WO2020045678A1 - Procédé de soudage par points par résistance - Google Patents

Procédé de soudage par points par résistance Download PDF

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Publication number
WO2020045678A1
WO2020045678A1 PCT/JP2019/034368 JP2019034368W WO2020045678A1 WO 2020045678 A1 WO2020045678 A1 WO 2020045678A1 JP 2019034368 W JP2019034368 W JP 2019034368W WO 2020045678 A1 WO2020045678 A1 WO 2020045678A1
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WO
WIPO (PCT)
Prior art keywords
energization
current
time
welding
main
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PCT/JP2019/034368
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English (en)
Japanese (ja)
Inventor
智伸 三浦
好則 大山
朋紀 柳川
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豊田鉄工株式会社
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Application filed by 豊田鉄工株式会社 filed Critical 豊田鉄工株式会社
Priority to JP2020539656A priority Critical patent/JPWO2020045678A1/ja
Publication of WO2020045678A1 publication Critical patent/WO2020045678A1/fr

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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
    • 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
    • B23K11/24—Electric supply or control circuits therefor

Definitions

  • the present invention relates to a resistance spot welding method, and more particularly, to a resistance spot welding method using an inverter DC welding machine.
  • press-formed steel sheets are often joined by spot welding, a type of resistance welding.
  • spot welding it is required to secure a nugget diameter that can secure the strength of the welded portion according to the plate thickness.
  • dust may occur in which the molten base metal scatters from the steel plate.
  • medium dust those that scatter from the overlapping surfaces of steel plates are called medium dust, and those that scatter from the contact surface between the steel plate and the electrode are called front dust. If such dust adheres to the car body of the automobile, the surface quality of the car body deteriorates. Further, if needle-shaped dust is left on the surface of the spot welded portion, the wire harness of the automobile may be damaged. Furthermore, if the scattered dust adheres to the movable part of the welding robot, the normal operation of the manufacturing equipment may be hindered.
  • Japanese Patent Application Laid-Open No. 2010-188408 discloses a two-stage current supply system in which the contact between the contact surfaces of the steel plates is improved by preliminary current supply and then the main current is supplied.
  • a spot welding method for suppressing generation of dust in welding is disclosed.
  • WO 2015/005134 discloses a method in which the steel sheet is covered with a coating having high electric resistance such as zinc oxide.
  • pre-energization is performed by pulsation energization that repeats energization and pause several times while pressing the steel sheet with the welding electrode, and then continuously for a longer time than the maximum energization time during pulsation energization
  • the pre-energization and the main energization are performed by pulsation energization, and the maximum current of the main energization is made higher than the maximum current of the pre-energization. A method of doing so is disclosed.
  • vibration due to thermal expansion and contraction is applied to the electrode contact surface of the steel sheet by repeatedly conducting and stopping during pre-energization, and the high melting point oxide layer is effectively eliminated outside the welded part.
  • the cooling effect of the electrode can be sufficiently exerted by suspending the current supply during the pulsation, and the rapid rise in the temperature of the welded portion can be suppressed. For this reason, adaptability between the contact surfaces of the steel plates can be improved in a short time.
  • an increase in current density at the contact interface can be suppressed and rapid nugget growth can be suppressed, generation of dust can be suppressed.
  • the nugget in the course of growth is too cold and temporarily becomes small, and the nugget is considered to be growing slowly while repeating expansion and contraction. .
  • the duration of the main energization is long in order to obtain a required nugget diameter.
  • the present inventors can suppress dust without increasing the welding time by adopting similar energizing conditions in pulsation energization using a DC power supply, based on knowledge about energizing conditions in an AC system. And proceeded with the study.
  • One aspect of the present invention is a method of performing resistance spot welding using an inverter DC type welding machine on a sheet assembly in which two or more steel sheets are overlapped.
  • the current value of the secondary current in the main current stage is 10 kA or less
  • the current supply time is 0.7 cycle or less based on 60 Hz
  • the pause time is such that the secondary current drops to 3 kA or less. It is a method to make time.
  • the energization time in the main energization stage is 0.3 cycles.
  • the pause time in the main energization stage is set to 0.2 cycle.
  • the number of pulses in the main energization stage is set to 40 times or more.
  • the use of the above method can suppress the dust without increasing the welding time.
  • FIG. 2 is a partially enlarged view of the current waveform of FIG. 1. It is a figure which shows the electric current waveform of the secondary side electric current (effective value) when the energization time of main energization performed by pulsation energization is set to 0.3 cycle, and a pause time is set to 0.1 cycle.
  • FIG. 4 is a partially enlarged view of the current waveform in FIG. 3.
  • 9 is a graph showing an example of a set waveform of a secondary current input to a power supply device in welding in which pre-energization and main energization are combined.
  • Hot stamped steel plate For the welding of the present method, a steel plate formed by hot stamping (hot press) (herein referred to as a hot stamped steel plate) may be used.
  • Hot stamping is a method in which a steel sheet material is heated to a temperature at which it can be quenched, austenitized, and then cooled and quenched simultaneously with press molding in a mold. Therefore, the hot stamped steel sheet has an oxide layer such as iron oxide on the surface.
  • the hot stamped steel sheet has a tensile strength of, for example, 1470 MPa or more.
  • a steel sheet (surface-treated hot-stamped steel sheet) obtained by subjecting a steel sheet material subjected to surface treatment such as zinc-based plating or aluminum-based plating to hot stamping may be used. Such plating is performed to prevent an oxide layer (scale) from being generated on the surface of the steel sheet when heated to a high temperature.
  • a surface-treated hot stamped steel sheet has an intermetallic compound or an iron-based solid solution formed on its surface by an alloying reaction between a zinc-based or aluminum-based plating film and a base steel, and further has an outer surface.
  • the surface-treated hot-stamped steel sheet has a higher contact resistance of 1 m ⁇ or more than a bare steel sheet, and generates a large amount of heat when energized.
  • Two or more hot stamped steel plates as described above are overlapped to form a plate assembly to be welded. It is preferable that any one of the steel plates to which the electrode contacts at the time of welding in the plate assembly is a surface-treated hot stamped steel plate.
  • Welding is performed by spot welding, which is a type of resistance welding. Welding is performed by a two-stage energization method that combines preliminary energization and main energization.
  • FIG. 5 shows an example of preliminary energization and main energization. This energization is for growing a nugget to be a weld.
  • the pre-energization is performed mainly for the purpose of improving the conformity of the region of the steel plate surface that contacts the electrode and the interface between the steel plates.
  • the welding machine uses an inverter DC type.
  • the inverter DC type has the advantage that the transformer (transformer) can be made smaller than other types such as a single-phase AC type, so that the inverter DC type can be mounted on a robot having a small payload.
  • the power supply device of the inverter type welding machine usually includes an inverter circuit (consisting of a switching element), a transformer and a rectifier circuit, and the AC pulse current (primary current) generated by the inverter circuit has a desired current value in the transformer. The current is converted into a current (secondary current), and the secondary current is passed between the electrodes as a welding current to perform welding.
  • the graph of FIG. 5 shows the waveform of the set secondary current.
  • the set waveforms of the pre-energization and the main energization that is, the set values of the durations t a and t b (or the number of pulses) and the currents I a and I b (the pulse heights) are input through a control device also called a timer.
  • the inverter direct current welding machine further includes a rectifier circuit on the secondary side of the transformer, and uses a secondary current converted into a direct current by the rectifier circuit as a welding current.
  • the inverter direct current welding machine for example, the one disclosed in JP-A-2000-158148 can be used. Any electrode can be used. For example, a DR (dome radius) type electrode can be used.
  • the DR electrode for example, one having a tip diameter of 6 mm and a tip curvature radius of 40 mm can be used. However, by setting the radius of curvature to 30 mm or less, the contact pressure acting on the steel plate at the electrode tip may be increased, and the effect of dispersing oxide on the steel plate surface may be increased.
  • the pressing force by this electrode can be set in a range usually used. However, by increasing the pressing force, the oxide layer on the steel sheet surface is broken and dispersed, and a part of the oxide layer is moved (excluded) in the direction outside the contact range of the electrode, thereby reducing the surface contact resistance.
  • the preliminary energization may be performed by continuous energization or pulsation energization.
  • FIG. 5 shows an example in which preliminary energization is performed by continuous energization.
  • the current value Ia is preferably set to 6 kA or less. This makes it possible to reduce the contact resistance on the steel sheet surface while suppressing the generation of dust. Further, it is preferable that the current value of the pre-energization be higher than the current value of the main energization.
  • the energization time t a of the preliminary energization it is preferable that the product I a t a between the energizing time and the current value set longer within a range equal to or less than 2 kA ⁇ ms. As a result, the effect of dispersing (removing) the oxide is increased, and the appropriate range of the current value can be expanded.
  • the main energization is started. As shown in FIG. 5, this energization is performed by pulsation energization using a DC current having a pulse waveform. At the boundary between the pre-energization, the current may be connected to the first pulse without turning off the current, or the first pulse may be entered after a minimum pause time.
  • the current value In this energized or less 10kA settings I b of the secondary side current. It should be noted that the current value may be changed gradually or within each pulse within a range of 10 kA or less as needed. For example, by gradually increasing the current value, it is possible to suppress the generation and rapid growth of the nugget at the time when the contact resistance is high at the beginning of energization. In general, the current in spot welding is controlled at a constant current.
  • the energization time (the pulse width of the set waveform of the secondary current) is set to 0.7 cycles (11.7 ms) or less.
  • the cycle referred to in the present application is a unit based on a frequency of 60 Hz, and one cycle is about 16.7 ms.
  • the pause time (pulse interval of the set waveform of the secondary current) is determined based on the response characteristic of the secondary current of the power supply device of the inverter DC welding machine. Since the secondary current generally responds to the change of the rectangular pulse of the primary current with a delay, the secondary current actually flowing between the electrodes even if the current value of the set waveform suddenly drops to 0 as shown in FIG.
  • the pause time is preferably such a time that the effective value of the secondary current drops to 3 kA or less.
  • the energization time can be 0.3 cycles (5 ms) and the pause time can be 0.2 cycles (3.3 ms).
  • the upper limit of the pause time may be set so that a required nugget diameter is obtained. If the pause time is long, the secondary side current value drops to 0, but there is no problem if the nugget grows. However, if the downtime is lengthened, the entire welding time becomes longer. Therefore, in order to increase the production efficiency, for example, the time may be reduced to 3 kA or less.
  • the number of pulses in the main energization is set according to the other conditions described above so that a desired nugget diameter can be achieved.
  • the number of pulses can be 40 or more.
  • the number of pulses varies depending on the nugget diameter as a target value for the plate thickness t (for example, 5 ⁇ t). If the pulse waveform (i.e. energizing time and pause time) is constant, the duration t b of the current is determined by the number of pulses. Those skilled in the art can determine the number of pulses experimentally or empirically from the total energizing time.
  • Hot stamping was performed on a 1470 MPa alloyed hot-dip galvanized steel sheet (GA) material having a thickness of 1.4 mm, a width of 30 mm, and a length of 100 mm, thereby preparing two hot stamped steel sheet samples.
  • Resistance spot welding was carried out by a two-stage energization method on a plate assembly in which the two samples were overlapped.
  • the spot welding machine used was an inverter DC type equipped with a DR type electrode (made of chrome copper) having a tip curved surface portion having a diameter of 6 mm and a curvature radius of 40 mm.
  • the preliminary energization was performed by continuous energization, the current set value was 4 kA, the energization time was 6 cycles (100 ms), and the pressing force was 4.5 kN.
  • This energization was performed by pulsation energization.
  • the current setting value of the main energization was variously changed, and the energization time and the pause time of the pulsation were variously changed in units of 0.1 cycle.
  • the pressurizing force at the time of this energization was 4.5 kN.
  • FIGS. 2 and 4 are partial enlarged views of the current waveforms of FIGS.
  • Table 1 shows that if the energization time is 0.7 cycles or less, dust does not occur when the lower limit of the current dropped during the pause time falls below 3 kA (conditions 3, 5, 6, 7, and 9). Can be read. 2 and 4, the lower limit of 3.0 kA is indicated by a broken line for easy understanding. In particular, it was found that when the power-supply time was 0.3 cycles (5 ms) and the pause time was 0.2 cycles (3.3 ms) (condition 3), the duration of the main power-supply could be extremely short.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Resistance Welding (AREA)

Abstract

La présente invention concerne un procédé de réalisation d'un soudage par points par résistance à l'aide d'une machine de soudage à courant continu à onduleur sur un ensemble de tôles obtenu par chevauchement de deux tôles d'acier ou plus. Selon l'invention : le procédé comprend une étape de conduction de courant électrique préliminaire, et une étape de conduction de courant électrique principale réalisée par conduction d'un courant électrique pulsé ; la valeur d'un courant côté secondaire dans l'étape de conduction de courant électrique principale est réglée à 10 kA ou moins ; un temps de conduction de courant électrique est réglé à 0,7 cycle ou moins en se basant sur 60 Hz ; et un temps de veille est réglé à un temps tel que le courant côté secondaire descend jusqu'à 3 kA ou moins.
PCT/JP2019/034368 2018-08-31 2019-09-02 Procédé de soudage par points par résistance WO2020045678A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114850643A (zh) * 2021-02-04 2022-08-05 杭州宝伟汽车零部件有限公司 超高强度热成形钢板点焊方法
WO2022219968A1 (fr) * 2021-04-12 2022-10-20 Ｊｆｅスチール株式会社 Procédé de soudage par points par résistance

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008093726A (ja) * 2006-10-16 2008-04-24 Nippon Steel Corp 重ね抵抗スポット溶接方法
JP2010207909A (ja) * 2009-02-12 2010-09-24 Sumitomo Metal Ind Ltd 高張力鋼板の抵抗溶接方法および抵抗溶接継手の製造方法
JP2010247215A (ja) * 2009-04-20 2010-11-04 Sumitomo Metal Ind Ltd 高張力鋼板の抵抗溶接方法

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6137337B2 (ja) * 2013-12-20 2017-05-31 新日鐵住金株式会社 抵抗スポット溶接方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008093726A (ja) * 2006-10-16 2008-04-24 Nippon Steel Corp 重ね抵抗スポット溶接方法
JP2010207909A (ja) * 2009-02-12 2010-09-24 Sumitomo Metal Ind Ltd 高張力鋼板の抵抗溶接方法および抵抗溶接継手の製造方法
JP2010247215A (ja) * 2009-04-20 2010-11-04 Sumitomo Metal Ind Ltd 高張力鋼板の抵抗溶接方法

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114850643A (zh) * 2021-02-04 2022-08-05 杭州宝伟汽车零部件有限公司 超高强度热成形钢板点焊方法
WO2022219968A1 (fr) * 2021-04-12 2022-10-20 Ｊｆｅスチール株式会社 Procédé de soudage par points par résistance

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