Kirjoittaja Aihe: Hot Extrusion Process and its Application for Steel (Luettu 513 kertaa)

upamfva · 22.06.23 - 08:29

Hot Extrusion Process and its Application for Steel

Extrusion is a compressive deformation process in which a block of metal is squeezed through an orifice or die opening in order to get a reduction in diameter and increase in length of the metal block. The resultant product has the desired cross-section. Extrusion involves forming of axisymmetric (symmetrical about an axis) parts. Dies of circular on non-circular cross-section are used for extrusion. Extrusion normally involves high forming forces. Large hydrostatic stress in extrusion helps in the process by improving the ductility of the material.Get more news about Micro Precision Cold Extrusion Part,you can vist our website!

Metals like aluminium, which are easily workable, can be extruded at room temperature. Other difficult to work metals are normally hot extruded or warm extruded. Both circular and non-circular parts can be obtained by extrusion. Channels, angles, rods, window frames, door frames, tubes, and aluminium fins are some of the extruded parts. Difficult to form materials such as steels, nickel alloys are extruded because of its inherent advantage, such as, no surface cracking because of reaction between the billet and the extrusion container. Extrusion results in better grain structure, better accuracy, and surface finish of the components. Less wastage of material in extrusion is another attractive feature of extrusion.

The applications of extrusions are constantly increasing because of the ability of the process to produce net bulk shapes in long lengths, frequently with complex cross sections. Depending on the alloy, extrusions serve the transportation, construction, mechanical, and electrical industries. Extrusions are used for durable goods, industrial equipment, heating and air conditioning applications, petroleum production, and the production of nuclear power. Practically all metals can be extruded, but extrudability varies with the deformation properties of the metal. Soft metals are easy to extrude. Hard (or high-strength) metals need higher billet temperatures and extruding pressures as well as higher-rated presses and dies.

A patent granted in 1797 by Joseph Bramah described a press in which Pb (lead) was forced through a die. This was the earliest consideration of the principle of extrusion which is hence be considered a modern process compared to other metal-forming processes like rolling and forging. Lead pipes were extruded in late 1700s in England. Later on, lead sheathing of electric cables was done by extrusion.

With the development of aluminum, which was commercially available in 1886, the extrusion process was established as an important industrial process. Today, extrusion is used in the manufacturing of several different products of different materials, but the major field of application is in the aluminum industry. In the production of complex shapes from aluminum billets, no other process can compete with extrusion.

The principle of extrusion is very simple. A billet is placed in a closed container and squeezed through a die by a ram. The design of the die opening determines the cross-section of the extruded product. When extruding tubes, a mandrel is inserted in the middle of the die. Unlike majority of the other deformation processes, all principal stresses are compressive during extrusion. Tensile stresses are only present in a small region at the exit of the die surface. When a material is plastically deformed under this state of multi-axial compression, very high strains can be reached since the workability is high at high hydrostatic pressure. The risk of metal rupture is reduced and materials, which crack in other processes, can be extruded without problems.