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Welding/Gas flow rate on mig welder


Lord wrote at 2007-11-28 14:24:30
Sorry to argue but shielding gas FLOW is not measured in PSI.  PSI is set at the factory and is regulated by the machine internally.  PSI is used to measure pressure not flow, two very different things.

Flow rates differ for different types of electrodes, (wire) weld process and weld transfers.  I will assume for the moment that you will be using GMAW, gas metal arc welding, using solid wire E70S-X.  I will also assume you are using the short circuit transfer method as this is the most common transfer used by homeowners.

For this type of welding with an electrode diameter od .035 your shielding gas flow rate, measured in CFH (cubic feet per hour) should be set between 25 - 30 CFH.  Gas flow is not affected by wind, drafts etc although the gas can be blown away resulting in porosity.  Turning up your flow rate will not combat a windy situation, it will however help to pull atmospheric gasses into your weld pool resulting in a poor quiality weld.  If you are experiencing windy conditions, shut the door.

Bryce wrote at 2008-06-24 17:25:07
Shielding gas flow rate is not measured in PSI (pounds per square inch) It is measured in volume per time such as CFH (cubic feet per hour)

Rick wrote at 2009-04-12 16:45:32
It depends on the type of regulator and the type of shielding gas used. For a typical gmaw or mig welding with an argon/co2 mixture, flow rate is 25-45cfh. For full co2 mixture, flow rate is 15-30cfh. the low range for indoors and the higher range for draft or cross ventilation.

Nate (CWI) wrote at 2010-03-23 15:08:21
There are several factors that determine proper gas flow rate, which is measured in cubic feet per hour (CFH) not PSI.  For the typical at home hobbyist 20 CFH may be sufficient, but in an automated factory setting with high travel speed, high depostion mig welding 40 CFH is the norm.  

Charlie wrote at 2010-08-04 19:39:05
Welding gas flow is measured in CFH not PSI. The numbers here are approximately correct however they should be CFH.

SpringHollow wrote at 2011-09-23 10:41:41
The answer says psi which is a pressure but really should be CFH (cubic feet per hour) which is a flow rate.

Randall Ireland wrote at 2012-12-15 09:30:10
The shield gas required should be measured in CFH.

The actual rate required for MIG welding depends on the cross section area of inside diameter of the nozzle.

Consider that the cross section area of the nozzle opening is calculated: 3.14 x the radius squared.

If a 1/2" nozzle opening is flowing 24 cfh, a 5/8" nozzle opening would have to flow 44% more or about 34.6 cfh to maintain the same gas velocity. Likewise a 3/4" nozzle opening would require about twice as much gas as the 1/2" nozzle.

I'm most familiar with robotic welding where the weld size is very consistent and the welding parameters are known and tightly controlled.

The nozzle size should be matched to the size of the weld, wire stickout and maximum weld voltages used.

Shield gas flow rates used in the examples below are for for mig welding steel using 10% to 18% CO2,/Argon.

Typically a short arc weld where the arc voltage is less then 24 VDC, wire stickout is about 1/2" and the weld bead is less then 3/8" wide can use a nozzle with a 1/2" inside diameter and a gas flow rate if 20 to 25 CFH. Pulsed mig, globular, or spray transfer welds where peak voltages are below 33 VDC, wires stickouts are 5/8" to 3/4" and weld beads are less then 1/2" wide use a 5/8" ID nozzle and a flow rate of about 35 CFH. For larger welds using a 3/4" nozzle, use flow rates of 40 to 50 CFH.

Higher flow rates are required for gas mixes containing Helium.  


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Bill C.


I can answer questions regarding welding techniques, equipment, safety etc. I am especially familiar with MIG and Oxy-Acetelene set-ups, as well as plasma cutters. I can also answer questions regarding general metal working techniques. I am not very familiar with industrial and automated welding, ask at your own risk


I worked as an aluminum welder building pontoon boats and aftermarket jeep bodies and now run a small part time welding business as well as do a lot of metalworking and welding as a hobby.

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