Chassis Material

[chrisdoha]

hello

We are a new team from dubai from the Birla Institute of Technology. Since this is the first time we are participating i need loads of help in various fields

Can anyone please suggest a good material for the chassis. Can anyone also provide me information on cold workin steel, t45 and steel 4130

thanks

[chrisdoha]

hello

We are a new team from dubai from the Birla Institute of Technology. Since this is the first time we are participating i need loads of help in various fields

Can anyone please suggest a good material for the chassis. Can anyone also provide me information on cold workin steel, t45 and steel 4130

thanks

[SNasello]

www.matweb.com (http://www.matweb.com) -database for material properties

[pucksaver]

We are also a first year team and we are planning on using plain ol' mild steel. Reason for this is so we can MIG weld it as we don't have very many people skilled in TIG. From what I understand you can't easily MIG 4130 steel. We might use 4130 on suspension components or other places where we can spend the time TIG'ing. Does this sound like a decent reason? I am open for other suggestions http://fsae.com/groupee_common/emoticons/icon_smile.gif

[HenningO]

Going for mild steel for the chassis is good idea. Since the rules specify most of the minimum dimensions, you can't save weight by going for a stronger alloy (and thus less material).

The dimensioning factor of your frame will most likely be stiffness. Since the young's modulus is pretty much the same for say 1020 and 4130 (or cro-moly which it is sometime refered as), you won't gain anything going for the more expensive 4130.

As for suspension components, like A-arms, after stiffness, the dimensioning factor is most likely going to be buckling due to compressive forces in the links. Once again, the buckling force is independent of the yield/tensile strength of the material. So you won't really gain anything going for 4130 there either.

While on the subject, formulas to calculate minimum buckling force uses young's modulus as the only material parameter. Something tells me that a material with higher yield stress wouldn't see local buckling as easy, and therefore should have a higher buckling force? Anyone know?

[BenB]

DO NOT USE MILD STEEL. I learned this lesson the hard way from my FSAE days.

I made a swaybar out of it. When I was doing my testing it deflected the amount I expected under a given load (i.e. its stiffness was correct), but when the load was taken off the bar stayed deflected haha. The problem is mild steel is not hardened at all so it has a very low yield strength. Also it has so little carbon in it that it basically cannot be heat treated. I was able to harden it just enough to save my ass, but it was pretty marginal.

Your chassis is basically a giant torsion spring. The last thing you want is your chassis to get twisted and not spring back to its original shape. Before long you'll have a 3-wheeler.

Stick with 4130 chromoly

[BenB]

Sorry HenningO I didn't mean to contradict you. I think we posted at the same time. I still stand by my post thoughhttp://fsae.com/groupee_common/emoticons/icon_smile.gif

[Mark TMV]

I don't see an issue with building a frame out of DOM 1020 tubing if it's properly designed.
You're not building a kart here, a spaceframe is not likely to 'take a set'.
But, yeah, trying to make a swaybar out of mild steel is a very silly idea http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif

[John Grego]

Ben - A sway bar is designed to deflect so yielding could be a problem. A chassis and suspension, however, are not deflecting members (or shouldn't be). You have 2 systems that function completely different. Therefore, material selection for one use may or may not work for another use.

[kmrobinson]

I don't know John, we could make a chassis out of cooked spaghetti!

[BenB]

I guess if you are not exceeding your yield strength you can use mild steel in either application.

If to get your required chassis stiffness you are sizing the tubes large enough that you are not exceeding the yield strength then mild steel does make sense.

Since young's modulus should be approximately the same for both materials the chassis will have the same stiffness no matter which one of these materials it is made out of.

I guess I shouldn't say never use mild steel for this application. I just had a bad experience with it. 4130 just seems a lot more efficient to me (structurally, not financiallyhttp://fsae.com/groupee_common/emoticons/icon_smile.gif) Well this is why it is engineering.

[Conor]

I would be weary of using 4130. The entire frame will need to be either preheated before welding or normalized after welding. Both can be a pain in the ass...

[Peter7307]

What Connor above said.

With 4130 it is not really difficult to get right but very , very easy to get it wrong.

If you are getting started stay with what you can handle to get experience and get fancy later on.

Pete.

[VFR750R]

never seemed that hard to me. if you've got a tig, it takes just a few hours of practice to lay some quality welds. I personally find it easier to weld then mild or stainless. We have normalized our engine mounts after welding while frame still on jig with no issues. I even think we remove the frame from jig after and normalize some more?...been awhile.

If you don't feel comfortable welding it, fine, but it doesn't take more then 20 bucks to get enough of it to practice on and see if you can do it. If cost is an issue, then mild should be fine, most steel dirtbike frames are mild...NOT chromoly.

Yes the modulus is the same but some frame members don't contribute substantially to stiffness. Since the strength is much higher, the frame can be redesigned to work with the stronger material.

In a perfect world, the frame you build with 4130 is not the same frame you would build with mild. Ex: tube A can be 1/3 the size because the strength is 3 times higher. Now i can put in tube B that stiffens the frame and it's still lighter then the mild steel frame. You end up with more but lighter tubes.

[mtg]

I'm going to agree with VFR, here. 4130 isn't hard to do right (shoot, my welds held up in a rollover crash, so it can't be that hard). Nowadays, I work with guys that weld for a living on aircraft parts now, and DAMN! those are some good welders.

If you leave the frame in the frame jig, and stress relieve it (the chalk like temp indicators work well), it will be fine as long as it was designed well in the first place.

Make sure your frame jig is way more stout than you think it should be, and you'll be good. This same thought holds true if you're trying to build aircraft....

[exFSAE]

Its been my experience that getting a variety of tube thicknesses, etc is much easier with 4130 than 1020.

And 4130 welds sooo nice.

If you find the right supplier your chassis steel bill shouldn't be more than $350, shipped.

[chrisdoha]

can anyone tel me wats the difference in properties in t45, steel 4130 and cold drawn steel. Also which is the best one and why?

thanx

[flavorPacket]

God forbid you actually do any work yourself...

[Pete M]

Cold drawn steel is the best, because it has a high buckling factor, excellent malleability and a low atomic weight.

But then you wouldn't trust a random cynical guy's response to a question that is trying to side-step the entire purpose of this competition, right?

[pucksaver]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">And 4130 welds sooo nice. </div></BLOCKQUOTE>

Doesn't it also have to be TIG welded and heat treated?

And i bet a good looking 4130 weld has a lot to do with the experience of your welder http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Brian Evans]

4130 was designed during WW2 to be weldable, in the dimensions used in typical tube frame structures like airplanes, using gas welding (Tig wasn't invented yet) or brazing, and without any significant post weld heat treatment. Think guy in a field with a torch repairing an airplane with people dropping bombs on him, and you've got a good picture...

I agree with the people who say mild steel is adequate for tube chassis, and I also agree that if you use 4130 you can design for lighter parts if yield strength is the limiting factor, not stiffness. Mild steel works just fine for anti-roll bars if you don't exceed it's yield limit - I've had them on cars for years. You just need to design them to take the material properties into account.

[VFR750R]

4130 does not need to be heat treated at all. It would actually not be desirable to heat treat. But, luckily, 4130 is still way stronger then mild in an annealed state. Normalizing is just stress releaving the welds that will be subject to concentrated vibration and high stress(engine mounts only). Even that is probably overkill. Cornell cars have had 4130 frames forever and I don't think i've ever heard of one cracking, at least without helphttp://fsae.com/groupee_common/emoticons/icon_wink.gif

[Christopher Catto]

http://www.fia.com/resources/documents/1546172967__Reco...Materials_a_2004.pdf (http://www.fia.com/resources/documents/1546172967__RecommendedMaterials_a_2004.pdf)

page 4 has info on T45. I assume it is reasonably reliable although sometimes the FIA does *cough* do stupid things

I dunno if T45 is called the same in the States. In fact i am wondering where the numbering originates from, what it stands for etc.

As for welding chassis, it is great. I know touring car teams used to use it to lets say remake the whole car while leaving it looking like a production car...

[Dave Gordon]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by chrisdoha:
hello

We are a new team from dubai from the Birla Institute of Technology. Since this is the first time we are participating i need loads of help in various fields

Can anyone please suggest a good material for the chassis. Can anyone also provide me information on cold workin steel, t45 and steel 4130

thanks </div></BLOCKQUOTE>

Chris - we are a supplier of 4130 tubing, and we have the ability to ship all over the world.

We have been supplying material to FSAE teams for many years.

Dave

[Nik]

Someone correct me if I am wrong about the following, but only if you really know. I already have plenty of anecdotal evidence.

The issue of preheating and/or normalizing with 4130 is all about the issue of martensite forming in the heat affected zone. Rapid cooling of the material (base metal or filler) forms martensite. Rapid cooling happens when there is a steep pressure gradient e.g. a red hot bead of TIG weld adjacent to a heat sink of a frame at room temperature. This can be avoided by preheating the base material to remove the heat sink. Or it can be fixed after the welding process by normalizing e.g. heating up the weld and adjacent area with an acetylene torch and allowing it to all cool slowly.

The martensitic phase is not always a bad thing. In the applications of a chassis which may someday be subjected to an impact in the form of a crash, it can be bad because it has low ductility and low toughness. It can also be bad in applications such as vibration in engine mounts.

All of this is not an issue in mild steel due to its lower carbon content not being suitable for the formation of martensite.

Are the above statements close or am I full of crap?

[Christopher Catto]

yes, i believe you write the truth. For many hard and tough steel components (like tripod housings or stub axles) I believe the heat treatment (and quenching and all related processes) are to create austenite.

Martensite is rather hard due to high carbon content (think diamons, they are pretty much 100% "compressed" carbon)

incidentally structure change also happens to stainless steel where at very high temp the structure changes so the cromium tends to go out of solution and form concentrations. then your stainless, becomes rust prone at the weld. not brittle, but properties change from what you were quoted by the manufacturer/supplier.

to preheat the joint is always a good idea provided it does not make the tubes expand enough to move your jig. hence make STRONG heavy jigs. also, when making wishbones or other stuff, DONT for christ sake quench the parts! put them under a bench out of reach and let them cool. beware of fire hazard though.

[overdrive535]

In our area, for some strange reason, we're able to get 4130 tube cheaper than mild steel tube. We still really don't know why this is, but it is.

We were also told by our steel supplier that we could use a MIG on it. They even donated a roll of wire just for this. Not being an expert, I don't know if special wire is needed, but I'm sure it doesn't hurt. That said, we still like to TIG our chassis. It keeps crappy welders like me from getting itchy fingers during chassis fab.

And I agree with Catto above me. Quenching parts is the worst thing you can do.

[Mike Sadie]

the most common fillers for 4130 are

70-s2 (70 ksi) - most recommended
80-s2 (80 ksi) - will result in a more brittle weld area
4130 - DO NOT use this unless if you plan to at least stress relieve the part. You will get a very brittle weld if you don't. I hear it is also a bit harder to use.

[Drew Price]

I don't think welding with 4130 vs. ER70-S2 is any more difficult, they flow very similarly. The only difference I noticed is that their melting points are a little different, you have to retract the ER70-S2 back away from the puddle between beads farther than the straight 4130 rod.

You use 4130 rod for weldments which will be tempered so that the hardness is uniform throughout the joint, which would be diluted and weaker than the parent metal if you were to use a mild steel filler, like 70-S2.

Best,
Drew

[Maverick]

which steel is called as steel spaceframe??

and which is better for chassis?mild steel or stailess steel?

if something is better than this two? then suggestion are open for the same.

regards

[J.R.]

Stainless, thats what they used in the Delorian, and that thing can travel through time. So if my correlation is correct, you can use stainless, and then travel from the start gates to the finish gates and have .001 second autocross times!

[Bazanaius]

You'd have to get up to 88 mph tho, and I'm not sure you could hit that on the straight of an FSAE course...

[cjanota]

Like Brian said, 4130 was developed to be easily weldable with a gas torch. But keep in mind that a gas torch will get enough of the surrounding metal hot that it will cool slower and be less brittle. TIG welding will cause a much faster cooling rate and make the metal more brittle. ER70-S2 will not suffer from this as much but it still doesn't hurt to normalize the welds while you still have the frame in the jig.

4130 as a material can be welded just fine with MIG. The main problem that you can run into is when you try to weld tubes of vastly different thicknesses (.095" to .028") It can be very tough to get the correct penetration on both tubes with MIG. The other thing that I like more about TIG is that you have better control of how much filler you are using and that can save weight on the car.

[LafayetteFSAE]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by mtg:
I'm going to agree with VFR, here. 4130 isn't hard to do right (shoot, my welds held up in a rollover crash, so it can't be that hard). Nowadays, I work with guys that weld for a living on aircraft parts now, and DAMN! those are some good welders.

If you leave the frame in the frame jig, and stress relieve it (the chalk like temp indicators work well), it will be fine as long as it was designed well in the first place.

Make sure your frame jig is way more stout than you think it should be, and you'll be good. This same thought holds true if you're trying to build aircraft.... </div></BLOCKQUOTE>

Can you elaborate on the stress relieving a little more...I will be welding a 4130 chassis next semester and would like some input so it does not get warped during cooling

[www.elmdonmetals.co.uk]

T45 is a nickname for the tube.
BS4T45 to BS4T100 is the correct specification.
The material is a Carbon Manganese based material which contains a 45/50ton minimum tensile strength.
The Material was designed during the war as a tube with superb strength and excellent elongtation. This allowed the War Plane Factories to use a Lighter wall thickness thus saving weight throughout the aircraft.

It is a British Specification still being produced today.
www.elmdonmetals.co.uk (http://www.elmdonmetals.co.uk)



<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Christopher Catto:
http://www.fia.com/resources/documents/1546172967__Reco...Materials_a_2004.pdf (http://www.fia.com/resources/documents/1546172967__RecommendedMaterials_a_2004.pdf)

page 4 has info on T45. I assume it is reasonably reliable although sometimes the FIA does *cough* do stupid things

I dunno if T45 is called the same in the States. In fact i am wondering where the numbering originates from, what it stands for etc.

As for welding chassis, it is great. I know touring car teams used to use it to lets say remake the whole car while leaving it looking like a production car... </div></BLOCKQUOTE>

[Mr. Cam]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by chrisdoha:
hello

We are a new team from dubai from the Birla Institute of Technology. Since this is the first time we are participating i need loads of help in various fields

Can anyone please suggest a good material for the chassis. Can anyone also provide me information on cold workin steel, t45 and steel 4130

thanks </div></BLOCKQUOTE>

[Drew Price]

Hellow new team member from Dubai.

Welcome to the competition.

To answer your question, PLEASE READ THIS THREAD, I THINK YOU WILL FIND IT ANSWERS YOUR QUERIES.


Best,
Drew

[nowhere fast]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Christopher Catto:
yes, i believe you write the truth. For many hard and tough steel components (like tripod housings or stub axles) I believe the heat treatment (and quenching and all related processes) are to create austenite.
</div></BLOCKQUOTE>

I realize this post is very old but I believe austenite only exists at high temperatures and that martensite is formed by rapid cooling (quenching) of austenite.