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Parks Stephenson
| | Posted on Wednesday, January 17, 2001 - 11:05 pm: | 
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The current myth of "inferior steel" evolved from pure hindsight. It is true that the steel provided to Harland & Wolff by Dalzell and D. Colvilles & Co. was produced in acid-lined open-hearth furnaces, which allowed for impurities (such as sulfur and phosphorous) in the steel. These impurities led to low fracture resistance, especially in cold water conditions that reduced ductility (ability of the steel to deform without yielding), by reducing the amount of manganese present to bind to the residual sulfur. With insufficient manganese, the sulfur combined with the iron to form the ferrous sulfide, which created paths of weakness (especially along grain boundaries) along which fractures could propagate. The manganese-sulfur ratio of Titanic's steel recovered from the wreck site has been determined to be 6.8:1, low in comparison to steels produced today that have ratios as high as 200:1. The presence of phosphorous, even in minute quantities, also played a significant role in the initiation of fractures.
However, most of steel used by British shipyards during this period was produced using the open-hearth method; in fact, the metallurgy of the steel did not change significantly until after 1947, when wartime experiences prompted closer examination of the elemental properties of steel. At the time of her construction, Titanic's builders used top-quality steel that would remain the industry standard for years to come. The steel used in the R.M.S. Queen Mary, which survives to this day, was produced by the same mill that provided steel for Titanic and is essentially the same in composition. To accuse Titanic's builders of using "inferior steel" is unfair, as it would be decades before the minor elements of steel would be more fully understood. |
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