Relationships among crystallographic texture, fracture behavior and Charpy impact toughness in API X100 pipeline steel

The crystallographic texture and Charpy impact toughness have been investigated in American Petroleum Institute (API) X100 pipeline steel, and the different rolling processes are applied to adjust the crystallographic texture for the sake of improving impact toughness. It has been found that the very weak textures exist in the steel only rolled in the recrystallization region of austenite, but the intensity of the unfavorable {001} 〈110〉 component is quite high. The {001} 〈110〉 texture is harmful for impact toughness and needed to be decreased in most cases. It is confirmed that the appropriate controlled rolling processes effectively reduce the intensity of the {001} 〈110〉 texture. By contrast, low temperature finish rolling in the non-recrystallization region produces the fine grain structures, beneficial textures and superior impact toughness at the low temperature. In addition, the occurrence of delamination in the ductile region generates the unfavorable cleavage crack on the fracture surface of Charpy specimen and inevitably reduces the impact energy in the upper shelf region. The delamination will occur continuously with decreasing temperature due to the large volume fraction of {001} planes parallel to the rolling plane.