[soft-compound]

Yes another one of my strange threads.
Basically long story short , my buddy managed to crack his frame after years of abuse
Around the drop outs on a keewee cromozone just were the seat stay attaches to the chainstay.
But people seem to think this can just be fixed by welding.
But i dont think this is the case or am i missing something very important?
Basically wouldnt the extreme welding temperatures anneal the steal and reverse the heat treatment process?
I was told it should not matter as it is not a high stress area.
Also was told that quenching could cause more issues when making a repair?

Help would be much appreciated as im planning on having some custom work done to a cromoly frame that i have and would like to know

 

[H8R]

It is possible to repair, but I would take it to a skilled frame builder for assessment.

 

[rideit]

Most steel frames don't go through a heat treating process.

 

[MinorThreat]

You can do it with a steady hand and an acetylene torch - - although some would argue that the weld will be a little more brittle than with a MIG or TIG outfit. Mild steel filler rod is fine but R-60 or R-65 is better.

 

[dcamp29]

yes- get it welded, no heat treat is required for 4130.

 

[0110-M-P]

Yes, just make sure you find someone who has experience tig welding 4130 and you should be fine.

http://www.lincolnelectric.com/en-us/support/welding-how-to/pages/chrome-moly-detail.aspx

 

[kidwoo]

acetylene torch -

no

tig

yes

 

[Kanye West]

You needed expert advice........so you came here??

lulz

 

[MinorThreat]

no

Your reasoning?

 

[H8R]

no



yes

Your reasoning?

I bet a lot of people would argue if you are steady and skilled enough to do a decent job with a gas welding rig, the TIG results would be even better.

I'd argue that anyway.

 

[0110-M-P]

Decent conversation about gas vs. tig welding 4130 tubing.

I particularly like this quote...

"Gas welding even when done by someone who has lots of practice and
high skill level is never as neat and controllable as a TIG weld
especially on thin sections -- some of this is caused by the oxidation
problems you get on the inside of the tube while welding which is
normally countered by inert gas purging while TIG welding frames. I
guess you could do this while gas welding but it seems like you may as
well go to TIG if you are going to go to that amount of trouble since
the weld will never be neat like a TIG weld. The other part of the
problem is that while it is reasonably easy to TIG parts of different
thickness like a down tube to a bottom bracket shell it is extremely
difficult to do the same with gas without overheating the thin tube."

https://groups.google.com/forum/#!topic/framebuilders/HplYp34zaEg

 

[bustanutley]

Yes you would need to heat treat the frame in order to make to bring the joint up to the same strength as the rest of the tube, however, its a lot less critical with any steel over aluminum. I would probably just weld it and not expect it to last the rest of forever, but, it will be fine for a long time. Add a gusset where it failed to increase the material size.

Also don't quench it, that will make it massively brittle, hard, but brittle.

 

[MinorThreat]

I bet a lot of people would argue if you are steady and skilled enough to do a decent job with a gas welding rig, the TIG results would be even better.

I'd argue that anyway.

. . . but it seems like you may as
well go to TIG if you are going to go to that amount of trouble since
the weld will never be neat like a TIG weld."

All true of course. There's nothing as pretty as a heliarc bead. That was revealed to me decades ago when I saw my first Sonic Weld flat track frame. Given a choice, yes, of course go TIG.

But there are a heck of a lot more of us with Oxy-acet outfits than have access to TIG rigs. (I still kick myself for not getting an old Lincoln TIG that went for song at an auction years ago.) Won't be as pretty - - or as strong without the inert gas shielding - - but it will be strong enough . . . and pretty enough if you know what you're doing.

 

[soft-compound]

Thanks for all the replies , yes i thought there may have been some people in the know how
On here in regards to this.
Yes i have been in contact with a very good frame builder in the Uk but when he mentioned annealing it scarred
Me.
Im also having him mode the rear end of a 2004 balfa BB7 welding in 12mm lugs making it 12mm bolt through.
Which he assures will be plenty strong enough without heat treatment

 

[atrokz]

Thanks for all the replies , yes i thought there may have been some people in the know how
On here in regards to this.
Yes i have been in contact with a very good frame builder in the Uk but when he mentioned annealing it scarred
Me.
Im also having him mode the rear end of a 2004 balfa BB7 welding in 12mm lugs making it 12mm bolt through.
Which he assures will be plenty strong enough without heat treatment

People who know what they're talking about:

http://bbs.homeshopmachinist.net/threads/32367-Does-4130-steel-tubing-need-to-be-heat-treated-for-maximum-strength

TLr: You're fine just TIG welding the crack, although it's better if it is indeed normalized, you can get away with it. 4130 is low enough carbon that the HAZ area sort of blends in (albeit just a little better than 4140 or some of the higher carbon, poor weld quality steels) but you're still increasing brittleness in those HAZ areas. So for your application it will probably be fine for years. Remember than many roll cages are welded without normalizing (although the best ARE in fact heat treated).

I know that sounds kind of muddled, but it goes like this: It *should* be heat treated, but for the application, it's probably not nessesary.

 

[TrumbullHucker]

iv been tig welding since college, and if i were you i would atleast pre-heat and post heat alittle bit. idk i feel like it would mesh the molecules in the HAZ ( heat affected zone, right next to the weld bead itself ) a bit better instead of just almost immediately melting it with an electric arc.

but if its not a high stress area you should be fine, just make sure the weld is good lol

 

[MinorThreat]

Remember than many roll cages are welded without normalizing (although the best ARE in fact heat treated).

It's always been my understanding that 1) forming roll cages out of 4130 is not desirable and 2) that heat-treating would be even worse. The whole goal of a roll cage (besides maintain integrity) is to absorb some of the energy of a crash. It has always been recommended for stocks and drag cars that roll cages be made of mild steel tubing[SUP]1[/SUP]

[SUP]1[/SUP] Ron Fournier, Metal Fabricator's Handbook, 1990

 

[shirk007]

Lots of whack info in this thread.

The most simple fix is to clean off the paint, slap some proper flux on it and seal up the crack by brazing in some nickle bronze.

No heat treat bs needed. Unless you completely goober it up by way over cooking it the structure of the metal will not have changed.

 

[atrokz]

Lots of whack info in this thread.

The most simple fix is to clean off the paint, slap some proper flux on it and seal up the crack by brazing in some nickle bronze.

No heat treat bs needed. Unless you completely goober it up by way over cooking it the structure of the metal will not have changed.

Please provide your professional credentials.

- Guy who studied metallurgy, Has a CofQ in T&D, Has welding Ticket, CET.

 

[atrokz]

It's always been my understanding that 1) forming roll cages out of 4130 is not desirable and 2) that heat-treating would be even worse. The whole goal of a roll cage (besides maintain integrity) is to absorb some of the energy of a crash. It has always been recommended for stocks and drag cars that roll cages be made of mild steel tubing[SUP]1[/SUP]

[SUP]1[/SUP] Ron Fournier, Metal Fabricator's Handbook, 1990

They are indeed heat treated and are recommended to do it that way , and that's the preferred method if using 4130. The idea of heat treating 4130 isn't to harden the structure, it's just to remove the areas that ARE in fact hardened by way of welding HAZ. Some people misunderstand the term 'heat treat' to think it means hardening. It can, but it can also mean normalizing, tempering, etc. It's just that: heat treatment. Note that I said some are. it's not recommended, and normalizing it is required under many rule books, NHRA included.

SCCA rules:

F. TUBING 1. Seamless or DOM mild steel tubing (SAE 1020 or 1025 recommended) or alloy steel tubing (SAE 4130) must be used for all roll cage structures.

Vehicle Weight/ Minimum Tubing Size (inches) /outer diameter x wall thickness) Up to 1700 lbs: 1.375 x .080

1701 - 2699 lbs: 1.500 x .095 1.625 x .080

2700 lbs and up 1.50 x .120 1.750 x .095 2.00 x 0.80

NHRA cars were using 4130. The current SFI specs for Funny Car (10.1E) and Top Fuel (2.3M):

All structural material for the roll cage, rear-end mounting, and suspension mounting must be normalized SAE 4130 chrome-molybdenum steel (SAE 4130N) purchased to the requirements of military specification MIL-T-6736B and its subsidiary documents or equivalent.

 

[atrokz]

iv been tig welding since college, and if i were you i would atleast pre-heat and post heat alittle bit. idk i feel like it would mesh the molecules in the HAZ ( heat affected zone, right next to the weld bead itself ) a bit better instead of just almost immediately melting it with an electric arc.

but if its not a high stress area you should be fine, just make sure the weld is good lol

Good advice from someone who can actually weld.

 

[shirk007]

Please provide your professional credentials.

- Guy who studied metallurgy, Has a CofQ in T&D, Has welding Ticket, CET.

Stress testing the bike on it's very first ride.

-Guy who has been studying steel frame building for many years and actually brazed a bike.

The theoretical world might say to post weld heat treat, but in the real world nobody post weld heat treats steel bike frames.

 

[atrokz]

Stress testing the bike on it's very first ride.

-Guy who has been studying steel frame building for many years and actually brazed a bike.

The theoretical world might say to post weld heat treat, but in the real world nobody post weld heat treats steel bike frames.

Cool beans, you built a bike.

The real world eh? I wonder where it is I've been working!! (go on IG and search my name.....or, for previous work you could look left to my avatar.....)

Building a bike is 'cute' and all though.......


Lesson for you to learn: Don't throw a blanket over everyone in a thread. Instead, quote the specific one you're referring to. If you think my comments are full of BS, you have a LOT to learn about both the 'theory' world and the 'real' world of manufacturing (again, I have a TIG ticket) where other peoples lives are at risk. If you read again, you can see I clearly stated he'd be ok without HT if done right, but that it's 'ideal' to normalize the assembly to remove HAZ areas. Please note that I did not say you were 'wrong' to suggest brazing (but you're definitely wrong about it not changing the molecular structure) and in fact, 4130 was originally designed to be gas welded. I just called you out on your ignorant statement about everything else being BS.

But hey, let's learn about metal fabrication and welding from what's arguably the worst industry in the world for both quality control, manufacturing process, and misinformation...


Here's a tidbit of theory:
"Always avoid brazing 4130 steel. The reason to not braze chromemoly is that this steel has a definite grain structure that actually opens up at medium red brazing temperatures. When brazing alloy is melted onto the steel surface, it flows easily into the many small cracks and crevices in the chromemoly steel. Then, as the braze joint cools, the brass will not compress and it forces major cracks to form in the 4130 steel. Often, a brazed 4130 steel part will crack completely in two before your eyes as it cools."
Performance Welding, Richard Finch, c. 1997, pg. 130.

 

[MinorThreat]

Some people misunderstand the term 'heat treat' to think it means hardening. It can, but it can also mean normalizing, tempering, etc. It's just that: heat treatment.

Point noted.

NHRA cars were using 4130. The current SFI specs for Funny Car (10.1E) and Top Fuel (2.3M):

"All structural material for the roll cage, rear-end mounting, and suspension mounting must be normalized SAE 4130 chrome-molybdenum steel (SAE 4130N) purchased to the requirements of military specification MIL-T-6736B and its subsidiary documents or equivalent."​

Weird. Was just looking at the NHRA rule book yesterday and it indicated use of either mild steel or 4130, just different diameter and wall thicknesses and has charts of specs for both for each cage component. Example:

"Section 20 - General Regulations 20.23

1 - Funny Car and altered with 6 points of attachment, use 1 1/2-inch x .058-inch chrome moly (CM) or .118-inch mild steel (MS). Funny Car and altered with 5 points of attachment, use code B, and C (upper framerail/shoulder hoop) becomes 1 1/2-inch x .058-inch CM or .118-inch MS."

http://www.nhra.com/UserFiles/file/General_Regulations.pdf

I'll temper my earlier statement by noting that Fornier has always been particularly adamant about mild steel roll cages. AFAIK, NASCAR still requires use of MS.

 

[atrokz]

They did change the rules recently iirc. I have a close friend who welds some of the chassis for some teams, and the redbull air race frames. I'll ask him what he's using now. But yea, still allows 4130 so long as it's N and not A.

Edit: looked through it. Indeed it's either 4130 or DOM, but you can run thinner 4130. So I'd assume they all run that to shave a few grams.

 

[atrokz]

I think we've successfully confused the OP. Our job is done here *dusts off hands*

 

[TrumbullHucker]

I think we've successfully confused the OP. Our job is done here *dusts off hands*

yup, mission successful

 

[0110-M-P]

I think we've successfully confused the OP. Our job is done here *dusts off hands*

Thread killing at its finest. Hats off to you sir!

 

[shirk007]

The real world eh? I wonder where it is I've been working!! (go on IG and search my name.....or, for previous work you could look left to my avatar.....)

The real world as it pertains to steel bikes, none of the millions upon millions of steel bikes build are or were heat treated. So in reference to this guy trying to fix the drop outs on his 50lbs huck machine heat treating is not needed. You can quote aircraft/nascar/nasa specs all you want, but it doesn't change what has been proven to work on bicycles.

Please note that I did not say you were 'wrong' to suggest brazing (but you're definitely wrong about it not changing the molecular structure) and in fact, 4130 was originally designed to be gas welded.

Here's a tidbit of theory:
"Always avoid brazing 4130 steel. The reason to not braze chromemoly is that this steel has a definite grain structure that actually opens up at medium red brazing temperatures. When brazing alloy is melted onto the steel surface, it flows easily into the many small cracks and crevices in the chromemoly steel. Then, as the braze joint cools, the brass will not compress and it forces major cracks to form in the 4130 steel. Often, a brazed 4130 steel part will crack completely in two before your eyes as it cools."
Performance Welding, Richard Finch, c. 1997, pg. 130.

See anything wrong here? It was designed for gas welding, but then you say it shouldn't be?

 

[atrokz]

The real world as it pertains to steel bikes, none of the millions upon millions of steel bikes build are or were heat treated. So in reference to this guy trying to fix the drop outs on his 50lbs huck machine heat treating is not needed. You can quote aircraft/nascar/nasa specs all you want, but it doesn't change what has been proven to work on bicycles.



See anything wrong here? It was designed for gas welding, but then you say it shouldn't be?

You really are missing the points here arent you.

1- was designed. Then people discovered its not ideal. Getting it yet?

2- Am I supposed to be sorry I know more about the subject than you? Both with regards to theory and real word?

3- Again, the bike industry is hardly a place to learn from. I mean, you sure can discover how to wax a moustache and ramble about how awesome brazing is, but learning to weld.....? Hardly. Just because millions of bikes were made the cheapest way possible because it 'works' doesnt discount the thousands of those bikes broken because ofthe same cheap refusal to do it right. Sorry but you learned wrong if you dont understand that taking stress away from a haz area is a good thing. Nothing has been proven in the bike industry other than its the wrong way. How many 4130 structured air frames that got normalized failed?.....

4- We already said he would be fine welding it. Is there something wrong with posting the right way to do it so he can actually learn something new? Does that offend you?


Play nice. Im sure youre subconciously learning something anyway.

 

[demonprec]

if the weld joint has been brazed you will not be able too weld over it using a filler rod process the joint will have too be re brazed as you can never remove all the old brazing from the joint too get a clean weld using a filler rod .

as for heattreating Moly that,s a very touchy subject when it comes too tubing , they tried it in a couple classes in NHRA and it cost a couple lives in crash situations . they do heat treat suspension parts in offroad racing put this is typically on plate material or billet parts .

i have not read all of the posts but after skimming thru it,s obvious some have never welded judging by the comments .

 

[HardtailHack]

I don't think I've ever seen frame repair done by someone specialised in that field that didn't add more metal to the damaged area.

I have been looking at a new frame and saw that the tubes used on one I was looking at were all of the same material but the seat stays weren't heat treated to give more compliance, so I guess no post weld heat treating on it.