Chrome-Moly frame? Heat treated prone to cracking?

[POLOLOUS]

Hi, I am in a debate over a bike frame. I want to ad a few tubes in the rear of the frame to brace it to prevent flex. It is made of Chrome-moly and was heat treated from the manufacture. The Manufacture and others say that it can't be welded, if it is it will crack for sure. I know that thin walled chrome-moly tubing if I don't heat treat it before welding (as long as its around 70F or more) it will hold and not crack. Heat-treating is for the thicker stuff.


I'm not sure cause this is already heat treated from the manufacture. So?

[Fat-Fab.com]

Hi, I am in a debate over a bike frame. I want to ad a few tubes in the rear of the frame to brace it to prevent flex. It is made of Chrome-moly and was heat treated from the manufacture. The Manufacture and others say that it can't be welded, if it is it will crack for sure. I know that thin walled chrome-moly tubing if I don't heat treat it before welding (as long as its around 70F or more) it will hold and not crack. Heat-treating is for the thicker stuff.


I'm not sure cause this is already heat treated from the manufacture. So?

I would weld it like normal and then "stress releave" it after all welding is compleated

Do I heat treat 4130 after welding?
NO! The term "heat treat" has been generically misused in the welding field, as has "normalizing." Heat treat and normalizing operations are extremely sensitive to heat control (preferably oven-controlled) and do metallurgically change the strength value of the parent material. Stress-relieving is the recommended practice and 1,100ºF is the optimum temperature for tubing applications. Use temperature crayon 900ºF and mark approximately 1" away from weld areas. Use Oxy/Acetylene torch with neutral flame and oscillate to avoid hot spots.
NOTE: Excessive stresses are induced by too much heat input, poor fit-up, or both, therefore stress relieving can be avoided if all fit-ups are precision (using tools like the "'Ol Joint Jigger") and applying minimum heat input, i.e. smaller welds. TIG welding should not require a weaving pattern in the welding technique.

http://www.tigdepot.com/faq.html
TJ

[84ZMike]

The Manufacture and others say that it can't be welded, if it is it will crack for sure.
They may just be trying to cover themselves as they have no idea your skill level etc.....
Good Luck,
Mike

[Peter]

hey all,

is it a bicycle frame we're talking about?

if so many are made from heat treated tubing- not heat treated after fabrication. it's similar thinking to a race car tube frame- joints are stress risers and need toughness rather than outright strength, hence the use of a mild steel filler. the weld bead typically reaults in a locally increased wall thickness to compenstate for the lower UTS

while a car tube frame would be made from normalized 4130, bicycle frames typically run wall thickness around 0.028 - 0.035" and are heat treated and often double butted (the tube has a thicker wall at the ends than in the middle to compensate for the reduction in strength from welding) to give the required strength.

welding obviously lowers the UTS but gives a tougher joint- if the entire thing was heat treated after fabrication the result would be comparetivly brittle joints. IF we are talking about bicycles/this sort of wall thickness, stress relielf is un-necessary. Fat-Fabs' comments regarding fit up/heat input are the important points.

[Sberry]

When I was a kid we welded all kinds of dirt bike stuff with a common stick welder, never came apart at the joints. Never cracked indiscriminately.

[Ivan]

I have been welding 4130 cromo bike frames for years with no problems and no heat treating. These frames take a beating and ive yet to break one or have one come back that wasnt hit by a car.

[leeschaumberg]

Welding 4130 thin walled tubing is done all the time. Strength of the finished product is very important. Many aircraft fusalages are gas welded using 4130 tubing. The use of the TIG welder just makes it easier. So when some one says you can't weld 4130 I don't think that one has been there.

[wojeepster]

4130 was developed originally to be gas welded. You can gas weld, mig weld, or tig weld 4130. Anyone who tells you otherwise is mistaken.

[Aerometalworker]

4130 was developed originally to be gas welded. You can gas weld, mig weld, or tig weld 4130. Anyone who tells you otherwise is mistaken.

Bingo! 4130 in aircraft has been arc (stick) and mig welded in production, but it was also heat treated after welding. Funny too that the Arc welds (1940's) have a better reputation than the modern Mig welds.
Gas welding is usually preferred or TIG with post weld annealing, but that usually begs the question, why bother with the TIG when I have to get the torch out anyway.

-Aaron

[leeschaumberg]

Buying a high stenght material can be hard if you don't know where to go! Aircraft Spruce & Specialty Co. is a great place to find a lot of things. Just call them toll free at 877-4-SPRUCE ang get one of thier catalogs. They are on line also at www.aircraftspruce.com . Thier catalog is only about 700 pages so they do have a few things. They are on the east and west coast so shipping won't be outrageus. They sell Lincoln welders but I don't know why they don't Sell MILLERS products. Thier tool section is more than 50 pages.
I am not a salesman of thiers!

[Tex]

Dang, ask a question about chromoly and all the aviation guys come out of the woodwork! Now I know the secret Aviators Unite! phrase :D
Still, I'll chime in. Weld that sucker!....TIG is waaaay better than gas for aircraft frames, by-the-way; even though I feel I'm betraying my aviation ancestors.:(

[leeschaumberg]

Every year (Late July) you can go to the EAA fly in and learn how to weld 4130. The EAA flyin is in Oshkosh,Wisconsin . Many vendors are there also. I've been there so many times over the years. I have flown factory built aircraft and homebuilt aircraft at Oshkosh. Please don't say that airplane nuts are antique people. Only if you are W. R. you are antique. In total of 100 years folks have gone to the moon and as fast as mach 5 and beyond. In the late 40s the first plane to fly faster than the speed of sound (mach 1) flew. I apologize if I carry on about aviation but it's the last frontier and besides the green cheese on Mars is better.:)

[Aerometalworker]

Weld that sucker!....TIG is waaaay better than gas for aircraft frames, by-the-way; even though I feel I'm betraying my aviation ancestors

Tex,
On what information do you base this? And no im not one of those " old timers not willing to accept new technology ".;)

Im just curious because I work in an engineering and metalurgical lab, ive done the fatigue and load testing of the typical tubing clusters.

Just curious if you had some data or if it was just an oppinion.
Thanks!!
-Aaron

[burninbriar]

I think a lot of people assume that since tig equipment costs so much, it must be better. The reasons I've heard for flame welding being better make sense to me, though I don't know for sure.
The flame slowly heats the entire area and after the weld the whole thing cools slowly allowing the molecules and grain patterns to normalize. (not sure if molecules is the right term) where as a tig weld instantly heats to a melting point and quickly cools. Preheating with a torch before tig welding basically does what a flame weld does by nature.At least this is my understanding, I could be wrong, I'm no professional welder. :confused:

[Billet Benny]

welding obviously lowers the UTS but gives a tougher joint- if the entire thing was heat treated after fabrication the result would be comparetivly brittle joints. IF we are talking about bicycles/this sort of wall thickness, stress relielf is un-necessary. Fat-Fabs' comments regarding fit up/heat input are the important points.

100% wrong. If you understand metallurgy and what a proper heat treatment does, along with understanding the words toughness and brittleness you'd know this isn't the case. Post fab heat treating creates a bike stronger than can be made, as welded. Brittle is very relative and you'd be surprised of the ductility of a properly treated and tempered 4130 structure. In fact it's toughness can be much higher than as as welded structure. Its resilience will always be much better when treated.

If you bicycle is operating with 4130 in a normalized condition you can pretty much weld to your hearts delight and be fine. If it is a frame that's designed with high yeild points of 4130 in the heat treated condition and runs a low factory of safety so it's very light, then it's not a great idea to weld on it. First you weaken the treated material in the area of the weld and create places for cracks not due to any brittleness factor, but because of the stresses and risers created from heating and cooling and changing the steel's condition.

If you wanna weld on your bike that's up to you. But know what you're working with. I'm sure people have been successful all the time, but it's going to depend on the particular bike and the particular mods.. If it's designed one way welding extra support is probably ok if it's designed another welding on it will only cause problems.

[arc]

who in there right mind is going to weld chromoly tubing with a flame.:eek: :eek: just realized that some people here have no idea what they are talking about!!!!!!!!!!! what planes do you guys build, never want to fly in those.

[burninbriar]

who in there right mind is going to weld chromoly tubing with a flame.:eek: :eek: just realized that some people here have no idea what they are talking about!!!!!!!!!!! what planes do you guys build, never want to fly in those.

Here is something you might enjoy reading.
http://www.lindsaybks.com/bks7/airweld/index.html

[leeschaumberg]

For some of the folks that don't know!
Torch welding of very strong 4130 Chrome Moly tubing has been done for many years. The torch I'm talking about is an oxy-acet torch! To get a totally unbiased opinion just go to your local airport and talk to an A and P mechanic!
By the way I'm a builder of an experimental aircraft that is registered by the FAA and flies fine.

[arc]

still dont care what u might use and if it works for ya fine but if you go to school and take a metallurgy class you might realize if you have the skills tig is much stronger and tougher than torch welding. may be your right but the guys i know here use tig to repair and build airplanes you just have to have the skills to go with it.

[Aerometalworker]

who in there right mind is going to weld chromoly tubing with a flame. just realized that some people here have no idea what they are talking about!!!!!!!!!!! what planes do you guys build, never want to fly in those.

*Sigh*

I guess people are quick to assume that the ol gas welding torch is not viable or used anymore....God forbid even better suited to some materials.
I have 2 of the best Tig machines made, but wont go near 4130 with them. Unfortunately in our modern society we are exposed to "technology brainwashing". Tig was not originally developed for 4130, or even aluminum ( I know a shock huh? ) It was patented by GE in the 1920's and Northrop developed the handheld tig torch in the 1940's to weld.......Inconel and Monel exhaust systems for aircraft ( which by the way was torch welded for years before, but was slower for war production ). All the aluminum and 4130 parts on WW2 aircraft were welded with the torch, a few companies arc welded 4130 but did entire assembly post heat treat.

Not to mention Boeing was gas welding its aluminum ducting on all its airliners until the late 1990's when the hyperactive MSDS people took the fluxes away.

So in short, if your affraid of gas welding on aircraft, you better like long car trips and walking:p .

[Buzz Job]

This gas welding verses tig debate is still alive I see. Seems like a hard one to kill.

Gas welding has worked and historically has a decent and long track record. I suspect the wrights brothers used it?
Tig on the other hand probably didn’t take over as the tool of choice till the 60 or 70s.

Now NO major aircraft manufacturer I know of uses gas torch welding.
This includes the top dogs in the aerobatic industry Zivco , Extra ,and Pitts you wont see any gas welding on any of there cro-mo trusses (fuselage) or cro-mo hardware.
There is a reason for this and I have done both gas and cro-mo fuselages So I think I can say with some certainty the following.
The total induced heat with a tig weld will be far less than that of a gas weld to produce the same penetration levels on a likeable joint and as a result will produce joints with far less distortion (Shrinkage) this will result in a truss with far less internal stress build up.
What that means is that most gas welded fuselages will not hold tolerance along there length as they have lots of built up stress pushing and pulling them off axis even before you add any flight loads on them. And if you torch normalize them they have the potential to go out of dimension and off axis (potentially dangerous) causing lots of additional work to make companion parts mate..
Gas welding is fine for a homebuilder who has the time to do all the additional work necessary to make it work. But really has no place in the current industrial environment
.
And tests over a span of 30 years of my welding has shown me, my poor tig welding to be better than my best gas welding.

Oops and about that bike frame?
If you bike is heat treated and you are not sure where and how its treated you take the risk of serious weakening. Some manufacturers are running 175 ksi tubing (treated) and a weld area may yield 70 ksi in the area that was 175 ksi so you must access the risk. And if unsure I suggest you leave it alone. The figures above are only a gustemate of of what I have seen.

[Aerometalworker]

Now NO major aircraft manufacturer I know of uses gas torch welding

Well that isnt exactly true.
Sukhoi in Russia.....gas welds their fusealages and Ti exhaust systems ( as well as the outlet ducts on the VT jets, but the process is a military protected affair )

The company building the Extra series is Tig welded ( with post weld annealing )

Aviat, the builders of the Pitts series does a combination of Tig, Mig and O/A depending on where the joint is.

The One Design is Gas welded ( design only not production )

Maule actually Mig welds.....but that is a tightly controlled process and only for mass production ( and there are numerous reported weld failures )

This really shouldnt even be a debate or fight between O/A and Tig, each process done correctly produces an almost identical result.

As far as fuse parts getting out of alignment, Ive never had an issue providing the welding sequence was designed and followed.

Here is a scary tale though, I worked on a modern Tig welded production fuse ( I wont say the name ) about 2 years ago, about an inch from every cluster, the tubing was so hard it could not be drilled with a HSS bit. We spent a couple hours annealing every cluster.

Hows that for a warm fuzzy feeling!
-Aaron

[burninbriar]

This really shouldnt even be a debate or fight between O/A and Tig, each process done correctly produces an almost identical result.



No, it shouldn't, its about welding a bicycle frame. I think it just got swayed this way because one member didn't realize you can weld 4130 with OA.

[Billet Benny]

Wow, for the record, there's more myths than facts in this thread.

[Sberry]

I think just because it was slow to be adopted doesn't mean it isn't as good as OA, it is used but is primitive, doesn't mean it wont work but its unlikely they invent something better if it was the ultimate answer. Do we think they would have welded alum parts with a torch if they had figured out they could have tigged them? I would think the tig with inert gas would be better almost anywhere than a hot open flame especially on alloys.

[Sberry]

Here is a thought that occurs to me more than some of the other concerns, if the welding is that critical is this a joint a layman should be designing anyway? Best weld in the world isn't going to mean squat if we have improper engineering.

[Aerometalworker]

I would think the tig with inert gas would be better almost anywhere than a hot open flame especially on alloys.
Why? Not a guess but fact please.
Do we think they would have welded alum parts with a torch if they had figured out they could have tigged them?
On thin Aluminum < .100" material ( especially fuel tanks ) O/A produces a better weld, higher weld density, better penetration all with no backpurge. This is Fact! Like it or not.

Remember, Tig isnt new....welding with an electric arc or with the O/A flame were developed at almost the same time. One isnt the best at doing everything, each has its place where it shines, and where it is downright a pain. Thats why O/A does beautiful on 4130 and aluminum sheet, Tig on stainless works wonderfully, Arc on Heavy structures and pipe, and Mig on automated assembly.

Unfortunately like everything else, welding is full of myth...some started by competing companies and technologies, some by people who were threatened by something they didnt understand.

You want to see an argument, ask a guy what glue is best for aircraft structural work.....ive seen downright yelling matches over it.

I believe we are all enthusiasts of the craftsmanship involved with welding, by any method. And we have more to learn from each other if everyone took the time to listen, educate themselves, and admit they dont know everything.

I dont know the first thing about welding a building, tractor-trailer, or and of the heavy large structures ( heck .25" is heavy to me! ). And if I wanted to learn, id ask the guy who knows it inside and out, and respect their knowledge and experience.

-Aaron

[leeschaumberg]

:) Aerometalworker -
Thank you for your intelligent posts. Not many people know that their grandmother or great grandmother worked as welders at the North American Co. back in the 40s. They used a lot of O/A welding for many things. Both steel and aluminum was welded. The German pilots just hated this. Although they came up with the turbojet engine we still caused much pain. I have welded with O/A , Stick , MIG , and TIG. In fact I TIG welded aluminum 30 some years ago using a Miller welder. The best test for good welding is putting one's life in the test. Again Thank You

[Tex]

By the way I'm a builder of an experimental aircraft that is registered by the FAA and flies fine.[/QUOTE]

What do ya got?:)

[Aerometalworker]

Tex,
If your referring to myself when asking " what do I got ", I will tell you.

A&P from Blackhawk
IA, recently finished the refresher thank goodness
Repairer of Certified aircraft and homebuilts
Contributor to the FAA's AC 43.13
Volunteer instructor for Aircraft Welding at the EAA
BS Mechanical Engineering
I work in an engineering lab working with fluid dynamics, metalurgy and design of structure anaylisis.
I dont spout oppinion, just proven facts.
Seeing that your also an A&P im supprized you havent seen all the NTSB reports of failed TIG and MIG welding on 4130 due to quench hardening near the weld. Bellenca had a big problem with this on Decathalons to the point they were failing wing attach fittings, and losing wings.

If you can tell me a single factual attribute that non post-processed TIG welding of 4130 in the Normalized condition, please let me know.
-Aaron

[Tex]

Sorry, I was asking Lee what kind of experimental airplane he had. I've always wanted to build a Wag Aero 2+2 or a Bearhawk.
Impressive credentials I might add! WOW:eek:
Matt

[Aerometalworker]

To Tex:
Sorry I completely misread your post.....my fault...plus I responded to that before I saw your personal message......figures:rolleyes:

Now all I need to do is start the fight between epoxy and plastic resin ( Avaition people will get it ) HA HA

Night All
-Aaron

[leeschaumberg]

Sorry, I was asking Lee what kind of experimental airplane he had. I've always wanted to build a Wag Aero 2+2 or a Bearhawk.
Impressive credentials I might add! WOW:eek:
Matt

Tex
A much modified liquid cooled B80 and a Long Eze. I have a com pilots license and instrument rating. I also have a repairman's certificate. But I don't have an A&P like you.I am designing and drawing a liquid cooled flat four diesel based on the Detroit 53 series. The case will be CNC machined from aluminum. This engine is for a high speed STOL plane which I will build when the engine is running.

[Fat-Fab.com]

I think just because it was slow to be adopted doesn't mean it isn't as good as OA, it is used but is primitive, doesn't mean it wont work but its unlikely they invent something better if it was the ultimate answer. Do we think they would have welded alum parts with a torch if they had figured out they could have tigged them? I would think the tig with inert gas would be better almost anywhere than a hot open flame especially on alloys.

Why? Not a guess but fact please.

On thin Aluminum < .100" material ( especially fuel tanks ) O/A produces a better weld, higher weld density, better penetration all with no backpurge. This is Fact! Like it or not.

Remember, Tig isnt new....welding with an electric arc or with the O/A flame were developed at almost the same time. One isnt the best at doing everything, each has its place where it shines, and where it is downright a pain. Thats why O/A does beautiful on 4130 and aluminum sheet, Tig on stainless works wonderfully, Arc on Heavy structures and pipe, and Mig on automated assembly.

Unfortunately like everything else, welding is full of myth...some started by competing companies and technologies, some by people who were threatened by something they didnt understand.

You want to see an argument, ask a guy what glue is best for aircraft structural work.....ive seen downright yelling matches over it.

I believe we are all enthusiasts of the craftsmanship involved with welding, by any method. And we have more to learn from each other if everyone took the time to listen, educate themselves, and admit they dont know everything.

I dont know the first thing about welding a building, tractor-trailer, or and of the heavy large structures ( heck .25" is heavy to me! ). And if I wanted to learn, id ask the guy who knows it inside and out, and respect their knowledge and experience.

-Aaron

To all I was lickey enough to see a race between and "old Lady" former aero plane maker from the war and a young man "kid"

The race was a 1F and a 3F and a 3G welds made on .080 or so Al. the kid using GTAW and the Lady using O/A shee kicked his but bad as far as time to finish goes and she had not welded in 30 years

I was 12-13 at the.


TJ

[Billet Benny]

I got to fly this a couple months ago! I'm the co-pilot. Plane was homebuilt but not by me.

[Carl W.]

That almost looks like the Keliher Lark, a EAA plane designed back in the 60's.
As an 'ex A&P we gas welded chromoly back in the early 70's, later A&P's would
only be required to recognize good welds.

[Buzz Job]

Yo Billet Benny that there is a nice Harmon Rocket you got to ride in.
I hope he did some max performance maneuvers as its got some great performance with a stock engine, and incredible performance with a modified engine.
It looks as if he is inspecting the titanium gear or is still working out some things with the project?.
Anyway I hope you enjoyed the ride.
But beware it’s a addictive sport if you got the $$$.

[Billet Benny]

Yo Billet Benny that there is a nice Harmon Rocket you got to ride in.
I hope he did some max performance maneuvers as its got some great performance with a stock engine, and incredible performance with a modified engine.
It looks as if he is inspecting the titanium gear or is still working out some things with the project?.
Anyway I hope you enjoyed the ride.
But beware it’s a addictive sport if you got the $$$.

Oh, I'm addicted now. Never in my life have I felt so comfortable and at peace. It was amazing. This thing was in the works for many years and the last touches were yet to be finished (such as the landing gear cowlings). He has just pulled it back apart recently to change some things and add some decals.. The instrumentation in the thing is phenominal. This is mainly due to his partner being a pilot for UPS.

We did do a barrel roll, but even better was a banked turn that produced 2.5 positive vertical g's. That was the best! I do wish I had one.