The sinking of the RMS Titanic, the most advanced ship of the day and often called unsinkable, ranks among the most captivating disasters of the early twentieth century. On the cold, clear night of April 15, 1912, the Titanic struck an iceberg in the North Atlantic Ocean and sank below the surface two-and-a-half hours later, coming to rest on the sea bottom over 12,000 feet below. According to most estimates, over 1500 passengers and crew perished in the icy waters that night. As the hundred-year anniversary of the Titanic disaster approaches, modern analytical techniques are bringing new understanding to causes behind the tragedy of the Titanic.
On March 7, 2012 Mines was visited by Bruce L. Bramfitt, Senior Metallurgical Consultant at ArcelorMittal-Steelton who gave his lecture entitled, “The RMS Titanic: 100 Years Later.” Bramfitt focused on what caused the ship to sink and worked to answer the question, “Why did she sink so fast?” He cited three major contributing factors to the accident – human error, construction of the ship, and the metallurgical characteristics of the hull. As with almost any large disaster, it was not just one factor that caused the Titanic disaster, but a combination of several.
Bramfitt said that the human error in the accident could be described more as “human arrogance.” Much has been written about the questionable decisions made by both the ship’s captain, Edward Smith, and J. Bruce Ismay, the owner of the White Star Line. Smith reportedly knew there were icebergs in the area – he had received warnings via the state-of-the-art wireless system on board. Ismay was under pressure to meet an April 17 arrival deadline in New York city for an elaborate promotional celebration. According to Bramfitt, “What [Smith] should have done is stopped or slowed down knowing ahead of him was a field of ice.” When the iceberg was spotted, Titanic was traveling at maximum speed just as it had been during previous days when the ocean was calm.
Other circumstances during the night made the iceberg more difficult to spot. The water was calm and the night was without much moonlight, so there was no visible froth around the iceberg at the waterline to give away its position. Even if the conditions had been better, the iceberg may not have been spotted until too late, because the binoculars for the crow’s nest had been left off the ship. These combined to make the spotting of the iceberg and the precautions taken to avoid it happen at the last second where it was ultimately too little too late. Said Bramfitt, “People feel if [Titanic had] hit the berg straight on, it could have been very different.”
The physical construction of the ship played a large role in why she sunk so quickly. The interior of Titanic was made up of 16 sealable watertight compartments, four of which could be breached without the ship sinking. When the ship hit the iceberg, five compartments were breached, but it was their construction which exacerbated the breaches. Instead of going from the bottommost deck of the ship to the uppermost deck, the compartments only went up to E-deck, which left the four decks above E-deck to run the length of the ship uninterrupted. As the compartments filled, water spilled over the tops of the compartments from the front of the ship to the back like a giant ice cube tray full of water.
After covering the human and large scale construction factors, Bramfitt explained how the steel and small scale ship construction influenced the disaster. When it was built, Titanic was constructed using the most advanced ship construction technique of the day, which was riveted plates. Over three million rivets were used in the ship’s construction with stronger steel rivets in the center of the ship and more flexible wrought iron rivets in the curved sections of the bow and stern.
Rivets were used because, “As the rivet cools, it shrinks and forms a very tight bond between the two plates,” said Bramfitt. There was a problem with the riveting process however, because, “The rivet holes were cold punched, which creates a burr on the opposite side of the plate which can contain tiny cracks.” Cracks contain sharp angles and corners which amplify stresses in the steel and can cause it to fail sooner than anticipated.
The steel itself circa 1910 is also suspect. Hull plates were produced at the Dalzell Works of David Colville & Sons in Scotland in an acid open hearth furnace. At the time, more steel was produced in this type of open hearth furnace than in any other, but by 1975, there was very little steel being made in acid open hearth furnaces. There are many differences in chemical composition between the Colville steel and modern steel.
Bramfitt was able to examine a piece of steel brought up from the wreck in 1996 as part of the Discovery Channel expedition, “Titanic, Anatomy of a Disaster.” He and his colleagues found that the Colville steel contained much higher levels of phosphorus and sulfur than modern steel and that it had a much lower ratio of manganese to sulfur. These combined to give the Colville steel a significantly lower yield strength than modern steel. The steel needed only a small impact to fail in the minus two degree Celsius waters of the North Atlantic.
A collision between the Titanic’s sister ship, the RMS Olympic, and the HMS Hawke provides a clue as to how Titanic’s hull might have failed when it contacted the iceberg. An image taken of the Olympic after its collision shows brittle fracture in the hull plate, fracturing between rivet holes, bending of the hull plate, and missing rivets. Said Bramfitt about the Titanic, “Back in 1912, they thought they developed a 300 foot gash on the starboard side below the waterline.” Modern ultrasound scans have shown six damaged locations along the side of the hull.
Metallographic analysis of the Titanic’s hull steel performed by Bramfitt showed numerous slag inclusions and striations. Having only examined modern steel until he looked at the Titanic’s hull steel, Bramfitt was surprised by the appearance of the inclusions because they contained white blobs and streaks. A backscatter image of the inclusions showed that the blobs were sulfur compounds and that the inclusions contained manganese silicate, as well as some titanium, which provides a clue that the iron for the Titanic came from Sweden. Said Bramfitt, “Ironically, it was called ‘titanic’ steel.” The Swedish iron was preferred over British iron because it was naturally of a higher quality.
While the steel used in the construction of the Titanic would never be used in the construction of a ship today, it was the best available at the time. Said Bramfitt, “They were kind of working in the dark.” Metallography was still in its infancy, and there was no standard test to measure the impact properties of steel. The ductile to brittle transition in steel was also not well known, and any tests that were made occurred at room temperature.
The sinking of the Titanic brought about many changes to the practice of passenger shipping. In addition to modifications to lifeboat and ship building regulations, the disaster also spurred on the creation of the International Ice Patrol to monitor the waters of the North Atlantic for icebergs. In regards to exactly what happened, Bramfitt said, “We will never truly know.” He concluded saying, “After 100 years, it is time to let the Titanic rest in peace at the bottom of the ocean.”
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