Introduction to Engineering/Exam 1 study guide/Answers

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.