Specification
Title of invention: Austenitic stainless steel weld metal and welded structure
Technical field
[0001]
　The present invention relates to an austenitic stainless steel weld metal and a welded structure having the same.
Background technology
[0002]
　TP316H regulated by American Society of Mechanical Engineers (ASME) SA213 and SA213M contains Mo and has excellent corrosion resistance at high temperature, so it is widely used as a material for heat transfer tubes and heat exchangers in thermal power plants and petrochemical plants. Has been done.
[0003]
　For example, Patent Literature 1 proposes an austenitic stainless steel containing Mo and Ce in the same manner as TP316H to improve high-temperature corrosion resistance. Further, Patent Document 2 proposes an austenitic stainless steel containing Nb, Ta and Ti to further enhance high temperature strength.
[0004]
　By the way, these austenitic stainless steels are generally used as a welded structure having a weld metal. The weld metal obtained by using a commercially available welding material for Ni-based heat-resistant alloys (for example, JIS Z 3334 (2011) SNi6082) is stable and has sufficient performance in terms of creep strength and toughness. It is expensive because it contains a large amount of. On the other hand, a weld metal obtained by using a commercially available welding material for Mo-containing stainless steel (JIS Z 3321 (2010) YS16-8-2) is inexpensive but has a brittle and hard σ phase during use at high temperatures. However, there is a problem in that the creep strength is greatly reduced.
[0005]
　Therefore, in Patent Document 3, the content of C and N is defined, and the creep strength is enhanced by positively utilizing Nb and Cu, and the content of P and B is further reduced. An inert gas shielded welding wire for Mo-containing austenitic stainless steel with improved weld crack resistance has been proposed. Further, in Patent Document 4, the balance between the Cr equivalent and the Ni equivalent is adjusted, and the welding strength for Mo-containing austenitic stainless steel that utilizes Nb and Cu to achieve both the creep strength and the reheat cracking resistance during heat treatment is compatible. Materials have been proposed.
Prior art documents
Patent literature
[0006]
Patent Document 1: JP 57-2869 JP
Patent Document 2: JP 61-23749 Patent Publication
Patent Document 3: JP-A 9-300096 Patent Publication
Patent Document 4: JP 2000-102891 JP
Summary of the invention
Problems to be Solved by the Invention
[0007]
　However, in the weld metal obtained by using the welding material described in Patent Document 1 or 2, for example, when the weld metal is used as a thick welded structure such as in an actual large-scale plant, highly restrained welding is performed. In the joint shape, it became clear that weld cracks may exist in the weld metal. Therefore, it is required to suppress weld cracking and realize excellent weld crack resistance.
[0008]
　On the other hand, even if weld cracking is suppressed, the welded structure may be inferior in creep strength when exposed to a high temperature environment (for example, 650° C. environment). Therefore, in addition to weld crack resistance, stability in high temperature environment It is required to realize such creep strength.
[0009]
　The present invention is a weld metal constituting a structure used in equipment used at high temperatures, which is an austenitic stainless steel weld metal having excellent weld crack resistance and high creep strength, and a welded structure having the same. For the purpose of providing.
Means for solving the problem
[0010]
　The present invention has been made in order to solve the above problems, and has as its gist the following austenitic stainless steel weld metal and welded structure.
[0011]
　(1) Chemical composition in mass %,
　C: 0.01 to 0.10%,
　Si: 0.20 to 0.70%,
　Mn: 0.8 to 2.5%,
　P: 0.035% Hereinafter,
　S: 0.0030% or less,
　Cu: 0.01 to 0.60%,
　Co: 0.01 to 1.00%,
　Ni: 8.0 to 12.0%,
　Cr: 14.5 to 17 0.5%,
　Mo: 1.0 to 2.2%,
　N: 0.02 to 0.10%,
　Al: 0.030% or less,
　O: 0.020% or less,
　Sn: 0 to 0.01% , 　Sb:
　0 ~ 0.01%, 　As: 0 ~ 0.01%, Bi: 0 ~ 　0.01%, V: 0 ~ 0.10%, Nb: 0 ~ 　0.10%, Ti: 0 ~ 0.10%, 　W:0 to 0.50%, 　B:0 to 0.005%, 　Ca:0 to 0.010%, 　Mg:0 to 0.010%,

　REM: 0 to 0.10%,
　balance: Fe and impurities,
　an
　austenitic stainless steel weld metal satisfying the following formulas (i) and (ii) .
　　17.5≦Cr+Mo+1.5×Si≦19.5 (i)
　　11.0≦Ni+30×(C+N)+0.5×(Mn+Cu+Co)≦17.0 (ii)
　However, in the above formula The element symbol of represents the content (mass %) of each element contained in the steel.
[0012]
　(2)
　The austenitic stainless steel according to (1), wherein the chemical composition contains, in mass%, one or more kinds selected from Sn, Sb, As and Bi in total of more than 0% and 0.01% or less. Steel weld metal.
[0013]
　(3) The chemical composition is% by mass,
　V: 0.01 to 0.10%,
　Nb: 0.01 to 0.10%,
　Ti: 0.01 to 0.10%,
　W: 0.01 ~ 0.50%,
　B: 0.0002 to 0.005%,
　Ca: 0.0005 to 0.010%,
　Mg: 0.0005 to 0.010%, and
　REM: 0.0005 to 0.10. %, 　the austenitic stainless steel weld metal according
　to the
above (1) or (2), containing at least one selected from the group consisting of:
[0014]
　(4) A welded structure comprising the austenitic stainless steel weld metal according to any one of (1) to (3) above.
Effect of the invention
[0015]
　According to the present invention, an austenitic stainless steel weld metal having a weld creep resistance and a high creep strength, which constitutes a structure used in equipment used at high temperatures, and a weld metal having the same A structure can be obtained.
Brief description of the drawings
[0016]
FIG. 1 is a schematic cross-sectional view showing the shape of a plate material that is groove processed in an example.
MODE FOR CARRYING OUT THE INVENTION
[0017]
　The present inventors conducted a detailed investigation in order to achieve both excellent weld crack resistance and stable creep strength as a structure. As a result, the following findings have been obtained.
[0018]
　As a result of investigating cracks generated in the austenitic stainless steel weld metal containing Mo, (a) cracks were generated at a position slightly apart from the columnar crystal association part of the weld metal and the lamination boundary of multilayer welding, (b) It has been found that the former is likely to occur in a component system in which the stability of the austenite phase is high, and (c) the latter is likely to occur when the S content is high.
[0019]
　From this, the former is so-called solidification cracking, where the stability of the austenite phase is increased, the solidification morphology of the weld metal is changed, P and S are likely to be solidified and segregated, and the melting point of the residual liquid phase is lowered. It was considered that the liquid film existed in the association part of the columnar crystals for a long time, and that part was a crack caused by opening due to thermal stress. The latter is a so-called ductility-decreasing crack, in which S segregated at the grain boundary in the thermal cycle of the subsequent pass during welding reduces the bond strength of the grain boundary, thermal stress exceeds the bond strength, and cracks formed by opening Was considered to be.
[0020]
　As a result of repeated studies, in order to prevent cracking in the austenitic stainless steel weld metal having the composition targeted by the present invention, Cr+Mo+1.5×Si is set to 17.5 or more, and Ni+30×( It has been found that it is necessary to limit C+N)+0.5×(Mn+Cu+Co) to 17.0 or less and to limit the S content to 0.0030% or less. In addition, it has been found that it is necessary to contain Cu and Co in a predetermined amount or more in order to sufficiently obtain the effect of reducing the weld crack susceptibility.
[0021]
　By the way, although the weld crack resistance of the weld metal was secured by these measures, Cr+Mo+1.5×Si exceeded 19.5, or Ni+30×(C+N)+0.5×(Mn+Cu+Co) was less than 11.0. On the contrary, it became clear that the austenite phase becomes unstable and the σ phase is generated during use at high temperature, and the creep strength is greatly reduced.
[0022]
　Further, S has an effect of increasing the penetration depth during the formation of the weld metal, and particularly improving the weldability during the initial layer welding, while having an adverse effect on the weld cracking. From the viewpoint of weld cracking, it was found that when the S content was controlled to 0.0030% or less, a sufficient penetration depth could not be obtained. To solve this, simply increasing the welding heat input during the formation of the weld metal increases the susceptibility to weld cracking.
[0023]
　Therefore, it was also found that it is effective to contain at least one selected from Sn, Sb, As, and Bi in a predetermined range in order to sufficiently obtain this effect. This is because these elements affect the convection of the molten pool during welding during the formation of the weld metal, and also evaporate from the surface of the molten pool and contribute to the formation of current-carrying paths, which promotes melting in the depth direction. It was thought to be to do so.
[0024]
　The present invention has been made based on the above findings. Hereinafter, each requirement of the present invention will be described in detail.
[0025]
　(A) Chemical composition The
　reasons for limiting each element are as follows. In addition, in the following description, "%" regarding the content means "mass %".
[0026]
　C: 0.01 to 0.10%
　C stabilizes the austenite phase and also combines with Cr to form fine carbides, which improves the creep strength during high temperature use. However, when C is excessively contained, a large amount of carbide is precipitated, which causes embrittlement. Therefore, the C content is set to 0.01 to 0.10%. The C content is preferably 0.02% or more, more preferably 0.03% or more. The C content is preferably 0.09% or less, more preferably 0.08% or less.
[0027]
　Si: 0.20 to 0.70%
　Si has a deoxidizing effect and is an element necessary for ensuring corrosion resistance and oxidation resistance at high temperatures. However, when Si is excessively contained, the stability of the austenite phase is lowered, and the creep strength is lowered. Therefore, the Si content is set to 0.20 to 0.70%. The Si content is preferably 0.25% or more, more preferably 0.30% or more. The Si content is preferably 0.60% or less, more preferably 0.50% or less.
[0028]
　Mn: 0.8 to 2.5%
　Mn is an element having a deoxidizing action, like Si. It also stabilizes the austenite phase and contributes to the improvement of creep strength. However, if the Mn content becomes excessive, the creep ductility decreases. Therefore, the Mn content is 0.8 to 2.5%. The Mn content is preferably 0.9% or more, more preferably 1.0% or more. The Mn content is preferably 2.2% or less, more preferably 2.0% or less.
[0029]
　P: 0.035% or less
　P is an element which is contained as an impurity and is solidified and segregated during welding to lower the melting point of the remaining liquid phase and enhance solidification cracking susceptibility. Furthermore, creep ductility is also reduced. Therefore, the upper limit of P content is set to 0.035% or less. The P content is preferably 0.032% or less, more preferably 0.030% or less. It is preferable to reduce the P content as much as possible, that is, the P content may be 0%, but the extreme reduction causes an increase in cost at the time of manufacturing the material. Therefore, the P content is preferably 0.0005% or more, more preferably 0.0008% or more.
[0030]
　S: 0.0030% or less
　S is contained as an impurity like P, and solidifies and segregates during welding to lower the melting point of the residual liquid phase and enhance solidification cracking susceptibility. Further, after solidification, the thermal cycle of the subsequent pass segregates the grain boundaries to increase the ductility-decay crack susceptibility. Therefore, the upper limit of S content is set to 0.0030% or less. The S content is preferably less than 0.0025%, more preferably 0.0020% or less. It is preferable to reduce the S content as much as possible, that is, the S content may be 0%, but the extreme reduction causes an increase in cost at the time of manufacturing the material. Therefore, the S content is preferably 0.0001% or more, and more preferably 0.0002% or more.
[0031]
　Cu: 0.01 to 0.60%
　Cu enhances the stability of the austenite phase and contributes to the improvement of creep strength. Further, as compared with Ni and Mn, the effects on segregation energies of P and S are small, and the effects of reducing solidification segregation and reducing weld crack susceptibility can be expected. However, when Cu is contained excessively, ductility is lowered. Therefore, the Cu content is 0.01 to 0.60%. The Cu content is preferably 0.02% or more, more preferably 0.03% or more. Further, the Cu content is preferably 0.55% or less, more preferably 0.50% or less.
[0032]
　Co: 0.01 to 1.00%
　Like Cu, Co is an element that enhances the stability of the austenite phase and contributes to the improvement of creep strength. Further, as compared with Ni and Mn, the effects on segregation energies of P and S are small, and the effects of reducing solidification segregation and reducing weld crack susceptibility can be expected. However, since Co is an expensive element, excessive inclusion causes an increase in the manufacturing cost of the material. Therefore, the Co content is set to 0.01 to 1.00%. The Co content is preferably 0.02% or more, more preferably 0.03% or more. Further, the Co content is preferably 0.90% or less, and more preferably 0.80% or less.
[0033]
　Ni: 8.0 to 12.0%
　Ni is an essential element for ensuring the stability of the austenite phase during long-term use. However, Ni is an expensive element, and a large amount of Ni causes an increase in the manufacturing cost of the material. Therefore, the Ni content is set to 8.0 to 12.0%. The Ni content is preferably 8.2% or more, and more preferably 8.5% or more. Further, the Ni content is preferably 11.8% or less, more preferably 11.5% or less.
[0034]
　Cr: 14.5 to 17.5%
　Cr is an essential element for ensuring the oxidation resistance and corrosion resistance at high temperatures. It also contributes to the formation of fine carbides to secure the creep strength. However, a large content lowers the stability of the austenite phase and, conversely, impairs the creep strength. Therefore, the Cr content is set to 14.5 to 17.5%. The Cr content is preferably 15.0% or more, and more preferably 15.5% or more. Further, the Cr content is preferably 17.2% or less, and more preferably 17.0% or less.
[0035]
　Mo: 1.0 to 2.2%
　Mo 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. In addition, it is also effective in improving corrosion resistance. However, if contained excessively, the stability of the austenite phase is lowered and the creep strength is impaired. Furthermore, since Mo is an expensive element, excessive inclusion causes an increase in the manufacturing cost of the material. Therefore, the Mo content is set to 1.0 to 2.2%. The Mo content is preferably 1.1% or more, more preferably 1.2% or more. Further, the Mo content is preferably 2.1% or less, and more preferably 2.0% or less.
[0036]
　N: 0.02 to 0.10%
　N stabilizes the austenite phase and also forms a solid solution or precipitates as a nitride to contribute to the improvement of high temperature strength. However, if it is contained excessively, ductility is lowered. Therefore, the N content is set to 0.02 to 0.10%. The N content is preferably 0.03% or more, more preferably 0.04% or more. The N content is preferably 0.09% or less, more preferably 0.08% or less.
[0037]
　Al: 0.030% or less When
　Al is contained in a large amount, the cleanability deteriorates and the ductility decreases. Therefore, the Al content is 0.030% or less. The Al content is preferably 0.025% or less, more preferably 0.020% or less. It is not necessary to set a lower limit on the Al content, that is, the Al content may be 0%, but an extreme reduction leads to an increase in the manufacturing cost of the material. Therefore, the Al content is preferably 0.0005% or more, more preferably 0.001% or more.
[0038]
　O: 0.020% or less
　O (oxygen) is included as an impurity. If the content is excessive, toughness and ductility are deteriorated. Therefore, the O content is 0.020% or less. The O content is preferably 0.018% or less, and more preferably 0.015% or less. Note that it is not necessary to set a lower limit for the O content, that is, the O content may be 0%, but an extreme reduction causes an increase in the manufacturing cost of the material. Therefore, the O content is preferably 0.0005% or more, more preferably 0.0008% or more.
[0039]
　As mentioned above, Cr, Mo and Si affect the stability of the austenite phase. Therefore, not only the content of each element falls within the above range, but also the following formula (i) needs to be satisfied. When the median value of the formula (i) exceeds 19.5, the stability of the austenite phase is reduced, and a brittle σ phase is generated during use at high temperature to lower the creep strength. On the other hand, when it is less than 17.5, the stability of the austenite phase is enhanced, but hot cracking during welding is likely to occur. The value on the left side of the equation (i) is preferably 17.8, and more preferably 18.0. On the other hand, the value on the right side of the expression (i) is preferably 19.2, and more preferably 19.0.
　　17.5≦Cr+Mo+1.5×Si≦19.5 (i)
　However, the element symbol in the above formula represents the content (% by mass) of each element contained in the steel.
[0040]
　Further, Ni, C, N, Mn, Cu and Co affect the stability of the austenite phase. Therefore, not only the content of each element falls within the above range, but also the following formula (ii) needs to be satisfied. When the median value of the formula (ii) is less than 11.0, the stability of the austenite phase is not sufficient, and a brittle σ phase is generated during use at high temperature to lower the creep strength. On the other hand, if it exceeds 17.0, the austenite phase becomes excessively stable, and hot cracking during welding tends to occur. The value on the left side of the equation (ii) is preferably 11.2, more preferably 11.5. On the other hand, the value on the right side of the equation (ii) is preferably 16.8, and more preferably 16.5.
　　11.0≦Ni+30×(C+N)+0.5×(Mn+Cu+Co)≦17.0 (ii)
　However, the element symbol in the above formula is the content (mass %) of each element contained in the steel. Represents.
[0041]
　In the chemical composition of the weld metal of the present invention, in addition to the above elements, one or more selected from Sn, Sb, As and Bi may be contained in the range shown below. The reason will be described.
[0042]
　Sn: 0 to 0.01%
　Sb: 0 to 0.01%
　As: 0 to 0.01%
　Bi: 0 to 0.01%
　Sn, Sb, As and Bi are used to form a weld metal, that is, during welding. The penetration depth is increased by affecting the convection of the molten pool and promoting heat transfer in the vertical direction of the molten pool, or by evaporating from the surface of the molten pool to form a current-carrying path and increasing the concentration of the arc. Have the effect of Therefore, one or more selected from these elements may be contained if necessary. However, excessive content increases weld cracking susceptibility, so the content of any element is set to 0.01% or less. The content of each element is preferably 0.008% or less, and more preferably 0.006% or less.
[0043]
　In order to obtain the above effect, the content of one or more selected from the above elements is preferably more than 0%, more preferably 0.0005% or more, and 0.0008% or more. Is more preferable, and 0.001% or more is even more preferable. When two or more elements selected from these elements are contained in a composite manner, the total content thereof is preferably 0.01% or less, more preferably 0.008% or less, It is more preferably 0.006% or less.
[0044]
　In the chemical composition of the weld metal of the present invention, in addition to the above elements, one or more selected from V, Nb, Ti, W, B, Ca, Mg and REM is further contained in the range shown below. Good. The reasons for limiting each element will be described.
[0045]
　V: 0 to 0.10%
　V combines with C and/or N to form fine carbides, nitrides or carbonitrides and contributes to creep strength, so V may be contained if necessary. .. However, if it is contained excessively, a large amount of carbonitrides are deposited, which causes a decrease in creep ductility. Therefore, the V content is 0.10% or less. The V content is preferably 0.09% or less, more preferably 0.08% or less. When it is desired to obtain the above effect, the V content is preferably 0.01% or more, more preferably 0.02% or more.
[0046]
　Nb: 0 to 0.10%
　Similar to V, Nb combines with C and/or N and precipitates in the grains as fine carbides, nitrides or carbonitrides, and creep strength and tensile strength at high temperature. Since it is an element that contributes to the improvement of the above, it may be contained if necessary. However, if it is contained in excess, a large amount of carbonitride precipitates, leading to a decrease in creep ductility. Therefore, the Nb content is 0.10% or less. The Nb content is preferably 0.08% or less, more preferably 0.06% or less. In order to obtain the above effect, the Nb content is preferably 0.01% or more, more preferably 0.02% or more.
[0047]
　Ti: 0 to 0.10%
　Similar to V and Nb, Ti combines with C and/or N to form fine carbide, nitride or carbonitride, and contributes to creep strength. May be included. However, if it is contained excessively, a large amount of carbonitrides are deposited, which causes a decrease in creep ductility. Therefore, the Ti content is 0.10% or less. The Ti content is preferably 0.08% or less, more preferably 0.06% or less. In order to obtain the above effect, the Ti content is preferably 0.01% or more, more preferably 0.02% or more.
[0048]
　W: 0 to 0.50%
　W is an element which, like Mo, forms a solid solution in the matrix and contributes to the improvement of creep strength and tensile strength at high temperatures, so W may be contained if necessary. However, if it is contained excessively, the stability of the austenite phase is lowered and the creep strength is rather lowered. Therefore, the W content is 0.50% or less. The W content is preferably 0.40% or less, more preferably 0.30% or less. In order to obtain the above effect, the W content is preferably 0.01% or more, more preferably 0.02% or more.
[0049]
　B: 0 to 0.005%
　B is also constant in that the grain boundary carbides are finely dispersed to improve the creep strength, and segregate at the grain boundaries to strengthen the grain boundaries to reduce the ductility-decay cracking susceptibility. Therefore, it may be contained if necessary. However, when it is contained excessively, the solidification cracking susceptibility is increased. Therefore, the B content is 0.005% or less. The B content is preferably 0.004% or less, and more preferably 0.003% or less. When it is desired to obtain the above effects, the B content is preferably 0.0002% or more, more preferably 0.0005% or more.
[0050]
　Ca: 0 to 0.010% Since
　Ca has an effect of improving hot deformability, it may be contained if necessary. However, if it is contained in excess, it binds to oxygen, significantly deteriorating the cleanliness and conversely deteriorating the hot deformability. Therefore, the Ca content is 0.010% or less. The Ca content is preferably 0.008% or less, more preferably 0.005% or less. When it is desired to obtain the above effects, the Ca content is preferably 0.0005% or more, more preferably 0.001% or more.
[0051]
　Mg: 0 to 0.010%
　Similar to Ca, Mg has an effect of improving hot deformability, and thus may be contained if necessary. However, if it is contained in excess, it binds to oxygen, significantly deteriorating the cleanliness and conversely deteriorating the hot deformability. Therefore, the Mg content is 0.010% or less. The Mg content is preferably 0.008% or less, more preferably 0.005% or less. In order to obtain the above effect, the Mg content is preferably 0.0005% or more, more preferably 0.001% or more.
[0052]
　REM: 0 to 0.10%
　Similar to Ca and Mg, REM has an effect of improving hot deformability, and thus may be contained if necessary. However, if it is contained in excess, it binds to oxygen, significantly deteriorating the cleanliness and conversely deteriorating the hot deformability. Therefore, the REM content is 0.10% or less. The REM content is preferably 0.08% or less, more preferably 0.06% or less. In order to obtain the above effects, the REM content is preferably 0.0005% or more, more preferably 0.001% or more.
[0053]
　Here, REM refers to a total of 17 elements of Sc, Y and lanthanoid, and the content of the REM means the total content of these elements.
[0054]
　In the chemical composition of the weld metal of the present invention, the balance is Fe and impurities. Here, the "impurity" is a component that is mixed in by raw materials such as ore and scrap when manufacturing steel industrially, and various factors in the manufacturing process, and is allowed within a range that does not adversely affect the present invention. Means something.
[0055]
　(B) Manufacturing Method
　The austenitic stainless steel weld metal according to the present invention is produced by welding a base material of austenitic stainless steel. In addition, when welding the base material, the austenitic stainless steel weld metal may be produced by using a welding material (a filler material).
[0056]
　The welding method for obtaining the austenitic stainless steel weld metal according to the present invention is not particularly limited, but examples thereof include TIG welding, MIG welding, covered arc welding, submerged arc welding, and laser welding.
[0057]
　As a method of producing an austenitic stainless steel weld metal so as to satisfy the above chemical composition, a method of controlling by adjusting the chemical composition of the base material of the austenitic stainless steel to be used, and further a welding material (filler material) When used, a method of controlling by also adjusting the chemical composition of the welding material can be mentioned.
[0058]
　For example, as the base material and welding material (filler material) of the austenitic stainless steel to be used, only the material satisfying the above chemical composition may be used so that the obtained weld metal may satisfy the above chemical composition. Further, by using a material that does not satisfy the above chemical composition as at least one of the base material and the welding material (filler material) of austenitic stainless steel, the weld metal obtained by adjusting the balance between the two compositions May be prepared so as to satisfy the above chemical composition.
[0059]
　The preferable composition of the austenitic stainless steel base material is not particularly limited. For example, the chemical composition of the base material is C: 0.04 to 0.12%, Si: 0.25 to 0.55%, Mn: 0.7 to 2.0%, and P: 0. 035% or less, S: 0.0015% or less, Cu: 0.02 to 0.80%, Co: 0.02 to 0.80%, Ni: 10.0 to 14.0%, Cr: 15.5. Up to 17.5%, Mo: 1.5 to 2.5%, N: 0.01 to 0.10%, Al: 0.030% or less, O: 0.020% or less, Sn: 0 to 0. 01%, Sb:0 to 0.01%, As:0 to 0.01%, Bi:0 to 0.01%, V:0 to 0.10%, Nb:0 to 0.10%, Ti: 0 to 0.10%, W: 0 to 0.50%, B: 0 to 0.005%, Ca: 0 to 0.010%, Mg: 0 to 0.010%, REM: 0 to 0.10. %, balance: Fe and impurities are preferred.
[0060]
　The chemical composition of the base material may contain, in mass%, one or more selected from Sn, Sb, As and Bi in total of more than 0% and 0.01% or less. Further, the chemical composition of the base material is, in mass %, V: 0.01 to 0.10%, Nb: 0.01 to 0.10%, Ti: 0.01 to 0.10%, W:0. 0.01 to 0.50%, B: 0.0002 to 0.005%, Ca: 0.0005 to 0.010%, Mg: 0.0005 to 0.010%, and REM: 0.0005 to 0. 10% may be included.
[0061]
　The method for producing the base material and welding material (filler material) of the above austenitic stainless steel is not particularly limited, but for the steel whose chemical composition is adjusted, hot forging, heat It can be manufactured by sequentially performing hot rolling, heat treatment, and machining.
[0062]
　(C) Welded structure The welded structure according to the
　present invention is a structure having the above-described austenitic stainless steel weld metal. For example, a welded structure is composed of a weld metal and a base material. The base material is made of a metal and is preferably a steel material, more preferably stainless steel, and further preferably an austenitic stainless steel. The specific shape of the welded structure and the specific mode (welding posture) of welding for obtaining the welded structure are not particularly limited.
[0063]
　Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.
Example 1
[0064]
　A plate material (base material) having a plate thickness of 15 mm, a width of 50 mm, and a length of 100 mm was formed from an ingot obtained by melting and casting steel having the chemical composition shown in Table 1 by hot forging, hot rolling, heat treatment and machining. A plate material having a plate thickness of 4 mm, a width of 200 mm and a length of 500 mm was produced. Further, using the above plate material having a plate thickness of 4 mm, a cut filler having a 2 mm square and a length of 500 mm was produced by machining. Using these, various performance evaluation tests shown below were performed.
[0065]
[table 1]

[0066]
　
　A groove in the shape shown in FIG. 1 was applied to the longitudinal end of the base material. Then, two base materials having a groove formed therein were butted, and butt welding was performed by TIG welding without using a filler material. With a heat input of 8 kJ/cm, two weld joints were produced for each base material. Of the obtained welded joints, those in which the back bead was formed over the entire length of the welding line were considered to have good weldability and were designated as “passed”. Among them, those having a back bead width of 2 mm or more over the entire length were judged to be “good”, and those having a part less than 2 mm were judged to be “good”. In addition, in some of the two welded joints, if there was a portion where the back bead was not formed, it was determined as "fail".
[0067]
　
　After that, the above-mentioned welded joint, in which only the first layer was welded, was restrained and welded on a commercially available steel plate for four rounds. The commercially available steel plate was a steel plate specified in JIS G 3160 (2008) of SM400B, and had a thickness of 30 mm, a width of 150 mm, and a length of 200 mm. In addition, the above-mentioned constraint welding was performed using a covered arc welding rod ENi6625 specified in JIS Z 3224 (2010).
[0068]
　Then, laminated welding was performed by TIG welding in the groove. The above-mentioned lamination welding was performed using a cut filler obtained from the same plate material as each base material as a filler material. The heat input was 9 to 15 kJ/cm, and two welded joints were produced for each base material. Then, one of the welded joints manufactured from each base material was sampled from five test pieces. The cross section of the collected test piece was mirror-polished and then corroded, and observed by an optical microscope to examine the presence or absence of cracks in the weld metal. Then, in all of the five test pieces, a welded joint having no crack was judged as “pass”, and a welded joint in which crack was observed was judged as “fail”. The chemical composition of Table 1 is synonymous with the chemical composition of the weld metal, because the base metal of the first layer weld metal remains molten and the base metal and the cut filler have the same composition.
[0069]
　
　Furthermore, a round bar creep rupture test piece was sampled from the remaining one of the welded joints that passed the evaluation of weld cracking resistance so that the weld metal was at the center of the parallel portion, A creep rupture test was performed under the conditions of 650° C. and 167 MPa at which the target rupture time of the base metal was about 1000 hours. Then, the case where the breaking time was 90% or more of the target breaking time of the base material was defined as “pass”.
[0070]
　The results are summarized in Table 2.
[0071]
[Table 2]

[0072]
　As can be seen from Table 2, Test Nos. using Steels A to F satisfying the requirements of the present invention as both the base metal and the filler metal. In Nos. 1 to 6, the workability and weld cracking resistance required when producing a welded joint were obtained, and the creep strength was excellent. In addition, the test No. 4 and the test No. As can be seen by comparing 5 and 6, when S was reduced, the welding workability was improved by incorporating one or more selected from Sn, S, As and Bi.
[0073]
　On the other hand, since the S content of Steel G, which is a comparative example, is out of the regulation, the test No. In No. 7, cracks considered to be ductility-decreasing cracks were generated in the vicinity of the laminated boundary of the multi-layered weld metal. Further, Steel H was below the lower limit of the formula (ii) and Steel I was above the upper limit of the formula (i), so that the stability of the austenite phase was insufficient. As a result, the test No. In Nos. 8 and 9, the σ phase was generated in the high temperature creep test, and the required creep strength was not obtained.
[0074]
　Steel J exceeded the upper limit of the equation (ii), steel K was below the lower limit of the equation (i), and steel L was below the lower limit of the equation (i) and exceeded the upper limit of the equation (ii). Therefore, the test No. In Nos. 10 to 12, the stability of the austenite phase was excessively increased, solidification segregation of S and P was promoted during solidification of the weld metal, and cracks considered to be solidification cracks were generated in the weld metal.
[0075]
　Furthermore, since the steels M, N and O do not contain one or both of Cu and Co, the test No. In Nos. 13 to 15, the grain boundary segregation reducing effect of P and S was not obtained, and cracks considered to be solidification cracks occurred in the weld metal.
Example 2
[0076]
　A plate material (base material) having a plate thickness of 15 mm, a width of 50 mm, and a length of 100 mm is formed from an ingot obtained by melting and casting steel having the chemical composition shown in Table 3 by hot forging, hot rolling, heat treatment and machining. It was made. Using this, various performance evaluation tests shown below were performed.
[0077]
[Table 3]

[0078]
　
　A groove in the shape shown in FIG. 1 was applied to the end portion in the longitudinal direction of the base material. After that, two base materials having a groove formed therein were butted against each other and restrained at their four circumferences on a commercially available steel plate which was grooved so as not to interfere with the back bead. The commercially available steel plate was a steel plate specified in JIS G 3160 (2008) of SM400B, and had a thickness of 30 mm, a width of 150 mm, and a length of 200 mm. In addition, the above-mentioned constraint welding was performed using a covered arc welding rod ENi6625 specified in JIS Z 3224 (2010).
[0079]
　Then, laminated welding was performed by TIG welding in the groove. The above-mentioned lamination welding was performed using a cut filler obtained from a plate material of steel A as a filler material. The heat input was 9 to 15 kJ/cm, and two welded joints were produced for each base material. Then, with respect to one of the welded joints manufactured from each base material, cutting chips were collected from the weld metal, chemical analysis was performed, and test pieces were collected from five locations. The cross section of the collected test piece was mirror-polished and then corroded, and observed by an optical microscope to examine the presence or absence of cracks in the weld metal. Then, in all of the five test pieces, a welded joint having no crack was judged as “pass”, and a welded joint in which crack was observed was judged as “fail”.
[0080]
　
　Further, a round bar creep rupture test piece was sampled from the remaining one body of the welded joint so that the weld metal was located at the center of the parallel portion, and the target rupture time of the base metal was about 1000 hours 650. A creep rupture test was conducted under conditions of 167 MPa and 167 MPa. Then, the case where the breaking time was 90% or more of the target breaking time of the base material was defined as “pass”.
[0081]
　The results are summarized in Tables 4 and 5.
[0082]
[Table 4]

[0083]
[Table 5]

[0084]
　As can be seen from Tables 4 and 5, the test No. in which the chemical composition of the weld metal satisfies the requirements of the present invention. In Nos. 16 to 18, the workability and weld cracking resistance required when producing a welded joint were obtained, and the creep strength was excellent.
[0085]
　As described above, it is understood that the necessary weldability, weld crack resistance, and excellent creep strength can be obtained only when the requirements of the present invention are satisfied.
Industrial availability
[0086]
　According to the present invention, an austenitic stainless steel weld metal having a weld creep resistance and a high creep strength, which constitutes a structure used in equipment used at high temperatures, and a weld metal having the same A structure can be obtained.
The scope of the claims
[Claim 1]
　The chemical composition is% by mass,
　C: 0.01 to 0.10%,
　Si: 0.20 to 0.70%,
　Mn: 0.8 to 2.5%,
　P: 0.035% or less,
　S : 0.0030% or less,
　Cu: 0.01 to 0.60%,
　Co: 0.01 to 1.00%,
　Ni: 8.0 to 12.0%,
　Cr: 14.5 to 17.5% ,
　Mo:
　1.0 ~ 2.2%, N: 0.02
　~ 0.10%, Al: 0.030% or
　less, O: 0.020% or
　less, Sn: 0 ~
　0.01%, Sb: 0 to 0.01%,
　As: 0 to 0.01%,
　Bi: 0 to 0.01%,
　V: 0 to 0.10%,
　Nb: 0 to 0.10%,
　Ti: 0 to 0.10. %,
　W: 0 to 0.50%,
　B: 0 to 0.005%,
　Ca: 0 to 0.010%,
　Mg: 0 to 0.010%,
　REM: 0 to 0.10%,
　balance: Fe and impurities,
　an
　austenitic stainless steel weld metal satisfying the following formulas (i) and (ii) .
　　17.5≦Cr+Mo+1.5×Si≦19.5 (i)
　　11.0≦Ni+30×(C+N)+0.5×(Mn+Cu+Co)≦17.0 (ii)
　However, in the above formula The element symbol of represents the content (mass %) of each element contained in the steel.
[Claim 2]

　The austenitic stainless steel weld metal according to claim 1, 　wherein the chemical composition contains, in mass %, one or more selected from Sn, Sb, As and Bi in total of more than 0% and 0.01% or less .
[Claim 3]
　The chemical composition is% by mass,
　V: 0.01 to 0.10%,
　Nb: 0.01 to 0.10%,
　Ti: 0.01 to 0.10%,
　W: 0.01 to 0.
　% 50,
　B: 0.0002 ~
　0.005%, Ca: 0.0005 ~ 0.010%, Mg: 0.0005 ~ 0.010%,
　and, REM: 0.0005 ~ 0.10%,
　from
　The austenitic stainless steel weld metal according to claim 1 or 2, containing at least one selected .
[Claim 4]
　A welded structure comprising the austenitic stainless steel weld metal according to any one of claims 1 to 3.