WO2020203334A1 - Tig溶接用溶加材 - Google Patents
Tig溶接用溶加材 Download PDFInfo
- Publication number
- WO2020203334A1 WO2020203334A1 PCT/JP2020/012214 JP2020012214W WO2020203334A1 WO 2020203334 A1 WO2020203334 A1 WO 2020203334A1 JP 2020012214 W JP2020012214 W JP 2020012214W WO 2020203334 A1 WO2020203334 A1 WO 2020203334A1
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- Prior art keywords
- less
- welding
- metal
- strength
- filler
- Prior art date
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Classifications
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- 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 degrees C
- B23K35/3053—Fe as the principal constituent
- B23K35/3073—Fe as the principal constituent with Mn as next major constituent
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- 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
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0255—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in welding
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- 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 degrees C
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- 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
-
- 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
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
Definitions
- the present invention relates to a filler material for TIG (Tungsten Inert Gas) welding, and more particularly to a filler material for welding high Mn steel materials used in an extremely low temperature environment.
- TIG Tungsten Inert Gas
- liquefied natural gas (hereinafter, also referred to as LNG) does not contain sulfur, it is said to be a clean fuel that does not generate air pollutants such as sulfide oxides, and its demand is increasing.
- the container (tank) for transporting or storing LNG is required to maintain excellent cryogenic impact toughness at a temperature of -162 ° C or lower, which is the liquefaction temperature of LNG. ..
- high Mn-containing steel containing about 10 to 35% of Mn in mass% (here, also referred to as high Mn steel). ) Is being considered.
- the high Mn steel is in the austenitic phase even at extremely low temperatures, does not undergo brittle fracture, and has a higher strength than the austenitic stainless steel. Therefore, there has been a demand for the development of a welding material capable of stably welding such a high Mn-containing steel material.
- Patent Document 1 proposes "a high-strength welded joint portion having excellent ultra-low temperature impact toughness and a flux cored arc welding wire for this purpose".
- the flux cored arc welding wire described in Patent Document 1 has a weight% of C: 0.15 to 0.8%, Si: 0.2 to 1.2%, Mn: 15 to 34%, Cr: 6% or less, Mo: 1.5.
- the Charpy impact test at a test temperature of -196 ° C has excellent low temperature toughness of 28 J or more and normal temperature tensile strength of 400 MPa or more. It is said that a welded joint with high strength can be effectively obtained, and the wire composition is adjusted to Mo: 1.5% or more, so that a welded joint with excellent high temperature crack resistance can be secured.
- Patent Document 2 proposes "welding material for cryogenic steel".
- the “welding material for ultra-low temperature steel” described in Patent Document 2 is "in mass%, C: 0.08% or less, Si: 2.0% or less, Mn: 8.0 to 18.0%, Ni: 12.5-20.0%, Cr. : 10.0 to 14.0%, Mo: 2.0 to 7.0%, N: 0.20% or less, S: 0.005% or less, the balance is a welding material consisting of iron and unavoidable impurities, and REM is in the range of 0.001 to 0.1%.
- S 0.005% or less
- the "welding material for extremely low temperature steel” described in Patent Document 2 is described. It is said that it is a welding material that can obtain good ultra-low temperature characteristics in the welded part and has excellent cracking resistance in the reheated part.
- Patent Document 1 the technique described in Patent Document 1 is a flux cored wire, so that the amount of fume generated during welding is large. Therefore, there is a problem that the welder is exposed to an environment with a large amount of fume, and there is also a problem that welding defects such as blow holes and poor fusion are likely to occur, and repair is difficult. According to the studies by the present inventors, it has been found that these fume problems can be avoided by using a solid wire (or rod).
- Patent Document 2 has a description that good cryogenic characteristics can be obtained, but there is no specific description about the strength of the welded portion. According to the studies by the present inventors, in the technique described in Patent Document 2, the strength of the obtained welded portion (welded metal) is low, and the desired material recently required for a material used in an extremely low temperature environment. There was a problem that high strength could not be satisfied.
- the present invention solves the above-mentioned problems of the prior art, and provides a welded joint portion having both high strength and excellent ultra-low temperature impact toughness, which is suitable as a welding material for high Mn steel materials used in an extremely low temperature environment. It is an object of the present invention to provide a filler material for TIG welding that can be produced.
- the "welding material” here refers to a wire-shaped or rod-shaped welding material.
- high strength here means that the normal temperature yield strength (0.2% proof stress) of the weld metal manufactured in accordance with JIS Z 3111 is 400MPa or more and the normal temperature tensile strength is 660MPa or more. It shall be said.
- Excellent cryogenic impact toughness means that the absorbed energy vE -196 of the charpy impact test at a test temperature of -196 ° C of the weld metal manufactured in accordance with JIS Z 3111 is 28J or more. It shall mean that.
- the present inventors first diligently studied a composition capable of ensuring the desired high strength to be retained by the weld metal (welded metal) for cryogenic temperatures. As a result, it was found that it is necessary to contain C, Mn, Cr and Mo in a certain amount or more in order to increase the strength of the weld metal (welded metal).
- a filler metal for TIG welding which has a large processing amount during wire drawing
- if a large amount of C, Mn, Cr, and Mo is contained in order to increase the strength of the weld metal (welded metal) the welding material is stretched. There is a problem that cracks and breaks are likely to occur during wire processing.
- the present inventors have found that wire drawing can be performed by suppressing boron nitride and carbides formed in steel.
- the composition of the filler material for TIG welding was adjusted to 0.2 to 0.8% for C, 0.15 to 0.9% for Si, 17.0 to 28.0% for Mn, and 0.01 to 10.0% for Ni.
- Cr a specific range of 0.4 to 4.0% and Mo to 0.01 to 3.5%, and further reducing the impurity B to less than 0.0010% and the charcoal-forming elements Ti, Nb, and V to 0.04% or less, respectively.
- the present invention has been completed by further studying based on such findings, and the gist of the present invention is as follows.
- a filler material for TIG welding which contains B: less than 0.0010% and N: 0.12% or less, and has a composition consisting of a balance Fe and unavoidable impurities.
- the composition is further selected from one or more selected from V: 0.04% or less, Ti: 0.04% or less, and Nb: 0.04% or less in mass%.
- the composition is further selected from Cu: 1.0% or less, Al: 0.1% or less, Ca: 0.01% or less, and REM: 0.02% or less in mass%.
- a filler material for TIG welding which comprises one or more of the above.
- a filler metal material for TIG welding which is excellent in manufacturability and can easily manufacture a welded joint portion having high strength and excellent ultra-low temperature impact toughness as a welding material for a steel material containing high Mn. It can be done and has a remarkable effect on the industry.
- the filler material for TIG welding of the present invention (hereinafter, also referred to as the filler material of the present invention) is a filler material suitable for TIG welding of high Mn-containing steel materials.
- the filler metal of the present invention can TIG weld high Mn-containing steel materials to each other, and the weld metal produced in accordance with JIS Z 3111 has a 0.2% toughness at room temperature of 400 MPa or more and a tensile strength at room temperature of 660 MPa or more.
- TIG welded joints that can have high strength and excellent ultra-low temperature impact toughness with an absorbed energy of 28J or more in the Charpy impact test at test temperature: -196 ° C, and have high strength and excellent ultra-low temperature impact toughness. It is a welding material that can be manufactured.
- the filler metal of the present invention has a basic composition of C: 0.2 to 0.8%, Si: 0.15 to 0.9%, Mn: 17.0 to 28.0%, P: 0.03% or less, S: 0.03% or less, Ni: It contains 0.01 to 10.0%, Cr: 0.4 to 4.0%, Mo: 0.01 to 3.5%, B: less than 0.0010%, N: 0.12% or less, and has a composition consisting of the balance Fe and unavoidable impurities.
- C 0.2-0.8% C is an element that has the effect of increasing the strength of the weld metal by strengthening the solid solution. C also stabilizes the austenite phase and improves the cryogenic impact toughness of the weld metal. In order to obtain such an effect, a content of 0.2% or more is required. However, if it is contained in excess of 0.8%, carbides are precipitated, the cryogenic impact toughness is lowered, and high temperature cracking is likely to occur during welding. Therefore, C was limited to the range of 0.2 to 0.8%. It is preferably 0.3 to 0.7%, more preferably 0.4 to 0.6%.
- Si acts as an antacid, increases the yield of Mn, increases the viscosity of the molten metal, and has the effect of stably maintaining the bead shape. In order to obtain such an effect, a content of 0.15% or more is required. However, if Si is contained in excess of 0.9%, the cryogenic toughness of the weld metal is reduced. In addition, segregation occurs during solidification to form a liquid phase at the interface of the solidified cell, which reduces high temperature crack resistance. Therefore, Si was limited to the range of 0.15 to 0.9%. It is preferably 0.2 to 0.7%.
- Mn 17.0-28.0%
- Mn is an element that stabilizes the austenite phase at low cost, and the content of Mn is required to be 17.0% or more in the present invention. If Mn is less than 17.0%, a ferrite phase is formed in the weld metal and the toughness at extremely low temperatures is significantly reduced. On the other hand, when Mn exceeds 28.0%, excessive Mn segregation occurs during solidification, inducing high-temperature cracking. Therefore, Mn was limited to the range of 17.0 to 28.0%. It is preferably 18.0 to 26.0%.
- P 0.03% or less
- P is an element that segregates at the grain boundaries and induces high-temperature cracking. In the present invention, it is preferable to reduce it as much as possible, but 0.03% or less is acceptable. Therefore, P was limited to 0.03% or less. It is preferably 0.02% or less. On the other hand, excessive reduction leads to an increase in refining cost. Therefore, P is preferably adjusted to 0.003% or more.
- S 0.03% or less S exists as a sulfide-based inclusion MnS in the weld metal. Since MnS is the starting point of fracture, it reduces cryogenic impact toughness. Therefore, S was limited to 0.03% or less. It is preferably 0.02% or less. On the other hand, excessive reduction leads to an increase in refining cost. Therefore, it is preferable to adjust S to 0.001% or more.
- Ni 0.01-10.0%
- Ni is an element that strengthens austenite grain boundaries and segregates at grain boundaries to improve cryogenic impact toughness. In order to obtain such an effect, a content of 0.01% or more is required.
- Ni also has the effect of stabilizing the austenite phase, so if the content is further increased, the austenite phase is stabilized and the cryogenic impact toughness of the weld metal is improved.
- Ni is an expensive element, and a content of more than 10.0% is economically disadvantageous. Therefore, Ni was limited to 0.01 to 10.0%. It is preferably 0.05 to 9.0%, and more preferably 1.0 to 8.0%.
- Cr acts as an element that stabilizes the austenite phase at cryogenic temperatures, improving the cryogenic impact toughness of weld metals. Cr also has the effect of improving the strength of the weld metal. In addition, Cr works effectively to increase the liquidus line of the molten metal and suppress the occurrence of high temperature cracking. Furthermore, Cr also works effectively to enhance the corrosion resistance of the weld metal. In order to obtain such an effect, a content of 0.4% or more is required. If Cr is less than 0.4%, the above effect cannot be ensured. On the other hand, if it is contained in excess of 4.0%, Cr carbides are formed, which causes a decrease in cryogenic impact toughness. Further, due to the formation of Cr carbide, the workability at the time of wire drawing of the filler metal is lowered. Therefore, Cr was limited to the range of 0.4 to 4.0%. It is preferably 0.8 to 3.0%.
- Mo 0.01-3.5%
- Mo is an element that strengthens the austenite grain boundaries and segregates at the grain boundaries to improve the cryogenic impact toughness of the weld metal. Such an effect becomes remarkable when the content is 0.01% or more. Further, if the content exceeds 0.01%, it also has an effect of improving the strength of the weld metal by strengthening the solid solution. On the other hand, if it is contained in an amount of more than 3.5%, it is precipitated as a carbide, which lowers the hot workability and induces cracking when the filler metal is drawn, which lowers the manufacturability. Therefore, Mo was limited to the range of 0.01 to 3.5%. It is preferably 0.1 to 3.2%, more preferably 1.0 to 3.0%.
- B Less than 0.0010% B mixed in steel as an impurity segregates at the austenite grain boundaries.
- B is mixed in at 0.0010% or more, boron nitride is formed at the austenite grain boundaries and the grain boundary strength is lowered. Due to this decrease in grain boundary strength, during wire drawing of the filler metal, the austenite grain boundary becomes the starting point of occurrence of fracture and causes disconnection, which lowers the wire drawing workability and lowers the filler metal manufacturability. Since this formation of boron nitride can be suppressed by limiting B to less than 0.0010%, B is limited to less than 0.0010%. It is preferably 0.0009% or less, and more preferably 0.0008% or less.
- N 0.12% or less
- N is an element that is inevitably mixed, but like C, it effectively contributes to improving the strength of the weld metal, stabilizes the austenite phase, and stabilizes the ultra-low temperature impact toughness. It can also be improved. Since such an effect becomes remarkable when the content is 0.003% or more, it is preferable to contain 0.003% or more. However, if it is contained in excess of 0.12%, a nitride is formed and the cryogenic impact toughness is lowered. Therefore, N was limited to 0.12% or less. It is preferably 0.10% or less, and more preferably 0.08% or less.
- the above-mentioned components are the basic components, and in the present invention, V: 0.04% or less, Ti: 0.04% or less, as necessary and optional components, are added to the above-mentioned basic composition. And Nb: 1 or more selected from 0.04% or less, and / or Cu: 1.0% or less, Al: 0.1% or less, Ca: 0.01% or less, and REM: 0.02% or less. One or more of the above can be selected and contained.
- these optional components will be described.
- V 0.04% or less
- Ti 0.04% or less
- Nb 0.04% or less
- V, Ti, Nb all promote the formation of carbides and the strength of the weld metal. It is an element that contributes to improvement, and can be selected as necessary and contains one or more.
- V 0.04% or less
- V is a carbide-forming element, which precipitates fine carbides and contributes to the improvement of the strength of the weld metal. In order to obtain such an effect, it is preferably contained in an amount of 0.001% or more. On the other hand, if it is contained in excess of 0.04%, the carbide becomes coarse and becomes a cracking starting point during wire drawing of the filler metal, which lowers the wire drawing workability and lowers the manufacturability of the filler metal. Therefore, when it was contained, V was limited to 0.04% or less.
- Ti 0.04% or less
- Ti is a carbide-forming element, which precipitates fine carbides and contributes to the improvement of the strength of the weld metal.
- Ti deposits carbides at the interface of the solidified cell of the weld metal and contributes to suppressing the occurrence of high temperature cracks. In order to obtain such an effect, it is preferably contained in an amount of 0.001% or more. However, if the content exceeds Ti: 0.04%, the carbide becomes coarse and becomes a starting point of cracking during wire drawing of the filler metal, which lowers the wire drawing workability and lowers the manufacturability of the filler metal. Therefore, when it was contained, Ti was limited to 0.04% or less.
- Nb 0.04% or less
- Nb is a carbide-forming element, which is an element that precipitates carbides and contributes to the improvement of the strength of the weld metal.
- Nb precipitates carbides at the interface of the solidified cell of the weld metal and contributes to suppressing the occurrence of high-temperature cracks. In order to obtain such an effect, it is preferably contained in an amount of 0.001% or more.
- Nb exceeds 0.04%, the carbide becomes coarse and becomes a cracking starting point during wire drawing of the filler metal, which lowers the wire drawing workability and lowers the manufacturability of the filler metal. Therefore, when it was contained, Nb was limited to 0.04% or less.
- Cu is an element that contributes to austenite stabilization
- Al is welded. It is an element that improves workability
- Ca and REM are elements that contribute to the improvement of workability, and can be selected as necessary and contain one or more.
- Cu 1.0% or less
- Cu is an element that stabilizes the austenite phase, stabilizes the austenite phase even at extremely low temperatures, and improves the extremely low temperature impact toughness of the weld metal. In order to obtain such an effect, it is preferably contained in an amount of 0.01% or more. However, if it is contained in a large amount exceeding 1.0%, the hot ductility is lowered and the manufacturability of the filler metal is lowered. Therefore, when it was contained, Cu was limited to 1.0% or less.
- Al acts as an antacid, increases the viscosity of the molten metal, and has an important effect of stably maintaining the bead shape.
- Al raises the liquidus temperature of the molten metal and contributes to suppressing the occurrence of high-temperature cracking of the weld metal. Since such an effect becomes remarkable when the content is 0.005% or more, it is preferable to contain 0.005% or more. However, if it is contained in excess of 0.1%, the viscosity of the molten metal becomes too high, and conversely, the beads do not spread and defects such as poor fusion increase. Therefore, when it was contained, Al was limited to the range of 0.1% or less. It is preferably 0.005 to 0.06%.
- Ca 0.01% or less Ca combines with S in the molten metal to form a high melting point sulfide CaS. Since CaS has a higher melting point than MnS, it maintains a spherical shape without advancing in the rolling direction during hot working of the filler metal, which is advantageous for improving the workability of the filler metal. Such an effect becomes remarkable when the content is 0.001% or more. On the other hand, if the content exceeds 0.01%, the amount of slag generated during welding increases, causing slag entrainment. Therefore, when it is contained, Ca is limited to 0.01% or less.
- REM 0.02% or less REM is a potent antacid and is present in weld metals in the form of REM oxides.
- the REM oxide acts as a nucleation site during solidification, thereby refining the crystal grains and contributing to the improvement of the strength of the weld metal. Such an effect becomes remarkable when the content is 0.001% or more.
- REM if it is contained in excess of 0.02%, the amount of slag generated increases and slag entrainment is caused. Therefore, when it was contained, REM was limited to 0.02% or less.
- the rest other than the above components consist of Fe and unavoidable impurities.
- the production of the filler material of the present invention does not need to be particularly limited except that the molten steel having the above composition is used and the annealing temperature is 900 to 1200 ° C. Any method can be applied.
- a casting step in which molten steel having the above composition is melted in a regular melting furnace such as an electric furnace or a vacuum melting furnace and cast into a mold having a predetermined shape to obtain a steel ingot, and the obtained steel ingot.
- a heating step of heating the steel to a predetermined temperature and a hot rolling step of hot rolling the heated steel ingot to obtain a steel material (rod shape) having a predetermined shape are sequentially performed, and then the obtained steel material is obtained.
- the filler metal of the present invention is obtained by performing a cold rolling step of cold rolling (cold wire drawing) a plurality of times (cold wire drawing) and, if necessary, annealing to obtain a filler metal having a desired size. Can be manufactured.
- the molten steel having the composition shown in Table 1 was melted and cast in a vacuum melting furnace to obtain 1000 kg of steel ingot.
- the obtained steel ingot is heated to 1200 ° C., then hot-rolled, then cold-rolled, and annealed (900-1200 ° C.) as necessary to weld to TIG welding with a diameter of 2.0 mm and a length of 1000 mm.
- a material (welding rod) was obtained.
- each filler metal was evaluated by measuring the rolling load (drawing load), observing cracks, and observing the cross section of the filler metal. If it is determined that rolling (drawing) processing is impossible due to a high rolling load (drawing load), cracks are found, or due to the cracks that have occurred, further steps are required. When it became impossible to proceed, it was evaluated as "defective”. Other than that, it was evaluated as "good”.
- a high Mn steel plate for cryogenic temperature (plate thickness: 12 mm) was prepared, and in accordance with JIS Z3111, a 45 ° V-shaped groove was formed by abutting, TIG welding was performed, and the opening was performed. Welded metal was obtained in the tip.
- the steel sheet used as the test plate was a high Mn steel sheet for cryogenic temperature having a composition of 0.5% C-0.4% Si-25% Mn-3% Cr-residue Fe in mass%.
- each filler metal (diameter 2.0 mm) manufactured from molten steel having the composition shown in Table 1 is used as a welding material, without preheating, in a downward posture, current: 200 A (DCEN), voltage: 12 V, welding.
- the test was carried out under the conditions of a speed: 8 cm / min, a filler feed speed: 10 g / min, a path interval: 100 to 150 ° C, and a shield gas: Ar.
- the electrode was a pure tungsten rod (3.2 mm ⁇ ).
- weld metal was observed with an optical microscope to determine the presence or absence of welding cracks.
- Weld cracks are high-temperature cracks, and when cracks are observed, they are evaluated as "defective” because the high-temperature crack resistance is reduced. When no cracking was observed, it was evaluated as "good” because of its excellent high temperature cracking resistance.
- a tensile test piece of the weld metal (parallel part diameter 6 mm ⁇ ) and a Charpy impact test piece of the weld metal (V notch) are collected in accordance with JIS Z 3111, and the tensile test and impact are performed. The test was carried out. The tensile test was carried out at room temperature with three test pieces each, and the average value of the obtained values (0.2% proof stress and tensile strength) was taken as the tensile property of the weld metal using the filler metal. ..
- the rolling load at the time of wire drawing was not high, cracks did not occur, and the filler material was excellent in manufacturability. Furthermore, there was no welding crack (high temperature crack) during welding, and it was excellent in high temperature crack resistance. Moreover, the yield strength (0.2% proof stress) at room temperature is 400 MPa or more, the tensile strength at room temperature is 660 MPa or more, and the absorbed energy vE -196 of the Charpy impact test at the test temperature: -196 ° C is 28 J or more, which is high strength. It was a welding material (welding material) for TIG welding from which a welded metal having excellent ultra-low temperature toughness could be obtained.
- the manufacturability of the filler metal is lowered, welding cracks (high temperature cracks) occur and the high temperature crack resistance is lowered, or 0.2% proof stress at room temperature is obtained.
- the B content of the fillering materials No. 15 and No. 16 exceeds the range of the present invention, and the filler material No. 17 (comparative example) has a Cr content.
- the filler metal No. 18 has an N content exceeding the range of the present invention, the wire drawing workability is lowered and the filler metal is stretched to a desired diameter. I could't make a line.
- filler material No. 19 has a P content
- filler metal No. 20 has a C content
- filler metal No. 21 has an Mn content. Since the Si content of the filler metal No. 22 (Comparative Example) exceeds the range of the present invention, welding cracks occur and the high temperature crack resistance is lowered. Further, since the filler metal No. 23 (Comparative Example) had an S content exceeding the range of the present invention, the cryogenic impact toughness was lowered.
- the filler material No. 24 (Comparative Example) has a Ni content and the filler metal No. 25 (Comparative Example) has a Mo content below the range of the present invention, the austenite grain boundaries are weak. , Very low temperature impact toughness was reduced. Further, since the filler material No. 26 (Comparative Example) has a C content and the filler metal No. 27 (Comparative Example) has a Cr content below the range of the present invention, the strength is lowered. The desired high strength could not be secured.
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Abstract
Description
C:0.2~0.8%、
Si:0.15~0.9%、
Mn:17.0~28.0%、
P:0.03%以下、
S:0.03%以下、
Ni:0.01~10.0%、
Cr:0.4~4.0%、
Mo:0.01~3.5%、
B:0.0010%未満および
N:0.12%以下
を含み、残部Feおよび不可避的不純物からなる組成を有することを特徴とするTIG溶接用溶加材。
Cは、固溶強化により、溶接金属の強度を上昇させる作用を有する元素である。また、Cは、オーステナイト相を安定化させ、溶接金属の極低温衝撃靭性を向上させる。このような効果を得るためには、0.2%以上の含有を必要とする。しかし、0.8%を超えて含有すると、炭化物が析出し、極低温衝撃靭性が低下し、さらに、溶接時の高温割れが生じやすくなる。そのため、Cは0.2~0.8%の範囲に限定した。好ましくは0.3~0.7%であり、より好ましくは0.4~0.6%である。
Siは、脱酸剤として作用し、Mnの歩留りを高めるとともに、溶融金属の粘性を高め、ビード形状を安定的に保持する効果がある。そのような効果を得るためには、0.15%以上の含有を必要とする。しかし、0.9%を超えてSiを含有すると、溶接金属の極低温靭性を低下させる。また、凝固時に偏析し、凝固セル界面に液相を生成して、耐高温割れ性を低下させる。そのため、Siは0.15~0.9%の範囲に限定した。好ましくは0.2~0.7%である。
Mnは、安価に、オーステナイト相を安定化する元素であり、本発明では17.0%以上の含有を必要とする。Mnが17.0%未満では、溶接金属中にフェライト相が生成し、極低温での靭性が著しく低下する。一方、Mnが28.0%を超えると、凝固時に過度のMn偏析が発生し,高温割れを誘発する。そのため、Mnは17.0~28.0%の範囲に制限した。好ましくは18.0~26.0%である。
Pは、結晶粒界に偏析し、高温割れを誘発する元素であり、本発明では、できるだけ低減することが好ましいが、0.03%以下であれば、許容できる。そのため、Pは0.03%以下に限定した。好ましくは0.02%以下である。一方、過度の低減は、精練コストの高騰を招く。そのため、Pは0.003%以上に調整することが好ましい。
Sは、溶接金属中では、硫化物系介在物MnSとして存在する。MnSは、破壊の発生起点となるため、極低温衝撃靭性を低下させる。そのため、Sは0.03%以下に限定した。好ましくは0.02%以下である。一方、過度の低減は、精練コストの高騰を招く。そのため、Sは0.001%以上に調整することが好ましい。
Niは、オーステナイト粒界を強化する元素であり、粒界に偏析し、極低温衝撃靱性を向上させる。このような効果を得るためには、0.01%以上の含有を必要とする。また、Niは、オーステナイト相を安定化する効果もあるため、さらに含有量を増加すれば、オーステナイト相を安定化させて、溶接金属の極低温衝撃靭性を向上させる。しかし、Niは高価な元素であり、10.0%を超える含有は、経済的に不利となる。そのため、Niは0.01~10.0%に限定した。好ましくは0.05~9.0%であり、より好ましくは1.0~8.0%である。
Crは、極低温ではオーステナイト相を安定化させる元素として働き、溶接金属の極低温衝撃靭性を向上させる。また、Crは、溶接金属の強度を向上させる作用も有する。また、Crは、溶融金属の液相線を高めて、高温割れの発生を抑制するのに有効に作用する。さらに、Crは、溶接金属の耐食性を高めるのにも有効に作用する。このような効果を得るためには0.4%以上の含有を必要とする。Crが0.4%未満では、上記した効果を確保できない。一方、4.0%を超えて含有すると、Cr炭化物が生成し、極低温衝撃靭性の低下を招く。さらに、Cr炭化物の生成により、溶加材伸線時の加工性が低下する。そのため、Crは0.4~4.0%の範囲に限定した。好ましくは、0.8~3.0%である。
Moは、オーステナイト粒界を強化する元素であり、粒界に偏析し、溶接金属の極低温衝撃靭性を向上させる。このような効果は0.01%以上の含有で顕著となる。また、0.01%を超える含有では、固溶強化により溶接金属の強度を向上させる作用も有する。一方、3.5%を超えて含有すると、炭化物として析出して、熱間加工性を低下させ、また、溶加材伸線時に割れを誘発させるなど、製造性が低下する。そのため、Moは0.01~3.5%の範囲に限定した。好ましくは0.1~3.2%であり、より好ましくは1.0~3.0%である。
不純物として鋼中に混入したBは、オーステナイト粒界に偏析する。Bが0.0010%以上混入した場合は、オーステナイト粒界で窒化ホウ素を形成し、粒界強度を低下させる。この粒界強度の低下によって、溶加材伸線加工時に、オーステナイト粒界が破壊発生起点となり断線を生じさせて、伸線加工性を低下させ、溶加材製造性を低下させる。この窒化ホウ素の形成は、Bを0.0010%未満に制限することで抑制できるため、Bは0.0010%未満に制限した。好ましくは0.0009%以下であり、より好ましくは0.0008%以下である。
Nは、不可避的に混入する元素であるが、Cと同様に、溶接金属の強度向上に有効に寄与するとともに、オーステナイト相を安定化して、極低温衝撃靱性を安定的に向上させることもできる。このような効果は、0.003%以上の含有で顕著となるため、0.003%以上含有することが好ましい。しかし、0.12%を超えて含有すると、窒化物を形成し、極低温衝撃靱性が低下する。そのため、Nは0.12%以下に限定した。好ましくは0.10%以下であり、より好ましくは0.08%以下である。
V、Ti、Nbはいずれも、炭化物の形成を促進し、溶接金属の強度向上に寄与する元素であり、必要に応じて選択して1種または2種以上を含有できる。
Vは、炭化物形成元素であり、微細な炭化物を析出させて、溶接金属の強度向上に寄与する。このような効果を得るためには0.001%以上含有することが好ましい。一方、0.04%を超えて含有すると、炭化物が粗大化して、溶加材の伸線加工時に割れの発生起点となり、伸線加工性を低下させ、溶加材の製造性を低下させる。そのため、含有する場合には、Vは0.04%以下に限定した。
Tiは、炭化物形成元素であり、微細な炭化物を析出させて、溶接金属の強度向上に寄与する。また、Tiは、溶接金属の凝固セル界面に炭化物を析出させて、高温割れの発生抑制に寄与する。このような効果を得るためには0.001%以上含有することが好ましい。しかし、Ti:0.04%を超えて含有すると、炭化物が粗大化して、溶加材の伸線加工時に割れの発生起点となり、伸線加工性を低下させ、溶加材の製造性を低下させる。そのため、含有する場合には、Tiは0.04%以下に限定した。
Nbは、炭化物形成元素であり、炭化物を析出させて、溶接金属の強度向上に寄与する元素である。また、Nbは、溶接金属の凝固セル界面に炭化物を析出させて、高温割れの発生抑制に寄与する。このような効果を得るためには0.001%以上含有することが好ましい。しかし、Nbが0.04%を超えると、炭化物が粗大化して、溶加材の伸線加工時に割れの発生起点となり、伸線加工性を低下させ、溶加材の製造性を低下させる。そのため、含有する場合には、Nbは0.04%以下に限定した。
Cuはオーステナイト安定化に寄与する元素であり、Alは溶接作業性を向上させる元素であり、Ca、REMは加工性向上に寄与する元素であり、必要に応じて選択して1種または2種以上を含有できる。
Cuは、オーステナイト相を安定化する元素であり、極低温でもオーステナイト相を安定化させて、溶接金属の極低温衝撃靭性を向上させる。このような効果を得るためには、0.01%以上含有することが好ましい。しかし、1.0%を超えて多量に含有すると、熱間延性が低下し、溶加材の製造性が低下する。そのため、含有する場合には、Cuは1.0%以下に限定した。
Alは、脱酸剤として作用し、溶融金属の粘性を高め、ビード形状を安定的に保持する重要な作用を有する。また、Alは、溶融金属の液相線温度を高め、溶接金属の高温割れ発生の抑制に寄与する。このような効果は、0.005%以上の含有で顕著となるため、0.005%以上含有することが好ましい。しかし、0.1%を超えて含有すると、溶融金属の粘性が高くなりすぎて、逆に、ビードが広がらず融合不良などの欠陥が増加する。そのため、含有する場合には、Alは0.1%以下の範囲に限定した。好ましくは0.005~0.06%である。
Caは、溶融金属中でSと結合し、高融点の硫化物CaSを形成する。CaSは、MnSよりも高融点であるため、溶加材の熱間加工時に圧延方向に進展せずに球形を維持し、溶加材の加工性向上に有利に働く。このような効果は0.001%以上の含有で顕著となる。一方、0.01%を超えて含有すると、溶接時にスラグの発生量が増加してスラグ巻込みを引き起こす。そのため、含有する場合には、Caは0.01%以下に限定した。
REMは、強力な脱酸剤であり、溶接金属中でREM酸化物の形態で存在する。REM酸化物は凝固時の核生成サイトとなることで、結晶粒を微細化し、溶接金属の強度の向上に寄与する。このような効果は0.001%以上の含有で顕著となる。一方、0.02%を超えて含有すると、スラグの発生量が増加してスラグ巻込みを引き起こす。そのため、含有する場合には、REMは0.02%以下に限定した。
本発明溶加材の製造は、上記した組成を有する溶鋼を用いること、および焼鈍温度を900~1200℃とする以外は、とくにその製造方法を限定する必要はなく、常用の溶加材の製造方法がいずれも適用できる。例えば、上記した組成を有する溶鋼を、電気炉、真空溶解炉等の常用の溶製炉で溶製し、所定形状の鋳型等に鋳造して鋼塊を得る鋳造工程と、得られた鋼塊を、所定温度に加熱する加熱工程と、加熱された鋼塊に、熱間圧延を施し、所定形状の鋼素材(棒状)を得る熱延工程と、を順次行い、ついで、得られた鋼素材(棒状)を複数回の冷間圧延(冷間伸線加工)と必要に応じて焼鈍とを施して、所望寸法の溶加材とする冷延工程を行うことで、本発明溶加材を製造することができる。
引張試験は、室温で、各3本の試験片にて実施し、得られた値(0.2%耐力および引張強さ)の平均値を、当該溶加材を用いた溶着金属の引張特性とした。また、シャルピー衝撃試験は、各3本の試験片にて実施し、試験温度:-196℃における吸収エネルギーvE-196を求め、その平均値を、当該溶加材を用いた溶着金属の極低温衝撃靭性とした。
得られた結果を表2に示す。
また、溶加材No.23(比較例)はS含有量が、本発明の範囲を上回っているため、極低温衝撃靭性が低下していた。
また、溶加材No.26(比較例)はC含有量が、溶加材No.27(比較例)はCr含有量が、それぞれ本発明の範囲を下回っているため、強度が低下し、所望の高強度を確保できていなかった。
Claims (3)
- 質量%で、
C:0.2~0.8%、
Si:0.15~0.9%、
Mn:17.0~28.0%、
P:0.03%以下、
S:0.03%以下、
Ni:0.01~10.0%、
Cr:0.4~4.0%、
Mo:0.01~3.5%、
B:0.0010%未満および
N:0.12%以下
を含み、残部Feおよび不可避的不純物からなる組成を有することを特徴とするTIG溶接用溶加材。 - 前記組成が、さらに、質量%で、V:0.04%以下、Ti:0.04%以下、およびNb:0.04%以下のうちから選ばれた1種または2種以上を含有することを特徴とする請求項1に記載のTIG溶接用溶加材。
- 前記組成が、さらに、質量%で、Cu:1.0%以下、Al:0.1%以下、Ca:0.01%以下およびREM:0.02%以下のうちから選ばれた1種または2種以上を含有することを特徴とする請求項1または2に記載のTIG溶接用溶加材。
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JP7029034B1 (ja) * | 2020-11-26 | 2022-03-02 | Jfeスチール株式会社 | 溶接継手およびその製造方法 |
WO2022054492A1 (ja) * | 2020-09-10 | 2022-03-17 | Jfeスチール株式会社 | 溶接継手及び溶接継手の製造方法 |
WO2022113473A1 (ja) * | 2020-11-26 | 2022-06-02 | Jfeスチール株式会社 | 溶接継手およびその製造方法 |
WO2022186097A1 (ja) * | 2021-03-01 | 2022-09-09 | Jfeスチール株式会社 | Tig溶接継手 |
JP2022552353A (ja) * | 2019-10-16 | 2022-12-15 | ポスコ | 溶接棒用線材及びその製造方法 |
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