HREW vs. DOM dent resistance

[cracker]

So I have heard / read different opinions on this. Can please someone clear this up?

[BrettM]

DOM is stronger, and 4130 (or 4340) is even stronger. Do you want percentages or something?

[cracker]

DOM is stronger, and 4130 (or 4340) is even stronger. Do you want percentages or something?

I understand 4130 is stronger and that is evident with my current LCAs.

I have heard from numorous people that DOM is not any more dent resistant than HREW which is contrary to what I had always understood. Just looking for the truth ;)

Another Pirate thread: http://www.pirate4x4.com/forum/showthread.php?s=&threadid=95244&goto=nextoldest

[BrettM]

get the specs for the steel from your supplier, if the tensile strength is higher on the DOM (which it should be!) then it is stronger for denting also.

[Capt. Nemo]

I have heard from numorous people that DOM is not any more dent resistant than HREW...

Same ones who sold you the kingpins??? :)

[cracker]

Same ones who sold you the kingpins???

Nope

There is another list of peeps. ;)

get the specs for the steel from your supplier, if the tensile strength is higher on the DOM (which it should be!) then it is stronger for denting also.

I think my mis understanding is the true definition of tensile strength. I understand structurally the DOM is stronger and what not (chromoly even more). I also know if I build a structure out of aluminum it can be strong as hell but alumimun can dent so much more easily.

For example (my real world experience with the material), I see bicycles made out of chromoly all day long having front end impacts. All the chromoly frames seem to bend at the head tube quite easily but the aluminum frames (visually) holds up and the fork folds in a heart beat. But as far as denting, the aluminum frames can dent a lot easier than the chromoly.

Here is chromoly:
http://webpages.charter.net/notjohndavid/suck2.jpg

[Weasel]

denting is different then tensile strength. Tensile strength is the strength as it's applied in tension hence the name. Denting has to do with impact strength. DOM and HREW should be pretty close to the same, except HREW will of course have a seam which might be a less on the seam. Otherwise I don't realy see a reason they should be different. Dent resistance should come more from the composition of the steel, most DOM and HREW are 1018 or 1020.

here s blurb on standardized testing for dent resistance:
http://www.sae.org/technical/standards/J2575_200406

[CartsXJ]

denting is different then tensile strength. Tensile strength is the strength as it's applied in tension hence the name. Denting has to do with impact strength. DOM and HREW should be pretty close to the same, except HREW will of course have a seam which might be a less on the seam. Otherwise I don't realy see a reason they should be different. Dent resistance should come more from the composition of the steel, most DOM and HREW are 1018 or 1020.

here s blurb on standardized testing for dent resistance:
http://www.sae.org/technical/standards/J2575_200406


Ding ding ding we have a winner.........dent resistance is completely different than what the tensile strength of the material is for. I bet if you take a hammer to the same OD, wall thickness tubing of HREW (not on the seam), DOM and 4130: the HREW and DOM will dent the same and with a little less denting on the 4130 because of impact dispersion and rebond characteristics of 4130.

This is why you don't see guys running thin wall 4130 lower links, they will have a higher tensile strength compared to DOM, but will fold on the first rock.

[Mr.OverKill]

Ding ding ding we have a winner.........dent resistance is completely different than what the tensile strength of the material is for. I bet if you take a hammer to the same OD, wall thickness tubing of HREW (not on the seam), DOM and 4130: the HREW and DOM will dent the same and with a little less denting on the 4130 because of impact dispersion and rebond characteristics of 4130.

This is why you don't see guys running thin wall 4130 lower links, they will have a higher tensile strength compared to DOM, but will fold on the first rock.i could have sworn that is what i told him about 2 months ago :lecture: ( not word for word but close ) some people you just cant teach!! :doh:

[SCW]

Any thoughts on how to decide on the best shape for an application? I'm thinking that round material on rock rails would put an infinite (in theory) amount of pressure on the point of contact and *might* dent more readily? Possibly using HSS would carry the load over a larger area in the same case?

TIA

[NXJ]

Is seamed (water) pipe generally useless for rock-contact areas? I have a pile, rusting away.

[Captain Ron]

So I have heard / read different opinions on this. Can please someone clear this up?

You did with the Pirate link. Accurate. Cold forming and carbon content. Something constantly overlooked is CREW...

Now, what is this applicable to? Cage material?

Looking at this from the other direction. :D

It's more a function of velocity and the rock you dent your tube on, as much as the tube you dent on the rock.

--ron

[cracker]

It's more a function of velocity and the rock you dent your tube on, as much as the tube you dent on the rock.

:laugh2:

[Goatman]

There was a recent article in one of the 4x4 mags about building a buggy, and they were deciding which type of tube to use. One of the tests they did was for denting, so they hit four types of tube with a hammer on the end of the tube. Of course, the aluminum dented the most, then the HREW, then the DOM , then the chromoly bent the least. There was a pretty good difference between how much the HREW and the DOM dented.

I ran out of 1" DOM, so I got some 1" HREW to finish up the cowl and the dash. There is a noticeable difference just cutting the 1" DOM and HREW with a cutting wheel......the DOM is just tougher and takes longer to cut.

[luvrox]

No numbers to offer but experience says 4130 is by far the toughest; Dom is next in ability to withstand dents and slide over rocks. Dom will dent, gall and tears rather than slide over rocks. My new chassis is all dom on exterior tubes.
P/s - - One caution a lightweight 4130 welded chassis will develop stress cracks in time. Then comes the question will you have a service truck there with a tig welder to do repairs?

[RWKHausSupply]

Avery check this out... Just what your looking for I think... REAL world type testing....

http://www.jeepaholics.com/support/topic.asp?whichpage=2&TOPIC_ID=45534񰰊

[Captain Ron]

...
REAL world type testing....
...


Got rocks?

:D

--ron

[luvrox]

No numbers to offer but experience says 4130 is by far the toughest; Dom is next in ability to withstand dents and slide over rocks. Crew will dent, gall and tears rather than slide over rocks. My new chassis is all dom on exterior tubes.
P/s - - One caution a lightweight 4130 welded chassis will develop stress cracks in time. Then comes the question will you have a service truck there with a tig welder to do repairs?


Same post with dom / crew corrected.

[Weasel]

P/s - - One caution a lightweight 4130 welded chassis will develop stress cracks in time. Then comes the question will you have a service truck there with a tig welder to do repairs?


This is not true, is you develop crack it will most likely be due to a poor design not 4130. And you do not need a TIG welder to repair 4130. Mig will work just fine. 4340 is a different story though and when welded usualy forms a state in which crack can occur.

[luvrox]

This is not true, is you develop crack it will most likely be due to a poor design not 4130. And you do not need a TIG welder to repair 4130. Mig will work just fine. 4340 is a different story though and when welded usualy forms a state in which crack can occur.

Oh really, step back and read what you just posted. Yes, you can probably repair anything with even a butane torch and the correct solder. The word that seems to have slipped by in your statement is "successfully".

[Weasel]

And why would that be. You do not have to tig weld chromoly, mig will work just as well.

[Captain Ron]

...
mig will work just as well.

Don't do it Weasel. ER80S-D2, ER70S-2 and -6 work with TIG only because the base material "mixes" during puddle flow and filler add. With MIG, you don't get this to the nessesary extent.

If you get a CroMo frame with big, ugly, crappy welds on it, take it back. TIG or not. If your chassis builder tries to fill a 1/16" gap in CroMo, fire him.

--ron

[luvrox]

And why would that be. You do not have to tig weld chromoly, mig will work just as well.

Of course you have to consider I learned this all in the sixties and I may be a little behind the times. First you will need a gas shield to make the perfict weld on 4130. A Mini tank and regulators aprox 60 lb. Then comes the wire issue, you will do best with a role of er70s. To stop the stress crack issue it's best to stress relieve the weld area by bringing the weld to around 1100 degees then feathering it out. That will require a a pair of oxy acetylene tanks and regulators. At aprox. 90 lbs.

Gas 60 lb.
Welder & wire and gun 40 lb.
Oxy / Acetylene 90 lb.

Or you could go with plan B and hook a couple of batteries together with a tube of 1310 and have your dom rig back in action with what? Maby about ten extra lbs.

[Captain Ron]

...
To stop the stress crack issue it's best to stress relieve the weld area by bringing the weld to around 1100 degees then feathering it out.
...

Not nessesary on anything .120" thick or less. In no way proven, but my gut feeling is that blowing it during this proceedure contributes to lamellar failure. Crack prone joints are usually simply a case of a poor fit, leading to excessive filler material addition and inadequate base material mixing.

--ron

[luvrox]

Not nessesary on anything .120" thick or less. In no way proven, but my gut feeling is that blowing it during this proceedure contributes to lamellar failure. Crack prone joints are usually simply a case of a poor fit, leading to excessive filler material addition and inadequate base material mixing.

--ron

Score one for Ron. :D

[Weasel]

Don't do it Weasel. ER80S-D2, ER70S-2 and -6 work with TIG only because the base material "mixes" during puddle flow and filler add. With MIG, you don't get this to the nessesary extent.

If you get a CroMo frame with big, ugly, crappy welds on it, take it back. TIG or not. If your chassis builder tries to fill a 1/16" gap in CroMo, fire him.

--ron

This is the frist I've heard of the "mixing" effect. Is this a proven welding method or just a idea. Not being a smart ass just asking. I have not heard fo this from any of the ASME or AWS procedures/info I have read.

The dnager with welding any low alloy high hardenable steel is the formation of maternsite. This is a highly brittle crystal structure that leads to cold cracks. The way to help this is to slow the cooling rate. This is where pre-heating comes into play, but preheat may or may-not be needed, you would have to consult the RPI tables for this. However I do know that you can weld 1/4" 4130 and the cooling rate will be slow enough that martensite is not formed. So for the tubing thicknesses we use the cooling rate should not be an issue.

I know what I said one the filler issue before, of using ER70-S2 but after learning a bit more about welding I think you can use 4130 filler (or not filler with TIG) without resulting in brittle welds. As long as you don't have a travel speed to high you should also be able to avoid any hot cracks, from liquid films.

However with 4340 it is much more hardenable and much harder to weld as just about any combination of welding on this steel will result on maternsite, so preheat is a must and care must be taken.

I guess I'm not sure what your getting at with the gas issue? All of our Mig and Tig machines use gas shields for the welds.

So what am I missing?

[Weasel]

Not nessesary on anything .120" thick or less. In no way proven, but my gut feeling is that blowing it during this proceedure contributes to lamellar failure. Crack prone joints are usually simply a case of a poor fit, leading to excessive filler material addition and inadequate base material mixing.

--ron

Actaully there are two forms of cracks that form in welds. Hot and Cold.

Hot cracks are due to "liquid films" and strains. Liquid films therioes are when the weld is cooling the liquid metal is pulled back from between the grain boundaries, if the liquid cannot fill the area fast enough then a hot crack forms.

Cold Cracks are from three different causes, hydrogen, thermal stresses, or the formation of martensite. See above for the martensite issues.

Filler material listed above doesn't have issues with martensite unless your using a high hardenable steel. Base metal mixing I don't think has much to do with it, the metal is melted and flows together.

[luvrox]

I guess I'm not sure what your getting at with the gas issue? All of our Mig and Tig machines use gas shields for the welds.
So what am I missing?

To make it simple, how well will those banks of bottles fit in the back of your XJ to do field repairs? :D

[Dan Fredrickson]

I say fillet braze the whole thing and get on with your life......:laugh3:

However, I am a believer in the fact that the same materials in the same thickness results in the same strength. But, with that in mind you can successfully use HREW in most applications where you can control where the welded seam is, in bent materials I prefer DOM because you do not need to be so aware of the seam location and the effect of the bend on the seam itself, which BTW, is welded perfectly by a computer in most cases.

Also, when buying tubeing be aware of too good of a deal, many dealers will sell you factory seconds with uneven wall thicknesses and never mention the fact you are getting such a good price because the material is a Factory Second. And another however, a "second" may be just the ticket in less important areas.

[Weasel]

To make it simple, how well will those banks of bottles fit in the back of your XJ to do field repairs? :D

Do it right and you don't need field repairs. ;) But yeah bottles would be a pain.