The requirements placed on steel plates for construc­tion and industrial machinery use have diversified in recent years, as exemplified by low temperature tough­ness to enable use in cold districts and improved weld­ability by lowering the preheating temperature for weld­ing. To meet these requirements, JFE Steel has developed new abrasion resistant steel plates, “JFE-EH360LE/EH500LE,” and a new high strength steel plate, “JFE-HITEN780LE,” with good weldability and low tempera­ture toughness guaranteed at -40°C. In the developed steel plates, high hardness or high strength was achieved by selecting the optimum C content and hardenability (D_I), while reducing the carbon equivalent (C_eq) in con­sideration of weldability. Low temperature toughness at -40°C was improved in the developed steel plates by applying microalloying and thermo-mechanical control process (TMCP)/controlled heat treatment process tech­nologies to refine prior austenite grains.