Operaciones de conformado de metales

                                       Metal Shaping:

All metal parts except the molten at some time of their production have been subjected to a forming operation at least metals, and often require several different operations. Thus, the steel used in the manufacture of pipes for the construction of chairs is forged, hot rolled several times, cold rolling to transform it into sheet, cut into strips, cold is given in tubular form, welded, welding is machined and sometimes also in cold stretching. This, apart from all treatments subsidiary. The metal forming theory can help determine how to use the machines in the most efficient manner possible, and to improve productivity.

1.Forging:
Forming by plastic deformation takes the shape of deformation ability of metals to cause some displacement of mass, more or less pronounced according to the characteristics of the metal and the application of the process temperature. As a result also occurs altering the internal structure modification of metal and its mechanical properties. 

A method of forming by plastic deformation in which, in addition to efforts external thermal energy is used, ie a hot working process. 

Forging may be free or die. The first does not impose any specific form of the tool, the latter requires the construction of an engraving reproducing the shape and dimensions of the piece to forging. The effects of forging, are: 

Elimination of internal defects: the crushing of the mass of metal, produces the flattening of the inner cavities, the walls, if not oxidized, it being perfectly welded together intimately.Similarly, segregations, the default of the combined heat and pressure, are decreased, improving the homogeneity of the material. 

Grain-Refining: depends on the operating temperature and strain rate. In some cases the decrease is achieved grain size and others is achieved in a better disposition of the fibers. In both cases improve the mechanical properties of the metal.

 2.Hot stamping:
The hot stamping is only one mechanical forging is employed in which a mold or die for forming the piece. Although then give a more precise definition and technique hot stamping. 

The hot metal stamping comprises subjecting a metal, by means of a press or ram, to a compressive stress between two steel molds denominated stamps. 

The prints are formed by two parts, the upper die and the lower or hammer or anvil. The top is fixed to the slide of the press and in the table below.

3.Rolling:

In metallurgy, lamination is a metal forming process in which metal material is passed through a pair of rollers. Rolling is classified according to the temperature of the metal rolled. If the metal temperature is above its recrystallization temperature, then the process is known as hot rolling. If the temperature of the metal is below its recrystallization temperature, the process is known as cold rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing process and cold rolling processes the most tonnage of all cold working processes.

4.Extrusion:

 In extrusion, a bar or metal is forced from an enclosed cavity via a die orifice by a compressive force applied by a ram. Since there are no tensile forces, high deformations are possible without the risk of fracture of the extruded material. The extruded article has the desired, reduced cross-sectional area, and also has a good surface finish so that further machining is not needed. Extrusion products include rods and tubes with varying degrees of complexity in cross-section.

 Examples of metals that can be extruded include lead, tin, aluminium alloys, copper, brass and steel. The minimum cross-sectional dimensions for extruded articles are approximately 3 mm in diameter for steel and 1 mm in diameter for aluminium. Some metals such as lead alloys and brass lend themselves to extrusion rather than drawing or rolling.

5.Tube and drawing:

The process of wire drawing involves the production of wire of close diameter and tolerance by drawing descaled hot-rolled rod through a die. The finished wire is coiled onto a motor driven block. The dies are manufactured from hard material e.g tungsten carbide. Diamonds dies are used for small diameter wire. Soap is used for lubrication. If large diameter reductions are required the rod is progressively drawn through several stages of dies and blocks.

In rotary piercing a rolling mill consisting of two rolls set at an angle to each other is used- see the figure above.   A metal billet is fed into the rolls which simultaneously rotate and draw the billet forward.   Because of the small diameter of the rolls the outside of the billet is deformed resulting in a tensile stress at its centre.  A cavity is induced in the centre of the billet,the formation of which is assisted and controlled by a profiled mandrel.  The type of rolling mill shown in the figure is the Mannesmann mill.

-English wheel:

The English wheel, also known in Britain as a machine of Wheeling, is a metal cutting tool that allows a craftsman to form compound (double curvature) curves flat sheets of metal, such as aluminum or steel. The process of using an English wheel is known as Wheeling. The panels produced in this way are expensive, due to the production method highly skilled and labor intensive, but has the major advantage that it can produce different flexible panels using the same machine. This is a forming machine for surface working and stretching action is related to the sheet metal processes. Is used whenever the low volume required curved panels compounds, generally the restoration of car bodies, car racing chassis dimensional complying with regulations requiring metal panels resemble vehicle serial production