I guess Nextel cup guys and Craftsmen truck series cars don't employ good tig welders. Every one is MIG welded. Mig welding is more popular than TIG. Strength can be had for both.

 

A do not agree. A lot of TIG welding can be done with very very little if any filler rod. When "high strength " & "suspension parts" are mentioned I assume 4130 CM or something. I don't know anything about NASCAR type racing. I can't find an NHRA rulebook handy but it seems like for PRO classes to be certified welding was to be done by the"TIG PROCESS" . Been a while since i've looked at a r. book. Perhaps someone has one handy? For mild steel or lower strength requirements MIG welding is adequate. MIG has the added plus of being very easy to learn. My 2 cents only,not trying to DIS anybody.

 

you don't have to agree, that just means your wrong


there are some instances in areas that don't recquire a high strength joint where filler isn't needed......but for a welded joint(say a butt joint, for argument's sake) to pass inspection, one of the criteria is that the welded area be the same thickness(within certain limits) as the thickness of the metal that it is joining together...that will not happen without filler metal.....

 

he is right about pro classes having to be done in the TIG process... they are looking for the most safe way to protect these drivers in drag racing... if mig was stronger why wouldnt they use it?

im not saying one is stronger than the other but if mig is stronger why dont they use it?

something to think about

 

most nascar chassis are mild steel migged, i think only 2 teams are using chromoly and tigging them. i think a thing that plays a big role is anyone can pick up a mig gun and weld, but will they be good strong welds, with tigging you kind of have to know how to get anywhere with it.

 

I would think nascar of everything would be running chromoly for its benefits and in large numbers. Whats their reasoning behind that?





-john

 

i really cant answer that, youd have to talk to a nascar chasssis builder. i belive i read the teams using TIG are Penske and Yates. i also read that in the chassis deflection tests done prove tig is slightly stronger, but it was at such an extreme that the cars could never meet that on the real track, therefore in track situations they are equal. TIG is preferred over MIG has to do with control of the temperature. With MIG there is no precise temperature control and it starts out hot, whereas TIG is even. Chromoly has a tendency to crack with vast temperature changes.
i found these nascar chasis mig welds, if they help anymore to show how good they look.

id also like to say that im assuming most people who mig weld dont even know the 3 different types of mig transfer.

 

what are they?

 

Short circuit, Globular and Spray arc. i dont feel like typing out all on what they consit of but im sure you can find them in any book on gmaw (mig).

 

Holy Crap! What are you guys having a pissing contest on who could be the most wrong??? WTF???

I believe that this might be the only entirely correct statement in the whole thread… at least as far as it applies to a small automotive shop.

Although 100% incorrect, it’s probably the only good reason to do what you’re asking to do with a TIG… because there is that perception by “those who know” that a TIG bead is stronger, and they know that TIGed parts are more expensive (because it takes 3-5x as long to run the same bead, if we’re talking short beads, much more if it is a long bead), so they are perceived to be stronger. The reason that I say that it’s the only good reason is that the fact is that no amount of convincing or flat out facts will sell parts faster then just TIGing them if any of your competition does. It doesn't make a difference if you're right, wrong, better, worse... the customer's opinion/perception has a bigger impact on if your parts are good then if they really are or not.

Ok, sorry, maybe a second OK post. But why do you say that a TIG welder is more suited for welding together a roll cage? If anything I prefer MIG over TIG there, especially in tight and upside down spots. What about TIG do you like better for the application?

Ok, in general…

¿Que? like someone has already said, filler metal is one place all welds, no matter the process get their strength from, but not the only one, the weld design also matters. Although generally my reaction in these arguments could be taken to agree with what you say here (it’s easier to weld with a MIG, but it’s harder to weld it right), the fact is that if you get ehough heat into the weld to run a proper bead that is sitting correctly… there is no way in hell that you won’t have penetration. The wire feed = welding current which roughly = penetration. If you don’t get penetration you do not get enough heat to melt the base metal sufficiently to get a proper weld and the weld just sits on top, and it’s blindingly obvious when that happens.

that being said, the only reason a good looking mig weld would be bad is if the operator doesn't know what he is doing......if you have the machine set up right, you can definetly be "guaranteed" the penetration you need to make the weld.....and then the strength comes from the filler metal, which in mose cases will be stronger than the base material

The other side of all this is that with a TIG you control what the heat input/current input is with the foot pedal and you can very easily make a superficial weld that is visually indistinguishable from a proper, good weld, at least without cutting the weld open and actually looking at it. It’s a simple process… take a TIG torch, strike an arc and feed some rod and melt it onto the cold surface of the base metal (it will sit there like a little ball of metal like a glob of solder or something), then give it some more pedal and wave the torch to either side of that blob, as you get the surface of the base metal hot enough to melt the blob will “wet out” and form a perfect little “dime” with absolutely zero, zilch, nada penetration.

Why?

Assuming that you’re using normalized 4130 vs say 1018 or 1020 (if you’re using a mild steel actually designed for tubular construction like 1026, then this conversation becomes almost laughable, so we’ll leave the better quality mild steel out of this), and lets say you’re using some ER70S2 or S6 filler (not that it would be a first choice, with either material I’d prefer some ER80S2, it will give a stronger joint and you’ll need less filler to get the same strength)…

It doesn’t matter which steel you’ll use they all have the same Young’s Modulus, in other words, they all have the same stiffness. If you look around the ‘net you’ll find that normalized 4130 has a yield strength of 90Ksi where the mild steel comes in at around 70Ksi… well, go look it up in an engineering text, you’ll find that people are quoting the extreme high end for the 4130, and quoting close to the bottom end for the mild steel (yes, there is a range, they’re all just alloys and the “same stuff” can range from junk to pretty good). More typical of decent, off the shelf DOM is about 72Ksi for 1020 and 74Ksi for the 4130. At this point ignoring the welds you have 2 materials that have the same stiffness and probably about a 2-3% difference in strength. Yea, I guess if you didn’t weld it you could justify going 2-3% thinner with the chrome molly piece then you could with the steel piece, assuming that the part doesn’t have to be as stiff.

BTW, in case you don’t know stiffness is really important in suspension pieces, but I guess that doesn’t really matter, keep comparing .095” 4130 to .118” 1020. At least you used chrome molly and you TIG welded it, so it’s the perfect part… yea right…

Anyway, now lets add a weld to the deal. You just used a ER70Swhatever filler metal… huh, guess what, you know what that ‘70’ in the name is? It’s a 70Ksi strength mild steel filler. So now your ACTUAL weld is no stronger either.

Huh.

There’s a funny thing about chrome molly, it self quenches. That means that when you run a weld bead on it the area around the bead actually gets quenched by the surrounding metal and hardens. Now you have spots between the main length of tube and the weld that are very hard and BRITTLE. Funny thing about brittle things, they shatter.

Now how about an interesting thing related to that about mild steel… it doesn’t harden, so when you weld it you end up with… well exactly what you started with, same strength, same hardness.

“But, but, but, I TIG welded it!” yea, so? TIG welding is a slower process, you apply less heat for alonger period of time, which makes for a larger heat effected zone (at least if you get the same penetration) then MIG, so guess what, you actually made that brittle area next to the weld BIGGER.

I’ll stop and post here while I ponder my comments about the rest of this thread

 

BULLSHIT! “Guys that have been certifying welds” wouldn’t dare give a real answer on if something is a good weld or bad weld if they are not allowed to destructively test it, at least cut through the middle of it and acid etch it or x-ray it. No one in their right mind would just look at a TIG weld and say “yep, that’s a strong one” because like I already described, the process lends itself to making pretty beads no matter what the conditions underneath are.

Have you ever seen a nascar chassis??? The reason to MIG is that it’s a MUCH faster, more efficient process then TIG. The reason to TIG is that it’s a more precise process that will do more delicate work then MIG, it also will allow you to work with a wider range of metals with fewer specialized pieces.

Um, yea… less heat stress… yea… which puts more heat into the weld, applying a 25,000* F arc for 1 minute or a 20,000 * arc for 5 minutes, yes, TIG has a slightly cooler arc and takes about 5x as long to run a longer bead. Hell, if you don’t believe it setup 2 identical test coupons for each, weld both and make sure you have the same penetration and then measure the HAZ (heat affected zone). Funny thing, TIG puts a lot more “heat stress” into a material, the reason that TIG might still get used someplace where temper or heat treat is important is if you don’t need the strength of a full weld in that location, you can put a much smaller weld down on the same base metal then you can with a MIG.

And
Cup, and other roundy roundy racers use MIG welded mild steel chassis (with the exception of Penski which is the only one that actually does a lot of TIG but still mild steel) because it’s NOT LEAGAL for them to use 4130 in their roll bars, they HAVE to use mild steel.

Do you remember what I said about welding 4130 and making brittle spots? Well do you know what happens when something is brittle and gets hit? It shatters, and usually shatters with sharp points. When you hit a wall at 180mph the last thing you need is for your chassis to shatter around you and come at you with sharp spears.

There are actually a bunch of very well known metal fabricators and engineers that will not allow 4130 to be used anywhere around a driver. Formier (Metal Fabricator’s Handbook) and Carrol Smith (the “_____ To Win” series of books discussing all aspects of engineering and preparation of race cars) have longer discussions about this in their books.

So what? Friction welding or any welding that applies heat to the weld area independent of filler can be done without filler. Not sure what your point is. If it’s structural/requires actual strength you’d never do it unless the joint was properly designed, which means that there was extra metal there to start with that gets used up as a filler for the weld (woops, I guess technically at that point you did use filler, huh?. In the case of a TIG weld you’d need overlapping parts for a strong, structural weld without filler, and that is not the case in any chassis designs that I’ve ever seen and you just plain wouldn’t do it so I don’t know why you even wasted our time implying it once and saying it flat out a second time.

Sure, maybe... BUT ONLY if it was welded with 4130 filler AND after welding was heat treated/hardened. NONE of the aftermarket suspension parts that we buy for our little street cars are heat treated, and I don’t even know someone who is capable of properly heating a complete chassis at >1200* for days and then controlling cooling for longer making this a moot argument for this discussion. Sure, indy and formula cars use TIG welded, 4130 and 4140 suspension bits and pieces… they’re also heat treated.

It is required for 4130 chassis required at <7.50 or under some cases <8.50, BUT:

yep, it is something to think about, and you’re right to be confused. The thing is that if you sat down with a good engineer (well, I guess he’d have to be practical also, since there are things that make sense in a strict, “book” environment which just don’t work the way things actually get done in the real world) and read through the NHRA rule book you’d find that he would be confused also, since there are a number of rules that make no sense whatsoever as far as safety and engineering are concerned. _I suspect_ that the current rules and some of their bits and pieces that don’t make sense partially evolved to where they are now for other reasons and partially got that way from misconceptions.

 

you'll fit right in then ;

No **** sherlock

i never said they didn't physically test the welds, did i? what i said was that they never had a tig welded piece fail after it passed visual......meaning that it ALWAYS passed the destructive testing after it passed the visual.....

and that last statement is ignorant; more than any other process the "condition underneath" is CRITICAL to making "pretty beads" while tig welding

try reading a little deeper next time

that's my whole point.....way to catch on quick

you'll get a perfect dime, but it's pretty obvious to anyone doing a visual insepection that there is no penetration, therefore it wouldn't pass...the bead would be too high, unless your talking about a "build-up" weld(like on a die edge), in which case the only way to inspect would be to cut it or x-ray or sound scan it...

 

Man o Man!! This was my lucky day!! To have reached know it all status in only 28 yrs!! I bet your co-workers love the advice I'm sure you provide. I sure wish you had been there to guide me 43 years ago when I learned to weld.

 

This thread was started about .095 wall CM tubing & 3/16 CM plate. My comments were based on the thread starters question. BTW... Mild steel has a shock absorbing "crush" which could be a consideration. NASCAR has a very high min. car weight (compared to Pro Drag Racing or definately Sprint cars which don't have any min. weight). I MIG some low strength things like alum. gas tanks because it's fast with a spool gun. Never on high strength areas like suspension parts.

 

anytime dude, just pm me with anymore questions



i love folks who are willing to be educated, and saying a thing like "the only reason to use a mig is if you can't learn to tig" shows you have a lot to learn.


i'm sure you're twice the welder i'll ever be, but there is so much misinformation out there about what you can and can't do with certain processes and what they are good for, that when you say something presumptious and wrong like "mig welding is never good for high strength", then i'm gonna call you out...

 

OK - The" never" comment is a little over the top. I did think we were responding about CM ,where I would not attempt a MIG weld. Part 0f the MIG concern is that some people slap some metal together ,slop on a mig weld & call that a strong weld. Part of the TIG process is that you must prepare the metal or it won't work at all. I doubt I am a better welder than you (or anyone) else. Most of us have a "pet process" .Heck,I still gas weld alum. sometimes just for fun. No DIS to all those that prefer MIG welders. Scott

 

right on dude.....

there are a lot of guys that come on here trying to learn about the processes, and too many times are given generalized answers that don't always hold true.....personally, i tig weld a lot of things i should pry mig

i think some folks have had success welding cm "trigger" mig welding....there was a welding web site forum that had a guy send his welds out to get tested using this method and they turned out plenty strong...

on a side note, i've been wanting to try gas welding aluminum......they only let us use mapp gas in the plant which is next to impossible to use on mild steel, but maybe it would work with aluminum? i don't know, but i should get an oxy/acetyline set up for home anyways....

 

If you weld chrome moly you have to heat treat it. Theres a procedure for it and im not going to go into it as its somthing you should learn before any body gets hurt. As far as mig chassis guys use it more for speed and repair. Tigging is better because its a 100% weld and it brings the heat on slow and cools down slower for normalization. The bummer about tigging is the time and patience it takes to weld a chassis or any thing. All joints have to be perfect for fittment and weld were mig it has to be close. The other bummer about tig is you have to jig everything and allow cool downs or you pull all over. Metal prep is were most welds win and lose and always ad filler rod and never cold weld a joint.

 

I ran on to a trick lens that made gas welding aluminum way easier but I can't remember where. The puddle was somewhat more defined . He used to sell metalworking specialty supplies. It might have been Kurt white? If anybody remembers, please post. I was real intimidated about TIG way back. I grew up on a farm & all we had was oxy. Anybody that can gas weld can learn to TIG I believe. BTW... those who decide to take up TIG,don't tell your buddies or they will drag all kinds of crap to your house so you can "do a little welding,won't take you a minute"! Scott

 

Are you saying anyone who TIG welds a chassis should heat treat it after it's welded?