Development of Steel HT60 with Low Susceptibility to Liquid Zinc Embrittlement for Power Transmission Tower

New steels HT60 whose goal is weight reduction, rationalization of fabrication and construction of power transmission tower are developed. In hot dip galvanizing process, weld heat affected zone cracking occurs occasionally due to liquid zinc embrittlement of steel. The larger the scale of fabricated sub-assembly for hot dip galvanizing, the larger is the thermal stress arised during the process. Improvement of susceptibility to liquid zinc embrittlement becomes, then, more important in development of new steels to be employed for larger scale tower. This report describes 1) an estimation of weight reduction of tower by employing HT60 steels, 2) establishing test methods for assessment of liquid zinc embrittlement of steel, 3) effect of alloying elements on liquid zinc embrittlement of steel, and 4) properties of steel pipes, plate and flange developed based on the results of studies above mentioned. New steels HT60 have satisfactory mechanical properties and weldability together with low susceptibility to liquid zinc embrittlement, and are favorable for the large scale power transmission tower application.