Cast Iron

[rScotty]

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?

You are right. They don't. Most of what is called "cast iron" is actually cast alloy steel. Like anything else, casting quality can vary. But cast steel alloy is basically a good tough material. All cast materials are difficult to weld. It isn't just a case of steel versus iron. One big difference is whether the metal is rolled, formed, hammered and hot-worked as is the case with most structural steel shapes....or just left to cool slowly as an alloy steel casting.
So the things you describe are due to what it's made of, it's how it's made.
enjoy, rScotty

 

[SPYDERLK]

G'day this would push the price up and the manufacturer is not going to absorb it , it will prob make the machine 3 times heavier than it is now, there for increasing transport costs, all this adds up to a dearer end product which makes it harder to sell. Bottom line is manufacturers are not going to make them heavier and miss out on sales because their machine is now $2k dearer than the opposition

Ranting is finished now

Jon

Right. Except by extent. It wouldnt take much extra material for the strength needed if that material was incorporated in the right places. A couple hundred pounds in the right places would suffice even on a pretty good sized tractor. New design and moulding would be expensive and would be a killer for those companies running "new" tractors from old design molds. ... Now if a design was starting from scratch, design of castings for enhanced durability under greater stresses would make it very cost effective and a selling point for the nominal extra sticker price. The benefits I see would be more and low CG weight, strength to make bracing unecessary thereby saving money and ground clearance with attachments, cleaner underside for servicing, etc.
larry

 

[mostly_gas]

Most of what is called "cast iron" is actually cast alloy steel. rScotty

Just curious why do you say that? Last time I looked at cast iron under the microscope, it did not not look anything like steel

 

[radioman]

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.

Of course there is. problem is the bean counters or YOUR wallet that keeps bring us back to cast iron.

 

[Brimstone10x]

I think masseywv is missing the point of a tractor . A tractor is intended to pull implements from the the draw bar or the three point. loaders , backhoes ect are all options that are like an after thought . we turn them into swiss army knifes. if you realy want a loader you buy a deadected wheel loader or if you want to excavate you buy an excavater. if the mfg were building tlbs they would use a fabricated steel frame not a cast frame. the cost of tractor that was desined to have a loader/hoe installed permanetly would be much too high for most buyers. my .02 cents















9

 

[RoyJackson]

I think masseywv is missing the point of a tractor . A tractor is intended to pull implements from the the draw bar or the three point. loaders , backhoes etc are all options that are like an after thought . we turn them into swiss army knifes. if you really want a loader you buy a dedicated wheel loader or if you want to excavate you buy an excavator. if the mfg were building TLBs they would use a fabricated steel frame not a cast frame. the cost of tractor that was destined to have a loader/hoe installed permanently would be much too high for most buyers. my .02 cents

Good points...

 

[MHarryE]

Somebody said that cast iron and cast steel are equally easy to pour, but that is not true. Cast iron has a lower melting point and flows through a mold better. Cast iron has improved vibration damping characteristics and is much more rust resistant than steel. It also has excellent abrasion resistance. But it does have more than 2% carbon and in standard grey iron the carbon is in flakes. The points on those flakes are stress risers so it is not at all ductile.

Nearly all the large steel castings with which I have worked have had foundry weld repair - surface voids and porosity. Appearance is also not as good as a grey iron casting. The foundry people tell me it is due to the higher pour temperature.

But sometimes you need the strength of steel, and especially all the alloys that are then available. And of course you can weld to steel. On large frames in Cat equipment we use castings for complex corners and then weld straight frame rails to the corner castings.

Cast iron makes a good engines and transmission housing because of its vibration damping, its machinability, and the fact that you can cast in a lot of ribs for stiffness. The last think you want your engine or transmission doing is deflecting a large amount under load throwing your bearings out of alignment.

 

[Soundguy]

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?

would you pay 40k$ for a tractor that could otherwise be sold for 20k$

think of the process involved in making the the entire machine from steel.

look at heavy equipment.. lots of steel.. almost no cast except the engine.

then look at the price tag of that yellow iron...

people wouldn't buy it enmasse. thus there's little market for it.. not to mention the $difficulty$ in mass producing it.

soundguy

 

[Egon]

Doesn't cast iron get harder with age? Carbon percipitating out at grain boundaries??

Seems I heard that Rolls Royce used to cure/age their cast iron cylinder blocks??

 

[mostly_gas]

Old timers would age cast iron castings for years. Had as much to do with stresses from casting as anything else. As cast structure has a lot of stress and machining will warp the castings. A stress relieving heat treat will accomplish the same thing in less time.