Introduction to Engineering/Exam 1 study guide/Answers

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HIGH SPEED STEELS

It is also known as HSS. High speed steel operates cutting speed 2-3 times higher than that of plane carbon steel. They can retain their properties at elevated temperature without the loss in physical and mechanical properties.

Classification of High speed steel :- They are mainly classified into four types according to their chemical composition of their alloying elements. They are -

1) 18-4-1 HSS

Percentage of chemical composition > Tungsten(W) 18% Chromium(Cr) 4% Vanedium(V) 1% Carbon(C) 0.75% It offers extreme hardness and wear resistance. It is extensively used in the manufacture of tools, lathe, planner and shaper machines. It is also used in the manufacture of drill-bits.

2) Cobalt HSS or 20-4-2 HSS

Percentage of chemical composition > Tungsten(W) 20% Chromium(Cr) 4% Vanedium(V) 2% Cobalt(Co) 12% It is also known as Super-high speed steel. It assures better hardness than 18-4-1 HSS. It can operate safely at a temperature higher than 620(C).

3) Molybdenum HSS

Percentage of chemical composition > Molybdenum(Mo) 6% Tungsten(W) 6% Chromium(Cr) 4% Vanedium(V) 2% It ensures high toughness. It shows good wear resistance and excellant cutting properties.

4) Vanedium HSS

Percentage of chemical composition > Vanedium(V) more than 1% Carbon(C) 0.7% Higher Vanedium and Carbon it this HSS offers superior properties over 18-4-1 HSS. Higher proportions of Vanedium shows better corosion resistance and wear resistance.