In this book advanced steel technologies mainly developed at the National Institute for
Materials Science (NIMS) Japan for structure control mechanical properties and the related
mechanisms are introduced and discussed. NIMS has long worked on developing advanced steel
techniques namely producing advanced steels by using only simple alloying elements such as
carbon manganese and silicon and also by utilizing steel scrap. The hope is that this
approach will lead to a technology of a so-called steel-to-steel recycling process with the
ultimate goal of a recycling process such as an automotive-steel-to-automotive-steel recycling
process to take the place of the current cascade-type recycling system. The main idea is to
utilize ultra-grain refining structures and hetero structures as well as martensite structures.
In particular the focus of this book is on tensile strength and toughness of advanced steels
from both the fundamental and engineering points of view. Fundamentally a unique approach to
analysis is taken based on fracture surface energy as effective grain size is employed to
better understand the mechanism of property improvement. From the engineering point of view in
fracture toughness such factors as crack tip opening displacement (CTOD) of advanced steels are
evaluated in comparison with those of conventional steels.
