Message-ID: <38A63127.7F41@tritel.net>
Date: Sat, 12 Feb 2000 21:20:55 -0700
From: Gene Davis <genedavis@tritel.net>
Reply-To: genedavis@tritel.net
Organization: Amoco Pipeline Co.
X-Mailer: Mozilla 3.01C-KIT (Win95; U)
MIME-Version: 1.0
To: "G. Simmons" <gls@4link.net>
Subject: Re: [oletrucks] Water from steel (was originally about POR-15)
References: <001801bf75cf$b2a4fb60$0e76efd1@grantsim>
G. Simmons wrote:
>
Hi guys, I dont know where the water comes from for sure, but would bet
its atmosheric in origin. I used to weld for a living and know that if
you want a good quality weld, especally on higher carbon steels, it is
important you preheat enough (>/= 300F)to get this water out of the
steel. Youve seen a welded piece break right next to the weld (called
the heat affected zone) well, water makes this worse. Its called
hydrogen embrittlement. The hydrogen comes from the water you see
leaving the steel when you warm it. Using low hydrogen welding rod
(E7018 for example) helps. Keeping your rod in a rod oven helps too.
> >When you burn propane or acetylene or any hydrocarbon, the hydrogen
> combines
> >with oxygen to form water. It condenses on anything cool.
> >2C2H2+5O2=4CO2+2H2O. 2 acetylene molecules combines with 5 Oxygen molecules
> >to form 2 carbon dioxides and 2 water molecules.
>
> Hi Bob,
>
> I knew somebody smart could help us. Next question, though, is does this
> actually mean that steel does not contain water? There are a couple of
> peculiarities about the appearance of water during heating that look more
> like water being drawn out than water being condensed.
>
> 1. The water only appears in the heated zone. You'd thing that if the
> water was a condensate by-product of the gas, that it would condense more on
> the cooler edges than in the heated middle.
>
> 2. The water appears at the beginning of the process and then disappears.
> This is consistent with the idea that the heat is forcing out a finite
> amount of water contained in the steel. If the water were coming from the
> gas, wouldn't it be deposited at a constant rate instead of appearing only
> at the beginning of the process?
>
> Of course, the steel may simply get too hot to allow further condensation on
> its surface, but what I'm talking about can be seen with a torch pass or two
> over the surface, which on a big piece of steel, doesn't put much heat into
> the outlying areas, so there ought to be plenty of cooler areas to see the
> condensation.
>
> Wish I'd paid more attention in school.
>
> Regards,
>
> Grant S.
>
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
|