CEMP-E
TI 809-26
1 March 2000
When SMAW low hydrogen electrodes are used, the required levels of preheat are lower, offering
economic and time-saving advantages to the contractor. AWS D1.1 and the AWS A5 filler metal
specifications do not currently define "low hydrogen." International Institute of Welding (IIW) documents
classify electrodes for diffusible hydrogen as follows: very low hydrogen (0-5 mL / 100 g deposited weld
metal), low hydrogen (5-10), medium hydrogen (10-15), and high hydrogen (15-20), but these definitions
are unrelated to AWS usage and specifications.
(4) SMAW electrodes are classified based on a four or five digit number that follows the letter E
(for electrode). The electrode classification is imprinted on the coating near the end of the electrode, as
well as on the electrode package. See Table C-1. In filler metal specification AWS A5.1, low hydrogen
carbon steel SMAW electrodes are identified with the last "X" number in the designator EXXXX as a 5, 6
or 8. A5.1 SMAW low hydrogen electrode classifications include E7015, E7016, E7018, E7018M, E7028,
and E7048. The E7015 electrodes operate using DCEP only. E7016 electrodes operate using either AC
or DCEP. The E7018 electrodes operate using AC or DCEP, and include approximately 25% iron powder
in their coatings to increase their deposition rate. An E7028 electrode contains approximately 50% iron
powder in the coating, enabling it to deposit metal at even higher rates. However, as the nomenclature
shows, the "2" would indicate that this electrode is suitable for flat position welding and, for fillet welds
only, the horizontal position. E7018M electrodes may be used only with DCEP, and have been tested for
absorbed moisture and diffusible hydrogen. E7048 electrodes are similar to E7018 electrodes in
composition, and may be used in any position, AC or DCEP, except for vertical welding in the upward
progression. E7048 electrodes are specifically designed for good welding in the vertical downward
progression.
(5) In the AWS A5.5 low-alloy steel SMAW electrode specification, a similar format is used to
identify SMAW electrodes. See Table C-2. The most significant difference in nomenclature from A5.1 is
the inclusion of a suffix letter and number indicating the alloy content. As an example, an E8018-C3
nickel steel electrode, with suffix "-C3", indicates the electrode nominally contains 1% nickel. A "-C1"
electrode nominally contains 2.5% nickel. Some electrodes carry the "-W" designation, indicating the
presence of alloys capable of giving the weld atmospheric corrosion resistance for exposed weathering
applications. Low hydrogen low-alloy SMAW electrodes are similarly identified with the last "X" number in
the designator EXXXX-Y as a 5, 6 or 8.
(6) Optional supplemental designators may be used to indicate the maximum level of hydrogen
that may be present in the test weld deposit. These designators are a part of the standard AWS
classification system and consist of the letter H followed by a single or double digit. For example "E7018-
H8" indicates that the deposit contains a maximum diffusible hydrogen content of 8 mL per 100 g of
deposited weld metal. Most standard low hydrogen electrodes must deposit weld metal with a maximum
of 16 mL per 100 g of diffusible hydrogen under test conditions. However, manufacturers may optionally
list an H8 or H4 designation if their particular SMAW electrodes are capable of delivering these extra low
levels of diffusible hydrogen.
(7) While "low-hydrogen" electrodes are required by AWS D1.1 for welding on structural steels with
minimum specified yield strength of 485 MPa (50 ksi) or greater, extra-low hydrogen levels should not be
specified unless necessary. There is generally a cost premium associated with the lower diffusible
hydrogen electrodes. Also, high notch toughness weld metal from electrodes with good operating
characteristics may not be available with the lowest hydrogen designations, and some electrodes with
very low diffusible hydrogen levels may have poor notch toughness.
(8) All low hydrogen electrodes listed in AWS A5.1 have minimum specified notch toughnesses of
C-2
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