0001]The present invention, welding material, relates to a process for the production of welded joints and welded joints, more particularly, welding material for ferritic heat-resistant steel, a method for producing a welded joint for ferritic heat-resistant steel for welded joints and ferritic heat-resistant steel.
Background technique
[0002]In recent years, the thermal power in order to increase the thermal efficiency, high temperature and high pressure of the steam conditions has been developed. In the future, 650 ° C., operating at ultra-supercritical conditions of 350 atm has been planned. Ferritic heat resistant steels are less expensive than austenitic heat-resistant steels and Ni-base heat-resistant steel. Ferritic heat-resistant steel further has the advantage of a heat-resistant steel that has a small thermal expansion coefficient. Therefore, the heat resistant ferritic steels are widely used in high temperature and high pressure environment.
[0003]
　JP-4-371551 (Patent Document 1), JP-A-4-371552 (Patent Document 2), and, JP 2002-241903 (Patent Document 3), future conditions as described above Suggest adaptable ferritic heat resistant steels severe of. Ferritic heat-resistant steels disclosed in Patent Documents 1 and 2, as well as optimize the W and Mo contents, containing Co and B. Accordingly, ferritic heat-resistant steels of these documents have a high strength. Furthermore, ferritic heat-resistant steel disclosed in Patent Document 3, M deposited on martensite lath boundaries 23 C 6 by active use of carbides and intermetallic phases, it has a high strength.
[0004]
　Meanwhile, the heat resistant ferritic steel is welded, which may be utilized in a structure as welded joints. In this case, the heat affected zone of welded joint (hereinafter, referred to as HAZ) creep strength may decrease. Therefore, JP 2004-300532 (Patent Document 4), JP-A-2010-7094 (Patent Document 5), and, WO 2008/149703 (Patent Document 6), a reduction creep strength at HAZ Suggest ferritic heat-resistant steel which suppresses. Ferritic heat-resistant steel disclosed in Patent Document 4, by containing B 0.003 ~ 0.03 wt% to suppress the grain refining in the HAZ. Accordingly, the creep strength reduction in HAZ is suppressed. Ferritic heat-resistant steels disclosed in Patent Documents 5 and 6, as well as contain a large amount of B, adjusting the C content in response to heat input or B content. Thus, while suppressing the strength reduction in the HAZ, liquation cracking during welding can be suppressed.
[0005]
　When welding ferritic heat resistant steel containing a large amount of B, and using general welding materials. Commercially available Ni-base heat-resistant alloy welding material (e.g., JIS Z 3334 (2011) SNi6082) weld metal formed with has a high creep strength and toughness. However, during welding, especially in the first layer weld dilution is large matrix, B flows from the base material in the weld metal. In this case, there is a case where solidification cracking occurs. Therefore, the welding material used for welding heat resistant ferritic steel containing B, not only a high creep strength and toughness of the weld metal obtained, also required solidification cracking suppression during welding.
[0006]
　JP-8-187592 (Patent Document 7), Japanese Patent 9-308989 (Patent Document 8), and, JP-A-9-122971 (Patent Document 9), creep strength, toughness and weldability Suggest excellent heat resistant ferritic steel for welding. Welding of Patent Document 7, the B containing 0.0005 to 0.006% by weight, and (Mo + W) / (Ni + Co) is 0.045 to 2.0. Welding of Patent Document 8, optionally together contain B 0.0005 ~ 0.006 wt%, (Mo + W) / (Ni + Co) and (0.5 × Co + 0.5 × Mn + Ni) is within a predetermined range There further, Cr eq is within a predetermined range. Welding of Patent Document 9, optionally can contain 0.02 mass% of B, further, a Mn content (0.0925-12.5 [% S])% to 2.0%, (Al + O) is less than 0.02%.
[0007]
　However, when used for welding heat resistant ferritic materials containing these welding material a large amount of B, sufficient creep strength of the weld metal may not be stably obtained.
CITATION
Patent Document
[0008]
Patent Document 1: JP-A-4-371551 JP
Patent Document 2: JP-A 4-371552 Patent Publication
Patent Document 3: JP 2002-241903 Patent Publication
Patent Document 4: JP 2004-300532 Patent Publication
Patent Document 5: JP 2010-7094 JP
Patent Document 6: WO 2008/149703 Patent
Patent Document 7: JP-a-8-187592
Patent Document 8: JP-a 9-308989 JP
Patent Document 9: JP-a 9-122971 JP
Summary of the Invention
Problems that the Invention is to Solve
[0009]
　An object of the present invention, in the case of welding the heat resistant ferritic steel containing B, high creep strength and the welding material for heat resistant ferritic steel weld metal capable of forming with toughness, heat resistant ferritic steel for welded joints and, it is to provide a method for producing a welded joint for ferritic heat resistant steels.
Means for Solving the Problems
[0010]
　Welding material for the heat resistant ferritic steel according to the invention, in mass%, C: 0.06 ~ 0.10% , Si: 0.1 ~ 0.4%, Mn: 0.3 ~ 0.7%, P 0.01% or less, S: 0.003% or less, Co: 2.6 ~ 3.4%, Ni: 0.01 ~ 1.10%, Cr: 8.5 ~ 9.5%, W: 2.5 ~ 3.5%, Mo: less than 0.01%, Nb: 0.02 ~ 0.08 %, V: 0.1 ~ 0.3%, Ta: 0.02 ~ 0.08%, B: 0.007 ~ 0.015%, N : 0.005 ~ 0.020%, Al: 0.03% or less, O: 0.02% or less, Cu: 0 ~ 1%, Ti: 0 ~ 0 .3% Ca: 0 - 0.05% Mg: 0 - 0.05% and rare earth element: 0 contain ~ 0.1%, with the balance being Fe and impurities, formula (1) having a chemical composition satisfying.
　0.5 ≦ Cr + 6Si + 1.5W + 11V + 5Nb + 10B-40C-30N-4Ni-2Co-2Mn ≦ 10.0 (1)
　wherein each element symbol in the formula (1), the content of the corresponding element (mass%) of It is assigned.
[0011]
　Welded joint according to the present invention includes a weld metal for ferritic heat-resistant steel having a chemical composition described above, and a base material made of ferritic heat resistant steel containing B.
[0012]
　Method for producing a welded joint according to the present invention, performed on the base material made of a ferritic heat-resistant steel, with a ferritic heat-resistant steel welding material mentioned above, the gas tungsten arc welding with welding heat input 6 ~ 20 kJ / cm forming a weld metal with respect to the weld metal formed on the base material, a heat treatment of from 0.5 to 4.0 hours per thickness 25.4mm of the base material at a heat treatment temperature of 740 ~ 780 ° C. and a step of performing.
Effect of the invention
[0013]
　Welding material for the heat resistant ferritic steel according to the invention, in the case of welding the heat resistant ferritic steel containing B, it can form a weld metal having high creep strength and toughness.
DESCRIPTION OF THE INVENTION
[0014]
　The present inventors have conducted research and studies in order to solve the problems described above. As a result, the present inventors have obtained the following findings.
[0015]
　If implemented weld the base material made of ferritic heat resistant steel containing B to form a weld metal, if the appropriate amount of B contained in the weld metal, increasing the creep strength of the weld metal. The reason is considered to be as follows. M prior austenite grain boundaries and martensite lath boundaries 23 C 6 carbides (M is an alloy element) is dispersed finely. The M 23 C 6 carbides by the delay in recovery of martensite lath, creep strength is increased. If the B content of the base metal is 0.005 to 0.020 percent, if 0.007% or more B content of the weld metal, or creep strength equivalent to the base metal can be obtained.
[0016]
　On the other hand, if the B content of the weld metal is too high, although high creep strength can be obtained, toughness is reduced. The reason is considered to be as follows. If the B content is too high, rapid extension of the martensite lath occurs during martensitic transformation. Thus the packet size becomes large, breaking unit against impact increases. Furthermore, B is a ferrite forming element, to facilitate the formation of δ ferrite in the weld metal, the area ratio of δ ferrite in the weld metal increases. Therefore, the toughness of the weld metal is considered to decrease.
[0017]
　Satisfies following the (A) ~ (C), the weld metal can be maintained high toughness can be obtained.
[0018]
　(A) If the B content of the weld metal and 0.015% or less, rapid extension of the martensite lath is suppressed.
　(B) in the chemical composition of the weld metal is defined as F1 = Cr + 6Si + 1.5W + 11V + 5Nb + 10B-40C-30N-4Ni-2Co-2Mn. If F1 is 10.0 or less, formation of δ ferrite is suppressed, the area ratio of the weld metal δ ferrite becomes 0.5% or less.
　(C) S segregates in the course of post-weld heat treatment or during the welding, reduces the fixing strength of the grain boundary. Therefore, the S content is set to 0.003 mass% or less. Thus increases the toughness of the weld metal.
[0019]
　Ferritic heat-resistant steel welding material of the present embodiment has been completed based on the above findings, by mass%, C: 0.06 ~ 0.10% , Si: 0.1 ~ 0.4%, Mn: 0 .3 ~ 0.7%, P: 0.01 % or less, S: 0.003% or less, Co: 2.6 ~ 3.4%, Ni: 0.01 ~ 1.10%, Cr: 8. 5 ~ 9.5%, W: 2.5 ~ 3.5%, Mo: less than 0.01%, Nb: 0.02 ~ 0.08 %, V: 0.1 ~ 0.3%, Ta: 0.02 ~ 0.08%, B: 0.007 ~ 0.015%, N: 0.005 ~ 0.020%, Al: 0.03% or less, O: 0.02% or less, Cu: 0 ~ 1%, Ti: 0 ~ 0.3%, Ca: 0 ~ 0.05%, Mg: 0 ~ 0.05%, and rare earth elements: 0 contain ~ 0.1%, with the balance being Fe and consists impurities, of satisfying the formula (1) Having the composition.
　0.5 ≦ Cr + 6Si + 1.5W + 11V + 5Nb + 10B-40C-30N-4Ni-2Co-2Mn ≦ 10.0 (1)
　wherein each element symbol in the formula (1), the content of the corresponding element (mass%) of It is assigned.
[0020]
　The chemical composition of the weld material may contain one or more elements selected from the first group to third group.
　Group 1: Cu: 0.05 ~ 1.00%,
　the second group: Ti: 0.02 ~ 0.30%,
　third group: Ca: 0.001 ~ 0.050%, Mg: 0.001 to 0.050%, and rare earth elements 0.001 to 0.10%
[0021]
　Area ratio of δ ferrite in the welding material is preferably 0.5% or less.
[0022]
　Welded joint according to the present invention includes a weld metal having a chemical composition described above, and a base material made of ferritic heat-resistant steel. Base material, in mass%, Cr: 8 ~ 10%, Co: 2 ~ 4%, W: 2 ~ 4%, and, B: having a chemical composition containing 0.005 to 0.020%.
[0023]
　Chemical composition of the base material, in mass%, C: 0.04 ~ 0.12%, Si: 0.05 ~ 0.60%, Mn: 0.1 ~ 0.8%, P: 0.02 % or less, S: 0.01% or less, Co: 2 ~ 4%, Ni: 0 ~ 0.4%, Cr: 8 ~ 10%, W: 2 ~ 4%, Nb and / or Ta: 0 total .02 ~ 0.18%, V: 0.05 ~ 0.40%, B: 0.005 ~ 0.020%, Nd: 0.01 ~ 0.06%, N: 0.002 ~ 0.025 %, Al: 0.03% or less, and, O: it contains 0.02% or less, and the balance may be Fe and impurities. Chemical composition of the base material, Ni: may contain 0.05 to 0.4%. Area ratio of δ ferrite of the weld metal, for example, 0.5% or less.
[0024]
　Method for producing a welded joint according to the present invention, in mass%, Cr: 8 ~ 10%, Co: 2 ~ 4%, W: 2 ~ 4%, and B: Chemical containing 0.005 to 0.020 percent against the base material made of ferritic heat-resistant steel having a composition, by using a heat resistant ferritic steel for welding materials described above, to form a weld metal by carrying out the gas tungsten arc welding with welding heat input 6 ~ 20 kJ / cm and a step for welding metal formed on the base material, and a step of performing a heat treatment of from 0.5 to 4.0 hours per thickness 25.4mm of the base material at a heat treatment temperature of 740 ~ 780 ° C..
[0025]
　Hereinafter, the welding material for the heat resistant ferritic steel according to the present invention will be described in detail a method for manufacturing the welded joint and welded joint. "%" Related elements, unless otherwise specified, it means mass%.
[0026]
　[Chemical composition of the ferritic heat resistant steel welding materials]
　Chemical composition of the ferritic heat resistant steel welding material of the present embodiment contains the following elements.
[0027]
　C: 0.06 ~ 0.10%
　carbon (C) inhibits the δ ferrite generation of the weld metal, the main structure of the weld metal and the martensitic structure. C further fine carbides (M at high temperature using 23 C 6 generates carbides), increasing the creep strength. If the C content is too low, these effects can not be obtained. On the other hand, if the C content is too high, coarse carbides large amount precipitates, the toughness of the weld metal decreases. Therefore, C content is from 0.06 to 0.10%. The preferable lower limit of C content is 0.07%. The preferable upper limit of C content is 0.09%.
[0028]
　Si: 0.1 ~ 0.4%
　silicon (Si), the deoxidizing steel. Si further enhance steam oxidation resistance of the weld metal. If Si content is too low, these effects can not be obtained. On the other hand, if the Si content is too high, promotes the generation of δ ferrite, with toughness is reduced in the weld metal, the creep ductility is also lowered. Therefore, Si content is 0.1 to 0.4%. A preferable lower limit of Si content is 0.25%. The preferable upper limit of the Si content is 0.35%.
[0029]
　Mn: 0.3 ~ 0.7%
　manganese (Mn), the deoxidation of steel as with Si. Mn further promote martensite tissues of the weld metal. If the Mn content is too low, these effects can not be obtained. On the other hand, if the Mn content is too high, the creep embrittlement is likely to occur in the weld metal. Therefore, Mn content is 0.3 to 0.7%. The preferable lower limit of the Mn content is 0.4%. The preferable upper limit of the Mn content is 0.6%.
[0030]
　P: 0.01% or less
　phosphorus (P) is an impurity. P lowers the toughness of the weld metal. Accordingly, P content is 0.01% or less. The preferable upper limit of the P content is 0.008%. P content is preferably as small as possible. However, from the viewpoint of material cost, the preferable lower limit of the P content is 0.0005%.
[0031]
　S: 0.003% or less
　sulfur (S) is an impurity. S segregates in the old austenite grain boundaries and lath boundaries in the weld metal containing B, and decrease the fixing strength of the grain boundaries and lath boundaries. Therefore, the toughness of the weld metal decreases. Therefore, the content of S is 0.003% or less. The preferable upper limit of the S content is less than 0.002%, more preferably less than 0.0015%. S content is preferably as small as possible. However, from the viewpoint of effect and material costs, the preferred lower limit of the S content is 0.0002%.
[0032]
　Co: 2.6 ~ 3.4%
　cobalt (Co) is to suppress the formation of δ ferrite is effective to obtain a martensite structure. Unlike the base material, since they are not the weld metal refining process, the lower limit of the Co content to sufficiently obtain the above effect is 2.6%. On the other hand, if the Co content is too high, rather creep strength is lowered, creep ductility is also lowered. Moreover, since Co is an expensive element, the material cost increases. Therefore, Co content is 2.6 to 3.4%. The preferable lower limit of the Co content is 2.8%. The preferable upper limit of the Co content is 3.3%.
[0033]
　Ni: 0.01 ~ 1.10%
　nickel (Ni) is to suppress the formation of δ ferrite is effective to obtain a martensite structure. Ni further enhance the toughness of the weld metal. If the Ni content is too low, these effects can not be obtained. On the other hand, if the Ni content is too high, the creep ductility is decreased. Moreover, since Ni is an expensive element, the material cost increases. Therefore, Ni content is 0.01 to 1.10%. A preferable lower limit of Ni content is 0.04%. The preferable upper limit of the Ni content is 1.00%.
[0034]
　Cr: 8.5 ~ 9.5%
　chromium (Cr) increases the steam oxidation resistance and corrosion resistance of the weld metal. Cr is further precipitated as carbides during use at high temperatures, increasing the creep strength. If the Cr content is too low, these effects can not be obtained. On the other hand, if the Cr content is too high, the stability of the carbides is reduced, the creep strength decreases. Further if the Cr content is too high, generation of δ ferrite is promoted, toughness is reduced. Therefore, Cr content is 8.5 to 9.5%. A preferable lower limit of Cr content is 8.7%. The preferable upper limit of the Cr content is 9.3%.
[0035]
　W: 2.5 ~ 3.5%
　tungsten (W) is a solid solution in the matrix, or precipitates for a long time in use as an intermetallic compound, enhances the creep strength at high temperatures of the weld metal. If the W content is too low, the effect can not be obtained. On the other hand, if the W content is too high, a large amount of precipitate formed. Furthermore, [delta] ferrite generation is accelerated, the toughness of the weld metal decreases. Therefore, W content is 2.5 to 3.5%. The preferable lower limit of the W content is 2.7%. The preferable upper limit of the W content is 3.3%.
[0036]
　Mo: less than 0.01%
　molybdenum (Mo) in the welding material of the present invention, which is an impurity. Mo is a solid solution in the matrix, increasing the creep strength of the weld metal. However, Mo is easily solidification segregation, decrease the intermetallic compound and long-term stability of the carbide containing W. Therefore, Mo content is it is preferably as low as possible, less than 0.01%.
[0037]
　Nb: 0.02 ~ 0.08%
　niobium (Nb) is precipitated in the grains as fine carbonitrides during use at high temperatures, increasing the creep strength of the weld metal. If the Nb content is too low, the effect can not be obtained. On the other hand, if the Nb content is too high, coarse carbonitrides are large amount of precipitation, creep strength and creep ductility is decreased. Furthermore, [delta] ferrite generation is accelerated, the toughness of the weld metal decreases. Therefore, Nb content is 0.02 to .08%. The preferable lower limit of Nb content is 0.03%. The preferable upper limit of Nb content is 0.07%.
[0038]
　V: 0.1 ~ 0.3%
　vanadium (V), like Nb, precipitates in the grains as fine carbonitrides during use at high temperatures, increasing the creep strength of the weld metal. If the V content is too low, the effect can not be obtained. On the other hand, if the V content is too high, coarse carbonitrides are large amount of precipitation, creep strength and creep ductility is decreased. Furthermore, [delta] ferrite generation is accelerated, the toughness of the weld metal decreases. Therefore, V content is 0.1 to 0.3%. The preferable lower limit of V content is 0.15%. The preferable upper limit of the V content is 0.25%.
[0039]
　Ta: 0.02 ~ 0.08%
　tantalum (Ta), like Nb and V, precipitation in the grains as fine carbonitrides during use at high temperatures, increasing the creep strength of the weld metal. If Ta content is too low, the effect can not be obtained. On the other hand, if Ta content is too high, coarse carbonitrides are large amount of precipitation, creep strength and creep ductility is decreased. Therefore, Ta content is from 0.02 to 0.08 percent. The preferable lower limit of the Ta content is 0.03%. The preferable upper limit of the Ta content is 0.07%.
[0040]
　B: 0.007 ~ 0.015%
　boron (B) increases the hardenability, is effective to obtain a martensitic structure in the weld metal. B further carbides were finely dispersed prior austenite boundary and martensite lath boundaries during use at high temperatures, to inhibit the recovery of the tissue, increasing the creep strength. If the B content is too low, these effects can not be obtained. On the other hand, if the B content is too high, martensite lath is rapidly extended during martensitic transformation, destruction unit increases. Furthermore, generation of δ ferrite is promoted. Therefore, toughness of the weld metal is extremely lowered. Therefore, B content is 0.007 to 0.015%. The preferable lower limit of the B content is 0.009%. The preferable upper limit of B content is 0.012%.
[0041]
　N: 0.005 ~ 0.020%
　nitrogen (N), the particle finely precipitated in a fine nitrides during use at high temperatures, increasing the creep strength. N further inhibiting the formation of δ ferrite. If the N content is too low, these effects can not be obtained. On the other hand, if the N content is too high, coarse nitrides during solidification of the weld metal is crystallized, the toughness of the weld metal decreases. Therefore, N content is 0.005 to 0.020%. The preferable lower limit of the N content is 0.008%. The preferable upper limit of the N content is 0.015%.
[0042]
　Al: 0.03% or less
　of aluminum (Al), the deoxidizing steel. If the Al content is too low, the effect can not be obtained. On the other hand, if the Al content is too high, detergency is lowered, toughness processability and weld metal of the weld material is lowered. Furthermore, the creep strength of the weld metal is reduced. Therefore, Al content is 0.03% or less. The preferable upper limit of the Al content is 0.01%. Considering the production cost, the preferable lower limit of Al content is 0.001%. In this specification, Al content sol. Means Al (acid soluble Al).
[0043]
　O: 0.02% or less
　oxygen (O) is an impurity. If the O content is too high, toughness processability and weld metal of the weld material is lowered. Therefore, the content of O is 0.02% or less. The preferable upper limit of the O content is 0.01%. Considering the effect and the manufacturing cost, the preferable lower limit of the O content is 0.001%.
[0044]
　The remainder of the chemical composition of the ferritic heat-resistant steel welding material according to the present embodiment is composed of Fe and impurities. Here, when the industrial production of the weld material for the heat resistant ferritic steel and impurities, the ore as a raw material, there is to be mixed etc. Scrap or manufacturing environment, ferritic heat resistant steel of the present embodiment It means what is acceptable to the extent that the use welding material does not adversely affect.
[0045]
　[For any element]
　above welding material may further contain one or more elements selected from the first group to third group follows. Below, will be described in detail these elements.
[0046]
　[Group
　1] Cu: 0 ~ 1%
　of copper (Cu) may not be contained is any element. If contained, Cu is effective in the generation of martensite structure. However, if the Cu content is too high, the creep ductility of the weld metal is reduced. Therefore, Cu content is 0-1%. The preferable upper limit of Cu content is 0.8%. The preferable lower limit of Cu content is 0.05%, more preferably 0.2%.
[0047]
　[Group
　2] Ti: 0 ~ 0.3%
　of titanium (Ti) may not be contained is any element. If contained, Ti is, Nb, similarly to V, and Ta, precipitates in the grains as fine carbonitrides during use at high temperatures, increasing the creep strength of the weld metal. However, if the Ti content is too high, or crystallized as coarse nitrides during welding, and a large amount of precipitate as coarse nitrides during use at high temperatures, reducing the toughness of the weld metal. Therefore, Ti content is 0 to 0.3%. A preferable lower limit of the Ti content is 0.02%, more preferably 0.05%.
[0048]
　[Group
　3] Ca:
　0 ~ 0.05%, Mg: 0 ~ 0.05%, and,
　rare earth elements (REM): 0 ~ 0.1%
　of calcium (Ca), magnesium (Mg), and rare earth elements (REM) may not be contained is any element. If contained, these elements enhances the hot workability of the welding material production. However, if the content of these elements is too high, these elements combine with oxygen to lower the cleanliness of the weld metal. In this case, it decreases the hot workability of the weld metal. Therefore, Ca content is from 0 to 0.05%, Mg content is from 0 to 0.05%, REM content is 0 to 0.1%. Ca content, and the preferred lower limit of the Mg content is 0.001%, respectively, more preferably 0.002%, respectively. Ca content, and the preferred upper limit of the Mg content is 0.02%, respectively. The preferable lower limit of the REM content is 0.001%, more preferably 0.003%. The preferable upper limit of the REM content is 0.06%.
[0049]
　REM herein, Sc, Y, and contains at least one lanthanoid (atomic number 57 No. La ~ 71 No. Lu). REM content means the total content of these elements.
[0050]
　[For formula (1)]
　the chemical composition further satisfying the equation (1).
　0.5 ≦ Cr + 6Si + 1.5 W + 11V + 5nb + 10B-40C-30 N-4Ni-2Co-2Mn ≦ 10.0
　(1) F1 = Cr + 6Si + 1.5 W + 11V + 5nb + 10B-40C-30 N-4Ni-2Co-2Mn, and defined. F1 is an indication of creep strength and δ ferrite content. Specifically, if F1 is too low, no sufficient creep strength can not be obtained, a low creep strength. On the other hand, if F1 is too high, and increases the amount of δ ferrite, the area ratio of the δ ferrite structure in the weld metal exceeds 0.5%. In this case, the toughness of the weld metal decreases. Thus, F1 is 0.5 to 10.0. A preferred lower limit of F1 is 1.0. Preferred upper limit F1 is 9.0.
[0051]
　[Welding for]
　the welding material for ferritic heat-resistant steel of the present invention is manufactured by known manufacturing methods. Welding, for example, filler rod, the filler wire for gas tungsten arc welding, are processed into the core wire or the like of the welding rod for shielded metal arc welding.
[0052]
　[Area ratio of δ ferrite structure of the weld material]
　structure of the weld material consists predominantly tempered martensite, an area ratio of δ ferrite in the structure is required to be 0.5% or less. If the area ratio of δ ferrite is high, that is, if δ ferrite amount is large, at the time of processing at high temperature of the welding material, deformability different tissues are mixed. As a result, processability is lowered. Further, if the area ratio of δ ferrite in the weld metal obtained by using the welding material of the present invention to 0.5% or less, high toughness can be obtained. For getting these effects stably, preferred upper limit of the area ratio of δ ferrite is 0.3%, more preferably 0.1%.
[0053]
　Area ratio of δ ferrite is measured by the following method. From any position of the welding material, taking a cross-section sample. Polishing the collecting surface of the sample. After polishing, using Birera (Vilella) reagent, etching the polished sample surface. An optical microscope (magnification 100 times, observation field 650μm × 860μm) using, in any five visual fields, identifying the δ ferrite in the etched surface. Particular, for example, well-known image processing software is used. For each organization (martensite, [delta] ferrite and the like) that is etched contrast of different, identifies the [delta] ferrite based on the contrast. The total area of ​​the δ ferrite identified in each field, the value obtained by dividing the total area of ​​the five fields (observation field 650μm × 860μm × 5), is defined as the area ratio of δ ferrite in the weld material (%).
[0054]
　Weld the joint]
　using ferritic heat-resistant steel welding material of the present invention, when welding the ferritic heat-resistant steels described later as a base material, a welded joint having a weld metal and a base metal of ferritic heat-resistant steel There are produced. The welded joint having excellent creep strength and toughness. It described in detail below preform and the weld metal of the welded joint.
[0055]
　[For the base material]
　base material consists of a ferritic heat-resistant steel. Chemical composition of the base material contains the following elements.
[0056]
　Cr: 8 ~ 10%
　chromium (Cr), as in the case of welding material, improve the steam oxidation resistance and corrosion resistance at high temperatures of the base material. Cr is further precipitated as carbides during use at high temperatures, increasing the creep strength of the base material. If the Cr content is too low, these effects can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, Cr content is also lower than that of the welding material, the above effect can be obtained. On the other hand, if the Cr content is too high, the stability of the carbides is lowered creep strength of the base material is lowered. Therefore, Cr content is 8-10%. A preferable lower limit of Cr content is 8.5%. The preferable upper limit of the Cr content is 9.5%.
[0057]
　Co: 2 ~ 4%
　cobalt (Co) is a structure of the base material to martensite, which is effective in increasing the creep strength. If the Co content is too low, the effect can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, Co content be lower than that of the welding material, the above effect can be obtained. On the other hand, if the Co content is too high, creep strength and creep ductility of the matrix is lowered. Moreover, since Co is an expensive element, the material cost increases. Therefore, Co content is 2-4%. The preferable lower limit of the Co content is 2.5%, a preferred upper limit of the Co content is 3.5%.
[0058]
　W: 2 ~ 4%
　tungsten (W), as in the case of welding material, or a solid solution in the matrix of the base material, or by deposition in a long time in use as an intermetallic compound, creep strength at high temperatures increased. If the W content is too low, the effect can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, W content be lower than that of the welding material, the above effect can be obtained. On the other hand, if the W content is too high, the effect is saturated. Therefore, W content, W: 2-4%. The preferable lower limit of the W content is 2.5%. The preferable upper limit of the W content is 3.5%.
[0059]
　B: 0.005 ~ 0.020%
　boron (B), as in the case of welding material, enhance the hardenability, it is effective to obtain a martensite structure. B further carbides prior austenite boundaries during the use at high temperatures, and finely dispersed in the martensite lath boundaries, and suppress the recovery of tissue, increasing the creep strength. If the B content is too low, the effect can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, B content be lower than that of the welding material, the above effect can be obtained. On the other hand, if the B content is too high, as in the case of the weld metal, toughness is reduced. Therefore, B content is 0.005 to 0.020%. The preferable lower limit of the B content is 0.007%. The preferable upper limit of B content is 0.015%.
[0060]
　If the base material containing an element described above, the base material is in the high temperature range, it has high creep strength and toughness.
[0061]
　Preferably, furthermore the chemical composition of the base material, containing the following elements, the balance being Fe and impurities. Here, when the industrial production of the weld material for the heat resistant ferritic steel and impurities, the ore as a raw material, there is to be mixed etc. Scrap or manufacturing environment, ferritic heat resistant steel of the present embodiment It means what is allowed in a range that does not adversely affect the base material made of.
[0062]
　C: 0.04 ~ 0.12%
　carbon (C) is effective to obtain a martensite structure. C is further generates fine carbides at high temperature use, improve the creep strength of the base material. If the C content is too low, these effects can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, C content is also lower than that of the welding material, the above effect can be obtained. On the other hand, if the C content is too high, the effect of creep strength improving saturation. Therefore, C content is 0.04 to 0.12%. The preferable lower limit of C content is 0.06%. The preferable upper limit of C content is 0.10%.
[0063]
　Si: 0.05 ~ 0.60%
　silicon (Si), the deoxidizing steel. Si further enhance steam oxidation resistance of the base material. If Si content is too low, these effects can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, Si content is even lower than that of the welding material, the above effect can be obtained. On the other hand, if the Si content is too high, creep ductility and toughness of the base material is lowered. Therefore, Si content is from 0.05 to 0.60 percent. A preferable lower limit of Si content is 0.10%. The preferable upper limit of the Si content is 0.40%.
[0064]
　Mn: 0.1 ~ 0.8%
　manganese (Mn), like Si, deoxidizing steel. Mn further, the structure of the base material to martensite. If the Mn content is too low, these effects can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, Mn content be lower than that of the welding material, the above effect can be obtained. On the other hand, if the Mn content is too high, the creep embrittlement is likely to occur. Therefore, Mn content is 0.1 to 0.8%. The preferable lower limit of the Mn content is 0.2%. The preferable upper limit of the Mn content is 0.7%.
[0065]
　P: 0.02% or less
　Phosphorus (P) is an impurity. If the P content is too high, the creep ductility is decreased. Accordingly, P content is 0.02% or less. The preferable upper limit of the P content is 0.018%. P content is preferably as small as possible. However, considering the material cost, the preferable lower limit of the P content is 0.0005%.
[0066]
　S: 0.01% or less
　of sulfur (S) is an impurity. If the S content is too high, the creep ductility is decreased. Thus, S content is 0.01% or less. The preferable upper limit of the S content is 0.005%. S content is preferably as small as possible. However, considering the material cost, the preferable lower limit of the P content is 0.0002%.
[0067]
　Nb and / or Ta: a total 0.02 to 0.18%
　niobium (Nb) and tantalum (Ta), as in the case of welding material, precipitated in the grains as fine carbonitrides during use at high temperatures and, increasing the creep strength. If Nb and / or Ta content is too low, the effect can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, the content of these elements be lower than that of the welding material, the above effect can be obtained. On the other hand, if Nb and / or Ta content is too high, coarse carbonitrides are a large amount of precipitation, creep strength and creep ductility is decreased. Accordingly, the total content of Nb and / or Ta is from 0.02 to 0.18 percent. The preferable lower limit of the total content of Nb and / or Ta is 0.05%. The preferable upper limit of the total content of Nb and / or Ta is 0.12%.
[0068]
　V: 0.05 ~ 0.40%
　vanadium (V), like Nb and Ta, precipitates in the grains as fine carbonitrides during use at high temperatures, increasing the creep strength. If the V content is too low, the effect can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, V content be lower than that of the welding material, the above effect can be obtained. On the other hand, if the V content is too high, coarse carbonitrides are a large amount of precipitation, creep strength and creep ductility is decreased. Therefore, V content is 0.05 to 0.40 percent. The preferable lower limit of V content is 0.10%. The preferable upper limit of the V content is 0.30%.
[0069]
　Nd: 0.01 ~ 0.06%
　neodymium (Nd) is to improve the creep ductility of the base material. If Nd content is too low, the effect can not be obtained. In the base material with no fear of decreasing the slag during welding, it can be effectively utilized the effects of Nd. On the other hand, if Nd content is too high, hot workability is deteriorated. Therefore, Nd content is from 0.01 to 0.06 percent. The preferable lower limit of the Nd content is 0.02%. The preferable upper limit of the Nd content is 0.05%.
[0070]
　N: 0.002 ~ 0.025%
　nitrogen (N), the particle finely precipitated in a fine nitrides during use at high temperatures, increasing the creep strength. If the N content is too low, the effect can not be obtained. However, the base material is different from the weld metal, solidification segregation is suppressed, it is used after being processed temper. Therefore, N content be lower than that of the welding material, the above effect can be obtained. On the other hand, if the N content is too high, nitrides are coarsened, creep ductility is decreased. Therefore, N content is 0.002 to 0.025%. The preferable lower limit of the N content is 0.005%. The preferable upper limit of the N content is 0.015%.
[0071]
　Al: 0.03% or less
　of aluminum (Al), as in the case of welding material, deoxidizing steel. However, if the Al content is too high, and decreases cleanliness of the base material workability is deteriorated. Furthermore if the Al content is too high, the creep strength decreases. Therefore, Al content is 0.03% or less. The preferable upper limit of the Al content is 0.01%. Considering the production cost, the preferable lower limit of Al content is 0.001%. In this specification, Al content sol. Means Al (acid soluble Al).
[0072]
　O: 0.02% or less
　oxygen (O) is the same as an impurity as in the weld material. If the O content is too high, the workability of the base material is lowered. Therefore, O content is 0.02% or less. The preferable upper limit of the O content is 0.01%. Considering material cost, preferable lower limit of the O content is 0.001%.
[0073]
　Matrix described above may further, in place of part of Fe, and may contain Ni.
　Ni: 0 ~ 0.4%
　nickel (Ni) is an optional element and may not be contained. If contained, Ni is effective in obtaining a martensitic structure. However, if the Ni content is too high, the effect is saturated. Therefore the Ni content is 0 to 0.4%. The preferable upper limit of the Ni content is 0.2%. A preferable lower limit of Ni content is 0.05%, more preferably 0.1%.
[0074]
　Preform having the above chemical composition, it has excellent ductility and creep strength even at high temperature range above 700 ° C..
[0075]
　[Welding Metal]
　weld metal is formed by welding in a manner to be described later with reference to ferritic heat resistant steel welding material mentioned above. Weld metal of the present invention has excellent creep strength and toughness. The chemical composition of the weld metal at any site in the weld metal is in the range of content of each element described in the chemical composition of the ferritic heat-resistant steel welding material mentioned above.
[0076]
　[Weld metal Organization
　weld metal structure after welding is mainly composed of martensite. Area ratio of δ ferrite in the structure of the weld metal is required to be 0.5% or less. If the area ratio of δ ferrite is high, that is, if δ ferrite amount is large, an increase in the starting point of cracking, toughness is reduced. Area ratio of δ ferrite in the structure of the weld metal of the present invention is less and less 0.5%. Therefore, the weld metal has a high toughness. The preferable upper limit of the area ratio of δ ferrite is 0.3%, more preferably 0.1%.
[0077]
　Area ratio of δ ferrite is measured by the following method. From an arbitrary position of the weld metal, taking samples. Polishing the collecting surface of the sample. After polishing, using Birera (Vilella) reagent, etching the polished sample surface. An optical microscope (magnification 100 times, observation field 650μm × 860μm) using, in any five visual fields, identifying the δ ferrite in the etched surface. Particular, for example, well-known image processing software is used. For each organization (martensite, [delta] ferrite and the like) that is etched contrast of different, identifies the [delta] ferrite based on the contrast. The total area of ​​the δ ferrite identified in each field, the value obtained by dividing the total area of ​​the five fields (observation field 650μm × 860μm × 5), is defined as the area ratio of δ ferrite in the weld metal (%).
[0078]
　[Method for welded joints]
　the production method of the above-described welded joint, the step (welding step) for welding using the welding material for the heat resistant ferritic steels with respect to the base material, with respect to the weld metal after welding and a step (heat treatment step) to carry out heat treatment. Below, it will be described in detail each of the steps.
[0079]
　[Welding process]
　by carrying out welded to the above-described base material to form the weld metal. The shape of the base material is not particularly limited. Base material may be a steel sheet, it may be a steel pipe.
[0080]
　The welding, using a heat resistant ferritic steel for welding materials described above. As welding method, it is preferable to employ a gas tungsten arc welding. Gas tungsten arc welding, incorporation of oxygen is small at the time of welding, because the reduction in the cleanliness of the weld metal can be suppressed. Welding conditions at the time of the gas tungsten arc welding is as follows.
[0081]
　Welding heat input range: 6 ~ 20kJ / cm
　in a gas tungsten arc welding, if the welding heat input is too low, depending on size and shape of the base material, incomplete fusion is likely to occur. Welding heat input further if too low, the cooling rate is too large, the growth of the martensite lath is promoted. In this case, breaking the unit is increased, the toughness of the weld metal decreases. On the other hand, if the welding heat input is too high, the welding material of the present invention containing B, solidification cracking occurs. Accordingly, the welding heat input is 6 ~ 20kJ / cm. A preferred lower limit of the heat input is 8 kJ / cm. The preferable upper limit of the heat input is 18 kJ / cm. If heat input range this condition is satisfied, it is easy to obtain an excellent toughness.
[0082]
　[Heat treatment step]
　After the formation of the weld metal and heat treatment is performed with respect to the weld metal. By heat treatment, increasing the toughness decreases the hardness of the weld metal. For example, the welding portion including the weld metal, by placing a heat treatment apparatus such as a band heater, and induction heater to perform the heat treatment. Or to heat the entire welded structure in a heating furnace. Heat treatment temperature in the heat treatment, and the retention time (heat treatment time) at the heat treatment temperature is as follows.
[0083]
　Heat treatment temperature: 740 ~ 780 ° C.
　heat treatment time: per thickness 25.4mm of the base material is 0.5 to 4.0 hours
　unit thickness of the base material of which is that a lot defined by a welding standards, 25. was 4mm (1 inch). If the heat treatment temperature is too low, or if the heat treatment time per unit of the base metal thickness is too short, tempered martensite structure is insufficient, no sufficient toughness can not be obtained. On the other hand, if the heat treatment temperature is too high, a portion of the weld metal exceeds the austenitic transformation temperature, toughness is reduced. Further, if the heat treatment time per unit of the base metal thickness is too long, the creep strength tempering becomes excessive decreases. Therefore, the heat treatment temperature is 740 ~ 780 ° C., the heat treatment time is 0.5 to 4.0 hours per thickness 25.4mm of the base material. The thickness of the base material, if the base material is a steel sheet a plate thickness, in the case of a steel pipe is thick. A preferred lower limit of the heat treatment time is 1.0 hours per thickness 25.4mm of the base material, the preferred upper limit is 3.0 hours. Satisfies the heat treatment temperature and heat treatment time of this condition, for example, the creep rupture time of the weld metal produced using a heat resistant ferritic steel for welding materials described above can be at least 3000 hours, and has excellent toughness The resulting easy.
Example
[0084]
　Manufactures welded joints in various chemical compositions and manufacturing conditions, it was evaluated and creep strength and toughness.
[0085]
　[Production of base material]
　was produced molten steel having the chemical compositions shown in Table 1. By using the molten steel, to produce an ingot.
[0086]
[Table 1]

[0087]
　Against the ingot, hot forging and hot rolling to produce a steel sheet was performed. By carrying out quenching and tempering with respect to the steel plate, thickness 12 mm, width 50 mm, the base material steel plate of length 200 mm (hereinafter, simply referred to as base material) was produced. The quenching after holding for one hour the steel sheet at 1100 ° C., and air-cooled (air-cooled quenching). In tempering, and the steel sheet after quenching and held for 1.5 hours at 770 ° C..
[0088]
　Production of welding material]
　Molten steels having the chemical compositions shown in Table 2 were prepared, to produce an ingot with molten steel. Hot forging relative ingot, hot rolling and then machined to produce a filler wire diameter 2.4 mm. And a filler wire made with the weld material.
[0089]
[Table 2]

[0090]
　[Area ratio of δ ferrite content of weld material]
　from the filler wire described above, were taken sectional microscopic specimens. The micro test piece in the same way as δ ferrite amount of area ratio of welding material mentioned above, polished, and corroded, and revealing the tissue. Any 5 visual field observed by 100 times to determine the area ratio of δ ferrite.
[0091]
　[Welded joint production]
　in the longitudinal direction of the base material, the angle 30 °, were processed V groove root thickness 1 mm. Butt V-groove of the pair of the base material, using a welding material described above was carried out welding. Specifically, the shielding gas by the gas tungsten arc welding and Ar, the weld material by laminating welded into the groove to form a weld metal, to produce a welded joint of each test number shown in Table 3. Heat input of the first layer welding in the welding, and heat input lamination welding were as shown in Table 3.
[0092]
[table 3]

[0093]
　Against the weld metal of the resulting welded joint was measured composition. Method of measuring the elemental composition of the weld metal was as follows. From the weld metal as the base material is not mixed, it was taken chips specimen. Using the collected chips, inductively coupled plasma emission spectroscopy, using a high-frequency combustion method, and analyzed. The elemental composition of the resulting weld metal is shown in Table 4 and Table 5. Incidentally, REM content in Table 5 shows the total content of REM except Nd.
[0094]
[Table 4]

[0095]
[table 5]

[0096]
　Against the weld joint after welding and heat-treated at a heat treatment temperature and heat treatment time are shown in Table 3. Specifically, the heat treatment temperature shown in Table 3, after holding the heat treatment time, and air-cooled.
[0097]
　[All weld metal fabrication]
　separately from the welded joint, in each test number, on the plate material of the base material shown in Table 3, using the welding material shown in Table 3, the gas tungsten arc shielding gas was Ar using welding at lamination welding heat input shown in Table 3, and multilayer welding until a 12mm thickness. This was made all the weld metal.
[0098]
　For all weld metal produced and heat-treated in the heat treatment conditions shown in Table 3.
[0099]
　[Creep strength evaluation test]
　from the production weld joints, weld metal were taken round bar creep rupture test specimen such that the center of the parallel portion (referred to joint specimens). Further, from the total weld metal was taken round bar creep rupture test specimens (referred welding test piece). For each specimen, 650 ° C. to target creep rupture time of about 3000 hours of the base material, the test conditions of 147 MPa, the creep rupture test on the round bar creep rupture test specimen of the welded joint and the total deposited metal carried did. From the results of the test, carried out the creep strength judgment in the evaluation of the following. Joint specimen was broken at the base material (HAZ), and the creep rupture time of溶金specimen was more than 5000 hours as "good". Joint specimen was broken at the base material (HAZ), and the creep rupture time of溶金specimen 3000 hours or more, and those less than 5000 hours as "good". Or fracture in the weld metal portion in the joint test piece, or the creep rupture time of溶金test piece was evaluated as "fail" to well below the 3000 hours.
[0100]
　[Charpy impact test]
　from above of the welded joint, to process the notch in the weld metal, and V-notch Charpy impact test piece full size (notch depth 2 mm) 3 present collected. For each test piece, at 0 ° C., it was performed Charpy impact test according to JIS Z2242 (2005). Based on the test results was carried out following as toughness determination. Charpy impact test pieces value of three test pieces what all exceeding 27J "good", but at least one of the Charpy impact test pieces value of this 3 is below 27J, those satisfying 27J mean value "Yes", and the average value of this 3 is a "fail" those below 27 J.
[0101]
　[[Delta] ferrite content area ratio]
　from all weld metal described above, were taken sectional microscopic specimens. Polished micro test piece taken from the total deposited metal by the method described above, corrode, and revealing the tissue. Any 5 visual field observed by 100 times to determine the area ratio of δ ferrite.
[0102]
　[Test Results]
　Table 3 also shows the results of the above test.
[0103]
　Table 3 referring to the welding material of Test Nos. 1 to 11, 16 to 20 and 22 has a suitable chemical composition and F1 value satisfies the equation (1). Therefore, the weld metal of these test numbers showed excellent creep strength and toughness. The resulting welded joint showed a sufficient creep strength and toughness.
[0104]
　On the other hand, in the welding material used in Test No. 12, the welding heat input is too low. Therefore, the Charpy impact value falls below 27 J, toughness had failed.
[0105]
　The welding material used in Test No. 13, the welding heat input is too high. Therefore, solidification cracking has occurred. Therefore, it did not perform the test.
[0106]
　The welding material used in Test No. 14, the heat treatment temperature after welding was too low. Therefore, the Charpy impact value falls below 27 J, toughness had failed.
[0107]
　The welding material used in Test No. 15, the heat treatment temperature after welding was too high. Therefore, the Charpy impact value falls below 27 J, toughness had failed.
[0108]
　The welding material used in Test No. 21, the heat treatment time after welding was too short. Therefore, the Charpy impact value falls below 27 J, toughness had failed.
[0109]
　The welding material used in Test No. 23, the heat treatment time after welding was too long. Therefore, with the creep test of a welded joint fracture in the weld metal, the creep rupture time of the entire deposited metal does not reach the 3000 hours which is the target, creep strength had failed.
[0110]
　The welding material of the code G used in Test No. 24, B content is too low. Therefore, although the creep test of a welded joint were broken in HAZ creep rupture time of the entire deposited metal does not reach the 3000 hours which is the target, creep strength had failed.
[0111]
　The welding material of codes H used in Test No. 25, B content is too high. Therefore, although excellent in creep strength, the average Charpy impact value falls below 27 J, toughness had failed.
[0112]
　The welding material of the code I used in Test No. 26 were F1 value is too high. Therefore, since the δ ferrite exceeding 0.5% in the weld metal is generated, the Charpy impact value falls below 27 J, toughness had failed.
[0113]
　The welding material of codes J used in Test No. 27, F1 value was too low. Therefore, with the creep test of a welded joint fracture in the weld metal, the creep rupture time of the entire deposited metal does not reach the 3000 hours which is the target, creep strength of the target can not be obtained.
[0114]
　The base material used in Test No. 28, B content contained in the base material was too low. Therefore, although the creep rupture time of all weld metal satisfies the objectives, as shown in Table 4 and Table 5 Test No. 28, in the weld metal of the welded joint, since the B content is not contained sufficiently fractured at the weld metal as a result, it is determined that failure.
[0115]
　Only when satisfying the requirements of this invention, the weld metal is clear that both the required creep strength and toughness, also resulting welded joint with sufficient creep strength and toughness.
Industrial Applicability
[0116]
　According to the present invention, the ferritic heat-resistant steel welding materials that can be used for welding heat resistant ferritic steel containing a large amount of B is obtained. Furthermore, the weld metal and welded joint having excellent creep strength and toughness by the use of this is obtained.
[0117]
　It has been described an embodiment of the present invention. However, the above-described embodiment is merely an example for implementing the present invention. Accordingly, the present invention is not limited to the embodiments described above, it can be implemented by changing the above-described embodiments without departing from the scope and spirit thereof as appropriate.

claims

で

mass%,
　C: 0.06 ~
　0.10%, Si: 0.1 ~ 0.4%, Mn: 0.3
　~ 0.7%, P: 0.01% or
　less, S: 0.003 % or
　less,
　of
　Co: 2.6 ~ 3.4%, of Ni: 0.01 ~ 1.10%,
　of Cr: 8.5 ~ 9.5%, W is: 3.5 of ~ 2.5%,
　of Mo: 0 not the Man
　.01%,
　of
　Nb: 0.02 ~ 0.08%, V: 0.1 ~
　0.3%, Ta: 0.02 ~ 0.08%, B: 0.007 ~
　0.015%, N : 0.005
　~ 0.020%, of Al: 0.03% or
　less, O: 0.02% or
　less,
　a Cu: ~ 0. 1%, of
　Ti: 0 ~ 0.3%, of Ca: 0.05% ~ 0 ,
　of Mg: 0 to 0.05%, andび,
　rare earth element: 0 to 0.1% of wo-containing shi, remnants wa Fe andびimpurities kara na ri, of formula (1) wo the Man ta su chemical composition wo have suru fu S Factory LITE heat resistant steels Welding material .
　0.5 ≦ Cr + 6Si + 1.5W + 11V + 5Nb + 10B-40C-30N-4Ni-2Co-2Mn ≦ 10.0 (1)
　wherein each element symbol in the formula (1), the content of the corresponding element (mass%) of It is assigned.
[Requested item 2]
　Furthermore a welding material for ferritic heat-resistant steel according to claim 1, in mass%, containing one or more elements selected from the first group to third group below, ferritic heat resistant steel welding material.
　Group 1: Cu: 0.05 ~ 1.00%,
　the second group: Ti: 0.02 ~ 0.30%,
　third group: Ca: 0.001 ~ 0.050%, Mg: 0.001 to 0.050%, and rare earth elements 0.001 to 0.10%
[Requested item 3]
　A welding material for ferritic heat-resistant steel according to claim 1 or claim 2,
　the area ratio of δ ferrite is 0.5% or less, the welding material for ferritic heat resistant steels.
[Requested item 4]
　A weld metal having a chemical composition according to any one of claims 1 to 3,
　and a base material made of ferritic heat-resistant steel,
　the base material is a mass%,
　Cr: 8 - 10% ,
　Co: 2 ~
　4% W: 2 ~ 4%
　and, B: having a chemical composition containing 0.005 to 0.020 percent, the weld joint for ferritic heat resistant steels.
[Requested item 5]
　A ferritic heat-resistant steel for welded joint according to claim 4,
　the chemical composition of the base material is a
　mass%,
　C: 0.04 ~ 0.12%, Si: 0.05 ~ 0.60% ,
　Mn: 0.1
　~ 0.8%, P: 0.02% or
　less, S: 0.01% or
　less,
　Co: 2 ~ 4%, Ni: 0
　~ 0.4%, Cr: 8 ~ 10% ,
　W: 2 ~
　4%, Nb and / or Ta:
　0.02 ~
　0.18% in total, V: 0.05 ~ 0.40%, B: 0.005 ~
　0.020%, Nd: 0
　~ 0.06% .01, N: 0.002
　~ 0.025%, Al: 0.03% or less,
　and, O: contains 0.02% or less, the balance being Fe and impurities, ferritic heat resistant steel for welded joints.
[Requested item 6]
　A ferritic heat-resistant steel for welded joint according to claim 5,
　wherein the base material,
　Ni: contains 0.05 to 0.4% welded joint for ferritic heat resistant steels.
[Requested item 7]
　A ferritic heat-resistant steel for welded joint according to any one of Claims 4 to 6,
　the area ratio of δ ferrite of the weld metal is less than 0.5%, for ferritic heat-resistant steel welded joints.
[Requested item 8]
　By mass%, Cr: 8 ~ 10% , Co: 2 ~ 4%, W: 2 ~ 4%, and B: Mother consisting ferritic heat-resistant steel having a chemical composition containing from 0.005 to 0.020 percent against wood, a step of using a heat resistant ferritic steel for welded material according to claim 1 or claim 2, by implementing the gas tungsten arc welding with welding heat input 6 ~ 20 kJ / cm to form a weld metal ,
　and a step of performing relative to the weld metal formed on the base material, a heat treatment of from 0.5 to 4.0 hours per thickness 25.4mm of the base material at a heat treatment temperature of 740 ~ 780 ° C. the method of the welded joint for ferritic heat resistant steels.