KR101964316B1 - Ferritic stainless steel for exhaust system heat exchanger having excellent sound absorption ability and method of manufacturing the same - Google Patents

Abstract

Disclosed are a ferritic stainless steel for an exhaust system heat exchanger excellent in sound absorption and a method of manufacturing the same. Ferritic stainless steel according to an embodiment of the present invention, in weight percent, carbon (C): 0.001 ~ 0.01%, nitrogen (N): 0.001 ~ 0.01%, silicon (Si): 0.2 ~ 1.0%, manganese ( Mn): 0.1-2%, Chromium (Cr): 10-30%, Nebium (Nb): 0.3-0.6%, Molybdenum (Mo): 0.3-2.5%, Tungsten (W): 0.3-2.5%, Titanium (Ti): 0.001 to 0.1%, aluminum (Al): 0.001 to 0.015%, balance iron (Fe) and unavoidable impurities, and satisfy the following formula (1).
W + 0.5 * Mo ≥ 1.5 ------ Equation (1)

Description

FERRITIC STAINLESS STEEL FOR EXHAUST SYSTEM HEAT EXCHANGER HAVING EXCELLENT SOUND ABSORPTION ABILITY AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a ferritic stainless steel for exhaust heat exchanger and a method of manufacturing the same, and more particularly to a ferritic stainless steel for exhaust heat exchanger excellent in sound absorption that can be used in a high temperature environment of 800 ℃ or more and a method for producing the same.

In recent years, in the automobile field, exhaust gas regulation has been tightened, and coping with carbon dioxide emission suppression has been progressed due to heightened awareness of environmental problems. In addition to coping with fuels such as bioethanol and biodiesel fuel, a heat exchanger for reducing weight and recovering exhaust heat can be installed to improve fuel efficiency, exhaust gas recirculation (EGR), diesel particulate filter (DPF), and exhaust manifold. Countermeasures such as providing an exhaust gas treating apparatus such as an exhaust manifold and the like have been made.

Here, an exhaust manifold having a function of inducing exhaust gas from an engine to a catalyst device is directly exposed to a high temperature environment of 700 ° C. or higher, thus requiring high safety in a long time operating environment.

The ferritic stainless steel has a low thermal expansion coefficient, which is excellent in thermal fatigue characteristics, excellent in oxidation resistance and oxide film adhesion at high temperatures, and excellent in corrosion resistance and high in price competitiveness compared to austenitic stainless steel. It is widely used.

Exhaust system heat exchanger has a problem that a lot of noise and vibration occurs, the quietness of the vehicle is hampered by such noise and vibration, and also there is a problem that the durability of the component is greatly reduced.

In order to solve this problem, an attempt has been made to improve sound absorption by controlling the number and shape of precipitates, solid solution C, N, and inclusions in an exhaust gas environment below 800 ° C., and the effects have been reported.

However, no attempt has been made to improve sound absorption in an exhaust gas environment of 800 ° C or higher.

Korean Unexamined Patent Publication No. 10-2016-0077515 (2016.07.04)

Embodiments of the present invention are to provide a ferritic stainless steel for an exhaust heat exchanger excellent in sound absorption that can improve the quietness and component durability when the ferritic stainless steel is used in the exhaust gas environment, such as the exhaust gas environment in 800 ℃ or more. .

The present invention also provides a method for manufacturing a ferritic stainless steel for an exhaust heat exchanger having excellent sound absorption by controlling a cold rolling annealing process of a ferritic stainless steel.

According to the ferritic stainless steel for an exhaust heat exchanger having excellent sound absorption according to an embodiment of the present invention, in weight%, carbon (C): 0.001 to 0.01%, nitrogen (N): 0.001 to 0.01%, and silicon (Si): 0.2-1.0%, Manganese (Mn): 0.1-2%, Chromium (Cr): 10-30%, Nebium (Nb): 0.3-0.6%, Molybdenum (Mo): 0.3-2.5%, Tungsten (W) : 0.3 to 2.5%, titanium (Ti): 0.001 to 0.1%, aluminum (Al): 0.001 to 0.015%, balance iron (Fe) and inevitable impurities, and satisfy the following formula (1).

W + 0.5 * Mo ≥ 1.5 ------ Equation (1)

In addition, according to an embodiment of the present invention, the ferritic stainless steel may satisfy the following formula (2).

C + N ≤ 0.018 ------ Equation (2)

In addition, according to one embodiment of the present invention, Cu: 0.01% ~ 0.15%, Mg: 0.0002 ~ 0.001%, Ca: 0.0004 ~ 0.002% may be further included.

In addition, according to an embodiment of the present invention, the ferritic stainless steel may satisfy the following formula (3).

 (W + Mo) / Ti ≥ 100 ------ Equation (3)

In addition, according to an embodiment of the present invention, the ferritic stainless steel may satisfy the following formula (4).

W + 0.5 * Mo-5 * Ti ≥ 1 ------ Equation (4)

In addition, according to an embodiment of the present invention, the sound absorption index of the stainless steel may be 10 * 10 ^{-4 or} more.

According to the ferritic stainless steel for an exhaust heat exchanger having excellent sound absorption according to an embodiment of the present invention, in weight%, C: 0.001 to 0.01%, N: 0.001 to 0.01%, Si: 0.2 to 1.0%, and Mn: 0.1 to 2%, Cr: 10-30%, Nb: 0.3-0.6%, Mo: 0.3-2.5%, W: 0.3-2.5%, Ti: 0.001-0.1%, Al: 0.001-0.015%, balance Fe and unavoidable impurities Manufacturing a ferritic stainless steel slab comprising a; Hot rolling and hot rolling annealing the slab; And cold rolling annealing the hot rolled sheet.

In addition, according to one embodiment of the present invention, the cold rolling annealing step, the first heat treatment step of maintaining for 30 seconds at 1000 + 20 * (W + 0.5Mo) ℃; And a second heat treatment step of quenching at a temperature of 900 + 20 * (W + 0.5Mo) ° C. and maintaining it for 60 seconds.

Embodiments of the present invention can control the solid solution Mo, W content and Ti content through the control of the component system and manufacturing process of the ferritic stainless steel, accordingly, when applying the ferritic stainless steel to the exhaust system heat exchanger, etc. Excellent sound absorption can be obtained, thereby improving the quietness and component durability of the exhaust system heat exchanger.

1 is a graph illustrating sound absorption of ferritic stainless steel according to an embodiment of the present invention.
2 is a graph showing a cold-rolled annealing pattern of the ferritic stainless steel according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are presented to sufficiently convey the spirit of the present invention to those skilled in the art. The present invention is not limited to the embodiments presented herein but may be embodied in other forms. The drawings may omit illustrations of parts not related to the description in order to clarify the present invention, and may be exaggerated to some extent in order to facilitate understanding.

MEANS TO SOLVE THE PROBLEM The present inventors obtained the following knowledge as a result of performing various examination in order to improve sound absorption when a ferritic stainless steel material is used for exhaust system parts of 800 degreeC or more.

In general, carbon steel is energy absorbed as C and N, which are dissolved during vibration, change position in the lattice, and as a result, absorb sound.

However, since the movement of C and N is sensitive to temperature, it has sound absorption only in a narrow temperature range, and corrosion resistance is also inferior. On the other hand, high Cr steels have excellent corrosion resistance and sound absorption effect due to the internal movement of C and N, because the sound absorption effect is increased due to energy loss caused by the movement of magnetic domain walls in grains. .

In general, a small amount of Nb is added to the ferritic stainless steel for exhaust heat exchanger to improve the high temperature strength.In the case of the Nb-added ferritic stainless steel, inevitably a large amount of Nb (N, C) in the ferrite matrix of the surface layer is precipitated, Since the Nb (N, C) precipitates inhibit the movement of the magnetic domain wall, which is one of the sound absorbing mechanisms during vibration, the sound absorption of ferritic stainless steel is inferior.

In addition, since C and N are mostly combined with Nb and Ti in the form of precipitates, there is almost no solid solution C and N in the ferritic base, and thus the sound absorbing mechanism due to the movement of the solid solution C and N during vibration is also expected. Can't.

On the other hand, Nb is added to ferritic stainless steel applied to exhaust system parts of 800 ° C. or higher for high temperature strength.

In addition, solid solution strengthening elements such as Mo and W may be additionally added. When vibration occurs in an environment of 800 ° C. or higher, sound absorption is improved by short range diffusion of the dissolved Mo and W elements.

The effect of such sound absorption improvement is further enhanced when Mo and W are simultaneously included.

However, when Ti is included in the matrix, Ti- (Mo, W) pairs are formed, and short range diffusion of Mo and W elements is suppressed, resulting in inferior sound absorption at high temperatures.

In the present invention, by increasing the Mo and W content dissolved in the base to improve the sound absorption of the ferritic stainless steel final cold rolled material.

Hereinafter, it will be described in detail with respect to the ferritic stainless steel for exhaust heat exchanger having excellent sound absorption according to an embodiment of the present invention.

Ferritic stainless steel for exhaust heat exchanger having excellent sound absorption according to an embodiment of the present invention, in weight%, carbon (C): 0.001 to 0.01%, nitrogen (N): 0.001 to 0.01%, silicon (Si): 0.2 1.0%, Manganese (Mn): 0.1-2%, Chromium (Cr): 10-30%, Nebium (Nb): 0.3-0.6%, Molybdenum (Mo): 0.3-2.5%, Tungsten (W): 0.3-2.5%, titanium (Ti): 0.001-0.1%, aluminum (Al): 0.001-0.015%, balance iron (Fe) and inevitable impurities.

C: 0.001-0.01%

Carbon (C) is an invasive element that improves the strength of the material. When the content thereof is excessive, the strength is excessively increased and the ductility is lowered. Therefore, the upper limit is limited to 0.01%. However, if the content is too low, it is difficult to obtain the desired sufficient strength, and the refining cost for making a high purity product increases, so the lower limit can be limited to 0.001%.

N: 0.001-0.01%

Nitrogen (N) is an element that serves to precipitate austenite during hot rolling to promote recrystallization. When the content thereof is excessively high, the strength is excessively increased and ductility is lowered, so the upper limit is limited to 0.01%. However, if the content is too low, the refining cost for making high-purity products increases, the lower limit can be limited to 0.001%.

Si: 0.2 ~ 1.0%

Silicon (Si) is an element added for deoxidation and ferrite stabilization of molten steel during steelmaking, and is added in the present invention at least 0.2%. However, when the content is excessive, the hardening of the material causes the ductility of the steel to be lowered, and the upper limit thereof may be limited to 1.0%.

Mn: 0.1 ~ 2%

Manganese (Mn) is an element effective for improving the corrosion resistance, and in the present invention, 0.1% or more is added, more preferably 0.5% or more. However, if the content is excessive, the weldability is deteriorated due to the rapid increase in the generation of Mn-based fumes during welding, and the ductility and corrosion resistance of the steel is deteriorated due to the formation of excessive MnS precipitates. May be limited to 1.5%.

Cr: 10-30%

Chromium (Cr) is the most important element to secure the corrosion resistance and oxidation resistance of stainless steel, in the present invention is added at least 10%. However, if the content is excessive, not only the manufacturing cost increases sharply, but also the problem of grain boundary corrosion occurs, so the upper limit can be limited to 30%.

Ti: 0.001-0.1%

Titanium (Ti) is an element effective in reducing the amount of solid solution carbon and solid solution nitrogen in steel by fixing carbon (C) and nitrogen (N) and improving corrosion resistance. High-temperature sound absorption is reduced by interrupting the short range diffusion of W and Mo, and the upper limit is limited to 0.1%. However, if the content is too low, the cost for ultra-low refinement of impurities is high, and Nb is combined with C and N to precipitate and the high temperature strength effect due to Nb solid solution is reduced, and the lower limit can be limited to 0.001%. have.

Al: 0.001-0.015%

Aluminum (Al) is a strong deoxidizer, serves to lower the content of oxygen in the molten steel is added in the present invention at least 0.001%. However, if the content is excessive, the sleeve defect of the cold rolled strip due to the increase in the non-metallic inclusions at the same time, deteriorating the weldability, the upper limit can be limited to 0.015%.

Nb: 0.3 ~ 0.6%

Nebium (Nb) preferentially bonds with carbon (C), which is an invasive element, to precipitate NbC to lower the solid solution C content. Accordingly, there is an effect of improving the corrosion resistance and high temperature strength is added in the present invention 0.3% or more. However, if the content is excessive, there is a problem of inferior moldability by inhibiting recrystallization, and the upper limit thereof may be limited to 0.6%.

Mo: 0.3 ~ 2.5%

Molybdenum (Mo) is an element that improves the corrosion resistance, high temperature strength and high temperature sound absorption, in the present invention is added 0.3% or more. However, if the content is excessive, brittle occurs due to the generation of intermetallic precipitates, and the upper limit thereof may be limited to 2.5%.

W: 0.3 ~ 2.5%

Tungsten (W) is an element which improves corrosion resistance, high temperature strength and high temperature sound absorption, and is added in the present invention at least 0.3%. However, if the content is excessive, brittle occurs due to the generation of intermetallic precipitates, and the upper limit thereof may be limited to 2.5%.

In addition, the ferritic stainless steel for exhaust heat exchanger excellent in sound absorption according to an embodiment of the present invention, C + N: 0.018% or less, P: 0.05% or less, S: 0.005% or less may be further included.

C + N: 0.018% or less

When the content of C and N is excessive, the strength of the steel is excessively increased and the ductility is lowered. Therefore, the upper limit of these sums may be limited to 0.018%.

P: 0.05% or less

Phosphorus (P) is an impurity inevitably contained in steel, and is an element that is a major cause of grain boundary corrosion during pickling or deterioration of hot workability. Therefore, it is preferable to control the content as low as possible. In the present invention, the upper limit of the P content is managed at 0.05%.

S: 0.005% or less

Sulfur (S) is an inevitable impurity contained in steel, and is an element which is segregated at grain boundaries and becomes a major cause of inhibiting hot workability. Therefore, it is preferable to control the content as low as possible. In the present invention, the upper limit of the S content is controlled to 0.005%.

In addition, the ferritic stainless steel for exhaust heat exchanger excellent in sound absorption according to an embodiment of the present invention, Cu: 0.01% ~ 0.15%, Mg: 0.0002 ~ 0.001%, Ca: 0.0004 ~ 0.002% may be further included.

Cu: 0.01% ~ 0.15%

Copper (Cu) is an element added to improve the corrosion resistance in the exhaust system condensate environment, in the present invention is added at least 0.01%. However, when the content is excessive, the ductility is lowered and the moldability is inferior, and the upper limit thereof may be limited to 0.15%.

Mg: 0.0002-0.001%

Magnesium (Mg) is an element added for deoxidation in the steelmaking process and remains as an impurity after the deoxidation process. However, if the content is excessive, the moldability is inferior, the content is limited to 0.001% or less, and because it is impossible to remove completely, the present invention manages the lower limit of the Mg content to 0.0002%.

Ca: 0.0004-0.002%

Calcium (Ca) is an element introduced for deoxidation in the steelmaking process and remains as an impurity after the deoxidation process. However, if the content is excessive, the corrosion resistance is inferior, it is limited to 0.002% or less? C is limited, and since it is impossible to remove completely, the present invention manages the lower limit of the Ca content to 0.0004%.

Ferritic stainless steel for exhaust heat exchanger having excellent sound absorption according to an embodiment of the present invention may satisfy the following formula (1).

W + 0.5 * Mo ≥ 1.5 ------ Equation (1)

As mentioned above, W and Mo are elements which improve the high-temperature sound absorption at the same time as the solid solution strengthening effect. When both elements are included, the above formula (1) must be satisfied to ensure sufficient sound absorption at a high temperature of 800 ° C. or higher.

For example, the ferritic stainless steel may satisfy the following formula (2).

(W + Mo) / Ti ≥ 100 ------ Equation (2)

When the above formula (2) is satisfied, short range diffusion of W and Mo is activated, and thus may effectively work to improve high temperature sound absorption. On the contrary, when the above formula (2) is not satisfied, W, Mo and Ti- (W, Mo) pairs in which Ti dissolved in matrix are dissolved are formed to form W, Mo and It is possible to obtain high temperature sound absorbency for the purpose of the present invention because it suppresses short range difference.

In addition, for example, the ferritic stainless steel satisfies both the formula (1) and formula (2), it may satisfy the following formula (3).

W + 0.5 * Mo-5 * Ti ≥ 1 ------ Equation (3)

In consideration of the content of W, Mo, which improves high temperature sound absorption, and Ti, which hinders short range diffusion of W and Mo dissolved in the matrix, the above formula (3) is satisfied. At high temperature, the sound absorption is more than doubled.

1 is a graph illustrating sound absorption of ferritic stainless steel according to an embodiment of the present invention.

Referring to FIG. 1, in comparison with the comparative examples in which the value of 'W + 0.5 * Mo − 5 * Ti' is less than 1, the sound absorption index (Q ⁻¹ ) is At a high temperature of 800 ° C., which is the main use environment of the exhaust heat exchanger, 10 × 10 ⁻⁴ or more may be satisfied, thereby confirming that sound absorbency more than twice that of the comparative examples can be obtained.

Thus, when the ferritic stainless steel according to an embodiment of the present invention is applied to an exhaust system heat exchanger or the like, excellent high temperature sound absorption can be obtained, thereby improving the quietness and component durability of the exhaust system heat exchanger.

2 is a graph illustrating a method of manufacturing a ferritic stainless steel according to an embodiment of the present invention.

According to an embodiment of the present invention for producing the ferritic stainless steel, the method for producing a ferritic stainless steel for exhaust heat exchanger having excellent sound absorption, in weight%, carbon (C): 0.001 ~ 0.01%, nitrogen (N) : 0.001-0.01%, silicon (Si): 0.2-1.0%, manganese (Mn): 0.1-2%, chromium (Cr): 10-30%, neobium (Nb): 0.3-0.6%, molybdenum (Mo) ): 0.3 ~ 2.5%, Tungsten (W): 0.3 ~ 2.5%, Titanium (Ti): 0.001 ~ 0.1%, Aluminum (Al): 0.001 ~ 0.015%, Ferritic system containing residual iron (Fe) and unavoidable impurities Manufacturing a stainless steel slab; Hot rolling and hot rolling annealing the slab; And cold rolling annealing the hot rolled sheet.

According to an embodiment of the present invention, a method of manufacturing a ferritic stainless steel for an exhaust heat exchanger having excellent sound absorption characteristics includes hot rolling a slab having the above component system, removing a surface scale of a hot rolled coil, and removing an internal stress of a material. After the hot-rolled annealing process, it may be subjected to cold rolling and cold rolling annealing process.

In general, the hot rolling process includes a rough rolling step for controlling the thickness and width of a heated slab, a finishing rolling step for finally controlling the dimensions of a target product after rough rolling, and a water cooling to match the material of the strip after finishing rolling. Step and winding the rolled strip with a hot rolled coil.

The cold rolling annealing step, the first heat treatment step of maintaining for 30 seconds at 1000 + 20 * (W + 0.5Mo) ℃; And a second heat treatment step of quenching to a temperature of 900 + 20 * (W + 0.5Mo) ° C. and maintaining it for 1 minute.

In the first heat treatment step, through the annealing heat treatment for 30 seconds at a temperature of 1000 + 20 * (W + 0.5 Mo) ℃, Laves phase containing Mo, W generated during playing-hot-rolled-annealed annealing The phase was sufficiently dissolved to increase the Mo and W content in the matrix.

In the secondary heat treatment step, by annealing heat treatment for 60 seconds at 900 + 20 * (W + 0.5 Mo) ℃ temperature, Nb-rich Laves phase is generated in advance, after which the main operating environment of the exhaust system heat exchanger It was intended to maximize the solid solution Mo and W content by suppressing the precipitation of solid solution Mo and W in the Laves phase at a high temperature of 800 ℃.

Hereinafter, a ferritic stainless steel for an exhaust heat exchanger having excellent sound absorption according to an embodiment of the present invention and a method of manufacturing the same will be described in detail with reference to examples.

Inventive steels 1 to 2 and comparative steels 1 to 3 having the composition (weight%) of the following Table 1 were prepared, and slabs were manufactured through continuous casting. Subsequently, the slabs were manufactured by using a rough mill and a continuous finishing mill to produce hot rolled plates, followed by hot rolling annealing and cold rolling.

Steel grade C N Si Mn P S Cr Ti Al Nb Mo W Inventive Steel 1 0.007 0.009 0.26 0.53 0.035 0.003 18.2 0.03 0.03 0.52 2.2 1.1 Inventive Steel 2 0.009 0.008 0.38 0.84 0.032 0.004 18.6 0.02 0.01 0.54 2 1.5 Comparative Steel 1 0.011 0.009 0.27 0.67 0.027 0.004 18.3 0.08 0.14 0.53 0.4 0.4 Comparative Steel 2 0.008 0.01 0.31 0.95 0.028 0.004 18.8 0.04 0.11 0.51 0.6 0.3 Comparative Steel 3 0.009 0.006 0.33 0.79 0.031 0.003 18.5 0.15 0.05 0.52 1.8 1.2

Inventive steels 1 and 2 are shown in Examples 1 and 2 by cold rolling annealing according to the cold rolling annealing pattern of the present invention according to FIG. 2 to obtain a cold rolled annealing plate having a thickness of 1 mm.

Comparative Examples 7 and 8 show cases in which the inventive steels 1 and 2 were subjected to ordinary cold annealing to obtain a cold rolled annealing plate having a thickness of 1 mm.

Comparative Examples 1, 3 and 5 show the cases where the cold rolled annealing plates having a thickness of 1 mm were obtained by treating the comparative steels 1, 2 and 3 with ordinary cold rolling annealing.

Comparative steels 1, 2, and 3 were subjected to cold rolling annealing according to the cold rolling annealing pattern of the present invention according to FIG. 2 to obtain cold rolled annealing plates having a thickness of 1 mm.

That is, when the heat treatment according to the cold-rolled annealing pattern of the present invention, after the first heat treatment for 30 seconds in the temperature range corresponding to 1000 ℃ + 20 * (W + 0.5 Mo) of 900 ℃ + 20 * (W + 0.5 Mo) A heat treatment was performed to quench to temperature and hold for 60 seconds.

On the contrary, in the case of the usual cold rolling annealing treatment, heat treatment was performed at a temperature of 1000 ° C. for 30 seconds.

Steel grade W + 0.5Mo (W + Mo) / Ti Annealing condition after cold rolling Hire W + 0.5Mo-5Ti Q ^-1 Example 1 Inventive Steel 1 2.8 110 Invention annealing pattern 1.5 11.3 Example 2 Inventive Steel 2 2.8 175 Invention annealing pattern 1.7 12.9 Comparative Example 1 Comparative Steel 1 0.6 10 1000 ° C. 30sec 0.1 3.5 Comparative Example 2 Comparative Steel 1 0.6 10 Invention annealing pattern 0.2 3.7 Comparative Example 3 Comparative Steel 2 0.8 23 1000 ° C. 30sec 0.3 4.2 Comparative Example 4 Comparative Steel 2 0.8 23 Invention annealing pattern 0.5 4.8 Comparative Example 5 Comparative Steel 3 2.4 20 1000 ° C. 30sec 0.4 4.3 Comparative Example 6 Comparative Steel 3 2.4 20 Invention annealing pattern 0.8 7.5 Comparative Example 7 Inventive Steel 1 2.8 110 1000 ° C. 30sec 0.7 7.1 Comparative Example 8 Inventive Steel 2 2.8 175 1000 ° C. 30sec 0.9 8.4

The precipitate residue extraction method was performed on the cold rolled annealing plate having a thickness of 1 mm to analyze the Mo and W contents dissolved through ICP analysis (Inductively Coupled Plasma Spectrometry).

Sound absorption was measured by the IMCE "RFDA LTVP800" instrument. The instrument applies a constant impact to a sample of 80 mm (length) * 20 mm (width) * 1 mm (thickness) to generate vibration at a natural frequency, and then measures the sound absorption index (Q ^-1 ) by measuring the degree of attenuation of the sound. .

The higher the sound absorption index, the faster the attenuation of the sound. That is, it means that the sound absorption is excellent. For each 1mm-thick cold-rolled annealing plate after the final heat treatment, the sound absorption index (Q ^-1 , * 10 ^-4 ) for the temperature of 800 ° C, which is the main operating environment of the exhaust system heat exchanger, was measured through the above equipment. It was.

1 is a graph illustrating sound absorption of ferritic stainless steel according to an embodiment of the present invention.

Referring to Figure 1, it can be seen the sound absorption index of the examples and comparative examples according to the 'W + 0.5 Mo-5 Ti' value.

Referring to Table 2 and Figure 1, in the case of Examples 1 and 2 that satisfies all the conditions proposed by the present invention, the sound absorption index (Q ^-1 ) is 10x10 at a high temperature of 800 ℃ the main operating environment of the exhaust system heat exchanger Satisfying more than ^-4 was able to secure more than twice the sound absorption than the comparative examples.

On the other hand, in case of comparative examples, sufficient solid solution W and Mo could not be obtained during hot-annealing, and thus the value of 'W + 0.5Mo-5Ti' was less than 1, indicating insufficient sound absorption.

As described above, the exemplary embodiments of the present invention have been described, but the present invention is not limited thereto, and a person skilled in the art does not depart from the spirit and scope of the following claims. It will be understood that various changes and modifications are possible in the following.

Claims (8)

By weight%, carbon (C): 0.001-0.01%, nitrogen (N): 0.001-0.01%, silicon (Si): 0.2-1.0%, manganese (Mn): 0.1-2%, chromium (Cr): 10 ~ 30%, Nebium (Nb): 0.3-0.6%, Molybdenum (Mo): 0.3-2.5%, Tungsten (W): 0.3-2.5%, Titanium (Ti): 0.001-0.1%, Aluminum (Al): 0.001 to 0.015%, balance iron (Fe) and inevitable impurities, and satisfy the following formula (1), formula (3) and formula (4),
Absorption index is 10 * 10 ^-4 or more ferritic stainless steel for exhaust heat exchanger with excellent sound absorption.
W + 0.5 * Mo ≥ 1.5 ------ Equation (1)
(W + Mo) / Ti ≥ 100 ------ Equation (3)
W + 0.5 * Mo-5 * Ti ≥ 1 ------ Equation (4) The method of claim 1,
The ferritic stainless steel is a ferritic stainless steel for exhaust heat exchanger excellent in sound absorption satisfying the following formula (2).
C + N ≤ 0.018 ------ Equation (2) The method of claim 1,
A ferritic stainless steel for an exhaust system heat exchanger excellent in sound absorption, which further contains Cu: 0.01% to 0.15%, Mg: 0.0002 to 0.001%, and Ca: 0.0004 to 0.002%. delete delete delete By weight% C: 0.001-0.01%, N: 0.001-0.01%, Si: 0.2-1.0%, Mn: 0.1-2%, Cr: 10-30%, Nb: 0.3-0.6%, Mo: 0.3-2.5 %, W: 0.3-2.5%, Ti: 0.001-0.1%, Al: 0.001-0.015%, balance Fe and inevitable impurities, satisfying the following formulas (1), (3) and (4) Manufacturing a ferritic stainless steel slab;
Hot rolling and hot rolling annealing the slab; And
It includes; and cold rolling annealing the hot rolled sheet
A sound absorption index is 10 * 10 ^-4 or more, a method for producing ferritic stainless steel for exhaust heat exchanger having excellent sound absorption.
W + 0.5 * Mo ≥ 1.5 ------ Equation (1)
(W + Mo) / Ti ≥ 100 ------ Equation (3)
W + 0.5 * Mo-5 * Ti ≥ 1 ------ Equation (4) The method of claim 7, wherein
The cold rolling annealing step,
A first heat treatment step of maintaining at 1000 + 20 * (W + 0.5Mo) ° C. for 30 seconds; And a second heat treatment step of quenching at a temperature of 900 + 20 * (W + 0.5Mo) ° C. and maintaining it for 60 seconds.

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