Art
[1]
The invention contains a ferritic stainless steel Sb to satisfy the pitting resistance and resistance to condensate corrosion resistance improved ferritic stainless steel for automobile exhaust system, and relates to a production method thereof, and more particularly, properties required for automobile exhaust system Sb was concentrated on the stainless steel surface steel formula resistance and condensate atmosphere to ensure the corrosion resistance of ferritic stainless steel for automobile exhaust system, which in and a process for their preparation.
BACKGROUND
[2]
Of stainless steel, especially a ferritic stainless cold-rolled product has excellent high-temperature characteristics such as thermal expansion coefficient, the thermal fatigue property and resistance to stress corrosion cracking. Accordingly, ferritic stainless steel is widely used in automotive exhaust system components, household appliances, construction, household appliances, elevator.
[3]
In general, automobile exhaust system members are separated by a high-temperature member (Hot part) and the low-temperature member (Cold part) depending on the temperature of the exhaust gas. Auto Parts of the hot members is excellent in the manifold (Exhaust manifold), the converter (Converter) and a bellows (Bellows) etc., and use temperatures of these components are mainly high-temperature strength and high thermal fatigue and high-temperature salt corrosion property to 600 Should be. On the other hand, the member, such as a low-temperature member (Cold part) is a muffler for reducing the noise of the automobile, mainly the exhaust gas temperature to within 400 (muffler) is sets. Automotive exhaust system low-temperature member (Cold part) is stainless steel, such as the outer surface balcheong corrosion properties according to condensate corrosion property, used in winter claim glossitis generated by the car sulfur (S) component in the fuel reasons (or STS) 409, 409L, 439, 436L or it has been used materials such as Al-coated stainless steel 409.
[4]
For example, stainless steel is the best STS 409L material of the steel may, and the primarily used for sensitizing the prevention and workability temperatures below 700 ℃ excellent grades of C, to stabilize the N to Ti weld to approximately 11% Cr car even against the condensate component generated in the exhaust system is the most widely used type of steel because it has less corrosion resistance.
[5]
And in a corrosive environment requiring corrosion resistance, and use of Cr of 17% STS and the STS 439 436L steel containing Mo about 1% in the STS 439 steel, but has a problem that the material cost is raised parts.
[6]
Recent automotive production penetration in the case of countries such as China, Latin America, India, and rapidly growing, and the situation in the sulfur (S) content is extremely rich in comparison with other developed countries, while gasoline components. For example, Korea, in the case of Japanese, but defines a sulfur (S) content of the gasoline components to 10ppm or less, in the case of Chinese and defined by 500ppm or less, and has actually contain more sulfur (S) component in accordance with the area .
[7]
Sulfur of the gasoline component (S) component is a sulfate ion (SO of the condensed water components of automobile exhaust gas 4 2- , and concentrated to), pH is a strong sulfuric acid (H corrosion resistance of less than 2 2 SO 4 to form a) atmosphere, and thus the existing STS 409L is not possible to ensure corrosion resistance, gradually and the application of stainless steel material of the STS 439, and the chromium Cr component, such as 436L containing more than 17% or Mo system. However, in the case of the material, so the problem of rising increasingly resource prices, Cr, expensive or not containing added elements or the development of the stainless steel material with a small amount of only one pitting corrosion and resistance to condensate corrosion additive elements such as Mo is required .
[8]
(Patent Document 0001) Korea Patent Publication No. 10-2008-0110662 Document No.
Detailed Description of the Invention
SUMMARY
[9]
Embodiments of the present invention for automotive exhaust system that can satisfy the properties required for automobile exhaust system, such as corrosion resistance in formula resistance and condensate atmosphere by containing Sb in the ferritic stainless steel for automobile exhaust system and stainless an Sb thickening of the river surface to provide a ferritic stainless steel.
[10]
In addition, embodiments of the present invention to provide a method for manufacturing a ferritic stainless steel for the automobile exhaust system.
Problem solving means
[11]
In ferritic stainless steel according to one embodiment of the present invention, in weight%, C: 0.01% or less, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 18%, N: 0.013% or less, Ti 0.15 to 0.5%, Sb: 0.03 to and including 0.5%, remainder iron (Fe) and other includes unavoidable impurities, Sb is the base material on the stainless steel surface portion there are over three times more concentrated.
[12]
Further, according to one embodiment of the present invention, Sb: it may comprise 0.05 to 0.5%.
[13]
Further, according to one embodiment of the present invention, it may be in the stainless steel surface portion Sb is concentrated more than seven times compared to the base metal.
[14]
Further, according to one embodiment of the invention, the critical current density of corrosion in automobile exhaust condensate solution is 5.5mA / m 2 or less, the formula potential be greater than or equal to 120mV.
[15]
According to the method for manufacturing ferritic stainless steel according to one embodiment of the present invention, in weight%, C: 0.01% or less, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 18%, N: 0.013% or less, Ti 0.15 to 0.5%, Sb: including 0.03% to 0.5% and the remainder iron (Fe) and other unavoidable impurities ferritic stainless steel to hot rolling comprising the , hot-rolled and annealed, hot rolled pickling, prepared by cold rolling and annealing.
[16]
Further, according to one embodiment of the present invention, the ferritic stainless steel can be manufactured in a conventional manufacturing process STS 409L.
Effects of the Invention
[17]
Embodiments of the present invention the conventional ferritic stainless steel at least about 0.05% of the conventional 11Cr stainless steel robust STS 409 of the steel without causing a cost increase and manufacturing deterioration to Sb addition, formulas resistance and condensate to the corrosion resistance produced excellent ferrite stainless steel can.
[18]
In addition, when using a ferritic stainless steel in accordance with embodiments of the present invention used as such for the exhaust end parts such as mufflers related materials for automotive exhaust systems, without any existing high-sulfur fuel region manufacturing cost increase in the area, such as China It can be manufactured for the automotive exhaust system components to ensure excellent corrosion resistance.
Brief Description of the Drawings
[19]
Figure 1 is a graph showing the anodic polarization characteristics of the stainless steel automotive exhaust system without addition of stainless steel added with Sb to the present invention the condensate solution graph.
[20]
Figure 2 is a graph showing the critical current density of the stainless steel in automotive exhaust system without addition of stainless steel added with Sb to the present invention the condensate solution graph.
[21]
3 is a formula showing the characteristics of the stainless steel in automotive exhaust system without addition of stainless steel added with Sb to the present invention the condensate solution graph.
[22]
4 is a formula showing the potential of the stainless steel in automotive exhaust system without addition of stainless steel added with Sb to the present invention the condensate solution graph.
[23]
Figure 5 is a picture measured using a transmission electron microscope (TEM) the stainless steel according to one embodiment of the present invention.
[24]
Figure 6 is a picture analysis mapping (mapping) using a transmission electron microscope (TEM) the stainless steel of FIG.
[25]
Figure 7 is a stainless steel surface concentrated region Sb of Fig. 5 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results.
[26]
Figure 8 is a stainless steel base metal area of ​​FIG. 5 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results.
[27]
Figure 9 is a photograph measured using a transmission electron microscope (TEM) the stainless steel according to one embodiment of the present invention.
[28]
Figure 10 is a picture analysis mapping (mapping) using a transmission electron microscope (TEM) the stainless steel of FIG.
[29]
Figure 11 is a stainless steel Sb first surface concentrated region in Fig. 9 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results.
[30]
Figure 12 is a stainless steel Sb second surface concentrated region in Fig. 9 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results.
[31]
Figure 13 is a stainless steel base metal area of ​​FIG. 9 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results.
Best Mode for Carrying Out the Invention
[32]
In ferritic stainless steel according to one embodiment of the present invention, in weight%, C: 0.01% or less, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 18%, N: 0.013% or less, Ti 0.15 to 0.5%, Sb: 0.03 to and including 0.5%, remainder iron (Fe) and other includes unavoidable impurities, Sb is the base material on the stainless steel surface portion there are over three times more concentrated.
Mode for the Invention
[33]
Hereinafter will be described in detail with reference to the accompanying drawings, an embodiment of the present invention. The following examples will be presented to fully convey the scope of the invention to those of ordinary skill in the art. The present invention is not limited to the embodiments described herein may be embodied in different forms. Figures may be somewhat exaggerated to express the size of the components, for clarity, not shown, and a portion not related to the description in order to clarify the invention.
[34]
According to one embodiment of the present invention, a ferritic stainless steel for automobile exhaust system is, percent, C parts by weight: not more than 0.01%, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01 % or less, Cr: 11 to 18%, N: 0.013% or less, Ti 0.15 to 0.5%, Sb: 0.03 to 0.5%, including, and includes the remainder iron (Fe) and other unavoidable impurities.
[35]
Ti (C, N) C and N to carbonitrides present in the interstitial a storage-forming element is, the higher the C, N content of Ti (C, N) without cargo forming carbonitride, C, is present in dissolved N is the material when lowering the elongation and low temperature impact properties and, for a long time in the post-weld below 600 ℃ Cr 23 C 6 is a carbide is produced, since the mouth system unit expression occurs in amounts to at most 0.01%, N 0.01% for C it is preferable to control.
[36]
As well as, C + N When the content is high, a problem that if the high addition of Ti content of the rigid receive a significant amount of surface defects, such as seukaep (scab) in the inclusions increases, and further clogging the nozzle when play has occurred and employment C, because the elongation and impact properties by increasing N deterioration C + N content is preferably controlled to 0.02% or less.
[37]
Si is the higher the stability of the ferrite element is increased when the content of ferrite-phase-forming elements are added as a deoxidizing element. Si is to be improved and oxidation characteristics of the official potential increase of the content is increased. In the present invention, it is preferred that the addition of at least 0.5% and for the purpose of improving the oxidation characteristics of formula potential. When the amount of Si is increased to more than 1.0%, it is preferred that the stiffness that controls that does not exceed a maximum of 1.0% or more increases, and a problem occurs such as the surface defect of the Si inclusions.
[38]
Mn lowers the pitting resistance by forming precipitates such as MnS the higher the content. However, excessive reduction of Mn is preferably controlled to 0.5% or less because it puts the like increase in the purification cost.
[39]
P, S should preferably more, such as to form a grain boundary segregation and MnS seokmul water lowers the hot workability small as possible. However, excessive reduction is preferably controlled because it puts the like increase in the refining cost in the case of P is less than 0.035%, S 0.01%.
[40]
Cr is a necessary element for ensuring the corrosion resistance of stainless steel. If the content of Cr is low when the corrosion resistance decreases in the condensate atmosphere is too high content of it is, but the improvement in corrosion resistance such as high strength and elongation, impact resistance, due to degradation and production cost increases is preferable to control the content of 10 to 18% .
[41]
Ti is an element effective for preventing intergranular corrosion caused by immobilizing the C, N. However, since the problem of mouth expression system unit generating the corrosion resistance or the like generated by degradation Ti / (C + N) ratio decreases, welds, Ti is preferably controlled to at least 0.15%. However, the addition amount of Ti becomes too high, the rigidity of inclusions is increased to receive a significant amount of surface defects, such as seukaep (scab), and also because the problem of clogging the nozzles when playing phenomenon occurs that the content to 0.5% or less it is preferable to control.
[42]
Sb is an essential element for ensuring the corrosion resistance of the formula and condensate atmosphere aim of the present invention.
[43]
In order to secure the formula resistance and corrosion resistance of condensate in the present invention preferably controls the Sb in at least 0.03%. However, because excessive addition results in a Sb normal manufacturing process due to the reduction in it is desirable to control the up to 0.5%. More preferably, the content of Sb may be controlled to 0.05 to 0.5%.
[44]
May be the manufacture of ferritic stainless steel in accordance with one embodiment of the invention after a step of annealing the ferritic stainless steel containing the above composition, hot-rolled, hot-rolled and annealed, hot rolled pickling, cold rolling and finishing, it is usually such a manufacturing process, of STS can be a 409L manufacturing process.
[45]
The ferritic stainless steel is the stainless steel surface portion according to one embodiment of the present invention, there is thickening of Sb is more than three times compared to the base metal. For example, more preferably, the ferritic stainless steel can be Sb is concentrated more than seven times compared to the base metal on the surface of stainless steel parts. Sb is concentrated on a surface portion of stainless steel, which is relatively oxygen affinity, this oxide scale formed is strong compared to the other elements.
[46]
Retrieving the Sb is concentrated region in the surface portion the stainless steel, do not include Sb, as compared with ferritic stainless steel that is not concentrated in the surface portion, and the critical current density is reduced, and improved formula potential, and therefore, it is an object pitting corrosion and which can be obtained in the condensate corrosion.
[47]
Figure 1 is a graph showing the anodic polarization characteristics of the stainless steel automotive exhaust system without addition of stainless steel added with Sb to the present invention the condensate solution graph. Figure 2 is a graph showing the critical current density of the stainless steel in automotive exhaust system without addition of stainless steel added with Sb to the present invention the condensate solution graph.
[48]
One to test a positive polarization characteristic of the automotive exhaust system condensate solution, first with respect to Cr in a high purity ferritic stainless steel containing 11%, simulating an automotive exhaust system response side resin solution (sulfuric acid (H 2 SO 4 ): 5,000ppm, sodium chloride (NaCl): 100ppm, pH: 3.0) was compared to a, stainless steel cathode polarization properties without addition of a stainless steel added with Sb in the steel of the present invention while maintaining the solution at a temperature of 30 ℃ comprising.
[49]
1, the value of the corrosion potential, regardless of the presence or absence of the addition of Sb in the 11% Cr stainless steel, has a corrosion potential values ​​similar to each other to be about -500mV to -600mV. However, stainless steel, the addition of Sb has a potential value is a value lower than that of stainless steel without addition of Sb, a transition region from the active region passivation.
[50]
2, a stainless steel, the addition of Sb can be seen that the critical current density values ​​in the active region has about 2 times lower value than that of stainless steel was not added Sb.
[51]
Further, as being the case of the corrosion current density in the passive range (passive holding current density), which represents a rather small passivation holding current density than stainless steel, the stainless steel by the addition of Sb is not added, this coating is more dense passive form It is determined. If more electrochemical anode Sb added from the polarization properties of stainless steel, Cl - ions, and SO 4 2- ions containing a large amount that pH was confirmed to have excellent corrosion resistance in an acidic atmosphere of the third degree.
[52]
For example, the ferritic stainless steel is critical corrosion current density in the automotive exhaust system condensate solution is 5.5mA / m 2 or less.
[53]
3 is a formula showing the characteristics of the stainless steel in automotive exhaust system without addition of stainless steel added with Sb to the present invention the condensate solution graph. 4 is a formula showing the potential of the stainless steel in automotive exhaust system without addition of stainless steel added with Sb to the present invention the condensate solution graph.
[54]
In order to evaluate the formula resistance, first Cr for while with respect to high purity ferritic stainless steel containing 11%, maintaining a solution containing 1% NaCl to a temperature 30 ℃, added steel and stainless addition of Sb in the present invention not compared the characteristics of stainless steel, not official.
[55]
3 and 4, a stainless steel, the addition of Sb in the 11% Cr stainless steel is found that has the formula potential value is about 13 to 36mV increase compared to stainless steel formula potential value is not added to Sb have.
[56]
For example, the ferritic stainless steel has the formula potential be greater than or equal to 120mV.
[57]
If more electrochemical anode stainless addition of Sb from the polarization characteristics Steel has been found that having a more excellent pitting resistance and corrosion resistance in corrosive conditions condensate containing sulfur content in a large amount. Here, the SO 4 2- ion and Cl% 1 - ion atmosphere of a pH of approximately 3 contained more than the corrosion conditions of a car muffler exhaust system materials in areas such as very high in China, so the 500ppm sulfur content of gasoline components strongly it reflects.
[58]
[59]
It will now be described in detail to a ferritic stainless steel for automobile exhaust system according to an embodiment of the present invention through the embodiments.
[60]
Example
[61]
Invention steel 1
[62]
To the ferritic stainless steel composition, such as the composition of the invention steel 1 in Table 1 was dissolved in a vacuum melting equipment 50Kg it was prepared an ingot (ingot) of 120mm thickness. The prepared ingot as described above, by hot rolling at a temperature of 1,150 ℃ to prepare a hot-rolled steel sheet of 3.0mmt. After annealing the hot-rolled steel sheet, acid pickling to prepare a cold-rolled steel sheet of 1.2mmt by cold rolling after the final annealing, pickling process to prepare a ferrite-based stainless steel products.
[63]
Invention steel 2
[64]
To was prepared in the same manner as the inventive steels 1, except that the composition of the invention steel 2 in Table 1.
[65]
Invention steel 3
[66]
To was prepared in the same manner as the inventive steels 1, except that the composition of Table 1, the inventive steels 3.
[67]
[68]
Comparative Example
[69]
Comparative Steel 1
[70]
To was prepared in the same manner as the inventive steels 1, except that the composition of the comparative steel 1 in Table 1.
[71]
Comparative Steel 2
[72]
To was prepared in the same manner as the inventive steels 1, except that the composition of Comparative Steel 2 of Table 1.
[73]
TABLE 1
division C And Mn P S Cr Ti Sb N Ti / (C + N)
Invention steel 1 0.005 0.597 0.30 0.021 <0.003 11.14 0.22 0.048 0.0074 17.4
Invention steel 2 0.005 0.613 0.31 0.023 <0.003 11.21 0.21 0.11 0.0089 15.1
Invention steel 3 0.006 0.592 0.30 0.019 <0.003 11.24 0.24 0.17 0.0072 18.2
Comparative Steel 1 0.005 0.62 0.30 0.023 <0.003 11.24 0.22 0 0.0074 17.7
Comparative Steel 2 0.006 0.594 0.30 0.020 <0.003 11.29 0.23 0.02 0.0072 18.8

[74]
[75]
Table 2 shows the results of the measurement of the critical current density of the stainless steel and the dislocations formula prepared according to the above-described invention steel and comparative steel.
[76]
TABLE 2
division The critical current density (mA / m 2 ) Official potential (mV) Concentrated layer Sb / Sb base
Invention steel 1 4.72 128 7.7
Invention steel 2 3.96 144 12.1
Invention steel 3 3.39 151 13.3
Comparative Steel 1 7 115 0
Comparative Steel 2 6.2 118 2

[77]
[78]
Evaluation of corrosion resistance is inherent analyze condensate components of Chinese local car muffler that uses the fuel sulfur to Cl - concentration: 100ppm, SO 4 2- concentration aqueous solution of 5,000pmm, temperature: measuring a stainless steel cathode polarization characteristics at 30 ℃ It was. After the test, the corrosion resistance evaluation was considered as a threshold corrosion current density in the active region. Furthermore, Cl - concentration: 1% solution, temperature: measured the resistance in formula 30 ℃. Further, the Sb content of the base metal and Sb were concentrated layer of stainless steel through the EDS (Energy-Dispersive Spectroscopy) analysis.
[79]
Figure 5 is a picture measured using a transmission electron microscope (TEM) the stainless steel according to the invention steel 2 of the present invention. Figure 6 is a picture analysis mapping (mapping) using a transmission electron microscope (TEM) the stainless steel of FIG. Figure 7 is a stainless steel surface concentrated region Sb of Fig. 5 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results. Figure 8 is a stainless steel base metal area of ​​FIG. 5 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results.
[80]
To 7 and by the composition of the main component in the surface concentrated region 1 and the base analysis according to the analysis of Figure 8 are shown in Table 3 below.
[81]
TABLE 3
(weight%) Surface concentrated region 1 Base metal Concentrated layer Sb / Sb base
Fe 85.72716 89.92776 12.1
Cr 12.00198 9.550383
Sb 1.651006 0.136
And 0.619852 0.385613

[82]
[83]
Referring to FIG. 5 to FIG. 8, adjacent the base region on a surface portion of stainless steel according to the invention steel 2 of the present invention can be seen that Sb is the thickening region (surface concentrated region 1) is formed. As shown in Table 2, inventive steels. 2 is reducing the critical current density as compared to the comparative steels, and has a formal potential unknown improved.
[84]
Figure 9 is a photograph measured using a transmission electron microscope (TEM) the stainless steel according to the invention steel 3 of the present invention. Figure 10 is a picture analysis mapping (mapping) using a transmission electron microscope (TEM) the stainless steel of FIG. Figure 11 is a stainless steel Sb first surface concentrated region in Fig. 9 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results. Figure 12 is a stainless steel Sb second surface concentrated region in Fig. 9 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results. Figure 13 is a stainless steel base metal area of ​​FIG. 9 EDS (Energy-Dispersive Spectroscopy) are graphs showing the analysis results.
[85]
By analyzing the composition of the surface concentrated region 2B and the major component in the base material to the 12 and 13 a surface concentrated region analysis on 2A, it is shown in Table 4.
[86]
TABLE 4
(weight%) Surface concentrated region 2A Surface concentrated region 2B Base metal Concentrated layer Sb / Sb base
Fe 80.53429 85.93238 90.0361 7.5~13.0
Cr 14.05519 11.53356 9.587077
Sb 3.725994 2.155875 0.286801
And 0.861019 0.378186 0.090026

[87]
[88]
Even if 9 to refer to Figure 13, adjacent the base region on a surface portion of stainless steel according to the invention steel 3 of the present invention can be seen that the Sb is concentrated region (surface concentrated region 2A, the surface concentrated region 2B) formed. As shown in Table 2, the inventive steels 3 and decreases the critical current density as compared to the comparative steels, a formula to find out the potential improvement.
[89]
In the above-described bar, although the description has been made to exemplary embodiments of the present invention, in the present invention is not limited to those skilled in the art without departing from the spirit and scope of the claims set forth in the following it will be appreciated from the various changes and modifications are possible.
Industrial Applicability
[90]
Pitting resistance and resistance to corrosive condensate is improved ferritic stainless steel for automobile exhaust system and the methods for their manufacture in accordance with embodiments of the present invention is applicable for automotive exhaust system components.
[91]
[92]

Claims
[Claim 1]
By weight%, C: 0.01% or less, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 18%, N: 0.013% or less, Ti 0.15 to 0.5%, Sb: 0.03 to and including 0.5%, remainder iron (Fe) and other unavoidable including impurities, and improves the stainless steel portion Sb the pitting resistance and resistance to condensed water corrosion resistance, which is thicker than three times the base material against the surface the ferritic stainless steel for automotive exhaust systems.
[Claim 2]
Claim 1 wherein, Sb to: a ferritic stainless steel for pitting resistance and the corrosion resistance is improved in the condensate automotive exhaust system comprising a 0.05 to 0.5%.
[Claim 3]
According to claim 1, wherein the stainless steel surface portion Sb in the base material than 7 times or more is a ferritic stainless steel for pitting resistance and the corrosion resistance is improved in the condensate automobile exhaust system, it characterized in that the thickening.
[Claim 4]
According to claim 1, wherein the car exhaust system condensate solution critical corrosion current density of 5.5mA / m in the second or less, the official potential is a ferritic stainless steel for pitting resistance and the corrosion resistance is improved in the condensate automobile exhaust system, characterized in that at least 120mV.
[Claim 5]
By weight%, C: 0.01% or less, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 18%, N: 0.013% or less, Ti 0.15 to 0.5%, Sb: 0.03 to and including 0.5%, remainder iron (Fe) and other inevitable for ferritic stainless steel containing impurities, hot-rolled, hot-rolled and annealed, hot rolled pickling, cold rolling and finish pitting resistance to annealing prepared by and a method for manufacturing a ferritic stainless steel for automobile exhaust system is improved in the condensate with caustic.
[Claim 6]
In the ferritic stainless steel is conventional STS 409L pitting resistance and method for manufacturing a ferritic stainless steel for corrosion resistance in the condensed water is improved automobile exhaust system, characterized in that produced by the production process according to claim 5.