A kind of low-carbon equivalent large-thickness q390gj steel plate for building structure and its manufacturing method

Abstract

The invention relates to a low-carbon equivalent large-thickness Q390GJ steel plate for building structures and a manufacturing method thereof. The chemical composition and weight percentage of the steel plate are C: 0.10% to 0.139%, Si: 0.20% to 0.39%, and Mn: 1.30%. ~1.44%, P≤0.010%, S≤0.003%, Nb: 0.020% ~ 0.039%, Ti: 0.006% ~ 0.016%, Al: 0.01% ~ 0.04%, Ceq: 0.32 ~ 0.38, the balance is iron and not Impurities to be avoided; the microstructure of the steel plate is dominated by fine polygonal ferrite + pearlite structure, among which the volume percentage of polygonal ferrite is 25% to 40%, the maximum thickness of the steel plate is 120mm, and the yield strength is ≥ 390MPa, tensile strength 550MPa, elongation after fracture ≥ 28%, yield ratio ≤ 0.77, Z-direction properties in the thickness direction ≥ 60%, impact energy at ‑40°C ≥ 200J. The product steel plate produced according to the chemical composition and production process requirements of the present invention has large thickness, high strength and toughness, high plasticity, low yield ratio, excellent welding performance and lamellar tear resistance.

Description

technical field [0001] The invention relates to the technical field of metal materials, in particular to a low-carbon equivalent large-thickness Q390GJ steel plate for building structures and a manufacturing method thereof. Background technique [0002] With the continuous development of construction engineering equipment manufacturing technology, the demand for green building steel structures is increasing, and there are more and more constructions of super high-rise and long-span building structures. In order to ensure the overall safety of high-rise buildings, high-strength, high-low temperature toughness, Steel plates for construction with good weldability and large thickness are in strong demand. Manufacture of high-strength toughness and large-thickness steel plate according to the conventional production method will inevitably require the slab with large-thickness cross-section to be rolled, and its carbon equivalent is relatively high. In addition, heat treatment suc...

AI Technical Summary

Problems solved by technology

Its disadvantages are: the steel plate has a high design component content, and the carbon equivalent exceeds the upper limit of the TMCP delivery product stipulated in the national standard GB / T19879-2015, which does not meet the requirements of the new national standard

Its shortcoming is that the steel plate has a high design component content, and the carbon equivalent reaches above 0.65, which has an adverse effect on the welding performance of the steel plate

Its disadvantages are: steel plate heat treatment adopts quenching + tempering, the process is more complicated, and the production cycle is longer

[0009] To sum up, the existing industry research on 390MPa low-carbon equivalent large-thickness steel for building structures is still insufficient

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