While waiting for a response from UMI, Spohn, and BMR, I figured I'd post a topic to see if anyone else has an answer.

The Chrome Moly products from UMI, Spohn, and BMR.... Are they heat treated, or are the just regular ol' Chrome Moly?

Seeing as Chrome Moly is more expensive, lighter, and stiffer than DOM, it really doesn't offer any more advantages than DOM unless it is heat treated. (That is in comparison to the most commonly used 1020 and 1026 DOM.)

So, in comparison of the materials, it seems as though if the companies are just using Chrome Moly without heat treatment it really isn't worth the extra cost as the cost outweighs the benefits. I simply can't justify an extra chunk of change for barely a noticeable improvement, unless, of course, it has the benefits of the heat treatment which would than make it far superior to DOM.

-Derek

 

i dont understand what you mean by heat treating?

mild steel and chrome moly steel weight the exact same. there is no weight difference in the material. The chrome moly parts are lighter because the material is stronger, so lighter guage material is used.

if you are not a hardcore weight **** and the rest of the car is already feather light,m there is no real benefit to the chrome moly in your application IMO

 

read post 9 here, its a pretty good description

https://www.thirdgen.org/forums/susp...oly-worth.html

 

Sorry, I originally wrote that incorrectly. Less mass 4130 is required to achieve the strength of DOM.

I have already read that, however, that does not really answer my specific question. Not only that, but 4130 is not always heat treated. It comes in several forms from normalized to hardened (Annealed) I have already received a response from UMI. They use annealed 4130.

Chrome Moly can be very advantageous over DOM if it is heat treated and be worth the extra cost.

As for what I mean by heat treating, here's a bit of reading, but it explains the process of heat treating carbon steels.

http://vacaero.com/News-Info-From-In...-Treating.html

 

Post 9 is way off in left field. Sorry, but 4130 is not what Kat states it as.

4130 isn't a heat treatment. 4130 is called chrome-moly because the steel is 98% Iron, 1% Chromium, and .5% Molybdenum with the remaining .5% being other elements: Carbon, Sulfur, and Silicon. 4130 is avaliable normalized, annealed, or water quenched & tempered.

4130 will experience elastic deformation at 29.7ksi, plastic deformation at 66.7ksi, and ultimate failure at 81.2ksi.

Mild steel, such as SAE 1020 cold roll or A36 hot roll (A36 is generally what you find in the hardware store), is 99% Iron with the remaining 1% being Carbon and other elements. SAE 1020 is avaliable cold rolled, cold drawn, hot rolled, or normalized. A36 is avaliable cold rolled, hot rolled, or cold drawn.

SAE 1020 will experience elastic deformation at 29.7ksi, plastic deformation at 50.8ksi, and ultimate failure at 60.9ksi. A36 will experience elastic deformation at 29ksi, plastic deformation at 36.3ksi, and ultimate failure between 58ksi and 79.8ksi.

Now, why are you guys all concerned here? Brittleness is the answer. When I had brittleness explained to me, I got the very simple answer. Brittleness is the relationship between a material's yield strength (plastic deformation) and ultimate strength (ultimate failure). The closer a material's yield strength is to its ultimate strength, the more brittle it is. 4130's yield strength is 82% of its ultimate, SAE 1020's yield strength is 83% of its ultimate, and A36's yield is 45%-63% of its ultimate.

Now, ASSUMING that brittleness can be expressed as a percent of ultimate, it appears that 4130 is no more brittle than SAE 1020 mild steel whereas both of them appear to be more brittle than A36. What this means for you is that a material with a high yield to ultimate relationship will have won't be able to deform a whole lot before breaking whereas a material with a low yield to ultimate relationship will be able to deform more before breaking. (I AM NOT AN ENGINEER, PLEASE CORRECT ME IF I AM WRONG!!!)

However, 4130 does become very brittle during welding, which requires the use of either ER70-S2, ER70-S6, or ER80S-D2 filler rods and post weld heat treatment to normalize the weld. The ER70 filler gives up ultimate strength for ductility whereas the ER80 rod sacrifices ductility for ultimate strength. Normalizing the weld is accomplished with use of a torch and you heat the metal to about 1100*F, a cherry red to low orange is generally the color you'll see at that temp.

So what does all this mean for you when selecting a suspension piece? Since 4130 has more strength than either SAE 1020 or A36, the part can be manufactured with thinner material while retaining the strength of the part made from thicker mild steel.

http://www.matweb.com/search/DataShe...ebf35b1b2b6259
http://www.matweb.com/search/DataShe...16b1b69f1cffbb
http://www.matweb.com/search/DataShe...a3a967f8909c3a
http://www.lincolnelectric.com/knowl...hrome-moly.asp

 

The terms they are using in there are achieved by quenching the material in oil or water or drawing it in an oven over several hours or days in order to achieve the desired properties.

Post weld heat treatment is done with a torch and allowed to air cool. Stress relieving (aka normalizing) and chemically altering the molecular structure of a metal through the controlled use of heat are vastly different processes.

I know its wikipedia, but its a good description of annealing:

http://en.wikipedia.org/wiki/Annealing_%28metallurgy%29

I wikied normalizing and it says that its the same as annealing, but air cooled outside the furnace instead of having the temperature gradually reduced over time inside the furnace:

http://en.wikipedia.org/wiki/Heat_treatment

 

I agree with what you're saying 89_RS, so by definition, there are several "styles" (if you will) of heat treatment. And by definition, wouldn't annealing become stronger the naturalizing? I'm no expert either, just picked up a metallurgy book mixed with some web research, so I could be wrong. I haven't read too far into it yet, only skimmed through a few sections.

It just seems as though the quicker it's cooled via different elements would increase the brittleness of the metal, would it not?

Granted, other than being able to say you have Chrome Moly suspension pieces makes you seem more sophisticated and expensive than Mild Steel, you're not really going to take advantage of it fully unless you're putting some serious stress on the component.

All together, that's why I'm trying to figure out which company uses what as far as finding the best product for the best price. For example, if a 5% increase in brittleness and strength is obtained for $20 it's a good deal seeing as the manufacturing costs would be a decent bit higher, but bulk deals for the company make it cheaper for them.

It's always good to know the manufacturing processes different companies use and just helps to compare products. (Just like looking at welds. If you see a weld that is sub par, you'll most like return or exchange the product would you not? Although welding is becoming more automated and perfected these days, so that's not so much of an issue anymore.) One other example would be tools. Outsourcing and lack of standards are making everything an issue these days. It's not uncommon to see a lot of car components being made of recycled steel. The qualities of steel is not so much looked at, companies just try to produce as much as they can while minimizing costs, so you'll never get the same thing twice.

Look at older cars, they rust nowhere near as easily or as quickly as others, which reflects the pureness of the materials used. I took a recent trip to the junkyard and saw a '55 or so Chevy that was sitting back there for at least 20 years underneath overgrown shrubbery. There was not a spec of rust on the frame. Compare that to a newer car and you'll see a difference.

All in all, that's pretty much why I'm trying to obtain this information. Not a very organized or short post, however it explains a bit of what I want to achieve.

 

You're a little off about not taking advantage of the 4130 unless its highly stressed. Where weights and materials are posted or have been previously stated on the parts in question, they're (mostly) using the 4130 to save weight so... there is an advantage. Question is, do you want to pay for that little bit of weight savings? Do you want to hope it was manufactured correctly as well?

Not really the explanation needed here. Some materials are more ductile than others. A material that is more ductile than another will allow more deformation than one that is less ductile. Aluminum does a lot of deforming before it breaks, whereas a high carbon steel will show very little if any deformation.

http://www.engineersedge.com/materia.../ductility.htm

"Ductility is more commonly defined as the ability of a material to deform easily upon the application of a tensile force, or as the ability of a material to withstand plastic deformation without rupture. Ductility may also be thought of in terms of bendability and crushability. Ductile materials show large deformation before fracture. The lack of ductility is often termed brittleness."

http://www.answers.com/topic/tensile-strength

Take a look at the two stress - strain curves about halfway down. This shows the behavior of the material beyond the yield point of aluminum and steel. You can also look at this:
http://en.wikipedia.org/wiki/Stress%...93strain_curve

That will show you where and how a "brittle" material will break.

I should also note that none of that really should matter. None of these parts should be getting anywhere near the yield point in practice (factor of safety), so how quickly it breaks or what it does after its overstressed is kind of pointless. Unless you have dimensional drawings and check your component often, you're most likely not going to know its going to break until it does. I would be a lot more concerned with the integrity of the welds (this is the point of failure I've always seen to date), than the properties of the materials themselves. I'd imagine any of the 4130 that might be used is plenty strong for what its being used for, given the OD and wall thicknesses I've seen them use. I would also caution worrying about things like heat treating for additional strength, IMO its not needed and only invites problems because IF you were to utilize this additional strength availability by using a thinner wall, you may (and probably will) run into issues with local buckling of the tubing. When designing anything structural, you have to look at EVERY possible point of failure, not just one such as tensile strength that most people tend to concentrate on. There are many other concerns and possible reasons for failure, if you ignore one it may just come back to bite you later.

 

Theres a yes-no answer there from what I've experienced while welding. A normalized 4130 weld won't fail if normalized properly, but the tube will fail at the edge of the heat affected zone that occurs during normalizing. If the entire part is annealed in an oven after welding, then the entire part takes on the properties of the normalized area. Once I got to the point where my welds were good and consistent, I normalized a weld, put it in a vise, and beat on the T-shaped tube with a 5lb sledge until the leg of the T broke off about 3/4" away from the weld. I proceeded to weld another T and normalize the whole thing and it broke off closer to the weld, but not at the weld itself.

I agree with madmax, if we are loading the suspension to the point of plastic deformation, somethings wrong or we are pushing the car super hard. The reason you want light weight suspension items is to reduce unsprung mass, which in turn makes the suspension more responsive and quicker to respond to changes in the car itself. Unsprung mass is anything not directly supported by the springs or shocks IIRC.

 

lots if interesting info here

the ultimate question in my mind is, what are you planning on doing/using? im curious.

 

My plan is just to build up the car for both autocross and racing, so I'm looking for something that'll hold up to both demands suspension wise. Something easily adjustable for each demand as well as strong. Trying to make the chassis as durable as possible while also having the ability to drive on the road as a daily driver.

So, adjustability and strength are my major concerns for the overall suspension system. I'm planning on spending the money necessary for a quality product, but not to spend an unnecessary amount for a slight increase.

So overall, a nice weight difference is always nice, but if I'm going to obtain a stronger, more durable product, I am all for it. That's my whole reason for obtaining the material specifications. Although I doubt I'll be able to obtain the EXACT specs as far as the manufacturing process goes, I'll be able to get the idea as far as what's going into the product.

Bringing a chart to the table of each product, the specifications, and the price, it'd be easier to tell "which is the best quality". Not saying that there's anything wrong with any of the companies or their products, I just feel as though it'd be nice to have a nice spreadsheet pertaining to the specifications.

When my dad isn't fishing, he's usually making knives, handles, cases, etc. He does extensive research into the qualities, pros, cons, etc. of each material. And since he's a perfectionist and I'm only 20 I've tended to pick up on all that **** from the time I was born.

 

thats quite fine, im a bit of a perfectionist myself, but honestly, i feel you may be over thinking/complicating this a little bit.

however i do agree completely with fully researching all your options before making a decision.

 

Spohn uses 4130N tubing in all their CM parts. The question you really need to be asking is if they do post weld heat treatment of their parts, not whether or not the material was annealed or normalized prior to manufacture of the part. You need to know if the welds have been normalized. Un-normalized welds in 4130 are very brittle and don't require a lot of force to break them.

 

i have always been curious about that, a good friend of mine is a welder/fabricator and when he does chrome moly work he always has preheated, post heated and insulated the parts to allow them to cool slowly and normalize. I would "assume" the parts manufactures do this if it is needed. I was under the impression that normalized CM tubing didnt need the pre/post heating though? i could be wrong, just thought i heard that somewhere?

 

The heat affected area during welding is what becomes brittle. That 1/8" wide area where your bead and 2 base materials meet is what needs to be normalized. If you normalized the weld correctly, the part should fail just past the weld bead by about 1/16" or greater. If you did it wrong, it will fail on the edge of the weld bead or in the bead itself.

 

another thing to keep in mind for racing applications (or street apps, really), if you get hit, do you want the more brittle material to break? or, do you want the slightly weaker steel to bend?

 

As far as the difference between mild steel or 4130 is concerned, its kind of a mute point. They are both fairly ductile. Aluminum acts as if its more brittle for some reason. This is from seeing the aftermath of destructive testing of parts on an MTS with two identical parts & loading and the only difference being one was made from steel and the other aluminum. The steel part deformed some whereas the aluminum part turned into something like a torn in two pancake.