TurboEM1

iTrader: (1)

Hey guys I have a question. Can you mig weld 4130 Chromoly tubing? I have heard mixed things about it not being able to be done to you can do it but its not strong.

Anyway can you mig chromoly?
Is it the wrong way to go about it?
Why would it be weaker?
What filler rods can you use/not use?

Thanks for all the help.

Janos Lin

Apparently you can, but the MIG welders dont make enough heat to actually penerate the material so the weld is not as strong so you might as well save your money and use mild steel instead or use a TIG setup. If someone says that they welded 4130 with a mig and no probs, then its because they havent stressed it enough to fail. At that failure point, TIG welded 4130 would have held up.

TIG++ its fun, I should post a pic of the stuff I made in class with it.

Janos

awill4x4

We weld Chrome/Moly every day here in Australia repairing and manufacturing Sprintcar chassis'. We Tig weld all our Chrome/Moly simply because it's what the customer wants and we get great "job satisfaction" from doing so.
That being said, yes you can Mig weld Chrome/Moly without any problems at all. Just use an ER70 S6 wire and it'll be fine so long as you have the necessary welding skills to do the job. A number of large circuit racing teams are switching back to Mig simply to try to cut down time in cage fabrication. They are however using high end pulse Mig machines.
Regards Andrew.

Janos Lin

Have you done destructive testing on those mig welded 4130 pieces? Is it a certifiable process?

Janos

still_slow

we have tigged at work but I have never seen it migged.

awill4x4

All motor racing cage assemblies in the "Supercar" class made out of Cr/mo here in Australia have to be engineered and undergo either destructive testing or some very sophisticated finite stress analysis before they reach approval. There are only a small number of engineering firms here in Oz with the necessary expertise in that field and they charge lots but it's still cheaper than destructive testing.
The "Supercar" cages (main hoops) have a maximum wall thickness of .065" and most of the other tubes are only .049". They are small thickness large diameter and lots of it.
The current trend is to use a specialist German tubing for straight sections which is nearly twice the tensile strength of Cr/Mo but it costs upward of $200 Aus per metre
Regards Andrew.

blueoval557

In motorsports its never MIG welded. Can it be? Absolutely. Many pipe lines, and oil rigging lines are mode of 4130, and MIG welded all day long. Motorsports have their own rules....understandably in some ways, but usually just to keep the indisutries happy(TIG is more money...less people can do it...companies who support the sport, are now making more money).
Kyle

vsmhatched

i've never seen it done with MIG...I was always taught to use Tig...so thats what I do

terr1bleone

you can do it just as well as tig on penetration. the reason its not used in roll cages is because the cold starts hot ends of your bead with mig. chromoly is very sensitive to heat changes.

arcboy

Isn't it a rule in NASCAR and NHRA that chassis have to use GTAW?

phatboycrxhf

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blueoval557 &raquo;</TD></TR><TR><TD CLASS="quote">In motorsports its never MIG welded. Can it be? Absolutely. Many pipe lines, and oil rigging lines are mode of 4130, and MIG welded all day long. Motorsports have their own rules....understandably in some ways, but usually just to keep the indisutries happy(TIG is more money...less people can do it...companies who support the sport, are now making more money).
Kyle</TD></TR></TABLE>

what ???? im sorry but will you prove this too me ive been working in the oil feild for 3 years and never have i seen a mig out on the line or even close to to the pipe ...I have seen a mig used in shops though ,but never on actual pipe ,more like sour tanks and stuff of that nature there must be diffrent guide lines or something up here in canada lol

9bells

They use mig on pipelines up here.
They have a folding-floor hut-thing that drops over
to protect the sheilding gas. They aren't everywhere, but some of
the smarter comapanies are using it. Much faster.

arcboy

FCAW Flux Cored Arc Welding is used on pipelines. Which is a form of GMAW (mig process)

turboteener

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Janos Lin &raquo;</TD></TR><TR><TD CLASS="quote">Apparently you can, but the MIG welders dont make enough heat to actually penerate the material so the weld is not as strong so you might as well save your money and use mild steel instead or use a TIG setup. If someone says that they welded 4130 with a mig and no probs, then its because they havent stressed it enough to fail. At that failure point, TIG welded 4130 would have held up.

TIG++ its fun, I should post a pic of the stuff I made in class with it.

Janos</TD></TR></TABLE>

Where did you hear that MIG welders can't make enough heat actually penetrate the material? That is the most asinine statement I have ever heard. I can make enough heat to burn slap through most chromoly items put in front of me. You can MIG weld chromoly just fine.

I have MIG'd all kinds of chromoly. I am very careful about cooling it though. Typically I bury it in sand so that it cools very slowly. I would not MIG a roll cage from 4130 though because of the way a MIG heats the object. The welds can come out brittle. But for most items you can weld it just fine. I have tested it on tubing before with destructive testing and the failure typically occurs far away from the welds. It takes quiet a bit of force to make it fail.

Janos Lin

Entirely depends on what kind of mig welder you're talking about. A lot of the smaller welders wont cut it at all. Clearly if you go big enough, you can eventually. However not everyone necessarily has access to such equipment, and I don't want to give people the impression that they can just whip out their $50 harbor freight special and weld up roll cages.

Janos

turboteener

OH, yeah totally agree, you better not even think about welding a cage with anything less than a 220V gas machine and plenty of time. Remember someones life is in your hands when you do something like this.

dfoxengr

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by arcboy &raquo;</TD></TR><TR><TD CLASS="quote">Isn't it a rule in NASCAR and NHRA that chassis have to use GTAW?</TD></TR></TABLE>

nope, nascar frames are migged, even COT frames. but theyre mild i believe.
and ive seen them bare so i know this for fact.

dfoxengr

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by terr1bleone &raquo;</TD></TR><TR><TD CLASS="quote">you can do it just as well as tig on penetration. the reason its not used in roll cages is because the cold starts hot ends of your bead with mig. chromoly is very sensitive to heat changes. </TD></TR></TABLE>

well thats what stress relieve and heat treatments are for.

terr1bleone

i was more talking about why nhra dosent allow chromoly to be migged.

Jared

You should check with your sactioning body always. This is from the NHRA rule book:
All 4130 chrome moly tube welding must be done by
approved TIG heliarc process; mild steel welding must be done by
approved MIG wire feed or approved TIG heliarc process.Welding
must be free of slag and porosity. Any grinding of welds prohibited.

turboteener

Many sanctioning bodies are going away from the use of chromoly because of the difficulty in post weld normalization techniques. NASCAR uses all mild steel. SCCA did away with the Chromoly regulations, so now there is no benefit to using it in a racing chassis. Not sure why NHRA still allows it, but they do some wierd stuff.

phatboycrxhf

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 9bells &raquo;</TD></TR><TR><TD CLASS="quote">They use mig on pipelines up here.
They have a folding-floor hut-thing that drops over
to protect the sheilding gas. They aren't everywhere, but some of
the smarter comapanies are using it. Much faster.</TD></TR></TABLE>

i guess they do ,ive worked all over alberta and havent seen this lol ,ive been sub contracted out to other companys and they all use stick , Sure it takes a lot of time to do the hot passes and cap but wouldent you think ,droping a hut thing your talking about on every joint take just as long ??? doesnt make sense to me ,I guess id have to see it or are you just talking about facility work ???

9bells

http://www.lincolnelectric.com...s.asp

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by arcboy &raquo;</TD></TR><TR><TD CLASS="quote">FCAW Flux Cored Arc Welding is used on pipelines. Which is a form of GMAW (mig process)</TD></TR></TABLE>

They also use Mig roots. Long time now.
The new STT method just seals the deal.
We use it at work on small vessels and some spooling.

The whole reason NHRA etc. ask for TIG on 4130 is so that some farmer doesn't weld it up with MIG. TIG machines were and still are to some extent more expensive, so not everybody and their brother could just buy one for a cage project. It is alot easier to tell if a welder has a grip on things from a visual inspection with TIG than MIG. I have seen some scary stuff done with MIG, but the truth is if you do it right, MIG is great.