JP2008001945A - Bright annealing-finished ferritic stainless steel sheet having excellent rusting resistance and workability and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Ti-added ferritic stainless steel sheet having remarkably improved rusting resistance and jointly having workability. <P>SOLUTION: Regarding a ferritic stainless steel sheet comprising, by mass, 0.001 to 0.010% C, 0.01 to 0.20% Si, 0.01 to 0.30% Mn, 0.005 to 0.050% P, 0.0001 to 0.0100% S, 14 to 22% Cr, 0.001 to 0.020% N, 0.05 to 0.30% Ti and 0.005 to 0.050% Al, in a final annealing stage, in an atmosphere with a dew point of ≤-40°C comprising ≥70 vol.% gaseous hydrogen, and the balance substantially gaseous nitrogen, the dew point of the atmospheric gas and residence time are respectively prescribed in a temperature rising stage, a soaking stage and a cooling stage, thus the concentration ratio of Cr/Fe in a surface oxide film is controlled to >0.5, and also, TiO<SB>2</SB>is incorporated into the surface oxide film, so as to increase the pitting potential V'c100 in the surface to ≥0.5 V. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a bright annealed ferritic stainless steel sheet excellent in rust resistance and workability and a method for producing the same.

  Ferritic stainless steel sheets are used in a wide range of fields such as kitchen equipment, home appliances, and electronic equipment. However, since it is inferior in workability as compared with an austenitic stainless steel sheet, its use may be limited. In recent years, improvement in refining technology has enabled extremely low carbon and nitrogenization, and ferritic stainless steel sheets with improved workability by addition of stabilizing elements such as Ti and Nb are being applied to a wide range of processing applications. This is because ferritic stainless steel is more economical than austenitic stainless steel to which a large amount of Ni is added.

  Ferritic stainless steel plates with improved workability often have a lower Cr content than SUS304 (18Cr-8Ni), which is a typical austenitic stainless steel plate, and there is a problem with corrosion resistance. For kitchen appliances such as stainless steel sinks and home electric appliances that require design properties, deterioration of surface properties due to corrosion such as initial rusting and stains is often a problem.

  In order to improve the above-mentioned galling resistance, there are a method of alloying Cr and Mo and a method of modifying a film formed on the steel sheet surface by bright annealing. The former is not preferable because it causes an increase in cost due to alloying and becomes a factor that hinders workability. The latter is an effective method from the viewpoint of suppressing an increase in material cost and a decrease in workability, and various inventions have been disclosed for film modification utilizing bright annealing.

Patent Document 1 discloses that the anti-glare property of a stainless bright annealing material is improved by forming a film mainly composed of amorphous silica (SiO ₂ ). Regarding the improvement of the rust resistance by the SiO ₂ film, it is disclosed in Patent Document 2 that it is improved by regulating the amount of Al in steel and the amount of Al in the film, and in Patent Document 3 that it is improved by coexistence with Nb oxide. ing.

  The improvement in the resistance to cracking using the bright annealing described above is made of Si as a main deoxidizing element, and is a ferritic stainless steel substantially containing 0.5% or more of Si. In recent years, for example, Patent Document 4 and Patent Document 5 disclose ferritic stainless steel sheets to which Si is reduced and Ti is added in order to improve workability. Regarding film reforming of ferritic stainless steel with low Si and Ti addition, for example, in Patent Document 6, Patent Document 7, and Patent Document 8, both Al and Ti are concentrated in the film to prevent rusting. It is disclosed that the performance is improved.

  In the ferritic stainless steel with low Si and Ti added, which is excellent in workability, the technology for improving the galling resistance utilizing bright annealing is based on the combined action of Al and Ti of the coating formed on the steel sheet surface. In order to obtain the above effect, it is necessary to concentrate Al in the film by bright annealing, and the Al content in the steel is substantially over 0.06% in Patent Document 6, Patent Document 7 and Patent In Document 8, it must be over 0.12%. That is, the improvement of rust resistance is not achieved by the effect of Ti alone. Al effectively acts as a deoxidizing element for ferritic stainless steel with low Si content, but if added in excess of the necessary amount of deoxidation exceeding 0.05%, the workability, toughness and weldability of the steel are impaired. Will do.

  As mentioned above, conventionally, the technology for improving the weathering resistance using bright annealing was achieved by positively adding deoxidizing elements such as Si and Al, and Ti addition with excellent workability No technology has yet been developed to significantly improve the weathering resistance of ferritic stainless steel. That is, there is no example of improving the rust resistance by the effect of Ti alone. Conventionally, the reason why Ti-added steel is not generally used for bright annealing is that temper color is likely to occur and nitride (TiN) is likely to be generated. The temper color significantly deteriorates the color tone and gloss of the surface, and also adversely affects the rust resistance. In addition, if coarse precipitates such as TiN are generated, it becomes the starting point of surface defects and impairs the design. Thus, it is an object of the present invention to provide a bright annealed plate having significantly improved galling resistance without using Si or Al that impairs workability in Ti-added ferritic stainless steel.

JP 58-197282 A JP-A 63-235461 JP 61-235540 A JP 2003-231954 A JP 2005-298854 A JP-A-7-180001 JP-A-9-202945 Japanese Patent Laid-Open No. 10-273760

  The present invention has been devised to improve the galling resistance of Ti-added ferritic stainless steel with excellent workability, and is a film during bright annealing without using Si or Al that impairs workability. An object of the present invention is to provide a steel sheet having improved rust resistance by modification and a method for producing the same.

(1) In mass%, C: 0.001 to 0.010%, Si: 0.01 to 0.20%, Mn: 0.01 to 0.30%, P: 0.005 to 0.050 %, S: 0.0001-0.0100%, Cr: 14-22%, N: 0.001-0.020%, Ti: 0.05-0.30%, Al: 0.005-0. Ferritic stainless steel sheet composed of 050%, the balance being Fe and inevitable impurities, Cr / Fe atomic concentration ratio in surface oxide film> 0.5, and surface oxide film containing TiO ₂ , surface pitting corrosion A bright annealed stainless steel plate excellent in galling resistance and workability, characterized in that the potential V′c100 is 0.5 V or more.
(2) The steel is further in mass%, 0.0050% or less, Nb: 0.6% or less, Mo: 2.0% or less, Ni: 2.0% or less, Cu: 2.0% or less. B: 0.0003-0.0050% of 1 type or 2 types or more are contained, The bright annealing finish stainless steel plate excellent in the weathering resistance and workability of Claim 1 characterized by the above-mentioned.
(3) In the final annealing step of producing a cold-rolled steel sheet by combining cold rolling and annealing, hot-rolling a ferritic stainless steel slab having the steel component according to claim 1 or 2 into a hot-rolled steel sheet In addition, the hydrogen gas in the atmosphere is 70% by volume or more, the balance is substantially made of nitrogen gas, and the dew point of the atmosphere gas is set to -40 ° C. or less, and bright annealing is performed. An excellent bright annealed stainless steel sheet manufacturing method.
(4) The atmospheric gas dew point is −45 ° C. or lower and the residence time is 60 to 600 seconds in the temperature rising process from normal temperature to 700 ° C., and the atmospheric gas dew point is −40 ° C. or lower in the soaking process of 700 to 1000 ° C. 4. The bright annealing is performed by setting the residence time to 1 to 60 seconds, and then performing the atmospheric gas dew point to −45 ° C. or less and the residence time to 180 seconds or less in the cooling process to 400 ° C. A method for producing a bright annealed stainless steel sheet with excellent rust resistance and workability.
(5) Prior to bright annealing, it includes a step of passing through a seal facility for spraying an inert gas on the surface of a steel sheet in a range from room temperature to 200 ° C. for 1 to 180 seconds. A method for producing a bright annealed stainless steel sheet with excellent rust resistance and workability.

The chemical state of the surface oxide film can be analyzed using an X-ray photoelectron spectrometer (XPS). The binding energy of Cr ₂ O ₃ (Cr ₂ P electrons) is 575 to 580 eV, and the binding energy of TiO ₂ (Ti ₂ P electrons) is 455 to 460 eV. The presence of TiO ₂ can be confirmed by peak detection at 455 to 460 eV. The pitting corrosion potential is measured in accordance with JISG0577 in a 30 ° C., 1 kmol / m ³ sodium chloride aqueous solution with the steel sheet surface left untreated. The electrode is AgCl, and the value of the pitting corrosion occurrence potential V′c100 is measured.

  As explained above, the bright annealed stainless steel sheet according to the present invention of (1) to (2) optimizes the chemical state of the film without using Si or Al that impairs workability. Therefore, it has a high pitting corrosion potential exceeding SUS304, and can improve the rust resistance remarkably. This bright annealed stainless steel sheet can be produced industrially and stably by the methods of the present invention (3) to (5).

  In order to solve the above-described problems, the present inventors have conducted various studies on the chemical state of the film expressing excellent weathering resistance and the method for producing these films in the Ti-added ferritic stainless steel sheet, The following new findings were obtained.

(A) The chemical state of the film formed by bright annealing can be analyzed by XPS as described above. A Ti-added ferritic stainless steel bright annealed plate with low amounts of Si and Al produces an oxide film mainly composed of Cr ₂ O ₃ , and the amount of Si and Al detected in the film is extremely small.

(B) It has been found that Ti is concentrated in the above-mentioned film and does not generate tempara, that is, exists in a TiO ₂ state in a surface state that does not impair the color tone.

(C) When the oxide film mainly composed of Cr ₂ O ₃ having a Cr / Fe atomic concentration ratio> 0.5 in the surface oxide film contains TiO ₂ , the pitting corrosion potential on the steel surface is determined according to the measurement conditions described above. The value becomes 0.5V or more. This numerical value shows high pitting corrosion resistance exceeding SUS304.

(D) In recent years, the rust resistance of stainless steel is often easily evaluated by an accelerated test such as salt spray not only by the manufacturing manufacturer but also by individual consumers. The steel sheet having the high pitting corrosion potential expresses excellent rust resistance exceeding SUS304 and SUS316L in these simple evaluations.

(E) The oxide film described in the above (c) can be industrially stably produced by optimizing the bright annealing conditions for finishing the cold-rolled steel sheet.

(F) The atmospheric gas used for bright annealing usually has a dew point of −40 ° C. or lower. Below the dew point of −40 ° C., Fe is in the reduction region, and the steel surface forms an oxide film mainly composed of Cr ₂ O ₃ by selective oxidation of Cr. Ti has the characteristics that the free energy of formation of oxide is lower than that of Cr and is easily oxidized, and the diffusion in the oxide is fast and the oxide is easy to grow. Therefore, it is assumed that Ti was concentrated in an oxide film mainly composed of Cr ₂ O ₃ and could exist as thermodynamically stable TiO ₂ .

(G) However, it is very difficult to industrially manage the dew point of bright annealing as described in (f). In other words, in industrial production, oxygen and moisture remaining on the steel surface are carried over into the furnace, the air enters the furnace, the moisture is released from the furnace wall, and other factors. It is considered that it is not easy to manage low. Furthermore, when the residence time at high temperature becomes longer, a temper color due to the growth of Ti oxide tends to occur.

(H) Based on the hypothesis of (g), as a result of investigating a method for managing the dew point near the steel surface low, the dew point of the heating process at 700 ° C. or lower is lowered, the residence time of the soaking process is shortened, 400 It has been found that lowering the dew point in the cooling process to 0 ° C. is effective for the production of the film described in (c).

(I) Further, in the manufacturing method described in (h), it is most effective to lower the dew point in the temperature rising process of 700 ° C. or less, and a process of blowing an inert gas to the steel surface prior to bright annealing is adopted. It has also been found that removing the oxygen source remaining on the surface is an effective means.

  The present inventions (1) to (5) have been completed based on the findings (a) to (i).

  Hereinafter, each requirement of the present invention will be described in detail. In addition, "%" display of the content of each element means "mass%".

(A) The reason for limitation of a component is demonstrated below.

  Since C deteriorates moldability and corrosion resistance, the lower the content, the better. Therefore, the upper limit was made 0.010%. However, excessive reduction leads to an increase in refining costs, so the lower limit was made 0.001%. Preferably, it is 0.002 to 0.005% in consideration of corrosion resistance and manufacturing cost.

  Si may be added as a deoxidizing element. However, since it is a solid solution strengthening element and its content is preferably as small as possible from the suppression of the decrease in elongation, the upper limit was made 0.20%. However, excessive reduction leads to an increase in refining costs, so the lower limit was made 0.01%. Preferably, considering the workability and manufacturing cost, 0.03 to 0.15%.

  Since Mn is a solid solution strengthening element like Si, the smaller the content, the better. The upper limit was made 0.30% in order to suppress the decrease in elongation. However, excessive reduction leads to an increase in refining costs, so the lower limit was made 0.01%. Preferably, considering the workability and the manufacturing cost, 0.03 to 0.15%.

  Since P is a solid solution strengthening element like Si and Mn, the smaller the content, the better. The upper limit was made 0.050% from the suppression of the decrease in elongation. However, excessive reduction leads to an increase in refining costs, so the lower limit was made 0.005%. Preferably, considering the manufacturing cost and workability, the content is made 0.010 to 0.020%.

  S is an impurity element and inhibits hot workability and corrosion resistance, so the smaller the content, the better. Therefore, the upper limit was made 0.0100%. However, excessive reduction leads to an increase in refining costs, so the lower limit was made 0.0001. Preferably, considering the corrosion resistance and the manufacturing cost, the content is made 0.0010 to 0.0050%.

  Cr is an essential element for ensuring corrosion resistance, and the lower limit is made 14% in order to ensure the pitting corrosion potential of the present invention. However, addition of more than 22% leads to an increase in cost and a decrease in workability which is regarded as important in the present invention. Therefore, the upper limit of Cr is 22%. Preferably, considering the corrosion resistance, manufacturability and workability, the content is made 16 to 18%.

  N, like C, deteriorates workability and corrosion resistance, so the lower the content, the better. Therefore, the upper limit was made 0.020%. However, excessive reduction does not cause TiN which becomes the nucleus of ferrite grain formation during solidification, and the solidified structure becomes columnar crystals, which may deteriorate the ridging resistance of the product. Therefore, the lower limit is made 0.001%. Preferably, considering the workability and corrosion resistance, the content is made 0.003 to 0.012%.

Ti is an extremely effective element for improving workability by fixing C and N, and is indispensable for improving the rust resistance by the film modification in the bright annealing of the present invention. Ti is concentrated and present as TiO ₂ in the film mainly composed of Cr ₂ O ₃ under the bright annealing conditions defined in the present invention. The effect of improving the glazing resistance of the bright annealed material is due to the presence of TiO ₂ in the film mainly composed of Cr ₂ O ₃ . In order to obtain such an effect of improving the rust resistance, it is necessary to add 0.05% or more of Ti. However, Ti is also a solid solution strengthening element, and excessive addition leads to a decrease in elongation. Furthermore, it is easy to produce a temper color at the time of bright annealing, and it leads to inhibiting surface color tone. Therefore, the upper limit is made 0.30%. Preferably, it is set to 0.10 to 0.20% in consideration of improvement of rust resistance and workability and manufacturability.

  Since Al is an effective element as a deoxidizing element, the lower limit was made 0.005%. However, excessive addition causes deterioration of workability, toughness and weldability, so the upper limit was made 0.050%. Preferably, considering the refining cost, 0.01 to 0.03%.

  Mg forms Mg oxide with Al in molten steel and acts as a deoxidizer, and also acts as a crystallization nucleus of TiN. TiN becomes a solidification nucleus of the ferrite phase in the solidification process, and by facilitating crystallization of TiN, the ferrite phase can be finely formed during solidification. By refining the solidified structure, surface defects caused by coarse solidified structures such as ridging and roping of the product can be prevented and workability can be improved. Aggressive formation in the molten steel of Mg oxide that becomes the crystallization nucleus of TiN is manifested from Mg 0.0001%. In order to obtain these effects, the lower limit was made 0.0001%. However, if it exceeds 0.0050%, the weldability deteriorates, so the upper limit was made 0.0050%. Preferably, considering the refining cost, 0.0003 to 0.0020%.

  Nb is an element that improves workability and corrosion resistance, and is added according to the required application. When added, the content is 0.01% or more where the effect is manifested. However, excessive addition increases the material strength and causes a decrease in elongation, so the upper limit was made 0.6%. Preferably, it is set to 0.1 to 0.3% in consideration of manufacturability and workability.

  Mo, Ni, and Cu are elements that improve corrosion resistance, and are added in applications that require corrosion resistance. When added, the content is 0.1% or more where the effect is manifested. However, excessive addition causes a decrease in workability, particularly elongation, so the upper limit was made 2.0%. Preferably, considering the manufacturability and workability, the content is made 0.5 to 1.5%.

  B is an element that improves secondary workability, and addition to Ti-added steel is effective. Since Ti-added steel fixes C with Ti, the strength of the grain boundary is lowered, and intergranular cracking is likely to occur during secondary processing. When added, the content is made 0.0003% or more where the effect is manifested. However, excessive addition causes a decrease in elongation, so the upper limit was made 0.0050%. Preferably, considering the refining cost and workability, 0.0005 to 0.0020%.

(B) The reason for limitation regarding the oxide film on the steel sheet surface will be described below.

  The ferritic stainless steel sheet of the present invention has the components described in the section (A), and defines the chemical state of the oxide film formed by bright annealing in order to improve the resistance to cracking. .

When TiO ₂ is present in a film mainly composed of Cr ₂ O ₃ with a Cr / Fe atomic concentration ratio> 0.5 in the surface oxide film, it has the effect of significantly improving the rust resistance on the steel surface. Although the detailed mechanism of action is unknown, the effect of improving rust resistance by TiO ₂ is remarkably exhibited when the presence of Fe detected from the steel surface is suppressed. Here, Fe exists mainly in a mixed state of FeOOH and Fe ₂ O _{3 on} the steel surface.

As already described, the chemical state of each element such as Cr, Ti, Fe on the steel surface in the present invention can be analyzed using an X-ray photoelectron spectrometer (XPS). FeOOH or Fe ₂ O ₃ bonding energy (Fe2p electronic) - is 708～712EV. Wherein the presence of the TiO ₂ is in the range of 450~470eV, 455~460eV to TiO ₂ in the X ray count present (cps) is X-ray count number is around the (cps) 100 cps or more to the high Suppose that it is in a state.

In order to improve the galling resistance with the pitting corrosion potential V′c100> 0.5 on the steel surface, the composition of the oxide film is Cr / Fe atomic concentration in the presence ratio of O and cation ions except C and N It is assumed that TiO ₂ exists in the film mainly composed of Cr ₂ O ₃ with a ratio> 0.5. Here, in order to remarkably improve the weathering resistance of the steel surface, it is preferable that TiO ₂ is present in the Cr ₂ O ₃ main film having a Cr / Fe atomic concentration ratio> 0.7.

  The concentrations of O and cation ions other than C and N in the oxide film are obtained by the following method. The surface composition change is measured by Auger electron spectroscopy while the oxide film on the steel surface is gradually scraped from the outermost surface by Ar ion sputtering. Here, the existence region of the oxide film was grasped, and the average atomic concentration (notation: atom%) of the detection element in the region was obtained.

  Since the thickness of the oxide film changes depending on the dew point, temperature, and time of bright annealing, a clear range cannot be defined, but the effect of the present invention is manifested if it is 20 angstroms or more. However, when the thickness exceeds 1000 angstroms, coloration by tempering colors occurs, which may impair the color tone of the surface. Therefore, the film thickness is 1000 angstroms or less. In consideration of weathering resistance and manufacturability, the film thickness is preferably 30 to 100 Å.

(C) The reason for limitation regarding the manufacturing method will be described below.

  In the ferritic stainless steel having the component described in the item (A), the finish bright annealing condition of the cold-rolled steel sheet is defined in order to generate the film described in the item (B).

  The atmosphere gas at the time of bright annealing is assumed to be 70% by volume or more of hydrogen gas, and the balance is substantially made of nitrogen gas. Since hydrogen gas has a reducing action of Fe-based oxides during bright annealing, it is preferably 80% or more. The balance may be an inert gas that does not contribute to the oxidation of steel, such as argon gas, but is preferably nitrogen gas in view of industrial cost.

The dew point of the atmospheric gas is that the Fe-based oxide in the oxide film is reduced to an oxide film mainly composed of Cr ₂ O ₃ , and the Cr / Fe atomic concentration ratio> 0.5, and at the same time, TiO _{2 in the} oxide film In order to make it exist, it is made into -40 degrees C or less. In order to sufficiently suppress the existence state of Fe to form a film mainly composed of Cr ₂ O ₃ and to make TiO ₂ exist, the temperature range of the heating process, the soaking process, and the cooling process as described below. It is preferable to define the dew point and the residence time according to the above.

  In the temperature raising process from room temperature to 700 ° C., it is preferable that the dew point is −45 ° C. or less and the residence time of the steel sheet in the atmospheric gas is 60 to 600 seconds. When the dew point exceeds −45 ° C. or the residence time exceeds 600 seconds, Fe and Ti oxides that cause temper color are likely to be generated. If the residence time is 600 seconds or less, the Cr / Fe atomic concentration ratio can be set to> 0.5. Setting the residence time to less than 60 seconds is practically difficult in an industrial furnace. Therefore, the lower limit of the residence time is 60 seconds.

  In the soaking process at 700 to 1000 ° C., the dew point is preferably −40 ° C. or less, and the residence time of the steel sheet in the atmospheric gas is preferably 1 to 60 seconds. When the dew point exceeds −40 ° C. or the residence time exceeds 60 seconds, Fe and Ti oxides that cause temper color are likely to be generated. If the residence time is 60 seconds or less, the Cr / Fe atomic concentration ratio can be set to> 0.5. Even if the dew point is lowered, if the residence time exceeds 60 seconds, the surface color tone and film composition are likely to change due to the growth of Ti oxide. It is practically difficult in an industrial furnace to set the residence time to less than 1 second. Therefore, the lower limit of the residence time is 1 second.

  In the cooling process from soaking to 400 ° C., the dew point is preferably −40 ° C. or less, and the residence time of the steel sheet in the atmospheric gas is preferably 180 seconds or less. When the dew point exceeds −40 ° C. or the residence time exceeds 180 seconds, the productivity of Fe and Ti, which is a factor of temper color, is likely to grow while the productivity is hindered. If the residence time is 180 seconds or less, the Cr / Fe atomic concentration ratio can be set to> 0.5.

  In addition to the above-mentioned bright annealing conditions, as a means for lowering the dew point near the steel surface more efficiently, a seal facility for blowing an inert gas to the steel surface in the range of room temperature to 200 ° C. prior to bright annealing is 1-180. It is preferable to include a step of passing for 2 seconds. Oxides generated and grown during the temperature rise process during bright annealing are largely due to oxygen sources contained in moisture adhering to the steel surface. Therefore, this can be efficiently removed by spraying an inert gas on the steel surface prior to bright annealing. Furthermore, by having the above-mentioned seal facility, air intrusion into the furnace is also prevented. The reason why the upper limit of the temperature is set to 200 ° C. is that if this temperature is exceeded, the oxidation is promoted. When the passage time is less than 1 second, the effect of removing the oxygen source remaining on the steel surface cannot be obtained. If it exceeds 180 seconds, there is a risk that the cost will increase due to the increase in seal facilities and the productivity may be impaired. Further, the inert gas is preferably nitrogen gas from the viewpoint of industrial cost.

  Hereinafter, the steel sheet of the present invention will be described in more detail with reference to examples.

  Ferritic stainless steel having the components shown in Table 1 was melted and hot rolled at a heating temperature of 1150 to 1200 ° C. to obtain a hot rolled steel sheet having a thickness of 3.8 mm. The hot-rolled steel sheet was annealed, cold-rolled to a sheet thickness of 0.4 mm after pickling, and subjected to finish bright annealing. The bright finish annealing was also performed in the range specified in the present invention shown in Table 1 and other conditions. For comparison, SUS304 (18% Cr-8% Ni) steel and SUS316 (17% Cr-12% Ni-2.0Mo) steel were used.

  About the bright annealing steel plate of thickness 0.4mm obtained as mentioned above, the surface color tone was determined visually. A case where no change in the color tone of the surface due to the tempara was confirmed was “◯”, and a case where a change in the color tone due to the tempera was generated was indicated as “x”.

  Various test pieces were collected and subjected to film state analysis, pitting corrosion potential measurement on the steel surface, salt spray test, and cast test.

  As described above, the Cr / Fe atomic concentration ratio of the film was analyzed using Auger electron spectroscopy, and the chemical state of the film was analyzed using XPS. The pitting potential was measured by a method based on JISG0577 described above.

  The salt spray test and the cast test were performed by a method based on JISZ2371. In each test, a bright annealed steel plate and a cylindrical deep-drawn processed product were used. The cylindrical deep drawing was performed with a blank diameter of 80 mm, a punch diameter of 40 mm, a die diameter of 42 mm, and a wrinkle holding pressure of 1 ton, and a film was used for lubrication. The test days were 7 days (168 hours). The degree of rusting is evaluated as “◯” when it is equal to or higher than SUS304, “×” when it is inferior, and “◎” when it is equal or higher than SUS316L, and the rust resistance is evaluated. did.

  Table 2 summarizes the test results.

From Table 2, the Ti-added ferritic stainless steel sheet satisfying the production conditions of the present invention with test numbers 1 to 7 shows no change in surface color tone, and Cr ₂ O ₃ with a Cr / Fe atomic concentration ratio> 0.5 is observed. The main surface oxide film has TiO ₂ and the surface pitting corrosion potential is 0.5 V or more. These bright annealed plates and cylindrical deep-drawn processed products exhibit galling resistance equal to or higher than that of comparative SUS304 (test number 8) or SUS316L (test number 9).

  On the other hand, the Ti-added ferritic stainless steel plates having test numbers 10 to 17 do not satisfy the manufacturing conditions defined in the present invention.

Although the Ti-added ferritic stainless steel plates of test numbers 10 to 12 have no surface color change, the pitting corrosion potential is not affected even if the Cr / Fe atomic concentration ratio of the coating is <0.5 and TiO ₂ is contained. Is less than 0.5V. Therefore, these bright annealed plates and cylindrical deep-drawn processed products are inferior in glazing resistance than the comparative SUS304 (test number 8).

The Ti-added ferritic stainless steel plates of Test Nos. 13 to 17 show a change in the color tone of the surface, and even when the Cr / Fe atomic concentration ratio of the coating is <0.5 and TiO ₂ is contained, the pitting potential is It is less than 0.5V. Therefore, these bright annealed plates and cylindrical deep-drawn processed products are inferior in glazing resistance than the comparative SUS304 (test number 8).

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to remarkably improve galling resistance, making use of the excellent workability of a Ti-added ferritic stainless steel sheet, and a ferrite that is more economical than an austenitic stainless steel sheet. Expansion of applicable applications of stainless steel sheets.

Claims (5)

In mass%, C: 0.001 to 0.010%, Si: 0.01 to 0.20%, Mn: 0.01 to 0.30%, P: 0.005 to 0.050%, S : 0.0001 to 0.0100%, Cr: 14 to 22%, N: 0.001 to 0.020%, Ti: 0.05 to 0.30%, Al: 0.005 to 0.050%, The balance is a ferritic stainless steel plate made of Fe and inevitable impurities, the Cr / Fe atomic concentration ratio in the surface oxide film> 0.5, and the surface oxide film contains TiO ₂ , and the surface pitting potential V ′ A bright-annealed finish stainless steel sheet excellent in galling resistance and workability, wherein c100 is 0.5 V or more.   The steel is further in mass%, Mg: 0.0050% or less, Nb: 0.6% or less, Mo: 2.0% or less, Ni: 2.0% or less, Cu: 2.0% or less, B: One or more of 0.0003 to 0.0050%, or a bright annealed finish stainless steel sheet excellent in scratch resistance and workability according to claim 1.   In a final annealing step, a ferritic stainless steel slab having the steel component according to claim 1 or 2 is hot-rolled to form a hot-rolled steel sheet, and then cold-rolled steel sheet is manufactured by combining cold rolling and annealing. Brightness excellent in sprinkling resistance and workability, characterized in that bright hydrogen annealing is performed with a hydrogen gas content of 70% by volume or more, the balance being substantially nitrogen gas, and a dew point of the atmospheric gas being −40 ° C. or lower. Manufacturing method of annealed stainless steel sheet.   The atmospheric gas dew point is −45 ° C. or lower and the residence time is 60 to 600 seconds in the temperature rising process from room temperature to 700 ° C., and the atmospheric gas dew point is −40 ° C. or lower and the residence time is 700 to 1000 ° C. in the soaking process. 4. The resistance to light emission according to claim 3, wherein bright annealing is performed for 1 to 60 seconds, and in the cooling process to 400 ° C., the dew point of the atmospheric gas is −45 ° C. or less and the residence time is 180 seconds or less. A method for producing a bright annealed stainless steel sheet with excellent fertility and workability.   5. The flame-proofing according to claim 3, comprising a step of passing through a seal equipment for spraying an inert gas on a steel sheet surface in a range from room temperature to 200 ° C. for 1 to 180 seconds prior to bright annealing. Of bright annealed stainless steel sheet with excellent heat resistance and workability.