Welding Chromoly Tubing

[katiebo]

A friend has asked me to work with him on a car to be used for SCCA racing. He would like to fab a cage from chormoly. As a result I have been doing some research here to learn more about what I will be needing to do.

My understanding is that chromoly tubing can be welded with either the MIG or TIG process. My friend for whatever reason is stuck on using the MIG process. My guess is that he has seen it done and believes it to be the fastest. However, I am not sure he saw it done correctly.

If using the MIG process my understanding is that the weld area should be preheated. The filler should be ER80-D2, ER70S-2 or ER70S-6.

If using the TIG process no preheat is required and the same filler metal as listed above is used. However the fit-up would be more critical than that for the MIG.

Am I on the right track?

I have been reading the "Driver Protection Structures" portion of the SCCA rules to better familiarize myself with what is required. It is also worth noting that the welding is to be done in accordance with AWS D1.1:2002 Structural Welding Code, Steel Chapter 10, Tubular Structures. If anyone has a copy of this code that they could share it would be greatly appreciated.

Thank you in advance for all the help.

[Billet Benny]

You're on the right track. Preheating is not a complete necessity with MIG, but is if you're getting welds that cool too quickly and that's obvious if they crack. If you lay proper convex mig welds with adequate heat, no cold lap, and smooth fusion, preheating may not (or shouldn't) be necessary if you're working in a room temperature or higher temp environment. As always I'd suggest a few test joints for judging settings, technique, and overall quality. However, a few hundred degrees of preheat will not hurt a thing.

BTW, does SCCA allow mig welded 4130? I know lots of racing rules prohibit that.

[Fat-Fab.com]

My understanding of AWS D1.1
To use GMAW (mig) you must first prove a wedding procedure, (PQR) This is a way of testing the weld procedure that you intend to use, that it will brake at the desired tensile. This very involved process. And requires special equipment as well as training.

I would be very careful with the fit up. Remove any burs left from the saw to the point of using a file an each cut. I would use acetone on all mating surfaces to ensure no oil contamination. I would use some small amount of pre-heat, if for no other reason than to reduce cold lap at starts and re starts. I would feather grind all re starts. I would use 75/25 mix gas and .030 or .035 wire. I would run it very hot the goal would be to make the mig weld look almost like a tig weld. Take your time do not rush this work remember your friends life may depend on your work. Also if it looks like a good weld ( looks like the pictures in the welding books) then is probably is. Do not hesitate to grind out a weld or just grind down excessive build up till you get down to a smooth transition between the parent metals and the filler.


I speak from knowledge. I am a Certified Welding Inspector (AWS -CWI). I am the chief safety inspector for the Alaska Sports Car Club, www.aksportscarclub.org . I have built many dozens of safety cages for automobiles and aircraft.
Good Luck and send progerss photos


TJCLARK@Fat-Fab.com

[90blackcrx]

http://www.lincolnelectric.com/knowledge/articles/content/chrome-moly.asp

[katiebo]

Thank you all for the replys.

Billet Benny,
The SCCA does not call out any specific process in their rules, instead they refer to the AWS code that I mentioned.

Fat-Fab.com,
It I have my way about it the fit-up will be as precise as humanly possible. I like to run as hot and fast as I can. I am not the most experienced but I plan on getting some tubing and practicing until I am comfortable with the results. Also because the work environment is likely to be cold I will most likely use preheat. One question though, you mention feather grinding the restarts, what exactly do you mean?

90blackcrx,
My initial research led me to that article already. Thanks for posting though.

[Fat-Fab.com]

Their is a post either on motorsports or welding project that shows a guy welding a fuel tank and he posted a few pics of his restart grinding.

Well let's see If I can describe it Spelling don't count here... right?


Say you can't get all the way round the tube in one trigger pull at the termination of the weld you take your grinder (I use a thin disc on a 4 " or a cutting wheel on a stick grinder) and releave a bit of the weld do you have a place to restart with out having a lot of build up and cold lap you make a ramp of sorts.


Lookup fusionking he has a post on this forum called feathering stops.
Not fusionking its Pilebuck sorry
TJ

[Bob Kraemer]

Use the ER80-D2 rod. I have spoken with several chassis builders about this & this is the rod to use. What ever you do don't go for the tiny pretty welds. Feed some rod to it.

[Billet Benny]

Thank you all for the replys.

Billet Benny,
The SCCA does not call out any specific process in their rules, instead they refer to the AWS code that I mentioned.


Sounds good then... If you can get a solid procedure down you should be good to go. Post pictures!

[Billet Benny]

Use the ER80-D2 rod. I have spoken with several chassis builders about this & this is the rod to use. What ever you do don't go for the tiny pretty welds. Feed some rod to it.

He's asking about GMAW and I think you're talking GTAW.

[Fat-Fab.com]

He's asking about GMAW and I think you're talking GTAW.

The E in the filler desination is Electrode denoting that it is the conductor.
Electrode Rod 80,000 Tensil don't know what D2 is.

TJ

[kelzweld]

If you are welding cages, I believe you should be welding to a standard where you do not have to grind your welds (feathering for stop starts excepted with the GMAW process). If you cannot weld to this standard, do you really want to sell your welds to someone who may trust their life to them? :eek: Just my 2 cents worth.

[/QUOTE]
Do not hesitate to grind out a weld or just grind down excessive build up till you get down to a smooth transition between the parent metals and the filler.


I speak from knowledge. I am a Certified Welding Inspector (AWS -CWI). I am the chief safety inspector for the Alaska Sports Car Club, www.aksportscarclub.org . I have built many dozens of safety cages for automobiles and aircraft.
Good Luck and send progerss photos


TJCLARK@Fat-Fab.com[/QUOTE]

[Bob Kraemer]

From what I understand & was told the ER80D2 spec. is for a triple deoxified rod.
I may be wrong because I am not even in the same ball park as 99.9% of the guys & gals here. I don't have any schooling in welding was shown the basics years ago & taught my self from there.

[Billet Benny]

The E in the filler desination is Electrode denoting that it is the conductor.
Electrode Rod 80,000 Tensil don't know what D2 is.

TJ

I know what E stands for.. I was speaking of his talk of avoiding pretty welds and feeding rod which leads me to believe he's not talking about mig. Has nothing to do with the filler he mentioned.

er80s-d2 is a low alloyed filler with additions of molybdenum that makes it different than typical -6 or -2. Many recommend it for 4130 to 4130 welds that will be used as welded. It will respond mildly to heat treating. I have used it a ton, myself, but still think -2 is often a better choice, but I don't feel like getting into it now, I've beaten this issue to death. Its tensile strength is in the 90,000 psi range.

[katiebo]

edit... but still think -2 is often a better choice, but I don't feel like getting into it now, I've beaten this issue to death. Its tensile strength is in the 90,000 psi range.

I have read many of your posts Benny, and will be using ER70S-2 for the tig work.

Just as a note, I was talking with my friend last night and it looks like we will probably go the TIG route is we end up using 4130. The SCCA rules permit the use of either DOM of alloy tubing. I will practice with both before embarking on any actual cages.

[Fat-Fab.com]

Sorry Billet Benny I did not intend to step on your toes. I hope my 13E's didnt leave any marks. :o


Kelzweld: Nothing in the code about not grinding. On the other hand I do take what you are saying if one is spending an inordinate amount of time grinding (on the cap) then maybe one should get some more practice.

When I first started inspecting the safety cages for the ASCC I was stunned at the bubble gum and bird droppings I found. A well designed cage for a street car will depend as much on the design as the welding for its strength. The weld just holds the main two hoops in place. Now I am not saying that I let them continue racing with out addressing the deficient welds. Triangulation is the one true key to a safe cage. The more triangles one can make the better. One of the biggest safety concerns is having the driver’s seat attached to the car chassis and the harness belts attached to the cage. In this scenario the driver and the car can move one direction and the cage and the belts move another. That’s sounds painful.

TJ

[dyn88]

sorry to jump in late but in reading a previous post from fat fab, "remove any burrs left from the saw". I think coping each and every joint to precise fitment, is a must for chromoly. A saw will not give you the fit you need for 4130, unless you have many hours of experience with said saw(this only counts if we are talking about a hole saw in a joint coping jig). In my opinion you should not fit 4130dom tubing with out a bridgeport or similar milling machine(lathes work well with the right clamp on the tool rest, as do those saning belts with interchangable rollers, for specific tube diameter). Precise fitment of 4130 is as, if not more, important than weding procedure, as the stresses in your joint need to be distributed through the tubing, not the weld. Dont get me wrong the weld is extremely important, but the fitment of the joint is more so. A tight joint will also reduce the amount of dwell time as welding there fore reducing heat input, and creating a strong non brittle joint. 4130 will become very brittle when overheated and crack easily with stress. Using a precise joint you could use er80 or er70 just to secure the joint. With mig I would use .023 er70 s-6, .023 because its so much easier to control the puddle, and reduces heat input greatly from .035, and a darn good amount from .030. er70 s-6 because its readily available has a good tensile streangth, the s-6 has a great deoxidizing additive that does not reduce the strength of the puddle. And as always with criticle work, clean clean clean, I use a stainless wire brush on a grinder motor then clean with acetone, before welding. And as far as starts and stops, wire brush and acetonebefore each start.

As this may seem like a lot of work, it is. Find a reputable chassis builder with a few notable vehicles under his belt and ask him for a price to build a chassis, youll find its a lot more than you think. Ive heard of guys charging upwards of $80,000 for just a chassis, no motor no trans no body no nothing just a chassis with no wheels. Its time consuming meticulus work, and very few of us(including myself) are able to achieve the level of craftsman ship these professionals have the patience to .do.

[fuelcarbuilder]

As this may seem like a lot of work, it is. Find a reputable chassis builder with a few notable vehicles under his belt and ask him for a price to build a chassis, youll find its a lot more than you think. Ive heard of guys charging upwards of $80,000 for just a chassis, no motor no trans no body no nothing just a chassis with no wheels. Its time consuming meticulus work, and very few of us(including myself) are able to achieve the level of craftsman ship these professionals have the patience to .do.
Well said...you get what you pay for. bOb

[kiwi]

Hello Katiebo,
I am very much a novice in this field, but I have a few pieces of information that may help you. There is an excellent publication "Performance Welding" by Richard Finch. He is a very experienced weldor who has done everything from aircraft to race cars. He has even welded on the Apollo rockets for NASA. This book covers every conceivable aspect of performance welding. In fact he strongly cautions preheating 4130 with a torch as it is detrimental to the weld. He goes on to say "This is incorrect, and doing so is one more way to "hurt" your 4130 steel structure. First of all, the experts say that preheating is not necessary for 4130 under 1/4 of an inch thickness. Then, the next reason to not torch-heat 4130 steel is that you really don't know what temperature it is heated to if you are just passing a flame over it...". If you read the Lincoln web site that was posted I do believe that they recommended it. Anyway if you are doing research this book is quite comprehensive. A great deal of the book is dedicated to 4130.

Capter 3 Fitting and Cleaning

Chapter 4 Jigging

Chapter 5 TIG Welding 4130 Steel Tubing

I hope this helps you.

Thanks,

Nick

[kiwi]

[QUOTE=dyn88;78828] joint will also reduce the amount of dwell time as I use a stainless wire brush on a grinder motor

Hey Dyn88,
In the book I referred to in my previous post the author Richard Finch says "do not attempt to remove mill scale or oxidation with a power wire brush because the brush will embed metal from its bristles into the metal to be welded, and this wire will contaminate your welds. Also, if the power wire brush is quite stiff, it will actually erode the parts to be welded and cause them to be weakened in the weld zone where you cleaned them." So is the use of a power wire brush an accepted practice on 4130 tubing?
Thanks,
Nick

[Billet Benny]

[QUOTE=dyn88;78828] joint will also reduce the amount of dwell time as I use a stainless wire brush on a grinder motor

Hey Dyn88,
In the book I referred to in my previous post the author Richard Finch says "do not attempt to remove mill scale or oxidation with a power wire brush because the brush will embed metal from its bristles into the metal to be welded, and this wire will contaminate your welds. Also, if the power wire brush is quite stiff, it will actually erode the parts to be welded and cause them to be weakened in the weld zone where you cleaned them." So is the use of a power wire brush an accepted practice on 4130 tubing?
Thanks,
Nick

I use sandpaper and sometimes powered scotchbrite.. Always acetone.. Never a powered wire brush.. This is for 4130 tube work. I do also say powered wire brush is a bad weld prep tool.

[Billet Benny]

sorry to jump in late but in reading a previous post from fat fab, "remove any burrs left from the saw"........


A hole saw is not such a bad tool.... It is absolutely no different fitment wise from what you will do on a mill with a large bit.. I'm looking to convert a horizontal mill into a dedicated notcher, but I still notch all my tube with a holesaw notcher. However, that is not the end of the process.. I guess I more or less rough to size and then flap disk to the proper shape and fit to remove all thin spots and cut marks.. If it fits then it's ready for weld prep and then good to go..

You speak a lot of reducing haz, but this is not the main thing to be conscious of when welding 4130 tubular structures. Tig is such a great process cause it's heat input per weld size is greater than that of gmaw.. If I were to MIG the stuff I would stay far away from .023 unless I'm doing really thin tube, but then it's really time to pull out the tig. With mig the heat input is borderline low and allows the weld to cool too fast thus leading to the hard, stress sensitive condition.. Rarely trouble occurs from "over-heating". I do say to minimize the haz, but this is not to say smaller is better.. It is to say excessive haz can be both detrimental and unnecessary but a certain sized haz is expected and proper.

[katiebo]

Thanks again for all the advice. I plan on getting some material and practicing alot. I think I will end up using TIG though. The ability to control heat input is just too compelling. I will post photos when I have some. Be patient though, it going to be a while before I have material and all the other things I need.

[dyn88]

the wirebrush seems to leave no residual cantamination, as far as eroding, its entirely possible if one were to have at it like a caveman,you may remove a substantial enough amount of material to affect the joint. A little finess and itll be fine. I agree that scotch brite is a better media, but you ever weld through a joint loaded with that fuzzy leftover(it often times get stuck between two materials on me), its tough to do, at least for me.
Thhe hole saw, I said was fine, is a great tool and I wasnt trying to take anything away from it. They work great, Ive never gotten the results I wanted out of one though. Perhaps I should spend a few more hours practicing with one. I preferr a milling machine, mainly because of the abbility to make small adjustments and remove just a little out of an existing joint. to get the perfect fit up with zero gaps all the way around the joint.

[Buzz Job]

My process of tube building goes something like this. And feel free to debate the process for the better. Note this is a aircraft frame.
Once designed and drafted, I set up a flat table with several references
relative to the plans to align the tubes in correct alignment relative to a
center point.

http://onedesign1.smugmug.com/photos/120392287-M.jpg

The whole frame is built prior to welding and will usually stay together in
proper alignment with only wooden jigging and masking tape

http://onedesign1.smugmug.com/photos/120392530-M.jpg

Once all notched and joined in proper alignment, (note I will spend nearly 1
hr per tube in more complex situations if not more) as no notcher or end
mill will do what good old experience will do in more complex joints as
there are too many variables going on to get optimum fit.
Once all fit up and I am happy with the dimensions and gaps then I note
where all the tubes go with a sharpie or masking tape.
Then disassemble all tubes and de scale, de burr and de grease inside and
out

http://onedesign1.smugmug.com/photos/120392545-M.jpg

To descale I prefer rough scotch bright and a lathe if the piece will chuck
up safely. And second choice is 220 grit emery cloths

To de burr and radius I use carbide burrs and my second choice is a sander
then a grinder.
You need to deburr and radius the inside as well so a burr is necessary
here.

To clean I use break cleaner and paper towels as I get it for free and I like how it works.
Clean the inside of the tube as well using a wetted paper towels with break
clean usinglike a wad and force it through like cleaning a gun barrel.

Now to re assemble all the tubes back into the jig table and what some
people may not know is that most tubes will not get welded all the way
around they will get welded only on the outside once loaded in to there
respective positions.

Once all in position I tack the tightest apex of all the clusters It’s the
hardest point to get to but in my experience it reduces total frame
distortion by reducing shrinkage by locking in the area of greatest
shrinkage.
http://onedesign1.smugmug.com/photos/68313967-M.jpg
Now I re check dimensions and tack to the outsides of the clusters to lock in the tubes in all axis usually 3 tacks per tube.
Once happy with the dimensions its time for the EASY part WELDING. I start from the tight apex and work from there one side then the other.
With work like this .035 tubing I make small welds as it reduces overall shrinkage and gives me a very accurate part.
http://onedesign1.smugmug.com/photos/97668064-M.jpg
And after a few months I am near finished with this custom aircraft frame. http://onedesign1.smugmug.com/photos/120410869-M.jpg
Proper fit is necessary to get the accuracy I strive for as any gapage will cause extra shrinkage
http://onedesign1.smugmug.com/photos/65929220-M.jpg

[dyn88]

now look at that fit. (whistle here) Very nice wok

[lramberson]

Buzz Job, Very impressive, I could really enjoy seeing that in person. Extremely accurate , I like your style:D :D

[FM117]

Looks solid enough for acro......what is it?
Dave P.

[Buzz Job]

Looks solid enough for acro......what is it?
Dave P.

Yes this is a acro capable design and should easily take 10Gs at 1200 # with 1.5 safety factor. It is my personal design and I haven’t figured on a name yet.

It is a designed from my last aircraft I built ((One design)pictured below)) but incorporates things I thought would help comfort and control.
http://onedesign1.smugmug.com/photos/42357821-M.jpg

Here is a web site I half started that has more info if you’re interested.
http://onedesign1.smugmug.com/

[katiebo]

Thank you all for your input, it is greatly appreciated. When things start moving along I will post photos.

[welder1]

A friend has asked me to work with him on a car to be used for SCCA racing. He would like to fab a cage from chormoly. As a result I have been doing some research here to learn more about what I will be needing to do.

My understanding is that chromoly tubing can be welded with either the MIG or TIG process. My friend for whatever reason is stuck on using the MIG process. My guess is that he has seen it done and believes it to be the fastest. However, I am not sure he saw it done correctly.

If using the MIG process my understanding is that the weld area should be preheated. The filler should be ER80-D2, ER70S-2 or ER70S-6.

If using the TIG process no preheat is required and the same filler metal as listed above is used. However the fit-up would be more critical than that for the MIG.

Am I on the right track?

I have been reading the "Driver Protection Structures" portion of the SCCA rules to better familiarize myself with what is required. It is also worth noting that the welding is to be done in accordance with AWS D1.1:2002 Structural Welding Code, Steel Chapter 10, Tubular Structures. If anyone has a copy of this code that they could share it would be greatly appreciated.

Thank you in advance for all the help.

you do not want to use pre heat or mig you also do not want to run it hot trust me i have welded and built many car i also seen top fuel cars being built and they do not run it hot chrome moly is very brittle when over heated you dont need to grind the starts either ive worked on car running 6 sec and never had a failure just my two cents that what i do.