Cast Iron

[MasseyWV]

After reading about tractors that have broke in half at or near the bell housing, which is typically made of cast iron or some other unobtanium material, I couldn't help but wonder why it is used instead of steel.

Cast iron is a very strong metal but it is brittle and can crack or break without warning, as evidenced by some tractors breaking in half. Also, cast iron is difficult to weld, thus making repairs impractiical or impossible.

I am no metallurgist but it seems to me that steel would be a much better material to use. Steel is very strong, more flexible, and can be easily welded, thus making repairs much easier.

Engine blocks I can understand, but why do tractor manufacturers use cast iron instead of steel for bellhousings, axles, and other components?

 

[kebo]

Steel would probably be better than cast iron, but it would have to be mostly machined to form up such intricate parts such as a transmission tunnel or a bell housing. The cost to machine such parts would be exhorbitant, which would drive up the cost of tractors significantly. It's much cheaper to make such parts out of a cast metal, then do some finishing machine work to get smooth surfaces, angles, and precise holes where needed. At least, this my take on it from what I know of metal working.

 

[tcartwri]

There is actually no such thing as cast iron. Cast steel is more apt. The alloys can be all over the place to give it different properties.

 

[mostly_gas]

There is actually no such thing as cast iron. Cast steel is more apt. The alloys can be all over the place to give it different properties.

No such thing as cast Iron? That news to the metallurgy world

 

[sandman2234]

After reading about tractors that have broke in half at or near the bell housing, which is typically made of cast iron or some other unobtanium material, I couldn't help but wonder why it is used instead of steel.

Cast iron is a very strong metal but it is brittle and can crack or break without warning, as evidenced by some tractors breaking in half. Also, cast iron is difficult to weld, thus making repairs impractiical or impossible.

I am no metallurgist but it seems to me that steel would be a much better material to use. Steel is very strong, more flexible, and can be easily welded, thus making repairs much easier.

Engine blocks I can understand, but why do tractor manufacturers use cast iron instead of steel for bellhousings, axles, and other components?

Main reason is the cost of manufacturing as was mentioned, but also the cast iron has a property you hit on without realizing. "MORE FLEXIBLE" is not good when it comes to some parts. Cast iron typically has very little bending whereas steel will bend more readily. Even some very minor bending when loading/stressing will equate to problems in the very near future when it comes to bending it back and forth. Using a metal that doesn't give till it is time for it to fail and then overdesigning that part will give you excellent results. Since the parts you mention typically have bearing surfaces and low tolerance part movement designed in them, having a part that the metal moved would most likely not be good. If a transmisson case bent as you loaded the bucket, can you imagine what that would do to the clearance on the gears as they meshed or the alignment of a shaft?
I think the best idea for a continued one piece tractor would be a sub-frame like is usually recommend on a backhoe. I know if I ever put a loader on a tractor, I am going to seriously look at reinforcing it with a subframe.
David from jax

 

[tcartwri]

No such thing as cast Iron? That news to the metallurgy world

not really. :thumbsup:

 

[sandman2234]

Maybe the alloy currently being used to make magnet attracting tractor parts from using a casting procedure can be called the metal in question of the O/P.
David from jax

 

[mostly_gas]

not really. :thumbsup:[/QUOTE}
Yes really. Grey Iron, Ductile Iron, Nodular Iron are NOT steel:thumbsup:

 

[Ford tractor]

After reading about tractors that have broke in half at or near the bell housing, which is typically made of cast iron or some other unobtanium material, I couldn't help but wonder why it is used instead of steel.

Cast iron is a very strong metal but it is brittle and can crack or break without warning, as evidenced by some tractors breaking in half. Also, cast iron is difficult to weld, thus making repairs impractiical or impossible.

I am no metallurgist but it seems to me that steel would be a much better material to use. Steel is very strong, more flexible, and can be easily welded, thus making repairs much easier.

Engine blocks I can understand, but why do tractor manufacturers use cast iron instead of steel for bellhousings, axles, and other components?

huh? Cast iron is in the same class as "unobtainium"?
Cast iron is one of the most utilized structural materials combining
incredible design flexibility, high strength and low cost. Parts that crack, are typically from poor design or the use exceeding the design spec. Backhoes are typically in that category by the way unless a STOUT sub-frame is in place.

 

[jones6780]

Good chart on strength of metals, both cast iron and cast steel.

Modulus of Elasticity, Strength Properties of Metals - Iron and Steel - Engineers Edge

Russell

 

[MasseyWV]

Cast iron is arguably stronger than steel but it's inherent weakness of being brittle seems to make it a bad choice of material for use in applications such as tractor bellhousings. For example: What metal is commonly used as an underframe to reenforce the structure for backhoes and loaders? Steel.

As for making complicated castings, my understanding is that molten steel is no more difficult to pour into a sand mould than iron and the machining process is roughly the same, so other than the cost of the metal itself, I can see no significant cost differences between iron and steel. Granted, steel is more flexible than iron but if flexibility were a problem, why make internal components such as bearings, gears, and axle shafts out of steel?

Again, I'm no metallurgist and I'm not trying to reinvent the wheel. I'm just curious if there might be a better way.

 

[Gary Fowler]

I have always considered that the steel in tractors is cast steel as you can readily weld on it with 7018 rods and it holds very well. Cast iron has a much higher carbon content which makes it much more brittle and practically unweldable (yeah I know with proper rods it can be welded but is very easy to crack afterward) I have welded a lot of things on my tractors over the years. Just recently I welded up the drawbar hitch on my LS with 7018 rods. I also welded up the stabilizer pads on a friends back hoe and added some steel bars to it for more flotation. All using 7018 rods on the "cast steel" components. Perhaps some of the older 8N Fords and such were high carbon cast iron. I also got tired of the bolts loosening off on my Yanmar 3 point lift arms and welded the heads to the bracket on one side, the other side, I welded it solid as the bolts had sheared off inside and I couldnt get them out, so I just welded the bracket to the axle housing. It is still holding after many hours with the bush hog swinging around on it. I wouldn't have been able to do that with cast iron.

 

[Mace Canute]

There is actually no such thing as cast iron. Cast steel is more apt. The alloys can be all over the place to give it different properties.

Carbon (C) and silicon (Si) are the main alloying elements, with the amount ranging from 2.1 to 4 wt% and 1 to 3 wt%, respectively. Iron alloys with less carbon content are known as steel.

 

[tcartwri]

Carbon (C) and silicon (Si) are the main alloying elements, with the amount ranging from 2.1 to 4 wt% and 1 to 3 wt%, respectively. Iron alloys with less carbon content are known as steel.

That's right, and you will almost never find 'cast iron' used in any manufacturing process anymore. Maybe in the cheapest of castings that undergo little or no stress.

That's why I find the term odd, when people refer to automotive or mechanical parts as 'iron' .

 

[Baby Grand]

Cast iron also provides a very nice level of structural damping. That's one reason it is favored for the bases and supports of large machine tools. makes for a "quiet" machine producing a nicely finished part.

 

[MasseyWV]

Carbon (C) and silicon (Si) are the main alloying elements, with the amount ranging from 2.1 to 4 wt% and 1 to 3 wt%, respectively. Iron alloys with less carbon content are known as steel.

Technically speaking, perhaps it is steel afterall.

I was just going on what limited information I had available, where it is commonly called cast iron. Either way, in some cases, it does seem to be overly brittle which could very well be the result of defective castings or poor quality metal being used.

That said, perhaps "steel" with a lower carbon count would be better?

 

[jimmysisson]

Aside from what it should be called, there's thousands upon thousands of tractors out there made of cast **** that aren't cracked, that were affordable to make and sell, and that have lasted many decades. Sounds like a good material to me.
Jim

 

[MasseyWV]

Aside from what it should be called, there's thousands upon thousands of tractors out there made of cast **** that aren't cracked, that were affordable to make and sell, and that have lasted many decades. Sounds like a good material to me.
Jim

This is true but...

Adding a loader and/or a backhoe typically requires the use of a steel underframe for increased structural support. Since these addons are so common, why not eliminate the need for an underframe by making the tractor itself stronger in the first place?

 

[mostly_gas]

Steel is an alloy of carbon and Iron (Fe). Just adding carbon to iron doe not make steel. Otherwise the steel making furnace(open hearth or BOF in US) would not be needed. you can tell very easy when machining as steel has stringy chips and cast iron chips look more like sand. For similar chemistry (C, Si,Mn) steel will have higher yield and higher tensile strength and much greater ductility(elongation). The "as-cast" structure of steel negates it's natural advantage over iron and heat treating the "as-cast" structure away is expensive.

 

[mostly_gas]

This is true but...

Adding a loader and/or a backhoe typically requires the use of a steel underframe for increased structural support. Since these addons are so common, why not eliminate the need for an underframe by making the tractor itself stronger in the first place?

how many times does failure happens because of loader mounting bolts come loose? I know it happen some because of the number of times people talk about check torque Loader mounting bolts. Then the is the issue of faulty castings and safety margin used to design and make the castings. i mention them together because bigger saftey margin allows more internal flaws w/o failure. Increasing either better casting process or safety margin costs more. Does that answer your question?