art, but has
become a science. It is, in fact an art; aided by science. The
human element in its manufacture is a decided factor, as will be
brought in the following remarks:

The heat treatment of steel in its broad aspect may be said to
commence with the melting furnace and end with the hardening and
tempering of the finished product. High-speed steel is melted by
two general types of furnace, known as crucible and electric. Steel
treaters, however, are more vitally interested in the changes that
take place in the steel during the various processes of manufacture
rather than a detailed description of those processes, which are
more or less familiar to all.

In order that good high-speed steel may be furnished in finished
bars, it must be of correct chemical analysis, properly melted and
cast into solid ingots, free from blow-holes and surface defects.
Sudden changes of temperature are to be guarded against at every
stage of its manufacture and subsequent treatment. The ingots are
relatively weak, and the tendency to crack due to cooling strains
is great. For this reason the hot ingots are not allowed to cool
quickly, but are placed in furnaces which are of about the same
temperature and are allowed to cool gradually before being placed
in stock. Good steel can be made only from good ingots.

Steel treaters should be more vitally interested in the important
changes which take place in high-speed steel during the hammering
operations than that of any other working the steel receives in
the course of its manufacture.

QUALITY AND STRUCTURE

The quality of high-speed steel is dependent to a very great extent
upon its structure. The making of the structure begins under the
hammer, and the beneficial effects produced in this stage persist
through the subsequent operations, provided they are properly carried
out. The massive carbides and tungstides present in the ingot are
broken down and uniformly distributed throughout the billet.

To accomplish this the reduction in area must be sufficient and the
hammer blows should be heavy, so as to carry the compression into
the center of the billet; otherwise, undesirable characteristics
such as coarse structure and carbide envelopes will exist and cause
the steel treater much trouble. Surface defects invisible in the
ingot may be opened up under the hammering operation, in which
event they are chipped from the hot billet.

Ingots are first hammered into billets. These bill