Preparation method of structural steel strip for electric iron tower

Abstract

The invention belongs to the technical field of steel production, and relates to a preparation method of a structural steel strip for an electric iron tower, and the structural steel strip comprises the following chemical components: 0.12-0.19% of carbon; 0.18% to 0.35% of silicon; not less than 1.0% of manganese; less than or equal to 0.025% of phosphorus; less than or equal to 0.015% of sulfur; 0.01 to 0.03 percent of niobium; 0.03 to 0.05 percent of titanium; greater than or equal to 0.015% of acid-soluble aluminum; 30-70ppm of nitrogen, less than or equal to 30ppm of oxygen and the balance of Fe and inevitable impurities. The preparation process comprises the procedures of blast furnace molten iron preparation, converter smelting, external refining, slab continuous casting, hot rolling, U-shaped pipe laminar cooling, acid pickling galvanization and the like. Through optimization of component design and process control, the strength surplus of the produced steel strip reaches 50-80 MPa, the thickness of a zinc coating is controlled to be 70-130 microns, and the steel strip has excellent corrosion resistance and post-process machining performance. Compared with the prior art, the method is low in production cost, good in economical efficiency, suitable for manufacturing of the high-strength electric iron tower and high in market application value.

Description

Technical Field

[0001] The invention belongs to the technical field of steel production and relates to a method for preparing a structural steel strip for an electric power tower. Background Art

[0002] Steel for power towers is a hot-rolled exclusive product specially used for manufacturing power transmission and transformation steel structure facilities. It is mainly used for manufacturing power transmission towers. According to its structural form, it can be divided into four-column angle steel towers, three-column steel pipe towers, independent pole towers, and three-column round steel cable towers. The product thickness specification is 3.0mm~50mm. Different strength levels correspond to different engineering projects. Under normal circumstances, the lower the grade, the larger the thickness specification. Due to the complex shape of automobile beams, in addition to strength and cold bending, it also requires good stamping forming performance. The product requires pure steel with few harmful and residual elements. The main products are Q345-T, Q390-T, Q420-T, Q460-T, etc. Due to the development of modern metallurgical technology and the need for lightweight, in order to ensure the durability and anti-destruction ability of the tower, high-strength steel for towers has gradually become the preferred material for Chinese electrical equipment manufacturers. As an entry-level high-strength steel product, the 420MPa grade has a material strength higher than the 345Mpa grade, which meets the usage requirements of downstream customers. It adopts a micro-alloying composition design scheme and has lower production and usage costs. At the same time, the product is suitable for multiple process steps such as cutting, punching and hot-dip galvanizing. The product has excellent comprehensive performance and has broad market prospects.

[0003] CN202011439802.4 discloses a weathering steel tower, wherein the weathering steel comprises the following components by mass fraction: C: ≤0.16%, Si: ≤0.65%, Mn: ≤1.5%, P: ≤0.020%, S: ≤0.010%, Cu: 0.25-0.55%, Cr: 0.30-1.25%, Ni: ≤0.65%, Sb: ≤0.2%, and Ti, V, Nb and Alt alloys, wherein the total amount of Ti, V, Nb and Alt alloys does not exceed 0.22%, and the rest is Fe and unavoidable impurities. The weathering steel profile is obtained by feeding the refined material into the furnace, smelting, refining, continuous casting, rolling, and cooling, and the profile is formed into an iron tower after being spliced ​​or welded after drilling and forming. The invention makes the thickness of the self-protective oxide layer of weathering steel reach 0.5mm, which can be used in the complex climate environment of Guizhou. The process of preparing iron towers with weathering steel is studied, the process flow is optimized, the material and production cost of weathering steel are saved, and the production efficiency is improved. However, the invention does not belong to the category of high-strength steel, but is a coating-free weathering steel, which leads to a low C content and a high Si content in the chemical composition design steel. More corrosion-resistant elements are added to the steel, the manufacturing cost is high, and the production economy is poor. In addition, it does not put forward relevant requirements for gas elements, and there are significant differences in the design concept. Summary of the invention

[0004] In view of this, the purpose of the present invention is to solve the production problem of steel for power towers and to provide a method for preparing structural steel strip for power towers.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a structural steel strip for an electric power tower, wherein the structural steel strip for an electric power tower comprises the following components by mass fraction:

[0007] Carbon: 0.12%~0.19%; Silicon: 0.18%~0.35%; Manganese: ≥1.0%; Phosphorus: ≤0.025%; Sulfur: ≤0.015%; Niobium: 0.01~0.03%; Titanium: 0.03~0.05%; Acid-soluble aluminum: ≥0.015%; Nitrogen: 30~70ppm, Oxygen: ≤30ppm, the rest is Fe and unavoidable impurities;

[0008] The preparation process of the structural steel strip for power tower is as follows: blast furnace molten iron → converter smelting → refining outside the furnace → slab continuous casting → slab heating → high-pressure descaling → rolling on a roughing mill with vertical rollers → finishing rolling 7-stand continuous rolling → U-tube laminar cooling → coiling and packaging on a coiler → surface spraying and side spraying of steel coils → surface size and quality inspection → sampling and inspection → labeling after passing the inspection → warehousing → unpacking → pickling → galvanizing → installation and forming.

[0009] Furthermore, in the blast furnace molten iron process, the molten iron temperature is ≥1300°C, and the silicon and sulfur are controlled to be <0.08%;

[0010] In the converter smelting process, the smelting time is less than 40 minutes, the carbon content of the steel is controlled to be 0.02-0.05%, and the oxygen content is less than 700ppm;

[0011] In the refining process outside the furnace, a double refining process of ladle furnace and vacuum furnace is adopted, the treatment time of ladle furnace is ≤1 hour, and the treatment time of vacuum furnace is 35~55min;

[0012] In the slab continuous casting process, the casting cycle of a single furnace steel is 35 to 45 minutes, and the slab pulling speed is ≤1.7m / s;

[0013] In the slab heating process, the charging temperature is ≤750℃, the preheating stage is 850~1100℃, the time is 25~40min, the heating stage is 1200~1300℃, the time is 60~80min, the soaking stage is 1150-1250℃, the time is 50~75min;

[0014] In the U-tube laminar cooling process, the front section cooling, laminar cooling header water outlet 3 / 4 mode, cooling water temperature is controlled within 40℃, cooling water flow ≥1100m 3 / h.

[0015] Furthermore, the surface oxide of the structural steel strip for power tower is mainly ferrous oxide and ferroferric oxide, and the thickness of the pickling galvanized layer is controlled at 70um to 130um.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The steel grade of the present invention has a reasonable chemical composition design, is economical, has high executability of the production process, and has a strength surplus of 50-80MPa; the surface oxide is mainly ferrous oxide and ferroferric oxide, and the average thickness of the pickling galvanized layer is 85um, which has good corrosion resistance. The mechanical properties of the steel used for the iron tower produced by the present invention all meet the requirements, and at the same time meet the use requirements of downstream customers. The product has good economic efficiency, excellent post-process processing performance and galvanizing process, and is a qualified raw steel plate for the iron tower.

[0018] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0020] A method for preparing a structural steel strip for an electric power tower, wherein the structural steel strip for an electric power tower comprises the following components by mass fraction:

[0021] Carbon: 0.12%~0.19%; Silicon: 0.18%~0.35%; Manganese: ≥1.0%; Phosphorus: ≤0.025%; Sulfur: ≤0.015%; Niobium: 0.01~0.03%; Titanium: 0.03~0.05%; Acid-soluble aluminum: ≥0.015%; Nitrogen: 30~70ppm, Oxygen: ≤30ppm, the rest is Fe and unavoidable impurities;

[0022] The preparation process of structural steel strip for power tower is: blast furnace molten iron → converter smelting → refining outside the furnace → slab continuous casting → slab heating → high pressure descaling → roughing mill rolling with vertical rollers → finishing rolling 7-stand continuous rolling → U-tube laminar cooling → coiling and packaging → steel coil surface spraying and side spraying → surface size and quality inspection → sampling and inspection → labeling after passing the inspection → storage → opening → unloading → pickling → galvanizing → installation and molding. Among them:

[0023] In the blast furnace hot metal process, the hot metal temperature is ≥1300℃, and the silicon and sulfur are controlled to be less than 0.08%;

[0024] In the converter smelting process, the smelting time is less than 40 minutes, the carbon content of the steel is controlled to be 0.02-0.05%, and the oxygen content is less than 700ppm;

[0025] In the refining process outside the furnace, a double refining process of ladle furnace and vacuum furnace is adopted, the treatment time of ladle furnace is ≤1 hour, and the treatment time of vacuum furnace is 35~55min;

[0026] In the slab continuous casting process, the casting cycle of a single furnace steel is 35 to 45 minutes, and the slab pulling speed is ≤1.7m / s;

[0027] In the slab heating process, the charging temperature is ≤750℃, the preheating stage is 850~1100℃, the time is 25~40min, the heating stage is 1200~1300℃, the time is 60~80min, the soaking stage is 1150-1250℃, the time is 50~75min;

[0028] In the U-tube laminar cooling process, the front section cooling, laminar cooling header water outlet 3 / 4 mode, cooling water temperature is controlled within 40℃, cooling water flow ≥1100m 3 / h.

[0029] The surface oxide of the structural steel strip for power tower finally obtained is mainly ferrous oxide and ferroferric oxide, and the thickness of the pickling galvanized layer is controlled at 70um to 130um. For specific implementation data, please refer to Appendix 1, 2 and 3.

[0030] Appendix 1 is an example of the melting composition of 4 batches of steel strips

[0031]

[0032] Appendix 2 is an example of process control for 4 batches of steel strips

[0033]

[0034] Appendix 3 is an example of the mechanical properties and process properties of 4 batches of steel strips

[0035] Test steel coil Thickness / mm Re / MPa Rm / MPa A / ％ 180 degree bending test 20℃KV2 Galvanizing layer thickness A 4.75 487 617 24.50 d=1a qualified / 70um B 9.85 492 614 22.00 d=1.5aPass 113 / 139 / 93 83um C 13.75 547 662 22.50 d=1.5aPass 155 / 103 / 138 103um D 16.15 498 623 23.50 d=2aPass 167 / 156 / 174 98um

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a structural steel strip for an electric power tower, characterized in that: The structural steel strip for electric power tower includes the following components by mass fraction: Carbon: 0.12% to 0.19%; Silicon: 0.18% to 0.35%; Manganese: ≥1.0%; Phosphorus: ≤0.025%; Sulfur: ≤0.015%; Niobium: 0.01~0.03%; Titanium: 0.03-0.05%; acid-soluble aluminum: ≥0.015%; nitrogen: 30-70ppm, oxygen: ≤30ppm, the rest is Fe and unavoidable impurities; The preparation process of the structural steel strip for power tower is as follows: blast furnace molten iron → converter smelting → refining outside the furnace → slab continuous casting → slab heating → high-pressure descaling → rolling on a roughing mill with vertical rollers → finishing rolling 7-stand continuous rolling → U-tube laminar cooling → coiling and packaging on a coiler → surface spraying and side spraying of steel coils → surface size and quality inspection → sampling and inspection → labeling after passing the inspection → warehousing → unpacking → pickling → galvanizing → installation and forming.

2. The method for preparing a structural steel strip for an electric power tower according to claim 1, characterized in that: In the blast furnace hot metal process, the hot metal temperature is ≥1300℃, and the silicon and sulfur are controlled to be less than 0.08%; In the converter smelting process, the smelting time is less than 40 minutes, the carbon content of the steel is controlled to be 0.02-0.05%, and the oxygen content is less than 700ppm; In the refining process outside the furnace, a double refining process of ladle furnace and vacuum furnace is adopted, the treatment time of ladle furnace is ≤1 hour, and the treatment time of vacuum furnace is 35~55min; In the slab continuous casting process, the casting cycle of a single furnace steel is 35 to 45 minutes, and the slab pulling speed is ≤1.7m / s; In the slab heating process, the charging temperature is ≤750℃, the preheating stage is 850~1100℃, the time is 25~40min, the heating stage is 1200~1300℃, the time is 60~80min, the soaking stage is 1150-1250℃, the time is 50~75min; In the U-tube laminar cooling process, the front section cooling, laminar cooling header water outlet 3 / 4 mode, cooling water temperature is controlled within 40℃, cooling water flow ≥1100m 3 / h.

3. The method for preparing a structural steel strip for an electric power tower according to claim 1, characterized in that: The surface oxide of the structural steel strip for power tower is mainly ferrous oxide and ferroferric oxide, and the thickness of the pickling galvanized layer is controlled at 70um to 130um.

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