Frames are hung on special racks in the heat treat oven to prevent distortion at
temperatures near 1100 degrees F. Intense photo Jeff Steber is both the founder and creative drive behind Intense cycles. Intense is unique to most North American bike brands because it still manufactures its aluminum frames in-house at its Temecula, California, factory. All welded-aluminum frames require some sort of post heat-treatment process to return the metal back to proper hardness and consistency. Because Intense has its own heat treatment oven, we asked Jeff to take Pinkbike readers through the process. Intense does its own heat treating in-house, which is pretty unusual for aluminum fabricators. How does this give you an advantage?Originally, we used to use a company called Alumatherm in Orange County to source all of our heat treating, but they did not specialize in bicycle frames, so we occasionally had problems with alignment and other issues. Plus, we had to make weekly trips from Temecula to Orange County, which was a considerable distance (over 50 miles, one way). We wanted more control over the process because it was one of the most critical parts of manufacturing our frames, so I began researching the possibility of doing it ourselves. I knew that Robert Reisinger at Mountain Cycles had a heat treating oven for sale that was just about perfect for us, so when he sold the assets of his company, we bought it.
What is a heat treating oven?Basically, it’s a big pizza oven that you put a number of frames into that are held in place with special racks. The frames are heated to a specific temperature that is close to the melting point of the aluminum alloy and held there for about an hour. A tank full of a water and glycol (antifreeze) mixture is rolled below the oven when the frames are ready. The frames are then dropped within seconds into the quench tank, which freezes the frames into an annealed state. When the frames are annealed, they are very soft and pliable – it is called ‘zero temper’ (T-0).
New frames waiting for the oven. The oven is elevated on the framework behind them. The quench tank is moved into place in the space below. Intense photo
TIG-welding an aluminum Tracer frame: the heat-affected zones in the weld
areas are annealed and would fail without a heat treatment. Intense photo Why heat-treat the frames?Actually, we are dealing with different degrees of temper within the different material we make the frame with. All of the different parts of the frame can vary from annealed condition to full temper before the frame is assembled. The tubes can arrive at the T-4 stage, which is about half strength, and the sheet that we construct the hydroformed parts is annealed at the T-0 stage. Machined parts, like the bottom bracket, dropouts and shock mounts are full hard, in the T-6 stage. Also, welding puts stresses into the frame, because the center of the welding zone is essentially annealed and very soft, while the areas around the zone can vary from soft to full hard. So, the heat-treat process is necessary to return the entire frame to a consistent level of hardness – which for us, is the T-6 temper.
Does welding and heat treating require the frames to be re-aligned?The water/glycol mixture helps the frames cool at a consistent rate during the quenching process, which prevents warping, but there is still some misalignment in the frame that we check for while the frames are annealed. We align the frames within 12 hours while they are soft, on a special fixture, and then we put them back in the oven to artificially age them. The aluminum will automatically begin to harden at room temperature, but the oven gives us control over the final temper, which is the optimal T-6 condition.
A batch of swingarms, just out of the annealing process, await their turn to be checked and straightened on Intense's four-inch-thick, steel alignment table. Intense photo
Explain the artificial aging process:After the frames have been annealed, the crystalline structure of the various elements within the aluminum is more or less lined up, so when the metal is stressed, they slip over each other quite easily, which causes the metal to be easily bent or deformed. As the alloy is aged at a temperature near 350 degrees F, the crystals begin to gravitate towards each other, which forms uneven pathways for stress within the alloy. This causes the aluminum to resist deformation and it becomes much more rigid. The aging process occurs at 350 degrees for about eight hours in the oven.
A simple Rockwell hardness test is used to accurately gauge the temper of the
heat-treated frames. Intense photo How can you be sure that the frames are annealed to the proper T-6 hardness?We use a simple Rockwell Hardness Tester on every frame that is basically a hand-press with a pointed probe that pushes exactly the right amount into the aluminum with a measured amount of force when the temper is right. Several times a year, we send samples to an independent lab where they perform a strip-tension test that indicates the metal’s ultimate tensile strength. We also have our ovens calibrated at regular intervals to ensure consistency.
If a frame is broken, can it be repaired, welded and then re-heat treated?Well, yeah. It depends upon whether it is repairable. Some say that it may not be
wise to re-heat-treat a frame, but we essentially are re-heat-treating each part of a frame when we first assemble them. The key to building or repairing a frame is that the aluminum cannot be contaminated with paint, grease or any foreign substance. We have a special washer that every part which will be assembled into a frame goes through and we also use it when we do a repair. The fact that 6000-series aluminum can be returned to full strength is what makes it such a good material for a frame - and makes it possible to repair them with good results.
What kinds of aluminum alloys do you use at Intense?All of our frames are made from 6000-series aluminum. Some parts are 6061, some are related alloys like 6009, and all require the same heat treat process. We use different alloys, like 7075 for non-welded items like suspension pivots, custom screws and rocker arms that we machine which have different strength requirements, and for parts that will be anodized later.
Intense Cycles
HAHA...occasionally.
And Giant/Spec, who are built overseas and don't snap all the time.
There is no correlation between country of origin and welding quality.
As for welding - my 951 has a very even weld seam. Very nice. The reartriangle bearings do have some bind - dont align perfectly - but then other designs - like the Commenca/Turner/Labyrinth/Scott Voltage variety keep the bearings in big blocks for easier alignment during machining and better riding.
Every bike company has made mistakes. Some companies are better than others about getting them fixed fast. Here we just saw intense admit the problem and show us how they fixed it (getting their own oven).
Kona didn't adapt their frame building to keep up and their oversight mangled their reputation for years.
Giant had a snap issue for a while too. People don't like to hear it but it is true. Not only that, but giant denied there was a problem for most of a year, then limited access to replacement links to people after they busted theirs, meaning it might have lead to a seriously catastrophic fail that broke other parts, both bike and person.
And both of these companies could only look to their Asian slave laborers to fix it.
The welders at Giant are well-trained, well paid, and are extremely good welders. The jobs are prestigious, sought after, and are often handed down from father to son for all the reasons I state.
Never mind. They started there, making frames for Nishiki and Schwinn. I hadn't realized they were an Asian bike company.
Props for any company that keeps the production local!!!!!!!!
Now take the top level and rotate it 45°, take the bottom level and rotate that 45° (both relative to the middle layer). How easily will the sides turn now? It will break first! The crystal structure of metal deforms when there is a common slip plane available. No common slip plane = rupture rather than deformation, but also means much higher strength.
Of course this is still over simplifying a whole ton of stuff involved, but still sheds a little light I hope...
The most common cracks I have seen on ally frames are either weld centreline failures, where the welding process has segregated all the impurities into the last place to cool down, or, more commonly, failures on the filler-parent metal join, where the material is frequently embrittled since it is a mix of filler and parent metal, necked down because of cooling shrinkage, or has a big stress concentrator where it goes from fat weld to thin tube.
www.asminternational.org/portal/site/www/SubjectGuideItem/?vgnextoid=5c3655c96bd9d210VgnVCM100000621e010aRCRD
Steps
1.Heating to the solution heat treating temperature and soaking long enough to put the alloy elements (i.e. not Aluminum) or compounds into solution
2.Quenching to room or some intermediate temperature (e.g., water) to keep the alloying elements or compounds in solution; essentially creating a supersaturated solid solution
3.Aging at either room temperature (natural aging) or a moderately elevated temperature (artificial aging) to cause the supersaturated solution to form a very fine precipitate in the aluminum matrix
I know enough to be dangerous, please correct me if wrong.
PMH
Kevin Cashen, a very knowledgeable blade smith has a lot of useful information on heat treating steel, but nothing on aluminum
1. solution treat
2. quench
3. Anneal (Age)
"2.Quenching to room or some intermediate temperature (e.g., water) to keep the alloying elements or compounds in solution; essentially creating a supersaturated solid solution"
Step 2 and step 3 are needed for a mechanism called precipitation hardening.
To my knowledge these heat treating steps are universal to both aluminum alloys and steels. Each Al alloy and steel have different recipes.
Just sayin!
I was just at the Taipei International Cycle Show (www.taipeicycle.com.tw) last week and managed to pick up two frames on the last day of the show from a company in China that didn't want to haul everything back home. My question is: Is there any sort of quick & easy test I can perform to ensure that the frames have indeed been heat treated? (I guess a potential follow-up question is if after testing it's shown that they have not yet been treated, what can I do about it?)
Thanks!
www.vitalmtb.com/photos/features/The-Making-of-a-Frame-with-Banshee-Bikes,4763/Slideshow,0/bturman,109
So why 6000 series Al.?
The welds are the weak point. When you heat treat after welding the entire frame has the same strenghth. Heat treating causes the grains to alighn and connect in a tighter matrix.
That said there is no perfect material. It all boils down to engineering and fabrication.
I love my M9!!
www.jyi.org/issue/the-boeing-787-dreamliner-designing-an-aircraft-for-the-future
Fixing aluminiumframes - not likely - they would have to look entirely different designwise, bolted/riveted/glued exchangeable sections. Imagine a 1950 Cessna.
Long life frames best made out of steel or titanium.
Nice choice of tubes:
en.wikipedia.org/wiki/Reynolds_Cycle_Technology
"A properly restored frame will also be just as strong as its unbroken original. One composite engineer at a major bike brand who spoke on the condition of anonymity said he has performed pedal and head-tube fatigue tests on repaired carbon frames and found they passed his company's internal standards. It's even possible a cracked frame can come back stronger if it was damaged in an underengineered area or failed due to a manufacturing defect."
www.bicycling.com/maintenance/repair-maintenance/resurrection-calfees-carbon-frame-repair
areas are annealed and would fail without a heat treatment."
P.D.: Sorry for my english
My conclution: welding a frame affects a lot the internal crystalline structure of the metal, and heat treatment helps it to order it and make and stronger-flexible frame.... Weld a frame it is not safe, but if you dont have the money it will help you to safe some bucks to buy a new frame and continue riding....
Sorry, but the crack happened because of the crash. I was already aware that not heat treating the weld was a risk, so inspected the weld after every ride. The crash ruined the rear rim as well so I had to walk the bike out.
It was a quality weld, but on a problem area (poor design), as lots of other MKIII frames crack in the same place:
dl.dropbox.com/u/8190002/Gusset.jpg
I kept riding the bike for a few months after the crack appeared, mainly because I thought even if it goes completely the rear triangle would still hang together (which it did, yay gaffa!). Gave up once it went all the way around:
dl.dropbox.com/u/8190002/IHCrack.jpg
Or is it because they need to hydroform a lot?
heat treated to 898°c I believe correct me if I'm wrong.
shop.upgradebikes.co.uk/Catalogue/Frames/DMR/DMR-898
digitalcommons.lmu.edu/cgi/viewcontent.cgi?article=1009&context=mech_fac (Nobble's link in a pinkbike thread)
Scroll to conclusion.
The bike manufacturers will get it right. Getting a bad reputation, and having to contend with warranty returns are great motivating reasons.. Even if they didn't get it right at the beginning, they will find out soon enough from examining return frames when looking for cause of failure. They can tweak the process until they get it right. However, for the average owner wanting to get powder coating done, that is entirely another story.
"The warranty will not cover normal wear and tear, normal maintenance items, damage, failure, accidents, crashing, abuse, mis-use, neglect, or any damage caused by bicycle components.
Intense frames are not intended for use in stunt riding, ramp riding, hucking or any similar activity."
i love a good ol engineering read or video espesh a bike one
Few bicycle mechanics EVER use a torque wrench though and I know of many shops that don't even own one, let alone home mechanics.... but with cars and motorcycles and especially aircraft mechanics... everyone owns their torque wrenches and they use them all religiously. But for some reason, bicyclists don't think the laws of metallurgy and physics apply to them.
Well guess what... FRO frames (For Race Only) are designed to be as light as possible! If you ride it nearly everyday and it cracks - don't complain! These bikes are highly engineered, it's not everyday you see some one drive a F1 or NASCAR to the supermarket!
Just thought I'd put that out there!
i dont know where people come up with this crap.
If you don't want to go back to school, then just look up high cycle fatigue, and you will soon realise that small impacts are insignificant compared to large ones. If you drop the stress 50%, you can expect an increase in cyclic stresses of about 1000 times.
edit:
Increase in lifetime of 1000 times.
Carbon has no expiration date, you can ride it till it breaks, it doesn't fatigue! You can break it if you overstress it, but it won't fatigue like most metals do!
And I'm studying engineering btw.
FRO (For Race Only) is a marketing acronym - Just a bunch of buzz words to make you think you're riding a highly engineered bike. Take Specialized's FSR (Future Shock Rear) for example, they don't actually come from the future!
What the hell is all this garbage about Carbon frames having a 'shelf life', it's not bread FFS!?