Preparation method of high-chromium high-molybdenum aluminum-containing ferritic stainless steel hot / cold-rolled sheet

Abstract

The invention relates to the technical field of high-chromium and high-molybdenum ferritic stainless steel, in particular to a preparation method of a high-chromium and high-molybdenum aluminum-containing ferritic stainless steel hot / cold-rolled plate. In order to solve the problems that in the prior art, in order to avoid brittle phase precipitation, the hot rolling and finish rolling temperature is high, and aluminum oxide particles and large-size carbon / nitride particles are likely to be formed, the novel preparation method of the high-chromium and high-molybdenum aluminum-containing ferrite stainless steel hot / cold-rolled sheet is provided. Comprising the following steps of smelting, casting, forging, hot rolling, annealing, acid pickling, cold rolling and recrystallization annealing, and through the forging process in the preparation method, large-size TiN and Ti / Nb (C, N) particles can be prevented from being formed; through the warm rolling process, a nanoscale Laves phase is separated out, meanwhile, a large deformation structure is formed, a large number of deformation microstructures such as shear bands and deformation bands are obtained, the problem of grain coarsening is solved, and the plasticity, toughness and corrosion resistance of the material are improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-chromium and high-molybdenum ferritic stainless steel, in particular to a method for preparing a high-chromium and high-molybdenum aluminum-containing ferritic stainless steel hot / cold rolled plate. Background Art

[0002] High-chromium and high-molybdenum ferritic stainless steel has good thermal conductivity, low linear expansion coefficient and good formability, and is widely used in acid production, seawater desalination, petrochemical and other fields. There is a greater risk of precipitation of brittle phases such as σ phase and χ phase in high-chromium and high-molybdenum ferritic stainless steel, which can easily deteriorate the plasticity, toughness and corrosion resistance of the material. In order to avoid the problem of brittle phase precipitation, the existing technology generally adopts high hot rolling final rolling temperature or alloying addition to avoid or hinder the precipitation of brittle phase.

[0003] In the prior art, for example, the patent number is 201110363876.9, and the patent name is a technical solution of a high-Cr ferritic stainless steel and its manufacturing method. By controlling the hot rolling final rolling temperature to 950-1000°C and subjecting the hot rolled plate to a high temperature 1100°C solid solution treatment, the harmful σ phase and χ phase precipitation can be completely eliminated. However, the hot rolling final rolling temperature is relatively high, and the control is relatively difficult. In the prior art, for example, the technical solution of Patent No. 202011559796.6, entitled "A method for preparing high-chromium, high-molybdenum ferritic stainless steel", uses strain-induced Laves phase precipitation at a high temperature while avoiding the precipitation of σ phase to solve the σ phase brittleness problem, but its hot rolling final rolling temperature is 960-1020°C, which is also difficult to control; In the prior art, for example, the technical solution with patent number 202211553095.0 and patent name “A super ferritic stainless steel and its preparation method” uses Al alloying to inhibit the precipitation of σ phase, and promotes the precipitation of Laves phase through solid solution treatment to refine the organization and optimize the texture. It also requires the hot rolling final rolling temperature to be ≥850°C, which is difficult to control. In addition, this solution is also very likely to cause the formation of alumina particles and coarse carbon / nitride particles in ferritic stainless steel, which in turn can easily deteriorate the plasticity, toughness and corrosion resistance of the material, seriously restricting the large-scale production and wide application of such products. Summary of the invention

[0004] In order to solve the problems in the prior art of avoiding the precipitation of brittle phases, such as high hot rolling final rolling temperature and easy formation of large-sized carbon / nitride particles and aluminum oxide particles, the present invention provides a new method for preparing high-chromium, high-molybdenum aluminum-containing ferritic stainless steel hot / cold rolled plates.

[0005] The present invention is achieved by adopting the following technical solutions: Solution 1: A method for preparing a high-chromium, high-molybdenum, aluminum-containing ferrite stainless steel hot-rolled plate comprises the following steps in sequence: 1) Melting: The weight percentage of each element in the smelting raw material is: 25.0%≤Cr≤30.0%, 0.5%≤Mo≤4.5%, 1.0%≤Ni≤4.0%, 0.15%≤Nb≤0.65%, 0.01%≤Ti≤0.35%, 0.5≤Al≤2.5%, Mn≤0.6%, Si≤1.0%, S≤0.005%, P≤0.005%, O≤0.004%, C>0%, N>0%, C+N≤0.025%, and Cr+3.3%×Mo≥35%, and the rest is Fe and unavoidable impurities. After the raw materials are configured according to the above element ratios, they are smelted to obtain molten steel; 2) Casting: The molten steel obtained in step 1) is poured into a casting in the furnace hood, and the casting is cooled to ≤1000°C in the furnace hood, and then slowly cooled to room temperature after being taken out, with a cooling rate of ≤20°C / h, and then ground; (slow cooling in the furnace reduces oxidation reaction and avoids the formation of alumina) 3) Forging: The ground ingot obtained in step 2) is heated to 1180-1280°C, the heating rate is ≤10°C / min, the temperature is kept for 1-4h, the start forging temperature is ≥1120°C, the final forging temperature is ≥960°C, and the ingot is immediately water-cooled to room temperature after forging, and the thickness after forging is 30-55mm; 4) Rough rolling: The forging blank obtained in step 3) is heated to 1100-1200°C, kept warm for 1-4 hours, and then rough rolled. If the outlet temperature of the rough-rolled plate is lower than 1000°C, it is necessary to perform secondary heating to 1100-1200°C, keep warm for 5-40 minutes, and continue rough rolling. If the outlet temperature of the rough-rolled plate is equal to or higher than 1000°C, it is not necessary to perform secondary heating and keeping warm, and continue rough rolling. The rough rolling is performed 3-10 times, and the single-pass reduction rate is ≥15%. The rough rolling is performed to a total reduction rate of ≥60%, which can reduce the thickness of the raw material, thereby reducing the number of rolling passes in the warm rolling stage, reducing the production cost, and obtaining the rough-rolled plate; (It is well known to those skilled in the art that the outlet temperature of the rough-rolled plate is higher by using the hot continuous rolling process, and secondary heating and keeping warm are not required, and the rough rolling can be directly continued again) 5) Warm rolling The rough rolled sheet obtained in step 4) is cooled to 650-800°C and warm rolled. If the outlet temperature of the hot rolled sheet is lower than 650°C, it is heated to 650-800°C and kept warm for 3-50 minutes, and warm rolled is continued. The above warm rolling steps are repeated until the sheet thickness is ≤6.5 mm, and then water-cooled to room temperature after warm rolling. 6) Solution treatment: The hot-rolled plate obtained in step 5) is subjected to solution treatment, with a heating temperature of 1030-1150°C and a holding time of 1-60 min, followed by rapid cooling to ≤10°C and a cooling rate of ≥10°C / s. (Solution treatment causes the hot-rolled stainless steel plate to recrystallize, and the Laves phase precipitation during warm rolling plays a role in pinning grain boundaries and refining grains, large deformation microstructures, shear bands, etc., improve deformation energy storage, and promote recrystallization) Principle description: The applicant has found that coarse Ti / Nb (C, N) and TiN particles are easily formed in high-chromium and high-molybdenum ferritic stainless steel, which deteriorates the plasticity and corrosion resistance of the material. The carbonitride reaction of Nb in steel overlaps with the precipitation temperature range of Laves phase, and there is a competition and transformation relationship between the two. Through large deformation and temperature control, the formation of coarse Nb carbonitride can be avoided, and nano-scale Laves phase can be formed instead. The nano-scale Laves phase can pin the recrystallization grain boundary and refine the grain. In addition, the applicant has found that the inhibitory effect of the Al element added to high-chromium-molybdenum ferritic stainless steel on the σ phase has a component upper limit. When the Al element is added more than 2.0%, its inhibitory effect on the σ phase does not increase. When the Al element is too high, that is, more than 2.5%, it is very easy to form coarse alumina particles, which reduces the plasticity and corrosion resistance of the material. Therefore, controlling the appropriate Al element and smelting process can effectively avoid the formation of alumina particles and coarse carbonitride particles.

[0006] Specifically, the C+N element added in the preparation method of the present invention does not exceed 0.025%, which weakens the formation of coarse Ti / Nb (C, N) and TiN particles to reduce the intergranular corrosion of ferritic stainless steel; adding Ni element can improve the toughness of ferritic stainless steel, and adding Nb and Ti elements is used to further eliminate the adverse effects of C and N; adding 0.5-2.5 % Al element can not only ensure the inhibition of precipitation of σ phase and χ phase, but also avoid the formation of coarse alumina particles due to excessive Al element, thereby reducing the plastic toughness of the material. In addition, vacuum melting can effectively reduce the oxidation reaction during the melting process, and Al has a low melting point. The order of adding Al element, the temperature during addition, and the added content can be controlled to allow other alloy elements to be fully melted and evenly distributed, so that Al element can be quickly mixed with the molten metal to reduce the formation of alumina. Step 3) Slow heating can avoid the occurrence of cracks due to large thermal stress inside the material, and at the same time, the elements can be fully dissolved. The final forging temperature ≥960℃ can avoid the segregation of Nb and Ti elements, thereby avoiding the formation of coarse TiN and Ti / Nb (C, N) particles. At this time, the forging temperature is in the Laves phase precipitation range, and large deformation structures and a large number of shear bands will be generated during forging, providing favorable nucleation sites for the formation of Laves phase. The large deformation structure and shear band generated at the final forging temperature can improve the deformation energy storage, which is beneficial to the recrystallization caused by the heat preservation before hot rolling, and promote the precipitation of the Laves phase. The nano-scale Laves phase plays a role in pinning the grain boundary and refining the grains for the recrystallization caused by the heat preservation before hot rolling; step 4) hot rolling and heat preservation at 1100~1200℃ can make the forging billet recrystallize and restore the plasticity of the forging billet, and at the same time make the heating temperature of the forging billet uniform, avoid the generation of cracks due to uneven temperature during hot rolling, and dissolve the Laves phase at the same time, so that it will not precipitate during the high-temperature hot rolling process; secondary heating and heat preservation can make the previous hot-rolled plate recrystallize inside, form new fine recrystallized grains, restore the plasticity of the previous hot-rolled plate, and further dissolve the Laves phase, providing element guarantee for the precipitation of the Laves phase in the warm rolling process in step 5); step 5) control the warm rolling temperature at 650~800℃ ℃, which is convenient for forming a large deformation organization, obtaining a large number of deformation microstructures such as shear bands, deformation bands, dislocation cells, etc., improving deformation energy storage, and promoting the occurrence of recrystallization during solid solution; heating and heat preservation during warm rolling can precipitate nano-scale Laves phase, which plays a role in pinning grain boundaries and refining grains for the recrystallization occurring during solid solution. If the warm rolling temperature is too low, its rolling resistance is large and the rolling mill requirements are high; step 6) the solid solution temperature is 1030~1150℃, so that the hot-rolled plate completes recrystallization, and under the joint action of the warm-rolled large deformation organization and the fine Laves phase, a fine recrystallized organization is formed, and finally a high-chromium, high-molybdenum aluminum-containing ferrite stainless steel hot-rolled plate with excellent plasticity, toughness and corrosion resistance is obtained.

[0007] Furthermore, in step 1), a vacuum induction furnace is used for smelting. During smelting, the smelting raw materials except Al are first added to the vacuum induction furnace for smelting to form a primary molten steel, and then Al is added to the primary molten steel. When Al is added, the temperature of the primary molten steel is 1500-1600°C; Furthermore, in step 4), the total reduction ratio during rough rolling is ≥ 60%.

[0008] Furthermore, in step 5), the total reduction ratio during warm rolling is ≥40%.

[0009] Option 2: A method for preparing a high-chromium, high-molybdenum, aluminum-containing ferrite stainless steel cold-rolled sheet comprises the following steps in sequence: 1) Melting: The weight percentage of each element in the smelting raw material is: 25.0%≤Cr≤30.0%, 0.5%≤Mo≤4.5%, 1.0%≤Ni≤4.0%, 0.15%≤Nb≤0.65%, 0.01%≤Ti≤0.35%, 0.5≤Al≤2.5%, Mn≤0.6%, Si≤1.0%, S≤0.005%, P≤0.005%, O≤0.004%, C≤0.015%, N≤0.010%, and Cr+3.3%×Mo≥35%, and the rest is Fe and unavoidable impurities. After the raw materials are configured according to the above element ratios, they are smelted to obtain molten steel; further, in step 1), a vacuum induction furnace is used for smelting. During the smelting, the smelting raw materials except Al are first added to the vacuum induction furnace for melting to form a primary molten steel, and then Al is added to the primary molten steel. When Al is added, the temperature of the primary molten steel is 1500-1600°C; 2) Casting: The molten steel obtained in step 1) is poured into a casting in the furnace hood, and the casting is cooled to ≤1000°C in the furnace hood, and then slowly cooled to room temperature after being taken out, with a cooling rate of ≤20°C / h, and then ground; (slow cooling in the furnace reduces oxidation reaction and avoids the formation of alumina) 3) Forging: The ground ingot obtained in step 2) is heated to 1180-1280°C, the heating rate is ≤10°C / min, the temperature is kept for 1-4h, the start forging temperature is ≥1120°C, the final forging temperature is ≥960°C, and the ingot is immediately water-cooled to room temperature after forging, and the thickness after forging is 30-55mm; 4) Rough rolling: The forging blank obtained in step 3) is heated to 1100-1200°C, kept warm for 1-4 hours, and then rough rolled. If the outlet temperature of the rough-rolled plate is lower than 1000°C, it is necessary to perform secondary heating to 1100-1200°C, keep warm for 5-40 minutes, and continue rough rolling. If the outlet temperature of the rough-rolled plate is equal to or higher than 1000°C, it is not necessary to perform secondary heating and keeping warm, and continue rough rolling. The rough rolling is performed 3-10 times, and the single-pass reduction rate is ≥15%. The rough rolling is performed to a total reduction rate of ≥60%, which can reduce the thickness of the raw material, thereby reducing the number of rolling passes in the warm rolling stage, reducing the production cost, and obtaining the rough-rolled plate; (It is well known to those skilled in the art that the outlet temperature of the rough-rolled plate is higher by using the hot continuous rolling process, and secondary heating and keeping warm are not required, and the rough rolling can be directly continued again) 5) Warm rolling The rough rolled sheet obtained in step 4) is cooled to 650-800°C and warm rolled. If the outlet temperature of the hot rolled sheet is lower than 650°C, it is heated to 650-800°C and kept warm for 3-50 minutes, and warm rolled is continued. The above warm rolling steps are repeated until the sheet thickness is ≤6.5 mm, and then water-cooled to room temperature after warm rolling. 6) Solution treatment: The hot-rolled plate obtained in step 5) is subjected to solution treatment, with a heating temperature of 1030-1150°C and a holding time of 1-60 min, followed by rapid cooling to ≤10°C with a cooling rate of ≥10°C / s to obtain a solution plate; 7) Pickling: The solid solution plate obtained in step 6) is pickled with a sulfuric acid mixture; 8) Cold rolling: The pickled solid solution plate obtained in step 7) is cold-rolled at room temperature, with a cold rolling reduction ratio of ≥50%, to obtain a cold-rolled plate; 9) Recrystallization annealing: The cold rolled sheet obtained in step 8) is subjected to recrystallization annealing at a temperature of 970-1070°C for a holding time of 0.5-120 min, and then immediately cooled to room temperature at a cooling rate of ≥50°C / s.

[0010] Principle description: The principles of steps 1) to 6) in Scheme 2 are the same as those in Scheme 1. In step 7), the oxide scale produced by solution treatment is removed by pickling to prevent the surface quality of the cold-rolled stainless steel sheet from being affected. The large cold rolling reduction rate in step 8) produces a large amount of cold-rolled deformation structure inside the material, which can provide nucleation points for the recrystallization annealing in step 9). In step 9), fine equiaxed grains are formed by controlling the annealing temperature and holding time.

[0011] Furthermore, in step 1), a vacuum induction furnace is used for smelting. During smelting, the smelting raw materials except Al are first added to the vacuum induction furnace for smelting to form a primary molten steel, and then Al is added to the primary molten steel. When Al is added, the temperature of the primary molten steel is 1500-1600°C; Furthermore, in step 4), the total reduction ratio during rough rolling is ≥ 60%.

[0012] Furthermore, in step 5), the total reduction ratio during warm rolling is ≥40%.

[0013] The beneficial effects of the present invention are as follows: the present invention realizes low-temperature hot rolling final rolling, which is convenient for controlling the hot rolling final rolling temperature. At the same time, the phenomenon that the carbonitride reaction of Nb and the precipitation temperature range of Laves phase overlap is discovered and utilized. Through large deformation and temperature control, the generation of coarse Nb carbonitride is avoided, and instead a nano-scale Laves phase is formed. In addition, by controlling the addition of Al content and controlling the addition order and addition temperature of Al during smelting, the formation of alumina is effectively reduced, thereby further improving the plasticity, toughness and corrosion resistance of the hot-rolled plate and cold-rolled plate finally generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0016] Figure 1 is the Laves phase diagram of the forging steel precipitation of the present invention; Figure 2 This is the hot-rolled structure diagram of the present invention; Figure 3 This is a recrystallized structure diagram formed after solution treatment of the present invention; Figure 4 This is a recrystallization structure diagram formed after the cold-rolled state is recrystallized; Figure 5 This is a corrosion morphology diagram of the present invention after immersion in 6% FeCl3+1% HCl solution (temperature 65±1°C) for 72 hours. DETAILED DESCRIPTION

[0017] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0018] In the description, it should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be understood as indicating or implying relative importance. It should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two elements. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0020] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Example 1

[0021] A method for preparing a high-chromium, high-molybdenum, aluminum-containing ferrite stainless steel cold-rolled sheet comprises the following steps in sequence: 1) Melting: The weight percentage of each element of the smelting raw material is: 29% Cr, 3.5% Mo, 1.0% Ni, 0.01% C, 0.01% N, 0.20% Nb, 0.01% Ti, 0.5% Mn, 0.6% Si, 0.005% S, 0.005% P, 1.5% Al, 0.004% O, and the rest is Fe and inevitable impurities. After the raw materials are configured according to the above element ratios, vacuum induction furnace smelting is carried out. During smelting, the smelting raw materials except Al are first added to the vacuum induction furnace for smelting to form primary molten steel, and then Al is added to the primary molten steel. When Al is added, the temperature of the primary molten steel is 1600° C. to obtain molten steel; 2) Casting: The molten steel obtained in step 1) is poured into a casting in a furnace hood, the casting is cooled to 1000° C. in the furnace hood, taken out and slowly cooled to room temperature at a cooling rate of 20° C. / h, and then ground; 3) Forging: The ground ingot obtained in step 2) is heated to 1180°C, the heating rate is 10°C / min, the temperature is kept for 2h, the start forging temperature is 1180°C, the final forging temperature is 960°C, and the ingot is immediately cooled to room temperature after forging. The thickness after forging is 40mm, and the ingot is obtained. Figure 1 As shown; 4) Rough rolling: The forging billet obtained in step 3) is heated to 1150°C, kept warm for 1 hour, and then rough rolled. If the outlet temperature of the rough-rolled plate is lower than 1000°C, it is necessary to perform secondary heating to 1150°C, keep warm for 5 minutes, and then continue rough rolling. If the outlet temperature of the rough-rolled plate is equal to or higher than 1000°C, it is not necessary to perform secondary heating and keeping warm, and then continue rough rolling. The single-pass reduction rate is 15%, and the total reduction rate of rough rolling is 70%, thereby obtaining a rough-rolled plate. 5) Warm rolling The rough rolled sheet obtained in step 4) is cooled to 800°C and warm rolled. The outlet temperature of the warm rolled sheet is lower than 650°C. The sheet is heated to 800°C and kept warm for 4 minutes. The warm rolling is continued. The above warm rolling steps are repeated until the sheet thickness is 5 mm and the total reduction rate is 50%. After warm rolling, the sheet is cooled to room temperature with water to obtain a warm rolled sheet. Figure 2 As shown; 6) Solution treatment: The warm rolled plate obtained in step 5) is subjected to solution treatment, with a heating temperature of 1050°C and a holding time of 40 min, followed by rapid cooling to 10°C at a cooling rate of 100°C / s to obtain a solution plate, which is a high-chromium and high-molybdenum ferrite stainless steel hot-rolled plate. The recrystallization structure diagram formed is as follows: Figure 3 As shown; The steel plates prepared by the above process were sampled and then subjected to microstructure observation and tensile property testing. The results are shown in Table 1.

[0022] Table 1

[0023] 7) Pickling: The solid solution plate obtained in step 6) is pickled with a sulfuric acid mixture; 8) Cold rolling: The pickled solid solution plate obtained in step 7) is cold rolled at room temperature with a cold rolling reduction rate of 80% to obtain a cold rolled plate; 9) Recrystallization annealing: The cold rolled sheet obtained in step 8) is subjected to recrystallization annealing at an annealing temperature of 1030°C for a holding time of 30 min, and then immediately cooled to room temperature at a cooling rate of 150°C / s to obtain a high chromium and high molybdenum ferrite stainless steel cold rolled sheet. The recrystallization structure diagram is shown in FIG. Figure 4 As shown in the figure, the corrosion morphology is as follows Figure 5 shown.

[0024] The steel plates prepared by the above process were sampled and then subjected to microstructure observation and tensile property testing. The results are shown in Table 2.

[0025] Table 2 Example 2

[0026] A method for preparing a high-chromium, high-molybdenum, aluminum-containing ferrite stainless steel cold-rolled sheet comprises the following steps in sequence: 1) Melting: The weight percentage of each element of the smelting raw material is: 27% Cr, 4.0% Mo, 2.0% Ni, 0.005% C, 0.005% N, 0.30% Nb, 0.01% Ti, 0.5% Mn, 0.7% Si, 0.005% S, 0.005% P, 1.5% Al, 0.004% O, and the rest is Fe and inevitable impurities. After the raw materials are configured according to the above element ratios, vacuum induction furnace smelting is carried out. During smelting, the smelting raw materials except Al are first added to the vacuum induction furnace for smelting to form primary molten steel, and then Al is added to the primary molten steel. When Al is added, the temperature of the primary molten steel is 1600° C. to obtain molten steel; 2) Casting: The molten steel obtained in step 1) is poured into a casting in a furnace hood, the casting is cooled to 950°C in the furnace hood, taken out and slowly cooled to room temperature at a cooling rate of 10°C / h, and then ground; 3) Forging: The ground ingot obtained in step 2) is heated to 1150°C, the heating rate is 7°C / min, the temperature is kept for 2 hours, the start forging temperature is 1150°C, the final forging temperature is 950°C, and the ingot is immediately water-cooled to room temperature after forging. The thickness after forging is 45 mm; 4) Rough rolling: The forging billet obtained in step 3) is heated to 1150°C, kept warm for 1 hour, and then rough rolled. If the outlet temperature of the rough-rolled plate is lower than 1000°C, it is necessary to perform secondary heating to 1150°C, keep warm for 5 minutes, and then continue rough rolling. If the outlet temperature of the rough-rolled plate is equal to or higher than 1000°C, it is not necessary to perform secondary heating and keeping warm, and then continue rough rolling. The single-pass reduction rate is 15%, and the total reduction rate of rough rolling is 75%, thereby obtaining a rough-rolled plate. 5) Warm rolling The rough rolled sheet obtained in step 4) is cooled to 800°C and warm rolled. The outlet temperature of the warm rolled sheet is lower than 650°C. The sheet is heated to 800°C and kept warm for 4 minutes. The warm rolling is continued. The above warm rolling steps are repeated until the sheet thickness is 5 mm and the total reduction rate is 50%. After warm rolling, the sheet is water-cooled to room temperature. 6) Solution treatment: The warm rolled plate obtained in step 5) is subjected to solution treatment, with a heating temperature of 1050°C and a holding time of 30 minutes, followed by rapid cooling to 10°C at a cooling rate of 100°C / s to obtain a solution plate; The steel plates prepared by the above process were sampled and then subjected to microstructure observation and tensile property testing. The results are shown in Table 3.

[0027] Table 3

[0028] 7) Pickling: The solid solution plate obtained in step 6) is pickled with a sulfuric acid mixture; 8) Cold rolling: The pickled solid solution plate obtained in step 7) is cold rolled at room temperature with a cold rolling reduction rate of 80% to obtain a cold rolled plate; 9) Recrystallization annealing: The cold rolled sheet obtained in step 8) is subjected to recrystallization annealing at a temperature of 1050°C for a holding time of 5 minutes, and then immediately cooled to room temperature at a cooling rate of 150°C / s.

[0029] The steel plates prepared by the above process were sampled and then subjected to microstructure observation and tensile property testing. The results are shown in Table 4.

[0030] Table 4

[0031] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of each embodiment, and they should all be covered by the protection scope of the claims. .

Claims

1. A method for preparing a high-chromium, high-molybdenum, aluminum-containing ferritic stainless steel hot-rolled plate, characterized in that: The steps are as follows: 1) Melting: The weight percentage of each element in the smelting raw materials is: 25.0%≤Cr≤30.0%, 0.5%≤Mo≤4.5%, 1.0%≤Ni≤4.0%, 0.15%≤Nb≤0.65%, 0.01%≤Ti≤0.35%, 0.5≤Al≤2.5%, Mn≤0.6%, Si≤1.0%, S≤0.005%, P≤0.005%, O≤0.004%, C>0%, N>0%, C+N≤0.025%, and Cr+3.3%×Mo≥35%, and the rest is Fe and unavoidable impurities. After the raw materials are configured according to the above element ratios, they are melted to obtain molten steel; 2) Casting: The molten steel obtained in step 1) is poured into a casting in a furnace hood, the casting is cooled to ≤1000°C in the furnace hood, taken out and slowly cooled to room temperature at a cooling rate of ≤20°C / h, and then ground; 3) Forging: The ground ingot obtained in step 2) is heated to 1180-1280°C, the heating rate is ≤10°C / min, the temperature is kept for 1-4h, the start forging temperature is ≥1120°C, the final forging temperature is ≥960°C, and the ingot is immediately water-cooled to room temperature after forging, and the thickness after forging is 30-55mm; 4) Rough rolling: The forging blank obtained in step 3) is heated to 1100-1200°C, kept warm for 1-4 hours, and then rough rolled. If the outlet temperature of the rough-rolled plate is lower than 1000°C, it is necessary to perform secondary heating to 1100-1200°C, keep warm for 5-40 minutes, and then continue rough rolling. If the outlet temperature of the rough-rolled plate is equal to or higher than 1000°C, it is not necessary to perform secondary heating and keeping warm, and then continue rough rolling. The rough rolling is performed 3-10 times, and the single-pass reduction rate is ≥15%. The rough rolling is performed to a total reduction rate of ≥60%, which can reduce the thickness of the raw material, thereby reducing the number of rolling passes in the warm rolling stage, reducing the production cost, and obtaining a rough-rolled plate; 5) Warm rolling The rough rolled sheet obtained in step 4) is cooled to 650-800°C and warm rolled. If the outlet temperature of the hot rolled sheet is lower than 650°C, it is heated to 650-800°C and kept warm for 3-50 minutes, and warm rolled is continued. The above warm rolling steps are repeated until the sheet thickness is ≤6.5 mm, and then water-cooled to room temperature after warm rolling. 6) Solution treatment: The hot rolled plate obtained in step 5) is subjected to solution treatment, with a heating temperature of 1030-1150°C and a holding time of 1-60 min, followed by rapid cooling to ≤10°C with a cooling rate of ≥10°C / s.

2. The method for preparing a high-chromium, high-molybdenum, aluminum-containing ferritic stainless steel hot-rolled plate according to claim 1, characterized in that: In step 1), a vacuum induction furnace is used for smelting. During smelting, the smelting materials except Al are first added to the vacuum induction furnace for smelting to form a primary molten steel, and then Al is added to the primary molten steel. When Al is added, the temperature of the primary molten steel is 1500-1600°C.

3. The method for preparing a high-chromium, high-molybdenum, aluminum-containing ferrite stainless steel hot-rolled plate according to claim 2, characterized in that: In step 4), the total reduction ratio during rough rolling is ≥ 60%.

4. The method for preparing a high-chromium, high-molybdenum, aluminum-containing ferritic stainless steel hot-rolled plate according to claim 3, characterized in that: In step 5), the total reduction rate during warm rolling is ≥40%.

5. A method for preparing a high-chromium, high-molybdenum, aluminum-containing ferritic stainless steel cold-rolled sheet, characterized in that: The steps are as follows: 1) Melting: The weight percentage of each element in the smelting raw material is: 25.0%≤Cr≤30.0%, 0.5%≤Mo≤4.5%, 1.0%≤Ni≤4.0%, 0.15%≤Nb≤0.65%, 0.01%≤Ti≤0.35%, 0.5≤Al≤2.5%, Mn≤0.6%, Si≤1.0%, S≤0.005%, P≤0.005%, O≤0.004%, C≤0.015%, N≤0.010%, and Cr+3.3%×Mo≥35%, and the rest is Fe and unavoidable impurities. After the raw materials are configured according to the above element ratios, they are smelted to obtain molten steel; 2) Casting: The molten steel obtained in step 1) is poured into a casting in a furnace hood, the casting is cooled to ≤1000°C in the furnace hood, taken out and slowly cooled to room temperature, the cooling rate is ≤20°C / h, and then ground; 3) Forging: The ground ingot obtained in step 2) is heated to 1180-1280°C, the heating rate is ≤10°C / min, the temperature is kept for 1-4h, the start forging temperature is ≥1120°C, the final forging temperature is ≥960°C, and the ingot is immediately water-cooled to room temperature after forging, and the thickness after forging is 30-45mm; 4) Rough rolling: The forging blank obtained in step 3) is heated to 1100-1200°C, kept warm for 1-4 hours, and then rough rolled. If the outlet temperature of the rough-rolled plate is lower than 1000°C, it is necessary to perform secondary heating to 1100-1200°C, keep warm for 5-40 minutes, and then continue rough rolling. If the outlet temperature of the rough-rolled plate is equal to or higher than 1000°C, it is not necessary to perform secondary heating and keeping warm, and then continue rough rolling. The rough rolling is performed 3-10 times, and the single-pass reduction rate is ≥15%. The rough rolling is performed to a total reduction rate of ≥60%, which can reduce the thickness of the raw material, thereby reducing the number of rolling passes in the warm rolling stage, reducing the production cost, and obtaining a rough-rolled plate; 5) Warm rolling The rough rolled sheet obtained in step 4) is cooled to 650-800°C and warm rolled. If the outlet temperature of the hot rolled sheet is lower than 650°C, it is heated to 650-800°C and kept warm for 3-50 minutes, and warm rolled is continued. The above warm rolling steps are repeated until the sheet thickness is ≤6.5 mm, and then water-cooled to room temperature after warm rolling. 6) Solution treatment: The hot rolled plate obtained in step 5) is subjected to solution treatment, with a heating temperature of 1030-1150°C and a holding time of 1-60 min, followed by rapid cooling to ≤10°C with a cooling rate of ≥10°C / s to obtain a solution plate; 7) Pickling: The solid solution plate obtained in step 6) is pickled with a sulfuric acid mixture; 8) Cold rolling: The pickled solid solution plate obtained in step 7) is cold-rolled at room temperature, with a cold rolling reduction ratio of ≥50%, to obtain a cold-rolled plate; 9) Recrystallization annealing: The cold rolled sheet obtained in step 8) is subjected to recrystallization annealing at a temperature of 970-1070°C for a holding time of 0.5-120 min, and then immediately cooled to room temperature at a cooling rate of ≥50°C / s.

6. The method for preparing a high-chromium, high-molybdenum, aluminum-containing ferritic stainless steel cold-rolled sheet according to claim 5, characterized in that: In step 1), a vacuum induction furnace is used for smelting. During smelting, the smelting materials except Al are first added to the vacuum induction furnace for smelting to form a primary molten steel, and then Al is added to the primary molten steel. When Al is added, the temperature of the primary molten steel is 1500-1600°C.

7. The method for preparing a high-chromium, high-molybdenum, aluminum-containing ferritic stainless steel cold-rolled sheet according to claim 6, characterized in that: In step 4), the total reduction ratio during rough rolling is ≥ 60%.

8. The method for preparing a high-chromium, high-molybdenum, aluminum-containing ferritic stainless steel cold-rolled sheet according to claim 7, characterized in that: In step 5), the total reduction rate during warm rolling is ≥40%.

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