Desert-climate-resistant coating-free weathering steel and preparation method thereof

Abstract

The invention discloses desert climate resistant coating-free weathering steel and a preparation method thereof. The desert climate resistant coating-free weathering resistant steel comprises the following components in percentage by mass: 0.045 wt% to 0.065 wt% of C, 0.15 wt% to 0.40 wt% of Si, 0.45 wt% to 0.55 wt% of Mn, 0.075 wt% to 0.085 wt% of P, 0.055 wt% to 0.075 wt% of Ti, 0.35 wt% to 0.55 wt% of Cr, 0.4 wt% to 0.6 wt% of Al, 0.13 wt% to 0.18 wt% of Cu, 0 to 0.015 wt% of S, preferably 0 to 0.01 wt% of S, and the balance of Fe. And the balance of Fe and inevitable trace elements. Compared with the proportion of traditional coating-free weathering steel, the desert climate-resistant coating-free weathering steel has the advantages that precious elements such as nickel, molybdenum and niobium are removed, the use of the copper element is reduced, and the corrosion resistance of the desert climate-resistant coating-free weathering steel is ensured by adopting more economical aluminum and phosphorus elements; the coating-free weathering steel used in a C3 environment specified in GB / T19292.1-2018 is obtained while the manufacturing cost is greatly reduced, and the coating-free weathering steel is suitable for dry desert climate.

Description

Technical Field

[0001] The present application belongs to the technical field of steel smelting, and in particular relates to a desert climate resistant paint-free weathering steel and a preparation method thereof. Background Art

[0002] The desert region has a dry climate with little rainfall throughout the year, and the temperature difference during the day is large, especially the daytime temperature reaches 40°C. The effective sunlight time in the desert region reaches 2,200 hours per year, and it has very rich solar energy resources with great development value.

[0003] At present, the construction of new energy sources such as solar thermal, photovoltaic, and wind power in desert areas requires a large amount of steel for solar thermal brackets, photovoltaic brackets, and transmission towers. The existing paint-free weathering steel contains a large amount of precious metals such as Ni, Cu, and Mo, which significantly increases the alloy cost of steel. Summary of the invention

[0004] The embodiments of the present application provide a desert climate resistant, paint-free weathering steel and a preparation method thereof. The constituent elements of the desert climate resistant, paint-free weathering steel of the present application do not contain precious metals such as Ni, Mo, Nb, etc., which greatly reduces the manufacturing cost while ensuring the performance.

[0005] In a first aspect, a desert climate resistant and paint-free weathering steel is provided, including the components, in mass percentage, of C: 0.045wt%~0.065wt%, Si: 0.15wt%~0.40wt%, Mn: 0.45wt%~0.55wt%, P: 0.075wt%~0.085wt%, Ti: 0.055wt%~0.075wt%, Cr: 0.35wt%~0.55wt%, Al: 0.4wt%~0.6wt%, Cu: 0.13wt%~0.18wt%, S: 0~0.015wt%, preferably S: 0~0.01%wt; and the remainder of Fe and unavoidable trace elements.

[0006] Compared with the proportion of traditional paint-free weathering steel, the desert climate resistant paint-free weathering steel of the present application removes precious elements such as nickel, molybdenum, niobium and reduces the use of copper elements, and adopts more economical aluminum and phosphorus elements to ensure the corrosion resistance of the desert climate resistant paint-free weathering steel, which greatly reduces the manufacturing cost and obtains the paint-free weathering steel for use in the C3 environment specified in GB / T 19292.1-2018, which is suitable for dry desert climate.

[0007] In some embodiments, the content of trace elements is ≤0.0065wt%, and the trace elements include N, O, and H, N: 0-0.0045wt%, O: 0-0.00015wt%, and H: 0-0.0015wt%.

[0008] In some embodiments, the metallographic structure of the desert climate resistant paint-free weathering steel includes 80% to 90% ferrite and 10% to 20% pearlite.

[0009] An appropriate amount of titanium is added to the desert climate resistant paint-free weathering steel of the present application, and TiC is used to form a TiC precipitation strengthening phase of about 10-30nm, which significantly improves the strength of the steel and saves the use of manganese.

[0010] In some embodiments, the desert climate resistant paint-free weathering steel meets one or more of the following conditions (1) to (4): (1) the yield strength of the desert climate resistant paint-free weathering steel is 550MPa to 620MPa; (2) the tensile strength of the desert climate resistant paint-free weathering steel is greater than 720MPa; (3) the elongation of the desert climate resistant paint-free weathering steel is greater than 18%; (4) the desert climate resistant paint-free weathering steel has the ability to be used without painting for 25 years under the bare use environment of C3 environment specified in GB / T 19292.1-2018, and the uniform thinning on both sides is less than 0.2mm.

[0011] In the second aspect, a method for preparing desert climate resistant and paint-free weathering steel comprises: providing RH refined molten steel, wherein the RH refined molten steel contains the components of the desert climate resistant and paint-free weathering steel of the first aspect; continuous casting, continuously casting the RH refined molten steel to obtain slabs; heating the slabs, using a multi-stage heating furnace to heat the slabs that have completed continuous casting to increase the temperature of the slabs; hot rolling, subjecting the heated slabs to rough rolling and finish rolling in sequence through a continuous rolling unit to obtain steel plates.

[0012] In some embodiments, a RH steel refining step is provided, including: desulfurization treatment, desulfurizing molten iron to obtain molten iron with S≤0.01wt%; converter smelting, smelting the molten iron with S≤0.01wt% to obtain molten steel, and the molten steel is treated with argon blowing to make the temperature and composition of the molten steel uniformly mixed, wherein the terminal temperature of the argon blowing treatment of the molten steel is ≥1535°C; LF refining, performing LF refining on the molten steel that has completed the argon blowing treatment to obtain LF refined molten steel; RH refining, performing RH refining on the molten steel that has completed the LF refining to obtain RH refined molten steel.

[0013] In some embodiments, the LF refining step includes: adjusting the temperature of the molten steel that has completed the argon blowing treatment to ≥1522°C; and / or, performing LF refining on the molten steel, the refining time is 40min~45min, to obtain LF refined molten steel, the outlet temperature of the LF refined molten steel is 1565°C~1580°C; and / or, adjusting the composition of the LF refined molten steel to meet the target content requirements, adjusting the temperature of the LF refined molten steel to ≥1538°C, for RH refining.

[0014] In some embodiments, the RH refining step includes: performing RH refining on the molten steel that has completed LF refining under a vacuum degree of ≤67 MPa, and the RH refining time is 22 min to 30 min.

[0015] In some embodiments, in the slab heating step, the slab entering the furnace temperature is 900℃~1000℃, the heating temperature of the heating furnace section at the front part of the heating furnace is 1200℃~1280℃, the slab exiting the furnace temperature is 1150℃~1180℃, the slab heating time in the furnace is ≥30min, and the excess air coefficient of the heating furnace is 0.95~1.05; and / or, before the steel slab after the slab heating is completed enters the continuous rolling mill for rolling, the heated steel plate is descaled by high-pressure water with a pressure of ≥200bar. In this embodiment, the heating furnace section at the front part of the heating furnace refers to the front half of the total number of heating furnace sections or half of the furnace sections increase or decrease by no more than 1-5 sections.

[0016] Higher heating temperature and longer heating time can fully dissolve titanium, aluminum, chromium and other elements, creating the prerequisite for the uniform precipitation of TiC particles. The solid solution of aluminum and chromium elements prepares the organization for the formation of uniform and fine α-FeOOH in the rust layer of the steel plate during service, thereby ensuring the improvement of strength and corrosion resistance. The excess air coefficient of the heating furnace is to ensure that the gas in the heating furnace is fully burned while maintaining a reducing atmosphere, thereby controlling the thickness of the oxide scale on the surface of the slab, on the one hand reducing the burning loss and improving the yield rate, on the other hand, it is conducive to descaling and reducing the oxide pressure on the surface of the steel plate.

[0017] In some embodiments, the process parameters of the continuous casting step are: the continuous casting pulling speed is 4.0m / min~4.5m / min, and the casting is carried out in a light pressure mode in the thickness direction; and / or, the continuous casting step also includes: adding continuous casting protection slag to the surface of the molten steel in the continuous casting mold to protect the surface of the molten steel, wherein the basicity of the continuous casting protection slag is 0.9~1.0, and the viscosity is 1.9P~2.2P.

[0018] In some embodiments, in the hot rolling step, the rough rolling temperature is 1130°C to 1160°C, and the final rolling temperature is 820°C to 870°C; and / or, the hot rolling step further includes: ultra-fast cooling the steel plate that has completed final rolling at a cooling rate of 100°C / s to 300°C / s, and then laminar cooling at a cooling rate of 10°C / s to 25°C / s to cool the steel plate to 600°C to 650°C.

[0019] In this embodiment, the present application adopts the production method of controlled rolling and accelerated cooling, and obtains the best effect through deformation recrystallization of the high-temperature austenite zone, deformation of the low-temperature austenite non-recrystallization zone and accelerated cooling after rolling.

[0020] In the preparation method of desert climate resistant weathering steel in the embodiment of the present application, the slab heating temperature and continuous casting and rolling process set by the preparation method in the embodiment of the present application are adopted, and the grain size of the prepared steel plate is one level lower than the grain size of the steel plate produced by the conventional production line. While refining the grains and ensuring high strength and toughness, it is also beneficial to improve corrosion resistance, and also has good precision cold bending forming and welding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0022] Figure 1 This is a metallographic diagram of the desert climate resistant and paint-free weathering steel according to one embodiment of the present application.

[0023] Figure 2 This is a corrosion rate diagram of the Turpan dry desert climate hanging piece of desert climate resistant and paint-free weathering steel according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0025] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0026] The above-mentioned inventive content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates an exemplary embodiment. In many places throughout the application, guidance is provided by a series of embodiments, which can be used in various combinations. In each example, the enumeration is only a representative group and should not be interpreted as exhaustive. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0027] As mentioned in the background technology, at present, the construction of new energy sources such as solar thermal, photovoltaic, and wind power in desert areas requires a large amount of steel for solar thermal brackets, photovoltaic brackets, and transmission towers. Existing paint-free weathering steel adds a large amount of precious metals such as Ni, Cu, and Mo, which significantly increases the alloy cost of steel.

[0028] In order to solve the existing problems, the inventors have conducted a lot of research, aiming to provide a desert climate resistant and paint-free weathering steel whose composition elements do not contain precious metals such as Ni, Mo, Nb, etc., thereby significantly reducing manufacturing costs while ensuring performance.

[0029] Desert climate resistant paint-free weathering steel

[0030] The first aspect embodiment of the present application provides a desert climate resistant, paint-free weathering steel. The components of the desert climate resistant, paint-free weathering steel include, in terms of mass percentage: C: 0.045wt%~0.065wt%, Si: 0.15wt%~0.40wt%, Mn: 0.45wt%~0.55wt%, P: 0.075wt%~0.085wt%, Ti: 0.055wt%~0.075wt%, Cr: 0.35wt%~0.55wt%, Al: 0.4wt%~0.6wt%, Cu: 0.13wt%~0.18wt%, S: 0~0.015wt%, preferably S: 0~0.01%wt; and the remainder of Fe and unavoidable trace elements.

[0031] According to the embodiments of the present application, the carbon element has a great influence on the organization control in the steel. A higher content of carbon is easy to form bainite or martensite with higher strength and hardness during the cooling process. However, too high a carbon content will increase the brittleness of the steel and reduce the plasticity and toughness of the steel; too low a carbon content will form a softer structure such as ferrite, and an appropriate amount of carbon and titanium will form a large number of nano-scale second phase precipitates, which can produce a strong precipitation strengthening effect and fine grain strengthening effect, while improving the strength and plasticity and toughness of the steel. In order to ensure good toughness in the present application, when the carbon content is greater than 0.065wt%, the carbon equivalent enters the peritectic reaction area, the CSP thin slab continuous casting machine is prone to leaking steel, and the production rhythm is difficult to guarantee. Considering the comprehensive mechanical properties and the stable production of continuous casting, the mass percentage of carbon in the steel is controlled within the range of 0.045wt% to 0.065wt%.

[0032] According to the embodiments of the present application, silicon can be deoxidized during the smelting process, but too high a content thereof will affect weldability and toughness. An appropriate amount of silicon dissolved in steel can improve strength. Taking all factors into consideration, the mass percentage of silicon in the steel is controlled within the range of 0.15wt% to 0.40wt%.

[0033] According to the embodiment of the present application, manganese is a weak carbide-forming element, which usually plays a role of solid solution strengthening in steel. High-strength steel coils are produced by thermomechanical rolling controlled cooling. Manganese dissipates the interface free energy across the diffusion interface, inhibits the diffusion control growth of the end face of the lamellar phase, and forms refined lamellar bainite, thereby improving the strength, toughness and other comprehensive properties of the steel plate. Excessive manganese content will increase the tendency of the slab to crack, and it is easy to form defects such as longitudinal cracks in the production of the slab. However, a lower manganese content has little effect on the strength of the steel. Carbon and other alloying elements must be added to ensure the strength performance. Adding too much carbon will deteriorate the welding performance of the steel, and adding too much precious alloying elements will increase the cost of the steel. Considering the comprehensive performance and cost, the mass percentage of manganese in the steel is controlled within the range of 0.45wt% to 0.55wt%.

[0034] According to the embodiments of the present application, in the low alloy steel system, chromium is a ferrite forming element, and the addition of chromium will enhance the hardenability of steel, while reducing plasticity and toughness. In weathering steel, an appropriate amount of chromium is added, and chromium and iron undergo a substitution reaction in Fe2O3, the main component of rust. During this period, through a series of phase changes, the β-FeOOH in the early stage of the rust layer can be promoted to be transformed into stable and fine α-FeOOH, forming a composite oxide (FeCr)2O3, improving the compactness of the rust layer, and increasing the role of the rust layer in protecting the matrix. Considering the corrosion resistance level of the desert dry climate environment, the mass percentage of chromium in the steel is controlled within the range of 0.35wt% to 0.55wt%.

[0035] According to the embodiments of the present application, phosphorus is an economical non-metallic element and is generally a harmful element in low alloy steel or metal alloys. The lower the content, the better. Too much phosphorus will cause grain boundary segregation and increase the brittleness of the steel. A certain amount of phosphorus can improve the weather resistance of steel. Adding phosphorus to weathering steel can significantly improve the weathering index and reduce the alloy cost. Taking all factors into consideration, the mass percentage of phosphorus in steel is controlled within the range of 0.075wt% to 0.085wt%.

[0036] According to the embodiments of the present application, aluminum is an effective deoxidizing element in the steelmaking process. Aluminum and a small amount of boron are conducive to the formation of acicular ferrite, but too high an aluminum content will damage the isotropic toughness of the steel. At the same time, a certain amount of aluminum in the steel can promote the refinement of α-FeOOH grains in the rust layer and significantly improve the weather resistance of the steel. Taking into account the mechanical properties and weather resistance, the mass percentage of aluminum in the steel is controlled within the range of 0.4wt% to 0.6wt%.

[0037] According to the embodiments of the present application, the copper element mainly plays a role in solid solution and precipitation strengthening in steel. At the same time, the electrochemical potential of copper is higher than that of iron, which can promote the formation of a dense rust layer on the steel surface. It works synergistically with chromium to improve the density of the rust layer of weathering steel, which is beneficial to the improvement of corrosion resistance. At the same time, an appropriate amount of copper combines with the residual sulfur in the steel to form a Cu2S protective film to alleviate corrosion in an acidic medium corrosive environment. However, too high a content of copper will not only damage the toughness of the welding heat affected zone, but also easily cause cracking during hot rolling, deteriorate the surface properties of the steel plate, and increase costs. Taking all factors into consideration, the mass percentage of the copper element in the steel is controlled within the range of 0.13wt% to 0.18wt%.

[0038] According to the embodiment of the present application, during the continuous casting solidification process, titanium and nitrogen combine to form TiN, which will inhibit the growth of austenite grains. The presence of TiN can inhibit the coarsening of grains in the welding heat affected zone. During the continuous rolling process, titanium and carbon form nano-scale TiC in a lower temperature range. Nano-scale TiC has significant precipitation strengthening and fine grain strengthening effects, which will significantly improve the strength and low-temperature impact performance of the steel plate. When the titanium content is too high, coarse square TiN particles will be formed. When the stress is concentrated near the TiN particles, a growth source of microcracks will be formed, which will reduce the fatigue performance of the steel. On the other hand, the solubility product of TiC in the high-temperature ingot is small, and it is difficult to dissolve in the slab heating process, and it does not play a role in precipitation strengthening. In summary, in order to ensure sufficient carbonitride precipitation, the yield strength can reach more than 550MPa, and the mass percentage of titanium in the steel is controlled within the range of 0.055wt% to 0.075wt%.

[0039] According to the embodiment of the present application, in titanium-containing steel, sulfur and nitrogen form TiS compounds during the solidification process of the plate, which reduces the proportion of effective titanium. Too high TiS and TiN content will deteriorate the performance of the steel. Therefore, the sulfur element in titanium-containing steel should be controlled. After comprehensive consideration, the mass percentage of sulfur in the steel is controlled within the range of ≤0.015wt%.

[0040] In some embodiments, the content of trace elements is ≤0.0065wt%, and the trace elements include N, O, and H, N: 0-0.0045wt%, O: 0-0.00015wt%, and H: 0-0.0015wt%.

[0041] According to the embodiments of the present application, gas elements such as nitrogen, oxygen, and hydrogen are extremely detrimental to the toughness of steel and should be strictly controlled. The mass percentages of nitrogen, oxygen, and hydrogen in steel are limited to ≤0.0045%, ≤0.00015%, and ≤0.0015%, respectively.

[0042] In some embodiments, Figure 1 As shown, the metallographic structure of the desert climate resistant and paint-free weathering steel includes 80% to 90% ferrite and 10% to 20% pearlite.

[0043] In some embodiments, the desert climate resistant paint-free weathering steel satisfies one or more of the following conditions (1) to (4): (1) the yield strength of the desert climate resistant paint-free weathering steel is 550MPa to 620MPa, for example, it can be 550MPa, 560MPa, 580MPa, 600MPa, 620MPa, or any combination range of the above values; (2) the tensile strength of the desert climate resistant paint-free weathering steel is greater than 720MPa, for example, it can be 725MPa, 730MPa, 750MPa, 780MPa, 800MPa, 850MPa, or any combination range of the above values; (3) the elongation of the desert climate resistant paint-free weathering steel is greater than 18%, for example, it can be 18.1%, 18.5%, 19%, 20%, 22%, 25%, or any combination range of the above values; (4) the desert climate resistant paint-free weathering steel meets the GB / T Under the C3 environment specified in 19292.1-2018, it can be used without painting for 25 years, and the uniform thinning on both sides is less than 0.2mm.

[0044] According to the embodiments of the present application, the desert climate resistant paint-free weathering steel of the present application, compared with the proportion of traditional paint-free weathering steel, removes precious elements such as nickel, molybdenum, niobium and reduces the use of copper elements, and adopts more economical aluminum and phosphorus elements to ensure the corrosion resistance of the desert climate resistant paint-free weathering steel, which greatly reduces the manufacturing cost and obtains the paint-free weathering steel for use in the C3 environment specified in GB / T19292.1-2018, which is suitable for dry desert climates.

[0045] Production method of desert climate resistant paint-free weathering steel

[0046] The second aspect of the present application also provides a method for preparing desert climate resistant and paint-free weathering steel, comprising: providing RH refined molten steel, the RH refined molten steel containing the components of the first aspect; continuous casting, continuously casting the RH refined molten steel to obtain slabs; heating the slabs, using a multi-stage heating furnace to heat the slabs that have completed continuous casting to increase the temperature of the slabs; hot rolling, subjecting the heated slabs to rough rolling and finish rolling in sequence through a continuous rolling unit to obtain steel plates.

[0047] In some embodiments, a RH refined molten steel step is provided, including: desulfurization treatment, desulfurizing molten iron to obtain molten iron with S≤0.01wt%, for example, the desulfurization treatment can adopt KR desulfurization; converter smelting, smelting molten iron with S≤0.01wt% to obtain molten steel, and the molten steel is treated with argon blowing to make the temperature and composition of the molten steel uniformly mixed, wherein the terminal temperature of the molten steel after the argon blowing treatment is ≥1535℃, for example, it can be 1535℃, 1540℃, 1550℃, 1560℃, 1580℃, or any combination range of the above values; LF refining, performing LF refining on the molten steel that has completed the argon blowing treatment to obtain LF refined molten steel; RH refining, performing RH refining on the molten steel that has completed the LF refining to obtain RH refined molten steel.

[0048] In some embodiments, the LF refining step includes: adjusting the temperature of the molten steel after the argon blowing treatment to ≥ 1522°C, for example, 1522°C, 1525°C, 1530°C, 1540°C, 1550°C, or any combination range of the above values; and / or, performing LF refining on the molten steel, the refining time is 40min to 45min, for example, 40min, 41min, 42min, 43min, 44min, 45min, or any combination range of the above values, to obtain The outlet temperature of the molten steel after LF refining is 1565℃~1580℃, for example, it can be 1565℃, 1570℃, 1575℃, 1580℃, or any combination range of the above numerical values; and / or, the composition of the molten steel after LF refining is adjusted to meet the target content requirement, and the temperature of the molten steel after LF refining is adjusted to ≥1538℃, for example, it can be 1538℃, 1540℃, 1545℃, 1550℃, 1560℃, or any combination range of the above numerical values, for RH refining.

[0049] In some embodiments, the RH refining step includes: performing RH refining on the molten steel that has completed LF refining under a vacuum degree of ≤67MPa, and the RH refining time is 22min to 30min, for example, it can be 22min, 23min, 25min, 28min, 30min, or any combination range of the above values.

[0050] In some embodiments, in the slab heating step, the slab entering the furnace temperature is 900°C to 1000°C, for example, it can be 900°C, 920°C, 950°C, 980°C, 1000°C, or any combination range of the above values, the heating temperature of the heating furnace section at the front part of the heating furnace is 1200°C to 1280°C, for example, it can be 1200°C, 1210°C, 1220°C, 1230°C, 1240°C, 1250°C, 1260°C, 1270°C, 1280°C, or any combination range of the above values, and the slab exiting the furnace temperature is 1150°C to 1180°C, for example, it can be The temperature is 1150°C, 1155°C, 1160°C, 1165°C, 1170°C, 1175°C, 1180°C, or any combination range of the above values, the slab heating time in the furnace is ≥30 min, and the excess air coefficient of the heating furnace is 0.95-1.05, for example, it can be 0.95, 0.98, 1.00, 1.02, 1.05, or any combination range of the above values; and / or, before the steel slab after the slab heating is completed enters the continuous rolling mill for rolling, the heated steel plate is descaled with high-pressure water with a pressure of ≥200 bar to ensure that the oxide is cleanly descaled.

[0051] In this embodiment, the heating furnace sections at the front part of the heating furnace refer to the front half of the total number of heating furnace sections or half of the sections increased or decreased by no more than 1-5 sections.

[0052] In this embodiment, the heating temperature of 1200℃~1250℃ and the heating time of ≥30min can fully dissolve elements such as Ti, Al, Cr, etc., creating the prerequisite for the uniform precipitation of TiC particles. The solid solution of Al and Cr prepares the organization for the formation of uniform and fine α-FeOOH in the rust layer of the steel plate during service, thereby ensuring the improvement of strength and corrosion resistance. The excess air coefficient of the heating furnace is to ensure the full combustion of the coal gas in the heating furnace while maintaining a reducing atmosphere, thereby controlling the thickness of the oxide scale on the surface of the slab, on the one hand reducing the burning loss and improving the yield rate, on the other hand, it is conducive to descaling and reducing the oxide pressure on the surface of the steel plate.

[0053] In some embodiments, during the heating of the slab, the temperature of the slab after continuous casting is 900°C to 1000°C, for example, it can be 900°C, 920°C, 950°C, 980°C, 1000°C, or any combination range of the above values, and enters the heating furnace at this temperature to maintain a high furnace entry temperature, thereby reducing the load for subsequent rapid heating and providing conditions for rapid solid solution of alloy elements and efficient production.

[0054] In some embodiments, the process parameters of the continuous casting step are: the continuous casting pulling speed is 4.0m / min~4.5m / min, for example, it can be 4.0m / min, 4.1m / min, 4.2m / min, 4.3m / min, 4.4m / min, 4.5m / min, or any combination range of the above values, and the ingot is cast in the thickness direction using a light pressure reduction mode; and / or the continuous casting step also includes: adding continuous casting protective slag to the surface of the molten steel in the continuous casting mold to protect the surface of the molten steel, wherein the basicity of the continuous casting protective slag is 0.9~1.0, for example, it can be 0.9, 0.92, 0.95, 0.98, 1.0, or any combination range of the above values, and the viscosity is 1.9P~2.2P, for example, it can be 1.9P, 1.95P, 2.0P, 2.05P, 2.1P, 2.15P, 2.2P, or any combination range of the above values.

[0055] In some embodiments, in the hot rolling step, the initial rolling temperature is 1130°C to 1160°C, for example, it can be 1130°C, 1135°C, 1140°C, 1150°C, 1160°C, or any combination range of the above values, and the final rolling temperature is 820°C to 870°C, for example, it can be 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, or any combination range of the above values; and / or, the hot rolling step further includes: The rolled steel plate is ultrafast cooled at a cooling rate of 100°C / s to 300°C / s, for example, 100°C / s, 150°C / s, 200°C / s, 250°C / s, 300°C / s, or any combination range of the above values, and then laminar cooled at a cooling rate of 10°C / s to 25°C / s to cool the steel plate to 600°C to 650°C, for example, 600°C, 610°C, 620°C, 650°C, or any combination range of the above values.

[0056] In this embodiment, the present application adopts the production method of controlled rolling and accelerated cooling, and obtains the best effect through deformation recrystallization of the high-temperature austenite zone, deformation of the low-temperature austenite non-recrystallization zone and accelerated cooling after rolling. In addition, the rough rolling temperature is 1130℃~1160℃, which can ensure that the rolling mill is not overloaded and ensure smooth rolling.

[0057] At the same time, the ultra-fast cooling of the present application can obtain a finer grain size of the finished product, and the laminar cooling with a cooling rate of 10°C / s to 25°C / s can avoid the existence of large internal stress in the steel plate, which causes poor plate shape, and can also avoid coarse steel structure, which causes performance fluctuations.

[0058] In some embodiments, the preparation method of the present application may also include: coiling, coiling the steel plate that has completed final rolling through a coiler to obtain a steel coil, wherein the temperature of the coiler is set to 600°C to 650°C, the produced plate shape is excellent, and the rolling yield is significantly higher than that of a conventional rolling line.

[0059] In the preparation method of the desert climate resistant and paint-free weathering steel in the embodiment of the present application, the slab heating temperature and continuous casting and rolling process set by the preparation method in the embodiment of the present application are adopted, and the grain size of the prepared steel plate is one level lower than the grain size of the steel plate produced by the conventional production line. While refining the grains and ensuring high strength and toughness, it is also beneficial to improve corrosion resistance, and also has good precision cold bending forming and welding performance.

[0060] In addition, the term "and / or" in this article is only a description of the association relationship between the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0061] It should be understood that in the embodiment of the present application, "B corresponding to A" means that B is associated with A, and B can be determined according to A. However, it should also be understood that determining B according to A does not mean determining B only according to A, and B can also be determined according to A and / or other information.

[0062] Example

[0063] The following examples more specifically describe the disclosure of the present application, which are intended for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0064] Example 1

[0065] A production method for desert climate resistant and paint-free weathering steel:

[0066] Desulfurization treatment, desulfurizing the molten iron to obtain molten iron with S: 0.0008wt%, for example, the desulfurization treatment can be carried out by KR desulfurization;

[0067] Converter smelting, smelting molten iron with S≤0.01wt% to obtain molten steel, the molten steel is treated with argon blowing to make the temperature and composition of the molten steel uniform, wherein the terminal temperature of the molten steel treated with argon blowing is ≥1538℃;

[0068] LF refining: for the molten steel that has completed the argon blowing treatment, the molten steel temperature is ≥1530℃, and LF refining is performed for 42 minutes to obtain LF refined molten steel. The outlet temperature of the LF refined molten steel is 1570℃. The composition of the LF refined molten steel is adjusted to meet the target content requirements, and the temperature of the LF refined molten steel is adjusted to 1540℃ for RH refining;

[0069] RH refining: RH refining is performed on the molten steel after LF refining under a vacuum degree of 60 MPa for 25 min to obtain RH refined molten steel. The RH refined molten steel contains the composition of Example 1 in Table 1 below.

[0070] The RH refined molten steel is continuously cast to obtain a slab having a thickness of 60 mm and a continuous casting speed of 4.3 m / min.

[0071] Slab heating, the slab furnace temperature is 950℃, and the slab is sent to the tunnel heating furnace for heating; the temperatures of zones 1-7 are 1250℃, 1260℃, 1280℃, 1250℃, 1230℃, 1235℃, 1200℃ respectively, the slab furnace time is 38min, and the excess air coefficient of the heating furnace is 1.02;

[0072] Before the heated steel slab enters the continuous rolling mill for rolling, high-pressure water with a pressure of ≥250 bar is used to descale the heated steel plate to ensure that the oxide is completely descaled.

[0073] Hot rolling: the mill inlet temperature is 1170°C, the finishing outlet temperature is 930°C, the steel plate after final rolling is ultra-fast cooled at a cooling rate of 180°C / s, and then the steel plate is cooled to 640°C at 15°C / s in a laminar cooling manner for coiling, and finally rolled into a thin-gauge desert-resistant, paint-free weathering steel plate with a thickness of 1.8 mm. The desert-resistant, paint-free weathering steel in this embodiment contains the composition of Example 1 in Table 1 below.

[0074] The material grain grade of the desert climate resistant and paint-free weathering steel obtained in this embodiment is 14, the steel plate yield strength is 580 MPa, the tensile strength is 750 MPa, the elongation is 21%, d=a, and the cold bending is qualified.

[0075] Example 2

[0076] A production method for desert climate resistant and paint-free weathering steel:

[0077] Desulfurization treatment, desulfurizing the molten iron to obtain molten iron with S: 0.0008wt%, for example, the desulfurization treatment can be carried out by KR desulfurization;

[0078] Converter smelting, smelting molten iron with S≤0.01wt% to obtain molten steel, the molten steel is treated with argon blowing to make the temperature and composition of the molten steel uniform, wherein the terminal temperature of the molten steel treated with argon blowing is ≥1538℃;

[0079] LF refining: for the molten steel that has completed the argon blowing treatment, the molten steel temperature is ≥1530℃, and LF refining is performed for 42 minutes to obtain LF refined molten steel. The outlet temperature of the LF refined molten steel is 1570℃. The composition of the LF refined molten steel is adjusted to meet the target content requirements, and the temperature of the LF refined molten steel is adjusted to 1540℃ for RH refining;

[0080] RH refining: RH refining is performed on the molten steel that has completed LF refining under a vacuum degree of 65 MPa. The RH refining time is 25 minutes to obtain RH refined molten steel.

[0081] The RH refined molten steel is continuously cast to obtain a slab having a thickness of 60 mm and a continuous casting speed of 4.3 m / min.

[0082] Slab heating, the slab furnace temperature is 950℃, and the slab is sent to the tunnel heating furnace for heating; the temperatures of zones 1-7 are 1250℃, 1260℃, 1280℃, 1250℃, 1230℃, 1235℃, 1200℃ respectively, the slab furnace time is 38min, and the excess air coefficient of the heating furnace is 1.02;

[0083] Before the heated steel slab enters the continuous rolling mill for rolling, the heated steel plate is descaled using high-pressure water at a pressure of 250 bar to ensure that the oxide is completely descaled.

[0084] Hot rolling: the mill inlet temperature is 1170°C, the finishing outlet temperature is 930°C, the steel plate after final rolling is ultra-fast cooled at a cooling rate of 180°C / s, and then the steel plate is cooled to 640°C at 15°C / s in a laminar cooling manner for coiling, and finally rolled into a thin-gauge desert-weather-resistant paint-free weathering steel plate with a thickness of 1.8 mm. The desert-weather-resistant paint-free weathering steel in this embodiment contains the composition of Example 2 in Table 1 below.

[0085] The material grain grade of the desert climate resistant and paint-free weathering steel obtained in this embodiment is 14, the steel plate yield strength is 565 MPa, the tensile strength is 770 MPa, the elongation is 22%, d=a, and the cold bending is qualified.

[0086] Example 3

[0087] A production method for desert climate resistant and paint-free weathering steel:

[0088] Desulfurization treatment, desulfurizing the molten iron to obtain molten iron with S: 0.0007wt%, for example, the desulfurization treatment can be carried out by KR desulfurization;

[0089] Converter smelting, smelting molten iron with S: 0.007wt% to obtain molten steel, the molten steel is treated with argon blowing to make the temperature and composition of the molten steel uniform, wherein the terminal temperature of the molten steel treated with argon blowing is 1540°C;

[0090] LF refining: for the molten steel that has completed the argon blowing treatment, the temperature of the molten steel is 1532°C, and LF refining is performed for 42 minutes to obtain LF refined molten steel. The outlet temperature of the LF refined molten steel is 1580°C. The composition of the LF refined molten steel is adjusted to meet the target content requirements, and the temperature of the LF refined molten steel is adjusted to 1542°C for RH refining;

[0091] RH refining: RH refining is performed on the molten steel after LF refining under a vacuum degree of 65 MPa for 24 minutes to obtain RH refined molten steel. The RH refined molten steel contains the composition of Example 3 in Table 1 below.

[0092] The RH refined molten steel is continuously cast to obtain a slab having a thickness of 60 mm and a continuous casting speed of 4.4 m / min.

[0093] Slab heating, the slab furnace temperature is 950℃, and the slab is sent to the tunnel heating furnace for heating; the temperatures of zones 1-7 are 1250℃, 1260℃, 1280℃, 1250℃, 1230℃, 1235℃, 1200℃ respectively, the slab furnace time is 38min, and the excess air coefficient of the heating furnace is 1.02;

[0094] Before the heated steel slab enters the continuous rolling mill for rolling, high-pressure water with a pressure of ≥200 bar is used to descale the heated steel plate to ensure that the oxide is completely descaled.

[0095] Hot rolling: the mill inlet temperature is 1170°C, the finishing outlet temperature is 930°C, the steel plate after final rolling is ultra-fast cooled at a cooling rate of 180°C / s, and then the steel plate is cooled to 640°C at 15°C / s in a laminar cooling manner for coiling, and finally rolled into a thin-gauge desert-resistant, paint-free weathering steel plate with a thickness of 1.8 mm. The desert-resistant, paint-free weathering steel in this embodiment contains the composition of Example 3 in Table 1 below.

[0096] The material grain grade of the desert climate resistant and paint-free weathering steel obtained in this embodiment is 14, the steel plate yield strength is 580 MPa, the tensile strength is 750 MPa, the elongation is 21%, d=a, and the cold bending is qualified.

[0097] Comparative Example 1

[0098] A type of plain carbon steel Q235 is selected, which contains the ingredients of Comparative Example 1 in Table 1 below. The yield strength of Q235 plain carbon steel is ≥235 MPa, the tensile strength is ≥390 MPa, and the elongation is ≥30%.

[0099] Table 1 Components and contents of the desert climate resistant coating-free weathering steel of Examples 1 to 3 and the plain carbon steel of Comparative Example 1

[0100]

[0101]

[0102] Test Section

[0103] The desert climate resistant and paint-free weathering steels of Examples 1 to 3 and the plain carbon steel of Comparative Example 1 were subjected to the Xinjiang Turpan dry desert climate corrosion test, and the test was carried out using the method of GB / T 19292.1-2018.

[0104] The relative corrosion rate of the desert climate-resistant unpainted weathering steel in the 0.01 mol / L sodium bisulfate cycle immersion test for 144 hours is 0.010 g / (m 2 ), the mathematical extrapolation curve comparison results of the dry desert climate corrosion results in Turpan, Xinjiang are as follows Figure 2 Through the extrapolation of the corrosion depth power index of the weathering steel rust layer, it is concluded that the desert climate-resistant and paint-free weathering steel of the present application has a single-sided thinning amount of less than 0.1 mm and a double-sided thinning amount of less than 0.2 mm after 25 years of service.

[0105] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A kind of desert climate resistant and paint-free weathering steel, characterized in that: The components of the desert climate resistant paint-free weathering steel include, by mass percentage: C: 0.045wt% ~ 0.065wt%, Si: 0.15wt% ~ 0.40wt%, Mn: 0.45wt% ~ 0.55wt%, P: 0.075wt% ~ 0.085wt%, Ti: 0.055wt% ~ 0.075wt%, Cr: 0.35wt% ~ 0.55wt%, Al: 0.4wt% ~ 0.6wt%, Cu: 0.13wt% ~ 0.18wt%, S: 0 ~ 0.015wt%, preferably S: 0 ~ 0.01%wt; and the remainder of Fe and inevitable trace elements.

2. The desert climate resistant paint-free weathering steel according to claim 1, characterized in that: The content of the trace elements is ≤0.0065wt%, and the trace elements include N, O, and H, where N: 0-0.0045wt%, O: 0-0.00015wt%, and H: 0-0.0015wt%.

3. The desert climate resistant paint-free weathering steel according to claim 1, characterized in that: The metallographic structure of the desert climate resistant and paint-free weathering steel comprises 80% to 90% of ferrite and 10% to 20% of pearlite.

4. The desert climate resistant paint-free weathering steel according to any one of claims 1 to 3, characterized in that: The desert climate-resistant paint-free weathering steel meets one or more of the following conditions (1) to (4): (1) The yield strength of the desert climate resistant paint-free weathering steel is 550MPa to 620MPa; (2) The tensile strength of the desert climate resistant paint-free weathering steel is greater than 720 MPa; (3) The elongation of the desert climate resistant paint-free weathering steel is greater than 18%; (4) The desert climate resistant paint-free weathering steel has the capability of being used for 25 years without painting under the bare environment C3 specified in GB / T 19292.1-2018, with uniform thinning of both sides less than 0.2 mm.

5. A method for preparing desert climate-resistant and paint-free weathering steel, characterized in that: include: Providing RH refined molten steel, wherein the RH refined molten steel comprises the components according to any one of claims 1 to 4; Continuous casting: RH refined molten steel is continuously cast to obtain slabs; Slab heating: a multi-stage heating furnace is used to heat the slab after continuous casting to increase the temperature of the slab; Hot rolling: The heated slab is subjected to rough rolling and finish rolling in sequence through a continuous rolling mill to obtain a steel plate.

6. The preparation method according to claim 5, characterized in that: The step of providing RH refined molten steel comprises: Desulfurization treatment, desulfurizing the molten iron to obtain molten iron with S≤0.01wt%; Converter smelting, smelting molten iron with S≤0.01wt% to obtain molten steel, the molten steel is treated with argon blowing to make the temperature and composition of the molten steel uniform, wherein the terminal temperature of the molten steel treated with argon blowing is ≥1535℃; LF refining, performing LF refining on the molten steel that has completed the argon blowing treatment to obtain LF refined molten steel; RH refining, RH refining is performed on the molten steel that has completed LF refining to obtain RH refined molten steel.

7. The preparation method according to claim 6, characterized in that: The LF refining step comprises: Adjust the temperature of the molten steel after argon blowing treatment to ≥1522℃; and / or, performing LF refining on the molten steel, the refining time is 40min-45min, to obtain LF refined molten steel, the outlet temperature of the LF refined molten steel is 1565°C-1580°C; And / or, adjusting the composition of the molten steel after LF refining to reach the target content requirement, and adjusting the temperature of the molten steel after LF refining to ≥1538°C for RH refining.

8. The preparation method according to claim 6, characterized in that: The RH refining step comprises: performing RH refining on the molten steel that has completed LF refining under the condition of vacuum degree ≤ 67 MPa, and the RH refining time is 22 minutes to 30 minutes.

9. The preparation method according to claim 5, characterized in that: In the slab heating step, the slab entering the furnace is at a temperature of 900°C to 1000°C, the heating temperature of the heating furnace section at the front of the heating furnace is at a temperature of 1200°C to 1250°C, the slab exiting the furnace is at a temperature of 1150°C to 1180°C, the slab heating time in the furnace is ≥30 minutes, and the excess air coefficient of the heating furnace is 0.95 to 1.05; And / or, before the steel slab after slab heating is entered into the continuous rolling mill for rolling, the heated steel plate is descaled by high-pressure water with a pressure of ≥200 bar.

10. The preparation method according to claim 5, characterized in that: The process parameters of the continuous casting step are as follows: the continuous casting speed is 4.0m / min to 4.5m / min, and the casting is performed in a light pressure reduction mode in the thickness direction; And / or, the continuous casting step also includes: adding continuous casting protection slag to the surface of the molten steel in the continuous casting mold to protect the surface of the molten steel, wherein the basicity of the continuous casting protection slag is 0.9-1.0 and the viscosity is 1.9P-2.2P.

11. The preparation method according to claim 5, characterized in that: In the hot rolling step, the rough rolling temperature is 1130°C to 1160°C, and the final rolling temperature is 820°C to 870°C; And / or, the hot rolling step further includes: ultra-fast cooling the steel plate that has completed final rolling at a cooling rate of 100°C / s to 300°C / s, and then laminar cooling at a cooling rate of 10°C / s to 25°C / s to cool the steel plate to 600°C to 650°C.

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