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I was wondering if you could give me some info on DOM tubing. Weight and strength comparisons to mild steel, 4130, etc.? What is the best method to weld and what wire to use? I will be welding together 1.5x.120 round tubing for a roll cage in an off road truck. I have a Miller 210 running 75/25 argon/co2 and .030 wire. Is this ok or can you recommend something else? thanks a lot
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DOM Tubing
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DOM Tubing
Mild steel ( 1020 ), welded seam ( ERS) mechanical tubing would have a yield strength of around 40,000psi
DOM tubing ( which is usually made from 1020 and has a welded seam ) , due to the additional cold working could have a yield strength around 70,000psi. Also , this tubing would be more uniform in wall thickness than the ERS tubing, and bends well.
4130 , normalized is similar to DOM in yield strength , but a higher ultimate tensile. The real advantage is the capability of being heat treated to much higher yield and ultimate tensile strengths. ( not practical for a roll cage ).
The weight of all three of these materials is identical , assuming equal diameter and wall thickness. The higher strength of the 4130 allows a thinner wall tube to be used. I would stick with NHRA wall thickness/O.D. recommendations shown in their rulebook.
I would prefer the DOM tubing like is commonly used in NASCAR. It has good ductility in a crash. ( remember , higher tensile also means harder ) and is readily MIG welded.
Your welder/gas/and wire sound O.K. for the ERS and the DOM , but I would use the TIG for 4130. Good luck.DMBComment
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To follow (make clearer) what David said, DOM IS mild steel. The only difference is it's much more accurately made, and much more reliable. Use the same exact settings for it as you would HR tube. It is slightly heavier due to the tight wall and OD tollerances. If you use 4130, make sURE it is 4130N (normalized) and USE A TIG!!!! Mig welding 4130N is just BEGGING for hot cracks in the HAZ (heat affected zone)
MattComment
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DOM Tubing
DOM is seamless. Are you saying that DOM is seamless mild steel?Comment
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Re ; DOM tubing
Yes DOM tubing is mild steel tubing.
DOM tubing is made by rolling mild steel sheet and then welding the seam, then a a mandrel is run through the center to accurately size the tubing and smooth the weld seam, The additional mechanical working adds strength to the tubing by "cold working". Also with an accurate wall thickness it is very uniform and predictible
True seamless tubing is another matter. This is made by taking a billet of steel and piercing it with a "bullit shape" to form a tube. This is expensive tubing as you can imagine..
A couple of corrections to my earlier "E" mail. I mentioned ERS tubing , I should have said ERW which stands fro "Electric Resistance Welded ".
Also the tensile strength of the normalzed 4130 ( 4130N) is closer to 125,000psi, This allows the thinner wall thickness compared to the DOM tubing.
DaveDMBComment
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