KR102260262B1 - High corrosion resistance austenitic stainless thick steel plate and method of manufacturing the same - Google Patents

Abstract

The present invention relates to high corrosion-resistance austenitic stainless steel having a broad width of no less than 2 m, capable of reducing the number of welding processes, and a rear plate manufacturing process having a thermal treatment process optimized for manufacturing the same. According to one embodiment of the present invention, a high corrosion-resistance austenitic stainless rear plate includes: 0.005 to 0.05 wt% of C; more than 0 to no more than 1.5 wt% of Si, 0.45 to 1.5 wt% of Mn, 18 to 22 wt% of Cr, 17 to 20 wt% of Ni, 5.0 to 6.5 wt% of Mo, 0.2 to 1.5 wt% of Cu, 0.2 to 0.3 wt% of N, and the remaining of Fe and inevitable impurities. The rear plate is no less than 2,000 mm in width and no less than 60 mm in thickness, a PREN value expressed in the following formula (1) is no less than 40, and an F_sigma (@950℃) value expressed in the following formula (2) is no more than 8. (1) PREN = Cr + 3.3*Mo + 16*N >= 40 (2) F_sigma(@950℃) = -43.3 + 2.73*Cr - 0.73*Ni + 3.74*Mo - 12.4*C - 0.68*Si - 51.9*N <= 8.

Description

High corrosion-resistance austenitic stainless steel plate and its manufacturing method {HIGH CORROSION RESISTANCE AUSTENITIC STAINLESS THICK STEEL PLATE AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a high corrosion-resistance austenitic stainless steel plate and a method for manufacturing the same, and more particularly, to a high-corrosion-resistant austenitic stainless steel having a width of 2 m or more, which can reduce welding man-hours, and a plate with an optimized heat treatment process for manufacturing the same It is about the manufacturing process.

In general, austenitic stainless steel with good workability and corrosion resistance uses Fe as a base metal, contains Cr and Ni as main raw materials, and adds other elements such as Mo and/or Cu to various types of steel to suit various uses. is being developed with

The 304 and 316 series austenitic stainless steels with excellent corrosion resistance and workability contain expensive raw materials such as Ni and Mo, and are high alloy steels requiring higher corrosion resistance. High-grade steels such as S31254 and N08367 are being developed.

Recently, as the International Maritime Organization's regulations on the sulfur content of ships' flue gas emissions have been strengthened from 3.5% to 0.5% from January 2020, the installation of _{desulfurization facilities (SO x scrubbers) in ships is increasing.} Since it is used in an atmosphere, ultra-high corrosion resistance is required. In addition, manufacturers of desulfurization equipment are demanding materials with a width of 2M or more in order to minimize welding lines during manufacturing, and since it is difficult to manufacture wide widths with general hot rolled materials, it is necessary to develop thick plate products that can increase the width. Since high-alloy steel is a high-strength material, it is necessary to derive heat treatment conditions that can secure the maximum width and minimum thickness when manufacturing a thick plate. Operating conditions for minimizing the sigma phase in order to solve the deterioration of corrosion resistance caused by the sigma phase when the cross-section of the material is exposed Derivation is also required.

The embodiments of the present invention are to solve the above-mentioned problems, and optimize the heating furnace operating conditions during thick plate rolling and the heat treatment conditions of the final product according to the width and thickness to maximize the sigma phase decomposition with high corrosion resistance suitable for desulfurization facilities. An austenitic stainless steel plate and a manufacturing method thereof are provided.

High corrosion resistance austenitic stainless steel plate according to an embodiment of the present invention, by weight, C: 0.005 to 0.05%, Si: 0 to 1.5% or less, Mn: 0.45 to 1.5%, Cr: 18 to 22%, Ni: 17 to 20%, Mo: 5.0 to 6.5%, Cu: 0.2 to 1.5%, N: 0.2 to 0.3%, including the remaining Fe and other unavoidable impurities, and has a width of 2,000 mm or more and a thickness of 6 mm or more, The PREN value expressed by the formula (1) is 40 or more.

(1) PREN = Cr + 3.3*Mo + 16*N ≥ 40

Also, according to an embodiment of the present invention, the value of F_sigma (@950°C) expressed by the following Equation (2) may be 8 or less.

(2) F_sigma(@950℃) = -43.3 + 2.73*Cr - 0.73*Ni + 3.74*Mo - 12.4*C - 0.68*Si - 51.9*N ≤ 8

In addition, according to an embodiment of the present invention, the weight loss at 50 ℃ G48A Norsok corrosion resistance evaluation criteria may be less than 4 g / m 2 .

The method of manufacturing a high corrosion-resistance austenitic stainless steel plate according to an embodiment of the present invention, by weight, C: 0.005 to 0.05%, Si: 0 to 1.5% or less, Mn: 0.45 to 1.5%, Cr: 18 to 22%, Ni: 17 to 20%, Mo: 5.0 to 6.5%, Cu: 0.2 to 1.5%, N: 0.2 to 0.3%, the remaining Fe and other unavoidable impurities, and the following formulas (1) and (2) Casting a slab that satisfies manufacturing a hot-rolled thick plate having a thickness of 6 to 15 mm by reheating the slab one or more times and rolling a thick plate; and heat-treating the hot-rolled thick plate material at a temperature range of 1,150 to 1,300° C. for 30 to 110 minutes according to the heat treatment index for each thickness.

(1) PREN = Cr + 3.3*Mo + 16*N ≥ 40

(2) F_sigma(@950℃) = -43.3 + 2.73*Cr - 0.73*Ni + 3.74*Mo - 12.4*C - 0.68*Si - 51.9*N ≤ 8

In addition, according to an embodiment of the present invention, in the reheating in the step of manufacturing the hot-rolled thick plate material, the temperature of the crack zone of the heating furnace may be in the range of 1,200 to 1,300 ℃.

In addition, according to an embodiment of the present invention, in the heat treatment step, the heat treatment index for each thickness is expressed by the following formula (3) and may have a range of 5.0 to 7.5.

(3) Heat treatment index by thickness = heat treatment time / thickness

In addition, according to an embodiment of the present invention, the width of the hot-rolled thick plate material may be 2,000 mm or more.

According to an embodiment of the present invention, it is possible to provide a wide stainless steel plate suitable for a desulfurization facility, and by securing a material width twice that of a hot rolled material, it is possible to reduce the number of welding man-hours by half when manufacturing a desulfurization facility. Reducing the number of welding labor can improve manufacturing economics such as shortening of welding time and shortening of manufacturing period.

In addition, when manufacturing highly corrosion-resistant heavy plates with a thickness of 6.0 mm or more, it is possible to minimize sigma phase precipitation and maximize sigma phase decomposition in the center, thereby securing high corrosion resistance of PREN 40 or higher suitable for desulfurization facilities.

1 is a photograph showing a cross-sectional sigma image of a slab and a hot-rolled coil of general high corrosion-resistance austenitic stainless steel.
2 is a state diagram of a high corrosion-resistance austenitic stainless steel plate according to the present invention.
3 is a graph showing the correlation between the sigma phase generation fraction and alloy components for deriving Equation (2) of the present invention.
4 is a graph showing the relationship between the slab heating furnace crack zone temperature and the material width/thickness ratio.
5 is a graph showing the final heat treatment conditions for each thickness of the thick plate at 1,190° C., which is the final heat treatment maximum temperature.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are presented in order to sufficiently convey the spirit of the present invention to those of ordinary skill in the art to which the present invention pertains. The present invention is not limited to the embodiments presented herein, and may be embodied in other forms. The drawings may omit the illustration of parts irrelevant to the description in order to clarify the present invention, and may slightly exaggerate the size of the components to help understanding.

The present invention relates to a high corrosion-resistance austenitic stainless steel plate suitable for desulfurization facilities. The materials used for desulfurization facilities are generally used in poor environments such as seawater or sulfuric acid atmosphere, so they require high corrosion resistance, and are manufactured in a large cylindrical shape. In order to reduce the number of welding man-hours, a wide material is required. The present invention intends to provide a wide, high corrosion-resistance austenitic stainless steel plate and a method for manufacturing the same in order to respond to these needs, and to provide a wide material with high corrosion resistance through heat treatment conditions and component control by utilizing the thick plate manufacturing process.

The high corrosion-resistance austenitic stainless steel plate according to the present invention is intended for a wide material with a width of 2,000 mm or more and a thick plate material with a thickness of 6 mm or more.

High corrosion resistance austenitic stainless steel plate according to an embodiment of the present invention, by weight, C: 0.005 to 0.05%, Si: 0 to 1.5% or less, Mn: 0.45 to 1.5%, Cr: 18 to 22%, Ni: 17 to 20%, Mo: 5.0 to 6.5%, Cu: 0.2 to 1.5%, N: 0.2 to 0.3%, remaining Fe and other unavoidable impurities.

Hereinafter, the reason for numerical limitation of the alloy component content in the embodiment of the present invention will be described. Hereinafter, unless otherwise specified, the unit is % by weight.

The content of C is 0.005 to 0.05%.

C is a strong austenite phase stabilizing element, and it is necessary to add 0.005% or more for the austenite phase stabilization effect. However, when the content is excessive, there is a problem of reducing the corrosion resistance by lowering the Cr content around the grain boundary because it forms carbides by combining with Cr effective for corrosion resistance at the grain boundary. Therefore, in order to secure sufficient corrosion resistance, it is necessary to limit the content of C to 0.05% or less.

The content of Si is more than 0 and 1.5% or less.

Si is essentially added as an element effective for deoxidation and improvement of corrosion resistance. The lower limit is preferably 0.25% or more. However, since Si is a ferrite phase stabilizing element, and if excessive, it promotes precipitation of intermetallic compounds such as sigma phase (σ phase), thereby reducing mechanical properties and corrosion resistance, so it is limited to 1.5% or less, more preferably limited to 0.8% or less Do.

The content of Mn is 0.45 to 1.5%.

Mn is an austenitic phase stabilizing element such as C and Ni, which is an element necessary for manufacturing austenitic stainless steel, but an increase in Mn content is involved in the formation of inclusions such as MnS, and there is a problem in that corrosion resistance and surface gloss are reduced. . Therefore, it is preferable to limit the Mn content to 0.45 to 1.5%.

The content of Cr is 18 to 22%.

Cr is the most important element for improving the corrosion resistance of stainless steel. 18% or more should be included to ensure sufficient corrosion resistance, but if Cr is excessively added, σ phase formation is promoted, which causes deterioration of mechanical properties and corrosion resistance. Therefore, it is preferable to limit the Cr content to 22% or less.

The content of Ni is 17 to 20%.

Ni is the most powerful element among the austenite phase stabilizing elements, and in order to increase corrosion resistance, it should be contained in an amount of 17% or more. However, since an increase in the Ni content is directly related to an increase in raw material price, it is preferable to limit it to 20% or less.

The content of Mo is 5.0 to 6.5%.

Mo is a useful element to improve corrosion resistance, and it is necessary to add at least 5.0% or more, but it is preferable to limit it to 6.5% or less because it promotes the formation of σ phase and causes deterioration of mechanical properties and corrosion resistance.

The content of Cu is 0.2 to 1.5%.

Cu is a useful element for stabilizing the austenite phase and can be used by substituting for expensive Ni, so it is necessary to add 0.2% or more to reduce the cost. However, when a large amount is added, a low-melting phase is formed and the hot workability is lowered, thereby lowering the surface quality. Therefore, it is preferable to limit it to 1.5% or less.

The content of N is 0.2 to 0.3%.

N is an element useful for stabilizing the austenite phase, and it is necessary to add 0.2% or more as an element useful for corrosion resistance. However, when a large amount is added, the hot workability is reduced and the surface quality of the steel is deteriorated, so it is preferable to limit it to 0.3% or less.

The remaining component of the present invention is iron (Fe). However, since unintended impurities from raw materials or the surrounding environment may inevitably be mixed in the normal manufacturing process, this cannot be excluded. Since the impurities are known to any person skilled in the art of a conventional manufacturing process, all details thereof are not specifically mentioned in the present specification.

In general, most of the ultra-high corrosion-resistance stainless steels are improved in corrosion resistance by adding a large amount of Cr and Mo components. As an indicator of such corrosion resistance, the pitting resistance index PREN is known, and the PREN index must have a value of 40 or higher to be classified as high corrosion-resistance stainless steel.

The high corrosion resistance austenitic stainless steel plate of the present invention has a PREN value of 40 or more expressed by the following formula (1).

(1) PREN = Cr + 3.3*Mo + 16*N ≥ 40

In the present invention having high corrosion resistance, the weight loss may be less than 4 g/m 2 at 50° C. based on the G48A Norsok corrosion resistance evaluation, as in Examples to be described later.

On the other hand, such high-alloy steel has high overall corrosion resistance, but the sigma phase generated during solidification remains in the segregation portion of the center of the thickness of the cast steel, causing local rusting around the sigma phase, thereby inhibiting corrosion resistance. 1 is a photograph showing a cross-sectional sigma image of a slab and a hot-rolled coil of general high corrosion-resistance austenitic stainless steel. Referring to FIG. 1, it can be seen that the undecomposed sigma phase remains in the center of the slab and the center of the hot-rolled coil.

The production temperature or content of the sigma phase is different depending on the steel type. In the case of S31254 steel, which is usually used in desulfurization facilities, it starts to be formed at about 1,100°C and shows a content of about 20% at 800°C. This can be confirmed through the state diagram, and FIG. 2 shows the state diagram of the high corrosion-resistance austenitic stainless steel plate according to the present invention.

The generation of the sigma phase can be reduced during solidification by lowering the temperature of the sigma phase or controlling the components to reduce the formation content. By drawing a phase diagram for various component conditions, the precipitation temperature and content of the sigma phase were checked, and the precipitation content of the sigma phase was investigated at a constant precipitation temperature of the sigma phase to derive the relationship between the components. In the present invention, the standard for the precipitation temperature of the sigma phase was set to 950° C., and the content of the sigma phase generated at this temperature was calculated. If the generation fraction of the sigma phase is confirmed by drawing a phase diagram with the target component of S31254 steel, it is about 8% at 950 ° C. It was attempted to improve corrosion resistance by setting the range so that the sigma phase was generated less than that of the existing S31254 steel.

3 is a graph showing the correlation between the sigma phase generation fraction and the alloy component for deriving Equation (2) of the present invention, and the following F_sigma (@950 ° C.) relational expression was derived from the relationship between each component and the sigma phase generation fraction. . According to an embodiment of the present invention, the value of F_sigma (@950° C.) expressed by Equation (2) below may be 8 or less.

(2) F_sigma(@950℃) = -43.3 + 2.73*Cr - 0.73*Ni + 3.74*Mo - 12.4*C - 0.68*Si - 51.9*N ≤ 8

Next, a method for manufacturing a high corrosion-resistance austenitic stainless steel plate will be described.

The method of manufacturing a high corrosion-resistance austenitic stainless steel plate according to an embodiment of the present invention, by weight, C: 0.005 to 0.05%, Si: 0 to 1.5% or less, Mn: 0.45 to 1.5%, Cr: 18 to 22%, Ni: 17 to 20%, Mo: 5.0 to 6.5%, Cu: 0.2 to 1.5%, N: 0.2 to 0.3%, the remainder including Fe and other unavoidable impurities, and formulas (1) and (2) are casting a satisfactory slab; Reheating the slab one or more times and rolling the thick plate to prepare a hot-rolled thick plate having a thickness of 6 to 15 mm; and heat-treating the hot-rolled thick plate material for 30 to 110 minutes in a temperature range of 1,150 to 1,300° C. according to the heat treatment index for each thickness.

The alloy composition range and the conditions of formulas (1) and (2) are the same as the high corrosion-resistance austenitic stainless steel plate described above. After a slab that satisfies all of these is manufactured through continuous casting, a hot-rolled thick plate with a thickness of 6 to 15 mm can be manufactured through one or more reheating and thick plate rolling.

Reheating and rolling of the thick plate may be performed one or more times according to the characteristics of the thick plate manufacturing process. For example, after reheating and rolling a 200 mm slab to prepare a 60 to 100 mm slab, it can be reheated and rolled to a final hot-rolled thick plate having a thickness of 6 to 15 mm.

At this time, reheating may be in the range of 1,200 to 1,300 ℃ the lower temperature of the crack zone of the heating furnace. As the steel plate manufacturing process is followed for the manufacture of wide materials, optimal heat treatment conditions for slabs are required in order to secure a width of 2 m or more and a minimum thickness.

4 is a graph showing the relationship between the slab heating furnace crack zone temperature and the material width/thickness ratio. In FIG. 4 , the ratio of the material width to the thickness is expressed as W/t, and the larger the W/t value, the wider and thinner the material. The material width W was assumed to be 2,000 mm or more suitable for the production of desulfurization equipment, and the thickness can be substituted with 6 to 15 mm. 4, it can be seen that the slab heat treatment temperature must be 1,200 ° C or higher in order to manufacture a material of wide width and thin thickness, and the W/t standard is set to 200 (width 2,000 mm, thickness 10 mm) or higher. In this case, the lower temperature of the crack zone of the heating furnace is preferably 1,220°C or higher. The upper limit of the lower temperature of the heating furnace crack zone may be increased depending on the manufacturing facility, but it is limited to 1,300°C in consideration of the limit, and preferably 1,280°C or less.

The manufactured hot-rolled thick plate material is subjected to annealing heat treatment at a temperature range of 1,150 to 1,300° C. for 30 to 110 minutes according to the heat treatment index for each thickness, and then pickling and polishing processes may be additionally performed.

The annealing heat treatment is preferably performed at as high a temperature as possible for the decomposition of the sigma phase, and 1,150° C. or higher is required for the smooth decomposition of the sigma phase. Considering the facility limit, the upper limit is limited to 1,300℃. Preferably, it may be carried out at 1,180°C or higher, and the upper limit may be sufficient if it is 1,250°C.

The annealing heat treatment time may be performed for 30 to 110 minutes depending on the heat treatment index for each thickness of the thick plate. The heat treatment index for each thickness is expressed by the following formula (3) and may have a range of 5.0 to 7.5.

(3) Heat treatment index by thickness = heat treatment time / thickness

5 is a graph showing the final heat treatment conditions for each thickness of the thick plate at 1,190° C., which is the final heat treatment maximum temperature. In the present invention, it was tested for material thicknesses of 8 mm and 12 mm by applying the maximum heat treatment temperature of 1,190°C. For the 8 mm material, the heat treatment time was tested from 22 to 60 minutes, and for the 12 mm material, from 36 to 90 minutes. The value obtained by dividing the heat treatment time by the material thickness was expressed as a heat treatment index for each thickness. The decomposition of the sigma phase at the center of the thickness of the material was good under the condition that the heat treatment index for each thickness was 5 or more, and the sigma phase remained in the center when the thickness was less than 5. The longer the heat treatment time, the more the decomposition of the sigma phase at the center of the material is accelerated, which helps to improve the corrosion resistance. However, the condition where the heat treatment index for each thickness exceeds 7.5, the heat treatment time takes too long, causing a problem in productivity, so it is limited to 7.5 or less.

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

Example

After casting steel having the alloy composition shown in Table 1 into 200 mm slabs through a continuous casting process, slab reheating and thick plate rolling were performed to produce 80 mm slabs. Then, it was reheated again and rolled to a thickness of 8 mm, 10 mm, and 12 mm. Thereafter, a hot-rolled thick plate was manufactured through an annealing and pickling process.

When rolling the thick plate, the slab heating temperature was 1220° C. or higher and the heating time was 200 minutes, and the first thick plate rolling was performed. After the 80 mm slab was manufactured, reheating was performed under the same conditions and the second plate rolling was performed. The final annealing heat treatment was carried out for 40 to 90 minutes according to thickness at the highest temperature of 1,190 ° C., and then the final thick plate product was manufactured through pickling and polishing processes.

division C Si Mn Cr Ni Mo Cu N Comparative Example 1 0.019 0.422 0.456 19.22 16.33 4.23 0.68 0.234 Comparative Example 2 0.017 0.324 0.576 19.46 16.96 4.32 0.80 0.237 Comparative Example 3 0.015 0.289 0.612 18.65 16.24 4.64 0.70 0.226 Comparative Example 4 0.012 0.322 0.587 18.34 18.85 5.31 0.72 0.210 Comparative Example 5 0.010 0.423 0.556 19.60 17.22 5.02 0.64 0.238 Invention Example 1 0.012 0.273 0.456 19.55 17.26 5.20 0.65 0.238 Invention Example 2 0.009 0.322 0.509 19.09 17.82 5.63 0.71 0.231 Invention example 3 0.012 0.410 0.505 19.26 17.42 5.56 0.62 0.235 Invention Example 4 0.010 0.344 0.502 20.45 19.99 5.15 0.73 0.249 Invention Example 5 0.011 0.265 0.489 18.22 19.20 6.06 0.64 0.213 Invention example 6 0.013 0.445 0.499 20.00 18.34 5.41 0.70 0.246 Invention Example 7 0.017 0.362 0.615 20.50 19.63 5.50 0.78 0.254 Invention Example 8 0.015 0.412 0.506 19.66 18.52 5.83 0.62 0.243 Invention Example 9 0.018 0.354 0.515 20.44 18.33 5.66 0.74 0.258 Invention example 10 0.010 0.264 0.677 20.24 18.20 5.75 0.71 0.255 Invention Example 11 0.012 0.456 0.502 20.31 17.03 5.94 0.79 0.261 Invention Example 12 0.011 0.410 0.488 19.12 19.38 6.45 0.66 0.234 Invention Example 13 0.014 0.432 0.615 20.83 19.93 5.79 0.80 0.263 Invention Example 14 0.016 0.367 0.555 20.00 18.27 6.10 0.64 0.253 Invention Example 15 0.015 0.389 0.650 19.10 17.65 6.45 0.68 0.238 Invention Example 16 0.013 0.411 0.567 20.50 19.21 6.13 0.64 0.262 Comparative Example 6 0.012 0.412 0.495 20.11 19.99 6.68 0.76 0.255 Comparative Example 7 0.019 0.387 0.455 20.13 18.06 6.37 0.80 0.258 Comparative Example 8 0.018 0.341 0.389 18.69 16.44 6.83 0.64 0.236 Comparative Example 9 0.012 0.287 0.445 20.62 18.33 6.27 0.68 0.268 Comparative Example 10 0.011 0.344 0.503 20.67 16.20 5.93 0.64 0.273 Comparative Example 11 0.012 0.355 0.565 20.77 17.92 6.31 0.61 0.274 Comparative Example 12 0.016 0.412 0.615 20.29 16.92 6.36 0.65 0.266 Comparative Example 13 0.014 0.445 0.645 20.22 19.84 7.00 0.80 0.260 Comparative Example 14 0.015 0.387 0.665 20.68 19.60 6.88 0.60 0.272

Table 2 below shows the PREN index value of Equation (1), the F_sigma (@950°C) value of Equation (2), and the weight loss value according to the corrosion resistance evaluation test at 50°C based on G48A Norsok of the Invention Examples and Comparative Examples .

division Formula (1)
PREN Equation (2)
F_sigma (@950℃) Corrosion resistance evaluation
Weight loss value (g/㎡) Comparative Example 1 36.92 0.40 4.5 Comparative Example 2 37.51 0.87 5.1 Comparative Example 3 37.56 1.00 7.3 Comparative Example 4 39.21 1.60 4.3 Comparative Example 5 39.97 3.65 4.2 Invention Example 1 40.52 4.23 3.5 Invention Example 2 41.37 4.54 0.3 Invention example 3 41.38 4.73 0.1 Invention Example 4 41.42 3.92 0.1 Invention Example 5 41.63 3.72 0.2 Invention example 6 41.78 4.91 2,5 Invention Example 7 42.72 5.27 0.3 Invention Example 8 42.77 5.58 0.5 Invention Example 9 43.23 6.43 0.2 Invention example 10 43.29 6.64 0.1 Invention Example 11 44.09 7.93 0.3 Invention Example 12 44.14 6.31 2.6 Invention Example 13 44.15 6.55 3.2 Invention Example 14 44.18 7.20 0.2 Invention Example 15 44.18 7.28 0.4 Invention Example 16 44.91 7.53 1.3 Comparative Example 6 46.24 8.33 4.3 Comparative Example 7 45.26 8.41 6.2 Comparative Example 8 45.02 8.56 5.3 Comparative Example 9 45.60 8.81 8.7 Comparative Example 10 44.60 8.94 7.4 Comparative Example 11 45.97 9.31 5.2 Comparative Example 12 45.55 9.24 10.5 Comparative Example 13 47.48 9.63 9.4 Comparative Example 14 47.72 10.01 5.3

Referring to Tables 1 and 2, Comparative Examples 1 to 5 showed that the PREN value did not reach 40, so that the weight loss value in the corrosion resistance evaluation test was 4 g/m 2 or more. Among them, Comparative Examples 1 to 3 had a Mo content lower than 5%, so the PREN value was low, and Comparative Examples 4 and 5 were both within the scope of the present invention, but the PREN value was slightly less than 40, confirming that the corrosion resistance was inferior. could

In Invention Examples 1 to 16, the alloy component system composition is all within the scope of the present invention, and the PREN value of Equation (1) calculated accordingly and the F_sigma (@950° C.) value of Equation (2) are 8 or less. Satisfied, the weight loss value in the corrosion resistance evaluation test was also good, less than 4 g/m 2 .

Comparative Examples 6 to 14 all contain an appropriate amount of Cr, but the Ni content is low or the Mo content is high. Due to the appropriate range or excessive Mo content, the PREN value has a high value of 45 or more, but the F_sigma (@950° C.) value exceeds 8 due to the low Ni content or high Mo content, and the sigma phase was not sufficiently decomposed and remained.

In particular, in Comparative Examples 7 and 11, the F_sigma (@950 ℃) value calculated by Equation (2) exceeds 8 even though both the alloy component system composition range of the present invention is satisfied, and the corrosion resistance evaluation weight loss value is 4 g/m 2 or more. could be seen to appear. As such, through Comparative Examples 7 and 11, it was confirmed that not only the alloy composition and the PREN value but also the sigma phase decomposition according to F_sigma (@950°C) acted as a major factor in the corrosion resistance.

In the foregoing, exemplary embodiments of the present invention have been described, but the present invention is not limited thereto, and those of ordinary skill in the art will not depart from the concept and scope of the following claims. It will be appreciated that various modifications and variations are possible.

Claims (7)

By weight %, C: 0.005 to 0.05%, Si: greater than 0 and up to 1.5%, Mn: 0.45 to 1.5%, Cr: 18 to 22%, Ni: 17 to 20%, Mo: 5.0 to 6.5%, Cu: 0.2 to 1.5%, N: 0.2 to 0.3%, the remainder including Fe and other unavoidable impurities,
Width of 2,000 mm or more and thickness of 6 mm or more,
A high corrosion-resistance austenitic stainless steel plate having a PREN value of 40 or more expressed by the following formula (1).
(1) PREN = Cr + 3.3*Mo + 16*N ≥ 40
(Here, Cr, Mo, and N mean the content (wt%) of each element) According to claim 1,
A high corrosion-resistance austenitic stainless steel plate having an F_sigma (@950℃) value of 8 or less expressed by the following formula (2).
(2) F_sigma(@950℃) = -43.3 + 2.73*Cr - 0.73*Ni + 3.74*Mo - 12.4*C - 0.68*Si - 51.9*N ≤ 8
(Here, Cr, Ni, Mo, C, Si, and N mean the content (wt%) of each element) According to claim 1,
G48A Norsok High corrosion-resistance austenitic stainless steel plate, characterized in that the weight loss is less than 4 g/m2 at 50°C based on the Norsok corrosion resistance evaluation. By weight %, C: 0.005 to 0.05%, Si: greater than 0 and up to 1.5%, Mn: 0.45 to 1.5%, Cr: 18 to 22%, Ni: 17 to 20%, Mo: 5.0 to 6.5%, Cu: 0.2 to 1.5%, N: 0.2 to 0.3%, including the remaining Fe and other unavoidable impurities, and casting a slab satisfying the following formulas (1) and (2);
manufacturing a hot-rolled thick plate having a thickness of 6 to 15 mm by reheating the slab one or more times and rolling a thick plate; and
Heat-treating the hot-rolled thick plate material at a temperature range of 1,150 to 1,300° C. for 30 to 110 minutes according to the heat treatment index for each thickness; a method of manufacturing a high corrosion-resistant austenitic stainless steel plate comprising a.
(1) PREN = Cr + 3.3*Mo + 16*N ≥ 40
(2) F_sigma(@950℃) = -43.3 + 2.73*Cr - 0.73*Ni + 3.74*Mo - 12.4*C - 0.68*Si - 51.9*N ≤ 8
(Here, Cr, Ni, Mo, C, Si, and N mean the content (wt%) of each element) 5. The method of claim 4,
In the step of manufacturing the hot rolled plate material, the reheating is
A method for manufacturing a high corrosion-resistance austenitic stainless steel plate, characterized in that the crack zone temperature of the heating furnace is in the range of 1,200 to 1,300 °C. 5. The method of claim 4,
In the heat treatment step, the heat treatment index for each thickness is,
A method of manufacturing a high corrosion-resistance austenitic stainless steel plate represented by the following formula (3) and having a range of 5.0 to 7.5.
(3) Heat treatment index by thickness = heat treatment time / thickness 5. The method of claim 4,
A method of manufacturing a high corrosion-resistant austenitic stainless steel plate having a width of 2,000 mm or more of the hot-rolled thick plate.

Images