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Re: [PSUBS-MAILIST] Seeing a pro welder at work
Hi Alec - I use a other way at the ends of the pipe.
During welding the single longitudinal weld of my regulator tanks -
I length the welding gap way at both end with a short peace of metal
of about 1-2 inch length and a grinded simulate gap on it.
The short metal plates was just light tack welded to the cylinder
with the tack welds just outside the welding way.
I start the longitudinal weld on this peace of metal - and ended at the
other side the same way. So the weld is about 2 inch longer than
nessesary.
After the final layer - I remove the both short plates with the grinder.
The weld will be perfect at the end - no thats not the right words : but
will
be the same quality at the end as the hole way long.
I started also with the inside weld, than removing the plates, grinding
the outside gap, make new plates on and do the outside weld.
Your old stick welder made everything right but if he stop the weld for
more than say 1 second - he has to remove the slag. Sometimes some
welder do not do that to save time and it works also - but it is tricky
.. Just a little to cold or waiting to long and the weld has problems
in.
If you MIG weld - you can go the hole weld without a stop in one turn,
and
if you have a stop - to change maybe your body position - you can start
without removing something - there is no slag at this process.
The only thing witch is better with the stick welding process against
the
MiG welding process is that the MIG welds are sometimes to cold at the
start end. For example : if you weld your encaps on - you have a first
start point. During this time the metal is cold and for this reason the
first 1/2 inch of the Mig weld could be bad quality. So If you get
around
and come back to the start - stop 2-3 inch before the meeting point and
grind
the first 1 inch out - before make the final closing.
This problem is not so difficult with a stick welder - seems this
process
is hoter on the start point.
best regards Carsten
> Alec Smyth schrieb:
>
> Uh-Oh, re-reading your message I see we're talking about two different
> things. Yes, he did remove the slag when changing rods. I was talking
> about when he reached the end of the pipe, not the end of a rod.
>
> - Alec
>
> -----Original Message-----
> From: Brad Mallard [mailto:bradmallard@hotmail.com]
> Sent: Wednesday, August 08, 2001 1:14 PM
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] Seeing a pro welder at work
>
> Alec, I think you did a good thing. My specialty is welding.
> I put myself through college as a certified welder only to
> get an engineering degree in metallurgy. So, I would say I
> am qualified to at least give my opinion.
>
> I agree with every step of his porcess, from correcting the
> gap between the plates, to puting the final touches on the
> cap ( or the weld that is on top). The only thing that I
> didn't follow is the retracing his weld without removing the
> slag at the overlaps when he had to change rods. This is a
> tricky process, and unless you are experienced; it would not
> be advisable. Slag can be traped when going back over a weld
> that has cooled, causing a void of slag, or even air. This
> is bad in any weld that matters. I don't want to doubt your
> guy, becuase I am sure he knows what he is doing, because
> when eveything is right the slag will just fall off. In the
> case where you have to beat your slag off, you may want to
> bump the heat up, just a touch...
>
> I just wanted to express my opinions, because retracing a
> weld is a tricky thing. My suggestion for the group is to do
> exactly what Alec did. For the external welds, I would go
> with a person that has put his reputation on it for a few
> years. It seems like a lot to pay a guy that amount, but
> implosion is not a pretty thing I am sure!
>
> Brad
>
> >From: Alec Smyth
> >Reply-To: personal_submersibles@psubs.org
> >To: "PSUBS (E-mail)"
> >Subject: [PSUBS-MAILIST] Seeing a pro welder at work
> >Date: Wed, 8 Aug 2001 12:45:41 -0400
> >
> >Last night I saw some interesting things I thought I'd
> share with the group.
> >Sorry if this is old news to the experienced folks.
> >
> >I can "stick metal together", but I'm no professional
> welder. I'm doing most
> >of my welding, but decided not to chance it when it comes
> to the pressure
> >boundary seams. Those I'm having done by a pro. So I called
> a local welding
> >supply store and they put me in touch with a gentleman who
> is a certified
> >pressure vessel welder and pressure vessel inspector, with
> 30 years
> >experience. Last night he came by and did the longitudinal
> seam on the
> >pressure hull. This is the single largest weld on the boat.
> >
> >1) The starting point was a cylinder 94" in length, of 516
> gr 70 plate 3/8"
> >thick. Per welder's instructions, I had ordered this with a
> double beveled
> >edge. The first surprise was that he prefers the edges not
> to touch. The
> >seam was just how he liked it, with a small gap about
> 1/16th between the
> >beveled edges. The reason for the gap is he wants to know
> he has filled it,
> >and without a gap he would be hoping (but not certain) that
> the metal had
> >melted to the center of the material.
> >
> >2) He started by doing a continuous weld on the inside with
> 7018 rods, 1/8".
> >Its interesting seeing the technique. When the rods were
> still long, he
> >actually held them with both hands -- two fingers were near
> the hot end, to
> >keep it perfectly steady. Sometimes he'd just be going
> straight down the
> >seam, other times going side to side "depending on what the
> puddle is
> >doing". The end result looked like it had been made by a
> machine. An
> >interesting detail was what he did at the ends of the
> seams. He'd get to the
> >end and then back up again and redo the last 2-3 inches,
> all in one movement
> >without removing the slag. He said this "avoids an end of
> the weld on the
> >end of the seam", which would be a potential weakness.
> >
> >3) He then went at the outside with a blowtorch and a 90
> degree nozzle. He
> >"torch-gouged" the beveled channel turning the V into a
> wider sort of U,
> >about 1/2" wide. He took it down so the material at the
> bottom of this U was
> >the inside weld. This also removed the tack welds, but was
> not limited to
> >the tack welds (he did the whole length). This step could
> have been done
> >with a grinder, but the torch was a noise reduction tactic
> -- I live in a
> >quiet residential neighborhood and try to minimize grinding
> on the driveway.
> >
> >4) He finished the channel with a light grinding. The
> result was a shiny and
> >very solid looking channel without discontinuities of any
> sort. This did get
> >one neighbor out onto the street, but fortunately she was
> one of the
> >friendly ones. Did I mention his welding equipment was gas
> powered and 1963
> >vintage? About as subtle as a locomotive.
> >
> >5) He welded the whole length from the outside. This weld
> filled the channel
> >to half its depth but covered its entire width.
> >
> >6) Removed slag, wire brushed, and laid another bead along
> the whole length
> >to bring it flush with the surface.
> >
> >One interesting thing is that there was almost no spatter,
> and the slag just
> >fell off almost on its own. He had a whole truck full of
> welding equipment,
> >but did not posess a chipping hammer... no need apparently.
> The slag
> >required at most a brush of the glove or a scrape with the
> end of a rod to
> >remove. For some reason I have to pound my welds.
> >
> >The entire process took 4 hours, working efficiently and
> without a break.
> >His rate was $65/hour which included all equipment and
> consumables. He
> >turned up with this self-contained welding-shop-on-a-truck
> and did
> >everything right there on the driveway. Boy do I have no
> regrets about this
> >one, the peace of mind is well worth it!
> >
> > >/>
> >
> >
>
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