Various systems of electrode specifications are used in different countries.
Most important ones are from:
1. International Organisation for Standardisation (ISO) 2. American Welding Society
3. Indian Standards Institution 4. British Standards Institution
5. Deutsches Institut Für Normung (DIN).
They cover some or all of the following groups of electrodes 1. Mild steel electrodes
2. Low alloy steel electrodes 3. Stainless steel electrodes 4. Surfacing electrodes 5. Cast iron electrodes
6. Copper and copper alloy electrodes 7. Nickel and nickel alloy electrodes
8. Aluminium and aluminium-alloy electrodes.
As mild steel and low alloy steel electrodes are most commonly used, the important welding electrode specification systems for these electrodes will be discussed in the following paragraphs.
4.5.1 International Standards Organisation System of Coding
ISO-2560-1973(E): Covered Electrodes for Manual Arc Welding of Mild Steel and Low-alloy Steel. Code for Identification.
Prefix E: indicates covered electrodes for manual arc welding. (See Fig. 4.10)
Next symbols: 43 or 51 indicate that all weld metal tensile strength is in the range of 430510 MPa or 510610 MPa respectively. Upper limits may exceed by 40 MPa.
For each range of tensile strength, there are six sub-groups based on elongation (on L
= 5d) and temperature for minimum impact value of 28 J (see Table 4.4).
Next come one or two letters symbol for covering type
A = Acid (iron-oxide) ; AR = Acid rutile; B = Basic ; C = Cellulosic ; O = Oxidising ; R = Rutile ; RR = heavy coated rutile ; S = other type Symbols up to this stage are compulsory, beyond this the symbols indicate :
Weld deposition efficiency in increments of 10 (110, 120, 130, etc.)
Next digit indicates welding position 1. all positions;
2. all positions except vertical down
3. flat butt ; flat fillet ; horizontal/vertical fillet weld 4. flat butt, flat fillet
5. as 3 plus vertical down.
Next comes the symbol for electrical characteristics i.e., whether the electrode oper-ates with a.c. as well as d.c. or d.c. alone, the polarity of d.c. and minimum open circuit voltage for a.c. necessary for sustaining the arc. It is given in Table 4.5.
The last symbol H is used only when the electrode is hydrogen controlled i.e. the weld deposit contains diffusible hydrogen content of less than 15 ml. per 100 g of deposited metal (determined by a standard method).
Table 4.4. Electrode designation according to ISO-2560
Electrode Tensile strength Min. elongation Temp. for minimum
designation MPa on L = 5 d impact value of 28 J
% °C
E 430 434510
E431 434510 20 + 20
E432 434510 22 0
E433 434510 24 20
E434 434510 24 30
E435 434510 24 40
E510 510610
E511 510610 18 + 20
E512 510610 18 0
E513 510610 20 20
E514 510610 20 30
E515 510610 20 40
Tolerance + 40 MPa, 1 J = 0.102 Kgf.m.
Table 4.5. Symbols for electrical characteristics in ISO-2560 Electrode polarity Nominal O.C.V. with Symbol with direct current alternating current
volts
0 + not used
1 + or 50
2 50
3 + 50
4 + or 70
5 70
6 + 70
7 + or 90
8 90
9 + 90
Example (a) ISO 2560
E 51 3B 160 2 1 (H)
Hydrogen controlled dc ep or en / ac (OCV 50)
all positions welding except vertically down deposition efficiency 160%
basic coating
tensile strength 510-610 MPa/elongation 20%
& impact value of 28J at –20°C
Covered electrodes for manual arc welding
Fig. 4.15 Example of electrode designation according to ISO-2560
4.5.2 British Standards Institute Coding Systems
B.S : 639 : 1976 Covered Electrodes for Manual Metal Arc Welding of Carbon Manganese Steels.
This is based on ISO 2560 except that E is followed by 4 digits instead of 3 digits in ISO.
This fourth digit gives more information on elongation and impact value.
In this system minimum yield stress is also specified as also in DIN. This system will be explained with an example (see Fig. 4.5).
Example (b)
E 51 32 B 150 1 2 (H)
indicates hydrogen-controlled ( 15 ml/100 g)£
Electrical chs. same as in ISO 2560 Position digits same as in ISO 2560 Deposition electrode covering Basic electrode covering Second digit for elongation and impact values (Table 4.7)
First digit for elongation and impact strength (Table 4.7)
Tensile strength (Table 4.6) Covered manual metal arc welding electrode
Fig. 4.6 Electrode designation according to BS : 639 : 1976
Table 4.6 Tensile strength BS 639 (1976) and DIN 1913 (1976) Electrode Tensile Minimum Yield Stress, MPa designation strength, MPa BS : 639 : 1976 DIN : 1913 : 1976
E43 430550 360 330
E51 510650 380 360
Table 4.7. First and Second digits elongation and impact strength First Min. elongation % Temp. for impact Second Min. elongation % Impact prop.
Digit L = 5D value of 28 J (°C) Digit L = 5D
E43 E51 E43 E51 Impact value Temp.
J °C
E43 E51
1 20 18 + 20 1 22 22 47 47 + 20
2 22 18 0 2 22 22 47 47 0
3 24 20 20 3 22 22 47 47 20
4 24 20 30 4 NR(a) 18 NR 41 30
5 24 20 40 6 NR 18 NR 47 50(b)
(a) NR = Not relevant
(b) In DIN all other things are the same for First and Second digits except the impact tempera-ture for second digit if 5 = 40°C and 6 as second digit does not exist.
4.5.3 German System of Coding for Electrodes
DIN 1913 (Jan. 1976) Coated Electrodes for the Welding of Unalloyed and Low-alloy Steels
The German coding system is also based on ISO : 2560 with some modifications as in BS 639. It starts with prefix E followed by two digits 43 or 51 indicating the range of tensile strengths as in ISO, with the addition that minimum yield strength is specified as 360 MPa and 380 MPa respectively (see Table 4.6).
These two digits are followed by another two digits indicating elongation and impact strength as given in Table 4.8. After this DIN has a departure from ISO 2560 and BS 639. It provides a classification based upon :
(a) coating type (b) welding position
(c) welding current condition
and then uses the classification number to designate each type of electrode. The details are as follows:
(a) Coating type is indicated by letter or letters as follows
Aacidic BBasic CCellulosic
Arutile (thin/medium) RRrutile (heavy coating)
ARacid-rutile (mixed) R(c) rutilecellulose (medium coated) RR(c)rutile-cellulose (heavy coated)
B(R)basic coated with non-basic components RR(B)rutile-basic (heavy coated)
They define :
Thin coated, having a coating factor (CF) of 120% ; medium coated, having a CF of 120155% and heavy coated having a CF of over 155%.
(b) Welding position 1. all position.
2. all positions except vertical down.
3. butt-weld flat, fillet-weld flat, fillet-weld horizontal.
4. butt-weld flat, fillet weld flat.
(c) Welding current conditions are same as in ISO 2560 and BS 639 except that in case of 0 (zero)
0 means dc only electrode positive or negative polarity 0+ means dc only with electrode positive polarity 0 means dc only with electrode negative polarity
Combining (a), (b) and (c) twelve classifications of electrodes are given in Table 4.9.
This electrode class coding is followed by a three digit number indicating the deposition efficiency, which is to be used only if it is more than 105%. This is identical to ISO 2560 and BS 639.
Table 4.8 First and second digit for elongation and impact strength in DIN 1913
First Min. elongation Temp. for min Second Temp. for digit L = 5d (%) impact value digit impact value
of 28 J (°C) of 47 J (°C)
0 Nil Nil 0 Nil
1 22 + 20 1 + 20
2 22 0 2 0
3 24 20 3 20
4 24 30 4 30
5 24 40 5 40
Table 4.9. Classification numbers of electrodes in DIN 1913
Electrode Welding position Current Coating see (a) Classification
type code* see (b) condition** above number
above
A1 1 5 thin coated A 1
A2 1 5 thin coated A
2
R2 1 5 thin coated R
R3 2(1) 2 medium coated R
3
R(C)3 1 2 medium coated R(C)
C4 1 + 0+(6) medium coated C 4
A5 2 5 heavy coated A 5
RR6 2 2 heavy coated RR
6
RR(C)6 1 2 heavy coated RR(C)
AR7 2 5 heavy coated AR
7
RR(B)7 2 5 heavy coated RR(C)
RR8 2 2 heavy coated RR
8
RR(B)8 2 5 heavy coated RR(B)
B9 1 0+(6) heavy coated B
9
B(R)9 1 6 heavy coated B(R)
B10 2 0+(6) heavy coated B
10
B(R)10 2 6 heavy coated B(R)
RR11 4(3) 5 RR with dep. eff. > 105%
11
AR11 4(3) 5 AR with dep. eff. > 105%
B12 4(3) 0+(6) B with dep. eff. > 120%
12 B(R)12 4(3) 0+(6) B(R) with dep. eff. >120%
*Bracketed code numbers for welding positions apply only to a smaller sizes and/or low levels of deposition efficiency.
**Bracketed code numbers for current conditions mean conditional qualification.
Favoured for vertical down.
4.5.4 Indian Standards System
IS : 815-1974 classification and coding of covered electrodes for metal arc welding of structural steels.
The code starts with a prefix E or R meaning thereby Eelectrode produced by solid extrusion
Rextruded with reinforcement Next come digits
First digit indicates the type of covering
Table 4.10. First digit for type of covering in IS : 815
First digit Type of Covering ISO : 2560
Equivalent
1 High cellulose content C
2 High titania giving viscous slag R 3 Appreciable titania, giving fluid slag RR 4 High oxides or silicates of iron or both
and manganese giving inflated slag A 5 High iron oxides or silicates or both
giving heavy solid slag O
6 High calcium carbonate and fluoride B 9 Any other covering not specified S
Second digit indicates welding position and third digit indicates welding current condi-tion as shown in Table 4.11.
Table 4.11. Second and third digit for welding position and current condition in IS : 815
Second Welding position Third Welding current
digit digit condition
0 F, H, V, D, O 0 D +
1 F, H, V, O 1 D +, A90
2 F, H 2 D , A70
3 F 3 D , A50
4 F, Hf (horizontal fillet) 4 D +, A70
9 Any other welding 5 D ±, A70
position not classified 6 D ±, A70
above 7 D ±, A50
9 other conditions not classified.
Fourth and Fifth digits are 41 or 51 indicating tensile strength range in combination with yield stress.
Sixth digit indicates percentage with impact strength as given in Table 4.12.
Table 4.12. Digits indicating mechanical properties in IS : 815
Fourth, fifth *Tensile Min. yield Min. elongation Temp. for min.
and sixth strength stress impact value
N./mm2 N/mm2 % of 47 J, °C
410 410510 330
411 410510 330 20 + 27
412 410510 330 22 0
413 410510 330 24 20
414 410510 330 24 30
415 410510 330 24 40
510 510610 360
511 510610 360 18 + 27
512 510610 360 18 0
513 510610 360 20 20
514 510610 360 20 30
515 510610 360 20 40
*Upper limit of tensile strength may be exceeded by + 40N/mm2.
The coding terminates with one or more of the following suffixes to be used when appro-priate.
Suffix letter Special property
H Hydrogen controlled electrode
J Iron powder covering deposition efficiency 110-130%.
K As J with deposition efficiency 130 150.
L As J with deposition efficiency of 150%.
P Deep penetration.
A hydrogen controlled electrode gives a weld deposit that gives not more than 10 ml of diffusible hydrogen/100 g weld deposit. Appendix A gives types of flux coverings according to DIN, 1913, IS : 815 and AWS.
Types of Flux Covering
IS : 815 describes the standard flux coverings as follows :
Type 1: Electrode with covering having a high cellulose content.
The covering contains at least 15% of material having a high cellulose content and up to 30% of titania (as rutile or titanium white). This type of electrode is characterised by a deep penetrating arc and rapid burn-off rate. Spatter loss is somewhat higher than that with elec-trodes having the mineral type of covering. A voluminous gas shield is formed as a result of the decomposition of the cellulosic material in the arc region. The weld finish is somewhat coarser than usual, the ripples being rather more pronounced and less evenly spaced. The deposit has a thin cover of slag, which is friable and thus easy to remove. Because of its arc characteristics
and the small volume of slag produced, the electrode is particularly easy to use in any welding position. With current values near to the maximum of the range, the electrode may be used in the flat position for deep-penetration welding. The electrode is suitable for all types of mild steel welding and is of particular value for applications involving changes in position of weld-ing, for example, in pipe weldweld-ing, storage tanks, bridges and ship building. Generally, this type of electrode is suitable for use with DC with the electrode connected to the positive pole.
Some types are available which contain arc stabilising materials and are suitable for use with AC.
Type 2: Electrode with covering having a high content of titania and producing a fairly viscous slag.
The covering contains a high proportion of titania (as rutile, titanium white or ilmenite) and the high content of ionisers provides excellent welding properties. An electrode of this type is suitable for butt and fillet welds in all positions and is particularly easy to use for fillet welds in the horizontal-vertical position. Sizes larger than 5 mm are not normally used for vertical and overhead welding. Fillet welds tend to be convex in profile and have medium root penetration. The electrode has smooth arc characteristics and normally produces very little spatter. The slag is dense and completely covers the deposit and is easily detached, except from the first run in a dc ep V-groove. The electrode is particularly suitable for use with AC, and on DC it may be used with the electrode connected to either pole.
Type 3: Electrode with covering containing an appreciable amount of titania and producing a fluid slag.
The covering contains an appreciable amount of titania (as rutile, titanium white or ilmenite), but the addition of basic materials yields a much more fluid slag than produced by electrodes of Type 2. Welding in the overhead and vertical (upwards) position is far easier with this type of electrode than with any other type of mild steel electrode, but its use is not con-fined to these positions. The electrode has smooth arc characteristics, medium penetration, and normally produces very little spatter. The slag is generally easy to detach, even from the first run in a deep V-groove. The deposit produced by this type of electrode will usually meet normal radiographic tests more readily than the one made with electrodes of Type 2. The electrode is suitable for use with AC and DC and may be used with the electrode connected to either pole.
Type 4: Electrode with covering producing an inflated slag and having high content of oxides and/or silicates of iron and manganese.
The covering consists principally of oxides or carbonates of iron and manganese, together with silicates. The electrode is generally produced with a thick covering and is used for welding in the flat position only. Certain varieties have a thinner covering, and these may be used for welding in all positions but have generally been superseded by other types of electrodes. Both the forms of covering produce a fluid, voluminous slag which freezes with a characteristic internal honeycomb of holes, the so-called inflated slag, which is very easily detached. The weld finish is smooth, the ripples being much less pronounced than on deposits produced by the other types of electrodes. In grooves and fillet welds, the weld profile is concave. The principal application for this type of electrode with a thick covering is for deep groove welding in thick plates, particularly where such welds are subject to strict radiographic acceptance
standards. Certain varieties of this type of electrodes are suitable for deep penetration welding.
The electrode is suitable for use with DC, usually with the electrode connected to the positive pole, and may be used on AC.
Type 5. Electrode with covering having a high content of iron oxides and/or silicates producing a heavy solid slag.
This type of electrode has a thick covering, consisting principally of iron oxides with or without oxides of manganese. An electrode of this type is used principally for single run fillet welds, where appearance is of primary importance. The covering melts with a pronounced cupped effect at the electrode tip, enabling the electrode to be used touching the work, this procedure being known as touch welding. The degree of penetration is low. A heavy solid slag is produced which is sometimes self-detaching, and in fillet welds, gives a smooth, concave weld metal has low carbon content and a particularly low manganese content. This type of electrode has been used with some success for the welding of certain high tensile steels and also steels having a higher content of sulphur than those used for structural welding, but on such steels the weld profile may be more irregular. Weld metal deposited by this type of elec-trodes usually has low mechanical properties, the reduction of area and Izod impact values being generally less than the values normally specified. The electrode is particularly suitable for use with AC and DC and may be used with the electrode connected to either pole.
Type 6: Electrode with covering having a high content of calcium carbonate and fluoride.
The covering of this electrode contains appreciable quantities of calcium carbonate and fluoride. The slag is fairly fluid and the deposit is usually convex to flat in profile. This class of electrode is generally suitable for welding in all positions. Electrodes of this class are also known as basic coated, and have the advantage of being particularly suitable for welding me-dium and high tensile structural steels and other applications, where high mechanical proper-ties and maximum resistance to cracking are required. They are also used for welding steels having higher carbon and sulphur contents than normal structural steels. During manufac-ture, these electrodes are baked at a high temperature and to obtain the best results they should be properly stored, and if necessary, thoroughly dried to the manufacturers recom-mendations before use. In welding with these electrodes, it is necessary to use a short arc and the correct electrode angle to achieve maximum soundness in the weld deposit. Properly used in this way, the electrode will produce welds to high radiographic acceptance standards. Most of the electrodes recently developed can be used with AC but with some types DC is preferred, in which case the electrode should be connected to the pole recommended by the manufac-turer. Coatings of this type are commonly used for electrodes dopositing high tensile and alloy weld metals.
Note: The addition of metal powder to any of the above types of covering may affect the charac-teristics described above.
4.5.5 American Coding System
AWS-A5.1 81 Specification for Carbon Steel Covered Arc Welding Electrodes The American Coding System starts with a prefix E which means an electrode. Then comes a two digit number 60 or 70 designating tensile strength in ksi (60 ksi or 70 ksi). The actual stipulated minimum tensile strength values and the associated yield strength values
vary according to the type of covering as given in Table 4.13. The impact strength require-ments are given in Table 4.14.
The third digit indicates the welding positions in which the electrode can be used satis-factorily, as follows:
1. F, H.V. OH 2. F, H-fillet
3. F, H, V-down, OH.
The last two digits together indicate current conditions and the type of covering. Table 4.15 gives complete classification and their significance.
Table 4.13. Strength and elongation requirements for all-weld-metal tension test in the as-weld condition (AWS.A-5.1)
AWS Min. tensile Min. yield Min. elongation
Code strength strength on L = 4d
Ksi MPa Ksi MPa %
E6010 62 430 50 340 22
E6011 62 430 50 340 22
E6012 67 460 55 380 17
E6013 67 460 55 380 17
E6020 62 430 50 340 22
E6022 67 460 Not required Not required
E6027 62 430 50 340 22
E7014 72 500 60 420 17
E7015 72 500 60 420 22
E7016 72 500 60 420 22
E7018 72 500 60 420 22
E7024 72 500 60 420 17
E7027 72 500 60 420 22
E7028 72 500 60 420 22
E7048 72 500 60 420 22
For each increase of 1% in elongation, the tensile strength or yield strength or both may decrease by 7 MPa to a minimum of 420 MPa for tensile strength and 330 MPa for yield strength for E60 series and to a minimum of 480 MPa for tensile and 400 MPa for yield strength for E70 series, except for E6012, E6013 tensile and yield strength may reduce to a minimum of 450 and 365 MPa respectively. Since E-6022 electrodes are for single-pass welding, the elongation and yield measurement is not necessary.
Table 4.14. Impact requirements as per AWS-A5.1 AWS classification CharpyV notch impact requirement, min E6010, E6011
E6027, E7015 27 J at 29°C
E7016, E7018*
E7027, E7048
E7028 27 J at 18°C
E6012, E6013
E6020, E6022 Not required
E6014, E7024
*Upon agreement between the supplier and the purchaser classified as E7018 may be supplied to a minimum Charpy-V notch impact requirement of 27 J at 46°C. Such electrodes shall be identified as E7018-1.
Table 4.15. Type of covering, welding position and type of current as per AWS-A5.1
AWS Welding Type of
classification Type of covering positions current**
E60 series electrodes
E6010 High cellulose sodium (C) F, V, OH, H D+ E6011 High cullulose potassium (C) F, V, OH, H D+, A E6012 High titania sodium (R) F, V, OH, H D, A E6013 High titania potassium (RR) F, V, OH, H D±, A
E6020 H-fillets D, A
E6022 High iron oxide (A) F D±, A
E6027 High iron oxide, iron powder (A) H-fillets, F D, A E70 series electrodes
E7014 Iron powder, titania (RR) F, V, OH, H D±, A
E7015 Low hydrogen sodium (B) F, V, OH, H D+
E7016 Low hydrogen potassium (B) F, V, OH, H D+, A E7018 Low hydrogen potassium F, V, OH, H D± , A
iron powder (B)
E7024 Iron powder, titania (RR) H-fillets, F D±, A E7027 High iron oxide, iron H-fillets, F D, A
powder (A)
E7028 Low hydrogen potassium,H-fillets, F D+, A iron powder (B)
E7048 Low hydrogen potassium F, OH, V, V-down D+, A iron powder (B)
*Letters in brackets indicate equivalent ISO 2560 symbols for types of covering.
** The standard refers to D + as reverse polarity and D as straight polarity and A as a.c.
Electrodes of the E6022 classification are for single-pass welds.
Chemical composition limits for weld-metal as per AWS-A5.1
For electrodes E6010, E6011, E6012, E6013, E6020, E6022, E6027, no specific chemi-cal limits are given.
AWS Chemical composition
classification Mn Si Ni Cr Mo V
E7018, E7027 1.6 0.75 0.3 0.2 0.3 0.08
E7014, E7015
E7016, E7024 1.25 0.9 0.3 0.2 0.3 0.08
E7028, E7048
Note: For obtaining above chemical composition dc en should be used.
The total of all elements for E7018, E7027 shall not exceed 1.75 except for silicon and in the case of other six electrodes it shall not exceed 1.5 except for silicon.
Apparently, ISO 2560 and the various national standards based on it have put forward a universal coding system, in which all possible electrodes could fit. The AWS standard has, on the other hand, considered the types which are in general industrial usage in the U.S.A. and then brought out a system to fit them.
AWS A5.1 has provided description of electrode classification in the Appendix. Follow-ing are the extracts:
AWS A5.1 has provided description of electrode classification in the Appendix. Follow-ing are the extracts: