8
This article was downloaded by: [York University Libraries] On: 12 November 2014, At: 07:43 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Welding International Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/twld20 Welding current supplies used in automatic and mechanised fusion welding V T Fed'ko , S B Sapozhkov & D E Kolmogorov a Branch of the Tomsk Polytechnical University (Yurga) b Branch of the Tomsk Polytechnical University (Yurga) c Branch of the Tomsk Polytechnical University (Yurga) Published online: 08 Jul 2010. To cite this article: V T Fed'ko , S B Sapozhkov & D E Kolmogorov (2005) Welding current supplies used in automatic and mechanised fusion welding, Welding International, 19:5, 406-412, DOI: 10.1533/wint.2005.3463 To link to this article: http://dx.doi.org/10.1533/wint.2005.3463 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions

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Page 1: Welding current supplies used in automatic and mechanised fusion welding

This article was downloaded by: [York University Libraries]On: 12 November 2014, At: 07:43Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK

Welding InternationalPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/twld20

Welding current supplies used in automatic andmechanised fusion weldingV T Fed'ko , S B Sapozhkov & D E Kolmogorova Branch of the Tomsk Polytechnical University (Yurga)b Branch of the Tomsk Polytechnical University (Yurga)c Branch of the Tomsk Polytechnical University (Yurga)Published online: 08 Jul 2010.

To cite this article: V T Fed'ko , S B Sapozhkov & D E Kolmogorov (2005) Welding current supplies used in automatic andmechanised fusion welding, Welding International, 19:5, 406-412, DOI: 10.1533/wint.2005.3463

To link to this article: http://dx.doi.org/10.1533/wint.2005.3463

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose ofthe Content. Any opinions and views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be reliedupon and should be independently verified with primary sources of information. Taylor and Francis shallnot be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to orarising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Page 2: Welding current supplies used in automatic and mechanised fusion welding

406 Fed'ko et al doi:10.1533/wint.2005.3463Welding International 2005 19 (5) 406–412Selected from Svarochnoe Proizvodstvo 2004 57 (12) 23–29; Reference SP/04/12/23; Translation 3463

The extensive application of mechanised and automaticwelding and at the necessity for further improvement ofthe efficiency of these welding methods are determinethe level of requirements on all sections of weldingequipment, including components, used in weldingtorches. The service properties of the torches forconsumable electrode arc welding are determined by thequality of the current-supplying guide and, in particular,by its wear resistance.1 During the passage of electrodewire, the guides are rapidly worn and, consequently,electrical contact is disrupted and the stability of thewelding process is reduced. This has a strong effect inincreasing the degree of splashing, burn-out andevaporation of electrode metal.2

The main physical processes taking place at the guide-welding wire contact, are characterised by two types ofwear: mechanical and electrical erosion.3 Mechanical wearforms as a result of the friction of the surfaces of bothcontacts (wire and can supply) and is expressed in themechanical transfer of metal particles of the current supplyto the electrode wire. This type of wear is strongly affectedby the hardness of materials, contacts pressure and theshear strength of the material. Electrical erosion wear isexpressed by ‘bridge‘, arc and spark erosion, arc corrosionand hot welding. The degree of electric erosion wearincreases with increase of the density of current and areduction of the stability of the contact. Electric erosionwear depends on the electro-physical properties of thematerial of the current-contacting guide.

Current transfer by sliding contact

In the great majority of automatic and semi-automaticwelding equipment, the current is transferred to theconsumable electrodes by means of sliding contacts.

In order to derive the main relationships, the authorsof Ref. 4 accepted the following scheme of the slidingcurrent-collecting device. The consumable electrodeslides with velocity, v, on the thick contact block,produced from an electrically-conducting material. Inevery cross-section, the width, B, of the area of contacton the electrode with the contact block is constant. Theelectrode is compressed of the block by the force, P,uniformly distributed in the direction of length, and theconductivity q in every elementary surface area of contactis also constant.

The current passing through the cross-section of theelectrode is:

0 ( ),I U Smth mL= σ [1]

where U0 is voltage, σ is the specific electrical conductivity

of the electrode material, S is the cross-sectional area ofthe electrode normal to the vector of the current, m is a

constant equal to qB

σ; L is the length of the contact.

The general conductivity of the contact is:

0

0

( ).I

Q SBqth mLU

= = σ [2]

Using these relationships for the given values of mand the maximum permissible values of current density,it is possible to determine the optimum contact length.

Welding current supplies used in automatic andmechanised fusion welding

V T F E D' K O, S B S A P O Z H K O V and D E K O L M O G O R O VBranch of the Tomsk Polytechnical University (Yurga)

The distribution of current and resistance inthe contact pair

The majority of automatic and semiautomatic weldingequipment are not fitted with devices strictly fixing thewelding wire in the channel of the guide and, consequently,the position of the contact is not constant with time.

In Ref. 5, the authors presented two cases of formationof physical contact in the electrode-current supply couple,in operation of automatic and semiautomatic weldingequipment:

• in several individual points of direct contact,• in a relatively large number of points (spots), the con-

tact area is comparable with the maximum possible area.

In the present study, attention is given to the case inwhich the contact pressure in the welding pair is nothigh and does not change the form of the microrelief ofthe surfaces of the pair and, consequently, has no effecton the nature of current transfer because the electricalresistance of the pair does not change in the examinedperiod.

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407Welding current supplies in fusion weldingdoi:10.1533/wint.2005.3463

The nature of the distribution of current indirect contact at several individual points

The equivalent scheme of a circuit of this type is shownin Fig. 1 and is described by the following relationships:

( ) ( )1 2

1 2

1' ; " ; '" ,

1 1

l lnr r r

S n q ld S n

ρ ρ−= =− π − [3]

where ρ1, ρ

2 is the specific resistance of the material of

the guide and the electrical wire, respectively, S1, S

2 are

their cross-sectional areas; q is the conductivity of theunit area of contact; l is the length of the contact part ofthe guide; n is the number of contacts; and d is the diameterof the channel of the guide.

The intensity of current in all sections of the circuit(Fig. 1) is determined by the method of contour currents.

The general resistance of the contours is:

( ) ( )1 '" '.Z k r n m r= − + − [4]

Here k has the values of 1,..., n, and m changes from k+1to n. Solving the system with the determinant |Z

jj| it is

possible to determine the value of n of the contourcurrents Ik.

Denoting by I’k and I’’

k of the current in the k-th section

of the guide and welding wire, respectively, gives:

' 2

1

; .n k

k j k jj k j

I I I I= =

= =∑ ∑ [5]

Total current I in the contact pair is:

1

.n

jj

I I=

= ∑ [6]

According to the calculations, the main fraction ofcurrent (95–99%) passes through the contact points inthe vicinity of the end section of the guide.

The nature of distribution of current indirectcontact in a relatively large number of points

In contact over a large area, the guide-electrode wiresystem is regarded as a circuit with the distributedparameters (Fig. 2).

In order to facilitate the solution, the so-called trialparameters are introduced:

• the resistance of the unit length of the guide:

11 2 2

2 1

;/ 4 / 4

rd d

ρ=π − π [7]

• the resistance of the unit length of the electrode wire:

22 2

1

;/ 4

rd

ρ=π [8]

• the conductivity of the unit length of the contact:

.sq q d= π [9]

The current passing through the guide and the wire isdetermined from the following relationships:

( ) 21 1 2sh x sh x ;

sh

r IIi r l r

Z Z = γ − − γ + γ γ γ [10]

( ) 12 1 2sh x sh x ,

sh

r IIi r l r

Z Z = γ − − γ + γ γ γ [11]

where ( ) ( )1 2 1 2; / .r r q Z r r qγ = + = +

1 Equivalent electrical scheme of the contact pair (E–voltagedrop in the contact pair; r’1,..., r’n–the resistance of the sectionsof the guide between the contact points; r’’1,..., r’’n–theresistance of the contact point; r1'’’,..., rn’’’–the resistance ofthe sections of the electrode between the contact point; A–the guide; B–electrode wire).

a b

2 Equivalent electrical scheme of the electrical circuit in thesection dx of the contact pair (a) and the distribution of currentin the section dx of the guide (b) (i1, i2–the current in theguide and the electrode wire).

a

bc

B

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408 Fed'ko et al doi:10.1533/wint.2005.3463

The characteristic relationships [10] and [11] arepresented in Fig. 3. It may be seen that the main fractionof current (more than 50%) passes through the sectionof the guide with the length 1/8 l.

In Ref. 6, in order to determine more accurately thenature of distribution and the area of current transferfrom the guide to the electrode wire, the authorsdeveloped a special current-supplying guide and a methodof measuring the current passing through the differentsections of the guide.

The electrical parameters were measured in the firstshort-circuit of the electrode with the component andarc excitation, in welding with a short arc in carbon dioxideand with a long arc in carbon dioxide and in argon.

The experimental results show that the current passingthrough the lower part of the current-supplying guideequals 88–95% of the total current and does not dip onthe parameters of the loading conditions nor on thecurvature of the welding electrode. Both in the period ofshort-circuiting of the electrode with the component andin the process of arcing, up to 90–95% of current issupplied to the electrode wire through the point of contactin the lower end section of the guide and not throughthe sections equalling 0.125–0.5 of the length of the guidechannel, as indicated in Ref. 5. The supply of current inthe vicinity of the end of the current-supplying guidesupports the local thermal effect, intensive electric erosionwear and abrasion of the metal of the relevant zone.

In Ref. 7, investigations were carried out into thevariation of the transition resistance in the guide-weldingwire contact in the welding process. The contact theresistance was determined in the following sequence:initially, measurements were taken of the resistance inthe sections of the guide-component circuit byoscillographic recording of the current and arc voltagefollowed by determination of the total resistance of thesection of the circuit.

The total resistance of the section of the guide-component circuit R

c includes the resistance in the guide-

welding wire contact Rk, the resistance of electrode

extension Re, and the resistance of the bridge R

b.

Consequently, the resistance in the guide-welding wire

contact is:

( ).K c e bR R R R= − + [12]

According to the calculations, the resistance of thebridge is two orders of magnitude lower than the examinethe values of R

c and R

k. Consequently, it was assumed

that:

.K c eR R R≅ − [13]

The resistance of electrode extension was calculatedfor the given parameters of the welding conditions usingthe equation of the thermal balance of the electrode:

( )01

,em he

e

R emF

ρ= [14]

where 20.24

f

me v

βδ=γ

; Fe is the area of the electrode, cm2;

ρ0 is the specific electrical resistance (in the case of Sv-

08G2S wire it is 30 · 10–6 ohm cm); he is the electrodeextension, cm; β is the temperature coefficient of specificresistance equal to 1.67 · 10–3 K–1; δ is current density,A/cm2; γ is the density equal to 7.85 g × cm–3; and v

f is

the feed the rate of the electrode, cm s–1.Determining the values of R

c and R

e and contact

resistance Rk, it was established that the resistance in

the guide-welding wire contact is (in the limiting stageof the guide) the main part of the total resistance of thecircuit in the section between the electrodes and is valueis not less than 80%.

On the basis of the experimental results it wasestablished that the limiting value of the contact theresistance for each diameter of the welding wire isconstant, does not depend on the material of the guideand determines the lifetime of the current-supplying guide,and the increase of contact resistance in feeding thewire with smooth feed rollers is higher in comparisonwith the use of profiled rollers.

Conditions of contact between the guide andthe electrode

Dust, oil and other contaminants, deposited on the surfaceof the welding wire, settle on the surfaces of the channelof the current correct the and reduce the probability ofdirect contact.

The duration of holding of the welding wire in contactwith the guide depends on the curvature of the electrodewire, of the spring properties of the wire, the internaldiameter of the channel of the guide, its length, wearresistance, etc. Possible variants of the position of thewelding wire in relation to the current-supplying guideare presented in Fig. 4.

When the electrode wire is coxial in relation to theguide, there is no direct contact (Fig. 4g). The strengthof the field on the surface of the electrode wire reaches

3 Characteristic variation of current in the guide i1(x) andelectrode wire i2 (x).

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409Welding current supplies in fusion weldingdoi:10.1533/wint.2005.3463

6–9 kV/cm (in welding with a wire with a diameter of 2mm). Since the breakdown strength of dry air in normalconditions is approximately 30 kV/cm, in the initialmoments of the welding process there is no currentbetween the contact guide and the electrode wire, untilthe gap is not reduced to 0.05–0.01 mm or the position ofthe welding wire changes in relation to the guide. Anyof the variants of contact, presented in Fig. 4, can beschematically represented as in Fig. 5.

Since the surface of physical contact is small, thedensity of current, passing through the contact is high,and the contact K

1 and K

2 are characterised by the

generation of the amount of heat which is sufficient forinstantaneous melting and evaporation of the contacts.One of the contacts through which high current passes,for example, K

1, melts and evaporates. After disruption

of the contact at point K1, the entire welding current

passes through contact K2 resulting in its immediate

melting and evaporation. Subsequently, prior to theformation of contact at K

1, the current passes through

the air gap between the guide and the electrode wire,field with the metal vapours. In this case, the currentbetween the diet and the wire does not flow through thepoint contacts but through considerably larger areas.Thus, in the absence of direct physical contact in theelectrode-guide pair, the conditions of current transferare determined by the electrophysical properties of thegas, filling the gap.

According to the diagram in Fig. 5, the position of thecontact constantly changes. These influences the changeof the decrease of voltage in the guide-electrode contact.It is well-known that the range of the permissible valuesof the variation of arc voltage in carbon dioxide welding,determined on the basis of the smaller degree of splashing,is greatly limited. Consequently, the changes in the voltagedrop in the contact may result in an acceptable deviationsof the arc voltage. In order to improve the contact in thetorches for automatic welding, it is necessary to usespecial compensating current supplies. Therefore, toimprove the conditions of current transfer, the materialof the current supplies should contain substancesreducing the breakdown time and voltage of the inter-electrode gap.8

The effect of the surface condition of weldingwire on the wear of guides and uniformity offeed

The electric erosion and mechanical wear of the current-supplying guide is are greatly affected by the surfacecondition of welding wire. In turn, this influences theuniformity of wire feed and the reliability of its electricalcontact with the current-supplying guide.9

The experimental results show that the lowest forceand the highest stability of the feed rate are obtainedwhen using the wire in the as-received condition. Thisis explained by the presence on the surface of the initialwire, of a large amount of technological lubricant withantifriction properties. At the same time, the technologicallubricant, being a dielectric material, least of the formationof electrical discharges, causing extensive electric erosionwere of the guide channel. The lowest degree of wear inthe guide is recorded in welding with copper-plated wire,because of the good current-conducting properties ofthe copper coating reducing the intensity of electricerosion processes. In this case, the degree of mechanicalwear is also well because of the relatively ductile coppercoating does not have any abrasive effect on the channelof the guide. However, the feed force of the copper-platedwire is slightly higher and the stability of the feed ratelower in comparison with the wire in the as-receivedcondition with the technological lubricant.

Different results were obtained when testing wireswhose surface was cleaned with the electrolyte dischargemethod and grinding paper. Prior to the start of welding,the feed force was 30–40% higher in comparison withthe wires in the as-received condition and after copperplating. The absence of the technological lubricant alsoresults in increase of the degree of mechanical wear of

a b c

d e f

g

4 Possible variants of contact of electrode wire with thecylindrical current supply (K1–K4– physical contacts).

5 The schematic image of the contact conditions of thecurrent supplying guide 1 and guide 2 (L1– arc length, L1 +L2– electrode extension; L2– the distance between thephysical contact of the electrode and the guide; K1–K2–contact points).

2 1

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Page 6: Welding current supplies used in automatic and mechanised fusion welding

410 Fed'ko et al doi:10.1533/wint.2005.3463

the direct channel. In the welding process, the feed forceof the wires with the clean the surface increases and thestability of the feed rate decreases. This is accompaniedby the periodic oscillations of electrode extension. Thistakes place independently of the material of the current-supplying guide. The main deceleration force in weldingwith the wire with the clean surface forms in the guidebecause of the welding of the wire to the surface of thechannel. The sections with the welded metal appear inthe guide channel as a result of the penetration of thefinest particles of the metal of welding wire into the channel.This takes place mainly in the zone with high currentdensity (Fig. 6).

When using a wire with a technological lubricant or acopper-plated wire, there is no welding of the metal inthe channel of the guide. The presence of thetechnological lubricant or copper on the surface of thewire prevents the failure of the wire in the feed rollers. Inaddition to this, the technological lubricant, whichevaporates, cools down the surface of the guide andalso leads to the formation, on the guide, of an organicfilm, complicating the welding of the wire particles tothe surface of the channel.

To ensure a stable feed rate, a layer of the antifrictionlubricant should be deposited on the surface of the cleaneda wire. This coating does not impair the welding andtechnological properties of the electrode wire. Of thestability of electrical contact of the guide and the wirewith the cleaned surface and the surface coated with athin layer of lubricant is slightly higher in comparisonwith the wire in the as-received condition.

In cases in which the presence of copper and theantifriction lubricant on the surface of the electrode wireis not permitted, the probability of wedging of the weldingwire with the cleaned surface is prevented when using awater-cooled guide, but the degree of wear of the guideswithout the antifriction lubricant is relatively high.

Materials used for the fabrication of current-supplying devices

The conventional current-supplying guides are producedfrom copper and its alloys (brass, bronze) but, accordingto the experimental results10, they are characterised bylow service stability. The lowest wear resistance is typicalof the guides made of copper alloys, and copper guideshave slightly higher resistance. Low resistance is alsotypical of current guides, produced from graphite or ametal bonded with graphite. However, they ensure reliable

current collection and the most favourable slidingconditions, because graphite does not stick to the surfaceof the wire and does not settle on the surface (Claim 63-72483, Japan).

In order to increase the productivity and quality ofmechanised and automatic welding, it is necessary touse current-supplying devices made of materials withhigher wear resistance. These materials include cermetcomposites based on copper, and Table 1 gives thecomposition of several of these materials.

The experimental results also show that the wearresistance of the current supplies made of compositematerials is three-four times higher in comparison withthe current supplies made of copper and its alloys.11 Thehighest wear resistance is typical of the current-supplyingdevices produced from MV70 composite material. Thewear resistance of these materials increases with increaseof the tungsten content, but the electrical conductivitydecreases which, for comparatively small wear of the hole,resulting bonding of the wire to the current supply.12

To increase the service life of the current supplies, ithas been proposed to use a composite material (Author’sCertificate 1706800, USSR), consisting of PN73Kh16S3R3alloy (1.0–2.0%), 0.5–0.7% of zirconium, and copper. Thismaterial is characterised by the high resistance to electricerosion were and is electrical conductivity is 80–90% ofthat of copper.

The sintered material (Author’s Certificate 1316773,USSR), consisting of the following components (%): 1.5–6.0 iron, 1.0–4.0 aluminium, 2.0–5.0 chromium, 1.0–2.0

6 Contact zones of the wire with the current-supplying guide:1, 2) the zone of low and high current density, respectively;3) the section of preferential distribution of the welded-onmetal.

lairetaM %,noitisopmoC

uC iN Ctot

iT lA2O

3W

05VM07VM1KKM2KKM

4.64

1.035.53

27.2

00.33.2

61.0

71.031.0

––

50.0

–––

4.0

ecnalab""–

Table 1

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411Welding current supplies in fusion weldingdoi:10.1533/wint.2005.3463

molybdenum disulphide, balance–copper, was developedfor the same purpose.

The current-supplying devices are often subject todifferent and contradicting requirements which neithermaterial can completely satisfy. In order to obtain theoptimum combination of the properties of differentmaterials (electrical conductivity and wear resistance),the current supplies are often produced from bimetals.In most cases, such a current supply consists of a casing(produced from copper or it is alloys) with a wear-resistantinsert, reinforcement or facing.12 The wear-resistantmaterial may be represented by cermet compositions(describes previously), tungsten or V K hard alloy (theclaim of the Russian Federation for useful model 18662,1866), or copper–chromium alloy (Claim number 0324066,European community). In order to increase the heatresistance of the current supply, the insert may beproduced from a material characterised by negativethermal EMF in relation to platinum at temperatures above0, for example, nickel, nickel alloy alumel or constantanalloy (Claim 2239204, Great Britain). In addition to thecombination of the metals with different properties,current-supplying devices may also include nonmetallicmaterials. For example, the guide produced from a copperalloy with a tip made of a ceramic material based on oxygen-three compounds (Claim 3-61545, Japan) or a ceramicguide, whose channel contains an electrically conductingcopper coating or a coating made of the copper alloy(Claim 4-18950, Japan), have been developed.

The design of current-supplying devices

The design of the current supplies greatly varies. Themain design features of the current supplies and theirclassification have been proposed in Ref. 12. Classificationwas carried out on the bases of the following features:

• the possibility of compensating the deviation of thedimensions of the electrically conducting channel fromthe design dimensions,

• the formation of contact pressure,

• the type of electrically conducting channel,

• the geometry of the working surface,

• the method of securing the current supply to the noz-zle,

• of the shape, dimensions of the cross-section of theelectrode, and the number of electrodes,

• the number of components and combination of the ma-terials of the components of the current supply.

The characteristics of several features are given below.

or continuously discretely compensating.13 The longestdurability in identical conditions is shown by the currentsupplies using the continuous and discrete methods ofcompensation.

Formation of contact pressure

The methods of forming contact pressure are dividedinto elastic, spring and elastic-spring. The currentsupplies, using the elastic method of develop in pressureare non-compensated or discreetly compensated, andthose using the spring and elastic-spring methods arecontinuously compensated or continuously discreetlycompensated.

The type of electrically conducting channel

According to this feature, of the current supplies aredivided into three groups: closed, open or semi-openchannels. The lowest endurance is shown by the currentsupplies with the close to channel because the productsof were and other contaminants settle in the channel,contaminated and disrupt the stability of the contact.

The number and combination of the materials ofthe components of the current supply

On the basis of the number of components, the currentsupplies are divided into a simple, consisting of a singlecomponent, and compound, consisting of severalcompliments. According to the combination of thematerials, they are divided into monometallic were allcomponents are produced from the same material, andbimetallic (described previously). The highest wearresistance is recorded in the case of the bimetallic currentsupplies.

The analysis of the results, published in Ref. 12, indicatethat the highest endurance is shown by the ban metalliccontinuously compensated current supplies with the openchannel. In practice, the selection of the design of currentsupply is determined not only by the considerations ofendurance that factors such as the welding methods,the dimensions of the cross-section of the electrode,the technological properties and cost of fabrication ofthe current supply, the type of welded component andthe design of the welded joints, restrictions regardingthe overall dimensions, weight, etc are also taken intoaccount.

Thus, taking into account the extensive applicationand the existence of a large variety of welding currentsupplies, for the development of specific recommendationsfor the application of these devices in production andfor the development of the optimum design of current-conducting systems, it is necessary to a carry out thefollowing investigations:

• investigate the mechanism of electric erosion and me-chanical wear of the current supplies, the effect of theseprocesses on the electrical and technological charac-teristics of the current supplies in the welding process,in relation to the conditions;

The possibility of compensating the deviation ofthe dimensions of the electrically conductingchannel from the design values

There are non-compensated 4, 6–11 and compensated currentsupplies. In turn, the compensating current supplies maybediscreetly compensating 4, 12,13 continuously compensating

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412 Fed'ko et al doi:10.1533/wint.2005.3463

• to investigate the effect of the weight, design and com-position of the material on the operating life of the cur-rent-supplying guide and the entire welding head; ex-amine the effect of wear of the current-supplying guideon the stability of the welding process and the qualityof the welded joints;

• prepare recommendations for the selection and intro-duction into welding production of materials for thefabrication of current-conducting guys in order to im-prove their electrical and technological characteristicsand the operating life of the welding torch.

Conclusions

1 High-intensity wear is found in the lower-end part ofthe current-supplying devise because of its higher ther-mal (heating from the arc temperature) and the electri-cal loading.

2 In mechanised welding in shielding gases it is recom-mended to use only tubular guides, representing non-compensated current supplies with the close to chan-nel, and the so-called shoe current supplies with dis-crete compensation. The other types of current sup-plies can be used only automatic welding, because oftheir overall dimensions and complicated design.

3 The current conducting guides used most widely inproduction are characterised by low durability affectingthe stability of the welding process, leading to in-creased splashing and labour content of the removal ofsplashes of electron metal from the surface of compo-

nents and the parts of welding equipment.

References

1 Shebeko L P: ‘Equipment and technology for automatic andsemi-automatic welding’. Publ Vysshaya Shkola, Moscow 1981.

2 Chubukov A A : ‘Effect of the wear of the current-supplyingguide on the technological parameters of welding’. Svar Proiz1980 (1) 26–27.

3 Smirnov V V (Ed): ‘Equipment for arc welding, a Handbook’.Publ Energoatimzdat, Leningrad 1986.

4 Vakhalin V A: ‘The problem of current transfer by slidingcontact’. Svar Proiz 1971 (1) 2.

5 Brigidin V Ya and Konotop D A: ‘The distribution of currentin the electrode wire-guide contact in automatic or semiauto-matic welding equipment’. Avt Svarka 1977 (6) 21–24.

6 Lenivkin V A and Klenov G G: ‘The distribution of currentand content the resistance in the current-supplying guide’.Svar Proiz 1990 (9) 27–29.

7 Chubukov A A: ‘The resistance in the guide-welding wire con-tact in carbon dioxide welding’. Svar Proiz 18-980 (12) 31–32 .

8 Brigidin V Ya: ‘The operation of current-contacting guides inarc welding’. Svar Proiz 1979 (8) 20–21.

9 Degtyareev V G et al: ‘Improvement of the operating condi-tions of the electrode wire-current conducting guide contactcouple’. Avt Svarka 1991 (4) 48–52.

10 Dymchenko V G and Popovich A P: ‘Sintered material forcurrent-conducting components of welding heads’. Avt Svarka1984 (3) 73–74.

11 Chvertko A I: ‘Examination of wear resistance and selectionof the material of the components of sliding current suppliesof automatic and semiautomatic welding equipment’. Avt Svarka1975 (1) 28.

12 Zil'bershtein B M: ‘Design special features of current suppliesof welding equipment’. Avt Svarka 1976 (6) 56–60.

13 Chernyi O M: ‘Current supply to the welding head for multipleapplication of replaceable guides’. Svar Proiz 1999 (9) 33.

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