Walk into any fabrication shop around Kurnool and you'll see peacock-blue argon cylinders next to the TIG sets, and CO₂ cylinders beside the MIG machines. Choosing the right shielding gas makes a real difference to weld quality, speed and cost. Here's a practical guide.
Why welding needs a shielding gas
Molten metal reacts with the oxygen, nitrogen and moisture in air. Without protection, welds come out porous (full of pinholes), brittle and discoloured. In TIG and MIG welding, a shielding gas flows out of the torch nozzle and blankets the arc and weld pool until the metal solidifies. (In stick or arc welding, the flux coating on the electrode does this job instead.)
TIG welding: use pure argon
For TIG (GTAW) welding of stainless steel, aluminium, copper and thin mild steel, pure argon is the standard choice. It's inert, gives a stable arc and protects the tungsten electrode.
- Never use CO₂ or argon–CO₂ mixes for TIG. They oxidise the tungsten and ruin the weld.
- For very thick aluminium or copper, some welders add helium to argon for extra heat. This is a specialist mix.
MIG welding: argon, CO₂ or a mix?
For MIG/MAG welding the answer depends on the metal:
| Metal | Common shielding gas | Notes |
|---|---|---|
| Mild steel | Pure CO₂ | Economical, good penetration, but more spatter and a rougher bead |
| Mild steel | Argon + CO₂ mix | Smoother arc, less spatter and cleanup, neater finish. Costs more per cylinder |
| Aluminium | Pure argon | CO₂ must not be used on aluminium |
| Stainless steel | Argon-based mixes | Ask about the right mix for your wire and job |
Many workshops doing gates, grills and structural work use pure CO₂ to keep costs down. Shops doing visible or finished work often switch to an argon–CO₂ mix, because the time saved on grinding spatter can outweigh the higher gas price.
What flow rate should I set?
More gas is not better. Too much flow causes turbulence that pulls air into the shield, and it wastes gas. As a starting point:
- TIG: typically around 8–15 litres per minute, depending on cup size and joint.
- MIG: typically around 12–20 litres per minute, depending on nozzle, wire size and current.
Increase flow a little when welding outdoors or near fans, or better, put up a screen to block the draught. Always follow your machine and wire manufacturer's recommendations.
Fixing porosity (pinholes) in your welds
If welds suddenly show porosity, check these in order:
- Draughts: fans, open doors and wind blow the shield away.
- Empty or low cylinder: check the gauge.
- Leaks: brush soapy water on the regulator, hose joints and torch connections and look for bubbles.
- Flow too low or too high.
- Dirty metal: oil, paint, rust and moisture on the joint.
- Clogged nozzle: spatter build-up disturbs gas flow.
Stop wasting shielding gas
- Close the cylinder valve at breaks and at the end of the day. A small leak overnight can empty a cylinder.
- Replace cracked hoses and worn fittings.
- Use a proper flowmeter-regulator and set the flow to what the job needs.
- Keep hoses short and neat. Long, looped hoses hold more gas that is wasted at each start.
Handling argon and CO₂ cylinders safely
Argon and CO₂ are not flammable, but both are heavier than air and can collect in pits, tanks and closed rooms, where they can cause suffocation. Keep your welding area ventilated, keep cylinders upright and chained, and keep CO₂ cylinders upright so liquid doesn't enter the regulator. Continuous CO₂ welding can freeze a regulator, which is why many shops use heated CO₂ regulators.
Buying argon and CO₂ in Kurnool
Parameswara Traders supplies argon gas, argon–CO₂ welding mix and CO₂ gas, with refilling, cylinders on deposit and delivery to workshops in Kurnool and nearby towns. We also stock regulators, flowmeters and welding electrodes. Call 094400 79857 or WhatsApp us with your cylinder size and quantity.