Shielding Gas & Gas Supply
From cylinder pressure to a clean weld — regulator, flowmeter, and the right gas
AI generated The displaces air from the weld pool — without it, every weld bead gets pores and . To make sure the gas arrives clean and constant, you need a well-thought-out chain: cylinder, regulator, flowmeter, solenoid valve, and nozzle.
The has a single job, but a crucial one: it keeps oxygen, nitrogen, and moisture away from the glowing weld pool. Without this invisible shield, the pool oxidizes immediately, picks up nitrogen, and the weld bead gets pores and . That's why the gas supply is the backbone of every process.
The chain from the cylinder contents to the nozzle:
• Cylinder: The gas is under high pressure (often 200 bar). The cylinder pressure is way too high for the torch.
• : It reduces the cylinder pressure to a low, constant working pressure. Without it, the flowmeter wouldn't withstand the pressure.
• : It sets the gas amount in liters per minute — the actual control variable for the gas shield.
• Solenoid valve: It opens and closes the gas automatically with the welding current, so no gas escapes unused.
• Hose package & nozzle: Carry the gas to the welding spot.
Two times are especially important:
• Pre-flow time: The gas flows for a short moment before the ignites — so the shield is already in place when it gets hot.
• : The gas continues to flow after the arc goes out to protect the hot electrode and the solidifying weld bead from heat tint.
For the gas itself, the basic rule is: Inert or active. Inert gases like (and helium) don't react with the molten metal — for TIG, MIG, and stainless steel. Active gases like or argon-CO₂ react in a controlled way with the pool — for MAG on mild steel.
The flow rate depends on nozzle size and process — typically 5–10 l/min for TIG, 12–18 l/min for MAG. Too little gas lets air reach the pool (porosity), too much creates turbulence and pulls in ambient air — so it can also do harm.
For practice: Check the chain regularly. A leaking hose, too high a flow rate, or a clogged nozzle will wreck the gas shield faster than you can look.