GTAW welding on SS

GTAW Welding on Stainless Steel

GTAW Welding on Stainless steel – SS

GTAW welding on SS

  • Produces very strong/tough weld compared to other process
  • Slow process
  • Good appearance
  • Mostly used for Root and hot pass & Low thickness material
  • Low heat input process
  • More controlled process, but requires good welder skills .
  • Electrode – Tungsten Rod (most common is 2% thoriated)

GTAW welding on SS

  • AWS Filler Specification : AWS A5.9
  • Example: ER 209, ER308Si, ER309L, ER316L, ER410
  • For CS to SS welding use any of ER 309, ER309LSi, ER 310, ER312
  • Use proper purging for Butt weld , where root side is open on the other side before welding .

GMAW / FCAW Welding on Stainless Steel

  • High speed, high deposition rate.
  • Suitable for Thick materials , better look than SMAW
  • AWS Specification :
    • AWS A5.9 – Solid wire
    • AWS A5.20- Flux Cored wire
    • AWS A5.22 – Metal Cored wire

Shielding Gas for GMAW-Solid Wire:

  • Normally shielding gases like Pure Argon are used .Ar+ 1-2% O2. Ar+ 1-2% CO2 and Ar+18-33% He+1-2% CO2 are good choices for spray transfer mode of solid wire.
  • However 90% He+7.5% Ar+2.5% CO2 (the most popular one)
  • Ar+2% O2 and Ar+25% CO2 are used in short circuiting transfer mode.

Shielding Gas for GMAW-Metal Cored Wire:

  • shielding gases like Ar+1-2% O2 and Ar+1-2% CO2 are good choices for spray transfer mode of Metal Cored Wire.

FCAW : CO2 or Ar + CO2

Pickling

  •      Process of removing the oxide layers form the surface
    • Due to heat , burnt – oxide layers are visible on the weld and HAZ areas
    • Where the chromium level has been reduced on the surface .
    • Pickling Solution : hydrochloric acid and sulfuric acid .

Welding on SS

Passivation 

  • Passivation is the process of creating the passive chromium oxide layer over the surface.
  • The passive oxide layer is essential to prevent corrosion ,
  • Passivation Solution : generally Nitric acid
  • Nitric Acid is a solution which dissolves all iron components and trace material , and also it is a strong oxidizing unit to make the chromium oxide layer
  • Nowadays Pickling gel or Solution does both Pickling and Passivation simultaneously.
  • Pickling gel may be mixture of Nitric acid, Sulfuric acid, Phosphoric acid & hydrofluoric acid.

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