400 MPa stage reinforcing steel bar and manufacturing method thereof

Abstract

The invention discloses a 400 MPa stage reinforcing steel bar and a manufacturing method thereof. The carbon equivalent of the 400 MPa stage reinforcing steel bar is smaller than or equal to 0.52%, and the 400 MPa stage reinforcing steel bar comprises, by mass percent, 0.20 to 0.25% of C, 0.55 to 0.80% of Si, 1.30 to 1.60% of Mn, and 0.006 to 0.012% of N, and further comprises one or multiple of Nb, Ti and Al, and the balance Fe and inevitable impurities; the mass percent of Nb, Ti and Al ranges from 0.01 to 0.04. The 400 MPa stage reinforcing steel bar has the advantages that no obvious yieldpoint elongations exist in a stress-strain curve in the tensile test, the customer needs are met, the yield strength is larger than or equal to 420 MPa, the yield ratio is smaller than or equal to 0.80, the specific elongation is larger than or equal to 18%, and the uniform ductility is larger than or equal to 8%.

Description

technical field [0001] The invention relates to the technical field of metallurgy, in particular to a 400MPa steel bar and a manufacturing method thereof. Background technique [0002] At present, my country's steel production accounts for 24% of my country's total steel production, accounting for 75% of the world's total steel production, 400MPa grade steel bars have good mechanical properties, seismic performance and welding performance, which is conducive to saving steel and improving the safety of building structures. It is widely used in buildings, bridges, tunnels, rail transit and other facilities; while the 335-400MPa level accounts for more than 70% of the steel bar products in my country. From November 1, 2018, the new national standard 1499.2-2018 will be implemented, and the 400MPa grade III steel bar It will be more widely used in the existing structural engineering in our country. [0003] Previously, domestic steel alloying mainly adopted vanadium microalloying...

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Problems solved by technology

[0004] Patents CN201610796288, CN201110000979, CN201010131447, CN200910094359, etc. all mentioned hot-rolled steel bars, through alloying design and structure control to meet the requirements of mechanics, welding, safety and earthquake resistance of building structures, but the content of niobium alloy elements used in them is relatively high. Niobium and vanadium are co-alloyed in some of the steel bars involved, which is not conducive to alloy cost control

[0005] Patent 201510286456 mentions a 400MPa-grade anti-seismic and corrosion-resistant steel bar, which contains alloy elements such as Ni, Cr, Nb, Mo, etc., and the cost of the alloy cannot be comprehensively considered

Patents CN201310566665 and CN200510085762 add Cr alloying elements, which is unfavorable to the weldability of steel bars

[0006] Patent CN200510094836 and patent CN201110373116 achieve alloy strengthening through niobium-titanium composite alloying, but the nitrogen content is low, and the content of Nb, Ti, and N is not limited, so the precipitation strengthening effect cannot be fully exerted, which is not conducive to reducing the alloy content and improving the alloy strength. Utilization

[0007] In summary, for 400MPa steel bars, a production method with good socio-economic and comprehensive mechanical properties has not been reported.

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