WO2018181231A1 - Production method for resistance spot welded joint - Google Patents

Production method for resistance spot welded joint Download PDF

Info

Publication number
WO2018181231A1
WO2018181231A1 PCT/JP2018/012259 JP2018012259W WO2018181231A1 WO 2018181231 A1 WO2018181231 A1 WO 2018181231A1 JP 2018012259 W JP2018012259 W JP 2018012259W WO 2018181231 A1 WO2018181231 A1 WO 2018181231A1
Authority
WO
WIPO (PCT)
Prior art keywords
energization
plate
steel plate
electrode
resistance spot
Prior art date
Application number
PCT/JP2018/012259
Other languages
French (fr)
Japanese (ja)
Inventor
央海 澤西
松田　広志
池田　倫正
Original Assignee
Ｊｆｅスチール株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ｊｆｅスチール株式会社 filed Critical Ｊｆｅスチール株式会社
Priority to KR1020197028628A priority Critical patent/KR102225221B1/en
Priority to CN201880021920.8A priority patent/CN110461528B/en
Priority to JP2018530804A priority patent/JP6410003B1/en
Publication of WO2018181231A1 publication Critical patent/WO2018181231A1/en

Links

Images

Classifications

    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/10—Spot welding; Stitch welding
    • B23K11/11—Spot welding
    • B23K11/115—Spot welding by means of two electrodes placed opposite one another on both sides of the welded parts
    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/10—Spot welding; Stitch welding
    • B23K11/11—Spot 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/16—Resistance welding; Severing by resistance heating taking account of the properties of the material to be welded
    • B23K11/18—Resistance welding; Severing by resistance heating taking account of the properties of the material to be welded of non-ferrous metals
    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/16—Resistance welding; Severing by resistance heating taking account of the properties of the material to be welded
    • B23K11/20—Resistance welding; Severing by resistance heating taking account of the properties of the material to be welded of different metals
    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/30—Features relating to electrodes

Definitions

  • the present invention relates to a method for manufacturing a resistance spot welded joint of dissimilar metal materials. Specifically, a resistance that produces a resistance spot welded joint by joining a plate assembly in which at least one kind of steel plate selected from a plated steel plate, a cold-rolled steel plate, and a hot-rolled steel plate and an aluminum plate are overlapped by resistance spot welding.
  • the present invention relates to a method for manufacturing a spot welded joint.
  • the resistance spot welding method is a method in which two or more stacked steel plates are sandwiched and pressed with a pair of electrodes from above and below, and a high current welding current is passed between the upper and lower electrodes for a short time to join by resistance heating. It is.
  • the aluminum plate is a general term for a pure aluminum plate and an aluminum alloy plate.
  • the strength of the joint, especially the cross can be reduced by reducing the thickness of the soft aluminum plate by pressing the electrode and forming a brittle intermetallic compound at the joint interface.
  • the peeling strength cannot be secured when a load in the peeling direction represented by tension or the like is generated.
  • Patent Document 1 describes a resistance spot welding method in which an iron / aluminum clad thin plate is inserted between a steel plate and an aluminum plate so that the same kind of materials face each other so that a high-strength joint can be obtained even at a low current. Yes.
  • Patent Document 2 by welding with one or more contact plates on both sides of a steel plate and an aluminum plate, the interface between the contact plate and the material to be joined generates resistance heat, and the steel and aluminum are resistance diffusion bonded.
  • a resistance spot welding method is described that provides a high strength joint.
  • Patent Document 3 when spot welding a steel material and an aluminum material, by optimizing each amount of Mn and Si in a steel plate and a steel plate surface oxide film, it is possible to suppress the occurrence of scattering while obtaining a large nugget diameter. It is described.
  • Patent Document 4 describes a dissimilar metal joining method that suppresses the growth of intermetallic compounds at the joining interface by optimizing the conditions for pulsation energization and increasing the pressure after completion of energization.
  • Patent Document 5 discloses a spot that can suppress the generation of dust from the surface of the steel sheet by optimizing the pre-energization and the subsequent energization conditions, reduce the welding current as much as possible, and obtain a dissimilar material joint having high joint strength. A welding method is described.
  • Japanese Patent No. 3117053 Japanese Patent No. 3504790 JP 2005-152958 A Japanese Patent No. 5624901 Japanese Patent No. 5572046
  • Patent Documents 1 and 2 require the use of a backing plate or a clad thin plate that is not necessary for the structure of the vehicle body, so that a significant increase in cost and weight cannot be achieved. There's a problem.
  • Patent Document 3 since it is necessary to limit the amount and distribution of alloy elements in the steel sheet and the oxide film, there is a problem that the use of the steel sheet that satisfies the required performance is restricted. In particular, the application of the invention of Patent Document 3 is extremely limited under the circumstances where high alloying is progressing with high strength in recent steel plates.
  • the energization time for pre-energization is 20 ms or less, and the energization time for pulsation energization is 10 ms or less, both of which are short. Required. Therefore, when the specific resistance of the steel plate is high or when the plate thickness is large, there is a concern that scattering occurs on the surface of the steel plate.
  • Patent Document 5 there is a problem that applicable plate sets are limited only to plate sets of cold-rolled steel plates and 6000 series aluminum alloy plates. In Patent Document 5, it is necessary to perform pre-energization under conditions that do not melt the aluminum alloy plate. However, since the aluminum alloy plate has a lower melting point than a steel plate, the appropriate condition range for pre-energization is extremely high depending on the plate assembly. There is also a problem of narrowing.
  • This invention is made
  • FIG. 1 is a diagram schematically showing a current distribution at the initial stage of energization in resistance spot welding.
  • FIG. 1 shows the distribution of current (welding current) when a plate assembly in which a steel plate 11 and an aluminum plate 12 are stacked is sandwiched between a pair of electrodes 13 and 14 and energized while being pressed. It is represented by reference numeral 21.
  • the present inventors examined welding conditions such as an energization pattern and electrodes that achieve both expansion of the joint diameter and reduction of heat input.
  • welding conditions such as an energization pattern and electrodes that achieve both expansion of the joint diameter and reduction of heat input.
  • a steel plate having a high specific resistance first generates heat, and the aluminum plate is melted by heat transfer from the steel plate to achieve joining. Therefore, the present inventors considered that it is important how to heat a wide range of steel plates in a short time in order to achieve both expansion of the joint diameter and reduction of heat input.
  • the present invention has been completed by further studies based on these findings, and the gist is as follows.
  • a plate assembly in which at least one type of steel plate selected from a plated steel plate, a cold-rolled steel plate and a hot-rolled steel plate and an aluminum plate are overlapped and one of the plates arranged on the outermost side is a steel plate and the other is an aluminum plate.
  • a resistance spot welded joint between a steel plate and an aluminum plate having good peel strength can be produced regardless of the components and the plate set of the steel plate and the aluminum plate.
  • FIG. 1 is a diagram schematically showing a current distribution at the initial stage of energization in resistance spot welding.
  • FIG. 2 is a diagram schematically showing resistance spot welding.
  • FIG. 3 is a diagram illustrating an energization pattern.
  • FIG. 4 is a diagram schematically illustrating a current distribution during energization in the second energization process.
  • FIG. 5 is a diagram showing the tip curvature radius and tip diameter of the electrode.
  • the method of manufacturing a resistance spot welded joint according to the present invention is such that at least one type of steel plate selected from a cold-rolled steel plate, a hot-rolled steel plate and a plated steel plate and an aluminum plate are overlapped and one of the plates arranged on the outermost side is a steel plate.
  • a plate assembly made of an aluminum plate on the other side is sandwiched between a pair of electrodes and joined by resistance spot welding, and then energized with a current I 1 (kA) for an energization time t 1 (ms).
  • a first energization step an energization deactivation step in which energization is suspended during an energization deactivation time t c (ms) after the first energization step, and an energization time t 2 (ms) with a current I 2 (kA) after the energization deactivation step.
  • the resistance spot welded joint is a generic name including a test piece used for strength test and cross-sectional observation, an automobile member joined by resistance spot welding, and the like.
  • FIG. 2 is a diagram schematically showing resistance spot welding.
  • FIG. 3 is a diagram illustrating an energization pattern.
  • FIG. 4 is a diagram schematically illustrating a current distribution during energization in the second energization process.
  • the present invention is a method of manufacturing a resistance spot welded joint, wherein a resistance spot welded joint is obtained by resistance spot welding in which a plate assembly in which a plurality of plates are stacked is sandwiched between a pair of electrodes and energized while being pressurized and joined (welded joint). is there.
  • the steel plate 11 and the aluminum plate 12 are overlapped to form a plate assembly.
  • one of the plates arranged on the outermost side is a steel plate 11 and the other is an aluminum plate 12.
  • the plates 13 and 14 are brought into contact with each other so as to become the steel plate 11 and the aluminum plate 12, respectively.
  • FIG. 2 although the example of the resistance spot welded joint of the board set of 2 sheets which piled up the steel plate 11 and the aluminum plate 12 one by one was shown, between the steel plate 11 and the aluminum plate 12, Furthermore, it is good also as a plate
  • the plate constituting the resistance spot welded joint is at least one type of steel plate selected from a plated steel plate, a cold rolled steel plate and a hot rolled steel plate, and an aluminum plate.
  • the plated steel sheet is a steel sheet having a metal plating layer on the surface, and examples of the metal plating layer include a Zn-based plating layer and an Al-based plating layer.
  • the Zn-based plating include general hot-dip galvanizing (GI), alloyed hot-dip galvanizing (GA), electrogalvanizing (EG), and Zn—Ni-based plating (for example, Zn containing 10 to 25% by mass of Ni).
  • the component of the steel plate 11 is not particularly limited. Further, the strength of the steel plate 11 is not particularly limited. For example, a JIS No. 5 tensile test piece is produced from the steel plate in a direction parallel to the rolling direction, and a tensile test is performed in accordance with the provisions of JIS Z 2241: 2011. The steel sheet has a tensile strength of 270 MPa to 1800 MPa (270 MPa to 1800 MPa class).
  • the component of the aluminum plate is not particularly limited, either a pure aluminum plate or an aluminum alloy plate.
  • the aluminum alloy plate include 5000 series (Al-Mg series), 6000 series (Al-Mg-Si series), 2000 series (Al-Cu series), and 7000 series (Al-Zn-Mg series) defined by JIS. And Al-Zn-Mg-Cu-based).
  • An oxide film is formed on the surface of the aluminum plate.
  • the thickness of the steel plate 11 or the aluminum plate 12 is not particularly limited, but is preferably in a range (about 0.5 to 4.0 mm) that can be used for a general automobile body.
  • the plate set in which the steel plate 11 and the aluminum plate 12 are overlapped is sandwiched between a pair of welding electrodes (electrode 13 and electrode 14), and energized while being pressed, and then the electrode is released from the steel plate.
  • a welding apparatus that can be used in the resistance spot welding method of the present invention, a welding apparatus that includes a pair of upper and lower electrodes and can arbitrarily control the pressure and welding current during welding can be used.
  • the pressurization mechanism air cylinder, servo motor, etc.
  • type stationary, robot gun, etc.
  • the present invention can be applied to both direct current and alternating current, and the type of power source (single-phase alternating current, alternating current inverter, direct current inverter) and the like are not particularly limited.
  • alternating current means “effective current”.
  • resistance spot welding is performed in a state that is always water-cooled.
  • the steel plate 11 and the aluminum plate 12 are overlapped so that one of the plates arranged on the outermost side is the steel plate 11 and the other is the aluminum plate 12 to form a plate set.
  • the plate assembly is sandwiched between a pair of welding electrodes (electrode 13 and electrode 14), energized while being pressurized, a nugget is formed by resistance heat generation, and the overlapped steel plate 11 and aluminum plate 12 are joined together, thereby providing resistance. A spot welded joint is obtained.
  • this energization is a specific pattern. That is, in the energization pattern of the present invention, for example, as shown in FIG. 3, the first energization step of energizing with the current I 1 (kA) for the energization time t 1 (ms) and the energization pause time after the first energization step. an energization stop process for stopping energization for t c (ms), and a second energization process for energizing for the energization time t 2 (ms) with the current I 2 (kA) after the energization stop process.
  • energization of one or more stages is performed as necessary, and then energization is performed after the third stage for the purpose of post heat treatment, for example, and then the energization is stopped.
  • the energization path is limited by the oxide film on the surface of the aluminum plate 12 at the beginning of energization. Therefore, in the present invention, first, in the first energization process (first stage energization), energization is performed for a longer time and at a lower current than in the second energization process (see the above formulas (1) and (2)). . Thereby, by destroying the oxide film on the surface of the aluminum plate 12, an energization path between the steel plate 11 and the aluminum plate 12 is secured, and an excessive increase in heat input is prevented. Further, the energization time t 1 of the first conducting step (see above formula (3)) by the above 40 ms, the current path between the steel plate 11 and aluminum plate 12 can be sufficiently secured.
  • FIG. 4 is a diagram schematically illustrating a current distribution during energization in the second energization process. As shown in FIG. 4, since the current density is high in the contact end vicinity 22 between the steel plate 11 and the electrode 13, heat generation in the contact end vicinity 22 is promoted as the current is increased.
  • the increase in current in the second energization step is effective in generating heat over a wide area by short-time energization, and the aluminum plate 12 can be melted over a wide area, thereby expanding the bonding diameter.
  • the center of the joint where the oxide film is initially destroyed in the first energization process and energization starts is at a higher temperature. Therefore, if the energization pause time t c in the energization pause process is short, since the re-heated from the hot junction center as was briefly and high current of the power supply of the second current supply step, heat input becomes excessively large easy.
  • the energization stop time t c is 5 ms or more (see the above equation (4)) and the energization stop step satisfying the above equation (5) is performed, and then the second energization step with a high current and a short time is performed. To do.
  • the temperature at the center of the joint portion once decreases in the energization suspending process, and thus energization in the second energizing process can promote heat generation in the vicinity of the contact end 22 between the steel plate 11 and the electrode 13 having a high current density.
  • the nugget diameter can be expanded while suppressing.
  • the relational expression (5) (that is, the right side of the above expression (5)) including similar parameters is set for the upper limit value of t c .
  • the energization time t 2 in the second energizing step for example, 5 ⁇ 100 ms is preferable.
  • the electrode 13 that satisfies the above formula (6) that is, the electrode 13 that is brought into contact with the steel plate 11 has a tip curvature radius R Fe of 20 mm or more. Must be used. This is because the contact area between the steel plate 11 and the electrode 13 is increased by increasing the tip curvature radius R Fe of the electrode 13 to be brought into contact with the steel plate 11, thereby increasing the energization area in the second energization step, and the heat generation range of the steel plate 11. This is because the bonding diameter can be increased.
  • the contact area between the steel plate 11 and the electrode 13 is increased, heat removal to the electrode 13 is promoted, and the energization stop time t c after the end of the first energization process can be shortened.
  • production of the scattering from the steel plate surface is also acquired by preventing the excessive increase in the current density in the contact end vicinity 22 of the steel plate 11 and the electrode 13.
  • the electrode 13 is brought into contact with the steel plate 11, tip curvature radius R Fe satisfies a relationship represented by the following formula (7), that the tip curvature radius R Fe it is preferable to use an electrode is at least 50mm.
  • the reason is suppression of surface scattering by enlarging the contact area of an electrode and a steel plate, and reducing a current density.
  • the type of the tip of the electrode 13 is, for example, DR type (dome radius type), R type (radius type), or D type (dome type) described in JIS C 9304: 1999.
  • FIG. 5 shows the tip radius of curvature R and the tip diameter D of the electrode.
  • FIG. 5A is a diagram showing the tip radius of curvature R and the tip diameter D of the radius electrode
  • FIG. 5B is a diagram showing the tip radius of curvature R and the tip diameter D of the dome radius electrode. . As shown in FIG.
  • the dome radius electrode has a curved surface on the tip side with a two-step curvature.
  • the radius of curvature of the tip of the electrode is a portion (center) that first contacts the plate to be resistance spot welded. Radius of curvature of the curved surface on the side.
  • the tip diameter D Fe of the electrode 13 in contact with the steel plate 11 is preferably 4 mm to 16 mm, for example, from the viewpoint of securing the contact area between the electrode and the steel plate.
  • the tip diameter D Fe of the electrode 13 is more preferably 6 mm to 16 mm, and further preferably 8 mm to 16 mm.
  • the specific electrode as the electrode 13 that is made in the specific energization pattern and brought into contact with the steel plate 11, excessive heat generation can be prevented while melting the aluminum plate 12 in a wide range. It is possible to achieve both the expansion of the bonding diameter and the suppression of growth of the intermetallic compound at the bonding interface by reducing the heat input. Therefore, in this invention, the resistance spot welded joint of the steel plate 11 and the aluminum plate 12 which has favorable peeling strength can be manufactured.
  • the presence or thickness of the metal plating layer on the surface of the steel plate or aluminum plate, the composition or thickness of the oxide film, the mother It can be applied regardless of material strength and plate thickness.
  • the electrode 14 in contact with the aluminum plate 12 satisfies the following formula (8) when the tip curvature radius of the electrode 14 in contact with the aluminum plate 12 is R Al (mm), that is, the tip curvature radius R Al is It is preferable that the electrode be 50 mm or more. Thereby, the effect of the present invention can be obtained more effectively. This is because the effect of suppressing the thickness reduction of the aluminum plate 12 due to energization can be obtained by reducing the surface pressure applied to the aluminum plate 12.
  • the tip radius of curvature R Al is more preferably 80 mm or more.
  • the type of the tip of the electrode 14 brought into contact with the aluminum plate 12 is, for example, DR type (dome radius type), R type (radius type), or D type (dome type) described in JIS C 9304: 1999.
  • the tip diameter D Al of the electrode 14 brought into contact with the aluminum plate 12 is preferably 4 mm to 16 mm, for example, from the viewpoint of reducing the surface pressure applied to the aluminum alloy plate.
  • the tip diameter D Al of the electrode 14 is more preferably 6 mm to 16 mm, and further preferably 8 mm to 16 mm. Also, there is no particular relationship between the tip diameter D Al of the electrode 14 on the aluminum plate 12 side and the tip diameter D Fe of the electrode 13 on the steel plate 11 side, and both may be the same or different. Also good.
  • energization time t 1 of the first energizing step is preferably set to 50ms or more, and more preferably, 60ms or more.
  • the upper limit of the energization time t 1 of the first energizing step is not particularly defined, in view of the tact time shortened, preferably, the energization time t 1 is less than 600 ms.
  • the aluminum plate 12 is melted during energization in the first energization process. Since the aluminum plate 12 is melted during energization in the first energization step, the oxide film on the surface of the aluminum plate 12 is completely removed, so that the energization path can be stabilized. However, in order to prevent excessive heat input, when the thickness of the aluminum plate 12 located on the outermost side and brought into contact with the electrode 14 is T (mm), the electrode 14 formed by energization in the first energization step is used.
  • the nugget diameter of the outermost aluminum plate 12 to be contacted is preferably 6 ⁇ T (mm) or less, and more preferably 5 ⁇ T (mm) or less.
  • the nugget diameter of the outermost aluminum plate 12 formed by energization in the first energization process and brought into contact with the electrode 14 is 2 ⁇ T (mm) or more.
  • the thickness T of the aluminum plate 12 uses mm as a unit, and the unit of 6 ⁇ T or 5 ⁇ T into which T is substituted is also mm.
  • the nugget diameter of the aluminum plate 12 is the maximum diameter of the nugget of the aluminum plate 12 at the mating surface (joint surface) between the aluminum plate 12 and the plate (steel plate 11 in FIG. 2) in contact with the aluminum plate 12. is there.
  • the “nugget” is a melted and solidified portion generated in a welded portion in lap resistance welding. In this specification, a melted portion that becomes a nugget when solidified (that is, a melted portion before solidifying) is also called a nugget. There is a case.
  • energization pause time t c is preferably greater than or equal to 10 ms, and more preferably to more than 20ms. And, energization pause time t c, it is preferable to satisfy the relation of formula (9), more preferably satisfies the following formula (10). The reason for this is that once the weld is cooled, a wide range of heat generation is promoted in the second energization step, and the joint strength is improved.
  • the welding current (current when energized) in the present invention is not particularly limited, and the welding current is, for example, 4 to 40 kA. However, since it is necessary to obtain a predetermined nugget diameter in construction, an excessive current value causes scattering, so the current I 1 in the first energization process is, for example, 4 to 20 kA, and the current in the second energization process the value I 2 is, for example, 10 ⁇ 40 kA.
  • the applied pressure is, for example, 2.0 kN to 7.0 kN, and the applied pressure may be changed during welding and before and after welding.
  • the steel plate and aluminum plate shown in Table 1-2 are not shown, but resistance spot welding is similarly performed, and another steel plate is provided between the steel plate 11 (lower plate) and the aluminum plate 12 (upper plate).
  • a resistance spot welded joint made of a three-layered plate assembly sandwiching 15 (medium plate) was produced.
  • the aluminum plate 12 used had an oxide film formed on the surface.
  • An inverter DC resistance spot welder was used as the welding machine, and the tip curvature radius and tip diameter of the electrodes 13 and 14 and the energization pattern were set as shown in Table 2.
  • the electrodes 13 and 14 were all DR type electrodes made of chromium copper. Resistance spot welding was performed at room temperature (20 ° C.), and the electrodes 13 and 14 were always water-cooled. The applied pressure was constant throughout the first energization process, the energization stop process, and the second energization process. In the first energization process, a part of the aluminum plate 12 was melted.
  • the resulting resistance spot welded joint was subjected to a cross tensile test based on JIS Z 3137 to evaluate the peel strength.
  • CTS cross tensile strength
  • Each case of CTS was evaluated as F and evaluated.
  • the evaluation results are shown in Table 2. In the example of the present invention, the evaluation was any one of A to C.
  • the first energization process was performed under the same conditions as described above, the cross section of the joint was observed, and the nugget diameter (mm) of the aluminum plate 12 formed by energization in the first energization process was obtained.
  • the nugget diameter of the aluminum plate 12 is such that the aluminum plate 12 and the plate in contact with the aluminum plate 12 (steel plate 11 or steel plate 15 in the case of the three-layered plate set shown in Table 1-2) are aluminum
  • the maximum diameter of the nugget on the plate 12 was measured. The measurement results are shown in Table 2.

Abstract

The present invention is for producing a resistance spot welded joint that comprises a stack of: aluminum sheets; and at least one type of steel sheet selected from among plated steel sheets, cold-rolled steel sheets, and hot-rolled steel sheets. The sheets are combined such that one of the outermost sheets is an aluminum sheet and the other is a steel sheet. The present invention includes: a first electrification step that is for applying a current I1 (kA) for an electrification time t1 (ms); an electrification suspension step that is after the first electrification step and is for suspending electrification for an electrification suspension time tc (ms); and a second electrification step that is after the electrification suspension step and is for applying a current I2 (kA) for an electrification time t2 (ms). The present invention satisfies expressions (1)-(6), in which TFe (mm) is the total thickness of the stacked steel sheets, RFe (mm) is the radius of curvature of the tip of an electrode that is made to contact the steel sheets, and DFe (mm) is the diameter of the tip of the electrode that is made to contact the steel sheets: (1) I1<I2, (2) t1>t2, (3) t1≥40, (4) tc≥5, (5) 3+0.04×√(I1 2×t1×TFe/DFe)≤tc≤495+√(I1 2×t1×TFe/DFe), and (6) RFe≥20.

Description

抵抗スポット溶接継手の製造方法Method of manufacturing resistance spot welded joint
　本発明は、異種金属材料の抵抗スポット溶接継手の製造方法に関する。具体的には、めっき鋼板、冷延鋼板および熱延鋼板から選択される少なくとも一種の鋼板とアルミニウム板とを重ね合わせた板組を、抵抗スポット溶接により接合し、抵抗スポット溶接継手を製造する抵抗スポット溶接継手の製造方法に関する。 The present invention relates to a method for manufacturing a resistance spot welded joint of dissimilar metal materials. Specifically, a resistance that produces a resistance spot welded joint by joining a plate assembly in which at least one kind of steel plate selected from a plated steel plate, a cold-rolled steel plate, and a hot-rolled steel plate and an aluminum plate are overlapped by resistance spot welding. The present invention relates to a method for manufacturing a spot welded joint.
　近年の自動車産業では、車体の軽量化による燃費向上を目的として、車体へのアルミニウム合金等の軽金属の適用が進められている。現在、車体における鋼板同士の接合には、他の溶接方法に比べてコストや効率面で優位にある抵抗スポット溶接法が最も多く用いられており、車１台あたりの打点数は３０００点から６０００点に及ぶ。抵抗スポット溶接法とは、重ね合わせた２枚以上の鋼板を挟んでその上下から一対の電極で加圧しつつ、上下電極間に高電流の溶接電流を短時間通電して抵抗発熱により接合する方法である。 In recent years, in the automobile industry, the application of light metals such as aluminum alloys to the vehicle body has been promoted for the purpose of improving fuel efficiency by reducing the weight of the vehicle body. At present, the resistance spot welding method, which is superior in cost and efficiency compared to other welding methods, is most often used for joining steel plates in a vehicle body, and the number of hits per vehicle is 3000 to 6000. To the point. The resistance spot welding method is a method in which two or more stacked steel plates are sandwiched and pressed with a pair of electrodes from above and below, and a high current welding current is passed between the upper and lower electrodes for a short time to join by resistance heating. It is.
　車体の生産工程のコストと効率の維持という観点からは、鋼板同士の場合の接合と同様に、アルミニウム板が混在する場合の接合においても抵抗スポット溶接法を用いることが有効である。なお、以下の説明において、アルミニウム板とは、純アルミニウム板とアルミニウム合金板の総称である。しかし、鋼とアルミニウムの異種金属材料接合においては、電極の加圧により軟質なアルミニウム板が大きく減厚したり、接合界面に脆弱な金属間化合物が形成したりすることで、継手強度、特に十字引張などに代表されるはく離方向への負荷が生じる際のはく離強度が確保できないという課題がある。 From the viewpoint of maintaining the cost and efficiency of the production process of the vehicle body, it is effective to use the resistance spot welding method in the joining in the case where aluminum plates are mixed, as in the joining in the case of steel plates. In the following description, the aluminum plate is a general term for a pure aluminum plate and an aluminum alloy plate. However, in joining dissimilar metal materials of steel and aluminum, the strength of the joint, especially the cross, can be reduced by reducing the thickness of the soft aluminum plate by pressing the electrode and forming a brittle intermetallic compound at the joint interface. There is a problem that the peeling strength cannot be secured when a load in the peeling direction represented by tension or the like is generated.
　上記の課題を解決するため、以下に述べるような抵抗スポット溶接方法が提案されている。例えば、特許文献１には、鋼板とアルミニウム板の間に、鉄／アルミニウムクラッド薄板を同種材同士が向かい合うようにインサートさせることで、低電流でも高強度の継手が得られる抵抗スポット溶接方法が記載されている。 In order to solve the above problems, a resistance spot welding method as described below has been proposed. For example, Patent Document 1 describes a resistance spot welding method in which an iron / aluminum clad thin plate is inserted between a steel plate and an aluminum plate so that the same kind of materials face each other so that a high-strength joint can be obtained even at a low current. Yes.
　特許文献２には、鋼板とアルミニウム板の両側に当て板を１枚以上添えて溶接を行うことで、当て板と被接合材料との界面が抵抗発熱し、鋼とアルミニウムが抵抗拡散接合されて高強度の継手が得られる抵抗スポット溶接方法が記載されている。 In Patent Document 2, by welding with one or more contact plates on both sides of a steel plate and an aluminum plate, the interface between the contact plate and the material to be joined generates resistance heat, and the steel and aluminum are resistance diffusion bonded. A resistance spot welding method is described that provides a high strength joint.
　特許文献３には、鋼材とアルミニウム材をスポット溶接するにあたり、鋼板および鋼板表面酸化皮膜におけるＭｎおよびＳｉの各量を適正化することで、大きいナゲット径を得つつ散り発生を抑制することができると記載されている。 In Patent Document 3, when spot welding a steel material and an aluminum material, by optimizing each amount of Mn and Si in a steel plate and a steel plate surface oxide film, it is possible to suppress the occurrence of scattering while obtaining a large nugget diameter. It is described.
　特許文献４には、パルセーション通電の条件を適正化するとともに、通電完了後の加圧力を増加させることで、接合界面の金属間化合物の成長を抑制する異種金属接合方法が記載されている。 Patent Document 4 describes a dissimilar metal joining method that suppresses the growth of intermetallic compounds at the joining interface by optimizing the conditions for pulsation energization and increasing the pressure after completion of energization.
　特許文献５には、前通電およびその後の通電条件を適正化することで、鋼板表面からのチリ発生を抑制するとともに、溶接電流もできるだけ小さくでき、高い接合強度を有する異材接合部が得られるスポット溶接方法が記載されている。 Patent Document 5 discloses a spot that can suppress the generation of dust from the surface of the steel sheet by optimizing the pre-energization and the subsequent energization conditions, reduce the welding current as much as possible, and obtain a dissimilar material joint having high joint strength. A welding method is described.
特許第３１１７０５３号公報Japanese Patent No. 3117053 特許第３５０４７９０号公報Japanese Patent No. 3504790 特開２００５－１５２９５８号公報JP 2005-152958 A 特許第５６２４９０１号公報Japanese Patent No. 5624901 特許第５５７２０４６号公報Japanese Patent No. 5572046
　しかしながら、特許文献１および２に記載の抵抗スポット溶接方法では、車体の構造上不要である当て板やクラッド薄板の使用が必要となるため、大幅なコスト増や重量低減が十分に図れないなどの問題がある。 However, the resistance spot welding methods described in Patent Documents 1 and 2 require the use of a backing plate or a clad thin plate that is not necessary for the structure of the vehicle body, so that a significant increase in cost and weight cannot be achieved. There's a problem.
　また、特許文献３では、鋼板および酸化皮膜中の合金元素量および分布を限定する必要があるため、要求性能を満たす鋼板の使用が制限されるなどの課題がある。特に、最近の鋼板での高強度化に伴う高合金化が進んでいる状況下では、特許文献３の発明の適用は極めて制限される。 Further, in Patent Document 3, since it is necessary to limit the amount and distribution of alloy elements in the steel sheet and the oxide film, there is a problem that the use of the steel sheet that satisfies the required performance is restricted. In particular, the application of the invention of Patent Document 3 is extremely limited under the circumstances where high alloying is progressing with high strength in recent steel plates.
　特許文献４では、前通電の通電時間は２０ｍｓ以下、パルセーション通電の通電時間は１０ｍｓ以下といずれも短時間であり、接合径を拡大するためには前通電・パルセーション通電ともに高電流化が必須となる。そのため、鋼板の固有抵抗が高い場合や、板厚が大きい場合には鋼板表面における散り発生の懸念がある。 In Patent Document 4, the energization time for pre-energization is 20 ms or less, and the energization time for pulsation energization is 10 ms or less, both of which are short. Required. Therefore, when the specific resistance of the steel plate is high or when the plate thickness is large, there is a concern that scattering occurs on the surface of the steel plate.
　特許文献５では、適用可能な板組は冷延鋼板と６０００系アルミニウム合金板との板組のみに限定されているという問題がある。また、特許文献５ではアルミニウム合金板を溶融させない条件で前通電を行う必要があるが、アルミニウム合金板は鋼板と比較して低融点であるため、板組によっては前通電の適正条件範囲が非常に狭くなるという問題もある。 In Patent Document 5, there is a problem that applicable plate sets are limited only to plate sets of cold-rolled steel plates and 6000 series aluminum alloy plates. In Patent Document 5, it is necessary to perform pre-energization under conditions that do not melt the aluminum alloy plate. However, since the aluminum alloy plate has a lower melting point than a steel plate, the appropriate condition range for pre-energization is extremely high depending on the plate assembly. There is also a problem of narrowing.
　本発明は、上記のような事情に鑑みてなされたものであり、鋼板とアルミニウム板の抵抗スポット溶接継手であって、鋼板やアルミニウム板の成分や板組によらず、鋼板とアルミニウム板間の良好なはく離強度を有する抵抗スポット溶接継手を製造することができる抵抗スポット溶接継手の製造方法を提供することを目的とする。 This invention is made | formed in view of the above situations, It is a resistance spot welded joint of a steel plate and an aluminum plate, Comprising: It is between a steel plate and an aluminum plate irrespective of the component and board set of a steel plate or an aluminum plate. It is an object of the present invention to provide a resistance spot welded joint manufacturing method capable of manufacturing a resistance spot welded joint having a good peel strength.
　本発明者らは、上記の目的を達成すべく、鋭意検討を重ねた結果、以下の知見を得た。図１は、抵抗スポット溶接の通電初期の電流分布を模式的に示す図である。図１には、鋼板１１とアルミニウム板１２とが重ね合わせられた板組を、一対の電極１３、１４で挟持し加圧しながら通電したときの電流（溶接電流）の分布が、図１中の符号２１で表されている。 As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge. FIG. 1 is a diagram schematically showing a current distribution at the initial stage of energization in resistance spot welding. FIG. 1 shows the distribution of current (welding current) when a plate assembly in which a steel plate 11 and an aluminum plate 12 are stacked is sandwiched between a pair of electrodes 13 and 14 and energized while being pressed. It is represented by reference numeral 21.
　鋼板とアルミニウム板の抵抗スポット溶接において良好なはく離強度を有するようにするために重要となるのは、接合部へ付与される応力を低減するために極力大きい接合径（ナゲット径）を得つつ、接合界面（鋼板とアルミニウム板の合わせ面）における脆弱な金属間化合物の成長を抑制することである。接合径を拡大するためには溶接電流や通電時間を増加させることが一般的に有効であるが、溶接電流や通電時間を増加させると入熱が大きくなり接合界面において金属間化合物が成長しやすくなってしまう。以上の理由から、鋼板とアルミニウム板の抵抗スポット溶接継手を良好なはく離強度を有するものとすること（剥離強度の確保）は困難であった。 In order to have a good peel strength in resistance spot welding of a steel plate and an aluminum plate, it is important to obtain a joint diameter (nugget diameter) that is as large as possible in order to reduce the stress applied to the joint, It is to suppress the growth of fragile intermetallic compounds at the bonding interface (the mating surface of the steel plate and the aluminum plate). Increasing the welding current and energizing time is generally effective to increase the joint diameter, but increasing the welding current and energizing time increases the heat input and facilitates the growth of intermetallic compounds at the joint interface. turn into. For the reasons described above, it has been difficult to ensure that the resistance spot welded joint between the steel plate and the aluminum plate has a good peel strength (ensure the peel strength).
　そこで本発明者らは、接合径の拡大と入熱の低減を両立させる通電パターンおよび電極等の溶接条件を検討した。一般的に、鋼板とアルミニウム板の抵抗スポット溶接では、まず固有抵抗の高い鋼板が発熱し、鋼板からの熱伝達によってアルミニウム板が溶融し、接合が達成される。そのため、本発明者らは、接合径の拡大と入熱の低減を両立させるには、如何に広範囲の鋼板を短時間で発熱させるかが重要であると考えた。 Therefore, the present inventors examined welding conditions such as an energization pattern and electrodes that achieve both expansion of the joint diameter and reduction of heat input. In general, in resistance spot welding of a steel plate and an aluminum plate, a steel plate having a high specific resistance first generates heat, and the aluminum plate is melted by heat transfer from the steel plate to achieve joining. Therefore, the present inventors considered that it is important how to heat a wide range of steel plates in a short time in order to achieve both expansion of the joint diameter and reduction of heat input.
　金属間化合物の成長を抑制するために入熱を低減するには、接合界面が高温状態となる時間を短縮することが有効である。そのためには通電パターンを短時間化・高電流化することが有効であるが、アルミニウム板の表面には強固な酸化被膜が存在するため通電経路が制限され、図１に示すように通電初期は加圧によって酸化被膜が破壊された接合部中心に電流が集中しやすい。故に、過度な短時間化・高電流化は接合部中心への入熱を増加・促進させることになるため、通電時間の短時間化・高電流化には限界がある。 In order to reduce the heat input in order to suppress the growth of intermetallic compounds, it is effective to shorten the time during which the bonding interface is in a high temperature state. For this purpose, it is effective to shorten the energization pattern and increase the current, but the energization path is limited because a strong oxide film exists on the surface of the aluminum plate, and as shown in FIG. Current tends to concentrate at the center of the joint where the oxide film is destroyed by pressurization. Therefore, excessively shortening the time and increasing the current increase and promote the heat input to the center of the joint, so there is a limit to shortening the energization time and increasing the current.
　本発明は、これらの知見に基づき、さらに検討を加えて完成されたものであり、要旨は以下のとおりである。 The present invention has been completed by further studies based on these findings, and the gist is as follows.
　［１］　めっき鋼板、冷延鋼板および熱延鋼板から選択される少なくとも一種の鋼板とアルミニウム板とを重ね合わせて最外側に配置される板の一方が鋼板で他方がアルミニウム板とした板組を、一対の電極によって挟み、抵抗スポット溶接により接合し、抵抗スポット溶接継手を製造するにあたり、
　電流Ｉ１（ｋＡ）で通電時間ｔ１（ｍｓ）の間通電する第１通電工程と、
第１通電工程の後に通電休止時間ｔｃ（ｍｓ）の間通電を休止する通電休止工程と、
通電休止工程の後に電流Ｉ２（ｋＡ）で通電時間ｔ２（ｍｓ）の間通電する第２通電工程とを有し、
　重ね合わせる鋼板の総板厚をＴＦｅ（ｍｍ）、鋼板と接触させる電極の先端曲率半径をＲＦｅ（ｍｍ）、鋼板と接触させる電極の先端径をＤＦｅ（ｍｍ）としたとき、
　前記第１通電工程、前記通電休止工程、および前記第２通電工程は、下記式（１）～（６）の関係を全て満たす、抵抗スポット溶接継手の製造方法。
Ｉ１＜Ｉ２　　　（１）
ｔ１＞ｔ２　　　（２）
ｔ１≧４０　　　（３）
ｔｃ≧５　　　（４）
３＋０．０４×√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）≦ｔｃ≦４９５＋√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）　　　（５）
ＲＦｅ≧２０　　　（６） [1] A plate assembly in which at least one type of steel plate selected from a plated steel plate, a cold-rolled steel plate and a hot-rolled steel plate and an aluminum plate are overlapped and one of the plates arranged on the outermost side is a steel plate and the other is an aluminum plate. In order to produce a resistance spot welded joint, sandwiched by a pair of electrodes and joined by resistance spot welding,
A first energization step of energizing with an electric current I 1 (kA) for an energization time t 1 (ms);
An energization stop step of stopping energization for an energization stop time t c (ms) after the first energization step;
A second energization step of energizing with an electric current I 2 (kA) for an energization time t 2 (ms) after the energization stop step;
When the total plate thickness of the steel plates to be stacked is T Fe (mm), the tip curvature radius of the electrode in contact with the steel plate is R Fe (mm), and the tip diameter of the electrode in contact with the steel plate is D Fe (mm),
The method of manufacturing a resistance spot welded joint, wherein the first energization step, the energization stop step, and the second energization step satisfy all the relationships of the following formulas (1) to (6).
I 1 <I 2 (1)
t 1 > t 2 (2)
t 1 ≧ 40 (3)
t c ≧ 5 (4)
3 + 0.04 × √ (I 1 2 × t 1 × T Fe / D Fe) ≦ t c ≦ 495 + √ (I 1 2 × t 1 × T Fe / D Fe) (5)
R Fe ≧ 20 (6)
　［２］　前記第１通電工程、前記通電休止工程、および前記第２通電工程は、さらに、下記式（７）の関係を満たす、［１］に記載の抵抗スポット溶接継手の製造方法。
ＲＦｅ≧５０　　　（７） [2] The method for manufacturing a resistance spot welded joint according to [1], wherein the first energization step, the energization stop step, and the second energization step further satisfy a relationship of the following formula (7).
R Fe ≧ 50 (7)
　［３］　アルミニウム板と接触させる電極の先端曲率半径をＲＡｌ（ｍｍ）としたとき、
前記第１通電工程、前記通電休止工程、および前記第２通電工程は、さらに、下記式（８）の関係を満たす、［１］または［２］に記載の抵抗スポット溶接継手の製造方法。
ＲＡｌ≧５０　　　（８） [3] When the tip curvature radius of the electrode brought into contact with the aluminum plate is R Al (mm),
The resistance spot-welded joint manufacturing method according to [1] or [2], wherein the first energization step, the energization stop step, and the second energization step further satisfy a relationship of the following formula (8).
R Al ≧ 50 (8)
　［４］　前記第１通電工程では、電極を接触させたアルミニウム板の少なくとも一部を溶融させる、［１］～［３］のいずれか一つに記載の抵抗スポット溶接継手の製造方法。 [4] The method of manufacturing a resistance spot welded joint according to any one of [1] to [3], wherein in the first energization step, at least a part of the aluminum plate in contact with the electrode is melted.
　本発明によれば、鋼板やアルミニウム板の成分や板組によらず、良好なはく離強度を有する鋼板とアルミニウム板の抵抗スポット溶接継手を製造することができる。 According to the present invention, a resistance spot welded joint between a steel plate and an aluminum plate having good peel strength can be produced regardless of the components and the plate set of the steel plate and the aluminum plate.
図１は、抵抗スポット溶接の通電初期の電流分布を模式的に示す図である。FIG. 1 is a diagram schematically showing a current distribution at the initial stage of energization in resistance spot welding. 図２は、抵抗スポット溶接を模式的に示す図である。FIG. 2 is a diagram schematically showing resistance spot welding. 図３は、通電パターンを説明する図である。FIG. 3 is a diagram illustrating an energization pattern. 図４は、第２通電工程での通電時の電流分布を模式的に示す図である。FIG. 4 is a diagram schematically illustrating a current distribution during energization in the second energization process. 図５は、電極の先端曲率半径と先端径を示す図である。FIG. 5 is a diagram showing the tip curvature radius and tip diameter of the electrode.
　本発明の抵抗スポット溶接継手の製造方法は、冷延鋼板、熱延鋼板およびめっき鋼板から選択される少なくとも一種の鋼板とアルミニウム板とを重ね合わせて最外側に配置される板の一方が鋼板で他方がアルミニウム板とした板組を、一対の電極によって挟み、抵抗スポット溶接により接合し、抵抗スポット溶接継手を製造するにあたり、電流Ｉ１（ｋＡ）で通電時間ｔ１（ｍｓ）の間通電する第１通電工程と、第１通電工程の後に通電休止時間ｔｃ（ｍｓ）の間通電を休止する通電休止工程と、通電休止工程の後に電流Ｉ２（ｋＡ）で通電時間ｔ２（ｍｓ）の間通電する第２通電工程とを有し、重ね合わせる鋼板の総板厚をＴＦｅ（ｍｍ）、鋼板と接触させる電極の先端曲率半径をＲＦｅ（ｍｍ）、鋼板と接触させる電極の先端径をＤＦｅ（ｍｍ）としたとき、第１通電工程、通電休止工程、および第２通電工程は、下記式（１）～（６）の関係を全て満たすものである。なお、本発明において、抵抗スポット溶接継手とは強度試験・断面観察などに用いられるテストピースや、抵抗スポット溶接により接合された自動車部材等を含めた総称とする。
Ｉ１＜Ｉ２　　　（１）
ｔ１＞ｔ２　　　（２）
ｔ１≧４０　　　（３）
ｔｃ≧５　　　　（４）
３＋０．０４×√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）≦ｔｃ≦４９５＋√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）　　　（５）
ＲＦｅ≧２０　　　（６） The method of manufacturing a resistance spot welded joint according to the present invention is such that at least one type of steel plate selected from a cold-rolled steel plate, a hot-rolled steel plate and a plated steel plate and an aluminum plate are overlapped and one of the plates arranged on the outermost side is a steel plate. In order to produce a resistance spot welded joint, a plate assembly made of an aluminum plate on the other side is sandwiched between a pair of electrodes and joined by resistance spot welding, and then energized with a current I 1 (kA) for an energization time t 1 (ms). A first energization step, an energization deactivation step in which energization is suspended during an energization deactivation time t c (ms) after the first energization step, and an energization time t 2 (ms) with a current I 2 (kA) after the energization deactivation step. second and a conduction step, the total thickness of the steel sheet superposing T Fe (mm), a tip radius of curvature of the electrode is contacted with the steel sheet R Fe (mm), the electrode contacting the steel tip is energized during When was the D Fe (mm), the first current supply step, the energization pause step, and the second energizing step is to satisfy all the relationships of the following formulas (1) to (6). In the present invention, the resistance spot welded joint is a generic name including a test piece used for strength test and cross-sectional observation, an automobile member joined by resistance spot welding, and the like.
I 1 <I 2 (1)
t 1 > t 2 (2)
t 1 ≧ 40 (3)
t c ≧ 5 (4)
3 + 0.04 × √ (I 1 2 × t 1 × T Fe / D Fe) ≦ t c ≦ 495 + √ (I 1 2 × t 1 × T Fe / D Fe) (5)
R Fe ≧ 20 (6)
　本発明を図２～４を用いて以下に具体的に説明する。図２は、抵抗スポット溶接を模式的に示す図である。図３は、通電パターンを説明する図である。図４は、第２通電工程での通電時の電流分布を模式的に示す図である。本発明は、複数の板を重ね合わせた板組を一対の電極によって挟み加圧しながら通電して接合（溶接接合）する抵抗スポット溶接により抵抗スポット溶接継手を得る、抵抗スポット溶接継手の製造方法である。 The present invention will be specifically described below with reference to FIGS. FIG. 2 is a diagram schematically showing resistance spot welding. FIG. 3 is a diagram illustrating an energization pattern. FIG. 4 is a diagram schematically illustrating a current distribution during energization in the second energization process. The present invention is a method of manufacturing a resistance spot welded joint, wherein a resistance spot welded joint is obtained by resistance spot welding in which a plate assembly in which a plurality of plates are stacked is sandwiched between a pair of electrodes and energized while being pressurized and joined (welded joint). is there.
　まず、鋼板１１とアルミニウム板１２を重ね合わせて板組とする。このとき、図２に示すように、最外側に配置される板の一方が鋼板１１で他方がアルミニウム板１２になるようにする。換言すると、電極１３、１４を接触させる板が、それぞれ鋼板１１とアルミニウム板１２となるように重ね合わせる。なお、図２おいては、鋼板１１とアルミニウム板１２を一枚ずつ重ね合わせた２枚組みの板組の抵抗スポット溶接継手の例を示したが、鋼板１１とアルミニウム板１２との間に、さらにもう１枚以上の鋼板あるいはアルミニウム板を挟んだ３枚重ね以上の板組としてもよい。 First, the steel plate 11 and the aluminum plate 12 are overlapped to form a plate assembly. At this time, as shown in FIG. 2, one of the plates arranged on the outermost side is a steel plate 11 and the other is an aluminum plate 12. In other words, the plates 13 and 14 are brought into contact with each other so as to become the steel plate 11 and the aluminum plate 12, respectively. In addition, in FIG. 2, although the example of the resistance spot welded joint of the board set of 2 sheets which piled up the steel plate 11 and the aluminum plate 12 one by one was shown, between the steel plate 11 and the aluminum plate 12, Furthermore, it is good also as a plate | board set of 3 or more sheets which pinched | interposed another 1 or more steel plate or aluminum plate.
　本発明において、抵抗スポット溶接継手を構成する板、すなわち、抵抗スポット溶接される板は、めっき鋼板、冷延鋼板および熱延鋼板から選択される少なくとも一種の鋼板と、アルミニウム板である。なお、めっき鋼板とは、表面に金属めっき層を有する鋼板であり、金属めっき層としては、例えばＺｎ系めっき層やＡｌ系めっき層が挙げられる。Ｚｎ系めっきとしては、一般的な溶融亜鉛めっき（ＧＩ）、合金化溶融亜鉛めっき（ＧＡ）、電気亜鉛めっき（ＥＧ）、Ｚｎ－Ｎｉ系めっき（例えば、１０～２５質量％のＮｉを含むＺｎ－Ｎｉ系めっき）、Ｚｎ－Ａｌ系めっき、Ｚｎ－Ｍｇ系めっき、Ｚｎ－Ａｌ－Ｍｇ系めっきなどが例示できる。また、Ａｌ系めっきとしては、Ａｌ－Ｓｉ系めっき（例えば、１０～２０質量％のＳｉを含むＡｌ－Ｓｉ系めっき）などが例示できる。鋼板１１の成分は、特に限定されない。また、鋼板１１の強度も特に限定されないが、例えば鋼板から圧延方向に対して平行方向にＪＩＳ５号引張試験片を作製し、ＪＩＳ　Ｚ　２２４１：２０１１の規定に準拠して引張試験を実施して求めた引張強さが、２７０ＭＰａ以上１８００ＭＰａ以下（２７０ＭＰａ級～１８００ＭＰａ級）の鋼板である。アルミニウム板の成分も特に限定されず、純アルミニウム板でもアルミニウム合金板でもよい。アルミニウム合金板としては、例えばＪＩＳで規定される５０００系（Ａｌ－Ｍｇ系）、６０００系（Ａｌ－Ｍｇ－Ｓｉ系）、２０００系（Ａｌ－Ｃｕ系）、７０００系（Ａｌ－Ｚｎ－Ｍｇ系、Ａｌ－Ｚｎ－Ｍｇ－Ｃｕ系）等が挙げられる。なお、アルミニウム板の表面には、酸化被膜が形成されている。また、鋼板１１やアルミニウム板１２の板厚についても特に限定はないが、一般的な自動車車体に用いられ得る範囲（０．５～４．０ｍｍ程度）であることが好ましい。 In the present invention, the plate constituting the resistance spot welded joint, that is, the plate to be resistance spot welded, is at least one type of steel plate selected from a plated steel plate, a cold rolled steel plate and a hot rolled steel plate, and an aluminum plate. The plated steel sheet is a steel sheet having a metal plating layer on the surface, and examples of the metal plating layer include a Zn-based plating layer and an Al-based plating layer. Examples of the Zn-based plating include general hot-dip galvanizing (GI), alloyed hot-dip galvanizing (GA), electrogalvanizing (EG), and Zn—Ni-based plating (for example, Zn containing 10 to 25% by mass of Ni). -Ni-based plating), Zn-Al-based plating, Zn-Mg-based plating, Zn-Al-Mg-based plating, and the like. Examples of the Al plating include Al—Si plating (for example, Al—Si plating containing 10 to 20% by mass of Si). The component of the steel plate 11 is not particularly limited. Further, the strength of the steel plate 11 is not particularly limited. For example, a JIS No. 5 tensile test piece is produced from the steel plate in a direction parallel to the rolling direction, and a tensile test is performed in accordance with the provisions of JIS Z 2241: 2011. The steel sheet has a tensile strength of 270 MPa to 1800 MPa (270 MPa to 1800 MPa class). The component of the aluminum plate is not particularly limited, either a pure aluminum plate or an aluminum alloy plate. Examples of the aluminum alloy plate include 5000 series (Al-Mg series), 6000 series (Al-Mg-Si series), 2000 series (Al-Cu series), and 7000 series (Al-Zn-Mg series) defined by JIS. And Al-Zn-Mg-Cu-based). An oxide film is formed on the surface of the aluminum plate. Further, the thickness of the steel plate 11 or the aluminum plate 12 is not particularly limited, but is preferably in a range (about 0.5 to 4.0 mm) that can be used for a general automobile body.
　次に、鋼板１１およびアルミニウム板１２を重ね合わせた板組を、一対の溶接電極（電極１３および電極１４）で挟み、加圧しながら通電した後に、電極を鋼板から解放する。本発明の抵抗スポット溶接方法で使用可能な溶接装置としては、上下一対の電極を備え、溶接中に加圧力および溶接電流をそれぞれ任意に制御可能な溶接装置を用いることができる。溶接装置の加圧機構（エアシリンダやサーボモータ等）や、形式（定置式、ロボットガン等）等はとくに限定されない。また、直流、交流のいずれにも本発明を適用でき、電源の種類（単相交流、交流インバータ、直流インバータ）など特に限定されるものではない。ここで交流の場合は、「電流」は「実効電流」を意味する。なお、常に水冷されている状態で抵抗スポット溶接を行う。 Next, the plate set in which the steel plate 11 and the aluminum plate 12 are overlapped is sandwiched between a pair of welding electrodes (electrode 13 and electrode 14), and energized while being pressed, and then the electrode is released from the steel plate. As a welding apparatus that can be used in the resistance spot welding method of the present invention, a welding apparatus that includes a pair of upper and lower electrodes and can arbitrarily control the pressure and welding current during welding can be used. There are no particular limitations on the pressurization mechanism (air cylinder, servo motor, etc.) or type (stationary, robot gun, etc.) of the welding apparatus. Further, the present invention can be applied to both direct current and alternating current, and the type of power source (single-phase alternating current, alternating current inverter, direct current inverter) and the like are not particularly limited. Here, in the case of alternating current, “current” means “effective current”. In addition, resistance spot welding is performed in a state that is always water-cooled.
　このように、鋼板１１とアルミニウム板１２とを、最外側に配置される板の一方が鋼板１１で他方がアルミニウム板１２となるように重ねて板組とする。この板組を、一対の溶接電極（電極１３および電極１４）で挟み、加圧しながら通電して、抵抗発熱によりナゲットを形成すると共に重ね合わせた鋼板１１とアルミニウム板１２を接合することで、抵抗スポット溶接継手が得られる。 Thus, the steel plate 11 and the aluminum plate 12 are overlapped so that one of the plates arranged on the outermost side is the steel plate 11 and the other is the aluminum plate 12 to form a plate set. The plate assembly is sandwiched between a pair of welding electrodes (electrode 13 and electrode 14), energized while being pressurized, a nugget is formed by resistance heat generation, and the overlapped steel plate 11 and aluminum plate 12 are joined together, thereby providing resistance. A spot welded joint is obtained.
　本発明においては、この通電を特定のパターンとする。すなわち、本発明の通電パターンは、例えば図３に示すように、電流Ｉ１（ｋＡ）で通電時間ｔ１（ｍｓ）の間通電する第１通電工程と、第１通電工程の後に通電休止時間ｔｃ（ｍｓ）の間通電を休止する通電休止工程と、通電休止工程の後に電流Ｉ２（ｋＡ）で通電時間ｔ２（ｍｓ）の間通電する第２通電工程とを有し、重ね合わせる鋼板の総板厚をＴＦｅ（ｍｍ）、鋼板と接触させる電極１３の先端曲率半径をＲＦｅ（ｍｍ）、鋼板と接触させる電極１３の先端径をＤＦｅ（ｍｍ）としたとき、上記式（１）～（５）の関係を全て満たす。なお、第２通電工程終了後は、必要に応じて、１段以上の通電を行った後、例えば、後熱処理などを目的とした３段目以降の通電を行なった後、通電を停止する。 In the present invention, this energization is a specific pattern. That is, in the energization pattern of the present invention, for example, as shown in FIG. 3, the first energization step of energizing with the current I 1 (kA) for the energization time t 1 (ms) and the energization pause time after the first energization step. an energization stop process for stopping energization for t c (ms), and a second energization process for energizing for the energization time t 2 (ms) with the current I 2 (kA) after the energization stop process. When the total plate thickness of the steel plate is T Fe (mm), the tip curvature radius of the electrode 13 in contact with the steel plate is R Fe (mm), and the tip diameter of the electrode 13 in contact with the steel plate is D Fe (mm), the above formula Satisfy all the relationships (1) to (5). In addition, after the second energization process is completed, energization of one or more stages is performed as necessary, and then energization is performed after the third stage for the purpose of post heat treatment, for example, and then the energization is stopped.
　上述したように、通電初期はアルミニウム板１２の表面の酸化被膜で通電経路が制限される。そのため、本発明においては、まず、第１通電工程（１段目の通電）で、第２通電工程よりも長時間且つ低電流の通電を行なう（上記式（１）、（２）を参照）。これにより、アルミニウム板１２の表面の酸化被膜を破壊することで鋼板１１とアルミニウム板１２間の通電経路を確保しつつ、過度な入熱増加が生じないようにする。さらに、この第１通電工程の通電時間ｔ１を４０ｍｓ以上とすることで（上記式（３）を参照）、鋼板１１とアルミニウム板１２間の通電経路を十分に確保することができる。 As described above, the energization path is limited by the oxide film on the surface of the aluminum plate 12 at the beginning of energization. Therefore, in the present invention, first, in the first energization process (first stage energization), energization is performed for a longer time and at a lower current than in the second energization process (see the above formulas (1) and (2)). . Thereby, by destroying the oxide film on the surface of the aluminum plate 12, an energization path between the steel plate 11 and the aluminum plate 12 is secured, and an excessive increase in heat input is prevented. Further, the energization time t 1 of the first conducting step (see above formula (3)) by the above 40 ms, the current path between the steel plate 11 and aluminum plate 12 can be sufficiently secured.
　そして、第１通電工程に続いて、所定の通電休止時間ｔｃ（ｍｓ）の間通電を休止し（通電休止工程）、この通電休止工程に続いて、第２通電工程（２段目の通電）で第１通電工程よりも短時間且つ高電流の通電を行なう。これにより、瞬間的に広範囲を発熱させることができる。図４は、第２通電工程での通電時の電流分布を模式的に示す図である。図４に示すように、鋼板１１と電極１３の接触端近傍２２では、電流密度が高いため、高電流化するほどこの接触端近傍２２での発熱が促進されることとなる。したがって、第２通電工程での高電流化は、短時間の通電で広範囲を発熱させるのに有効となり、広範囲のアルミニウム板１２を溶融させ、これにより接合径を拡大することができる。しかし、第１通電工程の通電終了時点では、第１通電工程において初期に酸化被膜が破壊されて通電が開始する接合部中心がより高温となっている。したがって、通電休止工程での通電休止時間ｔｃが短い場合は、第２通電工程の通電を短時間且つ高電流化したとしても高温の接合部中心から再昇温するため、入熱が過大となり易い。
　そこで本発明においては、通電休止時間ｔｃが５ｍｓ以上（上記式（４）を参照）で且つ上記式（５）を満たす通電休止工程を行なった後に、高電流且つ短時間の第２通電工程を行なうようにする。これにより、通電休止工程において接合部中心の温度が一旦低下するため、第２通電工程の通電では電流密度が高い鋼板１１と電極１３の接触端近傍２２の発熱を促すことができ、入熱を抑えつつ、ナゲット径を拡大できるのである。ここで、ｔｃの下限値は、第１通電工程における発熱量および第１通電工程終了後の電極への抜熱量に応じて設定することが効果的である。このため、ｔｃの下限値として、それらに影響を及ぼすパラメータであるＩ１、ｔ１、ＴＦｅ、ＤＦｅから成る関係式（５）（すなわち上記式（５）の左辺）を決定した。ＴＦｅが大きいと第１通電工程における鋼板の発熱量が増加するとともに、電極への抜熱も生じにくくなるため、ｔｃの下限値は大きくなる。また、ＤＦｅが大きいと、電極との接触面積が増加することで電極への抜熱が促されるため、ｔｃの下限値は小さくなる。また、ｔｃの過度な増加は生産効率を低下させるため、ｔｃの上限値についても、同様のパラメータから成る関係式（５）（すなわち上記式（５）の右辺）を設定した。なお、第２通電工程での通電時間ｔ２は、例えば５～１００ｍｓが好ましい。 Then, following the first energization process, energization is suspended for a predetermined energization suspension time t c (ms) (energization suspension process), and following this energization suspension process, the second energization process (second-stage energization process). ) For a shorter time and higher current than in the first energization step. As a result, a wide range of heat can be instantaneously generated. FIG. 4 is a diagram schematically illustrating a current distribution during energization in the second energization process. As shown in FIG. 4, since the current density is high in the contact end vicinity 22 between the steel plate 11 and the electrode 13, heat generation in the contact end vicinity 22 is promoted as the current is increased. Therefore, the increase in current in the second energization step is effective in generating heat over a wide area by short-time energization, and the aluminum plate 12 can be melted over a wide area, thereby expanding the bonding diameter. However, at the end of energization in the first energization process, the center of the joint where the oxide film is initially destroyed in the first energization process and energization starts is at a higher temperature. Therefore, if the energization pause time t c in the energization pause process is short, since the re-heated from the hot junction center as was briefly and high current of the power supply of the second current supply step, heat input becomes excessively large easy.
Therefore, in the present invention, the energization stop time t c is 5 ms or more (see the above equation (4)) and the energization stop step satisfying the above equation (5) is performed, and then the second energization step with a high current and a short time is performed. To do. As a result, the temperature at the center of the joint portion once decreases in the energization suspending process, and thus energization in the second energizing process can promote heat generation in the vicinity of the contact end 22 between the steel plate 11 and the electrode 13 having a high current density. The nugget diameter can be expanded while suppressing. Here, it is effective to set the lower limit value of t c according to the heat generation amount in the first energization process and the heat removal amount to the electrode after the first energization process. For this reason, as the lower limit value of t c, the relational expression (5) (that is, the left side of the above expression (5)) consisting of I 1 , t 1 , T Fe , and D Fe that are parameters affecting them was determined. If T Fe is large, the amount of heat generated by the steel sheet in the first energization process is increased, and it is difficult for heat to be removed to the electrode, so the lower limit of t c is large. In addition, when D Fe is large, the contact area with the electrode increases, and heat removal from the electrode is promoted, so the lower limit value of t c becomes small. Further, since an excessive increase in t c decreases production efficiency, the relational expression (5) (that is, the right side of the above expression (5)) including similar parameters is set for the upper limit value of t c . Incidentally, the energization time t 2 in the second energizing step, for example, 5 ~ 100 ms is preferable.
　さらに、本発明においては、上述した特定の通電パターンとすることに加えて、上記式（６）を満たす、すなわち、鋼板１１と接触させる電極１３として、先端曲率半径ＲＦｅが２０ｍｍ以上である電極を用いる必要がある。これは、鋼板１１と接触させる電極１３の先端曲率半径ＲＦｅの拡大により、鋼板１１と電極１３の接触面積が大きくなることで、第２通電工程における通電面積が大きくなり、鋼板１１の発熱範囲および接合径が拡大できるようにするためである。加えて、鋼板１１と電極１３の接触面積が拡大することで、電極１３への抜熱が促され、第１通電工程終了後の通電休止時間ｔｃを短縮することもできる。また、鋼板１１と電極１３の接触端近傍２２における電流密度の過大増加を防ぐことで、鋼板表面からの散り発生を抑制する効果も得られる。なお、鋼板１１と接触させる電極１３は、先端曲率半径ＲＦｅが下記式（７）の関係を満たす、すなわち先端曲率半径ＲＦｅが５０ｍｍ以上である電極を用いることが好ましい。その理由は、電極と鋼板の接触面積を拡大し、電流密度を低下させることによる表散りの抑制である。
ＲＦｅ≧５０　　　（７）
電極１３の先端の形式は、例えばＪＩＳ　Ｃ　９３０４：１９９９に記載されるＤＲ形（ドームラジアス形）、Ｒ形（ラジアス形）、Ｄ形（ドーム形）である。図５に、電極の先端曲率半径Ｒと先端径Ｄを示す。図５（ａ）はラジアス形の電極の先端曲率半径Ｒと先端径Ｄを示す図であり、図５（ｂ）はドームラジアス形の電極の先端曲率半径Ｒと先端径Ｄを示す図である。なお、図５（ｂ）に示すように、ドームラジアス形の電極は先端側の曲面が２段の曲率を有するが、電極の先端曲率半径は、抵抗スポット溶接する板に最初に接する部分（中心側の曲面）の曲率半径Ｒである。
鋼板１１と接触させる電極１３の先端径ＤＦｅは、電極と鋼板の接触面積確保の観点より、例えば４ｍｍ～１６ｍｍであることが好ましい。電極１３の先端径ＤＦｅは、より好ましくは６ｍｍ～１６ｍｍであり、さらに好ましくは８ｍｍ～１６ｍｍである。 Further, in the present invention, in addition to the specific energization pattern described above, the electrode 13 that satisfies the above formula (6), that is, the electrode 13 that is brought into contact with the steel plate 11 has a tip curvature radius R Fe of 20 mm or more. Must be used. This is because the contact area between the steel plate 11 and the electrode 13 is increased by increasing the tip curvature radius R Fe of the electrode 13 to be brought into contact with the steel plate 11, thereby increasing the energization area in the second energization step, and the heat generation range of the steel plate 11. This is because the bonding diameter can be increased. In addition, since the contact area between the steel plate 11 and the electrode 13 is increased, heat removal to the electrode 13 is promoted, and the energization stop time t c after the end of the first energization process can be shortened. Moreover, the effect which suppresses generation | occurrence | production of the scattering from the steel plate surface is also acquired by preventing the excessive increase in the current density in the contact end vicinity 22 of the steel plate 11 and the electrode 13. The electrode 13 is brought into contact with the steel plate 11, tip curvature radius R Fe satisfies a relationship represented by the following formula (7), that the tip curvature radius R Fe it is preferable to use an electrode is at least 50mm. The reason is suppression of surface scattering by enlarging the contact area of an electrode and a steel plate, and reducing a current density.
R Fe ≧ 50 (7)
The type of the tip of the electrode 13 is, for example, DR type (dome radius type), R type (radius type), or D type (dome type) described in JIS C 9304: 1999. FIG. 5 shows the tip radius of curvature R and the tip diameter D of the electrode. FIG. 5A is a diagram showing the tip radius of curvature R and the tip diameter D of the radius electrode, and FIG. 5B is a diagram showing the tip radius of curvature R and the tip diameter D of the dome radius electrode. . As shown in FIG. 5 (b), the dome radius electrode has a curved surface on the tip side with a two-step curvature. The radius of curvature of the tip of the electrode is a portion (center) that first contacts the plate to be resistance spot welded. Radius of curvature of the curved surface on the side.
The tip diameter D Fe of the electrode 13 in contact with the steel plate 11 is preferably 4 mm to 16 mm, for example, from the viewpoint of securing the contact area between the electrode and the steel plate. The tip diameter D Fe of the electrode 13 is more preferably 6 mm to 16 mm, and further preferably 8 mm to 16 mm.
　本発明においては、上記特定の通電パターンで行い、且つ、鋼板１１に接触させる電極１３として特定の電極を用いることにより、広範囲のアルミニウム板１２を溶融させつつ、過大な発熱を防ぐことができるため、接合径の拡大と入熱の低減による接合界面の金属間化合物の成長抑制とを両立させることが可能となる。したがって、本発明においては、良好なはく離強度を有する鋼板１１とアルミニウム板１２の抵抗スポット溶接継手を製造することができる。また、上述したように、鋼板やアルミニウム板の成分や板組によらず、具体的には、鋼板やアルミニウム板における表面の金属めっき層の有無や厚さ、酸化皮膜の組成や厚さ、母材強度、板厚によらず、適用することができる。 In the present invention, by using the specific electrode as the electrode 13 that is made in the specific energization pattern and brought into contact with the steel plate 11, excessive heat generation can be prevented while melting the aluminum plate 12 in a wide range. It is possible to achieve both the expansion of the bonding diameter and the suppression of growth of the intermetallic compound at the bonding interface by reducing the heat input. Therefore, in this invention, the resistance spot welded joint of the steel plate 11 and the aluminum plate 12 which has favorable peeling strength can be manufactured. In addition, as described above, regardless of the components and plate set of the steel plate or aluminum plate, specifically, the presence or thickness of the metal plating layer on the surface of the steel plate or aluminum plate, the composition or thickness of the oxide film, the mother It can be applied regardless of material strength and plate thickness.
　なお、アルミニウム板１２と接触させる電極１４は、アルミニウム板１２と接触させる電極１４の先端曲率半径をＲＡｌ（ｍｍ）としたとき、下記式（８）を満たす、すなわち、先端曲率半径ＲＡｌが５０ｍｍ以上である電極とすることが好適である。これにより、本発明の効果をより有効に得ることができる。これは、アルミニウム板１２に加わる面圧を低減させることで、通電によるアルミニウム板１２の減厚を抑制する効果が得られるためである。
ＲＡｌ≧５０　　　（８）
なお、先端曲率半径ＲＡｌは８０ｍｍ以上とすることが、より好ましい。
アルミニウム板１２と接触させる電極１４の先端の形式は、例えばＪＩＳ　Ｃ　９３０４：１９９９に記載されるＤＲ形（ドームラジアス形）、Ｒ形（ラジアス形）、Ｄ形（ドーム形）である。アルミニウム板１２と接触させる電極１４の先端径ＤＡｌは、アルミニウム合金板に加わる面圧低減の観点より、例えば４ｍｍ～１６ｍｍであることが好ましい。電極１４の先端径ＤＡｌは、より好ましくは６ｍｍ～１６ｍｍであり、さらに好ましくは８ｍｍ～１６ｍｍである。
　また、アルミニウム板１２側の電極１４の先端径ＤＡｌと、鋼板１１側の電極１３の先端径ＤＦｅとの大小関係については特に規定は無く、両者が同じであってもよいし、異なってもよい。 The electrode 14 in contact with the aluminum plate 12 satisfies the following formula (8) when the tip curvature radius of the electrode 14 in contact with the aluminum plate 12 is R Al (mm), that is, the tip curvature radius R Al is It is preferable that the electrode be 50 mm or more. Thereby, the effect of the present invention can be obtained more effectively. This is because the effect of suppressing the thickness reduction of the aluminum plate 12 due to energization can be obtained by reducing the surface pressure applied to the aluminum plate 12.
R Al ≧ 50 (8)
The tip radius of curvature R Al is more preferably 80 mm or more.
The type of the tip of the electrode 14 brought into contact with the aluminum plate 12 is, for example, DR type (dome radius type), R type (radius type), or D type (dome type) described in JIS C 9304: 1999. The tip diameter D Al of the electrode 14 brought into contact with the aluminum plate 12 is preferably 4 mm to 16 mm, for example, from the viewpoint of reducing the surface pressure applied to the aluminum alloy plate. The tip diameter D Al of the electrode 14 is more preferably 6 mm to 16 mm, and further preferably 8 mm to 16 mm.
Also, there is no particular relationship between the tip diameter D Al of the electrode 14 on the aluminum plate 12 side and the tip diameter D Fe of the electrode 13 on the steel plate 11 side, and both may be the same or different. Also good.
　また、本発明において、第２通電工程の通電で適用できる電流範囲を拡大したい場合は、第１通電工程で鋼板１１とアルミニウム板１２間に十分な通電経路を確保しておくことが有効となる。そのため第１通電工程の通電時間ｔ１は、５０ｍｓ以上とすることが好ましく、６０ｍｓ以上とするのがより好ましい。第１通電工程の通電時間ｔ１の上限は特に規定しないが、タクトタイム短縮の観点より、好ましくは、通電時間ｔ１が６００ｍｓ以下である。
また、この第１通電工程の通電時に、アルミニウム板１２は少なくとも一部が溶融することが好ましい。第１通電工程の通電時にアルミニウム板１２が溶融することによりアルミニウム板１２表面の酸化被膜が完全に除去されるため、通電経路の安定化が可能となる。ただし、入熱が過大となるのを防ぐため、最外側に位置し電極１４に接触させるアルミニウム板１２の板厚をＴ（ｍｍ）としたとき、第１通電工程の通電で形成する電極１４に接触させる最外側のアルミニウム板１２のナゲット径は、６√Ｔ（ｍｍ）以下であることが好ましく、さらに好ましくは、５√Ｔ（ｍｍ）以下である。また、第１通電工程の通電で形成する、電極１４に接触させる最外側のアルミニウム板１２のナゲット径は、２√Ｔ（ｍｍ）以上であることが好ましい。なお、アルミニウム板１２の板厚Ｔは単位としてｍｍを用い、このＴを代入した６√Ｔや５√Ｔの単位もｍｍとする。ここで、アルミニウム板１２のナゲット径は、アルミニウム板１２と該アルミニウム板１２と接する板（図２においては、鋼板１１）との合わせ面（接合面）における、アルミニウム板１２のナゲットの最大径である。なお、「ナゲット」とは、重ね抵抗溶接において溶接部に生じる溶融凝固した部分であるが、本明細書においては、凝固するとナゲットになる溶融部（すなわち凝固する前の溶融部）もナゲットと呼ぶ場合がある。 In the present invention, when it is desired to expand the current range that can be applied by energization in the second energization process, it is effective to secure a sufficient energization path between the steel plate 11 and the aluminum plate 12 in the first energization process. . Therefore energization time t 1 of the first energizing step is preferably set to 50ms or more, and more preferably, 60ms or more. The upper limit of the energization time t 1 of the first energizing step is not particularly defined, in view of the tact time shortened, preferably, the energization time t 1 is less than 600 ms.
Moreover, it is preferable that at least a part of the aluminum plate 12 is melted during energization in the first energization process. Since the aluminum plate 12 is melted during energization in the first energization step, the oxide film on the surface of the aluminum plate 12 is completely removed, so that the energization path can be stabilized. However, in order to prevent excessive heat input, when the thickness of the aluminum plate 12 located on the outermost side and brought into contact with the electrode 14 is T (mm), the electrode 14 formed by energization in the first energization step is used. The nugget diameter of the outermost aluminum plate 12 to be contacted is preferably 6√T (mm) or less, and more preferably 5√T (mm) or less. Moreover, it is preferable that the nugget diameter of the outermost aluminum plate 12 formed by energization in the first energization process and brought into contact with the electrode 14 is 2√T (mm) or more. In addition, the thickness T of the aluminum plate 12 uses mm as a unit, and the unit of 6√T or 5√T into which T is substituted is also mm. Here, the nugget diameter of the aluminum plate 12 is the maximum diameter of the nugget of the aluminum plate 12 at the mating surface (joint surface) between the aluminum plate 12 and the plate (steel plate 11 in FIG. 2) in contact with the aluminum plate 12. is there. The “nugget” is a melted and solidified portion generated in a welded portion in lap resistance welding. In this specification, a melted portion that becomes a nugget when solidified (that is, a melted portion before solidifying) is also called a nugget. There is a case.
　また、鋼板の板厚が大きい場合など、電極への抜熱が生じにくい板組においては、通電休止時間ｔｃは１０ｍｓ以上とすることが好ましく、２０ｍｓ以上とすることがより好ましい。かつ、通電休止時間ｔｃは下記式（９）の関係を満たすことが好ましく、下記式（１０）の関係を満たすことがより好ましい。その理由は溶接部を一旦冷却することで、第２通電工程で広範囲の発熱を促し、継手強度が向上するためである。
８＋０．０４×√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）≦ｔｃ≦４９５＋√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）　　　（９）
１５＋０．０４×√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）≦ｔｃ≦４９５＋√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）　　　（１０） Also, like the plate thickness of the steel sheet is large, in the heat removal is less likely to occur plate sets to the electrodes, energization pause time t c is preferably greater than or equal to 10 ms, and more preferably to more than 20ms. And, energization pause time t c, it is preferable to satisfy the relation of formula (9), more preferably satisfies the following formula (10). The reason for this is that once the weld is cooled, a wide range of heat generation is promoted in the second energization step, and the joint strength is improved.
8 + 0.04 × √ (I 1 2 × t 1 × T Fe / D Fe) ≦ t c ≦ 495 + √ (I 1 2 × t 1 × T Fe / D Fe) (9)
15 + 0.04 × √ (I 1 2 × t 1 × T Fe / D Fe) ≦ t c ≦ 495 + √ (I 1 2 × t 1 × T Fe / D Fe) (10)
　本発明における溶接電流（通電時の電流）は、特に限定されず、溶接電流は例えば４～４０ｋＡである。ただし、施工上は所定のナゲット径を得る必要があり、過大な電流値は散り発生の原因となるため、第１通電工程の電流Ｉ１は例えば４～２０ｋＡであり、第２通電工程の電流値Ｉ２は例えば１０～４０ｋＡである。 The welding current (current when energized) in the present invention is not particularly limited, and the welding current is, for example, 4 to 40 kA. However, since it is necessary to obtain a predetermined nugget diameter in construction, an excessive current value causes scattering, so the current I 1 in the first energization process is, for example, 4 to 20 kA, and the current in the second energization process the value I 2 is, for example, 10 ~ 40 kA.
　また、溶接中の加圧力には特に制限はなく、例えば、加圧力は、例えば２．０ｋＮ～７．０ｋＮであり、加圧力を溶接中および溶接前後に変化させてもよい。 Also, there is no particular limitation on the applied pressure during welding. For example, the applied pressure is, for example, 2.0 kN to 7.0 kN, and the applied pressure may be changed during welding and before and after welding.
　また、溶接中の抵抗値・電圧値といったパラメータを監視し、その変動に応じて電流値や通電時間を変化させる制御方法を用いても何ら問題無い。 Also, there is no problem if a control method is used in which parameters such as resistance value and voltage value during welding are monitored and the current value and energization time are changed according to the fluctuation.
　なお、本明細書において、上記各式は数値のみの関係を規定したものである。 In the present specification, the above formulas prescribe a relationship of only numerical values.
　本発明の実施例を以下に示す。なおこの実施例で用いた板組や溶接条件、電極形状は、本発明の効果を示すために適用した一例であるため、他の条件を用いてもよいのは言うまでもない。 Examples of the present invention are shown below. The plate set, welding conditions, and electrode shape used in this example are examples applied to show the effects of the present invention, and it goes without saying that other conditions may be used.
　（本発明例および比較例）
　供試材料として、表１－１および表１－２に示した鋼板１１とアルミニウム板１２を用いた。表１－１および表１－２に示した各鋼板の引張強さは、鋼板から圧延方向に対して平行方向にＪＩＳ５号引張試験片を作製し、ＪＩＳ　Ｚ　２２４１：２０１１の規定に準拠して引張試験を実施して求めた。表１－１に示した鋼板１１とアルミニウム板１２は、図２に示すようにして、抵抗スポット溶接を行ない、２枚重ねの板組からなる抵抗スポット溶接継手を製造した。表１－２に示した鋼板とアルミニウム板は、図示はしないが、同様に抵抗スポット溶接を行ない、鋼板１１（下板）とアルミニウム板１２（上板）との間にさらにもう１枚の鋼板１５（中板）を挟んだ３枚重ねの板組からなる抵抗スポット溶接継手を製造した。なお、用いたアルミニウム板１２は表面に酸化被膜が形成されていた。溶接機はインバータ直流式抵抗スポット溶接機を用い、電極１３、１４の先端曲率半径および先端径、ならびに、通電パターンを表２に示す条件とした。電極１３、１４は全てクロム銅製のＤＲ形電極を用いた。抵抗スポット溶接は室温（２０℃）で行い、電極１３、１４を常に水冷した状態で行った。また、加圧力は、第１通電工程、通電休止工程、第２通電工程にわたって一定とした。なお、第１通電工程では、アルミニウム板１２の一部が溶融していた。 (Invention Example and Comparative Example)
As test materials, the steel plate 11 and the aluminum plate 12 shown in Table 1-1 and Table 1-2 were used. The tensile strength of each steel sheet shown in Table 1-1 and Table 1-2 is as follows. JIS No. 5 tensile test piece was prepared from the steel sheet in a direction parallel to the rolling direction, and in accordance with the provisions of JIS Z 2241: 2011. The tensile test was performed. The steel plate 11 and the aluminum plate 12 shown in Table 1-1 were subjected to resistance spot welding as shown in FIG. 2 to produce a resistance spot welded joint consisting of a two-layer plate set. The steel plate and aluminum plate shown in Table 1-2 are not shown, but resistance spot welding is similarly performed, and another steel plate is provided between the steel plate 11 (lower plate) and the aluminum plate 12 (upper plate). A resistance spot welded joint made of a three-layered plate assembly sandwiching 15 (medium plate) was produced. The aluminum plate 12 used had an oxide film formed on the surface. An inverter DC resistance spot welder was used as the welding machine, and the tip curvature radius and tip diameter of the electrodes 13 and 14 and the energization pattern were set as shown in Table 2. The electrodes 13 and 14 were all DR type electrodes made of chromium copper. Resistance spot welding was performed at room temperature (20 ° C.), and the electrodes 13 and 14 were always water-cooled. The applied pressure was constant throughout the first energization process, the energization stop process, and the second energization process. In the first energization process, a part of the aluminum plate 12 was melted.
　得られた抵抗スポット溶接継手について、ＪＩＳ　Ｚ　３１３７に基づく十字引張試験を実施して、はく離強度を評価した。十字引張強度（ＣＴＳ）が、ＣＴＳ≧０．９ｋＮの場合をＡ、０．９ｋＮ＞ＣＴＳ≧０．８ｋＮの場合をＢ、０．８ｋＮ＞ＣＴＳ≧０．７ｋＮの場合をＣ、０．７ｋＮ＞ＣＴＳの場合をＦとして、それぞれ評価した。評価結果を表２に示す。本発明例では、評価はＡ～Ｃのいずれかであった。 The resulting resistance spot welded joint was subjected to a cross tensile test based on JIS Z 3137 to evaluate the peel strength. When the cross tensile strength (CTS) is CTS ≧ 0.9 kN, A, 0.9 kN> CTS ≧ 0.8 kN, B, 0.8 kN> CTS ≧ 0.7 kN, C, 0.7 kN> Each case of CTS was evaluated as F and evaluated. The evaluation results are shown in Table 2. In the example of the present invention, the evaluation was any one of A to C.
　また、上記と同様の条件で第１通電工程を行ない、接合部の断面観察を行い、第１通電工程の通電で形成した、アルミニウム板１２のナゲット径（ｍｍ）を求めた。なお、アルミニウム板１２のナゲット径は、アルミニウム板１２とアルミニウム板１２と接する板（鋼板１１、表１－２に示す３枚重ねの板組の場合には鋼板１５）との接合面における、アルミニウム板１２のナゲットの最大径を測定した。測定結果を表２に示す。 Also, the first energization process was performed under the same conditions as described above, the cross section of the joint was observed, and the nugget diameter (mm) of the aluminum plate 12 formed by energization in the first energization process was obtained. Note that the nugget diameter of the aluminum plate 12 is such that the aluminum plate 12 and the plate in contact with the aluminum plate 12 (steel plate 11 or steel plate 15 in the case of the three-layered plate set shown in Table 1-2) are aluminum The maximum diameter of the nugget on the plate 12 was measured. The measurement results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　１１、１５　鋼板
　１２　　　　アルミニウム板
　１３、１４　電極
　２１　　　　溶接電流
　２２　　　　鋼板と電極の接触端近傍 11, 15 Steel plate 12 Aluminum plate 13, 14 Electrode 21 Welding current 22 Near contact end of steel plate and electrode

Claims (4)

  1. 　めっき鋼板、冷延鋼板および熱延鋼板から選択される少なくとも一種の鋼板とアルミニウム板とを重ね合わせて最外側に配置される板の一方が鋼板で他方がアルミニウム板とした板組を、一対の電極によって挟み、抵抗スポット溶接により接合し、抵抗スポット溶接継手を製造するにあたり、
    　電流Ｉ１（ｋＡ）で通電時間ｔ１（ｍｓ）の間通電する第１通電工程と、
    第１通電工程の後に通電休止時間ｔｃ（ｍｓ）の間通電を休止する通電休止工程と、
    通電休止工程の後に電流Ｉ２（ｋＡ）で通電時間ｔ２（ｍｓ）の間通電する第２通電工程とを有し、
    　重ね合わせる鋼板の総板厚をＴＦｅ（ｍｍ）、鋼板と接触させる電極の先端曲率半径をＲＦｅ（ｍｍ）、鋼板と接触させる電極の先端径をＤＦｅ（ｍｍ）としたとき、
    　前記第１通電工程、前記通電休止工程、および前記第２通電工程は、下記式（１）～（６）の関係を全て満たす、抵抗スポット溶接継手の製造方法。
    Ｉ１＜Ｉ２　　　（１）
    ｔ１＞ｔ２　　　（２）
    ｔ１≧４０　　　（３）
    ｔｃ≧５　　　　（４）
    ３＋０．０４×√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）≦ｔｃ≦４９５＋√（Ｉ１ 2×ｔ１×ＴＦｅ／ＤＦｅ）　　　（５）
    ＲＦｅ≧２０　　　（６）     A pair of plates in which at least one plate selected from a plated steel plate, a cold-rolled steel plate and a hot-rolled steel plate and an aluminum plate are overlapped and one of the plates arranged on the outermost side is a steel plate and the other is an aluminum plate, In order to produce a resistance spot welded joint, sandwiched by electrodes and joined by resistance spot welding,
    A first energization step of energizing with an electric current I 1 (kA) for an energization time t 1 (ms);
    An energization stop step of stopping energization for an energization stop time t c (ms) after the first energization step;
    A second energization step of energizing with an electric current I 2 (kA) for an energization time t 2 (ms) after the energization stop step;
    When the total plate thickness of the steel plates to be stacked is T Fe (mm), the tip curvature radius of the electrode in contact with the steel plate is R Fe (mm), and the tip diameter of the electrode in contact with the steel plate is D Fe (mm),
    The method of manufacturing a resistance spot welded joint, wherein the first energization step, the energization stop step, and the second energization step satisfy all the relationships of the following formulas (1) to (6).
    I 1 <I 2 (1)
    t 1 > t 2 (2)
    t 1 ≧ 40 (3)
    t c ≧ 5 (4)
    3 + 0.04 × √ (I 1 2 × t 1 × T Fe / D Fe) ≦ t c ≦ 495 + √ (I 1 2 × t 1 × T Fe / D Fe) (5)
    R Fe ≧ 20 (6)
  2. 　前記第１通電工程、前記通電休止工程、および前記第２通電工程は、さらに、下記式（７）の関係を満たす、請求項１に記載の抵抗スポット溶接継手の製造方法。
    ＲＦｅ≧５０　　　（７）     2. The method of manufacturing a resistance spot welded joint according to claim 1, wherein the first energization step, the energization stop step, and the second energization step further satisfy a relationship of the following formula (7).
    R Fe ≧ 50 (7)
  3. 　アルミニウム板と接触させる電極の先端曲率半径をＲＡｌ（ｍｍ）としたとき、
    前記第１通電工程、前記通電休止工程、および前記第２通電工程は、さらに、下記式（８）の関係を満たす、請求項１または２に記載の抵抗スポット溶接継手の製造方法。
    ＲＡｌ≧５０　　　（８）     When the radius of curvature of the tip of the electrode brought into contact with the aluminum plate is R Al (mm),
    3. The method of manufacturing a resistance spot welded joint according to claim 1, wherein the first energization step, the energization stop step, and the second energization step further satisfy a relationship of the following formula (8).
    R Al ≧ 50 (8)
  4. 　前記第１通電工程では、電極を接触させたアルミニウム板の少なくとも一部を溶融させる、請求項１～３のいずれか一項に記載の抵抗スポット溶接継手の製造方法。 The resistance spot welded joint manufacturing method according to any one of claims 1 to 3, wherein in the first energization step, at least a part of the aluminum plate in contact with the electrode is melted.
PCT/JP2018/012259 2017-03-31 2018-03-27 Production method for resistance spot welded joint WO2018181231A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
KR1020197028628A KR102225221B1 (en) 2017-03-31 2018-03-27 Method of manufacturing resistance spot welded joints
CN201880021920.8A CN110461528B (en) 2017-03-31 2018-03-27 Method for manufacturing resistance spot-welded joint
JP2018530804A JP6410003B1 (en) 2017-03-31 2018-03-27 Method of manufacturing resistance spot welded joint

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2017-069474 2017-03-31
JP2017069474 2017-03-31

Publications (1)

Publication Number Publication Date
WO2018181231A1 true WO2018181231A1 (en) 2018-10-04

Family

ID=63676118

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2018/012259 WO2018181231A1 (en) 2017-03-31 2018-03-27 Production method for resistance spot welded joint

Country Status (4)

Country Link
JP (1) JP6410003B1 (en)
KR (1) KR102225221B1 (en)
CN (1) CN110461528B (en)
WO (1) WO2018181231A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109317801A (en) * 2018-12-03 2019-02-12 闫宇 A kind of microdot Welding of nickel-clad copper harness and copper sheet
WO2023117663A1 (en) * 2021-12-22 2023-06-29 Plansee Composite Materials Gmbh Spot-welding electrode cap
JP7363240B2 (en) 2019-09-12 2023-10-18 マツダ株式会社 Resistance welding equipment and resistance welding method

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4116455A4 (en) * 2020-03-05 2024-02-21 Jfe Steel Corp Resistance spot welding method and manufacturing method for resistance spot welded joint
JP7335196B2 (en) * 2020-04-15 2023-08-29 株式会社神戸製鋼所 Manufacturing method of resistance welded member
KR102348579B1 (en) * 2020-11-24 2022-01-06 주식회사 포스코 Method for resistance spot welding of steel sheet for hot-press forming
CN112548295B (en) * 2020-12-05 2022-11-29 钟丽慧 Automobile aluminum alloy resistance spot welding method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11156556A (en) * 1997-11-21 1999-06-15 Toyota Motor Corp Clad metal butt resistance welding method
JP2010172946A (en) * 2009-01-30 2010-08-12 Jfe Steel Corp Resistance spot welding method of high-strength steel sheet
JP2013111586A (en) * 2011-11-25 2013-06-10 Jfe Steel Corp Resistance spot welding method for high-strength steel plate
JP2013151018A (en) * 2011-12-27 2013-08-08 Mazda Motor Corp Welding method

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS504790A (en) 1973-05-12 1975-01-18
JPS5436790A (en) 1977-08-26 1979-03-17 Hitachi Ltd Magnetic pole piece for internal chill
JP4469165B2 (en) 2003-11-26 2010-05-26 株式会社神戸製鋼所 Dissimilar joints of steel and aluminum and their joining methods
JP3117053U (en) 2005-09-26 2006-01-05 株式会社細山田商事 Deodorization device
JP5572046B2 (en) 2010-09-13 2014-08-13 株式会社神戸製鋼所 Dissimilar material joining method
JP6160190B2 (en) * 2013-04-15 2017-07-12 マツダ株式会社 Resistance spot welding method for dissimilar metal materials
US10265797B2 (en) * 2013-07-11 2019-04-23 Nippon Steel & Sumitomo Metal Corporation Resistance spot welding method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11156556A (en) * 1997-11-21 1999-06-15 Toyota Motor Corp Clad metal butt resistance welding method
JP2010172946A (en) * 2009-01-30 2010-08-12 Jfe Steel Corp Resistance spot welding method of high-strength steel sheet
JP2013111586A (en) * 2011-11-25 2013-06-10 Jfe Steel Corp Resistance spot welding method for high-strength steel plate
JP2013151018A (en) * 2011-12-27 2013-08-08 Mazda Motor Corp Welding method

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109317801A (en) * 2018-12-03 2019-02-12 闫宇 A kind of microdot Welding of nickel-clad copper harness and copper sheet
JP7363240B2 (en) 2019-09-12 2023-10-18 マツダ株式会社 Resistance welding equipment and resistance welding method
WO2023117663A1 (en) * 2021-12-22 2023-06-29 Plansee Composite Materials Gmbh Spot-welding electrode cap

Also Published As

Publication number Publication date
JPWO2018181231A1 (en) 2019-04-04
KR20190126098A (en) 2019-11-08
CN110461528B (en) 2021-04-20
CN110461528A (en) 2019-11-15
JP6410003B1 (en) 2018-10-24
KR102225221B1 (en) 2021-03-08

Similar Documents

Publication Publication Date Title
JP6410003B1 (en) Method of manufacturing resistance spot welded joint
JP5359571B2 (en) Resistance welding method for high strength steel sheet and manufacturing method for resistance welding joint
JP6278154B2 (en) Resistance spot welding method and manufacturing method of welded member
WO2016088319A1 (en) Resistance spot welding method
JP5854172B2 (en) Resistance spot welding method
JP6593572B1 (en) Resistance spot welded joint manufacturing method
WO2018123350A1 (en) Resistance spot welding method
WO2015133099A1 (en) Resistive spot-welding method
JP7047535B2 (en) Resistance spot welding method
JP6168246B1 (en) Resistance spot welding method and manufacturing method of welded member
JP6399266B1 (en) Method of manufacturing resistance spot welded joint
WO2018159764A1 (en) Resistance spot welding method
JP6160581B2 (en) Resistance spot welding method
JP6584729B1 (en) Method of manufacturing resistance spot welded joint
JP7269191B2 (en) spot welding method
JP6372639B1 (en) Resistance spot welding method
JP6828831B1 (en) Resistance spot welding method, resistance spot welding joint manufacturing method
WO2023008263A1 (en) Resistance spot welding method
JP6811063B2 (en) Resistance spot welding method and resistance spot welding joint manufacturing method
JPH02200303A (en) Cold rolling method for extremely thin titanium alloy sheet
JPH04172184A (en) Aluminum alloy cladding plate and resistance spot welding method excellent in resistance spot weldability

Legal Events

Date Code Title Description
ENP Entry into the national phase

Ref document number: 2018530804

Country of ref document: JP

Kind code of ref document: A

121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 18777181

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 20197028628

Country of ref document: KR

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 18777181

Country of ref document: EP

Kind code of ref document: A1