JFE Steel has developed a series of high performance 610MPa class HSLA steel plates with excellent weldability (consisting of JFE-HITEN610U2 with high weldability, JFE-HITEN610U2L for low temperature use, and JFE-HITEN610E for high heat input welding) for the energy industry. Excellent properties of the plates and their weldments are brought about by the microalloying technology, and a direct-quenching and tempering process using Super-OLAC (on-line accelerated cooling) while including low C content, low weld cracking parameter (P_CM) value and free of B additive. JFE Steel has also developed a process for manufacturing high reliability heavy section steel plates with excellent internal quality by a combined forging and plate rolling process using high quality continuous casting slabs. Excellent internal properties can be obtained in the manufacture of heavy section SQV2B for pressure vessels and 200mm thickness class steel plates. All of these products have been applied in numerous plants.