Advances in Physical Metallurgy and Processing of Steels. Development of Steel Plates by Intensive Use of TMCP and Direct Quenching Processes.

Abstract

Historical progress of Thermo-Mechanical Processing (TMP) in steels during a last half century is briefly reviewed in the first part of this paper. On-line accelerated cooling process in a wide plate mill was developed by a Japanese steel mill in the end of 1970's, and its equipment was installed into major steel plate mills in Japan and Europe in 1980's. The combination of controlled rolling and accelerated cooling called as TMCP provided a powerful means for microstructural control of hot rolled steel plates. Subsequently, direct quenching (DQ)-tempering process was industrialized, where direct quenching after finish-rolling was performed at the highest cooling rate available in the accelerated cooling equipment. Since then, various new steel plates have been developed by intensive use of TMCP and direct quenching process particularly in Japan. In the latter part of this paper, newly developed steel plates by use of TMCP or DQ process during last two decades were summarized based on classification of line pipe steel, weldable HSLA steel plates used for shipbuilding, offshore construction, building, bridge or penstock, and austenitic stainless steel plate. Various strengthening mechanisms such as grain refinement, precipitation hardening or strengthening due to transformed microstructures have been utilized in development of numerous TMCP and DQ steel plates.