What material is primarily used to make compression rings in a piston assembly?

Compression rings in a piston assembly are primarily made from steel. Steel is chosen for its excellent strength, durability, and ability to withstand the high temperatures and pressures found in engine combustion chambers. Steel's hardness also contributes to its effectiveness in maintaining a proper seal within the cylinder, which is crucial for optimal engine performance and efficiency.

While other materials like iron and aluminum have their uses in engine components, steel's properties specifically make it the ideal choice for compression rings. Iron tends to be heavier and less effective for this particular application. Aluminum, while lightweight and having good thermal conductivity, does not have the necessary strength to withstand the intense conditions experienced at the piston assembly level. Graphite is mostly used for lubrication or in certain types of engine components but is not suitable for compression rings due to its brittleness. This makes steel the best option for manufacturing compression rings, ensuring they perform effectively in sealing and maintaining the engine's compression.