This is an interesting book on steel technology in 1921 by Fred
Colvin;
http://www.gutenberg.org/files/20282...-h/20282-h.htm


"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. "