Research and Development > JFE TECHNICAL REPORT >JFE TECHNICAL REPORT No.20 March 2015 - Special Issue on “Steel Plates” and “Welding and Joining” > Offshore Structural Steel Plates for Extreme Low Temperature Service with Excellent HAZ Toughness

No.20 March 2015 - Special Issue on “Steel Plates” and “Welding and Joining”

Offshore Structural Steel Plates for Extreme Low Temperature Service with Excellent HAZ Toughness

ICHIMIYA Katsuyuki      FUJIWARA Takaki      SUZUKI Shinichi

Abstract

Higher strength and toughness are required for offshore steel plates used for natural gas and petroleum resources development, as installation areas of structures move into arctic areas. The main property of offshore structure steel is the crack tip opening displacement (CTOD) property of weld joint, and the demand for satisfying −40°C of CTOD test temperature specification has increased. For the improvement of heat affected zone (HAZ) toughness, coarse austenite grain is suppressed by the pinning effect of TiN and oxysulfides, and low-C, -carbon equivalent (Ceq), -Si, -P, -Nb are adopted to decrease the martensite-austenite (M-A) constituents. Furthermore, by Ca inclusion which has the pinning effect of grain coarsening and ability to nucleate ferrite grain, finer bainite HAZ microstructure and excellent HAZ toughness ara achieved, and yield point (YP) 420 MPa class high strength steel was developed.

Full Pages