MMAW Consumables

Manual metal arc welding has been used extensively in the shipbuilding, defence, offshore, and power-generation industries for the fabrication of carbon-manganese and low-alloy steels.

An extensive range of MMAW consumables is now available covering the joining requirements of the more important engineering materials as well as repair, surfacing, cutting and gouging electrodes.

Areas of development of MMAW consumables:

The main developments that have taken place in these consumables have been in the following areas:

  •  improved toughness;
  •  improved hydrogen-controlled electrodes for ferritic steel;
  •  improved performance stainless-steel consumables                   

Improved toughness:

Many structures, particularly in the offshore and cryogenic industries, are expected to operate at temperatures well below 0°C. Considerable improvements in weld metal toughness of ferritic materials at temperatures below –40°C have been obtained by control of electrode formulation and the addition of nickel.

Improved hydrogen control

  • Hydrogen-induced or hydrogen-assisted cold cracking (HICC or HACC) has been a significant problem with low-alloy and higher-carbon steels, particularly when thicker sections are welded.
  • Control of the hydrogen content of the weld metal may be used to avoid this problem and this control may in turn be improved by electrode formulation, storage and packing.
  • Particular attention has been given to limiting the re-absorption of moisture (the main source of hydrogen) by the electrode coating, which is achieved by careful selection of the coating constituents and special packaging.
  • Basic hydrogen controlled electrodes that will give weld metal hydrogen contents of less than 50 ml kg–1 with ambient conditions of 35 °C and 90% humidity for up to ten hours after opening the packaging are now available.

MMA electrodes for stainless steel:

  • The operating performance of common austenitic stainless steel MMA electrodes has been considerably improved by the introduction of rutile (TiO2) based flux coatings. These coatings give improved arc stability and excellent weld bead surface finish.
  • Electrodes have also been developed for the fabrication of the new corrosion-resistant alloys and, in particular, duplex and high molybdenum stainless steels.
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