FLUX CORED ARC WELDING (FCAW):
FCAW welding was developed way back in mid 20th century. Indeed, the history of welding has always been the testimony of pursuits for joining with greater speed & efficiency to overcome the restrictions related to SMAW/MMAW welding process.
FCAW continuous electrode wire holds the flux-ingredients inside the folded metallic sheath or seamless tube and finally the flux set at the core unlike SMAW/MMAW electrodes covered from out side. Thus the flux-containing wires are recognized traditionally as Flux Cored Arc Welding electrodes, which are fed mechanically through a semi, fully-mechanized or automatic welding gun to establish an arc between the tip of wire electrode and the substrate. Intense arc energy melts the electrode tip & the base metal expeditiously to produce a sound weld deposit. The flux concealed inside the core performs all the functions essentially the same, as for flux covered electrodes.
Initially the large size, as 3.2 mm diameter, self-shielded flux-cored wire electrodes were manufactured and used in down hand predominantly for an overlaying or surfacing applications. The application of FCAW process has expanded noticeably by the end of 20th century, only, after the development of smaller size, as 1.2 mm diameter, CO2 or Ar+CO2 gas-shielded type wires with considerable reduction in spatters & fumes (>30%) with trouble-free slag removal as compared to the conventional self-shielded wires; which is the prime concern for the work environment and the rest being the necessities of quality, productivity and doing out-of-position welding with an ease by compensating the welder's lack of skill. Now, the use of FCAW process has increased rapidly year by year in fabrication of pressure vessels, marine and heavy-construction industries except in automotive & sheet metal fabrication.
This remarkable shift in welding industry has only been achieved after the introduction of non-copper coated, low cost flux-cored wire electrodes of folded type. These types of electrodes offer the benefits of manufacturing with an ease without the application of flux-ingredients, which are free from organic & hydrated minerals. They are customarily used in manufacturing seamless type FCAW electrode wires by filling the fine agglomerated flux inside the tubes and baked thereafter to remove moisture to reduce the diffusible hydrogen content into the weld deposit. Now the well accepted trend is emerging worldwide to manufacture folded type FCAW electrode wires, where the pulverized dry-flux-ingredients of extra fine textures are added on line straight to the U-shaped folded strip and thereafter concealed inside by folding for further drawing operation to bring to a very small size diameterof 1.6 mm or 1.2 mm continuous wire electrodes with an absolute freedom from the moisture & flux-less patches, which are highly detrimental for the quality of welding. FCAW electrodes are readily available for the purpose of hard-surfacing & welding of commonly used - structural steels, high strength C-Mn steels, low alloy Cr-Mo steels and micro alloyed high to very high strength steels ranging from a minimum 390MPa to 680MPa yield strength.
All types of FCAW electrodes are classified alike under the AWS/ASME specifications i.e. A/SFA- 5.20M for carbon steel and A/SFA-5.29M for low alloy steel welding meeting the required chemical analysis, mechanical & metallurgical properties of the weld.
Ref. - AWS/ASME: A/SFA- 5.20M for carbon steel welding:
Brand/Trade name AWS Class Brand/Trade name AWS Class
AUTOMIG FC 70-T2 E70T-2 AUTOMIG FC 71T-1 E71T-1
AUTOMIG FC 71T-1 E71T-1 AUTOMIG FC 71T-5 E71T-5CH4
[MOD]
Ref. - AWS/ASME: A/SFA-5.29M for low alloy steel welding:
Brand/Trade name AWS Class Brand/Trade name AWS Class
AUTOMIG FC 71T-5A1 E71T-5A1C AUTOMIG FC 80T-1G E80T-1GC
AUTOMIG FC 80T-5G E80T-5GC AUTOMIG FC 81T-1B2bb E81T-1B2C
AUTOMIG FC 90T-5K2 E90T-5K2C AUTOMIG FC 91T-1B3 E91T-1B3C
AUTOMIG FC 110T-5K4 E110T-5K4C
Exclusive Hard Facing Product of Ador Welding Limited:
Brand/Trade name Hardness* Brand/Trade name Hardness*
(after 3-layers) (after 3-layers)
AUTOMIG FC 510 275-325BHN AUTOMIG FC 520 310-375BHN
AUTOMIG FC 540 375-425BHN AUTOMIG FC 560 450-500BHN
AUTOMIG FC 580 550-600BHN
*as welded condition hardness.
High deposition rate up to 10 kg/hr arc time, metal recovery of up to 85%, operating arc time factor of 45 to 70% (for semi/fully-mechanized FCAW) enable this process as a boon for the fabricators to stand against intensified global stipulate for the quality & competitiveness of their fabricated product. Above all the process has also been deemed as pre-qualifiedWPS by the structural welding codes AWS D-1.1, which requires only the qualification of welders or operators but not the qualification of time consuming & extensive exercise of welding procedure qualification by the codes.
KEY PROCESS VARIABLES OF FCAW:
Brand/Trade Name - As per the guide lines of the Federal Emergency Management Agency, FEMA 353, it is an essential variable.
Electrode Diameter - As above (FEMA 353), to be used as supplemental recommendation for structural fabrication & erection subject to seismic loading.
Electrode Wire Class/Type.
Electrode extension.
Welding current & Wire feed rate.
Arc voltage.
Travel speed.
Electrode angles.
Shielding gas type & flow rate.
For further details.......
cmo@adorians.com
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