Workshop Technology
Extrusion

Is used to improve fatigue resistance of the metal by setting up compressive stresses in its surface
Is used for reducing the diameter of round bars and tubes by rotating dies which open and close rapidly on the work
Is extensively used for making bolts and nuts
Consists of pressing the metal inside a chamber to force it out by high pressure through an orifice which is shaped to provide the desired form of the finished part

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Workshop Technology
During hot working of metals

Porosity of the metal is largely eliminated
All of the listed here
Grain structure of the metal is refined
Mechanical properties are improved due to refinement of grains

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Workshop Technology
The welding set up is said to have straight polarity, when

Work is connected to the negative terminal and the electrode holder is earthed
Work is connected to the positive terminal and the electrode holder to the negative terminal
Work is connected to the negative terminal and the electrode holder to the positive terminal
Work is connected to the positive terminal and the electrode holder is earthed

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