Posted to News on 27th May 2021, 08:58
MMA electrode upgrade for critical offshore applications
Improved low hydrogen version brings fresh gains
MMA application welding in action.
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.
Strength and impact
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% 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.”
