Shielded Metal Arc Welding Electrode Classification System

The classification system for SMAW electrodes is identical between AWS (American Welding Society) and ASME BPVC. In this article, we shall take reference from ASME BPVC Section II Part C for studying various electrode classification.

The SMAW electrodes are classified under the following specifications in ASME Section II Part C.

  1. SFA 5.1: specification for carbon steel electrodes for SMAW,
  2. SFA 5.3: specification for aluminum and aluminum-alloy electrodes for SMAW,
  3. SFA 5.4: specification for stainless steel electrodes for SMAW,
  4. SFA 5.5: specification for low alloy steel electrodes for SMAW.

The classification system for carbon steel electrodes and low alloy steel electrodes bears some similarity, but the systems for aluminum alloys and stainless steels is completely different. In this article, we shall see each of these in brief.

SMAW Electrodes for Stainless Steels

SMAW electrodes for welding of stainless steels have been classified in the SFA 5.4 specification of the ASME Section II Part C.

The classification system generally consists of a ‘E’ followed by three numbers, followed by a dash, and a ‘15’,’16’, ‘17’, or a ‘26’ following the dash. The letter E indicates that it is an ‘electrode’. That is, it carries current.

The next three numbers are generally 2 series (as in 209, 219, 240, etc.), or 3 series (as in 304, 308, 309, 316, 321, 347…and so on), or 4 series (as in 410, 430, etc.). This set of three numbers is indicative of the chemical composition of the undiluted weld metal deposited by that electrode.

Sometimes, 2 or 3 letters follow these three numbers. These letters indicate a modification of the standard composition, by adding an alloying element such as niobium, molybdenum, or extra low carbon, and so on. So, for example, if a ‘Nb’ appears here, it indicates that niobium has been added as an extra alloying element, over the standard composition.

The two numbers (15 or 16 …etc.) following the dash indicate the type of welding current and position of welding. The meaning of these two numbers is defined as follows:

SuffixType of current for which the electrode is suitableWelding positions in which the electrode can be used
-15DCEPALL
-16DCEP and ACALL
-17DCEP and ACALL
-26DCEP and ACF, H-fillet

SMAW electrodes for Carbon Steels and Low Alloy Steels

The ASME Section II Part C classifies carbon steel electrodes under SFA 5.1 and low alloy steel electrodes under SFA 5.5. The system of classification is similar, although not same.

The first letter E at the beginning indicates that it is an electrode (that is, it carries current). The next two numbers after the E indicate the tensile strength of the undiluted weld metal deposited with that electrode. For ‘70’ indicates a weld metal of UTS of 70000 psi (or 70 ksi); ‘80’ indicates a weld metal of UTS of 80000 psi (or 80 ksi), and so on.

The SFA 5.1 specification contains only E60XX and E70XX electrodes, since the strength of carbon steels normally does not exceed 70 ksi. The chemical composition specified for the electrodes in SFA 5.1 has a wide range so that all carbon steel electrodes can be accommodated within them.

The SFA 5.5 specification contains classifications up to E120XX. This accounts for the fact that the strength of low alloy steels can sometimes go up to 120 ksi (or 840 MPa!). The chemical composition of these electrodes has a far narrower range than those in SFA 5.1.

The next two digits indicate three things: the welding position in which the electrode can be used, type of covering on the electrode, and the welding current with which the electrode may be used. For example, a ‘18’ indicates low hydrogen potassium, iron powder rich covering on the electrode, the electrode can be used for welding in all positions, and the electrode is usable with both ac or dcep.

Following these two numbers, a dash generally appears.

After the dash, if a ‘1’ appears, it indicates that the electrode meets the requirements of improved toughness over the ordinary variety. This ‘1’ is only found in carbon steel electrodes classified under SFA 5.1, and is not found in SFA 5.5 electrodes.

In low alloy steel electrodes classified under SFA 5.5, a combination of a letter and a numerical generally appears after the dash. This combination of letter and number may read as A1, C3, B2, D3, and so on. It indicates the chemical composition of the undiluted weld metal deposited by that electrode. For example, A1 indicates that the electrode is principally a carbon-molybdenum electrode; B followed by a number indicates that it is a chromium-molybdenum electrode; and so on.

After the dash, if a combination of letter and numerical in the form of HX appears (where X may be 2 or 4 or 8 or 16), it indicates that the electrode is a low hydrogen electrode. The weld metal deposited by this electrode would have no more than X grams of hydrogen per 100 ml of weld metal.

If a ‘R’ appears after the dash, it indicates that the electrode meets the requirements of absorbed moisture test.

SMAW electrodes for Aluminum and Aluminum Alloys

 The SMAW electrodes for aluminum and aluminum alloys are classified under SFA 5.3 of ASME Section II Part C. The system of classification is based on the chemical composition of the core wire and mechanical properties of the groove weld.

There are only three classifications present in this specification. These are E1100, E3003, and E4043.

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