Hot Extrusion Vs Cold Extrusion

Extrusion process used for metals is the heat based extrusion. Broadly there are two types of extrusions based on the level of heat. Hot Extrusion & Cold Extrusion. Choosing either of the two processes depends upon the malleability of the metal chosen. This article considers the comparison of hot and cold extrusion processes on a closer look for a better understanding and comprehension.

Hot Extrusion
Hot extrusion basically refers to the process where in the metals are heated at elevated temperatures, in order to make the extrusion process easier. The pressure range varies from 30 to 700 Mpa and the temperature maintained is between 50 percent to 75 percent. Exposing the metal to such high pressures But at the same time, high pressure and temperature levels have an adverse effect on the die in the longer run. It cannot be completely managed or eliminated but this effect can be curbed to a substantial level by using proper and sufficient lubrication. Oil and graphite based lubricants are comparatively more suitable for extrusions carried out at lower temperatures and glass powder lubrication for the higher temperature extrusion processes.

Cold Extrusion
After understanding the basic conceptual working of the hot extrusion process it is a child's play to decipher what cold extrusion process is all about. Cold extrusion process, just opposite to the hot extrusion, is carried out at room temperatures. The metals that undergo cold extrusion are not very ductile metals and therefore can withstand the pressure created by the extrusion process.

Comparison
After understanding the two different kinds of extrusion processes individually we can now look at them in comparison to have a better understanding for the purpose of carrying out these processes aptly and successfully. Cans, shock absorber cylinders & collapsible tubes are the common products of cold extrusion, whereas the hot extrusion products are the extruded trims for various industries, aircraft parts, railings, frames, etc.

The primary advantages of cold extrusion are elimination of oxidation, fair mechanical properties, good surface finish and no billet heating. On the other hand advantages of hot extrusion process include complex and strong shapes at low tooling costs and economy for producing even smaller quantities. The only disadvantage is the high equipment set up and maintenance cost.

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