Welding 6061 Aluminum Bike Frame with Crack: Expert Advice, Costs & Alternative Solutions

telecaster1951 wrote:

phanick wrote:

I wonder how these 100-120 kg cyclists ride like in my case at 65 kg, such miracles happen

This frame has manufacturing defects. Cracks at the weld seam, which means that either the material was wrong or the weld was defective.

Ergo comrade moderator totally untrue. The weld would be defective if it burst itself - the face of the weld. And it breaks on the border - correct. The frame is working, it is under stress - so the material gets tired, but it is not particularly resistant to the load. So it turns out that the frame is worn - it was not designed for such a big "jockey" and extreme use. Something for something - the lightness of the thin-walled structure itself, at the expense of mechanical strength. Instead of messing around with welding and investigating what went wrong after that, I'd just replace it, and that's it.

I agree with you, but there is one "but". The bicycle frame, when properly used, should not break at the edge of the weld. Little. It has no right to break. If it is a MTB bike, and it looks like it and it is not a Tesco frame for PLN 50, metal cannot be released in this place. The weakest part of the frame is the rear triangle.
Cracking at the edge of the weld may indicate a bad weld. With an incorrectly selected temperature, a microcrack appears at the edge of the weld. Slightly small, often hidden under the varnish. Over time, the crack will continue to develop until it finally shows up. In the robot, I have seen a vacuum armature more than once, bursting in exactly the same way. Except in this case, a microcrack means that the element ends up in the basket.

Added after 34 [seconds]:

Wait, read on now. This frame is 10 years old. What am I looking for. Mea Culpa. This frame is just worn out.

telecaster1951 wrote:

Cracking at the edge of the weld may indicate a bad weld. With an incorrectly selected temperature, a microcrack appears at the edge of the weld. Slightly small, often hidden under the varnish. Over time, the crack will continue to develop until it finally shows up. In the robot, I have seen a vacuum armature more than once, bursting in exactly the same way

I conclude that he never had a welding colleague from the practical side. At the weld / parent material interface, apart from the stresses caused by shrinkage of the cooling weld metal, there is always a narrowing of the material - caused by its drawing to the weld. Hence, it always breaks in this place - add fatigue changes to it.

telecaster1951 wrote:

The bicycle frame, when properly used, should not break at the edge of the weld

If my aunt had a mustache, she would be an uncle. It will break sooner at the weld boundary, where the structure of the material is changed, than where the material is in the "factory" condition. Nothing is forever - the frame tubes are squeezed, stretched, bent - it's not a 100% rigid structure.

Therefore, elements that work hard is not profitable to weld, but to replace them immediately with new ones. A colleague is now welding another crack and in two months it will crack elsewhere and so on and on until he scraps it.

bearq wrote:

Therefore, elements that work hard is not profitable to weld, but to replace them immediately with new ones. A colleague is now welding another crack and in two months it will crack elsewhere and so on and on until he scraps it.

And such a use of this aluminum frame that after 4 repairs it will weigh as much as a steel one

robokop wrote:

At the weld / parent material interface, apart from the stresses caused by shrinkage of the cooling weld metal, there is always a narrowing of the material - caused by its drawing to the weld. Hence, it always breaks in this place - add fatigue changes to it.

From my own experience as a welding technologist, I can say that what my colleague writes cannot appear in a properly made welded joint. The narrowing the colleague mentions is called an undercut and it is unacceptable.

robokop wrote:

The weld would be defective if it burst itself - the face of the weld. And it breaks on the border - correct.

This border is the heat-affected zone. Cracks are also not allowed at this point.
The only crack that can be considered not due to welding errors is a crack outside the heat affected zone.
Surface welding imperfections in joints
welded from metals by MSc Eng. J. Czuchryj and the relevant standards describe it exactly (this is exactly the PN-EN ISO 5817 standard).
The reason for the formation of these cracks, I could initially assume, was the non-compliance with the welding technology of this material (such an assumption). When too much linear energy is introduced in place of welding, cracks occur. Aluminum, or rather its alloys, are very sensitive to this value. But what has been "fixed" is a tragedy. The question remains whether the person performing the repair used the appropriate binder. As I know life, it is often like this: aluminum is aluminum wire, which alloy is not important anymore.

mariusz999 wrote:

From my own experience as a welding technologist, I can say that what my colleague writes cannot appear in a properly made welded joint. The narrowing the colleague mentions is called an undercut and it is unacceptable.

I am not a welding technologist there, but I did some welding in my life, I saw some welds and cracks in the welds themselves or in their vicinity. If the influence of arc welding on the structure of the material could be avoided, electron welding, soldering in some cases or braze welding would not be invented. But this is only my opinion, so the PhD thesis on the frame can be continued.

In general, the structure is tired with work, and it would be necessary to weld reinforcements in critical places, so I do, for example, with scaffolding tops and only then are they stiff as a cat's tail.

This frame is probably ZnAl with admixtures of other metals - if one of the better alloys is probably ALU7XXX. Eg 7005 T6 with Solidus 607 ° C and Liquidus 643 ° C. Composition e.g. ///// Al 91 - 94.7%, Zn 4.0 - 5.0%, Cr 0.06 - 0.20%, Cu up to 0.10%, Fe up to 0.40%, Mg 1.0 - 1.8%, Mn 0.20 - 0.70%, Si up to 0.35%
Ti 0.01 - 0.06% 0.01 - 0.06%, Zr 0.08 - 0.20% /////
In general, I do not recommend welding even the lower alloy ALU6XXX. Yes, it is done industrially for cost reasons, but the effect is precisely that the structure and homogeneity of the alloy are disturbed. In addition, there is a dimensional instability resulting from natural aging. I recommend soldering it. The strength of brazing will be much better than that of the weld, which may not seem intuitive, but unfortunately it looks like that. Ali will buy 3 meters of Al73Cu20Si5Ni2Bi0.01Be0.01Sr0.01 wire for around USD 7. Such Alu alloy should be cleaned of paint and heated, wrapped with mineral wool, preferably with a thermocouple applied to it, to a temperature not higher than 550 ° C. The solder will begin to flow at around 520 ° C. Trace amounts of bismuth and beryllium remove the aluminum oxide scum. Strontium improves the grain structure of the hard alloy, adding plasticity and strength. When the whole warms up, tap the wire at the connection point, rubbing it immediately after tapping. It is worth using a special flux. I also use Ali's QJ201 powder, containing compositions of alkali metals, rare earth metals, chlorides, fluorides and an active reagent. The powder is toxic! To be soldered with a burner outside !. I gave 15 USD for the powder and it will last for years. This powder improves the fluidity, thanks to which the meniscus is as smooth as a mirror, but most of all it completely removes the oxides. It also becomes a liquid above 500 ° C. The use of frame and thermocouple thermal insulation as a temperature indicator is quite important not to overheat the alloy, but not critical if you have experience.

"wesmar"
It's very interesting what you wrote.

A lot of knowledge. All in all, it would seem that bicycle frames should not be welded, but under production conditions there is no other option. And for soldering, you need a specialist with extensive experience Even if it could be done without thermal insulation with the burner only, measuring the temperature is not a problem, because with a little effort it would be possible to do it yourself, but as you can see it is a job for an experienced welder in soldering ...

It is alloy 6061.
Everyone complained about the fact that neither aesthetics nor skills. And this season, since April, I have done a record number of kilometers on this bike, not only on the road but also on large bumps, the weld is flawless.

phanick wrote:

It is alloy 6061.

OK !, sorry, you did write, and I was suggesting a side entry. Most of the old frames are 7005, you have a very good alloy, weldable and forgiving a lot! It seems they pressed 6 iPhones with 6xxx. But with "T6" you lost a lot. KOGA A-Limited has the highest quality aluminum alloy - 6069
Watch two videos of industrial pipe soldering:
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Today I had an 'interesting discovery' - the bike at the beginning of the day started to sizzle strangely when you stepped on the pedals. Initially, only when you were sitting on the saddle, and then even standing. And here is the culprit:


Since the thickest tube in the bike breaks, and in the most important triangle, in each of the three possible angles, it means that the frame has actually worn out

phanick wrote:

Since the thickest tube in the bike breaks, and in the most important triangle, in each of the three possible angles, it means that the frame has actually worn out

A crack in this place and in this pipe, in my opinion, proves very bad of the quality of the frame.

Hello As I also had a broken frame, I would like to share the results of my colleague's work. Pre-prepared welded for further work. Frame weight 1380 grams

What they did, or rather how they scratched the frame to the author of the thread, lends itself to the consumer ombudsman.
I have not seen such a messed up job yet.
People take away various trash from German rubbish bins, then repair them and review them more than once. But this is already the peak.
No matter, everyone does as they see fit.
On the other hand, there is one opinion about welding aluminum frames. To weld, mask, sell and look for a new one.
I know from several service technicians that such treatments will come out sooner or later. Especially in the cold. Only the intensity of use of the equipment can have an impact. The less tired it is, the longer the life potentially will be after 'resuscitation'.
One time I almost missed such a mold and since then only steel. There is mass, but at least at the cost of endurance.

TommyOne wrote:

Weld, mask, sell and look for a new one.

The author's photo proves a poor welder, your opinion proves you ...

Man, what right are you offending me? Family problems? Trouble at work? Do you want to take off on me?
Unless you can't read, ask your elementary school kids to translate for you before you start looking for square eggs again.

When the frame breaks, you need to weld, lashings so that the weld does not work, so I weld the poles to the roof of PB ON distributors, the weld itself would not last, but the welded triangles perfectly improve the situation.
Now 1 2 3 applause !!!!!!

It's that good, I don't know anything about it. The only thing I can advise you is to carefully check such frames under this account before buying and avoid any alterations and improved welds if you want to enjoy the bike for more than a few months.

Hello, what will you say about the 2-year-old Marin San Quentin bike 1. The fourteen-year-old came back crying because his frame broke, maybe he jumped from some wall, but it seems that there are some delicate places to weld it?

Reverend84 , the bicycle frames are not weldable.

You can weld, you just need to know how to do it. This frame has not been treated after welding has many stresses. People buy aluminum welders because they are now much cheaper and after a few minutes of melting the wire they pretend to be professionals.

This frame is junk. Marin is not a bush company. To contact. They might take it seriously.

The place of the crack is interesting because usually the frames break on the existing weld or in its vicinity. Here it broke at the narrowest point. I suspect the quick release was not tightened and during a stronger impact (e.g. jumping off / jumping on the curb), the axle hit the frame and it damaged it.

You can weld, a friend of mine welded two aluminum frames and nothing happened to them, but it was not as critical a place as in the photo above. You can probably forget about heating the welded frame in order to eliminate stresses, first that the whole varnish will go to hell, and two that who has such a big oven?

Manufacturers replace the frames during the warranty period.

If you "did" at least one "stiff" driveway and then drove down 100 km / h down the hill, then you would find out how much the broken frames are worth, how long the "grinds" are and how scabs itch hehe.
p.s. I drove, among others on glued "WAJA"