Patented by Henry Cort of Hampshire, the puddling process consisted of stirring molten pig iron in a reverberating furnace in an oxidising atmosphere to decarbonise it. Afterward, the iron was gathered into a ball, shingled and rolled out. The only issue with the process is that it could only use white cast iron and not grey, which was readily available in the UK. Between and , English inventor Sir Henry Bessemer took final credit for the creation of the Bessemer process with a patent.
He stated that he had been trying to reduce the cost of steel for military weapons and ammunition when he had made the discovery. This was the first inexpensive mass-production of molten pig iron to steel prior to open hearth methods. The key was to blow air over molten iron to remove all impurities by oxidation.
It made the production of steel fast and efficient and gave Bessemer a name in history. Many industries at this time were restricted by the lack of steel available, particularly the railways. Cast iron was unreliable to use for bridges and tracks. This new, cheaper and quicker steel production was welcomed by many engineers and designers and soon iron was replaced by steel. A short time later, the Siemens Martin process was created.
This process was one way to burn off excess carbon from pig iron to produce steel. It ultimately replaced the Bessemer process because during the Siemens Martin process the steel did not become brittle by exposing it to excessive nitrogen in the furnace, was easier to control and allowed the melting of large amounts of scrap iron and steel. Around , however, it was replaced by the electric arc furnace.
Boriding is a thermochemical surface hardening method which can be applied to a wide range of ferrous, non-ferrous and cermet materials. The process entails diffusion of boron atoms into the lattice of the parent metal and a hard interstitial boron compound is formed at the surface. The surface boride may be in the form of either a single phase or a double phase boride layer. In an article published in , Nobel prize winning Henri Moissan first described a method of hardening iron at red heat in a vapour of volatile boron halides.
Russian publications from the period describe salt bath borided parts in pumps used for oil exploration that lasted four times longer than parts that had been case hardened or induction hardened. Many efforts have been made since then to develop a more efficient boriding process from the gaseous phase. It was only in that an ultra-fast boriding process was scaled to industrial production capacity.
Bodycote partnered with Argonne to develop the technology through a cost-shared funding agreement with the United States Department of Energy. The electric arc furnace, developed by Paul Heroult of France, differs from the regular induction type. Material is exposed to an electric arc that is an ongoing plasma discharge that melts iron. The downside of the EA furnace was that it required huge amounts of electrical power, but many companies took advantages of off-peak pricing to run their machines.
On May 25th, , a patent application was filed by Adolf Machlet, working as a metallurgical engineer for the American Gas Company. The patent proposed that oxidation of steel components could be avoided by replacing the air atmosphere in the retort with ammonia. This patent was granted on June 24th, Patent 1,, This patent was submitted on March 19th and granted on June 24th , it was patent number 1,, It was this patent that represented the invention of the nitriding process in the United States.
In , Machet went on to patent the gaseous nitrocarburizing process on April 14th Patent 1,, During development, a similar process was developed in Germany for nitriding steel for surface hardening by A. Historically, the first ion implanter was helium based, constructed and operated in at Cavendish Laboratory in Cambridge by Ernest Rutherford and his students. Between and , commercial equipment manufacturing of ion implanters became firmly established.
In , Varian Associates developed the model DF-4, the first in-line, wafer-to-wafer, high-throughput about wafers per hour ion implanter and by the end of , it became the most widely used commercial ion implantation system in the world [6,7].
Initially, the development of ion implantation technology was utilised to dope semiconductor materials for the IC industries. Then, in the mid-seventies, these high energy ion beams were also used to enhance the surface properties of metals, where implantation of nitrogen or carbon into steel and other alloys resulted in increased wear and corrosion resistance with enhanced surface properties.
Flame spraying was invented by Dr. Max Schoop in Switzerland in the mids. While playing with his young son, firing a toy cannon, he found that hot lead shot projected from the cannon stuck to virtually any surface. Schoop began experiments with small cannons and tin and lead granules.
In the early s, Schoop and his associates developed equipment and techniques for producing coatings using molten and powder metals. In , in Berlin, he applied for the basic patent of the metal spraying process, which was issued after four years.
Several years later, their efforts produced the first instrument for the spraying of solid metal in wire form. This simple device was based on the principle that if a wire rod were fed into an intense, concentrated flame the burning of a fuel gas with oxygen , it would melt and, if the flame were surrounded by a stream of compressed gas, the molten metal would become atomised and readily propelled onto a surface to create a coating.
Madden, H. US Patent 1,,[TJ5]. At this time, there was an increasing need for refractory metal filaments for electric lamps. Powder metallurgy techniques, by conventional die compaction of fine powders, were necessary for the manufacture of small billets suitable for swaging and wire drawing.
Such difficulties were the incidence of cracks, laminations, non-uniform properties and lack of green strength sufficient to withstand the subsequent handling and working of the small billets without fracture.
Madden found that by isostatically pressing his powders, many of the problems associated with die compaction were overcome. Subsequently, further patents were taken out by McNeil in , Coolidge in , and Pfanstiehl in Anodising is used to produce protective and decorative oxide layers on aluminium, improving corrosion protection and wear resistance.
Different colours are created by dyeing or electrolytic colouring. The process was so named because the part to be treated forms the anode electrode of an electrical circuit. Anodising increases resistance to corrosion and wear, and provides better adhesion for paint primers and glues than bare metal.
Anodic films can also be used for a number of cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add interference effects to reflected light. The process was first used on an industrial scale in to protect Duralumin seaplane parts from corrosion. The process is still used today despite its legacy requirements for a complicated voltage cycle now known to be unnecessary.
Variations of this process soon evolved, and the first sulphuric acid anodising process was patented by Gower and O'Brien in Sulphuric acid soon became, and remains, the most common anodising electrolyte. Oxalic acid anodising was first patented in Japan in and later widely used in Germany, particularly for architectural applications.
Anodized aluminium extrusion was a popular architectural material in the s and s, but has since been displaced by less expensive plastics and powder coating. The phosphoric acid processes are the most recent major development, so far only used as pre-treatments for adhesives or organic paints.
A wide variety of proprietary and increasingly complex variations of all these anodising processes continue to be developed by industry, so the growing trend in military and industrial standards is to classify by coating properties rather than by process chemistry. Austempering is a heat treating process for medium-to-high carbon ferrous metals which produces a metallurgical structure called bainite.
It is used to increase strength, toughness, and reduce distortion. Bainite must have been present in steels long before its acknowledged discovery date, but was not identified because of the limited metallographic inspection techniques available and the mixed microstructures formed by the heat treatment practices of the time.
The technique was pioneered by Edgar C. Bain and Edmund S. Davenport who were working for the United States Steel Corporation. This structure was found to be tougher for the same hardness than tempered martensite; however, use of bainitic steel did not become common. Heat treatments at the time were not capable of producing fully bainitic microstructures. It was the advent of low carbon steels containing boron and molybdenum in that through continuous cooling, allowed the creation of fully bainitic steel.
Commercial use of bainitic steel came about as the result of new heat treatment methods which involved a step to hold the workpiece at a single fixed temperature for a period long enough to allow the transformation. This process became known as austempering. Up until the invention of the electron microscope, it was pure supposition as to what actually occurred during the hardening process.
Examinations of the microstructure of metal began in the 17th Century with the frequently performed assessment of fracture surfaces during sorting of cast iron grades and faggot steel. Macro-etching of polished specimens began in the 16th Century. Visual examinations were initially carried out with magnifying glasses.
Although light microscopes had already been developed in the 16th Century, they only became sufficiently powerful after Ernst Abbe had developed the theoretical principles in The invention of the electron microscope in increased the achievable magnification by more than two powers of ten.
Small amounts of other ores produce special-purpose brass. Tin and aluminum increase resistance to corrosion, for example. Zinc ore called calamine is difficult to mix with the copper ore, however, and brass appears later in the archaeological record as well as being far less common than bronze.
Iron is one of the commonest and cheapest metallic elements on the planet. It was not until about BC that iron became general for the production of tools because the temperatures needed to process the ore exceeded what most ancient kilns were able to reach.
Ancient pottery kilns sometimes also reached temperatures in this range, but it was rare to get far above it. Unfortunately, carbon also tended to contribute to the brittleness of the resultant products. Therefore the controlled introduction of carbon into iron ore remains a critical aspect of iron and steel production. Carbon is not used in the production of bronze. Carbon was not the only technological innovation involved, however.
Furnace structure and fuel were important in reaching the necessary temperatures. Hardwoods, such as those of the central African area, burn hotter than softer woods. This is probably the reason for the especially widespread mastery of iron in some areas of Africa. Further, the use of charcoal in place of wood allowed a yet hotter fire.
So did the eventual discovery of coal as a fuel. Similarly, the use of bellows to force air into the kiln produced more rapid burning and faster release of heat by increasing the oxygen available to the fire. Carbon-free iron heated to the maximum of ancient furnaces, while still not actually reaching its melting point, could be pounded forged to purify it and shape it, even without any admixture of carbon.
Iron worked in this way and containing only negligible carbon is called "wrought iron," and its production is necessarily quite time-consuming.
On the other hand, iron with high carbon content and as a result with a lower melting point could be melted and molded and is referred to as "cast iron.
However, in China iron casting dates to the s BC, when cast iron began to be used for the production of agricultural implements. Even once the technology was known, manufacturing iron was not easy and could easily fail if the ore was not sufficiently porous or if there was too much oxygen available or if the lumps of charcoal used to introduce carbon were too large. It is important to remember that throughout history more groups knew about iron, and valued it, than could produce or work it.
The term "Iron Age" is given to those periods around the world in which iron came into general use. The specific dates of course vary from region to region, and the rigidity with which one defines "general use. Iron appeared in Africa by BC, probably from Southwest Asia via Egypt, Nubia, and the Sahel corridor running south of the Sahara, and substantial iron working began in what is today Nigeria by the s.
In most parts of the world, the use of iron largely displaced the prior use of bronze, and hence the "Iron Age" succeeded the "Bronze Age. Steel is an alloy of carbon and iron the metallic element, not the finished product. It contains less carbon 0. High-carbon steel is harder and more brittle, while lower carbon content makes the product softer and easier to work.
Usually traces of such other metal oars as chromium, nickel, copper, tungsten, etc. The production of steel requires the removal of more of the impurities in iron ore than iron production does, often through the application of greater heat than ancient furnaces could produce. In general, steel is an improvement over iron in being less brittle, but its characteristics vary by the amount of carbon in the alloy. The introduction of other metallic ores allows the production of special purpose steels, such as stainless steel , made with chromium.
An important technique in modern and late historic steel production is "quenching," that is, heating the metal and then rapidly lowering its temperature again by plunging it into water. See below. The result is a dramatic increase in the strength of the metal, strength which can be increased yet further by repeating the process.
The earliest quench-hardened steel that we know about dates from about BC or so. Homer refers to the process. But steel was too difficult to produce dependably to come into wide use at that point.
Obviously there is a fine line between iron and steel, and some metallic products are difficult to classify as quite one or quite the other. Techniques for raising furnace temperatures, controlling carbon content, and quenching after raising the metal to just the right temperature were central to the production of iron-ore based tools that were actually superior to bronze ones rather than merely cheaper.
Lead is rarely found by itself, but rather is usually a by-product of the processing of other ores. It is also the final stage of radioactive decay of some unstable metals, such as uranium or radium. Dull gray in color, lead is quite soft. For example, in an account of her father's hunting in the mids, Waheenee, a Hidatsa woman, remarks that, "For shot he used slugs, bits of lead which he cut from a bar, and chewed to make round like bullets.
Powder and shot were hard to get in those days. In addition, lead is quite heavy, so that it is well used in weights. Thus archaeologically we find lead artifacts from quite early times. Various metals, such as tin, were and are sometimes combined with silica in ceramic glazes, to which they lend a hard, shiny surface, the color of which can be controlled by the combination of materials.
However most metals have a melting point above the capacity of the ancient kilns or in some cases simple dung fires used in ceramic manufacture. An admixture of lead could create alloys with a melting point within the range of relatively low-temperature ceramic production.
When higher temperatures were available, lead still often increased the flexibility of the glaze as well as its lustre. For this reason, lead has long been associated with the production of spectacular pottery glazes and porcelain ware.
Lead is a toxin, which builds up gradually in the body until it hits a threshold amount and begins to produce symptoms. Unfortunately, the effect is gradual enough that for many centuries what we now know to be lead poisoning was not associated specifically with lead.
Gradual lead poisoning can result from water carried through lead pipes such as those sometimes used in ancient Rome, for example, or from wine served from lead vessels, although the toxicity is apparently considerably less unto negligible in most alloyed forms. Because lead has been used as an ingredient in ceramic glazes, it has proven a source of potential poisoning to users of ceramics fired at low temperatures. The use of electric furnaces was to result in the large scale production of metals such as tungsten, chromium and manganese which when added to steel gave it useful properties such as improved hardness and resistance to wear.
The electric furnace also allowed the mass production of aluminum. Aluminum is widespread on the Earth but it was difficult and expensive to extract from its ore, bauxite, before the invention of the electric furnace.
The electric furnace produces aluminum by a process of high temperature electrolysis which produces molten aluminum in large quantities, although the process uses substantial quantities of electricity. It had been long recognized that the use of oxygen, rather than air, in steel making would produce higher temperatures, faster production and reduce fuel costs. The high cost of producing oxygen stopped its use in steel making, until the price fell substantially and in the L-D process for using oxygen in steel making was developed.
The L-D process involves blowing a jet of nearly pure oxygen at supersonic speed on to the surface of molten iron. The oxygen quickly burns out the carbon and other impurities resulting in faster production and reduced fuel costs. The social and cultural consequences of the discovery of metallurgy were initially quite minor. Copper was initially used mainly for ornaments and jewelry as it was too soft a material to replace the stone tools and weapons used in Neolithic times.
It was only when bronze was invented that metal tools and weapons replaced stone tools and weapons to create a Bronze Age. Bronze however was a reasonably expensive metal and when iron smelting was discovered by the Hittites the new metal soon replaced bronze as the principal material for tools and weapons.
Iron ores are reasonably widespread and iron is a harder material than bronze, making it better for both tools and weapons. Iron was used for a wide variety of purposes such as nails and tools, cooking pots and kitchen utensils, axes for clearing land and for the tips of ploughs. The use of iron tools and weapons gave humankind greater control of their environment leading to increased population and larger settlements.
Iron became the principal material for the Industrial Revolution being used in steam engines, industrial machinery, in railways for rails and locomotives, for bridges, buildings and in iron ships. The Bessemer and open-hearth steel making processes led to a great reduction in the price and increase in production of steel. Cheap steel replaced iron in a great variety of applications. Steel was used in railways and for ships and in bridge building.
Motor vehicles became one of the biggest users of steel in the 20th century and different types of steel began to be developed for different purposes. Cutting tools were made from steel containing chromium and tungsten as that steel remains hard even at high temperatures. Excavating machinery was made from wear resistant manganese steels and transformers, generators and motors were made from silicon steel due to its magnetic quality.
Stainless steel containing chromium and nickel was widely used in kitchens and in industrial plants vulnerable to corrosion as it does not rust. Steel coated in zinc or tin also resists rust and is used for cans containing food and for equipment used around the home. Metallurgy has had a great effect on human societies, certainly since the Bronze Age and increasingly since the Iron Age and particularly with the modern Steel Age where a vast range of products and structures contain metals.
If metals did not exist at all then we would be restricted to stone, bone and wood tools. This would have had an enormous effect on human history. It is doubtful whether the Industrial Revolution and the industrial world that emerged from it, would have been possible without metals.
It is hard to conceive of wooden or stone steam engines or internal combustion engines. Wooden engines would catch fire while it is doubtful that stone could be worked in a way that could create pistons and cylinders.
Without metals it is doubtful that there would be usable electricity, as the transfer of electricity over significant distances would be difficult or impossible. Even if there were metals, the properties of those metals would have had a major effect on human history. If the smelting and melting points of metals were different then human history would have been different. This can be seen by the use of counter-factuals. Given irons superior qualities to copper and bronze, iron would be used in preference to those two metals for most purposes, so there would have been no copper and bronze ages.
In this case hunter-gatherers could or would have developed iron and steel weapons and tools so that there would have been no stone age. The quote from Colin Renfrew illustrates a number of points. The first is that copper and bronze metallurgy in the Near East developed through a series of steps each to some extent dependent on the preceding step.
The development of metallurgy took place in a particular order and the order of development was a necessary and inevitable order. The order involved a move from simpler metallurgy to more complex metallurgy involving increasing specialization and skills as the metallurgy developed.
The reasons for this is that simpler forms occur to humans before more complex forms and the complex forms are often refinements or improvements of the simpler forms. In this sense the simpler forms will always come before the more complex forms. The progress of metallurgy started with the use of native copper and iron from meteorites as the metals were obtainable without smelting the metals from ores.
It was soon discovered that copper could be shaped by hammering a fairly easy discovery simply involving hitting the copper with a hard object. Annealing was soon discovered as it involved heating the copper in a fire and then hammering it, a relatively easy discovery as fire had been known to humans for hundreds of thousands of years. From about BC a few neolithic communities begin hammering copper into crude knives and sickles, which work as well as their stone equivalents and last far longer.
Some of the earliest implements of this kind have been found in eastern Anatolia. This intermediate period between the Stone Age when all weapons and tools are of flint and the first confident metal technology the Bronze Age has been given a name deriving from the somewhat awkward combination of materials.
It is called the Chalcolithic Period, from the Greek chalcos 'copper' and lithos 'stone'. An accident, probably frequent, reveals another of nature's useful secrets.
A nugget of pure copper, or perhaps a finished copper tool, falls into the hot camp fire. The copper melts. When it cools, it is found to have solidified in a new shape. And the magic of fire has yet more to offer. Certain kinds of bright blue or green stones are attractive enough to collect for their own sake. It turns out that when such stones are heated to a high temperature, liquid metal flows from them.
They are azurite and malachite, two of the ores of copper. The use of fire thus makes possible two significant new steps in the development of metallurgy: the casting of metal, by pouring it into prepared moulds; and the smelting of mineral ores to extract metal. Objects made from smelted copper, from as early as BC, are known in Iran. Many mineral ores are found on the surface of the earth, in outcrops of rock.
Chipping away at them, to pursue the metal-bearing lode down below the surface, leads inevitably to another technological advance - the development of mining. By BC deep shafts are cut into the hillside at Rudna Glava, in the Balkans, to excavate copper ore.
This robbing of the earth's treasures is carried out with due solemnity.
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