Restoring Overheated Steel

: 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

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peg was withdrawn and quenched at each of the temperatures indicated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.