Steel frame testing

[Demon Of Speed]

How do the inspection Judges make sure that the main roll hoop and whatnot are make of steel? Because not all steel is magnetic. For a metal to technically be steel in has to have (by weight) greater than 50% Fe, and less than 2.5% C.

[Demon Of Speed]

How do the inspection Judges make sure that the main roll hoop and whatnot are make of steel? Because not all steel is magnetic. For a metal to technically be steel in has to have (by weight) greater than 50% Fe, and less than 2.5% C.

[Hector]

Does this really matter?

[Dash]

Inspection holes must be drilled in those particular tubes. So you could maybe tell by sight. If there was any doubt though, they have a sonic thickness tester. It has to be calabrated to the material that will be tested( aka steel or aluminium ), otherwise it gives bad results. I used one myself at work today, and you definitely get funky numbers when you swap material properties.

[Demon Of Speed]

This is theoretical question, but still and some point a team is going to use some fucky steel.

I know of the inspection holes, but the holes are for finding the wall thickness on the tube. You could use an arc spectrometer, but that would require removing a piece to test. As for ultrasonic testing, it isn't useful for know what materiel you have.

[vandit]

The material supplier receipt which you attach in your SEF ideally should have basic properties and chemical composition.

Our material receipt from supplier includes basic Tensile test properties and % composition of carbon, phosphorous, manganese and sulphur.

I guess if your % composition of elements are not under acceptable limits then it will be reflected in your basic tensile properties.

[exFSAE]

I'd say the likelihood of a team making their frame from stainless is low.

[Ockham]

Why wouldn't they? Stainless is sometimes used for space frames thanks to its very predictable weld characteristics. The Noble M600 uses a stainless frame, IIRC. 4130 definitely isn't the only game in town.

[exFSAE]

Define "predictable weld characteristics"

You're on a cheapo budget, you want a variety of tubes, and you want something that's easy to weld for a novice on the TIG.

4130 is the way to go.

[Adambomb]

4130 is not cheapo enough for us. We prefer 1020 and just triangulate the blasted thing. I think chassis weight this year was in the neighborhood of 52 lbs, and we've never broken a chassis.

[AxelRipper]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
Define "predictable weld characteristics"

You're on a cheapo budget, you want a variety of tubes, and you want something that's easy to weld for a novice on the TIG.

4130 is the way to go. </div></BLOCKQUOTE>


actually I tend to find stainless quite easy to weld... then again thats how I was taught to tig... without filler rod or a foot pedal

[exFSAE]

Yes.. but I'd say most kids here aren't even really taught how to weld.

"Ok here's how you put the torch together... grind a pointy end on this piece of Tungsten... open the Argon and flip this big power switch. Away you go!"

That was my training anyway.

This just seems like a silly discussion point. Is it possible someone could make their frame out of something non-magnetic and have to prove it's steel... I haven't heard of it having ever happened.

Not the brightest idea ever, intentionally giving yourself headaches in tech.

Adam - you guys check Chassis Shop 4130 prices? IIRC we picked up all our frame and suspension steel for a few hundred bucks, shipped. Super cheap rates.

[D Collins Jr]

Really? I just looked at Chassis Shop's page, and while the prices look cheap, they're also per inch! So, by my rough figuring, 1 foot of 1" x .095" tubing for your roll hoops from CS is $7.08, while it is only $4.24 at Wicks. Fact is, 4130 isn't cheap, and if you find it for that cheap (or ever for less than 1020 Steel) I wouldn't trust that it is actually 4130.

[exFSAE]

Granted, last time I bought steel was 3 or 4 years ago and CS had been quoting everything in price per foot back then. It was very cost effective, and was definitely 4130. Certainly possible their prices have changed since then!

A big part of it was ordering in 8' lengths so they could ship it without using a flatbed truck.

[moose]

Yeah - Chassis used to be fairly cheap, although I think they became less so over the years. Wicks stayed pretty cheap - but certain tubes had been cheaper on one side or the other. Not that you won't get killed for the difference + by UPS by shipping 50 lbs of steel 2x.
I'd specify 8' + drop, so they'd cut the full lengths down for UPS shipping into 2 or 3. Also got a full-length discount, I believe. For the Roll-hoop that wasn't useful, but other sizes having a few short pieces didn't matter. There was always a 1 or 2' tube it could be used for.

[Adambomb]

We used to get all of our 1020 tubing free from a local supplier, but since times have gotten a bit tougher and a certain former team member burned some bridges with sponsors we were forced to actually pay for it this year. Was something like $525 with tons to spare, shipped.

Aside from the initial cost, also have to think about post-weld heat treating, otherwise you're not getting your money's worth anyway; not to mention wide fluctuation in properties in the HAZ resulting in lots of martensite right around your nodes (granted it could be torch annealed, but I personally wouldn't even trust myself to do that well).

Even if you found a place to heat treat your entire chassis for free you'd still have to spend an entire day or two hauling it around to get it done. All else aside, we're not strength-limited with 1020 on our chassis, so we see no need to bother with 4130. YMMV.

[Demon Of Speed]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
We used to get all of our 1020 tubing free from a local supplier, but since times have gotten a bit tougher and a certain former team member burned some bridges with sponsors we were forced to actually pay for it this year. Was something like $525 with tons to spare, shipped.

Aside from the initial cost, also have to think about post-weld heat treating, otherwise you're not getting your money's worth anyway; not to mention wide fluctuation in properties in the HAZ resulting in lots of martensite right around your nodes (granted it could be torch annealed, but I personally wouldn't even trust myself to do that well).

Even if you found a place to heat treat your entire chassis for free you'd still have to spend an entire day or two hauling it around to get it done. All else aside, we're not strength-limited with 1020 on our chassis, so we see no need to bother with 4130. YMMV. </div></BLOCKQUOTE>

I will agree with the fact that 90% of the schools don't gain anything by using 4130 steel, and 10xx steels are fine (all the same density until you get into crazy alloys). However, the teams that do get there frames treated after welding, I don't know why there do go with a 4340, better properties for the money.

[exFSAE]

It was my impression that there was generally a wider variety of tube sizes available in 4130 than 10XX (at least from where we sourced material). That was our reason to use it.

[Mike Cook]

In a crash, I would think 4130 would absorb more energy before failure than 1020.

[Demon Of Speed]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mike Cook:
In a crash, I would think 4130 would absorb more energy before failure than 1020. </div></BLOCKQUOTE>

It really depends on the post treatment of the metal, the size, the temperature, etc. I can not find any Data comparing similar specimen of 1020 and 4130. However, there is a direct correlation between C content and Charpy Impact test. The more C the less energy that will be absorbed (page 219, Metals Handbook Desk Edition). Additionally, The 4130 is going to be harder, and have a lower %Elongation, which would indicate that the energy that it is able to absorb during impact will be less.