Q550D high-strength steel plate with low-yield-ratio and manufacturing method thereof

Abstract

The invention provides a Q550D high-strength steel plate with a low yield ratio. The Q550D high-strength steel plate comprises the following components in percentage by weight: 0.04-0.10 percent of C, 1.50-2.0 percent of Mn, 0.10-0.40 percent of Si, less than or equal to 0.0050 percent of S, less than or equal to 0.015 percent of P, 0.030-0.070 percent of Nb, 0.008-0.020 percent of Ti, 0.020-0.060 percent of Alt, 0.0010-0.0025 percent of B, and the balance of Fe and Inevitable impurities. The invention further provides a manufacturing method of the Q550D high-strength steel plate with low-yield-ratio, a controlled rolling, controlled cooling, low-temperature quenching and tempering process is adopted, the structure of the steel plate is acicular ferrite+blocky ferrite+martensite with the grain size smaller than 2 microns and distributed uniformly, the yield strength is 610-700 MPa, the tensile strength is 720-810 MPa, the yield ratio is smaller than or equal to 0.85, and longitudinal impact energy is 100J and more.

Description

technical field [0001] The invention belongs to the technical field of iron and steel material engineering, and relates to a low-yield ratio Q550D high-strength steel plate and a manufacturing method thereof. Specifically, the microstructure characteristic is acicular ferrite+ Massive ferrite + granular martensite low yield ratio high strength steel plate. Background technique [0002] Q550 high-strength steel plate is widely used due to its good strength and toughness, but its yield ratio is generally high due to its production process, generally greater than 0.92. In engineering practice, the yield ratio of steel is usually used as an important index to measure the safety of structures. Therefore, the study of high-strength steel with low yield ratio is of great significance to improve the engineering safety index. [0003] In the 550MPa low yield strength ratio steel, there are a large number of patented technologies involving low yield strength ratio high strength steel...

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Problems solved by technology

Patent announcement numbers CN111206185A, CN110983158A, CN109811256A, CN110423938A, etc., are all composed of one or more combinations of precious elements Ni, Cr, Mo, Cu with different contents, the composition is complex, and the cost of the alloy is relatively high

Patent announcement numbers CN107326304A, CN110331345A, CN107326304A, CN105385955A, etc. use TMCP, TMCP+ tempering process or ultra-fast cooling technology to improve strength. The process is relatively simple, but the yield strength of steel is relatively high, and too high yield ratio directly affects the safety of the structure performance

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