960MPa-yield-strength low-yield-ratio maritime work steel plate and preparation method thereof

Abstract

The invention discloses a 960MPa-yield-strength low-yield-ratio maritime work steel plate and a preparation method thereof. The steel plate comprises the following chemical components in percentage by mass: 0.10 to 0.20 percent of C, 0.10 to 0.30 percent of Si, 1.00 to 1.50 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.005 percent of S, 0 to 0.50 percent of Cu, 0.20 to 0.60 percent of Cr, 0.50 to 3.00 percent of Ni, 0.20 to 0.80 percent of Mo, 0.20 to 1.00 percent of Co, 0 to 0.050 percent of Nb, 0.020 to 0.100 percent of V, 0.005 to 0.015 percent of Ti, 0.0005 to 0.0020 percent of B and the balance of Fe and inevitable impurities, and the carbon equivalent CEV is less than or equal to 0.75 percent. Based on the components, the medium-thickness steel plate with high strength and toughness and low yield ratio is prepared through smelting, controlled rolling and controlled cooling processes and (alpha+gamma) two-phase region annealing, complete austenitizing quenching and medium-low temperature tempering treatment processes. According to the prepared steel plate, the yield strength ReH is larger than or equal to 960 MPa, the tensile strength Rm is larger than or equal to 1100 MPa, the yield ratio YR is smaller than or equal to 0.95, the percentage elongation after fracture A is larger than or equal to 12%, and the impact toughness at the temperature of -40 DEG C is larger than or equal to 69 J. Compared with an existing 960MPa-grade medium-thickness steel plate, the product has good matching of strength, plasticity and toughness and low yield ratio, and is suitable for medium-thickness steel plate production.

Description

technical field [0001] The invention relates to the technical field of iron and steel materials, in particular to a steel plate for marine engineering with a yield strength of 960 MPa and a low yield strength ratio and a preparation method thereof. Background technique [0002] With the vigorous investment in national infrastructure construction in recent years, high-strength structural steel has been widely used in construction machinery, mining, hoisting mine trucks, offshore platforms, etc. Therefore, the use of high-strength structural steel Higher requirements are put forward for mechanical properties. Not only is it required to have high strength to meet the requirements of lightweight structures, but it should also have low yield ratio, excellent low-temperature toughness, weldability and corrosion resistance, etc., to meet the requirements of safety, reliability and longevity of steel structures. [0003] The demand trend of 960MPa high-strength marine steel with go...

AI Technical Summary

Problems solved by technology

However, due to the small reduction amount of large thickness steel plate, it will lead to limited grain refinement, resulting in uneven structure in the thickness direction of the plate, and finally lead to a large difference in mechanical properties in the direction of plate thickness

The traditional quenching and tempering heat treatment (quenching + high temperature tempering) has certain advantages in the production of steel plates with higher requirements for performance stability and uniformity, but after quenching of hot rolled steel plates, the grain refinement degree is limited, and high temperature tempering will lead Yield ratio increases, unable to meet engineering applications that require low yield ratio

[0005] To sum up, there are many deficiencies in the existing marine steels with a yield strength of 960 MPa, such as poor microstructure uniformity, poor performance stability, and high yield ratio.

To achieve yield strength R at the same time eH ≥960MPa, tensile strength R m ≥1100MPa, yield strength ratio YR≤0.95, elongation after fracture A≥12% and -40°C impact toughness ≥69J comprehensive performance requirements, and have good structure uniformity and performance stability, the existing alloy composition design and the process route has been difficult to meet

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