500MPa-grade niobium-containing screw-thread reinforcing steel bar and manufacturing method thereof

Abstract

The invention relates to a 500MPa-grade niobium-containing screw-thread reinforcing steel bar and a manufacturing method thereof, and belongs to the field of screw-thread reinforcing steel bar production. The reinforcing steel bar comprises 0.20 to 0.25 percent of C, 0.5 to 0.8 percent of Si, 1.2 to 1.6 percent of Mn, 0.01 to 0.04 percent of P, 0.01 to 0.04 percent of S, 0.005 to 0.02 percent of Ti, 0.001 to 0.01 percent of RE, 0.015 to 0.035 percent of Nb, 0.003 to 0.01 percent of O, 0.003 to 0.01 percent of N, and the balance Fe and inevitable impurities. In the reinforcing steel bar, the quantity of Nb-compound-containing precipitates with the equivalent diameter being 0.003 to 0.03mum is 50 to 500pcs/mum<2>; and the total quantity of RE-compound-containing and/or Tti-compound-containing occluded foreign substances with the equivalent diameter being 0.03 to 3mum is 2000 to 4000pcs/mm<2>. The preparation method of the 500MPa-grade niobium-containing screw-thread reinforcing steel barcomprises the steps of smelting, controlling the occluded foreign substances, continuously casting, heating a continuous casting blank, and rolling the reinforcing steel bar. The method can realize the low-cost high-quality production of the 500MPa-grade screw-thread reinforcing steel bars.

Description

technical field [0001] The invention belongs to the technical field of threaded steel bar production, in particular to a 500MPa niobium-containing threaded bar and a manufacturing method thereof. Background technique [0002] Rebar is an important raw material in construction, transportation, engineering and other fields. It has the largest output and widest application in steel products. The promotion and application of high-strength steel bars can reduce the amount of steel used and optimize the design of building structures, which is of great significance for promoting energy saving and emission reduction and eliminating backward production capacity. At present, the application of hot-rolled threaded steel bars in my country is mainly 400MPa grade, and the amount of 500MPa grade steel bars is relatively small, which still needs to be further promoted and applied. For a long time, the production of high-strength steel bars has been dominated by vanadium microalloying tech...

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Problems solved by technology

[0008] Aiming at the deficiencies in the prior art, the present invention provides a 500MPa grade niobium-containing threaded steel bar and its manufacturing method, which solves the problems of insufficient strengthening effect of niobium in the current niobium-containing steel bar or the difficulty of production by controlled rolling and controlled cooling technology, and reduces the Under the conditions of alloy cost and simplified rolling process, microstructure refinement and strength improvement of niobium-containing rebar are realized

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