chromemoly welding

[Silverback]

4130 welds exactly like steel till you overheat it, and then is starts cracking. (well, steel can do the same but you really have to overheat it a lot and usually multiple times and the cracking never becomes as big an issue with it)

[Billet Benny]

I agree with most if not all of your statements in this thread but you seem to leave out the reason why not to use 4130 filler on 4130 structures. Besides the fact that there is not strength/rigidity advantage, there is the disadvantage that if you get that joint just a little too hot it will have a tendency to crack, which it will not do with mild steel.

That's what I said above explaining why matching filler with 4130 is a bad idea. I believe it's more a problem of cooling rate, but excess heat could be one cause of that.

The only time it really makes sense to weld 4130 with a comparable filler is if you’re actually going to have the parts heat treated after you’re done (which I would argue is the only time it really makes sense to use 4130 to start with).

That is the one time it makes perfect sense to work with matching filler. However, I will disagree that heat treated parts are the only good use for 4130. 4130 makes sense used as fabricated in many many applications. However, and I've always said, I believe it's an experienced builder's tool.

Getting back to welding it… I’m not sure if ER80S-… filler is really that big a deal anyway, since yes, it is closer in strength to the 4130 (and to 1020, and especially 1026 which is designed for tubular structures), but the fillet/thicker section of the actual weld makes the minor difference in yield strength irrelevant, since the welded area if done correctly will be larger and stronger anyway.

Yes, I've been saying this so often now I'm turning blue.

This probably is my biggest issue with welding 4130 structures that will not be heat treated… I don’t know what increasing the HAZ does to improve your 4130 joint? It just gives you a bigger brittle area. Done properly, none of the welding processes should cause any cracking, and unless you have literally DAYS for the thing to sit at >1200& in a temperature controlled situation none of them will cool slowely enough to prevent a brittle area around the weld.

Increasing the haz creates a slower cooling rate of the area of most concern. It doesn't necessarily give you a "brittle" area. You'd be surprised how a little extra cooling time will help a structure like this in the as-welded condition. A slow furnace controlled cooling will anneal whatever you want, but remember the normalization process requires no controlled cooling rate, only cooling in still air which you can think of as being semi-like cooling from welding. And in the normalized condition is how this stuff is useful as fabricated. Now I'm not saying the bigger the haz the better, cause there's a limit somewhere and that comes w/ experience.

I do love how most people want to convince you that you can create a smaller HAZ with TIG… not at all unless you don’t get the same penetration as with the MIG…

I concur fully.

[Gary]

I found a article on the EAA website about a year ago. It is about 10 pages long, but interesting reading. I have a copy of this if anyone is interested send me a email and I will send it to you. I do not know how to attach this article without copying and pasteing in here but its too long.

Gary
[email protected]

[Gary]

I guess I attached it and now I don't know how I did it.
Gary

[Laiky]

The aviation feild has this just about nailed down. There are a few EAA articles on 4130. I wonder how their info relates to the heavier wall tubing car guys usually use?? Most A/C stuff is pretty thin. It's funny how O/A is considered one of the best methods for 4130. There are probably still more gas welded airframes in the worls than TIG. I recently purchased a gas A/C welding book that was a reprint from 1943, no updated info! There were the best looking gas beads i've ever seen. I wanted something that showed how things were done before TIG/MIG was around figuring they would have more indepth info since they couldn't leverage non-existant technology to get around any gas welding shortcomings. I'll find the isbn number if anybody is interested.

[burninbriar]

I guess I attached it and now I don't know how I did it.
Gary

Thanks Gary, that was interesting reading. As a kid growing up I was always told that an OA weld is the most sound weld possible when done right. I don't know that the article proves that but it certainly seems to favor the OA process for 4130.

[Silverback]

That is the one time it makes perfect sense to work with matching filler. However, I will disagree that heat treated parts are the only good use for 4130. 4130 makes sense used as fabricated in many many applications. However, and I've always said, I believe it's an experienced builder's tool.

Do you mind explaining?

As far as I can determine, you don’t end up with a more rigid structure (for the same weight), it’s barely if a all stronger and on impact is more likely to break rather then bend and absorb energy. I’m not sure what advantage non heat treated 4130 structures really have. As far as I can tell, NASCAR and the roundy roundy racers as well as fabricators like Formier and know it all’s like Carrol Smith got non heat treated 4130 structures right (illegal to use in the roll cage… in cup cars, Formier refuses to use it anywhere near a driver and Smith agrees and strongly cautions against it). From what I know, I believe that the NHRA and IHRA allowing thinner wall tubing if you use 4130 in a roll cage and only allowing 4130 past a certing speed is a mistake approaching on insane.

Am I missing some quality of 4130 that makes it better for some applications?

Increasing the haz creates a slower cooling rate of the area of most concern. It doesn't necessarily give you a "brittle" area. You'd be surprised how a little extra cooling time will help a structure like this in the as-welded condition. A slow furnace controlled cooling will anneal whatever you want, but remember the normalization process requires no controlled cooling rate, only cooling in still air which you can think of as being semi-like cooling from welding. And in the normalized condition is how this stuff is useful as fabricated. Now I'm not saying the bigger the haz the better, cause there's a limit somewhere and that comes w/ experience.

I guess that’s one of my pet peeves… there is almost never any benefit to allowing some part that you just welded to cool faster then necessary, and if possible I make sure that I do the welding in still air and if I have any clue that the material being welded may harden/be affected by heat I actually go to some extent to cause it to cool slowely (burry it or at least cover it with a welding blanket, stack of welding gloves…). If you did everything else correctly, if you’re going to end up with a crack or failure later on it’s going to be from letting the parts cool too quickly.

Gary, the article looks interesting but I’m going to refrain from commenting till I get the chance to sit down with it and read it.

[martymar333]

Do you mind explaining?

As far as I can determine, you don’t end up with a more rigid structure (for the same weight), it’s barely if a all stronger and on impact is more likely to break rather then bend and absorb energy. I’m not sure what advantage non heat treated 4130 structures really have. As far as I can tell, NASCAR and the roundy roundy racers as well as fabricators like Formier and know it all’s like Carrol Smith got non heat treated 4130 structures right (illegal to use in the roll cage… in cup cars, Formier refuses to use it anywhere near a driver and Smith agrees and strongly cautions against it). From what I know, I believe that the NHRA and IHRA allowing thinner wall tubing if you use 4130 in a roll cage and only allowing 4130 past a certing speed is a mistake approaching on insane.

Am I missing some quality of 4130 that makes it better for some applications?



I guess that’s one of my pet peeves… there is almost never any benefit to allowing some part that you just welded to cool faster then necessary, and if possible I make sure that I do the welding in still air and if I have any clue that the material being welded may harden/be affected by heat I actually go to some extent to cause it to cool slowely (burry it or at least cover it with a welding blanket, stack of welding gloves…). If you did everything else correctly, if you’re going to end up with a crack or failure later on it’s going to be from letting the parts cool too quickly.

Gary, the article looks interesting but I’m going to refrain from commenting till I get the chance to sit down with it and read it.

4130 without heat treating has a tensil strength of 90000to95000 therefore making it more attractive for certain applications.....we do alot of work that specs it, not heat treated just raw.....believe it or not there is quite a difference in 70000 and 90000.

marty

[Silverback]

I keep hearing values like that all over the net but I can’t find anything close in a reference book anywhere.

According to my Mark’s Engineering handbook the 10xx structural steels have a tensile strength of 65-90KSI, cold rolled as high as 100KSI. Normalized 4130 72-82KSI.

Young’s modulus (stiffness) is very close to the same, 29.5 for cold rolled vs 28.6 for normalized “alloys” and 28.6-30 for heat treated alloys. I didn’t even realize there was a difference at all, usually the answer is that the modulus is the same “about 29” for all steels, which is pretty close to accurate.

Again, I see no advantage to building structures out of 4130n, especially over a high strength carbon steel that is designed for tubular structures like 1026, unless I’m missing some quality…

[Buzz Job]

I keep hearing values like that all over the net but I can’t find anything close in a reference book anywhere.

According to my Mark’s Engineering handbook the 10xx structural steels have a tensile strength of 65-90KSI, cold rolled as high as 100KSI. Normalized 4130 72-82KSI.

Young’s modulus (stiffness) is very close to the same, 29.5 for cold rolled vs 28.6 for normalized “alloys” and 28.6-30 for heat treated alloys. I didn’t even realize there was a difference at all, usually the answer is that the modulus is the same “about 29” for all steels, which is pretty close to accurate.

Again, I see no advantage to building structures out of 4130n, especially over a high strength carbon steel that is designed for tubular structures like 1026, unless I’m missing some quality…

OK as for 1026 vs 4130 -here is a good read and if you know the physics just skip down to the chart and see where the yeald is, tensile is not everything.
I report you decide

http://exp-aircraft.com/library/heintz/material.html

[martymar333]

good article Buzzjob.

marty

[Billet Benny]

Do you mind explaining?

Of course not!

As far as I can determine, you don’t end up with a more rigid structure (for the same weight),

That's right. It'll never be more rigid. In fact, it will likely be less rigid if you use lighter wall tube to save weight which is one main reason for using 4130.

it’s barely if a all stronger and on impact is more likely to break rather then bend and absorb energy.

Here is a problem. 4130 normalized is in fact a good bit stronger than comparable 1026. I pulled some numbers from matweb.com here using 1 inch solid rounds for material strengths just for comparison purposes.

1026 cold rolled specs out at about 60,000 psi yield strength and 71,000 psi ultimate strength.
1026 hot rolled specs out at about 35,000 psi yield strength and 64,000 psi ultimate strength.
4130 normalized specs out at 63,000 yield strength and 97,000 psi ultimate strength.

Now, I'll be the first to say it's obvious that 1026 cold rolled and 4130 normalized look pretty equivalent so far because they yield around the same amount of stress. However, taking into account the ultimate strengths 4130 becomes a much tougher material. Also if you look at the 2 elongation percentages for each, 4130 specs out at 25% and 1026 cold rolled just 15%. This is proof that 4130 is much tougher than the comparable 1026 because toughness is the total area under the stress/strain curve.

A very large amount of the dom in 1026 you find is also going to be manufactured from hot rolled sheet, granted the drawing process cold works the material to make its strength numbers a little higher than just a raw hot rolled product.

Cold rolled 1026 is actually a much less ductile material than 4130 in the normalized condition. This is why I disagree with your assumption that 4130 is a bad decision because it "breaks" rather than bends and absorbs energy. This is actually not the case. In fact 4130 N will able to plastically deform and absorb more energy than 1026 cold rolled. It is not correct to look at 4130 as a material that will inherently fail drastically and break apart.

As always, design considerations need to come into play and highly stressed joints should be reinforced w/ proper gusseting to maintain joint integrity for situations such as crashes. But when comparing materials as a whole 4130 N outshines 1026 cr heavily.

4130 in the normalized condition more mimics hot rolled 1026 with respect to ductility and it's more of an apples to apples comparison. Once you compare the condition of the steels when ductility numbers are similar you see how much more yield and ultimate strengths are available with 4130.

I’m not sure what advantage non heat treated 4130 structures really have.

My answer here first stems from the strength and ductility advantages outlined above. The second thing that's so great is it's not much more difficult to fabricate with than any mild steel material. Extra precautions need to be taken but for the most part in the normalized condition it bends well, cuts well, and welds well just like 1026. Sure it's a little more difficult to cut and weld, but nailing down those procedures will net you a strength or (if you choose) a weight advantage.

As far as I can tell, NASCAR and the roundy roundy racers as well as fabricators like Formier and know it all’s like Carrol Smith got non heat treated 4130 structures right (illegal to use in the roll cage… in cup cars, Formier refuses to use it anywhere near a driver and Smith agrees and strongly cautions against it). From what I know, I believe that the NHRA and IHRA allowing thinner wall tubing if you use 4130 in a roll cage and only allowing 4130 past a certing speed is a mistake approaching on insane.

I do semi-agree with this. 4130 is not the answer in all cases. Nascar vehicles are mass produced and pretty overkill to begin with. In very many cases 1026 or other mild steels are more than adequate. And yes mild steels do allow a little more margin for error in fabrication and welding procedures. This is why I belive 4130 is a skilled and experienced builder's tool and it can be used in ways that negate its properties. I still almost always suggest mild steel for other people's cages and projects because it is less tempermental.

Am I missing some quality of 4130 that makes it better for some applications?

I hope I've shed a little thought on the subject. It's pretty easy to work with and very strong in the normalized condition.

I guess that’s one of my pet peeves… there is almost never any benefit to allowing some part that you just welded to cool faster then necessary, and if possible I make sure that I do the welding in still air and if I have any clue that the material being welded may harden/be affected by heat I actually go to some extent to cause it to cool slowely (burry it or at least cover it with a welding blanket, stack of welding gloves…). If you did everything else correctly, if you’re going to end up with a crack or failure later on it’s going to be from letting the parts cool too quickly.

Definitely one of my peeves too and I strongly agree with you.

[90blackcrx]

Primarily race car frames are welded with GTAW, most for cosmetics, racers like pretty welds. Cr-Mo Tube (typically 4130) can be welded with GMAW or GTAW processes and be equally strong.

Just like someone else stated, the rule books I have read state chromoly must be tig welded.

Here is a good link, but don't follow it to a T

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

I myself use ER80S-D2 filler when welding chromoly.

[vodomagoo]

Alot of off road trucks using cro-mo are mig welded. Its just easier to do with tig without overheating the metal so nhra and other orgs. mandate the use of tig so they can keep the margin of safety higher and not have a failure due to a overheated weld area.

[dandimand]

I can only state from personal experience for 20 yrs working with both building race cars so i wont go into technical stuff . Nhra tubing sz is typically form .049 to .083" . where as mild steel we have to use .118" . for us its a huge weight savings . secondly 4130 has more memory and is able to spring back more than mild steel . why not mig well for the most part i would say that the tubing is quite thin and it may be a little tougher to avoid cold laps on restarts and on race cars there are many stops and starts. thirdly if you bend this stuff for a living such as i do you will find the spring back on 4130 to be a lot more and its also harder to bend as in the pressure it takes to bend . there have been some issues though most of the time I have found in the repair side of things the weld hardly ever breaks. its the area just in front of the weld . I would also only state from experience that these type of cars kind of have a shelf life so to speak after alot of runs tire shake etc.. there can be cracked tubes after a while mostly on the thinner parts though such as .049 and .058 kind of just the cost of racing . for myself i typically just use 70s2 havent had any problems with it and i know most chassis builders this is the rod of choice so either way it works for me at this point dont see a need for myself personally to use 80s2 . ps make sure you drill vent holes under tubes when welding and fit up is very important if you try to fill gaps in 4130 your asking for trouble i also remove mill scale on all joints . scothbrite will do fine for this.