ALEACIONES NO FERREAS UTILIZADAS EN EL AUTOMÓVIL


Para hacer una introducción a los metale sno ferrosos los vamos a clasificar en tres grupos:

· Pesados: Son aquellos cuya densidad es igual o mayor a 5 gr/cm3. Se encuentran en
este grupo el cobre, el estaño, el plomo, el cinc, el níquel, el cromo y el cobalto entre
otros.
· Ligeros: Tienen una densidad comprendida entre 2 y 5 gr/cm3. Los más utilizados son
el aluminio y el titanio.
· Ultraligeros: Su densidad es menor a 2 gr/cm3. Se encuentran en este grupo el berilio y
el magnesio, aunque el primero de ellos raramente se encuentra en estado puro, sino
como elemento de aleación.


Las aleaciones no ferreas utilizadas en el automóvil principalmente son:

Las aleaciones de aluminio son las más importantes entre las no ferrosas principalmente por su ligereza, endurecimiento por deformación, resistencia a la corrosión y su precio relativamente bajo.
 

Las aleaciones de magnesio representan una alternativa a los actuales metales estructurales, postulándose como las aleaciones estructurales más atractivas para la industria del automóvil,uno de los principales problemas de la utilización del magnesio está en su elevada tendencia a la corrosión.
 

El cobre no aleado se usa en abundancia por su conductividad eléctrica, resistencia a la corrosión, buen procesado y costo relativamente bajo, el cobre se alea con el cinc para formar unas serie de latones que tienen mayor resistencia que el cobre sin alear.




Actualmente se presta mucha atención a las aleaciones de aluminio y de otros metales de baja densidad (Mg,Ti) como materiales utilizados en los transportes, debido al efecto de ahorro de combustible. Una importante característica de estos materiales es la resistencia específica, cuantificada como la relación entre resistencia a la tracción y densidad. Aunque una aleación de estos metales tenga una resistencia a la tracción inferior a la de un material más denso (acero), para un peso determinado puede aguantar una carga mucho mayor.

 

Non-Ferrous Metals Chooser Chart
Name	Composition	Properties	Uses
Aluminium	Pure Metal	Greyish-White, soft, malleable, conductive to heat and electricity, It is corrosion resistant. It can be welded but this is difficult. Needs special processes.	Aircraft, boats, window frames, saucepans, packaging and insulation, pistons and cranks.
Aluminium alloys- Duraluminium)	Aluminium +4% Copper+1%Manganese	Ductile, Malleable, Work Hardens.	Aircraft and vehicle parts.
Copper	Pure metal	Red, tough, ductile, High electrical conductor, corrosion resistant, Can work hard or cold. Needs frequent annealing.	Electrical wire, cables and conductors, water and central heating pipes and cylinders. Printed circuit boards, roofs.
Brass	65% copper +35%zinc.	Very corrosive, yellow in colour, tarnishes very easily. Harder than copper. Good electrical conductor.	Castings, ornaments, valves,forgings.
Lead	Pure metal	The heaviest common metal. Soft, malleable, bright and shiny when new but quickly oxidizes to a dull grey. Resistant to corrosion.	Protection against X-Ray machines. Paints, roof coverings, flashings.
Zinc	Pure metal	A layer of oxide protects it from corrosion, bluish-white, easily worked.	Makes brass. Coating for steel galvanized corrugated iron roofing, tanks, buckets, rust-proof paints
Tin	Pure metal	White and soft, corrosion resistant.	Tinplate, making bronze.
Gilding metal	85% copper+15% zinc.	Corrosion resistant, golden colour, enamels well.	Beaten metalwork, jewellery.

Una de las causas que tambien existe para el uso de aleaciones no ferrosas es la de evitar la oxidacion y la corrosion:
De forma rapida podemos decir que la corrosión es el deterioro de un material metálico a consecuencia de un ataque de su entorno (aire, agua, etc), mientras que la oxidación es el ataque del oxígeno (normalmente del aire o del agua) a un material produciendo en el material una corrosión (deterioro del material).







                                                      OXIDACION












CORROSION

 CONFORMADO DE METALES. METAL SHAPING

Metal shaping is the plastic deformation of a metal in order to produce a useful shape. Sheet metal can be formed through operations that shear, stretch, bend, or compress the metal.
 CUTTING

BENDING
When bending is done, the residual stresses cause the material to spring back towards its original position, so the sheet must be over-bent to achieve the proper bend angle. The amount of spring back is dependent on the material, and the type of forming. When sheet metal is bent, it stretches in length. The bend deduction is the amount the sheet metal will stretch when bent as measured from the outside edges of the bend. The bend radius refers to the inside radius. The formed bend radius is dependent upon the dies used, the material properties, and the material thickness.

















STRETCHING
Stretch forming is a very accurate and precise method for forming metal shapes, economically. The level of precision is so high that even intricate multi-components and snap-together curtainwall components can be formed without loss of section properties or original design function. Stretch forming capabilities include portions of circles, ellipses, parabolas and arched shapes.








METAL FOLDING
Sheet metal folding is the pressing and shaping sheet metal on a press brake (also known as a bend press), in order to make containers, enclosures, cases, brackets and sections.

 



LAMINATION
Lamination is one method used to produce shaped deformation elongated metal products of constant cross section.
This metallurgical process can be performed with various types of machines. The choice of the most suitable machine is a function of the type of sheet to be obtained (thickness and length) and the nature and characteristics of the metal. In the following link, sheet fabrication can be seen the great industrial and commercial use have the metal forming process in the manufacture of laminate articles, showing how large metal blocks are rolled up more than 45 times its initial thickness.
This is a process which reduces the thickness of material passing between a pair of rotating rollers. The rollers are generally cylindrical and produce flat products such as sheets or tapes. They can also be scored or engraved on a surface so as to change the profile and pattern embossed stamp. This deformation process may be conducted in either hot or cold.

 



THE ENGLISH WHEEL
The English wheel, in Britain also known as a Wheeling machine, is a metalworking tool that enables a craftsman to form compound (double curvature) curves from flat sheets of metal such as aluminium or steel. The process of using an English wheel is known as Wheeling. Panels produced this way are expensive, due to the highly skilled and labour intensive production method, but it has the key advantage that it can flexibly produce different panels using the same machine. It is a forming machine that works by surface stretching and is related in action to panel beating processes. It is used wherever low volumes of compound curved panels are required; typically in coachbuilding, car restoration, spaceframe chassis racing cars that meet regulations that require sheetmetal panels resembling mass production vehicles (Nascar) ,car prototypes and aircraft skin components. English wheel production is at its highest volumes, in low volume sports car production, particularly when more easily formed aluminium is used. Where high volume production runs of panels are required the wheel is replaced by a stamping press, that has a much higher capital set up cost and longer development time than an English Wheel, but each panel in the production run can be produced in a matter of seconds. This cost is defrayed across a larger production run, but a stamping press is limited to only one model of panel per set of dies. The English wheel model shown is manually operated, but when used on thicker sheet metals such as for ship hulls the machine may be powered and be much larger than the one shown here.