KR101246323B1 - A method of manufacturing cold-rolled steel sheet having excellent dent resistance in muffler of automobile. - Google Patents

Abstract

In the present invention, by weight%, C: 0% or more and 0.01% or less, Si: 0.1 to 0.3%, Mn: 0.3 to 0.5%, P: 0% or more and 0.015% or less, S: 0% or more and 0.015% or less, Al: 0.02-0.05%, N: 0% or less, 0.004% or less, Cu: 0.2 ~ 0.6%, Co: 0.01 ~ 0.04%, Ni: 0.2 ~ 0.4%, Cr: 0.1 ~ 0.3% and Nb: 0.005-0.05% T = 60-780 * C (%)-15 * Si (%)-20 * Mn (%)-12 * Cu (%)-10 * Co (%)-10 * Ni (%)-8 * The T value defined by Cr (%) is 35 or more, and the Nb / C ratio defined by Nb / C ratio = (Nb (%) / 93) / (C (%) / 12) is 0.5 to 2.0. Provided is a steel sheet for automotive mufflers composed of Fe and other unavoidable impurities.

In addition, the present invention is by weight% C: 0% or more 0.01% or less, Si: 0.1-0.3%, Mn: 0.3-0.5%, P: 0% or more 0.015% or less, S: 0% or more 0.015% or less, Al: 0.02-0.05%, N: 0% or less, 0.004% or less, Cu: 0.2 ~ 0.6%, Co: 0.01 ~ 0.04%, Ni: 0.2 ~ 0.4%, Cr: 0.1 ~ 0.3% and Nb: 0.005-0.05% T = 60-780 * C (%)-15 * Si (%)-20 * Mn (%)-12 * Cu (%)-10 * Co (%)-10 * Ni (%)-8 * The T value defined by Cr (%) is 35 or more, and the Nb / C ratio defined by Nb / C ratio = (Nb (%) / 93) / (C (%) / 12) is 0.5 to 2.0. Preparing a hot slab of Fe and other unavoidable impurities; reheating the slab and hot rolling the finishing temperature at a condition above Ar3 transformation temperature during the final rolling process to produce a hot rolled steel sheet; Cold rolling at a rolling rate provides a method for manufacturing a cold rolled steel sheet and a step of continuously annealing the cold rolled steel sheet in a temperature range of 500 ~ 900 ℃ 10 seconds or more.

Muffler, Condensate, Cold Rolled Steel, Corrosion Resistance

Description

Method for manufacturing cold rolled steel sheet for exhaust system with excellent dent resistance {A METHOD OF MANUFACTURING COLD-ROLLED STEEL SHEET HAVING EXCELLENT DENT RESISTANCE IN MUFFLER OF AUTOMOBILE.}

Figure 1 is a schematic diagram showing an experimental apparatus used for the corrosion resistance test for the condensate solution according to an embodiment of the present invention.

The present invention relates to a steel sheet used in a high temperature and corrosive environment, and more particularly to a high corrosion resistant automotive muffler steel sheet excellent in corrosion resistance, impact resistance and lifespan guarantee period for the condensate used in the muffler of the automobile and its manufacturing method will be.

Many parts made of steel are applied to automobiles and home appliances. Among the components used in such automobiles and home appliances, it is rarely used in a high temperature corrosion environment.

For example, among components used in a high temperature corrosion environment, there is a muffler for forming an exhaust system of an automobile.

Automotive muffler cools the high-temperature, high-pressure combustion gas emitted from the engine and discharges it to the outside and reduces exhaust noise. Such a muffler is generally composed of a muffler body and an exhaust pipe connected to the muffler body and a flange for interconnecting them. And although the muffler body is somewhat different depending on the type of car, many partitions and small pipes are generally installed in the interior to reduce noise.

The automotive muffler is not used at room temperature but is used in an environment in which the temperature rises to a high temperature and cools according to the driving condition of the vehicle. In addition, the automobile muffler passes the combustion gas burnt from the engine therein, and the combustion gas passing through the muffler reacts with moisture in the muffler to generate condensed water. The condensed water produced in this way, the _{^{SO 3 2-, NH 4 +,}} SO 4 2-, Cl -, NO 2 -, NO 3 - is that the exhaust gas containing corrosive ions such as.

When the car is operated for a long time, the muffler is internally corroded by the condensate generated from the inside, and external corrosion is caused by the snow removing agent such as calcium chloride sprayed on the road.

For this reason, automotive mufflers should be made of materials that are excellent in corrosion resistance, heat resistance and impact resistance.

Steel sheets used in automobile mufflers so far known are aluminum plated steel sheets and stainless steel sheets.

Steel plated with aluminum is not suitable as a muffler material because aluminum itself is more expensive than steel plate. In addition, the aluminum plated steel sheet has a problem that the aluminum plated layer is corroded when used for a long time, thereby causing the steel sheet of the corroded portion to corrode very quickly. In order to solve the corrosion problem, there is a method of increasing the thickness of the aluminum plating layer, but this method also has a problem in that the cost increases as the thickness of the aluminum plating layer is thicker. Also technically, there is a limit in increasing the thickness of the plating layer. Therefore, steel plated with aluminum has many problems in terms of corrosion resistance and manufacturing cost to be used as a muffler material for automobiles.

In the case of another automotive muffler material stainless steel sheet is known to be relatively excellent in corrosion resistance, but the price of the material itself is expensive. In addition, the muffler is used in an environment where the temperature change from high temperature to room temperature is severe, and thus the high temperature corrosion resistance of the stainless steel sheet itself becomes a problem in such an environment where the temperature change is severe.

In order to solve such a problem, a steel sheet is proposed to improve the properties of the plated layer plated on the steel sheet, change the components of the stainless steel sheet itself, or plate aluminum on the stainless steel.

As such prior art, there is Japanese Patent Laid-Open No. 1999-269605. The present invention relates to an aluminum plating layer, the composition of the steel sheet itself, C: 0.004 wt% or less, P: 0.04 to 0.08 wt%, S: 0.01 wt% or less, Ti: 0.02 to 0.10 wt%, N: 0.003 wt% or less Disclosed is a steel sheet containing a Zn-Al-based alloy containing Al: 30 to 70 wt% and Si: 0.5 to 2.5 wt% on one or both sides of the steel sheet, with the balance being Zn. .

However, this invention still has a problem that corrosion resistance is not sufficient.

Another prior art is Japanese Patent Laid-Open No. 1990-270521. This invention is to enhance the corrosion resistance by plating aluminum on stainless steel. And another prior art is Japanese Patent Laid-Open No. 1976-136792. This invention improves weldability etc. by adjusting the component of a steel plate.

However, the above two inventions still have disadvantages in that the production cost is high due to the addition of expensive ferroalloys such as Ni and Cr.

Accordingly, the present invention is to solve such a conventional problem, an object of the present invention is to provide a steel sheet for automobile muffler excellent in corrosion resistance exhibiting excellent condensate corrosion resistance and high strength while manufacturing cost is low.

It is still another object of the present invention to provide a method for manufacturing a steel sheet for automobile muffler having low manufacturing cost and excellent corrosion resistance exhibiting excellent corrosion resistance and high strength.

In order to achieve the above object, the present invention, by weight% C: 0% or more 0.01% or less, Si: 0.1-0.3%, Mn: 0.3-0.5%, P: 0% or more 0.015% or less, S: 0% More than 0.015% or less, Al: 0.02-0.05%, N: 0% or more and 0.004% or less, Cu: 0.2 to 0.6%, Co: 0.01 to 0.04%, Ni: 0.2 to 0.4%, Cr: 0.1 to 0.3% and Nb Contains: 0.005-0.05%, T = 60-780 * C (%)-15 * Si (%)-20 * Mn (%)-12 * Cu (%)-10 * Co (%)-10 * The T value defined by Ni (%)-8 * Cr (%) is 35 or more and the Nb / C ratio defined by Nb / C ratio = (Nb (%) / 93) / (C (%) / 12) Is 0.5 to 2.0, and provides a steel sheet for automobile muffler composed of the remaining Fe and other unavoidable impurities.

In addition, the present invention is by weight% C: 0% or more 0.01% or less, Si: 0.1-0.3%, Mn: 0.3-0.5%, P: 0% or more 0.015% or less, S: 0% or more 0.015% or less, Al: 0.02-0.05%, N: 0% or less, 0.004% or less, Cu: 0.2 ~ 0.6%, Co: 0.01 ~ 0.04%, Ni: 0.2 ~ 0.4%, Cr: 0.1 ~ 0.3% and Nb: 0.005-0.05% T = 60-780 * C (%)-15 * Si (%)-20 * Mn (%)-12 * Cu (%)-10 * Co (%)-10 * Ni (%)-8 * The T value defined by Cr (%) is 35 or more, and the Nb / C ratio defined by Nb / C ratio = (Nb (%) / 93) / (C (%) / 12) is 0.5 to 2.0. Preparing a hot slab of Fe and other unavoidable impurities; reheating the slab and hot rolling the finishing temperature at a condition above Ar3 transformation temperature during the final rolling process to produce a hot rolled steel sheet; Cold rolling at a rolling rate provides a method for manufacturing a cold rolled steel sheet and a step of continuously annealing the cold rolled steel sheet in a temperature range of 500 ~ 900 ℃ 10 seconds or more.

In addition, the manufacturing method of the steel sheet for automobile muffler according to the present invention includes the step of winding the hot rolled steel sheet in the winding temperature of 600 ℃ or more in the hot rolled steel sheet manufacturing step.

And the method of manufacturing a steel sheet for automobile muffler according to the present invention includes the step of performing the continuous annealing for 10 seconds to 30 minutes in the continuous annealing step.

Hereinafter, preferred embodiments of the present invention will be described in more detail.

Steel sheet for automotive muffler according to an embodiment of the present invention, in the weight% (hereinafter, in the present invention means% by weight unless otherwise specified), C: 0% more than 0.01%, Si: 0.1 ~ 0.3 %, Mn: 0.3-0.5%, P: 0% or more 0.015% or less, S: 0% or more 0.015% or less, Al: 0.02-0.05%, N: 0% or more 0.004% or less, Cu: 0.2-0.6%, Co: 0.01-0.04%, Ni: 0.2-0.4%, Cr: 0.1-0.3% and Nb: 0.005-0.05%, T = 60-780 * C (%)-15 * Si (%)-20 * Tn defined as Mn (%)-12 * Cu (%)-10 * Co (%)-10 * Ni (%)-8 * Cr (%) is 35 or more and Nb / C ratio = (Nb The Nb / C ratio, defined as (%) / 93) / (C (%) / 12), is between 0.5 and 2.0, consisting of the remaining Fe and other unavoidable impurities.

When explaining the reason for limiting the chemical composition of the steel sheet for automobile muffler according to an embodiment of the present invention as follows.

First, the content of carbon (C) is preferably 0.01% or less. Thus, the reason for limiting the content of carbon (C) is that when the carbon is 0.01% or more, the carbon content is high, the ductility is lowered, thereby greatly reducing the workability for processing the muffler. Therefore, the content of carbon (C) is preferably made 0.01% or less.

The content of silicon (Si) is preferably 0.1-0.3%. The reason for limiting the content of silicon as described above is that silicon reacts with moisture to form SiO ₂ oxide, which delays condensate corrosion. If the content of Si is less than 0.1%, the amount of SiO ₂ oxide is less and the corrosion resistance is less. When the content is 0.1% and the Si content exceeds 0.3%, the ductility is lowered and the moldability is inhibited, so the upper limit is preferably 0.3%.

The content of manganese (Mn) is preferably 0.3 to 0.5%. Manganese is known to play a role in preventing hot shortness caused by solid sulfur by precipitating sulfur dissolved in steel as MnS. In one embodiment of the present invention, the manganese reacts with the condensate to produce MnO to improve the condensate corrosion resistance. When the Mn content is less than 0.3%, the amount of MnO oxides produced is small, so that the corrosion resistance is less. Therefore, the lower limit is 0.3%. When the Mn content is more than 0.5%, the ductility is lowered and the moldability is inhibited, so the upper limit is preferably 0.5%.

The content of phosphorus (P) is preferably 0.015% or less. When the content of phosphorus exceeds 0.015%, it segregates at the grain boundaries and easily corrodes the grains, thereby greatly reducing corrosion resistance and decreasing ductility, thereby decreasing workability. Therefore, the upper limit thereof is preferably 0.015%.

The content of sulfur (S) is preferably 0.015% or less. Sulfur (S) does not significantly affect the corrosion resistance of the condensate, but if it is high, there is a fear that red brittleness may occur and the workability is lowered. Therefore, the upper limit thereof is preferably 0.015%.

The content of aluminum (Al) is preferably 0.02-0.05%. Aluminum is an element to be added as a deoxidizer to precipitate nitrogen in steel to prevent deterioration of formability due to solid nitrogen. In one embodiment of the present invention, if aluminum is less than 0.02%, the moldability may be lowered by solid solution nitrogen. Therefore, the lower limit thereof is 0.02%, and when the aluminum content exceeds 0.05%, the ductility decreases rapidly, so the upper limit thereof is 0.05%. It is desirable to.

The content of nitrogen (N) is preferably 0.004% or less. Since nitrogen is inevitably contained when the content exceeds 0.004%, the moldability is lowered, so the upper limit thereof is preferably 0.004%.

The content of copper (Cu) is preferably 0.2 to 0.6%. Copper is added to the steel and reacts with sulfate ions, which make up a large part of the condensate, to produce CuS. Such copper effectively consumes SO ₄ ^2- ions and SO ₃ ^2- ions in the steel, thereby greatly improving corrosion resistance. When the Cu content is less than 0.2%, the amount of SO ₄ ^2- ions and SO ₃ ^2- ions consumed is small, and the effect of improving corrosion resistance is small. Therefore, the lower limit thereof is 0.2%, and when 0.6% or more is added, Since the effect is small compared with the increase amount and moldability is also reduced, the upper limit is preferably 0.6%.

The content of cobalt (Co) is preferably 0.01 to 0.04%. Cobalt (Co) does not directly improve the condensate corrosion resistance, but when added to the steel serves as a catalyst in the production of CuS. Therefore, even if only a small amount is added, SO ₄ ^2- ions and SO ₃ ^2- ions are effectively removed from the condensate, thereby greatly improving corrosion resistance to the condensate. If the addition amount of Co is less than 0.01%, the lower limit is 0.01% since the effect of improving the corrosion resistance is small. If the addition amount is more than 0.04%, the upper limit is preferably 0.04% because the effect of improving the corrosion resistance decreases as the amount is increased. .

The content of nickel (Ni) is preferably 0.2 to 0.4%. Nickel (Ni) is a corrosion-resistant reinforcing element. When the added amount is 0.2% or less, the lower limit value is 0.2%. Therefore, when the added amount is 0.4% or more, the upper limit value is 0.4 because the corrosion resistance is not high and the cost increases. It is preferable to set it as%.

The content of chromium (Cr) is preferably 0.1 to 0.3%. Chromium (Cr) forms Cr ₂ O ₃ in steels that improves hydrochloric acid resistance, thereby enhancing corrosion resistance. If the addition amount of chromium is 0.1% or less, the lower limit is 0.1% since the effect of improving corrosion resistance is small. If the addition amount is 0.3% or more, the upper limit is 0.3% because the corrosion resistance is not increased and the cost increases due to the increase in the amount added. It is desirable to.

The content of niobium (Nb) is preferably 0.005-0.05%. Niobium (Nb) promotes the development of {111} aggregates, which precipitates carbon present in steel and improves drawability during annealing, thereby greatly improving the processability. If the content of Nb is less than 0.005%, there is little effect of improving texture processing due to the lack of aggregate development. If the added amount is more than 0.05%, the grain size becomes smaller and the processability is rather low. Therefore, the upper limit is 0.05%. desirable.

Moreover, as for Nb / C ratio defined by (Nb (%) / 93) / (C (%) / 12), 0.5-2.0 are preferable. Nb combines with the carbon remaining in the steel to precipitate NbC precipitates, thereby reducing the content of carbon remaining in solid solution that hinders the development of {111} aggregates during annealing. The lower limit is 0.5 because the amount of carbon remaining in the solid state is very small, and the effect of improving the processability is very small. It is preferable to make an upper limit into 2.0.

The T value correlates with the stretchability.T value indicating the stretchability is important because one or both kinds of workability are important depending on the processing method or the product. It can be called the workability index. T = 60-780 * C (%)-15 * Si (%)-20 * Mn (%)-12 * Cu (%)-10 * Co (%)-10 * Ni (%)-8 * Cr ( When the T value composed of%) is less than or equal to 35 or less, the stretchability is greatly reduced, and it is difficult to use it as a part of the muffler material. Therefore, the T value is preferably 35 or more.

The main cause of corrosion of automotive mufflers is hole corrosion caused by the reaction of sulfate ions in condensate inside the muffler with Fe ions in the steel sheet. In addition, sulfate ions contained in the condensate react with iron ions in the steel sheet to produce FeSO ₄ , and these FeSO ₄ are reconstructed by the condensate to regenerate sulfate ions to continuously cause corrosion.

Therefore, in one embodiment of the present invention is that the addition of copper produce a Cu ₂ S reacts with the sulfate ion by being suppressed to such a Cu ₂ S is that the sulfate regeneration by the FeSO ₄ formed on the surface of the steel plate is Corrosion is prevented by condensate.

And cobalt added in the embodiment of the present invention serves as a catalyst for the production of Cu ₂ S well.

Therefore, in the embodiment of the present invention, the added copper and cobalt interact to rapidly reduce the corrosion caused by condensate.

Hereinafter will be described a method of manufacturing a steel sheet for automotive muffler according to an embodiment of the present invention.

First, C: 0% or more and 0.01% or less, Si: 0.1 to 0.3%, Mn: 0.3 to 0.5%, P: 0% or more and 0.015% or less, S: 0% or more and 0.015% by weight in a conventional steelmaking process Al: 0.02-0.05%, N: 0% or more and 0.004% or less, Cu: 0.2 to 0.6%, Co: 0.01 to 0.04%, Ni: 0.2 to 0.4%, Cr: 0.1 to 0.3%, and Nb: 0.005- 0.05%, T = 60-780 * C (%)-15 * Si (%)-20 * Mn (%)-12 * Cu (%)-10 * Co (%)-10 * Ni (% The T value defined by -8 * Cr (%) is 35 or more, and the Nb / C ratio defined by Nb / C ratio = (Nb (%) / 93) / (C (%) / 12) is 0.5 to 2.0, to produce a steel slab consisting of the remaining Fe and other unavoidable impurities.

The slabs thus prepared are reheated under normal conditions and subjected to hot rolling. At this time, it is preferable to carry out the rolling temperature at the time of the above-mentioned Ar3 transformation temperature at the time of finish rolling of hot rolling.

This is because when the finish rolling temperature of hot rolling is lower than the Ar3 transformation temperature, not only the workability is degraded by the formation of the rolled grain but also the ductility is greatly reduced.

The coiling temperature of the hot rolled coil after finishing rolling is preferably 600 ° C. or higher. This is because when the coiling temperature of the hot rolled coil is less than 600 ° C., AlN is not precipitated in the steel and solid solution nitrogen remains in the steel, thereby degrading the formability of the steel sheet.

The hot rolled steel sheet manufactured as described above is cold rolled by a common cold rolling mill.

At this time, cold rolling is preferably performed at a reduction ratio of 50 to 90%. If the cold reduction rate is less than 50%, since the amount of nucleation due to recrystallization during annealing is small, the grains grow too large and the strength and formability of the steel sheet are reduced.

In addition, when the cold reduction rate exceeds 90%, the moldability is improved, but the amount of nucleation is so large that recrystallized grains by annealing may be too fine, which may lower the ductility of the steel sheet.

The cold rolled steel sheet as described above is continuously annealed in a continuous annealing furnace. At this time, the continuous annealing temperature during continuous annealing plays an important role in determining the material of the final steel sheet.

Therefore, in one embodiment of the present invention, it is preferable to perform continuous annealing in the temperature range of 500 ~ 900 ℃. If the temperature of the continuous annealing is less than 500 DEG C, recrystallization is not completed and the target ductility value cannot be secured. When the temperature of continuous annealing exceeds 900 ° C., the recrystallized grains coarsen and the strength of the steel sheet decreases.

And the annealing time during continuous annealing is different depending on the thickness of the steel sheet, but the time for recrystallization by annealing can be completed, for example about 10 seconds or more, preferably the continuous annealing time in the range of 10 seconds to 30 minutes Shall be.

Hereinafter, embodiments of the present invention will be described in more detail.

[Example]

First, a slab was manufactured to have a chemical composition shown in Table 1 below.

division Chemical composition (% by weight) Nb / C ratio C Si Mn P S Al N Cu Co Ti Ni Cr Nb Example 1 0.0025 0.18 0.47 0.01 0.009 0.033 0.0027 0.27 0.016 0 0.24 0.15 0.031 1.6 Example 2 0.0022 0.22 0.33 0.011 0.008 0.028 0.0016 0.36 0.024 0 0.28 0.22 0.015 0.88 Example 3 0.0015 0.26 0.37 0.009 0.011 0.035 0.0023 0.42 0.032 0 0.32 0.23 0.008 0.69 Comparative Example 1 0.033 0.14 0.34 0.01 0.012 0.037 0.0013 0.54 0.02 0 0.36 0.19 0 0 Comparative Example 2 0.0025 0.15 0.11 0.012 0.008 0.025 0.0022 0 0.25 0 0.32 0 0.027 1.39 Comparative Example 3 0.0032 0.08 0.11 0.009 0.01 0.032 0.0019 0.29 0 0 0 0.18 0.074 2.98 Comparative Example 4 0.0018 0.03 0.25 0.013 0.008 0.033 0.0028 0 0 0.04 0 0 0 0

The prepared slabs were reheated to 1200 ° C. in a reheating furnace, followed by hot rolling in a hot rolling mill, followed by finishing hot rolling at 900 ° C., and then wound at 650 ° C. in a winder to prepare hot rolled steel sheets.

The prepared hot rolled steel sheet was partially cut, pickled in 10% hydrochloric acid solution, and the oxidized scale formed on the surface of the steel sheet was removed. Subsequently, the steel sheet from which the oxidized scale was removed was cold rolled in a cold rolling mill at a cold reduction rate of 70%, and then charged into a continuous annealing furnace to perform continuous annealing.

The steel sheet charged to the continuous annealing furnace was heated at a rate of 10 ℃ / second and heated at 830 ℃ for 40 seconds.

The mechanical properties of the steel sheet manufactured by the above method were examined by the following method.

First, in order to investigate the mechanical properties of the manufactured steel sheet was processed standard specimens in accordance with the ASTM E-8 standard (ASTM E-8 standard).

The machined specimen was measured using a tensile tester (INSTRON, Model 6025) to measure yield strength, tensile strength, elongation, plastic anisotropy (r _m value; r _m = (r ₀ + 2r ₄₅ + r ₉₀ ) / 4) It was.

And the corrosion resistance to the condensed water of the prepared steel sheet was evaluated as follows.

First, a condensate solution having a composition similar to that of condensate generated in a muffler of an automobile was prepared as shown in Table 2 below.

Composition of Condensate Solution (ppm) Cl ^- SO ₄ ^2- CO ₃ ^2- NO ₃ ^- NH ₄ ⁺ HCOOH SO ₃ ^- CH3COO ^- pH 600 2000 2000 200 3000 200 1200 800 3.2

And the prepared steel sheet was cut into a size of 40mm X 40mm to prepare a test sample for condensate.

Thus prepared specimen was immersed in a condensate solution having a composition as shown in Table 2 and then heated to 80 ℃ and maintained for 12 hours. Ten cycles of experiments were carried out using this condensate test as one cycle, and then the thickness reduction rate of the specimen was measured to evaluate corrosion resistance of the specimen.

Corrosion resistance evaluation for the condensate was experimented using a double bath as shown in FIG. As shown in FIG. 1, the water is contained in the bath vessel 10 and then heated by a heating means (not shown), the test vessel 30 is installed in the bath vessel 10, and the test vessel 30 is placed in Table 2. Condensate solution 40, such as the appropriate amount is injected.

In this state, while heating the bath in the heating means, one specimen 50 is completely immersed in the condensate solution 40, another specimen 60 is not completely immersed in the condensate solution 40, the test vessel 30 A portion of the specimen is then immersed in the condensate solution 40 and the remaining portion is located outside the condensate solution 40. As such, placing another specimen outside the condensate solution 40 is to evaluate the corrosion resistance of the specimen 60 by steam generated while the condensate solution 40 is heated.

The mechanical properties of the steel sheets measured as described above, the corrosion resistance evaluation results for condensate, and the T values representing the workability of each specimen are shown in Table 3 below.

division Mechanical property 10 Cycle corrosion loss (g / m ² ) T value Yield strength
(MPa) The tensile strength
(MPa) Elongation
(%) Plastic Anisotropy Index (r _m ) Example 1 245 352 42 2.11 519 38.95 Example 2 239 364 40 1.84 529 39.264 Example 3 244 367 41 1.88 511 37.13 Comparative Example 1 279 385 32 1.39 505 13.56 Comparative Example 2 193 309 46 2.18 923 47.9 Comparative Example 3 229 352 38 1.66 789 49.184 Comparative Example 4 187 284 47 1.89 1093 53.146

As can be seen in Table 3, Examples 1 to 3 according to the present invention can be seen that all of the thickness reduction rate due to corrosion in the corrosion resistance evaluation for condensed water is expressed as 529g / m ² or less.

On the contrary, in the case of Comparative Examples 2 and 3, it can be seen that the thickness reduction rate due to corrosion is greater than or equal to 789 g / m ² in the corrosion resistance evaluation for the condensate. Particularly, in the case of Comparative Example 4 in which titanium was added, the thickness reduction rate due to corrosion was very high as 1000 g / m ² in the corrosion resistance evaluation for condensate.

In addition, in the case of Comparative Examples 2 and 3, the thickness reduction rate due to corrosion is much higher than that of Example, since Cu or Co is added alone, and thus Cu and Co did not exhibit a synergistic effect on corrosion resistance. However, in Comparative Examples 2 and 3 it can be seen that the corrosion resistance to the condensed water is superior to Comparative Example 4 added with titanium.

On the other hand, in the case of Comparative Example 1, the other element is included in the scope of the present invention is excellent in the thickness reduction rate due to corrosion is 505g / m ² , but the carbon content is out of the composition range of the present invention, Nb is not added, the plastic anisotropy The index is 1.39, very low, the T value is low, and the elongation is 32%.

As can be seen from the above experiment, the embodiment according to the present invention exhibited a much lower corrosion thickness reduction rate than the comparative examples as a whole, and thus, the steel sheet according to the present invention was found to have excellent corrosion resistance.

In addition, it can be seen that the mechanical properties are equivalent to or better than those of the comparative examples.

As described above, it can be seen that the corrosion resistance of the Example according to the present invention was greatly improved while maintaining the same or superior mechanical properties as the Comparative Example.

Although a preferred embodiment of the present invention has been described so far, the present invention is not limited to the steel sheet for muffler manufactured as described above, but it is possible to plate a corrosion-resistant alloy such as aluminum based on the steel sheet.

Therefore, the present invention can be modified and implemented in various ways within the scope of the claims and the detailed description of the invention, and this also belongs to the scope of the invention.

As described above, the steel sheet for automobile mufflers according to the present invention does not need to add an expensive alloy component such as Cr or Ni, thereby providing an inexpensive automobile muffler steel sheet.

In addition, the steel sheet for automobile muffler according to the present invention has the effect of ensuring the corrosion resistance to a very good condensate compared to the conventional muffler steel sheet.

In addition, the steel sheet for automobile muffler according to the present invention can be manufactured at a low cost as described above, while maintaining a high corrosion resistance, and also has an excellent effect to secure workability and high strength.

Therefore, the steel sheet for automobile mufflers according to the present invention has the physical and chemical properties as described above, and thus has an effect of sufficiently satisfying the long-term warranty requirements enhanced for automobile mufflers.

Claims (4)

By weight% C: More than 0% 0.01% or less, Si: 0.1-0.3%, Mn: 0.3-0.5%, P: 0% or more 0.015% or less, S: 0% or more 0.015% or less, Al: 0.02-0.05% , N: more than 0% and less than 0.004%, Cu: 0.2 to 0.6%, Co: 0.01 to 0.04%, Ni: 0.2 to 0.4%, Cr: 0.1 to 0.3%, and Nb: 0.005-0.05%, T = 60-780 * C (%)-15 * Si (%)-20 * Mn (%)-12 * Cu (%)-10 * Co (%)-10 * Ni (%)-8 * Cr (%) T is defined as 35 or more, Nb / C ratio = (Nb (%) / 93) / (C (%) / 12) Nb / C ratio is defined as 0.5 ~ 2.0, the remaining Fe and other unavoidable Steel sheet for automobile muffler made of impurities. By weight% C: More than 0% 0.01% or less, Si: 0.1-0.3%, Mn: 0.3-0.5%, P: 0% or more 0.015% or less, S: 0% or more 0.015% or less, Al: 0.02-0.05% , N: more than 0% and less than 0.004%, Cu: 0.2 to 0.6%, Co: 0.01 to 0.04%, Ni: 0.2 to 0.4%, Cr: 0.1 to 0.3%, and Nb: 0.005-0.05%, T = 60-780 * C (%)-15 * Si (%)-20 * Mn (%)-12 * Cu (%)-10 * Co (%)-10 * Ni (%)-8 * Cr (%) T is defined as 35 or more, Nb / C ratio = (Nb (%) / 93) / (C (%) / 12) Nb / C ratio is defined as 0.5 ~ 2.0, the remaining Fe and other unavoidable Manufacturing a steel slab made of impurities; Reheating the slab and hot rolling the sheet at a finish rolling condition under Ar3 transformation temperature to produce a hot rolled steel sheet; Manufacturing a cold rolled steel sheet by cold rolling the hot rolled steel sheet at a reduction ratio of 50 to 90%; And Continuously annealing the cold rolled steel sheet in a temperature range of 500 to 900 ° C .; Method for producing a steel sheet for automobile muffler comprising a. 3. The method of claim 2, The method of manufacturing a steel sheet for automobile muffler winding the steel sheet hot rolled in the hot rolled steel sheet manufacturing step at a winding temperature of 600 ℃ or more. In claim 3, The continuous annealing in the continuous annealing step is a method of manufacturing a steel sheet for automobile muffler is made for 10 seconds to 30 minutes.

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