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DOM tubing

V

voudoux

NAXJA Forum User
Location
Piedmont NC
I see on a lot of post concerning roll bar fabrication that DOM tubing is used,what is the reason for using DOM over plain or non DOM ? I don't understand why it is used,why is being sized on the inside an issue? Thanks
 
voudoux said:
I see on a lot of post concerning roll bar fabrication that DOM tubing is used,what is the reason for using DOM over plain or non DOM ? I don't understand why it is used,why is being sized on the inside an issue? Thanks
Click to expand...

The mandrel isn't so much for sizing, but the process makes the welded area stronger and less likely to break or bend. Pretty much all tubing starts out the same way, it is rounded and then welded. Extruding large tubing from scratch just takes too much work. DOM is brought up to a high temp and then run through almost the same process as extrusion. The welded seam is smoothed out and tempered to the same as the rest of the wall and this reduces the probability of stress cracking during flexing due to difference in hardening.

In many cases DOM is overkill, but a cage that might be called on to save you life isn't normally. If you go to the point of using DOM, I would also opt for TIG welding. There is a reason why competitions require DOM and TIG.
 
DOM CREW...is made from higher grade steel this is really all there is to know for this use...but HREW 1010 steel is fine...there is absoulutely no need to TIG weld DOM to gain the advantage of the better steel , and a proper MIG weld is just as strong as a TIG ...the TIG process also requires better fit up .


HREW is good enough...but it only costs about $100 more to use DOMand while HREW is good enough the steel in CREW Is the better of the TWO ...if you build a poor cage it will not matter if you make it out of chromo 2.0 .250 wall it will fail.
 
Thanks for the replies,now I know ,have run a welding/fabrication shop for over 20 years,have always stayed away from roll bars/cages a liability issue. I figured saying they they used DOM was just bragging rights. One thing I saw in the reply was the heating and drawing tempered the weld seam a very controlled machine weld and reduced the hardening at the edge of the weld. How about the manual and very variable welding at the joints. I would bet there are more failures at the joints than in the body of the tube. The remark about not having to fit the joints as well with a MIG welder is true but you have the back side of the weld exposed to no shielding gas, not the best weld. Thanks again
 
1-tonxj said:
DOM CREW...is made from higher grade steel this is really all there is to know for this use...but HREW 1010 steel is fine...there is absoulutely no need to TIG weld DOM to gain the advantage of the better steel , and a proper MIG weld is just as strong as a TIG ...the TIG process also requires better fit up .


HREW is good enough...but it only costs about $100 more to use DOMand while HREW is good enough the steel in CREW Is the better of the TWO ...if you build a poor cage it will not matter if you make it out of chromo 2.0 .250 wall it will fail.
Click to expand...

.250" wall goes along way to fix engineering problems! :looney:
 
Reasoning why some may say tig welding would be necessary is because a whip and pause motion with mig welding is actually an improper way to weld it. Stepping out of the puddle with a whip and pause or small cursive "e", or whichever method you prefer, leaves voids. Yeah it may look better, but incorrect technique.
 
831_xj said:
Reasoning why some may say tig welding would be necessary is because a whip and pause motion with mig welding is actually an improper way to weld it. Stepping out of the puddle with a whip and pause or small cursive "e", or whichever method you prefer, leaves voids. Yeah it may look better, but incorrect technique.
Click to expand...

Cold welds are more common with TIG they just look good ...lol...you can do what amiunts to brazibg with TIG and have a good clean looking bead...also making shapes is nit incorrect mig turning the heat down and whipping fast out of the puddle is but not simply making the shapes...lol...infact e...c...u...and v are how you bite in with arc.
 
Just how should I be MIG welding with out moving the torch in one of ways that you say is wrong? In my reply I was talking about,if tempering improves the DOM weld what about the joint weld. It has quite abit of localized heat that is cooled fairly fast by the colder (less hot) tube drawing the heat out of the weld and the fact of a not as good a fit letting more of the weld not being shielded by the gas,unless you flood the tube with gas. Thanks
 
TIG isn't necessary to weld a mild steel DOM cage. However, it is usually required for a Chromo DOM cage simply due to the required filler rod.

831_xj said:
Reasoning why some may say tig welding would be necessary is because a whip and pause motion with mig welding is actually an improper way to weld it. Stepping out of the puddle with a whip and pause or small cursive "e", or whichever method you prefer, leaves voids. Yeah it may look better, but incorrect technique.
Click to expand...

Every welder out there has their own opinion about what technique should be used when and where. However, at the end of the day if the weld has sufficient fusion and shape, it simply does not matter. Obviously it's little more complicated than that, but when I train welders I tell them to try out a bunch of techniques to find what works for them.

If done correctly, there is nothing wrong with the typical whip. However, If your loosing the arc, or getting cold edges by whipping too far, then your simply doing it wrong.
 
1-tonxj said:
Cold welds are more common with TIG they just look good ...lol...you can do what amiunts to brazibg with TIG and have a good clean looking bead...also making shapes is nit incorrect mig turning the heat down and whipping fast out of the puddle is but not simply making the shapes...lol...infact e...c...u...and v are how you bite in with arc.
Click to expand...

I swear, most of the time I end up confuddled on what your actually trying to say. It can't just be me?

;)
 
Boostwerks.com said:
I swear, most of the time I end up confuddled on what your actually trying to say. It can't just be me?

;)
Click to expand...

" confuddled" , what are you 80 ? After reading my cryptic post did you stand their shaking your fist in protest just before donning a fresh diaper and taking your nap on the porch.

I' m always "confuddled" when someone spends big cash on 4.0 forced induction vs a v8 swap...There I used the Word in a fancy sentence.
 
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1-tonxj said:
" confuddled" , what are you 80 ? After reading my cryptic post did you stand their shaking your fist in protest just before donning a fresh diaper and taking your nap on the porch.

I' m always "confuddled" when someone spends big cash on 4.0 forced induction vs a v8 swap...There I used the Word in a fancy sentence.
Click to expand...

Oh get over here you! :kissyou:
 
Boostwerks.com said:
Oh get over here you! :kissyou:
Click to expand...

Well got in town at 0500 slept at the work truck until 1130 then made the trip home stopping at Big-r , which I should had made the 15 minute extra trip to hobofreight as I spent $180 on , welll...not much...lol...they get almost $8 bucks for a flap disc $20 for a mig nozzle , and you get the point at those prices it is like doing Grocery shopping at 7-11 vs Safeway...anyway got to the house loaded my 240lb generator into the pickup alone and various tube and plate steel a Q cylinder fir the welder and the "portable" 210 handler and hooked the Jeep on trailer and drove it to the company drop lot in Commerce city where I can work without setting a fire or violating the burn ban...seems like a ton of work just to keep a project rolling towards done .
 
Actually, 4130 needs pure argon for shielding, not C02 mix so you can MIG weld it. It's chromium content is more sensitive to air so it's a challenge to keep it covered with most crappy MIG guns. Just switch to your TIG bottle.

You should weld 4130 with E-70s in most cases. Only use 4130 filler if the structure is going to be properly stress relieved and heat treated after welding.

4130 comes in three grades. Annealed, normalized and HT/hardened. Normalized is very strong but can still be bent or formed. Annealed is close to the same strength of 1020 before it's heat treated.

Good TIG welds have circular ringlets, no undercut, no porosity, no charcoal skin and be sized according to materials thickness. 4130 can be back-purged with argon when extra weld strength is required.

allowing a molten puddle to chill completely can cause hot-short cracks. whipping arc too far or using a pulse mode can do the same thing. It's pretty hard to properly weld a cage but easy to be "good enough".
 
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Um what? I don't agree on the gas. We welded ton of chromo with a Mig and zero issues. We even did an entire battery of strength tests for a project and the Mig was always the stronger weld. Tig for most stuff is a waste of time and I love to Tig.
 
there are a couple of reasons I use DOM instead of HREW

1. most of the time when I have used HREW it was not perfectly round, making it not fit in the bender die properly. I do not have this problem with DOM.

2. lack of weld seam means I can easily sleeve the inside for when I cut the length wrong.

3. it probably annoys 1-tonxj, so that's a plus :laugh:
 
voudoux said:
I see on a lot of post concerning roll bar fabrication that DOM tubing is used,what is the reason for using DOM over plain or non DOM ? I don't understand why it is used,why is being sized on the inside an issue? Thanks
Click to expand...

DOM
Tensile Strength, psi 87,000
Yield Strength, psi 72,000

Mild
Mechanical Properties Imperial
Tensile Strength, 58000 - 79800 psi
Tensile Strength, 36300 psi


I'm willing to pay $2.00 more a foot to save my life while barreling through the desert at 80mph
 
rockclimber said:
there are a couple of reasons I use DOM instead of HREW

1. most of the time when I have used HREW it was not perfectly round, making it not fit in the bender die properly. I do not have this problem with DOM.

2. lack of weld seam means I can easily sleeve the inside for when I cut the length wrong.

3. it probably annoys 1-tonxj, so that's a plus :laugh:
Click to expand...

I got a plethora of DOM as well ...
 
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