CN-117230358-B - Method for improving performance stability of deformed steel bar

Abstract

The invention discloses a method for improving the performance stability of screw steel, which relates to the technical field of steel smelting, and comprises the following steps of S1, converter smelting, S2, LF refining, slag forming and desulfurization, and alloy raw material addition in a furnace, S3, LF bottom nitrogen blowing, namely bottom nitrogen blowing according to the nitrogen content in molten steel, molten steel preparation, and S4, continuous casting, heating and rolling of molten steel in sequence. According to the invention, a heterogeneous nucleation mechanism is reasonably utilized, and proper Nb is added into steel, so that Nb (C, N) with higher precipitation temperature is generated in the cooling process of the steel, a nucleation base point is provided for V (C, N) which is precipitated later in the cooling process of the steel, and stable precipitation of V (C, N) is promoted. N in the screw-thread steel can effectively promote precipitation of nitrogen-containing compounds such as Nb (C, N) and V (C, N), and has the functions of stabilizing and improving the performance.

Inventors

• XU GUANG
• LI YANG
• XU HAO
• WANG JING
• LUO GANG
• LIANG LIANG
• QI JIANGHUA
• DENG ZHIXUN
• SHU CHUNYANG
• ZHANG SHUNKAI
• GUO HUANGXUN

Assignees

• 湖南华菱涟源钢铁有限公司

Dates

Publication Date

20260508

Application Date

20230922

Claims (3)

1. 1. A method for improving the performance stability of a deformed steel bar, comprising the steps of: s1, converter smelting, namely loading molten iron and scrap steel into a converter, adding slag, blowing oxygen to decarburize and dephosphorize, and entering a refining process after tapping; s2, LF refining, namely slagging and desulfurizing, and adding alloy raw materials into a furnace, wherein the alloy raw materials comprise silicon manganese, carbon powder, ferrosilicon, vanadium-nitrogen alloy and ferroniobium; S3, performing LF bottom blowing nitrogen according to the nitrogen content in molten steel, wherein the nitrogen blowing process comprises the steps of blowing nitrogen 10m 3 when N in the molten steel is less than 0.01%, blowing nitrogen 6m 3 when N is more than or equal to 0.01% and less than or equal to 0.015%, and not blowing nitrogen when N is more than or equal to 0.015%, so as to obtain molten steel; s4, carrying out continuous casting, heating and rolling on the molten steel in sequence to obtain the deformed steel bar; the mass fraction of N in the deformed steel bar is 0.012% -0.018%; the mass fraction of Nb in the deformed steel bar is 0.005% -0.006%; According to the method, the content of Nb and N is controlled, and a heterogeneous nucleation mechanism is utilized, so that the Nb (C, N) which is precipitated first provides a nucleation base point for the subsequent V (C, N), and the stability of the yield strength of the deformed steel bar is improved; The mass fraction of C in the deformed steel bar is 0.2% -0.25%; the mass fraction of P in the deformed steel bar is 0% -0.03%; The mass fraction of Si in the deformed steel bar is 0.35% -0.5%; the mass fraction of Mn in the deformed steel bar is 1.1% -1.5%; the mass fraction of S in the deformed steel bar is 0% -0.03%; the mass fraction of V in the deformed steel bar is 0.015% -0.03%.
2. 2. The method for improving the performance stability of the deformed steel bar according to claim 1, wherein the continuous casting is performed at a drawing speed of 3.0m/min to 3.5m/min.
3. 3. The method for improving the performance stability of the deformed steel bar according to claim 1, wherein the temperature of the cold bed after rolling is 850-900 ℃.

Description

Method for improving performance stability of deformed steel bar Technical Field The invention belongs to the technical field of steel smelting, and particularly relates to a method for improving the performance stability of screw-thread steel. Background The deformed bar HRB400E is a hot rolled ribbed deformed bar with yield strength greater than 400MPa and shock resistance, and is generally prepared by adding microalloy elements into a secondary deformed bar HRB335 and smelting by means of rolling and cooling control, so that the deformed bar HRB has higher yield strength, good plasticity, weldability and lower ductile-brittle transition temperature. The screw thread reinforcing steel bar HRB400E has low price, good mechanical property and elongation rate, and tensile strength of the screw thread reinforcing steel bar HRB400E is more than 400MPa, so that the screw thread reinforcing steel bar HRB400E becomes a main construction material in the engineering construction at the present stage, and the annual demand is huge along with the continuous increase of the foundation construction force, so that the product reliability has an important influence on the safety of the engineering construction. The instability of the mechanical properties of the deformed steel bar HRB400E caused by the fluctuation of yield strength in the related art is an important problem frequently faced in the production and service processes. Due to the influences of smelting level, continuous casting billet supply and other problems, continuous casting billets of many iron and steel enterprises have the phenomena of fluctuation of chemical components, uneven cooling of each parting line when cold billets and hot billets are mixed into a furnace, parting rolling and cooling after rolling to cause larger fluctuation of yield strength of finished steel bars, and the fluctuation value of the yield strength can reach 100MPa in severe cases, thereby bringing larger influence to the performance stability and service reliability of products. In the related art, a large amount of expensive alloy elements is generally used to secure the screw steel performance, but the addition amount of the alloy elements is excessively large, resulting in a drastic increase in production cost. Disclosure of Invention The present invention is directed to a method for improving the stability of the properties of a screw-thread steel, which solves at least one of the problems and disadvantages set forth in the background art. Specifically, the invention provides a method for improving the performance stability of deformed steel bars, which comprises the following steps: S1, converter smelting: charging molten iron and scrap steel into a converter, adding slag, blowing oxygen to decarburize and dephosphorize, and entering a refining process after tapping; s2, LF refining: Slagging and desulfurizing, and adding alloy raw materials into a furnace; S3, LF bottom blowing nitrogen: bottom blowing nitrogen is carried out according to the nitrogen content in the molten steel, so that molten steel is prepared; S4, carrying out continuous casting, heating and rolling on the molten steel in sequence to obtain the deformed steel bar; The mass fraction of N in the deformed steel bar is 0.012% -0.02%; the mass fraction of Nb in the deformed steel bar is 0.003% -0.01%. According to one of the technical schemes of the method, the method at least has the following beneficial effects: the method of the invention reasonably utilizes the characteristic of higher formation temperature of Nb (C, N), and can obviously improve the stability of precipitation of V (C, N) and the like by utilizing the heterogeneous nucleation theory, thereby ensuring the stability of precipitation strengthening and effectively stabilizing the yield strength. The excessively low content of N element in the V-Nb-N microalloyed deformed steel affects the formation of precipitates such as Nb (C, N) and V (C, N), and thus the precipitation strengthening effect is reduced. The N element cannot be too high, and the brittleness of the steel is improved due to the fact that the N element is too high, so that the use of the steel is affected. In conclusion, the stability of the steel yield strength can be obviously enhanced by nitrogen blowing and niobium adding, so that the method is convenient for lean production and cost reduction. According to some embodiments of the invention, the mass ratio of the molten iron to the scrap steel is 3-4:1. According to some embodiments of the invention, the mass fraction of C in the deformed steel bar is 0.2-0.25%. According to some embodiments of the invention, the mass fraction of P in the screw-thread steel is 0-0.03%. According to some embodiments of the invention, the mass fraction of Si in the screw-thread steel is 0.35-0.5%. According to some embodiments of the invention, the mass fraction of Mn in the screw-thread steel is 1.1-1.5%. According to some embodiments of th