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Mike Andersson

Coil spring

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I am trying to make some hot tools out of a coil spring. I get the working ends up to quenching temperature and I quench in oil. But they don't get as hard as I think they should. Do I have to do something special with this kind of metal?

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Lots of questions.  How hot are you getting the steel, what sort of oil, what makes you think they aren't hard?   Without knowing what the steel is, there is no way to know what you should do with the steel.

Coil spring is probably 5160, though it could be 1095, or 9250.  I suppose that for a given application it might be case hardened mild steel, but that would be strange.

Take a piece, heat it to non magnetic, and quench in water.  Give it a smack with a hammer.  It should shatter like glass.  That is your first step.  After that we can talk about process.

Geoff

Edited by Geoff Keyes

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Thanks Jeoff, I get it to non magnetic and quench it in peanut oil. When it cools I check it with a flat file and it states right off, but when I check it with a triangular file it digs in. I did the spark test on the metal before starting and looked like it was high carbon so I thought it would harden well. I'm going to try what you said about quenching it in water and hitting it with a hammer and see what happens.

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Sounds like your flat file is a bit dull and the triangle isn't.  If your spring is 5160 or 9260, nonmagnetic is not hot enough by about 175 degrees F and it won't harden fully.  If it's 1084 (Jason Knight says Toyota coils are 1084) nonmagnetic is around 50 degrees F too cold.  If your coil is off a post-2008 or so Ford it is not hardenable by conventional methods.

Finally, forge scale is harder than a file,  be sure to test a clean spot.

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A friend wanted to make tools from Land Rover coil spring, he straightened it, we squared it up, folded it double and did the heat treat in my kiln using the parameters for 5160, quenched in oil and it did not harden

Repeated and quenched in water, still no joy.

At least.......not as hard as I would expect it to be...... 

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Possible surface decarb from overworking the steel at elevated temperatures.  Might have to grind through that layer to reach hardened steel.  What is the thickest crossection that you are quenching?  Are you letting it fully cool down before pulling it out of the quenchant?  How well calibrated is your kiln?  How long does it take you to get the stock out of the kiln and into the quenchant?

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One thing to consider when making hot work tools.  The heat from the steel that you are working on will draw the temper in your tools so hardening and tempering the tool may just be spinning your wheel.  Even unhardened the hot work tool will be harder than the hot steel you're working on.

Doug

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On 2/10/2019 at 10:01 PM, Geoff Keyes said:

Take a piece, heat it to non magnetic, and quench in water.  Give it a smack with a hammer.

That sounds like fun lol I’m going to have to try that one.

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18 hours ago, Dan Hertzson said:

Possible surface decarb from overworking the steel at elevated temperatures.  Might have to grind through that layer to reach hardened steel.  What is the thickest crossection that you are quenching?  Are you letting it fully cool down before pulling it out of the quenchant?  How well calibrated is your kiln?  How long does it take you to get the stock out of the kiln and into the quenchant?

Possible, Mike did most of it in his coal forge, we squared the last bit using my gas forge.

it's about 0.5", and in the case of the oil and water it was in for a while....long enough for sure.

The kiln is brand new, used by many in this part of the world, and going on other results no reason to doubt it.

Klin to oil is 2 seconds at the most.

My Google-Fu was not strong enough to find out what steel is used by Land Rover, there's a heap of info out there about the colour codes of the springs, but nothing about the steel used.

11 hours ago, Doug Lester said:

One thing to consider when making hot work tools.  The heat from the steel that you are working on will draw the temper in your tools so hardening and tempering the tool may just be spinning your wheel.  Even unhardened the hot work tool will be harder than the hot steel you're working on.

Doug

I believe he wanted to make chisels for somebody that turns bowls on a lathe.

I don't agree with the method of the steel. but not my circus. :D

On 2/11/2019 at 8:01 AM, Geoff Keyes said:

Lots of questions.  How hot are you getting the steel, what sort of oil, what makes you think they aren't hard?   Without knowing what the steel is, there is no way to know what you should do with the steel.

Coil spring is probably 5160, though it could be 1095, or 9250.  I suppose that for a given application it might be case hardened mild steel, but that would be strange.

Take a piece, heat it to non magnetic, and quench in water.  Give it a smack with a hammer.  It should shatter like glass.  That is your first step.  After that we can talk about process.

Geoff

We used 830C as is suitable for 5160.

I did not think of trying to snap it, it was a long day of forging, many beers were consumed, and by the time we got around to HT the sun was down and the beer finished :P

Tested with a file, I got the impression it hardened, but not much.  Considering the last quench was in water makes me suspect the steel is unsuitable.

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