Development of 60 kgf/mm2 Steel for Power-transmission Pipe Tower and Its Resistance to Liquid Zinc Embrittlement

There are many recently constructed power-transmission steel towers that are larger in size than ordinary ones. Higher strength steel is considered necessary for the large size tower to reduce its weight. Besides usual mechanical properties, the steel must have the resistance to zinc coating-induced cracking (ZIC) due to liquid metal embrittlement (LME). 1) Testing methods are developed to evaluate the ZIC susceptibility quantitatively. 2) Index for the ZIG susceptibility (S400LM) is expressed as a function of chemical composition of steel. If the value of S400LM is larger than 42%, the ZIC would not occur. 3) New 60 kg/mm2 steels are developed as plate, UO pipe and ERW pipe for the use of a power-transmission tower. The steels show the excellent resistance properties to the ZIC and mechanical properties including buckling properties of pipes.