WO2019049792A1 - Welding method and joining member - Google Patents

Welding method and joining member Download PDF

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Publication number
WO2019049792A1
WO2019049792A1 PCT/JP2018/032428 JP2018032428W WO2019049792A1 WO 2019049792 A1 WO2019049792 A1 WO 2019049792A1 JP 2018032428 W JP2018032428 W JP 2018032428W WO 2019049792 A1 WO2019049792 A1 WO 2019049792A1
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Prior art keywords
welding
joint
heat
less
phase stainless
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PCT/JP2018/032428
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French (fr)
Japanese (ja)
Inventor
冨村 宏紀
延時 智和
徹 家成
義光 村田
朝田 博
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日新製鋼株式会社
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Publication of WO2019049792A1 publication Critical patent/WO2019049792A1/en

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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20Bonding
    • B23K26/21Bonding by welding
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/346Working by laser beam, e.g. welding, cutting or boring in combination with welding or cutting covered by groups B23K5/00 - B23K25/00, e.g. in combination with resistance welding
    • B23K26/348Working by laser beam, e.g. welding, cutting or boring in combination with welding or cutting covered by groups B23K5/00 - B23K25/00, e.g. in combination with resistance welding in combination with arc heating, e.g. TIG [tungsten inert gas], MIG [metal inert gas] or plasma welding
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00Arc welding or cutting
    • B23K9/23Arc welding or cutting taking account of the properties of the materials to be welded
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00Arc welding or cutting
    • B23K9/16Arc welding or cutting making use of shielding gas
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

Definitions

  • the present invention relates to a welding method and the like for welding ferritic single-phase stainless steels.
  • Laser welding uses (1) high-speed deep penetration welding as compared to arc welding such as TIG welding because it uses a concentrated high energy density heat source, and (2) the effect of welding heat is extremely small. (3) There is a feature that welding deformation is small.
  • Patent Document 1 is a method of refining the crystal grains of a ferrite single phase stainless steel weld metal portion, and when the temperature of the weld portion becomes 400 ° C. or less by penetrating welding with the first laser beam, the corresponding weld portion is lowered.
  • a method of partially welding is provided by irradiating a second laser beam of heat input.
  • this method of refining the grain of the weld metal by using two laser beams does not improve the reduction of the Vickers hardness of the contact bead center and the Vickers hardness of the base material.
  • Patent document 2 preheats to 250 degreeC or more before laser tube welding of ferrite single phase stainless steel, welds the protrusion height of an inner surface bead to 0.15 mm or more, and deteriorates a welding part in the plate thickness direction, and is processed.
  • preheating to at least 250 ° C before laser tube welding is not only a cost problem of attaching a heating device to tube forming equipment, but there is also the concern of a drop in corrosion resistance by applying an oxide film to a stainless steel base material. is there.
  • Japanese Patent Publication Japanese Patent Application Laid-Open No. 8-155665 (June 18, 1996)” Japanese Patent Publication "Japanese Patent Application Laid-Open No. 5-277769 (October 26, 1993)” Japanese patent publication "Tokukai 2015-526295" (released on September 10, 2015)
  • the hardness of the ferrite single-phase stainless steel is significantly increased by welding, as compared with the base material portion. In the welded portion, segregation of alloying elements and coarsening of the structure occur, and many factors of toughness decrease are included. That the hardness of the weld is high, in other words, the ductility is lowered, and it is important to reduce the hardness of the weld.
  • One aspect of the present invention aims to realize a welding method capable of manufacturing a joint member excellent in toughness.
  • welding concerning one mode of the present invention is in mass%, and (1) Ti: 0.05-0.50% and Nb: 0.05-0.50% A single ferrite system containing one or more, (2) C: 0.015% or less, (3) N: 0.020% or less, and (4) Cr: 11.0 to 35.0%.
  • a welding method for welding phase stainless steels comprising: a first heat input process for forming a joint portion in which the ferritic single phase stainless steels are joined by heat input from a first heat source; and the first heat input process Before the temperature of the bonding portion is reduced to 500 ° C./s or less in the temperature range of 1300 ° C. to 700 ° C. before the temperature of the bonding portion is cooled to 700 ° C.
  • a bonding member having excellent toughness can be manufactured.
  • FIG. 6 shows a solubility curve of It is a figure explaining the laser TIG compound welding method concerning the embodiment of the present invention. It is an example of the bead external appearance of the laser TIG composite welding member which concerns on embodiment of this invention. It is an example of the bead section of the laser TIG composite welding member concerning the embodiment of the present invention. It is a graph which shows the relationship of the distance from a bead center part, and a cross-sectional Vickers hardness about a laser * TIG composite welding member and a laser independent welding member which are the examples of the present invention.
  • the inventors of the present application focused attention on the cooling process immediately after welding as a means for reducing the hardness of the welded portion. More specifically, the inventors have found that carbonitrides of Ti and Nb can be precipitated by reducing the cooling rate in the cooling process, and have completed the present invention.
  • the precipitation of Nb-based carbonitrides and Ti-based carbides has temperature dependency of the following (1) and (2).
  • the present inventors precipitate carbides / nitrides of Ti and Nb by slow cooling the temperature range (700 to 1300 ° C.) where carbides / nitrides of Ti and Nb precipitate, and Ti, Nb in steel It has been found that it is possible to prevent solid solution in the matrix, and the present invention has been made.
  • C forms a carbide, which acts as a recrystallization nucleus of the randomization of the recrystallized ferrite in the final annealing.
  • C is an element that raises the strength after cold rolling annealing, and if it is too high, it causes a decrease in ductility, so it is made 0.015% or less.
  • N forms a nitride, which, like C, acts as a recrystallization nucleus of crystal orientation randomization of recrystallized ferrite in the final annealing.
  • N is an element that raises the strength of the cold-rolled annealed material, and if it is too high, it causes a decrease in ductility, so it was made 0.020% or less.
  • Ti is an element that fixes C and N and improves the workability and corrosion resistance, and the minimum amount of the effect is 0.05%.
  • the addition of Ti causes an increase in the cost of steel materials, and surface defects caused by Ti-based inclusions become a problem, so the upper limit of the Ti content was set to 0.50%.
  • Nb is an element that fixes C and N and improves impact resistance and secondary processability, and the minimum amount at which these effects appear is 0.05%. However, if Nb is added too much, the material hardens and adversely affects the processability. Further, the upper limit is made 0.50% because the recrystallization temperature is raised.
  • Cr needs to be contained at 11.0% in order to provide corrosion resistance as stainless steel. However, if the amount of Cr is increased, the toughness and the workability are reduced, so the upper limit of the Cr content is 35.0%.
  • Si is generally used for the purpose of deoxidation, but it has a high solid solution strengthening ability, and if its content is too large, the material hardens and causes a decrease in ductility, so the content is made 0.5% or less.
  • B is an alloy component having the function of fixing N and improving corrosion resistance and workability, and is added as necessary. In order to exhibit the said effect
  • Mo is an element effective for improving the corrosion resistance, but excessive addition causes a decrease in hot workability due to solid solution strengthening at high temperatures and a delay in dynamic recrystallization, so 3.0% or less did.
  • Ni is an austenite-forming element, and addition exceeding 2.0% causes hardening and cost increase, so 2.0% was made the upper limit.
  • Cu is unavoidably contained, such as mixing from scraps at the time of melting, but excessive addition causes the hot workability and corrosion resistance to deteriorate, so the content is made 2.0% or less.
  • Al is an element effective for deoxidation and oxidation resistance, but the upper limit is made 4.0% because excessive addition causes surface defects.
  • Mn is an austenite-forming element, has a small solid solution strengthening ability, and has little adverse effect on the material. However, if the content is high, manufacturability is lowered, for example, Mn fumes are formed during melting, so the component range is desirably made 2.0% or less.
  • P is an element harmful to hot workability.
  • the content exceeds 0.050%, the effect becomes significant, so the content is desirably 0.050% or less.
  • S is an element which is easily segregated at grain boundaries and promotes reduction in hot workability, etc. by grain boundary embrittlement. If the content exceeds 0.020%, the effect becomes significant, so the content is desirably 0.020% or less.
  • V is a useful element in view of processability improvement by the effect of precipitating solid solution C as carbides, and Zr in terms of processability and toughness improvement by capturing oxygen in steel as an oxide.
  • the productivity decreases, so the appropriate content of V and Zr is 0.01 to 0.30%.
  • Ca, Mg, Co, REM (rare earth metal) and the like may be contained in the melt from the scrap which is the raw material, but the ferrite single particle of the present invention is excluded except in the case where it is contained in a large amount. It does not affect the characteristics of duplex stainless welds.
  • the welding method according to one aspect of the present invention comprises, in mass%, one or more of (1) Ti: 0.05 to 0.50%, and Nb: 0.05 to 0.50%, (2) C A welding method for welding ferritic single phase stainless steels containing 0.015% or less, (3) N: 0.020% or less, and (4) Cr: 11.0 to 35.0%. is there.
  • the welding method according to one aspect of the present invention includes a first heat input step and a second heat input step.
  • the first heat source is not particularly limited, and for example, laser welding, TIG welding, plasma welding and the like can be used.
  • the ferrite single-phase stainless steels are melted and joined by heating the ferrite single-phase stainless steel to 1400 ° C. or more, more specifically to 1450 ° C. to 1700 ° C.
  • the second heat input step is a step of performing heat input to the bonded portion by the second heat source before the temperature of the bonded portion is cooled to 700 ° C. after the first heat input step. Specifically, in the temperature range of 1300 ° C. to 700 ° C. of the joint portion, the heat input to the joint portion is performed by the second heat source so that the cooling rate of the joint portion is 500 ° C./s or less. Do.
  • the second heat source is not particularly limited, for example, laser welding, TIG welding, plasma welding and the like can be used. However, since it is preferable to receive heat to the entire joint, the second heat source is preferably TIG welding and plasma welding which can perform heat input over a wider range.
  • the first heat source and the second heat source may be the same type of heat source.
  • a plurality of heat sources may be used as the second heat source. Thereby, the heat input can be applied to the joint in a wider range.
  • FIG. 1 (a) shows solubility curves of niobium nitride (NbN) and niobium carbide (NbC) in pure Fe base
  • FIG. 1 (b) shows titanium nitride (TiN in pure Fe base).
  • solubility curves of titanium carbide (TiC) were determined from theoretical solubility products. The right side of each solubility curve is a precipitation area, and the left side is a solid solution area.
  • NbN precipitates at about 1300 degreeC.
  • the lower limit temperature at which Nb is completely precipitated and Nb can form a solid solution in the ferrite matrix phase is about 700.degree.
  • Nb contained in the ferritic single phase stainless steel in the present invention is Nb: 0.05 to 0.50 mass%
  • the precipitation temperature of NbN is expected to be 700 to 1300 ° C.
  • the deposition temperatures of NbC and TiN are expected to be 700-1100 ° C. and 700-900 ° C., respectively.
  • the diagrams shown in (a) and (b) of FIG. 1 are pure Fe-based solubility curves. Therefore, when an alloying element mainly containing Cr is included as in ferrite single-phase stainless steel, the precipitation temperature range of NbN, NbC and TiN fluctuates somewhat.
  • the deposition amount of NbN, NbC and TiC can be increased in the welded portion.
  • the amount of precipitation of NbN, NbC, and TiC is increased by suppressing the cooling rate of the weld in the temperature range of 700 to 1300 ° C. low using the second heat source. More specifically, NbN, NbC, and NbC are obtained so that the joint member has good toughness by heat input so that the cooling rate of the weld in the temperature range of 700 to 1300 ° C. is 500 ° C./s or less. Deposit TiC.
  • the precipitation amount of NbN, NbC, and TiC is increased when the temperature of the bonding portion is 700 to 1000 ° C. Therefore, it is more preferable to receive heat so that the cooling rate of the weld in the temperature range of 700 to 1000 ° C. is 400 ° C./s or less. Furthermore, the present inventors (1) heat input so that the cooling rate of the weld portion is 900 ° C./s or less in the temperature range of the joint portion of 1300 to 1000 ° C., and (2) It has been found that it is more preferable to receive heat so that the cooling rate of the weld is 400 ° C./s or less in the temperature range of 1000 to 700 ° C.
  • FIG. 2 is a view for explaining TIG leading welding in the laser-TIG composite welding method according to the present invention.
  • reference numeral 1 is a beam of laser light for performing laser welding
  • reference numeral 2 is a TIG welding torch
  • symbol 3 is a ferrite single phase stainless steel material which is a raw material.
  • TIG welding with the TIG welding torch 2 precedes, followed by laser welding with the beam 1 of laser light.
  • FIGS. 3 and 4 show an example of the bead appearance and the bead cross section of a ferrite single-phase stainless steel welded member subjected to laser-TIG composite welding.
  • the ferrite single-phase stainless steel welding member according to the present embodiment is characterized in that spatter is small as shown in FIG. 3 and the undercut is as small as 0.1 mm as shown in FIG.
  • the Vickers hardness at the central portion of the joint is Hv (w)
  • the ferritic single-phase stainless steel is not affected by the thermal effects of the welds.
  • the Vickers hardness of the matrix is Hv (b)
  • a bonding member satisfying Hv (w) ⁇ Hv (b) ⁇ 50 can be obtained.
  • the bonding member in the present embodiment has good toughness because Hv (w) -Hv (b) ⁇ 50. In other words, the bonding member in the present embodiment has good processability.
  • the bonding member in the present embodiment includes one or more compounds selected from carbides of Nb, nitrides of Nb, and carbides of Ti, and the vertical cross section of the bonding portion (with respect to the extending direction of the bonding portion)
  • the area ratio of the above-mentioned compound is 1.8% or more when the vertical cross section is analyzed using FE-EPMA (field emission electron probe micro analysis, field emission electron probe micro analysis).
  • FE-EPMA field emission electron probe micro analysis, field emission electron probe micro analysis
  • Table 1 shows the component compositions of the ferritic single phase stainless steels 1 to 9 used in this example. All numerical values shown in Table 1 are values as mass%.
  • Ferrite-based single-phase stainless steels 1 to 6 shown in Table 1 are ferrite-based single-phase stainless steels satisfying the following condition 1 and ferrite-based single-phase stainless steels 7 to 9 shown in Table 1 do not satisfy the following condition 1 Ferrite-based single-phase stainless steel.
  • Condition 1 One or more of (1) Ti: 0.05 to 0.50% and Nb: 0.05 to 0.50%, (2) C: 0.015% or less, (3) N: 0.020% or less and (4) Cr: 11.0 to 35.0%.
  • the welding was performed by butt welding, and the end face was machined.
  • the welding conditions are as follows.
  • the distance between the torch for performing TIG welding and the beam for performing laser welding was 3 mm.
  • the assist gas for laser welding was used only when performing laser-only welding, and was not used when performing laser-TIG combined welding.
  • Placement TIG leading, or laser leading laser welding: 4 kW power, Spot diameter ⁇ 0.6 mm, Tilt 0 °, Assist gas Ar 100%, 10 L / min TIG welding: Reverse angle 30 °, Current 300A or 400A Arc length 1.5mm, Shield gas Ar 100%, 15 L / min Welding speed: Laser and TIG combined welding 8.0m / min, Laser only welding 4.0m / min TIG welding only 5.0 m / min.
  • Table 2 shows the Vickers hardness Hv (w) of the bead center after laser-TIG composite welding, the Vickers hardness Hv (b) of the base material, and their differences for these joining members. It shows.
  • Vickers hardness was calculated
  • the Vickers hardness of a base material part is defined by the three-point average value in the position of 1.5 mm, 1.75 mm, and 2.0 mm from the bead center before welding.
  • the cooling rate was calculated from the temperature at which the welded portion after welding was measured by a radiation thermometer.
  • the rating rate of the radiation thermometer was set in advance to fit the cooling curve by obtaining a cooling rate by attaching a thermocouple in the vicinity of the plate surface weld.
  • No. 4 which is an invention example of the present application, is heat input and joined such that the cooling rate of the welded portion in the temperature range of 700 to 1300 ° C. is 500 ° C./s or less.
  • the difference between the Vickers hardness (Hv (w)) of the weld bead central portion and the Vickers hardness (Hv (b)) of the base material portion satisfies 50 or less.
  • the difference in Vickers hardness is smaller in TIG welding than in laser welding.
  • No. 5 which is a comparative example of the present invention, is joined by heat input such that the cooling rate of the weld in the temperature range of 700 to 1300 ° C. is higher than 500 ° C./s.
  • the difference between the Vickers hardness (Hv (w)) of the weld bead central portion and the Vickers hardness (Hv (b)) of the base material in the joint members 14 to 18 and 22 was greater than 50. . This is considered to be because the precipitation rate of NbN, NbC and TiC is small because the cooling rate after welding is fast, and the hardness is increased by solid solution strengthening.
  • the amount of Cr contained in the ferritic single phase stainless steel is small, so a martentensite layer is formed during cooling, and the hardness of the bonding portion is increased.
  • the joining members 6 to 8 and 15 differ in the distance between the laser and the TIG in joining. As shown in Table 2, it can be seen that as the laser-TIG distance increases, the cooling effect acts between the two heat source supplies, and the cooling rate increases.
  • FIG. 5 shows No. 1 in Table 1 as the material.
  • No. 4 subjected to laser and TIG composite welding (TIG leading) using No. 4 ferrite single phase stainless steel.
  • No. 11 in which the welding members and the laser alone were welded.
  • It is a graph which shows the relationship of the distance from a bead center part, and a cross-sectional Vickers hardness about 22 joining members.
  • the Vickers hardness is the highest in the bead central part, when comparing the Vickers hardness difference between the bead central part and the base metal part, No. 4 to which laser-TIG composite welding was applied.
  • No. 11 joints were clearly laser-only welded. The increase in hardness is suppressed more than in the joint member 22.
  • the area ratio of the deposit in the weld was determined using FE-EPMA.
  • the conditions are as follows.
  • n was measured as 9 counts
  • a threshold N for identifying precipitates was measured as 20 counts.
  • the ratio of the field of view in which N is at least 20 counts was taken as the area ratio of precipitates.
  • the area ratio of the precipitate calculated by this method is overestimated than the area ratio of the actual precipitate.
  • a V-bending test was conducted using an autograph extrusion test apparatus.
  • the size of the test piece is 20 mm wide ⁇ 60 mm long, and includes a 20 mm wide weld at approximately the center in the length direction.
  • a bending test was performed by pressing a punch having a V-shaped tip so that the position of the welded portion of the test piece is a ridge of bending.
  • the radius of the tip of the punch was 1 mm, and the pressing speed was 30 mm / min.
  • test temperature was adjusted as follows.
  • the test piece equipped with a thermocouple was immersed in liquid nitrogen (-196 ° C), and maintained at that temperature for 1 minute after the temperature of the test piece fell below -180 ° C. Thereafter, the test piece was taken out of liquid nitrogen, and the V-bending test was conducted when the test piece reached -20 ° C. while the temperature of the test piece returned to normal temperature.
  • Table 3 shows the results of measurement of area ratio of precipitates in welds, V-curve test, and strain aging measurement.
  • the joint members 5 to 9 are No. 1 and Comparative example. ⁇ Hv was smaller than that of 15 to 17 bonding members. That is, no. It is understood that in the joints of the joint members 5 to 9, the amounts of Nb and Ti solid-solved in the weld are small.

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Abstract

The present invention realizes a welding method with which it is possible to manufacture a joining member having superior toughness. The welding method includes: a first heat-inputting step for forming a joined section in which ferrite-based single-phase stainless steels are joined with each other by inputting heat from a first heat source; and a second heat-inputting step for inputting heat to the joined section from a second heat source so that the cooling speed of the joined section reaches 500ºC/s. or less while the temperature of the joined section is in a range of 1300ºC to 700ºC after the first heat-inputting step and before the temperature of the joined section decreases to 700ºC.

Description

溶接方法および接合部材Welding method and joint member
 本発明は、フェライト系単相ステンレスどうしを溶接する溶接方法などに関する。 The present invention relates to a welding method and the like for welding ferritic single-phase stainless steels.
 レーザ溶接では、集光された高エネルギー密度の熱源を利用するため、TIG溶接に代表されるアーク溶接に比べ、(1)高速深溶込み溶接が可能、(2)溶接熱影響が非常に少ない、(3)溶接変形が少ない、という特長がある。 Laser welding uses (1) high-speed deep penetration welding as compared to arc welding such as TIG welding because it uses a concentrated high energy density heat source, and (2) the effect of welding heat is extremely small. (3) There is a feature that welding deformation is small.
 ただ、レーザ溶接は冷却速度がはやく、溶接部の硬度が母材部に比べ上昇し靭性低下が課題である。レーザ溶接部の加工性を確保するための従来の公知技術は、以下のとおりである。 However, laser welding has a rapid cooling rate, and the hardness of the welded portion is higher than that of the base metal portion, and the problem is a decrease in toughness. The prior art well-known techniques for ensuring the workability of a laser welding part are as follows.
 特許文献1は、フェライト単相ステンレス鋼溶接金属部の結晶粒を微細化する方法であり、第1レーザビームにより貫通溶接をし、溶接部の温度が400℃以下になると、該当溶接部に低入熱の第2レーザビームを照射して、部分的に溶接する方法を提供する。しかし、2つのレーザビームを用いて溶接金属部の結晶粒を微細化するこの手法は、接部ビード中央部ビッカース硬さと母材部ビッカース硬さの低減の改善にはならない。 Patent Document 1 is a method of refining the crystal grains of a ferrite single phase stainless steel weld metal portion, and when the temperature of the weld portion becomes 400 ° C. or less by penetrating welding with the first laser beam, the corresponding weld portion is lowered. A method of partially welding is provided by irradiating a second laser beam of heat input. However, this method of refining the grain of the weld metal by using two laser beams does not improve the reduction of the Vickers hardness of the contact bead center and the Vickers hardness of the base material.
 特許文献2は、フェライト単相ステンレス鋼のレーザ造管溶接前に250℃以上に予熱し、内面ビードの突出高さを0.15mm以上に溶接し、溶接部を板厚方向に悪化して加工性を向上させる方法を提供する。しかし、レーザ造管溶接前に250℃以上に予熱することは、造管設備に加熱装置を付帯させるコスト上の問題だけでなくステンレス母材に酸化皮膜を付与させることでの耐食性低下の懸念がある。 Patent document 2 preheats to 250 degreeC or more before laser tube welding of ferrite single phase stainless steel, welds the protrusion height of an inner surface bead to 0.15 mm or more, and deteriorates a welding part in the plate thickness direction, and is processed. Provide a way to improve However, preheating to at least 250 ° C before laser tube welding is not only a cost problem of attaching a heating device to tube forming equipment, but there is also the concern of a drop in corrosion resistance by applying an oxide film to a stainless steel base material. is there.
 本発明で着眼したレーザ・TIG複合溶接でステンレス鋼板に限った品質改善に着眼した例はない。特許文献3で金属材料全般の溶接でスパッタ低減にステンレス鋼も使用できると言及している程度である。 There has been no example focusing on quality improvement limited to stainless steel sheets by laser-TIG combined welding focused on in the present invention. It is a grade to which it is mentioned in patent documents 3 that stainless steel can also be used for spatter reduction by welding of metal materials in general.
日本国公開特許公報「特開平8-155665号公報(平成8年6月18日公開)」Japanese Patent Publication "Japanese Patent Application Laid-Open No. 8-155665 (June 18, 1996)" 日本国公開特許公報「特開平5-277769号公報(平成5年10月26日公開)」Japanese Patent Publication "Japanese Patent Application Laid-Open No. 5-277769 (October 26, 1993)" 日本国公開特許公報「特表2015-526295号公報(2015年9月10日公開)」Japanese patent publication "Tokukai 2015-526295" (released on September 10, 2015)
 フェライト単相ステンレス鋼は溶接を施すことで、母材部に比べ硬度が著しく上昇する。溶接部は合金元素の偏析や組織粗大化が起こり、靭性低下の要因を多く含んでいる。その溶接部の硬度が高いことは、言い換えれば延性が低下していることであり、この溶接部硬度低減が重要である。 The hardness of the ferrite single-phase stainless steel is significantly increased by welding, as compared with the base material portion. In the welded portion, segregation of alloying elements and coarsening of the structure occur, and many factors of toughness decrease are included. That the hardness of the weld is high, in other words, the ductility is lowered, and it is important to reduce the hardness of the weld.
 本発明の一態様は、靱性に優れた接合部材を製造することができる溶接方法を実現することを目的とする。 One aspect of the present invention aims to realize a welding method capable of manufacturing a joint member excellent in toughness.
 上記の課題を解決するために、本発明の一態様に係る溶接は、質量%で、(1)Ti:0.05~0.50%、およびNb:0.05~0.50%のうち1種以上と、(2)C:0.015%以下と、(3)N:0.020%以下と、(4)Cr:11.0~35.0%と、を含有するフェライト系単相ステンレスどうしを溶接する溶接方法であって、第1の熱源によって入熱することにより前記フェライト系単相ステンレスどうしを接合した接合部を形成する第1入熱工程と、前記第1入熱工程後に前記接合部の温度が700℃まで冷却される前に、前記接合部の温度が1300℃~700℃の温度範囲において、前記接合部の冷却速度が500℃/s以下となるように第2の熱源により当該接合部に対して入熱を行う第2入熱工程と、を含む。 In order to solve the above-mentioned subject, welding concerning one mode of the present invention is in mass%, and (1) Ti: 0.05-0.50% and Nb: 0.05-0.50% A single ferrite system containing one or more, (2) C: 0.015% or less, (3) N: 0.020% or less, and (4) Cr: 11.0 to 35.0%. A welding method for welding phase stainless steels, comprising: a first heat input process for forming a joint portion in which the ferritic single phase stainless steels are joined by heat input from a first heat source; and the first heat input process Before the temperature of the bonding portion is reduced to 500 ° C./s or less in the temperature range of 1300 ° C. to 700 ° C. before the temperature of the bonding portion is cooled to 700 ° C. A second heat input step of performing heat input to the joint portion with a heat source of Including.
 本発明の一態様によれば、靱性に優れた接合部材を製造することができる。 According to one aspect of the present invention, a bonding member having excellent toughness can be manufactured.
(a)は、純Feベースにおける、窒化ニオブ(NbN)および炭化ニオブ(NbC)の溶解度曲線を示す図であり、(b)は、純Feベースにおける、窒化チタン(TiN)および炭化チタン(TiC)の溶解度曲線を示す図である。(A) shows solubility curves of niobium nitride (NbN) and niobium carbide (NbC) in pure Fe base, and (b) shows titanium nitride (TiN) and titanium carbide (TiC) in pure Fe base Fig. 6 shows a solubility curve of 本発明の実施形態に係るレーザ・TIG複合溶接方法について説明する図である。It is a figure explaining the laser TIG compound welding method concerning the embodiment of the present invention. 本発明の実施形態に係るレーザ・TIG複合溶接部材のビード外観の一例である。It is an example of the bead external appearance of the laser TIG composite welding member which concerns on embodiment of this invention. 本発明の実施形態に係るレーザ・TIG複合溶接部材のビード断面の一例である。It is an example of the bead section of the laser TIG composite welding member concerning the embodiment of the present invention. 本発明の実施例である、レーザ・TIG複合溶接部材とレーザ単独溶接部材について、ビード中央部からの距離と断面ビッカース硬さの関係を示すグラフである。It is a graph which shows the relationship of the distance from a bead center part, and a cross-sectional Vickers hardness about a laser * TIG composite welding member and a laser independent welding member which are the examples of the present invention.
 以下、実施例に基づき本発明を更に詳細に説明するが、本発明はこれらの実施例に限定されることなく、特許請求の範囲に記載した発明の範囲内で種々の組合せが可能であり、それらも本発明の範囲に含まれる。なお、本明細書中の「A~B」は「A以上、B以下」を意味する。 Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples, and various combinations are possible within the scope of the invention described in the claims, They are also included in the scope of the present invention. In the present specification, “A to B” means “A or more and B or less”.
 初めに、フェライト単相ステンレス鋼の溶接部(接合部)の硬度が上昇する理由として、Nb系炭窒化物またはTi系炭化物の析出強化と、NbおよびTiの固溶強化とがあることが知られている。フェライト単相ステンレス鋼は溶接部の耐食性や成形性を維持するために、C、Nをマトリックス中に固溶させずにTiやNbの炭窒化物でC、Nを固定している。フェライト単相ステンレス鋼の溶接において、溶接により鋼が液相になった段階では、TiNを除いて液相中にTi、Mn、C、Nが固溶した状態である。この液相状態からの冷却過程において、まずは液相からフェライト相が生成する。このあと、平衡状態としてはフェライト相からNb系の炭窒化物ならびにTi系炭化物が析出する。 First, it is known that there are precipitation strengthening of Nb-based carbonitrides or Ti-based carbides and solid solution strengthening of Nb and Ti as the reason for the increase in hardness of welds (joints) of ferrite single-phase stainless steel. It is done. Ferrite single-phase stainless steel fixes C and N with carbonitrides of Ti and Nb without solid solution of C and N in the matrix in order to maintain the corrosion resistance and formability of the welded portion. In welding of ferrite single-phase stainless steel, when the steel turns into a liquid phase by welding, Ti, Mn, C, N are in a solid solution state in the liquid phase except TiN. In the cooling process from this liquid phase state, a ferrite phase is first generated from the liquid phase. After that, Nb-based carbonitrides and Ti-based carbides are precipitated from the ferrite phase as an equilibrium state.
 本願の発明者らは、析出強化よりも固溶強化が、溶接部の硬度を上昇させる度合いが高いことを見出した。しかしながら、Nb系の炭窒化物ならびにTi系炭化物がフェライト相中から析出するには析出までの潜伏期があり、また上記液相状態からの冷却過程における冷却速度も速いためTiやNbの析出物を形成しにくく、TiおよびNbがフェライト相中に過飽和に固溶した状態となる。 The inventors of the present application have found that solid solution strengthening has a high degree of increasing the hardness of the weld zone rather than precipitation strengthening. However, precipitation of Nb-based carbonitrides and Ti-based carbides from the ferrite phase has a latent period before precipitation, and because the cooling rate in the process of cooling from the liquid phase is also fast, the precipitates of Ti and Nb are It is difficult to form, and Ti and Nb are in a state of being solid-dissolved in supersaturation in the ferrite phase.
 そこで、本願の発明者らは、溶接部の硬度を低下させる手段として、溶接直後からの冷却過程に着眼した。より詳細には、冷却過程における冷却速度を遅くすることにより、TiおよびNbの炭窒化物を析出させることができることを見出し、本発明を完成させるに至った。ここで、Nb系の炭窒化物ならびにTi系炭化物の析出は、下記の(1)および(2)の温度依存性がある。 Therefore, the inventors of the present application focused attention on the cooling process immediately after welding as a means for reducing the hardness of the welded portion. More specifically, the inventors have found that carbonitrides of Ti and Nb can be precipitated by reducing the cooling rate in the cooling process, and have completed the present invention. Here, the precipitation of Nb-based carbonitrides and Ti-based carbides has temperature dependency of the following (1) and (2).
 (1)高温側:析出は拡散現象が伴うため、温度が高いほど析出しやすい。ただし、析出するNbおよびTi量は温度が高いと少なくなる。換言すれば、温度が高いと固溶した状態が安定状態になる。 (1) High temperature side: Since precipitation is accompanied by a diffusion phenomenon, the higher the temperature, the easier it is to precipitate. However, the amount of Nb and Ti deposited decreases as the temperature increases. In other words, when the temperature is high, the solid solution is stable.
 (2)低温側:拡散が起きにくくなるため、析出し難い。一方で、析出するNb、Ti量は多くなる。また、Nb、Tiが、その温度で理論的に固溶できるNb、Tiの量よりも過飽和にマトリックス中に固溶しているために、析出の駆動力が高くなる。 (2) Low temperature side: It is difficult to precipitate because diffusion hardly occurs. On the other hand, the amount of precipitated Nb and Ti increases. In addition, since Nb and Ti are solid-solved in the matrix in a supersaturated state more than the amounts of Nb and Ti that can theoretically form a solid solution at that temperature, the driving force for precipitation becomes high.
 このように、温度に応じて、TiおよびNbの析出しやすい要因と析出し難い要因とが混在している。本発明者らは、TiとNbの炭化物・窒化物が析出する温度域(700~1300℃)を緩冷却することにより、TiとNbの炭化物・窒化物を析出させ、鋼中のTi、Nbをマトリックス中に固溶させないようにすることができることを見出し、本発明に至った。 Thus, depending on the temperature, factors causing precipitation of Ti and Nb and factors causing precipitation are mixed. The present inventors precipitate carbides / nitrides of Ti and Nb by slow cooling the temperature range (700 to 1300 ° C.) where carbides / nitrides of Ti and Nb precipitate, and Ti, Nb in steel It has been found that it is possible to prevent solid solution in the matrix, and the present invention has been made.
 <フェライト系単相ステンレスの組成>
 本発明において使用するフェライト系単相ステンレスの組成について説明する。なお、各元素の含有量を示す「%」は特に示さない限り「質量%」を意味する。
<Composition of Ferritic Single-phase Stainless Steel>
The composition of the ferrite single phase stainless steel used in the present invention will be described. In addition, "%" which shows content of each element means "mass%" unless otherwise shown.
 Cは、炭化物を形成し、それが最終焼鈍での再結晶フェライトのランダム化の再結晶核として働く。しかしCは冷延焼鈍後の強度を上昇させる元素であり、あまり高いと延性の低下を招くため、0.015%以下とした。 C forms a carbide, which acts as a recrystallization nucleus of the randomization of the recrystallized ferrite in the final annealing. However, C is an element that raises the strength after cold rolling annealing, and if it is too high, it causes a decrease in ductility, so it is made 0.015% or less.
 Nは、窒化物を形成し、Cと同様にそれが最終焼鈍での再結晶フェライトの結晶方位ランダム化の再結晶核として働く。しかしNは冷延焼鈍材の強度を上昇させる元素であり、あまり高いと延性の低下を招くため、0.020%以下とした。 N forms a nitride, which, like C, acts as a recrystallization nucleus of crystal orientation randomization of recrystallized ferrite in the final annealing. However, N is an element that raises the strength of the cold-rolled annealed material, and if it is too high, it causes a decrease in ductility, so it was made 0.020% or less.
 TiはC,Nを固定し、加工性および耐食性を向上させる元素であり、その効果が現れる最低量は0.05%である。しかし、Tiを添加すると、鋼材コストの増大を招き、Ti系介在物が原因の表面欠陥が問題となることから、Ti含有量の上限を0.50%に設定した。 Ti is an element that fixes C and N and improves the workability and corrosion resistance, and the minimum amount of the effect is 0.05%. However, the addition of Ti causes an increase in the cost of steel materials, and surface defects caused by Ti-based inclusions become a problem, so the upper limit of the Ti content was set to 0.50%.
 Nbは、C,Nを固定し、耐衝撃特性や二次加工性を向上させる元素であり、これらの効果が現れる最低量は、0.05%である。しかし、Nbを添加しすぎると材料が硬化し加工性に悪影響をもたらす。また、再結晶温度を上げることから、上限を0.50%とする。 Nb is an element that fixes C and N and improves impact resistance and secondary processability, and the minimum amount at which these effects appear is 0.05%. However, if Nb is added too much, the material hardens and adversely affects the processability. Further, the upper limit is made 0.50% because the recrystallization temperature is raised.
 Crは、ステンレス鋼としての耐食性を備えるために、11.0%の含有が必要である。しかし、Cr量が高くなると、靭性や加工性の低下を招くためCr含有量の上限を35.0%とする。 Cr needs to be contained at 11.0% in order to provide corrosion resistance as stainless steel. However, if the amount of Cr is increased, the toughness and the workability are reduced, so the upper limit of the Cr content is 35.0%.
 以下の元素は請求項の中では記載していないが、含有してもさしつかえない。 The following elements are not described in the claims, but may be contained.
 Siは、通常脱酸の目的のために使用するが、固溶強化能が高く、あまりその含有量が多いと材質が硬化し延性の低下を招くので、0.5%以下とした。 Si is generally used for the purpose of deoxidation, but it has a high solid solution strengthening ability, and if its content is too large, the material hardens and causes a decrease in ductility, so the content is made 0.5% or less.
 Bは、Nを固定し、耐食性や加工性を改善する作用をもつ合金成分であり、必要に応じて添加される。上記作用を発揮させるためには0.0005%以上添加することが望ましい。しかし、過剰に添加すると熱間加工性の低下や溶接性の低下を招くため、上限を0.0100%に設定した。 B is an alloy component having the function of fixing N and improving corrosion resistance and workability, and is added as necessary. In order to exhibit the said effect | action, it is desirable to add 0.0005% or more. However, the upper limit is set to 0.0100% because excessive addition causes a decrease in hot workability and a decrease in weldability.
 Moは、耐食性を改善するために有効な元素であるが、過度の添加は高温での固溶強化や動的再結晶の遅滞により、熱間加工性の低下をもたらすので3.0%以下とした。 Mo is an element effective for improving the corrosion resistance, but excessive addition causes a decrease in hot workability due to solid solution strengthening at high temperatures and a delay in dynamic recrystallization, so 3.0% or less did.
 Niは、オーステナイト形成元素であり、2.0%を越える添加は硬質化やコスト上昇を招くため、2.0%を上限とした。 Ni is an austenite-forming element, and addition exceeding 2.0% causes hardening and cost increase, so 2.0% was made the upper limit.
 Cuは、溶製時のスクラップからの混入等、不可避的に含有されるが、過度の添加は熱間加工性や耐食性を低下させるので2.0%以下とした。 Cu is unavoidably contained, such as mixing from scraps at the time of melting, but excessive addition causes the hot workability and corrosion resistance to deteriorate, so the content is made 2.0% or less.
 Alは、脱酸や耐酸化性のために有効な元素であるが、過剰な添加は表面欠陥の原因となるため上限を4.0%とした。 Al is an element effective for deoxidation and oxidation resistance, but the upper limit is made 4.0% because excessive addition causes surface defects.
 Mnは、オーステナイト形成元素であり、固溶強化能が小さく材質への悪影響が少ない。しかし、含有量が多いと溶製時にMnヒュームが生成する等、製造性が低下するので、望ましくは成分範囲を2.0%以下とする。 Mn is an austenite-forming element, has a small solid solution strengthening ability, and has little adverse effect on the material. However, if the content is high, manufacturability is lowered, for example, Mn fumes are formed during melting, so the component range is desirably made 2.0% or less.
 Pは、熱間加工性に有害な元素である。とくに0.050%を超えるとその影響は顕著になるので望ましくは0.050%以下である。 P is an element harmful to hot workability. In particular, when the content exceeds 0.050%, the effect becomes significant, so the content is desirably 0.050% or less.
 Sは、結晶粒界に偏析しやすく、粒界脆化により熱間加工性の低下等を促進する元素である。0.020%を超えるとその影響は顕著になるので望ましくは0.020%以下である。 S is an element which is easily segregated at grain boundaries and promotes reduction in hot workability, etc. by grain boundary embrittlement. If the content exceeds 0.020%, the effect becomes significant, so the content is desirably 0.020% or less.
 Vは、固溶Cを炭化物として析出させる効果による加工性向上、Zrは鋼中の酸素を酸化物として捕えることによる加工性や靭性向上の面から有用な元素である。しかしながら、多量に添加すると製造性が低下するので、V、Zrの適正含有量は0.01~0.30%である。 V is a useful element in view of processability improvement by the effect of precipitating solid solution C as carbides, and Zr in terms of processability and toughness improvement by capturing oxygen in steel as an oxide. However, when added in large amounts, the productivity decreases, so the appropriate content of V and Zr is 0.01 to 0.30%.
 これら以外にもCa、Mg、Co、REM(希土類金属)などは、溶製中に原料であるスクラップ中より含まれることもあるが、とりたてて多量に含まれる場合を除き、本発明のフェライト単相ステンレス溶接部の特性に影響しない。 In addition to these, Ca, Mg, Co, REM (rare earth metal) and the like may be contained in the melt from the scrap which is the raw material, but the ferrite single particle of the present invention is excluded except in the case where it is contained in a large amount. It does not affect the characteristics of duplex stainless welds.
 <溶接方法>
 本発明の一態様の溶接方法は、質量%で、(1)Ti:0.05~0.50%、およびNb:0.05~0.50%のうち1種以上と、(2)C:0.015%以下と、(3)N:0.020%以下と、(4)Cr:11.0~35.0%と、を含有するフェライト系単相ステンレスどうしを溶接する溶接方法である。本発明の一態様の溶接方法は、第1入熱工程と、第2入熱工程とを含む。
<Welding method>
The welding method according to one aspect of the present invention comprises, in mass%, one or more of (1) Ti: 0.05 to 0.50%, and Nb: 0.05 to 0.50%, (2) C A welding method for welding ferritic single phase stainless steels containing 0.015% or less, (3) N: 0.020% or less, and (4) Cr: 11.0 to 35.0%. is there. The welding method according to one aspect of the present invention includes a first heat input step and a second heat input step.
 (第1入熱工程)
 第1の熱源によって入熱することによりフェライト系単相ステンレスどうしを接合した接合部を形成する工程である。第1の熱源は、特に限定されるものではないが、例えば、レーザ溶接、TIG溶接、プラズマ溶接などを用いることができる。第1入熱工程では、1400℃以上、より具体的には、1450℃~1700℃までフェライト系単相ステンレスを加熱することによりフェライト系単相ステンレスどうしを融解して接合する。
(First heat input process)
This is a step of forming a joint portion in which ferritic single-phase stainless steels are joined by heat input by a first heat source. The first heat source is not particularly limited, and for example, laser welding, TIG welding, plasma welding and the like can be used. In the first heat input step, the ferrite single-phase stainless steels are melted and joined by heating the ferrite single-phase stainless steel to 1400 ° C. or more, more specifically to 1450 ° C. to 1700 ° C.
 (第2入熱工程)
 第2入熱工程は、第1入熱工程後に接合部の温度が700℃まで冷却される前に、第2の熱源により当該接合部に対して入熱を行う工程である。具体的には、接合部の温度が1300℃~700℃の温度範囲において、前記接合部の冷却速度が500℃/s以下となるように第2の熱源により当該接合部に対して入熱を行う。
(2nd heat input process)
The second heat input step is a step of performing heat input to the bonded portion by the second heat source before the temperature of the bonded portion is cooled to 700 ° C. after the first heat input step. Specifically, in the temperature range of 1300 ° C. to 700 ° C. of the joint portion, the heat input to the joint portion is performed by the second heat source so that the cooling rate of the joint portion is 500 ° C./s or less. Do.
 第2の熱源は、特に限定されるものではないが、例えば、レーザ溶接、TIG溶接、プラズマ溶接などを用いることができる。ただし、接合部全体に対して入熱することが好ましいため、第2の熱源は、より広い範囲に入熱を行うことができるTIG溶接、およびプラズマ溶接が好ましい。また、第1の熱源と、第2の熱源とは、同じ種類の熱源であってもよい。 Although the second heat source is not particularly limited, for example, laser welding, TIG welding, plasma welding and the like can be used. However, since it is preferable to receive heat to the entire joint, the second heat source is preferably TIG welding and plasma welding which can perform heat input over a wider range. The first heat source and the second heat source may be the same type of heat source.
 また、第2の熱源として複数の熱源を用いてもよい。これにより、より広い範囲において接合部に対して入熱を加えることができる。 Further, a plurality of heat sources may be used as the second heat source. Thereby, the heat input can be applied to the joint in a wider range.
 図1の(a)は、純Feベースにおける、窒化ニオブ(NbN)および炭化ニオブ(NbC)の溶解度曲線を示す図であり、図1の(b)は、純Feベースにおける、窒化チタン(TiN)および炭化チタン(TiC)の溶解度曲線を示す図である。これらの溶解度曲線は、理論溶解度積から求めた。各溶解度曲線の右側が析出域、左側が固溶域である。 FIG. 1 (a) shows solubility curves of niobium nitride (NbN) and niobium carbide (NbC) in pure Fe base, and FIG. 1 (b) shows titanium nitride (TiN in pure Fe base). And solubility curves of titanium carbide (TiC). These solubility curves were determined from theoretical solubility products. The right side of each solubility curve is a precipitation area, and the left side is a solid solution area.
 図1の(a)に示すように、フェライト系単相ステンレスに含まれるNbが0.42質量%である場合、約1300℃でNbNが析出する。また、Nbが完全に析出してフェライト母相中にNbが固溶できる下限温度は約700℃である。本発明におけるフェライト系単相ステンレスに含まれるNbは、Nb:0.05~0.50質量%であるので、NbNの析出温度は、700~1300℃であると予想される。同様に、NbCおよびTiNの析出温度は、それぞれ700~1100℃および700~900℃であると予想される。ただし、図1の(a)および(b)に示す図は、純Feベースの溶解度曲線である。そのため、フェライト単相ステンレス鋼のようにCrを中心とした合金元素を含む場合、NbN、NbCおよびTiNの析出温度域は、多少変動する。 As shown to (a) of FIG. 1, when Nb contained in ferritic single phase stainless steel is 0.42 mass%, NbN precipitates at about 1300 degreeC. Further, the lower limit temperature at which Nb is completely precipitated and Nb can form a solid solution in the ferrite matrix phase is about 700.degree. Since Nb contained in the ferritic single phase stainless steel in the present invention is Nb: 0.05 to 0.50 mass%, the precipitation temperature of NbN is expected to be 700 to 1300 ° C. Similarly, the deposition temperatures of NbC and TiN are expected to be 700-1100 ° C. and 700-900 ° C., respectively. However, the diagrams shown in (a) and (b) of FIG. 1 are pure Fe-based solubility curves. Therefore, when an alloying element mainly containing Cr is included as in ferrite single-phase stainless steel, the precipitation temperature range of NbN, NbC and TiN fluctuates somewhat.
 したがって、接合部の温度が700~1300℃の温度範囲において溶接部の冷却速度を低く抑えることにより、溶接部においてNbN、NbC、およびTiCの析出量を増加させることができる。本実施形態では、第2の熱源を用いて700~1300℃の温度範囲において溶接部の冷却速度を低く抑えることにより、NbN、NbC、およびTiCの析出量を増加させる。より詳細には、700~1300℃の温度範囲における溶接部の冷却速度を500℃/s以下となるように入熱することにより、接合部材が良好な靱性を有するように、NbN、NbC、およびTiCを析出させる。 Therefore, by suppressing the cooling rate of the welded portion low in the temperature range of 700 to 1300 ° C. of the welded portion, the deposition amount of NbN, NbC and TiC can be increased in the welded portion. In the present embodiment, the amount of precipitation of NbN, NbC, and TiC is increased by suppressing the cooling rate of the weld in the temperature range of 700 to 1300 ° C. low using the second heat source. More specifically, NbN, NbC, and NbC are obtained so that the joint member has good toughness by heat input so that the cooling rate of the weld in the temperature range of 700 to 1300 ° C. is 500 ° C./s or less. Deposit TiC.
 また、図1の(a)および(b)に示すように、接合部の温度が700~1000℃において、NbN、NbC、およびTiCの析出量が多くなる。したがって、接合部の温度が700~1000℃の温度範囲における溶接部の冷却速度を400℃/s以下となるように入熱することがより好ましい。さらに、本発明者らは、(1)接合部の温度が1300~1000℃の温度範囲において溶接部の冷却速度が900℃/s以下となるように入熱するとともに、(2)接合部の温度が1000~700℃の温度範囲において溶接部の冷却速度が400℃/s以下となるように入熱することがさらに好ましいことを見出した。 Further, as shown in (a) and (b) of FIG. 1, the precipitation amount of NbN, NbC, and TiC is increased when the temperature of the bonding portion is 700 to 1000 ° C. Therefore, it is more preferable to receive heat so that the cooling rate of the weld in the temperature range of 700 to 1000 ° C. is 400 ° C./s or less. Furthermore, the present inventors (1) heat input so that the cooling rate of the weld portion is 900 ° C./s or less in the temperature range of the joint portion of 1300 to 1000 ° C., and (2) It has been found that it is more preferable to receive heat so that the cooling rate of the weld is 400 ° C./s or less in the temperature range of 1000 to 700 ° C.
 以下に、本実施形態における接合方法の一例としての、レーザ・TIG複合溶接方法について図に基づいて説明する。図2は、本発明に係るレーザ・TIG複合溶接方法についてTIG先行溶接を説明する図である。 Hereinafter, a laser-TIG composite welding method as an example of the bonding method in the present embodiment will be described based on the drawings. FIG. 2 is a view for explaining TIG leading welding in the laser-TIG composite welding method according to the present invention.
 図2において、符号1はレーザ溶接を行うレーザ光のビームであり、符号2はTIG溶接トーチである。また、符号3は、素材であるフェライト単相ステンレス鋼材である。 In FIG. 2, reference numeral 1 is a beam of laser light for performing laser welding, and reference numeral 2 is a TIG welding torch. Moreover, the code | symbol 3 is a ferrite single phase stainless steel material which is a raw material.
 この溶接方法によってレーザ・TIG複合溶接する場合、TIG溶接トーチ2によるTIG溶接が先行して行われ、続いてレーザ光のビーム1によるレーザ溶接が行われる。 In the case of laser-TIG combined welding by this welding method, TIG welding with the TIG welding torch 2 precedes, followed by laser welding with the beam 1 of laser light.
 図3および図4にレーザ・TIG複合溶接を施したフェライト単相ステンレス溶接部材のビード外観とビード断面の一例を示す。本例におけるフェライト単相ステンレス溶接部材では、図3に示すようにスパッタが少なく、かつ、図4に示すようにアンダーカットも0.1mmと小さい特徴がある。 FIGS. 3 and 4 show an example of the bead appearance and the bead cross section of a ferrite single-phase stainless steel welded member subjected to laser-TIG composite welding. The ferrite single-phase stainless steel welding member according to the present embodiment is characterized in that spatter is small as shown in FIG. 3 and the undercut is as small as 0.1 mm as shown in FIG.
 <接合部材>
 上記の溶接方法によって本実施形態におけるフェライト系単相ステンレスを接合することにより、接合部の中央部におけるビッカース硬さをHv(w)、フェライト系単相ステンレス鋼において溶接部の熱影響を受けない母相のビッカース硬さをHv(b)としたときに、Hv(w)-Hv(b)≦50を満たす接合部材とすることができる。本実施形態における接合部材は、Hv(w)-Hv(b)≦50となっていることにより、良好な靱性を有する。換言すれば、本実施形態における接合部材は、良好な加工性を有する。
<Joining member>
By joining the ferritic single-phase stainless steel in the present embodiment by the above-described welding method, the Vickers hardness at the central portion of the joint is Hv (w), and the ferritic single-phase stainless steel is not affected by the thermal effects of the welds. When the Vickers hardness of the matrix is Hv (b), a bonding member satisfying Hv (w) −Hv (b) ≦ 50 can be obtained. The bonding member in the present embodiment has good toughness because Hv (w) -Hv (b) ≦ 50. In other words, the bonding member in the present embodiment has good processability.
 また、本実施形態における接合部材は、Nbの炭化物、Nbの窒化物、およびTiの炭化物の中から選択される1種以上の化合物を含み、接合部の垂直断面(接合部の延伸方向に対して垂直な断面)をFE-EPMA(電界放出型電子線マイクロアナライザ、Field Emission - Electron Probe Micro Analysis)を用いて分析したときに、上記化合物の面積率が1.8%以上である。本発明者らは、上記面積率が1.8%以上である接合部を有する接合部材は、良好な加工性を有することを見出した。 Further, the bonding member in the present embodiment includes one or more compounds selected from carbides of Nb, nitrides of Nb, and carbides of Ti, and the vertical cross section of the bonding portion (with respect to the extending direction of the bonding portion) The area ratio of the above-mentioned compound is 1.8% or more when the vertical cross section is analyzed using FE-EPMA (field emission electron probe micro analysis, field emission electron probe micro analysis). The present inventors have found that a bonding member having a bonding portion in which the area ratio is 1.8% or more has good processability.
 本発明の溶接方法の実施例および比較例について以下に説明する。 Examples and comparative examples of the welding method of the present invention will be described below.
 表1に、本実施例において使用したフェライト系単相ステンレス1~9の成分組成を示す。表1に示す数値は、すべて質量%としての値である。 Table 1 shows the component compositions of the ferritic single phase stainless steels 1 to 9 used in this example. All numerical values shown in Table 1 are values as mass%.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
 表1に示すフェライト系単相ステンレス1~6は、下記の条件1を満たすフェライト系単相ステンレスであり、表1に示すフェライト系単相ステンレス7~9は、下記の条件1を満たしていないフェライト系単相ステンレスである。
条件1:(1)Ti:0.05~0.50%、およびNb:0.05~0.50%のうち1種以上と、(2)C:0.015%以下と、(3)N:0.020%以下と、(4)Cr:11.0~35.0%と、を含有する。
Ferrite-based single-phase stainless steels 1 to 6 shown in Table 1 are ferrite-based single-phase stainless steels satisfying the following condition 1 and ferrite-based single-phase stainless steels 7 to 9 shown in Table 1 do not satisfy the following condition 1 Ferrite-based single-phase stainless steel.
Condition 1: One or more of (1) Ti: 0.05 to 0.50% and Nb: 0.05 to 0.50%, (2) C: 0.015% or less, (3) N: 0.020% or less and (4) Cr: 11.0 to 35.0%.
 本実施例では、表1に示す成分・組成を有する板厚2.0mmのフェライト単相ステンレス鋼板(焼鈍材)を素材とし、レーザ・TIG複合溶接、レーザ単独溶接、またはTIG単独溶接を実施した。なお、溶加材は用いなかった。 In this example, using a ferrite single-phase stainless steel plate (annealing material) having a thickness of 2.0 mm and having the components and compositions shown in Table 1 as a raw material, laser-TIG combined welding, laser-only welding, or TIG-only welding was performed. . No filler was used.
 溶接は突合せ溶接で行い、端面は機械加工仕上げしたものを用いた。溶接条件は以下のとおりである。レーザ・TIG複合溶接を行う場合、TIG溶接を行うトーチとレーザ溶接を行うビームの間隔は3mmとした。また、レーザ溶接のアシストガスは、レーザ単独溶接を行う場合のみ使用し、レーザ・TIG複合溶接を行う場合は用いなかった。
配置: TIG先行、またはレーザ先行
レーザ溶接:出力 4kW、
      スポット直径φ0.6mm、
      傾斜0°、
      アシストガス Ar100%、10L/min
TIG溶接:後退角度30°、
      電流300A、または400A
      アーク長 1.5mm、
      シールドガス Ar100%、15L/min
溶接速度: レーザ・TIG複合溶接 8.0m/min、
      レーザ単独溶接 4.0m/min
      TIG単独溶接 5.0m/min。
The welding was performed by butt welding, and the end face was machined. The welding conditions are as follows. When performing laser-TIG combined welding, the distance between the torch for performing TIG welding and the beam for performing laser welding was 3 mm. In addition, the assist gas for laser welding was used only when performing laser-only welding, and was not used when performing laser-TIG combined welding.
Placement: TIG leading, or laser leading laser welding: 4 kW power,
Spot diameter φ 0.6 mm,
Tilt 0 °,
Assist gas Ar 100%, 10 L / min
TIG welding: Reverse angle 30 °,
Current 300A or 400A
Arc length 1.5mm,
Shield gas Ar 100%, 15 L / min
Welding speed: Laser and TIG combined welding 8.0m / min,
Laser only welding 4.0m / min
TIG welding only 5.0 m / min.
 本実施例では、表2に示す実験条件でNo.1~22の接合部材を作製した。また、表2には、これらの接合部材についての、レーザ・TIG複合溶接後のビード中央部のビッカース硬さHv(w)、母材部のビッカース硬さHv(b)、およびそれらの差も示している。 In the present example, under the experimental conditions shown in Table 2, no. 1 to 22 bonding members were produced. Table 2 also shows the Vickers hardness Hv (w) of the bead center after laser-TIG composite welding, the Vickers hardness Hv (b) of the base material, and their differences for these joining members. It shows.
 ビッカース硬さは、板厚中心t/2、板厚t/4(表裏)の計3点の平均から求めた。なお、母材部のビッカース硬さは、溶接前のビード中央から1.5mm、1.75mmならびに2.0mmの位置における3点平均値で定義している。 Vickers hardness was calculated | required from the average of a total of three points, thickness center t / 2 and plate thickness t / 4 (front and back). In addition, the Vickers hardness of a base material part is defined by the three-point average value in the position of 1.5 mm, 1.75 mm, and 2.0 mm from the bead center before welding.
 冷却速度は、溶接後の溶接部を放射温度計により測定した温度から算出した。放射温度計の評者率は、予め板表面溶接部近傍に熱電対をつけて冷却速度を求め、その冷却曲線に合うように設定した。 The cooling rate was calculated from the temperature at which the welded portion after welding was measured by a radiation thermometer. The rating rate of the radiation thermometer was set in advance to fit the cooling curve by obtaining a cooling rate by attaching a thermocouple in the vicinity of the plate surface weld.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
 表2に示すように、700~1300℃の温度範囲における溶接部の冷却速度が500℃/s以下となるように入熱して接合された、本願の発明例であるNo.1~13の接合部材では、溶接部ビード中央部のビッカース硬さ(Hv(w))と母材部のビッカース硬さ(Hv(b))との差が50以下を満足している。特に、TIG溶接先行のほうがレーザ溶接先行よりもビッカース硬さ差が小さくなる。 As shown in Table 2, No. 4 which is an invention example of the present application, is heat input and joined such that the cooling rate of the welded portion in the temperature range of 700 to 1300 ° C. is 500 ° C./s or less. In the joining members 1 to 13, the difference between the Vickers hardness (Hv (w)) of the weld bead central portion and the Vickers hardness (Hv (b)) of the base material portion satisfies 50 or less. In particular, the difference in Vickers hardness is smaller in TIG welding than in laser welding.
 No.1~13の接合部材では、溶接後の冷却速度が遅いため、NbN、NbCおよびTiCが析出し、その結果、接合部の硬度上昇を抑えることができたと考えられる。 No. In the joint members 1 to 13, since the cooling rate after welding is slow, NbN, NbC and TiC are precipitated, and as a result, it is considered that the increase in hardness of the joint can be suppressed.
 これに対して、700~1300℃の温度範囲における溶接部の冷却速度が500℃/sよりも大きくなるように入熱して接合された、本願の比較例であるNo.14~18、および22の接合部材では、溶接部ビード中央部のビッカース硬さ(Hv(w))と母材部のビッカース硬さ(Hv(b))との差が50よりも大きくなった。これは、溶接後の冷却速度が速いため、NbN、NbCおよびTiCの析出量が少なく、固溶強化によって硬度が上昇したと考えられる。 On the other hand, No. 5 which is a comparative example of the present invention, is joined by heat input such that the cooling rate of the weld in the temperature range of 700 to 1300 ° C. is higher than 500 ° C./s. The difference between the Vickers hardness (Hv (w)) of the weld bead central portion and the Vickers hardness (Hv (b)) of the base material in the joint members 14 to 18 and 22 was greater than 50. . This is considered to be because the precipitation rate of NbN, NbC and TiC is small because the cooling rate after welding is fast, and the hardness is increased by solid solution strengthening.
 No.19の接合部材では、フェライト系単相ステンレスに含まれるCの量が多いため、溶接部におけるCの固溶量が大きくなったため、接合部の硬度が高くなった。 No. In the 19 joint member, since the amount of C contained in the ferritic single phase stainless steel is large, the solid solution amount of C in the weld portion is large, and therefore the hardness of the joint portion is high.
 No.20の接合部材では、フェライト系単相ステンレスに含まれるNbおよびTiの量が少ないため、CおよびNを十分に固定することができなかった(換言すれば、析出することができなかった)ため、接合部の硬度が高くなった。 No. In the 20 joint members, C and N could not be sufficiently fixed because the amounts of Nb and Ti contained in ferritic single-phase stainless steel were small (in other words, they could not be precipitated) , The hardness of the joint increased.
 No.21の接合部材では、フェライト系単相ステンレスに含まれるCrの量が少ないため、冷却中にマルンテンサイト層が生成し、接合部の硬度が高くなった。 No. In the bonding member 21, the amount of Cr contained in the ferritic single phase stainless steel is small, so a martentensite layer is formed during cooling, and the hardness of the bonding portion is increased.
 No.6~8および15の接合部材は、接合する際のレーザ・TIG間距離が異なっている。表2に示すように、レーザ・TIG間距離が大きくなるにつれて、2つの熱源供給の間で冷却効果が働き、冷却速度が速くなることがわかる。 No. The joining members 6 to 8 and 15 differ in the distance between the laser and the TIG in joining. As shown in Table 2, it can be seen that as the laser-TIG distance increases, the cooling effect acts between the two heat source supplies, and the cooling rate increases.
 また、No.5の接合部材とNo.8の接合部材との結果から、後行に熱源が大きいTIG溶接を用いることにより冷却速度が遅くなることがわかる。 Also, no. No. 5 joint member and No. 5 From the results with the joint member 8, it is understood that the cooling rate is reduced by using TIG welding, which has a large heat source at the rear.
 また、No.6の接合部材とNo.9の接合部材との結果から、TIG電流値が大きくなるほど(換言すれば、熱源が大きくなるほど)、冷却速度が遅くなることがわかる。 Also, no. No. 6 joint member and No. From the result with the joining member of 9, it is understood that the cooling rate becomes slower as the TIG current value becomes larger (in other words, as the heat source becomes larger).
 具体例を図5に示す。図5は、素材として表1のNo.4のフェライト単相ステンレス鋼を用いて、レーザ・TIG複合溶接(TIG先行)を施したNo.11の接合部材と、レーザ単独溶接を施したNo.22の接合部材について、ビード中央部からの距離と断面ビッカース硬さとの関係を示すグラフである。ビード部中央部が最もビッカース硬さが高いが、ビード部中央部と母材部とのビッカース硬さ差を比較すると、レーザ・TIG複合溶接を施したNo.11の接合部材は、明らかにレーザ単独溶接を施したNo.22の接合部材よりも硬度上昇が抑制されている。 A specific example is shown in FIG. FIG. 5 shows No. 1 in Table 1 as the material. No. 4 subjected to laser and TIG composite welding (TIG leading) using No. 4 ferrite single phase stainless steel. No. 11 in which the welding members and the laser alone were welded. It is a graph which shows the relationship of the distance from a bead center part, and a cross-sectional Vickers hardness about 22 joining members. Although the Vickers hardness is the highest in the bead central part, when comparing the Vickers hardness difference between the bead central part and the base metal part, No. 4 to which laser-TIG composite welding was applied. No. 11 joints were clearly laser-only welded. The increase in hardness is suppressed more than in the joint member 22.
 次に、発明例であるNo.5~9の接合部材、および比較例であるNo.15~17の接合部材について、溶接部の析出物の面積率の測定、V曲試験、および、歪み時効測定を行った。 Next, in the invention examples No. The joint members 5 to 9 and the comparative example Nos. For the 15 to 17 joint members, measurement of the area ratio of precipitates in the weld, V-curve test, and strain aging measurement were performed.
 溶接部の析出部の面積率は、FE-EPMAを用いて行った。条件は、以下のとおりである。
使用装置:JXA-8530F(日本電子株式会社製)
加速電圧:15kV
分析領域:100μm×100μm (500×500視野、測定間隔0.2μm)
分析元素:Nb、Ti、C、N(ただし、TiN介在物は除く)
 当該試験では、面分析から、NbおよびTiの特性X線波長を基に析出物を同定した。NbおよびTi系の析出物がない固溶状態におけるNbおよびTiの特性X線のカウント数がnの場合、統計処理学に基づいて算出した下記の式(1)に示す値Nを析出部と判定する閾値とした(参考文献::副島啓義 : 「電子線マイクロアナリシス―走査電子顕微鏡、X線マイクロアナライザ分析法」,日刊工業新聞社,東京, (1987), 111-113.)。
N≧n+3√n ・・・(式1)
 当該試験では、nを9カウント、析出物と同定する閾値Nを20カウントとして測定した。Nが20カウント以上である視野の比率を析出物の面積率とした。なお、この方式で算出される析出物の面積率は、実際の析出物の面積率よりも過大評価される。
The area ratio of the deposit in the weld was determined using FE-EPMA. The conditions are as follows.
Device used: JXA-8530F (manufactured by Nippon Denshi Co., Ltd.)
Acceleration voltage: 15kV
Analysis area: 100 μm × 100 μm (500 × 500 field of view, measurement interval 0.2 μm)
Analysis elements: Nb, Ti, C, N (but excluding TiN inclusions)
In this test, precipitates were identified based on characteristic X-ray wavelengths of Nb and Ti from area analysis. When the count number of the characteristic X-rays of Nb and Ti in the solid solution state without Nb and Ti based precipitates is n, the value N shown in the following formula (1) calculated based on statistical processing theory is The threshold value to be judged was used (Reference :: Keishi Soejima: "Electron beam microanalysis-scanning electron microscope, X-ray microanalyzer analysis", Nikkan Kogyo Shimbun, Tokyo, (1987), 111-113.).
N n n + 3 n n (Equation 1)
In this test, n was measured as 9 counts, and a threshold N for identifying precipitates was measured as 20 counts. The ratio of the field of view in which N is at least 20 counts was taken as the area ratio of precipitates. In addition, the area ratio of the precipitate calculated by this method is overestimated than the area ratio of the actual precipitate.
 溶接部の靱性を評価するため、オートグラフの圧出試験装置を用いて、V曲げ試験を行った。試験片の大きさは幅20mm×長さ60mmであり、長さ方向のほぼ中央部に幅20mmの溶接部が含まれる。この試験片の溶接部の位置が曲げの稜線となるように、先端がV字形状となっているパンチを押込んで曲げ試験とした。パンチの先端のRは1mm、押込み速度は30mm/minとした。 In order to evaluate the toughness of the weld, a V-bending test was conducted using an autograph extrusion test apparatus. The size of the test piece is 20 mm wide × 60 mm long, and includes a 20 mm wide weld at approximately the center in the length direction. A bending test was performed by pressing a punch having a V-shaped tip so that the position of the welded portion of the test piece is a ridge of bending. The radius of the tip of the punch was 1 mm, and the pressing speed was 30 mm / min.
 試験温度は、以下のように調整した。熱電対を取り付けた試験片を液体窒素(-196℃)に浸漬し、試験片の温度が-180℃以下となってから1分間その温度を維持した。その後、試験片を液体窒素から取り出し、試験片の温度が常温に戻っていく過程で、試験片が-20℃になった段階でV曲げ試験を行った。 The test temperature was adjusted as follows. The test piece equipped with a thermocouple was immersed in liquid nitrogen (-196 ° C), and maintained at that temperature for 1 minute after the temperature of the test piece fell below -180 ° C. Thereafter, the test piece was taken out of liquid nitrogen, and the V-bending test was conducted when the test piece reached -20 ° C. while the temperature of the test piece returned to normal temperature.
 歪み時効測定では、400℃-20%の引張試験後の溶接部の硬度と、当該引張試験前の溶接部の硬度との差ΔHvを測定した。ΔHvが小さいほど、歪み時効が小さくなる。すなわち、ΔHvが小さいほど、溶接部に固溶しているNbおよびTiの量が少ないことを示唆する。 In the strain aging measurement, a difference ΔHv between the hardness of the weld after the tensile test at 400 ° C. and 20% and the hardness of the weld before the tensile test was measured. The smaller the ΔHv, the smaller the strain aging. That is, the smaller the ΔHv, the smaller the amount of Nb and Ti solid-solved in the weld zone.
 表3に、溶接部の析出物の面積率の測定、V曲試験、および、歪み時効測定の結果を示す。 Table 3 shows the results of measurement of area ratio of precipitates in welds, V-curve test, and strain aging measurement.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
 表3に示すように、発明例であるNo.5~9の接合部材では、析出物の面積率が1.8%以上であった。これに対して、比較例であるNo.15~17の接合部材では、析出物の面積率が1.8%よりも小さかった。 As shown in Table 3, No. 5 which is an invention example. In the joint members 5 to 9, the area ratio of precipitates was 1.8% or more. On the other hand, No. 1 which is a comparative example. In the 15 to 17 joint members, the area ratio of precipitates was smaller than 1.8%.
 また、No.5~9の接合部材では、V曲げ試験において割れが発生しなかった。これに対して、No.15~17の接合部材では、V曲げ試験において割れが発した。 Also, no. In the V-bending test, no cracks occurred in the joint members 5 to 9. On the other hand, no. In the 15 to 17 joint members, cracking occurred in the V-bending test.
 また、No.5~9の接合部材は、比較例であるNo.15~17の接合部材に比べて、ΔHvが小さかった。すなわち、No.5~9の接合部材における接合部では、溶接部に固溶しているNbおよびTiの量が少ないことがわかる。 Also, no. The joint members 5 to 9 are No. 1 and Comparative example. ΔHv was smaller than that of 15 to 17 bonding members. That is, no. It is understood that in the joints of the joint members 5 to 9, the amounts of Nb and Ti solid-solved in the weld are small.
 本発明は上述した各実施形態に限定されるものではなく、請求項に示した範囲で種々の変更が可能であり、異なる実施形態にそれぞれ開示された技術的手段を適宜組み合わせて得られる実施形態についても本発明の技術的範囲に含まれる。 The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.
 1 レーザ溶接を行うレーザ光のビーム
 2 TIG溶接を行うトーチ
 3 素材
1 Laser beam for laser welding 2 Torch for TIG welding 3 Materials

Claims (5)

  1.  質量%で、(1)Ti:0.05~0.50%、およびNb:0.05~0.50%のうち1種以上と、(2)C:0.015%以下と、(3)N:0.020%以下と、(4)Cr:11.0~35.0%と、を含有するフェライト系単相ステンレスどうしを溶接する溶接方法であって、
     第1の熱源によって入熱することにより前記フェライト系単相ステンレスどうしを接合した接合部を形成する第1入熱工程と、
     前記第1入熱工程後に前記接合部の温度が700℃まで冷却される前に、前記接合部の温度が1300℃~700℃の温度範囲において、前記接合部の冷却速度が500℃/s以下となるように第2の熱源により当該接合部に対して入熱を行う第2入熱工程と、を含むことを特徴とする溶接方法。
    (1) Ti: 0.05 to 0.50% and Nb: one or more of 0.05 to 0.50%, (2) C: 0.015% or less, (3 A welding method for welding ferritic single phase stainless steels containing N: 0.020% or less and (4) Cr: 11.0 to 35.0%,
    A first heat input step of forming a joint portion in which the ferritic single-phase stainless steels are joined by heat input by a first heat source;
    In the temperature range of 1300 ° C. to 700 ° C. before the temperature of the joint portion is cooled to 700 ° C. after the first heat input step, the cooling rate of the joint portion is 500 ° C./s or less And a second heat input step of performing heat input to the joint portion by a second heat source to be
  2.  前記第2入熱工程では、前記接合部の温度が1000℃~700℃の温度範囲において、前記接合部の冷却速度が400℃/s以下となるように入熱することを特徴とする請求項1に記載の溶接方法。 In the second heat input step, heat is input so that the cooling rate of the bonding portion is 400 ° C./s or less in the temperature range of 1000 ° C. to 700 ° C. of the bonding portion. The welding method as described in 1.
  3.  前記第2入熱工程では、
      前記接合部の温度が1300℃~1000℃の温度範囲において、前記接合部の冷却速度が900℃/s以下となるように入熱するとともに、
      前記接合部の温度が1000℃~700℃の温度範囲において、前記接合部の冷却速度が400℃/s以下となるように入熱することを特徴とする請求項1または2に記載の溶接方法。
    In the second heat input step,
    In the temperature range of 1300 ° C. to 1000 ° C. of the joint portion, heat is received so that the cooling rate of the joint portion is 900 ° C./s or less.
    The welding method according to claim 1 or 2, wherein heat is input so that the cooling rate of the joint becomes 400 ° C / s or less in the temperature range of 1000 ° C to 700 ° C of the joint portion. .
  4.  フェライト系単相ステンレスどうしを溶接することにより接合部を形成した接合部材であって、
     前記接合部は、Nbの炭化物、Nbの窒化物、およびTiの炭化物の中から選択される1種以上の化合物を含み、
     前記接合部における延伸方向に対して垂直な断面をFE-EPMA(Field Emission -Electron Probe Micro Analysis)を用いて分析したときに、前記化合物の面積率が1.8%以上であることを特徴とする接合部材。
    A joint member in which a joint portion is formed by welding ferrite-based single-phase stainless steels,
    The joint includes one or more compounds selected from carbides of Nb, nitrides of Nb, and carbides of Ti,
    The area ratio of the compound is 1.8% or more when a cross section perpendicular to the stretching direction in the joint is analyzed using FE-EPMA (Field Emission-Electron Probe Micro Analysis). Joining member.
  5.  フェライト系単相ステンレスどうしを溶接することにより接合部を形成した接合部材であって、
     前記接合部の中央部におけるビッカース硬さをHv(w)、フェライト系単相ステンレス鋼のビッカース硬さをHv(b)としたときに、Hv(w)-Hv(b)≦50を満たすことを特徴とする接合部材。
    A joint member in which a joint portion is formed by welding ferrite-based single-phase stainless steels,
    Hv (w) -Hv (b) ≦ 50, where Hv (w) is a Vickers hardness at the central portion of the joint, and Hv (b) is a Vickers hardness of a ferritic single phase stainless steel A joint member characterized by
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JP2006193770A (en) * 2005-01-12 2006-07-27 Nippon Steel & Sumikin Stainless Steel Corp Welded ferritic stainless steel tube with excellent tube expanding workability, and its manufacturing method

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111266739A (en) * 2020-02-06 2020-06-12 哈尔滨焊接研究院有限公司 Method for laser-MIG electric arc composite welding of low-nickel nitrogen-containing austenitic stainless steel

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