JPH0297648A - Austenitic stainless steel excellent in creep rupture strength and its production - Google Patents

Abstract

PURPOSE:To improve the creep rupture strength, corrosion resistance, and hot workability of the title steel by applying two-stage controlled rolling to an austenitic stainless steel in which respective contents of C, Si, Mn, Ni, Cr, N, and Nb are specified and forming the structure of the above steel into recrystallization working duplex structure. CONSTITUTION:An austenitic stainless steel having a composition consisting of, by weight, <=0.03% C, <=2% Si, <=10% Mn, 6-20% Ni, 16-30% Cr, 0.1-0.3% N, 0.02-0.25% Nb, and the balance Fe is refined. This steel is rough rolled at 1000-1200 deg.C and >=50% draft. After the above roughing, the steel is cooled for 10sec-5min. subsequently, the above steel is rolled at 800-1000 deg.C finish rolling temp. and >=30% draft and then cooled at >=4 deg.C/min cooling rate, by which the structure of the steel is formed into recrystallization working duplex structure. By this method, 1000hr creep rupture strength at 600 deg.C is regulated to >=30kgf/mm<2>.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to heat exchangers such as boilers, support materials for NaS batteries,
This invention relates to an austenitic stainless steel with excellent creep rupture strength used in valve stems, etc., and a method for producing the same.

[Prior Art] Since heat exchangers such as boilers and supporting materials for NaS batteries are used at high temperatures, they are required to have excellent creep rupture strength at 500 to 600°C.

Further, when a butterfly valve is used at high temperatures, the valve stem is similarly required to have excellent breaking strength at 500 to 600°C.

Conventionally, austenitic stainless steels such as 5US316 and 5US347 have been used as materials for these applications due to their high-temperature strength and corrosion resistance. However, these austenitic stainless steels
Because the creep rupture strength at 00 to 600°C is low,
Compared to materials used at room temperature, it has to be used as a thicker member, which is disadvantageous in terms of resource conservation and inevitably increases costs.

In addition, as a material for valve stems used at high temperatures,
Incoloy 800 or 2l with excellent high temperature strength and corrosion resistance
-4N etc. are used; however, they are expensive because they contain large amounts of Ni and C, and their creep rupture strength at 500 to 600°C is low, so to compensate for this, large diameter members have to be used. , which inevitably resulted in high costs.

By the way, the creep rupture strength of the conventional material at 600°C and 1000 hours is as shown in Figure 3, and as is clear from Figure 3, the required characteristic value is 30 kgf/am.
This is far less than that.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems of creep rupture strength at 500 to 600°C of austenitic stainless steel used in high-temperature environments. It is an object of the present invention to provide a significantly improved austenitic stainless steel and a method for producing the same.

[Means for Solving the Problems] The austenitic stainless steel of the present invention having excellent creep rupture strength contains C; O, o as essential components in weight ratio.
3% or less, Si; 2.0% or less, Mn; 10.0%
Below, Ni: 6-20%, Cr: 16-30%, N: 0
．． 1 to 0.3%, Nb; o, o: 2 to 0.25%, and the remainder consists of Fe and impurity elements, and its structure is a recrystallized double structure structure, and is heated at 600°C and 100°C.
Creep rupture strength at 0 hours is 30 kgf/m
e” or more, and M (1:4.0% or less,
CuH4.0% or less, S; O, o 1 of O2% or less
Se: 0.080% or less, Te: 0 as necessary to further improve machinability.
．． 080% or less, s;0, Os o% or less, P:0
．． 100% or less of Bi; 0.300% or less of Bi; and Pb:
0.300% or less, B, 0.0100% or less, and contains V, Ti, w, Ta, Hf, Zr as necessary to further improve strength.
, each containing one or more types of Al at 0.30% or less,
Furthermore, in order to improve hot workability, B; 0.
0005-0.0100%, Ca; 0.0005%-0
．． 0100%, Mg; 0.0005-0.0100%,
The gist is to contain one or more of 0.0005 to 0.0100% of rare earth elements.

Further, the method for manufacturing an austenitic stainless steel having excellent creep rupture strength according to the present invention has a weight ratio of c: 0.
03% or less, Si; 2.0% or less, Mr+; 10.0
% or less, Ni; 6-20%, Cr; 16-30%, N
: 0, 1~0, 3X, Nb; o, 02~0.2
5%, or in addition to this, Mo; 4.0% or less, C
A steel containing one or more of u: 4.0% or less, S: 0.002% or less, and the remainder consisting of Fe and impurity elements is heated to 1100 to 1300°C, and the rough rolling temperature is 1000 to 1000. Rolling is performed at 1200°C with a working amount of 50% or more, rough rolling f & 10 seconds to 5 minutes, followed by finishing rolling at a temperature of 800 to 1000°C with a working amount of 30% or more, and the cooling rate after rolling is 4°C. By cooling at a temperature of 600°C or more, the structure becomes a recrystallized double-structured structure.
Creep rupture strength at 1000 hours is 30kgf/
The gist is that it is not less than mm2.

The present invention is based on the new finding that the recrystallized double-structure structure improves the creep rupture strength of austenitic stainless steel at 500 to 600°C while maintaining its excellent toughness, strength, corrosion resistance, and weldability. be. The recrystallized double-structure structure is obtained when an alloy having the composition of the present invention is processed by the manufacturing method of the present invention.6 This high-temperature processed structure unique to the present invention is different from conventional structures that reduce creep rupture strength. Unlike the dislocation structure, the structure is created at a high temperature, so the dislocation structure is stable even at temperatures below 700°C, and excellent creep rupture strength can be obtained.

The structure of austenitic stainless steel is optically m
It consists of a microstructure of about 100 μm observed with a microscope and a substructure of about 1 μm observed with an electron microscope. Austenitic stainless steel is usually used after solution heat treatment, and the structure after solution heat treatment is
Figure 2 (a) shows the 00x one, and Figure 2 (b) shows the 20,000x one, and the conventionally known controlled rolling structure is shown in Figure 3 (a) and (b). As shown, the microstructure in (a) is a processed structure of mixed grains, and the substructure in (b) is also a processed structure.

FIG. 1 is a diagram showing the relationship between temperature and time for obtaining a recrystallized double structure structure according to the present invention. First, Nb precipitates are completely dissolved at a heating temperature of 1100 to 1300°C, and then rough rolling is performed at 1000 to 1200°C with a working amount of 50% or more. The cooling time after rough rolling is 10 seconds to 5 minutes, and the material is quickly cooled to a predetermined temperature from the final roll of rough rolling to the start of finish rolling, and recrystallized to obtain a v&string recrystallized structure. Finish rolling is 800-1000℃ processing amount 3
The cooling rate after finish rolling, which is carried out at 0% or more, is 4℃/haze in
The above shall apply.

Photographs of m-microstructures manufactured by the manufacturing methods of the present invention and comparative examples are shown in FIGS. 4 to 8.

Finish rolling start temperature is 1050℃, 980℃, 900℃,
(A) in each photo is 200 at 850℃ and 700℃
Multiply (b) is 20,000 times 0 Recrystallization processing according to the present invention 2
As is clear from the photographs in FIGS. 5 to 7, the multistructured microstructure consists of recrystallized structures of several tens of microns, which in turn consist of sub-recrystallized structures of several microns. The subgrains of this substructure are a processed structure having a high density of dislocations.

Here, if the finish rolling start temperature is made higher than 1ooo℃,
As shown in FIG. 4, almost no dislocations are seen in the sub-crystal grains, and there is almost no increase in creep rupture strength. On the other hand 8
If the temperature is lower than 00° C., as is clear from FIG. 8, no sub-recrystallized structure is formed and no improvement in creep rupture strength is obtained.

The present invention is based on the knowledge that it is important to lower the amount of C and add N and Nb in austenitic stainless steel in order to obtain excellent properties through the above-mentioned controlled rolling. According to the composition of the invention, the recrystallization temperature is significantly increased to facilitate controlled rolling and to easily obtain a fine crystal structure after rough rolling. Also, during finish rolling (C
r, Nb)N precipitates ultrafinely on dislocations or lower recrystallized grain boundaries due to strain, dispersion strengthening and solid solution Nb, N and (
Since Cr, Nb)N suppresses dislocation recovery, it increases the dislocation density in the lower recrystallized structure and achieves a significant improvement in creep rupture strength. Regarding C, it promotes Nb (C, N) precipitation, impairs hot workability, and at the same time (Cr, N)
b) Decrease the precipitation strengthening ability of N.

Furthermore, Cr2. It is most important to lower Cff1 since it also promotes the precipitation of C and reduces corrosion resistance.

The effects of the microalloy elements of C, N and Nb contained in the steel of the present invention will be described in more detail below.

First, regarding strength, in a solution heat treated structure, N contributes to solid solution strengthening. In addition, Nb (C, N) precipitates and refines the crystal grains, contributing to strength improvement. This effect is approximately twice as large as the normally known effect of N and Nb in solution heat treated structures. According to research conducted by the present inventors, this remarkable effect is due to ultrafine strain-induced precipitation of (CrNb)N on the dislocation structures and subgrain boundaries introduced during finish rolling, fixing them, and preventing dislocation recovery. It has been revealed that this is to delay the dislocation and increase the dislocation density.

Next, regarding the corrosion resistance, the corrosion resistance of the controlled rolled steel of the present invention containing 0.03% or less of C and appropriate amounts of N and Nb is that Cr23Cs is not formed at the grain boundaries, and due to the corrosion resistance improving effect of N, 18Cr-8N treated with solid solution strengthening heat treatment
The reason why the 0-grain boundary Cr23c@, which was found to be superior to the corrosion resistance of i steel, is not formed is that in stainless steel with low C and high N, Cr replaces C, r**Cs.
This is because t3(C,N)s precipitates, but the precipitation rate of this precipitate is extremely slow, and due to Nb, C, which is initially small, becomes NbC, so that there is almost no solid solution C.

As mentioned above, microalloy elements with low C and N%Nb are essential for improving the strength and corrosion resistance of controlled rolled materials, and only by combining these elements with controlled rolling can excellent creep rupture strength be achieved. The present invention was completed by discovering that an austenitic stainless steel having the following properties can be obtained.

The reasons for limiting the composition of the steel of the present invention will be explained below.

C: 0, o 3% or less C is an important element in the present invention, as it significantly impairs corrosion resistance after controlled rolling and hot workability during controlled rolling, and must be at least 0.03% or less. Also, the more C there is, the more Nb(C,N) grows, and (Cr,Nb)N
The upper limit was set at 0.03% because it interferes with the fine precipitation of carbon and causes a decrease in strength.

Si: 2.0% or less Si is an element that is added as a deoxidizing agent and also improves strength, but on the other hand, it is also an element that reduces hot cracking during welding and the amount of N solid solution during solidification. To obtain a good steel ingot 2.
It is necessary to keep the amount below 0%, and the upper limit is set at 2.0%.

Mn: 10.0% or less Mn is an element that is added as a deoxidizing agent and increases the solubility of N, but on the other hand, as the content increases, corrosion resistance and hot workability are impaired, so the upper limit is set at 10.0%. did.

NiH6-20% Ni is a basic element of austenitic stainless steel, and must be contained in an amount of 6% or more in order to obtain excellent corrosion resistance and an austenitic structure.

However, if the Ni content increases too much, weld cracking during welding,
Since this lowers hot workability, the upper limit was set at 20%.

Cr: 16-30% C is a basic element of stainless steel, and in order to obtain excellent corrosion resistance, it must be contained at least 16%. However, if the amount of Cr increases too much, the δ/ Since this would impair the balance of the γ structure, the upper limit was set at 30%.

N: 0.10 to 0.30% N has interstitial solid solution strengthening, grain refinement due to (CrNb)N precipitation, and precipitation strengthening effect to improve creep rupture strength and high temperature toughness, etc. It is the most major strengthening element in steel, and it is also an element that contributes to improving corrosion resistance after controlled rolling. To obtain these effects, the content must be 0.10% or more, and the lower limit is 0.10%.
%. However, as the N content increases, hot workability decreases and blowholes are more likely to occur during solidification and welding, so the upper limit was set at 0.30%.

Nb; 0.02-0.25% Nb fixes residual C as NbC, improves corrosion resistance after controlled rolling, and improves creep rupture strength and high-temperature toughness by refining grains through (CrNb)N precipitation. It is a main element in the present invention to improve the strength and strength after controlled rolling, and it is necessary to contain #J at least 0.02% or more. However, Nb is also an expensive element, and if it is included more than necessary, it impairs hot workability, so the upper limit was set at 0.25%.

Mo: 4.0% or less, Cu: 4.0% or less Both Mθ and Cu are elements that further improve the corrosion resistance of the steel of the present invention. However, Mo and Cu are also expensive elements, and
If the content exceeds 4%, hot workability will be impaired, so the upper limit was set at 4%.

S・0002% or less S is the source of improving corrosion resistance by significantly reducing its content! and improves the ductility and low-temperature toughness after controlled rolling, and the content is preferably as low as possible, at least 0.002% or less, preferably 0.0%.
It is preferable to make it 0.01% or less.

Se; 0.080% or less, s; 0, Os o% or less S, Se is an element that improves the stiffness of the steel of the present invention;
must exceed 0.020%, and Se must be contained at 0.005% or more. However, both S and Se are o and oso.
If the content exceeds 0.0%, the hot workability and corrosion resistance will decrease, so the upper limit should be set to o, os.

%.

Te: 0.080% or less Te is an element necessary to spheroidize MnS inclusions, improve toughness in the direction perpendicular to the rolling direction, and prevent a decrease in anisotropy, and is contained at least 0.0050% or more. This is desirable. Adding 0.080% or more inhibits hot workability, so the upper limit was set at 0.080%.

P; 0.100% or less P is an element added to improve rigidity, and is preferably contained in an amount of at least 0.04%. However, if it exceeds 0.100%, hot workability will be impaired, so the upper limit was set at 0.100%.

Bi: 0.300% or less, Pb, 0.300% or less Bi
and pb are elements necessary to improve machinability, and it is desirable to contain at least 0.03%. However, if it exceeds 0.300%, hot workability is inhibited, so The upper limit was set to 0.300%.

B: 0.0100% or less B is added to prevent hot workability from deteriorating when Bi and PB are added, but in order to obtain the above effect, at least 0.00050% or more is added. However, even if it is added in excess of 0.0100%, no improvement in the effect is expected, so the upper limit should be set at 0.0100%.
It was set to 0100%.

V, Ti, W, Ta, HE, Zr, Al; 0.30% or less V, Ti, W, Ta, Hf, Zr, Al are elements added to improve torsional strength and high temperature strength. Even if the content exceeds 0.30%, no improvement in the effect can be expected, so the upper limit was set at 0.30%.

B-0,0005-0.0100%, Ca; 0.000
5-0.01.00%, M8.0.0005-0010
0%, rare earth elements: 0.0005 to 0.0100% B, Ca, Mg, and rare earth elements are elements necessary to improve hot workability, and in order to improve hot workability, at least It is necessary to add 0.0005% or more. However, since no improvement in the effect can be expected even if 0.0100% or more is added, the upper limit was set at 0.0100%.

In addition, in controlled rolling, the heating temperature is set to 1100 to 130.
The reason for setting the temperature to 0°C is to reduce the deformation resistance during rolling and to sufficiently dissolve Nb precipitates in the steel. 1
This is because the deformation resistance is large at temperatures below 100°C, and it is difficult to completely dissolve Nb precipitates.
This is because heating above 0° C. melts some of the grain boundaries or coarsens the crystal grains, making rolling difficult.

The reason for setting the rough rolling temperature to 1000 to 1200°C is to obtain a fine recrystallized structure, and it is because it is not possible to obtain a fine recrystallized structure in the groove at 1000°C.
This is because the crystal grains become coarser due to recrystallization.

The reason why the amount of processing is set to 50% or more in rough rolling is that if the amount of processing is less than 50%, the energy of lattice defects is small and a fine structure cannot be obtained.

The reason why the finish rolling temperature was set to 800 to 1000°C is to obtain a recrystallized double structure structure. This is because if it is below 800°C, it becomes a processed structure and it is not possible to obtain a recrystallized double structure structure, and if it exceeds 1000°C, it becomes a recrystallized structure due to recrystallization.
was set as the upper limit.

The processing amount was 30% or more in finishing rolling and rolling.
This is because if it is less than 0%, a recrystallized double structure cannot be obtained because the processing strain is small.

The reason why cooling is performed for 10 seconds to 5 minutes after rough rolling is because it is the time required to cause recrystallization after rough rolling. In addition, the cooling rate after finish rolling was set to 4°C/min or more because slow cooling at 4°C/min or less was used for Cr23Ca or Crz
This is because N precipitates at grain boundaries and reduces corrosion resistance.

[Example] Next, the characteristics of the steel of the present invention and its manufacturing method will be clarified by comparing it with conventional steel and comparative steel through examples.

Table 1 shows the chemical composition (wt%) of these test steels.The test steels in Table 1 were subjected to controlled rolling by the method of the present invention and controlled rolling by other methods for comparison, and the microstructure, strength, Pitting potential, elongation, machinability, hot workability, creep rupture strength, and high temperature strength were measured, and the results are shown in Table 2.

Regarding the structure, the structure was observed using an optical microscope after performing electrolytic etching with 10% oxidized acid. Further, the electron microscopic structure was observed using a transmission electron microscope after forming the thin film.

Regarding the creep rupture strength, the rupture stress was measured for 103 hours in a creep rupture test at 600°C.

Regarding hot workability, 110
A high temperature tensile test was conducted at 0° C. and a tensile distance of 50 mm/sec, and the aperture value was measured.

Corrosion resistance was measured by measuring pitting potential in a 3.5% NaCl aqueous solution at 30°C.

Regarding machinability, 20 waso test pieces were used, and 5KH9 51 test pieces were used.
Using a φ drill, rotation speed 725 rps, feed rate 0
, 16 aml rev, and the results are shown below.

(Left below) As is known from Tables 1 and 2, No. 1
~3 and No. 11"12 are those of the composition of the first invention steel that are controlled rolled by the method of the invention, but 0.2
% proof stress, pitting potential, elongation (600℃), 600℃100
Satisfactory results were obtained in terms of 0 hr creep rupture strength, machinability, and hot workability. On the other hand, No. 4
~5 is 5US304, No. 6-7 is 5US316, N
o8-10 are comparative steels corresponding to 5US347, respectively.

No. 4, which was processed by a method other than the method of the present invention, but whose finish rolling temperature was high < 1050°C, obtained only a recrystallized structure, and had low 0.2% proof stress and creep rupture strength. Corrosion resistance is low, finish rolling temperature is low (700℃)
Similarly, No. 5 is inferior in 0.2% yield strength, creep rupture strength, and pitting potential. No. 6 was subjected to solution heat treatment after rolling, and was inferior in 0.2% yield strength, creep rupture strength, and pitting potential. No. 7 was subjected to one-step controlled rolling at 900°C and has a processed structure, and No.
, 8 is the processed structure obtained by one stage of controlled rolling at 700°C, No. 9 is the processed structure whose cooling rate after finish rolling is 3°C/min, and No. 10 is the processing rate in finish rolling. is as low as 10%, but all are inferior in 0.2% yield strength, elongation, creep rupture strength, and pitting potential.

Nos. 13 and 14 are comparative examples corresponding to Incoloy 800, but they are inferior in creep rupture strength.

Nos. 15 to 19 are steels with the composition of the second invention steel of the present invention that were subjected to controlled rolling according to the method of the present invention, and a recrystallized double structure structure was obtained, with a 0.2% yield strength and pitting potential. Excellent results were obtained in both elongation and creep rupture strength. In particular, it was confirmed that the material was excellent in terms of pitting potential and corrosion resistance. Nos. 20 to 21 are comparative examples corresponding to 2l-4N, but No. 20 is inferior in 0.2% yield strength and creep rupture strength, and No. 21 is finish rolling at 950 ° C. It was confirmed that although the .2% yield strength and creep rupture strength were excellent, the pitting potential was inferior.

No. 22 to 26 contain Se, Te, and Te to improve machinability.
Although it is the third invention steel with addition of S and P, by controlled rolling according to the method of the present invention, it becomes a recrystallized double structure structure and has a zero
．． Excellent results were obtained in terms of 2% yield strength, 2-pitting potential, elongation, and creep rupture strength. Furthermore, as a result of measuring the machinability, it was confirmed that excellent results were obtained.

No. 27 to 29 contain Bi, Pb, and
This is the fourth invention steel containing B, but by controlled rolling according to the method of the invention, it becomes recrystallized double i structure, and has a 0.2
Excellent results were obtained in terms of % yield strength, pitting potential, elongation, and creep rupture strength. Furthermore, as a result of measuring machinability and hot workability, it was confirmed that machinability was improved without reducing hot workability.

No. 30 to 38 are V, Ti, W,
This is the fifth invention steel with additions of Ta, Hf=Zr, and Al, but by controlled rolling according to the method of the invention, it becomes a recrystallized double structure structure, resulting in 0.2% proof stress, pitting corrosion potential, elongation, and creep rupture strength. Both achieved excellent results.

No. 39 to 43 are 85Ca to improve hot workability.
, MH5 is the sixth invention steel added with rare earth elements, but by controlled rolling according to the method of the present invention, it becomes a recrystallized double structure structure, and has excellent 0.2% proof stress, pitting corrosion potential, elongation, and creep rupture strength. Got the results. Furthermore, as a result of measuring hot workability, it was confirmed that the product had excellent hot workability.

Nos. 44 to 46 are the seventh invention steels to which all the above-mentioned elements are added to improve strength, corrosion resistance, machinability, and hot workability. Excellent results were obtained in terms of 0.2% yield strength, pitting potential, elongation, and creep rupture strength. In addition, machinability,
It was confirmed that excellent results were obtained in terms of hot workability as well.

[Effects of the Invention] As explained above, the crushed austenitic stainless steel with creep rupture strength and the manufacturing method thereof of the present invention are as follows.
Reduce the amount of C in austenitic stainless steel and add appropriate amounts of N and Nb! 7. The two-step controlled rolling process has been used to create a double-structured structure through recrystallization, which significantly improves the creep rupture strength of austenitic stainless steel at 600°C for 1000 hours, which cannot be obtained with conventional austenitic stainless steels. 30 kgf/
The austenitic stainless steel of the present invention, which has excellent creep rupture strength, has the creep rupture strength, high temperature strength, corrosion resistance, and hot resistance properties required as a high temperature material. It satisfies all processability properties of 0.degree. C., and is extremely useful as a material for heat exchangers such as boilers, support members for NaS batteries, and valve stems for butterfly valves.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between temperature and time in the controlled rolling process according to the method of the present invention, and Figure 2 (a) is a micrograph showing the recrystallized structure after solution heat treatment. Figures 3 (a) and (b) are reproductions of microscopic photographs showing the processed structure after finish rolling at 900°C, and Figures 4 (a) and (b) are recrystallization 2 at a finishing rolling start temperature of 1050°C. Figures 5 (a) and 5 (b) are copies of micrographs showing the heavy structure, and Figures 6 (a) and 6 (b) are copies of the micrographs showing the double structure texture processed by recrystallization at a finishing rolling start temperature of 980°C. ) is finish rolling start temperature 90
Figure 7 (a) and (b) are copies of micrographs showing the double structure structure of the recrystallization process at 0°C at a finishing rolling start temperature of 850°C; FIG. 8 (a) is a copy of a microscopic photograph showing the processed structure at a rolling start temperature of 700° C., and FIG. 9 is a diagram showing the creep rupture strength of a conventional material. w, 23 (a) Part c) Figure 3 (a) Procedure amendment writing method) January 9, 1989

Claims (9)

[Claims] (1) C: 0.03% or less, Si: 2.0 in terms of weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
02 to 0.25%, with the balance consisting of Fe and impurity elements, and the structure is a recrystallized double structure structure, and the creep rupture strength at 600°C for 1000 hours is 30 kgf/mm^2 or more Austenitic stainless steel with excellent creep rupture strength. (2) C: 0.03% or less, Si: 2.0 in terms of weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
02 to 0.25%, and further contains 1 of Mo: 4.0% or less, Cu: 4.0% or less, and S: 0.002% or less.
Contains one or more seeds, the balance is Fe and impurity elements, and the structure is a recrystallized double structure structure, and the creep rupture strength at 600°C for 1000 hours is 30 kgf/mm^2 or more. Austenitic stainless steel with excellent creep rupture strength. (3) C: 0.03% or less, Si: 2.0 in terms of weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
02 to 0.25%, and further Se; 0.080%
Contains one or more of Te: 0.080% or less, S: 0.080% or less, P: 0.100% or less, and the remainder consists of Fe and impurity elements, and the structure is regenerated. Consisting of crystal processed double structure structure, 600℃10
Creep rupture strength at 00 hours is 30kgf/mm
Austenitic stainless steel with excellent creep rupture strength characterized by a strength of ^2 or more. (4) C: 0.03% or less, Si: 2.0 in terms of weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
02 to 0.25%, and further Bi; 0.300%
Contains one or two of the following, Pb: 0.300% or less, and B: 0.0100% or less, with the balance consisting of Fe and impurity elements, and whose structure is a recrystallized double structure structure. An austenitic stainless steel with excellent creep rupture strength, characterized in that the creep rupture strength at 600°C for 1000 hours is 30 kgf/mm^2 or more. (5) C: 0.03% or less, Si: 2.0 in terms of weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
02 to 0.25%, and further contains V, Ti, W, Ta
, contains at least 0.30% or less of each of Hf, Zr, and Al, with the balance consisting of Fe and impurity elements, and has a recrystallized double structure structure, and is heated at 600°C.
Creep rupture strength at 1000 hours is 30kgf/
Austenitic stainless steel with excellent creep rupture strength, characterized by having a creep rupture strength of mm^2 or more. (6) C: 0.03% or less, Si: 2.0 in terms of weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
Contains 02-0.25%, B; 0.0005-0.0
100%, Ca; 0.0005% to 0.0100%, M
g; 0.0005-0.0100%, rare earth element 0.0
0.005 to 0.0100%, the remainder consists of Fe and impurity elements, and the structure is a recrystallized double structure structure, and is heated at 600℃ 10
Creep rupture strength at 00 hours is 30kgf/mm
Austenitic stainless steel with excellent creep rupture strength characterized by a strength of ^2 or more. (7) C: 0.03% or less, Si: 2.0 in terms of weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
02 to 0.25%, and further contains 1 of Mo: 4.0% or less, Cu: 4.0% or less, and S: 0.002% or less.
A species or two or more species, Se; 0.080% or less, Te;
0.080% or less, S; 0.080% or less, P; 0.1
00% or less and one or more of them and Bi: 0.3
00% or less, Pb; one or two of 0.300% or less and B; 0.0100% or less, V, Ti, W,
0.30% or less of each of Ta, Hf, Zr, and Al is 1
More than species, B; 0.0005 to 0.0100%, Ca;
0.0005% to 0.0100%, Mg; 0.0005
~0.0100%, rare earth elements 0.0005~0.01
00%, the balance is Fe and impurity elements, and the structure is a recrystallized double structure structure, and the creep rupture strength at 600°C for 1000 hours is 30kgf/mm^2 An austenitic stainless steel with excellent creep rupture strength. (8) C: 0.03% or less, Si: 2.0 in terms of weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
A steel containing 02 to 0.25% and the balance consisting of Fe and impurity elements is heated to 1100 to 1300°C and rolled with a working amount of 50% or more at a rough rolling temperature of 1000 to 1200°C. After cooling for 5 seconds to 5 minutes, rolling is performed at a finish rolling temperature of 800 to 1000°C with a processing amount of 30% or more, and the cooling rate after rolling is 4°C/min or more, so that the structure is recrystallized double structure. Composed of tissue, 600℃100
Creep rupture strength at 0 hours is 30kgf/mm^
A method for producing an austenitic stainless steel having an excellent creep rupture strength of 2 or more. (9) C: 0.03% or less, Si: 2.0 in weight ratio
% or less, Mn; 10.0% or less, Ni; 6 to 20%, C
r: 16-30%, N: 0.1-0.3%, Nb: 0.
02 to 0.25%, and further contains 1 of Mo: 4.0% or less, Cu: 4.0% or less, and S: 0.002% or less.
A steel containing one or more seeds and the remainder consisting of Fe and impurity elements is heated to 1100 to 1300°C, and rolled at a rough rolling temperature of 1000 to 1200°C with a working amount of 50% or more, and for 10 seconds after rough rolling. After cooling for ~5 minutes, rolling is performed at a finish rolling temperature of 800 to 1000°C with a processing amount of 30% or more, and the cooling rate after rolling is 4°C/min or more, so that the structure becomes a recrystallized double structure structure. consisting of 600℃100
Creep rupture strength at 0 hours is 30kgf/mm^
A method for producing an austenitic stainless steel having an excellent creep rupture strength of 2 or more.