I've read through what I could find on the topic, but could someone explain what the difference is between forging and casting? I know forged wheels can be stronger at a lighter weight, but I would like to know the actual processes involved.
If anyone would care to explain or have a link, it would be greatly appreciated!
Forged vs cast
Forged is where the piece is actually almost cut out of a large blank of steel, aluminum, etc. using a great deal of pressure. Forging allows the grain structure to be uniform and precludes the possibilities of bubbles inside etc. Casting is where there is a mold and molten metal is poured in and allowed to harden. This does nothing for the grain structure, and allows for bubbles etc. to form. In general, forging is a much better but more expensive process.
forging is not "cutting" things out, its using a ton of pressure in a die to beat something into shape(i think this is what you meant). monoblock forging is using a single block of alluminum and, using different forging peices, beating it with great pressure into the shape you want.
forging will align grain structure(as noted) and will allow the use of less materials for the same weight, assuming materials are the same(IE alluminum). A cast wheel and a forged wheel wont make a difference is they're engineered so they are the same strength, forging allows you to use less material sometimes, resulting in less weight.
-chetNote: there can be forging problems, such as incorrect dies and things that can cause imperfections.
forging will align grain structure(as noted) and will allow the use of less materials for the same weight, assuming materials are the same(IE alluminum). A cast wheel and a forged wheel wont make a difference is they're engineered so they are the same strength, forging allows you to use less material sometimes, resulting in less weight.
-chetNote: there can be forging problems, such as incorrect dies and things that can cause imperfections.
-
Grant@tirerack
- Posts: 722
- Joined: Thu Jul 17, 2003 9:17 am
- Car: Auto racing (AMLS, Cart,F1,IRL in that order), old show rods, classic monster and bad sci-fi movies,
- Contact:
Cast wheels are made by pouring the molten alloy into an open mold. This would be called gravity casting. They tend to be heavier and porus. Small air bubbles tend to form in the alloy from escaping gases etc. Under a microscope the alloy will look like a sponge. This type of process is cheaper and faster than other methods. They tend to be heavier than forged wheels since it takes more 'volume' of the alloy to make the wheel as strong. Some wheel makers use what is called low pressure casting which involves 'sucking' the alloy into the mold in a sealed atmosphere. This reduces some of the bubbles and makes for a slightly lighter wheel with less pores. Forging is sort of like PlayDough Fun Factory. They take the alloy ingot and smash it into the mold to get the rough shape of the wheel and then usually roll out the rim section of the wheel with high pressure rollers. This smashing makes the alloy much less porus. This allows the wheel to be just as strong with less metal volume and weight. If you look at a cross section of a forged wheel it looks almost completely solid, no little pores.
Yeah Chet, that's what I meant...although I was kinda mentally visualizing a giant ram smashing down on a block of metal and roughly knocking it into shape the first time while knocking a bit of excess off, then pounding it into the right shape. Then it gets machined...eh, at least I got the grain structure part right 