pipe crack (not crack pipe!)

Date 12-28-2007 15:19

Got a call from a rancher who broke his Hay Fork attachment on his tractor (for moving round hay bales), and wanted me to come repair it.

When I got out there, the Hay Fork had not bent any: It just snapped into. Nice, clean breaks, easy to weld back up.

The Hay Fork had been made from old 2.5" pipeline pipe, and it was easily 20 years old, and is always stored out in the weather. I welded it back up using 6011, DC+, at about 90 Amps - enough penetration to go almost through the pipe, and I didn't have to bother with cutting a V-groove in the 1/4" thick wall.

As I was going around the welds with my grinder using a wire brush, I got to noticing that the pipe was cracking close to where the root of the weld met the pipe.

This is the sort of thing I would expect from cast iron, not mild steel.

Did the pipe became brittle with age? What happened? Is there a technique to repairing this, or should we just make him another Hay Fork?

By hogan

Date 12-28-2007 15:27

it is most likely that the issue is the grade of pipe is unknown. the grade will determine the bes way to weld it. to the best of my knowledge, cs will not become brittle with age.

By MBSims

Date 12-28-2007 15:38

If it was pretty cold outside when it cracked, it may have just been a loss of fracture toughness and it cracked when he picked up the hay bales. It is also possible it was severely overloaded. A heavy load applied rapidly can cause ductile material to fail in a brittle manner. The toe of the weld is a point of stress concentration.

By welderdude (**)

Date 12-28-2007 23:46

You might do better by just making him a new fork. sometimes even if the weld is perfect, and the base metal is fine, the pipe will still crack when a load is put on it because the area right next to the weld (the heat affected zone or HAZ) isn't as strong as the rest of the pipe.

there is a way to solve that problem though. instead of making a nice square cut on the pipe joints, make them into an "S" shape so that they fit together to look like the u-joint on a truck but with curves. that way the HAZ isn't in a nice straight line for another crack to easily form.

we would fit joints on 6" x 6" x 1" square tubing like that at the drilling company. ofcourse, we wouldn't fit them with curved lines because it's square tubing, but with teeth that interlock on opposing sides. if the joint was just a straight and square joint w/ bevels the drill rig would easily snap it off down in the hole after hitting rocks.

you might not want to to through all that fitting if it's just gonna crack again though. if you can, find a nice piece of 2.5" Sch 80 pipe.

By DaveBoyer (*****)

Date 12-29-2007 06:40

Are You sure it was mild steel pipe? The nice cleen brake You described makes Me wonder. If the pipe is a heat treatable alloy You would need to pre & post heat treat and use a low hydrogen rod I would think.

By jp2welder (**)

Date 12-30-2007 00:36

I thought it was. Aren't pipelines in East Texas made with mild steel pipe?

Here's a cell phone pick - The crack is along the top of the weld's root.

Crappy, but better than nothing:

By JescoPressure (**)

Date 12-30-2007 06:15

maybe try cutting and sleeving the inside with a piece of round stock or smaller pipe and try lo/hi rod instead of cellulose rod

By 52lincoln (***)

Date 12-30-2007 09:54

that kinda looks like cast iron

By jp2welder (**)

Date 12-30-2007 14:00

I hadn't thought of that. I just assumed the pipe was old and rust pitted, but you know what happens whenever someone assumes!

So, how could I test the pipe to see if it is cast iron? Seems like I've heard of a file test. What does that do? What would I be looking for? Mild steel and cast iron both cut with a bastard file.

By DaveBoyer (*****)

Date 12-31-2007 03:59

You can test by grinding on it and comparing the sparks to materials You know. A die grinder will work better for this than a disc grinder. This is a pretty crude test, but with experience and a good selection of materials to compare against it can be fairly reliable. If it is a fabricated part it isn't cast iron. If it is a cast part it could be iron or steel.

By MBSims

Date 12-30-2007 18:15

If you were able to weld it with no preheat and mild steel electrode and it did not crack after welding, then it is probably not cast iron. With the crack being at the toe of the weld and your description of the break, I would suspect a fatigue failure from the heavy loading/unloading cycles of lifting bales. It would probably help to put some gussets on or beef the area up with a split section of larger size pipe.

By David Lee (*)

Date 12-30-2007 22:35

Looks like the "ole pot metal " as it called.
Your bead looks like you have some undercutting issue's, And possibly a weave effect.
Try a preheat of at least 150 deg. and multi pass the weld after filling the root opening.
If you had any type of a gap between your base metal you will need to increase the weld ( something has to hold it together).
You may have used a vertical progression as well, look's like a downward to me.
A gap, undercut, vertical down, no preheat. insufficent throat, incomplete penetration.
The reason I say IP is because with a wide root you will have problem's with BT ( blow through ) or some say ( burn through ).
This is limited on ASME.
But for a farm equip.
Anyhooh!!!