts by weight o~ titanium dioxide to 1 part
b~ weight of silicon dioxide, and most preferably not greater than
0.2 pa~ts by weight of titanium dioxide to 1 part by weight of
silicon dioxide.
For many open-arc-welding applications a ~asic flux
~orming material is to be preferred to an acidic flux-forming
material. This is because in the quantities in which the flux-
forming material is present in electrodes according to the present
--3--
~-~8~
invention electrodes ~ith a given quantity oE basic flu~ tend to
cleposit weld metal having metallurgical properties significantly
superior to that deposited by equivalent electrodes having the
same quantity oE acidic flux. However, where the superiority in
metallur~ical properties of weld metal deposited by electrodes
with basic flux-forming material over weld metal depositecl by
electrodes with acidic flux-forming material is not of signific-
ance the latter type of electrode is frequently -to be preferred
to the former. This is because for a given shielding gas, electrodes
incorporating acidic flux-forming material tend to give a smoother
arc action and less spatter than do electrodes incorporating
basic flux-forming material.
A preferred basic flux-forming material is a fluoride
or carbonate. In general, fluoride is preEerred to carbonate,
since the former is able to impart greater fluidity to the slag
than is the latter. One particularly suitable fluoride is calcium
fluoride which may be used in the form of the mineral fluorspar.
other fluorides, for example of alkaline metal earths other than
calcium, or of alkali metals may, however, be used in combination
with or alternatively to calcium fluoride. A suitable carbonate
is calcium carbonate, which may conveniently be in the form of
ground limestone. Other alkaline earth carbonates such as strontium
carbonate, or alkali metal carbonate~ may, however, b~e used.
A preferred basic flux-forming material is a fluoride
or carbonate. one particularly suitable fluoride i9 calcium
fluoride which may be used în the form of the mineral fluorspar.
Other fluorides, for example of alkaline metal earths other than
calcium or of alkali metals may, however, be u~ed in combination
with or alternatively to calcium fluoride. ~ suitable carbonate
is calci~m carbonate, which nlay conveniently be in the Eorm of
ground limestone. Other carbonates such as strontium carbonate
may, however, be used.
Irrespective of whether the core contains acidic flux
forming material, basic flux forming material, or a combination
of both acidic and basic materials, the optimum content of flux
forming material in the electrode is the maximum at which a small
but easy-to-remove residue is left on the surface of the weld
when the electrode is used in a gas-shielded open-arc-weLding
process. In general, for a given flux-forming material its optimum
content (expressed as a percentage by weight of the total weight
of the core) will be greater the lower is the quanti~y of core
material in the electrode (expressed as a percentage by weight of
the total weight of the electrode) and vice versa. If the core
contains flux-forming material solely of a basic nature, and in
particular if it contains fluoride but no other flux-forming
material, from 0.5 to 1.5% of its total weight is preferably pro-
vided by the flux-forming material. Most preferably for an
electrode whose core constitutes about 28% of the total weight
of the electrode. The preferred content of basic flux-forming
agent is preferably therefore in the range 0.14 to 0.28% by
; weight of the total weight of the electrode Erom 0.5 to 1.0% of
the total weight of the core is provided by basic flux forming
material such as fluoride. With such electrodes we have found
that if the flux forming material consists of fluoride and pro-
vides less than 0.5% by weight of the core, weld metal deposited
by the electrode according to the present invention tends not
to have such good metallurgical properties as weld mlatal deposited
by an electrdde according to the present invention hav:ing a con-
.
~v~
tent of fluorile ~reater than 0.5 per cent by weiyht of the core.
If the content of fluoride exceeds 1.5% by weight of the electrode
inconvenient quantities of slag rnay be formed on the weld surEace.
Indeed~ in general, with such electrodes, to ensure avoiding for-
mation of inconvenient quantities of slag on the weld surface a
content of fluoride of less than 1.0% by weight of the core should
be used.
we have found that if the flux-Eorming material is
acidic, e.g. a silicate or titanate, and if the flux-forming
material is an oxide it is preferably present in the electrode
in quantities in the range 1.5 to 2.5% by weight of the total
weight of the core if the core constitutes about 28% 0 f the total
weight oE the electrode. The preferred content is preerably
therefore in the range 0.4 to 0.7% by weight of the total weight
of the electrode. When present in such ~uantities an acidic
flux-forming materîal does not give rise to inconvenient quantities
of slag whilst making possible the deposition of metal having
better metallurgical properties than weld metal deposited by an
electrode containing no flux-forrtling material.
If desired the flux-forming material may comprise a
fluoridec~ carbonate or both, in combination with a silicate or
titanate, or both.
If the flux-forming material ~omprises a silicate the
; other ingredients of the core may be added to an aqueous solution
of the silicate the resulting suspension being mixed and then
dried to produce a finely blended free-flowing core cornposition.
If the core is not to contain silicate its ingredients may simply
be mixed together. The use of a silisate solution does however
facilitate even dis-tribution oE the flux-Eorming material through-
..
out the core.
The tubular casiny o-f the novel electrodes may consist
for example of soft steel (such as rimming ~teel) or an alloyed
steel e~g~ 18-8 c~romium/nickel steel. llhe casing ~ay have dif-
ferent shapes e.g. it may be cylindrical with butting edges or
it may have a complex cross-section with projections extending
into the core. The casing can be obtained, for example~ by the
known method of longitudinally folding a strip around the core
material.
Conveniently, the electrode of the invention is in the
form of an endless wire for use in automatic or semi-automatic
arc-welding processes.
The deoxidant typically comprise -Erom 5 to 20% (pre-
ferably 7 to 15% or more preferably 8 to 12%) by weight of the
core of silicomanganese and from 2 to 10% (preferably about 6%,
or less) by weight of the core of ferrosilicon. Sincs the typical
composition of commercial available silicomanganese is, by weight,
3~% silicon and 66% manganese and since the typical composition
of commercially available ferrosilicon is 50% iron and 50% si]icon
the electrode may therefore typically comprise from 3.3 to 13.3%
(preferably from 4.7 to 10% or more prefsrably 5.3 to 8%) by
wèight of the core of manganese and from 2.7 to 11.7% (preferably
in the order of 5 to 7%) by weight of the core of silicon. In
terms of a percentage by we~ght of the total weight of the electrode
(assuming that the core contribute6 28% of the total weight of
the electrode) the core of the electrode may therefore typically
include from 0.9 to 3.7% (pre~erably 1.3 to 2.~3% and more prefer-
ably 1.5 to 2.25%) of manganese by weight of the total weight
of the electrode and from 0O75 to 3.25% (preferably in the order
, .:
~ 198q~
of 1.4 to 1.95%) of silicon by weight of the total weight of the
electrode. Instead or in addition to including the manganese of
the core in silico-manganese the core may contain ferromanganese
or electrolytic manganese.
In addition, if the casing (or sheath) is of mild steel
it will typically contain 0.~% by weight of manganese. ThUs, in
theorder an extra 0~3% by weight of manganese may be contributed
by the casing to the total weight of the electrode. The total
weight of manganese in the electrode may therefore be in the
range 1.2 to 4.0% by weight thereof and is preferably in the
range 1.6 to 3.1% by weight thereof, more preferably being in
the range 1.8 to 2.55% by weight thereo. Provided that it is
less than the manganese content, the silicon content of the
electrode may be up to 2.0% of the total weight of the electrode
but generally should not be so great as to provide in the deposited
weld metal ~ore than 40% of the total content of silicon and
manganese in the depos~ted weld metal. Indeed~ it may be
advantageou 5 to keep the silicon content of the electrode below
1% of the total weight of the electrode and to use in addition
to the silicon and the manganese a third deoxidant typically
selected from aluminium, magnesium, titanium and zirconium. Since
the metals from which the third deoxidant is selected all exhibit
a greater affinity for oxygen that does manganese or silicon, it
is not necessary for the total weight of the silicon and the
third deoxidant to be the same as the wieght of silicon that
would be included in the electrode if no third deoxidant were used~
It is ~ell known that the presence of metal powder ~per-
ferably iron) in the core make possible rates of deposition faster
than those which can be achieved if metal powdex is abc;ent.
Incleed, we h~ve found that in the electrodes according to the
present invention the maximum welding speed attainabl.e increases
with increasing iron powder content. In order to yive good
welding speecls we have general.ly found that the content oE metal
powder (pre~rably all iron) in the core and th~ proportion of
the electrode constituted by the core should desirably be
selected such that the metal powder (preferably all iron) the
content of iron powder is .in the range 17 to 35% by weight of
the total electrode, and is most preferably in the range 22 to
30% by weight of the total electrode. With an iron powder con-
tent in this range we have found it possible to attain good
welding speeds whilst deposi-ting weld metal having good metal-
lurgical properties at 0C when performing fillet welds of 6.3 mm
leg length or smaller. For example, with a welding wire having
a diameter of 2.4 mm it is possible to weld manually a fillet of
6 mm leg length at a speed of 0.66 metres per minute using a
current of 460~. With an automatic welding machins the same size
fillet has been welded at a speed of over 1 m a minute using a
current of 550A.
Electrodes according to the present invention is used
for open-arc welding offer the advantage of enabling the deposition
of weld metal having better metallurgical properties better than
those of weld metal deposited from electrodes containing no flu~-
forming material. In addition, in comparison with electrodes
containing no flux, electrodes according to the present invention
give more stable arcs w~en used in open-arc-welding processes.
Moreover, electrodes according to the present invention
do not give large deposits of slag on the surface of the weld
metal unlike conventional 1ux-cored electrodes. Furthermore, in
_g _
comparison with conventional flux-cored electrodes, the electrodes
according to the present invention give Eas-ter rates of weld metal
deposition and welds of better shape. rrhe above co~bination of
advantages makes the electrodes according to the present invention
particularly attractive for general open-arc-welding purposes.
Pre~erred electrodes according to the present invention
are suitable for welding steels in a tensile range of 400 to 620
N/mm (26-40 tons per square inch).
An advantage of flux-cored welding wires according -to
the present in~ention is that they produce a weld metal with a
particularly low hydrogen content~ For example, wires containing
fluoride as the sole flux forming ingredient in accordance with
our invention after baking at abou~ 200C produce a weld metal
with a hydrogen content less than 5 ml per lOOg of weld metal
whereas most conventional flux-cored wires after a similar baking
process produce weld metal with a hydrogen content of 5 or more
ml per lOOg of weld metal.
An electrode according to the present invention also
offers the advantage of making possible open-arc welding in
horizontal-vertical, vertical and overhead positions as well as
the downhand position.
The electrodss according to the present invention mayke
employed for a range of welding and hard surfacing applications.
They ar~ particularly suitable for normal gas shielded open-arc-
welding processe~.
In open-arc welding processes the shielding gas pre-
~erably includes argon. We have discovsred that by using a
shielding gas consisting mainly of argon together with a small
proportion of carbon dioxide and, if desired, a small proportion
~10 -
:
~ 8~
of oxygen, the particulate :Eume content of the arc is less than
it is w~en the main or sole constituent of the sh.ielding gas is
carbon dioxide.
For example, welding with a shielding gas containing 5%
by volume of C02 and .1% by volume of O2and the remainder being
argon, the fume produced is approximately 50% of the fume that
occurs when welding with a shielding gas consisting of C02. We
have found that with a shielding gas mixture containing 5% by
volume of CO2 and if desired up to 1% of oxygen, the remainder
being argon, an open-arc welding process using an electrode
according tothe present invention avoids the finger-type weld
which is produced when using a welding wire containing no flux-
forming material.
If the shielding gas contains more that 20% by volume
f C2 the electrode may include up to 0.3% by weight of an arc
stabiliser of the.flux forming agent alone does not give the
desired arc stability. The arc stabiliser can be a compound of
either an alkali metal or a rare earth.
When welding with an electrode according to the present
invention an AC or D~ power source may be used. If a DC power
source is employed the electrode i5 preferably connected to the
negative terminal of the source,
The invention will now be illustrated by.reference to
the following examples whe.rein all parts are expressed on a
weight basis.
Example 1
A core material ~or an electrode was made by adding 6
.; parts of an a~ueous solution of potassium silicate (2 par-ts solid
to 4 parts water) to 100 parts to a mixture oE ]0% silicomanganese
1 1 ~ ,
,, . ~ , , .
(3~% by wei.ght Sl, 66% by weight Mn), 8% :Eerrosilicon (50% by
weight Si, (50% by weight Fe) and 82% iron powcler. The resultant
mixture wasthoro~y agitated and then dried in an oven for one
hour at 250/300 C. The dried blend was then encase~ in known
manner in a casing of mild steel containing 0.4% by weight of Mn
so as to give an electrode comprising 28% by weight of core material.
The electrode made as described having a diameter of
2.4 mm was employed in open arc welding with a gas shield 95% by
volume of argon and 5% by volume of carbon dioxide and w:ith a
welding current of 5S0 A to deposit weld metal in the flat or
horizontal positions at the rate of 24 lb per hour. The resul-tant
welds were of excellent shape and the slat detachability was good.
There was no excessive spatter.
Example 2
~ n electrode of diameter 1.6 mm made as described in
Example l was employed ~or welding in the vertical position using
an open arc with a welding current in excess of 200 A and with a ~ :
shielding gas of 95% by volume of argon and 5% by volume of
carbon dioxide. Both butt and :Eillet welds of excellent appearance
were obtained which were apprec.iably superior to those obtained
under comparable conditions using either a 1.6 mm in diameter
so~id wire or a 1.6 mm diameter flux-cored wire containing the
larger amount of slag-forming materials than did the electrode of
the inventionO
Example 3
A core for an electrode was made by intimately mixing .;
the ollowing ingredients in the proprtion stated:
iron powder 86.25
ferrosilicon (50% by wéight Si,
50% by weight Fe) 3
-12-
silicomanganese (3~% by weight Si,
66% by weight Mn) 10
fluorspar 0.75
The resultant mixture was dried and Eed into a U-shaped
strip of mild steel containing 0.~% by weight of manganese and
approximately 0.07 by weight of carbon~ The ends of the strip
were then folded toward one another so as to enclose the mixture
and to form an electrode as a wire containing 28% by weight of
the wire of core material,
Electrodes were made with diameters of 2.0 mm and 2.4~m.
Test welds were performed using these electrodes and a shielding
yas consisting of 95% by volume of argon and 5% by volume of
oxygen. Tests on the resultant weld metal gave the results
shown in Table 1.
The welds were of good appearance and was formed only
in the form of shallow riable deposits which covered only a
small proportion of the surface of the weld metal.
-13-
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-- 14 --
~8~
Exampl~ 4
An electrode of 1.6 mm diameter was made according to the methocl
describad in Exa~ple 3. The electrode had the following
composition:
~YI~
casing (mild steel3 72
core 28
The core had the following composition
~ by wei~ht of_core
10 iron powder 83~ ~
Fe Si (50~ Fe 50~ Si)6~ :
Si Mn (34~ Si 66% Mn)10
CaF2 (fluor3par) 1~ .
Weld metal deposited from the slectrode had the foll~wing i :
metallurgical properties.
Tensile strength - 40 ~on/in2 (620 N/mm~) ;
Yield strength - 36 Ton/in2 (560~/mm2)
Charpy V impact value:
: 20C 72 ft lb. (98J)
0C 57 ft lb. (77J)
-20C 30 ft lb (41J)
The weld~ w~re smooth and only a ~mall part o~ their
surfaces was covered by ~lag depo3its. Thi~ slag wa~ in ~he
form of sh~llow friabl2 depo~it~.
Exam~le 5
An electrode of 1.6 mm diameter wa3 made according to
the method de~cribed in Example 3. The electro~e had the
following composition:
- 15 -
339~
~ by~ qht of electrode
ca~ing (mild ~teel) 72~
core 28%
~he core had the following composition
~ of core
Fe powder 82
ferro~ilicon 6~
8 ilicomangane~e 10%
CaF2 (flUOr9Par) 2%
Weld metal deposited from the electrode had the
following properties:
Tensile strength : 38 Ton/in2 (590N/mm2)
Yield ~trength : 36 Ton/in2 (560/mm2)
Charpy V impact value 20C 55 lbs. (75J)
0C 50 lbs. (68J)
-?0C 28 lbs. (38J)
The welds were of good appearance with relatively little
slag being deposited, though the result~ in this re~p~ct were
not quite ~o good a~ those obtained with the elec rode~ of
Example~ 3 and 4.
Example~ 6 to 14
~ he electrodes of examples 6 to 14 below were all wire~
of 2.4 diameter and found to deposit weld metal having acceptable
metallurgical proparties for many general ga~-~hielded arc :~
welding purpo~esO All the electrode~ of examples 6 to 14 were
prepared by the method de~cribed in Example 3 and all had a mild
~te~l ca~ing constituting 72% by waight of the total weight of
the electrodeg the balanc~ being contributed by th~ flux. rhe
electrodes of Examples 7, 8 and 1~ wera found to be part.icularly
- 16 -
satisfactory wi~h regard to weld app~arance an~ arc action.
The composition of the flux for each example was as ~ollows:
Exam~le 6
o/O by wei~ht of the f.lux
Fe powder 83.5
Fe Si 6.0
SiMn 10.0
LiFi 0 5
Example 7
% by weight of the ~lux
Fe powder 83.5
Fe Si 6~0
Si ~ 10 o O
Feldspar 0.5
Example B
o/O b~ we ght_of the
~e powder 83.5
Fe Si 6.0
Si ~ . 10.0
Strontium carbonate 0.5
Example 9
% by weight of ~he core
Fe powder 83O5
Fe Si ~,o
Si ~ lGoO
Ba F2 0.5
Exam~le 10
% by wei~ht of~ co~e
Fe 80.0
Fe Si 6.0
Si ~ 10~0
iron oxide 2 ., O
CaF2 (fluorspar) 2.0
E~ample 11
% by weight o:E core
Fe 80.0 -
F2 Si 6.0
S~ 10.0
K Tio3 2 O 0
Ca~2 (fluorspar) 2~,0
Exam~le 12
% by wel~ht of core
Fe 83.5
Fe Si 6.0
~i Mn 10,0
CaC03 0 . 5
Exam,~le 13
Fe 82 . O
P~e Si 6.0
Sl Mn 10.0
Ceric oxide 2.0
An electrode of 2.4 mm diameter, 7:2% by weight
of mild 3teel casing, 2~3% by weight o core was forllled
according to the method described in l~xample 1.
The core had the ~ollowing composition:
Fe powder 84 part~ by weight
Fe Si 6 paxts by weight
Si Mn 10 par~s ~y weight
K Si 03 2 parts hy weight
Weld metal deposited ~rom the electrode was
found to have the following metallurgical property:
: Charpy V impact strength:
20C 37 ft lbs (50 J)
0C 24 ft lbs (33 J)
This show~ the considerable improvemen~ given
in impact strength by the inclusion of a small quantity
of fluxing agent.
Ex~mple 15
The ele~trodes of Example 3 (1.6 mm diameter
were used ~o per~orm the following welds.
, . .
(a) a vertical butt joint of two 20 mm plates,
were prepared to define thexebetween a
V-shaped gap o~ 60 included angle, the
root gap being 2.4 mm;
(b) an overhead but~ joint identical to ta~;
~c) an overhead fillet weld o~ ~ inch leg len~th;
td~ a horizontal-vsrtical fillet weld o~ 5/16 inch
leg length using a 1~ inch electrode
ex~ension;
~e) a horizontal-ver~ical ~ille~ weld of % inch
leg 10ngth using a 1~ inrh electrocle
exten~on . . . ~:
"'
_ 19 -- .
: . ~ . . . , , . . ~ ..
In each instance a shielding gas o~ 95% 2~ and
5% C2 was used.
The results showing the ast weld speeds achieved
are given in Table 2.
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For the avoidance o~ doubt ~here the deoxldiser
is included in an alloy with a metal such as iron which
is not a deoxidant, the non-deoxidising metal in the
alloy i5 to be considered a~ being part o~ the metal
powder rather than part ffl the deoxidiser.
