Corrosion-resistant high-chromium ferritic stainless steel for photovoltaic bracket and preparation method of corrosion-resistant high-chromium ferritic stainless steel

Abstract

The invention discloses corrosion-resistant high-chromium ferritic stainless steel for a photovoltaic support and a preparation method of the corrosion-resistant high-chromium ferritic stainless steel, and the preparation method comprises the working procedures of continuous casting sheet billet pouring, continuous casting sheet billet coping, hot continuous rolling, hot coil annealing and pickling and cold coil annealing and pickling. The yield strength of the high-chromium ferritic stainless steel is 380-410 Mpa, the tensile strength of the high-chromium ferritic stainless steel is 480-530 Mpa, the ductility of the high-chromium ferritic stainless steel is 25-32%, the corrosion rate of the high-chromium ferritic stainless steel in a simulated seawater solution is smaller than or equal to 0.01 g / (m < 2 >. H), the intergranular corrosion rate of the high-chromium ferritic stainless steel is smaller than or equal to 0.15 mm / month, the pitting potential of the high-chromium ferritic stainless steel is larger than or equal to 850 mV, the blunt current density of the high-chromium ferritic stainless steel in a 20% NaCl solution with the PH value of 2.0 is smaller than or equal to 1.0 (mA / cm < 2 >), and the corrosion rate of the and the use requirements of low cost and high corrosion resistance of the offshore photovoltaic system bracket are met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ferritic stainless steel manufacturing, and particularly relates to a high-chromium ferritic stainless steel for a corrosion-resistant photovoltaic support and a preparation method thereof. BACKGROUND

[0002] Offshore photovoltaic can make full use of marine space, reduce land resource occupation, and improve solar energy utilization rate and power generation efficiency due to the rich solar energy resources on the ocean surface. With the progress of technology and the reduction of cost, economic and environmental benefits will be further improved, and offshore photovoltaic is expected to become one of the important pillars in the future energy field. Photovoltaic support is an important part of a solar photovoltaic power generation system and supports the entire power generation system. Therefore, the service life of the support needs to be greater than or equal to the service life of the photovoltaic module. In view of the corrosion caused by high humidity and high salt in the complex offshore environment and problems such as wind and waves and typhoon, the corrosion resistance, strength and welding of the photovoltaic support material are required to be harsh. Conventional stainless steel has insufficient resistance to seawater corrosion or is high in cost, and is difficult to meet the requirements of offshore photovoltaic support systems. At present, most of the floating or installed photovoltaic supports use plating or coating for corrosion protection, but the plating or coating will accelerate the aging of the material under long-term ultraviolet radiation and marine climate conditions (high temperature, high humidity, high salt, etc.), and the maintenance difficulty is great. SUMMARY

[0003] To solve the above-mentioned problems in the prior art, the present application provides a high-chromium ferritic stainless steel for a corrosion-resistant photovoltaic support and a preparation method thereof.

[0004] In one aspect of the present application, the preparation method of the high-chromium ferritic stainless steel for a corrosion-resistant photovoltaic support comprises the following steps:

[0005] (1) Continuous casting slab pouring

[0006] The molten steel prepared by smelting is poured into a continuous casting slab, and the tundish temperature is controlled to be 1515-1525℃;

[0007] (2) Continuous casting slab grinding

[0008] The continuous casting slab is ground, the grinding temperature is controlled to be 350-450℃, and the temperature of the ground continuous casting slab is controlled to be 150-200℃;

[0009] (3) Hot continuous rolling

[0010] The continuous casting slab is heated at 1250-1270℃ for 220-240min, and then subjected to rough rolling, finish rolling and coiling to obtain a hot coil, the rough rolling temperature is controlled to be 1080-1100℃, the finish rolling outlet temperature is controlled to be 920-940℃, and the coiling temperature is controlled to be 350-400℃;

[0011] (4) hot coil annealing and pickling

[0012] The hot coil is continuously annealed and pickled, the hot annealing temperature is controlled as T 热退 =(850+2.5Cr+80Ti+30Al+150Nb+10Mo)℃, and the hot annealing time is controlled as 1.5min / mm.

[0013] (5) cold coil annealing and pickling

[0014] The hot coil is annealed and pickled after cold rolling, the cold annealing temperature is controlled as T 冷退 =(860+2.5Cr+80Ti+30Al+150Nb+10Mo)℃, the cold rolling reduction is controlled as 50%~70%, and the cold annealing time is controlled as 2.0min / mm.

[0015] Further, the chemical composition of the molten steel is that, in percentage by mass, C≤0.015%, Si≤0.50%, Mn=0.20~0.35%, P≤0.025%, S≤0.002%, Cr=26.00~27.50%, Ti=8(C+N)~0.40%, Nb=(Ti / 5)~0.15%, Ni≤0.60%, Mo=1.25~1.60%, N≤0.025%, Al≤0.10%, Cu=0.30~0.40%, and the rest is Fe and inevitable impurities.

[0016] Further, in the continuous casting slab grinding step, the surface grinding trace depth of the ground continuous casting slab is ≤0.15mm.

[0017] Further, in the hot continuous rolling step, the cooling mode is layer-by-layer cooling, the cooling speed is controlled as 20~25℃ / second, and the hot coil thickness is controlled as 4~5mm.

[0018] In another aspect of the present application, the chemical composition of the provided high-chromium ferritic stainless steel for corrosion-resistant photovoltaic support is that, in percentage by mass, C≤0.015%, Si≤0.50%, Mn=0.20~0.35%, P≤0.025%, S≤0.002%, Cr=26.00~27.50%, Ti=8(C+N)~0.40%, Nb=(Ti / 5)~0.15%, Ni≤0.60%, Mo=1.25~1.60%, N≤0.025%, Al≤0.10%, Cu=0.30~0.40%, and the rest is Fe and inevitable impurities.

[0019] Preferably, the mass percentage content of Cr element and Mo element satisfies: Cr+1.72Mo=28~29%.

[0020] Preferably, the mass percentage content of Ti element and Nb element satisfies: Ti=0.25-0.35% and Nb=(Ti / 5)-0.15%.

[0021] Preferably, the mass percentage content of Ni element, Cu element and Nb element satisfies: Ni=0.20-0.30% and Cu=0.30-0.40% and Ni+0.8Cu+0.5Nb=0.50-0.60%.

[0022] Preferably, the mass percentage content of Si element and Al element satisfies: Si=0.10-0.20% and Al=0.05-0.10%.

[0023] Preferably, the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support is a 1.4-2.0 mm steel coil, the yield strength is 380-410 Mpa, the tensile strength is 480-530 Mpa, the elongation is 25-32%, the corrosion rate in simulated seawater solution is ≤0.01 g / (m 热退 ·h), the intergranular corrosion rate is ≤0.15 mm / month, the pitting potential is ≥850 mV, the passivation current density in 20% NaCl, PH value 2.0 solution is ≤1.0 (mA / cm 冷退 ), and the corrosion rate in 5-10% sulfuric acid solution at 50°C is ≤0.02 g / m 2 / h.

[0024] The corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support and the preparation method thereof have the following advantages and beneficial effects:

[0025] The present application accurately controls the composition of molten steel, ensures the mechanical properties and corrosion resistance of ferritic stainless steel, and produces high-chromium ferritic stainless steel with yield strength of 380-410 Mpa, tensile strength of 480-530 Mpa, elongation of 25-32%, corrosion rate in simulated seawater solution of ≤0.01 g / (m 2 ·h), intergranular corrosion rate of ≤0.15 mm / month, pitting potential of ≥850 mV, passivation current density in 20% NaCl, PH value 2.0 solution of ≤1.0 (mA / cm 2 ), and corrosion rate in 5-10% sulfuric acid solution at 50°C of ≤0.02 g / m 2 / h, which meets the low-cost and high-corrosion-resistance requirements of offshore photovoltaic system support. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only used to further understand the present application and form a part of the present application. Based on these drawings, other drawings can be obtained by those skilled in the art without any creative effort. In the drawings:

[0027] Figure 1 is a flow chart of a preparation method of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of the present application; DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the following will clearly and completely describe the technical solutions of the present application with specific embodiments of the present application and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without any creative effort are within the scope of protection of the present application.

[0029] Referring to Figure 1 , the present application provides the following steps:

[0030] (1) Continuous casting slab pouring

[0031] The raw molten steel prepared by smelting is poured into a continuous casting slab with a thickness of 200 mm, and the tundish temperature is controlled to be 1515-1525℃;

[0032] (2) Continuous casting slab grinding

[0033] The continuous casting slab is ground, the grinding temperature is controlled to be 350-450℃, and the temperature of the ground continuous casting slab is controlled to be 150-200℃;

[0034] (3) Hot continuous rolling

[0035] The continuous casting slab is heated at 1250-1270℃ for 220-240 min, then rough rolling, finish rolling and coiling are performed to obtain a hot coil, the rough rolling temperature is controlled to be 1080-1100℃, the finish rolling outlet temperature is controlled to be 920-940℃, and the coiling temperature is controlled to be 350-400℃;

[0036] (4) Hot coil annealing and pickling

[0037] The hot coil is continuously annealed and pickled, the hot annealing temperature is controlled to be T 热退 =(850+2.5Cr+80Ti+30Al+150Nb+10Mo)℃, and the hot annealing time is controlled to be 1.5 min / mm;

[0038] (5) cold coil annealing pickling

[0039] The hot coil is annealed and pickled after cold rolling, the cold annealing temperature is controlled to be T 冷退 =(860+2.5Cr+80Ti+30Al+150Nb+10Mo)℃, the cold rolling reduction is controlled to be 50%-70%, and the cold annealing time is controlled to be 2.0min / mm.

[0040] Further, the chemical composition of the molten steel is that, in percentage by mass, C≤0.015%, Si≤0.50%, Mn=0.20-0.35%, P≤0.025%, S≤0.002%, Cr=26.00-27.50%, Ti=8(C+N)-0.40%, Nb=(Ti / 5)-0.15%, Ni≤0.60%, Mo=1.25-1.60%, N≤0.025%, Al≤0.10%, Cu=0.30-0.40%, and the rest is Fe and inevitable impurities.

[0041] Further, in the continuous casting slab grinding step, the surface grinding trace depth of the ground continuous casting slab is ≤0.15mm.

[0042] By controlling the surface roughness of the ground casting blank, the thickness uniformity of the oxidation layer of the casting blank in the heating process can be improved.

[0043] Further, in the hot continuous rolling step, the cooling mode is cast cooling, the cooling speed is controlled to be 20-25℃ / s, and the hot coil thickness is controlled to be 4-5mm.

[0044] As a specific embodiment, the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support produced by the corrosion-resistant high-chromium ferritic stainless steel manufacturing method for photovoltaic support of the application is a 1.4-2.0mm steel coil.

[0045] Preferably, the mass percentage content of Cr and Mo elements of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of the application satisfies: Cr+1.72Mo=28-29%.

[0046] By controlling the content and ratio of Cr and Mo elements, the pitting corrosion resistance and crevice corrosion resistance of the material are improved, the pitting corrosion potential reaches 850mV or above, and the material has good seawater corrosion resistance; meanwhile, the excessive content of Cr and Mo avoids the decline of the processing performance of the material and the rise of the cost.

[0047] Preferably, the mass percentage content of Ti and Nb elements of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of the application satisfies: Ti=0.25-0.35% and Nb=(Ti / 5)-0.15%.

[0048] By controlling the content of Ti and Nb elements, on the one hand, the intergranular corrosion resistance of the material is improved, and on the other hand, the suitable Ti content can inhibit the dissolution of non-metallic inclusions, thereby improving the pitting corrosion resistance of the material. In addition, in combination with a suitable Nb content, the adhesion between the surface oxide scale of the titanium-containing steel and the matrix can be reduced, which is beneficial to the removal of the surface oxide scale of the ferritic stainless steel, thereby improving the surface quality of the ferritic stainless steel.

[0049] Preferably, the mass percentage content of Ni element, Cu element and Nb element of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of the present application satisfies: Ni = 0.20-0.30% and Cu = 0.30-0.40% and Ni + 0.8Cu + 0.5Nb = 0.50-0.60%.

[0050] By controlling the content of Ni, Cu and Nb elements, the passivation current density of the material in a solution of 20% NaCl and PH value 2.0 is ≤1.0 (mA / cm 2 ).

[0051] Preferably, the mass percentage content of Si element and Al element of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of the present application satisfies: Si = 0.10-0.20% and Al = 0.05-0.10%.

[0052] Controlling the content of Si (0.10-0.20%) can reduce the aggregation of Si oxides at the bottom of the grinding marks, prevent the adhesion of the local oxide layer to the matrix, and facilitate the removal of the oxide layer.

[0053] The yield strength of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of the present application is 380-410 MPa, the tensile strength is 480-530 MPa, the elongation is 25-32%, the corrosion rate in the simulated seawater solution is ≤0.01 g / (m 2 ·h), the intergranular corrosion rate is ≤0.15 mm / month, the pitting potential is ≥850 mV, the passivation current density in a solution of 20% NaCl and PH value 2.0 is ≤1.0 mA / cm 2 , and the corrosion rate in a 5-10% sulfuric acid solution at 50°C is ≤0.02 g / m 2 / h.

[0054] The corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of the present application and the preparation method thereof will be further described below in combination with specific examples.

[0055] Example 1

[0056] The chemical composition of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of embodiment 1 of the present application is as follows in terms of mass percentage: Cr=26.3%, Si=0.15%, Mo=1.45%, Nb=0.06%, Ti=0.26%, Ni=0.22%, Mn=0.25%, C=0.013%, N=0.0156%, Cu=0.36%, Al=0.06%, P=0.023%, S=0.002, and the balance of Fe and inevitable impurities. The manufacturing method of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support of embodiment 1 specifically includes the following steps:

[0057] (1) Continuous casting slab pouring

[0058] The molten steel prepared by smelting is poured into a continuous casting slab;

[0059] (2) Continuous casting slab grinding

[0060] The continuous casting slab is ground, the grinding temperature is controlled to be 425°C, the grinding trace depth is 0.14mm, and the temperature of the ground continuous casting slab is controlled to be 150-200°C;

[0061] (3) Hot continuous rolling

[0062] The continuous casting slab is heated at 1265°C and then subjected to rough rolling, finish rolling and coiling to obtain a hot coil, the rough rolling temperature is 1095°C, the finish rolling outlet temperature is controlled to be 925°C, and the coiling temperature is controlled to be 376°C;

[0063] (4) Hot coil annealing and pickling

[0064] The hot coil is subjected to continuous annealing and pickling, and the hot annealing temperature is 962°C;

[0065] (5) Cold coil annealing and pickling

[0066] The hot coil is subjected to annealing and pickling after cold rolling, the cold rolling reduction is 60%, and the cold annealing temperature is 972°C.

[0067] Normal temperature mechanics is detected according to GB / T 228.1 "Metallic Materials Tensile Testing Part 1: Room Temperature Test Method"; the simulated seawater corrosion condition solution is 25% NaCl+0.38% Na2SO4+0.15% CaCl+0.03% MgCl2, PH=7, and the boiling state; intergranular corrosion is detected according to Y method of GB / T 32571-2016 "Metallic and Alloy Corrosion High Chromium Ferritic Stainless Steel Intergranular Corrosion Test Method", and the time is 120 hours; and spot corrosion is detected according to GB / T17897 "Stainless Steel Ferric Trichloride Spot Corrosion Test Method", the temperature is 35°C, and the time is 24 hours.

[0068] The test results of the embodiment 1 are as follows: tensile strength is 498 MPa, yield strength is 385 MPa, elongation is 29%, simulated seawater corrosion rate is 0.0070 g / (m 2 ·h), intergranular corrosion rate is 0.1042 mm / month, pitting corrosion rate is 0.2827, sulfuric acid corrosion rate is 0.0055 g / m 2 / h, passivation current density is 0.89 mA / cm 2 , and pitting potential is 861 mV.

[0069] Embodiments 2 and 3

[0070] The chemical composition of the high-chromium ferritic stainless steel for photovoltaic support with corrosion resistance in embodiments 2 and 3 of the present application is shown in Table 1 below:

[0071] Table 1 Chemical composition of steel plates in embodiments 2 and 3

[0072]

[0073] The process parameters of the high-chromium ferritic stainless steel for photovoltaic support with corrosion resistance in embodiments 2 and 3 of the present application are shown in Table 2 below:

[0074] Table 2 Process parameters in embodiments 2 and 3

[0075]

[0076] The performance indicators of the high-chromium ferritic stainless steel for photovoltaic support with corrosion resistance in embodiments 2 and 3 of the present application are shown in Table 3 below:

[0077] Table 2 Process parameters in embodiments 2 and 3

[0078]

[0079] In summary, the present application accurately controls the composition of molten steel, ensures the mechanical properties and corrosion resistance of ferritic stainless steel, and produces high-chromium ferritic stainless steel with yield strength of 380-410 MPa, tensile strength of 480-530 MPa, elongation of 25-32%, corrosion rate in simulated seawater solution ≤0.01 g / (m 2 ·h), intergranular corrosion rate ≤0.15 mm / month, pitting potential ≥850 mV, passivation current density ≤1.0 (mA / cm 2 ) in 20% NaCl, PH value 2.0 solution, and corrosion rate ≤0.02 g / m 2 / h in 50°C 5-10% sulfuric acid solution, which meets the low-cost and high-corrosion-resistance requirements of offshore photovoltaic system support.

[0080] It should be noted that the nomenclature and terminology used herein are intended to have their ordinary meaning to those skilled in the art unless specifically defined otherwise. Furthermore, where a range of values is disclosed, the disclosure is to be construed to include each and every value in that range. Further, where a range of values is stated as including both integers and values between the integers, the disclosure is to be construed to include each and every integer in that range. Additionally, where a plurality of ranges is provided, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein.

[0081] It should also be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component" or "the component" can include a plurality of such components unless the context clearly dictates otherwise.

[0082] Finally, it should be noted that the above-mentioned embodiments are merely intended to illustrate the technical solutions of the present application, rather than limiting the same. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent features, without departing from the scope of the present application.

Claims

1. A method for producing a corrosion-resistant high-chromium ferritic stainless steel for a photovoltaic support, characterized by, It comprises the following steps: (1) continuous casting slab pouring The molten steel prepared by smelting is poured into a continuous casting slab, and the tundish temperature is controlled at 1515-1525℃; (2) continuous casting slab grinding The continuous casting slab is ground, the grinding temperature is controlled at 350-450℃, and the temperature of the ground continuous casting slab is controlled at 150-200℃; (3) hot continuous rolling The continuous casting slab is heated at 1250-1270℃ for 220-240min, then rough rolling, finish rolling and coiling are carried out to obtain a hot coil, the rough rolling temperature is controlled at 1080-1100℃, the finish rolling outlet temperature is controlled at 920-940℃, and the coiling temperature is controlled at 350-400℃; (4) hot coil annealing and pickling The hot coil is continuously annealed and pickled, the hot annealing temperature is controlled to be T 热退 =(850+2.5Cr+80Ti+30Al+150Nb+10Mo)℃, and the hot annealing time is controlled to be 1.5min / mm; (5) cold coil annealing and pickling The hot coiled steel is cold-rolled and then annealed and pickled, the cold annealing temperature is controlled to be T 冷退 = (860 + 2.5Cr + 80Ti + 30Al + 150Nb + 10Mo) °C, the cold rolling reduction is controlled to be 50%~70%, and the cold annealing time is controlled to be 2.0 min / mm.

2. The method of claim 1, wherein the corrosion resistant high chromium ferritic stainless steel for photovoltaic racks is characterized by, The chemical composition of the molten steel is C≤0.015%, Si≤0.50%, Mn=0.20-0.35%, P≤0.025%, S≤0.002%, Cr=26.00-27.50%, Ti=8(C+N)-0.40%, Nb=(Ti / 5)-0.15%, Ni≤0.60%, Mo=1.25-1.60%, N≤0.025%, Al≤0.10%, Cu=0.30-0.40%, and the rest is Fe and inevitable impurities.

3. The method of making a corrosion resistant high chromium ferritic stainless steel for photovoltaic racking according to claim 1, characterized in that, In the continuous casting slab grinding step, the surface grinding depth of the ground continuous casting slab is ≤0.15mm.

4. The method of making a corrosion resistant high chromium ferritic stainless steel for photovoltaic racking according to claim 1, characterized in that, In the hot continuous rolling step, the cooling method is layer cooling, the cooling speed is controlled at 20-25℃ / s, and the thickness of the hot coil is controlled at 4-5mm.

5. A corrosion resistant high chromium ferritic stainless steel for photovoltaic racks, obtained by the method for producing a corrosion resistant high chromium ferritic stainless steel for photovoltaic racks according to any one of claims 1 to 4, characterized in that, The chemical composition of the corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support is: C≤0.015%, Si≤0.50%, Mn=0.20-0.35%, P≤0.025%, S≤0.002%, Cr=26.00-27.50%, Ti=8(C+N)-0.40%, Nb=(Ti / 5)-0.15%, Ni≤0.60%, Mo=1.25-1.60%, N≤0.025%, Al≤0.10%, Cu=0.30-0.40%, and the rest is Fe and inevitable impurities.

6. The corrosion resistant high chromium ferritic stainless steel for photovoltaic racking according to claim 5, characterized in that, The mass percentage content of Cr and Mo elements satisfies: Cr+1.72Mo=28-29%.

7. The corrosion resistant high chromium ferritic stainless steel for photovoltaic racking of claim 5, wherein, The mass percentage content of Ti and Nb elements satisfies: Ti=0.25-0.35% and Nb=(Ti / 5)-0.15%.

8. The corrosion resistant high chromium ferritic stainless steel for photovoltaic racking of claim 5, wherein, The mass percentage content of Ni, Cu and Nb elements satisfies: Ni=0.20-0.30%, Cu=0.30-0.40%, and Ni+0.8Cu+0.5Nb=0.50-0.60%.

9. The corrosion resistant high chromium ferritic stainless steel for photovoltaic racking of claim 5, wherein, The mass percentage content of Si and Al elements satisfies: Si=0.10-0.20% and Al=0.05-0.10%.

10. Corrosion resistant high chromium ferritic stainless steel for photovoltaic racks according to any one of claims 5 to 9, characterized in that, The corrosion-resistant high-chromium ferritic stainless steel for photovoltaic support has a thickness of 1.4-2.0 mm, a yield strength of 380-410 MPa, a tensile strength of 480-530 MPa, an elongation of 25-32%, a corrosion rate in simulated seawater solution of ≤0.01 g / (m 2 ·h), an intergranular corrosion rate of ≤0.15 mm / month, a pitting potential of ≥850 mV, a passivation current density in a solution of 20% NaCl, PH 2.0 of ≤1.0 (mA / cm 2 ), and a corrosion rate in a 5-10% sulfuric acid solution at 50°C of ≤0.02 g / m 2 / h.

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