What is the heat treating process ?

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7/28/2014 11:19 AM

What is the process when your frame is being
Heat treated ? Do they heat treat the whole frame?

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7/28/2014 11:28 AM

Depends on the company. Some heat treat just the tubes, some do a whole post weld treatment. Some temper, some use pressure, some have their own unique processes. Confusing as hell. Basically check the frame makers website and/or email them and ask.

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HardBMX_Tim wrote: I welded a peg to my pedal so I could do pedal grinds. I would rather wear a teletubbies speedo than a shirt with the word "Bitches" on it, or even worse, "Swag".

7/28/2014 11:35 AM

Heat frame up, cool frame down, can't explain that.

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7/28/2014 11:39 AM

Generally it's done pre weld (could be wrong) because heat can expand and change shapes, lengths and widths. Post word machining is done on better frames due to this same effect due to the heat caused by welding

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7/28/2014 11:44 AM

Okay thanks

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7/28/2014 11:45 AM
Edited Date/Time: 7/28/2014 11:45 AM

Xxohioanxx wrote:

Heat frame up, cool frame down, can't explain that.

I meant the fact that the specific process varies so widely from manufacturer to manufacturer.
Lol.

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HardBMX_Tim wrote: I welded a peg to my pedal so I could do pedal grinds. I would rather wear a teletubbies speedo than a shirt with the word "Bitches" on it, or even worse, "Swag".

7/30/2014 3:28 AM

I'm gonna nuke this out just a little bit here.

The term "heat treatment" is a little vague. The way you heat up and cool down metal affects grain formation (think of metals as little tiny crystals of metal stuck together) and therefore strength, hardness and flexability (they are related). There are a few different heat treatment that might be relevant in building BMX bikes/parts.

First, when you buy raw material (cromoly tube, billet aluminum) you can buy it with a specific temper (heat treatment). So if you are buying tube for something you need to bend a lot (handlebars) you can buy it softer and less likely to crack when it's bent. The trade off is once its finished, its more likely to bend in use.

Next, Post weld heat treatment is just like it sounds. When you weld two pieces of metal together, you introduce internal stresses. Post weld heat treatment involves normalizing those stresses by heating the entire assembly up and cooling it down in a controlled manner (recrystallizing it). What post weld heat treatment does is allow a manufactured to buy softer tempers to help during fabrication, than post weld heat treat it to a stronger temper. That's why parts with tight bend radii are more likely to be post weld heat treated.

The actual heat treatment processes are specified (e.g., heat to x degrees, hold for y minutes, quench at z degrees for y2 minutes) in detail by standards and specifications like the ATSM specs. The differences between manufacturers involve small changes here and there, or the inspection processes.

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7/30/2014 8:20 AM

tecnic1 wrote:

I'm gonna nuke this out just a little bit here.

The term "heat treatment" is a little vague. The way you heat up and cool down metal affects grain formation (think of metals as little tiny crystals of metal stuck together) and therefore strength, hardness and flexability (they are related). There are a few different heat treatment that might be relevant in building BMX bikes/parts.

First, when you buy raw material (cromoly tube, billet aluminum) you can buy it with a specific temper (heat treatment). So if you are buying tube for something you need to bend a lot (handlebars) you can buy it softer and less likely to crack when it's bent. The trade off is once its finished, its more likely to bend in use.

Next, Post weld heat treatment is just like it sounds. When you weld two pieces of metal together, you introduce internal stresses. Post weld heat treatment involves normalizing those stresses by heating the entire assembly up and cooling it down in a controlled manner (recrystallizing it). What post weld heat treatment does is allow a manufactured to buy softer tempers to help during fabrication, than post weld heat treat it to a stronger temper. That's why parts with tight bend radii are more likely to be post weld heat treated.

The actual heat treatment processes are specified (e.g., heat to x degrees, hold for y minutes, quench at z degrees for y2 minutes) in detail by standards and specifications like the ATSM specs. The differences between manufacturers involve small changes here and there, or the inspection processes.

That's exactly what I was about to say!! lol..no really, that's good shit there man..really on point!

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7/30/2014 10:27 AM

It means they put the frame in a microwave with their popcorn

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7/30/2014 10:45 AM

tecnic1 wrote:

I'm gonna nuke this out just a little bit here.

The term "heat treatment" is a little vague. The way you heat up and cool down metal affects grain formation (think of metals as little tiny crystals of metal stuck together) and therefore strength, hardness and flexability (they are related). There are a few different heat treatment that might be relevant in building BMX bikes/parts.

First, when you buy raw material (cromoly tube, billet aluminum) you can buy it with a specific temper (heat treatment). So if you are buying tube for something you need to bend a lot (handlebars) you can buy it softer and less likely to crack when it's bent. The trade off is once its finished, its more likely to bend in use.

Next, Post weld heat treatment is just like it sounds. When you weld two pieces of metal together, you introduce internal stresses. Post weld heat treatment involves normalizing those stresses by heating the entire assembly up and cooling it down in a controlled manner (recrystallizing it). What post weld heat treatment does is allow a manufactured to buy softer tempers to help during fabrication, than post weld heat treat it to a stronger temper. That's why parts with tight bend radii are more likely to be post weld heat treated.

The actual heat treatment processes are specified (e.g., heat to x degrees, hold for y minutes, quench at z degrees for y2 minutes) in detail by standards and specifications like the ATSM specs. The differences between manufacturers involve small changes here and there, or the inspection processes.

This is what I meant exactly.
It's all very interesting, and each process will bear different end results. Is love to see an independent study done to find out which process yields the best end results.

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HardBMX_Tim wrote: I welded a peg to my pedal so I could do pedal grinds. I would rather wear a teletubbies speedo than a shirt with the word "Bitches" on it, or even worse, "Swag".

7/30/2014 11:39 AM

It's a bit of a misnomer to say one process provides better results than another. Engineers/designers decide what they want the results to be and what trade offs they are willing to make and choose a process based on that.

For example, full post weld heat treatment generally makes the toughest parts, but there are a number of drawbacks. The obivous one is cost, but post weld heat treatment also introduces a certain amount of distortion. If you have ever gotten a crank arm that is just a real bitch to put together or thread a pedal into, you've met distortion. So on a frame, you would most like add a step to ream the headtube, bottom bracket and seat tube after heat treatment. However you've just made the frame really hard to machine by heat treating it, so you can only machine it so much. All this is why a Sunday frame cost $50-80 more than a comparable frame that isn't post weld heat treated.

Another drawback to using heat treated bike parts is that a tempered part tends to fail in fracture (break) before it yields plastically (bends). There are certain applications where a bent part is OK, but a broke part will fuck you up. Keep in mind, that the force required to break a tempered part is waaaay more than the force required to bend a softer part, but if you somehow exceed that force, there won't be any warning. Its straight to face plant.

I personally would love to see more fully post weld heat treated frames. Its just cool. The truth is however, I think we've reached a point in frames where most failures are a result of defects or craftsmanship issues, and that if you owned a frame company, your money would be better spent on testing and quality assurance. There are nondestructive testing methods that would identify the types of weld defects that cause most broken frames.

I don't have a TL;DR for that. I gotta get back to work.

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7/30/2014 7:20 PM

I like how this thread is going...
Actually learning something.

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HardBMX_Tim wrote: I welded a peg to my pedal so I could do pedal grinds. I would rather wear a teletubbies speedo than a shirt with the word "Bitches" on it, or even worse, "Swag".

7/30/2014 8:26 PM

I'd much prefer my handlebars to bend instead of snap. Regular slams aren't heat treated iirc

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7/30/2014 8:29 PM

buttmeate wrote:

I'd much prefer my handlebars to bend instead of snap. Regular slams aren't heat treated iirc

Not trying to put words in your mouth, but heat treated bars aren't always going to snap before they bend. If it's done right they'll bend before they snap. But then again, we all know how great most companies are at doing things right.

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7/31/2014 3:40 AM
Edited Date/Time: 7/31/2014 3:45 AM

buttmeate wrote:

I'd much prefer my handlebars to bend instead of snap. Regular slams aren't heat treated iirc

Xxohioanxx wrote:

Not trying to put words in your mouth, but heat treated bars aren't always going to snap before they bend. If it's done right they'll bend before they snap. But then again, we all know how great most companies are at doing things right.

I might have over simplified a bit.
Yeah, if you put a huge ass piece of pipe on the end of your handle bars and jumped on it, it might bend them.

But a more realistic loading would be to put a huge ass piece of pipe on the end of your bars and sit on it. Then stand up. Then sit on it again. Then stand up again. Repeat this process for a really long time and you have the cycle test in the Odyssey fork video.

So let's say you have fresh, rust free bars, and a spot with a very large number (call it about 10 million) incrementally higher drops. If you just started dropping off those drops, three things could happen:

(1) eventually drop from a height that causes the bars to bend
(2) eventually do so many drops that the bars fatigue and crack/break
(3) you keep dropping forever and nothing happens to your bars

The bigger drop you could do without ever causing your bars to fail due to fatigue is called the fatigue limit, and not every material has one. Even the smallest deformation will cause aluminum to fail in fatigue after enough cycles. That's why airplanes have cycle limits.

And in the context of heat treatment: when you heat treat bike parts, you increase the yield strength (force to bend the bars) high enough that it becomes more likely that you will see enough cycles that fatigue will be the primary failure mode.

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