TheStef

Really stupid question, I know what cast metal is less strong
then forged steel.

But what process do thye take to create forged parts and cast pasts?
what makes forged part so much stronger?

bigjack

Stef: A little Metal Shop 101.... cast parts start as molten (melted) metal shaped first by pouring, injecting, etc. Forged parts are either cold or hot when forged. This is basically a hammering into shape(like a blacksmith making hosreshpoes, etc. The hammer cab ebe just that or a huge multi ton machine capable of great striking force. The forging re-aligns the molecular structure of the metal thus giving it properties that are different/applicable to the part use. Crankshafts and pistons can be either cast or forged. Forged being able to withstand more punishment.

TheStef

is this the same with connecting rods also?

vader86

basically the same process yes

NHVett

Let's complete the lesson by discussion of Billet VS Cast VS Forged. Grain structure etc. Someone less lazy than moi?

scorp508

Billet = Carved outta one big chunk'o'metal.

timallard

Where does hypereutectic come into all this?

vader86

hyper is in between cast and forged in strength, but not much better than cast for forced induction

its basically a cast piston with high silicon content added to the aluminum alloy, it is a good piston for high rpms compared to cast because of its thermal properties

Darcane

Hypereutectic refers to the alloy it is made out of, not the means that it is made. Hypereutectic means it's an Aluminum Silicon alloy with more than about 12% Silicon (12% would make it Eutectic, and less would be Hypoeutectic). It's a very strong alloy, but rather brittle...

86Moon

Well that certainly increases my basic understanding of these terms. Thanks. While we're learning, could someone define CNC for me? :cheers:

TheStef

Billet VS Cast VS Forged

Witch one is the strongest?

And If I understand Hypereutectic is a simple cast piston with added silicon/aluminum to make the metal stronger, a bit like adding carbon to steel to make it stronger.

What about Titanium parts? do they exist in engine parts? it seems only logical that the big HP engines would benefit from this type of metal since it is stronger then steel.

I know one of my friends had Titanium parts custom made for his Skydoo, engine. Has any one on the forum even done something like this? or do any company sell these parts?

TrueBlue ChevyDude

Valvetrains are the main area that any of us "regulars" would even think to use titanium. Price a set of regular retainers vs. a set of titanium ones and see why it's price-prohibitive for "regular" cars like us to use titanium for much of anything.

The NSX's used titanium rods if I'm not mistaken. To handle the sky-high revs I guess.

CFI-EFI

CNC = Computer Numerical Control. A "CNC" machine is one one that uses a punch tape to tell it what to do. Parts made on a CNC machine are supposed to be identical. We often hear the term as applied to cylinder head porting. Once a porter experiments and reaches a shape he likes, the port can be mapped. The cutting process can then be automated on a CNC machine station so all the ports are the same as the proven port. It eliminates the "human" factor in the duplication process, not to mention man hours of labor.

Goody

CNC is the process where a Computer Numerical Control - Milling Machines will take a piece of metal and make specific cuts as per the 3D drawings or the program it is written to perform. You get the exact same result from each item.
Head porting companies use this technology now because they can set the program up to mill exactly what they want from any particular head. Unlike "old hand porting" that can differ from port to port, a CNC'd head will have the same exact tolerances in each port if programmed to do so. It does require changing the cutting elements after so many passes to make sure quality work is still produced.


[Modified by Goody, 11:43 AM 12/12/2003]

xs650

All else being equal, forged, "billet", cast in declining order. In the real world, all else is not equal, so you can have castings that are stronger than forgings, etc. But that's not real common.

A forging starts with a real honest to god billet and whomps it into shape. In a well designed forging the granular structure of the material get arranged in a way that increases that parts strength and more importantly it's toughness. And a very important point, forging quality control is easier than high strength casting quality control. The chances of a forging fully performing to it's material spec is much higher than a casting doing the same.

see: http://www.qcforge.com/defin1.html

"Billet" is an aftermarket parts marketing term for "machined from one piece of metal" I've even seen Hogly Ferguson "billet" parts that were machined form castings:lol: "Billet" parts are almost always machined from one solid, finsihed chunk of metal, usually not a true billet. They usually start with plate, bar or an extrusion A real billet is a semi finished chunk of metal that is normally used in forgings or other forming operations such as rolling or extruding before anything is made from it.

For casting, a bunch of molton metal is pured or forced into a mold of some type. Castings are usually but not always weaker than forgings or "billet" parts. High quality high strength casting take good, expensive, equipment and a lot of good, expensive expertise to make. Even at their best, castings tend to not be as forgiving as forgings and are more likely to break if severly overloaded.

Right, but the trick is -how- the silicon is added. It has to do with the amount of silicon and the silicom/aluminum grain microstructure.


Titanium isn't necessarily stronger that steel. The range of strengths of Titanium alloys is roughly comparable to high strength steel alloys. It's primary advantage is that it only ways 60% as much as steel while being a high strengths tough material. It, like steel is used in many different alloys.

My son made quite a few parts in a fairly light duty home machine shop. If a person understands how to machine titanium, it's easier to work than folk lore says. Still not nearly as forgiving to machine as steel or aluminum, you have to know what you are doing. I usually screwed titanium parts up when I tried to machine them, but it was no brainer for my son on the same machines.



[Modified by xs650, 10:46 AM 12/12/2003]

shaggy56

Recently I was reading about forged cranks and cast cranks. I read there were incidents where forged cranks were snapping. I read there was a discussion that possibly cast cranks had a dampening affect that forged cranks lacked. But this was all theory and couldnt be proven.

xs650

Sounds more like they didn't have the right people and equipment doing testing and failure analysis. Maybe the people holding the purse strings didn't think it was worth the $$$ to find out.

TheStef

I know I'm the one asking quesions here, but I did read something about that somewhere.. I can't remmeber were though??

vader86

You gotta work pretty damn hard to break a crank.

If its installed right.

86Moon

Thanks CFI and Goody for the info. I have learned a lot from this thread :seeya