TIG WELDING BOILER

[VicParticipant @vic]

Posted by fizzy on 30/09/2014 00:21:27:

Carl – vic…sorry but you clearly have absolutely no idea of what you are talking about! I offered help and advice, nothing more, and it is very valid advice. You don't believe me, then try for yourself! I was told that I couldn't do it, and on proving people wrong they respectfully changed their opinion, but unless you both have tried this route I suggest your opinions are ill informed! I am no armchair pundit and will only ever try to help others, but sometimes truth is what matters. Please vindicate yourselves by sharing with us the boilers you have completed?

Try actually reading what folks write. I won't speak for Carl but I was commenting on your attitude towards others not any skills you may or may not have.

[Bob Brown 1Participant @bobbrown1]

An interesting article on welding copper c/o The Welding Institute and it gives a reference to the rods to use.

**LINK**

Bob

[Keith HaleParticipant @keithhale68713]

Welding is not my bag so I will not speak for any producr but suggest you look at http://www.brazing.com/technique/procedures/copper_welding.asp.

It is a website run by Aufhauser with details on alloys available, joint designs etc.

Welding is not as straightforward as brazing albeit intrinsically cheaper. Pays your money and makes your choice!

Keith.

[Chris PickardParticipant @chrispickard93756]

Hi Julian/ Ron,

I slightly missed the point when i posted …not having a crystal ball i wasnt to know that materials had been purchased with a view to tig welding the boiler etc….

The correct grade of copper to be welded is C106…..this is copper in its deoxidised form and the only copper that will weld without cracking…..

the correct tig welding wire for this is Sifsilcopper no 985, a pure copper welding wire,which i use myself with excellent results….Available from 'Rapid welding supplies'…you can look them up…cost is around £60 /kg…( I have no connection to these just a good welding supplies company i use)..

If Rons son is a experienced tig welder ( of which i have no doubt)of alloys and suchlike then he should have little trouble welding copper…Its not the easiest material to weld but it does weld ok once you know how to handle it..

Couple of points:

1.6mm and 2.4mm dia wire is a good size to use…..

Pure agron can be used as a gas shield together as a backing gas….although results will be ok…the weld profile and finish of the weld is not perfect…..The better option is a shield gas of Argon/helium 75%/25%..the helium makes the weld pool slightly hotter and more fluid which helps you manipulate the copper as it tends to be sluggish at the onset of welding due to the heat being sucked away…

To aid this once the boiler is tacked up for welding…you can preheat the whole unit with a hot air gun to bring the material up to temp and gain some ground on the copper….that way you can actually bring down the amount of amps you need to start off as the heat isnt being zapped away..

weld preps need to be slightly adjusted from the normal 37.5'…slightly longer at around 40-42' with a sharp edge , anything over 3mm in thickness will need a gap to match the thickness of the material upto around 5mm, the gap shrinks once you start to weld as the copper pulls in like mad…but it works and will weld fine…

​When you are welding the boiler barrel or cutting out the sides for the outer wrapper on seamless drawn pipe, the butt welds will need to have a purge backing gas so a sealed unit oxy free for a nice clean root weld…if you a welding a boiler barrel, make some ends up so as you can purge the cylinder and away you go…ideal starting point for amps with this set up on a 3mm thickness would be around 135-140 amps…decreasing slighlty on a foot pedal as the copper heats up and flows freely…once youve completed your root run…clean once its slightly cooled with a power stainless wire brush…then capp with enough amps to make the wire flow….you should end up with a nice clean looking weld inside and out… the backing purge can be either pure argon or Argon/helium mix, ideally you need to check the oxy content with a oxy meter but if you leave for say 5 mins with a good flow then you wil be somewhere nr it..(oxy test is the surest way…should read .003 before you weld)

With the fillet welds around the outer wrapper and backhead a slight gap will aid penetration and produce a nice bead, usually 2.4mm wire is ideal, smaller fiddly places then 1.6mm wire works nicely…again fill with a backing gas so any penetration is not oxidised

Once this is completed, clean as per normal…

As for ndt on the finished components…..Visal inspection and dye pen by a third party will usually be sufficient for most…this shows up any flaws in the surface such as cracks or pores/ undercut…if you wanted to be totally belt and braces then xray on your butt welds would cover everything…

Copper and its alloys(cunifer) are not common amongst general fabrications, But they are used and welded very successfully…..having worked extensively with these materials over many years…there are a challenge but quite weldable to a experienced hand…

Anyway…Argons turned off now and screens put to bed untill the morning

Hope the above will be of help

Chris

[Chris PickardParticipant @chrispickard93756]

Ron

sorry …missed out the bs number for the copper welding wire

its En 14640 CU1898 (CUSNI)

Chris

[julian atkinsParticipant @julianatkins58923]

hi chris,

thank you for your most comprehensive and detailed reply. i am sure this will be of great interest to Ron and his boiler for his loco.

cheers,

julian

[nigel jones 5Participant @nigeljones5]

Hi Chris – very thorough! The big problem I have found exclusively with copper is the amps required are huge, even with massive pre-heat. On 5mm plate 150A wont touch it, and pretty much anything over this needs 3 phase so more expense. I used to use a dry gun and they got so hot that the plastic components literally melted! I opt for steel now as its a doddle by comparison but if I had 3phase I would love to weld copper again. And the gap contraction is a nightmare…id forgotten about that! Apparently ive got an attitude problem but if like me you have seen what can go wrong im sure you will understand!

[Ron HancockParticipant @ronhancock63652]

so many replies thank you i am more uncertain than ever with so much to take into consideration.

our boiler testers at our club in southern fed say no problem with Tig welded boilers.

My son uses 3 phase Tig welders so that will help Dave.

i am now thinking of making one in gas welded.

one in tig weld i can always build another Loco to use on,

I think the proof will be in the making and will take each part for our two testers to check as we go along.

many thanks especially to Julian as you have given me so constructive help.

Regards Ron

[Chris PickardParticipant @chrispickard93756]

Hi Frizzy…..Yes you are spot on with the amount of pre heat the copper needs…it just sucks heat away from the weld like mad…then turns the other way and runs away from you once its up to temp…….

im lucky as i have both 3 phase water cooled tig sets and smaller single phase for the lighter stuff……so can cover most material thicknesses….Carbon steel for your boiler is a much easier option when your looking at a welded boiler, Dosent cause any problems for a good welder at all…….ive just been working on a nice vertical steel boiler which is fully welded and quite an easy build to be honest……I know deffo what you mean about how it all goes wrong…spend half my life sorting out other peoples hash ups….

Looks a nice job you did on your steel boiler…very tidy. and passed with flying colours…

Ron i agree there are so many considerations to take in when you get into a welded boiler…as we all know its not just glueing together and hoping for the best…with the correct skills and materials its quite straight forward , Using sound engineering practice and the right know how…excellent results can be obtained…

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