Low-yield ratio and high-strength steel for bridges and manufacturing method thereof

Abstract

The invention discloses low-yield ratio and high-strength steel for bridges and a manufacturing method thereof. The steel comprises the following chemical components by weight percent : 0.06-0.10 percent of C, 0.20-0.45 percent of Si, 1.20-1.50 percent of Mn, no more than 0.010 percent of P, no more than 0.0020 percent of S, 0.30-.060 percent of Ni, 0.20-0.50 percent of Cu, 0.15-0.50 percent of Mo, 0.025-0.060 percent of Nb, no more than 0.035 percent of Ti, 0.020-0.040 percent of Alt, and Fe and unavoidable impurities in balancing amount. According to the invention, through smelting, refining, performing a reasonable thermo-mechanical control process (TMCP) and optimizing tempering heat treatment production, the tensile strength of the steel is 700-780 MPa, the yield strength is 530-600MPa, the extensibility is greater than or equal to 18 percent, the yield ratio is less than or equal to 0.80, and 40 below zero DEG C low-temperature longitudinal impact is greater than or equal to 100 J, so that the steel is good in obdurability matching and low in the yield ratio, is provided with excellent performance of shock prevention, and is stable in production process and strong in operability.

Description

technical field [0001] The invention relates to a high-performance structural steel and a manufacturing method thereof, in particular to a low yield ratio high-strength bridge steel and a manufacturing method thereof. Background technique [0002] my country's bridge construction is developing in the direction of high speed, heavy load, large span, fully welded joints, no coating, and high safety. The yield strength of currently used bridge steels generally ranges from 245 to 420 MPa; in order to meet the requirements of technological progress in bridges, high-performance structural steels that integrate high strength, high toughness, and earthquake resistance are ideal for future Shanghai-Tong, Qiongzhou Strait and It is the preferred material for key components of large-span heavy-duty railway bridges to be built in Bohai Bay and other batches, and the demand is clear. [0003] Foreign countries have developed and used high-performance bridge steel varieties. The United ...

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Problems solved by technology

[0005] The existing patents on the manufacturing method of steel for bridge engineering are mainly to obtain steel plates for bridge engineering through controlled rolling, controlled cooling and heat treatment. After searching, it is found that Chinese patent CN102021495 discloses 420MPa high-toughness weather-resistant bridge steel and its hot-rolled coils. Preparation method, the process flow is converter smelting→LF furnace refining→RH vacuum treatment→casting, the carbon content is designed to be 0.015-0.045%, and the steel used for high-toughness bridge engineering is produced. Since the composition is designed to be low-carbon, the strength of this steel is low , the yield strength ratio is too high, which can no longer meet the needs of high-performance bridge engineering steel

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