WO2022196540A1 - ガスシールドアーク溶接方法、溶接継手および溶接継手の製造方法 - Google Patents
ガスシールドアーク溶接方法、溶接継手および溶接継手の製造方法 Download PDFInfo
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- WO2022196540A1 WO2022196540A1 PCT/JP2022/010755 JP2022010755W WO2022196540A1 WO 2022196540 A1 WO2022196540 A1 WO 2022196540A1 JP 2022010755 W JP2022010755 W JP 2022010755W WO 2022196540 A1 WO2022196540 A1 WO 2022196540A1
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- 238000003466 welding Methods 0.000 title claims abstract description 230
- 238000000034 method Methods 0.000 title claims abstract description 61
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 84
- 239000010959 steel Substances 0.000 claims abstract description 84
- 239000000463 material Substances 0.000 claims abstract description 71
- 239000000919 ceramic Substances 0.000 claims abstract description 24
- 238000005304 joining Methods 0.000 claims abstract description 4
- 239000007789 gas Substances 0.000 claims description 33
- 239000011261 inert gas Substances 0.000 claims description 3
- 230000007547 defect Effects 0.000 description 12
- 239000011324 bead Substances 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 230000004927 fusion Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- 229910018068 Li 2 O Inorganic materials 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000003292 diminished effect Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
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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
- B23K37/00—Auxiliary devices or processes, not specially adapted to a procedure covered by only one of the preceding main groups
- B23K37/06—Auxiliary devices or processes, not specially adapted to a procedure covered by only one of the preceding main groups for positioning the molten material, e.g. confining it to a desired area
-
- 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
- B23K9/00—Arc welding or cutting
- B23K9/16—Arc welding or cutting making use of shielding gas
Definitions
- the present invention relates to a gas-shielded arc welding method, a welded joint obtained by using the method, and a method for manufacturing the welded joint. More particularly, the present invention relates to a first-layer welding method for narrow gap gas-shielded arc welding of steel materials.
- Narrowing of the groove can be cited as a method for improving welding efficiency.
- By reducing the groove area by narrowing the groove it is possible to reduce the number of welding passes and shorten the construction time.
- narrow gap welding insufficient fusion is likely to occur in the first layer welded portion, so studies are being conducted to secure the fusion depth.
- Patent Document 1 as a method of narrow groove welding, the first layer welding is performed in two or more passes, each pass is distributed to both sides of the bottom groove gap, and the welding wire supply angle supplied from the power supply tip at the tip of the welding torch is controlled in the range of 5° or more and 15° or less with respect to the perpendicular.
- a method is disclosed whereby it is possible to secure a melting depth of 1.5 mm or more at the bottom of the thick steel material.
- Patent Document 2 as a method of narrow groove welding, a pulse voltage is repeatedly applied, and the torch is positioned at both ends in the groove by reciprocating the torch in a direction that intersects the welding progress direction. Sometimes the arc length is controlled to create a buried arc. This discloses a method for ensuring the penetration depth.
- Patent Document 1 and Patent Document 2 disclose a narrow gap welding method using a backing metal.
- this backing metal may be undesirable from the point of view of joint integrity. That is, the shape between the base material and the backing metal is a sharp notch, which becomes a stress concentration portion. For this reason, in a welded joint using a backing metal, the notch may cause fatigue cracking or become a starting point of brittle fracture. Therefore, in order to avoid the presence of notches as described above, double-sided welding without a backing metal, or single-sided welding using a ceramic backing material that can be removed after welding, is used. Welding methods that result in the formation of a bead are believed to be preferred.
- Patent Document 1 and Patent Document 2 which disclose a narrow gap welding method, when a ceramic backing material having no conductivity (conductivity) is used, the current during welding cannot be ensured, and there is a problem that stable welding cannot be performed.
- the present invention realizes a narrow gap welding that can improve workability and a weld without a backing metal that may be the starting point of fatigue cracks and brittle fractures in a gas shielded arc welding method by butt of steel materials. Therefore, it is an object of the present invention to provide a gas shielded arc welding method for narrow groove single-sided butt using a ceramic backing material. Another object of the present invention is to provide a welded joint excellent in soundness using this welding method and a method for manufacturing the same.
- the inventors studied the conditions under which stable construction is possible when using a non-conductive ceramic backing material. As a result of extensive research, we found that by controlling the welding current and welding voltage and selecting the welding heat input that matches the root gap, a molten pool is formed directly under the arc to ensure conductivity, resulting in stable welding. found that it is possible. Furthermore, they found that a sound Uranami bead with no undercut in the first layer weld can be obtained.
- the backing material is made of ceramic
- the following method was found for the problem that the arc cannot be started because the conductivity cannot be secured.
- a steel tab with a steel backing is attached to the outside of a joint with a ceramic backing, and an arc is generated at the steel tab.
- the inventors discovered a method of scattering cut wires obtained by cutting the welding wire at the arc generation position inside the groove, thereby ensuring conductivity and starting the arc.
- a gas-shielded arc welding method for joining steel materials by multi-layer welding with a narrow gap The groove angle ⁇ of the steel material is set to 20 ° or less, and the root gap G (mm), which is the gap at the bottom of the groove, is set to 7 to 15 mm,
- a ceramic backing material is used
- the welding current I (A) is 250 to 400 A and the welding voltage V (V) is 25 to 45 V
- the value obtained by dividing the welding heat input Q (kJ/mm) by the root gap G (mm) [Q/G ] is in the range of 0.32 to 0.70, in one pass, Gas-shielded arc welding method.
- I welding current (A)
- V welding voltage
- S welding speed (mm/sec).
- the present invention in the gas shielded arc welding method by single-sided butt of steel materials, narrow gap welding that can improve workability and welds without backing metal that may be the starting point of fatigue cracks and brittle fractures and As a result, it is possible to provide a gas shielded arc welding method for single-sided narrow gap butt using a ceramic backing material, a welded joint excellent in soundness, and a method for manufacturing the same, which is very effective in the industry.
- FIG. 1 is a schematic perspective view of a welded joint with a steel tab attached according to one embodiment of the present invention
- FIG. 2 is a schematic back view of the welded joint with attached steel tab shown in FIG. 1.
- FIG. 3 is a schematic perspective view of a welded joint when the arc start method is cut wire scattering, according to another embodiment of the present invention.
- FIG. 4 is a schematic back view of a welded joint when the arc start method shown in FIG. 3 is cut wire scattering.
- FIG. 5 is a schematic cross-sectional view showing an example of groove shape according to the present invention.
- FIG. 6 is a correlation diagram showing the correlation between welding heat input Q and root gap G in the present invention.
- the present invention is a gas-shielded arc welding method for single-sided butt welding of steel materials.
- this welding method two steel materials having a predetermined plate thickness are butted together so as to form a predetermined groove, and these steel materials are joined by gas-shielded arc welding (hereinafter sometimes simply referred to as "welding"). do.
- the present invention defines the welding conditions for performing the first layer welding in this welding method. Specifically, it is a gas shield arc welding method for joining steel materials by multi-layer welding with a narrow groove, in which the groove angle ⁇ of the steel material is set to 20 ° or less, and the root that is the gap at the bottom of the groove The gap G is set to 7 to 15 mm.
- the welding current I is 250 to 400 A
- the welding voltage V is 25 to 45 V
- the welding heat input Q (kJ / mm) is set at the root gap G. Control is performed so that the divided value [Q/G] is in the range of 0.32 to 0.70, and one pass is performed.
- the steel material applied in the present invention is a thick steel plate used for steel structures such as buildings and ships.
- the steel type is not particularly limited as long as it is low carbon steel. Examples include 400 MPa class steel, 490 MPa class steel, 550 MPa class steel, 590 MPa class steel, and 780 MPa class steel.
- the plate thickness t (mm) of the steel material is preferably in the range of 20-100 mm. If the plate thickness is less than 20 mm, even if the groove shape is a conventional double groove or V groove, by reducing the root gap, in some cases, the groove can be wider than the groove of the present invention (narrow groove described later). Since the tip area becomes small, the advantage of the groove (narrow groove described later) of the present invention cannot be obtained.
- the upper limit of the plate thickness is generally 100 mm. Therefore, the upper limit of the plate thickness of the steel used in the present invention is preferably 100 mm or less.
- the plate thickness t of the steel material is more preferably 25 mm or more.
- the plate thickness t of the steel material is more preferably 90 mm or less, and still more preferably 70 mm or less.
- FIG. 5 shows, as an example, a cross-sectional view in the plate thickness direction of a groove shape in which two steel materials are butted against each other.
- the angle formed by the groove surfaces of the butted steel materials 1 is the groove angle ⁇ (°).
- a groove having a groove angle ⁇ of 20° or less is targeted.
- a groove having a groove angle ⁇ of 20° or less is referred to as a "narrow groove". This is because if ⁇ exceeds 20°, efficiency improvement, which is an advantage of a narrow groove, is diminished. The effect of the present invention can be obtained even if the groove angle .theta.
- the groove angle ⁇ is more preferably 5° or more, and still more preferably 10° or more.
- the root gap which is the narrowest lower gap between the butted steel materials 1
- G is represented by G (mm).
- the root gap G in the present invention is set to 7 to 15 mm. This is because if G is less than 7 mm, it is difficult to insert the welding torch into the groove, while if G exceeds 15 mm, efficiency, which is an advantage of a narrow groove, is diminished. Therefore, G should be 7 to 15 mm. G is preferably 8 mm or more and preferably 13 mm or less.
- Ceramic backing material In gas-shielded arc welding according to the present invention, a ceramic backing material that can be removed after welding is used as a backing material for preventing burn-through.
- the ceramic backing material is not particularly limited as long as it can prevent burn-through and form a backing bead.
- the ceramic backing material contains, for example, SiO 2 : 30-70%, Al 2 O 3 : 10-50%, MgO: 3-20%, ZrO 2 : 0-10%, NaO, K
- a glass fiber laminate on a ceramic backing material can also be used.
- the welding current I(A) for the first layer welding is set to 250-400A.
- the welding current I(A) is preferably 270 A or higher, more preferably 280 A or higher.
- the welding current I(A) is preferably 380 A or less, more preferably 360 A or less, and still more preferably 350 A or less.
- the welding voltage V (V) of the first layer welding is set to 25-45V.
- the welding voltage V (V) is preferably 28 V or higher, more preferably 30 V or higher.
- the welding voltage V (V) is preferably 40 V or less, more preferably 38 V or less.
- the range of the welding speed S for the first layer welding is preferably 1 to 8 mm/sec. If the welding speed S is out of the above range, the heat input will be too large or too small even with the appropriate current and voltage, resulting in welding defects and difficulty in sustaining the arc.
- the welding speed S is more preferably 1.2 mm/sec or more.
- the welding speed S is more preferably 6 mm/sec or less.
- the welding speed S can be appropriately selected within this range according to the balance between the welding current I and the welding voltage V.
- Welding heat input Q (kJ/mm) is [I ⁇ V/S/1000] where I is welding current (A), V is welding voltage (V), and S is welding speed (mm/sec).
- the above Q/G value is less than 0.32, the weld pool for ensuring conductivity is small, and the torch precedes the weld pool, so the arc cannot be maintained and welding becomes unstable. becomes.
- the value of Q/G is larger than 0.70, the liquid level of the molten pool becomes high and the input heat does not reach the bottom of the groove. As a result, unmelted portions are generated at the bottom of the groove, resulting in an undercut. Therefore, the above Q/G value is limited to the range of 0.32 to 0.70.
- the above Q/G value is preferably 0.40 or more, more preferably 0.43 or more.
- the above Q/G value is preferably 0.67 or less, more preferably 0.60 or less, and still more preferably 0.58 or less.
- the polarity at the time of welding of the first layer welding is positive polarity (connect the steel material as the positive pole and the welding wire as the negative pole) and reverse polarity (connect the steel material as the negative pole and the welding wire as the positive pole). Either can be selected.
- Wires of various standards can be used as the welding wire in the present invention. Examples thereof include YGW11, YGW18, G59JA1UC3M1T, G78A2UCN4M4T, G49AP3M1T, G59JA1UMC1M1T, G78A4MN5CM3T classified by JIS Z 3312.
- the wire diameter ⁇ is preferably 1.0 to 1.4 mm.
- the composition of the welding shield gas it is preferable to use a mixed gas containing 20% by volume or more of CO 2 gas and the rest as an inert gas such as Ar in order to stabilize the arc.
- the CO2 gas is more preferably 100% by volume.
- the gas flow rate is preferably 15 to 25 L/min from the viewpoint of stabilizing the arc and preventing the occurrence of welding defects.
- Arc start method There are, for example, the following two methods in order to ensure the electrical conductivity at the time of arc start.
- One is a method in which a steel tab is attached to the end (outside of the end) of the steel materials to be joined in the weld line direction, and an arc is generated by the steel tab.
- the other is a method of generating an arc after distributing a cut wire obtained by cutting a welding wire to an arc generating portion inside the groove.
- the welding wire is preferably a cut wire cut to a length of 3 mm, for example, and this cut wire 2g is placed at the arc start portion.
- the steel tab 2 is a steel member attached to the end of the steel material 1 in the weld line direction (that is, the starting end in the weld line direction) in order to effectively generate an arc at the end of the steel material. It's about.
- the steel backing material 3 is a member attached to the bottom side of the steel tub 2 . These materials are not particularly limited, and general steel materials (such as SM490) can be used.
- the above-mentioned "steel tab 2" is a structure in which two steel tabs 2 are arranged with a predetermined interval on the upper surface of one steel backing material 3, as in the examples shown in FIGS. do. Steel tabs 2 are arranged at the starting ends of two steel materials 1 in the direction of the weld line.
- a steel backing material 3 is arranged on the rear surface of the pair of steel tabs 2, and a ceramic backing material 4 is arranged adjacent thereto.
- a cut wire is a short cut welding wire, as described above.
- the cut wire is scattered on the bottom of the groove to facilitate arc generation.
- the arc start portion is composed of two steel materials 1 facing one side and a ceramic backing material 4 placed so as to overlap the bottom surfaces of the two steel materials 1. This is the area that is formed.
- the top side of the ceramic backing material 4 in this region is the above-mentioned "groove bottom" (see FIG. 3).
- the present invention is applied to the first layer welding of a narrow groove using a ceramic backing material. It is what is done.
- the number of welding layers after the first layer welding depends on the plate thickness of the steel material, but if the plate thickness is 20 to 100 mm, it is preferably 3 to 16 layers.
- Welding conditions after the first layer welding are preferably, for example, welding current: 180 to 400 A, welding voltage: 24 to 45 V, welding speed: 1 to 10 mm/sec.
- a welded joint (gas-shielded arc welded joint) of the present invention is a welded joint in which two butted steel materials are first-layer welded using the gas-shielded arc welding method described above.
- the steel materials are arranged such that the groove surfaces of the two steel materials have a predetermined groove angle ⁇ and the root gap G at the bottom of the groove is a predetermined distance. and a welding step of performing multi-layer welding on the steel material under specific welding conditions using the welding wire to form a weld bead. As a result, the two butted steel materials are joined together to produce a welded joint.
- the gas-shielded arc welding method described above is applied to the first layer welding of the multi-layer welding in the welding process.
- the welding conditions for subsequent passes after the first layer welding are appropriately set, and may be, for example, the same as the welding conditions for the first layer welding, or may be the welding conditions described in the multi-layer welding section. Since the explanation of the thick steel plate, welding conditions, etc. is the same as the above explanation, it is omitted.
- narrow gap welding that can improve workability and backing that may be the starting point of fatigue cracks and brittle fractures
- Gold-free welds can be achieved, and welded joints with excellent soundness can be obtained.
- excellent in soundness refers to the absence of weld defects such as undercuts, overlaps, and poor fusion.
- Example 1 As shown in FIG. 5, two thick steel plates (steel material 1) are butted together to form a groove, a ceramic backing material 4 is placed on the bottom of the groove, and a welded joint is formed by single-sided gas-shielded arc welding. manufactured. 100% by volume CO 2 gas was used as the welding shield gas. The welding shield gas flow rate was set to 20 L/min. Welding wires used were YGW11, YGW18, G59JA1UC3M1T, and G78A2UCN4M4T classified by JIS Z 3312 and having a diameter of 1.2 mm. The plate thickness t, the groove angle ⁇ , and the root gap G of the steel material 1 were set to the conditions shown in Table 1, respectively.
- First layer welding of single-sided gas-shielded arc welding was performed under the conditions shown in Table 1. Welding of the second and subsequent layers was performed at a welding current of 250 to 300 A, a welding voltage of 28 to 35 V, and a welding speed of 6 to 8 mm/sec.
- the ceramic backing material 4 contains, in mass %, SiO 2 : 30 to 70%, Al 2 O 3 : 10 to 50%, MgO: 3 to 20%, ZrO 2 : 0 to 10%. , NaO, K 2 O 3 and Li 2 O: 0.3 to 5% in total.
- “Polarity” shown in Table 1 indicates the polarity at the time of welding, "wire negative” refers to the positive polarity described above, and “wire positive” refers to the reverse polarity described above.
- Table 1 summarizes the above test conditions and evaluation results.
- the joint No. in Table 1 is used.
- No. 14 arc start method was as follows. Specifically, an arc is generated at 280 A-32 V at the lower end of one side of the groove, held for 1 second, a molten pool is secured for ensuring conductivity, and then the torch is moved to the center of the groove. , were welded at a welding speed of 3.0 mm/sec.
- the correlation between root gap G and welding heat input Q is shown in FIG.
- the welding current I for the first layer welding is 250 to 400 A
- the welding voltage V is 25 to 45 V
- the Q/G is within the range of 0.32 to 0.70.
- the welding stability was excellent and no welding defects occurred.
- the welding stability was inferior or welding defects occurred.
- the welding stability was inferior or welding defects occurred.
- Example 2 In Example 2, two thick steel plates having a plate thickness t shown in Table 2 were used, and the first layer welding of single-sided gas-shielded arc welding was performed under the welding shield gas and conditions shown in Table 2 to produce a welded joint. Other conditions, evaluation methods, and the like are the same as those in Example 1, and thus description thereof is omitted.
- the inventive examples were excellent in welding stability and had no weld defects.
- the welding stability is inferior and/or due to the fact that 20% by volume or more of CO 2 gas is not mixed in the composition of the welding shielding gas or the gas flow rate is insufficient. A weld defect had occurred.
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Abstract
Description
〔1〕 狭開先の多層溶接により鋼材を接合するガスシールドアーク溶接方法であって、
鋼材の開先角度θを20°以下の開先とし、該開先の下部の隙間であるルートギャップG(mm)を7~15mmとし、
初層溶接では、セラミック製の裏当て材を用い、
かつ、溶接電流I(A)を250~400Aおよび溶接電圧V(V)を25~45Vとし、溶接入熱Q(kJ/mm)を前記ルートギャップG(mm)で割った値〔Q/G〕が0.32~0.70の範囲として、1パスで行う、
ガスシールドアーク溶接方法。
ここで、前記溶接入熱Qは、Q=I×V/S/1000 であり、
式中に示す、I:溶接電流(A)、V:溶接電圧(V)、S:溶接速度(mm/秒)である。
〔2〕 接合される前記鋼材の端部外側に鋼製タブを取り付け、該鋼製タブでアークを発生させる、〔1〕に記載のガスシールドアーク溶接方法。
〔3〕 前記開先の内部のアークの発生部に溶接ワイヤを切断したカットワイヤを散布した後、アークを発生させる、〔1〕に記載のガスシールドアーク溶接方法。
〔4〕 前記初層溶接では、CO2ガスを20体積%以上と不活性ガスとからなる溶接シールドガスを用いる、〔1〕~〔3〕のいずれか1つに記載のガスシールドアーク溶接方法。
〔5〕 前記溶接シールドガスのガス流量は、15~25L/分である、〔4〕に記載のガスシールドアーク溶接方法。
〔6〕 〔1〕~〔5〕のいずれか1つに記載のガスシールドアーク溶接方法を用いて初層溶接された、溶接継手。
〔7〕 〔1〕~〔5〕のいずれか1つに記載のガスシールドアーク溶接方法の初層溶接を用いた、溶接継手の製造方法。
具体的には、狭開先の多層溶接により鋼材を接合するガスシールドアーク溶接方法であって、鋼材の開先角度θを20°以下の開先とし、該開先の下部の隙間であるルートギャップGを7~15mmとする。更に、初層溶接では、セラミック製の裏当て材を用い、かつ、溶接電流Iを250~400Aおよび溶接電圧Vを25~45Vとし、溶接入熱Q(kJ/mm)を上記ルートギャップGで割った値〔Q/G〕が0.32~0.70の範囲となるように制御して、1パスで行う。
本発明で適用される鋼材は、建築物や船舶などの鉄鋼構造物に用いられる厚鋼板である。鋼種としては、低炭素鋼であれば、とくに限定する必要は無い。例えば、400MPa級鋼材、490MPa級鋼材、550MPa級鋼材、590MPa級鋼材、780MPa級鋼材などが挙げられる。
図5には、一例として、2枚の鋼材を突き合わせた開先形状の板厚方向断面図を示す。図5に示すように、突き合わせた鋼材1同士の開先面のなす角度が開先角度θ(°)である。本発明においては、開先角度θが20°以下の開先を対象としている。本発明では、この開先角度θが20°以下の開先を「狭開先」と称する。θが20°を超えると、狭開先としての利点である効率化が減殺されるからである。
なお、厚鋼板の開先は小さいほどより高能率な溶接を可能とすることから、開先角度θは0°でも本発明の効果を得られる。開先角度θは、より好ましくは5°以上であり、さらに好ましくは10°以上である。
図5に示すように、本発明では、突き合わせた鋼材1の開先部分の最も狭い下部隙間であるルートギャップを、G(mm)で表わしている。本発明におけるルートギャップGは、7~15mmとする。Gが7mm未満では、開先内に溶接トーチを入れることが困難であり、一方、Gが15mmを超えると狭開先としての利点である効率化が減殺されるからである。したがって、Gは、7~15mmとする。Gは、好ましくは8mm以上であり、好ましくは13mm以下である。
本発明にかかるガスシールドアーク溶接においては、溶け落ちを防止するための裏当て材として、溶接後に取り外しが可能なセラミック製の裏当て材を使用する。セラミック製の裏当て材としては、溶け落ちを防止し、裏波ビードを形成できるものであれば、特に限定する必要は無い。セラミック製の裏当て材は、例えば、質量%で、SiO2:30~70%、Al2O3:10~50%、MgO:3~20%、ZrO2:0~10%、NaO、K2O3およびLi2Oのうちから選択された1種以上:合計で0.3~5%の組成のものが使用できる。
さらに、セラミック製の裏当て材の上にガラス繊維を積層したものも使用することができる。
初層溶接の溶接電流I(A)が250Aより低いとアーク圧力が低くなり、開先底部に溶け残りが生じることで、アンダーカットが生じる。一方、初層溶接の溶接電流I(A)が400Aより高いとアーク圧力が強くなり、通導性を確保するための溶融池を押しのけてしまい、アークを維持することができなくなる。そのため、初層溶接の溶接電流I(A)は、250~400Aとする。上記溶接電流I(A)は、好ましくは270A以上であり、より好ましくは280A以上である。また上記溶接電流I(A)は、好ましくは380A以下であり、より好ましくは360A以下であり、さらに好ましくは350A以下である。
また、初層溶接の溶接電圧V(V)が25Vより低いと安定してアークを維持することが出来ず、溶接が不安定になるとともに溶接ビードが凸形状になる。一方、初層溶接の溶接電圧V(V)が45Vより高いとアークが高い位置から発生し、溶融池の熱が開先底部に届きにくくなる。その結果、開先底部に溶け残りが生じ、アンダーカットとなる。そのため、初層溶接の溶接電圧V(V)は、25~45Vとする。上記溶接電圧V(V)は、好ましくは28V以上であり、より好ましくは30V以上である。また上記溶接電圧V(V)は、好ましくは40V以下であり、より好ましくは38V以下である。
初層溶接の溶接速度Sの範囲は、1~8mm/秒が好ましい。
溶接速度Sが上記範囲を外れる場合、適正電流と適正電圧であっても、過大な入熱、または過少な入熱となり、その結果、溶接欠陥が生じたり、アークの持続が困難となる。上記溶接速度Sは、より好ましくは1.2mm/秒以上である。上記溶接速度Sは、より好ましくは6mm/秒以下である。
上記溶接速度Sは、溶接電流Iと溶接電圧Vとのバランスにより、この範囲で適宜選定することができる。
さらに、アーク直下に通電性を確保するための溶融池を確保し、アンダーカットを防止するためには、ルートギャップG(mm)によって溶接入熱Q(kJ/mm)を調整することが必要である。そのため、溶接入熱QをルートギャップGで割った値〔Q/G〕は0.32~0.70の範囲に調整する。
初層溶接の溶接時の極性は、正極性(鋼材をプラス極とし、溶接ワイヤをマイナス極として接続すること)および逆極性(鋼材をマイナス極とし、溶接ワイヤをプラス極として接続すること)のいずれも選択することができる。
本発明における溶接ワイヤは、種々の規格のワイヤを用いることができる。例えば、JIS Z 3312で分類されるYGW11、YGW18、G59JA1UC3M1T、G78A2UCN4M4T、G49AP3M1T、G59JA1UMC1M1T、G78A4MN5CM3Tなどが挙げられる。ワイヤ径φは、1.0~1.4mmが好ましい。
溶接シールドガスの組成としては、アークを安定させるために、CO2ガスを20体積%以上、残りをAr等の不活性ガスとして含有する混合ガスを使用することが好ましい。溶接シールドガスのコストを考慮すると、より好ましくは、CO2ガス100体積%である。なお、ガス流量は、アークを安定させたり、溶接欠陥発生を防止する観点から、15~25L/分で行うことが好ましい。
アークスタート時の通電性を確保するために、例えば、次の2通りの方法が挙げられる。1つは、接合される鋼材の溶接線方向の端部(端部外側)に鋼製タブを取り付け、該鋼製タブでアークを発生させる方法である。もう1つは、開先の内部のアークの発生部に溶接ワイヤを切断したカットワイヤを散布した後、アークを発生させる方法である。
上記の「鋼製タブ2」とは、図1および図2に示す例のように、1つの鋼製裏当て材3の上面に所定間隔を設けて2つの鋼製タブ2を配置する構成とする。2枚の鋼材1の溶接線方向の始端部に鋼製タブ2をそれぞれ配置する。なお、図2に示すように、1対の鋼製タブ2の裏面には、鋼製裏当て材3を配置し、これに隣接してセラミック製の裏当て材4が配置される。
なお、本発明は、セラミック製の裏当て材を用いた狭開先の初層溶接に適用するものであり、本発明を実施するにあたり、初層溶接以降の後続パスの溶接条件は、適宜設定されるものである。初層溶接に続く2層目以降の溶接の層数については、鋼材の板厚などに拠るが、前述した板厚である20~100mmであれば、3~16層が好ましい。また、初層溶接以降の溶接条件は、例えば、溶接電流:180~400A、溶接電圧:24~45V、溶接速度:1~10mm/秒とすることが好ましい。
本発明の溶接継手の製造方法は、2枚の鋼材の開先面を所定の開先角度θとし、かつ、開先の下部のルートギャップGを所定の距離となるように鋼材を配置して突き合せる工程と、上記の溶接ワイヤを用いて、該鋼材に特定の溶接条件で多層溶接を行い、溶接ビードを形成する溶接工程と、を備える。これにより、突き合わせた2枚の鋼材を接合し、溶接継手を製造する。この製造方法における、溶接工程での多層溶接の初層溶接に、上述のガスシールドアーク溶接方法を適用する。
初層溶接以降の後続パスの溶接条件は、適宜設定されるものであり、例えば初層溶接の溶接条件と同様としてもよいし、あるいは上記多層溶接の項目で説明した溶接条件としてもよい。なお、厚鋼板や溶接条件等の説明は上述の説明と同様であるため、省略する。
図5に示すように、2枚の厚鋼板(鋼材1)を、突き合わせて開先を形成し、開先底面にセラミック製の裏当て材4を配置し、片面ガスシールドアーク溶接により溶接継手を製造した。溶接シールドガスは、100体積%CO2ガスを用いた。溶接シールドガスの流量は、20L/分とした。
溶接ワイヤは、JIS Z 3312で分類されるYGW11、YGW18、G59JA1UC3M1T、G78A2UCN4M4Tのφ1.2mmのワイヤを用いた。鋼材1の板厚t、開先角度θおよびルートギャップGは、それぞれ表1に示す条件とした。片面ガスシールドアーク溶接の初層溶接は、表1に示す条件で行った。2層目以降の溶接は、溶接電流:250~300A、溶接電圧:28~35V、溶接速度:6~8mm/秒の範囲で実施した。セラミック製の裏当て材4には、上述のとおり、質量%で、SiO2:30~70%、Al2O3:10~50%、MgO:3~20%、ZrO2:0~10%、NaO、K2O3およびLi2Oのうちから選択された1種以上:合計で0.3~5%の組成のものを用いた。表1に示す「極性」は溶接時の極性を示し、「ワイヤマイナス」とは上述の正極性であることを指し、「ワイヤプラス」は上述の逆極性であることを指す。
〔溶接安定性〕
溶接安定性は、次のように評価した。初層溶接(1パス)において、溶接長400mmを途中で停止せずに最後まで溶接できたものは「可」とし、最後まで溶接できなかったものは「不可」とした。
また、得られた溶接継手の溶接線方向中央位置から断面マクロを採取し、この断面マクロを用いて初層ビードの溶接欠陥の有無について、光学顕微鏡で観察し、評価した。光学顕微鏡の倍率は10倍とした。初層ビードに溶接欠陥(JIS Z 3001-4:2013を参照)がないものは「無」とし、アンダカットやオーバラップ、融合不良(JIS Z 3001-4:2013を参照)の溶接欠陥があるものは「有」とした。
なお、表1の継手No.14のアークスタート方法は次の通りとした。具体的には、開先の片側下端部にて280A-32Vでアークを発生させ、1秒保持し、導電性確保のための溶融池を確保し、その後、トーチを開先中央部に移動させ、溶接速度3.0mm/秒で溶接した。
一方、Q/Gが上記範囲内にはあったが、初層溶接の溶接電流Iまたは溶接電圧Vが本発明の範囲を外れる比較例では、溶接安定性に劣るか、溶接欠陥が発生した。
また、Q/Gが上記範囲外となる比較例では、溶接安定性に劣るか、溶接欠陥が発生した。
実施例2では、表2に示す板厚tとなる厚鋼板を2枚用い、表2に示す溶接シールドガスおよび条件で片面ガスシールドアーク溶接の初層溶接を行い、溶接継手を製造した。なお、その他の条件および評価方法等は、実施例1と同様のため、説明を省略する。
2 鋼製タブ
3 鋼製裏当て材
4 セラミック製の裏当て材
5 カットワイヤ
Claims (7)
- 狭開先の多層溶接により鋼材を接合するガスシールドアーク溶接方法であって、
鋼材の開先角度θを20°以下の開先とし、該開先の下部の隙間であるルートギャップG(mm)を7~15mmとし、
初層溶接では、セラミック製の裏当て材を用い、
かつ、溶接電流I(A)を250~400Aおよび溶接電圧V(V)を25~45Vとし、溶接入熱Q(kJ/mm)を前記ルートギャップG(mm)で割った値〔Q/G〕が0.32~0.70の範囲として、1パスで行う、
ガスシールドアーク溶接方法。
ここで、前記溶接入熱Qは、Q=I×V/S/1000 であり、
式中に示す、I:溶接電流(A)、V:溶接電圧(V)、S:溶接速度(mm/秒)である。 - 接合される前記鋼材の端部外側に鋼製タブを取り付け、該鋼製タブでアークを発生させる、請求項1に記載のガスシールドアーク溶接方法。
- 前記開先の内部のアークの発生部に溶接ワイヤを切断したカットワイヤを散布した後、アークを発生させる、請求項1に記載のガスシールドアーク溶接方法。
- 前記初層溶接では、CO2ガスを20体積%以上と不活性ガスとからなる溶接シールドガスを用いる、請求項1~3のいずれか1項に記載のガスシールドアーク溶接方法。
- 前記溶接シールドガスのガス流量は、15~25L/分である、請求項4に記載のガスシールドアーク溶接方法。
- 請求項1~5のいずれか1項に記載のガスシールドアーク溶接方法を用いて初層溶接された、溶接継手。
- 請求項1~5のいずれか1項に記載のガスシールドアーク溶接方法の初層溶接を用いた、溶接継手の製造方法。
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JPH05293653A (ja) * | 1992-04-16 | 1993-11-09 | Nkk Corp | 片面溶接における裏ビード制御方法 |
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