Ferritic stainless steel sheet having excellent brazability, heat exchanger, ferritic stainless steel sheet for heat exchangers, ferritic stainless steel, ferritic stainless steel for members of fuel supply systems, and member of fuel supply system

Abstract

One aspect of this ferritic stainless steel sheet contains, by mass %, C: 0.03% or less, N: 0.05% or less, Si: 1% or less, Mn: 1.2% or less, Cr: 14% or more and 28% or less, Nb: 8(C +N) or more and 0.8% or less, and Al: 0.1% or less, with a balance being Fe and inevitable impurities, in which a film satisfying Expression 1 is formed in a surface thereof. Expression 1 is d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f)2.0. In Expression 1, d.sub.f represents a thickness (nm) of the film, Cr.sub.f represents a Cr cationic fraction in the film, Si.sub.f represents a Si cationic fraction in the film, and Al.sub.f represents an Al cationic fraction in the film.

Claims

1. A ferritic stainless steel sheet comprising, by mass %: C: 0.03% or less; N: 0.002% or more and 0.05% or less; Si: more than 0.1% and 1% or less; Mn: 1.2% or less; Cr: 14% or more and 28% or less; Nb: 8(C+N) or more and 0.8% or less; and Al: 0.002% or more and 0.1% or less, with a balance being Fe and inevitable impurities, wherein a film satisfying Expression 1 is formed in a surface thereof,
d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f)2.0(Expression 1) in Expression 1, d.sub.f represents a thickness of the film in terms of nm, Cr.sub.f represents a Cr cationic fraction in the film, Si.sub.f represents a Si cationic fraction in the film, and Al.sub.f represents an Al cationic fraction in the film, wherein the ferritic stainless steel sheet has a brazing filler spreading coefficient of 2 or more.

2. The ferritic stainless steel sheet according to claim 1, further comprising, by mass %: one or more selected from Ni: 5% or less, Cu: 1.5% or less, and Mo: 3% or less.

3. The ferritic stainless steel sheet according to claim 1, further comprising, by mass %: one or more selected from V: 0.5% or less, W: 1% or less, B: 0.005% or less, Sn: 0.5% or less, Co: 0.2% or less, Mg: 0.002% or less, Ca: 0.002% or less, REM: 0.01% or less, Sb: 0.5% or less, Ta: 0.5% or less, and Ga: 0.01% or less.

4. A heat exchanger comprising: a heat exchange section including a joined member by brazing, wherein the member is composed of the ferritic stainless steel sheet according to claim 1.

5. A heat exchanger, comprising, the ferritic stainless steel sheet according to claim 1.

6. A heat exchanger, comprising, the ferritic stainless steel sheet according to claim 2.

7. A heat exchanger, comprising, the ferritic stainless steel sheet according to claim 3.

8. A ferritic stainless steel comprising, by mass %: C: 0.03% or less; N: 0.002% or more and 0.05% or less; Si: more than 0.1% and 1% or less; Mn: 1.2% or less; Cr: 15% or more and 23% or less; Nb: 8(C+N)+0.1% or more and 0.8% or less; and Al: 0.002% or more and 0.1% or less, with a balance being Fe and inevitable impurities, wherein a film satisfying Expressions 2 and 3 is formed in a surface thereof,
d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f)2.0(Expression 2)
0.18Cr.sub.f0.5(Expression 3) in Expression 2, d.sub.f represents a thickness of the film in terms of nm, Si.sub.f represents a Si cationic fraction in the film, and Al.sub.f represents an Al cationic fraction in the film, and in Expressions 2 and 3, Cr.sub.f represents a Cr cationic fraction in the film, wherein the ferritic stainless steel has a brazing filler spreading coefficient of 2 or more.

9. The ferritic stainless steel according to claim 8, further comprising, by mass %: one or more selected from Ni: 2% or less, Cu: 1.5% or less, and Mo: 3% or less.

10. The ferritic stainless steel according to claim 8, further comprising, by mass %: one or more selected from V: 0.5% or less, W: 1% or less, B: 0.005% or less, Sn: 0.5% or less, Co: 0.2% or less, Mg: 0.002% or less, Ca: 0.002% or less, REM: 0.01% or less, Sb: 0.5% or less, Ta: 0.5% or less, and Ga: 0.01% or less.

11. A fuel supply system part comprising: a joined member by brazing, wherein the member is composed of the ferritic stainless steel according to claim 8.

12. A fuel supply system part, comprising, the ferritic stainless steel sheet according to claim 8.

13. A fuel supply system part, comprising, the ferritic stainless steel sheet according to claim 9.

14. A fuel supply system part, comprising, the ferritic stainless steel sheet according to claim 10.

15. The ferritic stainless steel sheet according to claim 2, further comprising, by mass %: one or more selected from V: 0.5% or less, W: 1% or less, B: 0.005% or less, Sn: 0.5% or less, Co: 0.2% or less, Mg: 0.002% or less, Ca: 0.002% or less, REM: 0.01% or less, Sb: 0.5% or less, Ta: 0.5% or less, and Ga: 0.01% or less.

16. A heat exchanger comprising: a heat exchange section including a joined member by brazing, wherein the member is composed of the ferritic stainless steel sheet according to claim 2.

17. A heat exchanger comprising: a heat exchange section including a joined member by brazing, wherein the member is composed of the ferritic stainless steel sheet according to claim 3.

18. A heat exchanger comprising: a heat exchange section including a joined member by brazing, wherein the member is composed of the ferritic stainless steel sheet according to claim 15.

19. A heat exchanger, comprising, the ferritic stainless steel sheet according to claim 15.

20. The ferritic stainless steel according to claim 9, further comprising, by mass %: one or more selected from V: 0.5% or less, W: 1% or less, B: 0.005% or less, Sn: 0.5% or less, Co: 0.2% or less, Mg: 0.002% or less, Ca: 0.002% or less, REM: 0.01% or less, Sb: 0.5% or less, Ta: 0.5% or less, and Ga: 0.01% or less.

Description

EXAMPLES

(1) Hereinafter, the effects of the present invention are explained more clearly by reference to Examples. The present invention is not limited to the following Examples, and modifications can be appropriately made and implemented without departing from the features of the invention.

Example 1

(2) 30 kg of molten steels having chemical compositions shown in Table 1 were melted in a vacuum melting furnace to prepare 17 kg of flat steel ingots. Next, the ingots were subjected to hot rolling at a heating temperature of 1,200 C. to obtain hot-rolled steel sheets having a thickness of 4.5 mm. The hot-rolled steel sheets were subjected to annealing at a temperature of 950 C. and then scales were removed by alumina shot blasting. Then the steel sheets were subjected to cold rolling to have a thickness of 1 mm. Thereafter, the steel sheets were subjected to finish annealing and scales were removed by a salt method and immersion in nitric hydrofluoric acid.

(3) The finish annealing temperature was set to temperatures shown in Table 1 and the holding time was set to 1 minute.

(4) As a salt method, a method of heating a commercially available descaling alkali salt mainly containing NaOH and immersing a steel sheet in the alkali salt was applied and the heating temperature was set to temperatures shown in Table 1 and the immersion time was set to 5 seconds.

(5) In the immersion in nitric hydrofluoric acid, a 3% HF-10% HNO.sub.3 solution heated to 55 C. was used and the steel sheets were immersed in the solution for 10 seconds. The thus-obtained cold-rolled steel sheets (Invention Steels 1-1 to 1-12 and Comparative Steels 1-1 to 1-5) were used to evaluate brazing filler spreading abilities and analyze the surface film of the material.

(6) [Brazing Filler Spreading Abilities]

(7) Three steel sheets having a width of 40 mm and a length of 40 mm were sampled from each of the cold-rolled steel sheets and degreased using an organic solution. Next, 0.5 g of a pure Cu brazing filler metal (BCu-1) was put on the center of the steel sheet and the steel sheets were put into a vacuum furnace to heat the steel sheets at 1130 C. for 10 minutes. The degree of vacuum was approximately 50 Pa. The steel sheets were cooled after the heating and the size of the brazing filler metal was measured. From the result of measuring the size of the brazing filler metal, the area of the brazing filler metal was obtained to calculate a brazing filler spreading coefficient by the following Expression.
Brazing filler spreading coefficient=area of brazing filler metal after heat treatment/initial area of brazing filler metal

(8) In Table 2, brazing filler spreading coefficients are shown. Here, the brazing filler spreading coefficient is an average value of the three steel sheets. In the embodiment, a brazing filler spreading coefficient of 2 or more is good and a brazing filler spreading coefficient of 4 or more is further excellent.

(9) [Analysis of Surface Film of Material]

(10) The surface film of the material was analyzed by X-ray photoelectron spectroscopy (XPS). An XPS apparatus was manufactured by ULVAC-PHI, Inc. XPS was performed using mono-AlK ray as an X-ray source under the condition in which the beam diameter of an X-ray was approximately 100 m and the output angle thereof was 45 degrees and 90 degrees. From the result of quantitative analysis of the outermost surface by the XPS, the Cr cationic fraction Cr.sub.f, the Si cationic fraction Si.sub.f, and the Al cationic fraction Al.sub.f were obtained. Here, cations are only for metal elements. In addition, the thickness d.sub.f of the oxide film was obtained by an angle resolution method.

(11) In Table 2, the thickness d.sub.f of the oxide film, the Cr cationic fraction Cr.sub.f, the Si cationic fraction Si.sub.f, and the Al cationic fraction Al.sub.f and the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) (A value) are shown.

(12) As shown in Table 2, in Invention Examples in which the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) is 2.0 or less, the brazing filler spreading coefficient is 2 or more and brazeability is excellent.

(13) As shown in Comparative Examples, in the case where the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) is more than 2.0, the brazing filler spreading coefficient is less than 2 and brazeability is deteriorated.

(14) It is observed that although Invention Steel 1-3 and Comparative Steel 1-1 had similar chemical compositions, the brazing filler spreading coefficients thereof were different. This is because the Si cationic fraction Si.sub.f in the film was high and the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) was more than 2.0 in Comparative Steel 1-1 compared to Invention Steel 1-3. It is considered that the temperature of salt was low and thus Si oxides formed in the annealing process were not removed but concentrated in Comparative Steel 1-1 compared to Invention Steel 1-3.

(15) Although Comparative Steel 1-5 and Invention Steel 1-1 had the same chemical composition, in Comparative Steel 1-5, the annealing temperature was increased and the temperature of salt was lowered and thus the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) was more than 2.0. Therefore, the brazing filler spreading coefficient was greatly decreased in Comparative Steel 1-5, compared to Invention Steel 1-1. It is considered that this is mainly because in Comparative Steel 1-5, Si oxides formed in the annealing process were not removed but concentrated.

(16) TABLE-US-00001 TABLE 1 Chemical composition (mass %) C N Si Mn P S Cr Nb Al Ni Cu Mo Others Invention 1-1 Invention 0.010 0.015 0.50 0.09 0.026 0.0008 19.37 0.38 0.022 0.29 0.44 Example Steel 1-1 Invention 1-2 Invention 0.008 0.011 0.43 0.13 0.029 0.0033 21.58 0.36 0.024 0.42 0.79 Example Steel 1-2 Invention 1-3 Invention 0.007 0.009 0.17 0.18 0.022 0.0018 19.41 0.48 0.021 0.19 0.46 1.96 Example Steel 1-3 Invention 1-4 Invention 0.006 0.009 0.93 0.26 0.021 0.0010 14.08 0.43 0.075 Example Steel 1-4 Invention 1-5 Invention 0.007 0.011 0.22 1.18 0.035 0.0018 17.84 0.44 0.003 2.05 Example Steel 1-5 Invention 1-6 Invention 0.006 0.012 0.32 0.34 0.025 0.0003 27.84 0.21 0.002 Example Steel 1-6 Invention 1-7 Invention 0.018 0.017 0.39 0.48 0.026 0.0015 16.47 0.56 0.010 0.32 0.25 0.18Sn Example Steel 1-7 Invention 1-8 Invention 0.006 0.009 0.19 0.19 0.020 0.0010 17.25 0.46 0.029 0.92W, Example Steel 1-8 0.002REM Invention 1-9 Invention 0.008 0.012 0.21 0.20 0.020 0.0008 15.22 0.42 0.048 0.12V, Example Steel 1-9 0.0002Mg Invention 1-10 Invention 0.007 0.015 0.12 0.08 0.026 0.0007 17.45 0.35 0.018 1.05 0.1Sn, Example Steel 1-10 0.0005Ca, 0.0004B Invention 1-11 Invention 0.012 0.016 0.22 0.22 0.020 0.0010 14.19 0.41 0.089 0.07Zr, Example Steel 1-11 0.05Co Invention 1-12 Invention 0.008 0.010 0.21 0.23 0.022 0.0009 17.18 0.43 0.024 0.11Sb, Example Steel 1-12 0.21Ta, 0.003Ga Comparative 1-12 Comparative 0.005 0.009 0.16 0.19 0.029 0.0007 19.41 0.48 0.034 0.17 0.47 1.90 Example Steel 1-1 Comparative 1-13 Comparative 0.007 0.013 0.35 0.35 0.024 0.0005 29.12 0.25 0.009 Example Steel 1-2 Comparative 1-14 Comparative 0.007 0.011 1.37 0.27 0.022 0.0011 14.16 0.45 0.064 Example Steel -3 Comparative 1-15 Comparative 0.006 0.014 0.34 0.32 0.031 0.0008 20.05 0.29 0.12 Example Steel 1-4 Comparative 1-16 Comparative 0.010 0.015 0.50 0.09 0.026 0.0008 19.37 0.38 0.022 0.29 0.44 Example Steel 1-5 Finish annealing Salt method temperature ( C.) temperature ( C.) Invention Example 1-1 Invention Steel 1-1 980 510 Invention Example 1-2 Invention Steel 1-2 980 510 Invention Example 1-3 Invention Steel 1-3 990 510 Invention Example 1-4 Invention Steel 1-4 1010 520 Invention Example 1-5 Invention Steel 1-5 970 510 Invention Example 1-6 Invention Steel 1-6 970 500 Invention Example 1-7 Invention Steel 1-7 1030 500 Invention Example 1-8 Invention Steel 1-8 990 510 Invention Example 1-9 Invention Steel 1-9 980 500 Invention Example 1-10 Invention Steel 1-10 980 510 Invention Example 1-11 Invention Steel 1-11 980 500 Invention Example 1-12 Invention Steel 1-12 990 510 Comparative Example 1-12 Comparative Steel 1-1 990 470 Comparative Example 1-13 Comparative Steel 1-2 980 500 Comparative Example 1-14 Comparative Steel -3 1030 490 Comparative Example 1-15 Comparative Steel 1-4 970 500 Comparative Example 1-16 Comparative Steel 1-5 1010 470 Note: underlined values are out of the range of the present invention.

(17) TABLE-US-00002 TABLE 2 Brazeability Brazing filler spreading Surface film coefficient d.sub.f/nm Cr.sub.f Si.sub.f Al.sub.f A Invention 1-1 3.9 4.1 0.37 1.5 Steel 1-1 Invention 1-2 2.2 4.8 0.39 1.9 Steel 1-2 Invention 1-3 2.3 5.4 0.33 1.8 Steel 1-3 Invention 1-4 7.2 4.9 0.20 0.04 0.01 1.3 Steel 1-4 Invention 1-5 3.0 4.1 0.39 1.6 Steel 1-5 Invention 1-6 2.1 3.7 0.49 1.8 Steel 1-6 Invention 1-7 4.2 4.5 0.33 1.5 Steel 1-7 Invention 1-8 5.1 6.6 0.20 1.3 Steel 1-8 Invention 1-9 6.4 5.1 0.25 1.3 Steel 1-9 Invention 1-10 2.9 4.5 0.35 1.6 Steel 1-10 Invention 1-11 5.4 4.7 0.22 0.02 1.3 Steel 1-11 Invention 1-12 4.8 6.2 0.22 1.4 Steel 1-12 Comparative 1-12 1.1 5.0 0.26 0.21 2.4 Steel 1-1 Comparative 1-13 1.4 4.0 0.58 2.3 Steel 1-2 Comparative 1-14 1.6 5.5 0.19 0.22 0.07 3.2 Steel 1-3 Comparative 1-15 1.0 4.7 0.38 0.14 3.9 Steel 1-4 Comparative 1-16 1.4 4.6 0.30 0.17 2.2 Steel 1-5 A = d.sub.f Cr.sub.f + 5(Si.sub.f + 3Al.sub.f) The symbol in the result of surface film analysis indicates a value equal to or less than a detection limit.

Example 2

(18) 30 kg of molten steels having chemical compositions shown in Table 3 were melted in a vacuum melting furnace to prepare 17 kg of flat steel ingots. Next, the ingots were subjected to hot rolling at a heating temperature of 1,200 C. to obtain hot-rolled steel sheets having a thickness of 4.5 mm. The hot-rolled steel sheets were subjected to annealing at a temperature of 950 C. and then scales were removed by alumina shot blasting. Then, the steel sheets were subjected to cold rolling to have a thickness of 1 mm. Thereafter, the steel sheets were subjected to finish annealing and scales were removed (pickled) by a salt method and immersion in nitric hydrofluoric acid.

(19) The finish annealing temperature was set to temperatures shown in Table 4 and the holding time was set to 1 minute.

(20) As a salt method, a method of heating a commercially available descaling alkali salt mainly containing NaOH and immersing a steel sheet in the alkali salt was applied and the heating temperature was set to temperatures shown in Table 4 and the immersion time was set to 5 seconds.

(21) In the immersion in nitric hydrofluoric acid, a 3% HF-10% HNO.sub.3 solution heated to 55 C. was used and the steel sheets were immersed in the solution for 10 seconds.

(22) The thus-obtained cold-rolled steel sheets (Invention Steels 2-1 to 2-12 and Comparative Steels 2-1 to 2-7) were used to evaluate strength, corrosion resistance and brazing filler spreading abilities and analyze the surface film of the material. Invention Steel 2-4 has the same composition as that of Comparative Example 2-6.

(23) [Tensile (strength) Test at Room Temperature]

(24) A test piece of JIS 13B was sampled from each of the cold-rolled steel sheets in an L direction and the test piece was subjected to a tensile test at room temperature. The obtained 0.2% proof stress values are shown in Table 4.

(25) [Corrosion Test]

(26) A corrosion test was performed under the condition in which degraded biofuel by oxidation was simulated. Two test pieces having a width of 25 mm and a length of 100 mm were sampled from each of the cold-rolled steel sheets and were degreased using an organic solvent. As test solutions, aqueous solutions in which the amount of formic acid was 0.1%, the amount of acetic acid was 1%, and NaCl was dissolved to set the concentration of Cl ions to be 100 ppm were used. The test temperature was set to 95 C. and the test time was set to 168 h. Test conditions other than the above-described conditions were set according to JASO-M611-92-A.

(27) Corrosion products after the corrosion test were removed and then a corrosion mass loss of each test piece was measured and the presence of local corrosion was observed. The corrosion mass loss was calculated from variations in the mass before and after the test. The presence of local corrosion was determined as follows by observing the entire surfaces of the test piece using an optical microscope. That is, 10 m is a detection limit of the value of the depth of corrosion obtained by being measured using a focal depth method. A case in which a corrosion spot having a depth of more than 10 m was detected was defined as presence of local corrosion, and a case in which a corrosion spot having a depth of more than 10 m was not detected was defined as absence of local corrosion.

(28) A case in which at least one of two test pieces had a corrosion mass loss of 0.5 g.Math.m.sup.2 or more, which was equivalent to a detection limit, and/or local corrosion was present in at least one of two test pieces was determined to be a failure (x). In addition, a case in which both of two test pieces had a corrosion mass loss of less than 0.5 g.Math.m.sup.2 and local corrosion was not observed was determined to be a pass (). The results are shown in Table 4.

(29) [Brazing Filler Spreading Abilities]

(30) Three steel sheets having a width of 40 mm and a length of 40 mm were sampled from each of the cold-rolled steel sheets and degreased using an organic solution. Next, 0.5 g of a pure Cu brazing filler metal (BCu-1) was put on the center of the steel sheets and the steel sheets were put into a vacuum furnace to heat the steel sheets at 1130 C. for 10 minutes. The degree of vacuum was approximately 50 Pa. The steel sheets were cooled after the heating and the size of the brazing filler metal was measured. From the result of measuring the size of the brazing filler metal, the area of the brazing filler metal was obtained to calculate a brazing filler spreading coefficient by the following Expression.
Brazing filler spreading coefficient=area of brazing filler metal after heat treatment/initial area of brazing filler metal

(31) In Table 4, brazing filler spreading coefficients are shown. Here, the brazing filler spreading coefficient is an average value of the three steel sheets. In the embodiment, a brazing filler spreading coefficient of 2 or more is good and a brazing filler spreading coefficient of 4 or more is further excellent.

(32) [Analysis of Surface Film of Material]

(33) The surface film of the material was analyzed by X-ray photoelectron spectroscopy (XPS). An XPS apparatus was manufactured by ULVAC-PHI, Inc. XPS was performed using mono-AlK ray as an X-ray source under the condition in which the beam diameter of an X-ray was approximately 100 m and the output angle thereof was 45 degrees and 90 degrees. From the result of quantitative analysis of the outermost surface by the XPS, the Cr cationic fraction Cr.sub.f, the Si cationic fraction Si.sub.f, and the Al cationic fraction Air were obtained. Here, cations are only for metal elements. In addition, the thickness d.sub.f of the oxide film was obtained by an angle resolution method.

(34) In Table 4, the thickness d.sub.f of the oxide film, the Cr cationic fraction Cr.sub.f, the Si cationic fraction Si.sub.f, and the Al cationic fraction Al.sub.f and the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) (A value) are shown.

(35) As shown in Table 4, in Invention Examples 2-1 to 2-12, the 0.2% proof stress was 250 MPa or more and corrosion was not present in the corrosion test under the condition in which degraded biofuel by oxidation was simulated. Also, the brazing filler spreading coefficient was 2 or more and brazeability was excellent.

(36) In Comparative Example 2-1 in which the Cr content was less than 15%, the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) was 2.0 or less. However, the Cr cationic fraction Cr.sub.f was less than 0.18. The brazing filler spreading coefficient was 2 or more but under the environment in which degraded biofuel by oxidation was simulated, corrosion resistance was deteriorated.

(37) In Comparative Examples 2-2, 2-4 and 2-6 in which the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) was more than 2.0, the brazing filler spreading coefficient was less than 2 and brazeability was deteriorated.

(38) In Comparative Example 2-3, since the Cr content was high, the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) was more than 2.0, the Cr cationic fraction Cr.sub.f was increased, and the brazing filler spreading coefficient was less than 2.

(39) In Comparative Example 2-5, since the Nb content in the steel sheet was low, the 0.2% proof stress was less than 250 MPa and strength was deteriorated.

(40) In Comparative Example 2-7, since the Cr content was high, the value of d.sub.fCr.sub.f+5(Si.sub.f+3Al.sub.f) was more than 2.0, and the brazing filler spreading coefficient was less than 2.

(41) TABLE-US-00003 TABLE 3 Chemical composition (mass %) C N Si Mn P S Cr Nb Al Ni Cu Mo Others Invention Invention 0.009 0.015 0.48 0.48 0.032 0.0004 15.05 0.34 0.004 Example 2-1 Steel 2-1 Invention Invention 0.011 0.018 0.38 0.29 0.024 0.0012 17.07 0.39 0.014 Example 2-2 Steel 2-2 Invention Invention 0.013 0.011 0.11 0.12 0.019 0.0006 22.87 0.41 0.029 Example 2-3 Steel 2-3 Invention Invention 0.010 0.015 0.50 0.09 0.026 0.0008 19.37 0.38 0.022 0.29 0.44 Example 2-4 Steel 2-4 Invention Invention 0.008 0.011 0.43 0.13 0.029 0.0033 21.58 0.36 0.024 0.42 0.79 Example 2-5 Steel 2-5 Invention Invention 0.007 0.009 0.17 0.18 0.022 0.0018 19.41 0.48 0.021 0.19 0.46 1.96 Example 2-6 Steel 2-6 Invention Invention 0.007 0.011 0.22 1.18 0.035 0.0018 17.84 0.44 0.003 2.05 Example 2-7 Steel 2-7 Invention Invention 0.006 0.009 0.19 0.19 0.020 0.0010 17.25 0.46 0.029 0.92W, Example 2-8 Steel 2-8 0.002REM Invention Invention 0.008 0.012 0.21 0.20 0.020 0.0008 15.22 0.42 0.048 0.12V, Example 2-9 Steel 2-9 0.0002Mg Invention Invention 0.007 0.015 0.12 0.08 0.026 0.0007 17.45 0.35 0.018 1.05 0.1Sn, Example 2-10 Steel 2-10 0.0005Ca, 0.0004B Invention Invention 0.008 0.008 0.15 0.15 0.025 0.0044 15.14 0.25 0.002 0.11Zr, Example 2-11 Steel 2-11 0.06Co Invention Invention 0.008 0.010 0.21 0.23 0.022 0.0009 17.18 0.43 0.024 0.11Sb, Example 2-12 Steel 2-12 0.21Ta, 0.003Ga Comparative Comparative 0.006 0.009 0.93 0.26 0.021 0.0010 14.88 0.43 0.075 Example 2-1 Steel 2-1 Comparative Comparative 0.005 0.009 0.16 0.19 0.029 0.0007 19.41 0.48 0.034 0.17 0.47 1.90 Example 2-2 Steel 2-2 Comparative Comparative 0.007 0.013 0.35 0.35 0.024 0.0005 29.12 0.26 0.009 Example 2-3 Steel 2-3 Comparative Comparative 0.006 0.014 0.34 0.32 0.031 0.0008 20.05 0.29 0.12 Example 2-4 Steel 2-4 Comparative Comparative 0.004 0.006 0.11 0.07 0.016 0.0011 15.14 0.15 0.036 Example 2-5 Steel 2-5 Comparative Comparative 0.010 0.015 0.50 0.09 0.026 0.0008 19.37 0.38 0.022 0.29 0.44 Example 2-6 Steel 2-6 Comparative Comparative 0.011 0.013 0.12 0.14 0.023 0.0005 23.14 0.40 0.032 Example 2-7 Steel 2-7 Chemical composition (mass %) 8(C + N) + 0.1 Invention Example 2-1 Invention Steel 2-1 0.29 Invention Example 2-2 Invention Steel 2-2 0.33 Invention Example 2-3 Invention Steel 2-3 0.29 Invention Example 2-4 Invention Steel 2-4 0.30 Invention Example 2-5 Invention Steel 2-5 0.25 Invention Example 2-6 Invention Steel 2-6 0.23 Invention Example 2-7 Invention Steel 2-7 0.24 Invention Example 2-8 Invention Steel 2-8 0.22 Invention Example 2-9 Invention Steel 2-9 0.26 Invention Example 2-10 Invention Steel 2-10 0.28 Invention Example 2-11 Invention Steel 2-11 0.23 Invention Example 2-12 Invention Steel 2-12 0.24 Comparative Example 2-1 Comparative Steel 2-1 0.22 Comparative Example 2-2 Comparative Steel 2-2 0.21 Comparative Example 2-3 Comparative Steel 2-3 0.26 Comparative Example 2-4 Comparative Steel 2-4 0.26 Comparative Example 2-5 Comparative Steel 2-5 0.18 Comparative Example 2-6 Comparative Steel 2-6 0.30 Comparative Example 2-7 Comparative Steel 2-7 0.29 Note: underlined values are out of the range of the present invention.

(42) TABLE-US-00004 TABLE 4 Tensile at room Brazeability Finish Salt temperature Brazing filler annealing method Surface film 0.2 proof stress Corrosion spreading temperature temperature d.sub.f/nm Cr.sub.f Si.sub.f Al.sub.f A (MPa) test coefficient ( C.) ( C.) Invention 6.7 0.20 1.3 270 7.1 970 500 Example 2-1 Invention 5.3 0.22 1.2 312 6.9 970 500 Example 2-2 Invention 4.1 0.46 1.9 325 2.1 990 510 Example 2-3 Invention 4.1 0.37 1.5 315 3.9 980 510 Example 2-4 Invention 4.8 0.39 1.9 326 2.2 980 510 Example 2-5 Invention 5.4 0.33 1.8 364 2.3 990 510 Example 2-6 Invention 4.1 0.39 1.6 352 3.0 970 510 Example 2-7 Invention 6.6 0.20 1.3 343 5.1 990 510 Example 2-8 Invention 5.1 0.25 1.3 289 6.4 980 500 Example 2-9 Invention 4.5 0.35 1.6 278 2.9 980 510 Example 2-10 Invention 5.9 0.21 1.2 258 6.8 990 500 Example 2-11 Invention 6.2 0.22 1.4 339 4.8 990 510 Example 2-12 Comparative 4.9 0.17 0.04 0.01 1.2 295 x 7.2 1010 520 Example 2-1 Comparative 5.0 0.26 0.21 2.4 359 1.1 990 470 Example 2-2 Comparative 4.0 0.58 2.3 333 1.4 980 500 Example 2-3 Comparative 4.7 0.38 0.14 3.9 325 1.0 970 500 Example 2-4 Comparative 5.4 0.20 1.1 234 7.5 930 500 Example 2-5 Comparative 4.6 0.30 0.17 2.2 305 1.4 1010 470 Example 2-6 Comparative 4.4 0.50 2.2 321 1.4 1010 490 Example 2-7 [Corrosion test] : pass, and x: failure [Surface film] A = d.sub.f Cr.sub.f + 5(Si.sub.f + 3 Al.sub.f), and the symbol indicates a value which is equal to or less than a detection limit.

INDUSTRIAL APPLICABILITY

(43) The ferritic stainless steel sheet according to the first embodiment having excellent brazeability is suitably used as a material for a joined member by brazing, such as automotive parts such as such as an EGR cooler, an oil cooler, an exhaust heat recovery device, and a fuel delivery system part, and heat exchangers such as a secondary heat exchanger of a latent heat recovery type hot water supply by gas, a plate type heat exchanger of a CO.sub.2 refrigerant heat pump type hot water supply (commonly known as EcoCute (registered trademark)), and various types of plate type heat exchangers.

(44) The ferritic stainless steel according to the second embodiment is suitably used for automotive fuel supply system parts, particularly, direct injection engine fuel supply system parts in which pulsation resulting from variations in fuel pressure is easily generated and is applicable regardless of region. The ferritic stainless steel according to the second embodiment is particularly suitably used for parts, such as a delivery pipe, a fuel pump part, and a fuel pressure adjusting part, which are disposed in the proximity of an engine, used under a high pressure environment, and easily heated to a high temperature, among the fuel supply system parts.