Welding Tips and Tricks

There was a thread started on another subject and it got off into welding 4130 chromoly. We thought it would be a good topic to discuss at it is a area of interest to all of us especially those who are into automotive racing and aircraft. One of the arguments is do you need to pre and post heat chromoly? What about the 1/8" rule where it is said you do not need special fillers and don't need to do any pre and post heat? What about using ER80 wire? What is the correct fillers? What about 4140? Got you thinking yet?

I post these links to get the conversation going. I ask the other members to post their links and info from other threads here as well. Note; for some reason this 4130 welding seems to be a hot topic and I have actually been in a "discussion" where I was literally yelled at while discussing this topic. I don't believe that will be the case here but I throw this out there to keep it in check.

http://www.ntsb.gov/doclib/recletters/1990/A90_82.pdf
http://m.youtube.com/watch?v=Is47-VwkyNg
-Jonathan

Great topic going to watch this one!

Some of the best info I have read on this was posted on the Miller discussion forums. Search for it and you will come across it.

Oscar wrote:Some of the best info I have read on this was posted on the Miller discussion forums. Search for it and you will come across it.

Yes but we want the discussion over here I will look it up.
-Jonathan

I will start off saying that I am not a professional welder. I've learned everything I know first hand and a lot of Internet research. That being said, IF, I was to weld 4130, i would not use preheat. I would use er70-s2, and for tubing, holes would be drilled at joints to let expanding gases move from one tube to another to prevent blowouts.
Supposedly preheating can reduce overall strength of 4130, and if you don't have a way too heat treat everything after its welded, you need to try to keep heat input to a minimum.
Er70-s2, from what I've come across is preferred for 4130 because it is strong but ductile enough for 4130 to reduce the chance of cracked welds.
So that's what I've come across for 4130, I honestly don't know if any of that is true or not. I've never even struck an arc on 4130. But from what I've come across I don't think I'll try using it anytime soon.
I may have the opportunity to build a tube chassis drag car soon and even it will be mild steel.

Post up fellas....I want to hear/read more about the pros and cons in this topic.

Ok I will share one of my few experiences with 4130. I was asked to do a mobile TIG repair of a fuselage. I am not exactly sure what the thickness was but I believe everything was around .035. I made a few phone calls, my LWS and Lincoln Electric, and they both recommended ER80S-2 for the filler since it was below .125 and I was also welding chromoly to regular steel. The repairs only took a hour and consisted of literally tacking tubes and brackets that had broke since it was made in the 1940's or 1950's. I had no problems with the actual welding except for some of the joints were brazed together or had braze close to where I was welding. One of the local aircraft clubs has been very good customers and I will go out of my way to satisfy them.

So the really debated subjects are the pre and post weld heat treatment. I have been told that Lincoln Electric along with leading industry experts are the ones who concocted the .125 rule of no heat treatment. I have also heard there is this ulterior motive to sell machines. My guess is by saying that you don't need heat treatment it is more likely that a hobbyist will purchase a machine from them to weld a frame or roll cage up. Here is where I always get into the heated debates. I am not saying any of this is true just bringing it up for the sake of conversation and I imagine it will be brought up at one point or another.

Does anyone have supporting documents for their beliefs and procedures on welding 4130? Jody, you welded on 4130 in a former life, what can you add to this conversation? Sam, you have friends who have or do roll cages, what say you?
-Jonathan

dsmabe wrote:I will start off saying that I am not a professional welder. I've learned everything I know first hand and a lot of Internet research. That being said, IF, I was to weld 4130, i would not use preheat. I would use er70-s2, and for tubing, holes would be drilled at joints to let expanding gases move from one tube to another to prevent blowouts.
Supposedly preheating can reduce overall strength of 4130, and if you don't have a way too heat treat everything after its welded, you need to try to keep heat input to a minimum.
Er70-s2, from what I've come across is preferred for 4130 because it is strong but ductile enough for 4130 to reduce the chance of cracked welds.
So that's what I've come across for 4130, I honestly don't know if any of that is true or not. I've never even struck an arc on 4130. But from what I've come across I don't think I'll try using it anytime soon.
I may have the opportunity to build a tube chassis drag car soon and even it will be mild steel.

This is the exact opposite of what I've read. To keep heat input to a minimum would be to weld it like stainless steel. Even Jody says the exact opposite in his videos: weld it slower. If you keep the heat input to a minimum, the fast cooling rate is what is responsible for localized martensite, which is hard and brittle, which then its responsible for cracking. The whole point of preheating it is to slow the cooling rate of the entire piece too keep the martensite at bay.

I'll repost this and go from there ;

[ kiwi2wheels » Mon Dec 08, 2014 4:53 pm

dirtmidget33 wrote:
Any ti..........................As for normalizing 4130 I would avoid that at all cost. I was informed a few drag race manufacturers where doing this and had chassis failures. In the circle track world of Sprints, midgets, champ cars(silver crown cars), nascar (now that they or using it), minisprints there is not one chassis builder that I know that does this. You start taking a touch willy nilly to joints you start changing the crystalline structure of the steel. These chassis hold up very well in a lot of violent wrecks and the use of 4130 being TIG welded has been done for years now on these cars and still is done by drilling vents and NOT heating tubes with torch.

This may start a discussion that could have it's own thread ; anyway, this seems to be a subject of yeas/naes. As you say many chassis builders do not believe in stress relief, and I've seen some books that also advise against it. 4130 was originally designed for gas welding, many of us oldies go with the torch stress relief, as does the FAA , pg 23;

https://www.faa.gov/regulations_policie ... a_Ch05.pdf

Remember, you are taking the shrinkage stress out of the part also, and if is, say an A arm or sub frame, it will comply a lot closer dimensionally to the jig. It's critical that the oxy-acetylene plant holds a neutral flame, many don't these days, it's just seen as a source of heat.

Re drag chassis failures, an interesting read. http://www.bmeltd.com/Dragster/tubulartales.htm ]

Oscar wrote:[
This is the exact opposite of what I've read. To keep heat input to a minimum would be to weld it like stainless steel. Even Jody says the exact opposite in his videos: weld it slower. If you keep the heat input to a minimum, the fast cooling rate is what is responsible for localized martensite, which is hard and brittle, which then its responsible for cracking. The whole point of preheating it is to slow the cooling rate of the entire piece too keep the martensite at bay.

I'm in the Oscar camp on this, also about the Miller discussion forums. Re the FAA file, p23 , I've welded 4130N with straight 4130 rod for car stuff and always used the torch after, no problems, also on parts made from 4130N tube and machined 4140A. The usual " wall " test had material failure well away from the welded areas. I used the 4130 rod as it was the only .050" rod the LWS had on the shelf.

Other times with parts from 4130A sheet and machined 4130N used ER 80-SD 2 (also CMS 32 rod ), again with post weld heating. As most of the car stuff I was making was not going to be final machined, it was critical to hold tolerances.

Just to play devils advocate, I have a friend ( builder of drag chassis for 40+ years ) who never uses a torch after welding !
I've always believed that cleaning the material or tube internally ( no oil ), removal of mill scale and burrs is very important.
Notice the FAA mention hydrogen embrittlement can occur with the presence of oil ; I've had some heated arguments over this ( particularly with Europeans.... ) and believe that many failures can be attributed to this, especially on parts that have been hung during heat treatment.

About recommended aircraft practices, always remember on an aircraft you can't park it and walk away when something fails.........

kiwi2wheels,

I'll have to dig into my library, but I have a book from the EAA on the welding of 4130 tubing in aircraft structure. It specifically mentioned E80s2 rod, and discussed post-weld heat-treatment in some detail. Welding with gas and TIG were both discussed, and in neither case was pre-heat mentioned.

With my experience, I'd expect pre-heat to have been mentioned, and I'd think it valuable, but perhaps it has a "softening" effect on 4130?

Interesting topic.

Steve S

Oscar wrote:The whole point of preheating it is to slow the cooling rate of the entire piece too keep the martensite at bay.

This is something that I had been taught when dealing with welding thick sections of mild steel....the thick sections tend to be a huge heat sink and cooled the weld off too quickly, so adding preheat slowed down the rate of cooling to allow the material to go through the changes in phases slower.


keep posting, I'm learning...

Otto Nobedder wrote:kiwi2wheels,

I'll have to dig into my library, but I have a book from the EAA on the welding of 4130 tubing in aircraft structure. It specifically mentioned E80s2 rod, and discussed post-weld heat-treatment in some detail. Welding with gas and TIG were both discussed, and in neither case was pre-heat mentioned.

With my experience, I'd expect pre-heat to have been mentioned, and I'd think it valuable, but perhaps it has a "softening" effect on 4130?

Interesting topic.

Steve S

Steve, I just looked at the FAA file; it mentioned preheat over .120", other sources I've seen mentioned .090". For sure it helps a lot on, say a bush/housing that has a bronze plug as part of the jig assembly ,that is effectively a solid heat sink, in minimizing the chance of burn through. I was told its good practice to preheat ( take the chill off ) if the part/fixture is in a cold shop, even using a heat gun.

As I understand, the post weld area will effectively be in condition A ( annealed ) anyway.

I bring a little different set of cards to this table and that is actual use of these welded parts. Myself, my dad, and friends have basically been crash test dummies for welded 4130 tube frames for years. I share the same metallurgical parts with a race car in my body but my injuries where not due to weld failures. We have used the best safety devices available to us as time goes on, even using devices we where against that wound up saving our butts. Some of these improvements. We have gone threw are cages on cars, 5 point seat belts, high back seats, arm restraints, Hans device. Some of the early cars where gas welded, then heliarc (TIG with helium ) and gas welded, to the latest all TIG welded using argon. I have personally mangled and bent frames that should have broke but wound up with bent frames and collapsed tubing.
I did not weld my frames but the frames I did have where done with ER70S-2. The frame builders did not preheat tubing on frames. The thickest part on frame itself is 1 3/8 x .095 wall tubing. There was no heating afterwards to so called stress releave the frame. The axle is .120 wall and thicker these parts where preheated before welded to avoid the tubing from cooling the weld to fast, but again where not stress releaved after welding. Our cars held up very good during stresses of racing and wrecks. The idea of someone taking a torch and heating joints to try and normalize or stress releave scares the hell out of me. Afraid of them changing the characteristics of the tubing and annealing the frame creating soft spots that flex or give way. The way it was explained to me is after the ER70S-2 is diluted with the 4130 it gives a joint very similar to base metal and reason they prefer not to use ER80-D2 is the chemical composition of ER80 creates a more brittle weld. (was gonna add chemical compositions will have to later kids bothering me sorry )

An interesting read, re rods; http://www.millerwelds.com/resources/co ... post173905

and the rest;

http://www.millerwelds.com/resources/co ... oly-tubing

Differences between condition N and A;

http://www.aedmotorsport.com/catalog/pr ... t-annealed

http://www.westcoastpiet.com/images/Con ... pt%20I.pdf pg 14

Interesting topic and perfect timing as I have an aircraft frame repair job coming up...

Subscribed

If you look farther into the background of Dale Sr. And his wreck, most sources indicate that aside from the fact that his belts were slack, his chassis builder was preheating and postheating the chassis with a torch, which was attributed to the massive chassis failure.

An aside: dirtmidget33, have you ever piloted a Hawk or a Munchkin replica? If so, chances are that they were welded by either one of my teachers, or his lone employee Mark.

VERY intersting topic.

I'm thrilled to see so many opinions. There's apparently a lot to discuss.

Steve S

Even before reading the responses on this thread I've never had a desire to weld a 4130 tube chassis or roll cage. This is because of apparently how easy it is to weaken the material. That being said, I'm wondering if there are multiple ways to correctly weld 4130.

Possibly tig with er70-s2 with no pre or post heat.
Or
Er80-s2 with pre and/or post heat?

http://www.millerwelds.com/resources/co ... oly-tubing

some good info:

http://www.suppliersonline.com/propertypages/4130.asp

http://webfinder.hol.es/look/Tempering_ ... odG1s_blog

http://webfinder.hol.es/look/Tempering_ ... 2Mw==_blog

http://webfinder.hol.es/look/Tempering_ ... 1Mg==_blog

http://www.uvm.edu/~dhitt/me124/TensileTestNotes-II.pdf

http://www.scirp.org/journal/PaperDownl ... perID=2413

seems to correlate with what I found on the miller website, with one exception: the tempering (which is the hardness reduction of the super-hardened state after it is liquid quenched in order to regain ductilily by sacrificing some hardness) is only beneficial if done properly, meaning by quenching immediately after the austenitized non-magnetic state @ 1600°F, and then heating at one-hour-per-inch-of-thickness from 450°F up to around 1050°F, depending on the hardness/ductility desired. The higher the temper temperature the softer it gets. The lower the temper temperature, the more hardness (and accompanying brittleness) that is retained at the expense of ductility.

O/A or torch "PWHT" from what I can tell, will cause [unknown effects --maybe good, maybe bad] if it has already fast-cooled and has produced brittle martensite within the structure. From what I can tell, sure it hasn't super-cooled from oil/water quenching, but since some brittle martensite may [or may not] have been formed from unknown cooling rates, you don't know the current hardness level, and that is the most important factor in determining how much heat to apply and for how long in order to relieve that joint from the hardness/brittleness [simultaneously regaining some needed ductility] that may or may not have occurred.

dsmabe wrote:Even before reading the responses on this thread I've never had a desire to weld a 4130 tube chassis or roll cage. This is because of apparently how easy it is to weaken the material. That being said, I'm wondering if there are multiple ways to correctly weld 4130.

Possibly tig with er70-s2 with no pre or post heat.
Or
Er80-s2 with pre and/or post heat?

I've done both (rods, never pre or post heat.) and had successful results with a hydraulic break test on tubing joints. Personally, none of my welds have ever seen vehicular service (not on race chassis anyways) so I can't say with confidence how well they would hold up to a high impact situation.

I do know however that some of the chassis builders I've talked to will use ER70s-2 in "crash zones", so that the chassis will crumple in predetermined areas, absorbing as much of the energy as possible. The ER80SD-2 rod is a lot closer to the tensile strength of the 4130 than the ER70S-2, so the 70 is used in non-critical welds and crumple zones. I also know that some will weld the entire chassis with ER70S-2, and others used ER80SD-2. We used 80 in school when welding 4130 "dogbones" to hook up in the tester. Actually, I believe the handout they pass out for welding 4130 is a copy of an article that Jody wrote for Experimental Aircraft maybe?

@GreinTime,
Jody was credited for being a contributor to the entire handout but there was no individual mention of him authoring the section on 4130. I'm sure he could add to this discussion if he chose to, and I understand why most times he chooses not to chime in.

Len

Hey, I didn't know that using the @ symbol actually tagged someone in the post on here, that was the first time I was ever notified of it!

Greintime no I never drove a hawk chassis or the munchkin. The munchkin was a different breed in it self I will say that. I noticed that some makers of chassis where more prone to breaking then others and if you looked at the welds a lot of times they would be very small fillets or for awile everyone was pushing for very lightweight cars, and tubing was just to thin for certain placement on frames. Those where two major faults I seen with a few broken frames. Currently with the frame builders out there this is a thing of the past. However I won't name the companies name publicly, but there is one major chassis company out there that me personally I would avoid at all cost. This is from watching there frames during wrecks and on advice from a well trusted friend and chassis builder that dealt with owner in the past, but even there problems have seemed to smooth out.

I was going to list the chemical composition of fillers and explain why the ER80D2 produces a more brittle weld then the ER70S2, but a buddy of mine pointed out a video that talks about it so here that is, and you guys can get info from some engineer instead of me spelling it out.

Welding 4130 CrMoly: http://youtu.be/ytSrEggjz1A

I'm not saying you can't weld with the ER80 it really depends on your application. In some circumstances you want to have weld give a little versus the more ridge ER80 weld. No one alloy of steel covers all the needs out there as does one filler cover all the needs.

My main issue is I believe if welding with ER70S2 do not be trying to heat tubes to stress releave the welds. Weld them and be done. I know these welds hold up from personal experience and trusted my life and survived from very good welders using those techniques.

dsmabe wrote:Even before reading the responses on this thread I've never had a desire to weld a 4130 tube chassis or roll cage. This is because of apparently how easy it is to weaken the material. That being said, I'm wondering if there are multiple ways to correctly weld 4130.

Possibly tig with er70-s2 with no pre or post heat.
Or
Er80-s2 with pre and/or post heat?

Don't be afraid of 4130n. I personally love to weld the stuff to me it welds nice and smooth. The quality of the steel is so much easier to deal with then just standard garbage steel I use it for projects in place of regular low carbon steel, but I have a lot of it laying around is a lot easier to clean and prep versus regular hot rolled steel too. Also your question about welding it with different methods, yes definitely say depending on what qualities you want out of part depends on how it is done. It can be welded with 4130 filler if heat treated in an oven in a controlled environment. Plus if there is a WPS or FAA rule you need to follow for that application do it. Avoid the lawsuits you welded to there specs even if there is a better way to do it weld it to there codes or get an engineer to investigate and change code. My issue is heating with a torch to stress releave is not what I would consider a controlled environment. I see lot of margin for errors when proven methods for welding without doing that have been done for years. Now if someone says they want whole thing stress releaved, then I say do it in an oven. Then cut it apart examine crystalline structure if that's what they want then go for it.

I still have a lot of learning to do and don't feel comfortable welding 4130, from what ive come across in research, to have my dad going down the drag strip trusting evey weld in the chassis. I am however comfortable using mild steel, which is what the chassis kit is made of that I planned to use.
I still would like to get some 4130 to play with some, get used to it. Maybe build a go-kart out of to get a little small scale, real world testing. Id say a go-kart with no suspension bouncing around the yard should show if the welds are brittle or not!?

Anyway, I've always believed if you're not comfortable with something, don't do it! You can always start small/ non critical, and work up to large scale/ critical parts.

Hey GreinTime I take it you know Mike, I can't say I know the guys that welded on his cars, but what are your teachers names wondering if I know them. If they went to track and worked on cars might have met them. If you can P.M. names. A lot of times we don't even know what some people do for there regular jobs. Just that they drive or turn wrenches for so and so.