Extrusion Submitted to: submitted by: Asst. Prof. M.P.Gururajan Koduri Srikrishna (2008AMD2922)

Introduction Joseph Bramah, developer of extrusion process. It is a process by which a material is forced to flow through a die, which is shaped to produce the required cross-section. It is similar to the squeezing action of tooth paste. Courtesy: google images(direct extrusion)

Types of extrusion Hot extrusion Cold extrusion At elevated temperature No work hardening costly Cold extrusion At room temperature Work hardening Lack of oxidation, good surface finish.

Direct extrusion

Indirect extrusion Courtesy: google images (indirect extrusion)

Indirect extrusion Advantages: Disadvantages: Reduction of friction high contianer’s life billet moves more uniformly. So, less extrusion defects Disadvantages: Impurities and defects on surface. Length and area of extrusion depends on stem.

Hydrostatic extrusion

Extrusion force curves courtesy: wiki Fig: relations between forces applied and ram displacement in various processes

Copper alloys Composition of copper used is 55 to 65% As copper content increases, ease of extrusion decreases. In order to have hot working, Lead content should be low 600-1000oC Pressure-690MPa Tubes of 11cm outer diameter, with thickness of 2mm. Free cutting brass, hot stamping brass Manganese bronze alloys has marine applications

Steels 1100 to1250oC Dummy preheated to 800 to 900oC Glass lubrication Plain carbon steels to high alloyed steels Tubes of 20m long, diameter of 10mm,20mm.

Aluminium alloy 300 to600oC Press- 500 to 6000Tons Billets of 75mm diameter for small,1100mm diameter for big presses. A layer of metal remains on the surface after extrusion. Lubricants- graphite, molybdenum disulphide

Properties of materials Presence of impurities, gas, dross, etc Depending on degree of deformation Deformation is greater in outer zones. Therefore, differences in properties at these places. This variation is high, if extrusion ratio is low. Temperature at which work is carried out. Bismuth is brittle in cast state, but, it can be extruded without difficulty at 40oC

Extrusion defects Surface cracking Piping defect Internal cracking

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