gmaw on tube?

[jgibbens]

Can anyone point me to a resource for learning to mig weld structural tubing for automotive applications? I want to learn how to make critical welds for a rollcage and some other projects before that. I'm taking some mig classes at my local community college but they don't have much expertise on tube. I've seen a recommendation in another thread for the Ron Covell "Working with tube" dvd. Any opinions on it?

[bamacpl]

What state do you live in?

[davedarragh]

Can anyone point me to a resource for learning to mig weld structural tubing for automotive applications? I want to learn how to make critical welds for a rollcage and some other projects before that. I'm taking some mig classes at my local community college but they don't have much expertise on tube. I've seen a recommendation in another thread for the Ron Covell "Working with tube" dvd. Any opinions on it?

Excuse my "phunnie" by-lines, just trying to have some "pun.":eek:

Is this 4130? What is the wall thickness? You're going to get mixed reviews, but most everyone will suggest GTAW with E70S-2 filler metal.

Dave

[jgibbens]

I live in central IL near Hopedale. The material for most of my projects will probably be 1020 DOM in 1.75x.120 and 1.25x.120. I'm not planning on doing anything that will require CrMo. My planned projects are for my trail and rockcrawling rig. I have a mm180 set up with .030 wire and C25 gas. What I'm really looking for are some examples of good technique that will produce a weld suitable for high stress and impact loads.

[davedarragh]

May want to sollicit the judgements of FusionKing, and some of the other guys who regularly work with this low alloy, carbon steel.

Looking at the chemistry of 1020 DOM Tube it contains:

.15-.25 C
.30-.60 Mn
.040 Max P
.050 Max S
80 ksi tensile
70 ksi yield
RB 80 Rockwell Hardness

Might want to consider ER80S-Ni1 (Lincoln Super Arc LA-75) which is for applications that demand excellent low temperature impacts. (.035 wire)

ER80S-D2 (Lincoln LA-90) which is also good for applications needing strength after stress relieving. (.035 wire)

You could always SMAW the tubing with Excalibur 8018-C3 MR which is used on a wide variety of low alloy and carbon steels.


GTAW is favored in these applications with ER70S-2 by virtue of the "pre-heat" benefit of this welding process.

Hopefully, one of our many experts will contribute their recommendation(s).

Dave

[jgibbens]

thanks for the advice. I don't have a tig welder but I'd like to learn after I get more mig experience.

[Jack Olsen]

I can't speak to the utility of the Covell video, but you can rent it for ten bucks here:

http://smartflix.com/store/video/141/Working-with-Tubing

[Broccoli1]

Here ya go:

http://www.aws.org/wj/apr03/AWfeature.html

Mig it with ER70s-6

[jgibbens]

Thanks for all the filler material advice. Guess there must not be much out there for instructional videos on this stuff. I have a lot of basic questions so I'll start asking away..

My first weld that I'm trying for is a 90 degree joint with the notched tube vertical. For fitment, my instructor is suggesting that I try a small root gap to get better penetration. I have not seen anyone else doing this and most of the advice out there is go for a tight fitment. My practice scrap is 1 3/8 x .125. How would you all set this joint up for a mig weld? Specifically, how deep would you cut the notch, (I have a hole saw type notcher) and would you bevel or gap or gap the pieces?

[TS-Off-Road]

I do a lot of tube work. Mig is most commonly used for 1020 DOM cages. A gap isn't required. In fact, I have found if there is a gap, the tube will pull or distort more when welded. Make sure you grind away the thin edges of the tube after making a notch with the hole saw. After fitting the tube make 2 to 4 tacks around it to hold it. Position yourself so you can weld at least halfway around the joint continuously.

[jgibbens]

if .035 is appropriate, that would give me that advandage of working with the same wire size at home and at school. I have a mm180.

A 1020 DOM cage is my ultimate project goal. Thanks for the fitment pics. When you're joining two tubes of the same size how deep do you cut the notches? for 90 deg, I'm cutting them so that the hole saw will just barely touch the inner walls of the tube at the top and bottom as it passes through.

[TS-Off-Road]

TS- Do you think ER70S-6 wire is okay then? .035 for sure.

Dave

Yes, that is exactly what I use.

[TS-Off-Road]

if .035 is appropriate, that would give me that advandage of working with the same wire size at home and at school. I have a mm180.

A 1020 DOM cage is my ultimate project goal. Thanks for the fitment pics. When you're joining two tubes of the same size how deep do you cut the notches? for 90 deg, I'm cutting them so that the hole saw will just barely touch the inner walls of the tube at the top and bottom as it passes through.


Yup, you're doing it right!

[jgibbens]

Thanks TS,

Using the same 90 degree intersection setup, here are the problems I'm seeing with the current setup.

Starting at the top and running downhill gives me a nice *looking* bead with a complete lack of root penetration when I cut it open :eek:

Starting at the bottom and running up gives me a cold start that sags at the bottom.

Turning up my parameters to the point where the sag is gone has me on the verge of burning through. -excessive haz problems?

What working and travel angles would you use as you go around the tube? Push or pull?

Do you recommend grinding out the starts and/or stops?

Do you ever do any pre-heating?

Probably a stupid question, but would it be a good or bad idea to try sticking with .030 wire and switching to a gas mix that would allow for spray transfer with my little welder?

[nocheepgas]

Starting at the top and running downhill gives me a nice *looking* bead with a complete lack of root penetration when I cut it open :eek:


You can have a perfectly acceptable weld with no root penetration. A full penetration weld does require a root opening and bevel, but a fillet weld with no bevel or root opening can yield a weld with equal structural integrity. Just depends on your joint selection.

[jgibbens]

So if I'm looking at a weld cross section how much penetration should I be going for on a critical weld? (I am macro etching some of these) Starting with the same 90 degree joint.

[davedarragh]

TS: About your insistance in adapting an MVP to your Dynasty.

After MUCH admonition from Miller Techs, I don't trust your judgement regarding filler metal for 1020 DOM tubing.

Dave

[TS-Off-Road]

TS: About your insistance in adapting an MVP to your Dynasty.

After MUCH admonition from Miller Techs, I don't trust your judgement regarding filler metal for 1020 DOM tubing.

Dave

I don't see how one has anything to do with the other, but what ever floats your boat.

I won't lose any sleep over it.

[turbo38t]

All of the knowledgeable welders on here should know that DOM is just mild steel.....er70s6 is fine. I'd say on the millermatic 180 (just a guess) that heat would be set around 5 and wire speed around 40-50.....should give you a nice strong weld. DaveTS: About your insistance in adapting an MVP to your Dynasty.

After MUCH admonition from Miller Techs, I don't trust your judgement regarding filler metal for 1020 DOM tubing.

Dave

[jgibbens]

I just picked up some .035 wire and tips so we'll see what I can do with that.

[davedarragh]

All of the knowledgeable welders on here should know that DOM is just mild steel.....er70s6 is fine. I'd say on the millermatic 180 (just a guess) that heat would be set around 5 and wire speed around 40-50.....should give you a nice strong weld. Dave

I agree, that's why I posted the chemistry of 1020.

Compare to 4130, very similar in carbon, manganese, and tensile strength.

My concern was ER70S-6 tensile and yield strength comprimising the structural integrity of a base metal rated @ 80ksi tensile & 70ksi yield.

That's why I solicited "all of the knowledgeable weldors."

ER80S-Ni1 and ER80S-D2 were two specific solid wires I cited.

Dave

[bayweld]

I've been welding .120 wall mild steel tubing on dune buggies with .030 and .035 E70s-6 wire and co2 gas for many years with no weld failures..tight fits work the best, but if you get a gap, don't worry, just give a few more tacks in the gap area....Gussets in the high stress areas are a good idea....Tig is great but it takes a lot more time....good luck

[jgibbens]

Here's my first attempt with .035. The toes separated from the base metal in some places when I pulled it apart. My settings were 5 and 60. I'm having a hard time keeping a good travel angle.

EDIT: This is 1 3/8" x .125. I think its plain ERW.

[jgibbens]

Any thoughts on how that weld failed?

[tom37]

Somehow I missed this thread. But I was reading thru it tonight trying to maybe pick up a few tips for working with DOM and woof, the thread stopped.

I cant tell very good from the pic, but it almost looks as if the metal failed and not the weld. Like I said tho I really cant see that good in the pic. I did want to read about starting the weld running uphill across the top and back down, as to how the depth of penetration is affected by the different postilions.