Properties of Gray Cast Iron

Gray cast iron, recognized for its unique microstructure, combines a steel-like matrix with embedded graphite flakes. This structure classifies it into three primary types based on the matrix composition: ferritic, pearlitic, and ferrite-pearlitic mixtures.

The mechanical properties of gray cast iron are fundamentally influenced by both the matrix structure and the morphology of the graphite. The flake graphite acts as natural stress risers, particularly at sharp edges, leading to stress concentration. This results in tensile strength, ductility, and toughness significantly lower than those of cast steel, although its compressive strength remains comparable. Consequently, gray cast iron is often viewed as having moderate to limited mechanical performance within the cast iron family.

The matrix plays a critical role in performance. Ferritic gray iron, with its coarse graphite flakes, offers the lowest strength and hardness, limiting its industrial use. Pearlitic gray iron, characterized by finer graphite dispersion, provides superior strength and hardness, making it the preferred choice for critical components. The ferrite-pearlite matrix, with relatively thicker graphite, yields intermediate properties.

Despite its mechanical limitations, gray cast iron excels in key operational attributes: excellent castability, superior vibration damping, high wear resistance, good machinability, low notch sensitivity, and notable cost-effectiveness. These advantages ensure its widespread application across various industries.

Typical Applications by Grade:

• Grade 100 & 150: Used for covers, handwheels, frames, housings, benches, pump bodies, valves, pipes, and flywheels.

• Grade 200 & 250: Suitable for cylinders, gears, engine blocks, cylinder liners, pistons, gearboxes, brake drums, and compressor parts.

• Grade 300: Employed in heavy-duty machine tool beds, press frames, high-pressure hydraulic components, piston rings, camshafts, crankshafts, and cylinder heads.

For detailed technical specifications and material equivalence across DIN, ISO, ASTM, and GB standards, please refer to our comprehensive gray iron material comparison guide.