Quenched and tempered steel sheet and manufacturing method thereof

Abstract

The invention provides a 80kg extra-thick quenched and tempered steel sheet. The steel sheet comprises the following chemical compositions: 0.10 to 0.16 percent of C, less than or equal to 0.20 percent of Si, 0.85 to 1.25 percent of Mn, less than or equal to 0.013 percent of P, less than or equal to 0.0030 percent of S, 0.20 to 0.45 percent of Cu, 0.90 to 1.50 percent of Ni, 0.45 to 0.75 percent of Cr, 0.40 to 0.65 percent of Mo, 0.030 to 0.060 percent of V, 0.045 to 0.070 percent of Als, 0.006 to 0.012 percent of Ti, less than or equal to 0.0060 percent of N, 0.0006 to 0.0014 percent of B, 0.001 to 0.005 percent of Ca, and the balance of iron and inevitable impurities, wherein the chemical compositions meet the following conditions that: the Mn equivalent / C is more than or equal to 10 and less than or equal to 20; the Als is more than or equal to (Mn equivalent / c)*(N-0.292Ti); the Ni equivalent is more than or equal to 1.15 percent; the Mo equivalent is more than or equal to 0.25 percent; Ca / S is more than or equal to 0.80 and less than or equal to 3.00, and (Ca)(S)0.18 is more than or equal to 5*10<-4> and less than or equal to 2.5*10<-3>; and F*DI equals to the effective hardenability index Deff and is more than or equal to 1.00*t. The invention also relates to a method for manufacturing the quenched and tempered steel sheet. The technology of optimal recrystallization controlled rolling+offline quenching and tempering is adopted to ensure that the microstructure of the finished product steel sheet is a fine tempered bainite and tempered martensite, the average colony size is less than 25mu m, and excellent obdurability / plasticity matching and uniform mechanical performance along the direction of the sheet thickness can be acquired.

Description

technical field [0001] The invention relates to a quenched and tempered steel plate, in particular to an 80-kg super-thick (≥100mm) quenched and tempered steel plate and a manufacturing method thereof. Background technique [0002] As we all know, low-carbon (high-strength) low-alloy steel is one of the most important engineering structural materials, widely used in oil and gas pipelines, offshore platforms, shipbuilding, bridge structures, boiler containers, building structures, automobile industry, railway transportation and machinery manufacturing. middle. The properties of low-carbon (high-strength) low-alloy steel depend on its chemical composition and the process system of the manufacturing process, among which strength, toughness and weldability are the most important properties of low-carbon (high-strength) low-alloy steel, which ultimately determine the quality of the finished steel. microstructural state. With the continuous development of science and technology,...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to obtain the excellent strength, low-temperature toughness and strength-toughness matching of ultra-thick (≥100mm) quenched and tempered steel plates by combining the combined design of steel plate alloy elements with the special quenching and tempering process (RCR+QT). The weldability is also excellent, and successfully solved the problem of uneven strength and toughness of the ultra-thick quenched and tempered steel plate along the thickness direction of the steel plate

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