Rare-earth weather-proof structural steel for photovoltaic bracket and preparation method of rare-earth weather-proof structural steel

Abstract

The invention relates to the technical field of iron and steel smelting, and provides rare earth weather-proof structural steel for a photovoltaic support and a preparation method of the rare earth weather-proof structural steel. The invention discloses rare earth weather-proof structural steel for a photovoltaic bracket. The rare earth weather-proof structural steel consists of the following components: C, Si, Mn, P, S, Alt, Ti, N, Cr, Cu, Ni, rare earth elements and the balance of Fe and inevitable impurity elements. The rare earth element consists of the following components in percentage by mass: less than or equal to 0.0025% of La, less than or equal to 0.0030% of Ce, 0.0001-0.0005% of Pr and the balance of rare earth elements; the mass content relation of La, Ce and Pr is that the value of 3 * La + 2 * Ce + 3 * Pr is 0.0049%-0.0055%. According to the technical scheme, the problems of low strength and poor corrosion resistance of the steel for the photovoltaic bracket in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, specifically to a rare earth weathering structural steel for photovoltaic brackets and its preparation method. Background Technology

[0002] As a core supporting component of photovoltaic systems, the choice of materials for photovoltaic brackets directly affects the service life and safety of the system. Traditional photovoltaic brackets are mostly made of aluminum, hot-dip galvanized steel, and stainless steel. However, weathering structural steel, with its combined advantages of cost and weather resistance, has not only been widely used in many high-specification photovoltaic projects in China in recent years, but has also shown good development potential in overseas markets. With the leapfrog development of the photovoltaic industry, the annual demand for structural steel for photovoltaic brackets has exceeded 5 million tons and continues to grow rapidly. Weathering structural steel has also ushered in development opportunities for rising demand and market expansion in response to this market trend.

[0003] However, existing technologies for preparing weathering structural steel have insufficient mechanical strength and are difficult to fully adapt to the outdoor corrosive environment requirements of photovoltaic brackets, which limits their further promotion and application in the photovoltaic field. Therefore, developing a rare earth weathering structural steel for photovoltaic brackets with both mechanical and corrosion resistance advantages and its preparation method has become an urgent technical problem to be solved in the industry. Summary of the Invention

[0004] This invention proposes a rare earth weathering structural steel for photovoltaic brackets and its preparation method, which solves the problems of low strength and poor corrosion resistance of structural steel for photovoltaic brackets in related technologies.

[0005] The technical solution of the present invention is as follows: A rare earth weathering structural steel for photovoltaic brackets, comprising the following components by mass percentage: C 0.05%~0.15%, Si≤0.30%, Mn 0.9%~1.3%, P≤0.018%, S≤0.010%, Alt≤0.05%, Ti≤0.02%, N≤0.006%, Cr 0.20%~0.40%, Cu 0.20%~0.40%, Ni 0.01%~0.05%, rare earth elements 0.002%~0.0025%, with the balance being Fe and unavoidable impurity elements; The rare earth elements, by mass percentage, consist of the following components: La≤0.0025%, Ce≤0.0030%, Pr0.0001%~0.0005%; The mass content of La, Ce, and Pr is in the relationship of 3×La+2×Ce+3×Pr, with a value of 0.0049%~0.0055%, preferably 0.0053%.

[0006] As a further technical solution, the mass content relationship between La and Pr is La / Pr, with a value of 1 to 4, preferably 3.

[0007] This invention also proposes a method for preparing rare earth weathering structural steel for photovoltaic brackets, comprising the following steps: molten steel in a converter is refined and continuously cast to obtain a billet, and the billet is then subjected to heating, rough rolling, fine rolling, and coiling treatment in sequence to obtain rare earth weathering structural steel.

[0008] As a further technical solution, the tapping temperature of the molten steel in the converter is 1610~1630℃.

[0009] As a further technical solution, during the refining process, after the station is powered on, lime and fluorite balls are added for primary slag formation, with a primary slag formation time of ≥10 minutes; after the primary slag formation is completed, reducing white slag is formed, with a white slag formation time of ≥15 minutes.

[0010] As a further technical solution, the amount of lime added is 3~6 kg / ton of steel, and the amount of fluorite balls added is 1.5 kg / ton of steel.

[0011] As a further technical solution, rare earth wire is fed into the crystallizer during continuous casting, and the feeding speed is 7~8m / min.

[0012] As a further technical solution, the billet pulling speed during continuous casting is 0.95~1.15m / min.

[0013] As a further technical solution, the heating includes a first-stage heating, a second-stage heating, a third-stage heating, and a heat equalization stage; the heating rates of the first-stage heating, the second-stage heating, and the third-stage heating are different.

[0014] As a further technical solution, the heating process involves raising the temperature to 600-850°C at a first heating rate of 5-8°C / min to complete the first stage of heating; then raising the temperature to 950-1150°C at a second heating rate of 8-12°C / min to complete the second stage of heating; and then raising the temperature to 1230-1270°C at a third heating rate of 3-5°C / min to complete the third stage of heating, before entering the homogenization stage.

[0015] In this invention, the rare earth weathering structural steel for photovoltaic brackets and its preparation method involve sequentially performing segmented heating treatments on the cast billet to achieve a gradient-like uniform evolution of the internal structure of the steel: the first stage of heating, with a heating rate of 5~8℃ / min, slowly raises the steel from room temperature to the medium temperature zone, avoiding thermal stress concentration and uneven structure caused by excessively rapid heating, thus preparing for subsequent austenitization; the second stage of heating, with a heating rate of 8~12℃ / min, raises the steel to the high temperature zone, accelerating grain nucleation and uniform growth, and reducing brittle phase residue; the third stage of heating, with a lower heating rate of 3~5℃ / min, effectively inhibits abnormal grain growth, refines grain size, reduces compositional segregation, and improves the plastic deformation capacity of the steel, thereby increasing the elongation after fracture of the rare earth weathering structural steel for photovoltaic brackets.

[0016] As a further technical solution, the temperature of the heat spreader is 1220~1260℃, and the heating rate of the heat spreader is 0.5~1℃ / min.

[0017] As a further technical solution, during the rough rolling process, descaling R1 is performed in the first and second passes, and R2 is performed in the first and third passes.

[0018] As a further technical solution, the initial rolling temperature during finishing rolling is 1000~1100℃, the final rolling temperature is 830~860℃, and the reduction rate is 60%.

[0019] As a further technical solution, the temperature during the winding process is 570~610℃.

[0020] The working principle and beneficial effects of this invention are as follows: This invention, through a method for preparing rare-earth weather-resistant structural steel for photovoltaic supports, achieves a precise ratio and synergistic effect of the three rare-earth elements La, Ce, and Pr by limiting the mass content of 3×La+2×Ce+3×Pr to 0.0049%~0.0055%. La, Ce, and Pr preferentially combine with harmful impurities such as P, S, and O in the steel to form composite rare-earth inclusions that then spheroidize, altering the properties and morphology of the inclusions, reducing the electrode potential difference between the inclusions and the matrix, and decreasing electrochemical corrosion. Simultaneously, La and Ce agglomerate in the microstructure... The structure reduces interfacial energy, preventing surface and localized corrosion, and promotes the formation of a stable α-FeOOH rust layer, resulting in a dense surface rust layer that isolates air and effectively reduces chemical corrosion. By precisely controlling the ratio of the three rare earth elements, La, Ce, and Pr, the problem of component segregation or inclusion coarsening caused by excessive amounts of a single rare earth element can be avoided. Ultimately, the rare earth weathering structural steel for photovoltaic brackets maintains excellent mechanical strength while possessing superior corrosion resistance, meeting the long-term stress and weather resistance requirements of photovoltaic brackets in outdoor service. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A rare earth weathering structural steel for photovoltaic brackets, comprising the following components by mass percentage: C 0.06%, Si 0.20%, Mn 0.9%, P 0.01%, S 0.003%, Alt 0.02%, Ti 0.006%, N 0.0045%, Cr 0.25%, Cu 0.20%, Ni 0.01%, rare earth elements 0.002%, with the balance being Fe and unavoidable impurity elements; The rare earth elements, by mass percentage, consist of the following components: La 0.0012%, Ce 0.0005%, Pr 0.0003%; the mass content relationship is 3×La+2×Ce+3×Pr=0.0055%, and the value of La / Pr is 4. A method for preparing rare earth weathering structural steel for photovoltaic brackets includes the following steps: S1. Converter steel refining treatment: First, control the steel temperature to 1620℃ to complete the converter tapping; during subsequent refining, after power is supplied to the station, add lime (addition amount is 4.5kg / ton of steel) and fluorite balls (addition amount is 1.5kg / ton of steel) to carry out one slag treatment (one slag treatment time is 15min). After the slag treatment is completed, reducing white slag is formed and maintained for 20min. S2. Continuous casting: After feeding rare earth wire into the crystallizer at a feeding speed of 7.5 m / min, continuous casting is carried out at a billet pulling speed of 1.05 m / min to obtain a billet. S3. Heating: The billet is heated to 750℃ at a first heating rate of 5℃ / min to complete the first heating stage; then heated to 1050℃ at a second heating rate of 8℃ / min to complete the second heating stage; then heated to 1250℃ at a third heating rate of 3℃ / min to complete the third heating stage; and finally heated to 1255℃ at a heating rate of 0.5℃ / min to complete the soaking stage treatment. S4. Roughing and Finishing: During roughing, the R1 stand is opened for the first and second passes, and the R2 stand is opened for the first and third passes. After roughing, finishing is carried out. During the finishing stage, the initial rolling temperature is controlled at 1050℃ and the final rolling temperature is controlled at 850℃. The reduction rate is set to 60% to complete the rolling and obtain the finished steel plate. S5. Coiling the finished product: The precision-rolled steel plate is coiled at a temperature of 590℃ to obtain rare earth weathering structural steel.

[0023] Example 2 Compared with Example 1, the only difference in Example 2 is that the rare earth weathering structural steel for photovoltaic brackets in this example is composed of the following components by mass percentage: C 0.1%, Si 0.25%, Mn 1.1%, P 0.011%, S 0.005%, Alt 0.025%, Ti 0.012%, N 0.0047%, Cr 0.3%, Cu 0.3%, Ni 0.03%, rare earth elements 0.00225%, with the balance being Fe and unavoidable impurity elements; The rare earth elements, by mass percentage, consist of the following components: La 0.0008%, Ce 0.00125%, and Pr 0.0002%; the mass content relationship is 3×La+2×Ce+3×Pr=0.0055%, and the La / Pr ratio is 4.

[0024] Example 3 Compared with Example 1, the only difference in Example 3 is that the rare earth weathering structural steel for photovoltaic brackets in this example is composed of the following components by mass percentage: C 0.15%, Si 0.28%, Mn 1.3%, P 0.018%, S 0.010%, Alt 0.05%, Ti 0.018%, N 0.005%, Cr 0.40%, Cu 0.40%, Ni 0.05%, rare earth elements 0.0025%, with the balance being Fe and unavoidable impurity elements; The rare earth elements, by mass percentage, consist of the following components: La 0.0004%, Ce 0.002%, Pr 0.0001%; ​​the mass content relationship is 3×La+2×Ce+3×Pr=0.0055%, and the value of La / Pr is 4.

[0025] Example 4 Compared with Example 1, the only difference in Example 4 is that the rare earth elements in this example are composed of the following components by mass percentage: La 0.00075%, Ce 0.00125%, Pr 0.00025%; the mass content relationship is 3×La+2×Ce+3×Pr=0.0055%, and the value of La / Pr is 3.

[0026] Example 5 Compared with Example 1, the only difference in Example 5 is that, in this example, the rare earth elements are composed of the following components by mass percentage: La 0.0005%, Ce 0.00125%, Pr 0.0005%; the mass content relationship is 3×La+2×Ce+3×Pr=0.0055%, and the value of La / Pr is 1.

[0027] Example 6 Compared with Example 1, the only difference in Example 6 is that the rare earth elements in this example are composed of the following components by mass percentage: La 0.0006%, Ce 0.00145%, Pr 0.0002%; the mass content relationship is 3×La+2×Ce+3×Pr=0.0053%, and the value of La / Pr is 3.

[0028] Example 7 Compared with Example 1, the only difference in Example 7 is that, in this example, the rare earth elements are composed of the following components by mass percentage: La 0.0003%, Ce 0.00185%, Pr 0.0001%; ​​the mass content relationship is 3×La+2×Ce+3×Pr=0.0049%, and the value of La / Pr is 3.

[0029] Example 8 Compared with Example 1, the only difference in Example 8 is that in the preparation method of rare earth weathering structural steel for photovoltaic brackets in this example, step S3 is as follows: heating: the billet is heated to 750°C at a first heating rate of 5°C / min to complete the first heating stage; then heated to 1050°C at a second heating rate of 8°C / min to complete the second heating stage; then heated to 1250°C at a third heating rate of 4°C / min to complete the third heating stage; and then heated to 1255°C at a heating rate of 0.5°C / min to complete the soaking stage treatment.

[0030] Example 9 Compared with Example 1, the only difference in Example 9 is that in the preparation method of rare earth weathering structural steel for photovoltaic brackets in this example, step S3 is as follows: heating: the billet is heated to 750°C at a first heating rate of 5°C / min to complete the first heating stage; then heated to 1050°C at a second heating rate of 8°C / min to complete the second heating stage; then heated to 1250°C at a third heating rate of 5°C / min to complete the third heating stage; and then heated to 1255°C at a heating rate of 0.5°C / min to complete the soaking stage treatment.

[0031] Example 10 Compared with Example 1, the only difference in Example 10 is that in the preparation method of rare earth weathering structural steel for photovoltaic brackets in this example, step S3 is as follows: heating: the billet is heated to 750°C at a first heating rate of 5°C / min to complete the first heating stage; then heated to 1050°C at a second heating rate of 10°C / min to complete the second heating stage; then heated to 1250°C at a third heating rate of 4°C / min to complete the third heating stage; and then heated to 1255°C at a heating rate of 0.5°C / min to complete the soaking stage treatment.

[0032] Example 11 Compared with Example 1, the only difference in Example 11 is that in the preparation method of rare earth weathering structural steel for photovoltaic brackets in this example, step S3 is as follows: heating: the billet is heated to 750°C at a first heating rate of 5°C / min to complete the first heating stage; then heated to 1050°C at a second heating rate of 12°C / min to complete the second heating stage; then heated to 1250°C at a third heating rate of 4°C / min to complete the third heating stage; and then heated to 1255°C at a heating rate of 0.5°C / min to complete the soaking stage treatment.

[0033] Example 12 Compared with Example 1, the only difference in Example 12 is that in the preparation method of rare earth weathering structural steel for photovoltaic brackets in this example, step S3 is as follows: heating: the billet is heated to 750°C at a first heating rate of 6°C / min to complete the first heating stage; then heated to 1050°C at a second heating rate of 10°C / min to complete the second heating stage; then heated to 1250°C at a third heating rate of 4°C / min to complete the third heating stage; and then heated to 1255°C at a heating rate of 0.5°C / min to complete the soaking stage treatment.

[0034] Example 13 Compared with Example 1, the only difference in Example 13 is that in the preparation method of rare earth weathering structural steel for photovoltaic brackets in this example, step S3 is as follows: heating: the billet is heated to 750°C at a first heating rate of 8°C / min to complete the first heating stage; then heated to 1050°C at a second heating rate of 10°C / min to complete the second heating stage; then heated to 1250°C at a third heating rate of 4°C / min to complete the third heating stage; and then heated to 1255°C at a heating rate of 0.5°C / min to complete the soaking stage treatment.

[0035] Comparative Example 1 Compared with Example 1, the only difference in this comparative example is that the rare earth elements in this comparative example are composed of Ce and Pr in a mass ratio of 5:3.

[0036] Comparative Example 2 Compared with Example 1, the only difference in this comparative example is that the rare earth elements in this comparative example are composed of La and Pr in a mass ratio of 4:1.

[0037] Comparative Example 3 Compared with Example 1, the only difference in this comparative example is that the rare earth elements in this comparative example are composed of La and Ce in a mass ratio of 12:5.

[0038] Comparative Example 4 Compared with Example 1, the only difference in this comparative example is that the rare earth element in this comparative example is only Pr.

[0039] Comparative Example 5 Compared with Example 1, the only difference in this comparative example is that the rare earth element in this comparative example is Ce.

[0040] Comparative Example 6 Compared with Example 1, the only difference in this comparative example is that the rare earth element in this comparative example is only La.

[0041] Comparative Example 7 Compared with Example 1, the only difference in this comparative example is that it does not contain rare earth elements.

[0042] Comparative Example 8 Compared with Example 1, the only difference in this comparative example is that it does not contain Ni.

[0043] The photovoltaic support structures made of rare earth weathering steel prepared in Examples 1-13 and Comparative Examples 1-8 were tested according to the following method: 1. Tensile strength, lower yield strength, and elongation after fracture: The tensile strength, yield strength, and elongation after fracture of the samples were tested according to the test methods specified in GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Tests at room temperature," with a test rate of 0.002 s. -1 ; 2. Corrosion resistance: Refer to standard TB / T 2375 (1979-2023) "Test Method for Cyclic Immersion Corrosion of Weathering Steel for Railways", the test solution is NaHSO3 solution (1.0×10⁻⁶). -2 The experimental cycle was 60 min (mol / L, pH 4.5), including a 12 min immersion time. The experiment lasted for 144 h. The corrosion weight loss rate of Q355B steel was used as a comparison sample to calculate the relative corrosion rate of rare earth weathering structural steel for photovoltaic brackets. 3. Surface quality: The absence of cracks on the surface of the steel is considered "good".

[0044] The test results are shown in Tables 1 and 2: Table 1. Test results of yield strength, tensile strength, relative corrosion rate and surface quality of rare earth weathering structural steel for photovoltaic brackets.

[0045] A comparison of Examples 1-7 and Comparative Examples 1-7 shows that the addition of rare earth elements Pr, Ce, and La can significantly improve the lower yield strength, tensile strength, and corrosion resistance of rare earth weathering structural steel used in photovoltaic brackets. A comparison of Example 1 and Comparative Example 8 shows that the addition of Ni element improves the surface quality, yield strength, tensile strength, and corrosion resistance of rare earth weathering structural steel used in photovoltaic brackets.

[0046] Table 2. Test results of elongation after fracture of rare earth weathering structural steel for photovoltaic brackets

[0047] As shown in Table 2, during the preparation of rare earth weathering structural steel for photovoltaic brackets, the billet is heated to 600-850℃ at a first heating rate of 5-8℃ / min to complete the first heating stage; then heated to 950-1150℃ at a second heating rate of 8-12℃ / min to complete the second heating stage; and then heated to 1230-1270℃ at a third heating rate of 3-5℃ / min to complete the third heating stage, before entering the soaking stage. This heating method can maintain the elongation after fracture of rare earth weathering structural steel for photovoltaic brackets at the level of 27.0%-30.0%.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rare earth weathering structural steel for photovoltaic brackets, characterized in that, The rare earth weathering structural steel, by mass percentage, is composed of the following components: C 0.05%~0.15%, Si≤0.30%, Mn 0.9%~1.3%, P≤0.018%, S≤0.010%, Alt≤0.05%, Ti≤0.02%, N≤0.006%, Cr 0.20%~0.40%, Cu 0.20%~0.40%, Ni 0.01%~0.05%, rare earth elements 0.002%~0.0025%, with the balance being Fe and unavoidable impurity elements; The rare earth elements, by mass percentage, consist of the following components: La≤0.0025%, Ce≤0.0030%, Pr0.0001%~0.0005%; The mass content of La, Ce, and Pr is related by the value of 3×La+2×Ce+3×Pr, which is 0.0049%~0.0055%.

2. The rare earth weathering structural steel for photovoltaic brackets according to claim 1, characterized in that, The mass content relationship between La and Pr is that the value of La / Pr is 1 to 4.

3. A method for preparing rare earth weathering structural steel for photovoltaic brackets, used to prepare the rare earth weathering structural steel for photovoltaic brackets as described in any one of claims 1 to 2, characterized in that, Includes the following steps: After refining and continuous casting, molten steel from the converter is used to obtain a billet. The billet is then subjected to heating, rough rolling, finish rolling, and coiling processes to obtain rare earth weathering structural steel.

4. The method for preparing rare earth weathering structural steel for photovoltaic brackets according to claim 3, characterized in that, The tapping temperature of the molten steel from the converter is 1610~1630℃.

5. The method for preparing rare earth weathering structural steel for photovoltaic brackets according to claim 3, characterized in that, During continuous casting, rare earth wire is fed into the crystallizer at a feeding rate of 7-8 m / min.

6. The method for preparing rare earth weathering structural steel for photovoltaic brackets according to claim 3, characterized in that, The heating process includes a first-stage heating, a second-stage heating, a third-stage heating, and a homogenization stage; the heating rates of the first-stage heating, the second-stage heating, and the third-stage heating are different.

7. The method for preparing rare earth weathering structural steel for photovoltaic brackets according to claim 6, characterized in that, The heating process involves raising the temperature at a first heating rate of 5-8℃ / min to 600-850℃ to complete the first stage of heating; then raising the temperature at a second heating rate of 8-12℃ / min to 950-1150℃ to complete the second stage of heating; and then raising the temperature at a third heating rate of 3-5℃ / min to 1230-1270℃ to complete the third stage of heating, before entering the homogenization stage.

8. The method for preparing rare earth weathering structural steel for photovoltaic brackets according to claim 7, characterized in that, The temperature of the heat spreader is 1220~1260℃, and the heating rate of the heat spreader is 0.5~1℃ / min.

9. The method for preparing rare earth weathering structural steel for photovoltaic brackets according to claim 3, characterized in that, During the rough rolling process, descaling R1 is performed in the first and second passes, and R2 is performed in the first and third passes.

10. The method for preparing rare earth weathering structural steel for photovoltaic brackets according to claim 3, characterized in that, The initial rolling temperature during finishing rolling is 1000~1100℃, the final rolling temperature is 830~860℃, and the reduction rate is 60%.

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