Gray Iron Castings

Class 25,30,35,40 tensile and heat resistant irons.

Gray Iron has a dense gray structure and offers excellent machinability. Grades 25, 30, 35 and 40 can fill specific requirements for hardness and wear, and heat treatments can yield even higher mechanical properties. Popular applications for gray iron include diesel and gasoline engine blocks and cylinder liners, and structural machine components where vibration dampening is required.

Gray Iron
Specifying Body Spec. No. Use Grade or Class Min. Tensile Strength (PSI) Other Requirements
ASTM A126 Valves, flanges and pipe fittings A 21000 .15% S. Max. .75% P Max
B 31000
C 41000
ASTM A48 Castings intended for general engineering use where strength is a major consideration 25 25000
  1. Test bar size shall be related in cooling to the critical section of the casting and so specified.
  2. At least two test bars shall be cast and prepared for each casting lot, the lot size being designated.
  3. Test bars shall be cast in dry silica sand molds similar to that in which the castings are poured.
  4. Tension tests shall be under true axial loading.
40 40000
Brinell Hardness Micro-structure
Cast in sand molds for the automobile, truck, tractor, and allied industries G2500 170-229 Ferritic-Pearlitic
G3000 187-241 Pearlitic
G3500 207-255 Pearlitic
G4000 217-269 Pearlitic
ASTM A278 Pressure containing parts for use up to 650ºF 25 Castings for intended use above 450ºF should be stress relieved.