1. Field of application
in conjunction with the general technical delivery conditions specified in DIN 1690 Part 1, this standard specifies the properties of carbon and low alloy flake graphite cast iron ( grey cast iron) in castings manufactured in sand moulds or moulds of comparable thermal diffusivity.
The following characteristics to be considered are sistinguished:
a) the tensile strength in separately cast or cast-on (test) samples ( see table 1), or
b) the hardness of the material in the castings ( see talbe3)
gray iron standard DIN1694-flake-graphite-cast-iron-grey-cast-iron-properties.pdf
In fact, DIN 1691 has been superceded by DIN EN 1561. Grade GG 25 is now called EN-JL 1040 or EN-GJL-250,The equivalent ASTM standard and grade is A 48 Grade 40B.