JPH03191039A - Heat-resistant austenitic stainless steel - Google Patents

Abstract

PURPOSE:To obtain the heat-resistant stainless steel excellent in high temp. salt corrosion resistance, weld hot cracking resistance and hot workability by adding specified amounts of Si, Mo, etc., to an austenitic stainless steel and limiting its D value as the index value of ferrite crystallization into a specified range. CONSTITUTION:The austenitic stainless steel is the one contg., by weight, <0.06% C, 1 to 4% Si, 0.5 to 4% Mn, <0.035% P, <0.005% S, 10 to 17% Ni, 14 to 20% Cr, 1 to 4% Mo, 0.01 to 0.5% Al and <0.035% N, satisfying Si+Mo>=3% and 2.5Si+Mo<=11% and having 7 to 11D value as the index value of ferrite crystallization expressed by formula 1. Or, it is the heat-resistant austenitic stainless steel having a compsn. furthermore contg. 0.5 to 2.5% Cu and total 0.005 to 0.1% of one or 2 kinds among rare earth metals and, in this case, having 6 to 11D value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to repeated heating and cooling in high-temperature corrosive atmospheres, particularly in atmospheres where salt-containing corrosion is a problem, such as Manten salt corrosion or molten salt corrosion. The present invention relates to a heat-resistant austenitic stainless steel that has excellent high-temperature salt corrosion resistance, weld hot cracking resistance, hot workability, weldability, and high-temperature salt corrosion resistance of welded parts, and is used in applications such as high temperature salt corrosion resistance.

[Prior art and its problems]

High-temperature properties are required for heat-resistant steel used in harsh corrosive environments such as automobile exhaust gas purification systems, heating furnace parts, heat exchanger parts, and cooking appliances such as electric stoves and fish fryers. In addition to general properties such as strength properties, high temperature oxidation resistance, oxide scale peeling resistance, high temperature gas corrosion in combustion atmospheres or PBO, v20. Various oxides such as PbCρ2, NaCQ, Mgc4. It has high temperature oxidation resistance in environments containing chlorides such as , KCQ, and molten salt corrosion resistance at even higher temperatures. Furthermore, there is also the problem of moisture corrosion due to condensed water during cooling. Heat-resistant surface-treated steel sheets do not hold up under such harsh environments, and 5LIS30/I
Heat-resistant stainless steel t~ is used.

Areas where road surface de-icing agents are sprayed at incinerators used for large-scale waste processing, siding burners in pit furnaces, heavy oil boilers, exhaust gas pipes from internal combustion engines, etc.

Some parts used in environments where chlorides or ash are present have been found to suffer from severe high-temperature corrosion, which has become a problem. As a result of investigating these corrosion cases,
A common phenomenon is grain boundary erosion type accelerated oxidation, which is corrosion at high temperatures with salt attached or in a molten salt state, and it has been found that high-temperature corrosion caused by salts containing chlorides is particularly remarkable. Ta.

However, existing heat-resistant stainless steels 5US30/I, 5US321 and 5US3 are effective against this high-temperature corrosion.
10S is not sufficient for such applications.

In general, steels containing high Si and high Mo content are certainly effective in improving corrosion resistance, but on the other hand, their high alloying causes manufacturing problems such as poor hot workability, low yield, and poor surface quality. When it was put into practical use, problems arose with pipe forming and weldability during construction. In addition, in environments where highly concentrated salt water comes into contact with parts that are newly used at high temperatures, depending on the conditions, the base material may be sound, but the welding bong 1 to 1 may undergo significant selective corrosion due to high-temperature salt damage. It became clear.

JP-A No. 63-213643 discloses that C: 0 in single length.
．． 03% or less, Cr: 10-20%, Ni: 1
0-30%, 4n: 2% or less, Sl: 1-6%, Mo
: 0.5-5% and N: 0.02-0.4%, and the value of formula % is 500 or less. Excellent high-temperature corrosion resistance in the coexistence of chlorides. Stainless steel is disclosed. This steel can contain at least one of Ti, Zr, Nb, and Ta in a total amount of 0.1 to 1%. However, no consideration has been given to improving the weld hot cracking resistance of this steel.

Therefore, there is a need for a heat-resistant austenitic stainless steel that has excellent high-temperature salt corrosion resistance, welding hot cracking resistance, and hot workability as well as high-temperature salt corrosion resistance.

[Knowledge about problem solving]

The present invention aims to improve the high-temperature salt corrosion resistance of heat-resistant austenitic stainless steel, as well as the welding hot cracking resistance and hot workability. Si and M for improvement
If desired from the viewpoint of stress corrosion cracking or weather resistance, a limited amount of o may be added.

By adding a limited amount of Cu, the grain boundary corrosion resistance due to intergranular corrosion at high temperature and mixed corrosion during cooling, high temperature strength, and hot workability can be improved by adding a limited amount of Nb, Ti, and V. It was also found that hot workability and weld hot cracking susceptibility can be improved by adding B and REM in limited amounts.

[Structure of the invention]

The above objectives are: C: 0.06% or less Si: 1-4% Mn: 0.5-4% P: 0.035% or less S: 0.005% or less Ni: 10-17% Cr: 14-20 % Mo: 1 to 4% AI2: 0.01 to 0.5% N: 0.03% or less is the basic composition, and Cu: is added to this basic composition as necessary.
0.5-2.5%, and further, the basic composition and the total content of one or more of Nb, Ti, and V in the steel containing Cu: 0.05-0.5 % and/or B: 0.0005 to 0.02%, and further contains Cu in the basic composition and basic composition, and these steels contain 1 of Nb, Ti, and V.
A steel containing one or more types and/or B contains one or two types of REM: 0.005 to 0.1%, and the balance consists of Fe and inevitable impurities, as shown in the following formula (1) (Si% + Mo%) expressed by the formula is 3 or more,
(2,5Si%+Mo%) expressed by formula (2) is 11 or less, and the D value expressed by formula (3) is 6 or more when containing REM or B, and 7 when not containing it, from the viewpoint of weldability. The above can be achieved by using a heat-resistant austenitic stainless steel with a rating of 11 or less.

(Si%10No%)≧3 ・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・(1)(2,5S
i%+Mo%)≦11・・・・・・・・・・・・・・・
・・・・・・・・・・・・(2) D value = (Cr%+1
．． 55i%10%+3Al%+2.6Ti%+0.5
Nb%+0.5v%)=(Ni%+30C%+3ON%
+0.5Mn%+2Cu%)・・・・・・・・・・・・
・・・・・・・・・・・・・・・(3) All the D values based on the above formula of the steels shown in the steel examples of JP-A-63-213643 mentioned above are less than 4. . The inventors
By setting this value to 6 or 7 or more, welding hot cracking of high-Si, high-Mo steel can be successfully prevented.

The preferred composition of the steel of the present invention is C: 0.03 to 0.06.
0% or less, Si: 2-3%, Mn: 0.5-1%,
P: 0.03% or less, s: 0.005% or less, Ni: 12-16%, Cr: 16~]8%, Mo:
2-3.2%, l: 0.01-0.03%, N
20.03% or less, the remainder being Fe and unavoidable impurities.

Next, the reasons for limiting the composition of steel in the present invention will be explained below.

C: An inevitable component and a strong austenite-forming element.5 In steels that also require excellent hot workability and pipe forming properties, such as the steel of the present invention, it is a necessary element from the viewpoint of compositional balance. . It is also effective in saving expensive Ni.

Furthermore, C is an interstitial element that forms a solid solution and is an effective element for improving high-temperature strength. However, excessive addition of C causes embrittlement and also reduces workability, so the upper limit is set at 0.06%. On the other hand, reducing C is undesirable because it lengthens the X-melting time and increases manufacturing costs, and it is also undesirable to reduce C excessively to 0.603% or less in order to obtain the necessary high-temperature strength.

Sj: One of the most important elements for improving oxidation resistance and high mixed salt corrosion resistance, and 1% to obtain sufficient effect.
Above, preferably 2% is required.

On the other hand, Si promotes precipitation of the σ phase and causes a decrease in toughness, and also reduces hot workability, weldability, and formability, so the upper limit is set to 4%, preferably 3%.

Mn: S, which is harmful to welding hot cracking, is fixed as MnS,
Removes and reduces S in weld metal. If the Mn content is too low, MnS will exist in the form of a film at the grain boundaries, promoting a decrease in grain boundary strength at high temperatures; however, if the Mn content is high, MnS will become spheroidal and its influence on the decrease in grain boundary strength will be reduced.

For that, Mni is required to be 0.5% or more, and 4%
The effect is the same even if it exceeds . Therefore 0.5%
4% or less. Considering the D value, it is preferably 1% or less.

P: Same as S, it is harmful to welding hot cracking.
Although it is better to keep the content as low as possible, lowering it will increase manufacturing costs, so the upper limit is set to 0.035% or less.

S: As mentioned above, it is harmful to weld hot cracking, so it is preferable to keep it as low as possible, but lowering it causes an increase in manufacturing costs, so the upper limit is set at 0.005%.

Ni is one of the basic elements of niostenitic stainless steel.
Therefore, from the viewpoint of preventing hot weld cracking, it is necessary to have a composition in which δ ferrite is generated, so the lower limit was set at 10% in consideration of the composition balance.

The upper limit was set at 17% or less from the viewpoint of compositional balance and product cost. Considering the D value, 12 to 16% is preferable.

Cr is the most basic element for maintaining the oxidation resistance and corrosion resistance of stainless steel. If it is less than 14%, sufficient effects cannot be obtained in terms of high-temperature corrosive environments or simply high-temperature oxidation resistance. Moreover, if it exceeds 20%, it becomes difficult to adjust the compositional balance, and the amount of δ ferrite increases, resulting in a decrease in workability, so the upper limit was set at 20% or less. Considering the D value, 16 to 18% is preferable.

4o: It is an element that is effective in corrosive environments at high temperatures as well as high-temperature salt damage resistance and high-temperature strength, so it is an element that should be actively added. If it is less than 1%, the effect of addition is small, so the lower limit is set to 1% or more. On the other hand, Mo is expensive and also promotes precipitation of the σ phase, leading to a decrease in toughness.

Moreover, if added in excess of 4%, hot workability will be reduced, so the upper limit is set at 4%. Considering the D value, 2 to 3.2
% is preferable 6 Al: The most effective element for improving oxidation resistance, and
Since it is effective in increasing the cleanliness of steel, it is desired that it be contained in an amount of 0.01% or more. Further, Al is a strong ferrite-forming element, and from the viewpoint of compositional balance and toughness, the upper limit was set to 0.5% or less.

Considering the D value, 0.01 to 0.03% is preferable.

B: It is effective in increasing grain boundary strength and improving hot workability and weld hot cracking, but the effect does not appear when the content is less than o,ooos%, and when the content exceeds about 0.02% When compound B is prepared, the grain boundary strength decreases, so the content is set to 0.02% to 0.02%.

Nb, Ti, V: These elements combine with C and N to form fine precipitates, improving not only corrosion resistance but also high-temperature strength and
It is particularly effective in improving creep strength, and a clear addition effect can be obtained when the total amount added is 0.05% or more. If the amount added increases, workability and toughness will decrease, so the total amount should be 0.5% or less. Preferably 0.05-0.4
%.

REM: Effective in improving cracking susceptibility by fixing S, which is harmful to welding hot cracking, as a high melting point compound during the initial solidification process. It is also effective in increasing the peeling resistance of oxide scale when subjected to heating-cooling temperature cycles.

To obtain these effects, the total amount of REM is 0.005%.
On the other hand, if a large amount of REM is added, a large amount of REM oxide will precipitate at the grain boundaries, lowering the grain boundary strength at high temperatures and canceling out the effect of improving hot cracking susceptibility. Eyes should be 0.1% or less.

Cu: Effective in terms of stress corrosion cracking and weather resistance,
In that case, 0.5% or more is required. On the other hand, if added in a large amount, it segregates at grain boundaries and significantly impairs hot workability, so the upper limit is set at 2.5%. 1-1.3% considering the D value
is preferred.

N: Similar to C, it is an effective component for improving high temperature strength, but if added in excess, workability decreases, so add 0.0
3% or less.

Furthermore, the total amount of Si and Mo is also regulated as shown in equations (1) and (2) above. Lower limit value (Si%
The upper limit (2,5Si%+Mo%)≦11 is for improving the high-temperature salt corrosion resistance of the base metal, and the upper limit (2,5Si%+Mo%)≦11 is for improving hot workability, weld hot cracking resistance, and σ embrittlement. This is to minimize deterioration and moldability.

In addition, the D value expressed by the above equation (3) was defined and limited in order to improve the D value since steel containing high Si or high Mo is extremely susceptible to welding hot cracking.
The value is an index value for ferrite products.

The D value is 6 or more when containing REM or B, and 7 or more when not containing this element. If the amount of δ ferrite is too large, hot working cracks will occur, leading to a decrease in productivity, so the upper limit was set to D value = 11.

[Specific disclosure of the invention]

Next, the present invention will be specifically explained. As a basic experiment, the steels shown in Table 1 were vacuum melted and subjected to hot tensile tests and high temperature salt corrosion tests. Hot tensile test is performed using 20X20X110 from steel ingot.
Cut into mm pieces, heat treated at 1200℃ for 2 hours,
It was processed into a round bar test piece with a diameter of 10 mm.

For the high temperature salt corrosion test, a steel ingot was forged into a 30mm thick plate.
After heating to 1200°C, hot rolling to 511IIll,
Thereafter, a 2mm plate was produced by normal cold rolling and annealing, and 25X
It was processed into a 35 mm test piece, the entire surface of which was polished with I400, and used for testing.

First, in order to confirm the high mixed salt corrosion resistance, one cycle consisted of immersing the test material in saturated saline at 20°C for 5 minutes, heating it at 650°C for 2 hours, and cooling it in air for 5 minutes.
A high-temperature salt corrosion test was conducted using a 0-cycle method. Tests were taken out and scaled, and high mixed salt corrosion resistance was evaluated by corrosion weight loss. The results are also shown in Table 1. From this result, compared to the standard steel of S[JS30/I, 5US321,
5US302B, SUSXM15Jl containing high Si
It can be seen that the corrosion weight loss of E33 to E96 containing Si and To10 is significantly reduced. Figure 1 shows D of the steels shown in Table 1.
The influence of the amount of (Si + Mo) on the resistance to hot salt corrosion for those having a value of 7 or more and 11 or less is shown. This result shows that when the content of (Si + Mo) is 3% or more, the corrosion loss is significantly reduced, and it is extremely important to add 3% or more of (Si + Mo) in order to provide high mixed salt corrosion resistance. It turns out that it is effective. Generally, the excellent heat resistance of austenitic stainless steel is due to Cr formed on the steel surface.
0. Although this film exhibits excellent protection against atmospheric oxidation, it may not be a sufficient protective film in the high-temperature salt corrosion environment in which the steel of the present invention is used. It is severely corroded. On the other hand, (Si
It is believed that by adding 3% or more of 100% or more, it is possible to form a film that exhibits excellent protection in a high-temperature salt corrosion environment.

On the other hand, as the content of Si and Mo increases, hot workability improves.
It cannot be added in an unnecessarily large amount because it will cause hot welding cracking and deterioration of toughness. Figure 2 is 800-140
A hot high-speed tensile test was conducted at 0°C to determine the area of area at break, and the temperature at which the area of area at break became 0%, that is, the null1 point was determined. From this result, the null1 point decreases as Sl and Mo increase, especially when Si is M.

It is not preferable to increase the amount by a large amount because the amount becomes 2.5 times the amount. This is because as the content of Si and Mo increases, coagulation film embrittlement due to grain boundary melting is promoted by high temperature heating.

Therefore, from the viewpoint of hot workability, it is not possible to expect a large increase in the amount of Sl and ribs, and it is considered that (2,5Si+Mo) is preferably 11% or less.

In addition, as shown in the figure, when B is added, the number of null points is significantly lower than that of (Sj + Mo) steel at the same level.
-H is seen. This is because B increases grain boundary strength.
Effective for improving materials that are difficult to hot work.

From this background, the addition of Si and No is regulated based on the total amount, with the lower limit being regulated in terms of high mixed salt corrosion resistance, and the upper limit being regulated in terms of hot workability, weld hot cracking, and σ embrittlement. Si
Even if the upper limits of the amounts of Mo and Mo are strictly regulated, if there is still a problem with hot workability, B is added. B increases grain boundary strength and is therefore effective in improving hot workability.

Furthermore, in a high-temperature salt corrosion environment, as described above, the welded part may be severely corroded before the base metal is corroded. Figures 4, 5, and 6 are 5US shown in Table 1, respectively.
304, SUSXM15J1 and E57(7)ill
Hot rolled by a conventional method and cold rolled annealed to form a plate with a thickness of 0.3+nm or less, T
After IG welding, welded with a solution containing 5% NaCQ at 60℃ for 1
This is a microscopic photograph of a cross-section of a welded part at about 70 times magnification obtained by performing 10 cycles of wetting for 1 hour, drying at 60° C. for 3 days, and heating at 350° C. for 4 hours. 5 US
In No. 304, the welded portion corroded along the δ ferrite phase, and the bond portion was particularly corroded, so that it broke along the bond portion. SUSXM15J1 containing Si is 5
Although the bond portion did not break like in US304, the δ ferrite phase was selectively corroded considerably. In contrast to these two steels, E57 containing (Si 10 No) was not corroded at all.

This is 5US304 and 2SUSXM l 5J 1
This is thought to be due to the fact that the δ ferrite phase became base to the matrix and was electrochemically corroded significantly. On the other hand, the reason why the welded part of E57 is less likely to be corroded is because the corrosion resistance of the δ ferrite phase itself is increased by Si and No, which are effective in high mixed salt corrosion resistance. Therefore, adding Si and Mo is not limited to the base material;
It is also effective in improving the high mixed salt corrosion resistance of welded parts. One of the major features of the present invention is that it can be used in the severe corrosive environment described above, which was not possible with the addition of Si alone.

Materials that are highly susceptible to welding hot cracking are fatal when used in welded structures such as automobile exhaust gas parts, heating furnace parts, and heat exchanger parts. In particular, high-SiUJMo[ is a problem because it has high weld hot cracking susceptibility. This weld hot cracking is largely influenced by the δ ferrite phase generated during the solidification process.

In other words, in the case of austenite single-phase steel, since the initial product has only the austenite phase, impurity elements concentrate at the primary grain boundaries of the austenite phase and the austenite phase, weakening the grain boundary strength and preventing hot cracking. However, when δ ferrite exists, the initial δ ferrite 1 ~ transforms into austenite during the solidification process, and grain boundary movement occurs at that time, so impurities at the austenite grain boundaries are more likely to occur than in austenite r phase steel. It is said that high temperature cracking during welding is improved due to the small amount of elements. The present inventors have discovered that this δ ferrite i~
Using the steel shown in Table 2? The cracking susceptibility was examined in detail by an 8-junction hot cracking test, and the R1 results shown in FIG. 3 were obtained. The steel shown in Table 2 is vacuum melted into a steel ingot, forged into a 30 mm thick slab, heated to 1200°C, and then
Hot rolled into a 5mm thick plate, then normal cold rolled and annealed.
．． A 5 mm plate was prepared and processed into a 40 x 200 mm test piece. The welding hot cracking test was performed by chucking both i and t of the test piece and applying a tensile load in the longitudinal direction.
■Made G+8 contact. Using this method, 5 to 10 welded samples were prepared using various tensile loads. After welding, the amount of strain was measured from the position of the marking line that had been placed before the test, and the amount of strain generated during solidification was measured. The presence or absence of cracks in the welded part was observed, and the minimum strain that caused weld cracking was taken as the critical strain, and D, which is an index of the critical strain and the amount of δ ferrite.
The relationship with the values is plotted in Figure 3. From this result, even in steel containing high SJ and high XO, hot cracking is less likely to occur if an appropriate amount of δ ferrite is present in the weld bead.
It became clear that the D value was improved within the range of 7 or more and 11 or less. In addition, as shown in Figure 1, when B and REM are added to the basic components, the cracking sensitivity becomes weaker, and an improvement effect is observed compared to steel with the same D value.
In this case, a D value in the range of 6 to 11 is considered optimal.

As described above, it has become possible to provide a heat-resistant austenitic stainless steel containing high Sl/high Mo content by considering the high temperature salt corrosion resistance, hot workability, and weld hot cracking resistance.

〔Example〕

Next, the present invention will be explained with reference to examples. Steel having the composition shown in Table 3 was melted and prepared into the same samples as above. Table 3 also shows the corrosion weight loss obtained from the high temperature salt damage corrosion test, the critical strain obtained from the weld hot cracking test, and the null 1 point measurement results obtained from the hot tensile test. The preparation and testing methods for the samples used in these tests were exactly the same as those described in connection with FIGS. 1.2 and 3 above. From this table, the comparative steel E74, which does not meet the specified composition, has a low Si content and does not contain Mo, so its corrosion loss is large. E75 has a large corrosion loss because it does not contain Mo, and has a low null point because it has a large amount of Sl, and the composition balance has been adjusted so that the D value is 8.8 and the amount of δ ferrite in the weld is appropriate. However, since there are many 5ifts, the critical strain is very low. Since E76 has a large amount of Si and Mo, the null1 point is low, and the critical strain is also very low. Although F6 is a component within the range of the steel of the present invention, the D value is extremely low at 4.5 and is outside the range of the present invention, so the critical strain is extremely low. E77 is also a component within the scope of the steel of the present invention, but since its D value is too high, it corrodes along the delta ferrite, resulting in a large corrosion weight loss. In addition, the existing steel 5
US304 has a large corrosion loss and contains Si.
302B and SUSXMI5J1 have less corrosion loss than 5US304, but unlike the invention steel, they do not contain Mo, so the corrosion loss is greater than the invention steel.

On the other hand, in the steels of the present invention, Fl and E57 contain Si and A0, which are effective in resisting high-temperature salt damage and corrosion, so the corrosion loss is small, and the D value, which is the compositional balance, is 8.
．． Since it is adjusted to 5, the critical strain is high and the null1 point is also high. E60 is Si and M, which are effective in high temperature salt corrosion resistance.
It is a steel containing copper, which is effective for stress corrosion cracking resistance, and has a small corrosion loss, similar to Fl and E57, and a high critical strain and null1 point. E61-E66
Similarly to the above, F9 contains Si and Mo, so the corrosion loss is small. In addition, among these steels, E61 contains Nb and Ti, which are particularly effective for improving creep strength, and E62
E64 is a steel containing Cu, Nb, and V based on the same concept, and the composition has been adjusted to a D value of 6.2 to 8.5, a range that does not easily cause welding hot cracking, so both are critical. Strain is high. F9, E63, E65, and E66 contain Cu, Nb, Ti, or V, which is effective in improving hot workability, and therefore have a high null point.

As mentioned above, FIO and 1E67 to IE73 contain Si and Mo, which are effective in high mixed salt corrosion resistance, so the corrosion loss is small.

In addition, since it contains REM, which is effective in improving weld hot cracking resistance, the critical strain is high even though the D value, which is a one-composition balance, is relatively low. Among these steels, [E
67 is Cu, E68 is Nb, E71 is Cu and Nb
contains, but the null1 point is high. E69, E70. E
72 and [Nia 3 contain 13 in addition to REM or Nb, so the nul1 point is high.

It can be seen that the steel of the present invention described above is excellent in both stress corrosion resistance, weld hot cracking resistance, and hot workability.

〔Effect of the invention〕

With this invention! By limiting the composition of '+9', it has excellent high mixed salt corrosion resistance and at the same time excellent resistance to corrosion. By obtaining a heat-resistant austenitic stainless steel having 8-junction hot cracking properties and hot workability, the problems of the prior art are overcome, and an excellent heat-resistant austenitic stainless steel material is provided.

[Brief explanation of drawings]

Figure 1 shows the corrosion area fk (mg/csI) and SL +
Figure 2 is a diagram showing the relationship between Mo (%), Figure 2 is a diagram showing the relationship between the null1 point and heating temperature, Figure 3 is the critical strain E,
It is a figure showing the relationship between (%) and D value. Figures 4 to 6 show US304 steel, SUSXM15J1fi, and the present invention! (7) Approximately 7 indicates the state of corrosion of the welded part when the TIG welded part is repeatedly heated in the presence of NaCQ
This is a 0x micrograph.

Claims (1)

[Claims] 1. C: 0.06% or less Si: 1-4% Mn: 0.5-4% P: 0.035% or less S: 0.005% or less Ni: 10-17% Cr : 14-20% Mo: 1-4% Al: 0.01-0.5% N: 0.035% or less, with the balance consisting of Fe and unavoidable impurities, and the total content of Si and Mo A heat-resistant austenitic stainless steel that satisfies the following formula and has a D value expressed by the following formula of 7 to 11, which has excellent high-temperature salt corrosion resistance, weldability, salt corrosion resistance of welded parts, and hot workability. . (Si%+Mo%)≧3%・・・・・・・・・・・・
・・・・・・・・・・・・・・・(1)(2.5Si%+
Mo%)≦11%・・・・・・・・・・・・・・・・
・・・・・・・・・(2) D value=(Cr%+1.5Si%+
Mo%+3Al%+2.6Ti%+0.5Nb%+0.
5V%)-(Ni%+30C%+30N%+2Cu%+
0.5Mn%)・・・・・・・・・・・・・・・・・・
(3) The austenitic stainless steel according to claim 1, further comprising: 0.5 to 2.5% Cu. 3. Furthermore, total content of one or two REMs: 0.005 to 0
．． The austenitic stainless steel according to claim 1 or 2, containing 1%. However, in this case, the D value is 6-11. 4. C: 0.06% or less Si: 1-4% Mn: 0.5-4% P: 0.035% or less S: 0.005% or less Ni: 10-17% Cr: 14-20% Mo : 1-4% Al: 0.01-0.5% N: 0.035% or less Total content of one or more of Nb, Ti, and V: 0
．． 05 to 0.5% and/or B: 0.0005 to 0.02%, the balance consists of Fe and unavoidable impurities, and the total content of Si and Mo satisfies the following formula, and A heat-resistant product with excellent high-temperature salt corrosion resistance, weldability, salt damage corrosion resistance of welded parts, and hot workability, where the D value expressed by the formula is 6 to 11 when B is included, and 7 to 11 when it is not. Austenitic stainless steel. (Si%+Mo%)≧3%・・・・・・・・・・・・
・・・・・・・・・・・・・・・(1)(2.5Si%+
Mo%)≦11%・・・・・・・・・・・・・・・・
・・・・・・・・・(2) D value=(Cr%+1.5Si%+
Mo%+3Al%+2.6Ti%+0.5Nb%+0.
5V%)-(Ni%+30C%+30N%+2Cu%+
0.5Mn%)・・・・・・・・・・・・・・・・・・
(3) The austenitic stainless steel according to claim 4, further containing 0.5 to 2.5% of Cu. 6. The austenitic stainless steel according to claim 4 or 5, further comprising a total content of one or two REMs: 0.005 to 0.1%. However, in this case, the D value is 6 to 1
It is 1.