4130 welding, need advice 3

[400fnSport]

OK, I'm constructing an ATV frame out of 4130 cromolly. My question is all I have is a MIG welder, (Solar 2175) and have never done anything like this before with this type of alloy. I was told for a good weld with 4130, I need to TIG, but I don't have and can't afford a TIG just for this application. But I was told I could MIG with 100% argon and er70s-6 or es70-s5 wire. (I don't know which one of those I should use) But is this my only option, or could I oxy-acetelene it using a 4130 rod? I don't know which one is better, and don't really know the process of how to weld using a oxy-acetelene thorch. but I need the welds to be strong of course, but all stress points will be gusset. Any advice is appreciated.

 

[evelrod]

Welding is simply "melting two pieces of metal together". Welding 41xx TS is not rocket science. It welds as any other metal of equal size, MIG, TIG, stick, whatever. Chromoly steels require a post heat treatment in order to prevent the possibility of cracking and failure at the weld interface. It is the necessity of PHT that makes chromoly TS less than perfect for your stated application. IMHO, yoiu should use a mild steel DOM TS of suitable wall thickness. There will be very little loss of strength V weight and it's a bit cheaper.

Rod

PS---Brazeing and/or furnace brazing has always been used in tubeframe race car construction before TIG became popular.

 

[patdaly]

400fnsport
Yes, you can certainly OxyAc. weld 4130, Use a mild steel rod though ( coat hangers are my preferred rod, but Im sure thats not correct via. the book ) As Rod states, you should draw the weld areas back, and even then, you must accept the inevitability of a crack or two at some point in the future.
You can also MIG it, and the ER70S is a mild steel wire, I am not sure you would have to have 100 percent Argon, however it might help welding thin tubes.
I assume you are building a race frame where weight is paramount? Otherwise, I would also follow Rods suggestion to use mild steel, short of getting goofy on wall thickness, the weight savings shouldnt be more than a couple of Lbs.
As for welding technique with Oxy, think of it as a crude TIG, you are using the flame for the heat source instead of electricity.

 

[chiph]

pwht won't be necessary for wall thickness you would be using for your application. if you gusset, or cluster tubes you might consider it though. gmaw will be tough, but doable with a little practice. i would suggest 80ksi wire[.023 if available] with a 75/25 ArCO2 mix.
Historically, oxyfuel was the method for welding thinwall 4130 because the flame provided the pwht and you had great control of the weldment. that's why gtaw would be a better choice but i think you can do it with "what ya got".

 

[evelrod]

Pat, "coathangers are my preferred rod---" How horrible!!!
I haven't used coat hangers since I found out that PROPER weld rod could be had at the local welding emporium for literally pennies. Many different sizes including the 1/16" copperclad stuff that I favor. To be honest, I use the MIG for just about everything these days. I tend toward CO2 for most everything. Cheaper. For the bigger stuff, I switch to FluxCore.

Rod

PS to chiph---"Historically, oxyfuel was the method---"
True enough. BTDT but, IMHO, it requires a BIT more than basic skill with a torch to achieve a safely welded frame fapricated from chromoly TS.

 

[400fnSport]

Wow thanks too all, you all are sure helping me get cleared up on a lot of things. I may try doing a little research on oxyac, and give it a shot, if I have problems, then I will Mig it and make sure everything is re-enforced well. But what other metals do I have the option of using. A lot of after market frames come in 4130, but can someone help me on what maybe I could use that I could weld better with. A few extra pounds isn't going to hurt anything, plus if it saves me a little $$$ that's always good too. Thanks to all that respond, this site is very informative, glad I found it!

 

[chiph]

evelrod, i concur with your concern over the integrity of the weld but it "ain't gonna fly" so i think the risk of a failed weld is not nearly as critical as with an airframe.
on the same note, i think it is wise of 400fnSport to consider more forgiving steel alloys.1020 DOM tubing would be a good choice--lots of o.d. and i.d. combinations available and very forgiving to weld.

 

[patdaly]

Rod, sorry, that practice was instilled by my father, a Northrup graduate A&E. I am sure there are still many small aircraft flying with his welds. I always use ER70S6 for my TIG work though, just call it old habits. Actually, coat hanger wire is pretty doggone ductile stuff....

400fnSport, SAE1020 DOM tubing is a wise choice, depending on your wall thickness and tubing diameter. I have no direct experience with bikes or ATVs, but as an example, when we use 1020 for the 1-5/8" main roll cage hoop, we typically run .134 wall, but mostly to make sure we satisfy the NHRA .120 min wall mandate. For the 4130, we run 1-5/8" X .083 wall, so that will give you an idea of the difference in wall thickness. I would try and keep the same relative percentage of cross section as a starting point.

 

[evelrod]

I must agree. The SAE 1020 DOM was my choice for ALL the roll bars and roll cages I have fabbed over the years. A long, long time ago I used ERW in a pinch but, I do not recommend it(point of fact, it's not allowed in most race organizations). My vintage mini's 8 point cage is 1020 DOM 1 1/2" 0.095 and the whole shootin match comes in at under 1200 lbs. on track.


Rod

 

[400fnSport]

OK I've decided that I'm going to do a test frame with some cheap metal to make sure I get all the measurements correct, then I will construct a prototype out of 1020DOM. I will run it for one season to see how well I can build this, then if I feel confident, next year I'll tackle the 4130. You guys have been an amazing help to me. I'll be heading to Modern Welding tomorrow morning to pick up everything. Thanks all for the help

 

[jeffita]

Lots of good info here guys!
I build drag cars for a living and tig everything, even the 1020.I use 70s2 wire which is pretty much the industry standard for 4130 and 1020.
Ive been told that if you need to mig 4130 that you can use
70s2 wire with 95% argon 5% c02 and get good results.
All the work i do is to sfi specs. so i dont do to much mig
For 1020 mig i would use 75% argon 25% co2 and 70s2 wire.
Good luck and have fun!
Jeff

 

[boo1]

Although there are several good filler materials, ER80S-D2, is one you should consider. This filler material is capable of producing welds that approximate the strength of 4130. ER-70S-2 is an acceptable alternative to ER80S-D2, as is ER70S-6, although the weld strength will be slightly lower.

For parts thicker than .120", stress-relieving is recommended and 1,100ºF is the optimum temperature for tubing applications.

Cheers

 

[patdaly]

Boo1 or jeffita
I guess I have always been told the suffix on ERS70 was simply the fluxing action, which seems is incorrect. Do you have any information sites on the web that will explain the exact nomenclature and properties? I did a quick Google search, but came up with more advertising for sale than anything else. Thanks in advance!

 

[Merzi]

400Fn sport

4130 is not a standard carbon steel material, nd definately do not use 70s-2. 80 series electrodes and wires are ideal for 4130 material. And PWHT is definately recommended

Merzi

 

[boo1]

ER80S-D2

E stands for "Electrode"
R stands for "Rod"
The first two or three numbers are an abbreviation of the weld's strength. To figure out the strength of the weld, take the 2 digits, in this case 80, and multiply by 1000 to get the weld strength in PSI.
S stands for solid electrode or rod.

If there is a letter and number combination next, it relates to the chemical composition of the weld deposit.
D2 stands for 0.25-0.45%Mo 1.25-2%Mn

 

[jeffita]

Merzi,

Right or wrong, ALL of the top fuel dragster chassis that you see on the track today were tig welded with 70s2 wire.
The engineers that have worked with the manuf. have concluded that 70s2 is more forgiving as these cars flex an incredible amount.
the main rails from the driver forward are generaly .049 wall, with the main drivers area built of .058 and .065

None of these cars are pre or post heat treated.

In fact the AWS is releasing a new spec. in the near future addressing this.

I spent 16 years in aerospace as a tig weldor and was surprised that none of the builders used a higher tensile wire and didnt do any post annealing of the weld zone.

Its a case of past practice as being accepted as the industry standard.

 

[chiph]

400fnSport is probably getting more input on this question than he really wanted but, this has developed into a discussion/debate that i have been involved with for almost 20 years. My "current opinion" is that if ductility of the weld is important then it is ok to undermatch the filler and use a 70ksi wire. If your weld is single pass on base metal with less than .100 thickness, then the welding process alone seems sufficient to prevent any "hard areas", and pwht is not necessary. Now, if you use 4130 filler, or have welds in close proximity, or you just think it is a "stressed area", pwht is probably a wise choice.
Finally,I must admit, I have never gma welded 4130--just oxy-fuel and gta. i suspect the quick rise and fall of heat associated with gma welding might throw a monkey wrench into my "current opinion".

 

[patdaly]

Thanks Boo1 for the explanation!

 

[pipeingg]

cromolly:-
Chrome is used as it is resistant to corrosion and is very strong.
Molly= Mollibrium (SPELLING UNCHECKED) has properties that have great CREEP resistance, resisting being pulled a part hence ATV FRAMES strong durable and life span many more folds than M/Steel

 

[boo1]

Jeffita, as I indicated above ER-70S-2 is an acceptable alternative to ER80S-D2, as is ER70S-6, although the weld strength will be slightly lower. The ductily and stress strain relationships are simular. Some times products used becouse we have allways use them. For a full strenght weld the ER80S-D2 is the correct rod selection.