A production method for preventing edge cracking of a rare earth-containing iron-chromium-aluminum hot-rolled steel

Abstract

This invention belongs to the field of hot processing technology of rare earth iron-chromium-aluminum steel coils, specifically relating to a production method for preventing edge cracking of hot-rolled steel coils containing rare earth iron-chromium-aluminum, including: (1) transferring the rare earth iron-chromium-aluminum slab to a heating furnace for heating by using a hot-loading method; (2) rough rolling the rare earth iron-chromium-aluminum slab, with 7 passes and a deformation rate of 12%-16%, 18%-22%, 18%-22%, 24%-28%, 26%-30%, 28%-32%, and 30%-34% for each pass; (3) after rough rolling, heating compensation is applied to the edge of the intermediate slab; (4) after finishing rolling and coiling, a hot-rolled steel coil containing rare earth iron-chromium-aluminum is obtained. The production method of the present invention for preventing edge cracking of hot-rolled steel coils containing rare earth elements (iron, chromium, and aluminum) significantly reduces the problem of edge cracking in hot-rolled steel coils containing rare earth elements (iron, chromium, and aluminum). It can produce hot-rolled steel coils with a rare earth content of 0.02%-0.12%, a thickness of 3.0-3.5 mm, and a width of 1000-1300 mm, preventing edge cracking of hot-rolled steel coils, reducing the risk of breakage after uncoiling, and ensuring the smooth progress of subsequent production.

Description

Technical Field

[0001] This invention belongs to the field of hot working technology for steel coils containing rare earth iron, chromium, and aluminum, and specifically relates to a production method for preventing edge cracking of hot-rolled steel coils containing rare earth iron, chromium, and aluminum. Background Technology

[0002] Iron-chromium-aluminum alloy is an economical electrothermal alloy widely used in electric heating, transportation, environmental protection, and home appliances, playing a vital role in the national economy. Its high aluminum content increases resistivity, effectively converting electrical energy into heat and saving on heating materials. Furthermore, iron-chromium-aluminum alloy does not contain the precious metal Ni, making its cost approximately 30% lower than nickel-chromium and stainless steel alloys. Iron-chromium-aluminum alloy features excellent electrical resistance, high temperature resistance, strong oxidation resistance, and high cost-effectiveness. Its maximum operating temperature can reach 1400℃, and its maximum resistivity is 1.60 μΩ·cm. Combined with its economical price, this facilitates its widespread use.

[0003] Because the solidification structure is a single ferrite structure, during continuous casting, the iron-chromium-aluminum (FeCHA) steel rapidly solidifies from high-temperature molten steel. This process easily leads to the formation of coarse columnar crystals, resulting in poor toughness. As the billet temperature decreases, even with slow cooling, microcracks easily form between the dendrites of these coarse columnar crystals. Under the stress of thermal expansion and contraction, these microcracks propagate, affecting the hot working of the billet into steel plates. This is particularly noticeable at the edges of the billet, and edge cracking may even occur during subsequent hot rolling.

[0004] Extensive experimental observations have shown that adding rare earth elements to iron-chromium-aluminum alloys can improve their thermal stability, high-temperature strength, creep resistance, and oxidation resistance. Adding 0.02%-0.12% of rare earth elements La and Ce to iron-chromium-aluminum plates and strips can significantly improve the material's oxidation resistance at high temperatures. However, due to their large atomic radii, the addition of rare earth elements has a significant pinning effect, inevitably leading to a refinement of the iron-chromium-aluminum microstructure, a lag in dynamic recovery, and an inability to keep up with the hot-rolling deformation rate, thus exacerbating hot-rolling edge cracking.

[0005] In existing technologies, hot-rolled steel coils are produced using a "furnace coil rolling" process to improve the hot deformation conditions of rare-earth iron-chromium-aluminum steel. Furnace coil hot rolling keeps the steel coil at a constant temperature inside the furnace, reducing the rate of temperature drop and ensuring rolling within the optimal plasticity range. However, this process is severely constrained by rolling equipment, resulting in high energy consumption and low efficiency, thus limiting production output.

[0006] Therefore, a new production method based on hot continuous rolling equipment is needed to address the problem of edge cracking in hot rolling, specifically for rare earth iron-chromium-aluminum alloys. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a production method for preventing edge cracking of hot-rolled steel coils containing rare earth elements, iron, chromium, and aluminum.

[0008] Specifically, the production method of the present invention for preventing edge cracking of hot-rolled steel coils containing rare earth elements (iron, chromium, and aluminum) includes:

[0009] (1) The rare earth iron-chromium-aluminum slab is transferred to the heating furnace for heating by red-hot charging.

[0010] (2) Rough rolling of rare earth iron-chromium-aluminum slabs, with 7 passes and a deformation rate of 12%-16%, 18%-22%, 18%-22%, 24%-28%, 26%-30%, 28%-32%, and 30%-34% per pass;

[0011] (3) After rough rolling, the edges of the intermediate billet are heated for compensation;

[0012] (4) After precision rolling and coiling, hot-rolled steel coils containing rare earth iron, chromium and aluminum are obtained.

[0013] The above-mentioned production method for preventing edge cracking of hot-rolled steel coils containing rare earth iron, chromium, and aluminum involves transporting the slab containing rare earth iron, chromium, and aluminum in an insulated vehicle during the hot charging process. The time from the end of continuous casting to the furnace loading shall not exceed 12 hours, and the surface temperature of the slab shall not be lower than 200°C before loading.

[0014] The above-mentioned production method for preventing edge cracking of hot-rolled steel coils containing rare earth iron, chromium, and aluminum includes a heating furnace comprising a heat recovery section, a preheating section, a primary heating section, a secondary heating section, and a soaking section, with temperatures of 500-700℃, 950-1050℃, 1080-1120℃, 1130-1170℃, and 1140-1180℃, and times of 60-70min, 40-50min, 35-45min, 30-40min, and 25-30min, respectively.

[0015] The above-mentioned production method for preventing edge cracking of hot-rolled steel coils containing rare earth iron, chromium, and aluminum uses an edge heater for heating compensation, with the temperature compensation controlled within the range of 20-30℃.

[0016] The above-mentioned production method for preventing edge cracking of hot-rolled steel coils containing rare earth iron, chromium, and aluminum includes a finishing rolling process comprising 7 passes, with each pass having a deformation rate of 36%-40%, 35%-38%, 32%-35%, 24%-27%, 22%-25%, 16%-19%, and 8%-11%.

[0017] In the above-mentioned production method for preventing edge cracking of hot-rolled steel coils containing rare earth iron, chromium, and aluminum, the coiling temperature is controlled at 300-400℃.

[0018] The above production method for preventing edge cracking of hot-rolled rare-earth-containing iron-chromium-aluminum steel coils. The rare-earth-containing iron-chromium-aluminum alloy, by mass percentage, includes: 0 < C ≤ 0.08%, 0 < Si ≤ 0.5%, 0 < Mn ≤ 0.5%, 0 < P ≤ 0.025%, 0 < S ≤ 0.020%, 0 < N ≤ 0.03%, 13.0% < Cr ≤ 21.0%, 3.0% < Al ≤ 6.0%, 0 < Ti ≤ 0.30%, 0 < Nb ≤ 0.15%, 0.02% < RE ≤ 0.12%, and the balance is Fe and inevitable impurities.

[0019] The above production method for preventing edge cracking of hot-rolled rare-earth-containing iron-chromium-aluminum steel coils. The thickness of the rare-earth-containing iron-chromium-aluminum alloy slab is 180 - 200 mm, and the length is 7500 - 8500 mm; the thickness of the intermediate slab after rough rolling is 27 - 30 mm, and the thickness of the steel strip after finish rolling is 3.0 - 3.5 mm.

[0020] The above production method for preventing edge cracking of hot-rolled rare-earth-containing iron-chromium-aluminum steel coils. The temperature of rough rolling is 1040 - 1100 °C; the finishing rolling temperature is 900 - 940 °C.

[0021] The above production method for preventing edge cracking of hot-rolled rare-earth-containing iron-chromium-aluminum steel coils. The total residence time of the rare-earth-containing iron-chromium-aluminum alloy slab in the heating furnace is 10 - 12 min / 10 mm thickness.

[0022] The technical solution of the present invention has the following beneficial effects:

[0023] (1) The production method for preventing edge cracking of hot-rolled rare-earth-containing iron-chromium-aluminum steel coils of the present invention significantly reduces the problem of edge cracking of hot-rolled rare-earth-containing iron-chromium-aluminum steel coils, and can produce hot-rolled steel coils with a rare-earth content of 0.02% - 0.12%, a thickness of 3.0 - 3.5 mm, and a width of 1000 - 1300 mm, prevent edge cracking of the hot-rolled steel coils, reduce the risk of fracture after uncoiling, and ensure the smooth progress of subsequent production;

[0024] (2) The production method for preventing edge cracking of hot-rolled rare-earth-containing iron-chromium-aluminum steel coils of the present invention breaks through the restriction of rolling equipment, making it possible to stably produce hot-rolled rare-earth-containing iron-chromium-aluminum steel coils with a thickness of 3.0 - 3.5 mm and a width of 1000 - 1300 mm;

[0025] (3) The production method for preventing edge cracking of hot-rolled rare-earth-containing iron-chromium-aluminum steel coils of the present invention avoids the subsequent production cost of trimming edges, improves the成材率 (成材率 should be translated as "yield rate" in English), and significantly improves the product performance stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Various other advantages and benefits will become clear to those of ordinary skill in the art by reading the following detailed description of the preferred embodiments. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention.

[0027] Figure 1 It is a photo of the edge of a 3.0 mm thick 0Cr20Al6RE hot-rolled steel coil produced by the method of the present invention. Specific Embodiments

[0028] In order to fully understand the purpose, features and effects of the present invention, the present invention will be described in detail through the following specific embodiments. Except for the following content, the process methods of the present invention all adopt conventional methods or devices in the art. Unless otherwise specified, the following noun terms all have the meanings commonly understood by those skilled in the art.

[0029] When a numerical range is disclosed herein, the above range is considered continuous and includes the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0030] The present invention aims at the characteristics of rare-earth-containing iron-chromium-aluminum steel grades and the difficulties in the production process of hot-rolled steel coils. Through measures such as hot charging and direct delivery, controlling the heating temperature and time, specifying the rough rolling and finishing deformation rates, and using edge heaters, the hot continuous rolling of rare-earth-containing iron-chromium-aluminum slab is achieved, solving the problems of coil opening fracture and edge cracks of rare-earth-containing iron-chromium-aluminum hot-rolled steel coils, and producing hot-rolled coil plates with specifications of 3.0 - 3.5 mm and qualified surface and performance.

[0031] Among them, the rare-earth-containing iron-chromium-aluminum targeted by the present invention, by weight percentage, includes: 0 < C ≤ 0.08%, 0 < Si ≤ 0.5%, 0 < Mn ≤ 0.5%, 0 < P ≤ 0.025%, 0 < S ≤ 0.020%, 0 < N ≤ 0.03%, 13.0% < Cr ≤ 21.0, 3.0% < Al ≤ 6.0%, 0 < Ti ≤ 0.30%, 0 < Nb ≤ 0.15%, 0.02% < RE ≤ 0.12%, and the rest are Fe and inevitable impurities. Among them, RE is one or more of the elements La, Ce, Y, and Ha.

[0032] Specifically, the production method provided by the present invention for preventing edge cracking of rare-earth-containing iron-chromium-aluminum hot-rolled steel coils includes the following steps:

[0033] (1) Hot charge and directly deliver the rare-earth-containing iron-chromium-aluminum slab

[0034] Rare earth iron-chromium-aluminum slabs have a high Al content, resulting in well-developed columnar crystals and extremely high brittleness after cooling. If the slab cools down, thermal stress can cause micro-cracks to propagate into macro-cracks that affect hot working, especially at the edges. During hot rolling, these cracks can further expand into edge cracks. Therefore, slabs must be hot-loaded and transported in insulated cars during the process, with the time from the end of continuous casting to furnace loading not exceeding 12 hours, and the surface temperature of the slab not lower than 200°C before loading.

[0035] As a ferritic structure, the iron-chromium-aluminum (FeA) exhibits a significant size effect, meaning its ductility and brittleness are related to the cross-sectional thickness. To improve the toughness of the cast billet, its thickness is controlled at 180-200 mm, while the width remains at 1000-1300 mm. Considering the decrease in thermoplasticity due to temperature drop during subsequent hot rolling, the length is limited to 7500-8500 mm.

[0036] (2) The rare earth iron-chromium-aluminum slab is loaded into the heating furnace for heating.

[0037] Iron-chromium-aluminum grains grow very easily at high temperatures, so they are not suitable for prolonged high-temperature heating. Therefore, the heating furnace adopts a heating scheme with a longer low-temperature section and a shorter high-temperature section. That is, the heating furnace has five heating sections, with the temperature from low to high being the heat recovery section, preheating section, first heating section, second heating section and soaking section. The heat recovery section uses the recovered flue gas from the previous high-temperature section for heating. The furnace temperature in this area is 500-700℃ for 60-70 minutes, which minimizes the temperature rise of the billet and avoids heating stress. The preheating section starts heating with the burners, and the furnace temperature is controlled at 950-1050℃ for 40-50 minutes. The first heating section begins to raise the temperature to 1080-1120℃ for 35-45 minutes. The second heating section raises the furnace temperature to 1130-1170℃ for 30-40 minutes. The homogenization reaches 1140-1180℃ for 25-30 minutes, ensuring a furnace dwell time of 10-12 minutes per 10mm thickness (i.e., 10-12 minutes per 10mm of billet thickness).

[0038] This heating process achieves a billet temperature of over 1140℃ with a high-temperature period of less than 70 minutes, ensuring both uniform heating of the billet and reasonable control of the high-temperature period to prevent heating defects in the billet.

[0039] (3) Rough rolling of rare earth iron-chromium-aluminum slabs

[0040] Due to its poor thermoplasticity, rare earth-containing iron-chromium-aluminum (Fe-Chromium-Aluminum) requires a low-speed, low-deformation rolling process to ensure smooth rolling. Conventional Fe-Chromium-Aluminum rolling uses five passes, with high deformation rates and resistance to deformation in each pass. However, the thermoplasticity of rare earth-containing Fe-Chromium-Aluminum is insufficient to withstand such high deformation rates. Therefore, the number of rolling passes is increased to seven, with the deformation rates optimized to 12%-16%, 18%-22%, 18%-22%, 24%-28%, 26%-30%, 28%-32%, and 30%-34% for each pass. The intermediate slab thickness is rolled to 27-30 mm, and the roughing temperature is 1040-1100℃.

[0041] During the rough rolling process, the slab is constantly cooling down due to production at room temperature, especially at the edges. After seven rolling passes, the edge temperature of the intermediate slab is 20-30°C lower than that of the center. If microcracks exist at the edge of the slab, they will propagate rapidly under tension during the subsequent finish rolling process, making the edge cracking phenomenon more prominent. Therefore, an edge heater is used to compensate for the 20-30°C difference.

[0042] (4) Finish rolling and rapid cooling of rare earth iron-chromium-aluminum alloy.

[0043] Compared with conventional ferritic stainless steel, aluminum and rare earth elements provide significant solid solution strengthening, and rare earth iron-chromium-aluminum alloys exhibit significantly increased deformation resistance. To reduce the risk of edge cracking, a rush rolling strategy is adopted for finishing rolling, with large deformation in the high-temperature section and small deformation in the low-temperature section. The deformation rate per pass is 36%-40%, 35%-38%, 32%-35%, 24%-27%, 22%-25%, 16%-19%, and 8%-11%, corresponding to a strip thickness of 3.0-3.5 mm and a final rolling temperature of 900-940℃.

[0044] Both roughing and finishing rolling are carried out on a hot continuous rolling mill.

[0045] (5) Winding

[0046] To avoid the brittleness of rare earth iron-chromium-aluminum steel coils at 475℃, and to prevent secondary edge cracks caused by stress concentration during low-temperature coiling of the strip, the coiling temperature is controlled between 300-400℃.

[0047] Through practice, the production method for preventing edge cracking of hot-rolled steel coils containing rare earth iron-chromium-aluminum alloys provided by this invention reduces microcrack initiation by controlling flow time and temperature, optimizes furnace temperature and time to control grain growth and center perforation, and employs multi-pass roughing, finishing rolling, and edge heating to reduce crack propagation. As described above, the resulting hot-rolled steel coils containing rare earth iron-chromium-aluminum alloys are essentially crack-free (e.g., Figure 1 As shown in the figure, it can enter the continuous annealing and pickling process without trimming the edges, and there is no belt breakage during the production process, ensuring smooth production.

[0048] Example

[0049] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, are performed according to conventional methods and conditions.

[0050] Example 1

[0051] Using a 0Cr18Al4RE grade iron-chromium-aluminum continuous casting slab as raw material, its chemical composition by mass percentage is: C: 0.019%, Si: 0.17%, Mn: 0.09%, P: 0.014%, S: 0.001%, Cr: 17.3%, Al: 4.3%, Ti: 0.20%, Nb: 0.01%, N: 0.010%, La: 0.04%, with the remainder being Fe and other unavoidable impurities. The specifications of this rare earth-containing iron-chromium-aluminum continuous casting slab are: thickness 200mm, width 1242mm, and length 8200mm.

[0052] The production method of rare earth iron-chromium-aluminum hot-rolled steel coils in Example 1 includes the following steps:

[0053] (1) The continuous casting slab is sent to the heating furnace in an insulated car for 11 hours. The surface temperature of the slab before entering the furnace is 226-248℃.

[0054] (2) The slabs are loaded into the heating furnace. The furnace temperatures of each section are 600-640℃, 1000-1020℃, 1090-1110℃, 1140-1160℃, and 1150-1160℃, and the times are 63min, 43min, 42min, 37min, and 27min, respectively.

[0055] (3) Rough rolling after exiting the furnace, the rough rolling temperature is 1040-1060℃, and the rolling is done in 7 passes. The deformation rates are 14%, 19%, 19%, 26%, 27%, 28%, and 32%, respectively. The thickness of the intermediate billet is 29.8mm, and the edge heater is used to compensate for 22-26℃.

[0056] (4) Perform finishing rolling at a final rolling temperature of 900-920℃, rolling 7 times, with deformation rates of 38%, 36%, 34%, 26%, 23%, 17%, and 10% respectively, to obtain a steel strip with a thickness of 3.3mm, and a coiling temperature of 360-395℃.

[0057] Using the production method of rare earth iron-chromium-aluminum hot-rolled steel coil of Example 1, no edge cracking occurred during the production of 0Cr18Al4RE hot-rolled steel coil, and the hot rolling proceeded smoothly.

[0058] Example 2

[0059] Using a 0Cr20Al6RE grade iron-chromium-aluminum continuous casting slab as raw material, its chemical composition by mass percentage is: C: 0.022%, Si: 0.15%, Mn: 0.09%, P: 0.018%, S: 0.001%, Cr: 20.0%, Al: 5.5%, Ti: 0.13%, Nb: 0.13%, N: 0.008%, La: 0.08%, with the remainder being Fe and other unavoidable impurities. The specifications of this rare earth-containing iron-chromium-aluminum continuous casting slab are: thickness 180mm, width 1265mm, and length 7800mm.

[0060] The manufacturing method of the wide steel strip hot-rolled iron-chromium-aluminum alloy steel coil in Example 2 includes the following steps:

[0061] (1) The continuous casting slab is sent to the heating furnace in a heated car for 10 hours. The surface temperature of the slab before entering the furnace is 263-297℃.

[0062] (2) The slabs are loaded into the heating furnace. The furnace temperatures of each section are 660-680℃, 1020-1040℃, 1100-1120℃, 1150-1170℃, and 1160-1170℃, and the times are 64min, 46min, 42min, 35min, and 28min, respectively.

[0063] (3) Rough rolling after exiting the furnace, the rough rolling temperature is 1060-1080℃, 7 passes are rolled, the deformation rates are 13%, 18%, 19%, 25%, 27%, 29%, 31% respectively, the thickness of the intermediate billet is 27.9mm, and the edge heater is used to compensate for 24-28℃.

[0064] (4) Perform finishing rolling at a final rolling temperature of 920-940℃, rolling 7 times, with deformation rates of 38%, 36%, 34%, 26%, 24%, 18%, and 10% respectively, to obtain a steel strip with a thickness of 3.0mm, and a coiling temperature of 320-360℃.

[0065] Using the production method of rare earth iron-chromium-aluminum hot-rolled steel coils in Example 2, there are basically no cracks in the production process of 0Cr20Al6RE hot-rolled steel coils. The hot rolling is smooth and can enter the continuous line annealing and pickling production without trimming the edges.

[0066] Comparative Example 1:

[0067] Using a 0Cr18Al4RE grade iron-chromium-aluminum continuous casting slab as raw material, its chemical composition by mass percentage is: C: 0.020%, Si: 0.15%, Mn: 0.09%, P: 0.015%, S: 0.001%, Cr: 17.5%, Al: 4.2%, Ti: 0.25%, Nb: 0.01%, N: 0.009%, La: 0.05%, with the remainder being Fe and other unavoidable impurities. The specifications of this rare earth-containing iron-chromium-aluminum continuous casting slab are: thickness 200mm, width 1276mm, and length 8500mm.

[0068] The production method of rare earth iron-chromium-aluminum hot-rolled steel coils in Comparative Example 1 includes the following steps:

[0069] (1) The continuous casting slab is delivered to the heating furnace within 18 hours using a heat preservation car. The surface temperature of the slab before entering the furnace is 184-193℃.

[0070] (2) The slabs are loaded into the heating furnace. The furnace temperatures of each section are 580-620℃, 1030-1050℃, 1100-1120℃, 1160-1180℃, and 1180-1200℃, and the times are 68min, 48min, 43min, 38min, and 28min, respectively.

[0071] (3) Rough rolling after exiting the furnace, the rough rolling temperature is 1080-1100℃, rolling 5 times, with deformation rates of 20%, 29%, 34%, 37%, and 37% respectively, and the thickness of the intermediate billet is 29.8mm. No edge heater is used.

[0072] (4) Perform finishing rolling at a final rolling temperature of 880-900℃, rolling 7 times, with deformation rates of 32%, 36%, 30%, 25%, 22%, 17%, and 13% respectively, to obtain a steel strip with a thickness of 3.8mm, and a coiling temperature of 260-295℃.

[0073] Using the production method of rare earth iron-chromium-aluminum hot-rolled steel coils in Comparative Example 1, severe edge cracking occurred during the production of 0Cr18Al4RE hot-rolled steel coils, requiring edge trimming in the subsequent cold rolling process before normal production could proceed.

[0074] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art should understand that these embodiments are merely illustrative of the invention and should not be construed as limiting its scope. It should be noted that any variations and substitutions equivalent to these embodiments should be considered to be covered within the scope of the claims. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A production method for preventing edge cracking of hot-rolled steel coils containing rare earth elements (iron, chromium, and aluminum), characterized in that, Including: (1) Transfer the rare earth-containing iron-chromium-aluminum alloy slab to the heating furnace for heating by means of hot charging with insulation; Among them, the heating furnace includes a heat recovery section, a preheating section, a first heating section, a second heating section, and a soaking section, with temperatures of 500 - 700 °C, 950 - 1050 °C, 1080 - 1120 °C, 1130 - 1170 °C, 1140 - 1180 °C respectively, and times of 60 - 70 min, 40 - 50 min, 35 - 45 min, 30 - 40 min, 25 - 30 min respectively; (2) Rough roll the rare earth-containing iron-chromium-aluminum alloy slab, with 7 rough rolling passes, and the deformation rate for each pass is 12% - 16%, 18% - 22%, 18% - 22%, 24% - 28%, 26% - 30%, 28% - 32%, 30% - 34%; (3) After the rough rolling is completed, perform heating compensation on the edges of the intermediate billet; (4) Through finishing rolling and coiling, obtain a rare earth-containing iron-chromium-aluminum hot-rolled steel coil; Among them, the finishing rolling includes 7 passes, and the deformation rate for each pass is 36% - 40%, 35% - 38%, 32% - 35%, 24% - 27%, 22% - 25%, 16% - 19%, 8% - 11%.

2. The method according to claim 1, characterized in that, The hot charging with insulation uses a heat-insulated vehicle to transport the rare earth-containing iron-chromium-aluminum alloy slab, and the time from the end of continuous casting to furnace charging does not exceed 12 h, and the surface temperature of the slab before furnace charging is not lower than 200 °C.

3. The method according to claim 1, characterized in that, The heating compensation is carried out by using edge heaters, and the temperature compensation is controlled within the range of 20 - 30 °C.

4. The method according to claim 1, characterized in that, The coiling temperature is controlled at 300 - 400 °C.

5. The method according to claim 1, characterized in that, The rare earth-containing iron-chromium-aluminum alloy, by mass percentage, includes: 0 < C ≤ 0.08%, 0 < Si ≤ 0.5%, 0 < Mn ≤ 0.5%, 0 < P ≤ 0.025%, 0 < S ≤ 0.020%, 0 < N ≤ 0.03%, 13.0% < Cr ≤ 21.0%, 3.0% < Al ≤ 6.0%, 0 < Ti ≤ 0.30%, 0 < Nb ≤ 0.15%, 0.02% < RE ≤ 0.12%, and the rest is Fe and inevitable impurities.

6. The method according to claim 1, characterized in that, The thickness of the rare earth-containing iron-chromium-aluminum alloy slab is 180 - 200 mm, and the length is 7500 - 8500 mm; the thickness of the intermediate billet after rough rolling is 27 - 30 mm, and the thickness of the steel strip after finishing rolling is 3.0 - 3.5 mm.

7. The method according to claim 1, characterized in that, The temperature of the rough rolling is 1040 - 1100 °C; the finishing rolling final rolling temperature is 900 - 940 °C.

8. The method according to claim 1, characterized in that, The total residence time of the rare earth-containing iron-chromium-aluminum alloy slab in the heating furnace is 10 - 12 min / 10 mm thickness.

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