OK 73.15 low hydrogen MMA electrodes improved for critical offshore applicatons
June 29, 2021
ESAB has introduced an improved version of its OK 73.15 low hydrogen MMA electrode that provides improved weldability, better moisture resistance and low temperature toughness. OK 73.15 is now classified to AWS E8018-C3 H4R, where previously it was classified as AWS 8018-G H4R. This change of classification provides better definition of the weld metal chemistry. It is used for welding high strength steels in critical offshore, bridge, pressure vessels and other structural steel applications.
The C3 designation indicates a weld metal alloyed with 1% Ni. The addition of Ni, in combination with small amounts of Cr, Mo and Mn, provides OK 73.15 with low-temperature impact strength and makes the weld metal more resistant to cracking. C3 electrodes are permitted to be tested in the as-welded condition for classification purposes. Typical as-welded properties for OK 73.15 include a yield strength of 550 MPa, a tensile strength of 600 MPa and an impact value of 70 J at -50 °C. For applications that require stress relief, OK 73.15 may also undergo post-weld heat treatment (PWHT) at 620 °C and retain similar values.
The H4R designation indicates less than 4 ml of diffusible hydrogen per 100 g of deposited weld. Designed for moisture resistances, H4R electrodes also have less than 0.4 percent moisture absorption after 9 hours of exposure at 27 °C and 80% humidity. OK 73.15 is HIC (hydrogen-induced cracking) test compliant as per NACE TM0284 and SSC (sulfide stress cracking) test compliant as per NACE TM0177.
OK 73.15 is available in six different sizes 2.5, 3.2 and 4.0 x 350 mm and 3.2, 4.0 and 5.0 x 450 mm and comes in ESAB’s VacPac™ vacuum-sealed packages. The improved electrode provides excellent weld pool control, minimal spatter level, a good arc strike and easy slag removal.
“OK 73.15 expands ESAB’s line of low moisture absorption (LMA) EXX18 H4R electrodes for all-position welding in high strength steel applications,” says Jean-Philippe Ernoult, Global Product Manager Non- and Low-Alloyed Electrodes. “These structures operate in harsh environments and weld integrity is crucial for safety and longevity. ESAB designs its electrodes and packaging to specifically meet these demands.”
Packaged for Freshness
VacPac features a laminated, multi-layer aluminium foil that is hermetically sealed around a strong plastic inner box. Protected by a cardboard outer box, they do not require special warehouse conditions, provided they are handled with care and the foil is not damaged. Upon opening, fresh and dry electrodes are guaranteed when the vacuum is confirmed.
“Depending on the diameter, the VacPac contains 0.8 - 2.3 kg of electrodes because the average welder in an industrial operation consumes 2 kg of electrodes per shift,” says Ernoult. “VacPac reduces or eliminates the need to scrap unused electrodes at the end of the day or re-bake them in an electrode oven. VacPac packages are also much easier for operators to carry.”
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ESAB OK 73.15 now meet AWS E8018-C3 H4R classification. As-welded properties include a yield strength of 550 MPa, a tensile strength of 600 MPa and an impact value of 70 J at -50 °C.