Metallurgy

Source: Wikipedia, the free encyclopedia.

Casting
, the process of pouring molten metal into a mold

Metallurgy is a domain of

inter-metallic compounds, and their mixtures, which are known as alloys
.

Metallurgy encompasses both the science and the technology of metals, including the production of metals and the engineering of metal components used in products for both consumers and manufacturers. Metallurgy is distinct from the craft of metalworking. Metalworking relies on metallurgy in a similar manner to how medicine relies on medical science for technical advancement. A specialist practitioner of metallurgy is known as a metallurgist.

The science of metallurgy is further subdivided into two broad categories: chemical metallurgy and physical metallurgy. Chemical metallurgy is chiefly concerned with the reduction and oxidation of metals, and the chemical performance of metals. Subjects of study in chemical metallurgy include mineral processing, the extraction of metals, thermodynamics, electrochemistry, and chemical degradation (corrosion).[1] In contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. Topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms.[2]

Historically, metallurgy has predominately focused on the production of metals. Metal production begins with the processing of

non-ferrous metallurgy
, also known as colored metallurgy.

Ferrous metallurgy involves processes and alloys based on iron, while non-ferrous metallurgy involves processes and alloys based on other metals. The production of ferrous metals accounts for 95% of world metal production.[3]

Modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. Some traditional areas include mineral processing, metal production, heat treatment,

hydraulic-powered trip hammers, and double acting piston bellows.[4][5]

Etymology and pronunciation

Metallurgy derives from the

alchemist's term for the extraction of metals from minerals, the ending -urgy signifying a process, especially manufacturing: it was discussed in this sense in the 1797 Encyclopædia Britannica.[6]

In the late 19th century, metallurgy's definition was extended to the more general scientific study of metals, alloys, and related processes. In English, the /mɛˈtæləri/ pronunciation is the more common one in the United Kingdom. The /ˈmɛtəlɜːri/ pronunciation is the more common one in the United States US and is the first-listed variant in various American dictionaries, including Merriam-Webster Collegiate and American Heritage.

History

arsenic bronze
(in yellow), and tin (in bronze)

The earliest recorded metal employed by humans appears to be gold, which can be found free or "native". Small amounts of natural gold have been found in Spanish caves dating to the late Paleolithic period, 40,000 BC.[7] Silver, copper, tin and meteoric iron can also be found in native form, allowing a limited amount of metalworking in early cultures.[8]

Certain metals, such as tin, lead, and copper can be recovered from their ores by simply heating the rocks in a fire or blast furnace in a process known as

Pločnik, in present-day Serbia.[10]

The earliest evidence of copper smelting is found at the Belovode site near Pločnik.[11] The site produced a copper axe from 5,500 BC, belonging to the Vinča culture.[12]

The earliest use of lead was in the late

Arpachiyah in present-day Iraq. The artifacts suggest that lead smelting predated copper smelting.[13]

Copper smelting is also documented at this site at about the same time period (soon after 6,000 BC), although the use of lead seems to precede copper smelting. Early metallurgy is also documented at the nearby site of Tell Maghzaliyah, which seems to be dated even earlier, and completely lacks that pottery.[citation needed] The Balkans were the site of major Neolithic cultures, including Butmir, Vinča, Varna, Karanovo, and Hamangia.

The Varna Necropolis, Bulgaria, is a burial site in the western industrial zone of Varna, approximately 4 km from the city centre, internationally considered one of the key archaeological sites in world prehistory. The oldest gold treasure in the world, dating from 4,600 BC to 4,200 BC, was discovered at the site.[14] The gold piece dating from 4,500 BC, found in 2019 in Durankulak, near Varna is another important example.[15][16] Other signs of early metals are found from the third millennium BC in Palmela, Portugal, Los Millares, Spain, and Stonehenge, United Kingdom. The precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing.

In approximately 1900 BC, ancient iron smelting sites existed in Tamil Nadu. [17] [18]

In the Near East, about 3,500 BC, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. This represented a major technological shift known as the Bronze Age.

The extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. The process appears to have been invented by the Hittites in about 1200 BC, beginning the Iron Age. The secret of extracting and working iron was a key factor in the success of the Philistines.[19][20]

Historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. This includes the ancient and medieval kingdoms and empires of the

hydraulic-powered trip hammers, and double acting piston bellows.[4][5]

A 16th century book by

Georg Agricola, De re metallica, describes the highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. Agricola has been described as the "father of metallurgy".[21]

Extraction

Yuan Dynasty
in China

metallurgists are interested in three primary streams: feed, concentrate (metal oxide/sulphide) and tailings
(waste).

After mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or mostly waste. Concentrating the particles of value in a form supporting separation enables the desired metal to be removed from waste products.

Mining may not be necessary, if the ore body and physical environment are conducive to

leaching
. Leaching dissolves minerals in an ore body and results in an enriched solution. The solution is collected and processed to extract valuable metals. Ore bodies often contain more than one valuable metal.

Tailings of a previous process may be used as a feed in another process to extract a secondary product from the original ore. Additionally, a concentrate may contain more than one valuable metal. That concentrate would then be processed to separate the valuable metals into individual constituents.

Metal and its alloys

Iron, the most common metal used in metallurgy, is shown in different forms, including cubes, chips, and nuggets

Much effort has been placed on understanding iron–carbon alloy system, which includes steels and cast irons. Plain carbon steels (those that contain essentially only carbon as an alloying element) are used in low-cost, high-strength applications, where neither weight nor corrosion are a major concern. Cast irons, including ductile iron, are also part of the iron-carbon system. Iron-Manganese-Chromium alloys (Hadfield-type steels) are also used in non-magnetic applications such as directional drilling.

Other engineering metals include aluminium, chromium, copper, magnesium, nickel, titanium, zinc, and silicon. These metals are most often used as alloys with the noted exception of silicon, which is not a metal. Other forms include:

Production

In

hardness, corrosion, fatigue resistance and performance in temperature extremes. To achieve this goal, the operating environment must be carefully considered.[citation needed
]

Determining the hardness of the metal using the Rockwell, Vickers, and Brinell hardness scales is a commonly used practice that helps better understand the metal's elasticity and plasticity for different applications and production processes.

stress at elevated temperatures can creep
.

Metalworking processes

An open-die drop forging with two dies of an ingot, which is then further processed into a wheel
  • Casting – molten metal is poured into a shaped mold. Variants of casting include sand casting, investment casting, also called the lost wax process, die casting, and continuous castings. Each of these forms has advantages for certain metals and applications considering factors like magnetism and corrosion.[23]
  • billet
    is hammered into shape.
  • Rolling – a billet is passed through successively narrower rollers to create a sheet.
  • Extrusion – a hot and malleable metal is forced under pressure through a die, which shapes it before it cools.
  • milling machines and drills
    cut the cold metal to shape.
  • Sintering – a powdered metal is heated in a non-oxidizing environment after being compressed into a die.
  • gas cutters
    and bent and welded into structural shape.
  • Laser cladding – metallic powder is blown through a movable laser beam (e.g. mounted on a NC 5-axis machine). The resulting melted metal reaches a substrate to form a melt pool. By moving the laser head, it is possible to stack the tracks and build up a three-dimensional piece.
  • 3D printing – Sintering or melting amorphous powder metal in a 3D space to make any object to shape.

Cold-working processes, in which the product's shape is altered by rolling, fabrication or other processes, while the product is cold, can increase the strength of the product by a process called work hardening. Work hardening creates microscopic defects in the metal, which resist further changes of shape.

Heat treatment

A heat treating furnace at 1,800 °F (980 °C)

Metals can be

precipitation strengthening, quenching, and tempering:[24]

Often, mechanical and thermal treatments are combined in what are known as thermo-mechanical treatments for better properties and more efficient processing of materials. These processes are common to high-alloy special steels, superalloys and titanium alloys.

Plating

A simplified diagram of electroplating copper on a metal

Electroplating is a chemical surface-treatment technique. It involves bonding a thin layer of another metal such as gold, silver, chromium or zinc to the surface of the product. This is done by selecting the coating material electrolyte solution, which is the material that is going to coat the workpiece (gold, silver, zinc). There needs to be two electrodes of different materials: one the same material as the coating material and one that is receiving the coating material. Two electrodes are electrically charged and the coating material is stuck to the work piece. It is used to reduce corrosion as well as to improve the product's aesthetic appearance. It is also used to make inexpensive metals look like the more expensive ones (gold, silver).[25]

Shot peening

Shot peening is a cold working process used to finish metal parts. In the process of shot peening, small round shot is blasted against the surface of the part to be finished. This process is used to prolong the product life of the part, prevent stress corrosion failures, and also prevent fatigue. The shot leaves small dimples on the surface like a peen hammer does, which cause compression stress under the dimple. As the shot media strikes the material over and over, it forms many overlapping dimples throughout the piece being treated. The compression stress in the surface of the material strengthens the part and makes it more resistant to fatigue failure, stress failures, corrosion failure, and cracking.[26]

Thermal spraying

Thermal spraying techniques are another popular finishing option, and often have better high temperature properties than electroplated coatings. Thermal spraying, also known as a spray welding process,[27] is an industrial coating process that consists of a heat source (flame or other) and a coating material that can be in a powder or wire form, which is melted then sprayed on the surface of the material being treated at a high velocity. The spray treating process is known by many different names such as HVOF (High Velocity Oxygen Fuel), plasma spray, flame spray, arc spray and metalizing.

Electroless deposition

Electroless deposition (ED) or electroless plating is defined as the

cations
in a liquid bath.

Characterization

Metallurgists study the microscopic and macroscopic structure of metals using metallography, a technique invented by Henry Clifton Sorby
.

In metallography, an alloy of interest is ground flat and polished to a mirror finish. The sample can then be etched to reveal the microstructure and macrostructure of the metal. The sample is then examined in an optical or electron microscope, and the image contrast provides details on the composition, mechanical properties, and processing history.

Crystallography, often using diffraction of x-rays or electrons, is another valuable tool available to the modern metallurgist. Crystallography allows identification of unknown materials and reveals the crystal structure of the sample. Quantitative crystallography can be used to calculate the amount of phases present as well as the degree of strain to which a sample has been subjected.

See also

References

  1. .
  2. from the original on 24 June 2021. Retrieved 20 September 2020.
  3. ^ "Металлургия" Archived 18 January 2015 at the Wayback Machine. in The Great Soviet Encyclopedia. 1979.
  4. ^
  5. ^ .
  6. from the original on 1 August 2014. Retrieved 29 January 2011.
  7. ^ "History of Gold". Gold Digest. Archived from the original on 29 April 2007. Retrieved 4 February 2007.
  8. (PDF) from the original on 22 December 2015. Retrieved 1 January 2015.
  9. ^ H.I. Haiko, V.S. Biletskyi. First metals discovery and development the sacral component phenomenon. // Theoretical and Practical Solutions of Mineral Resources Mining // A Balkema Book, London, 2015, р. 227-233. Archived 8 December 2015 at the Wayback Machine.
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    .
  11. .
  12. ^ Neolithic Vinca was a metallurgical culture Archived 19 September 2017 at the Wayback Machine Stonepages from news sources November 2007
  13. from the original on 21 September 2020. Retrieved 19 March 2022.
  14. ^ [1] Archived 12 February 2020 at the Wayback Machine Gems and Gemstones: Timeless Natural Beauty of the Mineral World, By Lance Grande
  15. ^ "World's oldest gold". Archived from the original on 28 September 2019. Retrieved 28 September 2019.
  16. ^ Magazine, Smithsonian; Daley, Jason. "World's Oldest Gold Object May Have Just Been Unearthed in Bulgaria". Smithsonian Magazine. Archived from the original on 28 September 2019. Retrieved 28 September 2019.
  17. ^ "Ancient Smelting in Tamil Nadu India". www.indianexpress.com. Archived from the original on 4 October 2022. Retrieved 27 October 2023.
  18. ^ "Ancient high-carbon steel from southern Tamil Nadu India microstructural and elemental analysis" (PDF). www.currentscience.ac.in. Archived (PDF) from the original on 20 June 2023. Retrieved 27 October 2023.
  19. on 4 March 2016. Retrieved 1 January 2015.
  20. ^ "Metal Hardness Tests: Difference Between Rockwell, Brinell, and Vickers". ESI Engineering Specialties Inc. 14 June 2017. Archived from the original on 14 December 2017. Retrieved 13 December 2017.
  21. ^ "Casting Process, Types of Casting Process, Casting Process Tips, Selecting Casting Process, Casting Process Helps". www.themetalcasting.com. Archived from the original on 18 December 2017. Retrieved 13 December 2017.
  22. ^ Woodford, Chris (2017). "How electroplating works". Explain that Stuff. Archived from the original on 15 June 2019. Retrieved 20 May 2019.
  23. ^ "What is Shot Peening – How Does Shot Peening Work". www.engineeredabrasives.com. Archived from the original on 12 June 2018. Retrieved 4 January 2019.
  24. ^ "Thermal Spray, Plasma Spray, HVOF, Flame Spray, Metalizing & Thermal Spray Coating". www.precisioncoatings.com. Saint Paul, MN. Archived from the original on 14 August 2022. Retrieved 13 December 2017.