0001]The present invention relates to austenitic alloy material and austenitic alloy tube.
BACKGROUND
[0002]For the realization of future hydrogen economy, not dependent on fossil fuels, that is, development of a process for producing hydrogen by using clean energy without occurrence of carbon dioxide has become necessary. The method of hydrogen production, IS process incorporating thermal decomposition of sulfuric acid and hydrogen iodide, or the high temperature water electrolysis (steam electrolysis) or the like has been considered. IS process is also referred to as chemical hydrogen production, it is suitable for mass production of hydrogen. The principle is as follows, contains the degradation of hot sulfuric acid and hydrogen iodide, these reactions proceed by catalyst such as platinum.
[0003]
　H 2 SO 4　→ SO 3 + H 2 O (thermal decomposition of sulfuric acid: more than 300
　degrees) SO 3　→ SO 2 + 1 /. 2O 2 (SO 3 decomposition: ≧ 850 °
　C.) 2HI → H 2 + I 2 (hydrogen iodide decomposition: 400 °
　C.) SO 2 + I 2 + 2H 2 O → 2HI + H 2 SO 4 (Bunsen reaction: 200 °
　C.) H 2 O → H 2 + 1 /. 2O 2 (overall reaction)
[0004]
　The main object of the present process include the enhancement and improvement in performance of the catalyst of the corrosion resistance of the material used in the apparatus / plant. Since the reaction uses hot strong acid is equipment, corrosion or deterioration of the pipes becomes serious. Since particularly exposed to sulfuric acid decomposition unit is extremely strong corrosive environment, corrosion in the usual metallic material is inevitable. The process for using the catalyst has insufficient activity and durability of the catalyst itself, with the development of the catalyst material is chemical engineering efforts to enhance the contact efficiency of the gas or liquid phase has been advanced.
[0005]
　Non-Patent Document 1, the purpose of use of the IS system for plant materials, sulfuric acid or SO at elevated temperatures 3 corrosion resistance of corrosion-resistant alloy such as Alloy 600, Alloy800 under have been investigated.
[0006]
　Also includes a Cr-depleted zone in the surface Patent Document 1, the outside provided with the oxide scale layer of Cr principal to (surface side), stainless steel tube is disclosed which has a coking resistance and carburization resistance. It has been studied further application of ceramic or glass lining material such as a non-patent in Document 1 SiC. Most corrosion does not occur in these materials, the corrosion resistance is good.
CITATION
Patent Document
[0007]
Patent Document 1: JP 2005-48284 JP
Non-patent literature
[0008]
Non-Patent Document 1: Tanaka, Nobuyuki et al: Materials and Environmental, 55 (2006) pp. 320-324
Summary of the Invention
Problems that the Invention is to Solve
[0009]
　The high alloy material such Alloy600 or Alloy800, not obtained at all corrosion resistance enough for use as a device material in an environment containing sulfuric acid. On the other hand, the alloy material provided an oxide film around the chromium is corrosion resistance based on the barrier properties of the film are expected, is not sufficient corrosion resistance of the base material itself in such a high temperature sulfuric acid environment of the IS process. Ceramic or glass lining material is higher high material cost of having a corrosion resistance, also is likely to corrode at the junction for connection is difficult to occur. Furthermore ceramics also can damage the embrittlement easily, be used as plant equipment material it has a problem that it is difficult.
[0010]
　The present invention, in harsh environments such as exposure to high temperature steam or hot solution such as containing a sulfur oxide or hydrochloric acid containing sulfuric acid, excellent corrosion resistance, and to provide an austenitic alloy material and austenitic alloy tube of a low cost With the goal.
Means for Solving the Problems
[0011]
　The present invention has been made to solve the above problems, it is summarized as austenitic alloy material and austenitic alloy tube below.
[0012]
　(1) on at least a part of the surface of the base material has, provided with a coating comprising chromium oxide having a thickness of 0.1 ~ 50 [mu] m,
　the film, Cr concentration is the chemical composition at the depth position of maximum , O, as a percentage of components excluding C and N, in atomic% Cr: containing 50% or more,
　the chemical composition of the base material, in
　mass% C: 0.001 ~ 0.6%
　Si:
　0.01 ~ 5.0%, Mn: 0.1 ~
　10.0%, P: 0.08% or
　less, S: 0.05% or
　less, Cr: 15.0 ~
　55.0%, Ni :
　30.0 ~ 80.0%, N: 0.001 ~
　0.25%, O: 0.02% or
　less,
　Mo: 0 ~ 20.0%, Cu: 0 ~
　5.0%, Co: 0
　5.0%
~,
　W: 0 ~ 10.0%, Ta: 0 ~
　6.0%, Nb: 0 ~ 5.0%, Ti: 0
　~ 1.0%, B: 0 ~ 0.1% ,
　R:
　0 ～ 0.1 Pasento,
　Hf: 0 ～ 0.1 Pasento, Al: 0 ～ 1.0 Pasento,
　Mg:
　0 ~ 0.1%, Ca: 0 ~ 0.1%,
　the balance: Fe and impurities,
　austenitic alloy material.
[0013]
　(2) the chemical composition of the base metal, by
　mass%,
　Mo: 0.01 ~
　20.0%, Cu: 0.01 ~ 5.0%, Co: 0.01 ~
　5.0%, W:
　~
　10.0% 0.01, Ta:
　0.01 ~ 6.0%, Nb: 0.01 ~ 5.0%, Ti:
　0.01 ~ 1.0%, B: 0.001 ~ 0.
　%
　1,
　Zr: 0.001 ~ 0.1%, Hf: 0.001 ~
　0.1%, Al: 0.01 ~ 1.0%, Mg: 0.0005 ~ 0.1%,
　and, Ca : from 0.0005 to 0.1%,
　containing one or more selected from,
　austenitic alloy material according to (1).
[0014]
　(3) during said coating, Cu, V, W, includes one or more selected from Mo and the noble metal element,
　the (1) or austenitic alloy material according to (2).
[0015]
　(4) the chemical composition in the surface layer of the coating, satisfies the following (i) and (ii) expression,
　austenitic alloy material according to any one of (1) to (3). [Cu]
S + [V] S + [W] S + [Mo] S + [PM] S ≧ 30 · · · 　(i) [Cr] S ≦ 70 · · · (ii) 　where, in the formula each symbol, each element in the surface layer of the coating, O, represents the percentage (atomic%) to total components excluding C and N, PM is the meaning of the noble metal element.

[0016]
　(5) the chemical composition in a depth position where the Cr concentration is maximum, satisfying (iii) below formula,
　austenitic alloy material according to any one of (1) to (4).
　≦ 0.5 [Cu] P + [V] P + [W] P + [Mo] P + [PM] P ≦ 50 · · · (iii) 　wherein each symbol in the above formula, Cr concentration is maximum each element in the composed depth position, O, represents the percentage (atomic%) to total components excluding C and N, PM is the meaning of the noble metal element.
[0017]
　(6) the coating, Cu, V, including a complex oxide comprising at least one and a Cr selected from W and Mo,
　austenite alloy material according to any one of (1) to (5) .
[0018]
　(7) said coating, SO 3 has an action to degrade,
　austenitic alloy material according to any one of (1) to (6).
[0019]
　(8) SO 3 decomposition rate of, SO per unit area 3 feed rate: 0.0071G / cm 2 / min and the reaction temperature: in terms of ° C. 850, 8.0 × 10 -5 g / cm 2 / min at least,
　austenitic alloy material according to any one of (1) to (7).
[0020]
　(9) SO 3 decomposition rate of, SO per unit area 3 feed rate: 0.0071G / cm 2 / min and the reaction temperature: in terms of ° C. 850, 1.0 × 10 -3 g / cm 2 / min at least,
　austenitic alloy material according to any one of (1) to (8).
[0021]
　(10) made of austenitic alloy material according to any one of (1) to (9),
　austenitic alloy tube.
Effect of the invention
[0022]
　According to the present invention, it can be obtained in a high temperature harsh environments containing sulfur oxides or hydrogen halide such as sulfuric, austenitic alloy material and austenitic alloy tube which exhibits excellent corrosion resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023]
[Figure 1] Test No. It is a diagram showing a 3 concentration profile.
[Figure 2] Test No. Is a diagram showing the 10 concentration profile.
[Figure 3] Test No. 13 is a diagram showing the concentration profile.
DESCRIPTION OF THE INVENTION
[0024]
　The present inventors have found that the environment to use the hot strong acid such as IS process, in particular SO exceeding 800 ° C. 3 results in an environment containing steam and intensive studies in order to obtain an alloy material which exhibits excellent corrosion resistance, the following findings were obtained.
[0025]
　Film containing chromium oxide provided on the surface was found out to exhibit catalytic activity for the decomposition of the sulfur oxides is a step in the IS process. Here, the sulfur oxides, sulfuric acid (H 2 SO 4 ), sulfurous acid (H 2 SO 3 ), SO 3 , SO 2 , etc. SO x , S 2 O 8 are included, and the like.
[0026]
　In particular, as the cracking activity is high, corrosion resistance since it improves, believed to correlate with corrosion resistance and catalytic. SO catalytically 3 is decomposed, SO 2 is presumed to be because the corrosion resistance of the next sulfur oxides is reduced.
[0027]
　Furthermore, if Cu in addition to the chromium oxide in the coating, V, or W or Mo is contained, the surface layer side of the film, Cu, V, W, when including Mo or noble metal element, these intrinsic catalytic action is exerted catalysis of the film is enhanced, the corrosion resistance is improved as a result.
[0028]
　For these reasons, not only shows a high corrosion resistance as a device material such as pipes in chemical process using hot sulfur oxides or hydrogen halide, such as IS process, has a catalytic function, and contribute to the chemical production This has led to the development of the get austenitic alloy material.
[0029]
　The present invention has been made based on the above findings. It will be described in detail below each requirement of the present invention.
[0030]
　1. Chemical composition of the base material
　reasons for limiting each element are as follows. Incidentally, "%" for the content in the following description means "mass%".
[0031]
　C: 0.001 ~ 0.6%
　C is precipitated as Cr carbide in grain boundaries combined with Cr, is an element having an effect of enhancing the high temperature strength of the alloy. However, excessive content, toughness is deteriorated. Also forming a Cr-depleted layer in the grain boundaries, which may detract from the intergranular corrosion resistance. Therefore, C content is 0.001 to 0.6%. C content is preferably 0.002% or more. Further, it is preferable C content is 0.45% or less, and more preferably 0.3% or less.
[0032]
　Si: 0.01 ~
　5.0% Si, because affinity for oxygen is strong, has an effect of uniformly forming a film mainly composed of Cr. However, excessive content, weldability is deteriorated, organization becomes unstable. Therefore, Si content is 0.01 to 5.0%. Si content is preferably 0.03% or more. Further, Si content is preferably 3.0% or less, more preferably 2.0% or less.
[0033]
　Mn: 0.1 ~
　10.0% Mn is an element having a deoxidizing effect and workability improvement. Moreover, Mn since it is an austenite forming element, it is also possible to replace part of the expensive Ni. However, excessively contained, the chromium oxide film not only inhibits the generation in the case of forming the base material oxidation, which may deteriorate the workability and weldability of the base material. Therefore, Mn content is from 0.1 to 10.0%. Mn content is preferably 5.0% or less, and more preferably 2.0% or less.
[0034]
　P: 0.08% or less
　S: 0.05% or less
　P and S are segregated at the grain boundaries, thereby deteriorating the hot workability. Therefore, it is preferable to be reduced as much as possible. However, excessive reduction since the cost is high, P content 0.08% is less, S content is acceptable as long as 0.05% or less. P content is preferably not more than 0.05%, and more preferably not more than 0.04%. Further, it is preferable S content is 0.03% or less, and more preferably 0.015% or less.
[0035]
　Cr: 15.0 ～ 55.0
　Pasento Cr is an element that plays a central corrosion resistance of Otenaito alloy. Cr by such oxidation or corrosion of the base material 2 O 3 produced exerts a catalyst and corrosion resistance. However, excessive content decreases the structural stability at high temperature of the tube productivity and in use. Therefore, Cr content is 15.0 to 55.0%. Cr content is preferably 20.0% or more, more preferably 22.0% or more. Further, in order to prevent the deterioration of microstructural stability with workability, it is preferable Cr content is less 35.0%, and more preferably not more than 33.0%.
[0036]
　Ni: 30.0 ~
　80.0% Ni is an element necessary for obtaining a stable austenitic structure depending on the Cr content. Also, if the C has penetrated into the steel, there is a function of reducing the intrusion rate. However, excessively contained, leading to deterioration in productivity as well lead to cost. Therefore, Ni content is 30.0 to 80.0%. Ni content is preferably not more than 70.0, more preferably at most 60.0%, more preferably not more than 50.0%.
[0037]
　N: 0.001 ~ 0.25%
　N is an effective element for high-temperature strength improvement. However, excessive content, increased inhibit workability. Therefore, N content is 0.001 to 0.25%. N content is preferably at 0.002% or more, and preferably 0.20% or less.
[0038]
　O: 0.02% or less
　O (oxygen) is an element existing as an impurity. When O content exceeds 0.02%, oxide inclusions in the steel and a large amount present, workability not only decreases, causing the steel pipe surface flaws. Therefore, O content is 0.02% or less.
[0039]
　Mo: 0 ~ 20.0% Mo
　is an element effective for improving the high temperature strength as a solid solution strengthening element, an element for improving corrosion resistance in a superacid environment containing sulfuric acid or hydrochloric acid. In particular it is conceivable to enhance the corrosion resistance make MoS coating and sulfur. Therefore, it may be contained as necessary Mo. However, excessive content, to promote the precipitation of sigma phase, causing the weldability and workability occurs. Therefore, Mo content is from 0 to 20.0%. Mo content is preferably at most 15.0%, more preferably 10.0%. To obtain the above-mentioned effects, Mo content is preferably at least 0.01%, more preferably at least 0.5%, even more preferably 3.0 percent.
[0040]
　Cu: 0 ~ 5.0%
　Cu, as well to stabilize the austenite phase, is effective in improving the high temperature strength, also is an element which also improves corrosion resistance in a superacid environment containing sulfuric acid or hydrochloric acid and Mo. Therefore, it may be contained as needed Cu. However, excessive content reduces significantly hot workability. Therefore, Cu content is 5.0% or less. In order to obtain the effect described above, Cu content is preferably 0.01% or more. Cu content is preferably at least 0.5%, and preferably not more than 3.5%. In this range, it exhibits corrosion resistance and workability is ensured. Cu content is more preferably at 1.0% or more, more preferably 3.0% or less.
[0041]
　Co: 0 ~
　5.0% Co, in order to stabilize the austenitic phase, it is possible to replace a portion and Ni. Therefore, it may be contained as needed Co. However, excessive content reduces significantly hot workability. Therefore, Co content is at most 5.0%. Co content is preferably 3.0% or less. To obtain the above effect, Co content is preferably 0.01% or more.
[0042]
　W:
　0 ~ 10.0% Ta: 0 ~ 6.0%
　W and Ta, since both an element effective in improving the high temperature strength as a solid solution strengthening element, may be contained as needed. However, excessive content, inhibits structural stability not only deteriorates the workability. Therefore, W content is not more than 10.0%, Ta content is 6.0% or less. W content is preferably not less 8.0%. Further, Ta content is preferably 2.5% or less, and more preferably 2.0% or less. To obtain the above effect, at least one of the content of W and Ta preferably 0.01% or more.
[0043]
　Nb:
　0 ~ 5.0% Ti: 0 ~
　1.0% Nb and Ti, even the addition of very small amounts, high-temperature strength, since it is a large element contributing to the improvement of ductility and toughness, as required it may be contained Te. However, excessive content deteriorates the workability and weldability. Therefore, Nb content is not more than 5.0%, Ti content is 1.0% or less. To obtain the above effect, at least one of content of Nb and Ti preferably 0.01% or more.
[0044]
　B:
　0 ~ 0.1%
　Zr: 0 ~ 0.1% Hf: 0 ~
　0.1% B, Zr and Hf are all strengthen grain boundaries and improve hot workability and high temperature strength since an element effective for, it may be contained as needed. However, excessive content deteriorates the weldability. Accordingly, B, the content of Zr and Hf are both set to 0.1% or less. To obtain the above effect, B, one or more content selected from Zr and Hf preferably 0.001% or more.
[0045]
　Al:
　0 ~
　1.0% Mg: 0 ~ 0.1% Ca: 0 ~
　0.1% Al, Mg and Ca, since both an element effective for improving the hot workability, need it may be contained according to. However, excessive content deteriorates the weldability. Therefore, Al content is set to 1.0% or less, the content of Mg and Ca are both set to 0.1% or less. Al content is preferably not more than 0.6%, the content of Mg and Ca are preferably both at most 0.06%. To obtain the above effect, Al: 0.01% or more, Mg: 0.0005% or more and Ca: preferably 0.0005% or more for the inclusion of one or more selected. The content of Mg and Ca is more preferably 0.001% or more.
[0046]
　In the chemical composition of the base material of austenitic alloy and austenitic alloy tube of the present invention, the balance being Fe and impurities.
[0047]
　Here, the "impurities", when producing the alloy industrially, ores, raw material scraps, a component mixed by various factors of the manufacturing process, is allowed to the extent that the present invention does not adversely affect means shall.
[0048]
　2. Coating
　austenitic alloy material and austenitic alloy tube according to the present invention, at least a portion of the surface of the base material has, provided with a coating containing chromium oxide. Chromium oxide is an oxide mainly composed of chromium, for example, chromia (Cr 2 O 3 ) or chromium hydroxide (Cr (OH) 3 ), and the like.
[0049]
　Then, the above film, Cr concentration is the maximum depth position (hereinafter, also referred to as "maximum Cr depth position".) The chemical composition in the, O, as a percentage of components excluding C and N, atomic% in, it should contain more than 50% Cr. The presence of moieties containing more than 50% Cr in the coating, it is possible to obtain a dense and high shielding properties oxide film. To further improve the corrosion resistance by improving the denseness and catalytic, Cr content in the maximum Cr depth position is preferably to 70% or more, more preferably 90% or more.
[0050]
　Further, the chromium oxide has a decomposable as a catalyst to sulfur oxides. Therefore, the higher the Cr content in the coating, the catalyst performance is increased, thereby improving the decomposition efficiency. Positive correlation is observed between the degradable and corrosion resistance as described above. In perhaps the film surface, highly corrosive SO 3 corrosivity is decomposed mild SO 2 that become corrosive to the base material not only film is presumed to decrease.
[0051]
　The thickness of the coating is a 0.1 ~ 50 [mu] m. Thickness is rarely observed the effect of barrier property is less than 0.1 [mu] m. On the other hand, when the thickness exceeds 50 [mu] m, more stress accumulation in the coating, cracking and peeling is likely to occur. As a result, penetration of sulfur oxides and hydrogen halide is facilitated, lowering the corrosion resistance. The thickness of the chromium oxide coating is preferably at 0.5μm or more, preferably at 20μm or less, more preferably 10μm or less.
[0052]
　During coating, Cu, V, W, Mo (in the following description, collectively these metal elements may be referred to as "M".), And the noble metal element (Pt, Pd, Ag, Re, Ru comprises like, are collectively may be referred to as "PM".) one or more may be contained which is selected from. Because these elements having a catalytic As with chromium oxide, by containing these elements improves the catalytic decomposition of the sulfur oxides of the film itself, the corrosion resistance as a result is enhanced.
[0053]
　PM becomes to be included as a metal in the film. Meanwhile, M may be included as a metal, but may be included as a hydroxide or an oxide. Specifically, M is, CuO, Cu 2 O, CuOH, Cu (OH) 2 , MoO 3 , Mo (OH) 6 , WO 3 , W (OH) 6 may be included in the film in a like. As the existing form of M and PM, may be present in minute layers or dispersed film in which a main component Cr. Furthermore, M may be present in partially substituted chromium in chromium oxide.
[0054]
　Further, M in a film, may form a composite oxide of chromium. As the composite oxide, for example, CuCr 2 O 4 , CuCrO 2 , VCRO 4 , WCrO 4 , MoCrO 4 , Mo 2 (CrO 4 ) 3 and the like.
[0055]
　Furthermore, M and / or PM may be present to laminate the upper layer or lower layer of the layer mainly composed of chromium oxide. In this case, PM is will be present as a metal. Meanwhile, M may be present as a metal, may be present as an oxide, may be present as a complex oxide of chromium.
[0056]
　As described above, M and PM are to have an effect of improving the catalytic decomposition properties, it is preferred that the concentrated on the surface layer side of the film. Specifically, the chemical composition in the surface layer of the coating, it is desirable to satisfy the following (i) and (ii) expression. [Cu]
S + [V] S + [W] S + [Mo] S + [PM] S ≧ 30 · · · 　(i) [Cr] S ≦ 70 · · · (ii) 　where, in the formula each symbol, each element in the surface layer of the coating, O, represents the percentage (atomic%) to total components excluding C and N, PM is the meaning of the noble metal element.

[0057]
　There is no particular restriction on the form in which M and / or PM is concentrated on the surface layer side of the film, to a layer comprising M and / or PM may be formed on the upper layer of the layer mainly composed of chromium oxide, it may have a graded composition such that the concentration of the surface layer side as M and / or PM of the film becomes high.
[0058]
　M and / or PM may be included in the maximum Cr depth position. That, M and / or PM is the maximum Cr depth position, may be present as a complex oxide of dispersed or chromium in the chromium oxide. However, as described above, since the Cr content at the maximum Cr depth position is required to be 50% or more, the content of M and PM at the maximum Cr depth position, to satisfy the (iii) below formula It is desirable
　≦ 0.5 [Cu] P + [V] P + [W] P + [Mo] P + [PM] P ≦ 50 · · · (iii) 　wherein each symbol in the above formula, Cr concentration is maximum each element in the composed depth position, O, represents the percentage (atomic%) to total components excluding C and N, PM is the meaning of the noble metal element.
[0059]
　In the present invention, the measurement of the composition in the surface layer and the maximum Cr depth position of the coating, Ar + shall perform XPS combining sputtering, AES, the depth analysis using SIMS or the like. Here, the "surface layer" means the region of 10 ~ 30 nm from the outermost surface of the coating, and to use the mean value of the measurement results of the above area as a surface layer of chemical composition. Also it specifies the maximum Cr depth position from the concentration profile in the depth direction of the Cr. Although Cr concentration sometimes becomes maximum at the surface of the film, in that case, the fact that the surface layer and the maximum Cr depth position coincides. The maximum Cr depth position is when there are a plurality of them to be employed closest depth position in the base material.
[0060]
　Thereafter, the surface layer and the maximum Cr depth position, determine the concentration of all metal elements contained in the film, the concentration of the respective metal elements, O, calculated as a percentage (atomic%) to total components excluding C and N. Here, the metal element contained in the coating of the present invention, Cr, Cu, V, W, in addition to Mo and the noble metal element, in addition to Ni and Fe which is the main element in the matrix, Si, Ti in some cases, Al, Mn, Nb, etc. are included in the trace.
[0061]
　The thickness of the coating, may be determined by direct observation with a transmission electron microscope (TEM) or scanning electron microscope (SEM), XPS obtained by the above measurement, AES, it is preferable to determine the concentration profiles of SIMS. XPS, AES, when the concentration profile of SIMS, specifically, at the peak of the nearest O in the base material side, the base material side of the peak, the position where the half of the concentration of the maximum concentration of O, the film and the base determines that the boundary between the wood, the length from the coating surface to said boundary portion, the thickness of the coating. Measurement of composition and thickness of the coating is carried out in multiple locations, it is desirable to employ the average value. Also, the structure of each tissue that make up the coating, can be identified by using the XRD or Raman spectroscopy.
[0062]
　3. Catalyst performance (SO 3 degradation activity)
　austenitic alloy and austenitic alloy tube having the above coating on at least a portion of the base metal surface preferably has a catalytic activity in the decomposition of the sulfur oxides containing sulfuric acid. By having a decomposition, as well as improving the corrosion resistance of the base material, the use as a pipe material or the like in the chemical process that includes the degradation of sulfur oxides such as IS process, which contributes to the improvement of the decomposition efficiency as a process be able to.
[0063]
　SO having austenitic alloy material and austenitic alloy tube according to the present invention 3 is not provided any special restriction on the degree of cracking activity, SO per unit area 3 feed rate: 0.0071G / cm 2 / min and reaction temperature: 850 SO at conditions ° C. 3 decomposition rate of, 8.0 × 10 -5 g / cm 2 is preferably at / min or more. SO 3 decomposition rate of, 5.0 × 10 -4 g / cm 2 and more preferably at / min or more, 1.0 × 10 -3 g / cm 2 and more preferably at / min or more, 2 × 10 .0 -3 g / cm 2 and particularly preferably at / min or more. SO 3 degradation rate of (g / cm 2 / min), SO in the above conditions 3 decomposition amount (g / min) and the reaction area, i.e. the film area (cm which may contact with a gas 2) Refers to a value obtained by dividing.
[0064]
　Incidentally, SO 3 and the feed rate, SO at room temperature 3 concentration (g / L) × flow rate (L / min) / is calculated by the reaction area. May contact with the reaction gas from the reaction area refers to the area covered with a film comprising chromium oxide. The 0.0071G / cm 2 in / min feed rate or zero-order reaction, approaches the so-called reaction rate. Therefore, SO 3 in evaluating the degradation rate of, 0.0071G / cm 2 may be employed the feed rate of over / min.
[0065]
　SO 3 The method of measurement of the degradation rate of is not limited, and may be carried out as follows. SO constant concentration 3 an inert gas such as nitrogen or argon containing gas is passed through the reaction gas in the sample of the tubular such that the gas does not diverge at a constant rate, the temperature was raised to 850 ° C., SO 3 is decomposed the resulting SO 2 and / or O 2 and determining the concentration of, divided by the reaction area to calculate the amount of degradation (g / min) multiplied by the gas flow. SO 3 The concentration of, but are not limited to, the like measurement accuracy and ease of handling, preferably set to about 2 to 20% by volume. Flow rate, SO 3 feed rate 0.0071G / cm 2 so that / min or more, SO 3 may be appropriately set depending on the concentration.
[0066]
　Here, the austenitic alloy material in the present invention, not only plate-shaped and tubular material also includes granular or mesh-like material. Granular or mesh austenitic alloy material by placing the flow path of the reaction gas, it is possible to increase the contact area between the reaction gas and the film having an alloy material, SO 3 becomes possible to increase the amount of degradation .
[0067]
　4. Production process
　is not particularly limited for the preparation conditions of the austenitic alloy material and austenitic alloy tube according to the present invention. For example, in the case of obtaining the austenitic alloy tube, dissolution, casting, hot working, cold working, by means of welding or the like, seamless pipe may be formed into a desired steel shapes such as welded tubes. Furthermore, the technique of powder metallurgy or the like centrifugal casting may be molded into the desired steel pipe shape.
[0068]
　Not limited method of forming a film on the surface of the base material containing chromium oxide. For example, the components contained in the base material such as Cr, by thermal oxidation or corrosion (including etching), by diffusing or exposed on the surface, it is possible to form a film. Besides, the Cr and M and / or PM, it is also possible to form a film by externally applied by a method such as coating or vapor deposition. Further, it is also possible to combine two or more of these methods. Incidentally, after formation of the coating, and heat treatment is performed as necessary, to enhance the adhesion of the film, or a composite oxide of Cr and M, the crystallinity of the oxide particles constituting the film increased It may be or improve the catalytic ability Te.
[0069]
　A method of forming a layer comprising M and / or PM chromium oxide in the upper layer of the layer mainly composed, and a method of forming a coating having a graded composition such that the concentration of the more superficial side M and / or PM is higher is not particularly limited, for example, it is possible to use a method such as coating or vapor deposition. Particularly in the case of forming a film containing PM are chloroplatinic acid, a solution containing metal chloride compound such as palladium chloride, is deposited on the chromium oxide coating, then subjected to reduction treatment at 500 ° C. under a hydrogen atmosphere It may carry PM on the surface.
[0070]
　In the case of forming a film containing Cu, an element of V, etc., can be copper nitrate, it is deposited on Similarly chromium oxide film of a solution containing a compound such as vanadium nitrate, a heat treatment in a suitable atmosphere.
[0071]
　The following examples illustrate the present invention more specifically, the present invention is not limited to these examples.
Example
[0072]
　Various alloys having the chemical compositions shown in Table 1 was dissolved in a high-frequency heating vacuum furnace, hot forged in the conventional manner, by performing the hot rolling and cold rolling, outer diameter 20 mm, austenitic alloy tube wall thickness 2mm It was produced. Then subjected for 30 minutes to solution treatment in a temperature range of 1100 ~ 1200 ° C..
[0073]
　Preparation of film containing chromium oxide, in addition to the following two methods were carried out in three ways a combined method thereof.
[0074]
　A) during the solution heat treatment, it is mixed steam (1-10 vol%) in the atmosphere to form a film by oxidizing a base material (Test No.1 ~ 3,16 ~ 19,21,23 ~ 26 , 28, 29).
[0075]
　B) After the solution heat treatment, the desired coating composition (Cr 2 O 3 to form a film by a sol-gel coating method such that the mixed oxide of the metal oxide MO). Sol solution for the coating, metal nitrate, metal acetate or M (OC, n H 2n + 1 ) m the metal alkoxide represented by was dissolved in dehydrated alcohol, polymerization promoter catalyst such as nitric acid as needed, stability of diethanolamine It was prepared by adding of material (test No.5 ~ 7,14,22).
[0076]
　For method B, submitted composition of the coating is, Cr 2 O 3 was adjusted by mixing a Mo, Cu, W, and the sol liquid oxide selected from among V at a predetermined ratio. Formation of a film was carried out as follows. That was gelled by drying of the deposited 100 ° C. by dipping the mixed sol solution into the tube over the entire surface. This by heat treatment in an oxidizing atmosphere at 450 ° C., dehydrated, evaporate the organics, a film mainly containing chromium oxide by crystallization with burning to form the austenitic alloy pipe surface. Adjustment of the film thickness was performed by a plurality of times the sol-gel coating. It should be noted that the test No. For 7, after the heat treatment in the oxidizing atmosphere above 450 ° C., by heat treatment at more 850 ° C., a composite oxide (CuCr 2 O 4 was formed a film containing a).
[0077]
　Furthermore, for some of the samples indicated as "A + B" in Table 2, on the chromium oxide film produced by the method of A, to form a film containing an oxide of the PM or M. Specifically, the test No. In 4 and 20, a solution containing chloroplatinic acid or palladium chloride, after depositing onto the chromium oxide film, subjected to reduction treatment at 500 ° C. in a hydrogen atmosphere to carry the PM on the surface.
[0078]
　In addition, test No. In 10, 11, 12, 15, on the chromium oxide film produced by the method of A, the metal nitrates as the metal acetate or M (OC, n H 2n + 1 ) m the metal alkoxide represented by dehydration dissolved in an alcohol, a polymerization accelerator catalyst such as nitric acid, a sol solution prepared by adding a stabilizing material, such as diethanolamine was applied as necessary. Then heat-treated in an oxidizing atmosphere at 450 ° C., was formed on the chromium oxide coating as the metal oxide MO.
[0079]
　Test No. For 8, after the heat treatment in the oxidizing atmosphere above 450 ° C., further under an argon atmosphere containing 0.1% by volume of steam, by heat treatment at 850 ° C., a composite oxide (CuCrO 2 a) Chromium oxide formed on the object film.
[0080]
　Test No. In 9, on the chromium oxide film produced by the method of A, coated with a sol solution containing CuO, dried and then reduced at the 500 ° C. 100% hydrogen atmosphere, chromium oxide metal Cu film It was formed in the above.
[0081]
　Test No. In 13, on the chromium oxide film produced by the method of A, after coating the CuO in the method of B, by air annealing at a high temperature, the composite oxide (CuCr 2 O 4 ) in the chromium oxide film on the the formed.
[0082]
　In FIGS. 1-3, Test No. 3, 10 and 13 O in the depth direction of the shows the concentration profiles of the components except the C and N.
[0083]
[Table 1]

[0084]
[Table 2]

[0085]
　For austenitic alloy material of the present invention obtained as described above was evaluated and the corrosion resistance and catalyst performance by the following methods.
[0086]
　
　Place the cut into 10 mm × 30 mm × 2 mm quartz tube for the corrosion test samples were heated to 850 ° C. under flowing argon gas. Then SO pyrolyzed at 350 ° C. or higher concentrated sulfuric acid 3 mixed with argon gas to generate 2% of SO into the quartz tube 3 was passed through a gas. After 1000 hours was measured corrosion loss by the difference in weight before and after the test sample. Furthermore, changes in the morphology of the film, and, in consideration of the intergranular corrosion and oxidation presence of base material under the film was comprehensively evaluated the corrosion resistance of the alloy tube.
[0087]
　
　tubes in the distribution system evaluation apparatus (outer diameter 20 mm, inner diameter 16 mm, length 100 mm, inner area 50 cm 2 ) were placed and heated argon gas to 850 ° C. while flowing inside a test tube. Then SO obtained by thermal decomposition of concentrated sulfuric acid as the 3 were allowed to introduce and distribute the test tube while mixing with argon gas.
[0088]
　At this time, the reaction gas flow rate 1000 mL / min, SO 3 to give a concentration of 10% by volume, and adjusting the amount of decomposition and argon gas amount of concentrated sulfuric acid. Than the test conditions, SO 3 feed rate 0.0071G / cm 2 was / min. Evaluation of the reaction, after the produced gas was washed with iodine solution, O is one of the product 2 was carried out by concentration measured by gas chromatography. Then, SO per unit time 3 (calculated from the 2-fold amount of oxygen, g / min) amount of decomposition by dividing the area, SO 3 degradation rate of (g / cm 2 was calculated / min).
[0089]
　These results are also shown in Table 2.
[0090]
　As shown in Table 2, test all the provisions satisfaction of the present invention No. In 1-26, it can be seen that excellent corrosion resistance. Then, the film is a sound when observing the film, peeling or cracking did not occur. In addition, the state in which corrosion is also the base material was not observed. In the corrosion resistance evaluation are shown in Table 2, the corrosion weight loss is 0.0001 mg / cm 2 "A" less than / h, 0.0001 mg / cm 2 / h or higher 0.001 mg / cm 2 less than / h "B ", 0.001 mg / cm 2 / h or more 0.01 mg / cm 2 less than / h" C ", 0.01 mg / cm 2 was over / h" D ". However, if observed unhealthy characteristics such as cracking in the coating, and even with a small weight loss as "D".
[0091]
　Among them, the test provided a film containing Cu, Mo, W, V, or the PM on the chromium oxide coating No. 4,8 to 13 and 15 and 20, as can be seen from Table 2, the film is a sound corrosion was not observed. Further, SO 3 decomposition rate of, Cr 2 O 3 was increased significantly as compared with the case of the film alone. SO at the film surface by laminated film 3 for degradable is enhanced, it is considered to corrosion resistance was improved.
[0092]
　Further, the chromium oxide film in, Cu, Mo or W test was contained oxides, No. 5-7,14,22, despite a relatively thin film thickness, excellent corrosion resistance was confirmed. These oxides Cr 2 O 3 Similarly SO and 3 has a catalytic activity for the degradation of, and high SO same by coating 3 was obtained degradation rate.
[0093]
　For these, the test did not form a chromium oxide film No. At 27, it resulted in poor corrosion resistance. Also, test thickness of the chromium oxide film is outside the range defined No. In 28, the corrosion weight loss was not so large, and cause large cracks in the coating, corrosion had progressed starting from it. Furthermore, testing the Cr concentration in the base material below the predetermined value No. In 29, higher corrosion loss, peeling the film was observed.
Industrial Applicability
[0094]
　According to the present invention, it can be obtained in a high temperature harsh environments containing sulfur oxides or hydrogen halide such as sulfuric, austenitic alloy material and austenitic alloy tube which exhibits excellent corrosion resistance.

WE CLAIM

On at least a part of the surface of the base material has, provided with a coating comprising chromium oxide having a thickness of 0.1 ~ 50 [mu] m,
　the film, Cr concentration is the chemical composition at the depth position of maximum, O, as a percentage of components excluding C and N, in atomic% Cr: containing 50% or more,
　the chemical composition of the base material, in
　mass% C: 0.001 ~
　0.6% Si: 0
　~ 5.0% .01, Mn: 0.1 ~
　10.0%, P: 0.08% or
　less, S: 0.05% or
　less, Cr: 15.0 ~
　55.0%, Ni: 30.
　~ 80.0% 0, N: 0.001 ~
　0.25%, O: 0.02% or
　less,
　Mo: 0 ~ 20.0%, Cu: 0 ~
　5.0%, Co: 0 ~ 5.
　%
　0,
　W: 0 ~ 10.0%, Ta: 0
　~ 6.0%, Nb: 0 ~ 5.0%,
　Ti: 0 ~ 1.0%, B: 0 ~
　0.1%, Zr:
　0.1 Pasento ～,
　Hf: 0 ～ 0.1 Pasento, Al: 0 ～ 1.0 Pasento,
　Mg:
　0 ~ 0.1%, Ca: 0 ~ 0.1%,
　the balance: Fe and impurities,
　austenitic alloy material.
[Requested item 2]
　Chemical composition of the base metal, by
　mass%,
　Mo: 0.01 ~
　20.0%, Cu: 0.01 ~ 5.0%, Co: 0.01
　~ 5.0%, W: 0.01
　10.0%
~,
　Ta: 0.01 ~ 6.0%, Nb: 0.01 ~ 5.0%,
　Ti: 0.01 ~ 1.0%, B: 0.001 ~ 0.1%, 　Zr:
　0.001 ~ 0.1%, Hf: 0.001 ~ 　0.1%, Al: 0.01 ~ 1.0%, Mg: 0.0005 ~ 0.1%, 　and, Ca: 0. 0005 to 0.1%, 　containing one or more selected from, 　austenitic alloy material according to claim 1.

[Requested item 3]
　Wherein in the coating, Cu, V, W, includes one or more selected from Mo and the noble metal element,
　according to claim 1 or austenitic alloy material according to claim 2.
[Requested item 4]
　Chemical composition in the surface layer of the coating, satisfies the following (i) and (ii) expression,
　austenitic alloy material according to any one of claims 1 to 3. [Cu]
S + [V] S + [W] S + [Mo] S + [PM] S ≧ 30 · · · 　(i) [Cr] S ≦ 70 · · · (ii) 　where, in the formula each symbol, each element in the surface layer of the coating, O, represents the percentage (atomic%) to total components excluding C and N, PM is the meaning of the noble metal element.

[Requested item 5]
　The chemical composition satisfies the (iii) below formula, in a depth position where the Cr concentration is maximum
　austenitic alloy material according to any one of claims 1 to 4.
　≦ 0.5 [Cu] P + [V] P + [W] P + [Mo] P + [PM] P ≦ 50 · · · (iii) 　wherein each symbol in the above formula, Cr concentration is maximum each element in the composed depth position, O, represents the percentage (atomic%) to total components excluding C and N, PM is the meaning of the noble metal element.
[Requested item 6]
　The coating, Cu, V, including a complex oxide comprising at least one and a Cr selected from W and Mo,
　austenite alloy material according to any one of claims 1 to 5.
[Requested item 7]
　The coating, SO 3 has an action to degrade,
　austenitic alloy material according to any one of claims 1 to 6.
[Requested item 8]
　SO 3 decomposition rate of, SO per unit area 3 feed rate: 0.0071G / cm 2 / min and the reaction temperature: in terms of ° C. 850, 8.0 × 10 -5 g / cm 2 is / min or more ,
　austenitic alloy material according to any one of claims 1 to 7.
[Requested item 9]
　SO 3 decomposition rate of, SO per unit area 3 feed rate: 0.0071G / cm 2 / min and the reaction temperature: in terms of ° C. 850, 1.0 × 10 -3 g / cm 2 is / min or more ,
　austenitic alloy material according to any one of claims 1 to 8.
[Requested item 10]
　Consisting austenitic alloy material according to any one of claims 1 to 9,
　austenitic alloy tube.