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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

Heat treating 4130 steel at home



 
 
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  #1  
Old January 18th 04, 10:04 PM
John Olson
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Default Heat treating 4130 steel at home

Is it possible to heat-treat 4130 CroMo steel at home? Does anyone know of
an online reference that explains the process? I've got a kiln big enough
to do hold the piece, and it runs to over 1200 deg C. I'm looking at
building an anti-sway bar for a car I'm making, and I may have to make more
than one to get the values right.

Cheers

John



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  #2  
Old January 19th 04, 12:35 AM
Jack Hayes
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Default Heat treating 4130 steel at home


"John Olson" wrote in message
...
Is it possible to heat-treat 4130 CroMo steel at home? Does anyone know

of
an online reference that explains the process? I've got a kiln big enough
to do hold the piece, and it runs to over 1200 deg C. I'm looking at
building an anti-sway bar for a car I'm making, and I may have to make

more
than one to get the values right.

Cheers

John



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I only did this once so don't consider this expert advice. Heat the part to
the point that it is no longer attracted to a magnet, then quench in oil
till cool. Then heat to a much lower temperature in the range of 350 to 600
Deg. F for long enough to soak the complete part. A lower temperature will
provide a harder but more brittle part, and of course if you heat it high
enough you anneal it and are back where you started. I was making a wrench
and used 400 Deg F in my wife's gas cook stove oven. Other will likely
provide a better description and more precise temperatures.

Jack


  #3  
Old January 19th 04, 06:57 AM
amdinc
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Default Heat treating 4130 steel at home

John Olson wrote:

Is it possible to heat-treat 4130 CroMo steel at home? Does anyone know of
an online reference that explains the process? I've got a kiln big enough
to do hold the piece, and it runs to over 1200 deg C. I'm looking at
building an anti-sway bar for a car I'm making, and I may have to make more
than one to get the values right.

Cheers

John

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the trick is to get the metal to the right temp and have a accurate way
of measuring it. A thermocouple gauge is used in most ovens. an old
time way was to heat it until a magnet will not stick to it and then
quench it in warm oil. you must be able to completely submerge the
piece or you will not quench it properly and it will catch on fire. YOu
need at least a gallon of oil for every pound of metal to handle the
heat. also you should either agitate the piece in the oil or have a
circulator for the oil around the piece.

you now have to temper the piece (draw it back)... that is to remove
some of the hardness and make the metal tough. for this you need a chart
for the temperature to bring it up to for the hardness you want. then
you let it cool and if possible do a hardness test on it.


john
  #4  
Old January 19th 04, 02:19 PM
Ecnerwal
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Default Heat treating 4130 steel at home

amdinc wrote:

you let it cool and if possible do a hardness test on it.


Be very careful _where_ you do that, of you do. One of the case studies
that was mentioned in on of my materials science courses was a brake or
wheel part which was hardness tested to verify heat-treat - they started
failing, and the failures were traced back to cracks starting in the
divot where the hardness tester had been used.

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  #5  
Old January 19th 04, 03:21 PM
Roy J
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Default Heat treating 4130 steel at home

A sway bar is going to be a stinker to do in a home shop. 3'
long, several bends, possibly tube/bar combination. You need a
furnace big enough to hold the entire part at 1700 degrees or so,
then drop into an oil bath. Bar parts should be dropped into the
bath end first to minimize distortion and anomilies from one side
of the round to the other. So you will need something like a 30
gallon barrel on it's side for a furnace with a propane burner
plus another 30 gallon barrel with your quench medium.

Your heat treat specs are at http://www.matweb.com/index.asp?ckck=1
key in '4130' select the size and specs you need.

You might also want to look at 4140. Similar properties, a bit
more forgiving on the heat treat but typically wants an oil quench.

Be sure to design the bar with multiple holes in the end so you
can select a range of firmness without doing a new bar.

Other posters mentioned the safety issue: 4130 can be pushed to
some truely phenominal streght numbers. I've done tubing
assemblies over 200,000psi tensile with reasonable ductility. The
downside is that 4130 has a fairly narrow band between tensile
and yield. If the heat treat is not dead on, it tends to snap
with no warning. Not to mention the issues of surface finish,
stress risers, nicks and scratches, and warpage.

Cheers.

John Olson wrote:

Is it possible to heat-treat 4130 CroMo steel at home? Does anyone know of
an online reference that explains the process? I've got a kiln big enough
to do hold the piece, and it runs to over 1200 deg C. I'm looking at
building an anti-sway bar for a car I'm making, and I may have to make more
than one to get the values right.

Cheers

John



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  #6  
Old January 19th 04, 08:42 PM
Robert Scibienski
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Default Heat treating 4130 steel at home

Whether you are interested in racing cars or not, buy and read
(several times) Carroll Smith's "Engineer to Win". It contains the
best layman's introduction to metals and metallurgy that I have ever
read. When you are done you will know how to heat treat 4130, whether
you need to do so, and if so whether to do it yourself or to have it
done professionally- But you may also decide that you don't need to
use 4130 for your purposes.
Bob S.
  #7  
Old January 19th 04, 08:49 PM
Ed Huntress
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Default Heat treating 4130 steel at home

"Robert Scibienski" wrote in message
...
Whether you are interested in racing cars or not, buy and read
(several times) Carroll Smith's "Engineer to Win". It contains the
best layman's introduction to metals and metallurgy that I have ever
read. When you are done you will know how to heat treat 4130, whether
you need to do so, and if so whether to do it yourself or to have it
done professionally- But you may also decide that you don't need to
use 4130 for your purposes.
Bob S.


Yeah, I was going to point out that 4130 may be a waste of money and time,
and heat treating it may waste more of each. I remember learning about sway
bar design and materials back when I was involved in amateur racing but,
unfortunately, I have a crappy memory. g

However, it would surprise me if a sway bar designed for a high-performance
car would even approach the elastic limit of untreated, cold-rolled steel.
It shouldn't deflect a great deal. Much more likely to need fancy steel and
heat treatment is an ordinary street sedan, in which the bar would be less
stiff, and therefore would need more elasticity.

In any case, the difference in elastic limit between the normalized
condition and the hardened condition is not that great for 4130. It's fairly
strong as it is, and it isn't tremendously strong even when heat treated.

Ed Huntress


  #8  
Old January 20th 04, 12:45 AM
Roy J
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Default Heat treating 4130 steel at home

snip

However, it would surprise me if a sway bar designed for a high-performance
car would even approach the elastic limit of untreated, cold-rolled steel.
It shouldn't deflect a great deal. Much more likely to need fancy steel and
heat treatment is an ordinary street sedan, in which the bar would be less
stiff, and therefore would need more elasticity.

In any case, the difference in elastic limit between the normalized
condition and the hardened condition is not that great for 4130. It's fairly
strong as it is, and it isn't tremendously strong even when heat treated.


???????????

The modulus of elasticity is the same whether it is heat treated
or not. ie for a force of x, it will deflect y. The question is:
does the deflection make it exceed the yield strength? Annealed
4130 is about half again stronger (higher yield strength) than
equivilent cold rolled mild steel. (80-90kpsi versus 50-60kpsi)
The heat treated version of 4130 can easily push past 200kpsi or
more than double its unheateated version.

I agree that a flat track car might get along with a non heat
treated bar, but an off road racing vehicle needs all it can get
from the sway bar.

  #9  
Old January 20th 04, 01:33 AM
Ed Huntress
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Default Heat treating 4130 steel at home

"Roy J" wrote in message
...
snip

However, it would surprise me if a sway bar designed for a

high-performance
car would even approach the elastic limit of untreated, cold-rolled

steel.
It shouldn't deflect a great deal. Much more likely to need fancy steel

and
heat treatment is an ordinary street sedan, in which the bar would be

less
stiff, and therefore would need more elasticity.

In any case, the difference in elastic limit between the normalized
condition and the hardened condition is not that great for 4130. It's

fairly
strong as it is, and it isn't tremendously strong even when heat

treated.

???????????

The modulus of elasticity is the same whether it is heat treated
or not. ie for a force of x, it will deflect y.


The modulus is, but the elastic *limit* depends on its yield strength. In
fact, the elastic limit IS the yield strength.

This is a field in which terms always get misconscrewed. By more
"elasticity" I mean the ability to deflect farther without exceeding the
yield strength.

The question is:
does the deflection make it exceed the yield strength?


That's what I said. g

Annealed
4130 is about half again stronger (higher yield strength) than
equivilent cold rolled mild steel. (80-90kpsi versus 50-60kpsi)
The heat treated version of 4130 can easily push past 200kpsi or
more than double its unheateated version.


I don't think you want to make a spring -- or an anti-roll bar -- out of 200
kpsi 4130. If it's going to fail, you want ductile failure, and the
elongation at 200 kpsi strength is close to zilch.

The bigger point, though, is this: If you're loading 4130 to, say, 150 kpsi,
you're getting a lot of spring deflection at that load. In a
high-performance car you don't want a lot of spring in your anti-roll bar,
so you make it of a larger section or you use shorter arms. Of course, by
using shorter arms you also demand more twisting displacement from the bar
for a given amount of travel, so you could wind up loading the bar quite
heavily toward its ultimate strength if you compensate for a
smaller-diameter bar by using shorter torque arms.

The ideal is the longest practical arms. For the kind of deflection you want
in a race car or high-performance car, that means you want a bar of larger
diameter, which does less twisting in use. That keeps the specific torsional
load (the load per unit of metal) relatively low; low enough, IIRC, that
there should be no benefit whatsoever from using a high-strength bar.

Ed Huntress





  #10  
Old January 20th 04, 02:04 AM
jim rozen
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Default Heat treating 4130 steel at home

In article , Ed Huntress
says...

This is a field in which terms always get misconscrewed.


Well that's a new one. Are we talking about
gas regulators here??

:^)

Jim

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