Welding 4130 tubes .156 wall thickness pre/post heat...

[iliyahamovic]

Does anybody have experience with 4130 chromoly tubing?
I'm going to weld chassis out of .156 wall thickness and I'm wondering if pre and post heating is crucial?
I found on Internet that chromoly tube that are thicker then .120 should be pre and post heated... Thank you for any input...

[Cgotto6]

There is a ton to know to weld chromo properly. If you are asking this I would recommend you get a professional to weld this or use mild steel instead. Many racing bodies are not even certifying chromo chassis nowadays due to the high complexity and very high chance of improper welding. Especially if you have no welding certs, which seems may be the case.

[iliyahamovic]

There is a ton to know to weld chromo properly. If you are asking this I would recommend you get a professional to weld this or use mild steel instead. Many racing bodies are not even certifying chromo chassis nowadays due to the high complexity and very high chance of improper welding. Especially if you have no welding certs, which seems may be the case.

Thank you for kind reply.
I've been tig welding for few years now so I think I can do it, ain't rocket science right? Just tube welding that need some attention with applying heat.

This is supposed to be support forum not discourage forum.
And btw I'm stick,mig and tig certified welder.

Anybody else with some helpful tips? Thank you.

[Cgotto6]

Just saying that no local sanctioning bodies in my area will approve a chromo chassis unless engineering and a reputable fabrication shop can prove the entire chassis has been normalized post welding. Aka only very top dollar teams can do it. Besides pretty much every form of racing now days has weights that everybody ballasts up to, so why even hassle/risk with chromo when mild is cheap and easy. But good luck if you decide to go for it. What application, sanctioning body, and region are you building it for?

And btw, this is a support forum. Supporting you so you don't end up with a few grand a scrap when you don't pass tech. Figured since you had to look on the internets to learn about basic characteristics of chromoly it was over your head.

[awill4x4]

Any particular reason for using .156"?
It seems a very thick tube wall thickness especially when you are using Cr/MO.
As a comparison, the Sprintcar chassis' we repair, the tube thicknesses for the main top rails are only .095" and the rest of the chassis varies from .083", .065" and .049".
The main reason to use 4130 over CDW tubing is for the weight benefit where you can use thinner tubing to do the same work.
Don't be put of using 4130, it's just a nice high grade steel and it's really easy to weld.
Lots of guys post negative info regarding 4130 without any experience in it.
We've got lots of experience with it and we don't have any problems with welding it. You can even Mig weld it if you want to, LW1 Mig wire at ER70 S6 is well within the acceptable range of welding wires.
I often cut down Mig wire for some really small welds when required.
Regards Andrew from Oz.

[Jigantor]

I have TIG welded a fair few CrMO bike frames and have read thousands of pages on the subject. I have even contacted and had a tour of a heat treating works here in Brisbane that has an oven large enough to treat a semitrailer to futher my knowledge.
I am no expert on the subject but know quite alot.
Before any help can be given you must explain the application completely.

Ji

[Cgotto6]

You will notice he said an oven large enough to fit a semi trailer into...so do you have an over to heat treat the *entire* chassis after fab? That's the critical part here.

[iliyahamovic]

Any particular reason for using .156"?
It seems a very thick tube wall thickness especially when you are using Cr/MO.
As a comparison, the Sprintcar chassis' we repair, the tube thicknesses for the main top rails are only .095" and the rest of the chassis varies from .083", .065" and .049".
The main reason to use 4130 over CDW tubing is for the weight benefit where you can use thinner tubing to do the same work.
Don't be put of using 4130, it's just a nice high grade steel and it's really easy to weld.
Lots of guys post negative info regarding 4130 without any experience in it.
We've got lots of experience with it and we don't have any problems with welding it. You can even Mig weld it if you want to, LW1 Mig wire at ER70 S6 is well within the acceptable range of welding wires.
I often cut down Mig wire for some really small welds when required.
Regards Andrew from Oz.

Andrew thank you for reply and tips...
Main reason I'm using chromoly and thick as .156 is...
I'm building rigid frames for my choppers thru the years now, I used to use low carbon tubing and never head problems with cracking, now, here in NYC roads are notorious with pot holes and bad condition so our bikes takes lots of beating and since frames are rigid not suspended it happens sometimes that frame cracks...
For example I have customer comes to my shop with $70.000 Jesse James West Coast Chopper cracked on several places after bikes has been ridden in NYC for 5 years...
As well not only safety is what I'm concern but, these bikes cost lots of money to be build, paint job or exotic plating like nickel or chrome cost lots of money to do on frame, so if frame cracks there's lots of work and money to be invested.
So this is the reason why I went with with thick chromoly, these bikes don't need to be light since they have lots of torque and are not performance vehicles so little bit overkill in chromoly tubing can safe lots of money and trouble down the road.
And to mention that if these bikes are ridden in not such a harsh road conditions they would be fine and free of cracks for a lifetime.

Thank you, Iliya from Steelborn Choppers NYC.

[Cgotto6]

Hey I'm sorry for my posts. What I was saying does not apply to what your talking about. I saw your avatar and figured you must be talking about a race car... Don't usually hear a bike frame being referred to as a chassis. My mistake.

[iliyahamovic]

Hey I'm sorry for my posts. What I was saying does not apply to what your talking about. I saw your avatar and figured you must be talking about a race car... Don't usually hear a bike frame being referred to as a chassis. My mistake.

No worries, I should be more clear in my posts as well...

[gocirino]

This might help....


http://www.netwelding.com/Welding%204130.htm

[Jigantor]

No one here is going to tell you what you need to do. You are your own boss. Members will give you street names and suggest a path of travel but you will need to find your own way to your destination. The legal answer when the product you sell can hurt or kill a client or a third part is "I recommend you hire an engineer to calculate the stresses involved and recommend a suitable solution"
That said some times you have to have done the work first to know what questions to ask.

We all need more information before any real suggestions can be forwarded. First are the cracks in the same place on the chassis?
Is the cracking due to fatigue, catastrophic failure or temperature?
Have you got any photographs of the cracks to post so we can take a look?

I bike frames I have repaired have been dirt bike frames not street bikes. The loads transfer through the tyres up the shocks and into the frame from jumps and so forth. Damage usually occurs when flat landing off a jump, the shocks and forks bottom out leaving only the frame to flex. If the load is very high catastrophic failure is the end result, if the load is less, the resulting frame flexing will be added to the fatigue cycles. The other issue could be cold weather. If the bike was left outside on a freezing night the metal could shatter on the next pot hole.

Being a hard tail and a chopper the forces transfer in different vectors than a dirt bike. The tyres and frame make up the suspension for the frame. Frame flex can be solved by increasing the depth of chassis members not so much by wall thickness of tube. It can also be reduced by adding stiffening members like gusset plates or cross tubes. If you solve the cracking problem by increasing frame size the frame may be too stiff to ride with comfort as frame flex is required. There is no suspension as we know it in F1 cars. The engineers have worked out how much load it takes to flex the steering arms 25mm and that is the suspension. This saves weight but if they increased the steering arms to eliminate the flex the drivers would not be able to complete 60 laps.

Ji

[aametalmaster]

I know this info isn't for a bike or car frame per say but when i worked in the refinery some pipe had to be PWHT post weld heat treated. The pipes were already welded together 100's of feet long so a big oven is out. They had comapnies come in the specialized in heat treating. They brought in trailers of items. They wrapped the pipe with long firecracker looking things and wrapped with white insulation. Then everything was tied together to some welder looking machines where the temps were raised and lowered by computers. Heated so high then cooled slow taking 24 hours for some. Learned some watching but most of it was off limits. I did see the pipes glowing red hot during the high heat cycles...Bob

[Cgotto6]

jigantor, f1 cars do have suspension. Not that it has anything to do with the op's question . Not to be rude, just an f1 fanatic.

This is just ferrari's current set up. Has springs and dampers, like always, just in a new layout. http://www.formula1.com/news/technical/2012/0/937.html