I am going to be welding a buggy together soon using 1.5"x.188 wall 4130 . I have been doing a little reading and research on what the net has to say about chromoly welding. I have found quite a bit of assorted advise/info. Most information is from people who construct small airplanes.

My main reason for this post is to gather some information about Mig welding chromoly, but I don't want that to be all that this thread covers. There seems to be quite a bit of confusion/misunderstanding when it comes to chromoly, and it's properties that affect the way it is welded. I would like for this thread to turn into a well rounded, very informative thread that has some info for anyone who will be using chromoly in one way or another.

First of all Mig welding chromoly; Don't say that it is impossible to get good results or that is altogether wrong, because that is WRONG! There are many space frame manufacturers that use the Mig welding process to weld their chromoly structures together (All though all of these places likely have large ovens where they can heat treat the entire frame assembly, or subsections all at one time). It must be possible for someone with a well setup shop, and allot of time, to get good results.

Welding experts, Metallurgists, and those that have experience with chromoly, what have you to share? I know that there are plenty of you here. Let's take this in-depth with specific procedures, pre/post-heat temperatures, recommended filler material etc... for ANY kind of welding that you would do on chromoly. And if you have any advise to give about Mig welding that would be very helpful, at least to me.

As far as what I have.. I currently do not have good access to Tig welder. I could not count on the access that I have to be able to weld a buggy together. If I had access to a Tig, that I what I would use. but I don't, and can not afford one for myself at this time.
I do have a very nice Henrob oxy/ace welding torch which I am very confident with. It is a very nice setup. I COULD use it, but I surely don't look forward to welding a whole buggy together with it. It is a slow and HOT:eek: process to do any project like this with the Henrob.
I have a Miller 210 that is set up with dual spool/dual gas and is a pleasure to use.

Again, any information regarding any of the welding processes is welcome, and any information that you have that explains how Mig welding chromoly is possible will be especially appreciated by me.

Hopefully this will turn into a very informative thread.

Thanks,
Sean

Let be the first to say, 0.188" wall!:eek: "There shall be no dents!"

4130 is designed to be welded without a post heat treatment, at least in thinner sections.

Originally posted by DemoMike
Let be the first to say, 0.188" wall!:eek: "There shall be no dents!"

4130 is designed to be welded without a post heat treatment, at least in thinner sections.

Yes that is why I chose this size of small OD and heavy wall. I did not want tubing that would dent very easily. I know large OD and lighter wall would be overall structurally stronger, but I figure that because it is 4130 this size tubing should be quite a bit stronger in both tensile and yeild than the mild steel that many people use in their cages.

If I would have kept a larger OD and the thick wall, I would have had a very heavy, very expensive roll cage.

I think that this size is a good compromise in overall strength, and dent resistance.

I ended up getting this tubing at only $4.40/foot. Many here have claimed to spending more than that for mild steel DOM.

Sean

Google strikes again...

http://archive.metalformingmagazine.com/2001/01/Lincoln.pdf

wow, .188 wall! Many off road racers mig weld 4130 cages together, most do no pre or post heating, and hardly any of them actually heat treat anything. Most of these people just use ER70S wire, some experts suggest using ER80S to better match the strength of the base metal. They do make welding rod specifically for 4130, and some times it is called "4130 welding rod" I have seen many of the mig welded 4130 parts hold up just fine, however, they are not highly stressed. It still comes nowhere near the strength of a properly heat treated 4130 structure. As far as MIG vs TIG, you "could" have just a good of a MIG weld as a TIG weld or vise versa, depends on your welding skills. I wouldn't worry about it too much, as the tubing comes, 4130 is only about 10% stronger than DOM, so if your not heat treating it, you may have just made out of DOM.

I always use TIG for chrmo on my race cars but a local stock car place mig welds all their cars. I use an ER70S filler rod and am sure they byuy the same material in spools for their mig welders. For you thickness of tubing you may have to heat treat after welding go here for all you need to know.

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

Station,

I'll look up some info in my refs tomorrow.

But in a nutshell, I agree completely with Goat1...unless you have the ability to heat treat, there is no advantage to using the chr-mo, so I would buy the 1020 DOM and use that nice MIG machine, and make a killer buggy that will be every bit as good as what you could make with the Chr-mo.

Thanks, for the info, lets keep it coming. Here is a really good-long- read that really explains allot http://members.eaa.org/home/homebuilders/authors/whittier/The%20Welding's%20Done!%20%20Now%20What_.html

Going by the specs that the above link gives, 4130 is quite a bit stronger than mild steel in tensile and yeild.
65ksi tensile for mild
100ksi tensile for non-heat treated normalized 4130

It looks like a 400* pre-heat and a 1,200* stress relieving post-heat would be going above and beyond(In a good way as far as the steel is concerned) the general welding practice for 4130 despite the welding process used.

hmmm.... I know of a local place that does heat treating and has huge ovens. I know some people there too. 180 ksi tensile strength rollcage material possible..... hmmmm...:eek: :eek:

Not realy feasable , but still possibe.

Come on resident experts , lets have a discussion!

Sean

Find someone to heat treat it. Look around. Have your rig powder coated. Then you will kill two birds with one oven.
You went with cromo, you need to use it to its fullest potential.
Oh ya and hurry up Im comming to see this rig next month.:p
Dan

We learned a little bit about 4130 in aeronautics fabrication class, but I'm not sure that I remember much:

It is used where its tensile strength is paramount so it can save a lot of weight. Do you really need to save weight?

.188 is actually pretty thick for this tubing and welding it will require considerable heat input for proper welding. It may very well require heat treatment to avoid stress cracking and lamellar tearing. Check the AWS books for proper welding and heat treatment specifications.

Welding the joint with ER70s may be counter productive as the joint would have considerably less tensile strength unless it is reinforced or gusseted.

what about titanium, does anyone here have any experience with it? I know that you have to use a strait uip argon gas but other than that, what I have seen made no mention of special wires or anything along those lines?????

you need to tig weld chrome moly

I think you will do better with 1020 1.75x1.34. The complications of heat treatment combined with the expense and difficulty of proper fabrication shoot this one down IMNSHO. Wirking with anything thicker than .120 requires proper treatment to get the benefit of 4130 without the brittleness of post welding.

Anyone here actually weld 4130?? It require lots of patience and extreme amount of skill. Some of the skill requirement might be reduced by using mig but regardless it sounds like a problem waiting to happen.

I played with 4130 airframe tubing back in school 15 years ago. Even though many consider me a skilled welder, I found it to difficult to deal with and quickly decided against using it in my race car. (yep I had lots of dreams about the "right" way of doing things :D ) I was working with tig torch and after several days welding I finally got a technique that worked without the weld cracking :eek: Using the right filler metal is very important but the real work is in how you "close" the weld... I had to work on backing off slow and steady so I not sure how mig would do here since the heat is abruptly cut off... WTH it could be a good thing :D

Bottom line is unless you have access to a furnace and just love to blow cash out the window, dont do it. If you do have the cash and are gonna do it anyway dont forget Christmas is around the corner and there are a lot of needy kids out there so earmark some of the cash pile your sitting on to help them out as well :D :D

Oh yeah, go out and get some material and work it to see if I'm waaay off base or not. I've inhaled lots of fumes over the years :(

From "Engineer to Win" by Carroll Smith

" Welding 4130

Ther are a lot of myths surrounding the techniques of welding 4130 steel. Most of them are just that - myths. To be sure, care must be excercised. We have a narrow choice of suitable filler rods. Pre- and post-heat are important and become critical in thicker sections and all welds should be stress relieved after welding. But there are no great secrets involved.

Most racing welders do not believe that it is necessary to stress relieve welds made in 4130, especially TIG welds. They are wrong. Maybe explaining why will make some converts to the cause of righteousness. Contrary to popular opinion, the necessity for stress relieving 4130 weldments has little if anything to do with carbon content or weld contamination, and the superior shielding afforded by TIG welding does not help at all. In fact, we shall see, the need for stress relief is GREATER with TIF-welded 4130 than it is with oxyacetylene welds.

4130 is an "air hardening" steel. During welding, by whatever process, both edges of the joint are heated to the moltedn condition and then allowed to cool in air. This results in the creation of a series of "layers" in the heat-effected zone adjacent to the weld itself. In a short distance measured at right angles to the line of the weld we will find metal that has been heated considerably above the critical zone, just above it, not quite up to it, nowhere near it, and only slightly heated. As the weld puddle progresses, the heated metal behind it will be cooled both by exposure to the air, and by the quenching affect of the adjacent cooler metal. The heat=effected zone will thus cool more rapidly than if the whole part had been evenly heated and cooled as a unit. The weld is, in effect, quenched and is therefore considerably more brittle than the surrounding material. It doesn;t take a cold liquid to achieve a quench - all it takes is a source of RELATIVE cool. The weld is liable to be largely martensitic in structure and to fail under impact. In addition, the grain structure will vary throuought the entire heat-effected zone, and with larger grain size being found in the portion that has been hottest.
With TIG welding, the heat effected zone is geographically narrower than it is with torch welding. Far from being an advantage, this produces a steeper temperature gradient in the heat effected zone and, with air-hardening steels, a more brittle weld than a good torch weld - regardless of how skilled or careful the operator is about slow withdrawl and post purging.
The solution is simple, inexpensive, and not een time consuming. At the completion of welding, the entire area surrounding the welds should be evenly heated to about 1200*F (somewhere between dark cherry and medium cherry) and allowed either to cool in STILL AIR or covered in LIME or DRY SAND. Still air is best arranged by placing shields around large parts (like tube frames) or by placing a sheet metal box over the part until it has cooled. This, as you will have deduced by now, is also the reason that 4130 should always be pre-heated (gently warmed to 300-400* F) BEFORE starting a weld. It is a case of keeping the temperature gradient in the heat effected zone as gradual as practical. With higher-alloy steels, such as 4340, pre-heat and post-heat are an absolute necessity. Strictly speaking, it probably isn;t NECESSARY to either pre-heat or to normalize welds in 4130 if the sections are 0.065" or less in thickness, but it is damned good insurance. "


he then goes on about filler rods for 4130.....

They're his words and emphasis, not mine. And as anyone who's read his works will tell you, he's an opinionated SOB but he does seem to know his stuff. Note he never mentions MIG....he would probably have a stroke if you told him you were going to MIG it! But that doesnt mean he's the only one who is right.

I highly recommend you buy the book anyway, the theory sections are excellent and thorough. It's a very worthwhile read.

Over the past few years I have fabricated 4 different chassis out of thin walled 4130 (.049 and .065) for a student group. I did TIG weld them using low carbon filler rod, but there was no pre or post heat treatment. These chassis have held up to some serious abuse. One took a shot into a barrier wall at about 60 MPH and non of the welds snapped. Another has about 100 hrs of off road driving (20 -30 MPH) and there are no fatigue cracks that we have seen. It is my opinion that you could get the same results with a MIG welder. Because you are using a much thicker wall you may want to post heat treatment. Good Luck.

HOLY FAWK !!

That EAA article is excellent Station.

My favourite part was this:

"We came to feel that if the authors of several different books on welding were to be locked in a room to settle their differences about the matter, a fist fight would soon erupt."

Knowing you, I think you're in fine shape whatever you decide. Personally, I'd still use 1020 and a MIG but I'm lazy, stupid, and untallented!

I build my exo-cage out of 4130 (1-1/2 .100 wall). It is some tough sh!t! I have not seen any thickness of mild steel that can hold up to the abuse my thin wall chromo has taken. I even built my first set of lower control arms out of the same stuff. I ran them for a year, and when I replace them, they had a slight bow and lots of gouges, but no significant dents or collapsed areas.

Personally, I don't feel you need to go that thick. Something in the 125 - 150 wall would be as strong as you will ever realize. Going thicker will not give you the added rigidity that a larger dia would give, and you'll be amazed how tough this stuff is. I think the thick stuff will also compromise your welds more. You will need to preheat. Like Bill quoted, 4130 is air hardened. The thicker the material, the quicker it will cool and the harder (more brittle) the weld and surrounding material will be. I've seen a lot of race cages out of chromo, and IF there is a failure, it's not the weld it is at the heat effected zone right next to it. This is where the base metal hardened when it cooled. That's also why most builders use mild steel (70S) for the weld, to keep it for hardening in the weld it's self.

Originally posted by Station
Thanks, for the info, lets keep it coming. Here is a really good-long- read that really explains allot http://members.eaa.org/home/homebuilders/authors/whittier/The%20Welding's%20Done!%20%20Now%20What_.html

Going by the specs that the above link gives, 4130 is quite a bit stronger than mild steel in tensile and yeild.
65ksi tensile for mild
100ksi tensile for non-heat treated normalized 4130

It looks like a 400* pre-heat and a 1,200* stress relieving post-heat would be going above and beyond(In a good way as far as the steel is concerned) the general welding practice for 4130 despite the process used.

hmmm.... I know of a local place that does heat treating and has huge ovens. I know some people there too. 180 ksi tensile strength rollcage material possible..... hmmmm...:eek: :eek:

Not realy feasable , but still possibe.

Come on resident experts , lets have a discussion!

Sean

I think the link you posted is a little generalized, the tensile strength specs are a little off, If you look at most material supplier's specs, 1020 DOM has a tensile strength of about 80,000 psi, and 4130N is about 90,000 psi, like I said about 10% stronger. That's not a big difference, so why do people use 4130? well most people use it just to say it is "chrome-moly" even though it's not really necessary and it's made improperly (kind of like 300M is starting to be) and Other people (mostly in the aircraft and high-end racing industry) use if because it can (and actually is done) be heat treated to about 130,000 psi (RC 26-30).

I also think the term "heat treat" is thrown around a little loosely. To actually harden a 4130 fabrication to anywhere above it's normalized condition as the material comes, requires a stress relieve normalize at 1200 F, slow cooling, heating the chassis to 1550 F, water quenching, and then
1000 F temper to RC 26-30. This is commonly used for small parts like aircraft engine mounts, a-arms, and other suspension parts, your not going to be able to harden an entire chassis. At best you may be able to stress relieve a chassis, this will bring all the welds back the about 90,000 psi, you will never be able to have a180,000 psi tensile strength chassis.

The process of welding 4130 is no big deal, I have done a lot of it and it welds just fine, I would say that if most of us did blind test (I don't mean actually welding blind, like it looks like some people are doing:))using two pieces of metal, one 4130, the other mild steel, we would not know the difference. 4130 may actually weld better because the material is usually cleaner and more pure.

Originally posted by florida4x4
Anyone here actually weld 4130?? It require lots of patience and extreme amount of skill.

Here dude.......GOAT1's buggy all 4130 and TIG welded.

And stress relieved!

One thing I didn't mention is that I was using 4130 filler rod and not the iconel / stainless alloys that seem to be more popular and easier to work with. My instructor didn't have a clue apparently. :p

Also it's not that it cant be done, it's that it is probably a bad idea to jump in feet first and there's trouble brewing with .180 wall me thinks....

For what it's worth.... I've never actually done any of this but I know a couple guys that build chassis for front engine fuel cars and they were saying that the don't use straight 4130 filler rod as the welds crack very easily. They use a stainless rod or some variation there of for the maluabilty (sp?)




On a side note, I always love reading these threads and thinking about how people feel that the 4x4 crowd is just a bunch of uneducated, beer swilling, reanecks...... I wish those people could see the knowledge base floating around here.... :D

Originally posted by florida4x4
One thing I didn't mention is that I was using 4130 filler rod and not the iconel / stainless alloys that seem to be more popular and easier to work with. My instructor didn't have a clue apparently. :p

Also it's not that it cant be done, it's that it is probably a bad idea to jump in feet first and there's trouble brewing with .180 wall me thinks....

The 4130 filler rod is made to be used when you are going to heat treat the finished part, as to give it the same material properties as the base metal. If you are not going to heat treat it, use ER80S or similar. Many people use stainless rod, probably to get a clean pretty weld, many times if you have a cantaminated TIG weld that bubbles and get porosity, you can go over it with stainless rod to clean it up.

any high-strength ferrous alloy will harden signifigantly more than a mild steel in a welding process.
I don't think stress relieving is going to be a critical need in a fabricated roll cage. roll cages (properly designed) will act as space frames, and that distributes alot of the stress away from any specific weld. that big WHAM when you hit isn't what cracks welds most of the time, it's fatigue damage(WHAMWHAMWHAMWHAMWHAMWHAM). you can help prevent the cracks by grinding the welds smooth. it's a lot cheaper than putting your chassis in a 1000* oven for an hour.

Thanks for the good replys.

I see that we have some varying opinions as far how to go about the welding, and if it is worth while.

I have heard allot of local opinions, and viewpoints as well that closely match what I am eharing here. I have heard of Mig welded chromoly chassis working with no problems yet. I have heard of a Mig weded buggy chassis that had problems with stress fractures in the heat affected zone. I have heard of people with Tig welded frames and all sorts of problems. And I have heard some people who exclaim that there is nothing like it, and they wouldn't use anything else.

It sounds liek I am hearing much the same thing here. Opinions vary widely, all though those that have spoken up about their actual experience with 4130(Superdlux, and okcrawler) make the stuff sound great.

I have pondred on some of your advise and looked into pricing on some different sizes of tubing. These are the prices that I cam up with.

Prices at 300' quantity. Delivery to a business address included in the price.
1.75"x 0.134" 1020 DOM = $2.05/ft
1.75"x 0.125" 4130 = $3.45/ft
1.5"x 0.120" 4130 = 2.70/ft
1.5"x 0.156" 4130 = 3.70/ft

On the 1.5" 4130 I wanted a wall thickness between the two shown, but nothing was available in that size.

Right now I am leaning towards the 1.5"x 0.156" 4130 . It's a nice OD size for a full full tube buggy so that things do not get cramped, and the wall is sufficient enough that I can pass this thing on to my kids(If we are still rock crawling and not "Rugged Terrain Hovering" by that time):) .

rockdawgfj40: you need to tig weld chrome moly
Thank you for that input !


jeeper111: what about titanium, does anyone here have any experience with it?

You sure thats not too light of a material for you? You could lose some traction.:D :D Just kidding with you. I woukld like to know about welding titanium myself incase the need ever arises one day.

I should change the name of this thread to: "Welding Special Metals" I will see if this thread is going to grow any more first though.

Thanks,
Sean

I had to weld some titanium used it for body mounts for a funny car. It was not to bad. Contamination will happen very easy if you are not carefull. You need to flood the area inside and out with argon and use a titanium filler rod. For this the base material and the filler should be as close a match as you can find. You will know instantly if you screwed up as it turns from a straw color to bright blue if contaminated.

I work for an aircraft modification shop and put Rolls-Royce (Allison) 250-B17F/2 gas turbine engines on cessna 210's and the engine mounts are made out of 4130 condition N tubing.

We use 4130 filler wire on all the mounts without any post heat treating, only stress relieving before the finished mount is taken out of the jig.
Now I have welded lots of 4130 with er70s on sprint car chassis's and use on my cruisers with no failures so I really don't think you would run into any problems with er70s or er80s.

Opp's forgot to say that I use tig for most all the 4130 that I do at my home shop.

Here is a pic of the mounts that we build at work.

Originally posted by MetalMender
I work for an aircraft modification shop and put Rolls-Royce (Allison) 250-B17F/2 gas turbine engines on cessna 210's and the engine mounts are made out of 4130 condition N tubing.

We use 4130 filler wire on all the mounts without any post heat treating, only stress relieving before the finished mount is taken out of the jig.
Now I have welded lots of 4130 with er70s on sprint car chassis's and use on my cruisers with no failures so I really don't think you would run into any problems with er70s or er80s.

Opp's forgot to say that I use tig for most all the 4130 that I do at my home shop.

Here is a pic of the mounts that we build at work.

Theres one more boost of confidence to use chromoly.

Do you have any thoughts on MIGing it? I would definitely pre heat, and pressure relieve to help make up for it. I will have to pick a friend to start training with the torch so we can make this a two man job.

Thanks,
Sean

As soon as I get my hands on some 4130 I will try the mig process and let you know. Not sure if that will hvppen quick enuf though :D I'm about to build my cage and if it works out I'll do the 4130 thing - I already know I will TiG it, though :p

For anyone who hasn't see my "4130 Welding Scrap" post, I'mm looking for some scrap tubing/strap to test all the theories and filler rods out and will compile a FAQ. I will try and get some video too if my camera will pick it up alright...

BTW: MetalMender said he might have some scrap fo meh... :cool:

This is actually staying a good thread that has a lot of good info.
As for the type of rod to use in tig welding 4130 use ER 80S D-2, the D-2 is the amount of moly in the rod. This is what we use every day welding tube/ pipe for Dow Chemical. The mig process is a very practical process as long as the project justifies the use of such. Saying you have acces to a mig and not a tig, I would agree with you in wanting to mig it. It all comes down to knowing and having the experience to be able to weld it correctly. I'm not going to say 4130 is difficult to weld but you do need to control your heat input a little better when compared to mild steel. Mild steel is very forgiving, 4130 is a little more picky with the heat affected zone. I will try to find the link that my supplier gave me but the benifits of using 4130 over DOM was approx a 40% difference at thiat site. Now I don't want this to turn into a pissing match over what the percentages are. You could ask 10 dif people and get 10 diff answers possible but htis is the rule of thumb I have always used 40%. Now I've seen some talk of Titanium and this should be forgoten about unless you have a wallet with no bottom and a lot of time to weld it. Again we use this material for DOW Chemical for some of there lines and this is a slow process to cut/ grind/ weld. It requires a very very clean enviroment and as stated above it must be engulfed in argon. The only time Titanium get work on is after hours so there ids no contamination from carbon steel or stainless floating around in the air from other workers.