Production method of high-nickel ultrathin subcritical quenching and tempering plate

Abstract

The invention provides a production method of a high-nickel ultrathin subcritical quenching and tempering plate, and belongs to the technical field of steel plate smelting. The method comprises the steps of steelmaking, slab pretreatment, slab heating, rolling, subcritical quenching and tempering. According to the production method, the problems that in an existing production process, the control difficulty of the sheet shape of the thin sheet with the thickness specification of 5-6 mm is large, and the rejection rate is high are effectively solved, the production and manufacturing cost is reduced, and the production efficiency and the product quality are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel plate smelting, in particular to a production method of high-nickel ultra-thin intercritical quenching and tempering plate. BACKGROUND

[0002] High-nickel steel plates are widely used in various industrial fields such as petroleum and natural gas, chemical equipment, nuclear power, marine and ship engineering, etc. due to their excellent corrosion resistance, high-temperature strength, toughness and special physical properties. At present, the existing production process of high-nickel alloy steel plates in China mainly adopts hot rolling + secondary quenching + tempering process to optimize the low-temperature toughness. However, the existing production process has great difficulty in controlling the shape of thin plates below 5-6 mm thickness, and the unstable shape control in the production process results in high scrap rate and high production cost. SUMMARY

[0003] The present application is made in view of the above problems, and aims to provide a production method of high-nickel ultra-thin intercritical quenching and tempering plate for producing high-nickel tempered plate with a thickness of 5-6 mm.

[0004] Specifically, the present application provides a production method of high-nickel ultra-thin intercritical quenching and tempering plate, which comprises the steps of steelmaking, slab pretreatment, slab heating, rolling, intercritical quenching and tempering; The chemical composition of the steel in the steelmaking step comprises, by mass percentage, C 0.04-0.05%, Si 0.20-0.25%, Mn 0.69-0.74%, Ni 9.0-9.2%, Mo 0.01-0.02%, V 0.001-0.003%, Nb 0.001-0.004%, Ti 0.001-0.003%, AlT 0.022-0.040%, P≤0.004%, S≤0.002%, and the rest is Fe and unavoidable impurities.

[0005] Further, the slab pretreatment step comprises removing the oxide scale from the slab and spraying antioxidant coating, wherein the overall slab coating thickness is≥200μm, and the coating thickness in the range of 300mm at the head and tail of the slab is≥300μm.

[0006] Further, the removal of the oxide scale from the slab is performed by using a grinding machine or mechanical grinding method.

[0007] Further, in the slab heating step, the furnace temperature is≤1220℃, the slab discharge temperature is≤1220℃, the residual oxygen content is≤5%, and the total slab time in the furnace is≤200min.

[0008] Further, in the slab heating step, the hearth temperature and the slab discharge temperature are controlled in the range of 1210-1220℃, and / or the billet time in the furnace is controlled in the range of 190-200 minutes.

[0009] Further, in the rolling step, high nickel-chromium rolling rollers are adopted, and two-stage rolling is performed, including rough rolling and finish rolling. The rough rolling has at least three passes with a reduction rate greater than 20%, the intermediate billet thickness is 55-65mm, the rolling passes are 3, and high-pressure water phosphorus removal is performed 3 times. The finish rolling adopts hot rolling, and no water is sprayed after finish rolling, and air cooling is performed to room temperature.

[0010] Further, in the intercritical quenching step, the intercritical heating temperature is 690-710℃, and the heating time is the plate thickness x (1-4) minutes.

[0011] Further, in the intercritical quenching step, the quenching water pressure is 0.4-0.6 MPa, and / or the quenching water amount is 2800-3500 m 3 / h, and / or the quenching roller gap is 2-4 mm, and / or the quenching roller speed is 10-12 m / min.

[0012] Further, in the tempering step, the tempering temperature is 570-590℃, and the tempering time is the plate thickness x (1-4) minutes + (45-60) minutes.

[0013] Further, the tempering step is directly performed after quenching.

[0014] Further, the thickness of the quenched and tempered plate is 5-6mm.

[0015] The present application has the following beneficial effects: In the steelmaking step, the carbon content in the molten steel is controlled in the range of 0.04-0.05%, which can ensure a certain strength, and will not cause the toughness of the steel plate to decrease due to the too high carbon content. The reasonable addition of elements such as silicon and manganese helps to improve the strength and hardness of the steel plate. Especially, the nickel content reaches 9.0-9.2%, which greatly improves the corrosion resistance, high-temperature strength and toughness of the steel plate, so that it can adapt to the harsh working environment in the fields of oil and gas, chemical equipment, etc.

[0016] In the slab pretreatment step, the mill scale is removed and the antioxidant coating is sprayed, wherein the removal of the mill scale can avoid its influence on the surface quality and performance of the steel plate in the subsequent processing process, and the use of the antioxidant coating can effectively reduce the oxidation of the slab during the heating process, especially the special requirement of the coating thickness of the head and tail of the slab, which can better protect the key parts. During the heating process of the slab, the furnace temperature, the slab discharge temperature, the residual oxygen content and the time in the furnace are strictly controlled to prevent overheating and excessive oxidation of the steel plate and ensure the uniformity and stability of the internal structure of the steel plate.

[0017] In the rolling step, two-stage rolling is carried out by using high nickel-chromium rolls, multi-pass large reduction and high-pressure water phosphorus removal operation in rough rolling, which can refine the grain and improve the strength and toughness of the steel plate. After finish rolling, air cooling to room temperature is avoided, which avoids the problem of unstable plate shape caused by water cooling and effectively controls the plate shape. In the intercritical quenching step, the intercritical heating temperature of 690-710 DEG C and the reasonable heating time can make the steel plate obtain good microstructure and improve its comprehensive performance. The precise control of water pressure, water quantity, roll gap and roll speed during quenching further ensures the quenching effect.

[0018] The tempering step is directly carried out after quenching, the tempering temperature is 570-590 DEG C, and the tempering time is reasonably calculated according to the plate thickness, which can eliminate the quenching stress, stabilize the structure, and improve the toughness and plasticity of the steel plate. In summary, the production method of the present application effectively solves the problems of difficult plate shape control and high scrap rate of 5-6mm thick steel plate in the existing production process, reduces the production cost, improves the production efficiency and product quality. BRIEF DESCRIPTION OF DRAWINGS In order to more clearly illustrate the technical solutions in the embodiments or prior art of the present application, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the drawings, and other drawings can be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0019] Figure 1 The quenching state metallographic structure diagram of the 5mm produced steel plate is shown in the figure. Figure 2 The quenched and tempered state metallographic structure diagram of the 6mm produced steel plate is shown in the figure.

[0020] The realization of the purpose of the present application, the functional characteristics and the advantages will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION

[0021] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application is described and explained below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. Based on the embodiments provided by the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present application.

[0022] Obviously, the following description is only some examples or embodiments of the present application, and for those of ordinary skill in the art, the present application can also be applied to other similar scenarios without creative efforts. In addition, it can be understood that although the efforts made in the development process can be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some changes in design, manufacture or production and the like based on the technical content disclosed in the present application are only routine technical means, and should not be understood as insufficient disclosure of the present application.

[0023] The embodiments of the first aspect of the present application provide a production method of a high-nickel ultra-thin intercritical quenching and tempering plate, the production method comprising the steps of steelmaking, slab pretreatment, slab heating, rolling, intercritical quenching and tempering; The chemical composition of the steel in the steelmaking step comprises, by mass percent: C 0.04~0.05%, Si 0.20~0.25%, Mn 0.69~0.74%, Ni 9.0~9.2%, Mo 0.01~0.02%, V 0.001~0.003%, Nb 0.001~0.004%, Ti 0.001~0.003%, AlT 0.022~0.040%, P≤0.004%, S≤0.002%, and the rest is Fe and unavoidable impurities.

[0024] The chemical composition of the steel is controlled at 0.04-0.05% carbon (C), which is a key element affecting the strength and toughness of the steel plate. The appropriate amount of carbon can ensure the steel plate has a certain strength while avoiding the decline of the toughness of the steel plate due to excessive carbon content, ensuring that the steel plate can maintain good mechanical properties under different working conditions. The silicon (Si) content is 0.20-0.25%, and silicon mainly plays a deoxidizing role in the steelmaking process, while also increasing the strength and hardness of the steel plate to some extent, enhancing the comprehensive performance of the steel plate. The manganese (Mn) content is in the range of 0.69-0.74%, manganese can improve the hardenability of the steel, increase the strength and toughness of the steel plate, and reduce the brittle transition temperature of the steel, so that the steel plate can still maintain good performance in low temperature environment. The nickel (Ni) content is as high as 9.0-9.2%, and nickel is one of the core elements for improving the performance of the steel plate. It can significantly improve the corrosion resistance of the steel plate, making the steel plate have a longer service life in corrosive environments such as oil and gas, chemical equipment, etc. At the same time, nickel can also enhance the high temperature strength and toughness of the steel plate, so that the steel plate is still stable and reliable under harsh conditions such as high temperature and high pressure. The molybdenum (Mo) content is 0.01-0.02%, and molybdenum can refine the grain size, improve the strength and toughness of the steel, especially in high temperature environment, molybdenum can effectively improve the thermal strength and creep resistance of the steel. The content of vanadium (V), niobium (Nb) and titanium (Ti) is controlled at 0.001-0.003%, 0.001-0.004% and 0.001-0.003% respectively. These micro-alloying elements can form fine carbides and nitrides in the steel, which can refine the grain size and play a role in precipitation strengthening, further improving the strength and toughness of the steel plate. The total aluminum (AlT) content is between 0.022-0.040%, and aluminum is mainly used as a deoxidizer, while it can also refine the grain size, improve the impact toughness and fatigue resistance of the steel. Phosphorus (P) and sulfur (S) are harmful elements, and their content is strictly controlled, the phosphorus content is not more than 0.004%, and the sulfur content is not more than 0.002%. Because phosphorus can cause cold brittleness of the steel, reducing the plasticity and toughness of the steel; sulfur will form sulfide inclusions, reducing the hot working performance and corrosion resistance of the steel. By strictly controlling the content of these elements, the quality and performance of the steel plate can be ensured to reach the best state, meeting the needs of different industries for high-nickel ultra-thin intercritical quenching and tempering plate. In the present embodiment, the slab is cleaned of the iron oxide scale by means of a grinding machine or mechanical grinding, and is sprayed with an anti-oxidation coating, wherein the overall coating thickness of the slab is ≥ 200 μm, and the coating thickness in the range of 300 mm at the head and tail of the slab is ≥ 300 μm. The mechanical cleaning of the iron oxide scale and the protection by means of the spraying process in the pre-treatment of the slab can effectively reduce the generation of the iron oxide scale during heating and ensure the uniformity and stability of the heating.

[0025] In the present embodiment, in the slab heating step, the furnace temperature is ≤1220℃, the slab delivery temperature is ≤1220℃, the residual oxygen content is ≤5%, and the total slab time in the furnace is ≤200 min. Further, in the slab heating step, the furnace temperature and the slab delivery temperature are both controlled in the range of 1210-1220℃, and / or the total slab time in the furnace is controlled in the range of 190-200 min.

[0026] The slab heating step strictly controls the heating temperature and the heating time of the steel billet to obtain a good austenite structure, ensuring the uniformity of the steel billet temperature and composition. Specifically, the furnace temperature and the slab delivery temperature are controlled in the range of 1210-1220℃, which can make the alloying elements in the steel fully dissolved, providing a good organizational basis for subsequent rolling and heat treatment. At the same time, the residual oxygen content is controlled to be ≤5%, which can effectively reduce the oxidation of the steel billet during heating, avoiding the influence of the thick oxide skin on the surface quality of the steel plate. The total slab time in the furnace is controlled to be ≤200 min, and is further precisely controlled in the range of 190-200 min, which can not only ensure that the steel billet is heated sufficiently, but also prevent the grain from being coarse due to the excessive heating time, thereby affecting the mechanical properties of the steel plate.

[0027] In the present embodiment, the rolling step adopts high nickel-chromium rolls to perform two-stage rolling, including rough rolling and finish rolling; the rough rolling has at least three passes with a reduction rate greater than 20%, the intermediate billet thickness is 55-65 mm, the rolling passes are 3, and high-pressure water phosphorus removal is performed 3 times; the finish rolling adopts hot rolling, and no water is sprayed after finish rolling, and air cooling is performed to room temperature. The rough rolling uses large reduction and low deformation rate to make the deformation deep into the core of the slab, thereby improving the internal quality of the steel plate; the finish rolling uses control of the cumulative reduction rate to make the as-rolled structure fully refined.

[0028] In the rolling step, high nickel-chromium rolls are used to perform two-stage rolling, which is selected because the high nickel-chromium rolls have good wear resistance and thermal fatigue resistance, and can maintain good roll shape during rolling, thereby ensuring the rolling accuracy of the steel plate. The rough rolling has at least three passes with a reduction rate greater than 20%, which can make the grains in the steel billet fully broken and refined, thereby improving the strength and toughness of the steel plate. The intermediate billet thickness is controlled in the range of 55-65 mm, the rolling passes are 3, and high-pressure water phosphorus removal is performed 3 times, which can effectively remove the iron oxide scale on the surface of the steel billet, prevent the iron oxide scale from being pressed into the surface of the steel plate, and affect the surface quality of the steel plate. The finish rolling adopts hot rolling, no water is sprayed after finish rolling, and air cooling is performed to room temperature, which avoids the problem of unstable plate shape caused by water cooling, so that the steel plate can maintain good plate shape.

[0029] In the present embodiment, in the intercritical quenching step, the intercritical heating temperature is 690-710℃, the heating time is the plate thickness x (1-4) minutes; the quenching water pressure is 0.4-0.6 MPa, and / or the quenching water volume is 2800-3500 m 3 / h, and / or the quenching roller gap is 2-4 mm, and / or the quenching roller speed is 10-12 m / min. Using a single intercritical quenching process can meet the performance requirements of 5-6 mm thin plates while significantly improving the stability of the quenched plate shape. By adjusting the quenching water pressure, quenching water volume, quenching roller gap, and quenching roller speed, a batch of stable heat treatment quenching processes can be obtained.

[0030] The intercritical heating temperature is 690-710℃, and the heating time is the plate thickness x (1-4) minutes. Heating in this temperature range can make the steel plate obtain a mixed structure of partial austenite and unsolved ferrite, which can improve the toughness and plasticity of the steel plate. If the temperature is higher than 710℃, the proportion of austenite may be too high, resulting in a decrease in the toughness of the steel plate; if the temperature is lower than 690℃, the austenitization is insufficient, affecting the strength of the steel plate. The heating time is calculated according to the plate thickness, which can ensure that steel plates of different thicknesses can obtain appropriate heating effects and fully exert the advantages of intercritical quenching.

[0031] The quenching water pressure is controlled at 0.4-0.6 MPa, and appropriate water pressure can ensure that the quenching medium is in full contact with the steel plate, achieving rapid cooling and obtaining ideal quenching structure. If the water pressure is too low, the cooling speed is not enough, and the required structure may not be formed; if the water pressure is too high, it may cause damage to the surface of the steel plate. The quenching water volume is 2800-3500 m 3 / h, and the water volume is sufficient to carry away a large amount of heat released by the steel plate during quenching, ensuring the uniformity and stability of cooling. The quenching roller gap is 2-4 mm, and a reasonable roller gap can ensure that the steel plate passes through the quenching process smoothly, while also providing support and guidance to the steel plate, preventing deformation of the steel plate during quenching. The quenching roller speed is 10-12 m / min, and appropriate roller speed can make the steel plate stay in the quenching area for an appropriate time, ensuring the consistency of the quenching effect.

[0032] In the tempering step, the tempering temperature is 570-590℃, and the tempering time is the plate thickness x (1-4) minutes + (45-60) minutes. In the tempering step, the tempering temperature is 570-590℃, and the tempering time is the plate thickness x (1-4) minutes + (45-60) minutes, and is directly performed after quenching. The tempering treatment can eliminate the internal stress generated in the quenching process, stabilize the microstructure of the steel plate, improve the toughness and plasticity of the steel plate, and make the comprehensive performance more excellent. Through the tempering treatment, the brittleness of the steel plate can be reduced, the fatigue resistance can be improved, and the service life of the steel plate can be prolonged. By using a suitable tempering process, a more ideal microstructure and performance can be obtained to obtain stable physical properties.

[0033] In the embodiment, the thickness of the quenched and tempered plate is 5-6 mm. The high-nickel ultra-thin intercritical quenching and tempering plate produced by the present application has a thickness of 5-6 mm. Through a series of precise production steps and parameter control, the problem of difficult plate shape control and high scrap rate of the thin plate of this thickness specification in the existing production process is effectively solved. The produced quenched and tempered plate has good strength, toughness, corrosion resistance and high temperature performance, and can meet the stringent requirements of the oil and gas, chemical equipment and other fields on the thin plate.

[0034] Embodiment The following examples more specifically describe the disclosure of the present application, which are only used for illustrative purposes, because various modifications and changes within the scope of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available by conventional commercial routes or synthesized according to conventional methods, and can be used directly without further treatment. Unless otherwise stated, the instruments used in the examples are available by conventional commercial routes.

[0035] Example 1 The production method of the high-nickel quenched and tempered steel plate with a thickness of 5 mm comprises the following steps: Steelmaking: the composition of the steel contains C 0.05%, Si 0.25%, Mn 0.74%, P 0.004%, S 0.001%, Ni 9.2%, Mo 0.02%, V 0.003%, Nb 0.003%, Ti 0.002%, AlT 0.025%, and the balance is Fe and unavoidable impurities; Slab pretreatment: the slab grinder is repaired and ground to remove the iron oxide scale, and the antioxidant coating is sprayed, with a coating thickness of 210μm, and a coating thickness of 310μm at the head and tail of the slab; Slab heating: hearth temperature control 1215℃, slab discharge temperature 1210℃, residual oxygen content 4.95%, total slab time in the furnace 190min; Rolling: high nickel-chromium roller is used, rough rolling has three passes with reduction rate 20.1%, 20.3%, 20.1%, the intermediate blank thickness is 62mm, high-pressure water phosphorus removal is performed for 3 times; hot rolling is used for finishing rolling, 5mm steel plate is rolled, no water is sprayed, and air cooling is performed to room temperature.

[0036] Intercritical quenching: intercritical heating temperature is 705℃, heating time for slab thickness is 12.5min, intercritical quenching process is used after discharge to prevent the steel plate from generating serious edge wave, quenching water pressure is controlled at 0.6MPa, quenching water volume is controlled at 3000m 3 / h, quenching roller gap is controlled at 2mm, quenching roller speed is controlled at 12m / min; Tempering: direct tempering after quenching, tempering temperature is 586℃, tempering time is 57.5min.

[0037] The quenching state metallographic structure chart of the 5mm steel plate produced in the embodiment is shown in Figure 1 The structure is fine lath martensite + a small amount of fine and spherical unsolved ferrite. The structure is uniform, and the grain size can reach 10 levels or finer.

[0038] Example 2 The production method of the 6mm high nickel quenched and tempered steel plate includes the following steps: Steelmaking: the composition of the steel contains C 0.045%, Si 0.25%, Mn 0.74%, P 0.004%, S 0.001%, Ni 9.0%, Mo 0.02%, V 0.003%, Nb 0.003%, Ti 0.003%, AlT 0.040%, and the rest is Fe and inevitable impurities; Slab pretreatment: the slab grinder is repaired and ground to remove the iron oxide scale, and the anti-oxidation coating is sprayed, the coating thickness is 220μm, and the coating thickness of the slab head and tail is 330μm; Slab heating: hearth temperature control 1218℃, slab discharge temperature 1215℃, residual oxygen content 4.85%, total slab time in the furnace 192min; Rolling: high nickel-chromium roller is used, rough rolling has three passes with reduction rate 20.2%, 20.3%, 20.2%, the intermediate blank thickness is 65mm, high-pressure water phosphorus removal is performed for 3 times; hot rolling is used for finishing rolling, 6mm steel plate is rolled, no water is sprayed, and air cooling is performed to room temperature; Subcritical quenching: subcritical heating temperature 708℃, heating time 15 minutes, after discharging, subcritical quenching process is used to prevent the steel plate from generating serious edge waves, quenching water pressure is controlled at 0.58MPa, quenching water volume is controlled at 3200m3 / h, quenching roll gap is controlled at 4mm, and quenching roll speed is controlled at 10m / min; Tempering: directly tempering after quenching, tempering temperature 588℃, tempering time 60 minutes.

[0039] The microstructure diagram of the 6mm production steel plate in the embodiment in the quenched and tempered state is shown in Figure 2 The microstructure is tempered sorbite + uniformly distributed undissolved ferrite / carbide. The martensite lath morphology has disappeared, and the microstructure is more stable.

[0040] The present application realizes the refinement and multiphase of the microstructure through the accurate component design (such as Nb, Ti micro-alloying) and subcritical quenching. The undissolved Nb / Ti carbonitride can pin the grain boundary and inhibit the growth of austenite grains. The ferrite in the subcritical zone further refines the martensite after quenching. This multi-phase fine-grained microstructure is the fundamental reason for high strength and high toughness.

[0041] Comparative Example 1 The present comparative example is basically the same as Example 1, except that subcritical quenching is not performed, but the prior art is used: hot rolling at 1100℃, the first quenching temperature is 860℃, the second is 780℃, both are cooled by water cooling, the tempering temperature is 200℃, and air cooling is used.

[0042] Experimental Case 1 Using a laser flatness measuring instrument or a high-precision ruler and a flat ruler, the wave height (including edge waves and middle waves) is measured once every 500mm along the length direction of the steel plate. The maximum wave height value is recorded, and the ratio of the maximum wave height value to the sample length is calculated as the flatness deviation (unit: mm / m). The results are as follows: The average maximum wave height of the 5mm production steel plate in Example 1 is ≤8mm, and the flatness deviation is ≤1.3mm / m.

[0043] The average maximum wave height of the 6mm production steel plate in Example 2 is ≤7mm, and the flatness deviation is ≤1.2mm / m.

[0044] The average maximum wave height of the 5mm production steel plate in Comparative Example 1 is ≥25mm, and the flatness deviation is ≥4.2mm / m.

[0045] The present application adopts subcritical quenching (700±10℃), at which the structure is austenite and un-dissolved ferrite two-phase region. The un-dissolved ferrite phase has high strength and poor plasticity, and the phase change stress is significantly reduced during quenching cooling, thereby effectively inhibiting the edge wave problem caused by uneven phase change. At the same time, precise control of quenching water pressure, water volume, roll gap and speed ensures the uniformity of steel plate cooling, further ensuring the plate shape.

[0046] The quenching after twice complete austenitization of Comparative Example 1 generates huge microstructure stress and thermal stress. For ultra-thin plates, their rigidity is poor and it is difficult to resist such stress, resulting in serious warping and wave deformation.

[0047] Experimental Case 2 The production steel plates of Example 1 and Example 2 were subjected to the following tests: Room temperature tensile test: According to GB / T 228.1-2021 metal material tensile test standard, samples were taken from the longitudinal direction of the sample plate and processed into standard tensile test samples. The yield strength (Rp0.2), tensile strength (Rm) and elongation after fracture (A) were tested on a universal material testing machine. The results are as follows: The yield strength (Rp0.2) of the 5mm production steel plate in Example 1 was 730MPa, the tensile strength (Rm) was 800MPa and the elongation after fracture (A) was 23.2%.

[0048] The yield strength (Rp0.2) of the 6mm production steel plate in Example 2 was 770MPa, the tensile strength (Rm) was 845MPa and the elongation after fracture (A) was 23.5%.

[0049] The yield strength (Rp0.2) of the 5mm production steel plate in Comparative Example 1 was 710MPa, the tensile strength (Rm) was 790MPa and the elongation after fracture (A) was 21.8%.

[0050] The martensite structure obtained by subcritical quenching in the present application is finer, and the fine and uniformly distributed un-dissolved ferrite contained therein can hinder crack propagation, which is beneficial to improving toughness while maintaining high strength. The single subcritical quenching + tempering process path avoids the possible grain coarsening and performance fluctuation caused by secondary quenching, so the performance is stable.

[0051] Although the twice quenching of Comparative Example 1 can refine the grains, the process is complex and improper control can easily lead to uneven structure or excessive grain growth, with a large range of performance fluctuations.

[0052] Experimental Case 3 The production steel plates of Example 1 and Example 2 were subjected to the following tests: According to GB / T 10125 standard, the sample plates are processed into the specified size with consistent surface state. Put into the neutral salt spray test box, use 5% NaCl solution, continuously spray at 35℃. Observe once every 24 hours, record the time of first red rust. The test period is 500 hours, after the end, calculate the corrosion weight loss per unit area. The results are as follows: The first red rust time of 5mm production steel plate in Example 1 is 241h, the corrosion weight loss after 500h is 112g / m 2 ; The first red rust time of 6mm production steel plate in Example 2 is 242h, the corrosion weight loss after 500h is 113g / m 2 .

[0053] The first red rust time of 5mm production steel plate in Example 1 is 225h, the corrosion weight loss after 500h is 132g / m 2 .

[0054] Since the base composition of Example 1 and Example 2 is consistent with that of Comparative Example 1, the corrosion resistance mainly depends on the Ni content, so there is little difference. But the microstructure of Example 1 and Example 2 is more uniform and dense, reducing the driving force of microelectrochemical corrosion, so the corrosion resistance is slightly better. This proves that the present application does not sacrifice its core corrosion resistance while optimizing the plate shape and mechanical properties.

[0055] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A production method of a high-nickel ultra-thin intercritical quenched and tempered plate, characterized by, The production method comprises the steps of steelmaking, slab pretreatment, slab heating, rolling, intercritical quenching and tempering. The chemical composition of the steel in the steelmaking step comprises, by mass percentage, C 0.04-0.05%, Si 0.20-0.25%, Mn 0.69-0.74%, Ni 9.0-9.2%, Mo 0.01-0.02%, V 0.001-0.003%, Nb 0.001-0.004%, Ti 0.001-0.003%, AlT 0.022-0.040%, P≤0.004%, S≤0.002%, and the balance of Fe and inevitable impurities.

2. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 1, characterized in that, The slab pretreatment step comprises removing the oxide scale from the slab and spraying an antioxidant coating, wherein the overall slab coating thickness is≥200μm, and the coating thickness in the range of 300mm at the head and tail of the slab is≥300μm.

3. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 2, characterized in that, The removal of the oxide scale from the slab is performed by means of a grinding machine or mechanical grinding.

4. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 1, characterized in that, In the slab heating step, the furnace temperature is≤1220℃, and / or the slab discharge temperature is≤1220℃, and / or the residual oxygen content is≤5%, and / or the total slab time in the furnace is≤200min.

5. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 4, characterized in that, In the slab heating step, the furnace temperature and the slab discharge temperature are both controlled in the range of 1210-1220℃, and / or the slab time in the furnace is controlled in the range of 190-200min.

6. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 1, characterized in that, The rolling step is performed by using high-nickel-chromium rolls and two-stage rolling, including rough rolling and finish rolling. The rough rolling has at least three passes with a reduction rate of more than 20%, the intermediate slab thickness is 55-65mm, the rolling passes are 3, and high-pressure water is used for dephosphorization for 3 times. The finish rolling is performed by hot rolling, and no water is sprayed after the finish rolling, and the slab is air-cooled to room temperature.

7. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 1, characterized in that, In the intercritical quenching step, the intercritical heating temperature is 690-710℃, and the heating time is the slab thickness×(1-4)min.

8. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 7, characterized in that, The quenching water pressure in the sub-critical quenching step is 0.4-0.6 MPa, and / or the quenching water amount is 2800-3500 m 3 / h, and / or the quenching roller gap is 2-4 mm, and / or the quenching roller speed is 10-12 m / min.

9. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 1, characterized in that, In the tempering step, the tempering temperature is 570-590℃, and the tempering time is the slab thickness×(1-4)min+(45-60)min.

10. The production method of high nickel ultra-thin intercritical quenched and tempered plate according to claim 1, characterized in that, The thickness of the quenched and tempered plate is 5-6mm.

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