Production method of corrosion-resistant reinforcing steel bar based on rare earth material reinforcement

Abstract

The invention discloses a production method of a corrosion-resistant steel bar reinforced based on a rare earth material. The production method comprises the following steps: smelting in a converter; performing refining; continuous casting; rolling: heating the steel bar blank to a proper temperature interval of 1000-1100 DEG C, and then feeding the steel bar blank into a rolling mill for multi-pass rolling; the steel bar comprises the following chemical components in percentage by mass: 0.15%-0.25% of carbon, 0.30%-0.60% of silicon, 1.20%-1.60% of manganese, less than or equal to 0.045% of phosphorus, less than or equal to 0.045% of sulfur, 0.01%-0.02% of rare earth element (RE) and the balance of Fe and impurities. The problem that a traditional steel bar is poor in corrosion resistance is fundamentally solved, and meanwhile it is guaranteed that the mechanical properties such as strength, toughness and machinability and the technological properties of the steel bar completely meet the strict standard and specification requirements of constructional engineering.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a production method of corrosion-resistant steel bars reinforced with rare earth materials. Background Art

[0002] In the construction industry, from common residential buildings and commercial buildings to transportation infrastructure such as bridges and roads, and even hidden projects such as underground pipe galleries, steel bars are the core supporting materials of building structures, and their performance directly determines the safety, stability and service life of the building. This invention aims to utilize the unique advantages of the converter process to develop a new type of steel bar with excellent corrosion resistance to cope with the various complex environmental challenges faced during current construction and use.

[0003] In actual construction engineering scenarios, the service environment of steel bars is extremely complex and harsh. In coastal areas, the high humidity and salt-rich air make steel bars extremely vulnerable to corrosion by chloride ions, which in turn causes a series of serious problems such as pitting and rust; in industrial plants, acid and alkali waste gas and wastewater are discharged indiscriminately, causing strong chemical corrosion to steel bars, seriously damaging the internal microstructure of the steel bars, and greatly reducing the bearing capacity and durability of the steel bars. Traditional steel bars are mainly composed of iron, carbon and a small amount of alloy elements. Faced with such a harsh corrosive environment, their protection capabilities are obviously insufficient.

[0004] At present, there are many disadvantages in the commonly used methods to improve the corrosion resistance of steel bars. Although coating protection technology can isolate corrosive media to a certain extent, the coating is prone to damage and uneven thickness during construction. Moreover, with the passage of time and wear during use, the coating gradually falls off, eventually leading to protection failure. Traditional alloying methods mainly improve the corrosion resistance of steel bars by adding alloying elements such as chromium and nickel. However, excessive addition will not only greatly increase production costs, but also have a negative impact on other properties of steel bars, such as weldability and processing performance. Moreover, even if these alloying elements are added, when used for a long time in some special and extreme environments, the improvement of its corrosion resistance is still difficult to meet the actual needs of the project. Therefore, the development of a new type of steel bar material that can significantly enhance the corrosion resistance of steel bars, effectively control costs, take into account other properties, and has an efficient and feasible production process has become a key issue to be solved in the field of building materials. With its advantages of high efficiency, large-scale production and cost control, the converter process provides a new technical path and ideas for solving this problem. Summary of the invention

[0005] The object of the present invention is to provide a production method of corrosion-resistant steel bars strengthened by rare earth materials, introducing appropriate rare earth elements into the steel bar composition system, and giving full play to the advantages of the converter process in terms of composition control, melting efficiency, etc., so as to fundamentally solve the problem of poor corrosion resistance of traditional steel bars. It is not only necessary to ensure that the steel bars exhibit excellent corrosion resistance in various harsh environments, but also to ensure that their mechanical properties and process properties such as strength, toughness, and workability fully meet the strict standards and specifications of construction projects. At the same time, effective cost control is achieved throughout the production process, laying a solid foundation for the large-scale industrial production and wide application of this product.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A production method of corrosion-resistant steel bars strengthened by rare earth materials according to the present invention includes:

[0008] Converter melting: The iron ore, scrap steel, and alloy raw materials containing rare earth elements, which are carefully prepared in precise proportions, are accurately loaded into the converter; subsequently, high-purity oxygen is blown into the converter, and the oxygen instantly undergoes a violent oxidation reaction with the impurities in the molten iron. This process releases a large amount of heat, prompting the raw materials to quickly heat up and melt; during this process, the temperature in the furnace rapidly rises to the high-temperature range of 1600°C - 1700°C; with the help of the high-temperature environment in the furnace and the strong stirring action of the high-speed oxygen flow, various raw materials can be quickly and fully fused, and at the same time, the impurities can be efficiently oxidized and removed; during the melting process, by precisely controlling the oxygen flow rate, oxygen blowing time, and the addition sequence of raw materials, precise control of the carbon content and the proportion of other elements in the molten steel is achieved.

[0009] Refining: The molten steel after converter melting is quickly transferred to the refining furnace. In the refining furnace, first, the argon stirring technology is used. By blowing argon into the molten steel, a strong stirring flow field is formed, enabling the molten steel to be fully mixed, further promoting the collision, aggregation, and floating of inclusions, thereby effectively removing the tiny inclusions in the molten steel and improving the purity of the molten steel. At the same time, an advanced vacuum degassing process is adopted, placing the molten steel in a high-vacuum environment, enabling the gases such as hydrogen and nitrogen in the molten steel to quickly escape, significantly reducing the gas content in the molten steel, and greatly reducing the risk of defects such as pores and cracks generated due to the presence of gases during subsequent processing and use. In addition, according to the high-precision analysis results of the molten steel composition, various alloy micro-adjusters are accurately added to finely adjust the content of elements such as silicon, manganese, phosphorus, and sulfur in the molten steel to ensure that the content of each element fully meets the strict composition requirements of rare earth corrosion-resistant steel bars. During the refining process, special attention is paid to the content stability and distribution uniformity of rare earth elements. By precisely controlling the addition amount and reaction time of the refining agent, the loss and segregation of rare earth elements are prevented, ensuring that they can fully exert their unique performance advantages in the steel bars.

[0010] Continuous casting: The refined high-quality molten steel enters the continuous casting process; during continuous casting, the casting temperature is strictly controlled within the precise range of 1450°C - 1500°C, and the withdrawal speed is carefully adjusted according to the blank specifications, generally controlled at 1.5 m / min - 2.5 m / min;

[0011] Rolling: Heat the steel bar blank to the appropriate temperature range of 1000°C - 1100°C, and then send it into the rolling mill for multi-pass rolling;

[0012] The chemical composition of the steel bar by mass percentage: The carbon content is precisely controlled at 0.15% - 0.25%, the silicon content is 0.30% - 0.60%, the manganese content is 1.20% - 1.60%, the phosphorus content is strictly limited to ≤0.045%, the sulfur content is ≤0.045%, the rare earth element RE content is set at 0.01% - 0.02%, and the rest is Fe and impurities.

[0013] Furthermore, in the converter smelting process: At the initial stage of oxygen blowing, appropriately increase the oxygen flow rate, utilize the rapid reaction of oxygen with easily oxidized elements such as silicon and manganese to quickly remove these elements, and at the same time create favorable conditions for the subsequent oxidation of carbon; as the smelting process progresses, gradually reduce the oxygen flow rate according to the real-time detected molten steel composition data to precisely control the degree of carbon oxidation and ensure that the molten steel composition can accurately approach the target value; in the later stage of converter smelting, accurately add rare earth alloys according to the real-time detection results of the molten steel composition; at this time, utilize the high temperature and strong stirring environment in the converter to enable the rare earth elements to be evenly incorporated into the molten steel, laying a solid foundation for improving the comprehensive performance of the steel bar in the subsequent process.

[0014] Furthermore, the chemical composition of the steel bar by mass percentage: Carbon: 0.18%; Silicon: 0.40%; Manganese: 1.30%; Phosphorus: 0.035%; Sulfur: 0.030%; Rare earth element: 0.010%; The balance is iron and inevitable impurities.

[0015] Furthermore, the chemical composition of the steel bar by mass percentage: Carbon: 0.22%; Silicon: 0.50%; Manganese: 1.40%; Phosphorus: 0.040%; Sulfur: 0.035%; Rare earth element: 0.015%; The balance is iron and inevitable impurities.

[0016] Furthermore, in the continuous casting process: For small-sized blanks, due to their relatively fast heat dissipation, appropriately increase the withdrawal speed to ensure the solidification quality and production efficiency of the cast billet; for large-sized blanks, due to their relatively slow heat dissipation, reduce the withdrawal speed to ensure that the cast billet can solidify evenly and avoid various defects.

[0017] Furthermore, during the continuous casting process, by precisely controlling the cooling water flow rate of the mold, the billet can be cooled evenly, thereby obtaining a reinforcing bar billet with excellent surface quality and dense internal structure.

[0018] Furthermore, the mechanical properties of the prepared reinforcing bars are as follows: the yield strength is 450 MPa, the tensile strength is 580 MPa, and the elongation is 20%.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0020] Improve corrosion resistance: The addition of rare earth elements is the key core to enhancing the corrosion resistance of reinforcing bars. During the production and use of reinforcing bars, rare earth elements will preferentially react with oxygen on the surface of the reinforcing bars to form a rare earth oxide protective film that is extremely dense, stable and has self-healing ability. This protective film is like an indestructible barrier that can effectively block the intrusion of various external corrosive media, such as chloride ions, hydrogen ions, sulfate ions, etc., greatly slowing down the corrosion rate of the reinforcing bars. Thanks to the precise control of the composition by the converter process and the efficient melting and refining process, the distribution of rare earth elements in the reinforcing bars is more uniform, and the protective effect of the formed oxide film is more excellent. Through a large number of laboratory simulated accelerated corrosion experiments and long-term monitoring of actual engineering application cases, the results show that under the same corrosion environment, the corrosion rate of the rare earth corrosion-resistant reinforcing bars of the present invention is reduced by more than 50% compared with ordinary reinforcing bars, which means that the reinforcing bars of the present invention can serve stably for a long time in a harsh environment, significantly extending the service life of the reinforcing bars, and thus greatly improving the durability and safety of the building structure.

[0021] Improve mechanical properties: An appropriate amount of rare earth elements play a crucial role in refining the grains inside the reinforcing bars. After the grains are refined, the number of grain boundaries increases significantly, and the grain boundaries can effectively hinder the movement of dislocations, thereby significantly improving the strength, toughness and plasticity of the reinforcing bars. The efficient stirring and precise temperature control of the converter process enable the rare earth elements and other alloy elements to be fully fused and evenly distributed in the molten steel, further strengthening the grain refinement effect. Compared with ordinary reinforcing bars, the yield strength of the rare earth corrosion-resistant reinforcing bars of the present invention is increased by 10%-20%, the tensile strength is increased by 5%-15%, and the elongation is also increased to a certain extent. This fully shows that when subjected to the same external force, the reinforcing bars of the present invention are less likely to deform and break, can provide more reliable support for the building structure, and greatly improve the safety and reliability of the building structure.

[0022] Cost Advantage: The converter process is characterized by high efficiency and large-scale production, enabling continuous and automated production, thus effectively reducing production costs. Although rare earth elements are added to the steel bar composition, due to the relatively small amount of rare earth elements used, and the converter process does not require expensive special equipment and complex operation procedures, under the comprehensive control of raw material costs and production costs, while ensuring that the steel bar has excellent performance, the cost increase is relatively small. Compared with some corrosion-resistant steel bars using high-cost alloy elements or complex protection processes, the rare earth corrosion-resistant steel bar of the present invention has obvious economic benefits, is more conducive to large-scale promotion and application in the construction industry, and brings higher cost performance and broader development space to the field of construction engineering. Specific Embodiment

[0023] Example 1:

[0024] Chemical composition by mass percentage of the steel bar: Carbon (C): 0.18%; Silicon (Si): 0.40%; Manganese (Mn): 1.30%; Phosphorus (P): 0.035%; Sulfur (S): 0.030%; Rare earth element (RE): 0.010%; The balance is iron (Fe) and unavoidable impurities.

[0025] Preparation Process:

[0026] Converter Melting: Add the raw materials into the converter. First, blow in oxygen at a large flow rate. Utilize the rapid reaction between oxygen and impurities to quickly raise the temperature in the furnace to 1650°C. After the raw materials are basically melted, according to the real-time detected steel liquid composition data, accurately adjust the oxygen flow rate to precisely control the carbon content. In the later stage of melting, add rare earth alloy according to the predetermined addition amount and addition time, and through strengthened stirring measures, ensure that the rare earth elements are evenly incorporated into the steel liquid. The total melting duration is controlled within 30 minutes to ensure the high efficiency and stability of the melting process.

[0027] Refining: Quickly transfer the steel liquid after converter melting to the refining furnace. Stir with argon for 20 minutes. Utilize the stirring action of argon to make the inclusions in the steel liquid fully collide, aggregate and float. Then conduct vacuum treatment for 25 minutes to effectively reduce the gas content in the steel liquid. During the refining process, according to the high-precision steel liquid composition analysis results, accurately add alloy micro-adjusters to finely adjust the content of elements such as silicon, manganese, phosphorus, and sulfur in the steel liquid, especially pay attention to the rare earth element content, ensure that it is stable within the target range, and prevent the loss of rare earth elements by precisely controlling the addition amount and reaction time of the refining agent to ensure its effective role in the steel bar.

[0028] Continuous casting: The casting temperature is precisely controlled at 1480°C. Through an advanced temperature control system, the temperature fluctuation is ensured to be within a very small range. The casting speed is set at 2.0 m / min, and according to the real-time solidification situation of the billet, the casting speed is adjusted in real time. At the same time, by optimizing the distribution of the cooling water flow rate in the mold, the intelligent control system is used to achieve precise control of the cooling water flow rate, ensuring uniform cooling of the billet and obtaining a steel bar billet with good surface quality and dense internal structure.

[0029] Rolling: The billet is heated to 1050°C, and a high-efficiency heating device is used to ensure uniform heating of the billet. It is fed into the rolling mill for 8 passes of rolling. The reduction per pass is reasonably allocated according to the target size and performance requirements of the steel bar. During the rolling process, according to the characteristics of the converter-processed steel billet, the online monitoring equipment is used to monitor the rolling state of the steel bar in real time, and the rolling force and speed matching are appropriately adjusted to ensure stable performance of the steel bar. Finally, a steel bar product with a diameter of 16 mm is obtained.

[0030] Performance testing: The corrosion resistance of this steel bar product is tested. After being immersed in a simulated marine environment (3.5% NaCl solution) for 1000 hours, the advanced weight loss method is used to measure its corrosion rate. The result shows that its corrosion rate is 0.05 mm / a, while the corrosion rate of ordinary steel bars under the same conditions is 0.12 mm / a. At the same time, the mechanical properties of this steel bar are tested. Using a high-precision universal material testing machine and in accordance with strict standard test methods, the yield strength is 450 MPa, the tensile strength is 580 MPa, and the elongation is 20%. All performance indicators are excellent.

[0031] Example 2:

[0032] Chemical composition by mass percentage of the steel bar: Carbon (C): 0.22%; Silicon (Si): 0.50%; Manganese (Mn): 1.40%; Phosphorus (P): 0.040%; Sulfur (S): 0.035%; Rare earth elements (RE): 0.015%; The balance is iron (Fe) and inevitable impurities.

[0033] Preparation process: It is basically the same as that of Example 1, except that the converter melting temperature is adjusted to 1680°C. By optimizing the layout of the oxygen lance and the dynamic control of the oxygen flow rate, the melting efficiency is further improved. The melting time is shortened to 25 minutes, and the production efficiency is increased on the premise of ensuring the melting quality. The continuous casting temperature is 1460°C, and the casting speed is 1.8 m / min. During the continuous casting process, an advanced billet quality monitoring system is used to monitor the surface quality and internal structure state of the billet in real time, and the process parameters are adjusted in a timely manner according to the monitoring results. The rolling heating temperature is 1080°C, and the number of rolling passes is adjusted to 7 passes. During the rolling process, the rolling process curve is optimized to further improve the performance uniformity of the steel bar.

[0034] Performance test: After soaking in a simulated acid rain environment (a mixed solution of sulfuric acid and nitric acid with a pH value of 4.0) for 800 hours, the corrosion rate was measured using an advanced electrochemical testing method. The corrosion rate of this steel bar was 0.06 mm / a, while that of ordinary steel bars was 0.15 mm / a. The mechanical property test results were as follows: yield strength was 480 MPa, tensile strength was 610 MPa, and elongation was 18%, fully demonstrating the excellent performance of the steel bar of the present invention in different environments.

[0035] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing corrosion-resistant steel bars reinforced with rare earth materials, characterized in that: include: Converter smelting: Iron ore, scrap steel and alloy raw materials containing rare earth elements carefully mixed in precise proportions are accurately loaded into the converter; Subsequently, high-purity oxygen is blown into the converter, and a violent oxidation reaction occurs instantly between oxygen and impurities in the molten iron. This process releases a large amount of heat, causing the raw materials to heat up and melt rapidly. During this process, the temperature in the furnace quickly rises to a high temperature range of 1600°C-1700°C. With the help of the high temperature environment in the furnace and the strong stirring effect of the high-speed oxygen flow, various raw materials can be quickly and fully integrated, and impurities can also be efficiently oxidized and removed. During the smelting process, the carbon content and the proportion of other elements in the molten steel can be precisely controlled by precisely controlling the oxygen flow rate, oxygen blowing time, and the order of adding raw materials. Refining: The molten steel after smelting in the converter is quickly transferred to the refining furnace; in the refining furnace, argon stirring technology is first used to blow argon into the molten steel to form a strong stirring flow field, so that the molten steel is fully mixed, further promoting the collision, aggregation and floating of inclusions, thereby effectively removing tiny inclusions in the molten steel and improving the purity of the molten steel; at the same time, advanced vacuum degassing technology is used to place the molten steel in a high vacuum environment, so that the hydrogen and nitrogen gases in the molten steel can escape quickly, significantly reducing the gas content in the molten steel, greatly reducing the subsequent processing and use The risk of pores and cracks caused by the presence of gas during the process is eliminated. In addition, based on the high-precision analysis results of the molten steel composition, various alloy fine-tuning agents are accurately added to finely adjust the content of silicon, manganese, phosphorus and sulfur in the molten steel to ensure that the content of each element fully meets the strict composition requirements of rare earth corrosion-resistant steel bars. During the refining process, special attention is paid to the stability of the content and uniformity of the rare earth elements. By accurately controlling the amount of refining agent added and the reaction time, the loss and segregation of rare earth elements are prevented to ensure that they can give full play to their unique performance advantages in the steel bars. Continuous casting: The refined high-quality molten steel enters the continuous casting stage; during the continuous casting process, the casting temperature is strictly controlled within the precise range of 1450℃-1500℃, and the billet drawing speed is finely adjusted according to the billet specifications, generally controlled at 1.5m / min-2.5m / min; Rolling: The steel bar billet is heated to a suitable temperature range of 1000℃-1100℃ and then sent to the rolling mill for multiple passes of rolling; The chemical composition of the steel bar by mass percentage: the carbon content is precisely controlled at 0.15%-0.25%, the silicon content is 0.30%-0.60%, the manganese content is 1.20%-1.60%, the phosphorus content is strictly limited to ≤0.045%, the sulfur content is ≤0.045%, the rare earth element RE content is set at 0.01%-0.02%, and the rest is Fe and impurities.

2. The method for producing corrosion-resistant steel bars reinforced with rare earth materials according to claim 1, characterized in that: In the converter smelting process: at the initial stage of oxygen blowing, the oxygen flow rate is appropriately increased, and the rapid reaction of oxygen with silicon and manganese, which are easily oxidized elements, is utilized to quickly remove these elements, and at the same time, favorable conditions are created for the subsequent oxidation of carbon; as the smelting process gradually advances, the oxygen flow rate is gradually reduced according to the real-time detected steel liquid composition data, and the degree of carbon oxidation is accurately controlled to ensure that the steel liquid composition can accurately approach the target value; in the later stage of converter smelting, rare earth alloys are accurately added according to the real-time detection results of the steel liquid composition; at this time, the high temperature and strong stirring environment in the converter are utilized to enable the rare earth elements to be evenly integrated into the steel liquid, laying a solid foundation for the subsequent improvement of the comprehensive performance of the steel bars.

3. The method for producing corrosion-resistant steel bars reinforced with rare earth materials according to claim 1, characterized in that: The chemical composition of the steel bar by mass percentage: carbon: 0.18%; Silicon: 0.40%; Manganese: 1.30%; Phosphorus: 0.035%; Sulfur: 0.030%; rare earth elements: 0.010%; the balance is iron and inevitable impurities.

4. The method for producing corrosion-resistant steel bars reinforced with rare earth materials according to claim 1, characterized in that: The chemical composition of the steel bar by mass percentage: carbon: 0.22%; Silicon: 0.50%; Manganese: 1.40%; Phosphorus: 0.040%; Sulfur: 0.035%; rare earth elements: 0.015%; the balance is iron and inevitable impurities.

5. The method for producing corrosion-resistant steel bars reinforced with rare earth materials according to claim 1, characterized in that: In the continuous casting process: for small-sized billets, since they dissipate heat faster, the billet drawing speed is appropriately increased to ensure the solidification quality and production efficiency of the billet; for large-sized billets, since they dissipate heat relatively slowly, the billet drawing speed is reduced to ensure that the billet can solidify evenly and avoid various defects.

6. The method for producing corrosion-resistant steel bars reinforced with rare earth materials according to claim 1 or 5, characterized in that: During the continuous casting process, the cooling water flow rate of the crystallizer is precisely controlled to ensure uniform cooling of the ingot, thereby obtaining a steel ingot with excellent surface quality and dense internal structure.

7. The method for producing corrosion-resistant steel bars reinforced with rare earth materials according to claim 3, characterized in that: The mechanical properties of the prepared steel bars are as follows: yield strength of 450 MPa, tensile strength of 580 MPa, and elongation of 20%.