How are crankshafts made or forged? Can anyone explain me in detail?

Answer 1

There seems to be some confusion here about casting and forging. Most crankshafts are die cast, which means the rough shape is cast by pouring molten metal into a mold and after that has cooled enough for it to hold its shape, it is hammered into its general shape.

Hammering in this case means using a hydraulic drop hammer that exerts hundreds of thousands of pounds of force per square inch. Keeps the neighbors awake at night. The hammer has two shaped pieces of specially hardened steel--called "dies"--that come together with a sharp blow to force the metal into shape. In the process the steel of the crankshaft is made much harder and stronger.

In general, as in a crankshaft for a car or locomotive engine, separate dies are used to hammer each bearing journal and the protruding shafts at the ends. Not all of the crankshaft is hammered--only the bearing parts. If you look at a bare crankshaft, you will see that parts of it retain the slightly mottled or "mealy" finish of the original casting.

This is because the crankshaft is of a rather complex shape and does not lend itself to die-casting with a single pair of dies. There is no "draw line" on a crankshaft because the journal arms stick out in various directions.

After all the journals are hammered, the crankshaft is re-heated and annealed to further strengthen the parts that were not "hit" in the die-casting process.

Finally, the journal faces are machined on a special machine called a crankshaft lathe, that finishes all the journals to a smooth finish suitable for operation in the bearings of the engine. If you live in a town of more than, say, 25,000 people, there will probably be a crankshaft shop in town that will have a crankshaft lathe you can look at. They are in the yellow pages under "crankshaft" or "machine shops." They use it to re-surface worn or damaged journals.

Answer 2

Those are the four types I'm familiar with: billet cranks, forged cranks, nodular iron and cast cranks.

A billet crankshaft is completely machined from a solid piece of hardened steel. Very expensive to manufacture but the strongest of all of them.

A forged crankshaft is cast under great pressure which compresses the internal structure and greatly strengthens it.

A nodular iron crank is formulated and cast in such a way as to line up all of the metal grain with the stresses it will undergo - much better than a cast crank, not quite up to a billet or forged crank.

A cast crank is merely poured into a mold and later machined - adequate for most normal applications.

The cranks can also have the journals nitrited. This hardens the journals greatly and helps minimize scoring and maximize bearing life.

Answer 3

Crankshaft Forging Process

Answer 4

For the typical cast crankshaft, the factory starts by making a mold. This is typically made from sand with a bit of clay mixed in, and has a hollow crankshaft-shaped pocket. They then pour molten iron into this hollow pocket, allow it to cool, and then break up the sand and fish the crankshaft out. Then they trim off the area where the iron flowed into the mold and drill oil holes in it. Then they put it on a crankshaft grinder. This machine is a sort of special lathe that polishes all the places that they will put bearings. With a forged crankshaft, they start with two enormous dies. The workers put a piece of solid steel (which may or may not be heated) between the dies, and a hydraulic hammer squeezes the steel into the shape of a crankshaft. I think in some cases they may need to twist the crank to get the rod journals (the spots where the connecting rods attach) to line up correctly, but I'm not 100% sure on that one. The drilling and grinding steps remain the same.

Answer 5

Depending upon the forces that they have to encounter, they are either made of cast or forged. These steels allow hardening on their surface to have required hardened layer in the crankshaft journals. They have to be finely polished so as to have a soft bearing on the bearings. Depending upon the lubricating system holes are drilled through in the crankshafts. Finally they are balanced and counterweights are provided to properly balance them, this depends on the firing order when there are a no. of cylinders.
VR

Answer 6

both cast and forged ( sorry figured you would get help ! ) cast is metal that is poured into a mold - forged is the same except it is formed under heat and pressure making it stronger and less likely to have inclusions ( contaminates ) both are machined to a final shape and finish

Answer 7

Forged or cast then machined and balanced

Answer 8

check out this http://www.ohiocrank.com/tour1.html but this is a better link here http://en.wikipedia.org/wiki/Crankshaft