13 replies to this topic

[venkman]

Does anyone think it's worth while getting a "Adams gas/hobbyweld" gas bottles. After first buy their £16 extra to what I can get co2 for. Do you get a lot better weld than with co2, just got another mini and wondering if it would look better.
My other minis been on road for 4 years and passed MOTs fine,I ask each time to check welds and he keeps saying "there not the prettiest but their not cracking coming apart so don't worry" so stick to co2 or choose one of the others???

Thanks Ian

[sonikk4]

You do get a better finish with Argon CO2 mix, but the actual weld itself is down to you. Power and wire speed plus cleanliness of the area being welded play very major parts in producing a clean strong weld.

[ACDodd]

Look for 200 bar cylinders some of the suppliers only do 137 bar in the smaller 9/10litre bottles. The best option for restoration project with mig gas is to go for a 20 litre cylinder at 200 bar fill. Argon co2 mix is much better than co2. Go for 5% mix for car panel work. I use sgs gasses via Motorparts. Quality cylinders.

Ac

Edited by ACDodd, 10 August 2016 - 04:28 PM.

[venkman]

Look for 200 bar cylinders some of the suppliers only do 137 bar in the smaller 9/10litre bottles. The best option for restoration project with mig gas is to go for a 20 litre cylinder at 200 bar fill. Argon co2 mix is much better than co2. Go for 5% mix for car panel work. I use sgs gasses via Motorparts. Quality cylinders.
Ac

What difference would the pressure make?

Thanks both for replying.

[dyshipfakta]

Look for 200 bar cylinders some of the suppliers only do 137 bar in the smaller 9/10litre bottles. The best option for restoration project with mig gas is to go for a 20 litre cylinder at 200 bar fill. Argon co2 mix is much better than co2. Go for 5% mix for car panel work. I use sgs gasses via Motorparts. Quality cylinders.
Ac

What difference would the pressure make?

Thanks both for replying.

Much better value for money so last longer and give you a better "shroud" for longer.

[venkman]

Ah ok thanks for that will look into it. Did notice it worked out a bit cheaper than 2 bottles!

[ACDodd]

Higher the pressure the more gas. 20litre cylinder at 200bar is 4000litre of gas.

10litre at 137 bar is only 1370litres. Its important to know the amount of gas inside. Value for money.

I have just replaced my BOC oxygen cylinder, with a rent free option. For the amount I use I needed the 30litre cylinder for it to become cost effective.

Ac

Edited by ACDodd, 10 August 2016 - 08:01 PM.

[venkman]

Higher the pressure the more gas. 20litre cylinder at 200bar is 4000litre of gas.
10litre at 137 bar is only 1370litres. Its important to know the amount of gas inside. Value for money.
I have just replaced my BOC oxygen cylinder, with a rent free option. For the amount I use I needed the 30litre cylinder for it to become cost effective.
Ac

Well that does work out cheaper!!

One last thing if you don't mind ,now I have people's attention, what sort of pressure should be used when welding?

Thanks again Ian

[ACDodd]

Usually 10litres/min while welding. That's means, pull the trigger, then adjust the regulator to give 10litres/min while its flowing. If you are new to welding. Get the larger cylinder you will burn though the larger gas surprising quickly when learning. About 300 to 400mins welding time.

Ac

[tiger99]

The pressure as such is minimal at the point where your torch connects, only sufficient to get the desired flow rate. The regulator may be a true flow regulator, but most likely is a simple pressure regulator passing it's output through a small orifice which will establish the flow rate with much more pressure drop across the orifice as compared to the torch and it's hose. So the actual pressure will go a fair bit higher if you obstruct the outlet.

A flow rate regulator as used with argon etc is useless as a true pressure regulator as required for oxy-acetylene etc. But a pressure regulator will work, sort of, for argon, although you would be running very near the bottom of its range.

[tiger99]

Oh, and one of the fairly inexpensive flow rate gauges with the ball in a vertical tapered glass tube is a very good idea as the calibration on the regulator in terms of flow rate can be inaccurate depending on your torch and hose etc. The real flow rate gauge tells what you are actually getting and can help with weld quality and gas economy.

[sonikk4]

As a rule of thumb when I weld I do not use the gauge, I listen to the gas flow coming from the torch. Inside a garage etc then a gentle hiss is sufficient. A howling gale will just empty your bottle very quickly.

If I happen to be welding outside with a shelter around me I will up the gas pressure enough to ensure any sudden gusts of wind that happen to spring up do not affect the weld.

Not scientific at all, just using your hearing. Oh and been doing it this way for 25+ years now. You only need to look at the state of your welds to see if there is enough gas shrouding the weld.

[tiger99]

That is true. I was advised to decrease the gas flow to almost the point where weld quality was being affected, and it really did economise on gas. Unfortunately my MIG is broken at the moment, so I can't easily check, but think it might have been set as low as 5 litres/minute. Too low and you start to see brown iron oxide where there should be shiny metal, quite a simple test.

You need much more flow, and of course pure argon, for ali, and often a special setup with argon on the back of the weld too for stainless and other exotic metals but for car bodywork life is fortunately much simpler.

I must admit that I have never used MIG outdoors in anything except perfectly calm weather.

[venkman]

Thanks again guys for your answers, going to collect some panels tomorrow,use the last of my co2 to check flow rate then crack on.

Ian