Stinkyshoe
Member
Shear_Stress
This I heard from a very credible member of the American Pistol Smiths Guild. I assume he'd know.
Ss
This I heard from a very credible member of the American Pistol Smiths Guild. I assume he'd know.
Ss
Slamfire,
Some of those big diesel engines may have cast cranks but they are very low RPM engines.
It's high RPM that really stresses a crankshaft. But even so, I did a search and it appears that many diesel engines including Cummins and Caterpillar are using forged steel cranks
If we compare a forged steel crankshaft or con-rod with one of conventional spheroidal graphite or nodular cast iron the forged steel will generally be significantly better, at least for racing and high duty. That is not because of strength though but resistance to fatigue failure, which is admittedly much better for forged steel than any cast iron or even the general run of cast steel.
Fatigue is a big factor for cranks and rods, but not rifle receivers: a crank and rods will undergo more load cycles in a few seconds at full noise than a rifle receiver will undergo in its entire service life. That is why as well as specifying a forged crank your tuner will also be obsessive about radiusing all corners, shot peening and polishing, crack testing, and balancing, all to reduce the likelihood of fatigue cracks being initiated. None of this is relevant to rifle receivers.
There are better materials than these for racing car components too, such as Metal Matrix Composites, already seen and then banned from use in F1 pistons. MMCs are generally produced by casting or else powder metallurgy, and have particular advantages for pistons due amongst other things to the thermal loads.
F1 engines do use investment castings in the form of valves, valve-train components, blocks, gearbox housings and a myriad of others. The rules specify a steel crank though, so that is what is used.
a crank and rods will undergo more load cycles in a few seconds at full noise than a rifle receiver will undergo in its entire service life.
Cast parts may be perfectly fine for many applications but they are almost always specified only because they cost less to manufacture, not because they are better.
Boston,
My response, and then I am done with this:
One has only to view the scrap piles of visibly flawed and
mis-cast pieces behind Ruger's casting plant, which is proximal to
my own place of business, or interview several hundred current and
former Ruger employees who will candidly discuss the goings on
there in terms unseen in Ruger's promo videos... to get the idea
that their manufacturing, casting and QA process subsets do not
necessarily guarantee top quality results.
Watching them begin the re-grind/re-melt recycling process of all
of this scrap, tons of it, (not always perfectly sorted for alloy content
but then, dilution does wonders for that...right?), is entertaining in the extreme.
In response to the smugly pedantic "Daniel", the cooling rate must be
optimized to prevent the formation of dendrites and other cooling
related issues. It is apparent after examining many samples of Ruger
castings that their cooling process is not what we would call "consistently
optimized". But again, Ruger's sentiment on casting quality seems to be
that what you can't hit consistently through precision and repeatability,
you can hit haphazardly often enough to make it worthwhile to keep on
plugging away at it. Fortunately for them, casting is a cheap foundry
process and "do overs" are easy.
But for Daniel or anyone else who may be emotionally invested in their
investment cast guns or have a personal interest in promoting/selling them:
If you like that stuff, fine. Buy it, sell it, whatever.
It's your money, your life on the line and as always, YMMV.
Mine doesn't. It's a science thing.
Stay Sharp,
Mad Dog
Cheap shot.the smugly pedantic "Daniel",
This is why Rugers are known for breaking...But again, Ruger's sentiment on casting quality seems to be that what you can't hit consistently through precision and repeatability, you can hit haphazardly often enough to make it worthwhile to keep on plugging away at it.
Naturally, anyone who disagrees with the esteemed Mr. McClung must be doing so out of emotion or personal interest. Apparently he finds it unfathomable that there could be a disgreement based on any thing technical.But for Daniel or anyone else who may be emotionally invested in their investment cast guns or have a personal interest in promoting/selling them:
One has only to view the scrap piles of visibly flawed and
mis-cast pieces behind Ruger's casting plant, which is proximal to
my own place of business, or interview several hundred current and
former Ruger employees who will candidly discuss the goings on
there in terms unseen in Ruger's promo videos... to get the idea
that their manufacturing, casting and QA process subsets do not
necessarily guarantee top quality results.
My response, and then I am done with this...
for Daniel or anyone else who may be emotionally invested in their
investment cast guns or have a personal interest in promoting/selling them
the cooling rate must be optimized to prevent the formation of dendrites and other cooling related issues.
One has only to view the scrap piles of visibly flawed and
mis-cast pieces behind Ruger's casting plant…
…Watching them begin the re-grind/re-melt recycling process of all
of this scrap, tons of it, (not always perfectly sorted for alloy content
but then, dilution does wonders for that...right?), is entertaining in the extreme.
I don’t place all that much credence in one firearm supplier running down another’s product either, but that is all I see here. Where's the "science"?
The little "eye-rolling smiley= " is indicative of sarcasm.My question is, are Rugers really known for breaking?
Agree, the email is several paragraphs of attacks and innuendo with maybe a couple of sentences of technical information (being generous).I don’t place all that much credence in one firearm supplier running down another’s product either, but that is all I see here. Where's the "science"?
I understand the point, but didn't consider "smugly pedantic"Cheap shot.
Posting an email from someone else that insults a member on THR when you can't do it yourself per the forum rules.
Actually, I've no financial stake in any forged steel product.I note with some amusement though that Mr McClung in fact does have a financial stake in forged receivers, given that they are sold by his company – as of course does the fellow who chose him to provide “technical” input to a book he keeps mentioning.
Is it your contention that cast receivers of “hypoeutectoid” steelWith a medium carbon (“hypoeutectoid”) steel such as you might use for a receiver, cooled slowly from liquid, the steel doesn’t solidify all at once, but in fact the first thing to solidify is the ferrite, not the carbide.
Boston T. Party said:Assuming two bolt-action receivers of identical dimensions and
weight -- one constructed in forged steel and other in cast steel
(both of the best steel, process, and QC) -- would anybody here
assert that the cast version is of equal or superior tensile strength?
(Interestingly on this very point are two virtually identical rifle
receivers: the forged Win M70 Classic and Montana's cast version
of it. The Montana action may be heavier, however.)
I would assert that until they do some serious real-world testing and analysis of both receivers, nobody is qualified to state definitively which receiver is stronger. No science exists in a vacuum (except maybe pure mathematics).
With a medium carbon (“hypoeutectoid”) steel such as you might use for a receiver, cooled slowly from liquid, the steel doesn’t solidify all at once, but in fact the first thing to solidify is the ferrite, not the carbide. Ferrite is essentially pure iron (with a very small amount of dissolved carbon). Carbon is concentrated in the remaining liquid until it reaches about 0.8%, and this solidifies as a phase called pearlite, consisting of laminations of carbide and ferrite.
Not exactly:Moreeover, as I’ve said, the ferrite actually forms first in the steels we’re talking about, not the carbide, so the dendrites from which the crystals start to grow consist of this ferrite.
The area along which crystals meet, known as the grain boundary, is a region of mismatch. The boundaries are formed by materials that are not part of a lattice, such as impurities, which do not show a specific grain pattern. This leads to a noncrystalline (amorphous) structure at the grain boundary with the atoms irregularly spaced. Since the last liquid to solidify is generally along the grain boundaries, there tends to be a higher concentration of impurity atoms in that area.
http://info.lu.farmingdale.edu/depts/met/met205/crystallization.html
Well, yeah, but in the hypoeutectoid alloy, cooled slowly enough to avoid transformation to martensite or bainite, the carbide is all in the form of pearlite, which is a fine laminated structure – fine layers of hard carbide and soft ferrite combining to make a comparatively strong and tough structure.Hypoeutectoid alloys contain less carbon content than the maximum
dissolvable in the parent material of austenite. (The introduction of carbon
into austenite lowers its temperature of stability, but that effect peaks
at about 0.83% carbon content.)
Such alloys with <0.83% carbon will indeed form carbides, though only with
ferrite (called cementite, or Fe3C) because the austenite first dissolves carbons
until its saturation point of 0.83%. Cementite plus ferrite -- and slowly cooled --
is what creates the phase of pearlite (+ free ferrite), beginning at 0.20% carbon.
Beyond 0.83% carbon, you get free ferrite, pearlite, and non-ferrite carbides
(i.e., with the other alloys such as vanadium, tungsten, etc.).
No gun manufacturer wants pearlitic steel because the very definition
of pearlite means that the once-dissolved-in-austenite carbons were
foolishly allowed to precipitate out of the austenite solution to form
segregated cementites (Fe3C).
You are confusing a couple of important points here. First, investment castings are, in my experience, poured into investments (moulds) which have been preheated in a furnace to about 1000 degrees Celsius or so, and allowed to cool over a period of hours. It is not equilibrium cooling but nor is it anywhere near being quenching. You then clean off the mould material, do any finish machining and of course you are then at liberty to heat treat them any way you like. The same is true of forgings: you forge at temperatures above the austenite transformation temperature, cool slowly, and generally do your machining in the same normalised state, before heat treating to develop the final hardness. The reason is fairly simple: it is easier to do any machining before hardening. In either case though whenever you are ready you can quench and temper the product, or use some other heat treatment, to get the final properties you want.The whole point of a rapid cooling of
AISI 4140 gun receiver steel (which is oil quenched for 30 minutes from
an initial temp of some 1525°F/1625°F, by the way, not "slowly cooled"
as in your model) is to trap individual carbon atoms within the austenite
crystals, creating tough martensitic steel.
Except to the extent that, in direct contradiction of your earlier claims, carbides just don’t “segregate into dendrites” in these alloys.The fact that gun receiver steels such as AISI 4140 are <0.83%/hypoeutectoid
alloys is really immaterial regarding the issue of carbides segregating into
dendrites.
Quote:
The area along which crystals meet, known as the grain boundary, is a region of mismatch. The boundaries are formed by materials that are not part of a lattice, such as impurities, which do not show a specific grain pattern. This leads to a noncrystalline (amorphous) structure at the grain boundary with the atoms irregularly spaced. Since the last liquid to solidify is generally along the grain boundaries, there tends to be a higher concentration of impurity atoms in that area.http://info.lu.farmingdale.edu/depts...llization.html
If carbon solidifies last, then that helps to prove my point that carbides will
tend to accumulate along the grain boundaries, especially during internally uneven
parts crystallization.
Does forging more effectively distribute dissimilar alloys within the austerite?
Of course it does, that's one reason for the operation. There really can
be no disagreement about that.
Quality hot forging of carbon steel distributes the alloys, and the oil quench"freezes" this distribution in place for optimal strength. After nearly many
hours of research into all this, I'm really astounded that the matter can
seriously be called into question at all
Since McClung's thesis in my book (and thus its discouragementI do hope that the research you’ve done has sparked a bit of an interest, even though it is a bit late for your book
Assuming two bolt-action receivers of identical dimensions and
weight -- one constructed in forged steel and other in cast steel
(both of the best steel, process, and QC) -- would anybody here
assert that the cast version is of equal or superior tensile strength?