Welding Cast Iron Tractor Hubs

Date 02-12-2009 01:29

Hey All

I am welding a cast iron hub of some sort from a tractor, replacing worn away material.

PROCESS: I am using TIG--E Ni-Ci rod with the flux knocked off--preheat in electric oven to 900F to burn the crap off--letting it cool to around 600F before taking it out to weld--DCEN--thoriated tungsten--Argon 25 cfh--Wirebrush before each weld--1" pass--then peening with a ball peen hammer ('cause it's fun)--welding on it until the temp cools to around 350F--then tossing it back in the oven to get it back up to around 600F again.

I then will need to repeat this like 50 times because I have to build up a lot of material and there are two hubs. This hub must be ancient because the wear on it is pretty bad.

So I have two questions

1) Are all of the above steps unnecessary? If you could help me streamline the process that would be appreciated. And of course the possibility that I am doing it all wrong :-) So far I have no cracking or bad pitting in the welds. The welds are a purty yellow when done, with the granular fan pattern that titanium welds have, I am assuming it is the graphite or somthing.

2) Should I be finishing off the final pass with a harder material since it was so worn to begin with? How hard is this E Ni-Ci rod?

Thanks for the help--let me know if you need more info!

By Johnyutah (**)

Date 02-12-2009 03:44

I'm assuming that there was no way the machine the hubs out then press in a new face for it to ride on out of something harder.

By DaveBoyer (*****)

Date 02-12-2009 04:01

If the parts really ARE cast iron, thaen what You are doing is probably necessairy.

If they are ductile iron, nodular iron, malleable iron or cast steel You could just weld them like they were steel with steel filler.

There are 2 catagories of cast iron rods - ones that leave a machinable deposit, and ones that don't. What does the surface You are restoring do? Does it need to be machined after welding? What made it wear in the first place?

By rebekah (**)

Date 02-13-2009 15:48

I admit to not knowing that much about this and I need to polish up my interrogation tools because I didn't get much information to start with.

I got more now though...

Apparently, they are bearing surfaces for the axel of a Bobcat. The area worn is where the bearing races ride and they are really worn out. The material is cast steel--an assumption based on use and strength required for that use. The area that is worn has lots of 1/4" wide grooves that have worn over the 2" length of the circumference I am repairing, the depth goes down to 1" in some places.

I've decided to cut off the stub and machine a new one and weld that on instead of welding up the old piece. I'll machine a hole in the hub and put a shoulder on the stub so that it is centered correctly and weld the inside and the outside for strength. I'll be using TIG again and just 70S rod.

How do you tell for sure which type of cast material it is? Spark test, file test, educated guess? Good to know that the process that I was using was appropriate for cast iron but I need to know how to tell the difference for future possibilities.

As always, I appreciate your help and expertise.

Thx

By rlitman (***)

Date 02-13-2009 16:13

A spark test is probably your best bet.
You would do best to compare the sparks against sparks from known steel and iron, because the grinding wheel and ambient lighting can greatly affect the outcome, but the general idea is that iron will have short sparkling sprays of redder sparks, and steel will have longer streams of yellower (to whitish) sparks.

Here's another description of the process:
http://www.ohiosteel.org/homepage/Spark%20Testing%20for%20Mystery%20Metals.pdf

By DaveBoyer (*****)

Date 02-14-2009 01:59

"Spark test, file test, educated guess? "
All the above, You might even spot drill a non critical area to see what the chips are like.

The hubs on a Bobcat take a lot of abuse due to the skid steering, weld accordingly.
Good luck with the repair.

By 803056

Date 02-14-2009 22:44

Bearings for low RPM applications can be cast iron. The graphite in the cast iron acts as a lubricant. The harder material will wear faster than the softer material because the grit embeds into the softer steel and abrades the harder material (cast iron).

You would be well advised to buy the Ni rod for GTAW that provides the proper chemistry rather than knocking the flux off the SMAW electrode. The flux is an important part of the make-up of the final weld chemistry. The electrode core provides some of the alloying constituents, but the flux also adds to the alloy composition.

You may want to consider torch welding the bearings with cast iron rod (actual a piece of cast iron) so that you retain the characteristics of the original cast iron bearing. I've had better luck repairing cast iron with the oxy-acetylene torch than with either SMAW or GTAW. As a matter of fact, I've repaired many cast iron parts welded by other welders that used SMAW and GTAW. The torch never failed me. I've have a printing press in town that has been in daily operation that I repaired about twenty years ago and it's still humming along very nicely.

Best regards - Al

By yesindeed Date 06-05-2009 23:43

see the great photos of the excellent job done here http://imageevent.com/gmachine/caseandterratracrepairs/terratracaxlerebuild