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Distortion of A2 air-hardening steel

opscimc

Stainless
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Jan 24, 2012
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If I use an acetylene torch to heat a 2"-long rod of 1"-diameter A2 steel that is "perfectly" straight to begin with, to red hot and then allow it to cool, how much can I expect it to warp along its length?
 
Never done anything like that, I would hope a couple tenths max,
BUT I also if I cared how straight it stayed would fixture it in a lathe and spin it fairly quick move back and forth as quick as possible, to heat it as evenly as possible
wont know til yah try!:D
 
The answer depends a lot on your skill with a torch. Scaling on the part should be a greater problem than straightness.
 
would fixture it in a lathe and spin it fairly quick move back and forth as quick as possible, to heat it as evenly as possible
Thanks for the suggestion. Although the maximum speed of my welding positioner is only 5 rpm, it's much more appropriate for such use (abuse) than my lathe. Still, I would like to know how much warping, i.e. loss of straightness, to expect.
 
If I use an acetylene torch to heat a 2"-long rod of 1"-diameter A2 steel that is "perfectly" straight to begin with, to red hot and then allow it to cool, how much can I expect it to warp along its length?
Using a torch to heat treat A2 is not a good practice. It should pre-heated; held at the preheat temperature and then be raised to quenching temperature in a furnace. We might get away with using a torch on much smaller dia. rod.
Roger
 
How long is a piece of string. All that can ever be definitively said about hardening is that it will move, sometimes it grows sometimes it shrinks and sometimes it bends no one ever knows exactly how much.

When I did flame hardening which was as an absolute last resort I would build a little oven/enclosure with refractory bricks to ensure consistent soak. ON quench or cooling never cool a long side that will cause warping.
 
Your question has been answered.
It will distort and no one can say how much.
You will get scale.
You will get questionable results.

All of the above will range from so-so to terrible based on your skill level.
 
If I use an acetylene torch to heat a 2"-long rod of 1"-diameter A2 steel that is "perfectly" straight to begin with, to red hot and then allow it to cool, how much can I expect it to warp along its length?

so what's stopping you trying it yourself?

Heaven forbid you learn something from the experiment.
Not trying to be a dick, but what's the worst that's going to happen?

It's what $5-10 for the material and a few cents for the gas?

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It may not be straight (depends on how even the temp is thru the part) and the surface will look like hell if heated with a torch and air cooled.
 
Just throwing this out there. Red hot isn’t hot enough. Salmon to light orange will take you to 16-1700°F needed.
 
You haven't bought any acetylene lately, have you?

Nope. I use my neighbours :)

usually costs me a double burger special down at Mike's Burgers. I figure he comes out ahead.
 
You haven't bought any acetylene lately, have you?

Nope. I use my neighbours :)

usually costs me a double burger special down at Mike's Burgers. I figure he comes out ahead.
You should take him to a curry joint after a few hours you won't need any acetylene :D
 
so what's stopping you trying it yourself?

Heaven forbid you learn something from the experiment.
Not trying to be a dick, but what's the worst that's going to happen?

It's what $5-10 for the material and a few cents for the gas?
$54 for a 1 ft. length of 1-1/4" from McMaster-Carr. There's no point wasting the time or money if someone already has done the experiment and knows the answer. That's why I asked the question. If no one here knows the answer, I'll have to do it myself, but hope springs eternal someone who actually knows will respond.
 
$54 for a 1 ft. length of 1-1/4" from McMaster-Carr. There's no point wasting the time or money if someone already has done the experiment and knows the answer. That's why I asked the question. If no one here knows the answer, I'll have to do it myself, but hope springs eternal someone who actually knows will respond.
The experiment has been done countless times over the years and anybody that tells you that you will not get distortion during heat treatment is full of shit. You get certain processes and materials that have minimal distortion however there is a phase change taking place so no distortion is a physical impossibility. The amount of distortion can be determined by controlling every single aspect of the process and from that you can obtain the data that will give you a operating window. You want to use a torch in an uncontrolled environment and expect someone to tell you how much distortion to expect.
 
You want to use a torch in an uncontrolled environment and expect someone to tell you how much distortion to expect.
Well, yes. As you say, the experiment has been done countless times, so someone knows the answer. My question is about a 1"-dia. rod that's 2" long. Irrespective of the lack of control, and while the warping very likely will be more than 0.000", it definitely will be less than 2". Under the circumstances, would the maximum be, say, 0.1"? 0.050"? or ___?
 
Well there is no way of telling the warp because its relative to the process but, As I looked into this, I don't know shit about heat treating, but seems it will change dimension more than your worry about bend.
A2 heat treat
 
Educated guess, it will grow or shrink or warp less than .002" overall (assuming you heat it evenly, not all from one side) but you will need to remove at least that much material to clean the scale off the surface to be able to measure any deformation. That's why it's usually heat treated in stainless foil (to limit the amount of scale) or in a vacuum to eliminate it.
 
Educated guess, it will grow or shrink or warp less than .002" overall ...
If that is truly based on experience, it is quite useful. Thanks. I need to make an odd cutting tool, harden it, and then form it to final size with a tool post grinder. The closer I can make it to the final size prior to hardening, the less material I'll have to (slowly) remove with the grinder. Having a reasonable estimate of the heat-caused distortion is valuable because, obviously, making it 0.005" oversize would be a lot better than making it 0.050" oversize.
 








 
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