KR20190022127A - Ferritic stainless steel with improved impact toughness at low temperature and method of manufacturing the same - Google Patents

Abstract

Disclosed are ferritic stainless steel with improved low temperature impact toughness and a manufacturing method thereof. According to one embodiment of the present invention, the ferritic stainless steel comprises: 18.0 to 20.0 weight percent of Cr; 0.4 to 2.0 weight percent of Nb; 0.1 weight percent or less of Ti (excluding zero weight percent); 0.03 weight percent or less of C; 0.03 weight percent or less of N; and the remainder including Fe and inevitable impurities. In the ferritic stainless steel, a fraction of a γ-fiber (111) phase is 24.0% or more, a ratio of a crystal with a size of 55μm or more is 10.0% or less, and the thickness is 1.8 mm or more. Accordingly, a Charpi impact test value at -40°C is 140 J/cm^2 or more, ductile to brittle transition temperature (DBTT) is -45°C or less, and thus a low temperature impact toughness is able to be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a ferritic stainless steel having improved low temperature impact toughness and a method of manufacturing the ferritic stainless steel.

The present invention relates to a ferritic stainless steel and a method of manufacturing the ferritic stainless steel, and more particularly, to a ferritic stainless steel having improved low temperature impact toughness and a method of manufacturing the ferritic stainless steel.

Among ferritic stainless steels, ferritic stainless steels are widely used in building materials, kitchen containers, and household appliances.

Ferritic stainless steels are lower in workability, toughness and high temperature strength than austenitic stainless steels, but are less expensive because they do not contain a large amount of Ni, and have recently been used in automotive exhaust system components because of their small thermal expansion.

However, in general, ferritic stainless steels containing high Cr and containing Nb and Ti have poor workability and impact toughness as their thickness becomes thicker than those of austenitic stainless steels. Therefore, brittle brittle brittle cracks may occur during cold rolling at a target thickness after hot rolling, cracks may be generated when the plate is broken due to crack propagation, or when the final cold rolled product is formed into a predetermined shape And it is difficult to develop an aggregate structure related to workability, so that it is difficult to manufacture cold-rolled products themselves.

In addition, ferritic stainless steels containing Nb and Ti are firstly reacted with carbon (C) and nitrogen (N), which are interstitial elements, during precipitation of Ti in molten steel at a high temperature, When the various types of carbon / nitride are segregated in the grain boundaries by reaction with N, resistance to propagation of stress and propagation of potential is increased by interfering with the propagation of dislocations generated during processing, and the plastic deformation rapidly decreases.

In addition, when Nb is contained more than Ti, excess Nb remaining after reaction with C and N reacts with Fe to form laves phase, which is an intermetallic compound having a dense packed structure of Fe ₂ Nb type which causes brittleness There is a problem that the impact toughness is further lowered.

Further, when hot-rolling a ferritic stainless steel having a thickness of 5.0 mm or more, it is difficult to obtain fine crystal grains, and coarse and non-uniform crystal grains are formed.

Korean Patent Publication No. 10-2014-0080351 (June 30, 2014)

Embodiments of the present invention are to provide a ferritic stainless steel improved in low temperature impact toughness through grain refinement and aggregate structure control through control of an alloy component and a manufacturing process of a ferritic stainless steel and a method for manufacturing the ferritic stainless steel.

The ferritic stainless steel improved in low temperature impact toughness according to an embodiment of the present invention includes 17.0 to 20% of Cr, 0.05 to 1.0% of Nb, 0.05 to 0.45% of Ti, 0.03% or less of C (Excluding 0), N: not more than 0.03% (excluding 0), the balance of Fe and other unavoidable impurities, satisfies the following formulas (1) to (3) and has a thickness of 1.8 mm or more.

A: (Nb + Ti) / (C + N)? 22 - ????? (1)

B: γ-fiber (111) phase fraction ≥ 24.0% ------ Equation (2)

C: a crystal grain fraction of 55 μm or more ≤ 10.0% - (3)

Here, the? -Fibre (111) refers to a group of aggregates of orientations generated in a direction orthogonal to the (111) plane of the texture.

Further, according to an embodiment of the present invention, the ferritic stainless steel can satisfy the following formula (4).

(A * B) - (A * C) / 100? 3.08 ------ (4)

In addition, according to one embodiment of the present invention, there is provided a method for manufacturing a semiconductor device, comprising the steps of: providing an alloy containing at most 0.6% of Si (excluding 0), 0.5% or less of Mn (excluding 0) 0.01% or less (excluding 0).

According to an embodiment of the present invention, the ferritic stainless steel may be a cold rolled annealed steel sheet having a thickness of 1.8 to 2.2 mm.

Also, according to one embodiment of the present invention, the Charpy impact test value at -40 캜 may be 140 J / cm ^{2 or} more.

Also, according to an embodiment of the present invention, the Ductile to Brittle Transition Temperature (DBTT) value may be less than -45 ° C.

A method of manufacturing a ferritic stainless steel having improved low temperature impact toughness according to an embodiment of the present invention includes: 17 to 20% of Cr, 0.05 to 1.0% of Nb, 0.05 to 0.45% of Ti, 0.03 to 0.03 of C, % Or less (excluding 0), N: 0.03% or less (excluding 0), the balance of Fe and other unavoidable impurities, and satisfying the following formula (1): Reheating the slab at a temperature of 1,220 占 폚 or less and subjecting the slab to hot rolling; And cold rolling the hot rolled hot rolled sheet. In the cold rolling step, the cold rolled annealed steel sheet is cold rolled at a temperature of not higher than 1,050 캜 to produce a cold rolled annealed steel sheet having a final thickness of at least 2.0 mm.

A: (Nb + Ti) / (C + N)? 22 - ????? (1)

According to an embodiment of the present invention, in the hot rolling step, the reduction rate in the last rolling of the rough rolling is 35% or more, the temperature at the rear stage of rough rolling is 950 to 1,050 占 폚, Lt; 0 > C or less to produce a hot-rolled steel sheet having a final sheet thickness of 5.0 to 8.0 mm.

According to an embodiment of the present invention, hot rolling may be performed at a temperature of 1,050 ° C or lower after hot rolling.

Further, according to an embodiment of the present invention, the cold-rolled and annealed steel sheet may satisfy the following formulas (2) and (3).

B: γ-fiber (111) phase fraction ≥ 24.0% ------ Equation (2)

C: a crystal grain fraction of 55 μm or more ≤ 10.0% - (3)

According to an embodiment of the present invention, the cold-rolled and annealed steel sheet may have a Charpy impact test value of 140 J / cm ² or more at -40 ° C and a DBTT of -45 ° C or less.

Embodiments of the present invention provide a ferritic stainless steel improved in low temperature impact toughness which can be used in cold regions and winter months through grain refinement and aggregate structure control by controlling alloy components and manufacturing processes of ferritic stainless steels and a method for manufacturing the ferritic stainless steels can do.

1 is a graph for explaining impact toughness of a ferrite stainless steel of 2 mm thickness according to an embodiment of the present invention.
2 is a graph showing measured phase fractions of the texture of the hot-rolled steel sheets of Examples and Comparative Examples.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to a person having ordinary skill in the art to which the present invention belongs. The present invention is not limited to the embodiments shown herein but may be embodied in other forms. For the sake of clarity, the drawings are not drawn to scale, and the size of the elements may be slightly exaggerated to facilitate understanding.

The ferritic stainless steel improved in low temperature impact toughness according to an embodiment of the present invention includes 17.0 to 20% of Cr, 0.05 to 1.0% of Nb, 0.05 to 0.45% of Ti, 0.03% or less of C (Excluding 0), N: 0.03% or less (excluding 0), the balance Fe and other unavoidable impurities.

Hereinafter, the reason for limiting the numerical value of the content of the component component in the embodiment of the present invention will be described. Unless otherwise stated, the unit is wt%.

Cr : 17.0 to 20%

Chromium (Cr) is the most important element added for securing the corrosion resistance and oxidation resistance of stainless steel. In the present invention, it is added in an amount of 17.0% or more. However, if the content is excessive, not only the production cost increases but also the intergranular corrosion occurs, so that the content is limited to 20% or less.

Nb : 0.05 to 1%

NbN is preferentially bonded with intercalation elements carbon (C) and nitrogen (N) to form a precipitate that inhibits deterioration of corrosion resistance. NbN attaches to TiN and precipitates. When NbN precipitates, TiN A small amount of a Cr-depleted region is formed so as not to affect the corrosion resistance.

If the content of Nb is less than 0.05%, there is a problem that the high temperature strength of the material is lowered and the grain size becomes coarse because the amount of Nb contained in the material is small. When the content of Nb exceeds 1%, not only the raw material cost rises, Thereby impeding the propagation of the electric potential, increasing the resistance to the propagation of stress and electric potential, and degrading the plastic deformation, thereby deteriorating toughness.

Ti : 0.05 to 0.45%

Titanium (Ti) is an element effective in reducing the amount of solid carbon and solid nitrogen in steel by fixing carbon (C) and nitrogen (N) and improving the high temperature strength and corrosion resistance of steel. But also surface defects are formed due to the formation of Ti inclusions, and the elongation and the low-temperature impact toughness are weakened by increasing the amount of solute Ti, which is limited to 0.45% or less.

However, if the content is too low, the cost for the impurity low-temperature refining becomes high, and Nb is precipitated in combination with C and N, and the effect of high-temperature strength due to Nb solid solution is reduced. have.

C: 0.03% or less (excluding 0)

The carbon (C) is an interstitial element that improves the strength of the material. When the content is excessive, the impurities increase and the elongation and the work hardening index (n value) DBTT) increases and the impact characteristic is weakened, so that the upper limit is limited to 0.03%.

However, when the content is too low, it is difficult to obtain a desired sufficient strength, and the refining cost for producing a high-purity product increases, so that the lower limit can be limited to 0.002%.

N: 0.03% or less (excluding 0)

Nitrogen (N) is an element that accelerates recrystallization by precipitation of austenite during hot rolling. However, when the content is excessive, impurities increase and elongation and work hardening index (n value) decrease, The brittle transition temperature (DBTT) rises and the impact characteristic is weakened, so that the upper limit is limited to 0.03%.

However, if the content is too low, the refining cost for producing a high purity product increases, so that the lower limit can be limited to 0.002%.

For example, the ferritic stainless steel may contain not more than 0.6% of Si (excluding 0), 0.5% or less of Mn (excluding 0), 0.5% or less of Ni (excluding 0), 0.05 to 0.4% of Cu, Al: 0.01% or less (excluding 0).

Si : 0.6% or less (excluding 0)

Silicon (Si) is an element added for deoxidation of molten steel and stabilization of ferrite during steelmaking. However, if the content is excessive, the material is hardened and ductility of the steel is deteriorated, and it is limited to 0.6% or less. Preferably, the content of Si may be 0.01 to 0.5%.

Mn: 0.5% or less (excluding 0)

Manganese (Mn) may be added in an amount of 0.01% or more as an element to be added in terms of corrosion resistance. However, when 0.5% or more is exceeded, there is a problem that the impurities of the material increase and the elongation and the corrosion resistance are deteriorated. Preferably, the content of Mn may be 0.01 to 0.5%.

Ni : 0.5% or less (excluding 0)

Nickel (Ni) is an element added to improve corrosion resistance. However, if the content is excessive, stress cracking may occur, so it is limited to 0.5% or less. Preferably, the content of Ni may be 0.1 to 0.5%.

Cu: 0.05 to 0.4%

Copper (Cu) may be added in an amount of 0.05% or more as an element added for improving corrosion resistance. However, if the content is excessive, the workability may deteriorate, and therefore, it is preferable to limit the content to 0.4% or less.

Al: 0.01% or less (excluding 0)

Aluminum (Al) is a powerful deoxidizer, which serves to lower the oxygen content in molten steel. However, if the content is excessive, a sleeve defect of the cold-rolled strip occurs due to the increase of non-metallic inclusions, and at the same time, the weldability is deteriorated. Preferably, the content of Al may be 0.001 to 0.1%.

P: not more than 0.05%, S: not more than 0.005%

P is an impurity inevitably contained in the steel, and is an element that causes grain boundary corrosion during pickling or hinders hot workability. Therefore, it is preferable to control the content as low as possible. In the present invention, the upper limit of the content of P is controlled to 0.05%.

S is an impurity inevitably contained in steel, and is an element that segregates in grain boundaries and is a main cause of inhibiting hot workability. Therefore, it is preferable to control the content to be as low as possible. In the present invention, the upper limit of the content of S is controlled to 0.005%.

Generally, ferritic stainless steels containing a large amount of Nb and Ti are firstly reacted with carbon (C) and nitrogen (N), which are interstitial elements during the cooling of Ti at a high temperature, , There is a problem that the propagation of the potential generated during processing interferes with resistance to the propagation of stress and the propagation of dislocations, resulting in a drastic decrease in plastic deformation.

When Nb is contained in a larger amount than Ti, the surplus Nb remaining after reaction with C and N is converted into Fe (Nb), which is an intermetallic compound having a dense packed structure of Fe ₂ Nb type, phase is formed and the impact toughness is weakened.

In addition, it is difficult to obtain fine crystal grains due to a shortage of the rolling reduction of ferritic stainless steels having a thickness of 2.0 mm or more during cold rolling, and brittleness is further increased due to the formation of coarse grains and unevenly sized grains.

In order to overcome this disadvantage, in the present invention, the reheating temperature of the material before hot rolling is lowered, the rough rolling load distribution at the time of hot rolling is moved to the rear end, and strong rolling is performed at a lower temperature, (homogeneous and fine crystals were obtained by accelerating the recrystallization and homogenization of the inner crystals during annealing after cold rolling.

Further, by controlling the manufacturing process, the phase fraction of the γ-fiber 111, which is known to improve the toughness of the material, is increased to have a thickness of 1.8 mm or more, and a ferritic stainless steel final cooled To improve the impact resistance at low temperatures.

Here, the? -Fibre (111) refers to a group of aggregates of orientations generated in a direction orthogonal to the (111) plane of the texture.

That is, the ferritic stainless steel according to one embodiment of the present invention is a cold-rolled annealed steel sheet having a thickness of 1.8 mm or more, for example, a cold-rolled annealed steel sheet having a thickness of 1.8 to 2.2 mm.

The ferritic stainless steel satisfies the following formula (1).

A: (Nb + Ti) / (C + N)? 22 - ????? (1)

When the value of (Nb + Ti) / (C + N) is less than 22, there is a problem that the content of Nb and Ti is low and the high temperature strength and the thermal fatigue are deteriorated. Is lowered.

The ferritic stainless steel satisfies the following formula (2).

B: γ-fiber (111) phase fraction ≥ 24.0% ------ Equation (2)

The γ-fiber (111) is a texture known to improve the toughness of the material and can increase the phase fraction of the γ-fiber (111) texture by accumulating strain energy through the control of hot rolling conditions. When the value of B is less than 24.0%, sufficient low temperature impact toughness desired in the present invention can not be obtained. The fraction of the γ-fiber (111) phase can be achieved by controlling the hot rolling condition of the present invention, and the ferritic stainless steel produced according to the conventional process has a γ-fiber (111) phase fraction of less than about 20.0% And a Charpy impact test value of -40 DEG C of less than 20 J / cm < ² > (See Table 1)

The ferritic stainless steel satisfies the following formula (3).

C: Ratio of crystal grains having an average grain diameter of 55 μm or more ≦ 10.0% - (3)

If the value of C is more than 10.0%, there is a problem that the coarse crystal grains excessively deteriorate in embrittlement.

The ferritic stainless steel satisfies the following formula (4).

(A * B) - (A * C) ≥ 3.08 ------ (4)

Accordingly, the ferritic stainless steel according to one embodiment of the present invention has a Charpy impact test value of 140 J / cm ² or more at a temperature of -40 ° C, thereby improving the low-temperature impact resistance of the stainless steel.

The ferritic stainless steel satisfies the following formula (5).

D: DBTT ≤ -45 ℃ ------ (5)

DBTT (Ductile to Brittle Transition Temperature) is a ductile brittle transition temperature, and the fracture behavior is changed from soft fracture to brittle fracture based on the DBTT temperature. Accordingly, the ferritic stainless steel according to one embodiment of the present invention has DBTT It has a value of minus 45 ° C or less and can be improved in workability even at a low temperature.

In order to form sufficient deformation structure in the final cold-rolled material, the slab reheating temperature, rough rolling reduction ratio, and finish rolling out temperature (FDT) should be controlled during the hot rolling process.

According to an embodiment of the present invention, a ferritic stainless steel for producing the ferritic stainless steel according to the present invention comprises 17.0 to 20% of Cr, 0.05 to 1% of Nb, 0.05 to 0.45% of Ti, %, C: not more than 0.03% (excluding 0), N: not more than 0.03% (excluding 0), the balance Fe and other unavoidable impurities are produced in a usual manner to produce a slab.

Then, in order to solve the impact toughness problem, in the disclosed embodiment, it is possible to maintain the reheating temperature of the slab before the hot rolling at 1,220 DEG C or less in order to increase the residual stress at the low temperature as low as possible.

Thereafter, in the hot rolling step, the rough rolling load distribution can be shifted to the lower end temperature, which is lower than the shearing temperature.

That is, when the hot rolling is performed at the final rolling, it is strongly pressed down to 35% or more, so that the nucleation site can be induced as much as possible to increase the fine and uniform crystal grains. At this time, the temperature at the downstream end of the hot rough rolling can be controlled to 950 to 1,050 ° C.

Further, the finishing mill delivery temperature (FDT) designed to be higher than the recrystallization temperature is maintained at 920 ° C or lower so that sufficient deformation energy is given to the inside of the slab so that recrystallization may actively occur during hot rolling and annealing. Preferably, the finish rolling-out temperature (FDT) may be 850 DEG C or less.

If the reheating temperature and the finish rolling temperature are too low during the hot rolling, the frictional pressure between the rolled material and the roll becomes high, and the surface of the material scratched on the roll, resulting in sticking defects. Therefore, .

Such a low temperature hot rolling step affects the texture of the hot rolled annealed structure and the final cold rolled steel, thereby improving the workability during cold rolling and the formability of the final cold rolled annealed material.

Thereafter, the hot-rolled and annealed heat treatment is performed at a temperature of 1,050 占 폚 or lower, whereby a hot-rolled annealed steel sheet having a final thickness of 5.0 mm or more can be produced.

According to the ferritic stainless steel producing method for producing the ferritic stainless steel according to the embodiment of the present invention, the hot rolled annealed steel sheet is cold-rolled to a thickness of 2.0 mm, A cold-rolled and annealed steel sheet having a final grain thickness of 2.0 mm or more having fine and uniform crystal grains both in the width direction and the longitudinal direction of the cross-section of the work can be produced by accelerating the recrystallization and homogenization of the grain inside the work.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.

Example

19Cr-0.4Nb STS 430J1L Steel slabs were reheated to 1,200 ° C in a heating zone and subjected to a rolling reduction of 35% at each of the final rolling (R4) and pre-rolling (R3) of the rough rolling, The hot rolled coil was controlled to 1,020 占 폚 and the finish rolling out temperature (FDT) was 850 占 폚 to produce a hot rolled coil having a thickness of 5 mm. Annealing heat treatment at 900 占 폚, cold rolling and cold annealing at 900 占 폚 are performed to produce a cold-rolled annealed coil having a final thickness of 2.0 mm.

Comparative Example

Except that the conventional hot-rolling process was carried out in the first embodiment.

The Charpy impact values of the above Examples and Comparative Examples were measured and are shown in Table 1 below. The Charpy impact value was measured by Charpy impact test according to ASTM E 23 standard.

Temp. (° C) Comparative Example Example Impact Energy (J / cm ² ) Impact Energy (J / cm ² ) -60 5.9 4.1 -40 10.3 146.6 -20 130.1 155.6 0 132.1 164.7 20 133.4 158.7 40 131.4 158.0 60 131.7 158.3

FIG. 1 is a graph showing a Charpy impact test value by temperature for explaining the impact toughness of a 2 mm thick ferritic stainless steel cold-rolled annealed steel sheet according to an embodiment of the present invention.

FIG. 1 is a graph showing the Charpy impact energy of the embodiment and the comparative example.

Referring to FIG. 1, DBTT values of a steel sheet (example) lowered to 1200 ° C or lower and 35% lower than that of a conventional steel sheet (comparative example) reduced to 25% It can be seen that it moved to the left, which is generally low temperature.

Further, even at the same temperature, most of Examples show an improved impact value of 20 J / cm ² or more as compared with Comparative Examples.

Fig. 2 is a graph showing measured phase fractions of the texture of the hot-rolled steel sheets of the examples and comparative examples. Fig.

Referring to FIG. 2, in the case of a steel sheet (Example) which has a low temperature of 1200 ° C or lower and a temperature lowered to 35% at the downstream end compared with a conventional steel sheet (Comparative Example) Fiber (111) phase fraction growing in the (111) direction, which is known to improve the toughness of the γ-fiber, is more than 24%.

Referring to Table 1, as a result of the impact test at minus 40 ° C, the impact value of a cold-rolled annealed steel sheet (example) having a thickness of 2.0 mm and a temperature lowered by 35% or more at a low temperature hot- / cm < ² >, indicating that the impact resistance at low temperatures is significantly improved compared with the existing materials.

This is because a uniform distribution of fine crystal grains and an increase in the phase fraction occupied by the? -Fibers (111).

As a result, in order to improve the impact toughness of the hot-rolled steel sheet of the ferritic stainless steel, control of the alloy component and control of the slab reheating temperature, the reduction rate and the rolling temperature at the time of hot rolling, It can be seen that the impact toughness of the steel can be improved.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited thereto. Those skilled in the art will readily obviate modifications and variations within the spirit and scope of the appended claims. It will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

Claims (11)

C: 0.03% or less (excluding 0), N: 0.03% or less (excluding 0), the balance of Fe and other unavoidable elements (in percent by weight), Cr: 17.0 to 20%, Nb: 0.05 to 1.0%, Ti: 0.05 to 0.45% 1. A ferritic stainless steel comprising an impurity and satisfying the following formulas (1) to (3) and having a thickness of 1.8 mm or more and having improved low temperature impact toughness.
A: (Nb + Ti) / (C + N)? 22 - ????? (1)
B: γ-fiber (111) phase fraction ≥ 24.0% ------ Equation (2)
C: a crystal grain fraction of 55 μm or more ≤ 10.0% - (3)
Here, the? -Fibre (111) refers to a group of aggregates of orientations generated in a direction orthogonal to the (111) plane of the texture. The method according to claim 1,
The ferritic stainless steel satisfies the following formula (4) and has improved low temperature impact toughness.
(A * B) - (A * C) / 100? 3.08 ------ (4) The method according to claim 1,
(Excluding 0), Ni: not more than 0.5% (excluding 0), Cu: 0.05 to 0.4%, and Al: not more than 0.01% (excluding 0) Ferritic stainless steel improved in low temperature impact toughness. The method according to claim 1,
The ferritic stainless steel has a thickness of 1.8 to 2.2 mm and has improved low temperature impact toughness. The method according to claim 1,
A ferritic stainless steel improved in impact resistance at low temperatures with a Charpy impact test value of 140 J / cm ² or more at -40 ° C. The method according to claim 1,
Ferritic stainless steel improved in low temperature impact toughness with DBTT (Ductile to Brittle Transition Temperature) of -45 ℃ or less. C: 0.03% or less (excluding 0), N: 0.03% or less (excluding 0), the balance of Fe and other unavoidable elements (in percent by weight), Cr: 17.0 to 20%, Nb: 0.05 to 1.0%, Ti: 0.05 to 0.45% Preparing a ferritic stainless steel slab containing impurities and satisfying the following formula (1);
Reheating the slab at a temperature of 1,220 占 폚 or less and subjecting the slab to hot rolling; And
And cold-rolling the hot-rolled hot-rolled sheet,
In the cold rolling step,
A cold-rolled and annealed steel sheet having a cold-rolled annealed steel sheet having a final thickness of 2.0 mm or more by cold-rolling at a cold-rolling annealing temperature of 1,050 占 폚 or lower.
(Nb + Ti) / (C + N)? 22 - ????? (1) 8. The method of claim 7,
In the hot rolling step,
Hot rolled at a final rolling temperature of rough rolling of not less than 35% at a final rolling temperature of 950 to 1,050 캜 and a finish rolling rolling temperature of not more than 920 캜 at a tempering temperature of the rough rolling end, A method for producing a ferritic stainless steel improved in impact resistance at low temperature, which comprises producing a hot rolled annealed steel sheet. 9. The method of claim 8,
A method for manufacturing a ferritic stainless steel improved in low temperature impact toughness, further comprising: performing hot rolling and then performing hot rolling annealing at 1,050 占 폚 or lower. 8. The method of claim 7,
Wherein the cold-rolled and annealed steel sheet satisfies the following formulas (2) and (3).
γ-fiber (111) phase fraction ≥ 24.0% ------ Equation (2)
55 탆 or more ≤ 10.0% - (3) 11. The method of claim 10,
Wherein the cold-rolled and annealed steel sheet has a Charpy impact test value of 140 J / cm ² or more at -40 캜, and a DBTT of -45 캜 or lower and improved impact toughness at low temperatures.

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