From: Wayne Harris (papercu@hotmail.com)
Date: Wed Sep 29 2004 - 16:59:35 PDT
"There is a name which escapes me for shotgun barrels made by hammnering
thin strips of steel
together around a madrel until desired design of barrel is arrived at,
another example of metal structure being changed."
That would be a "damascus barrel". Wayne
>From: "everette" <194cbteng@bellsouth.net>
>To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
>Subject: [MV] Spring Failure
>Date: Wed, 29 Sep 2004 18:08:42 -0500
>
>Mr. Fareber wrote
>
>"""""
>I don't want to be rude, but when and where has a failure of springs been
>caused by media blasting? I did 6 sets of springs with al. oxide and had
>to
>cut some serious scale. Never a problem.
>
>I would like to know of real world failure of metal (on our scale... MVs)
>caused by media cleaning or hydrogen emrittlelment.
>
>By reading this discussion, all my MVs should shatter into pieces when I
>hit
>a bump due to cleaning with media and rust prevention with phosphoric acid.
>
>Pls. provide proof (and not some lab experiment or some yahoo eating 2/3rd
>the way through metal with abrasives) that these things are actual
>concerns.
>
>Or is this list full of old wives and their old wives tales """
>
>Hydrogen emrittlelment.is a scientific fact, no discussion necesssary-- it
>just happens.
>
> I once put a throttle spring into dilute Hydrocholoric acid --. left
>for
>1/2 hour or less, spring was clean, rinsed it off and painted with primer
>paint. Spring had been taken off when carburator was removed, and dropped
>in acid to clean oil and grease off it. When stretched to reinstall, it
>broke as soon as it was pulled on.
>
>I had an accident in 3/4 ton 4WD pickup that from factory had single leaf
>front springs, accident caused one spring to bend. The company I was
>working for at the time was big enough that they were self insured. There
>was a complete inspection of truck before repairs were authorized. The
>fellow who did inspection made specific instructions for repair of truck,
>he
>specificaly said that replacement spring must be new from GMC, not from
>salvage yard, and could NOT be media blasted, acid or caustic dipped. He
>further said old sping must be torch-cut into three pieces.
>
>And to address scale on metal - this is not something that falls out of air
>and attaches to metal. Scale -rust- is metal that has been disolved by
>chemicals in the surrounding air, or something that has gotten on metal
>some other way; and this caused chemical structure change that creates
>scale; hence if you take scale off, aside from embrittlement the remaining
>metal is thinner than before scale showed up. I am reasonably sure that
>springs are over-built and minor rust damage is acceptable. But there is
>no
>doubt that anything done to them will affect performance.
>
>Embrittlement can be compared to the effect on metal by prolonged
>hammering,
>much like swords were made by hammering a thick piece of steel until metal
>lost much of the impurities that were in it when made before steel makers
>learned how to make steel without so many impurities. There is a name
>which
>escapes me for shotgun barrels made by hammnering thin strips of steel
>together around a madrel until desired design of barrel is arrived at,
>another example of metal structure being changed
>by mechical means.
>
>I do not mind being considered an 'OLD WIFE" or even tale of old wife, I
>had much rather err on side of caution than to consider myself smarter than
>people who have the responsibitly of metalurgy design.
>
>
>Sorry to have made such a long post but I have been involved in the
>manufacture of chemical cleaning products both acid and base for several
>years.
>
>Everette
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