Gonna be building a partial exo to keep my windshield safe, but I can't stand how ugly most exos are because they stick off the body too far. So I'm keeping mine as close to the body as possible. Not worried about body damage, just don't want the cab to flex and brake the glass. So I'm thinking of going chromo to keep it beefy without a lot of extra weight up there.

What kind of wall thickness would you think is appropriate? And what kind of price range? It's all gonna be 1 1/2", BTW.

And how does the strength of the chromo compare to DOM? Can chromo be MIG welded just like standard steel?

Originally posted by Im4yotas
Gonna be building a partial exo to keep my windshield safe, but I can't stand how ugly most exos are because they stick off the body too far. So I'm keeping mine as close to the body as possible. Not worried about body damage, just don't want the cab to flex and brake the glass. So I'm thinking of going chromo to keep it beefy without a lot of extra weight up there.

What kind of wall thickness would you think is appropriate? And what kind of price range? It's all gonna be 1 1/2", BTW.

And how does the strength of the chromo compare to DOM? Can chromo be MIG welded just like standard steel?

Do a search, I remeber seeing tensile strength #ers on the board.

Like Pig said, do a search, its been covered. You might even turn up a thread like THIS ONE (http://www.pirate4x4.com/forum/showthread.php?s=&threadid=84559&highlight=cromo) in your search.:flipoff2:

Wow thanks for the usefull tech:flipoff2:

I read till my eyes were sore, and couldn't get a definitive answer about the welding. Some say it needs to be heat treated, some not, some say use this rod, some say use that one. All that was about TIG and oxy/acet. So has anyone actually MIGed 4130?


Did find this, though:
Originally posted by twinpinion
I have similar numbers from EMJ Metals:

4130 (seamless chromoly, usually about 4-times more expensive than HREW)
Tensile: 90 ksi
Yield point: 70 ksi


DOM 1020
Tensile: 80 ksi
Yield point: 70 ksi


HREW 1010
Tensile: 45 ksi
Yield point: 32 ksi

Use whatever you like. I don't care. DOM is the best bang for the buck.
:flipoff2:

So it looks like even when done correctly, the chromo is only mildly stronger than the DOM. But what do the tensile and yeild numbers translate to in cage strength?

Also, it seems that the DOM is about twice as strong as the HREW. Does that mean that I could use 1 1/2" x .060 DOM and get roughly the same strength tube as 1 1/2" x .120 HREW for the cage? And what kinda thickness would you experts suggest for my situation with very minimal deflection in a sound design and weight still somewhat of an issue?

Originally posted by Im4yotas
So has anyone actually MIGed 4130?

Yep, MIG'd just fine. But the weld material is now weaker than the tube (I don't think it will be an issue, as the weld will probably never break in the first place)

What wire and gas?

do a search for the GC that bender exo'd. That should give you an idea of how to build one without havin it flex into the cab.

Dallas

Originally posted by Im4yotas
What wire and gas?

ER70S & C25.

chromo is a waste unless you are heat treating it. Use DOM and miging will be fine.

Yeah, I remember seein that one. What I'm gonna do is run the halo and A-pillar as exo, then tie into my existing in cab B-pillar through the roof, and run an X brace behind the cab tied to a FB. Then I'm probably gonna weld the exterior bars to the cab itself. Just not sure how thick...guess I'm leaning towards .120 DOM. Maybe the chromo still, depending on price and if I'll be able to weld it.

Originally posted by Weasel
chromo is a waste unless you are heat treating it. Use DOM and miging will be fine.

Care to elaborate? Read this elsware, but haven't heard any convincing evidence for or against it.


And thanks, Joel:D

Originally posted by Weasel
chromo is a waste unless you are heat treating it.



I kinda agree. I bought a stick with the intention of having my links TIG'd and heat treated, but it turns out that no one in Sac can heat treat anything longer than 2 ft & everyone seemed to want WAY too much $$$ to tig weld on the ends. So, I just used it for my upper A-link instead & MIG'd it.

So you don't think it's any stronger just MIGed and not treated, or you just don't think the little strength gain is worth the extra $$?

And could someone explain what yield and tensile strength is and what that means to a cage?

Why use Moly? I think you are getting away from the point. If I understand you correctly, you are trying to re-enforce your cab to protect against a roll over, and to keep the windsheild from flexing and breaking, am I right? Then just go with DOM. If you are going to be in a situation where you might shatter your winsheild because you used DOM instead of moly, then I would suggest chopping the cab, and doing a full cage because the windsheild was doomed anyway. The weight you save by going with a moly cage as apposed to a DOM cage aint gonna be much concidering the rig you are in, and Moly costs two to three times as much as DOM anyway. DOM is fairly strong, and I wouldn't hesitate for a minute to build a cage out of the stuff. If DOM isn't strong enough, then I would doubt that moly would be your answere. My .02

I just wanted to answer a few of your questions. First of all I don't have my standards book with me this morning so I can't verify the strength numbers on the different metals, but the DOM numbers seem a little high. The other thing you need to remember is that DOM and HREW are processes while 4130 and 1020 are metals. You could have DOM 4130. If I remember correctly 4130 is substantially stronger then 1020, but again I don't have my book with me so I can't answer that.

As for tensile strength and yield strength and what they me to cage design. Both tensile and yield point are measured by placing a piece of the metal in a device and pulling it until it fails. The tensile strength is the ratio of the stress (force) over the strain (stretch). This number is used to calculate the strength of a particular tube geometry or for analysis of a structure (the cage in your case) The yield point is the stress the metal can take before it starts to deform plastically (stretch and stay that way). What these mean for a cage is a difficult question to answer. Higher strength metal means your cage will be lighter for a given strength. You could use DOM 1020 and build a cage that is the same strength as one built from 4130, but the 1020 DOM cage will be heavier than the 4130 cage. The strength of the tubing depends on the diameter and thickness of the tube and the strength of the metal. The only time we use 4130 in cage construction is when weight is an issue (racing chassis).

We have built a number of chassis out of thin walled (.049) 4130 and we TIG them most of the time. Mainly because we have a TIG welder. When we do that we use a low copper, low carbon rod and make a nice fillet. We don't heat treat the chassis when we are finished. I have never tested the strength of the weld specifically, but I can state that the cars have taken some extreme hit (30+ MPH) and we have never had a weld fail. Normally the tube buckles or the rod end shears before the welds snap. As for MIG welding, we will MIG 4130 on occasion and we just use a low carbon wire and a argon/carbon dioxide gas. This works well and we have had no problems with the resulting welds.

One last note on heat treatment. Heat treatment is used to control the size of the carbon grains in a metal. As the carbon content (the last two numbers in the steels number) increases the likelihood that large grains of carbon will form increases. If you use a low carbon rod/wire when you weld high carbon steel you reduce the carbon content of the weld and reduce the likelihood of large grains forming. This reduces the strength of the metal at the weld, but you typically increase the amount of metal at the weld to compensate for the decreased strength. The heat effected zone around the weld can also rearrange its grain structure and form large grains, but if you keep the zone small (this happens with a TIG) you decrease the likelihood of having an weak area near the weld.

I hope that clears up some of your questions. My advice would be to use the 1020 DOM and just MIG the whole thing. The cage will look the same, it will just be slightly heavier.

The tensile strength is the ratio of the stress (force) over the strain (stretch). This number is used to calculate the strength of a particular tube geometry or for analysis of a structure (the cage in your case)

I'm not following you here, the ratio of stress to strain is the modulus of elasticity or Young's Modulus or "E", not the tensile strength. Young's modulus is typically used for finding the deflection of a part. The problem is, all steels have the same modulus of elasticity, so it's not a good way to compare 1020 DOM vs 4130 vs HREW.

Im4yotas, are you worried about plastic deformation("tube flexing") or are you more worried about permanent deformation (tube is bent or dented)? In a roll cage or any other structure you have stregth and stiffness, they are two different things and use different material properties. Stiffness has to do with the geometry of the cage, the size and wall thickness of the tubing (moment of inertia, I), and the modulus of elasticity of the material, E. Now since all steels have the same E, the stiffness of the cage will be the same wether you use 1020 DOM, 4130 or HREW. The only way to make a cage stiffer is to change the geometry (triangulation, many nodes) or increase I of the tubing by increasing diameter or wall thickness, BTW, increasing tube dia makes more of a diffrerence to I than increasing wall thickness.

Now the strength of a cage depends on the stiffness of the cage and the strength of the material. You can have a stronger cage by using 4130 but it won't be any stiffer. Or you can have a more flexible, lighter (thiner wall, smaller OD) 4130 cage that is the same strength of a heaver ( thicker wall/ bigger OD, mild steel cage.

Say you hit a rock in the middle of a tube span, 4130, 1020 DOM and HREW (same OD, same wall) will all deflect the same (may hit sheet metal on an exo), but you might hit so hard, the HREW will permanently bend, where the 1020 DOM and 4130 will spring back. You can use a smaller OD and/ or thinner wall 4130 that will permanently bend the same amount with the same hit, but it will have deflected more (hit sheet metal more on an exo).

Now mig welding 4130 on an exo is no problem, many off-road race cars are mig welded 4130 with RE70S-2 with no problems. It would be stronger to TIG weld it, but the MIG will be strong enough, the joint will not likely be a failure point.

My EMJ book lists Sy and Su for 1020 DOM as 80 and 90 ksi, and Sy and Su for 4130 N is 90 and 120. The 4130 has only a 10-15% increase in yield strength. I would use DOM, the 4130 would probably be more of a waste of money for you. Like someone said earlier, you get alot of strength gains when you heat treat 4130.

something to keep in mind ... JRT's is 1.25" hrew and he never rolls

I did HREW 1010 2in 120 wall.
The larger diamater makes it harder to bend but easier to dent,
1.5in tube wouls resist denting better but would be easier to bend.

I didnt want pay for $$ DOM So I decided to just go larger diamater and go cheep HREW for like $1.40 a ft bought 360 feet delivered to my house form EMJ.

HTH

I'm not following you here, the ratio of stress to strain is the modulus of elasticity or Young's Modulus or "E", not the tensile strength. Young's modulus is typically used for finding the deflection of a part. The problem is, all steels have the same modulus of elasticity, so it's not a good way to compare 1020 DOM vs 4130 vs HREW.

I'm sorry, I guess I didn't look at that correctly. I was talking about Young's Modulus when I said tensile strength. After looking at it I assume that the tensile strength listed is the ultimate tensile strength. But Young's modulus does change for different steels, the Shear Modulus is the same for all steels. Either way it doesn't change anything. The strength (and stiffness) of your cage are entirely based on the design of your cage and are mostly independent of the materials used. Save yourself some money and go with the cheaper material.

But Young's modulus does change for different steels, the Shear Modulus is the same for all steels

No, the modulus of elasticity (Young's Modulus) and the Shear modulus of elasticity are the constant for steel, alloy or not.

read what Goat1 said. The chromo is only worth the money if you are going to heat treat it. That when you gain a huge increase in strength over Dom 1020. Mild(1020) doesn't repond to heat treatment either. So for the extra money of 4130 you only get 10% strength increase.

MIG is fine and probably a better solution then TIG since TIG requires you to pre/post heat more then MIG according to Carroll Smith. If your worried about brittle welds and want to take the time pre/post heat while MIG would be ok.

And yes heat treating a cage or frame of chromo is expensive and few places do it. Same for any large pieces of chromo. Most of the time you will have to ship it to a failicty that can heat treat it. Ends up being $$.

Originally posted by GOAT1


No, the modulus of elasticity (Young's Modulus) and the Shear modulus of elasticity are the constant for steel, alloy or not.

stainless is a smidge lower on the E (28ksi-ish?)

Good info guys. Thanks.

Goat, I'm looking for the cage to not deflect more so than not dent. I have a feeling, the windshield is doomed anyways, but I'd like to prolong its life, and be able to maintain the framing so I can install a new one or maybe some speed glass.
Hmm, maybe I should go 1 3/4". Still want to keep it inconspicuous, so the smaller, the better as far as asthetics.

It is NOT necessary, nor is it necessarily even desireable to "heat treat" a weld on chrome moly steel tubing.

First, in order to actually heat treat, you have to have an oven capable of brining the part you want treated up to temperature in a slow and controlled manner, maintaining that temperature, and then cooling it properly. Of course, you also have to know what temperature and for how long. Second, if you think that you are heat treat stress relieving your welded chrome moly joint by heating it with a torch until it is bright red and letting it air cool, you are sadly mistaken.

Properly welded (TIG or MIG) with the correct filler material, chrome moly requires NO heat treat or hot stress relieving.

You can use an alloy wire (such as ERS100S6) in a MIG with 75/25 gas to weld chrome moly, so long as you and the machine are up to the task. Just make sure you get mil spec certified 100% pure wire.

Having seen the results of the use of ERW, DOM., and chrome moly materials in race cars and aircraft for over 20 years, I can say I wouldn't use anything less than mil spec certified DOM for any fabrication project. I also don't use anything but mil spec certified 100% pure filler wire and rod. I don't like seamed tubing, and I don't like the tolerances allowed in its manufacture.

DOM has a seam....are you talking about seamless tube? I think that stuff is major $$$ but I'm not sure.

Originally posted by Im4yotas
What I'm gonna do is run the halo and A-pillar as exo, then tie into my existing in cab B-pillar through the roof, and run an X brace behind the cab tied to a FB. Then I'm probably gonna weld the exterior bars to the cab itself.

Something I just thought of but how would you heat treat it after welding it to the truck? Building it in the shop,heat treating and then welding it to the truck would kinda defeat the purpose of heat treating :confused: right :confused:

You could heat treat the whole truck :laughing: :laughing: :p

I vote for just using DOM if you got the cash. If it were me I would use HREW. I used 1 1/4" pipe on mine and am happy with it but kinda kick myself wishing I woulda used HREW. There's no way in hell I'm gonna scrap it and start over. It did save me a pile of cash though at $0.80 a foot

Originally posted by desertCJ
DOM has a seam....are you talking about seamless tube? I think that stuff is major $$$ but I'm not sure.

I've never seen real mil spec certified DOM (DOM stands for Drawn Over Mandrel, hence there is no need for a seam) with a seam, and I've bought a bunch. ERW is the tubing with a seam (Extruded Rolled Welded).

And no, DOM is not that high. Besides, if I'm going to go to all the hassle of bending cutting, notching, and welding a bunch of tubing, I'm going to use good material. I just don't use anything less than mil spec certified DOM or chrome moly, and the lowest grade wire I use is ER80S6, also mil spec certified 100% pure. Any other filler wire, especially that stuff with copper "plating", is likely to have so many impurities in it it ain't funny. Go buy the good tubing and wire sometime and see how much better it welds and how much better the appearance is.

Well I don't know about the "mill-spec" stuff, but just because it is DOM does not mean that it doesn't have a seam. True seamless tubing starts as a solid rod of steal and is peirced to make it hollow. Most DOM starts as a sheat of metal and is rolled into shape and then is Drawn over a Mandrel which smoothes the inside. This eliminates the flashing of the weld and cold works the metal. There is a distinct difference between SEAMLESS tubing and DOM.

In all of our stock cars we use 1 1/2" and 1 3/4" HREW or DOM tubing. Chromolly is not even an issue because it will not flex like the other's and every place it is welded (with Mig) unless it is re heat treated it actually has a weak spot... Save some money. Use DOM or HREW. The HREW would probably be your best bet!

Originally posted by Raptorman57


Something I just thought of but how would you heat treat it after welding it to the truck? Building it in the shop,heat treating and then welding it to the truck would kinda defeat the purpose of heat treating :confused: right :confused:

You could heat treat the whole truck :laughing: :laughing: :p

I vote for just using DOM if you got the cash. If it were me I would use HREW. I used 1 1/4" pipe on mine and am happy with it but kinda kick myself wishing I woulda used HREW. There's no way in hell I'm gonna scrap it and start over. It did save me a pile of cash though at $0.80 a foot



I knew from the start heat treating wouldn't be an option. I'm not gonna use HREW there either, cuz I want as much strength as reasonably possible without too much weight. The rest of the cage and bed will be HREW, though, except the existing B-pillar is already DOM.


May as well talk design, too, since that will play a major part in how stiff it is. Here's what I'm thinking: gray bars would be the exo portion, and either DOM or 4130, black v-bars will be 1" x .120, and the red will be under the fenders and cowl, and be 1 1/2" x .120 HREW, except the bottom of the A-pillar. The red with punch through the front of the fenders to a stinger on a new bumper. There will also be a flatebed with an X brace at the front of it tieing to the exo, and the inner B-pillar.
Watcha think?

I think your cab is gonna get fawked up unless you have an externall B-pillar and C-pillar. Especially since you have an extra cab. Why bother if your only gonna do it half way? Oh ya and I say use 1 1/4 schd 40 pipe:D

Cab is already fawked up. C pillar will be behind the cab with an X-brace, though. What I'm trying to do is keep it closed off to the elements and any would be thiefs, cuz it stays parked in front of the house.

I would fawk up a Toy cab faster and easier than a 'Vegas hooker:D That's why I would do an external B and C pillar. But hey it's your rig and you can do whatever you want;) A full exo might keep you from breaking the rear side windows out though.

Yeah, the half windows are doomed, too. I'm just gonna replace the glass with aluminum sheet metal. Like I said, sides of the cab are already hammered. The truck doesn't look as good as it did when that pic was taken. Might cut em out at a later date and have some 1/8" plate formed to the same shape for protection, or just some easily replaceable sheetmetal.

Here's my quick take. 4130 shines when just a little bit of weight is an issue. If a few pounds isn't what you want to save then you need dom. Dom tho not technically "seamless" is referred to as such by many due to the drawing over a mandrel that eliminates you seeing the seam..

demo
http://www.steeltubeinstitute.org/process/Dom_Process.html


Chromo can be welded properly without the need for heat treating. All the heat treating talk is a little over the edge although done properly to an entire chassis it sure wouldn't hurt. Chances are the welded joints won't be the weak point in a well designed cage anyway. But chromo is imo only worth the money for ultimate strength or weight savings. DOM is the best bang for the buck.

Damn it people! Heat treating is not the same as pre/post heating a weld! No it's not neccesary but is a msut in things like F! racing. It's all about what level you want to take it too.

I have not read the whole thread, but I thought I'd add something.

First, I am a Mechanical Engineer and I my main work is in the design and construction of welded structures and machines using everything from mild steel through chrome-molys, stainless steels and up to nickel and cobalt alloys.

From a welding point of view, chrome moly is one of the hardest alloys to get done properly. High alloy chrome molys like 4130 are VERY difficult. It requires very, very careful and well thought through welding procedures. These ALWAYS include preheat and postheat requirements. It is still nearly impossible to produce welds with properties equivalent to the parent metal. In my work, we would only ever weld 4130 IF the weld was in a non critically stressed area.

So, my advice. Unless you are very knowledable and are following well developed welding procedures, there is not much point.

If you just weld it up like you were welding mild steel, areas within and near the weld will be no stronger the mild steel. PLUS you will develop some very brittle areas which will be prone to failure from impact.

For an off road chassis use, good quality mild steel is your best choice. It is ductile and thus absorbs lots of energy prior to failure. Plus producing welds of equivalent strength to the base material is relatively easy.

Originally posted by desertCJ
Well I don't know about the "mill-spec" stuff, but just because it is DOM does not mean that it doesn't have a seam. True seamless tubing starts as a solid rod of steal and is peirced to make it hollow. Most DOM starts as a sheat of metal and is rolled into shape and then is Drawn over a Mandrel which smoothes the inside. This eliminates the flashing of the weld and cold works the metal. There is a distinct difference between SEAMLESS tubing and DOM.


The procedure you describe for creating seamless tubing is called Drawing Over a Mandrel. Having fabricated race cars for the better part of 25 years, I can honestly say I've never seen a stick of properly marked as certified DOM with a seam in it. True DOM is certified and is marked with a stenciled paint or dye that incleds the dimensions of the tubing and the lot number, and carries with it the "material certs" which is the certification for the content.

Well arguing with you about it is pointless, but I am quite certain that the 1.5"x.250" DOM I have DOES in fact have a seam. Just because it is DOM doesn't mean it didn't start as a flat strip of metal.

Originally posted by Weasel
Damn it people! Heat treating is not the same as pre/post heating a weld! No it's not neccesary but is a msut in things like F! racing. It's all about what level you want to take it too.


Yeah, no shit, welding chromoly is one of the biggest misunderstood practices I have seen in fabricating. Everyone has their own tricks and opinions, yet 95% have no actual metellurgic or mechanical testing to back it up. There is only one way to do it right, it's not a mystery, but people are too lazy or can't justify the cost to do it right.

I think the term "heat treating" is used rather loosely or broadly. To me, there is heat treating (hardening), stress relieving, normalizing, annealing, etc. they are all different processes and do different things. People refer to stress relieving or the attempted stress relieving with a rosebud torch as heat treating, which can be a little confusing sometimes.

Originally posted by desertCJ
Well arguing with you about it is pointless, but I am quite certain that the 1.5"x.250" DOM I have DOES in fact have a seam. Just because it is DOM doesn't mean it didn't start as a flat strip of metal.

2nd this. "DOM" tubing usually is welded then drawn over a mandrel to further cold work the metal and tighten dimensional tolerances.

Seamless is also drawn over a mandrel, but that's because it is the only way to manufacture it.

Originally posted by desertCJ
Well arguing with you about it is pointless, but I am quite certain that the 1.5"x.250" DOM I have DOES in fact have a seam. Just because it is DOM doesn't mean it didn't start as a flat strip of metal.

I'll have to agree with you here. You basically have CREW, HREW, DOM and CDS(cold drawn seamless). My EMJ book defines DOM as quote "DOM is formed from strip and electric-resistence welded, then cold drawn to size. The cold drawing process causes the weld line to virtually disapear." What is commonly refered to as DOM is 1020 or 1026. 4130 is available as CDS, DOM or HFS, but CDS normalize is most common. Either way, DOM has a seam, you just dont see it.

The procedure you describe for creating seamless tubing is called Drawing Over a Mandrel.

No, actually it isn't. It's called "extruding", same way you make pasta. different from DOM entirely, though there are similarities. The point is, I'm afraid you may have been mistaken for 25 years. DOM is rolled, welded, and drawn. Seamless is extruded.

Seamless really only sees use in high pressure apps (to my knowledge).

Bottom line all DOM tubing has a seam, by definition. If it doesn't it isn't DOM.

DesertCJ - you're all over it dude, and the "mil spec" is simply a quality control assurance - doesn't change the basics, which you have quite correct

My .02

I went through this build an exo to save the windshield process last year. I don't think it was worth the effort and limited me in what I could have done by having to work around the cab. I just recently did a half flop onto the drivers side and caught the point of a boulder that was sticking out right in the windshield. I have since removed the windshield and actually like not haveing it there. It makes communication with spotters and trail leaders easier. The only reason that I really wanted to keep the thing was to keep me dry but now I live in the desert and don't remeber what rain looks like.

So good luck, build it if you want but understand that no windshield is really safe.

Theoretical Question:

Cage built from 1.75" x .083 wall Chromo. Tig welded.

Is the heat from powder coating the cage enough to stress relieve?

Ed

no. To post heat a chromo weld you need to heat it to about 1200F( dark cherry to medium cherry). At that temp the powercoating would be history.

Originally posted by Rock Taxi
Theoretical Question:

Cage built from 1.75" x .083 wall Chromo. Tig welded.

Is the heat from powder coating the cage enough to stress relieve?

Ed

Works for 7005 alum. though!

Well this is about beat to death but 90% of the tubing you see on this site is HREW, the major drawback that matters for your (our application IMO) is the inconsistency of the material, some .120 wall stuff can get thin so it may deform during a bend (if your lucky) or from a bump after it's all welded in and painted. I would suggest using DOM (seamed then drawn basically work hardened) because if it's said to be a .120 wall then it is.
If you are going to do all the work of staying inside the fender I would consider doing a lip inside the fender opening of something like a 1". I saw it on a Toyota up here in WA that I saw about 15 times before I even realized it was there and it would suck to totally screw one of yours up to the point of having to replace it if your welding the inner stuff to it.
There is plenty of good reading and info in this thread but for what you want to do IMO this is the only way.

I understand and acctually did understand before this thread the difference in proccesses of hrew and dom, BUT

the steel grades associated with dom 1020 and 1026, is this a steel grade of the raw material before formation or is it the grade after the "cold forming" when making dom..

reason why is this question:

is it possible to get 1020 or even 1026 grade hrew?

Austin,

1020 is 1020 before and after. The mumbers are as follows - 10 (the first 2) denote the group, in this case plain low carbon steel, and the last 2 digits represent percent carbon copntent. In this case 1020 = plain low carbon steel with 0.20 % carbon.

The DOM process doesn;t change the chemical composition.

So yes, in theory you can have 1020 HREW, though in practice, often only certain grades are made into certain products.

That's actually the reson for the oft confusing use of the term "DOM" to describe a material, rather than a process. That is, because VERY often DOM mechnical tubing is 1020 DOM mechanical tubing, people drop the "1020" and the "mechanical tubing" parts, and just say "DOM", and then nerdy guys like me pipe up and say stuff like " ahem...actualy DOM is a process, not a material" ;)

Somewher in the tech pages, I think the tech ref section, there are some good linke - one to the steel tubinf institue of America and some catologues and such which should give you a good idea of what product/process combos are available and/or common

Anyone wanna talk about how A53A schd 40 pipe is damn near the same thing as 1010 HREW:D Stirring the pot:flipoff2:

Originally posted by desertCJ
Anyone wanna talk about how A53A schd 40 pipe is damn near the same thing as 1010 HREW:D Stirring the pot:flipoff2:


How about cold drawn 1012 to cold drawn A106C? Or the fact that SAE specs are based on average values and ASTM/ASME pipe specs. are based on min/max. values?

Not that we haven't had enough miss-information fests on this particular subject.:rolleyes:

Originally posted by BillaVista


Seamless really only sees use in high pressure apps (to my knowledge).



Correct in all my applications... I've used it for reactor main steam lines.

KEVIN

ok after a lot of searching I have to ask, does anyone know how much strength is gained in the dom process? I imagine some is gained from the certainty that the wall is the right thickness but how much from the cold working?
and second as you cold work the tube when you bend it for your cage does that make the bends close to the same strength or??
the reason I ask is the same as everyone having this argument in the shop, I am all for saving a lot of money by going to a larger erw tube instead of using dom of a size smaller but how much bigger is required to match the strength assuming the same base material is used say 1020, or would going up a wall thickness be better? for me weight is not an issue.

erw - 30-40 ksi
dom - 50-60 ksi
4130 - 90 ksi

Bends usually thin the wall of the tube, so it's probably a bit weaker.

Here are some specs for different grades of pipe...

MANUFACTURE
SPECIFICATION PROCESS
TYPE MINIMUM YIELD (PSI) MINIMUM TENSILE (PSI)
ASTM A53F Continous Weld 25,000 45,000
ASTM A53A ERW or Seamless 30,000 48,000
ASTM A53B ERW or Seamless 35,000 60,000
ASTM A106B Seamless 35,000 60,000
ASTM A252-2 ERW, Smls or DSAW 35,000 60,000
API 5LA CW, ERW, Smls or DSAW 30,000 48,000
API 5LB CW, ERW, Smls or DSAW 35,000 60,000
API 5LX-42 ERW, Smls or DSAW 42,000 60,000
API 5LX-52 ERW, Smls or DSAW 52,000 66,000
API 5LX-60 ERW, Smls or DSAW 60,000 75,000

ok the numbers point in the right direction but I'm looking for a more direct answer. lets say how does 2 inch .090 wall dom compare to 2 inch .125 erw? I notice that the stronger erw listed is 40k while the weaker dom is 50k and if I assume those numbers then the thicker wall erw is actually stronger, is this the case or??

I don't know off hand. If you really wanted to know you would have to calculate your srentgh valves.

Originally posted by mytzlflick
ok the numbers point in the right direction but I'm looking for a more direct answer. lets say how does 2 inch .090 wall dom compare to 2 inch .125 erw? I notice that the stronger erw listed is 40k while the weaker dom is 50k and if I assume those numbers then the thicker wall erw is actually stronger, is this the case or??

Typical DOM is usually about 80 ksi for the yield strength, 1010 HREW is listed as 40 ksi, but I dont know what actual numbers are, they probably don't do any material certs because no one uses it (or shouldnt) for any thing critical. What kind of strength are you looking for? axial tension, bending, torsion, buckling, and you can compare stiffness in any one of these loading situations, you have to look at these different loadings individually, they will call compare differently with different materials and tube sizes.