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After reading this article you will learn about the classification and coding of electrodes.

Classification and Coding of Covered (Heavy Coated) Electrodes:

Electrodes for Carbon and Carbon-Manganese Structural Steels (IS 814: 1991):

Basis for Coding:

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Pure Tungsten: Color Code – Green. AWS Classification – EWP. 99.50% Tungsten. These electrodes produce welds that are typically stronger than welds made with carbon steel electrodes, and have minimum tensile strengths of 80 to 120 ksi (550 – 827 MPa). Their electrode classification numbers are similar to carbon steel electrodes, including similar (but less) usability designation classifications.

(i) A prefix letter,

Carbon steel electrode classification definition

(ii) Letter(s) to denote the type of covering.

(iii) A code number of four digits,

(iv) In some cases a suffix, consisting of one or more letters, to indicate special characteristic(s).

(i) Prefix Letter:

E is used as the prefix letter to indicate a covered electrode for shielded metal arc welding manufactured by extrusion process.

(ii) Letter(s) to Denote Type of Covering:

Types of coverings shall be indicated by the following letters:

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A – Acidic Covering

B – Basic Covering

C – Cellulosic Covering

R – Rutile Covering

RR – Rutile Covering-heavy coated

S – Any other type not mentioned above

(iii) Code Number:

The first two digits give the mechanical properties of the weld metal deposit and last two digits give the performance characteristics of the coverings.

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(A) Mechanical Properties of Weld Metal Deposit:

First digit—indicates ultimate tensile strength in combination with yield strength of the deposited weld metal.

Second digit—indicates the percentage elongation in combination with impact values of the weld metal deposited.

(B) Performance Characteristics:

Third digit—Welding position(s) in which the electrode may be used.

Fourth digit—Current and voltage conditions in which the electrode is to be used.

(iv) Suffix Letter(s):

H1 — hydrogen controlled electrodes with diffusible hydrogen up to 15 M1/100 g of weld metal deposited,

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H2 — hydrogen controlled electrodes with diffusible hydrogen up to 10 M1/100 g of weld metal deposited,

H3 — hydrogen controlled electrodes with diffusible hydrogen up to 5nil/100 g of weld metal deposited,

J — iron powder covering giving a metal recovery of 110—129%,

K — iron powder covering giving a metal recovery of 130—149%,

L — iron powder covering giving a metal recovery of 150% and above.

X — radiographic quality weld.

Detailed description of each digit follows:

(A) Mechanical Properties of Weld Metal Deposited:

First Digit:

Two ranges of tensile strength i.e., 410—510 N/mm2 and 510—610 N/mm2 with corresponding yield strength of 330 N/mm2 and 360 N/mm shall be indicated by the first digit being 4 and 5 respectively.

Second Digit:

The combination of percentage elongation and impact properties of all weld metal deposit for the two tensile ranges shall be as given in Table 5.2.

Example 1:

Explain the meaning, as per BIS, of carbon and car­bon-manganese structural steels arc welding code ER 4317 H1 JX.

Solution:

E — Core wire for electrode is manufactured by extrusion process and is suitable for SMAW i.e. manual metal arc welding,

R — electrode covering contains a large quantity of rutile or com­ponents derived from titanium dioxide,

4 — the range of tensile strength of deposited weld metal is 410- 510 N/mm2 with minimum yield strength of 330 N/mm2,

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3 — the minimum percentage elongation in tensile test of deposited weld metal should be 24% in a gauge length of 5.65 √s and the minimum impact strength of deposited weld metal is 47 J at – 20°C,

1 — the electrode is suitable for use in all welding positions viz., F, V, D, O,

7 — welding current conditions are D±, A 90i.e. if used with direct current then any polarity can be used and if employed for use with ac the minimum OCV should be 90 volts,

H1 —it is hydrogen controlled electrode with diffusible hydrogen up to 15 ml/100 g of deposited weld metal,

J — covering contains iron powder to give a metal recovery rate of 110—129%,

X — the deposited weld metal will be of radiographic quality.

Classification and Coding of Electrodes for SMAW/MMAW of Low and Medium Alloy Steels:

This standard deals with specification of coated/covered electrodes for shielded metal arc welding (SMAW) or manual metal arc welding (MMAW) of a wide variety that includes C-Mo, Cr-Mo, Ni. Mn-Mo and other miscellaneous alloy steels with chemical composition of all weld metal as given in Table 5.2 (A).

In this standard the electrode characteristics are indicated by rather a complex combination of letters and digits and consists of seven parts as detailed below:

Part One:

Prefix letter E indicates the suitability of the electrodes 01 SMAW/MMAW.

Part Two:

Minimum tensile properties of the weld metal are indi­cated by two digits as follows:

Part Three (Type of Flux Covering):

The type of flux covering is indicated by a letter symbol as follows:

Part Four (Chemical Composition):

The electrodes are divided into six groups A, B, C, D, G and M followed by a digit and/or a digit and a letter L (in case where low carbon deposits are required) to indicate the chemical composition group and sub-groups as shown in Table 5.2 (A).

Part Five (Welding Position):

This fifth part of the classification system comprises a one digit code indicating the different positions of weld­ing in which the electrode can be used.

Part Six (Current and Voltage Characteristics):

The sixth part is a symbol for the welding characteristics of the electrodes. Thus, the welding current and open circuit voltage (OCV) are symbolised by a digit as given below corresponding to the characteristics of the welding power source (P.S.) required in order to ensure working conditions free of arc instability or inter­ruptions.

Steel

Note:

Electrode polarity given above for d.c. are reversed and the electrode is used exclusively on d.c.

The OCV necessary for initiation and maintenance of arc when electrodes are used on d.c. is dependent on the dynamic characteristics of the welding power source. Consequently no indication of minimum OCV for d.c. power source can be given.

The frequency of the a.c. is assumed to be 50 or 60 Hz (Hertz).

The OCV necessary for striking the arc varies according to the diameter of the electrode used. A reference diameter is required for standardisation. The current conditions given above apply to electrode diameters greater than or equal to 2.5 mm.

Part Seven (Metal Recovery Rate):

The following suffixes are used to indicate the use of iron powder in the coating/covering and the extent of metal recovery with reference to tine weight of the core wire:

Fe — Iron powder in the covering/coating to give a metal recovery of minimum 110%.

J — Iron powder in the covering/coating to give a metal recovery of 110 to 130%.

K — Iron powder in the covering/coating to give a metal recovery of 130 to 150%.

L — Iron powder in the covering to give a metal recovery of over 150%.

Example 2:

Explain the meanings of E55RB2L23Fe as per BIS specification for Low and Medium Alloy Steel Covered Electrodes for SMAW.

Solution:

E — Electrode is suitable for SMAW/MMAW

55 — Minimum tensile strength 550 MPa

R — Rutile medium coated electrode

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B2L — Weld metal chemistry as given in Table 5.2 (A), i.e.

C = 0.05%. Mn = 0.35% (min.), P = 0.30%, S = 0.030%,

Si = 0.45%, Cr = 1.00- 1.50%, Mo = 0.40 – 0.65%

Carbon Steel Electrode Classification Calculator

2 — All positions of welding except vertical down

Carbon Steel Electrode Classification Calculator

3 — Current conditions required are d.c.e.p. or a. c. with OCV of 50 volts.

Fe — Covering/coating to contain iron powder to the extent as to give metal recovery rate of a minimum of 110%.

Carbon Steel Electrode

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