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26-547: This steel mill is notable as it still produces steel (as of 2024) using the old-fashioned open hearth furnaces - which due to their slow operation became obsolete on industrial scales in the 1970s. After the collapse of the USSR and the independence of Ukraine , the mill fell into the hands of the Ukrainian government. When privatization began in the mid-1990s, Vasily Khmelnytsky , an ambitious politician-turned-businessman,

52-463: A bidding war that included other Zaporizhstal shareholders. However, The Wall Street Journal reports that the mill was sold in an offshore transaction that included five separate companies and was financed by Russian state-owned Vnesheconombank . It's unclear how this reporting relates to the UK court record of the sale to Troika. A Ukrainian holding company, Metinvest , eventually became full owners of

78-464: A process called teeming , or it may be used in continuous casting in the rolling mill. The regenerators are the distinctive feature of the furnace and consist of fire-brick flues filled with bricks set on edge and arranged in such a way as to have a great number of small passages between them. The bricks absorb most of the heat from the outgoing waste gases and return it later to the incoming cold gases for combustion. Carl Wilhelm Siemens developed

104-400: Is a method of manufacturing where the products are made as specified groups or amounts, within a time frame. A batch can go through a series of steps in a large manufacturing process to make the final desired product. Batch production is used for many types of manufacturing that may need smaller amounts of production at a time to ensure specific quality standards or changes in the process. This

130-508: Is added, together with pig iron from blast furnaces . Once all the steel has melted, slag-forming agents such as limestone are added. Atmospheric oxygen in contact with molten pig iron directly oxidizes the carbon in excess it contains to form carbon monoxide (CO). Additionally, Fe(II) present in iron(II) oxide (FeO) and other impurities also contribute to decarburize the pig iron by oxidizing carbon into CO and simultaneously reducing Fe(II) into metallic Fe. The formed carbon monoxide (CO)

156-509: Is considered to be one of the largest polluting companies in Ukraine. Open hearth furnace An open-hearth furnace or open hearth furnace is any of several kinds of industrial furnace in which excess carbon and other impurities are burnt out of pig iron to produce steel . Because steel is difficult to manufacture owing to its high melting point , normal fuels and furnaces were insufficient for mass production of steel, and

182-457: Is flushed away in the fumes, while steel is formed. To increase the oxidizing power of the "heat", more iron oxide ore can be added. The process is far slower than that of the Bessemer converter and thus easier to control and sample for quality assessment. Preparing a heat usually takes eight to eight and a half hours, and longer to finish the conversion into steel. As the process is slow, it

208-413: Is good for quality control. For example, if there is a mistake in the process, it can be fixed without as much loss compared to mass production. This can also save money by taking less risk for newer plans and products etc. As a result, this allows batch manufacturing to be changed or modified depending on company needs. In certain cases, batch production may require less expensive equipment, thus reducing

234-476: Is not necessary to burn all the carbon away as in the Bessemer process, but the process can be terminated at any given point when the desired carbon content has been achieved. The furnace is tapped in the same way a blast furnace is tapped; a hole is drilled in the side of the hearth and the raw steel flows out. Once all the steel has been tapped, the slag is skimmed away. The raw steel may be cast into ingots,

260-409: Is opposed to large mass production or continuous production methods, where the product or process does not need to be checked or changed as frequently or periodically. In the manufacturing batch production process, the machines are in chronological order directly related to the manufacturing process. The batch production method is also used so any temporary changes or modifications can be made to

286-469: The Siemens regenerative furnace in the 1850s, and claimed in 1857 to be recovering enough heat to save 70–80% of the fuel. This furnace operates at a high temperature by using regenerative preheating of fuel and air for combustion . In regenerative preheating, the exhaust gases from the furnace are pumped into a chamber containing bricks, where heat is transferred from the gases to the bricks. The flow of

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312-620: The basic oxygen furnace or electric arc furnace . Whereas the earliest example of open-hearth steelmaking is found about 2000 years ago in the culture of the Haya people , in present day Tanzania , and in Europe in the Catalan forge , invented in Spain in the 8th century, it is usual to confine the term to certain 19th-century and later steelmaking processes, thus excluding bloomeries (including

338-522: The Catalan forge), finery forges , and puddling furnaces from its application. The open-hearth process is a batch process and a batch is called a "heat". The furnace is first inspected for possible damage. Once it is ready or repaired, it is charged with light scrap, such as sheet metal, shredded vehicles or waste metal. The furnace is heated using burning gas. Once the charge has melted, heavy scrap, such as building, construction or steel milling scrap

364-510: The Siemens regenerative furnace is the rapid production of large quantities of basic steel, used for example to construct high-rise buildings. The usual size of furnaces is 50 to 100 tons, but for some special processes they may have a capacity of 250 or even 500 tons. The Siemens–Martin process complemented rather than replaced the Bessemer process . It is slower and thus easier to control, allowing production of better product. It also permits

390-482: The furnace is then reversed so that fuel and air pass through the chamber and are heated by the bricks. Through this method, an open-hearth furnace can reach temperatures high enough to melt steel, but Siemens did not initially use it for that. In 1865, the French engineer Pierre-Émile Martin took out a license from Siemens and first applied his regenerative furnace for making steel. The most appealing characteristic of

416-642: The largest steel mill in the world that still produces steel using the Open-Hearth Furnaces is the Zaporizhstal steel mill in central Ukraine - which has seven 500-ton capacity OHF's as well as four blast furnaces. The availability of fuel oil in large, cheap quantities, as well as the ongoing invasion largely contribute to their profitability despite the slow process and well as the prohibitively high cost of upgrading to new furnace technologies. Batch production Batch production

442-492: The melting and refining of large amounts of scrap steel, further lowering steel production costs and recycling an otherwise troublesome waste material. One of its important drawbacks is that melting and refining a charge takes several hours. This was an advantage in the early 20th century, as it gave plant chemists time to analyze the steel and decide how much longer to refine it. But by about 1975, electronic instruments such as atomic absorption spectrophotometers had made analysis of

468-517: The mill in 2013. In 2003, the company produced 4,355,000 tonnes of raw steel (market share of 12%) and 3,625 ths. tonnes of finished steel products (11% share). Exports, delivered to 59 countries, accounted for 70% of Zaporizhstal's 2003 sales, with China, Middle Eastern states and the CIS among the main destinations. In 2015, the company has made 3.81 million tonnes of cast iron, 3.98 million tonnes of steel, 3.35 million tonnes of rolled steel. Zaporizhstal

494-511: The open-hearth furnace. It rapidly superseded both the Bessemer and Siemens–Martin processes in western Europe by the 1950s and in eastern Europe by the 1980s. Open-hearth steelmaking had superseded the Bessemer process in UK by 1900, but elsewhere in Europe, especially in Germany, the Bessemer and Thomas processes were used until the late 1960s when they were superseded by basic oxygen steelmaking. The last open-hearth furnace in former East Germany

520-453: The open-hearth type of furnace was one of several technologies developed in the nineteenth century to overcome this difficulty. Compared with the Bessemer process , which it displaced, its main advantages were that it did not expose the steel to excessive nitrogen (which would cause the steel to become brittle ), was easier to control, and permitted the melting and refining of large amounts of scrap iron and steel . The open-hearth furnace

546-415: The product if necessary during the manufacturing process. For example, if a product needed a sudden change in material or details changed, it can be done in between batches. As opposed to assembly production or mass production where such changes cannot be easily made. The time between batches is called cycle time. Each batch may be assigned a lot number . Because batch production involves small batches, it

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572-544: The steel much easier and faster. The work environment around an open-hearth furnace is said to be extremely dangerous, although that may be even more true of the environment around a basic oxygen or electric arc furnace. On the one hand, the process achieves lesser economies of scale than the Bessemer, so its steel was costlier in former's heyday, but on the other, it was more suitable for countries which couldn't produce lots of steel anyway due to limitations of natural resources. Basic oxygen steelmaking eventually replaced

598-520: Was first developed by German -born engineer Carl Wilhelm Siemens . In 1865, the French engineer Pierre-Émile Martin took out a licence from Siemens and first applied his regenerative furnace for making steel . Their process was known as the Siemens–Martin process or Martin–Siemens process , and the furnace as an "open-hearth" furnace. Most open hearth furnaces were closed by the early 1990s, not least because of their slow operation, being replaced by

624-671: Was named manager of the state's stake in the plant, and subsequently engineered the insider sale of many shares of the plant to his own investment company. The Ukrainian government began offering shares in Zaporizhstal in cash auctions in 1999. By 2001, Vasyl Khmelnytsky and a consortium led by the Midland Group controlled 93% of the mill. According to court documents, the Midland Group sold its 50% stake in 2009 to then-independent investment bank Troika Dialog following

650-649: Was shut down in 2001. The process in the form of Twin Hearth Furnace was in use in India's Steel Authority of India Bhilai Steel Plant and some parts of Ukraine. Russia retired its last hearth furnace in March 2018, and was considering preserving it as a museum artifact. India's SAIL shut it down in April 2020 with the advent of COVID19 because of nonavailability of manpower to run the labor intensive process. As of 2024,

676-513: Was stopped in 1993. In the US, steel production using the Bessemer process ended in 1968 and the open-hearth furnaces had stopped by 1992. In Hunedoara steel works , Romania the last 420-tonne capacity open-hearth furnace was shut down on 12 June 1999 and demolished and scrapped between 2001 and 2003, but the eight smokestacks of the furnaces remained until February 2011. The last open-hearth shop in China

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