KR20180074322A - Austenite stainless steel excellent in corrosion resistance and hot workability - Google Patents

Abstract

Disclosed is austenitic stainless steel reducing expensive Mo, improving corrosion resistance by Cr, N, and Si content control, and excellent in hot workability reducing the occurrence of an edge crack that can be caused in conjunction. The austenitic stainless steel according to the present invention contains 0.03 wt% or less (excluding 0 wt%) of C, 1.0 to 2.0 wt% of Si, 1.0 wt% or less of Mn, 20.0 to 24.0 wt% of Cr, 8.0 to 12.0 wt% of Ni, 0.5 wt% or less of Mo, 1.0 wt% or less of Cu, 0.14 to 0.25 wt% of N, remaining Fe, and other unavoidable impurities, in which the CPT value expressed by the following formula (1) satisfies 35 to 46. (1) CPT = -31.5+2.99Cr+1.03Mo-Si+43.3N.

Description

AUSTENITE STAINLESS STEEL EXCELLENT IN CORROSION RESISTANCE AND HOT WORKABILITY "

The present invention relates to austenitic stainless steels excellent in corrosion resistance and hot workability, and more particularly to austenitic stainless steels excellent in corrosion resistance and corrosion resistance by controlling the content of Cr, N and Si while reducing the amount of expensive Mo, And austenitic stainless steel excellent in corrosion resistance and hot workability with reduced generation.

In general, to improve the corrosion resistance of stainless steel, the content of Cr, Mo and N is increased to improve the resistance to corrosion and crevice corrosion. The main component of STS304 steel, which is the basic steel of austenitic stainless steels, is 18Cr-8Ni, and STS316 steel with 2 wt% Mo content is added to improve corrosion resistance. In addition, STS317 steel with increased Mo content and Super Austenitic STS for seawater atmosphere further improved the corrosion resistance by further increasing Cr, Mo and N contents.

Existing commercially used standardized STS 316L / 1.4404 grades contain 16.8 to 17.8 wt.% Cr, 10 to 10.5 wt.% Ni and 2.0 to 2.3 wt.% Mo. The Ni and Mo included in the steel are expensive elements, and the cost of manufacturing STS316L / 1.4404 stainless steel is high because at least the price of Ni fluctuates greatly.

JP Patent Publication No. 2006-291296 discloses a steel containing 5% by mass or less of Mn, 15-20% by mass of Cr, 5-15% by mass of Ni and 3% by mass or less of Mo, Md ₃₀ temperature and SFI (Stacking-fault difficulty index) of 30 or more. However, the JP patent mentions Ni as an expensive element, and the maximum content is preferably 13 mass%.

CN Patent No. 101724789 discloses an austenitic stainless steel containing not more than 4% by weight of Mo and at least one rare earth element of Ce, Dy, Y and Nd in an amount of not more than 0.3% by weight. It is compared to STS 316L, stating that it has good mold toughness and improved yield strength while maintaining the same level of plasticity and formability for the stainless steel. However, the CN patent does not mention any manufacturing cost.

US Patent Publication No. 2015-0010424 discloses a Lean austenitic stainless steel having the above-described concept, but it has a high content of Mn for compensating for reduction in Ni and thus has a high possibility of adversely affecting the corrosion resistance. There is a possibility that the raw material cost may be increased by adding W.

WO Patent Publication No. 2009-082501 discloses an austenitic stainless steel containing 3.0 to 6.0 wt% Mn, and WO Patent Publication No. 2011-053460 discloses an austenitic stainless steel containing 2.0 to 9.0 wt% Mn. They exhibit improved corrosion resistance and moldability while reducing the contents of Ni and Mo, which include Mn of at least 2% by weight which is not uncommon in the 300 grade steels. Stainless steels with a high Mn content have problems in distribution of scrap because they are not guaranteed the value in the price of raw materials during distribution.

In order to satisfy the same corrosion resistance level as STS316L and higher corrosion resistant stainless steels and to develop low cost steels by reducing Mo content, it is inevitably required to additionally add corrosion resistance improving elements such as Cr and N. However, the addition of these elements may lead to various problems in the production of steel such as cracking during hot working and surface defects due to nitrogen gas formation, though it may improve corrosion resistance. Therefore, it is necessary to design components that minimize the defects that cause the deterioration of productivity while satisfying the required corrosion resistance by appropriately controlling these elements for improving corrosion resistance.

Japanese Patent Application Laid-Open No. 2006-291296 (published on October 26, 2006) Chinese Patent Laid-Open Publication No. 101724789 (published on June 6, 2010) U.S. Published Patent Application No. 2015-0010424 (published on August 1, 2015) PCT Published Patent Publication No. 2009-082501 (Published on July 2, 2009) PCT Published Patent Publication No. 2011-053460 (disclosed on May 5, 2011)

The present invention aims at providing a low-cost high corrosion resistant steel which can have excellent corrosion resistance compared to STS316L steel, while eliminating expensive Mo addition added to improve corrosion resistance in austenitic stainless steels. Also, it is an object of the present invention to provide austenitic stainless steel excellent in hot workability capable of suppressing cracks which may occur in the steel production.

The austenitic stainless steel excellent in corrosion resistance and hot workability according to one embodiment of the present invention is characterized by containing 0.03% or less of C (excluding 0%), 1.0 to 2.0% of Si, 1.0% or less of Mn, 1.0% or less of Cr : 20.0 to 24.0%, Ni: 8.0 to 12.0%, Mo: 0.5% or less, Cu: 1.0% or less, N: 0.14 to 0.25%, balance Fe and other unavoidable impurities, And the CPT value satisfies 35 to 46.

(One) CPT = -31.5 + 2.99Cr + 1.03Mo-Si + 43.3N

Here, Cr, Mo, Si and N mean the content (weight%) of each element.

Also, according to an embodiment of the present invention, the stainless steel may have a critical temperature of 35 ° C or higher.

Also, according to an embodiment of the present invention, the stainless steel may have an average potential of 450 mV or higher.

Also, according to an embodiment of the present invention, the stainless steel may satisfy the Cr _eq / Ni _eq value represented by the following formula (2) in the range of 1.4 to 1.8.

(2) (Cr + Mo + 1.5Si) / {Ni + 0.5Mn + 30C + 30 (N-0.045) + 0.33Cu}

Here, Cr, Mo, Si, Ni, Mn, C, N and Cu mean the content (weight%) of each element.

Also, according to an embodiment of the present invention, the stainless steel may satisfy the 隆 -ferrite fraction expressed by the following formula (3) in the range of 1.4 to 12.3%.

(3) [(Cr + Mo + 1.5Si + 0.5Nb + 2Ti + 18) / {Ni + 30 (C + N) + 0.5Mn + 36} +0.262] * 161-161

Here, Cr, Mo, Si, Nb, Ti, Ni, C, N and Mn mean the content (weight%) of each element.

The austenitic stainless steel according to the embodiment of the present invention can reduce the manufacturing cost of the STS 316L steel by reducing the amount of Mo, which is a high-priced element in the steel sheet.

In addition, the austenitic stainless steel according to the embodiment of the present invention can suppress the occurrence of edge cracks during hot working and maintain high productivity.

FIG. 1 is a graph showing a relationship between a critical temperature estimated value and a critical temperature measured value according to an alloy element content in an embodiment of the present invention. FIG.
2 is a photograph of an edge of a comparative steel 1 according to an embodiment of the present invention.
3 is a photograph of the edge of the comparative steel 5 according to the embodiment of the present invention.
4 is a photograph of an edge of an inventive steel 8 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.

In order to solve the above problems, the effect of the contents of Cr, Si, Mo, and N on the corrosion resistance of austenitic stainless steels was examined. The above elements are the main elements for exhibiting the corrosion resistance of stainless steel. In order to reduce the high Mo content, the contents of Cr, Si and N should be controlled and optimized. When the Mo content is reduced, the content of Cr, Si, and N is increased by the reduction of the Mo content, so that the corrosion resistance can be compensated. Generally, Cr and N are known to be an element that positively affects the improvement of corrosion resistance of austenitic stainless steel. Therefore, when added in large amounts, corrosion resistance can be expected. However, when a large amount of Cr is added alone, there is a high possibility of occurrence of surface defects such as sticking during hot rolling due to a high Cr component. When a large amount of N is added, pin holes are formed due to the formation of nitrogen gas There is a risk of occurrence of edge cracks during hot rolling. In addition, when a large amount of the two elements are added at the same time, the impact toughness due to Cr ₂ N formation may be lowered and the corrosion resistance of the welded portion may be lowered.

The effect of δ-ferrite, which is a microstructure affecting edge cracks or surface defects, which can occur during hot rolling, was investigated in order to improve the corrosion resistance and to secure the hot workability to be described later. The optimum fraction of δ-ferrite and the contents of Cr, N, Si, Mn, etc. were optimized by various component simulations. The extent of cracking by δ-ferrite fraction was quantified through actual hot rolling, and the optimum δ-ferrite fraction was determined based on this, and the range of alloying elements satisfying the fraction was derived.

The austenitic stainless steel excellent in corrosion resistance and hot workability according to one embodiment of the present invention is characterized by containing 0.03% or less of C (excluding 0%), 1.0 to 2.0% of Si, 1.0% or less of Mn, 1.0% or less of Cr : 20.0 to 24.0%, Ni: 8.0 to 12.0%, Mo: 0.5% or less, Cu: 1.0% or less, N: 0.14 to 0.25%, balance Fe and other unavoidable impurities.

The role and content of each component contained in the austenitic stainless steel according to the present invention will be described below. % ≪ / RTI > by weight refers to weight percent.

The content of C is more than 0 and 0.03% or less.

C is an element effective for increasing the strength of a material by solid solution strengthening, but it may easily interfere with corrosion resistance by being easily bonded with a carbide forming element when the content is excessive. Since the intergranular carbides such as Cr ₂₃ C ₆ decrease the Cr content around the grain boundaries and reduce the corrosion resistance, the content of C is limited to 0.03% or less. In order to minimize the risk of precipitation of carbide which may hinder corrosion resistance, it is preferable to limit the content of C to 0.02% or less.

The content of Si is 1.0% or more and 2.0% or less.

Si, which also acts as a ferrite phase stabilizing element, is an element capable of improving the corrosion resistance by forming an oxide on the surface of the steel. In the present invention, the content of Si is increased by 1.0% or more along with the increase of Cr and N contents, thereby improving the corrosion resistance by Si. In addition to the Cr ₂ O ₃ passivation film, corrosion resistance can be expected by the formation of SiO ₂ oxide which is stable on the surface when Si is added. However, if it is excessive, it promotes precipitation of intermetallic compounds to lower the mechanical properties related to the impact toughness, and cracking during hot rolling is facilitated by lowering the hot workability due to the increase of the δ-ferrite fraction. Do.

The content of Mn is 0 or more and 1.0% or less.

Mn is a useful element for improving the fluidity of the molten metal when it is used in an appropriate amount and improves the solubility of N and is widely used as an austenite phase stabilizing element. However, when high corrosion resistance is required, an increase in the Mn content may be involved in the formation of inclusions such as MnS, and therefore, it is desirable to limit the Mn content to 1.0% or less in order to secure corrosion resistance.

The Cr content is 20.0% or more and 24.0% or less.

Cr is the most element among the elements improving the corrosion resistance of stainless steel and is a basic element, but has a relatively small influence on the deterioration of hot workability. In order to compensate for the corrosion resistance due to Mo reduction, a content of 20.0% or more is required. However, when it is contained in an amount of more than 24.0%, surface cracks such as sticking due to a high Cr component may occur during hot rolling, and there is a fear of embrittlement of steel due to the formation of the σ phase.

The content of Ni is 8.0% or more and 12.0% or less.

Ni is the most powerful element among the austenite phase stabilizing elements, and plays an important role not only in enhancing the stability of the austenite structure but also in improving the front corrosion resistance. However, the increase in Ni content is directly related to the increase of raw material price, so it needs to be minimized. Therefore, the range of the Ni content is limited to 8.0 to 12.0% in consideration of the contents of Mn and N which are the same austenite stabilizing elements.

The content of Mo is 0 or more and 0.5% or less.

Mo is a strong corrosion resistance enhancement element along with Cr. However, the cost is high, and when added in large amounts, there is a high possibility of forming a sigma phase with Cr to embrittle the steel. Further, as a strong ferrite phase stabilizing element, cracks can be easily generated by increasing the fraction of the ferrite phase upon addition. Therefore, in the present invention, the minimum content is added to ensure the corrosion resistance of the steel, and the range is limited to 0.5% or less.

The content of Cu is 0 to 1.0%.

Cu has an advantage of improving the corrosion resistance in a sulfuric acid atmosphere and is an austenite stabilizing element. However, in the chlorine atmosphere, the Cu content is limited to 1.0% or less because there is a disadvantage in reducing the formal resistance and lowering the hot workability.

The content of N is 0.14% or more and 0.25% or less.

N is a useful element that not only improves corrosion resistance in a chlorine atmosphere but also can enhance strength, which is a merit of stainless steel. However, when the content of N is excessive, Cr ₂ N is formed and there is a fear of lowering the corrosion resistance of the welded part, and the hot workability is decreased and the yield rate is decreased. Therefore, it is preferable to limit the content of N to a range of 0.14 to 0.25% in consideration of the contents of Cr and Mo for securing corrosion resistance.

In the case of the austenitic stainless steels having the above alloy composition, the content of Cr, Si, and N can be controlled while reducing the Mo content to reduce the cost, and it is possible to secure superior corrosion resistance equal to or higher than that of STS316L steel.

The austenitic stainless steel according to one embodiment of the present invention can improve the corrosion resistance by controlling the CPT value expressed by the following formula (1) so as to satisfy the range of 35 to 46.

(One) CPT = -31.5 + 2.99Cr + 1.03Mo-Si + 43.3N

Here, Cr, Mo, Si and N mean the content (weight%) of each element.

In the present invention, instead of reducing the content of Mo, the content of Cr, Si, and N is optimized to have excellent corrosion resistance as compared with STS316L steel containing 2.0 to 2.3% of Mo. The relationship between the content of each element and the critical pitting temperature (CPT) on the corrosion resistance is derived from the equation (1).

FIG. 1 is a graph showing a relationship between a critical temperature estimated value and a critical temperature measured value according to an alloy element content in an embodiment of the present invention. FIG. As can be seen in FIG. 1, the content of each element and the critical temperature (CPT) satisfy a linear proportionality.

For example, the austenitic stainless steel according to an embodiment of the present invention may have a critical temperature (CPT) of 35 ° C or higher.

Also, for example, an austenitic stainless steel according to an embodiment of the present invention may have an average potential of 450 mV or higher.

On the other hand, even if the steel has excellent corrosion resistance, it is not meaningful if the edge or surface cracks occur in the process of manufacturing the steel sheet and the yield rate is decreased. Therefore, it is necessary to design the component that does not cause the above defects during hot rolling. The content of Cr, Si, and N added in place of expensive Mo necessarily increases in order to secure corrosion resistance equal to or higher than that of existing steels. However, the above elements have a great influence on the microstructure such as the δ-ferrite fraction and the martensite phase transformation during the transformation as well as the corrosion resistance, and have a great influence on the crack occurrence during hot rolling as described above. As described above, the increase and the combined increase of the Cr and N contents alone cause a cause of surface defects during processing, and even if the Si content is excessively increased, the hot workability becomes weak and causes a break during rolling, Optimization is required.

The occurrence of edge or surface cracks during hot rolling of austenitic stainless steels depends largely on the fraction of δ-ferrite present in the microstructure. If δ-ferrite remains at a certain fraction, anomalous reverse rolling of austenite and δ-ferrite becomes inevitable during hot rolling, and edge cracking can occur when δ-ferrite is produced in a specific fraction range. Since the fraction of delta -ferrite is determined not by the specific component but by the various elements contained in the steel, the Cr equivalent (Cr _eq ) and the Ni equivalent (Ni _eq ) are controlled in addition to the above- The δ-ferrite fraction can be controlled.

The austenitic stainless steel according to one embodiment of the present invention can improve the hot workability by controlling the Cr _eq / Ni _eq value represented by the following formula (2) to satisfy the range of 1.4 to 1.8.

(2) Cr _eq / Ni _eq = (Cr + Mo + 1.5Si) / {Ni + 0.5Mn + 30C + 30 (N-0.045) + 0.33Cu}

In the case of the austenitic stainless steels of the present invention, it is important to control the Cr equivalent and the Ni equivalent value in order to improve the hot workability depending on the fraction of δ-ferrite.

Cr equivalent is generally known as an index obtained by converting the influence of ferrite generating elements Cr, Mo, Si and Nb into the influence of Cr in stainless steel. In the present invention, since Nb is not contained in the alloy component, the Nb term is excluded from the Cr equivalent equation. The degree of contribution of the alloying elements of Cr, Mo, and Si to the stability of the ferrite phase can be indexed by the Cr equivalent index. On the other hand, the Ni equivalent is an index obtained by converting the influence of the austenite generating elements C, Mn, Ni, Cu, and N into the influence of Ni in the stainless steel. The degree of contribution of the alloying elements of C, Mn, Ni, Cu, and N to the stability of the austenite phase can be indexed by the Ni equivalent index.

When the Cr _eq / Ni _eq value of the formula (2) satisfies the above range, the austenitic stainless steel according to the present invention can suppress edge cracking during hot working.

Also, the austenitic stainless steel according to one embodiment of the present invention can improve the hot workability by controlling the 隆 -ferrite fraction expressed by the following formula (3) to satisfy the range of 1.4 to 12.3%.

(3) [(Cr + Mo + 1.5Si + 0.5Nb + 2Ti + 18) / {Ni + 30 (C + N) + 0.5Mn + 36} +0.262]

When the? -Ferrite fraction of the formula (3) satisfies the above range, the austenitic stainless steel according to the present invention can suppress edge cracking during hot working.

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

Invention river  And Comparative steel

On the basis of the derived component system, the corrosion resistance of the inventive steel and the occurrence of edge and surface cracks during hot rolling were evaluated through ingot manufacturing and demonstrated.

In this embodiment, austenitic stainless steels having varying contents of Cr, Mo, Ni, N, and Si were prepared in the form of a 50 kg ingot having a thickness of 140 mm in a vacuum induction melting furnace. It was heat treated at 1,250 ℃ for 2 hours and then rolled up to 3mm to prepare a plate. After the hot rolling, the shape of the edge was evaluated immediately after hot rolling and water cooling. The corrosion resistance of the steel was evaluated by polishing the surface of the steel after heat-treating the hot-rolled steel at a temperature of 1,100 ° C for 30 seconds. The components of the ingots dissolved in this embodiment are shown in the following Table 1, and the comparative steels 1 used the dissolving materials of the same components as the conventional STS316L steels.

division C Si Mn Cr Ni Mo Cu N Comparative River 1 0.015 0.45 1.1 16.6 10.1 2.0 0.20 0.050 Comparative River 2 0.021 2.01 1.00 19.8 7.9 0.0 0.00 0.120 Comparative Steel 3 0.022 3.05 0.99 19.9 7.9 0.0 0.00 0.123 Comparative Steel 4 0.010 1.00 0.98 21.9 8.0 0.0 0.00 0.132 Comparative Steel 5 0.019 1.02 1.01 20.0 8.0 1.2 0.00 0.160 Inventive Steel 1 0.019 0.96 1.10 20.2 8.0 0.0 0.00 0.145 Invention river 2 0.020 0.99 0.98 20.1 8.0 0.0 0.00 0.190 Invention steel 3 0.022 1.00 0.97 20.0 8.1 0.0 0.00 0.257 Inventive Steel 4 0.018 1.03 1.04 20.2 8.0 0.0 1.00 0.143 Invention steel 5 0.019 0.97 1.10 21.1 10.0 0.5 0.00 0.160 Invention steel 6 0.018 1.02 0.99 20.9 9.0 0.5 0.98 0.160 Invention steel 7 0.019 1.00 0.98 20.9 9.0 0.0 0.00 0.145 Inventive Steel 8 0.020 1.04 1.05 21.0 9.1 0.5 0.00 0.198 Invention river 9 0.022 0.99 1.00 22.0 10.0 0.0 0.00 0.210 Invented Steel 10 0.018 1.00 1.00 23.1 11.9 0.5 0.00 0.150 Invention steel 11 0.017 1.80 0.95 23.3 12.1 0.5 0.00 0.230 Invention steel 12 0.021 1.00 0.98 24.0 12.1 0.5 0.00 0.160

The critical temperature (CPT) of the steel was evaluated by the method according to ASTM G150. The surface temperature of the steel was exposed to 1M NaCl solution, and the temperature was gradually increased to the temperature at which the pitting occurred Respectively. At this time, the surface of the steel was polished with a # 120 grit abrasive paper and then evaluated.

As a method of evaluating the corrosion resistance, the pitting potential was measured. The measurement of the formal potential was carried out by exposing the surface of the steel to 3.5% NaCl solution and measuring the potential generated by the formula using a Potentiostat equipment at a temperature of 30 ° C. The surface of the steel was abraded with a # 120 grit The surface after polishing was applied. The critical temperature and the formal potential of the comparative and invention steels are shown in Table 2 below.

division Critical temperature (° C) Formula potential (mV) Comparative River 1 20 335 Comparative River 2 31 551 Comparative Steel 3 30 459 Comparative Steel 4 35 447 Comparative Steel 5 36 646 Inventive Steel 1 35 519 Invention river 2 35 586 Invention steel 3 36 568 Inventive Steel 4 35 465 Invention steel 5 42 1000 Invention steel 6 40 1000 Invention steel 7 37 1000 Inventive Steel 8 41 1000 Invention river 9 42 1000 Invented Steel 10 44 1000 Invention steel 11 46 1000 Invention steel 12 45 1000

As shown in Table 2, in the case of the STS316L tough comparative steel 1, the critical temperature is estimated to be 20 ° C on the average, while the inventive steel shows a critical temperature of 35 ° C or higher. , Which is superior to the comparative steel 1 STS316L by 335mV.

On the other hand, in order to evaluate the corrosion resistance and the hot workability of the steel, the shape of the edge cracks of the invented steel and the comparative steel immediately after the hot rolling was evaluated. The degree of edge cracking was evaluated according to Cr equivalent, Ni equivalent and δ-ferrite fraction of each steel, and the degree of occurrence of edge cracks was quantitatively evaluated in order of 1 (20 mm or more), 3 (5 mm or less) Respectively. Table 3 below shows Cr equivalent, Ni equivalent, δ-ferrite fraction and edge crack evaluation index calculated from the alloy composition of the inventive steel and the comparative steels.

division Cr _eq Ni _eq Cr _eq / Ni _eq δ-ferrite
(%) Edge crack
Rating index Comparative River 1 19.24 11.32 1.70 4.5 5 Comparative River 2 22.84 11.30 2.02 16.3 One Comparative Steel 3 24.47 11.40 2.15 21.4 One Comparative Steel 4 23.40 11.43 2.05 17.8 One Comparative Steel 5 12.53 12.53 1.81 12.5 One Inventive Steel 1 12.12 12.12 1.79 10.2 5 Invention river 2 13.43 13.43 1.61 6.7 5 Invention steel 3 15.57 15.57 1.38 1.4 5 Inventive Steel 4 12.33 12.33 1.76 10.8 5 Invention steel 5 14.60 14.60 1.58 8.4 5 Invention steel 6 13.80 13.80 1.66 10.8 5 Invention steel 7 13.10 13.10 1.71 10.1 5 Inventive Steel 8 14.77 14.77 1.56 8.0 5 Invention river 9 16.14 16.14 1.46 6.0 5 Invented Steel 10 16.09 16.09 1.56 11.0 5 Invention steel 11 18.64 18.64 1.42 9.2 5 Invention steel 12 16.67 16.67 1.56 12.3 5

2 is a photograph of an edge of a comparative steel 1 according to an embodiment of the present invention. In addition, as shown in Table 3, STS316L tough comparative steel 1 was calculated to have a Cr equivalent / Ni equivalent value of 1.7 corresponding to 1.4 to 1.8 of the present invention and a δ-ferrite fraction of 4.5% The edge cracks did not occur. However, the comparative steels 2 to 5, in which the contents of Si, Cr and N are increased and the contents of Ni and Mo are decreased compared with the comparative steels 1 and the compositions are different, the value of Cr equivalent / Ni equivalent exceeds 1.8, The fraction was more than 12.5%, and the edge cracks were found to be more than 20 mm. Fig. 3 shows a photograph in which edge cracks have occurred in the comparative steel 5. Fig.

In the inventive steels 1 to 12 according to the alloy element composition of the present invention, all of the edge crack evaluation indexes were evaluated to be 5, and the Cr equivalent / Ni equivalent value satisfied the range of 1.4 to 1.8. FIG. 4 is a photograph of an edge of an inventive steel 8 according to an embodiment of the present invention, showing a good edge without edge cracks. Therefore, it was confirmed that the edge crack shape of the austenitic stainless steel was satisfactory when the Cr equivalent / Ni equivalent and the? -Ferrite fraction range according to the present invention were satisfied.

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 recognize that other embodiments may occur to those skilled in the art without departing from the scope and spirit of the following claims. It will be understood that various changes and modifications may be made.

Claims (5)

(% By mass), Si: 1.0 to 2.0%, Mn: 1.0% or less, Cr: 20.0 to 24.0%, Ni: 8.0 to 12.0% 1.0% or less, N: 0.14 to 0.25%, balance Fe and other unavoidable impurities,
Austenitic stainless steel excellent in corrosion resistance and hot workability satisfying a CPT value of 35 to 46 expressed by the following formula (1): "
(1) CPT = -31.5 + 2.99Cr + 1.03Mo-Si + 43.3N
Here, Cr, Mo, Si and N mean the content (weight%) of each element. The method according to claim 1,
The stainless steel is an austenitic stainless steel excellent in corrosion resistance and hot workability with a critical temperature of 35 ° C or higher. The method according to claim 1,
The stainless steel is an austenitic stainless steel excellent in corrosion resistance and hot workability with an official dislocation of 450 mV or more. The method according to claim 1,
Wherein the stainless steel is an austenitic stainless steel excellent in corrosion resistance and hot workability satisfying a Cr _eq / Ni _eq value of 1.4 to 1.8 as expressed by the following formula (2)
(2) (Cr + Mo + 1.5Si) / {Ni + 0.5Mn + 30C + 30 (N-0.045) + 0.33Cu}
Here, Cr, Mo, Si, Ni, Mn, C, N and Cu mean the content (weight%) of each element. The method according to claim 1,
Wherein the stainless steel is an austenitic stainless steel excellent in corrosion resistance and hot workability satisfying the 隆 -ferrite fraction expressed by the following formula (3) in the range of 1.4 to 12.3%
(3) [(Cr + Mo + 1.5Si + 0.5Nb + 2Ti + 18) / {Ni + 30 (C + N) + 0.5Mn + 36} +0.262]
Here, Cr, Mo, Si, Nb, Ti, Ni, C, N and Mn mean the content (weight%) of each element.

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