open-hearth furnace

metallurgy

Also known as: OHF, Siemens regenerative gas furnace, Siemens-Martin furnace(Show More)

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July 1, 2026

Quick Summary

The open-hearth process was a significant steelmaking technique that dominated production for much of the 20th century. It involves using a reverberatory furnace with a regenerator to convert pig iron and scrap metal into steel.12

The Process

In this method, fuel and air are preheated in regenerator chambers, which significantly increases the flame temperature. The furnace is charged with materials like pig iron, steel scrap, iron ore, and limestone. The heat generated by combustion melts the charge, and impurities are removed through reactions between the slag and molten metal. This process allowed for flexibility in the metallic charge, accommodating various combinations of molten pig iron and cold scrap.1345

While largely replaced by the basic oxygen process and electric arc furnaces, the open-hearth process still accounts for about one-sixth of global steel production.14

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crucible process
After 1870 the Siemens regenerative gas furnace replaced the coke-fire furnace; it produced even higher temperatures. The Siemens furnace had a number of combustion holes, each holding several crucibles, and heated as many as 100 crucibles at a time. All high-quality tool steel and high-speed steel was long…
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After 1870 the Siemens regenerative gas furnace replaced the coke-fire furnace; it produced even higher temperatures. The Siemens furnace had a number of combustion holes, each holding several crucibles, and heated as many as 100 crucibles at a time. All high-quality tool steel and high-speed steel was long…
Read More

Sir William Siemens
…in his patent for the open-hearth furnace that was heated by gas produced by low-grade coal outside the furnace. This invention, first used in glassmaking, was soon widely applied in steelmaking and eventually supplanted the earlier Bessemer process of 1856. William’s achievements were recognized by his membership in the Institution…
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…in his patent for the open-hearth furnace that was heated by gas produced by low-grade coal outside the furnace. This invention, first used in glassmaking, was soon widely applied in steelmaking and eventually supplanted the earlier Bessemer process of 1856. William’s achievements were recognized by his membership in the Institution…
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Pierre-Émile Martin
…Sir William Siemens invented the open-hearth furnace, which could produce and sustain much higher temperatures than any other furnace. Martin obtained a license to build such furnaces and developed a method of producing steel by using scrap steel and pig iron. His steel products were awarded a Gold Medal at…
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…Sir William Siemens invented the open-hearth furnace, which could produce and sustain much higher temperatures than any other furnace. Martin obtained a license to build such furnaces and developed a method of producing steel by using scrap steel and pig iron. His steel products were awarded a Gold Medal at…
Read More