Changed gas, something is wrong

[Tatey]

I recently changed from straight CO2 to argon mix (my workmate has given me his virtually full bottle + regulator). When I was welding with CO2 I had no issues, I would get a slight brown residue around welds but I had read that this was ok when welding with CO2. However since changing to argon mix my welds have a massive brown patch around them, I've never seen it happen before so I am wondering what might have gone wrong. Here are some pictures:





I have tried playing with the gas rates, ranging from barely any to way to much, but nothing seems to solve it. The welding wire is the same stuff i've been using with CO2 and its always been fine, it is still bright and has no rust. The shroud is clean so isnt restricting gas flow and the welds look fine other than for the brown mess left around them.

Does anyone have any ideas of why this is happening and how to stop it?

I thought it could be the gas is not actually argon mix but my workmate has welded with it and said it has always been fine for him.

Try cleaning the steel up first, ideally no surface rust.

[alga]

I think I've read somewhere that excessive brown residue indicates insufficient flow of shielding gas. But since you've tried more gas, *shrug*.

[shaun]

Not sure if I'm correct but, I seem to remember getting this brown residue when I was holding the nozzle a bit far away from the material. Hope it makes sense.

[Tatey]

I thought it may have been that as its been a month or 2 since i last welded so i got the shroud very close to the work but no joy. The mig welding forum has suggested it is due to a lack of welding gas, and it is possible that the valve in the torch is partially blocked causing the gas shortage. I have another valve at home in newcastle which ill be trying out on sunday, so hopefully that will be the problem solved.

[Tatey]

Thanks for the info Talon. I took the welder apart last night to try and find out where the blockage was. First of all I tested the pressure of the gas from the reg feed tube against my cheek. Then took the torch apart and tested the torch feed (pre valve) against my cheek, this was pretty much the same. Then I tested it with the just the valve on and low and behold there is a massive difference, so much so you can barely feel it. I tried using a faulty valve to see if that would make any difference (it leaks as the valve wont shut properly) but that seemed to give out the same feed rate.

So I either have 2 blocked valves, or the valves are fine and it is giving me the flow rate I need. I will test my welder with a valve I have in a spare torch at home and see if that is any better. If it is not then I will buy a peashooter flow tester to see what flow is coming out before the welder and after to see if I can find the problem. I also have a complete torch/hose setup at home so I will try that out as well to see if that improves it.

[CaptainCrash1971]

Try holding an empty polythene bag over the nozzle and depress the trigger. It should fill the bag with gas. You should be able to work out flow rate by timing how long it takes to fill a bag, then working out how much the bag will hold. e.g. a large food bag might hold 5 litres, if it fills in 30 seconds you flow rate will be 10 l/min. I know it's not very accurate and a but primitive, but you will get a rough idea of your flow rate.
You can measure the volume of the bag by filling with water from a jug.
Obviously you'll need to squeeze the air out of the bag first, and hold it tightly around the nozzle.
Hope this helps

[Tatey]

Brilliant idea, I'll be trying that out tonight! I'll let you kno how it goes.

[alga]

Oooh, excellent, simple and effective idea with the bag!