Welding cast iron

[kunkernator]

Tomorrow I need to weld a crack in a motor mount that is made of cast iron. I just want to make sure I am going about this correctly. My welding skills are up to par, but I have never welded cast iron before.

I have decided to stick weld it. I have already prepped by cutting "V's" in the cracks. I will start by pre-heating the piece with an oxy-acet torch slowly, and then weld the crack. Afterward I am planning to put the piece directly into a bucket of sand to provide a slow cooling process.

Does this process seem acceptable? Any additions?
I am also considering "stop drilling" the cracks before welding. Is this a good idea, or even necessary?

Thanks guys!

 

[mopar65]

drill the ends of the cracks is good.i weld just short sections at a time.are you going to use nickel rod? when i get done welding i put the piece in front of my blast heater to cool it off.

 

[56rpm]

Make sure you keep the hot welded part away from any wind until it has cooled.

 

[kunkernator]

drill the ends of the cracks is good.i weld just short sections at a time.are you going to use nickel rod? when i get done welding i put the piece in front of my blast heater to cool it off.

I honestly do not know what kind of rod it is. I am going over to a buddy's place to do it, and I know he only has one type of rod. Is it a huge deal if it is not a specific type?

I also like the idea of using a blast heater, but I need to transport it back to my house, so that is why I am planning to use a bucket of sand.

 

[64Trvlr]

When I weld cast iron I drill the ends of the crack(s), vee the crack with a grinder, pre heat with an oven or rosebud, weld with nickel rod, peen the hell out of it, then cool slowly in either an oven or pack it in hot sand.

If it was me I'd buy some nickel rod and use it to weld your piece otherwise it will probably not work for you.

If you have any oxy/acet skill you can also braze it.

 

[sbgmetaldesign]

Hot sand is critical.

Sand at room temperature will just cool it.

Here is a pretty good video from Lincoln on welding cast iron.

 

[dieselgarage]

Follow the good suggestions in this post on the welding part. I would weld in and bury it in a box of sand until it's cool.

 

[readhead]

Go to the welding supply and pick up some nickel rod. Read the instructions. All good tips here. Absolutely drill the ends or you will keep chasing the crack.

 

[Twitchr]

Nickel rod can be purchased at TSC or Norther Tool / Farm Fleet. Its about 25 bucks for 10 sticks when I bought it. For a motor mount, I wouldn't skimp, kind of alot of money riding on that functioning.

 

[nicholasbailey1993]

I don't know if anyone else does this, but i have found that a 6011 rod works about the same as a nickel rod on cast iron. I've never really welded anything that has a real big stress load with it, but my dad welded up a crack in an engine block and it's held for over 10 yrs.

 

[kald]

I have some NI55 rods I picked up on sale some years ago and have never used them. I have never had confidence in welding, especially since it seems to be iffy at best with welders much better than I am.

I have always defaulted to brazing with pretty good success.

 

[kevin47]

Anything but Ni rod will pick up carbon from cast iron...Making machining impossible...Doesn't grind so easy either...

 

[MoonRise]

Anything but Ni rod will pick up carbon from cast iron...Making machining impossible...Doesn't grind so easy either...

Not just the machining aspect ...

by putting molten mild steel (low carbon, as pretty much most 'common' welding filler is all low-carbon mild steel stuff such as 6010, 6013, 7018, ER70S-6, etc) into the welding puddle with the very high carbon cast iron, you turned that formerly low-carbon steel into a very-high carbon steel.

Which is hard as heck (hence the very difficult machining).

As well as being brittle as heck. Which often leads to the dreaded sound of "Ting!" as the formerly hot metal cools and contracts and then cracks.

My approach is to weld it hot-hot-hot, use nickle filler (even though it does cost $$$$), and cool it s-l-o-w-l-y.

Hot as in really-really-really hot, full-up red hot (1000-1200F).

Weld it up.

Heat it back up.

Let it cool so that it takes 12+ hours to cool back down to room temperature (cooling rate around 100F per hour). Yeah, s-l-o-w cooling. You don't want the weld or the rest of the cast iron to crack.

http://www.lincolnelectric.com/en-us/support/welding-how-to/pages/cast-iron-category.aspx

 

[budss396]

I use my air hammer with a dull punch to peen the weld as I go, I weld about 1/4 to 3/8 of an inch and then peen it with a hammer. post heat is very important to prevent cracking.

 

[Bondo]

I use my air hammer with a dull punch to peen the weld as I go, I weld about 1/4 to 3/8 of an inch and then peen it with a hammer. post heat is very important to prevent cracking.

Ayuh,... I agree, really short welds, 'n lots of 'em...

Ya oughta pre-heat yer box of sand in the ole lady's oven, good 'n hot, before ya put the piece in it though...

 

[kevin47]

Moonrise...? Sounds like you been there done that...It's gotta be one of the least fun stuff to weld...I just hate the whole idea...Somebody tell him about "Stitching" engine block cracks...Much better way to go IMO...

 

[djkeev]

For cooling process like that, long term, I've access to an electric ceramic kiln that you program to slowly back off the heat as the item cools, that would be ideal.

Dave

 

[Kevin54]

Just out of curiosity, what is the motor mount on that it is made from Cast Iron?

 

[03protege]

Vee cut out the crack, if you can see the ends of the crack (didn;t go through the whole part) you need to drill as mentioned.

Pre heating wouldn't hurt, but focus needs to be taken on cooling as mentioned above.

 

[brownbagg]

wouldnt it be cheaper to buy a new motor mount

 

[yhprum]

Brazing seem the safest way to go. It will be strong, and the chance of craking seems less. There is a thread on here called brazing the wonder glue of something like that.

 

[Doug Arthurs]

I usually preheat to 800f. Weld with nickel rod and then leave it in my shop Woodstock overnight. Hmm I guess I have never welded cast iron on the summer.

 

[NASTYZEN]

Brazing seem the safest way to go. It will be strong, and the chance of craking seems less. There is a thread on here called brazing the wonder glue of something like that.

I second that.
The thread is Brazing 101, the wonder glue.
I prefer brazing things that vibrate like engine mounts and things. Very tough stuff. And it's cheap and versatile.

Here is the link.
http://www.garagejournal.com/forum/showthread.php?t=120122

 

[joe49]

Hi temp flux and cast iron brazing rods.

 

[bgarrett]

I have been using a Henrob to weld cast for 14 years. Quick easy, no pre heat needed, can be drilled, tapped

 

[Jason280]

Just to be curious, what's the point of hammering/peening the weld aftwerwards?

Also, what are your options when you don't have a realistic method of slow cooling the part after welding? Reason I ask, I'm building a Ford 8.8 rearend to go in a '94 Jeep YJ, and will be welding the axle tubes to the pumpkin. Of course, the pumpkins on these are cast, whereas the tubes are regular steel. Heating with a rosebud isn't an issue, but controlling the cooling will be a problem.

Not trying to hijack the thread, but it seems to fit in with the discussion.

 

[64Trvlr]

Just to be curious, what's the point of hammering/peening the weld aftwerwards?

Stress relieving the weld.

 

[Bondo]

Just to be curious, what's the point of hammering/peening the weld aftwerwards?

Also, what are your options when you don't have a realistic method of slow cooling the part after welding? Reason I ask, I'm building a Ford 8.8 rearend to go in a '94 Jeep YJ, and will be welding the axle tubes to the pumpkin. Of course, the pumpkins on these are cast, whereas the tubes are regular steel. Heating with a rosebud isn't an issue, but controlling the cooling will be a problem.

Not trying to hijack the thread, but it seems to fit in with the discussion.

Ayuh,... That's cast Steel, not cast Iron... Very different materials...

 

[R.Anderson]

hammering/peening a weld

when a weld cools it shrinks which causes cracks and or distortion.
peening expands the weld to fill in for the shrinkage. Think Blacksmithing, hammer a piece of metal and it widens.