A nickel-free 900MPa grade high edge quality atmospheric corrosion resistant steel and its manufacturing method

Abstract

The present invention discloses a nickel-free 900MPa-grade high-edge-quality atmospheric corrosion-resistant steel and a manufacturing method thereof. The steel comprises the following chemical components: C 0.07%-0.10%; Si 0.40%-0.60%; Mn 1.30%-1.70%; S ≤ 0.005%; Cr 0.70%-1.00%; Cu 0.25%-0.30%; Ti 0.13%-0.15%; Alt 0.020%-0.040%; and N ≤ 0.0040%, wherein effective Ti = Ti-3.42N-1.5S ≥ 0.11%, and a weathering index I > 6.0. The present invention realizes the 900MPa-grade high-edge-quality atmospheric corrosion-resistant steel by single Ti strengthening, wherein the steel has a yield strength ≥ 800MPa, a tensile strength ≥ 900MPa, and A ≥ 18%, and the weathering index I > 6.0, and the steel has good atmospheric corrosion resistance and edge quality.

Description

Technical Field

[0001] The invention belongs to the field of steel material manufacturing, and in particular relates to a nickel-free 900 MPa grade high edge quality atmospheric corrosion resistant steel and a manufacturing method thereof. Background Art

[0002] The use of special heavy-duty containers can reduce the number of loading and unloading operations when goods are transferred between different modes of transportation, thereby reducing the resulting process costs. Replacing ordinary weathering steel SPA-H with high-strength weathering steel is a key measure to achieve lightweight containers and increase load capacity.

[0003] A large amount of precious metal elements such as chromium, nickel and copper are added to high-strength weathering steel. Among them, copper can significantly improve the corrosion resistance and antibacterial properties of steel materials. However, copper is a low-melting-point element with a melting point of only 1083°C. It is easy to precipitate along the grain boundary during heating to form a brittle phase, affecting the high-temperature plasticity of the slab. Since the edge of the slab is heated from the top, bottom and sides, the heating rate is faster than other parts of the slab, resulting in a larger amount of brittle phase. After rolling, a large amount of brittle phase falls off, resulting in serious serration defects in the hot rolled edge, reducing the qualified rate of the product, and at the same time affecting the welding of downstream users, greatly reducing the finished product rate, such as Figure 1 shown.

[0004] Currently, the industry's primary method for preventing serration defects in hot-rolled copper-containing steel is to add the precious metal element nickel. This effectively increases the solid solubility of copper in austenite, forming a nickel-copper phase with the copper in the steel, raising the melting point by 200°C and effectively improving the quality of the hot-rolled edge. However, nickel is a precious metal element and is expensive.

[0005] Chinese patent CN 105838996A discloses an 800MPa-grade high-strength weathering steel plate and its production method. The chemical composition adds 0.10-0.45% Mo as an element to improve corrosion resistance. Cr, Ni, and Cu, which are commonly added in the weathering steel industry, are not added. The alloy is expensive, and the specific corrosion resistance indicators are not mentioned.

[0006] Chinese patent CN 106756468A discloses a high-strength weathering steel for 800MPa transmission towers. The addition of 0.7-1.2% Al improves corrosion resistance. Al has a melting point of only 660°C, and the carbon content is relatively high, reaching 0.16-0.19%. Such large additions of Al and C significantly reduce the castability of the molten steel, making it very likely to cause steel leaks and slab surface quality defects.

[0007] Chinese patents CN 114411041A and CN 113278879A both disclose a method for producing 800 MPa grade high-strength weathering steel, but the addition amount of precious metal Ni is 0.05% to 0.10% and 0.12% to 0.30% respectively, resulting in high alloy cost. Summary of the Invention

[0008] The object of the present invention is to provide a nickel-free 900MPa grade high-edge quality atmospheric corrosion-resistant steel and a manufacturing method thereof. The present invention realizes a 900MPa grade high-edge quality atmospheric corrosion-resistant steel with a yield strength ≥800MPa, a tensile strength ≥900MPa, and A ≥18% through single Ti strengthening, and its weathering index I>6.0, with good atmospheric corrosion resistance and edge quality.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] Disclosed is a nickel-free 900 MPa grade high-edge quality atmospheric corrosion-resistant steel, comprising the following chemical components in weight percentage: C: 0.07% to 0.10%; Si: 0.40% to 0.60%; Mn: 1.30% to 1.70%; P: ≤0.015%; S: ≤0.005%; Cr: 0.70% to 1.00%; Cu: 0.25% to 0.30%; Ti: 0.13% to 0.15%; Alt: 0.020% to 0.040%; N ≤0.0040%; O ≤0.0030%, with the balance being Fe and unavoidable inclusions; wherein effective Ti = Ti-3.42N-1.5S ≥0.11%, and the weathering index I >6.0.

[0011] The weathering index (I) of this steel is calculated according to the modified Legault-Leckie formula in the American Society for Testing and Materials standard ASTM G101-01: I = 26.01 (%Cu) + 3.88 (%Ni) + 1.20 (%Cr) + 1.49 (%Si) + 17.28 (%P) - 7.29 (%Cu) × (%Ni) - 9.10 (%Ni) × (%P) - 33.39 (%Cu) 2 .

[0012] The thickness specification of the hot-rolled nickel-free 900 MPa grade high-edge quality atmospheric corrosion-resistant steel is 2.0 mm to 6.0 mm.

[0013] The metallographic structure of the nickel-free 900 MPa grade high-edge quality atmospheric corrosion-resistant steel is ferrite+pearlite, the ferrite grain size is 12-13 levels, and a large amount of nano-scale TiC precipitation phases are distributed in the ferrite.

[0014] The nickel-free 900 MPa grade high-edge quality atmospheric corrosion resistant steel has a yield strength of ≥800 MPa, a tensile strength of ≥900 MPa, and A of ≥18%.

[0015] The present invention also provides a method for manufacturing the nickel-free 900MPa grade high-edge quality atmospheric corrosion-resistant steel, which comprises the following steps: molten iron pretreatment → converter smelting → "LF+RH" double refining → continuous casting → slab heating → rough rolling → finishing rolling → laminar cooling → coiling; in the slab heating step, the walking beam in the heating furnace adopts a porous beam, and the blackness of the last two sections of the furnace wall is above 0.90.

[0016] The molten iron is pretreated with deep desulfurization to [S] ≤ 0.005%, and the refining adopts "LF+RH" double treatment to further reduce the content of non-metallic inclusions and the residual N, S and O contents, improve the cleanliness of the molten steel, and lay the foundation for the effective Ti content of subsequent products ≥ 0.11%.

[0017] In the continuous casting step, the entire process of molten steel casting adopts a long nozzle and uses protective slag to protect casting, argon sealing, the slab pulling speed is ≤1.5m / min, the superheat is controlled at 10℃~25℃, the secondary cooling water adopts weak cooling mode, the secondary cooling water inlet pressure is 1.15MPa, and the secondary cooling water flow rate is controlled at 360~600Nm 3 / h, with a specific water content of 0.73-0.97 L / kg. If abnormal fluctuations in parameters, casting speed, or liquid level occur during the continuous casting process, the slab surface should be flame-cleaned after it leaves the production line. These measures can effectively suppress cracks at the corners of the slab that span the wide and narrow sides, thereby preventing edge serration defects after hot coiling.

[0018] During the slab heating step, the hot rolling mill utilizes a walking beam furnace, which is divided into five sections: preheating, preheating, heating section one, heating section two, and soaking section. The first section, the preheating zone, lacks flame nozzles. Since the five sections are interconnected, this section primarily serves to collect heat and minimize waste. The remaining four sections are equipped with flame nozzles for heating.

[0019] In the last two sections of the heating furnace, without changing the original furnace structure, a large number of "chimney" shaped radiation devices with a blackness greater than 0.90 are installed on the furnace to increase the effective radiation area of the last two sections of the furnace wall to the workpiece and improve the radiation coefficient of heat transfer from the furnace to the workpiece. Figure 2 shown.

[0020] In the slab heating step, the slab after continuous casting is hot charged into the furnace to ensure that the slab entry temperature is ≥400°C, and physical heat is used to shorten the heating time of the slab in the furnace; the temperature of the slab at the end of the first heating stage is ≤1050°C; to ensure that the slab is burned through, the second heating stage is full flow and steel is burned; the soaking stage is quickly heated, and the slab heating rate in the soaking stage is ≥2°C / min; compared with the first three stages of the heating furnace, the air-fuel ratio in the last two stages of the heating furnace is reduced by >0.2, and the gas flow rate is increased by >60%, so as to reduce the heat loss carried away by the flue gas, and at the same time create conditions for rapid heating of the slab after the temperature exceeds 1050°C, thereby minimizing the time the slab is in the high temperature zone; the sum of the time of the second heating stage and the soaking stage is <60min, and the furnace discharge temperature is controlled at 1190°C to 1210°C.

[0021] In the slab heating step, the atmosphere in the heating furnace is controlled to be a reducing atmosphere, with an excess air coefficient less than 1.0, preferably 0.90 to 0.95, to reduce the generation of an oxide layer on the slab surface.

[0022] After the slab leaves the heating furnace, high-pressure descaling water is used to blow it to remove the surface oxide scale.

[0023] In the rough rolling step, in order to reduce the rolling load of the rolling mill, "3+5" round-trip rough rolling is adopted, and the temperature of the last rough rolling pass is 1050℃~1080℃ to prevent the sudden increase of rolling force due to the low slab temperature. At the same time, it is ensured that the temperature of the intermediate billet after rough rolling is outside the thermal crack sensitive temperature range. It is prohibited to use edge heaters after rough rolling.

[0024] In the finishing rolling step, 7 stands are used for continuous rolling in the austenite non-recrystallization zone, and the finishing rolling temperature is 860-900°C.

[0025] In the coiling step, the coiling temperature is controlled at 590-640° C., and the steel sheet is air-cooled to room temperature after coiling.

[0026] In the nickel-free 900 MPa grade high edge quality atmospheric corrosion resistant steel provided by the present invention, the functions and controls of the various components are as follows:

[0027] C (Carbon): As the carbon content increases, the strength of the steel increases. However, higher carbon content increases the tendency toward peritectic reaction, making it more likely for air gaps to form between the shell and the mold wall. Premature air gap formation can lead to uneven shrinkage and uneven shell thickness, which can easily cause cracks in weak spots, leading to breakouts and surface defects. Therefore, the carbon content is controlled between 0.07% and 0.10%.

[0028] Si (silicon) and Mn (manganese): Both Si and Mn increase the strength of steel, with Si being particularly effective in improving its atmospheric corrosion resistance. However, excessive Si and Mn content can significantly reduce the steel's plasticity and toughness. Therefore, the Si content is controlled between 0.40% and 0.60%, and the Mn content is between 1.30% and 1.70%.

[0029] Phosphorus (P): While P increases the strength and hardness of steel, it significantly reduces its plasticity and toughness. Especially at low temperatures, it makes the steel noticeably brittle, a phenomenon known as "cold brittleness." Cold brittleness impairs the cold working and weldability of steel. Higher P content increases the tendency toward cold brittleness, so the P content in steel is strictly controlled. Both P and Cu have low melting points and can easily precipitate brittle phases along grain boundaries, leading to surface defects. Therefore, in this application, the P content is strictly controlled to ≤ 0.015%.

[0030] Ti (titanium), N (nitrogen), S (sulfur), and O (oxygen): S reduces the ductility and toughness of steel, easily causing cracks during rolling, adversely affecting weldability, and reducing corrosion resistance. The fine, dispersed TiC particles precipitated during layer cooling and post-cooling coiling exhibit a strong precipitation strengthening effect, which is the primary reason for Ti's precipitation strengthening. Since Ti's precipitation strengthening is primarily due to the large, dispersed precipitation of fine TiC, the formation of large N and S precipitates is detrimental to Ti's precipitation strengthening, thus affecting the effective Ti content in the steel. Ti has a strong affinity for the other alloying elements in steel, O, N, and S. Fluctuations in these chemical compositions during smelting directly affect the effective Ti content, leading to significant fluctuations in product performance. Therefore, Ti is controlled to be 0.13% to 0.15%, N ≤ 0.0040%, O ≤ 0.0030%, and S ≤ 0.005%, with effective Ti = Ti - 3.42N - 1.5S ≥ 0.11%.

[0031] Cr (chromium): Cr is one of the more economical elements for improving the atmospheric corrosion resistance of steel. However, too high a Cr content will reduce welding performance and affect user use. Therefore, the Cr content is controlled to Cr: 0.70% ~ 1.00%.

[0032] Cu (copper): The prominent role of Cu in steel is to improve the atmospheric corrosion resistance of ordinary low-alloy steel. However, the melting point of Cu is only 1083°C. It is easy to precipitate along the grain boundaries to form a brittle phase, which has an adverse effect on the high-temperature plasticity of the ingot and the toughness and surface quality of the steel plate. The effect is particularly significant in nickel-free steel. Therefore, the Cu content is controlled to 0.25% to 0.30%.

[0033] In the manufacturing method of nickel-free 900MPa grade high edge quality atmospheric corrosion-resistant steel provided by the present invention, in order to address the edge quality problem that is prone to occur in nickel-free copper-containing steel, process control is performed on the entire process from continuous casting to rough rolling, targeting the nickel-free copper-containing steel within the thermal crack sensitive temperature range. At the same time, the structure of the walking beam heating furnace is optimized to form a series of key supporting processes, which effectively suppresses the edge serration defects of nickel-free copper-containing steel, ensures the excellent quality of the surface of the produced slab and the edge of the hot coil, and ensures the stability of continuous casting and rolling production.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. Without changing the original furnace structure, the present invention increases the effective radiation area of the rear two sections of the furnace wall to the workpiece, uniformizes the furnace wall blackness and increases it to above 0.90, thereby increasing the radiation coefficient of heat transfer from the furnace to the workpiece, reducing the fuel consumption of the heating furnace while making the slab heated more evenly.

[0036] 2. The slab contacts the solid walking beam in the heating furnace, causing uneven heat conduction. This not only affects the heating rate, but also leads to uneven slab temperature, affecting subsequent rolling stability. To address this issue, the present invention replaces the solid beam in the heating furnace with a porous beam that allows heat to pass through. This ensures that the slab can be fully burned through and achieve uniform temperature even under low-temperature, fast-firing conditions, thereby improving rolling stability.

[0037] 3. This invention achieves a yield strength of 800 MPa or higher, a tensile strength of 900 MPa or higher, and an A of 18% or higher through single-component Ti strengthening. By controlling the steel composition to meet a weathering index (I) greater than 6.0, the steel exhibits excellent atmospheric corrosion resistance. In a 72-hour cyclic immersion corrosion test conducted in accordance with TB / T2375-93, "Test Method for Cyclic Immersion Corrosion of Railway Weathering Steel," the corrosion rate was less than 85% of that of conventional weathering steel SPA-H, demonstrating superior atmospheric corrosion resistance.

[0038] 4. The present invention controls the entire process from continuous casting to rough rolling, targeting nickel-free copper-containing steel within the thermal crack-sensitive temperature range. At the same time, it optimizes the structure of the walking beam heating furnace to form a series of key supporting processes, effectively suppressing the edge serration defects of nickel-free copper-containing steel, ensuring the excellent quality of the surface of the produced slab and the hot rolled edge, and ensuring the stability of continuous casting and rolling production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of surface defects of copper-containing steel, a is a crack defect on the billet surface, b is a sawtooth defect on the hot rolled edge;

[0040] Figure 2 Schematic diagram of the radiation device installed in the furnace of the heating furnace, with a blackness greater than 0.90;

[0041] Figure 3 Schematic diagram of the walking beam in the heating furnace before and after the transformation, a is before the transformation, b is after the transformation;

[0042] Figure 4 Figure 2 shows the metallographic structure of the nickel-free 900 MPa high-edge quality atmospheric corrosion-resistant steel and its nanoscale TiC dispersed precipitate phase (a) and EDS spectrum (b). The white round particles in Figure a are nanoscale TiC dispersed precipitate phases.

[0043] Figure 5 Schematic diagram of the pickling surface quality of the slab corners obtained under different secondary cooling water cooling methods and slab pulling speeds during continuous casting; a shows the pickling surface quality of the slab corners obtained with strong cooling and a slab pulling speed of 1.6 m / min, and b shows the pickling surface quality of the slab corners obtained with weak cooling and a slab pulling speed of 1.4 m / min;

[0044] Figure 6 Figures a and b are the temperature distribution along the slab length before and after the heating furnace renovation, and the rolling force distribution at each pass after rolling. Figures a and b are the temperature distribution along the slab length, and b are the rolling force distribution at each pass.

[0045] Figure 7 It is the quality of hot rolled edge obtained after rolling with different heating processes. DETAILED DESCRIPTION

[0046] The invention provides a nickel-free 900 MPa grade high-edge quality atmospheric corrosion-resistant steel, comprising the following chemical components in weight percentage: C: 0.07% to 0.10%; Si: 0.40% to 0.60%; Mn: 1.30% to 1.70%; P: ≤0.015%; S: ≤0.005%; Cr: 0.70% to 1.00%; Cu: 0.25% to 0.30%; Ti: 0.13% to 0.15%; Alt: 0.020% to 0.040%; N≤0.0040%; O≤0.0030%, with the balance being Fe and unavoidable inclusions; wherein effective Ti=Ti-3.42N-1.5S≥0.11%, and the weathering index I>6.0.

[0047] The method for manufacturing the nickel-free 900 MPa grade high-edge quality atmospheric corrosion-resistant steel comprises the following steps: molten iron pretreatment → converter smelting → "LF+RH" duplex refining → continuous casting → slab heating → rough rolling → finishing rolling → laminar cooling → coiling; in the slab heating step, the walking beam in the heating furnace adopts a porous beam, and the blackness of the last two sections of the furnace wall is above 0.90.

[0048] The molten iron is pretreated with deep desulfurization to [S] ≤ 0.005%, and the refining adopts "LF+RH" double treatment to further reduce the content of non-metallic inclusions and the residual N, S and O contents, improve the cleanliness of the molten steel, and lay the foundation for the effective Ti content of subsequent products ≥ 0.11%.

[0049] In the continuous casting step, the entire process of molten steel casting adopts a long nozzle and uses protective slag to protect casting, argon gas is sealed, the slab pulling speed is ≤1.5m / min, the superheat is controlled at 10°C to 25°C, slow cooling treatment is adopted in the crystallizer, and weak cooling mode is selected for secondary cooling water.

[0050] In the slab heating step, the hot rolling is heated by a step-beam heating furnace, which is divided into 5 sections, namely preheating section, preheating section, heating section 1, heating section 2 and equalizing section. The first section is the preheating zone, which has no flame nozzle. Since the spaces of the 5 sections are interconnected, the main function of this section is to collect heat and reduce heat waste. The last 4 sections are equipped with flame nozzles and have heating capabilities. In the last 2 sections of the heating furnace, without changing the original furnace body structure, a large number of "chimney" shaped radiation devices with a blackness greater than 0.90 are installed on the furnace, which increases the effective radiation area of the furnace wall of the last 2 sections to the workpiece while increasing the radiation coefficient of heat transfer from the furnace to the workpiece, such as Figure 2 shown.

[0051] In the slab heating step, the slab after continuous casting is hot charged into the furnace to ensure that the slab entry temperature is ≥400°C; the temperature of the slab at the end of the first heating stage is ≤1050°C; the steel is burned at full flow in the second heating stage; the slab heating rate in the soaking stage is ≥2°C / min; compared with the first three stages of the heating furnace, the air-fuel ratio in the last two stages of the heating furnace is reduced by >0.2, and the gas flow rate is increased by >60%; the sum of the time of the second heating stage and the soaking stage is <60 minutes, and the furnace discharge temperature is controlled at 1190°C to 1210°C.

[0052] In the slab heating step, the atmosphere in the heating furnace is controlled to be a reducing atmosphere, and the excess air coefficient is less than 1.0, preferably 0.90 to 0.95.

[0053] After the slab leaves the heating furnace, high-pressure descaling water is used to blow it to remove the surface oxide scale.

[0054] In the rough rolling step, in order to reduce the rolling load of the rolling mill, "3+5" passes of back-and-forth rough rolling are adopted, and the temperature of the final rough rolling pass is 1050°C to 1080°C.

[0055] In the finishing rolling step, 7 stands are used for continuous rolling in the austenite non-recrystallization zone, and the finishing rolling temperature is 860-900°C.

[0056] In the coiling step, the coiling temperature is controlled at 590-640° C., and the steel sheet is air-cooled to room temperature after coiling.

[0057] The present invention is described in detail below with reference to the embodiments.

[0058] The chemical composition of each embodiment and comparative example of the present invention was tested according to GB / T 4336 "Spark Source Atomic Emission Spectrometric Analysis of Carbon Steel and Medium and Low Alloy Steel (Conventional Method)". Specific data are shown in Table 1.

[0059] Table 1 Chemical compositions of various embodiments and comparative examples of the present invention

[0060]

[0061] The main rolling process parameters and properties that affect the mechanical properties of the hot coils in the examples and comparative examples are shown in Table 2. The mechanical properties test was carried out in accordance with GB / T 228.1-2010 "Tensile tests on metallic materials - Part 1: Room temperature test methods".

[0062] Table 2 Main process parameters and mechanical properties of rolling process of embodiment and comparative examples 1 to 3

[0063]

[0064] A 72h immersion corrosion test was conducted according to TB / T 2375, using SPA-H, a weathering steel commonly used in containers, as a comparative sample. The test results are shown in Table 3. The corrosion rate of the example relative to SPA-H was less than 85%, indicating good atmospheric corrosion resistance.

[0065] Table 3 Atmospheric corrosion resistance of various embodiments and comparative examples

[0066] Relative SPA-H corrosion rate / % Example 1 84 Example 2 83 Example 3 82 Comparative Example 1 84 Comparative Example 2 102 SPA-H 100

[0067] The effects of continuous casting process parameters (secondary water cooling method, slab casting speed) on slab surface quality are shown in Table 4.

[0068] Table 4 Continuous casting process parameters and slab surface quality

[0069]

[0070] The temperature distribution along the slab length and the rolling force distribution after each pass are shown in Figure 6 After the reheating furnace renovation, the temperature uniformity along the length of the slab was significantly improved, and the overall temperature rose by 20 to 30°C. The rolling force in each pass was significantly reduced by 2750 kN to 7500 kN.

[0071] Regarding the heating process, this application uses a slab with the same chemical composition as Example 1, and obtains comparative examples a~c and examples a~c through different heating processes. The heating process parameters are shown in Table 5, and the other process parameters are the same as Example 1.

[0072] Table 5 Heating process parameters of Examples and Comparative Examples a to c

[0073]

[0074] The corresponding hot rolled edge quality after rolling of comparative examples a to c and examples a to c is shown in FIG. Figure 7 The statistical results are shown in Table 6.

[0075] Table 6

[0076]

[0077]

[0078] As can be seen from the above, the present invention achieves yield strength ≥800MPa, tensile strength ≥900MPa, A ≥18%, and weathering index I>6.0 through single Ti strengthening, and has good atmospheric corrosion resistance. At the same time, from continuous casting to rough rolling, process control is performed on the entire process of nickel-free copper-containing steel in the hot crack sensitive temperature range. At the same time, the structure of the walking-beam heating furnace is optimized to form a series of key supporting processes, which effectively suppresses the edge serration defects of nickel-free copper-containing steel, ensures the excellent quality of the surface of the produced slab and the edge of the hot coil, and at the same time ensures the stability of continuous casting and rolling production, significantly reducing the losses of downstream users caused by hot coil trimming.

[0079] The above-mentioned reference embodiments provide a detailed description of a nickel-free 900 MPa grade high-edge quality atmospheric corrosion-resistant steel and its manufacturing method. It is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A nickel-free 900MPa grade high edge quality atmospheric corrosion resistant steel, characterized in that: The chemical composition includes the following weight percentages: C: 0.07% to 0.10%; Si: 0.40% to 0.60%; Mn: 1.30% to 1.70%; P: ≤ 0.015%; S: ≤0.005%; Cr: 0.70%~1.00%; Cu: 0.25%~0.30%; Ti: 0.13%~0.15%; Alt: 0.020%~0.040%; N≤0.0040%; O≤0.0030%, the balance is Fe and unavoidable inclusions; effective Ti = Ti-3.42N-1.5S≥0.11%, weathering index I>6.0; The method for manufacturing nickel-free 900 MPa high-edge-quality atmospheric corrosion-resistant steel comprises the following steps: molten iron pretreatment → converter smelting → "LF+RH" duplex refining → continuous casting → slab heating → rough rolling → finishing rolling → laminar cooling → coiling; during the slab heating step, the walking beam in the heating furnace is a porous beam, and the blackness of the last two sections of the furnace wall is greater than 0.90; In the slab heating step, the slab after continuous casting is hot charged into the furnace to ensure that the slab entry temperature is ≥400°C, the temperature of the slab at the end of the first heating stage is ≤1050°C, the steel is burned at full flow in the second heating stage, and the slab heating rate in the soaking stage is ≥2°C / min. Compared with the first three stages of the heating furnace, the air-fuel ratio in the last two stages of the heating furnace is reduced by >0.2, and the gas flow rate is increased by >60%; the sum of the time of the second heating stage and the soaking stage is <60 minutes, and the furnace discharge temperature is controlled at 1190°C~1210°C.

2. The nickel-free 900 MPa grade high edge quality atmospheric corrosion resistant steel according to claim 1, characterized in that: The metallographic structure of the nickel-free 900 MPa grade high-edge quality atmospheric corrosion-resistant steel is ferrite+pearlite, the ferrite grain size is 12-13, and a large amount of nano-scale TiC precipitation phases are distributed in the ferrite.

3. The nickel-free 900 MPa grade high edge quality atmospheric corrosion resistant steel according to claim 1, characterized in that: The nickel-free 900 MPa grade high-edge quality atmospheric corrosion-resistant steel has a yield strength of ≥800 MPa, a tensile strength of ≥900 MPa, and A ≥18%.

4. The method for producing nickel-free 900 MPa grade high edge quality atmospheric corrosion resistant steel according to any one of claims 1 to 3, characterized in that: The manufacturing method includes the following steps: molten iron pretreatment → converter smelting → "LF+RH" duplex refining → continuous casting → slab heating → rough rolling → finishing rolling → laminar cooling → coiling; in the slab heating step, the walking beam in the heating furnace adopts a porous beam, and the blackness of the last two sections of the furnace wall is above 0.

90.

5. The manufacturing method according to claim 4, characterized in that In the continuous casting step, the entire process of molten steel casting adopts a long nozzle and uses protective slag to protect casting, argon sealing, the slab pulling speed is ≤1.5m / min, the superheat is controlled at 10℃~25℃, slow cooling treatment is adopted in the crystallizer, the secondary cooling water adopts weak cooling mode, the secondary cooling water inlet pressure is 1.15MPa, and the secondary cooling water flow rate is controlled at 360~600Nm 3 / h, specific water volume 0.73~0.97L / kg.

6. The manufacturing method according to claim 4, characterized in that In the slab heating step, the atmosphere in the heating furnace is controlled to be a reducing atmosphere, and the excess air coefficient is less than 1.

0.

7. The manufacturing method according to claim 4, characterized in that In the rough rolling step, "3+5" round-trip rough rolling is adopted, the temperature of the final rough rolling pass is 1050°C~1080°C, and the edge heater is prohibited from being used after the rough rolling.

8. The manufacturing method according to claim 4, characterized in that In the finishing rolling step, 7 stands are used for continuous rolling in the austenite non-recrystallization zone, and the finishing rolling temperature is 860-900°C.

9. The manufacturing method according to claim 4, characterized in that In the coiling step, the coiling temperature is controlled at 590-640° C., and the steel sheet is air-cooled to room temperature after coiling.

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