Restoring Overheated Steel
:
HARDENING CARBON STEEL FOR TOOLS
:
The Working Of Steel
The effect of heat treatment on overheated steel is shown graphically
in Fig. 65 to the series of illustrations on pages 137 to 144. This
was prepared by Thos. Firth & Sons, Ltd., Sheffield, England.
The center piece Fig. 65 represents a block of steel weighing about
25 lb. The central hole accommodated a thermo-couple which was attached
to an autographic recorder. The curve is a copy of the tempe
ature
record during heating and cooling. Into the holes in the side of
the block small pegs of overheated mild steel were inserted. One
peg was withdrawn and quenched at each of the temperatures indicated
by the numbered arrows, and after suitable preparation these pegs
were photographed in order to show the changes in structure taking
place during heating and cooling operations. The illustrations here
reproduced are selected from those photographs with the object
of presenting pictorially the changes involved in the refining of
overheated steel or steel castings.