800MPa-grade high-strength and high-weathering-resistance steel as well as preparation method and application thereof

Abstract

The invention provides 800MPa-grade high-strength and high-weathering-resistant steel which comprises the following components in percentage by mass: less than or equal to 0.09% of C, 0.35%-0.45% of Si, 0.80%-1.00% of Mn, 0.070%-0.090% of P, less than or equal to 0.008% of S, 1.00%-1.250% of Cr, 0.25%-0.30% of Cu, 0.060%-0.070% of Ti, less than or equal to 0.02% of Nb, 0.0010%-0.0050% of Als and the balance of Fe. The invention further provides a preparation method and application of the 800MPa-grade high-strength and high-weathering-resistance steel. According to the high-strength and high-weathering-resistant steel provided by the invention, through cooperation of component design, a thermal regulation and rough rolling, finish rolling, controlled cooling and other means in the rolling process, the rolling stability of the high-strength and thin-gauge photovoltaic hot-rolled weathering-resistant steel is guaranteed, the surface quality is controllable, the mechanical property is stable, and the corrosion resistance is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of hot rolling, and in particular to an 800MPa-grade high-strength and high-weathering steel, a preparation method thereof, and applications thereof. Background Art

[0002] Photovoltaic brackets are crucial supporting and protective structures for photovoltaic power generation devices. The choice of bracket material directly impacts the operational safety, breakage rate, construction investment, and subsequent maintenance costs of photovoltaic modules. Photovoltaic power stations are typically built in harsh environments such as coastal mudflats, deserts, Gobi deserts, and water surfaces, potentially subject to extreme weather conditions such as strong winds, hail, and heavy snow. Furthermore, the design life of photovoltaic brackets in photovoltaic power stations should be no less than 25 years, necessitating very high load-bearing capacity and corrosion resistance requirements. Hot-rolled high-strength photovoltaic weathering steel offers advantages such as high durability, high load-bearing capacity, low-cost, green construction, and lightweight construction. This makes it a widely used high-strength weathering steel type in photovoltaic power generation projects and a product that various steel industries are competing to develop.

[0003] 800MPa-grade thin-gauge (thickness h = 1.5-2.50mm) hot-rolled photovoltaic weathering steel is the main type and specification of steel used in photovoltaic brackets. Ensuring the product has high weather resistance, high strength, lightweight and low cost is the key to its application. Of course, the development and production of this type and specification have the following technical difficulties, which restrict industrial stable production and product quality. These are also common technical difficulties in the hot rolling field. The key common technical difficulties and bottlenecks are as follows:

[0004] (1) To ensure the market competitiveness of the product, the alloying route of the product needs to adopt a low-cost design. The existing technology of "Ni-high Cr microalloying" can achieve excellent corrosion resistance, but the cost is relatively high;

[0005] (2) There are many types of alloy elements added to high-strength weathering steel. During the hot rolling process of high-strength and thin-gauge strip steel, due to the characteristics of high rolling speed, rapid temperature drop, and large rolling load, the strip steel has high deformation resistance and is extremely sensitive to temperature changes. The stability of the thin-gauge finishing rolling and steel running process is extremely poor, resulting in poor plate shape, unstable dimensional accuracy, and low yield rate during the rolling process.

[0006] Therefore, providing a high-strength weathering steel with high strength, high weather resistance, good surface quality and low cost is of great significance for expanding its application range. Summary of the Invention

[0007] The technical problem solved by the present invention is to provide an 800MPa grade high-strength and high-weathering resistant steel and a preparation method thereof. The 800MPa grade high-strength and high-weathering resistant steel provided in this application has the characteristics of excellent surface quality, stable mechanical properties and excellent corrosion resistance, and has low cost and a stable rolling process.

[0008] In view of this, the present application provides an 800MPa grade high-strength and high-weathering resistant steel, which includes, by mass percentage: C≤0.09%, Si 0.35%~0.45%, Mn 0.80%~1.00%, P0.070%~0.090%, S≤0.008%, Cr1.00%~1.25%, Cu 0.25%~0.30%, Ti0.060%~0.070%, Nb≤0.02%, Als 0.0010%~0.0050%, and Fe balance.

[0009] In some specific embodiments, the C content is 0.05-0.08%, and / or the Si content is 0.37-0.42%, and / or the Mn content is 0.83-0.98%.

[0010] In some specific embodiments, the P content is 0.073-0.086%, and / or the S content is 0.005-0.007%, and / or the Cr content is 1.13-1.21%.

[0011] In some specific embodiments, the Cu content is 0.27-0.29%, and / or the Ti content is 0.062-0.068%, and / or the Nb content is 0.010-0.015%, and / or the Al content is 0.002-0.004%.

[0012] The present application also provides a method for preparing the high-strength and high-weathering steel, comprising the following steps:

[0013] S1) preheating, heating and soaking the high-strength and high-weathering steel billet in sequence;

[0014] The preheating temperature is 800-950°C, the heating temperature is 1050-1200°C, the heating rate is 6-8°C / min, and the soaking temperature is 1230-1260°C;

[0015] S2) performing rough rolling and finish rolling on the steel billet obtained in step S1);

[0016] The rough rolling adopts 0+5 rolling mode;

[0017] The finishing rolling adopts F1-F7 full-stand lubrication rolling, and the oil-water ratio is set as follows: F1 = 0.15%-0.25%, F2 = 0.20%-0.30%, F3 = 0.45%-0.65%, F4 = 0.45%-0.65%, F5 = 0.45%-0.65%, F6 = 0.20%-0.30%, F7 = 0.15%-0.20%;

[0018] The finishing rolling adopts F1-F7 full-frame high-tension rolling, and the tension ratio is specifically: F1 / F2=6.50-8.50N / mm 2 , F2 / F3=7.50~9.50N / mm 2 , F3 / F4=10.5~11.6N / mm 2 , F4 / F5=12.50~14.50N / mm 2 , F5 / F6=18.50~21.50N / mm 2 , F6 / F7=21.50~23.5N / mm 2 ;

[0019] S3) The steel billet obtained in step S2) is subjected to shape control, followed by laminar cooling and finishing.

[0020] In some specific embodiments, in step S1), the heating time is 30 to 40 minutes, and / or the soaking time is 15 to 20 minutes, and / or the total time of the preheating, the heating and the soaking is 120 to 150 minutes.

[0021] In some specific embodiments, in step S1), the air-fuel ratio of the preheating is 2.4-2.8, the air-fuel ratio of the heating is 2.1-2.6, and the air-fuel ratio of the equalization is 1.8-2.2.

[0022] In some specific embodiments, in step S2), the descaling pressure of the rough rolling is 18 to 25 MPa; and / or the strip threading speed of the finishing rolling is greater than or equal to 9.5 m / s and less than 10.5 m / s; and / or the F1E widening amount of the finishing rolling is 0 to 5 mm; and / or RAC adjustment and DWC adjustment are introduced during the finishing rolling process.

[0023] In some specific embodiments, in step S2), the plate shape control is performed in a circulation mode of bending rolls and shifting rolls with a step distance of 5 to 10 mm; and / or, the flow ratio of the upper and lower headers of the laminar cooling is (45% to 55%): (25% to 35%), and only the upper header is in cooling mode.

[0024] The present application also provides a steel for a photovoltaic support, including the high-strength and high-weathering steel described in the above scheme or the high-strength and high-weathering steel prepared by the preparation method described in the above scheme.

[0025] The present application provides an 800MPa grade high-strength and high-weathering resistant steel, which comprises, in mass percentage: C≤0.09%, Si 0.35%~0.45%, Mn 0.80%~1.00%, P 0.070%~0.090%, S≤0.008%, Cr 1.00%~1.25%, Cu 0.25%~0.30%, Ti 0.060%~0.070%, Nb≤0.02%, Als 0.0010%~0.0050%, and Fe balance; the 800MPa grade high-strength and high-weathering resistant steel provided in the present application adopts Cr micro-alloying with high P content and does not add Ni in the element ratio, thereby reducing the cost while ensuring the mechanical properties and corrosion resistance of the high-strength and high-weathering resistant steel.

[0026] The present application also provides a method for preparing 800MPa grade high-strength and high-weathering steel, which sequentially performs a preheating, heating and equalization heating system on the high-strength and high-weathering steel billet to ensure the stability of subsequent rolling. At the same time, the principle of "high temperature and fast burning" is adopted to avoid the "copper brittleness" temperature range and heating time, and then the rough rolling and finish rolling are carried out and the above-mentioned rolling process is controlled to ensure the rolling stability and the controllable steel surface quality.

[0027] Therefore, the 800MPa grade high-strength and high-weathering steel provided in this application ensures the rolling stability and quality controllability of high-strength and thin-gauge weathering steel through the control of composition design, heating system and rolling process, and has good mechanical properties and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 These are the actual quality photos and application photos of the photovoltaic weathering strip prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0030] In view of the performance requirements of 800MPa-grade thin-gauge hot-rolled photovoltaic weathering steel in the existing technology for high weather resistance, high strength, light weight and low cost, the present application provides an 800MPa-grade high-strength and high-weathering steel and its preparation method. Through the unique process system during the heating process, it realizes the "low C-no Ni-no Nb-controlled Cr-increased Ti" composition design route of replacing "Ni-high Cr microalloying" with "appropriate amount of P-medium Cr microalloying". At the same time, Ti microalloying is adopted to effectively control the edge crack defects in the heating process under low cost conditions, thereby ensuring the surface quality of the weathering steel. At the same time, the combination of rolling process and alloying elements ensures the rolling stability, product quality, yield rate and other technical quality indicators of thin-gauge high-strength and high-weathering steel. Specifically, an embodiment of the present invention discloses an 800MPa grade high-strength and high-weathering resistant steel, which includes, by mass percentage: C≤0.09%, Si 0.35%~0.45%, Mn 0.80%~1.00%, P0.070%~0.090%, S≤0.008%, Cr1.00%~1.25%, Cu 0.25%~0.30%, Ti0.060%~0.070%, Nb≤0.02%, Als 0.0010%~0.0050%, and Fe balance.

[0031] This application first provides the composition of 800MPa grade high-strength and high-weathering resistant steel, which adopts the design of "high P content and medium Cr content microalloying". P is beneficial to improving weather resistance, but too high a content will also affect the quality of the steel. Cr is beneficial to improving the corrosion resistance and mechanical properties of the steel. This composition design achieves low cost of the steel and ensures the mechanical properties and corrosion resistance of the steel; an appropriate amount of Cu element significantly reduces the alloy cost; in particular, the addition of 0.060-0.070% Ti is beneficial to reducing the segregation of copper-rich phases per unit area and inhibiting the generation of copper brittle defects.

[0032] In the present application, C≤0.09%, specifically, the C content is 0.05-0.08%; for example, the C content in the present application is 0.01%, 0.02%, 0.03%, 0.04%, 0.06%, and 0.07%.

[0033] The Si content is 0.35-0.45%, specifically, the Si content is 0.37-0.42%, more specifically, the Si content is 0.38-0.40%; for example, the Si content in this application is 0.36%, 0.39%, 0.41%, 0.42%, 0.43%, and 0.44%.

[0034] The Mn content is 0.80-1.00%, specifically, the Mn content is 0.83-0.98%, more specifically, the Mn content is 0.85-0.92%; for example, the Mn content in this application is 0.81%, 0.82%, 0.84%, 0.86%, 0.87%, 0.88%, 0.89%, 0.90%, 0.91%, 0.94%, 0.93%, 0.95%, 0.96%, 0.97%, and 0.99%.

[0035] The P content is 0.070-0.090%, specifically, the P content is 0.073-0.086%, more specifically, the P content is 0.078-0.082%; for example, the P content in this application is 0.071%, 0.072%, 0.074%, 0.075%, 0.076%, 0.077%, 0.079%, 0.080%, 0.081%, 0.084%, 0.083%, 0.085%, 0.087%, 0.088%, and 0.089%.

[0036] The S content is ≤0.008%. Specifically, the S content is 0.005-0.007%. For example, the S content in this application is 0.001%, 0.002%, 0.003%, 0.004%, and 0.006%.

[0037] The Cr content is 1.00-1.25%, specifically, the Cr content is 1.13-1.21%, more specifically, the Cr content is 1.15-1.19%; for example, the Cr content in this application is 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.10%, 1.11%, 1.12%, 1.14%, 1.16%, 1.17%, 1.18%, 1.20%, 1.22%, 1.23%, and 1.24%.

[0038] The content of Cu is 0.25-0.3%. Specifically, the content of Cu is 0.27-0.29%. For example, the content of Cu in this application is 0.26% and 0.28%.

[0039] The Ti content is 0.060-0.070%, specifically, the Ti content is 0.062-0.068%; more specifically, the Ti content is 0.064-0.067%; for example, the Ti content in this application is 0.061%, 0.063%, 0.065%, 0.066%, and 0.069%.

[0040] The Nb content is ≤0.02%. Specifically, the Nb content is 0.010-0.015%. For example, the Nb content in this application is 0.011%, 0.012%, 0.013%, 0.014%, 0.016%, 0.017%, 0.018%, and 0.019%.

[0041] The content of Als is 0.0010-0.0050%, specifically, the content of Als is 0.0020-0.0040%. For example, the content of Als in this application is 0.0003% and 0.0040%.

[0042] The 800MPa-grade high-strength and high-weathering steel provided in the present application does not contain Ni. The risk of edge cracking (copper embrittlement) defects during the heating process of the ingot is very high, and the thermal system control is difficult. At the same time, the "low C-no Ni-no Nb-controlled Cr-increased Ti" composition design route of "Ti microalloying" instead of "high Nb-Ti microalloying" is adopted to achieve rolling load optimization and eliminate the impact of temperature sensitivity of Nb-containing steel on rolling stability. Therefore, the present application provides a method for preparing 800MPa-grade high-strength and high-weathering steel, which includes the following steps:

[0043] S1) preheating, heating and soaking the high-strength and high-weathering steel billet in sequence;

[0044] The preheating temperature is 800-950°C, the heating temperature is 1050-1200°C, the heating rate corresponding to the heating temperature is 6-8°C / min, and the soaking temperature is 1230-1260°C;

[0045] S2) performing rough rolling and finish rolling on the steel billet obtained in step S1);

[0046] The rough rolling adopts 0+5 rolling mode;

[0047] The finishing rolling adopts F1-F7 full-stand lubrication rolling, and the oil-water ratio is set as follows: F1 = 0.15%-0.25%, F2 = 0.20%-0.30%, F3 = 0.45%-0.65%, F4 = 0.45%-0.65%, F5 = 0.45%-0.65%, F6 = 0.20%-0.30%, F7 = 0.15%-0.20%;

[0048] The finishing rolling adopts F1-F7 full-frame high-tension rolling, and the tension ratio is specifically: F1 / F2=6.50-8.50N / mm 2 , F2 / F3=7.50~9.50N / mm 2 , F3 / F4=10.5~11.6N / mm 2, F4 / F5=12.50~14.50N / mm 2 , F5 / F6=18.50~21.50N / mm 2 , F6 / F7=21.50~23.5N / mm 2 ;

[0049] S3) The steel billet obtained in step S2) is subjected to shape control, followed by laminar cooling and finishing.

[0050] In the preparation process of high-strength and high-weathering steel, the present application first preheats, heats and soaks the high-strength and high-weathering steel billets in sequence. The above is the thermal system of the preheating section, heating section and soaking section of the high-strength and high-weathering steel billets; the preparation of the high-strength and high-weathering steel billets is prepared according to methods well known to those skilled in the art, and this application does not impose any special restrictions on this. Before the billets are preheated, the billets are hot-delivered and hot-loaded, that is, the high-temperature billets produced by continuous casting are directly sent into the heating furnace for thermal processing. It is preferred to adopt the method of direct delivery and direct loading of billets. For some billets that cannot be hot-loaded (directly loaded), they are centrally stacked under high temperature, and a certain amount of high-temperature accompanying billets are arranged around them, and are arranged for charging and heating within 24 hours; the charging temperature of the billets is ≥400°C, specifically, the converter temperature of the billets is 450-550°C, more specifically, the converter temperature of the billets is 450-480°C or 500-545°C. The preheating temperature is 800-950°C, specifically 820-930°C, more specifically 850-900°C, and even more specifically 860-880°C. The heating temperature is 1050-1200°C, with a heating rate of 6-8°C / min, specifically 1080-1170°C, with a heating rate of 6.3-7.8°C / min, and even more specifically 1100-1150°C, with a heating rate of 6.8-7.3°C / min. The heating process utilizes a "high-temperature, fast-burning" method, whereby the billet is rapidly heated to 1050-1200°C in the heating section and reaches the target temperature within 100 minutes, avoiding the "copper brittleness" temperature range and heating time. The heating time is 30-40 minutes, specifically 32-37 minutes. The temperature of the said equalization is 1230-1260°C, specifically, the temperature of the said equalization is 1235-1254°C, more specifically, the temperature of the said equalization is 1238-1243°C. The time of the said equalization is 15-20 minutes, specifically, the time of the said equalization is 16-18 minutes. The total time of the said thermal system is 120-150 minutes, specifically, the total time of the said thermal system is 125-145 minutes, more specifically, the total time of the said thermal system is 130-140 minutes. After equalization, the temperature of the steel billet out of the furnace is 1250±20°C, the temperature difference between the inside and outside is ≤15°C, and the temperature difference between the furnaces is ≤15°C.In this thermal system, a weakly reducing atmosphere is maintained in the soaking section to slow oxidation reactions and to increase the air-fuel ratio in the preheating section to ensure complete combustion of incompletely burned fuel gas. Specifically, the air-fuel ratio for preheating is 2.4-2.8, the air-fuel ratio for heating is 2.1-2.6, and the air-fuel ratio for soaking is 1.8-2.2. More specifically, the air-fuel ratio for preheating is 2.5-2.7, the air-fuel ratio for heating is 2.2-2.5, and the air-fuel ratio for soaking is 1.9-2.1. These air-fuel ratios are used to control the heating atmosphere and oxidation. This thermal system is carried out in a weakly reducing atmosphere.

[0051] In the above thermal system, if the rolling time is long during the heating process, and the rolling time exceeds 240 minutes, the steel will be returned to the furnace for treatment.

[0052] This application then performs rough rolling and finish rolling on the steel billets after the above-mentioned thermal system in sequence; wherein, the rough rolling adopts a 0+5 rolling mode, "0" means: there is no tension control on the inlet side of the rolling mill, the uncoiler does not participate in the tension adjustment, and is in a free state or a low tension state, and "5" means: 5 tension sensors are used on the outlet side of the rolling mill to achieve high-precision tension adjustment to ensure a stable rolling process. The dephosphorization pressure of the rough rolling is 18 to 25 MPa, specifically, the dephosphorization pressure of the rough rolling is 20 to 23 MPa. The strip threading speed of the finish rolling is greater than or equal to 9.5 m / s and less than 10.5 m / s, specifically, the strip threading speed of the finish rolling is 9.8 to 10.3 m / s, and two-stage speed-up rolling is adopted, with the maximum rolling speed reaching 13 to 14 m / s; a group of descaling manifolds near the flying shear side are used for descaling at the entrance of the finish rolling, and the descaling pressure is 28 to 30 MPa. Furthermore, during the finishing rolling process, F1E is activated, i.e., the width change at the exit side of the first stand is controlled to 0-5mm to ensure centering of the strip at the finishing head and rolling stability. During the finishing rolling process, all seven stands (F1-F7) are lubricated, i.e., lubricating oil is applied to all seven rolling mills, with the oil-to-water ratio of each stand being set as follows: F1 = 0.15%-0.25%, F2 = 0.20%-0.30%, F3 = 0.45%-0.65%, F4 = 0.45%-0.65%, F5 = 0.45%-0.65%, F6 = 0.20%-0.30%, and F7 = 0.15%-0.20%. This ensures a 10%-15% reduction in rolling load, improves roll surface quality, and stabilizes the rolling state and strip quality. Furthermore, F1 = 0.18% to 0.23%, F2 = 0.23% to 0.26%, F3 = 0.50% to 0.60%, F4 = 0.50% to 0.60%, F5 = 0.50% to 0.60%, F6 = 0.22% to 0.27%, F7 = 0.16% to 0.18%. During the finishing rolling, the lubricating oil is turned on and off according to a special "ramp" process to reach a stable flow or reduce to zero. The cooling water of the F1 to F4 roll gap is turned on, and the lubricating oil of the F4 to F7 rolling mill is turned off according to the timing control of the frame steel throwing and the rolling lubricating oil of the frame. At the same time, the rolling adopts F1 to F7 full-frame high tension rolling, and the tension ratio of adjacent rolling mills is specifically: F1 / F2 = 6.50 to 8.50 N / mm 2 , F2 / F3=7.50~9.50N / mm 2 , F3 / F4=10.5~11.6N / mm 2 , F4 / F5=12.50~14.50N / mm 2 , F5 / F6=18.50~21.50N / mm 2 , F6 / F7=21.50~23.5N / mm 2During the hot rolling process, the tension has the function of automatically correcting the deviation and reducing the rolling force; further, F1 / F2=7.70~8.20N / mm 2 , F2 / F3=8.00~9.20N / mm 2 , F3 / F4=10.8~11.3N / mm 2 , F4 / F5=13.10~14.30N / mm 2 , F5 / F6=19.30~21.20N / mm 2 , F6 / F7=22.00~23.0N / mm 2 ; Further, F1 / F2=7.90~8.00N / mm 2 , F2 / F3=8.70~9.10N / mm 2 , F3 / F4=10.9~11.0N / mm 2 , F4 / F5=13.70~14.00N / mm 2 , F5 / F6=20.00~20.80N / mm 2 , F6 / F7=22.60~22.90N / mm 2 .

[0053] In the above process, RAC adjustment and DWC adjustment can be introduced according to the specifications of the strip steel. RAC adjustment means laminar cooling of the steel billet after hot rolling and then rolling it for 1 to 2 passes. DWC adjustment means real-time adjustment of the strip steel width during hot rolling to avoid deviation problems.

[0054] According to the present invention, the shape of the steel billet is then controlled, specifically by adopting a cycle mode of bending and shifting rolls with a step distance of 5 to 10 mm.

[0055] This application then performs laminar cooling on the steel billet with good plate shape and flatness, and the flow ratio of the upper and lower headers of the laminar cooling is (45% to 55%): (25% to 35%), and only the upper header turns on the cooling mode; specifically, the flow ratio of the upper and lower headers of the laminar cooling is 55%:35%.

[0056] In a specific embodiment, the laminar cooling further includes finishing, which is performed using a small leveling force control technology, and the leveling rolling force is 150 to 200 tons.

[0057] The present application also provides a steel for photovoltaic brackets, including the high-strength and high-weathering steel described in the above scheme. In practical applications, the high-strength and high-weathering steel described in the above scheme of the present application can be used as steel for photovoltaic brackets.

[0058] The 800MPa grade high-strength and high-weathering steel provided in this application ensures stable performance, excellent surface and stable production of high-strength and high-weathering steel through adjustment of composition design, heating system and rolling technology; it is adapted to the production of high-strength, high-weathering resistance and surface-quality thin-gauge products for photovoltaics by hot continuous rolling; the high-strength and high-weathering steel provided in this application has been used in industrial production of more than 30,000 tons of strip steel and 23,000 tons of 800MPa grade high-weathering hot-rolled photovoltaic weathering steel with specifications of 1.5-2.5mm. The products have good surface quality, stable mechanical properties and excellent corrosion resistance.

[0059] In order to further understand the present invention, the 800MPa grade high-strength and high-weathering steel and its preparation method provided by the present invention are described in detail below in combination with the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0060] Example 1

[0061] Specifications of 800MPa grade hot-rolled photovoltaic weathering steel: finished product specifications: 1.5mm×1250mm (thickness×width), slab specifications 200mm×1280mm×11000mm (thickness×width×length), a total of 23 pieces, 506 tons; in terms of mass percentage, the chemical composition includes: C=0.08%, Si=0.39%, Mn=0.98%, P=0.080%, S=0.0065%, Cr=1.130%, Cu=0.27%, Ti=0.060%, Nb=0.010%, Als=0.0030%, Fe balance.

[0062] The prepared slabs were hot-transferred and hot-charged for heating treatment, with the charging temperature at 452-480°C and the slab discharge temperature at 1260-1270°C. The slabs were kept in the furnace for an average of 134 minutes. The temperature in the preheating section was 930°C, and the temperature was increased at a rate of 6.7°C / min to 1185°C in the heating section, with an average heating time of 32 minutes. The slabs then entered the soaking section, with a temperature of 1260°C and an average soaking time of 32 minutes. The air-fuel ratio in the preheating section was 2.5, the air-fuel ratio in the heating section was 2.3, and the air-fuel ratio in the soaking section was 2.1.

[0063] The slab after soaking is sequentially subjected to finishing and roughing rolling; wherein, the roughing rolling adopts the 0+5 mode, the roughing descaling pressure is 18MPa, the finishing descaling pressure is 28MPa, the hot coil box is put into use, the average starting temperature of the finishing rolling is 1089℃, F1E adopts 5mm variable width control, the extrusion pressure is 18-20 tons, the finishing strip threading speed is 10.30m / s, the finishing rolling mill is lubricated and put into use, the oil-water ratio is set as: F1=0.15%, F2=0.30%, F3=0.50%, F4=0.45%, F5=0.45%, F6=0.25%, F7=0.15%, the lubricating oil is turned on and off according to a special "ramp" process to reach a stable flow or reduce to zero, the cooling water of the F1-F4 roll gap is turned on, and high tension rolling is adopted: F1 / F2=7.70N / mm 2 , F2 / F3=8.70N / mm 2 , F3 / F4=11.0N / mm 2 , F4 / F5=13.10N / mm 2 , F5 / F6=19.30N / mm 2 , F6 / F7=22.00N / mm 2 ,At the same time, the RAC and DWC regulation functions are put into use;

[0064] The plate shape of the rolled slab is controlled. The bending and shifting of the plate shape control system adopts a cycle mode with a step distance of 5mm.

[0065] The slab after shape control is subjected to laminar cooling, and the laminar cooling adopts a mode with an upper and lower header flow ratio of 55%:35%; finally, finishing is carried out: according to the actual shape of the strip, the rolling force of the flattening process is 160 to 180 tons to obtain the finished photovoltaic weathering strip.

[0066] The finished photovoltaic weathering steel strip prepared in this embodiment has the following advantages: (1) good surface quality, with no defects such as "copper brittleness" and edge cracks in the strip; (2) good strip shape, with an unevenness of 5 to 8 mm after leveling; (3) mechanical properties: yield strength ReL = 720 to 750 MPa, tensile strength Rm = 840 to 860 MPa, elongation A% = 24% to 26%, and the mechanical properties meet the requirements of technical standards.

[0067] Figure 1 These are the actual quality photos and application photos of the photovoltaic weathering strip prepared in this embodiment. The first figure is a photo of the strip after slitting. It can be seen from the figure that the strip has a good shape after slitting. The second figure is a photo of the finished strip. It can be seen from the figure that the surface quality of the finished strip is excellent. The third and fourth figures are application photos of a 250MW photovoltaic project and a 200MW photovoltaic project, respectively.

[0068] Example 2

[0069] 800MPa grade hot-rolled photovoltaic weather-resistant thin specifications: finished product specifications: 1.97mm×1170mm (thickness×width), slab specifications 200mm×1200mm×11000mm (thickness×width×length), a total of 26 pieces, 572 tons; in terms of mass percentage, the chemical composition includes: C=0.07%, Si=0.37%, Mn=1.00%, P=0.070%, S=0.007%, Cr=1.20%, Cu=0.28%, Ti=0.070%, Nb=0.015%, Als=0.0040%, Fe balance.

[0070] The prepared slabs were hot-transferred and hot-charged for heating treatment, with a charging temperature of 505-542°C and a slab discharge temperature of 1250-1260°C. The slabs were kept in the furnace for an average of 129 minutes. The temperature in the preheating section was 917°C, and the temperature was increased at a rate of 7°C / min to 1200°C in the heating section, with an average heating time of 35 minutes. The slabs then entered the soaking section, with a soaking section temperature of 1254°C and an average soaking section time of 30 minutes. The air-fuel ratio in the preheating section was 2.5, the air-fuel ratio in the heating section was 2.3, and the air-fuel ratio in the soaking section was 2.1.

[0071] The slab after soaking is sequentially subjected to finishing and roughing rolling; wherein, the roughing rolling adopts the 0+5 mode, the roughing descaling pressure is 18MPa, the finishing descaling pressure is 28MPa, the hot coil box is put into use, the average starting temperature of the finishing rolling is 1081℃, F1E adopts 5mm variable width control, the extrusion pressure is 18-20 tons, the finishing strip threading speed is 10.00m / s, the finishing rolling mill is lubricated and put into use, the oil-water ratio is set as: F1=0.20%, F2=0.25%, F3=0.50%, F4=0.45%, F5=0.45%, F6=0.24%, F7=0.20%, the lubricating oil is turned on and off according to a special "ramp" process to reach a stable flow or reduce to zero, the cooling water of the F1-F4 roll gap is turned on, and high tension rolling is adopted: F1 / F2=7.90N / mm 2 , F2 / F3=9.10N / mm 2 , F3 / F4=11.60N / mm 2 , F4 / F5=13.70N / mm 2 , F5 / F6=20.00N / mm 2 , F6 / F7=22.60N / mm 2 ,At the same time, the RAC and DWC regulation functions are put into use;

[0072] The plate shape of the rolled slab is controlled. The bending and shifting of the plate shape control system adopts a cycle mode with a step distance of 5mm.

[0073] The slab after shape control is subjected to laminar cooling, and the laminar cooling adopts a mode with an upper and lower header flow ratio of 55%:35%; finally, finishing is carried out: according to the actual shape of the strip, the rolling force of the flattening process is 150 to 160 tons to obtain the finished photovoltaic weathering strip.

[0074] The finished photovoltaic weathering steel strip prepared in this embodiment has the following advantages: (1) good surface quality, with no defects such as "copper brittleness" and edge cracks in the strip; (2) good strip shape, with an unevenness of 4 to 7 mm after leveling; (3) mechanical properties: yield strength ReL = 730 to 755 MPa, tensile strength Rm = 835 to 860 MPa, elongation A% = 25% to 27%, and the mechanical properties meet the requirements of technical standards.

[0075] The corrosion resistance test of the 800MPa high-strength thin-gauge photovoltaic bracket steel prepared in this embodiment shows that the corrosion rate relative to Q355B steel is 22.7% to 31.1%, meeting the technical requirement of a relative corrosion rate of Q355B of ≤35%; the comprehensive yield rate of the product reaches 98.17%.

[0076] Comparative Example 1

[0077] 800MPa grade hot-rolled photovoltaic weather-resistant thin specifications: finished product specifications: 1.97mm×1170mm, slab specifications 200mm×1200mm×11000mm, a total of 17 pieces, 323 tons; in terms of mass percentage, the chemical composition includes: C=0.08%, Si=0.39%, Mn=0.97%, P=0.090%, S=0.006%, Cr=1.16%, Cu=0.29%, Ti=0.065%, Nb=0.010%, Als=0.0045%, Fe balance.

[0078] The prepared slabs were hot-transferred and hot-charged for heating treatment, with a charging temperature of 505-542°C and a slab discharge temperature of 1250-1260°C. The slabs were kept in the furnace for an average of 226 minutes. The temperature in the preheating section was 900°C, and the temperature was increased at a rate of 7°C / min to above 1200°C in the heating section, with an average heating time of 105 minutes. The slabs then entered the soaking section, with a soaking section temperature of 1245°C and an average soaking section time of 45 minutes. The air-fuel ratio in the preheating section was 2.5, the air-fuel ratio in the heating section was 2.3, and the air-fuel ratio in the soaking section was 2.1.

[0079] The slab after soaking is sequentially subjected to finishing rolling and roughing rolling; wherein, the roughing rolling adopts the 0+5 mode, the roughing descaling pressure is 18MPa, the finishing descaling pressure is 28MPa, the hot coil box is put into use, the average starting temperature of the finishing rolling is 1090℃, F1E adopts 5mm variable width control, the extrusion pressure is 18-20 tons, the finishing strip threading speed is 10.00m / s, the finishing rolling mill is lubricated and put into use, the oil-water ratio is set as: F1=0.20%, F2=0.25%, F3=0.50%, F4=0.45%, F5=0.45%, F6=0.24%, F7=0.20%, the lubricating oil is turned on and off according to a special "ramp" process to reach a stable flow or reduce to zero, the cooling water of the F1-F4 roll gap is turned on, and high tension rolling is adopted: F1 / F2=8.00N / mm 2 , F2 / F3=9.00N / mm 2 , F3 / F4=12.00N / mm 2 , F4 / F5=13.20N / mm 2 , F5 / F6=20.50N / mm 2 , F6 / F7=23.20N / mm 2 ,At the same time, the RAC and DWC regulation functions are put into use;

[0080] The plate shape of the rolled slab is controlled. The bending and shifting of the plate shape control system adopts a cycle mode with a step distance of 5mm.

[0081] The slab after shape control is subjected to laminar cooling, and the laminar cooling adopts a mode with an upper and lower header flow ratio of 55%:35%; finally, finishing is carried out: according to the actual shape of the strip, the rolling force of the flattening process is 150 to 160 tons to obtain the finished photovoltaic weathering strip.

[0082] The corrosion resistance test of the 800MPa high-strength and thin-gauge photovoltaic bracket steel prepared in this embodiment shows that the corrosion rate relative to Q355B steel is 31% to 33%, which meets the technical requirement of a relative corrosion rate of Q355B of ≤35%, and the process mechanical properties meet the standard requirements. The comprehensive yield rate of the product reaches 98.06%, but the edges of the strip steel after rolling all have edge crack defects of varying degrees.

[0083] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0084] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An 800MPa grade high-strength and high-weathering steel, comprising, by mass percentage: C≤0.09%, Si 0.35%~0.45%, Mn 0.80%~1.00%, P 0.070%~0.090%, S≤0.008%, Cr 1.00%~1.25%, Cu0.25%~0.30%, Ti 0.060%~0.070%, Nb≤0.02%, Als 0.0010%~0.0050%, Fe balance.

2. The high-strength and high-weathering steel according to claim 1, characterized in that: The C content is 0.05 to 0.08%, and / or the Si content is 0.37 to 0.42%, and / or the Mn content is 0.83 to 0.98%.

3. The high-strength and high-weathering steel according to claim 1, characterized in that: The P content is 0.073-0.086%, and / or the S content is 0.005-0.007%, and / or the Cr content is 1.13-1.21%.

4. The high-strength and high-weathering steel according to claim 1, characterized in that: The Cu content is 0.27-0.29%, and / or the Ti content is 0.062-0.068%, and / or the Nb content is 0.010-0.015%, and / or the Al content is 0.002-0.004%.

5. The method for preparing the high-strength and high-weathering steel according to any one of claims 1 to 4, comprising the following steps: S1) preheating, heating and soaking the high-strength and high-weathering steel billet in sequence; The preheating temperature is 800-950°C, the heating temperature is 1050-1200°C, the heating rate is 6-8°C / min, and the soaking temperature is 1230-1260°C; S2) performing rough rolling and finish rolling on the steel billet obtained in step S1); The rough rolling adopts 0+5 rolling mode; The finishing rolling adopts F1-F7 full-stand lubrication rolling, and the oil-water ratio is set as follows: F1 = 0.15%-0.25%, F2 = 0.20%-0.30%, F3 = 0.45%-0.65%, F4 = 0.45%-0.65%, F5 = 0.45%-0.65%, F6 = 0.20%-0.30%, F7 = 0.15%-0.20%; The finishing rolling adopts F1-F7 full-frame high-tension rolling, and the tension ratio is specifically: F1 / F2=6.50-8.50N / mm 2 , F2 / F3=7.50~9.50N / mm 2 , F3 / F4=10.5~11.6N / mm 2 , F4 / F5=12.50~14.50N / mm 2 , F5 / F6=18.50~21.50N / mm 2 , F6 / F7=21.50~23.5N / mm 2 ; S3) The steel billet obtained in step S2) is subjected to shape control, followed by laminar cooling and finishing.

6. The preparation method according to claim 5, characterized in that In step S1), the heating time is 30 to 40 minutes, and / or the soaking time is 15 to 20 minutes, and / or the total time of the preheating, the heating and the soaking is 120 to 150 minutes.

7. The preparation method according to claim 5, characterized in that In step S1), the air-fuel ratio of the preheating is 2.4-2.8, the air-fuel ratio of the heating is 2.1-2.6, and the air-fuel ratio of the equalizing is 1.8-2.

2.

8. The preparation method according to claim 5, characterized in that In step S2), the descaling pressure of the rough rolling is 18 to 25 MPa; and / or the strip threading speed of the finishing rolling is greater than or equal to 9.5 m / s and less than 10.5 m / s; and / or the F1E widening amount of the finishing rolling is 0 to 5 mm; and / or RAC adjustment and DWC adjustment are introduced during the finishing rolling process.

9. The preparation method according to claim 5, characterized in that In step S2), the plate shape control is carried out in a circulation mode of bending and shifting rolls with a step distance of 5 to 10 mm; and / or the flow ratio of the upper and lower headers of the laminar cooling is (45% to 55%): (25% to 35%), and only the upper header is in cooling mode.

10. Steel for photovoltaic supports, comprising the high-strength and high-weathering steel according to any one of claims 1 to 4 or the high-strength and high-weathering steel prepared by the preparation method according to any one of claims 5 to 9.

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