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Welding temperature versus frame stiffness at BB

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Welding temperature versus frame stiffness at BB

Old 05-20-24, 12:55 AM
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Originally Posted by unterhausen
Lots of bikes are designed by non-engineers who have very little clue about fatigue failures, and even engineers can fail to properly take fatigue failure into account.
Used to be, lots of bikes (nearly all) were designed by non-engineers, who had no access to advanced design tools. Even the big makers didn't have the horsepower to solid model a frame and do FEA in ANSYS 40 years ago.

Now, I think there are more engineers involved, but even non-degreed designers, can do solid modeling and FEA on a *laptop*, and desktop computing now has huge power. There's tons of technical data and advice online, and some amazing software packages for FREE. Like in the computer industry, there a lot of non-degreed folks who specialize in a particular skill and are doing good designs in industry. So I think in terms of technical analysis, things are better than they've even been in the bike industry. The only downside I see is that, with the ease of computer modeling and sending directly to computer-aided-manufacturing, it's so much easier and so fast, designs are often produced before sufficient analysis and validation testing, in the same way as with computers, smartphones, and software, there's a hard push from management to "move fast, and SHIP". There's less rigor in checks and safeguards enforced than, in say, automotive. I think time is the bigger factor now than lack of skill and analysis tools available.

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Old 05-23-24, 06:27 AM
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Originally Posted by unterhausen
I'm not sure where you're getting this stuff about atmospheric nitrogen being a problem post-weld. I couldn't find any references to that. Apparently people want to use pure nitrogen as a post-weld purge gas because it's cheap, but there seems to be some evidence that it can cause issues.

Hydrogen embrittlement is definitely something that welders worry about and take steps to avoid. I haven't seen evidence that there is a widespread issue with it in framebuilding. Tig welded 4130 has been used in bicycle framebuilding since the mid '80s. I'm pretty sure everyone has a pretty good handle on the processes by now, and the information about how to weld it correctly is widely available. The welding industry is pretty good at publishing good information and sponsoring research.

From what I have seen looking at bike failures, there are far easier ways to get a bike to fail than the joining process. Lots of bikes are designed by non-engineers who have very little clue about fatigue failures, and even engineers can fail to properly take fatigue failure into account. We really couldn't cover all the different ways that bikes can fail in one thread. It would be an amorphous mess of very little utility.

So you can admit hydrogen embrittlement is real but because you cant find any literature on nitrogen your disregarding it, just because the titanic wasnt found in the first 50 years doesnt mean it wasnt there does it.

Youve even admitted using nitrogen as a purging gas causes problems.... ive stated the reason.

Your also saying im not a bike builder no im not but some how because you build bikes you know everything about metal?

Im a welder fabricator by trade, went to college etc so i have the theory side not just some practical skill

Ive linked the website for nitrogen embrittlement but seems your disregarding half of what im saying as ive had to say about 4 times im not talking about during welding and after that youve finally got half the point
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Old 05-23-24, 07:25 AM
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I found lots of info about nitrogen embrittlement, so if there was some evidence of atmospheric nitrogen causing problems post-weld, it would be well studied.
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Old 05-23-24, 03:26 PM
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I don't need to read any academic papers to note that CrMo frames welded in the 1930s and every decade since then are still being ridden (not to mention aerospace, motorsport etc.), So this is just another of those non-issues I am grateful to not have to think about. At all.

Apologies in advance for not reading any further replies in this thread.
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Old 05-24-24, 09:15 PM
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Just for my own knowledge sake... I'm a little confused. Why would there need to be a *post*-weld purge? I know little about welding, but I imagine if there needed to be displacement of any gas, it would be before and during weld.

Me, in 1990s: "Are those dampers gas-charged with nitrogen?"
Damper expert: "They are pressurized with a complex mix of 78% nitrogen, 21% oxygen, 1% argon..."
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Old 05-24-24, 11:39 PM
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Originally Posted by Jordanjw
I did have half of this written up last night heres a link on chromo and embrittlemenr https://masteel.co.uk/news/chromium-...20are%20formed.

https://f3timbertech.com/the-effects...%20of%20cracks.

Also says somewhere in there materials that are highly ductile are more likely to have nitrogen embrittlement

Thats coatings used om fasteners but as the top link proves it happens the coating can be used for the chromo too. I think its more a newer thing like epoxy coatings can be a good barrier but i doubt youd be able to find a bath big enough to zinc plate the bike even though you probably wouldnt want to


Also yes purging does protect during welding, it stops oxizidation from forming during welding

As i said before chromium in general is a brittle material granted harder than steel but not usable for structures due to if their struck its certain a failure will happen.

Also i know this is strange saying all this even though no one has had any real problems but is anyone actually able to test the nitrogen levels in their bike composition to confirm no embrittlement hasnt taken place

i did have another link ill have to find it
How did you come to decide to be concerned by nitrogen embrittlement in an application that doesn't have a high failure rate?

It also seems that the nitrogen embrittlement of concern is not from atmospheric nitrogen but nitrogen deposited in the steel when forged.


Here is some common nitrogen "embrittled" steel:


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Old 05-25-24, 12:30 AM
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Originally Posted by Kontact
How did you come to decide to be concerned by nitrogen embrittlement in an application that doesn't have a high failure rate?

It also seems that the nitrogen embrittlement of concern is not from atmospheric nitrogen but nitrogen deposited in the steel when forged.


Here is some common nitrogen "embrittled" steel:


Hmm. I have a screwdriver and security bit set from harbor freight where the bits fracture if you sneeze at them. Can nitrogen embrittlement be baked out at home-oven temps? When I derusted some files with hydrochloric acid many years back, after rinsing and blowing off dry, I would put on the electric oil-fin heater for a few hours, don't know if it did anything with regard to any hydrogen embrittlement. I'll try looking up both now. EDIT: Looks like for hydrogen, yes, but higher temps, 600F and some hours. Nitrogen, I see no indication of bake-out. I know of a particular good low-cost knife steel that has added N as part of the mix, and it has both excellent hardness and toughness.

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Old 05-25-24, 11:38 AM
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Originally Posted by Duragrouch
Hmm. I have a screwdriver and security bit set from harbor freight where the bits fracture if you sneeze at them. Can nitrogen embrittlement be baked out at home-oven temps? When I derusted some files with hydrochloric acid many years back, after rinsing and blowing off dry, I would put on the electric oil-fin heater for a few hours, don't know if it did anything with regard to any hydrogen embrittlement. I'll try looking up both now. EDIT: Looks like for hydrogen, yes, but higher temps, 600F and some hours. Nitrogen, I see no indication of bake-out. I know of a particular good low-cost knife steel that has added N as part of the mix, and it has both excellent hardness and toughness.
Nitrogen embrittlement isn't a real thing. That's why Jordanjw is posting articles that are little more than advertising on commercial websites written by experts like "Brian".

Nitrogen is used as a surface hardening ingredient in nitride or nitrocarburizing treatments and as an alloying ingredient H class precipitation hardening steels. Clearly, nitrogen is not a danger to steel.

No, you can't and don't want to remove the nitriding from your drill bits. It's the only thing that makes them sharp.
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Old 05-25-24, 08:08 PM
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Originally Posted by Kontact
Nitrogen embrittlement isn't a real thing. That's why Jordanjw is posting articles that are little more than advertising on commercial websites written by experts like "Brian".

Nitrogen is used as a surface hardening ingredient in nitride or nitrocarburizing treatments and as an alloying ingredient H class precipitation hardening steels. Clearly, nitrogen is not a danger to steel.

No, you can't and don't want to remove the nitriding from your drill bits. It's the only thing that makes them sharp.
Sounds like you know what you are talking about. Thanks.

I may have to try baking those screwdriver bits on the off-chance it's hydrogen embrittlement. I've never seen brittle this bad. Maybe they are just high carbon with high temp, high quench heat treatment, no alloying elements for toughness. I wish I had access to a Rockwell tester.
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Old 05-25-24, 11:24 PM
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Hydrogen embrittlement happens when water is present during welding. Since there is no welding involved in making a screwdriver, those screwdrivers aren't suffering from hydrogen embrittlement. Even if they were formed hot in a rainforest, I don't believe hydrogen embrittlement would be present.

Your HF screwdrivers are just made from crummy metal. The tips on good screwdrivers are hardened. AKA, they undergo an embrittlement process. But they are no doubt made from a better base metal in the first place. I save crummy screwdrivers for opening paint cans and other things that good screwdrivers shouldn't be used for. Life is too short to actually use them on fasteners. I'm pretty happy with Wera screwdrivers. I have a set which is also made to be used as a chisel. Wera knows their customers. They also have wrenches that are designed to be used as a hammer.

HF has started selling better tools, but they generally charge the same price for them as everyone else.
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