Question

(Manufacturing Technology)

1. Do a summary what happen to titanic in the aspect of material(body) and the ductile brittle temperature(DBT) of the material

Answer 1

On analyzing a piece of the hull steel obtained from the titanic wreckage, it was discovered that it had sharp and jagged edges , a tell tale sign of brittle fracture. Also, the pieces showed no signs of any deformation. This was baffling to most researchers, as the steel used in hulls are expected to be a lot more ductile. They would typically deform rather than break. When a Charpy test was performed on the piece of hull steel, it was clear that brittle fracture contributed to the failure of the titanic. Obviously, this warranted further investigation. When a study was performed on the microstructure of the piece of steel, it showed high level of oxygen and Sulphur content. This in turn meant that the steel was a semi-kilned low carbon steel manufactured using an open furnace.

Temperature is the intrinsic property of a material that defines whether it is ductile or brittle. Below the ductile to brittle transition temperature , ductility of a material is directly proportional to temperature. Now the high oxygen content of the titanic hull steel causes this DBT temperature to be increased; meaning that the steel could turn brittle even at higher temperature. For steel used in most modern ship hulls , this temperature is -60C, which was about 30C for titanic. Furthermore, the high sulphur content caused an increase in the brittleness of the steel by disrupting its grain structure. Sulphur can also combine with magnesium to form magnesium sulphide which helps in propagation of cracks.