Dark Roots Options

[David 46]

Good Morning,

I think this Question will be for a metalagist.

Stainless steel 2mm wall Pipe made within the company from Sheet metal.

All materials are within Standard with Heat numbers and DIN/EN numbers , 1.4301.
Filler wire is 1.4316, Process is MAG (135) Gas 2,5%C0² in Argon. Full Automatic Process.

Material 1:A really good Process is running for Butt joints no problems with the Root or annealing colours light yellow.

Material 2: The Root itself is ok butt now the annealing colours are allmost black.

The Purging is Exactly the same for both materials I have tried changing the presures and times but it does not make any differance. The wire is the same (same roll) and the welding parameters are the same, also the same Cylinder or gas.

What is it that causes this to happen? if I had an analasis done what would I be looking for?
Which Elements would be differant?

David.

[Technic Al]

Black is almost certainly oxygen. You are getting contamination from somewhere. Look at the pipes and connections, anywhere that could result in air ingress.

[David 46]

Thanks Al,

I have checked all that and its all ok.

I was intouch with the Stainless Steel Compitence Center in Düsseldorf this morning. I am pleased to say I now know why.

It is the Material:

one is cold rolled and the other is hot rolled. The Hot rolled is the easier of the two to work with slightly yellow after purging (1D). The second one is the difficult one of the two (2B). The results are now descent but nothing to brag about. I turned the Purge gas up to 25lt/min and let it run a little longer than what I would usually set.

Thanks for your quick reply.

David.

[Technic Al]

So are they saying that the hot rolled has a more oxidised surface?

[David 46]

Yes thats what they are saying and they seem to be right. I got it up and running about 30 mins ago. I had to clean the material with a solvent and just went over it with a stainless Brush, a long Pre-purge to be sure the pipes are full of Argon and a high amount while welding (28Lt/min). The Pipes are 154mm inside dia.

It works. So I can stay longer now to Prove it.

Thanks again Al.

David.

[Ballbearing]

TA/David,
Just reinforces what we are talking about on another post.
Just fill 'er up and away you go may work for fuelling your car but is definitely not recommended for welding anything that needs purging,
Cheers,
BB

[skaginn]

Hi David
I you are in a position I would recommend you use 90% Argon 20% Hydrogen for your purge known as Forming or Former gas, I have used this before and the results are much better than using pure Argon especially when it comes to colouration due to heat.
If you want to see an example the following link was posted by 3.1 Inspector some time ago.

http://www.polysoude.com/documents/english...ding_result.pdf

JC

[David 46]

Thanks for the Info Skagin,

I would prefer to use a Formier gas. The thing is these tests I am doing are Pre-production tests for a Customer. They do all their Purging with 4.6 Argon and the Production will eventually be Fully Automated. Also with the 20% H² comes the chance of Explosion (from 10%H²).
I totally agree with you about the Formier Gas. I was thinking maybe of trying to change them over to N² as long as there is no Ti in any of the Material or Fillers that they use it should be ok.

I must admit though this was the worst I have ever seen, I am hoping its a one-off. If my Info. is correct the Material originated from Italy.

Thanks again,

David.

[Ballbearing]

Skaginn,
Formier gas is a combination of Nitrogen and Hydrogen, not Argon and Hydrogen.
And you would have a big problem fitting 90% Argon and 20% Hydrogen into a gas bottle (unless they have special bottles in the UK that hold 110%. LOL !) Sorry, couldn't resist,
Cheers,
BB

[skaginn]

Yes BB you are correct
Used it on two occasions once was on a S/S test it was a 80/20 mix.
but never used it on the job.
I also used a 90/10 mix recently, when you see the results you can see why those involved in food and drinks manufacturing are leaning towards its use.
I can understand the safety issues, the 80/20 was burning as it came out of the butt.
The 90/10 was OK even when purging 600mm Tees.
I like using it simply because it makes the job much easier.

JC

This post has been edited by skaginn: Jul 21 2010, 07:45 PM

[nanjing]

If u require a high standard, even with 304 stainless steel (1.4301) for optimum results clean internal surface with a flapper disc then wipe with acetone. High purity argon should be used for the back-purge, no need for ultra-high purity or a gas mix. Purge time/flow rates vis a vis diameter and dam spacing is discussed on a current thread which should also help you.

[David 46]

May-be just May-be the 110% will fit in a 300 bar Cylinder. What do think???

David.

[Captain]

Hi lads,
I used Formier gas in conjunction with 99.9% Argon as a purge a few years back on a job in Finland.
I was welding 316L & 321 stainless pipework, and using 99% pure argon and Formier gas together.
The Argon and Formier went through a flowmeter at around 12 L.P.M. per minute each and were then joined using a "Y" piece for the purge pipe with a diffuser on the end.
The results were superb, clean & shiney!!!!
The Formier would also produce a blue flame out of the root gap as Skaggin mentions.
The Scandanavians seem to use the Formier all of the time.

Captain

[boilermaker]

Used 80/20 Argon/Hydrogen for both shield and purge on 10" Duplex flowline orbitals back in 81. The only significant problem was porosity caused by welders trying to blow the flame out !