# 4130, TIG and Heat Treat?



## Nockpoint 01 (Mar 4, 2009)

Hi: Specifically, I was wondering if a frame has to be "normalized" after the welding operation?
Many thanks!


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## BigHank53 (May 19, 2011)

Short answer: no.

Welding textbooks will say yes. However, most welding texts were written by people building big, heavy things like pipelines, ocean liners, and bridges, where "thin material" meant "thinner than my finger.

The reason for normalization was that the huge power poured into a thick section (they build welders that go to 750 amps for a reason) combined with the lousy conductivity of steel doesn't heat the piece evenly, and you wind up with a HAZ that can be smaller than the weld itself, and absolutely filled with stresses. Thin sections like bicycle tubes have a huge HAZ in comparison to the welds, and don't have this problem.

Millions of un-normalized frames have demonstrated this.


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## jucasan (Mar 18, 2012)

What about aluminum frames?


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## BigHank53 (May 19, 2011)

7005: no heat treatment.

6061: required.


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## j-ro (Feb 21, 2009)

BigHank53 said:


> 7005: no heat treatment.
> 
> .


But reccomended....

To the OP, 4130 does'nt need heat treating unless you use 4130 filler rod.


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## ROSKO (Oct 11, 2009)

j-ro said:


> ...To the OP, 4130 does'nt need heat treating unless you use 4130 filler rod.


and if you were to go that route they would indeed normalize as part of the process.


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## jucasan (Mar 18, 2012)

Can you do the heat treatment "in a garage" or you need fancy machines to do that? 
What is it, an oven?


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## LemonFool (Mar 20, 2012)

Oxy-acetylene torch has been my experience. I don't see any reason MAPP gas, or butane torch wouldn't work since their temperature range is greater than the normalization point.

As a further question, I can see where it might not be _critical_ to stress relieve the frame (although I'd be most temped to do at least the head tube), but what are the opinions on stress relieve forks? I've seen a few pictures of fork failures right by a weld while reading up in the fora.


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## jucasan (Mar 18, 2012)

Just with an oxy torch? Any recomendation for the temperature?


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## ROSKO (Oct 11, 2009)

any reference you see to stress relieving 4130 using oxy/ace is using thick walled tubing of .120 or greater. Nothing like what is used in most bicycles. 

If you are serious about having welded 4130 structures heat treated do your due diligence and get to work with the search function of your browser. You'll find it a very exact science and should be treated as such.


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## LemonFool (Mar 20, 2012)

h t t p:/ /i. i mgur.com/4ZtlN.j pg (Without spaces since I'm new here, and this might be the only way to have a look.)

We did a little test at the beginning of the year at our shop for our chassis welds with a crappy tubing bender applying pressure in the middle. A quick synopsis: We quenched the bottom one for the heck of it. It failed quickly, and as expected. The non stress relieved is next up, and failed at the weld. The top one was stress relieved with our usual method, and the material failed before the weld. We used 0.065 wall thickness 4130. Not a rigorous scientific test, but a little bit of info for us. I'm tempted to do it with .028 today out of curiosity. 

Having shown that, I'd definitely take the experience and practicality of those in the industry for what's necessary. The benefits of stress relieving such thin walled tubing are possibly pretty small in this case, and an oxygen/acetylene torch and sharpie aren't exactly a science like normalization of production materials. 

I'd still like to know if those that build rigid steel mountain forks do stress relieving?


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## Teague (Jul 2, 2005)

LemonFool said:


> We did a little test at the beginning of the year at our shop for our chassis welds with a crappy tubing bender applying pressure in the middle. A quick synopsis: We quenched the bottom one for the heck of it. It failed quickly, and as expected. The non stress relieved is next up, and failed at the weld. The top one was stress relieved with our usual method, and the material failed before the weld. We used 0.065 wall thickness 4130. Not a rigorous scientific test, but a little bit of info for us. I'm tempted to do it with .028 today out of curiosity.


I assume you used 4130 filler? I'm curious as to how a higher tensile strength filler would affect this test. I would probably expect them to fail at the HAZ rather that the weld itself. With the stress relieved part it looks like tube failed nowhere near the weld, so it seems the stress relieving completely removed the HAZ? Makes sense, but i hadnt previously seen it demonstrated so effectively! Thanks!

Edit: actually now that i look at it again it does look like it crumpled in the HAZ. hmm..


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## LemonFool (Mar 20, 2012)

I don't remember off the top of my head whether it was ER70s or ER80s.

For the HAZ, the material did yield from the load, but the weld proximity didn't fail (the weld itself is intact, although squished). We were loading it until the material crushed or weld failed. Notice it also did yield at the other load (reaction) points. Big difference between cracked weld and crushed tubing from a ridiculous load!


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## ROSKO (Oct 11, 2009)

If you have a 4130 tube welded using er70s rod failing AT THE WELD- this is not an issue of heat treat it is an issue with the weldor. Using that combination and proper technique the material should always fail before the weld.

back to the OT- to get a 4130 structure heat treated is easy. Just make the phone call. The folks at your local HT company should be able to walk you through the whole affair and recommend routines for your application. The process involves heat cycles to the entire pieces for specific times and at specific temperatures. Uniformity is key. Solution heating in a salt bath furnace. They can even guarantee optimal results. Really there is NO way to do this repeatably by hand.

For some funny old school welding and metallurgy here's a bit that's simple to digest:
Heat Treated 4130

Steel metallurgy is some wild stuff, it's crazy that this alloy has been around for so long yet techniques are still being developed to optimize it's properties. Down the rabbit hole you go... enjoy!


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