BRASS USES
After the Copper (Chalcolithic) Age came the Bronze Age, followed later by the Iron Age. There was no 'Brass Age' because, for many years, it was not easy to make brass. Before the 18th century, zinc metal could not be made since it melts at 420ºC and boils at about 950ºC, below the temperature needed to reduce zinc oxide with charcoal. In the absence of native zinc it was necessary to make brass by mixing ground smithsonite ore (calamine) with copper and heating the mixture in a crucible.
Only in the last millennium has brass been appreciated as an engineering alloy. Initially, bronze was easier to make using native copper and tin and was ideal for the manufacture of utensils. Pre-dynastic Egyptians knew copper very well and in hieroglyphs copper was represented by the ankh symbol 'C' also used to denote eternal life, an early appreciation of the lifetime cost-effectiveness of copper and its alloys.
Several Roman writers refer to brass, calling it 'Aurichalum.' It was used for the production of sesterces coins and many Romans also liked it especially for the production of golden colored helmets. They used grades containing from 11 to 28 per cent of zinc to obtain decorative colors for all types for ornamental jewelry.
As mentioned, in medieval times there was no source of pure zinc. When Swansea, in South Wales, was effectively the center of the world's copper industry, brass was made in Britain from calamine found in the Mendip hills in Somerset. China, Germany, Holland and Sweden had brass making industries with good reputations for quality.
One of the principal industrial users of brass was the woolen trade, on which prosperity depended prior to the industrial revolution. In Shakespearean times, one company had a monopoly on the making of brass wire in England. This caused significant quantities to be smuggled in from mainland Europe. Later the pin trade became very important, about 15-20% of zinc was usual with low lead and tin to permit significant cold working to size. Because of its ease of manufacture, machining and corrosion resistance, brass also became the standard alloy from which were made all accurate instruments such as clocks, watches and navigational aids.
With the coming of the industrial revolution, the production of brass became even more important. In 1738, William Champion was able to take out a patent for the production of zinc by distillation from calamine and charcoal. Cast brass was hammered to make wrought plate in a water-powered 'battery'. Rods cut from the plate were then pulled through dies by hand to make the vital stock needed for pins for the textile weaving industry.
In 1894, Alexander Dick invented the extrusion press that revolutionized the production of good quality low-cost rods. Subsequent developments in production technology have kept pace with customers' demands for better, consistent quality in products produced in large quantities.
No comments:
Post a Comment