WO2018003341A1 - Laser welded joint and method for manufacturing laser welded joint - Google Patents

Laser welded joint and method for manufacturing laser welded joint Download PDF

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Publication number
WO2018003341A1
WO2018003341A1 PCT/JP2017/018837 JP2017018837W WO2018003341A1 WO 2018003341 A1 WO2018003341 A1 WO 2018003341A1 JP 2017018837 W JP2017018837 W JP 2017018837W WO 2018003341 A1 WO2018003341 A1 WO 2018003341A1
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bead
weld
mass
laser
welded joint
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PCT/JP2017/018837
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French (fr)
Japanese (ja)
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恭兵 前田
励一 鈴木
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株式会社神戸製鋼所
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Publication of WO2018003341A1 publication Critical patent/WO2018003341A1/en

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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
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/21—Bonding by welding
    • 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
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/32—Bonding taking account of the properties of the material involved
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese

Definitions

  • the present invention relates to a laser welded joint and a method for manufacturing a laser welded joint.
  • steel sheets used in automobile bodies and the like are thin plates with a thickness of about 0.5 to 3.0 mm in order to achieve both improved safety at the time of collision and weight reduction for the purpose of reducing fuel consumption.
  • High-strength steel sheets are increasingly being adopted.
  • laser welding is performed by irradiating a laser beam with the laser beam focused on the metal, and locally melting and solidifying the metal to join the metals. Since laser is light having a single wavelength and no phase difference, it can be focused on an extremely small point by a lens of an optical system and given high density energy to join metals.
  • At least one sheet is a high-tensile steel plate, and the component composition of the weld metal is 0.05 mass% ⁇ C ⁇ 0.08 mass%, or C ⁇ 0.05 mass%, and P + S ⁇ 0.
  • the laser welding for forming a welded portion of 0.03 mass% at a position within 8 mm from the flange end a technique for defining laser welding conditions is described.
  • laser welding conditions defined by output, welding speed, condensing diameter, and bead thickness, laser output p (w), welding speed v (mm / sec), and the total thickness of the overlapped parts to be welded Is t (mm), and the focused diameter is d (mm), the laser welding conditions satisfying the expression ⁇ p / v / t 1/2 ⁇ d 2 ⁇ 12.5 ⁇ Control and prevent solidification cracking.
  • Patent Document 2 describes a technique for reducing the shrinkage strain applied to the bead and preventing solidification cracking by controlling the solidification mode of the laser weld. Specifically, TiN is generated by laser welding in a N 2 gas atmosphere to a steel type containing more than 0.02% by mass of Ti, to suppress cracks during solidification at the initial solidification stage of the weld. An advantageous equiaxed crystal is formed in the bead to suppress solidification cracking during welding.
  • C is one of the most useful elements for increasing the tensile strength, and the steel plates can be easily increased in strength and tempered to improve ductility and the like. It is.
  • the high-tensile steel sheet one containing 0.10% by mass ⁇ C ⁇ 0.30% by mass is used.
  • Patent Documents 1 and 2 are described to suppress the occurrence of solidification cracking, but in Patent Document 1, C is a technique related to a high-tensile steel sheet having a mass of less than 0.1% by mass, and in Patent Document 2, the cost is assumed since it is a steel material containing Ti amount, further, while blowing welding gas containing N 2 gas, limited to the laser welding, there is room for improvement.
  • the present invention has been made in view of the above-described problems, and its purpose is to provide a laser welded joint in which crater cracking is unlikely to occur at the terminal end of a weld bead that penetrates the overlapped portion of a high-tensile steel plate from the front surface to the back surface. It is another object of the present invention to provide a method for manufacturing a laser welded joint.
  • the inventors have conducted extensive research to solve the above problems, and it is generally known that in arc welding, the solidification cracking susceptibility decreases as the ratio D / W between the bead thickness D and the bead width W decreases. On the other hand, in welding with a narrow bead width such as laser welding, on the contrary, it was found that the susceptibility to solidification cracking is lowered by increasing D / W.
  • the overlapped portion in which the plurality of high-tensile steel plates are overlapped has a weld bead penetrating from the front surface to the back surface, and has a crater at the end of the weld bead
  • the component composition of the weld metal in the weld bead is 0.10% by mass ⁇ C ⁇ 0.30% by mass, P + S ⁇ 0.03% by mass
  • the weld bead is a laser welded joint satisfying that a bead width W is 0.1 mm or more and 2.0 mm or less, and a ratio D / W between the bead thickness D and the bead width W is 2.6 or more.
  • the composition of the weld metal in the weld bead is 0.10% by mass ⁇ C ⁇ 0. .30% by mass, P + S ⁇ 0.03% by mass, Laser output, welding speed, shield so that the bead width W of the weld bead is 0.1 mm or more and 2.0 mm or less, and the ratio D / W between the bead thickness D and the bead width W is 2.6 or more.
  • the overlapped portion where a plurality of high strength steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are overlapped penetrates from the front surface to the back surface.
  • the weld bead is provided with a crater at the end of the weld bead, and the composition of the weld metal in the weld bead is 0.10% by mass ⁇ C ⁇ 0.30% by mass and P + S ⁇ 0.03% by mass. is there.
  • the weld bead has a bead width W of 0.1 mm or more and 2.0 mm or less, and a ratio D / W between the bead thickness D and the bead width W of 2.6 or more, thereby suppressing crater cracking at the weld end. can do. Moreover, the low temperature crack of a weld bead can also be prevented by suppressing the crater crack in a welding termination
  • the overlapped portion in which a plurality of high-tensile steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are overlapped is formed from the front surface to the back surface.
  • the weld bead is provided with a crater at the end of the weld bead, and the component composition of the weld metal in the weld bead is 0.10 mass% ⁇ C ⁇ 0.30 mass%, P + S ⁇ 0.03 mass %.
  • the ratio D / W between the bead thickness D and the bead width W is D / W ⁇ [C] +2.3, so that crater cracking at the weld end is suppressed. can do.
  • the low temperature crack of a weld bead can also be prevented by suppressing the crater crack in a welding termination
  • the laser beam is applied to the overlapped portion where a plurality of high strength steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are overlapped. Irradiate and weld the overlap. At that time, a weld bead penetrating from the front surface to the back surface of the overlapped portion is formed, and a crater is formed at the end portion of the weld bead.
  • the component composition of the weld metal in the weld bead is 0.10% by mass ⁇ C ⁇ 0.30% by mass, P + S ⁇ 0.03% by mass, the bead width W of the weld bead is 0.1 mm to 2.0 mm, and the ratio D / W of the bead thickness D to the bead width W is 2. Since at least one of the laser output, welding speed, shield gas, condensing spot diameter, and condensing position is controlled so that it becomes 6 or more, crater cracking at the welding end portion hardly occurs, and as a result, the low temperature of the weld bead A laser weld joint in which cracking is prevented is obtained.
  • FIG. 2 is a sectional view taken along line II-II in FIG.
  • FIG. 3 is a sectional view taken along line III-III in FIG. 1. It is a graph which shows the range of this invention by the relationship between C mass% and D / W. It is a schematic perspective view of two high-tensile steel plates to be laser welded.
  • a flange portion 12 in which one end of a high-tensile steel plate 11 is bent and a flat high-tensile steel plate 13 are overlapped to overlap each other.
  • the laser processing head 1 is moved along the both ends 14 of the high-tensile steel plate 11 (flange portion 12) and the high-tensile steel plate 13 while irradiating the overlapping portion 19 with the laser light L, and the high-tensile steel plate 11.
  • a weld bead 16 penetrating from the front surface 12a of the flange portion 12 to the back surface 13a of the high-tensile steel plate 13 the high-tensile steel plates 11 and 13 are joined to each other.
  • the plate thickness t is 0.5 to 3.0 mm.
  • the lower limit of the plate thickness t is set to 0.5 mm because it is defined in consideration of the plate thickness of a steel plate generally used for a structure such as an automobile, and the upper limit of the plate thickness t is set to 3.0 mm. This depends on the welding ability of a normal laser welding machine.
  • the high-tensile steel plates 11 and 13 of the present embodiment are intended for the high-strength class having a tensile strength of 780 MPa or more, and include, for example, those of 980 MPa and 1180 MPa.
  • the weld metal component is an average component calculated from the base material component values of the superposed high-strength steel plates 11 and 13 and the plate thickness t when no filler material such as filler is added.
  • the materials of the high-tensile steel plates 11 and 13 are selected so as to satisfy 0.10% by mass ⁇ C ⁇ 0.30% by mass and P + S ⁇ 0.03% by mass.
  • the material of each high-tensile steel sheet 11 and 13 is selected so that the said value may be satisfy
  • the applicant of the present invention through welds the overlapped portion where the high strength steel plates 11 and 13 having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are overlapped,
  • the composition of the weld metal satisfies 0.10 mass% ⁇ C ⁇ 0.30 mass% and P + S ⁇ 0.03 mass%
  • the bead width W, the bead thickness D, and the bead width W It was found that the crater cracking can be suppressed by controlling the ratio D / W to the range defined by the present invention.
  • the weld bead 16 of the present embodiment has a bead width W of 0.1 mm or more and 2.0 mm or less, and a ratio D / W between the bead thickness D and the bead width W of 2.6 or more.
  • the bead width W referred to here is the bead width at the joint interface 17 between the flange portion 12 of the high-tensile steel plate 11 and the high-tensile steel plate 13.
  • the bead thickness D is the total thickness of the plate thickness t of the high strength steel plates 11 and 13 because the weld bead 16 penetrates from the front surface 12a of the flange portion 12 to the back surface 13a of the high strength steel plate 13.
  • the bead width W is preferably 1.0 mm or less, and the ratio D / W between the bead thickness D and the bead width W is preferably 2.7 or more, more preferably 2.8 or more. Moreover, although it is not necessary to specifically limit the upper limit of the ratio D / W, for example, the upper limit may be set to 30.
  • Laser welding with a bead width W of 0.1 mm to 2.0 mm and a bead thickness D to bead width W ratio of D / W 2.6 or more includes laser output, welding speed, shielding gas, condensing spot diameter, and This is achieved by controlling the amount of heat input by controlling at least one welding condition at the condensing position.
  • the gap between the two high-strength steel plates 11 and 13 is preferably set to, for example, 0.3 mm or less so that the beads can be easily welded through during welding.
  • a YAG laser, a fiber laser, a DISK laser, or the like can be used as a laser oscillator.
  • crater cracks tend to be approximately proportional to C mass% in the high-tensile steel plates 11 and 13, and the ratio D / bead thickness D to bead width W when the mass% C is [C]. W can also suppress the occurrence of crater cracks by satisfying D / W ⁇ [C] +2.3.
  • the occurrence of crater cracks can be suppressed in the range of 0.10 mass% ⁇ C ⁇ 0.30 mass% and D / W ⁇ [C] +2.3. it can.
  • D / Ws of Examples 1 to 7 and Comparative Examples 1 to 5 described later are plotted.
  • the center portion C of the crater 20 which is the most recessed portion of the crater 20 and the end surface in the weld line direction of the high-tensile steel plates 11 and 13.
  • the distance X to 18 is 3 to 10 mm.
  • the laser welding machine used a fiber laser, the processing point output was 2 to 4 kW, and the welding speed was 0.75 to 4 m / min.
  • the condensing position was from the upper plate surface to the upper plate surface + 9 mm, and the condensing spot diameter was 0.45 to 0.6 mm.
  • Ar gas was used as the shielding gas, and the flow rate was 15 L / min.
  • the presence or absence of crater cracks was evaluated by observing the cross section of the weld end portion along the line AA perpendicular to the weld line.
  • the high-tensile steel plate specified in the present invention was used, the bead width W was 0.1 mm or more and 2.0 mm or less, and the ratio D / W between the bead thickness D and the bead width W was 2.6.
  • the ratio D / W between the bead thickness D and the bead width W was outside the specified range of the present invention, it was confirmed that crater cracking occurred at the weld end portion. It was done.
  • any of Examples 1 to 7 satisfies D / W ⁇ [C] +2.3, and the effectiveness of the formula can be confirmed.
  • a plurality of high-tensile steel plates 11 and 13 having a tensile strength of 780 MPa or more and a plate thickness t of 0.5 to 3.0 mm are overlapped.
  • the overlapping portion 19 in which the plurality of high-tensile steel plates 11 and 13 are overlapped has a weld bead 16 penetrating from the front surface 12a to the back surface 13a, and a crater 20 is provided at a terminal portion 16a of the weld bead 16, and welding is performed.
  • the component composition of the weld metal in the bead 16 is 0.10% by mass ⁇ C ⁇ 0.30% by mass and P + S ⁇ 0.03% by mass.
  • the weld bead 16 satisfies a bead width W of 0.1 mm to 2.0 mm and a ratio D / W of the bead thickness D to the bead width W of 2.6 or more. Thereby, the crater crack in the welding termination
  • the laser welded joint 10 of the present embodiment instead of defining the bead width W and D / W of the weld bead 16, if the mass% of C is [C], the bead thickness D and the bead width The ratio D / W with W satisfies D / W ⁇ [C] +2.3.
  • the welding termination is performed. Crater cracks in the portion 16a can be suppressed.
  • the low temperature crack of the weld bead 16 can also be prevented by suppressing the crater crack in a welding terminal part.
  • the laser weld joint 10 to be welded through is desirable from the viewpoint of quality assurance in the automobile field, but it is disadvantageous for crater cracking. For this reason, in this embodiment, since the ratio D / W satisfies 2.6 or more, or D / W ⁇ [C] +2.3, crater cracking is suppressed. As a result, the laser welded joint 10 of the present embodiment can achieve both penetration welding and crater crack suppression, and can solve the problem of quality assurance in the automobile field.
  • a plurality of high strength steel plates 11 and 13 having a tensile strength of 780 MPa or more and a plate thickness t of 0.5 to 3.0 mm are overlapped to form a plurality of high strength steel plates 11.
  • 13 is irradiated with a laser beam L, and the overlapping portion 19 is welded.
  • the weld bead 16 penetrating from the front surface 12 a to the back surface 13 a of the overlapping portion 19 is formed, and the crater 20 is formed at the end portion 16 a of the weld bead 16.
  • the component composition of the weld metal in the weld bead is 0.10% by mass ⁇ C ⁇ 0.30% by mass and P + S ⁇ 0.03% by mass, and the bead width W of the weld bead 16 is 0.1 mm or more and 2.0 mm or less.
  • at least one of laser output, welding speed, shield gas, condensing spot diameter, and condensing position is controlled so that the ratio D / W of the bead thickness D and the bead width W is 2.6 or more. Therefore, the crater crack of the welding end portion 16a is hardly generated, and as a result, the laser welded joint 10 in which the cold crack of the weld bead 16 is prevented can be obtained.
  • the present invention is not limited to the above-described embodiments and examples, and modifications, improvements, and the like can be made as appropriate.
  • two high-tensile steel plates are overlapped and laser-welded, but the high-tensile steel plates to be laser-welded are not limited to two, and even if three or more, It is possible to weld without causing crater cracks.
  • the shape of the overlapping portion is not limited to that of the present embodiment.
  • the flange portions of two high-strength steel plates may be overlapped with each other, or flat high-tensile steel plates may be overlapped with each other. But you can.
  • the present invention is based on a Japanese patent application (Japanese Patent Application No. 2016-129135) filed on June 29, 2016, the contents of which are incorporated herein by reference.

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Abstract

Provided is a laser welded joint (10) formed by overlapping and laser welding a plurality of high tensile strength steel plates (11, 13) having tensile strength of 780 MPa or greater and a plate thickness 0.5 - 3.0 mm, wherein: the overlapping part (19) wherein the plurality of high tensile strength steel plates (11, 13) overlaps has a welding bead (16) penetrating from the front surface (12a) thereof to the back surface (13a) thereof and is also provided with a crater (20) on the final end part (16a) of the welding bead (16); the composition of the weld metal in the welding bead (16) is 0.10 ≤ C ≤ 0.30% by mass and P + S < 0.03% by mass; and the welding bead (16) has a bead width (W) of 0.1 - 2.0 mm and a ratio (D/W) of bead thickness (D) and bead width (W) of 2.6 or greater.

Description

レーザ溶接継手およびレーザ溶接継手の製造方法Laser welded joint and method for manufacturing laser welded joint
　本発明は、レーザ溶接継手およびレーザ溶接継手の製造方法に関する。 The present invention relates to a laser welded joint and a method for manufacturing a laser welded joint.
　近年、自動車の車体等に用いられる鋼板には、衝突時の安全性の向上と、低燃費化を目的とした軽量化を両立するために、板厚が０．５～３．０ｍｍ程度の薄板の高張力鋼板が採用されることが多くなっている。 In recent years, steel sheets used in automobile bodies and the like are thin plates with a thickness of about 0.5 to 3.0 mm in order to achieve both improved safety at the time of collision and weight reduction for the purpose of reducing fuel consumption. High-strength steel sheets are increasingly being adopted.
　また、このような高張力鋼板を溶接する方法としてレーザ溶接を適用する例も散見されるようになってきている。レーザ溶接は、レーザ光を熱源として金属に集光した状態で照射し、金属を局部的に溶融、凝固させることによって金属を接合させる。レーザは、単一波長で位相差のない光であるため、光学系のレンズで極めて小さな点に集光して高い密度のエネルギーを与えて金属を接合することができる。 In addition, examples of applying laser welding as a method of welding such high-tensile steel plates are also frequently seen. Laser welding is performed by irradiating a laser beam with the laser beam focused on the metal, and locally melting and solidifying the metal to join the metals. Since laser is light having a single wavelength and no phase difference, it can be focused on an extremely small point by a lens of an optical system and given high density energy to join metals.
　さらに、自動車分野などにおいては、品質保証の観点から、複数の高張力鋼板の重ね合せ部を表面から裏面まで貫通するように溶接する（以後、「貫通溶接」とも称す）ことが求められている。 Furthermore, in the automotive field, etc., from the viewpoint of quality assurance, it is required to weld a plurality of high-tensile steel plates so as to penetrate through the overlapped portion from the front surface to the back surface (hereinafter also referred to as “through welding”). .
　ところで、高強度鋼板の重ね合せ部をレーザ溶接すると、凝固割れが発生しやすいことから、この凝固割れを防止する技術が種々考案されている（例えば、特許文献１及び２参照）。 Incidentally, when laser welding is performed on the overlapped portion of high-strength steel sheets, solidification cracks are likely to occur, and various techniques for preventing such solidification cracks have been devised (see, for example, Patent Documents 1 and 2).
　特許文献１では、少なくとも１枚が高張力鋼板であり、溶接金属の成分組成が０．０５質量％≦Ｃ≦０．０８質量％、あるいは、Ｃ＜０．０５質量％、且つ、Ｐ＋Ｓ≧０．０３質量％である溶接部を、フランジ端から８ｍｍ以内の位置に形成するレーザ溶接において、レーザ溶接条件を規定する技術が記載されている。即ち、出力、溶接速度、集光径、ビード厚によって規定されるレーザ溶接条件を、レーザ出力をｐ（ｗ）、溶接速度をｖ（ｍｍ／ｓｅｃ）、重ね合わされた被溶接部の合計板厚をｔ（ｍｍ）、集光径をｄ（ｍｍ）とした際、式｛ｐ／ｖ／ｔ１／２×ｄ２＜１２．５｝を満足するレーザ溶接条件とすることで、入熱量を制御し、凝固割れを防止している。 In Patent Document 1, at least one sheet is a high-tensile steel plate, and the component composition of the weld metal is 0.05 mass% ≦ C ≦ 0.08 mass%, or C <0.05 mass%, and P + S ≧ 0. In the laser welding for forming a welded portion of 0.03 mass% at a position within 8 mm from the flange end, a technique for defining laser welding conditions is described. That is, laser welding conditions defined by output, welding speed, condensing diameter, and bead thickness, laser output p (w), welding speed v (mm / sec), and the total thickness of the overlapped parts to be welded Is t (mm), and the focused diameter is d (mm), the laser welding conditions satisfying the expression {p / v / t 1/2 × d 2 <12.5} Control and prevent solidification cracking.
　また、特許文献２では、レーザ溶接部の凝固形態を制御することで、ビードに付与される収縮ひずみを低減し、凝固割れを防止する技術が記載されている。具体的には、０．０２質量％超のＴｉを含有した鋼種に対して、Ｎ２ガス雰囲気でレーザ溶接することで、ＴｉＮを生成させ、溶接部の凝固初期に、凝固時の割れ抑制に有利となる等軸晶をビード内に形成させて、溶接時の凝固割れを抑制している。 Patent Document 2 describes a technique for reducing the shrinkage strain applied to the bead and preventing solidification cracking by controlling the solidification mode of the laser weld. Specifically, TiN is generated by laser welding in a N 2 gas atmosphere to a steel type containing more than 0.02% by mass of Ti, to suppress cracks during solidification at the initial solidification stage of the weld. An advantageous equiaxed crystal is formed in the bead to suppress solidification cracking during welding.
日本国特開２０１０－２７９９９１号公報Japanese Unexamined Patent Publication No. 2010-279991 日本国特開２０１４－２１０２８３号公報Japanese Unexamined Patent Publication No. 2014-210283
　ところで、高張力鋼板に含まれる各種合金元素のうち、Ｃは高張力化に最も有用な元素のひとつであり、鋼板を容易に高強度化できるとともに、延性などを向上させるための調質も容易である。高張力鋼板においては、０．１０質量％≦Ｃ≦０．３０質量％含有するものが使用されている。 By the way, among various alloy elements contained in high-tensile steel plates, C is one of the most useful elements for increasing the tensile strength, and the steel plates can be easily increased in strength and tempered to improve ductility and the like. It is. In the high-tensile steel sheet, one containing 0.10% by mass ≦ C ≦ 0.30% by mass is used.
　しかしながら、本発明者らが検討したところ、上記のような０．１０質量％≦Ｃ≦０．３０質量％含有し、且つ、引張強度が７８０ＭＰａ以上の高張力鋼板をレーザにより貫通溶接した場合に、凝固割れが発生しやすく、加えて、凝固割れ部に残留応力が集中することで発生する割れの進展も判明した。特に、溶接終端部（本明細書では、「溶接ビードの終端部」とも言う。）のクレータでは、溶融金属量が少ないため、クレータ割れが顕著となる。 However, when the present inventors examined, when high-tensile steel plate containing 0.10 mass% ≦ C ≦ 0.30 mass% as described above and having a tensile strength of 780 MPa or more was through-welded by laser. It has also been found that solidification cracks are likely to occur, and in addition, the development of cracks that occur due to the concentration of residual stress in the solidification cracks. In particular, in the crater at the welding end portion (also referred to as “the end portion of the weld bead” in the present specification), the amount of molten metal is small, and thus crater cracking becomes significant.
　特許文献１及び２に記載の方法は、凝固割れの発生を抑制することが記載されているが、特許文献１では、Ｃが０．１質量％未満の高張力鋼板に関する技術であり、また、特許文献２では、Ｔｉ量を含有する鋼材であることからコストアップが想定され、さらに、Ｎ２ガスを含む溶接ガスを吹き付けながら、レーザ溶接するものに限られ、改善の余地があった。 The methods described in Patent Documents 1 and 2 are described to suppress the occurrence of solidification cracking, but in Patent Document 1, C is a technique related to a high-tensile steel sheet having a mass of less than 0.1% by mass, and in Patent Document 2, the cost is assumed since it is a steel material containing Ti amount, further, while blowing welding gas containing N 2 gas, limited to the laser welding, there is room for improvement.
　本発明は、前述した課題に鑑みてなされたものであり、その目的は、高張力鋼板の重ね合せ部にその表面から裏面まで貫通する溶接ビードの終端部において、クレータ割れが生じにくいレーザ溶接継手およびレーザ溶接継手の製造方法を提供することにある。 The present invention has been made in view of the above-described problems, and its purpose is to provide a laser welded joint in which crater cracking is unlikely to occur at the terminal end of a weld bead that penetrates the overlapped portion of a high-tensile steel plate from the front surface to the back surface. It is another object of the present invention to provide a method for manufacturing a laser welded joint.
　発明者等が上記課題を解決すべく鋭意研究したところ、アーク溶接では、ビード厚さＤとビード幅Ｗの比Ｄ／Ｗが小さいほど凝固割れ感受性が低下することが一般的に知られているのに対して、レーザ溶接のようなビード幅が狭い溶接では、逆にＤ／Ｗを大きくすることで凝固割れ感受性が低下することを見出した。 The inventors have conducted extensive research to solve the above problems, and it is generally known that in arc welding, the solidification cracking susceptibility decreases as the ratio D / W between the bead thickness D and the bead width W decreases. On the other hand, in welding with a narrow bead width such as laser welding, on the contrary, it was found that the susceptibility to solidification cracking is lowered by increasing D / W.
　凝固割れは板厚方向に貫通する液相が形成された際に、延性の低い液相にひずみが加わることで生じるといわれている。アーク溶接では、通常ビードがＶ字形状となるため、表ビード幅が大きくなるほど裏面が先に凝固し易くなり、板厚方向に貫通する液相が形成されにくい。一方、レーザ溶接では、ワインカップ状のビードが形成されるため、板厚方向に貫通する液相が形成されやすい。本発明者らは、レーザ溶接においては、Ｄ／Ｗが小さくなるような高入熱条件では、クレータ割れが助長される一方、ビード幅Ｗを小さくし、Ｄ／Ｗを大きくすることで、ひずみ量が低減されるとともに、Ｐ、Ｓなどの偏析が抑制され、クレータ割れを抑制可能であるという知見を得た。 It is said that solidification cracking occurs when a liquid phase penetrating in the thickness direction is formed and strain is applied to a liquid phase having low ductility. In arc welding, since the bead is normally V-shaped, the larger the front bead width, the easier the back surface solidifies first, and the liquid phase penetrating in the plate thickness direction is less likely to be formed. On the other hand, in laser welding, since a wine cup-shaped bead is formed, a liquid phase penetrating in the plate thickness direction is easily formed. In the laser welding, the crater cracking is promoted under high heat input conditions where D / W is reduced, while the bead width W is reduced and the D / W is increased. The amount was reduced, segregation of P, S, etc. was suppressed, and the knowledge that crater cracking can be suppressed was obtained.
　従って、本発明の上記目的は、下記の構成により達成される。
（１）　引張強度が７８０ＭＰａ以上、且つ板厚が０．５～３．０ｍｍである複数の高張力鋼板が重ね合わされたレーザ溶接継手であって、
　前記複数の高張力鋼板が重ね合された重ね合せ部は、その表面から裏面まで貫通した溶接ビードを有すると共に、該溶接ビードの終端部にクレータを備え、
　前記溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％であり、
　前記溶接ビードは、ビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤと前記ビード幅Ｗとの比Ｄ／Ｗが２．６以上であることを満足する、レーザ溶接継手。
（２）　前記クレータの中心部は、前記溶接ビードの溶接線方向における前記高張力鋼板の端面から３～１０ｍｍである、（１）に記載のレーザ溶接継手。
（３）　引張強度が７８０ＭＰａ以上、且つ板厚が０．５～３．０ｍｍである複数の高張力鋼板が重ね合わされたレーザ溶接継手であって、
　前記複数の高張力鋼板が重ね合された重ね合せ部は、その表面から裏面まで貫通した溶接ビードを有すると共に、該溶接ビードの終端部にクレータを備え、
　前記溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％であり、
　Ｃの質量％を［Ｃ］とすると、前記ビード厚さＤと前記ビード幅Ｗとの比Ｄ／Ｗが、Ｄ／Ｗ≧［Ｃ］＋２．３である、レーザ溶接継手。
（４）　前記クレータの中心部は、前記溶接ビードの溶接線方向における前記高張力鋼板の端面から３～１０ｍｍである、（３）に記載のレーザ溶接継手。
（５）　前記重ね合せ部は、前記複数の高張力鋼板のうちの少なくとも一つの前記高張力鋼板のフランジ部によって構成される、（１）～（４）のいずれかに記載のレーザ溶接継手。
（６）　（１）に記載のレーザ溶接継手の製造方法であって、
　前記重ね合せ部の表面から裏面まで貫通した溶接ビードを形成すると共に、該溶接ビードの終端部にクレータを形成し、前記溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％であり、
　前記溶接ビードのビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤと前記ビード幅Ｗとの比Ｄ／Ｗが２．６以上となるように、レーザ出力、溶接速度、シールドガス、集光スポット径、及び集光位置の少なくとも１つを制御する、レーザ溶接継手の製造方法。 Therefore, the above object of the present invention is achieved by the following configuration.
(1) A laser welded joint in which a plurality of high-tensile steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are superimposed,
The overlapped portion in which the plurality of high-tensile steel plates are overlapped has a weld bead penetrating from the front surface to the back surface, and has a crater at the end of the weld bead,
The component composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0.30% by mass, P + S <0.03% by mass,
The weld bead is a laser welded joint satisfying that a bead width W is 0.1 mm or more and 2.0 mm or less, and a ratio D / W between the bead thickness D and the bead width W is 2.6 or more.
(2) The laser welded joint according to (1), wherein a center portion of the crater is 3 to 10 mm from an end face of the high-tensile steel plate in a weld line direction of the weld bead.
(3) A laser welded joint in which a plurality of high-tensile steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are superimposed,
The overlapped portion in which the plurality of high-tensile steel plates are overlapped has a weld bead penetrating from the front surface to the back surface, and has a crater at the end of the weld bead,
The component composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0.30% by mass, P + S <0.03% by mass,
A laser welded joint in which a ratio D / W between the bead thickness D and the bead width W is D / W ≧ [C] +2.3, where C is% by mass.
(4) The laser welded joint according to (3), wherein a center portion of the crater is 3 to 10 mm from an end face of the high-tensile steel plate in a weld line direction of the weld bead.
(5) The laser weld joint according to any one of (1) to (4), wherein the overlapping portion is configured by a flange portion of at least one of the plurality of high-tensile steel plates.
(6) A method of manufacturing a laser welded joint according to (1),
A weld bead penetrating from the front surface to the back surface of the overlapped portion is formed, and a crater is formed at the end of the weld bead. The composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0. .30% by mass, P + S <0.03% by mass,
Laser output, welding speed, shield so that the bead width W of the weld bead is 0.1 mm or more and 2.0 mm or less, and the ratio D / W between the bead thickness D and the bead width W is 2.6 or more. A method for manufacturing a laser welded joint, wherein at least one of a gas, a focused spot diameter, and a focused position is controlled.
　本発明のレーザ溶接継手によれば、引張強度が７８０ＭＰａ以上、且つ板厚が０．５～３．０ｍｍである複数の高張力鋼板が重ね合された重ね合せ部は、その表面から裏面まで貫通した溶接ビードを有すると共に、該溶接ビードの終端部にクレータを備え、溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％である。溶接ビードは、ビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが２．６以上であるので、溶接終端部でのクレータ割れを抑制することができる。また、溶接終端部でのクレータ割れを抑制することで、溶接ビードの低温割れも防ぐことができる。 According to the laser welded joint of the present invention, the overlapped portion where a plurality of high strength steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are overlapped penetrates from the front surface to the back surface. The weld bead is provided with a crater at the end of the weld bead, and the composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0.30% by mass and P + S <0.03% by mass. is there. The weld bead has a bead width W of 0.1 mm or more and 2.0 mm or less, and a ratio D / W between the bead thickness D and the bead width W of 2.6 or more, thereby suppressing crater cracking at the weld end. can do. Moreover, the low temperature crack of a weld bead can also be prevented by suppressing the crater crack in a welding termination | terminus part.
　また、本発明のレーザ溶接継手によれば、引張強度が７８０ＭＰａ以上、且つ板厚が０．５～３．０ｍｍである複数の高張力鋼板が重ね合された重ね合せ部は、その表面から裏面まで貫通した溶接ビードを有すると共に、該溶接ビードの終端部にクレータを備え、溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％である。Ｃの質量％を［Ｃ］とすると、ビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが、Ｄ／Ｗ≧［Ｃ］＋２．３であるので、溶接終端部でのクレータ割れを抑制することができる。また、溶接終端部でのクレータ割れを抑制することで、溶接ビードの低温割れも防ぐことができる。 Further, according to the laser welded joint of the present invention, the overlapped portion in which a plurality of high-tensile steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are overlapped is formed from the front surface to the back surface. The weld bead is provided with a crater at the end of the weld bead, and the component composition of the weld metal in the weld bead is 0.10 mass% ≦ C ≦ 0.30 mass%, P + S <0.03 mass %. When the mass% of C is [C], the ratio D / W between the bead thickness D and the bead width W is D / W ≧ [C] +2.3, so that crater cracking at the weld end is suppressed. can do. Moreover, the low temperature crack of a weld bead can also be prevented by suppressing the crater crack in a welding termination | terminus part.
　また、上述したレーザ溶接継手の製造方法によれば、引張強度が７８０ＭＰａ以上、且つ板厚が０．５～３．０ｍｍである複数の高張力鋼板が重ね合された重ね合せ部にレーザ光を照射して、該重ね合せ部を溶接する。その際、重ね合せ部の表面から裏面まで貫通した溶接ビードを形成すると共に、該溶接ビードの終端部にクレータを形成し、溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％であり、溶接ビードのビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが２．６以上となるように、レーザ出力、溶接速度、シールドガス、集光スポット径、及び集光位置の少なくとも１つを制御するので、溶接終端部のクレータ割れが生じにくく、ひいては、溶接ビードの低温割れが防止されたレーザ溶接継手が得られる。 Further, according to the laser welded joint manufacturing method described above, the laser beam is applied to the overlapped portion where a plurality of high strength steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are overlapped. Irradiate and weld the overlap. At that time, a weld bead penetrating from the front surface to the back surface of the overlapped portion is formed, and a crater is formed at the end portion of the weld bead. The component composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0.30% by mass, P + S <0.03% by mass, the bead width W of the weld bead is 0.1 mm to 2.0 mm, and the ratio D / W of the bead thickness D to the bead width W is 2. Since at least one of the laser output, welding speed, shield gas, condensing spot diameter, and condensing position is controlled so that it becomes 6 or more, crater cracking at the welding end portion hardly occurs, and as a result, the low temperature of the weld bead A laser weld joint in which cracking is prevented is obtained.
本発明に係る高張力鋼板のレーザ溶接継手の一実施形態であり、高張力鋼板からなる平板とフランジ部とのレーザ溶接継手の概略斜視図である。It is one Embodiment of the laser welded joint of the high-tensile steel plate which concerns on this invention, and is a schematic perspective view of the laser welded joint of the flat plate and flange part which consist of a high-tensile steel plate. 図１のＩＩ－ＩＩ線断面図である。FIG. 2 is a sectional view taken along line II-II in FIG. 図１のＩＩＩ－ＩＩＩ線断面図である。FIG. 3 is a sectional view taken along line III-III in FIG. 1. 本発明の範囲をＣ質量％とＤ／Ｗとの関係で示すグラフである。It is a graph which shows the range of this invention by the relationship between C mass% and D / W. レーザ溶接される２枚の高張力鋼板の概略斜視図である。It is a schematic perspective view of two high-tensile steel plates to be laser welded.
　以下、本発明に係るレーザ溶接継手の一実施形態を図面に基づいて詳細に説明する。
　図１に示すように、本実施形態のレーザ溶接継手１０では、高張力鋼板１１の一端が折り曲げ形成されたフランジ部１２と、平板状の高張力鋼板１３と、を重ね合わせて重ね合せ部１９を構成する。そして、重ね合わせ部１９にレーザ光Ｌを照射しつつ、高張力鋼板１１（フランジ部１２）、及び高張力鋼板１３の両端部１４に沿ってレーザ加工ヘッド１を移動させて、高張力鋼板１１のフランジ部１２の表面１２ａから高張力鋼板１３の裏面１３ａまで貫通する溶接ビード１６を形成することにより、高張力鋼板１１，１３を互いに接合している。 Hereinafter, an embodiment of a laser welded joint according to the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, in the laser welded joint 10 of the present embodiment, a flange portion 12 in which one end of a high-tensile steel plate 11 is bent and a flat high-tensile steel plate 13 are overlapped to overlap each other. Configure. Then, the laser processing head 1 is moved along the both ends 14 of the high-tensile steel plate 11 (flange portion 12) and the high-tensile steel plate 13 while irradiating the overlapping portion 19 with the laser light L, and the high-tensile steel plate 11. By forming a weld bead 16 penetrating from the front surface 12a of the flange portion 12 to the back surface 13a of the high-tensile steel plate 13, the high- tensile steel plates 11 and 13 are joined to each other.
　ここで、レーザ溶接は、溶接ビード１６の端部が、高張力鋼板１１，１３の溶接線方向における端面１８から離れた位置となるように行われる。このため、溶接ビード１６の終端部１６ａには、クレータ２０が形成されている。 Here, laser welding is performed so that the end of the weld bead 16 is located away from the end face 18 in the weld line direction of the high- tensile steel plates 11 and 13. For this reason, a crater 20 is formed at the end portion 16 a of the weld bead 16.
　本実施形態の高張力鋼板１１，１３では、板厚ｔが０．５～３．０ｍｍとしている。板厚ｔの下限を０．５ｍｍとしたのは、自動車などの構造物に一般的に使用される鋼板の板厚を考慮して規定したもので、板厚ｔの上限を３．０ｍｍとしたのは、通常のレーザ溶接機の溶接能力による。 In the high- tensile steel plates 11 and 13 of the present embodiment, the plate thickness t is 0.5 to 3.0 mm. The lower limit of the plate thickness t is set to 0.5 mm because it is defined in consideration of the plate thickness of a steel plate generally used for a structure such as an automobile, and the upper limit of the plate thickness t is set to 3.0 mm. This depends on the welding ability of a normal laser welding machine.
　本実施形態の高張力鋼板１１，１３では、引張強度が７８０ＭＰａ以上の高強度クラスのものが対象であり、例えば、９８０ＭＰａや１１８０ＭＰａのものが含まれる。 The high- tensile steel plates 11 and 13 of the present embodiment are intended for the high-strength class having a tensile strength of 780 MPa or more, and include, for example, those of 980 MPa and 1180 MPa.
　さらに、レーザ溶接では、溶接金属の成分は、フィラー等の溶加材を別途添加しない場合、重ね合せた各高張力鋼板１１、１３の母材成分値及びその板厚ｔから計算される平均成分であり、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％を満たすように、各高張力鋼板１１、１３の材質が選定される。また、溶加材を加える場合には、その添加量も考慮して、上記値を満たすように、各高張力鋼板１１、１３の材質が選定される。 Furthermore, in laser welding, the weld metal component is an average component calculated from the base material component values of the superposed high- strength steel plates 11 and 13 and the plate thickness t when no filler material such as filler is added. The materials of the high- tensile steel plates 11 and 13 are selected so as to satisfy 0.10% by mass ≦ C ≦ 0.30% by mass and P + S <0.03% by mass. Moreover, when adding a filler material, the material of each high- tensile steel sheet 11 and 13 is selected so that the said value may be satisfy | filled also considering the addition amount.
　ここで、本出願人は、上記の如く、引張強度が７８０ＭＰａ以上、且つ板厚が０．５～３．０ｍｍである高張力鋼板１１、１３が重ね合された重ね合せ部を貫通溶接し、溶接金属の成分組成が、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％を満足するレーザ溶接継手１０において、ビード幅Ｗ、及びビード厚さＤとビード幅Ｗとの比Ｄ／Ｗを、本発明の規定する範囲内に制御することで、クレータ割れを抑制できることを見出した。 Here, the applicant of the present invention, as described above, through welds the overlapped portion where the high strength steel plates 11 and 13 having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are overlapped, In the laser welded joint 10 in which the composition of the weld metal satisfies 0.10 mass% ≦ C ≦ 0.30 mass% and P + S <0.03 mass%, the bead width W, the bead thickness D, and the bead width W It was found that the crater cracking can be suppressed by controlling the ratio D / W to the range defined by the present invention.
　即ち、本実施形態の溶接ビード１６は、ビード幅Ｗが、０．１ｍｍ以上２．０ｍｍ以下、且つ、ビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが、２．６以上となるように、レーザ溶接によって形成される。図２に示すように、ここで言うビード幅Ｗは、高張力鋼板１１のフランジ部１２と、高張力鋼板１３との接合界面１７におけるビード幅のことである。また、ビード厚さＤは、溶接ビード１６がフランジ部１２の表面１２ａから高張力鋼板１３の裏面１３ａまで貫通しているので、高張力鋼板１１，１３の板厚ｔの合計厚さとなる。 That is, the weld bead 16 of the present embodiment has a bead width W of 0.1 mm or more and 2.0 mm or less, and a ratio D / W between the bead thickness D and the bead width W of 2.6 or more. In addition, it is formed by laser welding. As shown in FIG. 2, the bead width W referred to here is the bead width at the joint interface 17 between the flange portion 12 of the high-tensile steel plate 11 and the high-tensile steel plate 13. Further, the bead thickness D is the total thickness of the plate thickness t of the high strength steel plates 11 and 13 because the weld bead 16 penetrates from the front surface 12a of the flange portion 12 to the back surface 13a of the high strength steel plate 13.
　このように、ビード幅Ｗが狭くなるようにレーザ溶接を行うことにより、クレータ割れに繋がる溶接ビード１６での引張方向の歪み量を低減し、かつ、Ｐ及びＳの物質移動による偏析を少なくすることができ、クレータ割れの発生を抑制することができる。なお、ビード幅Ｗは、１．０ｍｍ以下が好ましく、さらに、ビード厚さＤとビード幅Ｗとの比Ｄ／Ｗは、好ましくは２．７以上であり、さらに好ましくは２．８以上である。
　また、上記比Ｄ／Ｗの上限を特に限定する必要はないが、例えば、上限は３０とすればよい。 Thus, by performing laser welding so that the bead width W becomes narrow, the amount of strain in the tensile direction at the weld bead 16 that leads to crater cracking is reduced, and segregation due to mass transfer of P and S is reduced. And the occurrence of crater cracks can be suppressed. The bead width W is preferably 1.0 mm or less, and the ratio D / W between the bead thickness D and the bead width W is preferably 2.7 or more, more preferably 2.8 or more. .
Moreover, although it is not necessary to specifically limit the upper limit of the ratio D / W, for example, the upper limit may be set to 30.
　ビード幅Ｗ０．１ｍｍ以上２．０ｍｍ以下、及びビード厚さＤとビード幅Ｗとの比Ｄ／Ｗ２．６以上とするレーザ溶接は、レーザ出力、溶接速度、シールドガス、集光スポット径、及び集光位置の少なくとも１つの溶接条件を制御して入熱量を抑制することで達成される。
　上記溶接条件以外にも、２枚の高張力鋼板１１，１３間のギャップは、溶接時にビードが貫通溶接しやすいように、例えば、０．３ｍｍ以下とするのがよい。
　なお、レーザ溶接において、レーザ発振器として、例えば、ＹＡＧレーザ、ファイバレーザ、ＤＩＳＫレーザなどを使用することができる。 Laser welding with a bead width W of 0.1 mm to 2.0 mm and a bead thickness D to bead width W ratio of D / W 2.6 or more includes laser output, welding speed, shielding gas, condensing spot diameter, and This is achieved by controlling the amount of heat input by controlling at least one welding condition at the condensing position.
In addition to the above welding conditions, the gap between the two high- strength steel plates 11 and 13 is preferably set to, for example, 0.3 mm or less so that the beads can be easily welded through during welding.
In laser welding, for example, a YAG laser, a fiber laser, a DISK laser, or the like can be used as a laser oscillator.
　また、クレータ割れは、高張力鋼板１１，１３中のＣ質量％に略比例する傾向があり、Ｃの質量％を［Ｃ］としたとき、ビード厚さＤとビード幅Ｗとの比Ｄ／Ｗは、Ｄ／Ｗ≧［Ｃ］＋２．３を満足することでも、クレータ割れの発生を抑制することができる。 Further, crater cracks tend to be approximately proportional to C mass% in the high- tensile steel plates 11 and 13, and the ratio D / bead thickness D to bead width W when the mass% C is [C]. W can also suppress the occurrence of crater cracks by satisfying D / W ≧ [C] +2.3.
　即ち、図４に示すグラフに示すように、０．１０質量％≦Ｃ≦０．３０質量％、且つＤ／Ｗ≧［Ｃ］＋２．３の範囲において、クレータ割れの発生を抑制することができる。なお、Ｄ／Ｗは、クレータ割れの発生をより確実に抑制する範囲として、Ｄ／Ｗ≧［Ｃ］＋２．４が好ましく、Ｄ／Ｗ≧［Ｃ］＋２．５がさらに好ましい。
　なお、図４では、後述する実施例１～７及び比較例１～５のＤ／Ｗがプロットされている。 That is, as shown in the graph shown in FIG. 4, the occurrence of crater cracks can be suppressed in the range of 0.10 mass% ≦ C ≦ 0.30 mass% and D / W ≧ [C] +2.3. it can. In addition, D / W> = [C] +2.4 is preferable and D / W> = [C] +2.5 is still more preferable as a range which suppresses generation | occurrence | production of a crater crack more reliably.
In FIG. 4, D / Ws of Examples 1 to 7 and Comparative Examples 1 to 5 described later are plotted.
　また、図３にも示すように、溶接ビード１６の溶接線方向の断面において、クレータ２０の最も凹んだ部分であるクレータ２０の中心部Ｃと、高張力鋼板１１，１３の溶接線方向における端面１８との距離Ｘは、３～１０ｍｍとなっている。クレータ２０の中心部Ｃと端面１８との距離Ｘを３ｍｍ以上とすることで、高張力鋼板１１，１３の端面１８が溶融して溶け落ちてしまうのを防ぐことができ、また、１０ｍｍ以下とすることで、十分な接合強度を得ることができる。 Further, as shown in FIG. 3, in the cross section in the weld line direction of the weld bead 16, the center portion C of the crater 20 which is the most recessed portion of the crater 20 and the end surface in the weld line direction of the high- tensile steel plates 11 and 13. The distance X to 18 is 3 to 10 mm. By setting the distance X between the central portion C of the crater 20 and the end face 18 to 3 mm or more, the end face 18 of the high- tensile steel plates 11 and 13 can be prevented from melting and melting, and 10 mm or less. By doing so, sufficient bonding strength can be obtained.
　本発明の効果を確認するため、本発明に係る実施例と、該実施例と比較する比較例について説明する。実施例及び比較例ともに、表１に示す５種類の高張力鋼板を用い、図５に示すように同種の高張力鋼板同士を２枚重ね合わせ、端面から５ｍｍ離れた位置から溶接長さ２０ｍｍで重ね合わせ部をレーザ溶接してレーザ溶接継手を作製し、レーザ溶接継手のクレータ割れの有無を調査した。なお、表１に示す高張力鋼板は、いずれも本発明が規定する板厚、引張強度、及び、溶接継手の組成成分を満足する。 In order to confirm the effect of the present invention, examples according to the present invention and comparative examples to be compared with the examples will be described. In both Examples and Comparative Examples, five types of high-tensile steel plates shown in Table 1 were used, two high-strength steel plates of the same type as shown in FIG. 5 were overlapped, and the weld length was 20 mm from a position 5 mm away from the end surface. A laser welded joint was prepared by laser welding the overlapped part, and the presence of crater cracks in the laser welded joint was investigated. In addition, all the high-tensile steel plates shown in Table 1 satisfy the plate thickness, tensile strength, and composition components of the welded joint defined by the present invention.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　また、レーザ溶接機はファイバレーザを使用し、加工点出力を２～４ｋＷ、溶接速度を０．７５～４ｍ／ｍｉｎとした。集光位置は上板表面～上板表面＋９ｍｍとし、集光スポット径は０．４５～０．６ｍｍとした。また、シールドガスとして、Ａｒガスを使用し、流量を１５Ｌ／ｍｉｎとした。クレータ割れの有無は、溶接線に直交するＡ－Ａ線での溶接終端部の断面観察により評価した。 The laser welding machine used a fiber laser, the processing point output was 2 to 4 kW, and the welding speed was 0.75 to 4 m / min. The condensing position was from the upper plate surface to the upper plate surface + 9 mm, and the condensing spot diameter was 0.45 to 0.6 mm. Further, Ar gas was used as the shielding gas, and the flow rate was 15 L / min. The presence or absence of crater cracks was evaluated by observing the cross section of the weld end portion along the line AA perpendicular to the weld line.
　各実施例及び比較例の結果を、各試験条件と共に表２に示す。 The results of each example and comparative example are shown in Table 2 together with each test condition.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２に示すように、本発明で規定する高張力鋼板を用い、ビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが２．６以上である実施例１～７では、いずれの実施例でも溶接終端部にクレータ割れが生じることながなかった。これに対し、ビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが、本発明の規定範囲外となっている比較例１～５では、溶接終端部にクレータ割れが生じていることが確認された。 As shown in Table 2, the high-tensile steel plate specified in the present invention was used, the bead width W was 0.1 mm or more and 2.0 mm or less, and the ratio D / W between the bead thickness D and the bead width W was 2.6. In Examples 1 to 7 as described above, crater cracks did not occur at the weld end portion in any of the Examples. In contrast, in Comparative Examples 1 to 5 where the ratio D / W between the bead thickness D and the bead width W is outside the specified range of the present invention, it was confirmed that crater cracking occurred at the weld end portion. It was done.
　また、いずれの実施例１～７も、Ｄ／Ｗ≧［Ｃ］＋２．３を満足しており、当該式の有効性を確認することができる。 Also, any of Examples 1 to 7 satisfies D / W ≧ [C] +2.3, and the effectiveness of the formula can be confirmed.
　以上説明したように、本実施形態のレーザ溶接継手１０によれば、引張強度が７８０ＭＰａ以上、且つ板厚ｔが０．５～３．０ｍｍである複数の高張力鋼板１１，１３が重ね合わされる。複数の高張力鋼板１１，１３が重ね合された重ね合せ部１９は、その表面１２ａから裏面１３ａまで貫通した溶接ビード１６を有すると共に、該溶接ビード１６の終端部１６ａにクレータ２０を備え、溶接ビード１６における溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％である。溶接ビード１６は、ビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが２．６以上を満足する。これにより、溶接終端部１６ａでのクレータ割れを抑制することができる。また、溶接終端部でのクレータ割れを抑制することで、溶接ビード１６の低温割れも防ぐことができる。 As described above, according to the laser welded joint 10 of this embodiment, a plurality of high- tensile steel plates 11 and 13 having a tensile strength of 780 MPa or more and a plate thickness t of 0.5 to 3.0 mm are overlapped. . The overlapping portion 19 in which the plurality of high- tensile steel plates 11 and 13 are overlapped has a weld bead 16 penetrating from the front surface 12a to the back surface 13a, and a crater 20 is provided at a terminal portion 16a of the weld bead 16, and welding is performed. The component composition of the weld metal in the bead 16 is 0.10% by mass ≦ C ≦ 0.30% by mass and P + S <0.03% by mass. The weld bead 16 satisfies a bead width W of 0.1 mm to 2.0 mm and a ratio D / W of the bead thickness D to the bead width W of 2.6 or more. Thereby, the crater crack in the welding termination | terminus part 16a can be suppressed. Moreover, the low temperature crack of the weld bead 16 can also be prevented by suppressing the crater crack in a welding terminal part.
　また、本実施形態のレーザ溶接継手１０によれば、溶接ビード１６のビード幅Ｗ、及びＤ／Ｗの規定の代わりに、Ｃの質量％を［Ｃ］とすると、ビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが、Ｄ／Ｗ≧［Ｃ］＋２．３を満足する。これにより、溶接終端部１６ａのクレータ割れが発生しやすくなるＣの質量％が多い高張力鋼板１１，１３においても、Ｃの質量％との関係で、Ｄ／Ｗを規定することで、溶接終端部１６ａのクレータ割れを抑制することができる。また、溶接終端部でのクレータ割れを抑制することで、溶接ビード１６の低温割れも防ぐことができる。 Further, according to the laser welded joint 10 of the present embodiment, instead of defining the bead width W and D / W of the weld bead 16, if the mass% of C is [C], the bead thickness D and the bead width The ratio D / W with W satisfies D / W ≧ [C] +2.3. As a result, even in the high- tensile steel plates 11 and 13 having a large mass% of C in which the crater cracking of the weld termination portion 16a is likely to occur, by defining D / W in relation to the mass% of C, the welding termination is performed. Crater cracks in the portion 16a can be suppressed. Moreover, the low temperature crack of the weld bead 16 can also be prevented by suppressing the crater crack in a welding terminal part.
　通常、貫通溶接されるレーザ溶接継手１０は、自動車分野においては、品質保証の観点から望ましいが、クレータ割れに対しては不利となる。このため、本実施形態では、比Ｄ／Ｗを２．６以上、或いはＤ／Ｗ≧［Ｃ］＋２．３を満足するものとしたので、クレータ割れが抑制される。この結果、本実施形態のレーザ溶接継手１０は、貫通溶接とクレータ割れ抑制を両立でき、自動車分野における品質保証の課題を解決することができる。 Usually, the laser weld joint 10 to be welded through is desirable from the viewpoint of quality assurance in the automobile field, but it is disadvantageous for crater cracking. For this reason, in this embodiment, since the ratio D / W satisfies 2.6 or more, or D / W ≧ [C] +2.3, crater cracking is suppressed. As a result, the laser welded joint 10 of the present embodiment can achieve both penetration welding and crater crack suppression, and can solve the problem of quality assurance in the automobile field.
　また、レーザ溶接継手の製造方法によれば、引張強度が７８０ＭＰａ以上、且つ板厚ｔが０．５～３．０ｍｍである複数の高張力鋼板１１，１３が重ね合わされ、複数の高張力鋼板１１，１３が重ね合された重ね合せ部１９にレーザ光Ｌを照射して、該重ね合せ部１９を溶接する。溶接工程は、重ね合せ部１９の表面１２ａから裏面１３ａまで貫通した溶接ビード１６を形成すると共に、該溶接ビード１６の終端部１６ａにクレータ２０を形成する。溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％であり、溶接ビード１６のビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤとビード幅Ｗとの比Ｄ／Ｗが２．６以上となるように、レーザ出力、溶接速度、シールドガス、集光スポット径、及び集光位置の少なくとも１つを制御するので、溶接終端部１６ａのクレータ割れが生じにくく、ひいては、溶接ビード１６の低温割れが防止されたレーザ溶接継手１０を得ることができる。 Further, according to the method of manufacturing a laser welded joint, a plurality of high strength steel plates 11 and 13 having a tensile strength of 780 MPa or more and a plate thickness t of 0.5 to 3.0 mm are overlapped to form a plurality of high strength steel plates 11. , 13 is irradiated with a laser beam L, and the overlapping portion 19 is welded. In the welding process, the weld bead 16 penetrating from the front surface 12 a to the back surface 13 a of the overlapping portion 19 is formed, and the crater 20 is formed at the end portion 16 a of the weld bead 16. The component composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0.30% by mass and P + S <0.03% by mass, and the bead width W of the weld bead 16 is 0.1 mm or more and 2.0 mm or less. In addition, at least one of laser output, welding speed, shield gas, condensing spot diameter, and condensing position is controlled so that the ratio D / W of the bead thickness D and the bead width W is 2.6 or more. Therefore, the crater crack of the welding end portion 16a is hardly generated, and as a result, the laser welded joint 10 in which the cold crack of the weld bead 16 is prevented can be obtained.
　尚、本発明は、前述した実施形態及び実施例に限定されるものではなく、適宜、変形、改良、等が可能である。
　例えば、上記実施形態では、２枚の高張力鋼板を重ね合わせてレーザ溶接したが、レーザ溶接される高張力鋼板は２枚に限定されず、３枚、あるいはそれ以上であっても同様に、クレータ割れを生じることなく溶接することができる。
　また、重ね合わせ部の形状は、本実施形態のものに限定されず、例えば、２枚の高張力鋼板のフランジ部同士を重ね合せるものでもよく、或いは、平板の高張力鋼板同士を重ね合せるものでもよい。 Note that the present invention is not limited to the above-described embodiments and examples, and modifications, improvements, and the like can be made as appropriate.
For example, in the above embodiment, two high-tensile steel plates are overlapped and laser-welded, but the high-tensile steel plates to be laser-welded are not limited to two, and even if three or more, It is possible to weld without causing crater cracks.
Further, the shape of the overlapping portion is not limited to that of the present embodiment. For example, the flange portions of two high-strength steel plates may be overlapped with each other, or flat high-tensile steel plates may be overlapped with each other. But you can.
　本発明は、２０１６年６月２９日出願の日本特許出願（特願２０１６－１２９１３５）に基づくものであり、その内容はここに参照として取り込まれる。 The present invention is based on a Japanese patent application (Japanese Patent Application No. 2016-129135) filed on June 29, 2016, the contents of which are incorporated herein by reference.
１０  　レーザ溶接継手
１１，１３  　高張力鋼板
１２  　フランジ部
１２ａ      　表面
１３ａ      　裏面
１６  　溶接ビード
１６ａ      　溶接終端部（溶接ビードの終端部）
１８  　端面
１９  　重ね合せ部
２０  　クレータ
Ｃ    　クレータの中心部
Ｄ／Ｗ      　ビード厚さとビード幅との比
Ｌ    　レーザ光
ｔ    　板厚
Ｗ    　ビード幅 DESCRIPTION OF SYMBOLS 10 Laser welded joint 11, 13 High-tensile steel plate 12 Flange part 12a Front surface 13a Back surface 16 Weld bead 16a Weld termination part (end part of weld bead)
18 End face 19 Overlapping part 20 Crater C Center part of crater D / W Ratio of bead thickness to bead width L Laser light t Plate thickness W Bead width

Claims (6)

  1. 　引張強度が７８０ＭＰａ以上、且つ板厚が０．５～３．０ｍｍである複数の高張力鋼板が重ね合わされたレーザ溶接継手であって、
    　前記複数の高張力鋼板が重ね合された重ね合せ部は、その表面から裏面まで貫通した溶接ビードを有すると共に、該溶接ビードの終端部にクレータを備え、
    　前記溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％であり、
    　前記溶接ビードは、ビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤと前記ビード幅Ｗとの比Ｄ／Ｗが２．６以上であることを満足する、レーザ溶接継手。     A laser welded joint in which a plurality of high-tensile steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are superimposed,
    The overlapped portion in which the plurality of high-tensile steel plates are overlapped has a weld bead penetrating from the front surface to the back surface, and has a crater at the end of the weld bead,
    The component composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0.30% by mass, P + S <0.03% by mass,
    The weld bead is a laser welded joint satisfying that a bead width W is 0.1 mm or more and 2.0 mm or less, and a ratio D / W between the bead thickness D and the bead width W is 2.6 or more.
  2. 　前記クレータの中心部は、前記溶接ビードの溶接線方向における前記高張力鋼板の端面から３～１０ｍｍである、請求項１に記載のレーザ溶接継手。 The laser welded joint according to claim 1, wherein the central portion of the crater is 3 to 10 mm from the end face of the high-tensile steel plate in the weld line direction of the weld bead.
  3. 　引張強度が７８０ＭＰａ以上、且つ板厚が０．５～３．０ｍｍである複数の高張力鋼板が重ね合わされたレーザ溶接継手であって、
    　前記複数の高張力鋼板が重ね合された重ね合せ部は、その表面から裏面まで貫通した溶接ビードを有すると共に、該溶接ビードの終端部にクレータを備え、
    　前記溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％であり、
    　Ｃの質量％を［Ｃ］とすると、前記ビード厚さＤと前記ビード幅Ｗとの比Ｄ／Ｗが、Ｄ／Ｗ≧［Ｃ］＋２．３である、レーザ溶接継手。     A laser welded joint in which a plurality of high-tensile steel plates having a tensile strength of 780 MPa or more and a plate thickness of 0.5 to 3.0 mm are superimposed,
    The overlapped portion in which the plurality of high-tensile steel plates are overlapped has a weld bead penetrating from the front surface to the back surface, and has a crater at the end of the weld bead,
    The component composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0.30% by mass, P + S <0.03% by mass,
    A laser welded joint in which a ratio D / W between the bead thickness D and the bead width W is D / W ≧ [C] +2.3, where C is% by mass.
  4. 　前記クレータの中心部は、前記溶接ビードの溶接線方向における前記高張力鋼板の端面から３～１０ｍｍである、請求項３に記載のレーザ溶接継手。 The laser welded joint according to claim 3, wherein the center of the crater is 3 to 10 mm from the end face of the high-tensile steel plate in the weld line direction of the weld bead.
  5. 　前記重ね合せ部は、前記複数の高張力鋼板のうちの少なくとも一つの前記高張力鋼板のフランジ部によって構成される、請求項１～４のいずれか１項に記載のレーザ溶接継手。 The laser weld joint according to any one of claims 1 to 4, wherein the overlapping portion is configured by a flange portion of at least one of the plurality of high-tensile steel plates.
  6. 　請求項１に記載のレーザ溶接継手の製造方法であって、
    　前記重ね合せ部の表面から裏面まで貫通した溶接ビードを形成すると共に、該溶接ビードの終端部にクレータを形成し、前記溶接ビードにおける溶接金属の成分組成は、０．１０質量％≦Ｃ≦０．３０質量％、Ｐ＋Ｓ＜０．０３質量％であり、
    　前記溶接ビードのビード幅Ｗが０．１ｍｍ以上２．０ｍｍ以下、且つビード厚さＤと前記ビード幅Ｗとの比Ｄ／Ｗが２．６以上となるように、レーザ出力、溶接速度、シールドガス、集光スポット径、及び集光位置の少なくとも１つを制御する、レーザ溶接継手の製造方法。     It is a manufacturing method of the laser weld joint according to claim 1,
    A weld bead penetrating from the front surface to the back surface of the overlapped portion is formed, and a crater is formed at the end of the weld bead. The composition of the weld metal in the weld bead is 0.10% by mass ≦ C ≦ 0. .30% by mass, P + S <0.03% by mass,
    Laser output, welding speed, shield so that the bead width W of the weld bead is 0.1 mm or more and 2.0 mm or less, and the ratio D / W between the bead thickness D and the bead width W is 2.6 or more. A method for manufacturing a laser welded joint, wherein at least one of a gas, a focused spot diameter, and a focused position is controlled.
PCT/JP2017/018837 2016-06-29 2017-05-19 Laser welded joint and method for manufacturing laser welded joint WO2018003341A1 (en)

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