Re: [PSUBS-MAILIST] Re: Pressure vessel welding

[Jon Wallace <jonw@psubs.org>]

Interesting that I was just looking at stick welders yesterday on the 
web.  Miller has the CST280 that can use 1 or 3 phase power.  I'd be 
happy to go with 3 phase, but I don't think there's any chance of the 
power company bringing it out to my rural setting unless I pay an 
exuberant price (which I'm not going to do).  For one phase they show 
50% duty @ 200A and 100% duty at 150A.

The thing I'm still stuck on is, how many amps (what size welder) and AC 
or DC.  I've read alot of material saying DC provides better 
penetration, but you can also get a magnetism effect with it that makes 
the welds bad.  So Dan, or any of you other pro welders, how about a 
laundry list for SMAW?  Is something like the CST280 big enough? 

stick: 7018 (thanks Dan)
amps:
AC or DC:

Jon




Dan H. wrote:
> If you not a pro, stick weld with easy to get easy to use 7018 and a 
> welder heavy enough to burn it in and just put up with the smoke it 
> produces.  7018 is a low hydrogen rod with 70 PSI tensile strength.  
> Good for what your doing.  If you have a MIG use it for things like 
> assembling the frames and pods, stuff where welds aren't as critical 
> but use stick for your important and water tight welds. Stick welding 
> has been around for years and years and it "ain't rocket science." 
> Sure, it may be crude by TIG standards, but really, a subs pressure 
> hull is in compression and so are most of the welds.  If there are a 
> few specks of slag inclusion, it's not going to scrap your hull.  
> Better to have a few specks of slag in the welds then poor adhesion 
> with a MIG pass that wasn't burnt in properly. 
>
> The most critical welds of your sub is in the area where the conning 
> tower attaches to the hull.  If your not comfortable have someone else 
> do them.
>  
> Don't be afraid to use a grinder to grind out anything you see that 
> doesn't look right.  With stick welding, you'll see it if you goofed.
>  
> But most of all, learn how to weld first on a ton of scrap or take a 
> welding course, if your not already competent.  If you still don't 
> feel you can get it done properly, have someone else do it.  Like any 
> other trade, professional welding takes professional training and 
> experience, but you can become an adequate welder and do adequate work 
> if you use a less technical procedures and spend some time 
> practicing.  I'm not saying stick welding is easy, as you'll soon see 
> yanking off stuck rods if you haven't done much of it, but it's less 
> technical and when you knock of the slag you can see what you get,
>  
> Ok, I'm finished talking and
> waiting for the flood of disagreement..
> Dan H.




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