WELDING ELECTRODES SPECIFICATION SYTEMS

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 Fur 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 430—510 MPa or 510—610 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 oper­ates 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

designation

Tensile strength MPa

Min. elongation on L = 5 d

%

Temp. for minimum impact value of 28 J °C

E 430

434—510

E431

434—510

20

+ 20

E432

434—510

22

0

E433

434—510

24

— 20

E434

434—510

24

— 30

E435

434—510

24

— 40

E510

510—610

E511

510—610

18

+ 20

E512

510—610

18

0

E513

510—610

20

— 20

E514

510—610

20

— 30

E515

510—610

20

— 40

Tolerance + 40 MPa, 1 J = 0.102 Kgf. m.

Table 4.5. Symbols for electrical characteristics in ISO-2560

Symbol

Electrode polarity with direct current

Nominal O. C.V. with 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

2 1

(H)

E 51 3B 160

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 IS0-2560

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).

E 51 32 B 150 1 2 (H)

impact values (Table 4.7)

Example (b)

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

430—550

360

330

E51

510—650

380

360

Table 4.7. First and Second digits elongation and impact strength

First

Digit

Min. elongation % L = 5D

Temp. for impact value of 28 J (°C)

Second

Digit

Min. elongation % L = 5D

Impact prop.

E43

E51

E43

E51

Impact value J

Temp.

°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 tempera­ture for second digit if “5” = — 40°C and 6 as second digit does not exist.

Оставить комментарий