CA1080094A

CA1080094A - Welding electrodes

Info

Publication number: CA1080094A
Application number: CA237,403A
Authority: CA
Inventors: Herbert C. Buckingham; Raymond Elliott
Original assignee: Canadian Oxygen Ltd
Current assignee: Canadian Oxygen Ltd
Priority date: 1974-11-15
Filing date: 1975-10-07
Publication date: 1980-06-24
Also published as: IT1043705B; SE7512840L; IE42217B1; ES442145A1; BE833957A; NL7513420A; GB1510120A; LU73807A1; FR2290988B1; DE2538874A1; DK484575A; ZA757148B; JPS5165050A; IE42217L; FR2290988A1

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides a flux-cored welding or hard surface electrode in the form of 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 1% by weight of flux-forming material intimately distributed throughout the core material, the remainder of the core being substantially metallic deoxidants.
The core will generally comprise from 22 to 45% by weight of the total weight of the electrode, and preferably from 20 to 30% by weight of the total weight of the electrode.

Description

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 ~-~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 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.

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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:

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 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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A flux-cored welding or hard surfacing electrode in the form of 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, substantially the remainder of the core being metallic deoxidants and the core constituting from 22 to 45% of the total weight of the electrode.

2. An electrode as claimed in claim 1, in which the flux-forming material comprises an acidic compound.

3. An electrode as claimed in claim 1, in which the flux-forming material comprises a silicate or titanate.

4. An electrode as claimed in claim 3, in which the flux-forming material is an alkali metal silicate or an alkali metal titanate.

5. An electrode as claimed in claim 1 in which the flux-forming material comprises one or more of silica, titanium dioxide, magnesium oxide, and aluminium oxide, an oxide of a transition metal and an oxide of a rare earth.

6. An electrode as claimed in claim 5, in which the transition metal is nickel, zirconium, molybdenum, iron or chromium.

7. An electrode as claimed in claim 5 in which the rare earth is yttrium, cerium or lanthanium.

8. An electrode as claimed in any one of claims 2, 3 and 4, in which the flux-forming material is present in the electrode in the range 1.5 to 2.5% by weight of the core.

9. An electrode as claimed in any one of claims 2, 3 and 4, in which the flux-forming material is present in the electrode in the range 0.4 to 0.7% by weight of the total weight of the electrode.

10. An electrode as claimed in claim 1, in which the flux-forming material is basic.

11. An electrode as claimed in claim 10, in which the flux-forming material comprises a fluoride or a carbonate or both.

12. An electrode as claimed in claim 11, in which the carbonate is strontium carbonate.

13. An electrode as claimed in claim 11, in which the fluoride is calcium fluoride.

14. An electrode as claimed in claim 11, in which the electrode contains by weight of the core from 0.5 to 1.5%
of the flux-forming material.

15. An electrode as claimed in claim 14, in which the electrode contains by weight of the core from 0.5 to 1.0% of the flux forming material.

16. An electrode as claimed in claim 13, in which the electrode contains by weight of its total weight from 0.14 to 0.42% of flux-forming material.

17. An electrode as claimed in claim 16, in which the electrode contains by weight of its total weight from 0.14 to 0.28% of flux forming material.

18. An electrode as claimed in any one of claims 1, 2 and 3, in which the electrode contains in the core from 8 to 12% by weight of the core of silicomanganese.

19. An electrode as claimed in claim 1, in which the electrode contains in the core by weight of the total weight of the electrode from 1.3 to 2.8% of manganese.

20. An electrode as claimed in claim 19 in which the electrode contains in the core by weight of the total weight of the electrode from 1.5 to 2.25% of manganese.

21. An electrode as claimed in claim 1, in which the total weight of manganese in the electrode is from 1.6 to 3.1% by weight thereof.

22. An electrode as claimed in claim 21, in which the total weight of manganese in the electrode is from 1.8 to 2.55% by weight thereof.

23. An electrode as claimed in any one of claims 1, 2 and 3, in which about 6% by weight of the core is constituted by ferrosilicon.

24. An electrode as claimed in any one of claims 1, 2 and 3, in which the electrode contains by weight of its total weight in the order of 1.4 to 1.95% of silicon.

25. An electrode as claimed in any one of claims 1, 2 and 3, in which the electrode contains up to 1.0% by weight of silicon and in addition one or more of titanium, aluminium, magnesium and zirconium.

26. An electrode as claimed in claim 1, in which the elemental metal powder comprises iron powder.

27. An electrode as claimed in claim 26, in which the elemental metal powder also includes one or more of nickel powder, chromium powder and molybdenum powder.

28. An electrode as claimed in claim 26, in which the electrode contains from 17 to 35% by weight of iron powder.

29. An electrode as claimed in claim 28, in which the electrode contains from 22 to 30% by weight of iron powder.

30. A method of welding or hardsurfacing in which the electrode claimed in claim 1 is used.

31. A method of open-arc gas-shielded welding in which the electrode claimed in claim 1 is employed.

32. A method as claimed in claim 31, in which the shielding gas contains argon and carbon dioxide, argon being the major constituent.

33. A method as claimed in claim 32, in which the shielding gas additionally contains a small proportion of oxygen.

34. A method as claimed in claim 31 in which the sole or major constituent of the shielding gas is carbon dioxide and the flux-forming material contains up to 1% by weight of the core of an arc stabiliser comprising an alkali metal compound or a compound of a rare earth.

35. A method as claimed in any one of claims 31, 32 and 34, in which a DC power source is employed, the electrode being connected to the negative terminal of the source.