Harvey armor
Encyclopedia
Harvey armor was a type of steel
armor developed in the early 1890s in which the front surfaces of the plates were case hardened
. The method for doing this was known as the Harvey process.
This type of armor was used in the construction of capital ship
s until superseded by Krupp armor
in the late 1890s. It was invented by the American
engineer
Hayward Augustus Harvey.
to absorb the shock of projectile impact. Compound armor appeared in the mid-1880s and was made from two different types of steel
, a very hard but brittle high-carbon
steel front plate backed by a more elastic low-carbon wrought iron
plate. The front plate was intended to break up an incoming shell, while the rear plate would catch any splinters and hold the armor together if the brittle front plate shattered.
Compound armor was made by pouring molten steel between a red-hot wrought iron backing plate and a hardened steel front plate to weld
them together. This process produced a sharp transition between the properties of the two plates in a very small distance. As consequence, the two plates could separate when struck by a shell, and the rear plate was often not elastic enough to stop the splinters. With the discovery of nickel
-steel alloy
s in 1889, compound armor was rendered obsolete.
and heated to approximately 1200 degrees Celsius for two to three weeks. The process increased the carbon content at the face to around 1 percent; the carbon content decreasing gradually from this level with distance into the plate, reaching the original proportion (approximately 0.1–0.2 percent) at a depth of around an inch. After cementing, the plate was chilled first in an oil bath, then in a water bath, before being annealed
to toughen the back of the plate. The water bath was later replaced with jets of water to prevent the formation of a layer of steam which would insulate the steel from the cooling effect of the water. The process was further improved by low temperature forging
of the plate before the final heat treatment.
While the American navy used nickel steel for Harvey armor (roughly carbon 0.2 percent, manganese 0.6 percent, nickel 3.5 percent), the British used normal steels since their tests had shown that ordinary steel subjected to the Harvey process had the same resistance to penetration as nickel steel, although it was not quite so tough.
Harvey armor was taken up by all of the major navies, since 13 inches of Harvey armor offered the same protection as 15.5 inches of nickel-steel armor. It was in turn rendered obsolete by the development of Krupp armor
in the late 1890s.
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
armor developed in the early 1890s in which the front surfaces of the plates were case hardened
Case hardening
Case hardening or surface hardening is the process of hardening the surface of a metal, often a low carbon steel, by infusing elements into the material's surface, forming a thin layer of a harder alloy...
. The method for doing this was known as the Harvey process.
This type of armor was used in the construction of capital ship
Capital ship
The capital ships of a navy are its most important warships; they generally possess the heaviest firepower and armor and are traditionally much larger than other naval vessels...
s until superseded by Krupp armor
Krupp armour
Krupp armour was a type of steel armour used in the construction of capital ships starting shortly before the end of the 19th century. It was developed by Germany's Krupp Arms Works in 1893 and quickly replaced Harvey armour as the primary method of protecting naval ships.The initial manufacturing...
in the late 1890s. It was invented by the American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
engineer
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...
Hayward Augustus Harvey.
Predecessors
Before the appearance of compound armor in the 1880s, armor plating was made from uniform homogenous iron or steel plates backed by several inches of teakTeak
Teak is the common name for the tropical hardwood tree species Tectona grandis and its wood products. Tectona grandis is native to south and southeast Asia, mainly India, Indonesia, Malaysia, and Burma, but is naturalized and cultivated in many countries, including those in Africa and the...
to absorb the shock of projectile impact. Compound armor appeared in the mid-1880s and was made from two different types of steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, a very hard but brittle high-carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
steel front plate backed by a more elastic low-carbon wrought iron
Wrought iron
thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...
plate. The front plate was intended to break up an incoming shell, while the rear plate would catch any splinters and hold the armor together if the brittle front plate shattered.
Compound armor was made by pouring molten steel between a red-hot wrought iron backing plate and a hardened steel front plate to weld
Weld
Weld most commonly refers to a joint formed by welding.Weld may also refer to:-People:* Weld family, an extended family of New England** Theodore Dwight Weld** Tuesday Weld* Weld-Blundell family* Cecil Weld-Forester, 1st Baron Forester...
them together. This process produced a sharp transition between the properties of the two plates in a very small distance. As consequence, the two plates could separate when struck by a shell, and the rear plate was often not elastic enough to stop the splinters. With the discovery of nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
-steel alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
s in 1889, compound armor was rendered obsolete.
Production process
Harvey armor used a single plate of steel, but re-introduced the benefits of compound armor. The front surface was converted to high carbon steel by "cementing". In this process, the steel plate would be covered with charcoalCharcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...
and heated to approximately 1200 degrees Celsius for two to three weeks. The process increased the carbon content at the face to around 1 percent; the carbon content decreasing gradually from this level with distance into the plate, reaching the original proportion (approximately 0.1–0.2 percent) at a depth of around an inch. After cementing, the plate was chilled first in an oil bath, then in a water bath, before being annealed
Annealing (metallurgy)
Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...
to toughen the back of the plate. The water bath was later replaced with jets of water to prevent the formation of a layer of steam which would insulate the steel from the cooling effect of the water. The process was further improved by low temperature forging
Forging
Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: '"cold," "warm," or "hot" forging. Forged parts can range in weight from less than a kilogram to 580 metric tons...
of the plate before the final heat treatment.
While the American navy used nickel steel for Harvey armor (roughly carbon 0.2 percent, manganese 0.6 percent, nickel 3.5 percent), the British used normal steels since their tests had shown that ordinary steel subjected to the Harvey process had the same resistance to penetration as nickel steel, although it was not quite so tough.
Harvey armor was taken up by all of the major navies, since 13 inches of Harvey armor offered the same protection as 15.5 inches of nickel-steel armor. It was in turn rendered obsolete by the development of Krupp armor
Krupp armour
Krupp armour was a type of steel armour used in the construction of capital ships starting shortly before the end of the 19th century. It was developed by Germany's Krupp Arms Works in 1893 and quickly replaced Harvey armour as the primary method of protecting naval ships.The initial manufacturing...
in the late 1890s.