Steel for 500MPa-grade photovoltaic support and manufacturing method thereof

Abstract

The invention relates to steel for a 500MPa-grade photovoltaic bracket. The steel comprises the following components in percentage by weight: less than or equal to 0.085% of C, 0.15%-0.30% of Si, 0.80%-1.40% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, 0.040%-0.090% of Ti, less than or equal to 0.0050% of N and the balance of Fe and inevitable impurities. The yield strength of the steel plate is 550 to 615 MPa; the tensile strength is 650 to 680 MPa; and the elongation is greater than or equal to 25%. Low carbon and high manganese are adopted, a trace amount of Ti element is added, an LF furnace is adopted for smelting, the purity of molten steel is guaranteed, the Ti element precipitation strengthening process is controlled by controlling the coiling temperature, the strength performance of the steel for the photovoltaic support is improved, and good economical efficiency is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and in particular to a 500MPa grade steel for photovoltaic brackets and a manufacturing method thereof. Background Art

[0002] Photovoltaic power generation is one of the main means to replace traditional power generation models and reduce carbon emissions. Its characteristics of low pollution, no noise and easy maintenance make it the most promising energy development field. Its broad development space and prospects have also received major attention from the country.

[0003] Photovoltaic bracket is an important supporting and protective structure of photovoltaic power generation device. At present, most of them are made of Q235 and Q345 steel coils or lightweight profiles to prevent corrosion. However, its strength is low and cannot meet the current use requirements.

[0004] Low-alloy high-strength weathering steel is an ideal product for photovoltaic brackets. At present, the domestic production of photovoltaic bracket steel generally adopts the addition of higher content of precious alloy elements such as V and Nb to achieve the purpose of improving strength, but it increases the production cost, and the strength is not high enough.

[0005] Therefore, it is of great significance to develop a low-cost, high-strength 500MPa-grade steel for photovoltaic brackets. Summary of the invention

[0006] In order to overcome the defects of the prior art, the technical problem solved by the present invention is to provide a 500MPa grade steel for photovoltaic brackets and a manufacturing method thereof, by adding Ti for micro-alloying without adding other alloying elements, and by controlling nano-scale precipitation to improve the strength, thereby obtaining low-cost and high-strength steel for photovoltaic brackets.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A 500MPa grade steel for photovoltaic brackets, whose components are as follows by weight percentage: C: ≤0.085%, Si: 0.15%-0.30%, Mn: 0.80%-1.40%, P: ≤0.020%, S: ≤0.010, Ti: 0.040%-0.090%, N: ≤0.0050%, and the rest is Fe and unavoidable impurities.

[0009] Its yield strength: 550~615MPa; tensile strength: 650~680MPa; elongation: ≥25%.

[0010] A method for manufacturing 500MPa grade photovoltaic support steel comprises the following steps:

[0011] 1) Smelting:

[0012] The molten iron is pretreated for desulfurization, and the top and bottom combined blowing converter is used for smelting to dephosphorize and decarbonize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, and the converter process temperature is controlled at 1570-1580℃, and the steel tapping temperature is 1640-1660℃; then the molten steel after converter smelting is subjected to LF refining outside the furnace, the refining temperature is ≥1560℃, and the argon flow rate is controlled at 30-60Nm 3 / h;

[0013] 2) Continuous casting of molten steel:

[0014] The superheat of slab continuous casting is less than 25℃, the thickness of the tundish protective slag layer is 8-15mm, and the casting speed is controlled at 1.5-1.8m / s;

[0015] 3) Slab heating:

[0016] The qualified slabs are sent to the heating furnace for heating. The slab temperature out of the furnace is 1210-1250℃. The slab heating time is controlled at 140min-210min. The soaking time of the heating furnace is not less than 30min.

[0017] 4) Slab rolling:

[0018] The rough rolling + finishing rolling method is adopted, wherein the rough rolling adopts 3+3 rolling, the two rough rolling mills R1 and R2 are reversibly rolled for three passes, the rough rolling temperature is controlled at 1040-1110°C, the rough rolling outlet speed is 4.5-5.5m / s, and the rough rolling intermediate billet thickness is 38-45mm; the finishing hot rolling mill performs multiple continuous rolling, the finishing rolling temperature is 860-930°C, and the finishing rolling outlet speed is 8-13.5m / s;

[0019] 5) Cooling:

[0020] The hot-rolled plate is subjected to laminar cooling and then coiled to obtain steel for photovoltaic brackets.

[0021] The cooling rate is 15-25°C / S, and the coiling temperature is 600-660°C.

[0022] The hot finishing mill performs 7 continuous rolling passes.

[0023] During the continuous casting process, the taper of the crystallizer is 0.9-1.2% / m.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The present invention adopts the addition of trace Ti alloy components combined with steelmaking hot rolling process to produce 500MPa grade photovoltaic bracket steel. The photovoltaic bracket steel not only meets the strength requirements but also reduces the production cost.

[0026] 2) The present invention controls nano-scale precipitation to improve strength, thereby obtaining low-cost and high-strength photovoltaic bracket steel. Low-carbon high-manganese and trace Ti elements are added, and LF furnace smelting is used to ensure the purity of molten steel. The Ti element precipitation strengthening process is controlled by controlling the coiling temperature, thereby improving the strength performance of photovoltaic bracket steel and having good economic efficiency. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are further described below:

[0028] The present invention provides a 500MPa grade photovoltaic support steel, the components of which are as follows by weight percentage:

[0029] C: ≤0.085%, Si: 0.15%~0.30%, Mn: 0.80%~1.40%, P: ≤0.020%, S: ≤0.010, Ti: 0.040%~0.090%, N: ≤0.0050%, the rest are Fe and unavoidable impurities.

[0030] Its yield strength: 550~615MPa; tensile strength: 650~680MPa; elongation: ≥25%.

[0031] A method for manufacturing 500MPa grade photovoltaic support steel comprises the following steps:

[0032] 1) Smelting:

[0033] The molten iron is pretreated for desulfurization, and the top and bottom combined blowing converter is used for smelting to dephosphorize and decarbonize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, and the converter process temperature is controlled at 1570-1580℃, and the steel tapping temperature is 1640-1660℃; then the molten steel after converter smelting is subjected to LF refining outside the furnace, the refining temperature is ≥1560℃, and the argon flow rate is controlled at 30-60Nm 3 / h;

[0034] 2) Continuous casting of molten steel:

[0035] The slab continuous casting superheat is less than 25°C, the mold taper is 0.9-1.2%, the tundish protection slag layer thickness is 8-15mm, and the casting speed is controlled at 1.5-1.8m / s;

[0036] 3) Slab heating:

[0037] The qualified slabs are sent to the heating furnace for heating. The slab temperature out of the furnace is 1210-1250℃. The slab heating time is controlled at 140min-210min. The soaking time of the heating furnace is not less than 30min.

[0038] 4) Slab rolling:

[0039] The rough rolling + finishing rolling method is adopted, in which the rough rolling adopts 3+3 rolling, the two rough rolling mills R1 and R2 are reversibly rolled three times, the rough rolling outlet temperature is controlled at 1040~1110℃, the rough rolling outlet speed is 4.5~5.5m / s, and the rough rolling intermediate billet thickness is 38~45mm; the finishing hot rolling mill performs 7 continuous rolling, the finishing rolling final rolling temperature is 860~930℃; the finishing rolling outlet speed is 8~13.5m / s. During the finishing rolling process, the plate shape control adopts the computer three-level mode management, the third level issues the plate shape control target (convexity 30-60μm), the second level determines the plate shape control layer bending roll force and roll shifting value parameters according to the material specifications, and the first level realizes online automatic control through plate shape feedback. The finishing rolling operator monitors the rolling plate shape indicators through instrument feedback. When the plate shape control is abnormal, it can be adjusted quickly by adjusting the bending roll force value and the roll shifting value.

[0040] 5) Cooling:

[0041] The hot-rolled plate is subjected to laminar cooling and then coiled to obtain steel for photovoltaic brackets.

[0042] The cooling rate is 15-25°C / S, and the coiling temperature is 600-660°C.

[0043] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0044] The chemical composition of each example steel is shown in Table 1, the continuous casting process parameters are shown in Table 2, the slab heating and rolling parameters are shown in Table 3, and the product tensile properties are shown in Table 4.

[0045] Table 1 Chemical composition

[0046] Example Carbon Silicon Mn Phosphorus S-sulfur N Titanium Example 1 0.0747 0.2408 0.9237 0.01454 0.00241 0.0032 0.0734 Example 2 0.0766 0.2436 0.9482 0.0127 0.00527 0.0061 0.0757 Example 3 0.0816 0.255 0.9476 0.01371 0.00523 0.0064 0.0741 Example 4 0.0798 0.2393 0.9342 0.01341 0.00501 0.0032 0.0758 Example 5 0.0781 0.2486 0.9474 0.01148 0.00273 0.003 0.0726

[0047] Table 2 Smelting and continuous casting process parameters

[0048] Example Converter process temperature Steel tapping temperature Refining temperature Argon flow rate Slab continuous casting superheat Crystallizer taper Thickness of tundish protection slag layer Pulling speed Example 1 1575 1650 1565 45 19 1.0 10 1.6 Example 2 1570 1652 1568 40 8 1.0 12 1.7 Example 3 1573 1655 1563 55 12 1.0 9 1.6 Example 4 1576 1653 1566 40 7 1.0 10 1.6 Example 5 1577 1650 1567 45 15 1.0 13 1.7

[0049] Table 3 Slab heating and rolling parameters

[0050]

[0051] Table 4 Product tensile properties

[0052] Example Specification Yield Tensile strength MPa Elongation, % Example 1 3.1 615 672 26 Example 2 2.6 580 668 26 Example 3 3.1 592 661 27 Example 4 3.1 607 667 28 Example 5 3.1 614 664 30

[0053] According to the above results, it can be concluded that the photovoltaic support steel prepared by the present invention has a yield strength of 550-615 MPa, a tensile strength of 650-680 MPa, and an elongation of ≥25%, and has high strength and can meet application requirements.

[0054] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. In addition, the various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A 500MPa grade photovoltaic support steel, characterized in that: Its components are as follows by weight: C: ≤0.085%, Si: 0.15%-0.30%, Mn: 0.80%-1.40%, P: ≤0.020%, S: ≤0.010, Ti: 0.040%-0.090%, N: ≤0.0050%, and the rest are Fe and unavoidable impurities.

2. The 500MPa grade photovoltaic support steel according to claim 1, characterized in that: Its yield strength: 550~615MPa; tensile strength: 650~680MPa; elongation: ≥25%.

3. The method for manufacturing a 500MPa grade photovoltaic support steel according to claim 1, characterized in that: The following steps are involved: 1) Smelting: The molten iron is pretreated for desulfurization, and the top and bottom combined blowing converter is used for smelting to dephosphorize and decarbonize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, and the converter process temperature is controlled at 1570-1580℃, and the steel tapping temperature is 1640-1660℃; then the molten steel after converter smelting is subjected to LF refining outside the furnace, the refining temperature is ≥1560℃, and the argon flow rate is controlled at 30-60Nm 3 / h; 2) Continuous casting of molten steel: The superheat of slab continuous casting is less than 25℃, the thickness of the tundish protective slag layer is 8-15mm, and the casting speed is controlled at 1.5-1.8m / s; 3) Slab heating: The qualified slabs are sent to the heating furnace for heating. The slab temperature out of the furnace is 1210-1250℃. The slab heating time is controlled at 140min-210min. The soaking time of the heating furnace is not less than 30min. 4) Slab rolling: The rough rolling + finishing rolling method is adopted, wherein the rough rolling adopts 3+3 rolling, the two rough rolling mills R1 and R2 are reversibly rolled for three passes, the rough rolling temperature is controlled at 1040-1110°C, the rough rolling outlet speed is 4.5-5.5m / s, and the rough rolling intermediate billet thickness is 38-45mm; the finishing hot rolling mill performs multiple continuous rolling, the finishing rolling temperature is 860-930°C, and the finishing rolling outlet speed is 8-13.5m / s; 5) Cooling: The hot-rolled plate is subjected to laminar cooling and then coiled to obtain steel for photovoltaic brackets.

4. The method for manufacturing a 500MPa grade photovoltaic support steel according to claim 3, characterized in that: The cooling rate is 15-25°C / S, and the coiling temperature is 600-660°C.

5. The method for manufacturing a 500MPa grade photovoltaic support steel according to claim 3, characterized in that: The hot finishing mill performs 7 continuous rolling passes.

6. The method for manufacturing a 500MPa grade photovoltaic support steel according to claim 3, characterized in that: During the continuous casting process, the taper of the crystallizer is 0.9 to 1.2%.

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