History
Contenido
El hierro fundido y el hierro forjado pudieron producirse accidentalmente al fundir cobre utilizando mineral de hierro como fundente.[4].
Los primeros artefactos de hierro fundido datan del siglo a. C., y fueron descubiertos por los arqueólogos en el actual condado de Luhe, Jiangsu, en China, durante el período de los reinos combatientes. Esto se basa en un análisis de las microestructuras de los objetos hallados.[2].
Debido a que el hierro fundido es comparativamente frágil, no es adecuado para fines que requieran un borde afilado o flexibilidad. Es resistente a la compresión, pero no a la tensión. El hierro fundido se inventó en China en el siglo a. C. y se vertió en moldes para fabricar rejas de arado y ollas, así como armas y pagodas.[5] Aunque el acero era más deseable, el hierro fundido era más barato y, por lo tanto, se utilizaba en la antigua China más comúnmente para producir objetos cotidianos, mientras que el hierro forjado o el acero se utilizaban para fabricar armas.[2] Los chinos desarrollaron un método de recocido del hierro fundido manteniendo las piezas fundidas calientes en una atmósfera oxidante durante una semana o más con el fin de quemar algo de carbono cerca de la superficie, con el fin de evitar que la capa superficial fuera demasiado frágil.[6].
En Occidente, donde no estuvo disponible hasta el siglo , sus primeros usos fueron el cañón y las armas de fuego. Enrique VIII inició la fundición de cañones "Cañón (artillería)") en Inglaterra. Pronto, los trabajadores del hierro ingleses que utilizaban altos hornos desarrollaron la técnica de producir cañones de hierro fundido, que, aunque eran más pesados que los cañones de bronce predominantes, eran mucho más baratos y permitieron a Inglaterra armar mejor a su marina de guerra. La tecnología del hierro fundido fue transferida desde China. Al-Qazvini, en el siglo , y otros viajeros observaron posteriormente una industria del hierro en los Alburz al sur del Mar Caspio. Esto está cerca de la ruta de la seda, por lo que es concebible el uso de tecnología derivada de China.[7] Los maestros metalúrgicos del Weald continuaron produciendo hierros fundidos hasta la década de 1760, y el armamento fue uno de los principales usos de los hierros después de la restauración inglesa.
En muchos altos hornos ingleses se fabricaban entonces ollas de hierro fundido. En 1707, Abraham Darby patentó un nuevo método para fabricar ollas (y marmitas) más finas y, por tanto, más baratas que las fabricadas por métodos tradicionales. Esto significó que sus hornos de Coalbrookdale se convirtieron en proveedores dominantes de ollas, actividad a la que se unieron en las décadas de 1720 y 1730 un pequeño número de otros altos hornos de coque.
La aplicación de la máquina de vapor para accionar los fuelles de fundición (indirectamente mediante el bombeo de agua a una rueda hidráulica) en Gran Bretaña, que comenzó en 1743 y se incrementó en la década de 1750, fue un factor clave para aumentar la producción de hierro fundido, que se disparó en las décadas siguientes. Además de superar la limitación de la energía hidráulica, el alto horno accionado por agua bombeada a vapor proporcionó temperaturas más altas a los hornos, lo que permitió el uso de mayores proporciones de cal, permitiendo la conversión del carbón vegetal, cuyos suministros de madera eran inadecuados, al coque.[8].
cast iron bridges
The use of cast iron for structural purposes began in the late 1770s, when Abraham Darby III built the Iron Bridge, although short beams had already been used, such as in the Coalbrookdale blast furnaces. Other inventions followed, including one patented by Thomas Paine. Cast iron bridges became commonplace as the Industrial Revolution accelerated. Thomas Telford adopted the material for his upstream bridge at Buildwas, and later for the Longdon-on-Tern Aqueduct, a navigable aqueduct canal at Longdon-on-Tern on the Shrewsbury Canal. It was followed by the Chirk Aqueduct and the Pontcysyllte Aqueduct, which are still in use after recent restorations.
The best way to use cast iron for bridge construction was by using arches, so that all the material is in compression. Cast iron, like masonry, is very resistant to compression. Wrought iron, like most other types of iron and, indeed, like most metals in general, is strong in tension, and also hard - resistant to fracture. The relationship between wrought iron and cast iron, for structural purposes, can be considered analogous to the relationship between wood and stone.
Cast iron girder bridges were widely used by early railways, such as the Water Street Bridge in 1830 at the Manchester terminus of the Liverpool-Manchester branch line, but the problems of their use became all too apparent when a new bridge carrying the Chester and Holyhead Railway across the River Dee at Chester collapsed killing five people in May 1847, less than a year after it opened. The Dee Bridge disaster was caused by excessive loading on the center of the girder by a passing train, and many similar bridges had to be demolished and rebuilt, often in wrought iron. The bridge had been poorly designed, having been built with wrought iron braces, which were mistakenly thought to reinforce the structure. The centers of the beams were placed in bending, with the lower edge in tension, where cast iron, like masonry, is very weak.
However, cast iron continued to be used inappropriately in structures, until the Tay Railway Bridge disaster of 1879 seriously questioned the use of the material. The lugs crucial to securing the tie bars and struts on the Tay Bridge had been integrally fused to the columns, and failed in the early stages of the accident. Additionally, the bolt holes had also been molded, rather than drilled. Thus, due to the angle of inclination of the castings, the tension in the tie bars was located at the edge of the hole instead of being distributed along it. The replacement bridge was built of wrought iron and steel.
However, further bridge collapses occurred, culminating in the Norwood Junction railway accident of 1891. Thousands of cast iron girder bridges were eventually replaced by steel equivalents around 1900 due to widespread concern about cast iron bridges on Britain's railway network.
Buildings
Cast iron columns, first used in mill buildings, allowed architects to construct multi-story buildings without the enormously thick walls required by masonry buildings of any height. They also allowed us to expand factory space and sight lines in churches and auditoriums. By the middle of the century, cast iron columns were common in warehouses and industrial buildings, combined with wrought or cast iron beams, eventually leading to the development of steel-framed skyscrapers. Cast iron was also sometimes used for decorative facades, especially in the United States, and the Soho district of New York has numerous examples. It was also occasionally used for complete prefabricated buildings, such as the historic Iron Building (Watervliet Arsenal) in Watervliet, New York, United States.
Textile factories
Another important use was in textile factories. The air in the factories contained flammable fibers from cotton, hemp or wool being spun. Therefore, textile factories had an alarming propensity to catch fire. The solution was to build them completely with non-combustible materials, and the convenience was found to provide the building with an iron structure, largely cast, to replace the flammable wood. The first building of this type was the Ditherington Flax Mill in Shrewsbury, Shropshire. Many other warehouses were built using cast iron columns and beams, although inadequate designs, defective beams or overloading sometimes led to building collapses and structural failures.
During the Industrial Revolution, cast iron was also widely used for frames and other fixed parts of machinery, including spinning and later weaving machines in textile mills. The use of cast iron became widespread, and many cities had foundries that produced industrial and agricultural machinery.