A 600mpa grade anti-large deformation steel bar and its production method

Abstract

The invention discloses a 600MPa grade anti-large deformation steel bar and a production method thereof. The chemical composition of the steel bar includes: C 0.18-0.24% by weight, Mn+Cr+Mo+Ni 1.4-2.2%, and at least Mn, Ni Two elements, N 0.02~0.06%, Nb+V 0.3~0.6%, Alt≤0.01%, the balance is Fe and inevitable impurities, and the steel bar composition satisfies: V=(3~7)N+0.15; Nb+V=(10~17)N‑0.05; Ceq=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15≤0.54. In the invention, the nitrogen content in the steel is controlled between 0.03% and 0.06% by controlling the addition of the nitrogen-enhancing agent and the soft stirring parameters in the steel-making process, so that more than 80% of the added vanadium is precipitated as carbonitride to strengthen the matrix. The yield strength of high-strength and large-deformation steel bars is ≥685MPa, the yield-strength ratio is ≤0.78, and the maximum elongation is ≥15%.

Description

technical field [0001] The invention belongs to the field of high-strength steel bar production, and in particular relates to a 600MPa-level large-deformation-resistant steel bar and a production method thereof. Background technique [0002] In recent years, the annual output of steel bars in my country has exceeded 200 million tons, accounting for about 75% of the world's total steel bar output; however, the strength level of steel bars in my country is generally 1 to 2 levels lower than that of foreign countries. In my country's steel products, the 335-400MPa level accounts for more than 70%, while the construction steel bars in developed countries in Europe are mainly 500MPa, and the ultra-high-strength seismic steel bars with a yield strength of 685MPa have been applied in the construction of high-rise buildings in Japan. On the one hand, low-grade steel bars increase steel consumption, increase resource and energy consumption, and aggravate environmental burdens; on the...

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Problems solved by technology

[0003] At present, the composition system of high-strength steel bars above 600MPa level includes: 1) medium-high carbon composition design, representative steel grade Japan USD685B, yield strength ≥ 685MPa, yield ratio ≤ 0.85, elongation after fracture ≥ 10%, but its carbon content ≤ 0.50 %, far exceeding the ≤0.28% required by the new national standard of GB 1499.2-2018, the welding process is poor, ductility and plasticity are prone to problems, which is not conducive to popularization and application; 2) The composition design of medium carbon microalloys, representing steel grades SD600 and Russian A600c, yield strength ≥600MPa, tensile strength ≥710MPa, elongation after fracture ≥10%, but there is no clear requirement for the yield ratio, which is not conducive to seismic design; 3) The composition design of medium carbon alloy steel + fine-rolled threaded steel bars, such as PSB785, yield Strength ≥ 785MPa, tensile strength ≥ 980MPa, elongation after breaking ≥ 7%, maximum total elongation ≥ 3.5%, high strength, poor plasticity, high cost, not easy to weld, use anchors to connect, construction Increased cost, limited application fields

[0004] Patent CN 106967928 A proposes a steel for 650MPa high-strength anti-seismic steel bars and its preparation method, but its average carbon equivalent is as high as 0.75, which is not conducive to the actual welding of steel bars, and limits the large-scale promotion of steel bars in terms of welding process performance; Patent CN 103893408 A proposes a 700MPa grade threaded steel bar and its production method, but its yield ratio is 0.82, the maximum total elongation is ≥9%, the steel bar does not have outstanding continuous and uniform deformation ability, and cannot effectively resist natural disasters , to resist external damage; patents CN 102732787 A and CN 102732787 A both proposed a production method of 600MPa grade steel bar, but on the one hand, its carbon content and carbon equivalent design are at a relatively high level, on the other hand, its yield strength margin On the small side, lack of market competitiveness in this strength class

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