800 MPa-grade high-toughness weather-resistant thick steel plate and preparation method thereof

Abstract

The invention discloses an 800 MPa-grade high-toughness weather-resistant thick steel plate. The 800 MPa-grade high-toughness weather-resistant thick steel plate is characterized by being prepared by smelting the following components of, in mass percentage, less than or equal to 0.12% of C, 0.05%-0.55% of Si, 1.20%-1.70% of Mn, less than or equal to 0.010% of P, less than or equal to 0.001% of S, 0.45%-1.20% of Cr, 0.30%-1.20% of Cu, 0.30%-1.40% of Ni, greater than or equal to 0.030% of Alt, 0.002%-0.030% of Ti, 0.002%-0.10% of V, 0.10%-0.80% of Mo, 0.0001%-0.0030% of B, 0.001%-0.010% of Ce, 0.80%-1.60% of Cr+Cu, 2.00%-3.00% of Cr+Mn+Mo, greater than 6.5% of I, less than or equal to 0.64% of CEV, less than or equal to 0.27% of Pcm and the balance Fe and inevitable impurities. A heat treatment method of the thick steel plate comprises the following steps of quenching the steel plate twice, and carrying out heat preservation for 2.5-4.5 min / mm under the temperature 400-720 DEG C and then carrying out tempering so as to obtain a fine and uniform lath-shaped microstructure of tempered bainite or tempered sorbite with ferrite. The steel plate has the advantages of being large in thickness, low in yield ratio, high in strength, good in toughness, resistant to atmospheric corrosion and the like, and can be widely applied to construction of steel structures such as large bridges and buildings.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular relates to an 800MPa grade strong and tough weather-resistant thick steel plate used for manufacturing steel structures such as large bridges and a preparation method thereof. Background technique [0002] Since the 1970s, the United States, Japan, Europe and other countries and regions have gradually increased the strength of the steel used in bridge engineering within a certain range, and used coating-free weather-resistant steel and better weldability and comprehensive performance. High-performance steel. In the 1990s, 800MPa high-performance bridge steel began to be used in bridge projects in the United States and Japan. At present, my country's bridge construction is in the ascendant. my country has become a big bridge construction country and is moving towards a bridge construction power. The demand for high-strength, weather-resistant, high-performance bridge steel is ...

AI Technical Summary

Problems solved by technology

[0006] The patent document with Chinese patent application number 201510021680.X discloses a low yield ratio high-performance bridge steel and its manufacturing method. The thickness of the steel plate is only 12mm, and the Φ450mm two-roll reversible hot rolling experimental rolling mill is rolled without heat treatment. Emphasis on ultra-rapid cooling after rolling, the microstructure is composed of high-temperature and low-temperature bainite and refined Ma-O island components, which is not applicable to thick steel plates

[0007] The patent document with Chinese patent application number 201510125485.1 discloses a low-yield-ratio high-strength and tough thick steel plate with excellent low-temperature impact toughness and its manufacturing method. It needs to add more than 3.5% of precious alloy Ni, which greatly increases the cost and is not weather-resistant.

[0013] ⑶, steel plate yield ratio is low, yield ratio (Rp0.2 / Rm) ≤ 0.85;

Images