anybody where I can buy chrome moly tubing near nyc, I want to do 2 roll cages and im trying to save on the shipping. Maybe if it's not to far i can pick it up.

 

Try searching for "chromoly". There has to be someone in the NYC area that stocks it. You do know there's a special process for making a roll cage out of chromoly, right?

 

how many feet do you need and what size? i'm around philly could meet halfway.

 

any local metal supplier should be able to get it.

in for details on this "special process" for 4130 cages...

 

SCCA GCR rules state:

http://cms.scca.com/documents/2011%2...%20version.pdf

4. It is recommended that all joints of the roll cage be welded. All
welding must include full penetration, no cold lap, no surface
porosity, no crater porosity, no cracks, no whiskers, and so
forth. Welds shall be continuous around the entire tubular
structure. Procedures for welding alloy steel shall be in accordance
with accepted industry practice. It is recommended that
a certified AWS D1.1 welder do all welding.

Elsewhere in the rules, it specifies that alloy steel is 4130 steel. The rules used to state that chromoly cages required "normalising" of weld joints, and recommended against it's use for these reasons, or that it be done by qualified welders.

 

Thanks but this isn't my first cage, this will be my first non pre bent cage. As far as the welding goes I got that under control. When i googled chromoly nothing local came up/ or worth driving to cost wise.

 

There are lots of topics in this section about welding 4130 and ER70-S2

 

The cheapest I found 4130 chromoly locally to me was at $9/ft. That's pretty spendy stuff.

 

ah, c'mon jac! most of that is just common sense! of course you don't want crappy welds on something like a cage, regardless of material! i don't think 4130 is allowed really anywhere outside of nhra anyway, is it? as for doing it properly, i think the biggest thing is proper filler selection. normalising is really only necasary on 4130 thicker than .25" i believe.

 

SCCA allows it for club racing (meaning any form of road racing they sanction). I'm not a very knowledgeable person here, just ensuring the OP knows there are differences between putting together a mild steel cage versus a chromoly one.

 

Im still waiting to hear about these differences. most everyone is gonna us e70s2 and not a chromoly filler so there is no post weld heat treating necessary. what else is different besides heat treating the weld, which isnt going to have to happen anyways?

 

Now that I look more closely at the OP's signature, I see that he is most certainly "qualified" in the area. I'll just go away now.

 

I'm definately what you would consider a new welder but I did take a Chassis and Fabrication class where we covered alot of these topics. Maybe it's already known or maybe not but from our lectures the main downside to the cost of CroMo was the fact of after it is completely welded the entire finished piece needs to be "baked" in a oven. This was do to is being more sensitive to becoming "brittle" after the welding. I don't have a degree in metalology or anything like that but from our lectures I had gathered that to do a CroMo cage "properly" the costs didnt justify for how long they safely last for the average person. I'm more than positive there will be conflicting views on this but I am just giving information based on what I was taught. Only bring this up because someone had asked about the "special process" so from what I understand the entire finished piece must be baked in a oven big enough to fit it. There-in alot of costs are incured. I understand that probably 95% of chroMo cages do not recieve this treatment but it is the "proper" method.

 

http://www.lincolnelectric.ca/knowle...hrome-moly.asp

i'll go with what a welder manufacturer suggests. they've probably done more research on it than anyone else.

 

Yes, but I have a few books by some very respected engineers in the field that explain why SS is a terrible idea. Not sure why Lincoln continues to call it "acceptable", but it isn't.
The funny thing is, when I took the advanced motorsport course, I discussed this with the instructor, and he agreed it should not be listed as an option.
When it's slow next year at work, I'm going to do some extensive testing with our resident experts in the lab under controlled conditions. I'll find out for sure if it's as bad as it sounds.
Otherwise, yes, Lincoln's advise is sound as far as filler options go.

 

Complete waste of time unless 4130 filler is used, and on thicker sections. (above .125")
That misinformation can cause more harm than good if somebody reads into it and tries to do their "own" heat treatment.

 

Yea, we were also told stories about people that try to accomplish this themselves with torches ect. I made sure to state that i'm a new welder and the information was purely out of the context on my classroom lectures. So you're saying that you only need to worry about the heat treatment if specific fill rod is used? Cause we were told that it's due to the actual ChroMo tubing that is heated from the weld not necessarily the weld joint itself.

 

There can be some minor hardening at the edge of the HAZ, but nothing to get worried about. The fact that NHRA is moving more into 4130, and all the small grassroots bodies for road racing,etc are moving away from it puzzles me. The average backyard MIG disaster is a safety hazard, and I wonder if that's why NHRA has gotten away from mild of the SFI stuff?

 

Use e70s2 or er80s-d2 filler rod. Don't worry about metallurgy and just weld it and take the concern for heat-treating out of the picture. They're both acceptable and I am a certified AWS D17.1 welder.

wierTech's link gives good explanation on the proper methods on how you should weld 4130 and also includes a weld schedule.

Good luck!

 

My only question persay that I have left is that we were taught once the heat treat process is done or completed the cage is only "legal" for a couple of years? Maybe a reason that Joe Shmoe doesnt use it in his ride? The cost of replacement would be to much to justify for the average Saturday night car.