RMS Titanic: A Metallurgical Problem

Historical Context

• Construction and Launch: The RMS Titanic was built by Harland and Wolff for the White Star Line, with its keel laid in 1909 and launched in 1911. It was part of a trio of ships intended to offer luxurious accommodations rather than compete on speed.
• Voyage and Collision: On its maiden voyage in April 1912, the Titanic struck an iceberg, leading to the sinking of the ship within 2 hours and 40 minutes.

Metallurgical Analysis

• Steel Quality: The steel used in the Titanic was typical for its time but inferior by modern standards. It had high sulfur and phosphorus content, which contributed to its brittleness.
• Notch Toughness: The steel’s notch toughness was very low at the water temperature of -2°C, making it prone to brittle fracture. The Charpy impact test showed the steel had an impact energy of only 4 joules at this temperature.
• Chemical Composition: The steel contained 0.21% carbon, 0.47% manganese, 0.045% phosphorus, and 0.069% sulfur. Modern steel has significantly lower levels of these impurities, resulting in better mechanical properties.

Mechanical Properties

• Tensile Strength: The steel met the design tensile strength requirements of 234 to 310 MPa, but its overall mechanical properties were inferior to modern steel.
• Fracture Behavior: The steel exhibited brittle fracture behavior at low temperatures, which was a critical factor in the rapid sinking of the Titanic.

Microstructure and Inclusions

• Microstructure: The steel’s microstructure included pearlite and acicular ferrite, with significant banding and inclusions.
• Non-metallic Inclusions: The steel was “dirty” by modern standards, containing a high volume of sulfides and silicates, which further reduced its toughness.

Modern Comparisons

• Improved Steelmaking: Modern steelmaking processes produce much cleaner steel with better mechanical properties. The modern steel used for comparison had a Mn:S ratio of 39:1, compared to 7:1 for the Titanic steel, resulting in higher notch toughness and lower ductile-brittle transition temperatures.

Conclusion

• Contributing Factors: The inferior quality of the steel, combined with design faults and poor seamanship, contributed to the rapid sinking of the Titanic. The study highlights the significant advancements in steelmaking over the past century.