Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60

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Hi everyone,

Does anyone have any data on the compressive yield strength of 4140 &
A2 tool steel hardened to both 55 & 60 RC ? Perhaps there is a chart
out there but I have not been able to find anything, especially with
regards to 4140. I would suspect the A2 is higher, but I would like to
compare them.

A chart showing compressive yield strength of various steels at
different hardnesses would be helpful. Any links or web sites you could
refer me to would be helpful. I already tried www.matweb.com. I'm also
interested in comparing S5 & S7 tool steel at the same two hardnesses.

Thanks
John


Re: Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60
snipped-for-privacy@yahoo.com says...
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Tensile strength correlates pretty closely with hardness in most steels,
so there's not going to be a lot of difference between various materials
at equal hardness. Rc55 is about as hard as 4140 gets as quenched in
small sections, and it's not generally used without tempering to a lower
hardness.

Uconeer is an excellent free units converter with a hardness conversion
function that includes hardness to tensile strength.
http://www.katmarsoftware.com/uconeer.htm

This is an online converter...
http://www.unified-eng.com/scitech/hardness/hardness.html

Crucible has a lot of good data on tool steels, though finding it on
their website is not always easy.
http://www.crucibleservice.com /

Ned Simmons

Re: Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60
Hi Ned,

Thanks for your reply.

Will the tensile strength generally be comparable to the compressive
yield strength ?

I have a chart showing the tensile strength of 4140 at RC 52.5 at
240,000 PSI and a Tensile "fittted" strength of 230,000 PSI. I'm not
sure how this relates to compressive yield strength though.

Do you think the 4140 and A2 would have comparable compressive yield
strengths at RC55?

I would like to find a cam material that has a compressive yield
strength of at least 260,000 PSI after heat treatment. The cam rotates
so slow I think the application could be considered static.

I think I remember reading in Timoshenko's book on the strength of
materials that hardened steel can handle Hertz contact stresses of over
450,000 PSI in static applications owing to the fact that at the center
of the ellipse of contact, the material is compressed not only in the
direction of the force but also in the lateral direction.  I don't
think it mentioned what type of steel or how hard. I do not presently
have a copy of the book.

Thanks again,
John

Ned Simmons wrote:
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Re: Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60
Ned,

I forgot to mention my maximum Hertz contact stress is about 260,000
PSI so I would think the compressive yield strength of the material
should be at least this amount or a little higher for safety. However,
Timoshenko seemed to be suggesting that this might not be the case,
unless I misunderstood what I read.

Also, thanks for the links you gave.

John

John2005 wrote:
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Re: Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60

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Clarification:
Timoshenko only suggested this for static applications, not
applications with dynamic forces that need to be accounted for.

John

John2005 wrote:
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Re: Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60
snipped-for-privacy@yahoo.com says...
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The yield is obviously going to be somewhat less than ultimate tensile,
but the spread will be less percentage-wise than at lower hardness.

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My graph for 4140 shows a tensile of 260 ksi, and a yield of 235 ksi at
RC52.

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I think so, but I bet A2 will be tougher at that hardness. Rc55 is at
the low end of A2's toughness peak, Rc58-60 may be a better range.

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I'm getting that feeling of deja vu all over again. I think I
recommended SAE 52100 before and will do so again.

<http://www.nnbr.com/NN%20Ball%20&%20Roller/Product %
20Information/Rollers/Materials/Chrome.html>

Quoted yield at Rc60-66 is 295ksi

Ned Simmons

Re: Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60
snipped-for-privacy@nedsim.com says...

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There's some interesting test data here on 52100 and a hi-tech (and
preumably high-dollar) alternative to 52100...
http://www.crucibleservice.com/datash/dsvimcru20.pdf

Ned Simmons

Re: Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60
Hi Ned,

Thanks for the additional feedback,

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John:

Yes, I did go through this before and decided on A2 hardened to at
least 55RC, but my machinist suggested to use 4140, I guess because
they feel it machines easier or because it's more readily available or
cheaper from a material standpoint.

I could not find much data on the compressive strength of 4140 at RC55,
so I posted in hopes I could get a little data for comparison. It was
also suggested by crucible to use S5 or S7 Tool steel with A2 as a good
second choice. I think I decided on A2 because it had good dimensional
stability and seemed to have a compressive yield of over 300,000 PSI at
55RC according to a www.crucibleservice.com chart.

At the online hardness conversion link you gave, it calculated the
tensile strength of steel at about 303,000 PSI at 55RC. Perhaps the
4140 would work OK and be better from a cost standpoint, but I also
feel the A2 would be tougher, and the same would probably apply to S5 ,
S7, and SAE 52100.

I will also keep the SAE 52100 in mind and will suggest that as an
alternative.

Thanks again for your help, both times :-)

Take care and happy holidays.

John

Ned Simmons wrote:
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Re: Compressive yield strength of 4140 versus A2 tool steel hardened to RC 55-60

John2005 wrote:

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Although Ned seems to know about your application, you may be more
successful by explaining what the application is to the rest of us.

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than those numbers you've posted. The successful application of various
types of tool steels is generally very dependant on the type of
conditions and wear mechanisms the part will experience while in use.

Additionally, if this is a stamping application, there may be
significantly greater forces working on your part during tryout or in
the case of a crash. You should be aware that a 20% increase in
material strength is trivial compared to a 1000%+ increase in force in
the worst case. Dies are over-built for a reason.

Also, machining is a major concern in tool steels. Certain steels are
significantly more difficult/expensive to machine and you should listen
closely to your machinist/toolmaker when they explain why they're
making recommendations about material choices, especially if you're
paying by the hour/cutting tool.

Regards,

Robin


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