KR20170117967A - Austenitic stainless steel having exceelent orange peel resistance and method of manufacturing the same - Google Patents

Abstract

An austenitic stainless steel excellent in orange peel resistance and a method for producing the same are disclosed. The disclosed austenitic stainless steel has an average grain size (Gs) of surface grains contained in a first region corresponding to a depth of 10% or less from the surface of the austenitic stainless steel with respect to the total thickness of the austenitic stainless steel, And a ratio (Gs / Gi) of an average grain size (Gi) of the inner crystal grains contained in a second region corresponding to a depth of more than 10% from the surface of the austenitic stainless steel is 0.5 or less. Therefore, it is possible to prevent the deterioration of the surface roughness caused by the orange peel on the surface of the steel sheet, while increasing the grain size to reduce the strength of the austenitic stainless steel. In addition, The cost can be reduced.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to austenitic stainless steel having excellent orange fill resistance and a method for manufacturing the same. 2. Description of the Related Art Austenitic stainless steels,

The present invention relates to austenitic stainless steels excellent in orange peel resistance and a method for producing the same. More specifically, the present invention relates to austenitic stainless steels having excellent orange peel resistance, and more particularly, To an austenitic stainless steel excellent in orange peel resistance which can prevent deterioration of surface roughness caused by orange peel on the surface of a steel sheet and a method for producing the same.

Conventionally, attempts have been made to apply stainless steel to air conditioner refrigerant piping for domestic and automobile use. This is because it is not only excellent in corrosion resistance but also relatively low in material cost.

However, since air conditioning refrigerant piping construction is limited, installation work such as bending piping by manpower is essential in many cases of piping construction. Conventional copper pipes or aluminum pipes have sufficient materials However, there is a problem that general stainless steel does not have the flexibility required to be provided at the time of piping construction.

The metal material is characterized in that, when subjected to deformation such as tensile or compression, work hardening occurs and the deformation becomes stronger as the metal material is deformed. The bending of the pipe is a complex action of tension and compression, and as the degree of bending increases, the material becomes harder. In particular, 304 steel, which is most widely used as an austenitic stainless steel, has a severe degree of work hardening, and it is very difficult to bend a pipe by manpower in a space where an air conditioner piping construction is required.

As a method for reducing the strength to solve this problem, the strength of the stainless steel can be reduced by increasing the grain size, that is, the grain size. Strength of stainless steel decreases as the particle size increases. However, as the grain size increases, it is difficult to reduce the strength of the stainless steel simply by increasing the size of the grain because the orange peel, which is a defect of the concavo-convex shape, appears on the surface during processing. Such an orange fill is not a cosmetically good material to be removed, and if it is removed through polishing, it is costly and time consuming.

Korean Patent Publication No. 10-2010-0020446

The embodiments of the present invention can control the average crystal grain size of the steel sheet by increasing the grain size in order to reduce the strength of the steel sheet and to prevent the degradation of the surface roughness due to the orange peel on the surface of the steel sheet in the post- And provides excellent austenitic stainless steels.

In addition, the embodiments of the present invention can prevent the surface roughness deterioration due to the orange peel by suppressing the growth of the surface crystal grains by controlling the content of the delta ferrite phase by casting austenitic stainless steel by strip casting Provided is a method for producing an austenitic stainless steel excellent in orange peel resistance.

The austenitic stainless steel excellent in orange peel resistance according to an embodiment of the present invention is characterized in that the austenitic stainless steel has a thickness in a first region corresponding to a depth of 10% or less from the surface of the austenitic stainless steel with respect to the total thickness of the austenitic stainless steel (Gs / Gi) of an average crystal grain size (Gs) of the surface grain included and an average crystal grain size (Gi) of the inner crystal grains contained in a second region corresponding to a depth greater than 10% from the surface of the austenitic stainless steel, Is 0.5 or less.

According to an embodiment of the present invention, the austenitic stainless steel may contain 0.1 to 0.65% silicon (Si), 1.0 to 3.0% manganese (Mn), and 6.5 to 6.5% nickel (Ni) 10.0%, Cr: 16.5 to 18.5%, Cu: not more than 6.0% (excluding 0), carbon (C) + nitrogen (N): not more than 0.13% It may contain unavoidable impurities.

Also, according to an embodiment of the present invention, the average grain size (Gs) of the surface grains may be 100 탆 or less.

Also, according to an embodiment of the present invention, the stainless steel may be manufactured by strip casting.

Also, according to one embodiment of the present invention, the content of the delta ferrite phase remaining in solidification in the casting of the stainless steel by strip casting may be 5% or more.

Also, according to an embodiment of the present invention, the cold rolled structure of the stainless steel may have a content of delta ferrite phase of 0.5% or more.

The austenitic stainless steels excellent in orange peel resistance according to an embodiment of the present invention are manufactured by strip casting which is cooled to a solid while passing between a pair of rolls rotated during casting of the stainless steel, and austenitic stainless steels The hot-rolled steel sheet is manufactured by controlling the component according to the following formula (1) so that the content (Delta) of the delta ferrite phase remaining in the solidification during casting is 5% or more.

Delta = ((Cr + Mo + 1.5Mn + 0.5Nb + 2Ti + 18) / (Ni + 0.3Cu + 30 * (C + N) + 0.5Mn + 36) +0.262) --------------- Equation (1)

Here, the symbol of the element in the formula (1) is the mass% of the element.

According to an embodiment of the present invention, the austenitic stainless steel may contain 0.1 to 0.65% silicon (Si), 1.0 to 3.0% manganese (Mn), and 6.5 to 6.5% nickel (Ni) 10.0%, Cr: 16.5 to 18.5%, Cu: not more than 6.0% (excluding 0), carbon (C) + nitrogen (N): not more than 0.13% It may contain unavoidable impurities.

According to an embodiment of the present invention, the hot-rolled steel sheet is subjected to heat treatment and then cold-rolled to a total rolling reduction of 50% or more to produce a cold-rolled steel sheet. The cold rolled steel sheet has a content of delta ferrite of 0.5% Or more.

Embodiments of the present invention can prevent deterioration of surface roughness due to orange peel on the surface of a steel sheet even after post-processing of stainless steel while increasing grain size to reduce the strength of austenitic stainless steel. The cost can be reduced by replacing the tube with a stainless steel tube.

In addition, embodiments of the present invention can prevent the deterioration of surface roughness due to orange peel by suppressing the growth of surface crystal grains by controlling the content of delta ferrite phase by casting austenitic stainless steel by strip casting .

1 is a schematic view of an apparatus for explaining a strip casting process for manufacturing austenitic stainless steel according to an embodiment of the present invention.
2 is a cross-sectional view illustrating an austenitic stainless steel cold rolled steel sheet according to an embodiment of the present invention.
3 is a photograph showing a state in which an austenitic stainless steel pipe according to an embodiment of the present invention is bent at 90 °.
4 is a photograph showing the surface of the austenitic stainless steel pipe according to Fig.
5 is a photograph showing the surface of a conventional austenitic stainless steel pipe.
Fig. 6 is a photograph showing the cross-sectional microstructure of the austenitic stainless steel pipe according to Fig. 1;
7 is a photograph showing a cross-sectional microstructure of a conventional austenitic stainless steel pipe.
8 is a graph for explaining the grain size of the austenitic stainless steel and the surface roughness after bending the austenitic stainless steel pipe by 90 ° 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 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 austenitic stainless steel excellent in orange peel resistance according to an embodiment of the present invention comprises 0.1 to 0.65% of silicon (Si), 1.0 to 3.0% of manganese (Mn), 6.5% of nickel (Ni) (Excluding 0), and the remainder is Fe (Cr), 16.5 to 18.5%, Cu (Cu): not more than 6.0% And inevitable impurities.

The reasons for limiting the numerical values of the components constituting the austenitic stainless steel excellent in flexibility of the present invention will be described below.

Silicon (Si) is added by adjusting within the range of 0.1 to 0.65 wt%.

Since silicon (Si) is an essential element added for deoxidation, 0.1% or more is added.

However, when an excessively high content of Si is added, the material is hardened and the upper limit is limited to 0.65% because the corrosion resistance is lowered by forming inclusions in combination with oxygen.

Manganese (Mn) is added in a controlled amount within a range of 1.0 to 3.0% by weight.

Manganese (Mn) is not only essential for deoxidation but also increases the stability of the austenite phase and is added in an amount of 1.0% or more to maintain the austenite balance. However, the addition of Mn in an excessively high content reduces the corrosion resistance of the material, so the upper limit is limited to 3.0%.

Nickel (Ni) is added in a controlled amount within a range of 6.5 to 10.0 wt%.

Nickel (Ni) is added not only to chromium (Cr) but also to corrosion resistance such as corrosion resistance. When the content of Ni is increased, softening of austenite steel can be achieved.

It is also an element contributing to the improvement of the phase stabilization of the austenitic stainless steel. In order to maintain the austenite balance, at least 6.5% is added. However, the addition of an excessively high content of nickel (Ni) leads to an increase in the cost of the steel, thus limiting the upper limit to 10.0%.

Chromium (Cr) is added by adjusting within the range of 16.5 to 18.5 wt%.

Chromium (Cr) is an essential element for improving corrosion resistance, and in order to be used for general purpose, 16.5% or more should be added. However, the addition of an excessively high content of chromium (Cr) causes an austenite phase hardening and increases the cost, thus limiting the upper limit to 18.5%.

Copper (Cu) is added in a controlled amount within a range of 6.0 wt% or less.

Copper (Cu) may cause softening of the austenitic steel. However, the addition of an excessively high content of copper (Cu) deteriorates the hot workability and can rather harden the austenite phase, so that the upper limit is limited to 6.0%.

Carbon (C) + nitrogen (N) should be added in an amount of 0.13 wt% or less.

Carbon (C) and nitrogen (N) not only harden the austenitic stainless steel as an interstitial solid solution strengthening element but also increase the work hardening degree of the material by hardening the modified organic martensite generated at the processing do. Therefore, there is a need to limit the content of carbon (C) and nitrogen (N). In the present invention, the content of C + N is limited to 0.13% or less.

The austenitic stainless steel excellent in orange peel resistance according to an embodiment of the present invention is austenitic stainless steel having a thickness of 10% or less from the surface of the austenitic stainless steel with respect to the total thickness of the austenitic stainless steel (Gs / Gi) of the average crystal grain size (Gs) of the surface grain included and the average crystal grain size (Gi) of the inner crystal grains contained in the second region corresponding to the thickness exceeding 10% from the surface of the austenitic stainless steel, Is 0.5 or less.

That is, the size of the surface crystal grains distributed in the first region adjacent to the surface of the austenitic stainless steel is kept smaller than the inner crystal grains of the austenitic stainless steel so that the austenitic stainless steel pipe is prevented from having an orange peel can do.

For example, the average grain size (Gs) of the surface grains may be 100 탆 or less. On the other hand, the average grain size Gi of the inner crystal grains may be more than 100 mu m to reduce the strength of the stainless steel sheet.

The austenitic stainless steel excellent in orange peel resistance according to an embodiment of the present invention is manufactured by strip casting which is cooled to a solid while passing between a pair of rolls rotated during casting of stainless steel.

1 is a schematic view of an apparatus for explaining a strip casting process for manufacturing austenitic stainless steel according to an embodiment of the present invention.

The strip casting process is a process of producing a hot rolled strip of a steel product directly from a molten steel and is a steel process process capable of drastically reducing manufacturing cost, facility investment cost, energy consumption, pollution gas discharge, etc. by omitting the hot rolling process.

1, the molten steel is received in the ladle 2, flows into the tundish 3 along the nozzle, and the molten steel introduced into the tundish 3 is fed into the tundish 3, The molten steel is supplied through the molten steel injection nozzle 4 between the edge dams 6 provided at both ends of the casting roll 1 and between the casting rolls 1 to start solidification. At this time, in order to prevent oxidation, the molten metal between the casting rolls 1 is protected with a meniscus shield 5 and an appropriate gas is injected to appropriately control the atmosphere. The thin plate 7 is manufactured while being pulled out from the roll nip where both rolls meet, rolled through the rolling machine 8 while being pulled out, then cooled, and wound around the winding machine 9.

In the strip casting process, a hot-rolled coil is manufactured using a twin-roll type strip castor by directly casting molten steel of liquid phase into a plate of 1 to 5 mm thickness and applying a rapid cooling rate to the casting plate. The double-roll type strip casters are characterized in that molten steel is supplied between a casting roll (1) rotating in opposite directions and an edge dam (6) provided on a side and casting while releasing a large amount of heat through a water- At this time. A solidification cell is formed at a rapid cooling rate on the roll surface, and a thin hot-rolled steel sheet having a thickness of 1 to 5 mm is produced by in-line rolling performed continuously after casting. In the strip casting process, since the thin plate is directly cast, there is an advantage that the slab production by the continuous casting and the hot rolling process can be omitted.

In particular, the austenitic stainless steel is produced from the delta ferrite phase at the initial stage of solidification and then solidified into the austenite phase in order to ensure the stability of the solidification phase in the continuous casting under normal conditions. At this time, the content of residual delta ferrite phase in the casting is about 1 to 10% for each type of steel. That is, in a typical slab casting, a delta ferrite phase remains in the slab.

However, since the slab is heated in a reheating furnace for 2 hours or more for hot rolling, most of the delta ferrite phase is decomposed into austenite phase due to solid phase transformation and then hot rolling is also performed at a high temperature, The delta ferrite phase present in the cast structure is mostly decomposed. Therefore, the delta ferrite content of a typical austenitic stainless steel hot-rolled coil is less than 0.5%.

Since the strip casting process casts a thin plate directly from molten steel using a water-cooled roll, the content of the delta ferrite phase is higher than 5% because the reheating and hot rolling process of the slab is omitted, and the delta ferrite phase is formed on the surface of the stainless steel plate And the presence of the above-mentioned delta ferrite phase can suppress the growth of the crystal grains.

Therefore, the content of the delta ferrite phase remaining in the final product can be increased by controlling the content of the delta ferrite phase remaining in the structure of the austenitic stainless steel hot-rolled steel sheet produced according to the strip casting process to 5% Accordingly, the size of the surface crystal grains distributed in the region adjacent to the surface of the austenitic stainless steel can be smaller than that of the austenitic stainless steel.

That is, the content of the delta ferrite phase remaining on the austenitic stainless steel hot-rolled steel sheet according to an embodiment of the present invention may be 5% or more.

In order to control the content (Delta) of the delta ferrite phase remaining in solidification during casting of the austenitic stainless steel to be 5% or more, the component can be controlled according to the following formula (1).

Delta = ((Cr + Mo + 1.5Mn + 0.5Nb + 2Ti + 18) / (Ni + 0.3Cu + 30 * (C + N) + 0.5Mn + 36) +0.262) --------------- Equation (1)

Here, the symbol of the element in the formula (1) is the mass% of the element.

Thereafter, the hot-rolled steel sheet is subjected to heat treatment and then cold rolled at a total reduction ratio of 50% or more to produce an austenitic stainless steel cold-rolled steel sheet.

The cold rolled steel sheet of the austenitic stainless steel cold rolled steel sheet according to an embodiment of the present invention which is cold rolled through the cold rolling process may have a content of delta ferrite phase of 0.5% or more.

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

In Table 1, austenitic stainless steels were produced by controlling the content (Delta) of the delta ferrite phase of the hot-rolled steel sheet manufactured and cast by a strip casting method to be 5 or more as shown in the present invention. Thereafter, the cold rolled steel sheet was subjected to cold rolling at a total rolling reduction of 50%, and a cold rolled steel sheet was prepared, and the surface roughness (orange fill) was measured after 15% stretching. In tension, standard tensile specimens may be prepared as in JIS13B, or the sheet may be directly stretched. 15% is for comparison under the same conditions, and the characteristics of the present invention are not necessarily exhibited only at 15% tensile.

(Gs) of surface grains contained in a region corresponding to a depth of 10% or less from the surface of the austenitic stainless steel with respect to the total thickness of the austenitic stainless steel and an average grain size (Gs / Gi) of the average crystal grain size (Gi) of the inner crystal grains contained in the region corresponding to the depth exceeding the crystal grain size was measured.

Here, the average grain size (Gs) of the surface grains means the average grain size of the grains contained in the region corresponding to the depth of 10% or less from the surface of the austenitic stainless steel with respect to the total thickness of the austenitic stainless steel . The average grain size Gi of the inner crystal grains means the average grain size of the grains contained in the region corresponding to the depth of more than 10% from the surface of the austenitic stainless steel with respect to the total thickness of the austenitic stainless steel .

Delta fair Gs / Gi Whether orange peel Example 1 5.1 Strip casting 0.47 ○ Example 2 6.2 Strip casting 0.42 ○ Example 3 7.2 Strip casting 0.37 ○ Example 4 8.5 Strip casting 0.42 ○ Comparative Example 1 5.5 Continuous casting 1.03 × Comparative Example 2 6.4 Continuous casting 0.95 × Comparative Example 3 4.1 Strip casting 0.74 × Comparative Example 4 6.2 Continuous casting 0.97 ×

Referring to Table 1, when the austenitic stainless steel is manufactured by the strip casting process and the content of the delta ferrite phase is controlled to 5% or more, it can be seen that orange peel does not occur in the final product. It can also be seen that the ratio (Gs / Gi) of the mean grain size (Gs) of the surface grains and the average grain size (Gi) of the inner grains is 0.5 or less when the content of the delta ferrite phase is controlled to 5% or more.

The surface particle sizes of Examples 1 to 4 and Comparative Examples 1 to 4 were measured and shown in Table 2 below.

Surface size (Gs, μm) Whether orange peel Example 1 14 ○ Example 2 40 ○ Example 3 58 ○ Example 4 85 ○ Comparative Example 1 105 × Comparative Example 2 145 × Comparative Example 3 192 × Comparative Example 4 280 ×

Referring to Table 2, the orange peel was good in a stainless steel plate having a surface particle size Gs of 100 탆 or less, and orange peel was apparent in a stainless steel plate having a surface grain size of more than 100 탆 as in Comparative Example.

The surface particle size and internal particle size of the above-mentioned Examples 1 to 4 and Comparative Examples 1 to 4 were measured, and the ratios thereof are shown in Table 3 below.

Surface size (Gs, μm) Internal size (Gi, 탆) Gs / Gi Whether orange peel Example 1 14 30 0.47 ○ Example 2 40 95 0.42 ○ Example 3 58 155 0.37 ○ Example 4 85 201 0.42 ○ Comparative Example 1 105 102 1.03 × Comparative Example 2 145 153 0.95 × Comparative Example 3 192 260 0.74 × Comparative Example 4 280 290 0.97 ×

Table 3 shows that the orange fill resistance characteristic is good under the condition that the surface particle size Gs satisfies 100 탆 or less and the ratio (Gs / Gi) of the surface particle size Gs to the internal size Gi is 0.5 or less .

In the following Table 4, austenitic stainless steels were produced by controlling the content (Delta) of the delta ferrite phase of the hot-rolled steel sheet manufactured and cast by the strip casting method to be 5 or more as shown in the present invention.

Thereafter, an austenitic stainless steel pipe was produced by cold rolling at a total reduction of 50%. The stainless steel pipe was bent by 90 ° using a hand bender, and the surface roughness (orange peel) of the bent portion was observed. Handbenders are used to impart strain to a uniform radius of curvature, and need not necessarily be a handbender. Further, the angle of 90 [deg.] Is for applying a common amount of deformation, and the characteristics of the present invention can not always be obtained only at this angle.

2 is a cross-sectional view illustrating an austenitic stainless steel cold rolled steel sheet according to an embodiment of the present invention. 3 is a photograph showing a state in which an austenitic stainless steel pipe according to an embodiment of the present invention is bent at 90 °.

The average grain size Gs of the surface grains contained in the first region A1 corresponding to the depth of 10% or less from the surface of the austenitic stainless steel 100 with respect to the total thickness of the austenitic stainless steel 100, ) And the average grain size Gi of the inner crystal grains contained in the second region A2 corresponding to the depth of more than 10% from the surface of the austenitic stainless steel were measured and the ratio (Gs / Gi) thereof was shown.

Surface size (Gs, μm) Whether orange peel Example 1 35 ○ Example 2 50 ○ Example 3 69 ○ Example 4 95 ○ Comparative Example 1 110 × Comparative Example 2 150 × Comparative Example 3 170 × Comparative Example 4 250 ×

As shown in Table 4, orange peel was good in a pipe having a surface particle size (Gs) of 100 m or less, and orange peel was apparent in a pipe having a surface particle size (Gs)

Therefore, in order to reduce the strength of the stainless steel by increasing the grain size of the stainless steel while maintaining the surface grain size (Gs) of 100 탆 or less as the orange peel occurs in the pipe having the surface grain size exceeding 100 탆, ).

For example, the average grain size Gi of the inner crystal grains of the austenitic stainless steel may be more than 100 mu m.

Surface size (Gs, μm) Internal size (Gi, 탆) Gs / Gi Whether orange peel Example 1 35 101 0.35 ○ Example 2 50 152 0.33 ○ Example 3 69 169 0.41 ○ Example 4 95 210 0.45 ○ Comparative Example 1 110 102 1.08 × Comparative Example 2 150 153 0.98 × Comparative Example 3 170 260 0.65 × Comparative Example 4 250 201 1.24 ×

When the surface particle size (Gs) satisfies 100 탆 or less and the ratio (Gs / Gi) of the surface particle size (Gs) to the internal size (Gi) is 0.5 or less as in the embodiment of Table 5, .

4 is a photograph showing the surface of the austenitic stainless steel pipe according to Fig. 5 is a photograph showing the surface of a conventional austenitic stainless steel pipe. Fig. 6 is a photograph showing the cross-sectional microstructure of the austenitic stainless steel pipe according to Fig. 1; 7 is a photograph showing a cross-sectional microstructure of a conventional austenitic stainless steel pipe.

4 and 6 are surface and cross-sectional microstructures of the austenitic stainless steel pipe according to the third embodiment. Figs. 5 and 7 are graphs showing the surface and the cross-sectional microstructure of the austenitic stainless steel pipe according to the third comparative example and Figs. Sectional microstructure.

Referring to Table 4, Table 5 and FIG. 4 to FIG. 7, it can be seen that orange peel does not occur on the surface of the austenitic stainless steel pipe according to the embodiment of the present invention, The grains in the region adjacent to the surface have an average size of 100 mu m or less and the grains inside the stainless steel have an average size exceeding 100 mu m so that the size of the grains in the region adjacent to the surface of the stainless steel is finer . In addition, it can be seen that orange peel occurs on the surface of the austenitic stainless steel pipe according to the comparative example, and the aesthetic pipe is in the open state. In the cross-sectional microstructure, the grain size in the region adjacent to the surface of stainless steel, , It can be seen that the grains in the region adjacent to the surface of the stainless steel have an average size exceeding 100 mu m.

8 is a graph for explaining the grain size of the austenitic stainless steel and the surface roughness after bending the austenitic stainless steel pipe by 90 ° according to an embodiment of the present invention.

Referring to FIG. 8, the grain size (Gs) of the surface is limited by the present invention to produce a stainless steel pipe in which orange peel is suppressed while increasing the average crystal grain size of the entire stainless steel in order to reduce the strength of the stainless steel material . That is, in the comparative examples of FIG. 8, the orange peel occurs when the surface roughness (R _Z ) exceeds 10 μm, whereas in the embodiments, the surface roughness R _Z ) Is less than 10 탆, the orange peel is suppressed.

8, an example in which the average grain size Gi of the inner crystal grains is 100 탆 is an austenitic stainless steel pipe manufactured according to the above-mentioned Example 1, and has a surface roughness (R _Z ) And the average grain size Gi of the inner crystal grains is 150 탆 is an austenitic stainless steel pipe manufactured according to the above Example 2. The surface roughness R _Z is about 4.8 탆 and orange peel is generated And the average crystal grain size Gi of the inner crystal grains is 200 탆 is an austenitic stainless steel pipe manufactured according to the above Example 4, and the surface roughness (R _Z ) is about 5.2 탆, .

On the other hand, in the comparative example in which the average crystal grain size Gi of the inner crystal grains is 100 탆, an austenitic stainless steel pipe manufactured according to Comparative Example 1 has an orange peel with a surface roughness (R _Z ) of about 12 탆 And an average crystal grain size Gi of the inner crystal grains of 150 mu m is an austenitic stainless steel pipe manufactured according to Comparative Example 2, an orange fill is generated with a surface roughness (R _Z ) of about 19 mu m, In the comparative example in which the average crystal grain size Gi of the crystal grains is 200 탆, an austenitic stainless steel pipe produced according to Comparative Example 4 has an orange peel with a surface roughness (R _Z ) of about 22 탆 .

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.

1: casting roll 2: ladle
3: Tundish 4: Molten steel injection nozzle
5: Meniscus Shield 6: Edge Dam
7: Sheet metal 8: Rolling machine
9: Winding equipment 100: Stainless steel plate

Claims (7)

With respect to the total thickness of the austenitic stainless steel,
An average grain size (Gs) of surface grains contained in a first region corresponding to a depth of 10% or less from the surface of the austenitic stainless steel and a second grain size (Gs) corresponding to a depth of 10% or more from the surface of the austenitic stainless steel. (Gs / Gi) of the average crystal grain size (Gi) of the inner crystal grains contained in the region is 0.5 or less,
Wherein an average grain size (Gs) of the surface crystal grains is limited to 100 탆 or less by strip casting. Austenitic stainless steel having excellent orange peel resistance. The method according to claim 1,
The austenitic stainless steel according to any one of the preceding claims, wherein 0.1 to 0.65% of silicon (Si), 1.0 to 3.0% of manganese (Mn), 6.5 to 10.0% of nickel (Ni), and 16.5 to 18.5 (Excluding 0), copper (Cu): not more than 6.0% (excluding 0), carbon (C) + nitrogen (N): not more than 0.13% (excluding 0), and Fe and unavoidable impurities Austenitic stainless steel excellent in resistance. The method according to claim 1,
Wherein the content of the delta ferrite phase remaining during solidification in the casting of the stainless steel by strip casting is 5% or more. The method according to claim 1,
Wherein the cold rolled structure of the stainless steel has a content of delta ferrite phase of 0.5% or more. Austenitic stainless steel excellent in orange peel resistance. A method for producing an austenitic stainless steel excellent in orange peel resistance by strip casting which is cooled to a solid state while passing between a pair of rolls rotated during casting of stainless steel,
Comprising the step of preparing a hot-rolled steel sheet by controlling the component according to the following formula (1) so that the content (Delta) of the delta ferrite phase remaining during solidification after casting austenitic stainless steel is not less than 5% A method for manufacturing an austenitic stainless steel.
Delta = ((Cr + Mo + 1.5Mn + 0.5Nb + 2Ti + 18) / (Ni + 0.3Cu + 30 * (C + N) + 0.5Mn + 36) +0.262) --------------- Equation (1)
Here, the symbol of the element in the formula (1) is the mass% of the element. 6. The method of claim 5,
The austenitic stainless steel according to any one of the preceding claims, wherein 0.1 to 0.65% of silicon (Si), 1.0 to 3.0% of manganese (Mn), 6.5 to 10.0% of nickel (Ni), and 16.5 to 18.5 (Excluding 0), copper (Cu): not more than 6.0% (excluding 0), carbon (C) + nitrogen (N): not more than 0.13% (excluding 0), and Fe and unavoidable impurities A method for producing an austenitic stainless steel excellent in resistance. 6. The method of claim 5,
Further comprising a step of subjecting the hot-rolled steel sheet to heat treatment, followed by cold rolling at a total reduction ratio of 50% or more to produce a cold-rolled steel sheet,
Wherein the cold rolled steel sheet has a content of delta ferrite phase of 0.5% or more.

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