7018 use on cast iron

[gwdixon]

Boy, going through the posts and searching the Internet sure has conflicting advice on using 7018 for cast iron!

An old Mott flail mower that I sold to my neighbor had a Zerk guard on the roller snap at the single mounting hole. It is about 6" long and 2" wide.

The break looks to be the grainy structure of cast iron but it could be cast steel. It is not a load-bearing or vital piece for the operation of the implement. In fact, I took off the remainder of the broken piece and told him to get back to mowing and I'd come up with something for a repair. (Photos soon.)

So now I'm looking for you experts to bail me out.

I want to avoid brazing and he wants to avoid a high dollar repair rod (nickel, Certanium, and the like). The piece does run in the dirt on occasion.

So here is my plan and criticism is welcomed:

>Bevel the broken edges on both sides.
>Tack the two pieces together.
>Heat the heck out of it with a propane weed torch.
>Weld 1/2" to 3/4" lengths of 3/32" 7018 at 80 amps and immediately peen with an air powered needle scaler.
>Repeat on both sides until the bevels are filled.
>Bury the finished piece in a galvanized bucket of sand to cool.
>Grind the mounting side weld flat to allow installation.

Another issue with the piece is that a small chunk was lost when the break happened. Can that be filled with 7018 using the method above?

Thanks ahead for feedback.


EDIT: Forgot to mention that DC stick welding is my preferred method. Well, I do have O/A and a 110 Hobart flux-core.

 

[r8nger]

Nickel rod isn't that much, it will be brittle and easily break off if you use. 7018 .Just my thoughts and previous experiences

 

[Texasmark]

I have some cast iron rods that I bought years ago. Don't recall them being all that expensive....wouldn't have been able to afford them. However, I never used them so I can't attest to their functionality. Can't help you with 7018 even though that in the 3/32 is my rod of choice for most all my stick work.

Mark

 

[Shield Arc]

I use to get stuck repairing cast steel pile driving equipment. Started out using Super Missileweld, then went to 312-Stainless steel, then to 7018.
If you have cast iron, or cast steel I'd pre-heat to at least 300-degrees, and do everything you listed above.
Super Missileweld | The Harris Products Group

 

[gwdixon]

Thanks for the replies. It looks like I'd only need one, or maybe two, of the Ni99 rods but they run about $3 each nowadays and are sold in packs of 10 (at Tractor Supply).

Thanks ShieldArc, at least someone has done such a repair with 7018. Not that my skills approach yours at all but it gives me some confidence to give the project a try.:thumbsup:

Here are photos mentioned in the OP:
View attachment 373143
View attachment 373144
View attachment 373145
View attachment 373146

 

[k0ua]

Did you see the repair that Chucke2009 did on his cast iron vise with 7018?

Stick Welding Cast Iron with 7018 - YouTube

 

[Shield Arc]

No, I've never used 7018 to repair cast IRON, only cast STEEL!

 

[gwdixon]

No, I've never used 7018 to repair cast IRON, only cast STEEL!

C'mon, you've done it ALL. You're just holding back like always. :laughing:

 

[gwdixon]

Did you see the repair that Chucke2009 did on his cast iron vise with 7018?

Stick Welding Cast Iron with 7018 - YouTube

Yes, I've watched that video a couple of times. He put plenty of torque on that vice for just welding around the outside of the main shaft (whatever it is called).

It seems he did not know for sure if it was cast steel or cast iron or maybe that comment was in the discussion section on YouTube.

 

[k0ua]

Here is another idea using TIG with some kind of "magic fill rod" for cast iron

How to Weld Cast Iron WITHOUT Pre-Heating | TIG Time - YouTube

 

[rankrank1]

Not to cloud this issue but I have had very good luck on welding cast implement parts like you pictured with 0.030 flux core E71T-11 wire (Hobart 21B) ran in a Lincoln SP-135P which is a 115 volt wire feeder. So your little 115volt Hobart wire feeder is also a possibility.

I used: No preheat, No slow cool downs, no excessive peening other than to remove slag between weld build up layers. Really did nothing special at all and some of my parts have taken remarkable stressful beatings without failure.

 

[Arc weld]

Should be easy enough to determine if it's cast steel or cast iron. You could do a grind test or even see if it will cut with a cutting torch. Cast steel cuts with a torch. Could probably even ask Alamo that bought Mott. Cast steel can be welded with 7018 without any problems. As kind of a last resort 7018 can be used on cast iron. The problem is it broke through a bolt hole and needs 100% penetration and a good repair so it doesn't break again at the bolt hole. If you determine it is cast steel, it can be built up with 7018 no problem. If it's cast iron, why wouldn't you want to braze it?

 

[gwdixon]

Should be easy enough to determine if it's cast steel or cast iron. You could do a grind test or even see if it will cut with a cutting torch. Cast steel cuts with a torch. Could probably even ask Alamo that bought Mott. Cast steel can be welded with 7018 without any problems. As kind of a last resort 7018 can be used on cast iron. The problem is it broke through a bolt hole and needs 100% penetration and a good repair so it doesn't break again at the bolt hole. If you determine it is cast steel, it can be built up with 7018 no problem. If it's cast iron, why wouldn't you want to braze it?

I'm still gathering information and techniques before taking on this little project. The responses so far have been a big help. Again, thanks to all for contributing.

If I understand correctly, brazing cast iron is preferred because the brazing material is comparatively soft and malleable so cracking is not an issue. The concern is that this piece runs in the dirt and is impacted occasionally so I'd like it to be rock solid, although not brittle. That may not be possible.

I have brazed a little and have all the materials to do such a repair but lack confidence in the technique for this application. For example, it would seem that V-ing out the crack with a grinder is not necessary. Just clean the surfaces and allow capillary action to draw the molten brass into the crack. With the unit hot enough the brass should be able to make a 100% penetration. Or not?

The other issue with brazing is the missing piece of the unit. It is not a large chunk but is at the mounting hole so would structurally need something there to return the unit to OEM strength.

Apparently, the first thing to do is to determine if it is cast iron or cast steel and then go from there. Cast iron gives off red sparks according to some sources. The piece is not large enough to test it using a cutting torch without losing material.

Obviously, the repair method is "under development".

 

[Gary Fowler]

I have welded cast iron and cast steel with 7018 with pretty good success. The problem with cast iron is that it tends to crack when cooling if it is an intricate shape (cast iron heater grates for instance) and I haven't had good success with that but solid pieces like you have work pretty well. 300F preheat and weld with 7018 should work. Do your build up area first.

 

[CNC Dan]

I would just make another part out of steel. Add hardfacing if it needs it.

 

[Mark @ Everlast]

Just use a 6011 if you are going to weld it like that. When I first started to weld decorative iron, which combines steel and cast iron, I called the company that sold me the decorative items and they told me that they used and recommended 6011 due to the cellulose in the flux is compatable with the carbon in the weld. Of course a nickel cast rod is best...but the cost differential is great! It definitely won't crack as bad as the 7018 on the decorative stuff. It still isn't meant to hang on either, but for tacking items and making short welds it works fine. Brazing your item would be best, simplest and an ideal repair method here...but that isn't in the works it seems.

 

[ThomasH]

The problem with cast iron is that when you weld it, there is a really good chance that there will be heat related molecular changes in the material right around the weld, where things like carbide and graphite will separate out of the base metal. You can see this if you try to cut through the material with a hacksaw after welding it, it's as if the area is case hardened. The surface of the material hardens and becomes more brittle, so it cracks much more easily. Even if it doesn't crack immediately from heat caused differential stresses when the weld cools, there is a much higher chance of it cracking when stressed later.

One of the reasons for brazing is that much less heat is used, and it is typically not concentrated on the immediate spot that is being worked to the degree that an arc weld operation concentrates heat. So with brazing, you heat the whole area of the repair to at least 300 degrees, then play the torch on where you want to deposit material, dip the rod in flux (or use pre-fluxed rod) and heat to the point of the rod melting and sticking to the cast iron.

One of the challenges of brazing or welding cast iron is that the base metal typically also has at least some junk in it, and a few things I have welded with nickel-rod in the past had *lots* of non-iron ingredients (nickle, lead, etc.) which start bubbling up to the surface when you started melting the base metal. This problem, plus any oil that has soaked into the casting will cause you grief. Cast iron is a bit like a sponge, and absorbs a surprising amount of oil, diesel fuel, etc. So I have had to bake a couple of smaller items that I needed to braze, and then go over them with some flap wheels to clean up the surface, before I have brazed them. It wasn't about heating them to do the brazing, it was about burning out the junk, so much to my wife's consternation I broiled them in the oven for several hours (after opening some windows) to get rid of the junk. I have seen others throw pieces in a wood stove for several hours to do the same thing.

So after baking the casting, abrading it with abrasives to clean the surface, I have had 100% success with brazing cast iron peices, and then just throwing a welding blanket folded up to 4 thicknesses over it to slow down the cooling a bit. The silicone bronze rods I have used are a pretty hard braze material when they cool, so it's not as if they will easily wear down with a dirt contact attachment. I am sure it would wear faster than iron or steel would, especially if you are constantly running into rock, but it's not a soft repair such as soldering might be.

Just something to consider...

 

[Tractor Seabee]

Back in the 60s there was an "Eutectic" bronze alloy arc rod we used for repairing cast iron plus a lot of things like joining copper/brass/cupro-nickle to steel and SS. It was a great tool in the box for industrial repairs and even some fabrications. And it was easy to learn the technique. They were bought out by a French company, they are on the internet. A call to them may reveal they still make something. Searching the net this popped up http://www.stoodyind.com/Catalogs/FISC/05catpg353.pdf
The WELCO 223 sounds like what we did. Expensive, yes but what bis the project worth. Then you will be ready for anything with the lefty over.

Ron

 

[Arc weld]

You need to figure what material it is before you go any further. If it's cast steel, weld it with 7018 and be done with it. If it's cast iron, poses more potential problems.

 

[gwdixon]

Update:

A spark test seemed to indicate that the piece is cast steel (I hope!). So I "V'ed" out the break from both sides to get a 100% weld.

Then heated it with a propane grass burner for about 10 minutes but it did not glow red. Used 3/32" 7018 at 80A for about an inch and immediately hit it with a needle scaler. Repeat, repeat, repeat.

The missing piece was filled with 1/8" 7018 at 125A but was a bit dicey (too hot). So back to 3/32" to finish.

The wear side was filled a bit with 3/32" 7018 and then topped with 5/32" Stoody 31 hardfacing at 150A (a bit cold for this rod).

The piece is currently in a bucket of sand for overnight cooling. Maybe it will come out in one piece tomorrow.

Then it will be on to grinding the critical surfaces that mate with flail mower. Since it doesn't have to be pretty the other welds may be left as is...a bit built up.

Update tomorrow. Thanks for all of the suggestions. Maybe down the line another member can benefit from this discussion as much as I have.