35
OF ENGINEERING FORMULÆ.
Notes on Ibon—continued.
FOREIGN SUBSTANCES IN IBON AND STEEL.
Silicon is generally excluded as slag, its pre-
sence makes iron hard and brittle; but up to
•08 per cent, it will do no harm, provided ’3 of
Manganese is present with it.
Sulphur makes iron and steel “ red-short."
Phosphorus. 0'5 to 0'8 per cent, is sufficient
to produce cold-shortness in iron; in steel, phos-
phorus to an extent of 0 2 per cent, does not
affect the working or hammering of steel; but
rails with more than ’08 per cent, will not stand
the required tests.
Manganese. 0 • 5 per cent, is sufficient to make
iron cold-short; it is valuable in iron to be con-
verted into steel.
Arsenic produces red-shortness in iron, but is
valuable in chilling; it increases the hardness of
steel at the expense of toughness.
Copper renders steel red-short.
Tungsten renders steel hard and tenacious.
Vanadium improves the ductility of iron for
wire-drawing.
Carbon. -25 per cent, gives malleable iron;
•50 per cent, gives steel; 1’75 gives the limit of
welding steel; 2'00 gives the lowest limit of cast
iron. ,
MALLEABLE CASTINGS.
Malleable castings are formed by subjecting
the castings to a process of annealing in boxes
with hematite iron ore or black oxide of iron.
The boxes are kept in an annealing oven under
equable heat, the duration of the process depend-
ing on the form and size of the castings.
D 2