[TheForge] Welding advice -- Now Heavy Welds

[David E. Smucker]

As to Andy's original question I would guess that the heavy plate sections 
were welded using a submerged arc weld system.  These are down hand welds --  
the plate is horizontal and a powder flux is used.  At least this is what is 
being used today for very heavy sections welds for heavy heavy equipment 
applications where the plate is 2 to 30 inches thick.  Welding is semi 
automatic or automatic today with a "wire feed"  the wire being 2 each of at 
least 5/16 dia.  Takes a small about of current (Smile)  For these very 
heavy section multi passes are needed.

On the other hand I know of at least one very heavy section thermit weld 
that has been in active use since the mid 1950's.  When the New Special 
Plate Mill for Air Force Product was built for Alcoa at it Davenport Works 
the mill builder "Continental" could not cast the housing (cast steel) large 
enough so each housing was cast in two "U" shape pieces  and the two U's 
welded together to make a tall "O".  This was done with a thermit weld. 
Cross section of each housing post is about 24 inches by 36 and two welds 
would have been done at the same time.  The housing would have been welded 
laying down.  This mill has been in service without problems for 50 years 
(Installed in 1955 if I remember right.)

In more recent years SMS AG (Germany) has made some very large plate mill 
housing by welding 4 pieces together but these welds used submerged arc.

Also for some very large mill rolls the top neck is cast on using a thermit 
process.  While the rolls are used horizontal, they are cast in a vertical 
molding system.  To make sure the "top" neck gets very good metal. the poor 
quality metal that comes to the top of the cast is removed and then the top 
neck is cast on to the already solid rest of the roll.  A thermit process is 
used to prepare the top of the solid roll before the top molten metal is 
placed.  Timing is in seconds.

Dave Smucker
----- Original Message ----- 
From: "Andrew Vida" <osan at netlabs.net>
To: <munlaw2 at hcsmail.com>; "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Tuesday, March 01, 2005 12:26 PM
Subject: Re: [TheForge] Welding advice


> f
>
> Ron Childers wrote:
>> Maybe thermit? That's what is used for rr rails.
>
> I'd considered that.  The only way I can see this as viable, would be to 
> dope the thermit with alloying elements that would, presumably produce a 
> filler with the right structural properties, lest the welds become weak 
> points.  Thermit produces ultra-hot pure iron.  I cannot imagine that pure 
> iron would be nearly strong enough for the duties to which a battleship 
> would be subjected.  Just think of the stresses due to the sheer weight of 
> the vessel.  Forget about withstanding the forced of a torpedo or 
> artillery shell.  The welds are the weak link.  And how would the iron be 
> carburized to the correct level?
>
>
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