Steel C22.8 is a non-alloy (carbon) steel specifically designed for pressure vessels, boilers, and general engineering applications. Its chemical composition is standardized under EN standards such as EN 10222-2, ensuring consistent quality and performance.

Typical chemical composition of C22.8 steel (approximate ranges):

• Carbon (C): 0.18 - 0.24 %
• Silicon (Si): ≤ 0.40 %
• Manganese (Mn): 0.40 - 0.70 %
• Phosphorus (P): ≤ 0.025 %
• Sulfur (S): ≤ 0.020 %
• Chromium (Cr): ≤ 0.30 %
• Nickel (Ni): ≤ 0.30 %
• Copper (Cu): ≤ 0.30 %
• Molybdenum (Mo): ≤ 0.08 %
• Vanadium (V): ≤ 0.02 %
• Aluminum (Al): often present in small amounts (e.g., 0.02-0.06 %) as a deoxidizer
• Iron (Fe): balance

The carbon level around 0.22% makes C22.8 a low-to-medium carbon steel, providing:

• Excellent weldability compared to higher-carbon steels
• Reasonable strength when normalized or heat-treated
• Superior toughness for pressure equipment applications

Phosphorus and sulfur are maintained at very low levels (≤ 0.025% and ≤ 0.020%) to:

• Enhance toughness and ductility
• Reduce brittleness risk, especially at low temperatures
• Improve weldability and resistance to cracking

Manganese (0.40-0.70%) contributes to:

• Slight strengthening of the steel
• Improved hardenability
• Enhanced deoxidation and overall steel cleanliness

Other alloying elements (Cr, Ni, Cu, Mo) are limited to low levels, maintaining the steel's classification as non-alloy while ensuring predictable mechanical properties, excellent weldability, and compliance with boiler and pressure-vessel codes.

Due to its balanced composition, C22.8 steel is commonly specified for:

• Pressure vessel forgings (flanges, nozzles, fittings)
• Boiler components and parts
• General mechanical components requiring moderate strength and superior toughness

The controlled composition, particularly the low phosphorus and sulfur content, is essential for safety-critical components subjected to pressure, temperature variations, and cyclic loading conditions.