A kind of production method of high strength and toughness bridge structure steel plate

Abstract

A method for producing high-strength and tough bridge structural steel plates, the chemical composition weight percentage of the steel is: C=0.03%~0.08%, Si=0.30%~0.50%, Mn=1.50%~2.00%, P≤0.015%, S≤ 0.005%, Al=0.02%~0.05%, Ti=0.008%~0.030%, Nb=0.03%~0.08%, Cr=0.30%~0.50%, Cu≤0.20%, the balance is Fe and unavoidable impurity elements . This method adopts low-carbon composition design, does not add alloy elements Ni and Mo, and produces bridge structural steel plates with a yield strength of Q500q level through thermomechanical controlled rolling, multi-stage controlled cooling, tempering heat treatment, etc., and its yield strength is ≥500MPa , Tensile strength ≥ 630MPa, yield ratio ≤ 0.85, elongation ≥ 18%, ∑-40°C impact energy ≥ 120J, no plastic transition temperature NDT ≤ - 70°C, - 40°C crack tip opening displacement CTOD ≥ 0.50mm , Conditional fatigue limit ≥ 500MPa, and can realize welding without preheating at the same time, which better meets the engineering application requirements of long-span bridge steel structures.

Description

technical field [0001] The invention belongs to the technical field of low-alloy structural steel production, and in particular relates to a production method of a high-strength and tough bridge structural steel plate. Background technique [0002] In recent years, bridge steel structures have been developing rapidly in the direction of large span, heavy load, light weight, greening, all-welded joints, and high safety. For this reason, the engineering application of bridge structural steel is required to gradually increase from Q345q, Q370q, Q420q to strength The higher-level Q500q and even the Q690q are boosted. However, as the strength level increases, bridge structural steel not only needs to add more precious alloys such as Ni and Mo, which increases the cost of bridge construction, but also affects the yield ratio, weldability, fracture resistance, fatigue resistance, etc. of the steel plate. Difficulty controlling performance. [0003] Chinese patent CN103352167A ado...

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Problems solved by technology

However, with the increase of the strength level, the bridge structural steel not only needs to add more precious alloys such as Ni and Mo, which increases the cost of bridge construction, but also affects the yield ratio, weldability, fracture resistance, and fatigue resistance of the steel plate. Difficulty in controlling performance

[0003] Chinese patent CN103352167A adopts controlled rolling and controlled cooling process and tempering heat treatment process. The Q500q steel plate produced has high strength and toughness, and the yield ratio can be controlled below 0.80, but it is added with at least 0.30% Ni, 0.15% Mo, and 0.20% Cu and other alloying elements, the cost of the alloy is high; Chinese patent CN103233169A adopts a low-temperature and large-reduction process, which can control the grain size of the steel plate above 9.5 grades. Although the steel plate uses relatively low alloying elements and has good strength and toughness, its yield High strength ratio; Chinese patent CN104711490A adopts Mo-free design, through two-stage controlled rolling and ultra-fast cooling process after rolling, the matching of high strength and toughness and low yield ratio of bridge steel is realized, but the steel plate produced by this method has residual stress High, and high carbon equivalent, poor welding performance

In addition, most of the research on improving the fracture toughness and fatigue performance of steel focuses on the composition design of steel, the control of inclusions, the refinement of grains, the uniformity of structure, etc., such as Chinese patent CN109112392A, etc. Few researches on the fracture toughness and fatigue properties of Q500q high-strength and toughness bridge structural steel plates

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