Abstract: A nickel-free LPG marine steel plate and a manufacturing method therefor belong to the technical field of high-strength structural steels; the steel plate consists of the following chemical components by mass percentage: 0.18 to 0.24% of C, 0.10 to 0.19% of Si, 16.1 to 18.9% of Mn, less than or equal to 0.012% of P, 0.15 to 0.35% of Mo, 0.10 to 0.25% of RE, and the balance of Fe and inevitable impurities; the steel plate has a yield strength of ?410 MPa and an impact absorption work of ?66 J at 150° C., has good low-temperature mechanical properties, can replace 5Ni and 9Ni-based steel, and is used for constructing an LPG storage tank and a relevant structural member at low costs.

Abstract: The present disclosure discloses a 690 MPa high-strength medium-manganese steel with low yield ratio and medium thickness and a manufacture method thereof, which relates to the technical field of steel smelting. The 690 MPa high-strength medium-manganese steel with low yield ratio and medium thickness is composed of the following chemical composition in mass percentage: C: 0.05%-0.10%, Mn: 4.1%-4.7%, Si: 0.15%-0.4%, P?0.010%, S?0.003%, Ti: 0.01%-0.05%, Ni+Cr+Mo?0.6%, and the balance of Fe and unavoidable impurities. The steel plate manufactured meets the safety performance and construction cost requirements of the construction machinery on the ultra-high-strength steel in complex environments.