Back purging stainless... Argoshield light vs nothing...

[Aesgarth]

I'm making a small stainless bottle. Mostly as a practice project so not critical. I realise back purging should be done with pure argon but I don't have a splitter and only one bottle. Is it worth purging with argoshield light or would that be a waste of time, with no benefits? (will be using argon through the torch)

I will be investing in a splitter and extra flow meter for the argon bottle ASAP, this is likely to be a one-off...

Thanks.

 

[Ruffian]

Order a splitter today and will be with you probably thursday. Most jobs can wait a couple of days and then do it right?

 

[Aesgarth]

Order a splitter today and will be with you probably thursday. Most jobs can wait a couple of days and then do it right?

I don't have the money for a splitter this week. Things are tight at the moment. And I'm using some downtime for a bit of practice..

 

[Brad93]

5% CO2 will end up with grain growth and grey appearance, lower corrosion resistance, no good for hygienic use.

 

[Aesgarth]

5% CO2 will end up with grain growth and grey appearance, lower corrosion resistance, no good for hygienic use.

OK. Thanks. Hopefully I'll be able to order a splitter at the end of this week so I can do it properly.

 

[backpurge]

Save your Argoshield and wait until you get a splitter

 

[Aesgarth]

Today has been incredibly frustrating. I can't get consistency at all. Some welds are bright and shiny (although, nor REALLY shiny...) , most are dull and grey and look awful. Sometimes it welds nicely, sometimes I'm blowing holes all over the place, seemingly at random.

I don't know what I'm doing wrong but I've had enough for today.

Even making the thread adapter for the back purging didn't go to plan... I used the wrong sized bolt.

 

[Brad93]

Obviously you need to make sure your purge is good. I.e. less than 100ppm of oxygen should give a straw coloured weld. Get down to less than 40ppm you’re getting silver with a band of gold. 20ppm or less is what you need for titanium.

stainless is all about heat input. High travel speed and regular additions of filler to chill the pool.

you can use chill bars of aluminium or copper to suck more heat out of the part too.

 

[Aesgarth]

Obviously you need to make sure your purge is good. I.e. less than 100ppm of oxygen should give a straw coloured weld. Get down to less than 40ppm you’re getting silver with a band of gold. 20ppm or less is what you need for titanium.

stainless is all about heat input. High travel speed and regular additions of filler to chill the pool.

you can use chill bars of aluminium or copper to suck more heat out of the part too.

Thanks. I actually seemed to be getting worse results when adding filler - my best (I use the term very lightly) results were autogenous. I'll work on improving tomorrow. Can't face any more of this today. Am I right in thinking there's no way to recover on this one and I might as well scrap it?

 

[Liquid Metal]

Most often autogenous welding leaves a better coloured surface. It's because it's usually hot and fast. Once you start adding filler, you slow down, and it ups the heat input. Unless you turn up the amperage settings and speed up.
Gas coverage does play a part in it, but not as much as people think

 

[Aesgarth]

Ok. I'll have a go upping the power and speeding up tomorrow. As well as improving the shielding.

Thanks guys.

 

[Aesgarth]

1.5mm thickness and I think i was around 110A (pulsed) - is that vaguely in the right ballpark?

 

[Brad93]

Most often autogenous welding leaves a better coloured surface. It's because it's usually hot and fast. Once you start adding filler, you slow down, and it ups the heat input. Unless you turn up the amperage settings and speed up.
Gas coverage does play a part in it, but not as much as people think

From the horses mouth there.

@Richard. Or @Paul. Have probably done a guide to welding stainless steel somewhere

 

[Paul.]

From the horses mouth there.

@Richard. Or @Paul. Have probably done a guide to welding stainless steel somewhere

I did the tutorial, (with Malcolm on the camera) and I also wrote the FAQ wiki

https://www.mig-welding.co.uk/tig-tutorial.htm

https://www.mig-welding.co.uk/wiki/TIG_Welding_FAQ

1.5mm thickness and I think i was around 110A (pulsed) - is that vaguely in the right ballpark?

One thing that can make a big difference is to make sure that you keep the hot end of the filler rod inside the gas shield, pull it out while its red hot and it will oxidise, then you just put an oxidised rod back into the pool, also I would be using 1mm filler on that joint, it will melt faster and enable you to move a bit quicker keeping the heat input down, I would weld that at around 80 amps max, no pulse, 1.6 tungsten ground to a sharp point and a no. 7 or 8 ceramic to give a decent gas coverage, keep the arc tight with the torch leaning back around 15 to 20 deg,

 

[Aesgarth]

I did the tutorial, (with Malcolm on the camera) and I also wrote the FAQ wiki

https://www.mig-welding.co.uk/tig-tutorial.htm

https://www.mig-welding.co.uk/wiki/TIG_Welding_FAQ



One thing that can make a big difference is to make sure that you keep the hot end of the filler rod inside the gas shield, pull it out while its red hot and it will oxidise, then you just put an oxidised rod back into the pool, also I would be using 1mm filler on that joint, it will melt faster and enable you to move a bit quicker keeping the heat input down, I would weld that at around 90 amps no pulse, 1.6 tungsten ground to a sharp point and a no. 7 or 8 ceramic to give a decent gas coverage, keep the arc tight with the torch leaning back around 15 to 20 deg,

Thanks Paul. I'll give that a go tomorrow.

 

[Aesgarth]

From the horses mouth there.

@Richard. Or @Paul. Have probably done a guide to welding stainless steel somewhere

Thanks again for your help

 

[Aesgarth]

I have another question. If I do short bursts (say 2-3cm at a time) and pause to cool I get nice shiny silver welds. If I keep going I seem to lose shielding behind the cup and get a dull grey weld or at best multicoloured.

Do I need to speed up? Slow down? Gas issue? If I get a chance I'll do a test weld and take some photos later today.

 

[backpurge]

Firstly, do not get paranoid about the weld discolouring, so long as it does not start to come up it is perfectly normal, not a problem and easily cleaned off.

The reason the short runs do not discolour is because they will still have a gas cover whilst they are cooling down

 

[Aesgarth]

Firstly, do not get paranoid about the weld discolouring, so long as it does not start to come up it is perfectly normal, not a problem and easily cleaned off.

The reason the short runs do not discolour is because they will still have a gas cover whilst they are cooling down

Thanks. I wasn't worried about the shiny multicoloured welds, but the dull grey ones did worry me a bit.

 

[backpurge]

Thanks. I wasn't worried about the shiny multicoloured welds, but the dull grey ones did worry me a bit.

If you wire brush them whilst the weld is still warm does the oxide layer come off to reveal clean metal underneath