Sulphur

: COMPOSITION AND PROPERTIES OF STEEL
: The Working Of Steel

SULPHUR is another element (symbol S) which is always found in

steel in small quantities. Some sulphur is contained in the ore

from which the iron is smelted; more sulphur is introduced by the

coke and fuel used. Sulphur is very difficult to get rid of in

steel making; in fact the resulting metal usually contains a little

more than the raw materials used. Only the electric furnace is

able to produce the necessary heat nd slags required to eliminate

sulphur, and as a matter of fact the sulphur does not go until

several other impurities have been eliminated. Consequently, an

electric steel with extremely low sulphur (0.02 per cent) is by

that same token a well-made metal.



Sulphur is of most trouble to rolling and forging operations when

conducted at a red heat. It makes steel tender and brittle at that

temperature--a condition known to the workmen as red-short. It

seems to have little or no effect upon the physical properties

of cold steel--at least as revealed by the ordinary testing

machines--consequently many specifications do not set any limit

on sulphur, resting on the idea that if sulphur is low enough not

to cause trouble to the manufacturer during rolling, it will not

cause the user any trouble.



Tool steel and other fine steels should be very low in sulphur,

preferably not higher than 0.03 per cent. Higher sulphur steels

(0.06 per cent, and even up to 0.10 per cent) have given very good

service for machine parts, but in general a high sulphur steel

is a suspicious steel. Screw stock is purposely made with up to

0.12 per cent sulphur and a like amount of phosphorus so it will

cut freely.



Manganese counteracts the detrimental effect of sulphur when present

in the steel to an amount at least five times the sulphur content.