Re: [PSUBS-MAILIST] Stainless Welding Question

[MerlinSub@t-online.de]

Hi James they are wrong. Use the right wire. Pre-upheating is important and downheating also. 
150 degree C° in a bigger area around. Use maybe a infrared thermometer pistol to check.

During the welding process some of the special metals like chrom and vandium burns away. That means your stainless is not longer stainless.. Therefore the weldwire must have a higher ration of this metals  to compensate this. Means if not your fittings tends to rust and crack close to the weld if you use plain steel or plain stainless wire. Therefore you have to use the right stainless steel wire. We call him here black-and-white wire. 
Its a better stainless steel than the normal one. As your weld wire shop. And don't purchase the wire in a supermarket..  The right gases are also important.

Small fitting should be Tig welds. Bigger ones takes really long in TIG but we get good result with a one round of tig weld to close the base and heat the hole area heavy up that way also in one step. And than the fill welds with electrodes or WIG welds. 

If you use wig weld for troughhull from the first layer and without preheating you have a good chance of a failtures. 
Cold starts and ends, cracks etc. Do it in winter time outside and I will garanture that there will be cracks and failtures. 

The gap should be the right size.. for round troughhull fittings there is a lot of shrinking stress later on the weld. Make the gap small as possible helps. On the other size the gap should be there to get full penetration. Means zero gap is also wrong. 

PS: In the weld shop you get also the white and red chemical to make later a crack check.. 

vbr Carsten  -not an experience welder but an experience shipbuilder..-  


"James Frankland" <james@guernseysubmarine.com> schrieb:
> Hi All,
> 
> Finally i am getting on with my sub again and am ready to install all the through hulls into the hull.
> 
> The plans call for welding all the stainless parts in with stainless wire.  309L if i remember correctly.
> 
> Speaking to some very experienced welders here, they tell me to weld the parts in using ordinary wire.  One of the guys is a shipbuilder and he says they weld all the ship I/O spigots using ordinary mild steel wire as it is less likely to crack.   
> 
> As long as its 70,000psi wire, does it really matter?  Of course there is the corrosion issue, but the parts will be painted anyway along with the rest of the hull.
> 
> I suspect the answer to this will be to use stainless wire but i would like to know why its needed.
> 
> Any ideas?
> Many thanks
> James
> 
> 




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