Iron+and+Steel

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**What are the advantages of iron and steel over stone and brick?**
==== The iron and steel provide far stronger and taller structures with less expenditure of material than stone, brick, and wood. Also they can produce greater unsupported spans over openings and interior or exterior spaces. ====

What is the importance of steel and iron after the 20th. Century?
==== In the 20th century, the iron loses importance and is replaced by steel, because the steel is more uniformly strong, elastic, and workable, and its high resistance in all stresses. The steel took a lot of importance and various products derived from him. An important event is the development of welding. This allowed produce fused joints with less labor and material.. This was a big change for the technique of architecture. ====

What are the disadvantages of steel and what solutions have been found?
==== Steel has the disadvantage to be a corrosive material and to protect him the surface must be covered. The man has developed alloys such as "stainless steel" for using in exposed surfaces. The alloy of aluminum and other light metals have come to be favorite for exterior construction because their weathering resistance. ====

What is welding? What is its importance?
==== Welding is a manufacturing process where the union is made of two metallic materials. It is very important because it allows the union of two pieces of metal and the union of these does not occupy much space, is very resistant and does not require much expenditure of materials . ====

// "the old cast iron buildings died out. I'm not really sure whether the new skyscrapers killed them, or the new esthetics " //
// In my opinion, the disappearance of old cast iron building obeys to the apparition of steel as a more resistant material to all kinds of stresses. This versatility led to changes in the concept of wall and support as well as innovations in construction techniques, giving birth to a new architecture with modern glass facades and the possibility to reach new heights in the constructions of buildings. Finally in the 19th century, steel replaced cast iron in becomes the constructions material for excellence. I think that Skyscrapers and new esthetics are consequence of the apparition of steel. //

**Timeline of the evolution in the use of metals**