Drawing of steel tubes

[napoleon11090]

Hi,
I am new to this forum so apologies for any mistakes. We have received order for drawn tubes of 62.8 mm Inner diameter with 8 mm wall thickness and 12 feet length. Can we make such a tube by drawing an erw steel pipe through a draw bench? The customer has asked for inner surface smooth enough to be used in hydraulic pumps.

 

[boslab]

I think no matter how it would be honed in there?
Mark

 

[WizardOfBoz]

Most of the hydraulic cylinder material I see is honed or chrome-plated and honed. I understand that skiving and roller burnishing is also done. Much DOM tubing is mild steel (it has a weld seam, so it needs to be welded, and this and higher ductility favor mild steel). For hydraulic tube, one sometimes wants something stronger (hydraulic forces are enormous) and harder (to lessen wear). But 1018/1020/1026 is easier to draw. So the mild steel is used, and is hard chromed. If you look online, some DOM tubes are offered in "honed" or "suitable to hone" states.

So I don't think that you'll get the finish or dimensional accuracy needed for hydraulic tubes right off the mandrel. You'll have to hone.

Should be noted that once you weld an eye on one end and a flange for the gland* on the other, you likely have to hone the cylinder near the welded areas anyway because they will be undersized after the welding and cooling processes. It takes some expertise and touch to just hone the ends, leaving the middle of the tube untouched, with the original hone.

But if the customer wants hydraulic-ready tubes, you probably need to draw the tubes, then use a Sunnen or other hone machine to finish them.

*Probably you need to hone even if you turn and thread the end for a threaded gland fitting.

 

[hvnlymachining]

ERW tube is going to be difficult to get smooth enough to hone even after a subsequent draw. Depending on the quality of the draw you can accomplish of course, honing can require minutes to days of honing per tube. Not to mention a LOT of consumables in the form of hones. Even a small line the length of the tube can cause big trouble. You'll have to remember to calculate the amount of materials to be honed out of the ID before drawing, that alone may require some trial and error.

Some of the larger cylinder shops use HFS,CDS or DOM material and ream close to diameter before honing. Your customer should have a stated finish, at least ask, if burnished is ok you may be able to go that route. But burnishing in a pump tube sounds iffy. Either way you're going to need a long lathe or honing machine.

Is this by chance oilfield tube? If so, somebody may have set you up for trouble by not giving you all of the specs!

 

[WizardOfBoz]

Kurtis, at Cutting Edge Engineering in Queensland Australia, makes a lot of videos showing how he fixes hydraulic tubes, pistons, shafts and seals. A lot of cutting out the old tube, welding in a new tube, and then honing. Great videos, btw. Here's him using his new Sunnen hone on a cylinder.

I found the videos really interesting. The guy seems to know his stuff.

 

[napoleon11090]

ERW tube is going to be difficult to get smooth enough to hone even after a subsequent draw. Depending on the quality of the draw you can accomplish of course, honing can require minutes to days of honing per tube. Not to mention a LOT of consumables in the form of hones. Even a small line the length of the tube can cause big trouble. You'll have to remember to calculate the amount of materials to be honed out of the ID before drawing, that alone may require some trial and error.

Some of the larger cylinder shops use HFS,CDS or DOM material and ream close to diameter before honing. Your customer should have a stated finish, at least ask, if burnished is ok you may be able to go that route. But burnishing in a pump tube sounds iffy. Either way you're going to need a long lathe or honing machine.

Is this by chance oilfield tube? If so, somebody may have set you up for trouble by not giving you all of the specs!

Its not oilfield tube but meant for low end hydraulic jacks. The customer sells these jacks to ghana and the requirement is to create a tube good for lifting a few tons of loaded tractor trollies.

 

[john.k]

Jacks may be low end,but have 10,000 psi working pressure......I buy a fair bit of hydraulic tube ,and its always got proof test certificates available .......its solid drawn and has a mirror internal finish .............the internal finish is good enough for gun barrels.

 

[napoleon11090]

So,
A tube good for hydraulic jacks can be made by drawing? If yes, then what kind of drawing process will give the best result?

Jacks may be low end,but have 10,000 psi working pressure......I buy a fair bit of hydraulic tube ,and its always got proof test certificates available .......its solid drawn and has a mirror internal finish .............the internal finish is good enough for gun barrels.