JP5919711B2 - Method for producing Al-containing ferritic stainless steel hot-rolled steel strip, Al-containing ferritic stainless steel hot-rolled steel strip, stainless steel foil, and catalyst carrier for automobile exhaust gas purification device - Google Patents

Description

  The present invention relates to a method for producing an Al-containing ferritic stainless hot-rolled steel strip excellent in surface properties and toughness, an Al-containing ferritic stainless hot-rolled steel strip, a stainless steel foil, and a catalyst carrier for an automobile exhaust gas purification device.

  Ferritic stainless steel made of Fe-Cr-Al alloy has excellent oxidation resistance at high temperatures, so it is processed into a foil shape with a thickness of 100 μm or less, and is a member for exhaust gas purification devices such as automobiles, motorcycles, marine bikes, motor boats, etc. In addition to being used for (for example, catalyst carriers, various sensors, etc.), it is also used for heating elements such as heaters, gas burners, heating furnace members, or heaters utilizing its high electrical resistivity characteristics. Has a wide range of uses.

  The exhaust gas regulations are expected to be further strengthened in the future, and the temperature of the exhaust gas itself tends to rise to improve fuel efficiency. The stainless steel foil used for the catalyst carrier for the exhaust gas purifying apparatus to be used in a harsher environment has been required to have higher strength at high temperature in addition to oxidation resistance at high temperature. Therefore, the present applicant has added 15 to 35 mass% Cr steel including a component system with an increased Cr content in addition to the Al-containing ferritic stainless steel represented by the 20 mass% Cr-5 mass% Al system. Ferrite-based Al-containing stainless steel with enhanced strength at high temperatures and oxidation resistance at high temperatures by adding Mo, W and appropriate amounts of REM to the base, and further reducing the contents of Nb, Ta, and Ce Steel was invented (Japanese Patent Application Nos. 2011-051279 and 2011-081600). According to the present invention, not only strength at high temperature but also salt corrosion resistance can be improved, and the application range of Al-containing ferritic stainless steel is remarkably expanded.

  While Al-containing ferritic stainless steels have the advantages described above, hot-rolled sheet toughness is significantly inferior to other ferritic stainless steels, often during hot-rolled coil deployment or cold rolling. The plate broke and caused equipment trouble. In particular, the ferritic Al-containing stainless steel having improved strength at high temperatures and oxidation resistance at high temperatures invented by the present applicant, because the hot-rolled sheet toughness is lowered and cracking is likely to occur because the strength is increased. Establishment of a stable production method has been desired.

  In general, as a factor of hot rolled sheet toughness reduction of ferritic stainless steel, precipitation of carbonitride and intermetallic compound generated during hot rolling or cooling after completion of hot rolling and brittleness at 475 ° C. can be mentioned, It is known that when it is held at around 800 ° C. and around 475 ° C., it appears and lowers the hot rolled sheet toughness. These embrittlements become prominent when the Cr content exceeds about 20% by mass. Therefore, in order to improve the hot-rolled sheet toughness of the high Cr ferritic stainless steel, the embrittlement occurs during cooling after hot rolling. It is important to pass through the temperature range as quickly as possible. Therefore, for example, Patent Document 1 discloses a method in which a coil is wound at a temperature of more than 500 ° C. and less than 850 ° C. after the hot rolling is completed, and then the coil is water-cooled. A method is disclosed in which coil rolling is performed immediately after coiling at 600 [deg.] C. or lower after coiling is finished, followed by bell annealing at 700 to 850 [deg.] C. and then coil water cooling again. Patent Document 3 discloses a method in which water-cooling is performed at a cooling rate of 10 ° C./second or more after the hot rolling is completed, and winding is performed at 450 ° C. or less.

JP 2004-270026 A Japanese Patent Laid-Open No. 5-148548 JP 60-228616 A

  However, the methods described in Patent Document 1 and Patent Document 2 require special equipment for water-cooling or heating the hot-rolled coil, which leads to an increase in cost, and the hot-rolled coil that has been wound due to shrinkage during cooling. Deviations occurred in the coil, causing defects such as scratches and baldness. Further, in the method described in Patent Document 3, winding is performed at a temperature significantly lower than that of a general stainless steel hot-rolled steel strip manufacturing method of 450 ° C. or lower, so that the shape changes during rapid cooling after hot rolling. Occurs, and the surface of the hot-rolled sheet has many defects. When rapidly cooling and winding at a low temperature of 450 ° C. or lower, surface defects occur due to contact with the guide portion due to meandering of the steel strip deformed during rapid cooling, and entanglement of fragments generated in the coil at that time There was also. Surface defects caused by hot rolling tend to remain in the final product, causing defects such as surface flaws and holes after cold rolling. Such a defective portion needs to be temporarily stopped during cold rolling and removed by cutting, partial polishing, or the like, which causes a decrease in production efficiency. That is, in any technique, the hot-rolled steel strip is rapidly cooled to a low temperature for the purpose of improving toughness, but the surface properties of the hot-rolled sheet are lowered, leading to a decrease in productivity.

  The present invention solves these problems, improves the surface properties without reducing toughness, and can produce a high Al content ferritic stainless steel hot rolled steel strip that can be produced in a stable production process, and a high Al content An object is to provide a ferritic stainless steel hot-rolled steel strip, a stainless steel foil, and a catalyst carrier for an automobile exhaust gas purification device.

  The inventors of the present invention have intensively studied to solve the above problems, and can achieve the above object by appropriately controlling the Al content and setting appropriate cooling and winding conditions after hot rolling. I found. That is, the present invention is summarized by the features shown in the following [1] to [8].

  [1] By mass%, C: 0.05% or less, Si: 2.0% or less, Mn: 1.0% or less, S: 0.003% or less, P: 0.05% or less, Cr: 15 0.0 to 35.0%, Ni: 0.05 to 0.30%, Al: 3.0 to 10.0%, N: 0.10% or less, Ti: 0.02% or less, Nb: 0.0. 02% or less, Ta: 0.02% or less, Zr: 0.005 to 0.20%, Ce: 0.02% or less, REM excluding Ce: 0.03 to 0.20%, among Mo and W When hot-rolling a steel containing at least one kind in a total of 0.5 to 8.0% and the balance being Fe and inevitable impurities, the hot rolling is finished at a temperature of 850 ° C. or higher, and then 10 ° C. Al-containing ferrule characterized in that it is wound into a hot-rolled coil after being rapidly cooled to 500 ° C. to 650 ° C. at a cooling rate of at least / sec. Method for producing a preparative stainless hot rolled steel strip.

  [2] The steel is further characterized by containing, by mass%, Hf: 0.01 to 0.20%, mass ppm, Ca: 10 to 300 ppm, and Mg: 15 to 300 ppm. The method for producing an Al-containing ferritic stainless steel hot-rolled steel strip according to [1].

  [3] The Al-containing ferritic stainless steel hot-rolled as described in [1] or [2] above, wherein a surface defect occurrence rate is 3% or less and a ductile-brittle transition temperature is 150 ° C. or less. Steel strip manufacturing method. However, the defect occurrence rate is a value obtained by (defect occurrence area / inspection execution area × 100), and the ductility-brittle transition temperature is a value obtained by conducting a Charpy impact test on a hot-rolled steel strip.

  [4] By mass%, C: 0.05% or less, Si: 2.0% or less, Mn: 1.0% or less, S: 0.003% or less, P: 0.05% or less, Cr: 15 0.0 to 35.0%, Ni: 0.05 to 0.30%, Al: 3.0 to 10.0%, N: 0.10% or less, Ti: 0.02% or less, Nb: 0.0. 02% or less, Ta: 0.02% or less, Zr: 0.005 to 0.20%, Ce: 0.02% or less, REM excluding Ce: 0.03 to 0.20%, among Mo and W When hot-rolling a steel containing at least one kind in a total of 0.5 to 8.0% and the balance being Fe and inevitable impurities, the hot rolling is finished at a temperature of 850 ° C. or higher, and then 10 ° C. Al-containing, characterized in that it was obtained as a hot-rolled coil after being rapidly cooled to 500 ° C. to 650 ° C. at a cooling rate of at least / sec. Ferritic stainless hot rolled steel strip.

  [5] The steel further includes, in mass%, Hf: 0.01 to 0.20%, mass ppm, Ca: 10 to 300 ppm, and Mg: 15 to 300 ppm. The Al-containing ferritic stainless steel hot-rolled steel strip according to [4].

  [6] The hot-rolled steel strip according to the above [4] or [5], wherein the surface defect occurrence rate is 3% or less and the ductile-brittle transition temperature is 150 ° C. or less. However, the defect occurrence rate is a value obtained by (defect occurrence area / inspection execution area × 100), and the ductility-brittle transition temperature is a value obtained by conducting a Charpy impact test on a hot-rolled steel strip.

  [7] A stainless steel foil obtained by rolling the Al-containing ferritic stainless steel hot-rolled steel strip according to any one of [4] to [6], wherein the foil thickness is 100 μm or less.

  [8] A catalyst carrier for an automobile exhaust gas purification apparatus using the stainless steel foil according to [7].

  According to the present invention, it is possible to obtain a hot-rolled steel strip having excellent surface properties and toughness of stainless steel which is excellent in strength at high temperature and oxidation resistance at high temperature, and also excellent in salt corrosion resistance. Furthermore, it is possible to remarkably reduce manufacturing troubles and greatly improve productivity.

It is a figure which shows the influence of Al content on the hardness change at the time of aging at various temperatures.

  Hereinafter, the present invention will be described in detail. Regarding chemical components,% means mass%, and ppm means mass ppm.

(1) Chemical component C: 0.05% or less When the C content exceeds 0.05%, the strength at high temperature decreases and the oxidation resistance at high temperature also decreases. Moreover, the fall of manufacturability by the fall of toughness is also caused. Therefore, the C content is 0.05% or less, preferably 0.02% or less, but more preferably reduced as much as possible.

Si: 2.0% or less When the Si content exceeds 2.0%, the toughness is lowered, and the production becomes difficult due to the lowered workability. Therefore, the Si content is 2.0% or less, preferably 1.0% or less.

Mn: 1.0% or less When the Mn content exceeds 1.0%, the oxidation resistance at high temperatures decreases. In addition, the salt corrosion resistance is reduced. Therefore, the Mn content is 1.0% or less, preferably 0.5% or less.

S: 0.003% or less When the S content exceeds 0.003%, the adhesion of the Al ₂ O ₃ film on the catalyst carrier and the oxidation resistance at high temperatures are lowered. Therefore, the S content is 0.003% or less, preferably 0.001% or less, but more preferably reduced.

P: 0.05% or less When the P content exceeds 0.05%, the adhesion of the Al ₂ O ₃ film on the catalyst carrier and the oxidation resistance at high temperatures are lowered. Therefore, the P content is 0.05% or less, preferably 0.03% or less, but more preferably reduced.

Cr: 15.0-35.0%
Cr is an indispensable element for securing strength and oxidation resistance at high temperatures, so 15.0% or more is added. However, if the Cr content exceeds 35.0%, brittleness at 475 ° C. is promoted, so that the toughness is remarkably lowered, and it becomes difficult to suppress embrittlement using the technique of the present invention. Therefore, the Cr content is 15.0 to 35.0%, preferably 18.0 to 32.0%. However, particularly when high temperature strength and oxidation resistance are required, it is more preferable to add 25.0 to 32.0%.

Ni: 0.05-0.30%
Since Ni has an effect of improving the brazing property at the time of molding the catalyst carrier, its content is set to 0.05% or more. However, when the content of Ni, which is an austenite stabilizing element, exceeds 0.30%, solid solution Al in the foil decreases during oxidation at high temperature, and austenite is generated when Cr begins to be oxidized. As a result, the coefficient of thermal expansion of the foil is changed, and defects such as foil constriction and breakage (cell breakage) occur. Therefore, the Ni content is 0.05 to 0.30%, preferably 0.08 to 0.20%.

Al: 3.0 to 10.0%
Al is an element that plays a very important role in the present invention. Al forms a highly protective Al ₂ O ₃ film on the surface and improves oxidation resistance at high temperatures. If the Al content is less than 3.0%, sufficient oxidation resistance cannot be obtained. On the other hand, if the Al content exceeds 10.0%, the workability is remarkably lowered and rolling becomes difficult.

  Furthermore, the present inventors added that Al of 3.0% or more has an effect of suppressing precipitation of intermetallic compounds such as σ phase and brittleness at 475 ° C., which occurs during cooling after hot rolling. I found out. Steel No. shown in Table 1 1 to 6 steel (C: 0.004 to 0.009%, Si: 0.15 to 0.18%, Mn: 0.13 to 0.16%, S: 0.0007 to 0.0009%, P: 0.023 to 0.025%, Cr: 24.8 to 25.9%, Ni: 0.10 to 0.16%, Al: 0.01 to 10.8%, N: 0.005 0.008%, Ti: 0.004-0.006%, Nb: 0.005-0.012%, Ta: 0.002-0.009%, Zr: 0.031-0.039%, Ce : 0.005 to 0.010%, La: 0.062 to 0.092%, Mo: 2.83 to 3.12%, Ca: 15 to 30 ppm, Mg: 13 to 30 ppm, the balance being Fe And an alloy composed of inevitable impurities), and the amount of change in hardness of samples quenched in water after aging at various temperatures for 100 hours. The effect of the to Al content shown in FIG. Here, the amount of change in hardness is the difference between Vickers hardness before aging and after aging, and generally the toughness tends to decrease as the hardness increases. When the Al content was less than 3.0%, σ brittleness due to precipitation of intermetallic compounds occurred at 800 ° C aging, and 475 ° C brittleness occurred at 500 ° C aging. With the increase in the hardness, an increase in hardness at 800 ° C. and 500 ° C. was suppressed. This effect becomes remarkable by containing 3.0% or more. Therefore, the Al content is set to 3.0 to 10.0%. Preferably it is 4.5 to 6.5%. In addition, although hardly any change in hardness was observed at aging at 600 ° C. and 1000 ° C., it is considered that precipitation of intermetallic compounds and brittleness at 475 ° C. do not occur at these temperatures.

N: 0.10% or less When the N content exceeds 0.10%, the toughness is lowered, and the production becomes difficult due to the lowered workability. Therefore, the N content is 0.10% or less, preferably 0.05% or less.

Ti: 0.02% or less Ti is an element that is easily oxidized. When the content exceeds 0.02%, a large amount of Ti oxide is mixed in the Al ₂ O ₃ film, the brazing property is remarkably lowered, and the oxidation resistance at high temperature is also lowered. Therefore, the Ti content is 0.02% or less, preferably 0.01% or less, but more preferably reduced as much as possible.

Nb: 0.02% or less If the Nb content exceeds 0.02%, a non-protective oxide film of (Fe, Al) NbO ₄ is formed, and the oxidation resistance at high temperatures is significantly reduced. In addition, (Fe, Al) NbO ₄ has a large coefficient of thermal expansion, which facilitates deformation of the foil and causes catalyst peeling. Therefore, the Nb content is 0.02%, preferably 0.01% or less, but more preferably reduced as much as possible.

Ta: 0.02% or less Similar to Nb, when the Ta content exceeds 0.02%, (Fe, Al) TaO ₄ has no protective property, and an oxide film having a large coefficient of thermal expansion is generated. While the oxidation resistance is remarkably lowered, the deformation of the foil is promoted and the catalyst is peeled off. Therefore, the Ta content is 0.02%, preferably 0.01% or less, but more preferably reduced.

  The total content of Nb and Ta is more preferably 0.03% or less, and further preferably 0.02% or less.

Zr: 0.005 to 0.20%
Zr combines with C and N in the steel to improve the creep characteristics. In addition, the toughness is improved and the workability is improved to facilitate the production of the foil. Furthermore, it concentrates in the Al ₂ O ₃ grain boundary in the Al ₂ O ₃ film to improve the oxidation resistance at high temperature, the strength at high temperature, particularly the deformation resistance. In order to obtain such an effect, the Zr content needs to be 0.005% or more. On the other hand, if the Zr content exceeds 0.20%, an intermetallic compound such as Fe is produced, and the oxidation resistance is lowered. Therefore, the Zr content is 0.005 to 0.20%, preferably 0.01 to 0.05%.

Ce: 0.02% or less When the Ce content exceeds 0.02%, a CeO-type oxide is formed at the interface between the Al ₂ O ₃ coating and the base steel surface, and the strength at high temperatures, particularly deformation resistance, is increased. Remarkably deteriorates and causes shape defects. Therefore, the Ce content is 0.02% or less, but it is more preferable to reduce it as much as possible.

REM excluding Ce: 0.03-0.20%
REM excluding Ce refers to 14 elements such as La, Nd, and Sm excluding Ce having atomic numbers 57 to 71. Generally, REM improves the adhesion of the _Al 2 _{O 3} film has a very significant effect on peeling resistance improving _Al 2 _{O 3} film. In order to obtain such an effect, the REM content excluding Ce needs to be 0.03% or more. On the other hand, when the REM content excluding Ce exceeds 0.20%, these elements concentrate and precipitate at the crystal grain boundaries, melt during high-temperature heating, and cause surface defects of the hot-rolled sheet. Therefore, the REM content excluding Ce is 0.03 to 0.20%, preferably 0.05 to 0.10%.

At least one of Mo and W: 0.5 to 8.0% in total
Mo and W increase the strength at high temperature, particularly Young's modulus and breaking stress, and the life of the catalyst carrier is improved. These elements simultaneously stabilize the Al ₂ O ₃ film and improve the salt corrosion resistance. In order to obtain such an effect, the content of at least one of Mo and W needs to be 0.5% or more in total. On the other hand, if the content of at least one of Mo and W exceeds 8.0% in total, manufacturing becomes difficult due to a decrease in workability. Therefore, the total content of at least one of Mo and W is 0.5 to 8.0%, preferably 2.5 to 6.5%.

  The balance other than the above-described component elements is Fe and inevitable impurities, but for the reason of improving the oxidation resistance of the foil, Hf: 0.01 to 0.20%, Ca: 10 to 300 ppm, and Mg: At least one of 15 to 300 ppm can be contained individually or simultaneously.

(2) Manufacturing method Next, the mechanism that makes it possible to obtain a hot-rolled steel strip excellent in surface properties according to the present invention will be described. The present inventors diligently studied on the problem and came to obtain the following knowledge.

(A) Brittleness at 475 ° C., which causes a decrease in toughness of high Cr ferritic stainless steel, is suppressed as the Al content increases. In particular, when 3.0% or more of Al is contained, even if soaking is performed for a long time at around 475 ° C., the embrittlement hardly occurs. (See Figure 1)
(B) By setting the coiling temperature to 500 ° C. to 650 ° C., the shape change due to rapid cooling becomes small, and the surface properties of the hot-rolled steel strip are remarkably improved. Preferably, it is 500-600 degreeC, More preferably, it is 520-580 degreeC. In the conventional high Cr content ferritic stainless steel manufacturing technology, in order to avoid embrittlement due to brittleness at 475 ° C., winding was performed after cooling to a low temperature of, for example, 450 ° C. or lower. Since embrittlement is suppressed by the effect of Al as described above, excessive rapid cooling is unnecessary, and winding at a relatively high temperature is possible.

  (C) When the Al-containing stainless steel is wound at a high temperature of 850 ° C. or higher after the end of hot rolling, carbonitride precipitates and the hot-rolled sheet toughness decreases, but it is 10 ° C./second or higher, preferably 20 ° C. It is possible to substantially suppress the precipitation of carbonitride by rapidly cooling to the coiling temperature at a cooling rate of 30 ° C./second or more, more preferably 30 ° C./second or more. In addition, σ brittleness that occurs when high Cr stainless steel is held at around 850 ° C is suppressed by the effect of Al as well as 475 ° C brittleness. However, since precipitation of carbonitride occurs, winding at 850 ° C or higher Then, the toughness decreases.

  The present invention has been made based on such findings. Conventionally, it has become possible to increase the coiling temperature, which had to be performed at a low temperature in order to ensure hot-rolled sheet toughness, by the effect of containing Al, and a hot-rolled steel strip excellent in both toughness and surface properties. It can be obtained.

  For the production of the Al-containing ferritic stainless steel, ordinary stainless steel production equipment can be used. Steel containing the above-described component composition is melted in a converter or electric furnace and secondarily refined by VOD or AOD, and then made into a steel slab by ingot-bundling rolling or continuous casting. Since the slab after casting may be cracked when cooled to room temperature, it is desirable to quickly charge the slab into the hot rolling furnace in the next step while keeping the temperature as high as possible. If reheating is difficult due to the factory operation schedule, a heat-retaining furnace or the like may be used, or heat retention may be performed by stacking a plurality of high-temperature slabs. In any case, it is desirable that the slab temperature does not fall below 170 ° C. The heat-retained slab is charged into a heating furnace, heated to 1150 ° C. to 1250 ° C., and then subjected to a general hot rolling process. After completion of hot rolling, it is possible to obtain a hot-rolled steel strip excellent in surface properties and toughness by quenching with, for example, a spray-type water-cooling device and winding up at a temperature of 500 to 650 ° C. to form a hot-rolled coil. it can. About the hot-rolled steel strip obtained in this manner, the surface scale is removed by shot blasting, pickling, mechanical polishing, etc., and cold rolling and annealing are repeated a plurality of times to obtain a stainless steel foil having a foil thickness of 100 μm or less. When the thickness of the foil is used as a catalyst carrier for an exhaust gas purifying apparatus, particularly when vibration resistance and durability are required, the thickness is set to about 50 to 100 μm, and particularly when high cell density and low back pressure are required. It is preferable that the thickness is about 25 μm to 50 μm.

  The present invention will be specifically described below based on examples. Steel Nos. Shown in Table 2 by the vacuum melting method. Steels having a chemical composition of 7 to 16 were melted and hot rolled, cooled and wound under the conditions shown in Table 3 to form hot rolled steel strips having a thickness of 3.5 mm. The following tests were conducted on the hot-rolled steel strip thus obtained.

  Toughness: The toughness of the hot-rolled steel strip was evaluated by a Charpy impact test. Samples were taken so that the longitudinal direction of the specimen was parallel to the rolling direction, and a V-notch was made perpendicular to the rolling direction. The test piece was prepared based on a JIS standard (JIS Z 2202 (1998)) V-notch test piece, but only the plate thickness (width in the JIS standard) was made as a raw material to 3.5 mm. The test was performed three times at each temperature based on the JIS standard (JIS Z 2242 (1998)), the absorption energy and the brittle fracture surface ratio were measured, and the transition curve was obtained. The ductile-brittle transition temperature (DBTT) was set to a temperature at which the transition curve of the brittle fracture surface ratio was 50%. DBTT evaluated less than 120 degreeC (double-circle), 120 to 150 degreeC (circle), and what exceeded 150 degreeC was evaluated as x. If the DBTT obtained by the Charpy impact test is 150 ° C. or lower, it has been confirmed in advance that cold rolling can be stably carried out at room temperature. Is preferably less than 120 ° C. for more stable threading.

  Surface property: The surface property was determined by taking a sample for inspection from a hot-rolled steel strip produced under each condition and a foil obtained by rolling the hot-rolled steel strip, and determining the defect area ratio (area where defects occurred / Inspected area × 100) was determined. The defect area ratio of the hot-rolled steel strip is less than 1%, and the surface area defect is hardly observed over the entire length ◎, the defect area ratio of the hot-rolled steel strip is 1 to 3%, some defects were recognized However, those that can be easily removed by the usual surface care processes such as shot blasting, pickling, mechanical polishing, etc. after that, the defect area ratio of the hot-rolled steel strip exceeds 3%, and obvious cracks and A plurality of such items were confirmed, and those that required partial grinding with a grinder or excision of defective portions were evaluated as x. Even if no serious defects were found at this point, when a stainless steel foil having a thickness of 100 μm or less was formed during cold rolling or after cold rolling, defects such as scratches and scabs were observed in an area exceeding 3%. Was also rated as x. In addition, steel No. whose Al content is outside the scope of the present invention. For No. 16, the above evaluation was not performed because severe cracking occurred during hot rolling.

  As shown in Table 3, the hot-rolled steel strip having the components, the coiling temperature and the cooling rate within the scope of the present invention is excellent in both surface properties and toughness. Furthermore, since these steel strips are excellent in surface properties and toughness, there was no problem even if they were used in the subsequent foil rolling process, and they could be produced efficiently. On the other hand, those whose manufacturing conditions deviate from the scope of the present invention have deteriorated at least one of the surface texture and toughness, and it is necessary to perform partial maintenance etc. by interrupting the rolling operation. Is unsuitable.

  According to the present invention, it is possible to stably produce a high Al-containing ferritic stainless steel excellent in both surface properties and toughness, which has been difficult to achieve at the same time, which is very effective industrially.

Claims (6)

In mass%, C: 0.05% or less, Si: 2.0% or less, Mn: 1.0% or less, S: 0.003% or less, P: 0.05% or less, Cr: 15.0 to 35.0%, Ni: 0.05 to 0.30%, Al: 3.0 to 10.0%, N: 0.10% or less, Ti: 0.02% or less, Nb: 0.02% or less , Ta: 0.02% or less, Zr: 0.005 to 0.20%, Ce: 0.02% or less, REM excluding Ce: 0.03 to 0.20%, at least one of Mo and W When hot-rolling a steel containing 0.5 to 8.0% in total and the balance being Fe and inevitable impurities, the hot rolling is finished at a temperature of 850 ° C. or higher, and then 10 ° C./second or higher. in the cooling rate, characterized in that the hot rolled coil by performing the winding after quenched to 500 ° C. to 650 ° C. is a coiling temperature, Defect rate of the surface is 3% or less, and ductile - method for producing Al-containing ferritic stainless hot rolled steel strip is brittle transition temperature is 0.99 ° C. or less. However, the defect occurrence rate is a value obtained by (defect occurrence area / inspection execution area × 100), and the ductility-brittle transition temperature is a value obtained by conducting a Charpy impact test on a hot-rolled steel strip.   2. The steel according to claim 1, further comprising, by mass%, Hf: 0.01 to 0.20%, mass ppm, Ca: 10 to 300 ppm, and Mg: 15 to 300 ppm. A method for producing an Al-containing ferritic stainless steel hot-rolled steel strip as described in 1. In mass%, C: 0.05% or less, Si: 2.0% or less, Mn: 1.0% or less, S: 0.003% or less, P: 0.05% or less, Cr: 15.0 to 35.0%, Ni: 0.05 to 0.30%, Al: 3.0 to 10.0%, N: 0.10% or less, Ti: 0.02% or less, Nb: 0.02% or less , Ta: 0.02% or less, Zr: 0.005 to 0.20%, Ce: 0.02% or less, REM excluding Ce: 0.03 to 0.20%, at least one of Mo and W contains 0.5 to 8.0% in total, Ri formed from the balance Fe and unavoidable impurities,
An Al-containing ferritic stainless steel hot-rolled steel strip having a surface defect occurrence rate of 3% or less and a ductile-brittle transition temperature of 150 ° C. or less . However, the defect occurrence rate is a value obtained by (defect occurrence area / inspection execution area × 100), and the ductility-brittle transition temperature is a value obtained by conducting a Charpy impact test on a hot-rolled steel strip. Said steel further contains, by mass%, Hf: 0.01 to 0.20%, in mass ppm, Ca: 10 to 300 ppm and Mg: claim 3, characterized in that it contains at least one kind of 15~300ppm An Al-containing ferritic stainless steel hot-rolled steel strip as described in 1. A method for producing a stainless steel foil, comprising rolling the Al-containing ferritic stainless steel hot-rolled steel strip according to any one of claims 3 and 4 so that a foil thickness is 100 µm or less. Method for producing a catalyst carrier for automobile exhaust gas purifying apparatus using the stainless steel foil obtained by the process for producing a catalyst carrier for automobile exhaust gas purification apparatus according to claim 5.

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