Metalworking - Historical Perspective

A

Metalworking is one of three major technologies used to fabricate metal products; the others are casting and powder metallurgy. However, metalworking is perhaps the oldest and most mature of the three. The earliest records of metalworking describe the simple hammering of gold and copper in various regions of the Middle East around 8000 B.C. The forming of these metals was crude because the art of refining by smelting was unknown and because the ability to work the material was limited by impurities that remained after the metal had been separated from the ore. With the advent of copper smelting around 4000 B.C., a useful method became available for purifying metals through chemical reactions in the liquid state. Later, in the Copper Age, it was found that the hammering of metal brought about desirable increases in strength (a phenomenon now known as strain hardening). The quest for strength spurred a search for alloys that were inherently strong and led to the utilization of alloys of copper and tin (the Bronze Age) and iron and carbon (the Iron Age). In the Iron Age, which can be dated as beginning around 1200 B.C., followed the beginning of the Bronze Age by some 1300 years. The reason for the delay was the absence of methods for achieving the high temperatures needed to roll and to refine iron ore.

B

Most metalworking was done in hand until the 13th century. At this time, the tilt hammer was developed and used primarily for forging bars and plates. The machine used water power to raise a lever arm that had a hammering tool at one end. It was called a tilt hammer because the arm tilted as the hammering tool was raised. After raising the hammer, the blacksmith let it fall under the force of gravity, thus generating the forging blow. This relatively simple device remained service for some centuries.

C

The development of rolling mills followed that of forging equipment Leonardo da Vinci's notebook includes a sketch of a machine designed in 1480 for the rolling of lead for stained glass windows. In 1045 da Vinci is reported to have rolled at sheets of precious metal on a hand-operated two-roll mill for coin-making purposes. In the following years, several signs for rolling mills were utilized in Germany, Italy, France, and England. However, the development of large mills capable of hot rolling ferrous materials took almost 200 years. This relatively slow progress was primarily due to the limited supply of iron. Early mills employed flat rolls for making sheet and plate, and until the middle of the 18th century, these mills were driven by water wheels.

D

During the Industrial Revolution at the end of the 18th century, processes were devised for making iron and steel in large quantities to satisfy the demand for metal products. A need arose for forging equipment with larger capacity. This need is answered with the invention of the high-speed steam hammer, in which the hammer is raised by steam power, and the hydraulic press, in which the force is supplied by hydraulic pressure. From such equipment came products ranging from rearms to locomotive parts. Similarly, the steam engine spurred developments in rolling, and in the 10th century, a variety of steel products were rolled in significant quantities.

E

The past 100 years have seen the development of new types of metalworking equipment and new materials with special properties and applications. The new types of equipment have included mechanical and screw presses and high-speed idem tolling mills. The materials that have benefited from such developments in equipment range from the ubiquitous л-carbon steel used in automobiles and appliances to specialty aluminum-, titanium-, and nickel-base alloys. In the last years, the formulation of sophisticated mathematical analyses of forming processes has led to higher-quality products and increased efficiency in the metalworking industry.

Exercises