Microstructure and properties of intercritically reheated coarse-grained heat affected zone in X65 pipeline steel with pre-strain

The properties of the intercritically reheated coarse-grained heat affected zone (ICCGHAZ) in X65 pipeline steel with large deformation are studied. The ICCGHAZ is composed of acicular ferrite, granular bainite and lath bainite. With the increasing t8/5 (the time for specimens to cool from 800 degrees C to 500 degrees C), the sulfide stress corrosion cracking (SSCC) resistance with and without pre-strain both increases, and the secondary cracks propagate along the necklace-type martensite-austenite (M-A)/matrix interface or near the M-A constituents, and the fracture toughness decrease. When t8/5 = 30 s, ICCGHAZ has the most ideal performance on fracture toughness and stress corrosion resistance.