SULPHUR
Sulphur is another impurity and high sulphur is even a greater detriment to steel than phosphorus. High sulphur up to 0.09 per cent helps machining properties, but has a tendency to make the steel "hot short," i.e., subject to opening up cracks and seams at forging or rolling heats. Sulphur should never exceed 0.06 per cent nor phosphorus 0.08 per cent.
Steel used for tool purposes should have as low phosphorus and sulphur contents as possible, not over 0.02 per cent.
We can sum up the various factors something as follows for ready reference.