Detrimental Elements





Sulphur and phosphorus are two elements known

to be detrimental to all steels. Sulphur causes red-shortness

and phosphorus causes cold-shortness. The detrimental effects

of these two elements counteract each other to some extent but

the content should be not over 0.02 sulphur and 0.025 phosphorus.

The serious detrimental effect of small quantities of sulphur and

phosphorus is due to their not being uniformly distributed, owing

to their tendency to segregate.



The manganese and silicon contents are relatively unimportant in

the percentages usually found in high-speed steel.



The detrimental effects of tin, copper and arsenic are not generally

realized by the trade. Small quantities of these impurities are

exceedingly harmful. These elements are very seldom determined

in customers' chemical laboratories and it is somewhat difficult

for public chemists to analyze for them.



In justice to the manufacturer, attention should be called to the

variations in chemical analyses among the best of laboratories.

Generally speaking, a steel works' laboratory will obtain results

more nearly true and accurate than is possible with a customer's

laboratory, or by a public chemist. This can reasonably be expected,

for the steel works' chemist is a specialist, analyzing the same

material for the same elements day in and day out.



The importance of the chemical laboratory to a tool-steel plant

cannot be over-estimated. Every heat of steel is analyzed for each

element, and check analyses obtained; also, every substance used

in the mix is analyzed for all impurities. The importance of using

pure base materials is known to all manufacturers despite chemical

evidence that certain detrimental elements are removed in the process

of manufacture.



The manufacture of high-speed steel represents the highest art

in the making of steel by tool-steel practice. Some may say, on

account of our increased knowledge of chemistry and metallurgy,

that the making of such steel has ceased to be an 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.





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