welding 4130 chromoly tubing

[jrscgsr]

If it were my frame I would order up er80s-d2 and weld the frame up like mentioned earlier with a tight arc length and enough amps to have the toes wet in well than let the welds air cool and be done with it. Welded several dragsters this way with no failures after hundreds of passes. Stress reliving the joints after welding on a recumbant bike frame in my opinion is a waste of time and materials If I was building an air craft engine mount or something super critical, than I would weld it with 4130 filler and post heat treat.

[cncmachinist]

i did i project similar to this later year i race 4cross and downhill mtb and frames are $$$ so i found a deign i liked changed it up a bit and fabricated it my self out of 4130 and used plain old er70s-6 tig wire to weld it up chromed out the bike is beautiful and rides great i got to dig out the camera and post a pic of it


anyway good luck with it mines ridden great all of last year and was cheaper than buying the same style

[Aerometalworker]

Thus the "take it for what it's worth" comment This test probably wasn't the best indicator of how it would handle the stress a bike frame would endure.

The man responsible for the testing is working on certifying a procedure for welding up an aircraft frame, and he's a cwi, and he's pretty freaking ****, thus the testing. I can see how 1" tubing could act somewhat differently, but why would it be "entirely" different? I would think the results would by somewhat similar?
The elongation was measured to the point where the tubes fractured to give some sense of ductlity. The fractures were characturized as "ductile" in nature, I haven't seen them yet. Then just for the heck of it he put some additional samples in an apperatus he built to break stuff at a certain shock force(a swinging hammer) and rather than break, they bent over.

Just like in engineering, in welding there's usually more than one way to skin a cat!

Very good to see the testing done. As far as a different tubing size being completely different, its very common. More mass quenching area means diffrerent cooling rates, mass versus welding length, etc. Even the joint configuration does things entirelt differently at times, a tee joint in tubing cools differently then a butt weld. The only testing I havent seen you mention is fatigue testing. Unfortunately its the most laborious to test, and the single highest mode of failure in aircraft 4130 structures. A simple impact or tensile test wont show the problems. Your friend could probably find a facility to do the testing for them. Again this is geting a bit off the original discussion, but its good to see people actually testing their work, and caring. A flyer friend of mine that was a production welder for Piper had a cute saying for the people that carelessly welded components: " Zapp and Go , Soon 6 feet below ".

-Aaron

[jdustu]

How was the ductility determined?

Good to see that kind of testing done! However, the results from a test are only valid for that exact application, I.E. 1" tubing could act entirely differently. Thats why in engineering, the only "hard set" rules are those that are very conservative.

Thus the "take it for what it's worth" comment This test probably wasn't the best indicator of how it would handle the stress a bike frame would endure.

The man responsible for the testing is working on certifying a procedure for welding up an aircraft frame, and he's a cwi, and he's pretty freaking ****, thus the testing. I can see how 1" tubing could act somewhat differently, but why would it be "entirely" different? I would think the results would by somewhat similar?
The elongation was measured to the point where the tubes fractured to give some sense of ductlity. The fractures were characturized as "ductile" in nature, I haven't seen them yet. Then just for the heck of it he put some additional samples in an apperatus he built to break stuff at a certain shock force(a swinging hammer) and rather than break, they bent over.

Just like in engineering, in welding there's usually more than one way to skin a cat!

[Aerometalworker]

I was doing some certs up at our tech center a few months ago and helped do some welding on a procedure qualification for 4130(3/8 dia. tubing, .062 wall). I'm back up there again this week, and I got a chance to see the results today.
Some of the test coupons were done with er70s-6, and some were done with er80s-b2. Some were not pre- or post heated, some were done with one and not the other(300pre, 500 post air cooled), some were stress relieved(1150 then furnaced cooled), others were tempered(500 for 2 hours then air cooled). All of them passed the tests. The specimens welded with er80s-b2 had a higher ultimate load, were more ductile, and had higher tensile strength, but not to an extreme extent. The visual inspection, bend test and etching was done at the center, the pieces were sent out to a lab for the other results.

Take it for what it's worth

How was the ductility determined?

Good to see that kind of testing done! However, the results from a test are only valid for that exact application, I.E. 1" tubing could act entirely differently. Thats why in engineering, the only "hard set" rules are those that are very conservative.

[jdustu]

I was doing some certs up at our tech center a few months ago and helped do some welding on a procedure qualification for 4130(3/8 dia. tubing, .062 wall). I'm back up there again this week, and I got a chance to see the results today.
Some of the test coupons were done with er70s-6, and some were done with er80s-b2. Some were not pre- or post heated, some were done with one and not the other(300pre, 500 post air cooled), some were stress relieved(1150 then furnaced cooled), others were tempered(500 for 2 hours then air cooled). All of them passed the tests. The specimens welded with er80s-b2 had a higher ultimate load, were more ductile, and had higher tensile strength, but not to an extreme extent. The visual inspection, bend test and etching was done at the center, the pieces were sent out to a lab for the other results.

Take it for what it's worth

[weldr123]

Yes you can use the GMAW wire as a filler for GTAW as long as it's classification is ER70S-6 etc. The S in the filler metal classification tells you that this is a solid wire. Hope this helps!

[Aerometalworker]

Looks like another person has yet been led down the path of hassle of welding with 4130 filler rod by a good salesman even after being told by others that it is not the best choice.

I can't help but think of all the bickering on usenet in the 1990's on the homebuilt aircraft newsgroups about welding 4130 tubing, and how many people ended up eating humble pie over this after learning the hard way.

At least he's not building an airplane!

Yeah tell me about it. That and people worrying about the strength of the filler. You can have a 150ksi fillet if you want, but there is an area outside of the weld thats annealed to about 75ksi anyway. Thats why the engineering books use the annealed strength of the material when doing weldment design.
-Aaron

[Bodybagger]

Wow.

Looks like another person has yet been led down the path of hassle of welding with 4130 filler rod by a good salesman even after being told by others that it is not the best choice.

I can't help but think of all the bickering on usenet in the 1990's on the homebuilt aircraft newsgroups about welding 4130 tubing, and how many people ended up eating humble pie over this after learning the hard way.

At least he's not building an airplane!

[ASKANDY]

Er80s-d2

Most of the 4130 tube chassis we do in Drag racing or 4130 suspension parts we use the ER80S-D2. The strength is closer to than the 4130 base metal and does NOT rely so much on base metal dillution with the filler to make up the strength loss in using the lower ER70S-2. The elongation percentages are great and it does not require post stress relieve like a full 4130 filler. Because 4130 is heat sensative, keep your tig arc lengths low but use enough amperage to properly tie in the toes of the weld. Higher arc lengths will cause the machine to have to put out more voltage to keep the amperage steady and since Volts X Amps = total watts and watts is heat, keeping the arc length lower will be better.

hope this helps.

A

[Laiky]

i would just mail order .045" or 1/16" filler from cyberweld.com or who ever. The mig wire always wan'ts to curl up and is never straight.

[Aerometalworker]

OK,
So I went to my local welding store to pick up some ER70S-6. Not only did they not have it but no one thought that would be the right filler for 4130 anyway. They thought maybe ER80S-6 at first, but after asking around they think I should be using actual 4130 filler rod. So I got two lbs just to save a trip back. What does everyone think of this?

Also, they didn't have ER70S-6, however my local harborfreight retail store has a MIG spool of ER70S6 on sale. Can I buy this spool and just use the wire like it was a straight piece of filler? It does not have a flux core or coating.

Thanks

First problem was asking a welding store a question like that. Anyway Per the real welding and engineering handbooks, normally 4130 filler is only used when the entire part will recieve an actual post weld heat treatement. I cant believe they didnt have ER70s-2 or -6 in stock. Yes you can use the -6 from a mig spool, just get the heaviest you can to avoid "tiny weld" syndrome. Note that there is one individual in this country pushing 4130 filler and TIG, cant believe everything you read in a Home Depot welding book. When looking at strengths of a weldment, it must be remembered that there is interalloying between base and filler material, so just because a filler is 70ksi , does NOT mean the weld itself will be 70 KSI.

-Aaron

[swamper8]

OK,
So I went to my local welding store to pick up some ER70S-6. Not only did they not have it but no one thought that would be the right filler for 4130 anyway. They thought maybe ER80S-6 at first, but after asking around they think I should be using actual 4130 filler rod. So I got two lbs just to save a trip back. What does everyone think of this?

Also, they didn't have ER70S-6, however my local harborfreight retail store has a MIG spool of ER70S6 on sale. Can I buy this spool and just use the wire like it was a straight piece of filler? It does not have a flux core or coating.

Thanks

[Aerometalworker]

Well I like to do things right so i will probably try my hand at annealing. Do I have to anneal the joint soon after welding? Or could I fab up my frame, assemble my components and fully test my design to make sure I won't be cutting/modifying any of my joints? It'd seem like a waste of time to weld and anneal a joint then possibly have to modify it later because my design needs tweaking.
Where can I get temp sticks? Would my local welding supply store have such a thing?
Thanks

Nope you can go through the joints after the whole frame is welded, no time limit. I buy my temp sticks from MSC ( www.mscdirect.com).

Another little tip, if you use a jig of any kind, dont make it too ridgid. If you restrain the parts while welding you can have "hot cracking" of the material as it cools. Allow some slop in the jig for expansion and contraction. For what your doing 1/8" allowance should be fine for most of the parts. Jigs that slip ( i.e. magnetic clamps) are fine as well as they allow the parts to move upon cooling.

Oh and be careful when using the term "annealing". Technically its tempering, but historicly its been called "Stress relieving" , " Torch annealing" , and "Normalizing". I too find myself using different names for it depending on the audience.


-Aaron

[swamper8]

Well I like to do things right so i will probably try my hand at annealing. Do I have to anneal the joint soon after welding? Or could I fab up my frame, assemble my components and fully test my design to make sure I won't be cutting/modifying any of my joints? It'd seem like a waste of time to weld and anneal a joint then possibly have to modify it later because my design needs tweaking.
Where can I get temp sticks? Would my local welding supply store have such a thing?
Thanks