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always meet the design/service need for the offshore industry. Failure

analysis studies on several salvaged structures have shown that low

notch toughness, laminations, lamellar tearing and poor weldability

were major contributors to the failures. This made offshore operators

and certifying authorities conscious of the need for more restrictive
standards to ensure that the steel is of high quality and satisfies strict

fracture toughness and weldability requirements.

* Therefore, standards such as API 2H, 2Y and 2W were developed. The

structural steels addressed in these standards include: killed fine grain

normalised, controlled rolled, quenched and tempered, and controlled

rolled and accelerated cooled (referred to as TMCP - Thermo-

Mechanical Control Process) These improvements resulted in

significant control on alloying elements (e.g. C, Mn, Nb, V, AI), major

reduction of impurities (e.g. S, P. N,) and improved uniformity of

composition and properties.

* The API 2W specification covers TMCP steel plates whose minimum

yield strength is between 290 and 414 MPa (42-60 ksi). TMCP steels

have been successfully used in many applications such as offshore

structures, pipelines, vessels and TLP tendons. A capacity that needs to

be assessed when using TMCP steel is the potential of softening of the

heat-affected zone (HAZ) combined with the presence of local brittle

zones (LBZ). While LBZ is not unique to TMCP steels, the potential of

HAZ softening is generally associated mainly with TMCP steels.

However, the presence of LBZ requires special attention for TMCP steels

because unlike normalised steel in which the HAZ yield strength is

higher than the base plate, the HAZ yield strength of TMCP steels tends

to be lower than both the weld metal and the base plate. The

combination of lower structural redundancy, higher stresses and the

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