Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550°C
  • B23K35/3053—Fe as the principal constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550°C
  • B23K35/3053—Fe as the principal constituent
  • B23K35/3066—Fe as the principal constituent with Ni as next major constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550°C
  • B23K35/3053—Fe as the principal constituent
  • B23K35/3073—Fe as the principal constituent with Mn as next major constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550°C
  • B23K35/3053—Fe as the principal constituent
  • B23K35/308—Fe as the principal constituent with Cr as next major constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C30/00—Alloys containing less than 50% by weight of each constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C30/00—Alloys containing less than 50% by weight of each constituent
  • C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/02—Iron or ferrous alloys
  • B23K2103/04—Steel or steel alloys

Definitions

• This disclosure relates to welded metals, welded joints, and welded structures.
• Ni-based low-temperature steel containing 6 to 9% Ni is used for the steel materials used in liquid hydrogen tanks, liquid carbon dioxide tanks, LNG tanks, etc., because of the need to ensure toughness at the extremely low temperature of -196°C.
• austenitic welding materials that can provide weld metals with excellent low-temperature toughness are used to form weld metals. These welding materials are mainly designed with a Ni content of 70%.
• Patent Document 1 describes a welding material with a Ni content of 70% as follows: "Ni content is 35 to 70%, and the flux contains TiO 2 , SiO 2 and ZrO 2 in a total amount of 4.0 mass% or more with respect to the total mass of the wire, and further contains Mn oxides in an amount of 0.6 to 1.2 mass% calculated as MnO 2 , and when the contents of TiO 2 , SiO 2 , ZrO 2 and MnO 2 (converted amounts) are [TiO 2 ], [SiO 2 ], [ZrO 2 ] and [MnO 2 ], respectively, the ratio [TiO 2 ]/[ZrO 2 ] is 2.3 to 3.3, the ratio [SiO 2 ]/[ZrO 2 ] is 0.9 to 1.5, and the ratio ([TiO 2 ]+[SiO 2 ]+[ZrO 2 ])/[MnO 2 ] is 0.9 to 1.5.”
• the publication discloses a flux-cored
• the object of the present invention is to provide a weld metal that is inexpensive and has excellent low-temperature toughness, a weld joint having the weld metal, and a welded structure having the weld joint.
• the means for solving the problems include the following aspects. ⁇ 1>
• the chemical composition, expressed as mass% relative to the total mass of the weld metal, is C: 0.030 to 1.000%, Si: 0.03 to 0.50%, Mn: 4.1 to 30.0%, P: 0 to 0.050%, S: 0 to 0.050%, Cu: 0 to 5.0%, Ni: 1.0 to 30.0%, Cr: 0 to 20.0%, Mo: 0 to 10.0%, Nb: 0 to 1.000%, V: 0 to 1.00%, Co: 0 to 1.00%, Pb: 0 to 1.00%, Sn: 0 to 1.00%, W: 0 to 20.0%, Mg: 0 to 5.0%, Al: 0 to 0.100%, Ca: 0 to 5.0%, Ti: 0 to 0.100%, B: 0 to 0.5000%, REM: 0 to 0.500%, Zr: 0 to 0.500%, N: 0 to 0.5000%, O: 0.0010
• ⁇ 2> The weld metal according to ⁇ 1>, in which the total of the Mn content, the Ni content, and the Cr content (Mn+Ni+Cr) is 15.0% or more.
• ⁇ 3> The weld metal according to ⁇ 1> or ⁇ 2>, wherein the fcc ratio determined by a magnetic induction method is 70% or more.
• ⁇ 4> The weld metal according to any one of ⁇ 1> to ⁇ 3>, wherein a mass ratio (Ni/Mn) of the Mn content to the Ni content is 0.10 or more.
• ⁇ 5> The weld metal according to ⁇ 4>, wherein the mass ratio (Ni/Mn) is 1.00 or more.
• ⁇ 6> The weld metal according to any one of ⁇ 1> to ⁇ 5>, wherein the Ti content is Ti: 0.003 to 0.100%.
• ⁇ 7> The weld metal according to any one of ⁇ 1> to ⁇ 6>, wherein the C content is C: 0.110 to 1.000%.
• ⁇ 8> A welded joint having the weld metal according to any one of ⁇ 1> to ⁇ 7>.
• ⁇ 9> A welded structure having the weld joint according to ⁇ 8>.
• This disclosure provides an inexpensive weld metal with excellent low-temperature toughness, a weld joint having the weld metal, and a welded structure having the weld joint.
• the weld metal according to the present disclosure has a predetermined chemical composition.
• the weld metal according to the present disclosure can be obtained at low cost and with excellent low-temperature toughness.
• the weld metal according to the present disclosure was discovered based on the following findings.
• the present inventors have investigated a technique for obtaining a weld metal that can improve the low-temperature toughness of the weld metal even if the Ni content is reduced and the Mn content is increased. As a result, the following findings have been obtained.
• Both Ni and Mn are austenite stabilizing elements.
• the Ni content is reduced or the Mn content is increased excessively, the stacking fault energy is reduced and the toughness is deteriorated. Therefore, the Ni and Mn contents are controlled to prevent the decrease in stacking fault energy.
• the chemical composition of the weld metal is: C: 0.030 to 1.000%, Si: 0.03 to 0.50%, Mn: 4.1 to 30.0%, P: 0 to 0.050%, S: 0 to 0.050%, Cu: 0 to 5.0%, Ni: 1.0 to 30.0%, Cr: 0 to 20.0%, Mo: 0 to 10.0%, Nb: 0 to 1.000%, V: 0 to 1.00%, Co: 0 to 1.00%, Pb: 0 to 1.00%, Sn: 0 to 1.00%, W: 0 to 20.0%, Mg: 0 to 5.0%, Al: 0 to 0.100%, Ca: 0 to 5.0%, Ti: 0 to 0.100%, B: 0 to 0.5000%, REM: 0 to 0.500%, Zr: 0 to 0.500%, N: 0 to 0.5000%, O: 0.0010 to 0.1500%, and the balance: Fe and impurities; and the sum of the Mn content and the Ni content
• C is an element that improves the strength of the weld metal and ensures the strength of the weld metal.
• the C content of the weld metal is set to 0.030 to 1.000%.
• the lower limit of the C content of the weld metal may preferably be 0.050%, 0.100%, 0.110%, 0.120%, 0.140%, 0.150%, 0.200%, or 0.250%.
• the upper limit of the C content of the weld metal is preferably 0.900%, 0.800%, 0.700%, 0.600%, 0.550%, 0.500%, 0.450%, or 0.400%.
• Silicon is a deoxidizing element. If the silicon content of the weld metal is too low, the phosphorus content of the weld metal increases. On the other hand, Si has a low solid solubility in the austenite phase, and the greater the Si content, the greater the amount of brittle phases such as intermetallic compounds and ⁇ ferrite that are generated at high temperatures, resulting in a deterioration in high-temperature ductility. Therefore, the Si content in the weld metal is set to 0.03 to 0.50%.
• the lower limit of the Si content in the weld metal is preferably 0.04%, 0.05%, or 0.08%.
• the upper limit of the Si content in the weld metal is preferably 0.48%, 0.45%, 0.40%, 0.35%, 0.30%, or 0.20%.
• Mn is an austenite stabilizing element. If the Mn content in the weld metal is too low, the austenitization of the weld metal is difficult to proceed, and low-temperature toughness is deteriorated. Mn is also an element that functions as a deoxidizer to improve the cleanliness of the weld metal. Mn is also an element that renders S in the weld metal harmless by forming MnS, thereby improving the low-temperature toughness of the weld metal. In addition, Mn has the effect of preventing high-temperature cracking.
• the Mn content of the weld metal is set to 4.1 to 30.0%.
• the lower limit of the Mn content of the weld metal is preferably 4.2%, 4.5%, 5.0%, 7.0%, 9.0%, or 10.0%.
• the upper limit of the Mn content of the weld metal is preferably 28.0%, 25.0%, 23.0%, 20.0%, 18.0%, 15.0%, or 14.5%.
• the P content of the weld metal is set to 0%.
• the P content of the weld metal should be 0.003% or more.
• the P content of the weld metal is set to 0 to 0.050%.
• the P content of the weld metal is preferably 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, or 0.010% or less.
• the S content of the weld metal is set to 0%.
• the S content of the weld metal should be 0.003% or more.
• the S content of the weld metal is set to 0 to 0.050%.
• the S content of the weld metal is preferably 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, or 0.010% or less.
• Cu is a precipitation strengthening element and may be contained in the weld metal to improve the strength of the weld metal.
• Cu is also an austenite stabilizing element and may be contained in the weld metal to improve the low temperature toughness of the weld metal.
• the Cu content in the weld metal is set to 0 to 5.0%.
• the lower limit of the Cu content in the weld metal is preferably 0.3%, 0.5%, or 0.7%.
• the upper limit of the Cu content in the weld metal is preferably 4.5%, 4.0%, or 3.5%.
• Ni is an austenite stabilizing element. If the Ni content in the weld metal is too low, the austenitization of the weld metal becomes difficult to proceed, and the low-temperature toughness deteriorates. On the other hand, increasing the Ni content of the weld metal increases the cost of the weld metal. Therefore, the Ni content of the weld metal is set to 1.0 to 30.0%.
• the lower limit of the Ni content in the weld metal is preferably 2.0%, 3.0%, 3.2%, 3.7%, 5.0%, or 7.0%.
• the upper limit of the Ni content in the weld metal is preferably 28.0%, 25.0%, 23.0%, 20.0%, 18.0%, or 15.0%.
• Cr is an austenite stabilizing element and may be contained in the weld metal to improve the low-temperature toughness of the weld metal.
• the Cr content of the weld metal is set to 0 to 20.0%.
• the lower limit of the Cr content of the weld metal is preferably 1.0%, 2.0%, or 3.0%.
• the upper limit of the Cr content of the weld metal is preferably 18.0%, 15.8%, 15.3%, 15.0%, 13.3%, 13.0%, 10.0%, 9.0%, 8.0%, or 7.0%.
• Mo is a precipitation strengthening element and may be contained in the weld metal to improve the strength of the weld metal.
• Mo content in the weld metal is set to 0 to 10.0%.
• the lower limit of the Mo content in the weld metal is preferably 1.0%, 2.0%, or 3.0%.
• the upper limit of the Mo content in the weld metal is preferably 9.0%, 8.0%, or 7.0%.
• Nb is an element that forms carbides in the weld metal and increases the strength of the weld metal, and therefore may be contained in the weld metal.
• the Nb content of the weld metal is set to 0 to 1.000%.
• the lower limit of the Nb content in the weld metal is preferably 0.010%, 0.050%, 0.100%, 0.150%, or 0.200%.
• the upper limit of the Nb content of the weld metal is preferably 0.950%, 0.900%, 0.850%, or 0.800%.
• V (V: 0 to 1.00%) V is an element that forms carbonitrides in the weld metal and increases the strength of the weld metal, and therefore may be contained in the weld metal.
• the V content of the weld metal is set to 0 to 1.00%.
• the lower limit of the V content of the weld metal is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.
• the upper limit of the V content of the weld metal is preferably 0.95%, 0.90%, 0.85%, or 0.80%.
• Co (Co: 0 to 1.00%) Co is an element that increases the strength of the weld metal through solid solution strengthening, and therefore may be contained in the weld metal.
• the Co content of the weld metal is set to 0 to 1.00%.
• the lower limit of the Co content in the weld metal is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.
• the upper limit of the Co content of the weld metal is preferably 0.95%, 0.90%, 0.85%, or 0.80%.
• Pb 0 to 1.00%
• Pb has the effect of improving the toe formability between the base steel material and the weld metal and improving the machinability of the weld metal, and therefore may be contained in the weld metal.
• the Pb content of the weld metal is set to 0 to 1.00%.
• the lower limit of the Pb content of the weld metal is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.
• the upper limit of the Pb content of the weld metal is preferably 0.95%, 0.90%, 0.85%, or 0.80%.
• Sn is an element that improves the corrosion resistance of the weld metal and may be contained in the weld metal.
• the Sn content of the weld metal is set to 0 to 1.00%.
• the lower limit of the Sn content of the weld metal is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.
• the upper limit of the Sn content of the weld metal is preferably 0.95%, 0.90%, 0.85%, or 0.80%.
• W is a solid solution strengthening element and may be contained in the weld metal to improve strength.
• the W content of the weld metal is set to 0 to 20.0%.
• the lower limit of the W content of the weld metal is preferably 0.5%, 1.0%, or 2.0%.
• the upper limit of the W content of the weld metal is preferably 19.0%, 18.0%, 17.0%, 16.0%, or 15.0%.
• Mg is a deoxidizing element and is effective in reducing oxygen and improving toughness, and therefore may be contained in the weld metal.
• the Mg content in the weld metal is set to 0 to 5.0%.
• the lower limit of the Mg content in the weld metal is preferably 0.02%, 0.05%, 0.1%, or 0.2%.
• the upper limit of the Mg content of the weld metal is preferably 4.8%, 4.5%, 4.3%, or 4.0%.
• Al is a deoxidizing element and may be contained in the weld metal in order to suppress welding defects and improve the cleanliness of the weld metal.
• Al content in the weld metal is set to 0 to 0.100%.
• the lower limit of the Al content in the weld metal is preferably 0.010%, 0.020%, or 0.030%.
• the upper limit of the Al content of the weld metal is preferably 0.090%, 0.080%, or 0.070%.
• Ca 0 to 5.0%
• Ca has the effect of changing the structure of sulfides in the weld metal and of reducing the size of sulfides and oxides in the weld metal, and is therefore effective in improving the ductility and toughness of the weld metal, so Ca may be contained in the weld metal.
• the Ca content in the weld metal is set to 0 to 5.0%.
• the lower limit of the Ca content in the weld metal is preferably 0.01%, 0.02%, or 0.03%.
• the upper limit of the Ca content in the weld metal is preferably 4.8%, 4.5%, 4.3%, or 4.0%.
• Ti is a deoxidizing element and may be contained in the weld metal in order to suppress welding defects and improve the cleanliness of the weld metal.
• the Ti content in the weld metal is set to 0 to 0.100%.
• the lower limit of the Ti content in the weld metal is preferably 0.003%, 0.010%, 0.020%, or 0.030%.
• the upper limit of the Ti content in the weld metal is preferably 0.090%, 0.080%, or 0.070%.
• B is an austenite stabilizing element and an interstitial solid solution strengthening element, and may be contained in the weld metal to improve the low temperature toughness and strength of the weld metal.
• M 23 (C, B) 6 precipitates, causing a deterioration in toughness. Therefore, the B content of the weld metal is set to 0 to 0.5000%.
• the lower limit of the B content of the weld metal is preferably 0.0005%, 0.0010%, or 0.0020%.
• the upper limit of the B content of the weld metal is preferably 0.4800%, 0.4500%, 0.4300%, or 0.4000%.
• REM 0 to 0.500%
• REM is an element that stabilizes the arc during welding work to obtain the weld metal, and therefore may be contained in the weld metal.
• the REM content of the weld metal is set to 0 to 0.500%.
• the lower limit of the REM content of the weld metal is preferably 0.001%, 0.002%, or 0.005%.
• the upper limit for the REM content of the weld metal is preferably 0.480%, 0.450%, 0.430%, or 0.400%.
• Zr 0 to 0.500%
• Zr can stabilize the bead shape during the welding operation for obtaining the weld metal, and therefore may be contained in the weld metal.
• the Zr content in the weld metal is set to 0 to 0.500%.
• the lower limit of the Zr content of the weld metal is preferably 0.001%, 0.002%, or 0.005%.
• the upper limit of the Zr content of the weld metal is preferably 0.480%, 0.450%, 0.430%, or 0.400%.
• N is an austenite stabilizing element and an interstitial solid solution strengthening element, and may be contained in the weld metal to improve the low temperature toughness and strength of the weld metal.
• the N content of the weld metal is set to 0 to 0.5000%.
• the lower limit of the N content of the weld metal is preferably 0.0010%, 0.0100%, or 0.0500%.
• the upper limit of the N content of the weld metal is preferably 0.4500%, 0.4000%, or 0.3500%.
• O (O: 0.0010 to 0.1500%) O is contained in the weld metal as an impurity.
• the upper limit of the O content in the weld metal is set to 0.1500% or less.
• the lower limit of the O content in the weld metal is set to 0.0010% or less.
• the lower limit of the O content in the weld metal is preferably 0.0020% or 0.0030%.
• the upper limit of the O content in the weld metal is preferably 0.1300% or 0.1000%.
• the remaining components in the chemical composition of the weld metal are Fe and impurities.
• impurities refers to components that are mixed in due to raw materials such as ores or scraps, or various factors in the manufacturing process, when industrially producing weld metal, and are acceptable within a range that does not adversely affect the properties of the weld metal.
• Mn and Ni are each an austenite stabilizing element and improve the low-temperature toughness of the weld metal.
• Ni is an expensive metal
• the Mn content and Ni content in the weld metal each satisfy the above-mentioned range, and the total content of Mn and Ni (Mn + Ni) is set to 5.0% or more.
• the total content of Mn and Ni in the weld metal (Mn+Ni) is preferably 5.2% or more, 6.2% or more, 6.7% or more, 7.0% or more, 10.0% or more, or 15.0% or more.
• the Mn content and the Ni content in the weld metal each satisfy the above-mentioned range, and that the sum of the Mn content and the Ni content (Mn + Ni) is 37.0% or less.
• the total content of Mn and Ni (Mn+Ni) in the weld metal is more preferably 35.0% or less, 32.0% or less, or 30.0% or less.
• Mn, Ni, and Cr are each an austenite stabilizing element and improve the low-temperature toughness of the weld metal.
• Ni is an expensive metal, so in order to improve the low-temperature toughness of the weld metal while suppressing the cost of the weld metal, it is preferable that the Mn content, Ni content, and Cr content in the weld metal each satisfy the above-mentioned ranges, and that the total of the Mn content, Ni content, and Cr content (Mn+Ni+Cr) be 15.0% or more.
• the total of the Mn content, Ni content and Cr content (Mn+Ni+Cr) in the weld metal is more preferably 17.0% or more, 19.0% or more, 20.0% or more, 22.0% or more, 24.0% or more, 26.0% or more, 28.0% or more, or 30.0% or more.
• the Mn content is not excessive, the stacking fault energy is not too low and toughness can be ensured. Furthermore, since the Cr content is not excessive, the amount of low melting point compounds in the molten metal can be reduced, and the solid-liquid coexistence temperature range of the molten metal can be prevented from widening, so that the occurrence of hot cracks can be suppressed.
• the Mn content, Ni content, and Cr content in the weld metal each satisfy the above range, and the total of the Mn content, Ni content, and Cr content (Mn + Ni + Cr) is 47.0% or less.
• the total content of Mn, Ni and Cr (Mn+Ni+Cr) in the weld metal is more preferably 45.0% or less, 42.0% or less, or 40.0% or less.
• Mn and Ni are each an austenite stabilizing element and improve the low temperature toughness of the weld metal.
• Ni is an expensive metal, and if Mn is excessively increased, the stacking fault energy decreases and the toughness deteriorates. Therefore, from the viewpoint of improving the low-temperature toughness of the weld metal while suppressing the cost of the weld metal, it is preferable that the mass ratio of the Mn content to the Ni content (Ni/Mn) in the weld metal be 0.10 or more.
• the lower limit of the mass ratio (Ni/Mn) of the Mn content to the Ni content in the weld metal is more preferably 0.20, 0.30, 0.50, 0.70, 0.73, 1.00, 1.10, or 1.20.
• the upper limit of the mass ratio (Ni/Mn) of the Mn content to the Ni content in the weld metal is preferably 10.00, 8.00, or 5.00.
• Nb, Ti, V, and Al are all elements that improve the strength of the weld metal by precipitation strengthening, so the weld metal contains one or more of these elements, and their total content (Nb+Ti+V+Al) is set to be 0.005% or more.
• the lower limit of the total of Nb, Ti, V, and Al (Nb+Ti+V+Al) in the weld metal is preferably 0.010%, 0.020%, 0.050%, 0.100%, 0.300%, or 0.500%.
• the upper limit of the total of Nb, Ti, V, and Al (Nb+Ti+V+Al) in the weld metal is not particularly limited, but is preferably 2.000%, 1.800%, 1.500%, or 1.300% in order to prevent deterioration of toughness due to excessive formation of precipitates.
• the fcc proportion in the weld metal is 70% or more.
• the fcc proportion is more preferably 80% or more, or 90% or more, and may be 100%.
• the remainder of the structure is bcc.
• the tensile strength of the weld metal is preferably, for example, 590 to 1200 MPa.
• the tensile strength can be measured by conducting a tensile test on the weld metal in accordance with JIS Z3111:2005.
• the weld joint according to the present disclosure includes the weld metal according to the present disclosure.
• the weld joint according to the present disclosure includes a steel material serving as a base material, and a welded portion including a weld metal and a weld heat affected zone.
• a welded structure according to the present disclosure has the welded joint according to the present disclosure.
• the welded joint according to the present disclosure contains the weld metal according to the present disclosure, so it is inexpensive and has excellent low-temperature toughness.
• the welded joint according to the present disclosure can be manufactured by welding the base steel material with a welding material.
• the method of manufacturing a welded joint according to the present disclosure is obtained by gas-shielded arc welding of steel material using a flux-cored wire.
• the chemical components of the weld metal include components derived from the flux-cored wire, which is the welding material, and the steel material, which is the base material.
• the manufacturing method of the welded joint according to the present disclosure is obtained by submerged arc welding using a solid wire and flux.
• a solid wire and flux For example, in submerged arc welding, granular flux is spread on the weld line in advance, a solid wire is fed into it, and welding is performed by the arc heat generated from the arc between the solid wire and the steel material in the flux.
• the chemical components of the weld metal include components derived from the solid wire and flux, which are the welding materials, and the steel material, which is the base material.
• the manufacturing method of the welded joint according to the present disclosure can be obtained by a welding method such as, for example, shielded metal arc welding, simple electrogas arc welding, electroslag welding, TIG welding, and gas shielded welding using a solid wire.
• a welding method such as, for example, shielded metal arc welding, simple electrogas arc welding, electroslag welding, TIG welding, and gas shielded welding using a solid wire.
• the chemical components of the weld metal include components derived from the welding material and the base steel material.
• the base material of the welded joint according to the present disclosure i.e., the type of steel material (material to be welded) used in the manufacturing method of the welded joint described above, is not particularly limited, but for example, Ni-based low-temperature steel containing 6-9% Ni with a plate thickness of 20 mm or more can be suitably used.
• Weld metals were obtained by the following methods: shielded metal arc welding (SMAW) using a shielded metal arc welding rod, gas metal arc welding (GMAW) using a flux-cored wire, and submerged arc welding (SAW) using a solid wire and flux.
• SMAW shielded metal arc welding
• GMAW gas metal arc welding
• SAW submerged arc welding
• Shielded metal arc welding (SMAW) using a shielded metal arc welding electrode> (Manufacture of covered electrodes)
• the covered electrode was manufactured by the method described below. First, a core wire having the chemical composition shown in Tables 2-A and 2-B was coated with a flux having the composition shown in Table 2-C, and then baked at a temperature range of 300 to 500°C for 1 to 3 hours to produce a prototype covered metal arc welding rod. The final welding rod diameter of the obtained covered metal arc welding rod was ⁇ 6.0 mm, and the average thickness of the flux was 1.0 mm.
• the configurations of these covered metal arc welding rods (numbers 1 to 3, 15, A1, and A4) are shown in Tables 2-A to 2-C.
• the units of the contents of the chemical components of the core wire shown in Tables 2-A and 2-B are “mass % relative to the total mass of the core wire.”
• the units of the contents of the components of the flux (oxides, fluorides, and metal carbonates) shown in Table 2-C are “mass % relative to the total mass of the flux.”
• TiO 2 indicates the sum of the TiO 2 converted values of Ti oxides
• SiO 2 indicates the sum of the SiO 2 converted values of Si oxides
• Al 2 O 3 indicates the sum of the Al 2 O 3 converted values of Al oxides
• MgO indicates the sum of the MgO converted values of Mg oxides
• K 2 O indicates the sum of the K 2 O converted values of K oxides.
• the remainder of the core wire shown in Tables 2-A and 2-B is iron and impurities.
• blanks in the tables relating to the chemical composition of the core wire and the content of the flux components mean that the content of the component is less than the significant digits. These components may be unavoidably mixed or generated in amounts less than the significant digits.
• GMAW Gas shielded arc welding
• the flux-cored wire was produced by the method described below. First, a steel strip was fed in the longitudinal direction and formed into a U-shaped open tube using a forming roll. Flux was supplied into the open tube through the opening of the open tube, and the opposing edges of the opening of the open tube were butt-welded to obtain a seamless tube. This seamless tube was drawn to obtain a flux-cored wire without slit-like gaps. In this manner, a flux-cored wire having a final wire diameter of ⁇ 1.2 mm was produced.
• the flux-cored wires were annealed for 4 hours or more at a temperature range of 650 to 950°C. After the prototypes were made, a lubricant was applied to the wire surface.
• the compositions (chemical components of the entire wire, components of the flux) of these flux-cored wires (numbers 4 to 9, A2) are shown in Tables 3-A to 3-C.
• the balance of the chemical composition of the entire wire shown in Tables 3-A and 3-B is iron and impurities.
• Each element contained in the flux-cored wire shown in Tables 3-A and 3-B is in the form of a steel sheath or metal powder.
• blanks in the tables relating to the chemical composition of the entire wire and the contents of the components of the flux mean that the contents of the components are less than the significant digits. These components may be unavoidably mixed or generated in amounts less than the significant digits.
• the obtained flux-cored wires (numbers 4 to 9, A2) were used for vertical upward gas-shielded arc welding to produce welded joints having weld metals.
• As the steel plate to be welded 9% Ni steel (steel plate conforming to JIS G 3127 SL9N590) having a plate thickness of 50 mm was used.
• the type of welding gas used during welding was Ar-20% CO2 gas. All welding currents used during welding were direct current, and all wire polarities were positive.
• the welding conditions were those for "flux-cored wire (GMAW)" as shown in Table 5.
• the chemical compositions of the weld metals in the welded joints produced are shown in Tables 1-A to 1-C (numbers 4 to 9, A2). In Tables 1-A to 1-C, values outside the ranges specified in this disclosure are underlined.
• Solid wire manufacturing Submerged Arc Welding (SAW) using Solid Wire and Flux> (Solid wire manufacturing)
• the solid wire was manufactured by the method described below. First, steels having the chemical compositions shown in Tables 4-A and 4-B were melted and then forged. The steels were then rolled into rods, which were then drawn to obtain solid wires. In this manner, solid wires (Nos. 10 to 14, 16 to 17, A3, and A5) each having a final wire diameter of ⁇ 2.4 mm were produced. The chemical components of the obtained solid wire were analyzed and found to be as shown in Tables 4-A and 4-B. After the prototype was made, a lubricant was applied to the wire surface.
• the balance of the wires shown in Tables 4-A and 4-B is iron and impurities.
• the blanks in the table for the contents of the chemical components of the wires mean that the contents of the chemical components are less than the significant digits. These chemical components may be unavoidably mixed or generated in amounts less than the significant digits.
• the obtained solid wires (Nos. 10 to 14, 16 to 17, A3, and A5) were used to perform submerged arc welding in a downward position to produce welded joints having weld metals. Specifically, the solid wires were used in combination with NITTETSU FLUX 10H manufactured by Nippon Steel & Sumitomo Metals Co., Ltd., which is a flux for submerged arc welding, to perform submerged arc welding.
• the steel plate to be welded was a 9% Ni steel (steel plate conforming to JIS G 3127 SL9N590) having a plate thickness of 40 mm. All welding currents during welding were direct current, and all wire polarities were positive.
• the welding conditions were those of "submerged arc welding (SAW)" as shown in Table 5.
• SAW submerged arc welding
• Tables 1-A to 1-C numbers 10 to 14, 16 to 17, A3, and A5
• Tables 1-A to 1-C values outside the ranges specified in this disclosure are underlined.
• weld metal of the present disclosure has excellent low-temperature toughness.
• the comparative examples did not satisfy any of the requirements defined in this disclosure and therefore failed in low temperature toughness.

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