ASTM A48 CLASS 40 GRAY CAST IRON
No. 40 is a middle grade of gray
cast iron in USA. There is no equal grade for other
countries. In China, it could be taken as the grade between HT250
and HT300, or between GG25 and GG30.
Physical properties of class 40:
Tensile strength tested from test bar min. 276 Mpa. As for gray cast
iron, there was no requirements to the yield strength and elongation
normally. The hardness should be about 200-250 Brinell Hardness.
However, this range is only for reference. According to the
characters of castings and application, the iron foundries and
clients could produce and require the special hardness range.
Chemical composition of class 40:
As for this grade, the chemical composition is not required in the
standards, the cast iron manufacturers could adjust their
composition according to their experience, as long as the tensile
strength could meet the requirement. The following is the common
chemical components just for reference.
C: 2.80-3.30, Si: 1.20-1.70, Mn: 0.70-1.20, P≤0.15, S≤0.12, Carbon
Actually, this grade is only can be found in ASTM standard, so it is
not used widely. Most of designer will choose to use lower grade
class 35 or higher grade class 45 as a replacement.
In China, most of iron foundries could produce grade class 35, but
few are willing to produce class 45. It is mainly because the
hardness of class 45 is more difficult to control. For some
positions with thin wall thickness, the high hardness will happen,
and will affect the machining works.
The following product sprocket wheel for boilers was manufactured by
ASTM A48 Gr 45.