Ron Tebo wrote:
>
> jarrid_gross(at)juno.com wrote:
> >
> > On Sat, 13 Sep 1997 11:56:48 -0700 CHUCK NICODEMUS <SEALMSTR(at)ICCOM.COM>
> > writes:
> >
> > >Jarrid, it is my summation that by hitting it with a hammer you my
> > >hear
> > >the different tones emmited by the "cast" v "forged?
> > >but then you would have to have one each to decypher the difference??
> > >
> > >chuck
> >
> > This is the common way "as I have been tought" to differentiate between
> > common cast cranks, and the superior forged pieces.
> >
> > The tonal quality and the length of the ring is a dead giveaway.
> >
> > To the person/persons performing the ring test....
> >
> > Be certain to compare the ring of the SV crank against another
> > known forged crank "IE an EN-16 1600cc 3 main crank".
> >
> > I performed this test, along with other peoples, long ago, and the
> > differences
> > are un-mistakable. The tonal quality of the SV cranks ring was slightly
> > superior to nodular iron cranks, and all the cortina type formula ford
> > cranks I rung out, but in comparison with an 8740 sb chevy crank or
> > the 3 main alpine, night and day.
> >
> > Once again, could these cranks be cast steel?
> > Tom Wiencek, metalurgist et al?
> >
> > Cheers, and of course, keep me informed.
> >
> > Jarrid
>
> Jarrid:
>
> I have been waiting for the metallurgist, but since he hasn't
> answered...my 2 cents worth.
>
> As a journeyman weldor, I learned some metallurgy since you have to be
> able to match rod to the metal. I really doubt that any crankshaft since
> very early times was actually made from (grey) "cast iron" (low
> shock resistance and high tensile strength) What may have been used is
> what is called a semi-steel or alloy casting that has chrome,
> molybdenum, nickel, etc.added to it or a special grade of pig iron and
> foundry scrap that has been annealed called "malleable cast".
> However, I think it would be much more likely that most shafts would be
> made from a manganese alloy steel blank that is rolled and forged.
> The reasoning here is that manganese increases shock resistance, wear
> resistance, and hardenability, and with carbon, makes steel
> non-deforming. The reason that I think the forging process would be used
> is that this allows the grain of the rolled blank to follow the form of
> the part (eg. around the throws and through the journals)
> to increase the torque shock resistance needed on a crank.
>
> The case-hardening process used to be done by blacksmiths who would
> encase the metal in a layer of shavings from horse's (cow goat deer
> etc.) hooves, wrapped in cloth, then encased in a firebrick plaster
> and left in a forge or steam boiler over night (1700 F.). This
> illustrates the "pack" carburising method of case-hardening which might
> be done now with materials such as Kasenit. The idea is to produce a
> hard wear resistant skin through adding carbon to a thin outer layer
> while leaving the inner metal resistant to shock and sometimes ductile.
> Quenching in oil or water and tempering required.
>
> Liquid carburizing or cyaniding, done in a bath of molten sodium
> cyanide (about 600-800 degrees F) differs in that iron nitride needles
> are formed in the case that are harder than the iron carbide formed in
> the previous process.
> parts are usually not machined after this process.
>
> Gas carburizing is done where it is necessary to machine or grind parts
> after treatment and is done in a sealed drum with natural gas or propane
> providing the carbon at about 1700 degrees F.
>
> Carbonitriding is done with ammonia gas in an air-tight container at a
> lower temperature (900--1150 degrees F.)but takes much longer. It is
> used when a hard shallow layer on machined parts is required with little
> distortion (Valve lifters?)
>
> Since all these methods are available to permit low carbon steel (=
> cheap and non-heat treatable) to be used in places where wear resistance
> is necessary, I really wonder why cast-iron would be used for lifters
> (unless it was chilled iron, which has a hard surface but is mainly used
> for crusher rolls, etc.). But, flake and spheroidal graphite present in
> cast-iron could cause uneven carburising and very brittle spots in
> case-hardening which you have noticed on some lifters.
> Your musical method of checking material is a pretty rough indicator,
> but the clunk from the camshaft might indicate a low carbon base with
> case-hardening. A better method would be spark-testing parts that are
> already damaged.
>
> I haven't bothered with austenite, pearlite, cementite, martensite
> etc. and critical points because this is usually more than anybody
> really wants to know. Hope this helps.
>
> Ron Tebo - Series I - B9000627
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