Welding of ports onto Hydraulic cylinder tube

[Fredster]

Hi Everyone.
So forgive me ahead of time for asking about welding procedures. I'm a general machinist operating manual machines. Don't have a lot of experience welding and our welder isn't really open to any ideas I have. Somewhat justified with what I know on welding.
Here's my situation.
We build cylinders for a machine we build. It's a large haybale stacker. Diameters of 2 1/2" - 5 1/2" cylinder tubes.. All 1/4" pre-honed tubing. Distortion of the tube being the issue when welding the port on. We have no engineers here. Just some guys with creative thinking....
Procedure has been to run a tig weld and then follow with a mig weld. The weld is anywhere from a 1 1/2" - 2 1/4" back from the front of the tube. The tube distorts approximately +.015 at the port and of course goes about a -.012 90 degrees to the port. It was recommended to me to carefully squeeze the tube back to a more round diameter in the press. I've had pretty good success at this. Generally get it within .002 -.004 round. But always have to use a flapper wheel heavily to clean up the tight spot at the port area. I've got a batch of approximately 100 cylinders to do. I'd rather not have to do this. I recommended going to just one weld. Well.... he says I'm trying to reinvent the wheel... So after some fussing he says he'll try it... But only with a tig weld. I don't know why he doesn't want to mig it. He's using 3/32" tungsten but says he thinks he should go 3/16". I'm thinking geez..... Aren't you going to be pouring in a bunch of heat with that size??? The whole idea from me is to get a good strong weld without putting so much heat into the part and distorting it... So again... I'm not a welder. But looking to you guys for tips that I can somehow get this guy to accept and try. My philosophy on life, and work.... is always be teachable. There's always someone with more experience and skill that you can learn from. My pops taught me this. I was an automotive machinist for 23 years and have now been a general machinist for 18years. I'm still learning... Thanks for any help.

 

[Garwood]

It should not be TIG welded. MIG or dual shield weld it correctly and done.

A flap wheel in a grinder for deburring is fine, but if the tube is distorted after straightening you should run a rigid hone through to make sure you're good.

 

[Rob F.]

The weldor probably had trouble in the past with pinhole leaks with just the mig so the tig is just insurance against leaks. I dont think the little tig will change the warpage weather it is there or not, the bigger mig weld will do what it is going to do irregardless of the little tig bead. I would do dual shield by itself and not look back.
You also might try to have some sort of clamp to pre-warp the cylinder before welding so the weld will bring it bak to round. It will probably still need to honed no matter what you do.

 

[john.k]

The only way to avoid shrinkage is preheat .....which may be impractical with a big cylinder .

 

[memphisjed]

“Why tig if you can mig”? Is always a good start. Most cylinders I see have been dual shield mig or submerged arc.
Tig warps metal- a lot.
I am becoming a fan of tig tacks then mig welding. You do not have the tack from mig to interrupt your weld.

 

[trevj]

Not to put too fine a point on it, but why are the ports in a part of the tube where warpage might be of concern?

Almost all the cylinders on the farm equipment I use, have the ports located in places the seals never reach.

 

[Rob F.]

Not to put too fine a point on it, but why are the ports in a part of the tube where warpage might be of concern?

Almost all the cylinders on the farm equipment I use, have the ports located in places the seals never reach.

Yes, the seals cant go over openings for ports, they wont seal anymore... but welding the port (or supply tube) near the end of the cyl will cause it to be out of round and the end cap may not fit & seal correctly.

 

[Fredster]

Not to put too fine a point on it, but why are the ports in a part of the tube where warpage might be of concern?

Almost all the cylinders on the farm equipment I use, have the ports located in places the seals never reach.

True. the seals are not sealing in that area. The cylinder bore distorts enough where the piston diameter won't slide through. The piston has .008 clearance to the intended bore size. The gland seal is further to the front of the tube and that area does not get distorted compared to back at the port.

 

[Fredster]

It should not be TIG welded. MIG or dual shield weld it correctly and done.

A flap wheel in a grinder for deburring is fine, but if the tube is distorted after straightening you should run a rigid hone through to make sure you're good.

Is the reason you say not to TIG because of the heat? Or is there another thing to be aware of... Just trying to be prepared with a good answer..

 

[Garwood]

Yes, TIG puts heat in over a longer time.

 

[bigjon61]

Yes, the seals cant go over openings for ports, they wont seal anymore... but welding the port (or supply tube) near the end of the cyl will cause it to be out of round and the end cap may not fit & seal correctly.

....Weld the end cap on first?

 

[mattthemuppet]

can you pre-squeeze the tube before welding? If it's 0.015" out of round, squish it the same about in the opposite direction. Then the weld might pull it round, maybe.

 

[Fredster]

....Weld the end cap on first?

The rear port doesn't have the same issue. The piston doesn't have to travel past it. It's up front where the piston has to slide through.

 

[Fredster]

can you pre-squeeze the tube before welding? If it's 0.015" out of round, squish it the same about in the opposite direction. Then the weld might pull it round, maybe.

I've thought of that also. Just haven't had the courage to try it yet.... But it may happen....

 

[Mr. Atoz]

We make many thousands of hydraulic cylinders every year. You will have warpage no matter what. The outside diameter of the pistons we use are .045 smaller than the honed bore of the cylinder. We have been making them like that for decades with no problem. What you need is to redesign your piston. Our cylinders can operate up to 3000 p.s.i.

 

[DrHook]

The only 2 things guaranteed to happen on every weld is 1- it will get hot, and 2- it will warp. Tig is the only way to guarantee no leaks, (IMO) but it will put more heat into the part (in a smaller area) than mig, so a CORRECTLY done mig weld would likely warp it less. However, as others have said, put something inside the tube to push it opposite the warpage before welding, and it should pop back round. May take some trial and error, and or preheat, too.

 

[dlaw]

Hi Everyone.
So forgive me ahead of time for asking about welding procedures. I'm a general machinist operating manual machines. Don't have a lot of experience welding and our welder isn't really open to any ideas I have. Somewhat justified with what I know on welding.
Here's my situation.
We build cylinders for a machine we build. It's a large haybale stacker. Diameters of 2 1/2" - 5 1/2" cylinder tubes.. All 1/4" pre-honed tubing. Distortion of the tube being the issue when welding the port on. We have no engineers here. Just some guys with creative thinking....
Procedure has been to run a tig weld and then follow with a mig weld. The weld is anywhere from a 1 1/2" - 2 1/4" back from the front of the tube. The tube distorts approximately +.015 at the port and of course goes about a -.012 90 degrees to the port. It was recommended to me to carefully squeeze the tube back to a more round diameter in the press. I've had pretty good success at this. Generally get it within .002 -.004 round. But always have to use a flapper wheel heavily to clean up the tight spot at the port area. I've got a batch of approximately 100 cylinders to do. I'd rather not have to do this. I recommended going to just one weld. Well.... he says I'm trying to reinvent the wheel... So after some fussing he says he'll try it... But only with a tig weld. I don't know why he doesn't want to mig it. He's using 3/32" tungsten but says he thinks he should go 3/16". I'm thinking geez..... Aren't you going to be pouring in a bunch of heat with that size??? The whole idea from me is to get a good strong weld without putting so much heat into the part and distorting it... So again... I'm not a welder. But looking to you guys for tips that I can somehow get this guy to accept and try. My philosophy on life, and work.... is always be teachable. There's always someone with more experience and skill that you can learn from. My pops taught me this. I was an automotive machinist for 23 years and have now been a general machinist for 18years. I'm still learning... Thanks for any help.

 

[david n]

MIG and be done with it..........dual shield wire likes clean oil/grease free metal............for some reason it likes to pin hole more than solid wire.

 

[dlaw]

Given that I have not fabricated any hydraulic cylinders.
Redesign of the piston may be the best way to get around this issue as Mr.Atoz said.
trevj asked about the location of the ports in an area where welding will cause distortion.

I would ask if the ports could be moved to the cylinder cap? which would eliminate
cylinder distortion & the need for remedial work.
My concern is support of the fabrication process in the future. If welding shops are changed it may cause your straightening process to fail.

 

[Fredster]

Given that I have not fabricated any hydraulic cylinders.
Redesign of the piston may be the best way to get around this issue as Mr.Atoz said.
trevj asked about the location of the ports in an area where welding will cause distortion.

I would ask if the ports could be moved to the cylinder cap? which would eliminate
cylinder distortion & the need for remedial work.
My concern is support of the fabrication process in the future. If welding shops are changed it may cause your straightening process to fail.

Can't move the port to cylinder cap. End of tube is threaded and a threaded end cap is then spun on retaining the gland. The port sits back behind the threads on the tube.