Corrosion-resistant reinforcing steel and its production method

Abstract

The present application relates to the field of steel smelting technology, and more particularly to a corrosion-resistant rebar and a method for producing the same. The corrosion-resistant rebar contains, by weight, 0.03-0.15% C, 0.8-2.0% Si, 0.8-2.0% Mn, 0.10-0.50% Cu, 0.08-0.2% P, 0.005-0.01% S, Nb≦0.1%, V≦0.2%, Ti≦0.1%, Al≦0.1%, and the remainder is Fe and unavoidable impurities, with 0.6≦Si / Mn≦2.0 and 0.25%≦Cu+P+S≦0.62%. In the present application, alloy elements such as Si, Mn, Cu, P, and S are comprehensively designed, and the strengthening and corrosion-resistant effects of each element are taken into consideration, thereby solving the problem of the prior art that corrosion resistance, mechanical properties, and cost cannot be achieved at the same time, and overcoming the technical prejudice of the prior art that Cr, Ni, or Mo must be added to improve corrosion resistance.

Description

[Technical Field]

[0001] This application belongs to the field of steelmaking technology, and more specifically, to corrosion-resistant reinforcing bars and methods for producing them.

[0002] This application claims priority to the Chinese patent application filed with the China National Intellectual Property Office on March 16, 2023, with application number 202310252937.7, titled "Corrosion-resistant reinforcing steel and method for producing the same," and all of its contents are incorporated into this application by reference. [Background technology]

[0003] The main reason for insufficient durability in reinforced concrete structures is the corrosion of the reinforcing steel. Conventional technology improves the corrosion resistance of reinforcing steel by adding large amounts of alloying elements such as chromium, molybdenum, and nickel, but the high cost of the alloys and the difficulty of production make large-scale widespread adoption and application difficult.

[0004] Chinese patent document CN114790532A discloses an alloy corrosion-resistant reinforcing bar and a method for manufacturing the same. This alloy corrosion-resistant reinforcing bar has the following composition by weight %, C: 0.05~0.25%, Si: 1.05~2%, Mn: 0.3~1.5%, Cr: 0.5~2.5%, Ni: 0.05~1%, O: 0.001~0.005%, S: 0.001~0.0035%, Ti: 0.005~ This reinforcing steel contains 0.1% of A1, 0.005-0.1%, V, 0.005-0.03%, and Nb, with the remainder being Fe and unavoidable impurities. The Si and Mn content satisfies 2 ≤ Si / Mn ≤ 5, the Si and Cr content satisfies 0.75 ≤ Si / Cr ≤ 1.5, and the Ti and Al content satisfies 0.02% ≤ Ti + Al ≤ 0.2%. This corrosion-resistant reinforcing steel ensures good corrosion resistance without adding Mo by comprehensively designing elements such as Si, Ti, and Al. However, it also requires the addition of Cr and Ni elements, and the high content of Cr and Ni increases costs. Therefore, researching and developing reinforcing steel that has good corrosion resistance without adding alloying elements such as Cr, Ni, and Mo is significant for this field. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Therefore, the technical problem that this application aims to solve is to provide corrosion-resistant reinforcing steel and a method for producing it, in order to overcome the shortcomings of the conventional technology, such as the high production cost and difficulty of production of reinforcing steel, which are due to the need to add alloying elements such as Cr, Ni, and Mo in order to improve the corrosion resistance of reinforcing steel. [Means for solving the problem]

[0006] Therefore, this application provides the following technical solutions.

[0007] This application describes a material containing, by weight percent, C: 0.03~0.15%, Si: 0.8~2.0%, Mn: 0.8~2.0%, Cu: 0.10~0.50%, P: 0.08~0.2%, S: 0.005~0.01%, Nb≦0.1%, V≦0.2%, Ti≦0.1%, Al≦0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with the following properties: 0.6 ≤ Si / Mn ≤ 2.0 and 0.25% ≤ Cu + P + S ≤ 0.62%.

[0008] The aforementioned corrosion-resistant reinforcing steel is (1) The above C is 0.05 to 0.12%. (2) The Si content is 0.9 to 1.7%. (3) The amount of Mn is 0.9 to 1.8%. (4) The amount of Cu is 0.2-0.3%. (5) The P is 0.11 to 0.18%. It satisfies at least one of the following conditions.

[0009] The aforementioned corrosion-resistant reinforcing steel is (1) The above C is 0.06 to 0.09%. (2) The Si content is 1.0 to 1.3%. (3) The amount of Mn is 1.0 to 1.5%. (4) The P is 0.13 to 0.17%, satisfies at least one of the following.

[0010] This application provides a production process of the corrosion-resistant reinforcing bar, including the processes of smelting, refining, continuous casting, slab heating, and hot continuous rolling.

[0011] The continuous casting process is as follows. (1) A low-carbon steel mold powder with a carbon content of 0.15% or less is used, and the thickness of the mold powder layer is 8 to 10 mm. (2) The water flow rate of the crystallization device is 1950 to 2050 L / min. (3) For the crystallization device, the electromagnetic stirring current is 330 A to 370 A, the frequency is 3 to 5 Hz, and at the end, the electromagnetic stirring current is 380 A to 420 A, and the frequency is 10 to 12 Hz. (4) The drawing speed is 2.5 to 3.5 m / min. satisfies at least one of the following.

[0012] The smelting process is as follows. (1) The tapping temperature is 1600 to 1640 °C. (2) For deoxidation alloying during tapping, silicon manganese - ferrosilicon - lime are added in this order. The addition amount of the silicon manganese is 10 to 30 kg / t, and the addition amount of the ferrosilicon is 15 to 30 kg / t. (3) The bottom blowing pressure is 0.4 to 0.5 MPa in the early stage and 0.3 to 0.4 MPa in the later stage. satisfies at least one of the following.

[0013] The early stage refers to the process from the start to the end of alloy addition. The later stage refers to the process from when the molten steel composition reaches the target composition to the end of smelting.

[0014] In the slab heating process, the heating temperature is 1200 to 1250 °C.

[0015] In the aforementioned hot continuous rolling process, the temperature of the reinforcing bars transferred to the cooling bed is 850-900°C.

[0016] The aforementioned refining process is, (1) The refining process includes the step of adding ferrophosphor and copper, (2) The stirring time for the refining is 10 minutes or more. (3) The tapping temperature is 1580-1600°C. It satisfies at least one of the following conditions.

[0017] The phosphorus content in the ferrophosphor is 20-25% by mass. The amount of ferrophosphol added is 3-6 kg / t. The amount of copper added is 1.5 to 3.5 kg / t. [Effects of the Invention]

[0018] The technical solution of this application has the following advantages:

[0019] 1. In the corrosion-resistant reinforcing steel according to this application, the reinforcing steel contains, by weight %, C: 0.03~0.15%, Si: 0.8~2.0%, Mn: 0.8~2.0%, Cu: 0.10~0.50%, P: 0.08~0.2%, S: 0.005~0.01%, Nb≦0.1%, V≦0.2%, Ti≦0.1%, Al≦0.1%, with the remainder being Fe and unavoidable impurities, with 0.6≦Si / Mn≦2.0 and 0.25%≦Cu+P+S≦0.62%. In this application, alloying elements such as Si, Mn, Cu, P, and S are comprehensively designed, and the strengthening and corrosion-resistant effects of each element are comprehensively considered, thereby solving the problem of reduced corrosion resistance of steel due to the absence of Cr, Ni, and Mo, and reducing the production cost of reinforcing steel. By having each element work in a specific proportion to fully exhibit corrosion resistance and strengthening effects, this invention solves the problem of conventional technology where corrosion resistance, mechanical properties, and cost cannot be combined, and overcomes the technical prejudice that Cr, Ni, or Mo must be added to improve corrosion resistance. In particular, the synergistic bonding between Si, Mn, Cu, and S improves chlorine corrosion resistance and the strength-plasticity compatibility of the steel. The corrosion-resistant reinforcing steel according to this invention can combine corrosion resistance and low cost, overcoming the problem of conventional technology where it is difficult to match corrosion resistance properties with alloy cost, and significantly extending the service life of construction projects in chlorine erosion environments.

[0020] Carbon (C) acts as a strengthening element, and if its content is too high, it can easily form carbides, reducing the corrosion resistance, plasticity, toughness, and weldability of the steel. Si (Si) acts as a deoxidizing agent, significantly reducing the oxygen content in the steel and decreasing the formation of oxide inclusions. A high Si content is advantageous for improving corrosion resistance by forming a silicate phase on the surface of the steel, which prevents the penetration and accumulation of erosion media. Si is also a strengthening element and a ferrite-forming element, and a high Si content is advantageous for regulating strength and plasticity, overcoming the brittleness problem caused by excessively high Cu and P content, and optimizing mechanical properties. However, an excessively high Si content is disadvantageous for welding. Mn can significantly improve the strength of steel through solid solution strengthening. If the Mn content is too high, hardenability improves, and Mn and S readily form MnS inclusions, reducing the plasticity and corrosion resistance of the steel. By controlling the Mn content and Cu element, Cu consumes S, suppressing the formation of MnS, preventing the occurrence of MnS corrosion behavior, and improving corrosion resistance. Cu is a corrosion-resistant element that concentrates in the rust layer to form CuS with S, improving corrosion resistance. However, if the Cu content is too high, copper tends to become brittle. P can improve the corrosion resistance of reinforcing bars, and when combined with Cu, the optimal effect is obtained. If the P content is too high, the cold brittleness of the steel improves. S and Cu form dense CuS, which can prevent the penetration of the corrosive medium, which is advantageous for improving corrosion resistance. S and Mn readily form inclusions, but CuS is formed more easily than MnS. Therefore, an appropriate amount of sulfur is a beneficial element for this invention, and its corrosion resistance can be improved by combining it with copper.

[0021] Ti is both a corrosion-resistant and strengthening element, improving the corrosion potential and corrosion resistance of steel. It can also improve the mechanical properties of steel through fine-grain strengthening. However, if the Ti content is too high, oxides are easily formed, which can clog nozzles during continuous casting. Al is deoxidized during the smelting process, reducing the oxygen content in the molten steel. Al can also form oxides in the steel, concentrating in the rust layer and improving corrosion resistance. However, if its content is too high, it can easily clog nozzles during continuous casting. V and Nb are both strengthening elements, forming carbonitrides in the steel and improving the mechanical properties of steel through fine-grain strengthening and precipitation strengthening. This strengthening effect is related to the C and N content.

[0022] This invention utilizes a low-carbon alloy steel composition, comprehensively designing each element and adjusting its content to fully exhibit the corrosion resistance and strengthening properties of each element. By precisely controlling the alloy ratio and multiphase structure, it solves the problem of conventional technologies that cannot combine corrosion resistance, mechanical properties, and low cost.

[0023] 2. In the production process for corrosion-resistant reinforcing bars according to this application, the corrosion-resistant reinforcing bars produced by this process have good resistance to chlorine corrosion without the addition of Cr, Ni, and Mo, thus reducing costs and the difficulty of the production process. The structure of the reinforcing bars obtained by this process is made of perlite and ferrite, with a ferrite content of 50-75%, a yield strength of 400 MPa or more, an elongation after fracture of 30% or more, a total elongation at maximum force of 20% or more, and a tensile strength-to-yield strength ratio of 1.30 or more. In a chlorine corrosion environment (5% NaCl, 35°C, 70% humidity), the relative corrosion rate is 35% or less compared to ordinary reinforcing bars HRB400.

[0024] 3. In the production process for corrosion-resistant reinforcing bars according to this invention, by controlling the type and method of adding alloys in the production process of the reinforcing bars, fine control of the multi-component alloy content and low-cost production are achieved. Control of the ferrite / pearlite multiphase structure is achieved through controlled rolling and controlled cooling processes (heating temperature of the cast slab, temperature of the reinforcing bars transferred to the cooling bed, etc.), ensuring the strengthening effect of the alloying elements, optimizing the corrosion resistance and strength-plasticity compatibility of the reinforcing bars, and aiming to develop low-cost, highly corrosion-resistant alloy reinforcing bars.

[0025] The tapping temperature in the smelting process of this invention ensures (1) that the scrap steel is completely melted during smelting, and (2) that the molten steel maintains the temperature at the start of refining. This is because adding alloys during the smelting and tapping processes lowers the temperature of the molten steel, affecting the refining temperature. By controlling the smelting process, this invention enables efficient smelting and precise composition control.

[0026] Since ferrophosphorus is an easily oxidized element, adding it during the refining process, or at other stages, results in a lower elemental yield. The refining temperature is 1580-1600°C, which is related to the continuous casting temperature. This is because the refining temperature determines the continuous casting temperature, which is calculated based on the alloy composition and is directly related to the content of each element in the reinforcing steel.

[0027] Low-carbon steel mold powder is used in continuous casting, with a mold powder layer thickness of 8-10 mm. This (1) reduces the influence of carbon in the mold powder on the carbon content of the molten steel, ensuring fine control of the carbon content of the final product, meeting low-carbon requirements, and preventing carbides from affecting corrosion resistance, and (2) the mold powder layer reduces contact and convection between the molten steel and air, maintaining the stability of the molten steel temperature. Electromagnetic stirring parameters are closely related to the uniformity of the molten steel composition. The product of this application is corrosion-resistant steel, and corrosion resistance improves with higher purity of molten steel. The water flow rate of the crystallizer primarily functions for cooling. Due to the large cross-sectional size of the blank, a temperature difference exists between the surface and the core, and if the water flow rate ratio is not appropriate, the surface quality deteriorates, resulting in defects such as cracks. The drawing speed is affected by the temperature of the molten steel, cooling capacity, etc. An appropriate drawing speed ensures a highly uniform cast slab while simultaneously avoiding steel breakout.

[0028] The heating temperature of a cast slab affects the melting of alloying elements and grain size, significantly impacting the product's structure and mechanical properties. This parameter is determined based on the alloy composition (elemental melting temperature) and grain size. The temperature of the reinforcing steel transferred to the cooling bed is related to the cooling method and is primarily designed based on the continuous cooling curve of supercooled austenite reinforcing steel. [Modes for carrying out the invention]

[0029] The following embodiments are provided to better illustrate the present application and are not limited to the best embodiments described herein, nor do they limit the content or scope of protection of the present application. Any product identical or similar to the present application, obtained by suggestion of the present application or by combining the features of the present application with other prior art features, falls within the scope of protection of the present application.

[0030] If specific experimental procedures or conditions are not specified in the examples, they should be carried out according to the standard experimental procedures or conditions described in the literature in this field. If the manufacturer of the reagents or equipment used is not specified, they are all standard reagent products available commercially.

[0031] The following specific examples, in weight percent, contain C: 0.03~0.15%, Si: 0.8~2.0%, Mn: 0.8~2.0%, Cu: 0.10~0.50%, P: 0.08~0.2%, S: 0.005~0.01%, Nb≦0.1%, V≦0.2%, Ti≦0.1%, Al≦0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with the following properties: 0.6 ≤ Si / Mn ≤ 2.0 and 0.25% ≤ Cu + P + S ≤ 0.62%.

[0032] With optional selection, C is between 0.05% and 0.12%, and with further optional selection, it is between 0.06% and 0.09%. Si content is 0.9-1.7%, and further optionally 1.0-1.3%. The Mn is 0.9-1.8%, and further, with arbitrary selection, it is 1.0-1.5%. The Cu content is 0.2-0.3%. The p-value is 0.11–0.18%, and further, 0.13–0.17% for random selection.

[0033] The above-mentioned production process for corrosion-resistant reinforcing steel includes the following steps. Smelting: Molten steel is smelted in a converter, and the tapping temperature is 1600°C. The temperature was set to ~1640°C, and for the deoxidation and alloying of the tapped steel, alloys and fluxes were added in the order of silicomanganese-ferrosilicon-lime. Based on 1 ton of molten steel, the amount of silicomanganese added was 10-30 kg / t, and the amount of ferrosilicon added was 15-30 kg / t. Before tapping, the argon gas bottom injection control valve of the tundish was opened, and argon gas was injected throughout the tapping process. The bottom injection pressure was set to 0.4-0.5 MPa in the early stages and 0.3-0.4 MPa in the later stages. Refining: During refining, ferrophosphor and copper plate were added, the refining soft stirring time was set to 10 minutes or more, and the tapping temperature was set to 1580-1600°C. Based on 1 ton of molten steel, the amount of ferrophosphor added was 3-6 kg / t, the phosphorus content in the ferrophosphor was 20-25 wt%, and the amount of copper plate added was 1.5-3.5 kg / t. Continuous casting: Low-carbon steel mold powder is used, with a mold powder layer thickness of 8-10 mm, a drawing speed of 2.5-3.5 m / min, a crystallization apparatus water flow rate of 1950-2050 L / min, an electromagnetic stirring current of 330 A-370 A and a frequency of 3-5 Hz in the crystallization apparatus, and an electromagnetic stirring current of 380 A-420 A and a frequency of 10-12 Hz at the end. Slab heating: The heating temperature is 1200-1250°C. Hot continuous rolling: The temperature of the reinforcing bars transferred to the cooling bed is set to 850-900°C, and after rolling, they are allowed to cool naturally to room temperature. Controlling the cooling rate after rolling and the temperature of the reinforcing bars transferred to the cooling bed is advantageous for obtaining a suitable structure.

[0034] Example 1 This example contains, by weight %, C: 0.06%, Si: 1.0%, Mn: 1.0%, Cu: 0.2%, P: 0.13%, S: 0.005%, Nb: 0.075%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn = 1.0 and Cu+P+S = 0.34%. The production method for the above corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1630°C, and silicomanganese (FeMn) is added to the tapped steel based on 1 ton of molten steel. 65 S 17 )20 kg / t added, ferrosilicon (FeSi 72 20 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.4 MPa in the early stage and 0.3 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 4kg / t), copper plate (Cu content 99%, added amount 1.5kg / t), ferroniobium (Nb content 65%, added amount 1.2kg / t), refining soft stirring time 12 min, continuous pouring steel temperature 1600℃. Continuous casting process: Mold powder layer thickness 8mm, withdrawal speed 2.8m / min, crystallizer water flow rate 2000±50L / min, electromagnetic stirring current 350A, frequency 3Hz in the crystallizer, electromagnetic stirring current 400A, frequency 10Hz at the end, cast slab cross-section size 140mm x 140mm (width x height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1220°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 880°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 20 mm.

[0035] Example 2 This example contains, by weight %, C: 0.08%, Si: 1.28%, Mn: 1.0%, Cu: 0.25%, P: 0.15%, S: 0.005%, V: 0.15%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn = 1.28 and Cu+P+S = 0.41%. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1630°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )20 kg / t added, ferrosilicon (FeSi 72 23 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.42 MPa in the early stage and 0.32 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 4.5 kg / t), copper plate (Cu content 99%, added amount 1.8 kg / t), and ferrovanadium (V content 48%, added amount 3.3 kg / t) are added, followed by a soft stirring time of 13 mins and a continuous pouring steel temperature of 1595°C. Continuous casting process: Mold powder layer thickness 10 mm, withdrawal speed 3.0 m / min, crystallizer water flow rate 2000 ± 50 L / min, electromagnetic stirring current 330 A, frequency 5 Hz in the crystallizer, electromagnetic stirring current 390 A, frequency 10 Hz at the end, slab cross-sectional size 140 mm × 140 mm (width × height). Slab heating and hot continuous rolling process: The heating temperature was 1250°C, the temperature of the reinforcing bar transferred to the cooling bed was 890°C, and after rolling, it was naturally cooled to room temperature. The diameter of the reinforcing bar was 28 mm.

[0036] Example 3 This example contains, by weight percentage, C: 0.09%, Si: 1.3%, Mn: 1.5%, Cu: 0.3%, P: 0.17%, S: 0.01%, Nb: 0.10%, Ti: 0.01%, Al: 0.01%, and the balance is Fe and inevitable impurities. It provides a corrosion-resistant reinforcing bar with Si / Mn = 0.87 and Cu + P + S = 0.48. The production method of the above corrosion-resistant reinforcing bar includes the following steps. Steelmaking process: The molten steel was steelmade in a converter, the tapping temperature was 1630°C, and during tapping, 25 kg / t of silicomanganese (FeMn 65 S 17 ) was added, and 23 kg / t of ferrosilicon (FeSi 72 ) was added. Argon gas was blown in during the tapping process. Regarding the bottom blowing pressure, it was controlled at 0.45 MPa in the early stage and 0.35 MPa in the later stage. Refining process: Ferrophosphorus (P content 23%, addition amount 5 kg / t), copper plate (Cu content 99%, addition amount 2.0 kg / t), ferroniobium (Nb content 65%, addition amount 1.6 kg / t), ferrotitanium (Ti content 30%, addition amount 0.5 kg / t), aluminum particles (Al content 99%, addition amount 0.15 kg / t), refining soft stirring time 15 min, continuous pouring tapping temperature 1595°C. Continuous casting process: The thickness of the mold powder layer is 9 mm, the drawing speed is 2.6 m / min, the water flow rate of the crystallization device is 2000 ± 50 L / min. In the crystallization device, the electromagnetic stirring current is 370 A, the frequency is 3.5 Hz, at the end, the electromagnetic stirring current is 420 A, the frequency is 11 Hz, and the slab cross-sectional size is 140 mm × 140 mm (width × height). Slab heating and hot continuous rolling process: The heating temperature was 1200°C, the temperature of the reinforcing bar transferred to the cooling bed was 900°C, and after rolling, it was naturally cooled to room temperature. The diameter of the reinforcing bar was 32 mm.

[0037] Example 4 This example contains, by weight percent, C: 0.05%, Si: 0.9%, Mn: 1.49%, Cu: 0.5%, P: 0.11%, S: 0.01%, Nb: 0.03%, V: 0.15%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn = 0.60 and Cu+P+S = 0.62. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1630°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )25 kg / t added, ferrosilicon (FeSi 72 18 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.4 MPa in the early stage and 0.3 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 3.5 kg / t), copper plate (Cu content 99%, added amount 3.5 kg / t), ferroniobium (V content 65%, added amount 0.5 kg / t), ferrovanadium (V content 48%, added amount 3.3 kg / t), refining soft stirring time 11 min, continuous pouring steel temperature 1600℃. Continuous casting process: Mold powder layer thickness 8mm, withdrawal speed 3.5m / min, crystallizer water flow rate 2000±50L / min, electromagnetic stirring current 350A, frequency 5Hz in the crystallizer, electromagnetic stirring current 380A, frequency 12Hz at the end, slab cross-sectional size 140mm x 140mm (width x height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1250°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 850°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 16 mm.

[0038] Example 5 This example contains, by weight percent, C: 0.12%, Si: 1.7%, Mn: 0.9%, Cu: 0.1%, P: 0.18%, S: 0.01%, and Ti: 0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn = 1.89 and Cu+P+S = 0.29. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1630°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )11 kg / t is added, and ferrosilicon (FeSi 72 25 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.5 MPa in the early stage and 0.4 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 5.5 kg / t), copper plate (Cu content 99%, added amount 1.5 kg / t), ferrotitanium (Ti content 30%, added amount 5 kg / t), refining soft stirring time 15 min, continuous pouring steel temperature 1590℃. Continuous casting process: Mold powder layer thickness 10 mm, withdrawal speed 2.5 m / min, crystallizer water flow rate 2000 ± 50 L / min, electromagnetic stirring current 350 A, frequency 5 Hz in the crystallizer, electromagnetic stirring current 400 A, frequency 12 Hz at the end, slab cross-sectional size 140 mm × 140 mm (width × height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1250°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 880°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 10 mm.

[0039] Example 6 This example contains, by weight percent, C: 0.03%, Si: 0.8%, Mn: 0.8%, Cu: 0.3%, P: 0.08%, S: 0.005%, V: 0.2%, Ti: 0.01%, Al: 0.01%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn=1 and Cu+P+S=0.39%. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1610°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )10 kg / t added, ferrosilicon (FeSi 72 15 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.4 MPa in the early stage and 0.3 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 3kg / t), copper plate (Cu content 99%, added amount 2kg / t), ferrovanadium (V content 48%, added amount 4kg / t), ferrotitanium (Ti content 30%, added amount 0.5kg / t), aluminum particles (Al content 99%, added amount 0.15kg / t), refining soft stirring time 10 min, continuous pouring steel temperature 1595℃. Continuous casting process: Mold powder layer thickness 9.5 mm, withdrawal speed 2.6 m / min, crystallizer water flow rate 2000 ± 50 L / min, electromagnetic stirring current 345 A, frequency 3.5 Hz in the crystallizer, electromagnetic stirring current 405 A, frequency 11 Hz at the end, cast slab cross-section size 140 mm × 140 mm (width × height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1200°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 900°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 18 mm.

[0040] Example 7 This example contains, by weight percent, C: 0.15%, Si: 2%, Mn: 2%, Cu: 0.25%, P: 0.2%, S: 0.01%, Al: 0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn=1 and Cu+P+S=0.46. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1640°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )30 kg / t added, ferrosilicon (FeSi 72 30 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.5 MPa in the early stage and 0.4 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 6kg / t), copper plate (Cu content 99%, added amount 1.8kg / t), aluminum particles (Al content 99%, added amount 1.5kg / t), refining soft stirring time 15 min, continuous pouring steel temperature 1600℃. Continuous casting process: Mold powder layer thickness 8.5 mm, withdrawal speed 2.6 m / min, crystallizer water flow rate 2000 ± 50 L / min, electromagnetic stirring current 350 A, frequency 5 Hz in the crystallizer, electromagnetic stirring current 410 A, frequency 12 Hz at the end, cast slab cross-section size 140 mm × 140 mm (width × height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1250°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 900°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 25 mm.

[0041] Example 8 This example contains, by weight percent, C: 0.08%, Si: 2%, Mn: 1%, Cu: 0.145%, P: 0.1%, S: 0.005%, Nb: 0.05%, V: 0.05%, Ti: 0.1%, Al: 0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn=2 and Cu+P+S=0.25. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1630°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )20 kg / t added, ferrosilicon (FeSi 72 30 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.4 MPa in the early stage and 0.3 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 3.5 kg / t), copper plate (Cu content 99%, added amount 1.9 kg / t), ferroniobium (Nb content 65%, added amount 0.8 kg / t), ferrovanadium (V content 48%, added amount 1 kg / t), ferrotitanium (Ti content 30%, added amount 5 kg / t), aluminum particles (Al content 99%, added amount 1.5 kg / t), refining soft stirring time 15 min, continuous pouring steel temperature 1600℃. Continuous casting process: Mold powder layer thickness 10 mm, withdrawal speed 2.6 m / min, crystallizer water flow rate 2000 ± 50 L / min, electromagnetic stirring current 350 A, frequency 5 Hz in the crystallizer, electromagnetic stirring current 395 A, frequency 12 Hz at the end, cast slab cross-section size 140 mm × 140 mm (width × height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1250°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 900°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 28 mm.

[0042] Comparative Example 1 This comparative example contains, by weight %, C: 0.25%, Si: 0.5%, Mn: 1.5%, Cu: 0.3%, P: 0.035%, S: 0.0035%, Nb: 0.05%, and Ti: 0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn = 0.33 and Cu+P+S = 0.34%. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1600°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )20 kg / t added, ferrosilicon (FeSi 72 5 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.4 MPa in the early stage and 0.3 MPa in the later stage. Refining process: No ferrophosphor added, copper plate (Cu content 99%, added amount 2kg / t), ferroniobium (Nb content 65%, added amount 0.8kg / t), ferrotitanium (Ti content 30%, added amount 5kg / t), refining soft stirring time 15 min, continuous pouring steel temperature 1600℃. Continuous casting process: Mold powder layer thickness 8mm, withdrawal speed 2.6m / min, crystallizer water flow rate 2000±50L / min, electromagnetic stirring current 350A, frequency 4Hz in the crystallizer, electromagnetic stirring current 400A, frequency 11Hz at the end, slab cross-sectional size 140mm x 140mm (width x height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1250°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 900°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 25 mm.

[0043] Comparative Example 2 This comparative example contains, by weight %, C: 0.08%, Si: 2.5%, Mn: 0.5%, P: 0.035%, S: 0.0035%, V: 0.15%, Ti: 0.1%, Al: 0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn = 5 and Cu+P+S = 0.04%. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1600°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )8 kg / t is added, and ferrosilicon (FeSi 72 35 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.5 MPa in the early stage and 0.4 MPa in the later stage. Refining process: No ferrophosphor or copper plate added, ferrovanadium (V content 48%, added amount 3kg / t), ferrotitanium (Ti content 30%, added amount 5kg / t), aluminum particles (Al content 99%, added amount 1.5kg / t), refining soft stirring time 15 min, continuous pouring steel temperature 1590℃. Continuous casting process: Mold powder layer thickness 10 mm, withdrawal speed 2.5 m / min, crystallizer water flow rate 2000 ± 50 L / min, electromagnetic stirring current 350 A, frequency 4 Hz in the crystallizer, electromagnetic stirring current 400 A, frequency 11 Hz at the end, slab cross-sectional size 140 mm × 140 mm (width × height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1200°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 850°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 20 mm.

[0044] Comparative Example 3 This comparative example contains, by weight %, C: 0.25%, Si: 0.6%, Mn: 2.5%, Cu: 0.5%, P: 0.2%, S: 0.01%, V: 0.15%, and Ti: 0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn = 0.24 and Cu+P+S = 0.71. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1600°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )35 kg / t is added, and ferrosilicon (FeSi 72 8 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.5 MPa in the early stage and 0.4 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 6kg / t), copper plate (Cu content 99%, added amount 3.5kg / t), ferrovanadium (V content 48%, added amount 3kg / t), ferrotitanium (Ti content 30%, added amount 5kg / t), refining soft stirring time 15 min, continuous pouring steel temperature 1610℃. Continuous casting process: Mold powder layer thickness 5 mm, withdrawal speed 2.5 m / min, crystallizer water flow rate 2000 ± 50 L / min, electromagnetic stirring current 350 A, frequency 4 Hz in the crystallizer, electromagnetic stirring current 400 A, frequency 11 Hz at the end, slab cross-sectional size 140 mm × 140 mm (width × height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1250°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 880°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 16 mm.

[0045] Comparative Example 4 This comparative example contains, by weight percent, C: 0.25%, Si: 2.5%, Mn: 2.5%, Cu: 1%, P: 0.2%, S: 0.01%, Nb: 0.05%, Ti: 0.1%, Al: 0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn=1 and Cu+P+S=1.21. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1640°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 )35 kg / t is added, and ferrosilicon (FeSi 72 35 kg / t was added. Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.5 MPa in the early stage and 0.4 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, added amount 6kg / t), copper plate (Cu content 99%, added amount 4kg / t), ferroniobium (Nb content 65%, added amount 0.8kg / t), ferrotitanium (Ti content 30%, added amount 5kg / t), aluminum particles (Al content 99%, added amount 1.5kg / t), refining soft stirring time 15 min, continuous pouring steel temperature 1610℃. Continuous casting process: Mold powder layer thickness 11 mm, withdrawal speed 2.5 m / min, crystallizer water flow rate 2000 ± 50 L / min, electromagnetic stirring current 350 A, frequency 5 Hz in the crystallizer, electromagnetic stirring current 400 A, frequency 12 Hz at the end, slab cross-sectional size 140 mm × 140 mm (width × height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1250°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 900°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 32 mm.

[0046] Comparative Example 5 This comparative example contains, by weight %, C:0.15%, Si:0.7%, Mn:1.35%, Cu:0.3%, P:0.015%, S:0.005%, Nb:0.015%, Cr:1.35%, Ni:0.3%, Mo:0.1%, with the remainder being Fe and unavoidable impurities. We provide corrosion-resistant reinforcing steel with Si / Mn = 0.52 and Cu+P+S = 0.32. The above method for producing corrosion-resistant reinforcing steel includes the following steps. Smelting process: Molten steel is smelted in a converter, the tapping temperature is set to 1630°C, and silicomanganese (FeMn) is added to the tapped steel. 65 S 17 ) 27 kg / t, ferrosilicon (FeSi 7214 kg / t of ferrochrome (Cr content 65%) was added, along with 30 kg / t of ferromolybdenum (Mo content 55%). Argon gas was blown in throughout the tapping process, and the bottom blowing pressure was controlled to 0.4 MPa in the early stage and 0.3 MPa in the later stage. Refining process: Ferrophosphor (P content 23%, addition amount 1kg / t), copper plate (Cu content 99%, addition amount 2kg / t), ferroniobium (Nb content 65%, addition amount 0.3kg / t), nickel plate (nickel content 99%, 2kg / t), refining soft stirring time 12min, continuous pouring steel temperature 1600℃. Continuous casting process: Mold powder layer thickness 8mm, withdrawal speed 2.8m / min, crystallizer water flow rate 2000±50L / min, electromagnetic stirring current 350A, frequency 3Hz in the crystallizer, electromagnetic stirring current 400A, frequency 10Hz at the end, cast slab cross-section size 140mm x 140mm (width x height). Cast slab heating and hot continuous rolling process: The heating temperature was set to 1220°C, the temperature of the reinforcing bars transferred to the cooling bed was set to 880°C, and after rolling, the bars were allowed to cool naturally to room temperature, resulting in a reinforcing bar diameter of 20 mm.

[0047] Test example This test example provides the characteristics of reinforcing bars obtained in each example and comparative example, and the details are as follows. Yield strength test method: Tests were conducted according to the national standard GB / T228.1-2010 Tensile Tests for Metallic Materials, Part 1: Room Temperature Test Method, and the tensile strength-to-yield strength ratio was calculated. Tensile strength-to-yield strength ratio = tensile strength / yield strength. The test results are shown in Table 1. Test method for tensile strength: Refer to National Standard GB / T228.1-2010, Part 1, Tensile Testing of Metallic Materials. Test method for elongation after fracture: Refer to National Standard GB / T228.1-2010 Tensile Testing of Metallic Materials, Part 1. Maximum force total elongation: Refer to National Standard GB / T228.1-2010 Tensile Testing of Metallic Materials, Part 1. Relative Corrosion Rate: The chlorine corrosion resistance of the corrosion-resistant reinforcing bars produced in the examples and comparative examples was tested, and the improvement factor of their chlorine corrosion resistance compared to the model HRB400 reinforcing bar was calculated. The specific test method is as follows: A 100 mm length of corrosion-resistant reinforcing bar was cut and turned using a lathe to obtain a test sample with a diameter of 10 mm. Under conditions of 35°C and 70% humidity, the test sample was placed in a corrosive solution and subjected to a salt spray corrosion test. The corrosive solution used for the test was a 5 wt% sodium chloride solution with a pH of 7.0, and the test period was 14 days. The weight of the test sample before and after corrosion was measured using an electronic microbalance. The calculation formula is: Relative Corrosion Rate = (Change in weight of corrosion-resistant reinforcing bar before and after corrosion / Change in weight of HRB400 before and after corrosion) × 100%. Test Method for Ferrite and Pearlite: Using a Zeiss optical microscope, the microstructure types of corrosion-resistant reinforcing bars manufactured in the examples and comparative examples were observed at a magnification of 200x, and the volume percentage of ferrite was calculated. Under an optical microscope, ferrite appears white, and pearlite appears black. The volume ratio of each microstructure per unit area was calculated from this color difference. The results are shown in Tables 1 and 2.

[0048] [Table 1]

[0049] [Table 2]

[0050] As can be seen from the above results, the present invention can achieve good corrosion resistance without adding Cr, Ni, or Mo, and the corrosion-resistant reinforcing steel of the present invention can combine corrosion resistance, mechanical properties, and low cost. Furthermore, the relative corrosion rate of the corrosion-resistant reinforcing steel of the present invention is 35% or less.

[0051] From Comparative Examples 1 to 4, it was found that in the present invention, by controlling Si / Mn and Cu+P+S, the reinforcing bar can possess excellent corrosion resistance, mechanical properties, and strength-plastic compatibility. Compared with Comparative Example 5, it was found that the reinforcing bar according to the present invention has superior mechanical properties such as elongation after fracture and total elongation at maximum force compared to the reinforcing bar with added Cr. This indicates that in the present invention, it is possible to produce reinforcing bars with excellent strength and mechanical properties at a lower cost without adding Cr, Ni, and Mo.

[0052] Clearly, the embodiments described above are merely illustrative examples and do not limit the embodiments. Those skilled in the art may make other different forms of variations or modifications based on the above description. It is not necessary, nor is it possible, to cover all embodiments comprehensively. Furthermore, obvious variations or modifications arising therefrom remain within the scope of the application.

Claims

1. Corrosion-resistant reinforcing steel characterized by containing, by weight percent, C: 0.03-0.15%, Si: 0.8-2.0%, Mn: 0.8-2.0%, Cu: 0.10-0.50%, P: 0.08-0.2%, S: 0.005-0.01%, Nb ≤ 0.1%, V ≤ 0.2%, Ti ≤ 0.1%, Al ≤ 0.1%, with the remainder being Fe and unavoidable impurities, with 0.6 ≤ Si / Mn ≤ 2.0, 0.25% ≤ Cu + P + S ≤ 0.62%, and the reinforcing steel structure being pearlite and ferrite, with a ferrite content of 50-70%.

2. (1) The content of C is 0.05 to 0.12%. (2) The Si content shall be 0.9 to 1.7%. (3) The Mn content shall be 0.9 to 1.8%. (4) The Cu content shall be 0.2 to 0.3%. (5) The content of P is 0.11 to 0.18%. The corrosion-resistant reinforcing bar according to claim 1, characterized in that it satisfies at least one of the following conditions.

3. (1) The content of C is 0.06 to 0.09%. (2) The Si content shall be 1.0 to 1.3%. (3) The Mn content shall be 1.0 to 1.5%. (4) The content of P is 0.13 to 0.17%. The corrosion-resistant reinforcing bar according to claim 1 or 2, characterized in that it satisfies at least one of the following conditions.

4. A method for producing corrosion-resistant reinforcing bars according to claim 1, characterized by including the steps of smelting, refining, continuous casting, slab heating, and hot continuous rolling.

5. The aforementioned smelting process is, (1) The tapping temperature shall be 1600 to 1640°C. (2) For the deoxidation alloying of the steel, silicomanganese, ferrosilicon, and lime are added in this order. The amount of silicomangane added is 10 to 30 kg / t, and the amount of ferrosilicon added is 15 to 30 kg / t. (3) The bottom-blowing pressure is 0.4 to 0.5 MPa in the early period and 0.3 to 0.4 MPa in the later period. The production method according to claim 4, characterized in that it satisfies at least one of the following conditions.

6. The production method according to claim 4, characterized in that the heating temperature in the slab heating step is 1200 to 1250°C.

7. The production method according to claim 4, characterized in that the temperature of the reinforcing bars transferred to the cooling bed in the hot continuous rolling process is 850 to 900°C.

8. The aforementioned refining process is, (1) The refining process includes the step of adding ferrophosphor and copper. (2) The stirring time for the refining shall be 10 minutes or more. (3) The tapping temperature shall be 1580 to 1600°C. The production method according to claim 4, characterized in that it satisfies at least one of the following conditions.

9. The phosphorus content in the ferrophosphor is 20 to 25% by mass. The amount of ferrophosphol added is 3 to 6 kg / t. The production method according to claim 8, characterized in that the amount of copper added is 1.5 to 3.5 kg / t.

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