Title of invention: Austenitic heat resistant steel weld metal, welded joint, welding material for austenitic heat resistant steel, and method for manufacturing welded joint
Technical field
[0001]
　The present invention relates to an austenitic heat resistant steel weld metal, a welded joint, a welding material for austenitic heat resistant steel, and a method for manufacturing a welded joint.
Background technology
[0002]
　In recent years, from the viewpoint of reducing the environmental load, high temperature and high pressure operating conditions are being promoted on a global scale in thermal power generation boilers and the like. Materials used for superheater tubes and reheater tubes are required to have excellent properties such as high temperature strength and corrosion resistance.
[0003]
　Conventionally, various austenitic heat-resistant steels containing a large amount of nitrogen and a large amount of nickel (hereinafter, austenitic heat-resistant steels containing a large amount of nitrogen and a large amount of nickel are referred to as "high nitrogen A high nickel content austenitic heat resistant steel) has also been developed.
[0004]
　For example, in Patent Document 1, N is 0.02% to 0.3%, Ni is 17% to 50%, Cr is 18% to 25%, and Nb is 0.05% to 0.6%. %, Ti of 0.03% to 0.3%, and Mo of 0.3% to 5%, which are austenitic heat resistant steels excellent in high temperature strength have been proposed.
[0005]
　Further, in Patent Document 2, N is added to 0.1% to 0.30%, Ni is added to 22.5% to 32%, Cr is added to 20% to 27%, and W is added as a strengthening element to 0.4%. An austenitic heat resistant steel containing 4% to 4% and 0.20% to 0.60% Nb and excellent in high temperature strength has been proposed.
[0006]
　Further, in Patent Document 3, N is contained in an amount of more than 0.05% to 0.3%, Ni in an amount of more than 15% to 55%, Cr in an amount of more than 20% to less than 28%, and Nb of 0.1% to 0%. Austenitic heat-resistant steels containing 0.8%, V of 0.02% to 1.5%, and W of 0.05% to 10% and having excellent creep characteristics and hot workability have been proposed.
[0007]
　Further, in Patent Document 4, N exceeds 0.013% to 0.35%, Ni exceeds 26% to 35%, Cr contains 20% to 26%, and Nb contains 0.01% to 0.1%. %, V of 0.01% to 1%, and W of 1% to 5.5%, an austenitic heat-resistant steel having excellent creep properties has been proposed.
[0008]
　These austenitic heat resistant steels are generally used as welded structures. Therefore, various welding metals and welding materials that can utilize the performance of these austenitic heat resistant steels have been proposed.
[0009]
　For example, Patent Document 5 contains Nb in an amount of 0.25% to 0.7%, N in an amount of 0.15% to 0.35%, and Ni in an amount corresponding to Cr, Si, C, and N amounts. It is disclosed that the welding material for austenitic heat-resistant steel in which P and S are regulated has both high temperature strength and solidification crack resistance.
[0010]
　Patent Document 6 discloses that N is 0.2% to 0.4%, Nb is 0.01% to 0.7%, Mo is 0.5% to 1.5%, and Ni is 18% to 30%. It is disclosed that the welding material for austenitic heat-resisting steel, which contains and regulates the total of P and S to 0.02% or less, has both high temperature strength and weldability.
[0011]
　In Patent Document 7, Nb: 0.5% to 3.5%, N: 0.1% to 0.35%, Mo: 0.2% to 1.8%, and Ni: 30% to 45%. Austenitic heat-resistant steel welding material containing, and Nb: 0.3% to 3.5%, N: 0.1% to 0.35%, Mo: 0.2% to 1.8%, and An austenitic heat resistant steel weld metal containing Ni: 35% to 45% is disclosed.
[0012]
　In Patent Document 8, Nb: 0.8% to 4.5%, N: 0.1% to 0.35%, Mo: 0.2% to 1.8%, and Ni: 30% to 50%. Welding material for austenitic heat-resistant steel, containing Nb: 0.5% to 4%, N: 0.1% to 0.35%, Mo: 0.2% to 1.8%, and Ni: Austenitic heat resistant steel weld metal containing 30% to 50% is disclosed.
[0013]
　Patent Document 9 contains Nb: 0.15% to 1.5%, W: 0.5% to 3%, N: 0.1% to 0.35%, and Ni: 15% to 25%. Welding material for austenitic heat resistant steel, Nb: 0.1% to 1.5%, W: 0.5% to 3%, N: 0.1% to 0.35%, and Ni: 15% to An austenitic heat resistant steel weld metal containing 25% is disclosed.
[0014]
　Patent Document 10 discloses austenite containing Nb: 0.1% to 0.6%, W: 1% to 5%, N: 0.1% to 0.35%, and Ni: 23% to 32%. A heat-resistant steel is disclosed.
Prior art documents
Patent literature
[0015]
Patent Document 1: JP 59-173249 Patent Publication
Patent Document 2: JP-T 2002-537486 Patent Publication
Patent Document 3: Japanese Patent No. 3838216 discloses
Patent Document 4: JP 2017-88957 JP
Patent Document 5: Japanese Patent No. 2722893 JP
Patent Document 6: JP-a 07-060481 JP
Patent Document 7: Japanese Patent No. 3329262 discloses
Patent Document 8: Japanese Patent No. 3918670 discloses
Patent Document 9: Japanese Patent No. 3329261
Patent Document 10: JP 2017-14576 Bulletin
Summary of the invention
Problems to be Solved by the Invention
[0016]
　The welding material for austenitic heat-resistant steel disclosed in Patent Document 2 and the austenitic heat-resistant steel weld metal disclosed in Patent Document 10 have excellent creep strength at 700°C. However, when assuming use at higher temperatures, it is difficult to secure creep strength with the austenitic heat-resistant steel welding material disclosed in Patent Document 2 and the austenitic heat-resistant steel weld metal disclosed in Patent Document 10. Is.
[0017]
　Further, since the austenitic heat-resistant steel weld metal and welding material disclosed in Patent Documents 7 to 9 mainly utilize Nb as a precipitation strengthening element, they certainly satisfy excellent characteristics such as high strength and corrosion resistance. To do. However, since the austenitic heat-resistant steel weld metals and welding materials disclosed in Patent Documents 7 to 9 have a very large strengthening ability, they are excessively strengthened inside the grains at the time of use at high temperature, and the relative grain boundary strength is increased. In some cases, a sharp decrease in toughness at the beginning of use, and an increase in susceptibility to hot cracking may occur.
[0018]
　Therefore, there has been a long-awaited development of a weld metal capable of fully utilizing the performance of a high-nitrogen-high-nickel-containing austenitic heat resistant steel, and a welded joint having the weld metal.
[0019]
　The present invention has been made in view of the current situation described above, and when using a high nitrogen high nickel content austenitic heat resistant steel as a welded structure, fully utilizes the performance of the high nitrogen high nickel content austenitic heat resistant steel. It is an object of the present invention to provide an austenitic heat-resistant steel weld metal having low susceptibility to hot cracking and excellent creep strength, and a welded joint having the same. Another object of the present invention is to provide a welding material suitable for welding a high nitrogen, high nickel content austenitic heat resistant steel, and a method for manufacturing a welded joint.
Means for solving the problem
[0020]
　The present inventors have conducted various studies on austenitic heat-resisting steel containing high nitrogen and high nickel containing W and Nb. As a result, the following matters were found.
[0021]
　Similar to Nb, by adding V that precipitates carbonitrides, it is possible to secure the creep strength during long-term use.
[0022]
　Further, in a high-nitrogen, high-nickel content austenitic heat resistant steel, nitrides composed of Cr, Ni and N may precipitate in the high temperature region, resulting in a decrease in the amount of solid solution nitrogen in the matrix. Since this nitride has a large amount of precipitation as the amount of Si increases for structural stability, the amount of solute nitrogen in the matrix decreases when the amount of Si increases, leading to a decrease in creep strength. Therefore, it is possible to secure the creep strength during long-term use by reducing the amount of Si.
[0023]
　Further, in order to secure the required creep strength at a high temperature exceeding 700° C., it is necessary to add a high content of W.
[0024]
　Nb, V, W, N and B contribute to the improvement of creep strength, and reducing Si contributes to the improvement of creep strength. As a result of conducting various experiments on these elements, it was found that the contribution of each element to the creep strength was applied to the coefficient and fn1=10(Nb+V)+1.5W+20N+1500B-25Si can be arranged as an index showing the creep strength. In order to secure the creep strength at high temperature, the value obtained by fn1 needs to be 10 or more.
[0025]
　The present invention has been completed by repeating the above studies. That is, the gist of the present invention is as follows.
[0026]
<1> Chemical composition in mass %,
　C: 0.06% to 0.14%,
　Si: 0.1% to 0.6%,
　Mn: 0.1% to 1.8%,
　P :0 0.025% or less,
　S: 0.003% or less,
　Ni: 25% to 35%,
　Cr: 20% to 24%,
　W: more than 4.5% and 7.5% or less,
　Nb: 0.05% to 0.5%,
　V: 0.05% to 0.4%,
　N: 0.1% to 0.35%,
　Al: 0.08% or less,
　O: 0.08% or less,
　B: 0.0005 ~ 0.005%,
　Ti: 0% to 0.25%,
　Cu: 0% to 4%,
　Co: 0% to 2%,
　Mo: 0% to 2%,
　Ta: 0% to 1%,
　Ca: 0% to 0.02%,
　Mg: 0% to 0.02%,
　REM: 0% to 0.06%,
　balance: Fe and impurities,
　An austenitic heat resistant steel weld metal, wherein fn1 represented by the following formula (1) is 10 or more.
　　fn1=10(Nb+V)+1.5W+20N+1500B-25Si (1) In
　Nb, V, W, N, B, and Si in the formula (1), the content of the corresponding element is substituted in mass %. R.
[0027]
<2> The austenitic heat resistant steel weld metal according to <1>,
　wherein the chemical composition is mass%
　: Ti: 0.01% to 0.25%,
　Cu: 0.01% to 4%,
　Co: 0.01% to 2%,
　Mo: 0.01% to 2%,
　Ta: 0.01% to 1%,
　Ca: 0.0005% to 0.02%,
　Mg: 0.0005% to 0 　Austenitic heat-resistant steel weld metal containing one or more elements selected from the group consisting of 0.02% and
　REM: 0.0005% to 0.06%
.
[0028]
<3> A
　welded joint comprising the austenitic heat resistant steel weld metal according to <1> or <2> and a base material of the austenitic heat resistant steel.
[0029]
<4> The welded joint according to <3>,
　wherein the chemical composition of the base material is% by mass,
　C: 0.02% to 0.14%,
　Si: 0.05% to 1%,
　Mn. : 0.1% to 3%,
　P: 0.04% or less,
　S: 0.002% or less,
　Ni: 26% to 35%,
　Cr: 20% to 26%,
　W: 1% to 7%,
　Nb : 0.01% to 1%,
　V: 0.01% to 1%,
　N: 0.1% to 0.6%,
　B: 0.0005% to 0.008%,
　REM: 0.003% to 0.06%,
　Al: 0.3% or less,
　O: 0.02% or less,
　Ti: 0% to 0.5%,
　Co: 0% to 2%,
　Cu: 0% to 4%,
　Mo: 0 % To 4%,
　Ta: 0% to 1%,
　Ca: 0% to 0.02%,
　Mg: 0% to 0.02%,
　balance: Fe and impurities, welded joint.
[0030]
<5> The welded joint according to <4>,
　wherein the chemical composition of the base metal is mass%
　: Ti: 0.01% to 0.5%,
　Co: 0.01% to 2%,
　Cu : 0.01% to 4%,
　Mo: 0.01% to 4%,
　Ta: 0.01% to 1%,
　Ca: 0.0005% to 0.02%, and
　Mg: 0.0005% to 0 A
　welded joint containing one or more selected from the group consisting of 0.02% .
[0031]
<6> Chemical composition in mass %,
　C: 0.06% to 0.14%,
　Si: 0.1% to 0.4%,
　Mn: 0.1% to 1.2%,
　P :0 0.01% or less,
　S: 0.003% or less,
　Ni: 28% to 35%,
　Cr: 20% to 24%,
　W: more than 4.5% and 7.5% or less,
　Nb: 0.05% to 0.5%,
　V: 0.05% to 0.35%,
　N: 0.1% to 0.35%,
　Al: 0.08% or less,
　O: 0.08% or less,
　B: 0.0005 ~ 0.005%,
　Ti: 0% to 0.25%,
　Cu: 0% to 4%,
　Co: 0% to 2%,
　Mo: 0% to 2%,
　Ta: 0% to 1%,
　Ca: 0% to 0.02%,
　Mg: 0% to 0.02%,
　REM: 0% to 0.06%,
　balance: Fe and impurities,
　A welding material for austenitic heat-resistant steel, wherein fn1 represented by the following formula (1) is 10 or more.
　　fn1=10(Nb+V)+1.5W+20N+1500B-25Si (1) In
　Nb, V, W, N, B, and Si in the formula (1), the content of the corresponding element is substituted in mass %. R.
[0032]
<7> The welding material for austenitic heat resistant steel according to <6>,
　wherein the chemical composition is mass%
　: Ti: 0.01% to 0.25%,
　Cu: 0.01% to 4% ,
　Co: 0.01% to 2%,
　Mo: 0.01% to 2%,
　Ta: 0.01% to 1%,
　Ca: 0.0005% to 0.02%,
　Mg: 0.0005% to 　Welding material for austenitic heat-resistant steel, containing one or more elements selected from the group consisting of 0.02% and
　REM: 0.0005% to 0.06%
.
[0033]
<8> A method for producing the welded joint according to
　<4>, wherein the base material having the chemical composition according to <4> is welded using the welding material for austenitic heat resistant steel according to <6>. A method for manufacturing a welded joint.
Effect of the invention
[0034]
　According to the present invention, a welding material suitable for welding high-nitrogen and high-nickel-containing austenitic heat-resistant steel, as well as capable of fully utilizing the performance of the high-nitrogen-high-nickel-containing austenitic heat-resistant steel, low hot cracking susceptibility, and creep. Provided are an austenitic heat-resistant steel weld metal having excellent strength and a weld joint having the same.
MODE FOR CARRYING OUT THE INVENTION
[0035]
　Hereinafter, an austenitic heat-resistant steel weld metal, austenitic heat-resistant steel welding material, a welded joint, and a method for manufacturing the same according to one embodiment of the present invention will be described. In the present specification, a numerical range represented by “to” means a range including the numerical values ​​before and after “to” as a lower limit value and an upper limit value, unless otherwise specified. However, when there is a notice such as “exceeding” and “less than”, it means that the numerical values ​​before and after “to” are not included as at least one of the lower limit and the upper limit.
[0036]
　 In the
　present invention, the reason for limiting the chemical composition of the austenitic heat resistant steel welding metal and the welding material for austenitic heat resistant steel is as follows.
[0037]
　In the following description, “%” display of the content of each element means “mass %”. Further, the chemical composition of the weld metal is determined by quantifying the chemical composition of the portion of the weld metal where the influence of the dilution of the base metal is not significant. More specifically, the chemical composition of the weld metal was determined by quantifying the chemical composition in the vicinity of the central portion of the weld metal, and if possible, quantifying the chemical composition of the portion 0.5 mm or more away from the fusion line. I shall. Further, the “impurity” is a component that is mixed in from an ore as a raw material, scrap, a production environment, or the like when industrially producing an austenitic heat-resistant steel, and refers to a component that is not intentionally included.
[0038]
　C: 0.06% to 0.14% (welding metal)
　　　0.06% to 0.14% (welding material)
　Carbon (C) stabilizes the austenite structure, forms fine carbides, and has a high temperature. Improves creep strength during use. In order to sufficiently obtain these effects, it is necessary to contain C by 0.06% or more. However, when the C content is excessive, a large amount of carbide is present in the weld metal, so that the ductility and toughness deteriorate. Therefore, the upper limit of the C content is 0.14% or less. The lower limit of the C content is preferably 0.07% or more, more preferably 0.08% or more. The upper limit of the C content is preferably 0.13% or less, more preferably 0.12% or less.
[0039]
　Si: 0.1% to 0.6% (welding metal)
　　　　0.1% to 0.4% (welding material)
　Silicon (Si) has a deoxidizing effect and also has corrosion resistance and oxidation resistance at high temperature. It is an effective element for improvement. In order to obtain the effect, Si needs to be contained by 0.1% or more. However, when Si is excessively contained, a nitride consisting of Cr, Ni and N is deposited for structural stability, the amount of solid solution nitrogen in the matrix phase is reduced, and the creep strength is reduced. Therefore, the upper limit of the Si content is 0.6% or less in the weld metal and 0.4% or less in the welding material. The lower limit of the Si content is preferably 0.12% or more, and more preferably 0.15% or more for both the weld metal and the welding material. The upper limit of the Si content of the weld metal is preferably 0.58% or less, more preferably 0.55% or less, and further preferably 0.40% or less. The upper limit of the Si content of the welding material is preferably 0.38% or less, more preferably 0.35% or less.
[0040]
　Mn: 0.1% to 1.8% (welding metal)
　　　　0.1% to 1.2% (welding material)
　Manganese (Mn) has a deoxidizing action like Si. Further, Mn stabilizes the austenite structure and contributes to the improvement of creep strength. In order to obtain these effects, Mn needs to be contained at 0.1% or more. However, if the Mn content becomes excessive, embrittlement is caused, and further, the creep ductility decreases. Further, when it is used as a welding material, solidification cracking susceptibility during welding is increased. Therefore, the upper limit of the Mn content is 1.8% or less for the weld metal and 1.2% or less for the welding material. The lower limit of the Mn content is preferably 0.15% or more, and more preferably 0.2% or more for both the weld metal and the welding material. The upper limit of the Mn content of the weld metal is preferably 1.6% or less, more preferably 1.4% or less. The upper limit of the Mn content of the welding material is preferably 1.1% or less, more preferably 1.0% or less.
[0041]
　P: 0.025% or less (welding metal)
　　　0.01% or less (welding material)
　Phosphorus (P) is an element contained as an impurity and reducing the creep ductility. Further, when used as a welding material, P enhances solidification cracking susceptibility during welding. Therefore, the upper limit of the P content is set to 0.025% or less in the weld metal and 0.01% or less in the welding material. The upper limit of the P content of the weld metal is preferably 0.023% or less, more preferably 0.020% or less. The upper limit of the P content of the welding material is preferably 0.008% or less, more preferably 0.006% or less. Although it is desirable to reduce the P content as much as possible, the extreme reduction leads to an increase in manufacturing cost. Therefore, the lower limit of the P content is preferably 0.0005% or more, and more preferably 0.0008% or more for both the weld metal and the welding material.
[0042]
　S: 0.003% or less (welding metal)
　　　0.003% or less (welding material)
　Sulfur (S), like P, is contained as an impurity and segregates at the columnar boundaries of the weld metal at the initial stage of use at high temperature. And reduce toughness. Further, it also enhances solidification cracking susceptibility during welding. In order to suppress these in a stable manner, it is necessary to set the upper limit on the S content to 0.003% or less. The S content is preferably 0.0025% or less, more preferably 0.002% or less. Although it is desirable to reduce the S content as much as possible, the extreme reduction leads to an increase in the manufacturing cost of the welding material. Therefore, the lower limit of the S content is preferably 0.0001% or more, and more preferably 0.0002% or more for both the weld metal and the welding material.
[0043]
　Ni: 25% to 35% (welding metal)
　　　　28% to 35% (welding material)
　Nickel (Ni) enhances the stability of the austenite structure during long-term use and contributes to the improvement of creep strength. In order to sufficiently obtain the effect, it is necessary to contain 25% or more of Ni in the weld metal and 28% or more of Ni in the welding material. However, Ni is an expensive element, and the inclusion of a large amount causes an increase in cost. Therefore, the upper limit of the Ni content is set so that the content of both the weld metal and the welding material is 35% or less. The lower limit of the Ni content of the weld metal is preferably 25.5% or more, more preferably 26% or more. The lower limit of the Ni content of the welding material is preferably 28.5% or more, more preferably 29% or more. The upper limit of the Ni content is preferably 34.5% or less, and more preferably 34% or less for both the weld metal and the welding material.
[0044]
　Cr: 20% to 24% (welding metal)
　　　　20% to 24% (welding material)
　Chromium (Cr) is an essential element for ensuring oxidation resistance and corrosion resistance at high temperatures. It also contributes to the formation of fine carbides to secure the creep strength. In order to sufficiently obtain the effect, it is necessary to contain Cr in an amount of 20% or more. However, if the Cr content exceeds 24%, the stability of the austenite structure at high temperatures deteriorates, resulting in a significant decrease in creep strength. Therefore, the Cr content is set to 20% to 24%. The lower limit of the Cr content is preferably 20.5% or more, more preferably 21% or more. The upper limit of the Cr content is preferably 23.5% or less, more preferably 23% or less.
[0045]
　W: More than 4.5% and 7.5% or Less (Welding Metal) More
　　　than 4.5% and 7.5% or Less (Welding Material)
　Tungsten (W) forms a solid solution in the matrix and creep strength at high temperature. It is also an element that greatly contributes to the improvement of tensile strength. In order to bring out the effect sufficiently, W must be contained at least in excess of 4.5%. However, since W is an expensive element, excessive inclusion of W causes an increase in cost and also lowers the structural stability. Therefore, the upper limit of the W content is 7.5% or less. The lower limit of the W content is preferably 4.7% or more, more preferably 5% or more, and further preferably 5.5% or more. The upper limit of the W content is preferably 7.3% or less, more preferably 7% or less.
[0046]
　Nb: 0.05% to 0.5% (welding metal)
　　　　0.05% to 0.5% (welding material)
　Niobium (Nb) has a strong affinity with carbon and nitrogen and is a fine carbonitride grain. It precipitates inside and contributes to the improvement of creep strength and tensile strength of the weld metal at high temperature. In order to obtain the effect sufficiently, it is necessary to contain Nb in an amount of 0.05% or more. However, when the content of Nb becomes excessive, the amount of precipitation at the initial stage of use at high temperature increases, resulting in a decrease in toughness. Therefore, the upper limit of the Nb content is 0.5% or less. The lower limit of the Nb content is preferably 0.08% or more, and more preferably 0.1% or more for both the weld metal and the welding material. The upper limit of the Nb content of the weld metal is preferably 0.48% or less, more preferably 0.45% or less. The upper limit of the Nb content of the welding material is 0.47% or less, more preferably 0.4% or less.
[0047]
　V: 0.05% to 0.4% (welding metal)
　　　0.05% to 0.35% (welding material)
　Vanadium (V) forms fine carbonitrides like Nb. In comparison, it has a weaker affinity for carbon and nitrogen. Therefore, V contributes to the improvement of the creep strength of the weld metal without affecting the toughness at the initial stage of use as much as Nb. In order to obtain this effect, V must be contained at 0.05% or more. However, when V is contained in excess, a large amount of V precipitates, and the coarsening of the precipitate becomes remarkable, leading to a decrease in creep strength and ductility. Therefore, the upper limit of the V content is 0.4% or less for the weld metal and 0.35% or less for the welding material. The lower limit of the V content is preferably 0.08% or more, more preferably 0.1% or more. The upper limit of the V content of the weld metal is preferably 0.38% or less, more preferably 0.35% or less. The upper limit of the V content of the welding material is preferably 0.32% or less, more preferably 0.3% or less.
[0048]
　N: 0.1% to 0.35% (welding metal)
　　　0.1% to 0.35% (welding material)
　Nitrogen (N) stabilizes the austenite structure, and at high temperature due to solid solution strengthening or precipitation strengthening. It contributes to the improvement of strength. In order to obtain the effect, N needs to be contained by 0.1% or more. However, when N is contained in excess of 0.35%, a large amount of nitride precipitates, leading to a decrease in toughness. Therefore, the N content is set to 0.1% to 0.35%. The lower limit of the N content is preferably 0.12% or more, more preferably 0.15% or more. The upper limit of the N content is preferably 0.32% or less, more preferably 0.3% or less.
[0049]
　Al: 0.08% or less (welding metal)
　　　　0.08% or less (welding material)
　Aluminum (Al) is contained as a deoxidizing agent during the production of the base metal and is also included as a deoxidizing agent during the production of the welding material. It As a result, the weld metal also contains Al. Ductility decreases when a large amount of Al is contained. Therefore, the upper limit of the Al content needs to be 0.08% or less. The upper limit of the Al content is preferably 0.06% or less, more preferably 0.04% or less. It is not necessary to set the lower limit of the Al content in particular, but the extreme reduction of the Al content causes an increase in manufacturing cost. Therefore, the desirable lower limit of the Al content is 0.0005% or more, and the desirable lower limit is 0.001% or more.
[0050]
　O: 0.08% or less (welding metal)
　　　0.08% or less (welding material)
　Oxygen (O) is contained in the welding metal as an impurity. However, if the content of O is excessive, toughness and ductility are deteriorated. Therefore, the upper limit of the O content is 0.08% or less. The upper limit of the O content is preferably 0.06% or less, more preferably 0.04% or less. Although it is not necessary to set a lower limit for the O content, an extreme reduction causes an increase in manufacturing cost. Therefore, a desirable lower limit of the O content is 0.0005% or more, and a further desirable lower limit thereof is 0.0008% or more.
[0051]
　B: 0.0005% to 0.005% (welding metal)
　　　0.0005% to 0.005% (welding material)
　Boron (B) improves the creep strength of the welding metal by finely dispersing carbides. At the same time, it strengthens the grain boundaries and contributes to the improvement of toughness. In order to exert the effect, B needs to be contained at 0.0005% or more. However, when B is contained in excess, it increases the susceptibility to solidification cracking during welding. Therefore, the upper limit of the B content is 0.005% or less. The upper limit of the B content is preferably 0.004% or less, more preferably 0.003% or less, and further preferably 0.002% or less. A desirable lower limit of the B content is 0.0007% or more, and a further desirable lower limit thereof is 0.001% or more.
[0052]
　fn1=10(Nb+V)+1.5W+20N+1500B-25Si:10 or more
　As described above, Nb, V, W, N and B contribute to the creep strength improvement, and Si reduces to contribute to the creep strength improvement. In order to secure the creep strength at high temperature, the value obtained by fn1=10(Nb+V)+1.5W+20N+1500B-25Si needs to be 10 or more. fn1 is preferably 12 or more, more preferably 12.5 or more, and further preferably 13 or more.
[0053]
　The balance of the chemical composition of the austenitic heat-resistant steel weld metal and the welding material for austenitic heat-resistant steel according to the present embodiment is Fe and impurities.
[0054]
　The austenitic heat-resistant steel weld metal and the austenitic heat-resistant steel welding material according to the present embodiment include one or more selected from the group consisting of Ti, Cu, Co, Mo, Ta, Ca, Mg, and REM. It may contain an element. All of these elements are selective elements. That is, the austenitic heat resistant steel weld metal and the welding material for austenitic heat resistant steel of the present embodiment may not contain these elements. Each component will be described below.
[0055]
　Ti: 0% to 0.25% (welding metal)
　　　　0% to 0.25% (welding material)
　Titanium (Ti) forms fine carbonitrides like Nb and V, and creeps at high temperature. It contributes to the improvement of strength and tensile strength. Therefore, you may contain as needed. However, when the Ti content becomes excessive, a large amount of Ti precipitates in the initial stage of use as in the case of Nb, resulting in a decrease in toughness. Therefore, the upper limit of the Ti content is 0.25% or less. The upper limit of the Ti content is preferably 0.23% or less, more preferably 0.2% or less. The lower limit of the Ti content is preferably 0.01% or more, more preferably 0.03% or more.
[0056]
　Cu: 0% to 4% (welding metal)
　　　　0% to 4% (welding material)
　Copper (Cu) enhances the stability of the austenite structure and finely precipitates to contribute to the improvement of creep strength. However, if Cu is excessively contained, ductility is lowered. Therefore, the upper limit of the Cu content is 4% or less. The upper limit of the Cu content is preferably 3.8% or less, more preferably 3.5% or less. The lower limit of the Cu content is preferably 0.01% or more, more preferably 0.03% or more.
[0057]
　Co: 0% to 2% (welding metal)
　　　　0% to 2% (welding material)
　Cobalt (Co), like Ni and Cu, is an austenite forming element, which improves the stability of the austenite structure and improves creep strength. Contribute to. However, since Co is an extremely expensive element, excessive inclusion of Co causes a significant cost increase. Therefore, when Co is contained, the upper limit of the Co content is 2% or less. The upper limit of the Co content is preferably 1.8% or less, more preferably 1.5% or less. The lower limit of the Co content is preferably 0.01% or more, more preferably 0.03% or more.
[0058]
　Mo: 0% to 2% (welding metal)
　　　　0% to 2% (welding material)
　Molybdenum (Mo), like W, forms a solid solution in the matrix and contributes to the improvement of creep strength and tensile strength at high temperature. .. However, when Mo is excessively contained, it lowers the structural stability and may lower the creep strength. Furthermore, since Mo is an expensive element, excessive inclusion causes an increase in cost. Therefore, the upper limit of the Mo content is 2% or less. The upper limit of the Mo content is preferably 1.5% or less, more preferably 1.2% or less. The lower limit of the Mo content is preferably 0.01% or more, more preferably 0.03% or more.
[0059]
　Ta: 0% to 1% (welding metal)
　　　　0% to 1% (welding material)
　Tantalum (Ta) forms a carbonitride and improves high temperature strength and creep rupture strength as a solid solution strengthening element. On the other hand, if the Ta content exceeds 1%, the workability and mechanical properties of steel are impaired. Therefore, when Ta is contained, the upper limit of the Ta content is 1% or less. The lower limit of the Ta content is preferably 0.01% or more, more preferably 0.05% or more, and further preferably 0.1% or more. The upper limit of the Ta content is preferably 0.7% or less, more preferably 0.6% or less.
[0060]
　Ca: 0% to 0.02% (welding metal)
　　　　0% to 0.02% (welding material)
　Calcium (Ca) has the effect of improving the hot deformability, so it may be included if necessary. Good. However, the excessive content of Ca combines with oxygen and significantly deteriorates the detergency, and rather deteriorates the hot deformability. Therefore, the upper limit of the Ca content is 0.02% or less. The upper limit of the Ca content is preferably 0.015% or less, more preferably 0.01% or less. The lower limit of the Ca content is preferably 0.0005% or more, more preferably 0.001% or more.
[0061]
　Mg: 0% to 0.02% (welding metal)
　　　　0% to 0.02% (welding material)
　Magnesium (Mg) has an effect of improving hot deformability like Ca, and therefore, if necessary, It may be contained. However, an excessive content of Mg binds to oxygen and significantly deteriorates the cleanability, and rather deteriorates the hot deformability. Therefore, the upper limit of the Mg content is 0.02% or less. The upper limit of the Mg content is preferably 0.015% or less, more preferably 0.01% or less. The lower limit of the Mg content is preferably 0.0005% or more, more preferably 0.001% or more.
[0062]
　REM: 0% to 0.06% (welding metal)
　　　　　0% to 0.06% (welding material) A
　rare earth element (REM) is necessary because it has an effect of improving hot deformability, like Ca and Mg. You may make it contain according to. However, an excessive content of REM combines with oxygen, and significantly deteriorates the cleanability, and rather deteriorates the hot workability. Therefore, the upper limit of the REM content is 0.06% or less. The upper limit of the REM content is preferably 0.04% or less, more preferably 0.03% or less. The lower limit of the REM content is preferably 0.0005% or more, more preferably 0.001% or more.
[0063]
　In addition, "REM" is a general term for a total of 17 elements of Sc, Y, and a lanthanoid, and the content of REM refers to the total content of one or more elements of REM. Further, REM is generally contained in misch metal. Therefore, for example, REM may be contained in the form of misch metal so that the content of REM falls within the above range.
[0064]
　REM is difficult to stably exist in a molten state. Therefore, from the viewpoint of the stability of the characteristics of the welded joint, it is preferable that the welding material does not contain REM.
[0065]
　The welding material for austenitic heat resistant steel according to the present embodiment can be manufactured by a usual method. For example, an alloy having the chemical composition of the above-mentioned welding material is melted to form an ingot, and after undergoing steps such as hot forging, hot rolling, cold rolling or cold drawing, and heat treatment, an outer diameter of several mm (for example, 1 A welding material can be obtained by using a wire rod having a diameter of 0.0 mm to 2.4 mm.
[0066]
　The weld metal according to the present embodiment can be manufactured, for example, by welding austenitic heat resistant steel using the above-mentioned welding material.
[0067]
　
　A welded joint according to one embodiment of the present invention includes the above-described weld metal and a base material of austenitic heat resistant steel. Specifically, the welded joint has a weld metal of the joint portion and two base materials made of austenitic heat resistant steel sandwiching the weld metal. The specific shape of the welded joint, the specific aspect of welding to obtain the welded joint (welding posture) is not particularly limited, and for example, when butt welding is performed after groove-processing a steel pipe, after groove-processing a thick plate. It may be applied when butt welding is performed.
[0068]
　
　The base material of the welded joint according to the present embodiment preferably has the following chemical composition.
[0069]
　C: 0.02% to 0.14%
　Carbon (C) stabilizes the austenite structure and forms fine carbides to improve the creep strength during high temperature use. Therefore, the lower limit of the C content is preferably 0.02% or more. However, when C is contained excessively, a large amount of carbide is precipitated, and the creep ductility and toughness deteriorate. Therefore, the upper limit of the C content is preferably 0.14% or less. The upper limit of the C content is more preferably 0.03% or more, and further preferably 0.04% or more. The lower limit of the C content is more preferably 0.13% or less, and further preferably 0.12% or less.
[0070]
　Si: 0.05% to 1%
　Silicon (Si) is an element that has a deoxidizing effect and is effective in improving corrosion resistance and oxidation resistance at high temperatures. Therefore, the lower limit of the Si content is preferably 0.05% or more. However, when Si is excessively contained, a nitride consisting of Cr, Ni and N is deposited for structural stability, the amount of solid solution nitrogen in the matrix phase is reduced, and the creep strength is reduced. Therefore, the upper limit of the Si content is desirably 1% or less. The lower limit of the Si content is more preferably 0.08% or more, and further preferably 0.1% or more. The upper limit of the Si content is more preferably 0.8% or less, further preferably 0.5% or less.
[0071]
　Mn: 0.1% to 3%
　Manganese (Mn) has a deoxidizing action like Si. Further, Mn contributes to stabilization of the austenite structure. Therefore, the lower limit of the Mn content is desirably 0.1% or more. However, if the Mn content becomes excessive, embrittlement is caused, and further, the creep ductility decreases. Therefore, the upper limit of the Mn content is desirably 3% or less. The lower limit of the Mn content is more preferably 0.3% or more, and further preferably 0.5% or more. The upper limit of the Mn content is more preferably 2.5% or less, and further preferably 2% or less.
[0072]
　P: 0.04% or less
　Phosphorus (P) is contained in the alloy as an impurity and segregates in the grain boundaries of the heat-affected zone of the welding during welding to enhance liquefaction cracking susceptibility. Furthermore, the creep ductility after long-term use is also reduced. Therefore, the upper limit of the P content is preferably 0.04% or less. The upper limit of the P content is more preferably 0.028% or less, and further preferably 0.025% or less. Although it is desirable to reduce the P content as much as possible, extreme reduction causes an increase in manufacturing cost. Therefore, the lower limit of the P content is preferably 0.0005% or more, more preferably 0.0008% or more.
[0073]
　S: 0.002% or less
　Sulfur (S) is contained in the alloy as an impurity like P and is segregated at the grain boundaries of the heat affected zone during welding to enhance liquefaction cracking susceptibility. Therefore, the upper limit of the S content is preferably 0.002% or less. The upper limit of the S content is more preferably 0.0018% or less, and further preferably 0.0015% or less. Although it is desirable to reduce the S content as much as possible, the extreme reduction leads to an increase in manufacturing cost. Therefore, the lower limit of the S content is more preferably 0.0001% or more, and further preferably 0.0002% or more.
[0074]
　Ni: 26% to 35%
　Nickel (Ni) is an element for ensuring the stability of the austenite structure during long-term use and for ensuring the creep strength. Therefore, the lower limit of the Ni content is preferably 26% or more. However, Ni is an expensive element, and the inclusion of a large amount causes an increase in cost. Therefore, the upper limit of the Ni content is desirably 35% or less. The lower limit of the Ni content is more preferably 27% or more, further preferably 28% or more. The upper limit of the Ni content is more preferably 34% or less, and further preferably 33% or less.
[0075]
　Cr: 20% to 26%
　Chromium (Cr) is an element for ensuring oxidation resistance and corrosion resistance at high temperatures. It also contributes to the formation of fine carbides to secure the creep strength. Therefore, it is desirable that the lower limit of the Cr content be 20% or more. However, if the Cr content exceeds 26%, the stability of the austenite structure at high temperatures deteriorates, leading to a decrease in creep strength. Therefore, it is desirable that the Cr content be 20% to 26%. The lower limit of the Cr content is more preferably 20.5% or more, and further preferably 21% or more. The upper limit of the Cr content is preferably 25.5% or less, more preferably 25% or less.
[0076]
　W: 1% to 7%
　Tungsten (W) is an element that forms a solid solution in the matrix and greatly contributes to the improvement of creep strength and tensile strength at high temperatures. Therefore, it is desirable that the lower limit of the W content be 1% or more. However, even if W is contained excessively, the effect is saturated or the creep strength is lowered in some cases. Furthermore, since W is an expensive element, excessive inclusion of W causes an increase in cost. Therefore, the upper limit of the W content is desirably 7% or less. The lower limit of the W content is more preferably 1.2% or more, and further preferably 1.5% or more. The upper limit of the W content is preferably 6.8% or less, more preferably 6.5% or less.
[0077]
　Nb: 0.01% to 1%
　Niobium (Nb) precipitates in the grains as fine carbonitrides and contributes to the improvement of creep strength and tensile strength at high temperatures. Therefore, the lower limit of the Nb content is preferably 0.01% or more. However, if the content of Nb is excessive, a large amount of carbonitrides are deposited, which causes deterioration of creep ductility and toughness. Therefore, the upper limit of the Nb content is preferably 1% or less. The lower limit of the Nb content is more preferably 0.05% or more, and further preferably 0.1% or more. The upper limit of the Nb content is more preferably 0.9% or less, and further preferably 0.8% or less.
[0078]
　V: 0.01% to 1%
　Vanadium (V), like Nb, forms fine carbonitrides and contributes to the improvement of creep strength and tensile strength at high temperatures. Therefore, the lower limit of the V content is preferably 0.01% or more. However, if the V content becomes excessive, a large amount of V precipitates, causing a decrease in creep ductility and toughness. Therefore, the upper limit of the V content is desirably 1% or less. The lower limit of the V content is more preferably 0.05% or more, and further preferably 0.1% or more. The upper limit of the V content is more preferably 0.9% or less, and further preferably 0.8% or less.
[0079]
　N: 0.1% to 0.6%
　Nitrogen (N) stabilizes the austenite structure and precipitates as a solid solution or a nitride, which contributes to improvement in high temperature strength. Therefore, the lower limit of the N content is preferably 0.1% or more. However, when N is contained excessively, a large amount of fine nitrides are precipitated in the grains during long-term use, which leads to deterioration of creep ductility and toughness. Therefore, the upper limit of the N content is preferably 0.6% or less. The lower limit of the N content is preferably 0.12% or more, more preferably 0.15% or more. The upper limit of the N content is preferably 0.58% or less, more preferably 0.55% or less.
[0080]
　B: 0.0005% to 0.008%
　Boron (B) improves the creep strength by finely dispersing grain boundary carbides and segregates at grain boundaries to contribute to grain boundary strengthening. Therefore, the lower limit of the B content is preferably 0.0005% or more. However, if the B content is excessive, the susceptibility to liquefaction cracking of the heat affected zone during welding is increased. Therefore, the upper limit of the B content is preferably 0.008% or less. The upper limit of the B content is more preferably 0.006% or less, and further preferably 0.005% or less. The lower limit of the B content is preferably 0.0006% or more, more preferably 0.0008% or more.
[0081]
　REM: 0.003% to 0.06%
　Rare earth element (REM) contributes to improvement of hot deformability during manufacturing. Therefore, the lower limit of the REM content is preferably 0.003% or more. However, an excessive content of REM binds with oxygen and significantly deteriorates the cleanability, and adversely affects the hot deformability. Therefore, the upper limit of the REM content is preferably 0.06% or less. The upper limit of the REM content is more preferably 0.04% or less, further preferably 0.03% or less. The lower limit of the REM content is preferably 0.005% or more, more preferably 0.007% or more.
[0082]
　Al: 0.3% or less
　Aluminum (Al) is contained as a deoxidizer at the time of manufacturing the base material. However, if a large amount of Al is contained, the cleanliness of steel deteriorates and the hot workability deteriorates. Therefore, the upper limit of the Al content is preferably 0.3% or less. The upper limit of the Al content is more preferably 0.25% or less, and further preferably 0.2% or less. It is not necessary to set the lower limit of the Al content in particular, but an extreme reduction causes an increase in manufacturing cost. Therefore, the lower limit of the Al content is preferably 0.0005% or more, more preferably 0.001% or more.
[0083]
　O: 0.02% or less
　Oxygen (O) is contained in the alloy as an impurity, and if contained in excess, hot workability is deteriorated and toughness and ductility are deteriorated. Therefore, the upper limit of the O content is preferably 0.02% or less. The upper limit of the O content is more preferably 0.018% or less, and further preferably 0.015% or less. It is not necessary to set a lower limit for the O content, but an extreme reduction causes an increase in manufacturing cost. Therefore, the lower limit of the O content is preferably 0.0005% or more, and more preferably 0.0008% or more.
[0084]
　The balance of the chemical composition of the base material of the welded joint according to the present embodiment is Fe and impurities.
[0085]
　The base material of the welded joint according to the present embodiment may contain one or more elements selected from the group consisting of Ti, Co, Cu, Mo, Ta, Ca, and Mg. Each component will be described below.
[0086]
　Ti: 0% to 0.5%
　Titanium (Ti), like Nb and V, forms fine carbonitrides and contributes to the improvement of creep strength and tensile strength at high temperatures. Therefore, you may contain as needed. However, when the Ti content becomes excessive, a large amount of Ti precipitates in the initial stage of use as in the case of Nb, resulting in a decrease in toughness. Therefore, the upper limit of the Ti content is preferably 0.5% or less. The upper limit of the Ti content is more preferably 0.3% or less, and further preferably 0.2% or less. The lower limit of the Ti content is preferably 0.01% or more, more preferably 0.03% or more.
[0087]
　Co: 0% to 2%
　Cobalt (Co) is an austenite forming element like Ni and Cu, and contributes to the improvement of the stability of the austenite structure and the improvement of the creep strength. Therefore, you may contain as needed. However, since Co is an extremely expensive element, excessive inclusion of Co causes a significant cost increase. Therefore, the upper limit of the Co content is preferably 2% or less. The upper limit of the Co content is more preferably 1.8% or less, and further preferably 1.5% or less. The lower limit of the Co content is preferably 0.01% or more, more preferably 0.03% or more.
[0088]
　Cu: 0% to 4%
　Cu (copper) enhances the stability of the austenite structure and finely precipitates during use to contribute to the improvement of creep strength. Therefore, you may contain as needed. However, if Cu is excessively contained, ductility is lowered. Therefore, the upper limit of the Cu content is preferably 4% or less. The upper limit of the Cu content is more preferably 3.8% or less, and further preferably 3.5% or less. The lower limit of the Cu content is preferably 0.01% or more, more preferably 0.03% or more.
[0089]
　Mo: 0% to 4%
　Molybdenum (Mo), like W, is an element that forms a solid solution in the matrix and contributes to the improvement of creep strength and tensile strength at high temperatures. Therefore, you may contain as needed. However, when Mo is excessively contained, it lowers the structural stability and may lower the creep strength. Furthermore, since Mo is an expensive element, excessive inclusion causes an increase in cost. Therefore, the upper limit of the Mo content is preferably 4% or less. The upper limit of the Mo content is more preferably 2% or less, further preferably 1.2% or less. The lower limit of the Mo content is preferably 0.01% or more, more preferably 0.03% or more.
[0090]
　Ta: 0% to 1%
　tantalum (Ta) forms a carbonitride and improves high temperature strength and creep rupture strength as a solid solution strengthening element. Therefore, you may contain as needed. On the other hand, if the Ta content exceeds 1%, the workability and mechanical properties of steel are impaired. Therefore, the upper limit of the Ta content is preferably 1% or less. The upper limit of the Ta content is more preferably 0.7% or less, further preferably 0.6% or less. The lower limit of the Ta content is preferably 0.01% or more, more preferably 0.05% or more, and further preferably 0.1% or more.
[0091]
　Ca: 0% to 0.02%
　Calcium (Ca) has an effect of improving hot deformability, and thus may be contained if necessary. However, the excessive content of Ca combines with oxygen and significantly deteriorates the detergency, and rather deteriorates the hot deformability. Therefore, the upper limit of the Ca content is preferably 0.02% or less. The upper limit of the Ca content is more preferably 0.015% or less, and further preferably 0.01% or less. The lower limit of the Ca content is preferably 0.0005% or more, more preferably 0.001% or more.
[0092]
　Mg: 0% to 0.02%
　Magnesium (Mg) has an effect of improving hot deformability like Ca, and thus may be contained if necessary. However, an excessive content of Mg binds to oxygen and significantly deteriorates the cleanability, and rather deteriorates the hot deformability. Therefore, the upper limit of the Mg content is preferably 0.02% or less. The upper limit of the Mg content is more preferably 0.015% or less, and further preferably 0.01% or less. The lower limit of the Mg content is preferably 0.0005% or more, more preferably 0.001% or more.
[0093]
　The welded joint according to the present embodiment is not limited to this, but can be manufactured by welding the above-mentioned base material using the above-mentioned welding material.
Example
[0094]
　Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples. It is obvious to those skilled in the art that various changes or modifications can be conceived within the scope of the idea described in the claims, and naturally, they also belong to the technical scope of the present invention. Understood.
[0095]
　[Welding material] The
　following two types of plate materials are produced by hot forging, hot rolling, heat treatment and machining from an ingot obtained by melting and casting a material (steel material) having the chemical composition shown in Table 1 in a laboratory. did.
　Plate (1): thickness 4 mm, width 100mm, length 100mm
　plate (2): plate thickness 4 mm, width 200 mm, length 500mm
　Further, using a sheet material (2), by machining, 2 mm square, 500mm length of A cut filler was produced.
[0096]
[table 1]

[0097]
　[Trans-Valrestrain Test]
　Trans-Valrestrain test pieces were collected from the above plate (1). After that, bead-on-plate welding was performed by GTAW under the conditions of a welding current of 100 A and a welding speed of 15 cm/min. When the molten pool reached the central portion in the longitudinal direction of the test piece, bending deformation was applied to the test piece, and additional strain was applied to the weld metal to cause cracking. The additional strain was 2% at which the maximum crack length was saturated. In the evaluation, the maximum crack length generated in the weld metal was measured and used as an evaluation index of solidification crack sensitivity of the welding material. The crack length was set to 1.3 mm or less, which is the maximum crack length evaluated by the Transvarestraint test of Alloy 800H weld metal that undergoes complete austenite solidification.
[0098]
　[Creep rupture test]
　Using a cut filler made from the plate material (2), buttering welding to the groove surface by manual TIG welding using Ar as a shielding gas, and then laminating welding in the groove to perform a total weld metal test. Pieces were made. During welding, the heat input was 9 kJ/cm to 12 kJ/cm, and the interlayer temperature was 150° C. or lower. Pre-welding heat treatment (preheating) and post-welding heat treatment were not performed. Then, a round bar creep rupture test piece was sampled from the entire weld metal part. Then, a creep rupture test was performed under the conditions of 750° C. and 127 MPa, and those having a target breaking time of more than 1000 hours under these conditions were “passed”, and those having a breaking time of 1000 hours or less were rejected.
[0099]
　Table 2 also shows the results of the above tests.
[0100]
[Table 2]

[0101]
　From Table 2, it is clear that the welding materials with reference numerals 1 to 6 whose chemical composition is within the range defined by the present invention have low weld hot crack susceptibility and satisfy the target creep rupture time.
[0102]
　On the other hand, the welding material having a W content lower than the range of the present invention of reference numeral 7, the welding material of the reference numerals 8 and 13 not containing B, and the welding material of a reference numeral 9 having a Si content higher than the scope of the present invention. The welding material had a low susceptibility to hot cracking, but the creep strength was below the target. Regarding the welding material of reference numeral 10, which satisfied the component range of the present invention but had a low value of fn1, the creep strength was lower than the target although the hot cracking susceptibility was low. In addition, the welding material with the reference numeral 11 having a B content higher than the range of the present invention and the welding material with the reference numeral 12 having a Nb content higher than the range of the present invention had increased creep susceptibility, although creep strength was not a problem.
[0103]
　As described above, it can be seen that the welding material satisfying the requirements of the present invention has low hot cracking susceptibility and also satisfies creep strength. This shows that the welding material for austenitic heat resistant steels of the present invention can be a welding material suitable for welding austenitic heat resistant steels containing high nitrogen and high nickel.
[0104]
　[Welding metal and welding joint
　] From an ingot obtained by melting and casting a material having a chemical composition shown in Table 3 in a laboratory, by hot forging, hot rolling, cold rolling, heat treatment and machining, a plate thickness of 12 mm, A plate material (plate material (1)) having a width of 50 mm and a length of 120 mm was produced. The plate material (1) was used as a welding base material.
[0105]
　Furthermore, a plate material having a thickness of 4 mm, a width of 200 mm, and a length of 500 mm was formed by hot forging, hot rolling, heat treatment and machining from an ingot obtained by melting and casting a material having a chemical composition shown in Table 4 in a laboratory ( A plate material (2) was produced. A cut filler of 2 mm square and 500 mm length was produced from the plate material (2) by machining.
[0106]
[Table 3]

[0107]
[Table 4]

[0108]
　After processing a V groove having an angle of 30° and a root face (root face) of 1 mm in the longitudinal direction of the plate material (1), a commercially available steel plate (SM400B specified in JIS G 3160 (2008), thickness 25 mm, A width of 150 mm and a length of 200 mm) was restrained and welded on four sides using a covered arc welding rod (“DNiCrFe-3” specified in JIS Z3224 (1999)).
[0109]
　Then, using the produced cut filler, laminated welding was performed in the groove by manual TIG welding using Ar as a shielding gas to produce a welded joint. During welding, the heat input was 9 kJ/cm to 15 kJ/cm.
[0110]
　In the cross section obtained by cutting the weld metal of the obtained welded joint perpendicularly to the longitudinal direction, the widthwise center and the sheet thickness direction center were cut by a drill by about 1 mm to collect chips, and the weld metal was chemically analyzed. Table 5 shows the results.
[0111]
[Table 5]

[0112]
　[Welding crack resistance]
　Samples were taken from five points of the weld metal of each welded joint produced so that the observation surface was the cross section of the joint (cross section perpendicular to the weld bead). The collected sample was mirror-polished and corroded, and then examined under an optical microscope to examine the presence or absence of cracks in the weld metal. Weld joints in which no cracks were observed in all five samples and weld joints in which cracks were observed in one sample were judged as "pass". Welded joints in which cracks were observed in two or more samples were judged as "fail".
[0113]
　[Creep Rupture Test] From
　each welded joint, a round bar creep rupture test piece with the weld metal in the center of the parallel portion was sampled. Then, a creep rupture test is performed under the conditions of 750° C. and 127 MPa, and those having a rupture time of more than 1000 hours, which is about 80% of the target rupture time of the base material, are regarded as “pass”, and those having a rupture time of 1000 hours or less are “passed”. Rejected.
[0114]
　Table 6 also shows the results of the above tests.
[0115]
[Table 6]

[0116]
　From Table 6, the welded joints having the weld metals of the symbols A1 to A4, B1 to B4, C1 to C4, and D1 to D4, whose chemical compositions are within the range specified by the present invention, have low weld hot cracking susceptibility and creep. It is clear that the breaking time satisfies 80% or more of the target breaking time of the base material.
[0117]
　On the other hand, in the welded joints having the weld metals A5 and B5, the W content of the weld metal was less than 4.5%, which is the lower limit of the range of the present invention, and thus the creep strength was less than the target. .. Furthermore, in the welded joints having the weld metals A6 and B6, the Si content of the weld metal exceeded the upper limit of 0.6% of the range of the present invention, so the creep strength was below the target. Further, in the welded joints having the weld metals A7 and B7, the B content of the weld metal exceeded 0.005%, which is the upper limit of the range of the present invention, so that the weld hot cracking susceptibility was increased. Further, in the welded joints having the weld metals A8 and B8, the Nb content of the weld metal exceeded 0.5%, which is the upper limit of the range of the present invention, so that the weld hot crack susceptibility was increased. Further, in the welded joints having the weld metals A9 and B9, the value of fn1 was less than 10.0, so the creep strength was below the target.
[0118]
　As described above, the weld metal satisfying the requirements of the present invention has low hot cracking susceptibility and also satisfies the creep strength required as a welded structure, so that the performance of the high nitrogen, high nickel content austenitic heat resistant steel is sufficient. You can see that it can be used.
Industrial availability
[0119]
　Utilizing the present invention, when using a high nitrogen and high nickel content austenitic heat resistant steel as a welded structure, its performance can be fully utilized, low hot crack sensitivity, excellent austenitic heat resistant steel weld metal. And a welded joint having the same can be provided. Therefore, the weld metal of the present invention and the weld joint having the same are high-nitrogen and high-nickel-containing austenitic heat-resistant steel, and the weld metal constituting a welded structure applied to equipment used at high temperatures such as a boiler for thermal power generation. And is useful as a welded joint having it.
The scope of the claims
[Claim 1]
　The chemical composition is% by mass,
　C: 0.06% to 0.14%,
　Si: 0.1% to 0.6%,
　Mn: 0.1% to 1.8%,
　P: 0.025% Below,
　S: 0.003% or less,
　Ni: 25% to 35%,
　Cr: 20% to 24%,
　W: more than 4.5% and 7.5% or less,
　Nb: 0.05% to 0.5 %,
　V: 0.05% to 0.4%,
　N: 0.1% to 0.35%,
　Al: 0.08% or less,
　O: 0.08% or less,
　B: 0.0005 to 0. 005%,
　Ti: 0% to 0.25%,
　Cu: 0% to 4%,
　Co: 0% to 2%,
　Mo: 0% to 2%,
　Ta: 0% to 1%,
　Ca: 0% to 0.02%,
　Mg: 0% to 0.02%,
　REM: 0% to 0.06%,
　balance: Fe and impurities,
　An austenitic heat resistant steel weld metal, wherein fn1 represented by the following formula (1) is 10 or more.
　　fn1=10(Nb+V)+1.5W+20N+1500B-25Si (1) In
　Nb, V, W, N, B, and Si in the formula (1), the content of the corresponding element is substituted in mass %. R.
[Claim 2]
　The austenitic heat-resisting steel weld metal according to claim 1,
　wherein the chemical composition is mass%
　: Ti: 0.01% to 0.25%,
　Cu: 0.01% to 4%,
　Co:0.
　0.01 % to 2%, Mo: 0.01% to 2%,
　Ta: 0.01% to 1%,
　Ca: 0.0005% to 0.02%,
　Mg: 0.0005% to 0.02% , And
　REM: 0.0005% to 0.06%,
　an austenitic heat resistant steel weld metal containing one or more elements selected from the group consisting of 0.0005% to 0.06% .
[Claim 3]
　A
　welded joint comprising the austenitic heat resistant steel weld metal according to claim 1 or 2 and a base material of the austenitic heat resistant steel.
[Claim 4]
　The welded joint according to claim 3,
　wherein the chemical composition of the base material is
　C: 0.02% to 0.14%,
　Si: 0.05% to 1%,
　Mn: 0. 1% to 3%,
　P: 0.04% or less,
　S: 0.002% or less,
　Ni: 26% to 35%,
　Cr: 20% to 26%,
　W: 1% to 7%,
　Nb: 0. 01% to 1%,
　V: 0.01% to 1%,
　N: 0.1% to 0.6%,
　B: 0.0005% to 0.008%,
　REM: 0.003% to 0.06 %,
　Al: 0.3% or less,
　O: 0.02% or less,
　Ti: 0% to 0.5%,
　Co: 0% to 2%,
　Cu: 0% to 4%,
　Mo: 0% to 4 %,
　Ta: 0% to 1%,
　Ca: 0% to 0.02%,
　Mg: 0% to 0.02%,
　balance: Fe and impurities, welded joint.
[Claim 5]
　The welded joint according to claim 4,
　wherein the chemical composition of the base material is, in mass %,
　Ti: 0.01% to 0.5%,
　Co: 0.01% to 2%,
　Cu: 0. 01% to 4%,
　Mo: 0.01% to 4%,
　Ta: 0.01% to 1%,
　Ca: 0.0005% to 0.02%, and
　Mg: 0.0005% to 0.02% A
　welded joint containing one or more selected from the group consisting of.
[Claim 6]
　The chemical composition is% by mass,
　C: 0.06% to 0.14%,
　Si: 0.1% to 0.4%,
　Mn: 0.1% to 1.2%,
　P: 0.01% Below,
　S: 0.003% or less,
　Ni: 28% to 35%,
　Cr: 20% to 24%,
　W: more than 4.5% and 7.5% or less,
　Nb: 0.05% to 0.5 %,
　V: 0.05% to 0.35%,
　N: 0.1% to 0.35%,
　Al: 0.08% or less,
　O: 0.08% or less,
　B: 0.0005 to 0. 005%,
　Ti: 0% to 0.25%,
　Cu: 0% to 4%,
　Co: 0% to 2%,
　Mo: 0% to 2%,
　Ta: 0% to 1%,
　Ca: 0% to 0.02%,
　Mg: 0% to 0.02%,
　REM: 0% to 0.06%,
　balance: Fe and impurities,
　A welding material for austenitic heat-resistant steel, wherein fn1 represented by the following formula (1) is 10 or more.
　　fn1=10(Nb+V)+1.5W+20N+1500B-25Si (1) In
　Nb, V, W, N, B, and Si in the formula (1), the content of the corresponding element is substituted in mass %. R.
[Claim 7]
　The welding material for austenitic heat-resistant steel according to claim 6,
　wherein the chemical composition is mass%
　: Ti: 0.01% to 0.25%,
　Cu: 0.01% to 4%,
　Co: 0.01% to 2%,
　Mo: 0.01% to 2%,
　Ta: 0.01% to 1%,
　Ca: 0.0005% to 0.02%,
　Mg: 0.0005% to 0.02 %, and
　REM: 0.0005% to 0.06%, a
　welding material for austenitic heat-resisting steel, containing one or more elements selected from the group consisting of 0.0005% to 0.06% .
[Claim 8]
　A method for producing the welded joint according to
　claim 4, wherein the base material having the chemical composition according to claim 4 is welded using the welding material for austenitic heat resistant steel according to claim 6. Joint manufacturing method.