89FormulaLS2

iTrader: (1)

I've been seeing terms like "Forged 383 stroker," or "Forged LS6"

What does "forged" mean? Is it referring to something special done with the pistons? Something else? Someone please explain.

Just Floor It

Im not sure of an exact definition, Im not good at making definitions, but when it is forged, it is able to withstand more power. If you have forged internals, you can run high(er) amounts of boost, or use nitrous....If you are putting down alot of power, its wise to use forged internals....Some forged internals include Crankshaft, Rods and Pistons...

Someone else can give you more of a "definition," but hope this helps

Squintz Palladoris

iTrader: (1)

I suck with definitions too but I am really good with this whole copy n past thing lol.

A cast part is made from material being forced or poured into a mold. The part will have thicker and thinner areas, and takes shape from this molten state. Therefore the material must have good castability . One of the main properties of a material that has good castability is that it does not form internal voids on cooling. As a material cools, it shrinks. If there are thick and thin areas, the thick areas will cool slower than the thin ones, and the thick areas can form voids, and the part can warp out of shape or crack, or worse, form internal stresses that come out when the part is used, then crack. That’s why when you look at an engine block for example, they often have scalloped out areas to make the wall thickness more even. These materials are typically more brittle. A cast crankshaft is “weaker” because it is made from cast or nodular cast iron, not because it is cast. It is cast because the material is very castable, but it is impossible to forge. A billet may be cast, but the shape is very very even and symetrical, so the above concerns do not come into play as in a cast part of some odd shape.
A forged part is made from a chunk of metal. It is then usually heated, and it is pounded into shape in a forging die. The extra metal oozes out from between the forging dies and must be ground off. This is why there is a large wide parting line on forged parts. A forged crank is stronger because of the steel it is made from. It could be an alloyed 4340 steel with .40% carbon, or a weaker 1020 steel that is not alloyed and has less (.20%) carbon. The early Chevy forged steel cranks crack so regularly mostly because of the weak material they were forged from. It was something like a 1020 (I’m not positive, but you get the idea). A forged piston is strong because of the material it is made from. It is forged because the material is not very castable. The forging process DOES add grain flow and add strength to the part as above, but it is primarily the higher material Ultimate Tensile Strength (UTS) and Yield Strength (YS) that make it strong. The yield point is the point at which a part first starts to plastically deform. Take a paper-clip, and straighten it. You can flex it to some degree without bending it. Once you permanently bend it, you have hit the yield point. The UTS is where the part actually breaks. The more brittle a material is, the closer together the UTS and the YS are. Also remember, steel can have a yield strength of as little as 40,000 psi to 300,00 psi (those numbers are off the top of my head and may not be exact). Now a forged part generally is more ductile than a cast part. 4340 steel is probably the most common material for rod and crank forgings. One of the reasons is its balance of high tensile strength and ductility. It also responds positively to heat treating, so the surface hardness and the overall material tensile strength can be increased after machining. It is cheaper to machine the part when soft, then heat treat it hard.

Thank god for copy n paste if I had to type all of that I would have been here all day

Brad

Just Floor It

Nice Work!

BigBronco

iTrader: (2)

ok here is a little cut down of that...

Cast is when you take a metal mix of so many different metals... and melt them down into a mixutre, and them pour it into a cast and then it is chilled and hardened. Cast is not as strong as forged and this is why.



Forged is when they take a whole block of a material, say aluminum, and then they cut away from it until you are left with the finish product. or they press and melt it into what you want and then cut away the left metal that oozed out from the press.

Forged internals can be gone trough a process called hardening and it will make them even stronger. That is why when people that have motors that are going to go through a lot of boost, Nitrous, or turn a LOT of rpms will use forged internals, inluding crank, rods, and pistons

Tiger2o69

iTrader: (16)

Ever seen movies where they put the swords in fires and then beat them into shape. Same thing.

1BADFNZ

Yeah that's the basic Idea of forging... now if you took molten metal and poured it into a mold and let it cool it's cast.

RahuL

iTrader: (10)

Lord of the Rings .. saw how the ring and swords were "Forged"

badhoopty

cast is pretty much pouring metal into a mold. billet is machining the product out of a block of material. forging takes an extra step by heat & pressure treating the material making it mucho stronger.

when things are forged it arranges the molecules in a more consistant configuration so they grab onto each better and can handle alot more stress.

Nesto

dammit GTX beat me to it.

i was gonna say that ring that was forged in Mount Doom is pretty f'in strong.

89FormulaLS2

iTrader: (1)

Thank you all for the replies!

Sounds like this one sentence really sums it up, and was kind of what I suspected. Makes much sense now, though - especially as to "why" certain parts would need to be forged.

Adam