Nat Holmes, age 14, of Galveston, Texas, for his question:
HOW IS METAL FORGED?
Forging is a method of shaping metal by heating it and then hammering or pressing it into a desired form. Most metal forged items are made by big forging hammers.
When metal is forged, its internal make up changes. It loses its grainy structure and becomes more fiberlike. This fiberlike structure gives forged articles more strength. Forging is particularly useful for objects that take heavy wear, such as turbine blades for jet engines, propeller shafts for ships and locomotive parts.
A single, forging hammer may be as tall as a four story building and weigh more than 1 million pounds. Five men operating this machine can turn out more forgings in an hour than five blacksmiths could make in a year.
A single forged piece, or forging, can weigh more than 200,000 pounds.
In forging with hammers, tools called dies shape the desired article. One die fits on the top of the article and another fits on the bottom. When the dies are pressed together, they squeeze hot metal into the desired shape.
Smith, or flat die, forgings are made on machines called open frame, or double frame, hammers. The lower die is held stationary while the upper die moves up and down in a series of blows by steam power.
Drop hammer, or impact die, forgings are produced when the heated metal is forced into impressions cut into the upper and lower dies. In the same manner as in flat die forging, the upper die moves up and down repeatedly with steam or electric power.
A drop hammer can turn out articles many times faster than flat die forging, and produce shapes that are impossible by flat die methods.
Press forging uses a squeezing action, rather than a series of blows. The dies are similar to those used for impact die forging.
Upset forging covers such operations as the forming of heads on nails or bolts. The forging is held firmly for part of its length. The free end is forced into the impression of a die. The work in upset forging is done horizontally, rather than vertically.
Forging by hand is one of the oldest shaping operations known to man. The simplest kind of forging is that done by a blacksmith. The blacksmith heats the metal until it is red hot in a furnace, or forge.
The furnace is an open fireplace with a blower, or set of bellows, to force air into the fire and make it hotter. The blacksmith lifts the hot metal from the furnace with a pair of tongs. Then he holds it against an anvil and beats it into shape with a hand hammer.
Blacksmiths, in olden times, used to make horseshoes this way.
Almost any metal or combination of metals can be forged. Some of the forgeable materials are iron, steel, nickel, titanium, aluminum and bronze.