Indian Standards — Meaning of Cast Iron Grade FG 150 According to Indian Standard designations, what does 'FG 150' signify for a cast iron?

Introduction / Context:
Standardised grade designations allow engineers to select materials confidently. In Indian Standards (IS) for grey cast iron, the designation “FG” denotes “Flake Graphite,” followed by a number indicating mechanical performance.

Given Data / Assumptions:

• We refer to grey cast iron grading under older/common IS conventions (FG grades).
• The numeric suffix represents a specific mechanical property value.
• Units are megapascals (MPa) for tensile strength unless otherwise noted.

Concept / Approach:
“FG 150” indicates a grey cast iron where the minimum specified tensile strength is 150 MPa. The “FG” prefix identifies grey iron (flake graphite microstructure). BHN (Brinell hardness number) is not encoded in this grade name, nor are compressive or yield strengths implied by the numeric suffix.

Step-by-Step Solution:
Decode “FG”: Flake Graphite → grey cast iron.Interpret “150”: minimum tensile strength = 150 MPa.Eliminate options interpreting the number as BHN or compressive strength.Select the option that pairs grey iron with 150 MPa tensile strength.

Verification / Alternative check:
IS conventions and many textbooks explicitly list FG 150, FG 200, etc., with the number indicating minimum tensile strength in MPa.

Why Other Options Are Wrong:
BHN links hardness, not tensile grade naming.White or malleable irons use different designations; “FG” is specific to grey irons.

Common Pitfalls:
Confusing hardness numbers with strength grades; they are specified separately.

Final Answer:
grey cast iron with 150 MPa as the minimum tensile strength