Aluminum Extrusion Principles

Metal extrusion

metal pressing, in particular, aluminum and its alloys, called plastic deformation process, wherein the cold or heated preform, usually part of a round ingot ("pillar"), продавливается через специальный инструмент с с одним или несколькими отверстиями заданной формы – матрицу (рисунок 1).

Pressing of aluminum and aluminum alloy

For aluminum extrusion used special equipment - extrusion presses, usually, hydraulic, которые обеспечивают на штоке (пресс-штемпеле), which directly "pushes" the workpiece, effort by 500 by 4000 tonnes, and sometimes more, depending on the application and performance of the press.

See. also Aluminum extrusion: from billet to finished profile

Pressing = extrusion

The English term «extrusion» just indicates the term "ejection, squeezing ". The compression can be hot or cold depending on the alloy and the method used. When hot-pressing the preform is preheated to facilitate plastic deformation.

profiles, tubes, rods, stripes

Aluminum profiles, which receive compression, but not, let us say, rolling or flexible, and called – aluminum extrusions. Under profiles often understand all kinds of molded products, Although standards differ "profiles", "Pipe", "Rods" and "strip" and even chipboard panels, for example, for rolling stock- and aircraft. profiles, in turn, may be, solid and hollow, standard and special, pipes - general purpose and seamless, and bars - round, square, rectangular, hexagon. And there are molded and extruded wire полуфабрикаты для дальнейшей обработки: прокатки, drawing, bending, etc..

The main methods of pressing aluminum and aluminum profiles are two – direct and back. Most industrial presses operate direct compression method.

compression molding

princip-pressovaniya

Figure 1

The principle of direct compression is clearly visible from the figure 1. The heated preform is placed in a container and by a so-called ram, "Pushed" through the matrix. Прямое прессование применяют при производстве сплошных профилей (простых прутков и сложных специальных профилей), tubes and hollow profiles. When direct compression direction of metal flow coincides with the direction of movement of the slide. During this process the preform slides relative to the container walls. To overcome arises when this friction force spent a considerable part of the efforts of the press. A plot of the load or pressure on the displacement of the slide type generally has a, shown in Figure 2. Выделяют три стадии процесса: 1 – распрессовка (осадка) заготовки и начало прессования, 2 - the pressure drop and the, what is called a steady state, 3 - the pressure is at its minimum, followed by its sharp rise in the formation of the discard.

izmenenie-nagruzki-pressa

Figure 2

reverse pressing

При обратном прессовании алюминия матрица располагается на переднем конце полого пресс-штемпеля и перемещается вместе с ним внутрь контейнера (рисунок 3) . In this case there is no relative movement between the workpiece and the container. Therefore no frictional forces between the workpiece surface and the container. There is also no movement of the center of the workpiece relative to peripheral portions of the workpiece. load and pressure changes with the advancement of the ram for pressing the reverse shown in Figure 2. Reverse compression is usually used for pressing the pressed hard alloys and rigid requirements on the cross-sectional size and homogeneity properties over the cross section and length of the profile.

obratnoe-pressovanie Figure 3

compression molding “joint to joint”

For the extrusion of aluminum alloys, которые легко свариваются при температуре и давлении прессования применяют метод «стык в стык»: каждую последующую заготовку загружают в контейнер в стык предыдущей. The length of the extruded profile in the process is limited by the length of the output section and can reach 50 and more meters. Final welding workpiece in the container with the next workpiece takes place, when the joint passes through the matrix deformation zone. The principle of the method of pressing "joint to joint," with the removal of the discard shown in Figure 4: новая заготовка приваривается к оставшемуся в матрице или так называемом питателе металлу, remaining from the previous workpiece.

prjamoe-pressovanie

Figure 4

compression molding “joint to joint” without removal of the discard

Намного реже применяют вариант прессования «стык в стык» без удаления пресс-остатка: торец следующей заготовки придвигается в контейнере вплотную к торцу остатка предыдущей заготовке, еще находящегося в контейнере (рисунок 5). Compression without removal of the discard requires additional costs, including, to ensure a clean surface of the preform and especially their ends. Therefore, such a molding is mainly used only in special cases, for example, при изготовлении изделий-заготовок (подката, полуфабриката) в бухтах для дальнейшей переработки, for example, drawing.

prjamoe-pressovanie-bez-press-ostatka

Figure 5

Legkopressuemye aluminum alloys

For pressing "butt joint" requires the ability of aluminum alloys welded at a temperature and pressure compaction. Такими качествами обладают так называемые легко прессуемые («мягкие») сплавы: все марки алюминия, alloys of Al-Mn (серия 3ххх) и alloys of Al-Mg-Si (серия 6ххх), including the most popular alloy AD31, а также «нормально» прессуемые («среднепрочные») сплавы: Al-Mg (серия 5ххх) при содержании магния до 3 %, and сплавы Al-Zn-Mg (серия 7ххх) без легирования медью, for example, 1915 GOST 4784 (7005 по международной классификации).

Difficulty pressed aluminum alloys

So-called hard alloys compressible, which include all the alloys Al-CinMg (серия 2xxx), alloys AlMg (серия 5ххх) при содержании магния более 3 % and alloys AlZnMg-Сu (серия 7ххх) обычно не прессуют методом «стык в стык». To apply them separately compressing each blank.

Источник: Saha К. P.