Ed Huntress wrote:
On Sun, 09 Nov 2014 13:05:58 -0600, F. George McDuffee
wrote:

On Sun, 9 Nov 2014 09:47:38 -0800 (PST), Sandarpan Mukherjee
wrote:

snip
The bar will be at least 190000 psi tensile st=
rength with 170000 psi yield strength.
/snip

You are talking about very expensive HY210 submarine hull
steel. I don't know if this is available in the civilian
market.

These specs seem excessive for even Olympic class lifters.
A quick google search indicates less than 300Kg for any
single lift. http://tinyurl.com/lmoxl6a

He's around the high end for heat-treated 4340. The thing is, with
yield of 170 kpsi and ultimate tensile of 190, when that bar is
overloaded, it's going to go "Bang!"

It doesn't sound like something you'd want in a barbell. g


Actually his numbers are at the minimum that are allowed in an Olympic bar.
The lower end bars are 170K tensile. The good ones are up around 210K!

The idea is that the bar has to flex when you lift, that helps you by
storing energy that helps you flip during the lift. The bars also have
bearing inside the weight sleeves so that as you lift the plates don't
apply any torque to the bar and spoil the lift.

I have friends who lift HEAVY and most seem to use Eleiko, York or
Werksan bars. They are not cheap but they do seem to last.

When they do clean/jerk lifts that bar looks like a wet noodle.

--
Steve W.

On Mon, 10 Nov 2014 10:43:15 -0500, "Steve W."
wrote:

Ed Huntress wrote:
On Sun, 09 Nov 2014 13:05:58 -0600, F. George McDuffee
wrote:

On Sun, 9 Nov 2014 09:47:38 -0800 (PST), Sandarpan Mukherjee
wrote:

snip
The bar will be at least 190000 psi tensile st=
rength with 170000 psi yield strength.
/snip

You are talking about very expensive HY210 submarine hull
steel. I don't know if this is available in the civilian
market.

These specs seem excessive for even Olympic class lifters.
A quick google search indicates less than 300Kg for any
single lift. http://tinyurl.com/lmoxl6a

He's around the high end for heat-treated 4340. The thing is, with
yield of 170 kpsi and ultimate tensile of 190, when that bar is
overloaded, it's going to go "Bang!"

It doesn't sound like something you'd want in a barbell. g


Actually his numbers are at the minimum that are allowed in an Olympic bar.
The lower end bars are 170K tensile. The good ones are up around 210K!

The idea is that the bar has to flex when you lift, that helps you by
storing energy that helps you flip during the lift. The bars also have
bearing inside the weight sleeves so that as you lift the plates don't
apply any torque to the bar and spoil the lift.

I have friends who lift HEAVY and most seem to use Eleiko, York or
Werksan bars. They are not cheap but they do seem to last.

When they do clean/jerk lifts that bar looks like a wet noodle.

That's really pushing what you can do without really good material
specification and very expert heat treating. You can get the ultimate
tensile strength, but avoiding brittleness at that level of tensile
strength is a job for the experts.

--
Ed Huntress

replying to Steve W. , Sandarpan Mukherjee wrote:
csr684 wrote:

Actually his numbers are at the minimum that are allowed in an Olympic
bar.
The lower end bars are 170K tensile. The good ones are up around 210K!
The idea is that the bar has to flex when you lift, that helps you by
storing energy that helps you flip during the lift. The bars also have
bearing inside the weight sleeves so that as you lift the plates don't
apply any torque to the bar and spoil the lift.
I have friends who lift HEAVY and most seem to use Eleiko, York or
Werksan bars. They are not cheap but they do seem to last.
When they do clean/jerk lifts that bar looks like a wet noodle.
--
Steve W.



What you are saying is absolutely true. This link ebay. co
m.au/itm/F-OLB-Force-USA-Olympic-Lifting-Bar-20-Kg-Cross-Fit-Warranted-for-Crossfit-Use-/321487232831
(delete the spaces) advertises a bar of 216000 psi TS and it's mentioned
that the bar is made from SCM 440 (same as AISI 4140) heat treated steel.
What's bothering me is the hardness. Firstly I want to machine the bar and
I also don't want it to be too brittle. Even if the yield strength is
exceeded, I want the bar to bend not break.

Thanks

--


--
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http://www.polytechforum.com/metalwo...ll-605857-.htm
using PolytechForum's Web, RSS and Social Media Interface to
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On Sat, 15 Nov 2014 18:18:01 +0000, Sandarpan Mukherjee
wrote:

replying to Steve W. , Sandarpan Mukherjee wrote:
csr684 wrote:

Actually his numbers are at the minimum that are allowed in an Olympic
bar.
The lower end bars are 170K tensile. The good ones are up around 210K!
The idea is that the bar has to flex when you lift, that helps you by
storing energy that helps you flip during the lift. The bars also have
bearing inside the weight sleeves so that as you lift the plates don't
apply any torque to the bar and spoil the lift.
I have friends who lift HEAVY and most seem to use Eleiko, York or
Werksan bars. They are not cheap but they do seem to last.
When they do clean/jerk lifts that bar looks like a wet noodle.
--
Steve W.



What you are saying is absolutely true. This link ebay. co
m.au/itm/F-OLB-Force-USA-Olympic-Lifting-Bar-20-Kg-Cross-Fit-Warranted-for-Crossfit-Use-/321487232831
(delete the spaces) advertises a bar of 216000 psi TS and it's mentioned
that the bar is made from SCM 440 (same as AISI 4140) heat treated steel.
What's bothering me is the hardness. Firstly I want to machine the bar and
I also don't want it to be too brittle. Even if the yield strength is
exceeded, I want the bar to bend not break.

Thanks

It's not easy to find specific elongation properties of 4140 when it's
heat-treated to 216 kpsi tensile. At the extreme end, 285,000 psi,
elongation is 11% and machineability is 65%. Hardness is 578 Brinell
or Rc 55.

That's more machineable than I expected, although it's carbide-only at
285 kpsi, and I didn't even know that it could develop 285 kpsi
tensile strength. That kind of tensile strength, in diameters larger
than wire, usually is associated with fairly brittle specialty steels
and very low elongation.

So, at 216,000, elongation can be expected to be over 11%. That's not
terrible. It shouldn't be inclined to break as soon as the yield
strength is exceeded.

The thing is, heat-treating sounds tricky -- normalize, reheat for
time, oil-qnench and extended temper -- and it probably requires real
expertise to achieve those extreme properties without brittleness. You
can buy it normalized but the time/temperature sounds like a job for
carefully controlled furnaces.

http://www.matweb.com/search/datashe...a46a1f1 eb1c3

Good luck!

--
Ed Huntress

replying to Ed Huntress , Sandarpan Mukherjee wrote:
huntres23 wrote:

On Sat, 15 Nov 2014 18:18:01 +0000, Sandarpan Mukherjee
It's not easy to find specific elongation properties of 4140 when it's
heat-treated to 216 kpsi tensile. At the extreme end, 285,000 psi,
elongation is 11% and machineability is 65%. Hardness is 578 Brinell
or Rc 55.
That's more machineable than I expected, although it's carbide-only at
285 kpsi, and I didn't even know that it could develop 285 kpsi
tensile strength. That kind of tensile strength, in diameters larger
than wire, usually is associated with fairly brittle specialty steels
and very low elongation.
So, at 216,000, elongation can be expected to be over 11%. That's not
terrible. It shouldn't be inclined to break as soon as the yield
strength is exceeded.
The thing is, heat-treating sounds tricky -- normalize, reheat for
time, oil-qnench and extended temper -- and it probably requires real
expertise to achieve those extreme properties without brittleness. You
can buy it normalized but the time/temperature sounds like a job for
carefully controlled furnaces.

http://www.matweb.com/search/datashe...a46a1f1 eb1c3
Good luck!
--
Ed Huntress



Thanks Ed,

At this point I'm not overly concerned with heat treatment procedures.
Heat treatment in general is a tricky thing. I am just trying to zero in
on the actual material.

--


--
posted from
http://www.polytechforum.com/metalwo...ll-605857-.htm
using PolytechForum's Web, RSS and Social Media Interface to
rec.crafts.metalworking and other engineering groups