Volume 5, Issue 8 (September 2008)
Accelerated Cooling of Steel Plates: The Time Has Come
The accelerated cooling of steel plates is an already standard process that increases the competitiveness of this product and their users, as it allows the adoption of a leaner alloy design and the development of new mechanical property combinations with improved weldability. The maximum cooling rate achievable under industrial conditions depends on plate thickness, from 80°C/s (10 mm) to about 1°C/s (80 mm), in order to assure minimum temperature gradients along plate thickness and greater uniformity of mechanical properties. The main process variants of this process apply cooling over different temperature ranges: interrupted accelerated cooling, between 800 and 500°C, and direct quenching, between 900 and 200°C. In the first case it is aimed at a microstructural grain refining effect; in the latter one a fully martensitic microstructure is desired. The advantages promoted by these new process routes are already benefiting the main fields of application of heavy steel plates, like shipbuilding, civil construction, linepipes, penstocks, and so on. This paper is a brief status report about this technology and its future developments.