For the purpose of reducing alloys additions and then its cost of conventionally combined Nb-V microalloyed Q460 grade steel plates for construction,a HSLA steel alloying design with only V-N microalloying of 0.06-0.08%V and free of niobium,and corresponding thermal mechanical controlled process were facilitated by better understanding the third generation TMCP concept and V-N microalloying technology.These resulted in successfully commercializing gauge 50mm V-N microalloyed Q460GJC steel plates with good combination of high strength>470MPa and improved toughness of Akv@0℃>150 J,and low YS/UST ratio of 80%as well.Theoretical calculation indicated that the contribution by fined-grain and precipitate strengthening amount to~66%of yield strength of the newly developed plate steels.