JP2010082665A - Welding apparatus for metallic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding apparatus for metallic materials by which a heat treatment such as a tempering treatment is performed by a partial temperature rising in temperature in a spot welding. <P>SOLUTION: In the welding apparatus 1 for metallic materials, a metallic material 9 is clamped with a pair of electrodes 4, 4, and energized with the position of the pair of electrodes 4, 4 maintained in one region relative to the metallic material 9, and different regions of the metallic material 9 are heated. The apparatus 1 includes: a first heating means 6 that is connected to the pair of electrodes 4, 4 and applies an electric power of a low first frequency to the metallic material 9 to heat and weld the inside of a circle for which the axial cross section of the electrode is projected to the metallic material; a second heating means 8 that applies an electric power of a second frequency higher than the first to heat a ring-shaped region along the circle; and an energization controller 10 that independently controls the first and second heating means 6, 8 respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a metal material welding apparatus. More specifically, the present invention relates to a metal material welding apparatus for forming a nugget on a work that is a metal material with power from a spot welding power source and further heating the work with power from a high frequency power source.

A spot welding apparatus is used for welding stacked steel plates. FIG. 24 is a cross-sectional view schematically showing spot welding between the steel plates 50. As shown in FIG. 24, spot welding between the steel plates 50 is performed by sandwiching the overlapping portion of the steel plates 50 with a pair of electrodes 52 and applying a predetermined force to the electrodes 52 in the direction of the arrows to press the steel plates 50 together. .
Next, a large current of kA order is applied to the electrode 52 while maintaining the pressurized state, and the crimped portion between the steel plates 50 is instantaneously melted by Joule heating to form a molten lump called a nugget 54 having a predetermined diameter. (For example, refer nonpatent literature 1).

In recent years, in spot welding used in a vehicle production line, an ultra-high-strength steel sheet has been used as a material for a vehicle body in order to achieve both weight reduction and safety of the vehicle.
FIG. 25 is a plan view of a sample used in a tensile test for investigating the spot weld strength of a high-tensile steel plate, where (A) shows a sample of a lap joint and (B) shows a sample of a cross joint. . In the sample of the overlap joint shown in FIG. 25 (A), two rectangular steel plates 50 are overlapped at the ends in the longitudinal direction and spot welded at the ends. In the cross-joint sample shown in FIG. 25B, two rectangular steel plates 50 are crossed in a cross shape, and the crossing spot is spot-welded. A substantially oval portion surrounded by a dotted line is a nugget 54 formed by welding, and a force 56 applied in a tensile test is indicated by an arrow.

  In the spot weld strength of high-tensile steel plates, the tensile strength of the lap joint increases as the material strength increases, but the peel strength of the cross joint does not increase easily as the material strength increases. It has been reported that it becomes difficult. The reason why a stable tensile strength cannot be obtained with a peeling type load of the cross joint is that the stress concentration on the circumference of the nugget 54 is extremely high and the strength of the base material is high, It is considered that the increase in the surrounding restraining force occurs at the same time. For this reason, in order to ensure the toughness of the weld zone strength, when applying a high strength steel plate to the actual vehicle body, the compositional surface such as keeping the carbon amount below a certain level so that the weld zone does not become too hard. The current situation is that they are regulated by

  On the other hand, the use of a high-strength steel plate is a method that can efficiently reduce the weight of the vehicle body, and a high-strength steel plate that has improved both strength and ductility is desired. Further weight reduction can be expected by further improving the strength of the steel plate for vehicle bodies. By improving the ductility of the steel plate for vehicle bodies, it is possible to ensure press formability and sufficient deformability at the time of collision in the product state. Usually, a steel plate for a vehicle body tends to decrease ductility when the strength is increased. It is effective to increase the carbon content of the material to improve the strength and ductility of the steel plate for car bodies at the same time. .

  Various efforts have been made so far to solve the strength of such spot welds by a welding method. For example, after forming the melt-bonded portion to a predetermined size, it has been attempted to perform tempering by post-energization. However, in resistance spot welding for assembling the car body, the process time required per one hit point is required to be within 1 second at most, and the tempering effect is extremely limited when the current welding equipment is tempered by post-energization. Will be. Or when it is going to acquire sufficient effect by tempering, the time which exceeds the request | requirement time of a process significantly is needed. This is based on the basic problem of resistance welding in that since the current density of the welded portion decreases due to the increase in the energization area after the nugget 54 is formed, efficient heat generation cannot be obtained in a short time. .

  Further, Patent Document 1 discloses a spot welding apparatus including a spot welder and high-frequency induction heating means in order to improve the fatigue strength of a spot welded portion of a high-tensile steel plate. The high-frequency induction heating means includes a heating coil that induction-heats a welded portion of a workpiece and a high-frequency power source that supplies high-frequency power to the heating coil.

JP 2005-21934 A Edited by the Japan Welding Society, “Welding and Joining Handbook”, Maruzen Co., Ltd., September 30, 1990, pp. 392-398

  In an apparatus for heating while welding a pair of electrodes between metal materials, the heating location is only a method with the center of the electrode as the apex, and the temperature profile is only a single one. For example, in the spot welding apparatus of patent document 1, the space for installing the heating coil which induction-heats the to-be-welded part of a workpiece | work is needed. However, since the periphery of the electrode of the spot welding apparatus is very narrow, it is difficult to separately install a new heating means. That is, the heating coil becomes larger than the electrode diameter of the spot welder. For this reason, there exists a subject that only the outer periphery of the nugget 54 which needs reheating most cannot be heated.

  In view of the above problems, an object of the present invention is to provide a metal material welding apparatus capable of performing heat treatment such as tempering by partial temperature increase in spot welding.

In order to achieve the above-mentioned object, the metal material welding apparatus of the present invention has a metal material different between metal materials by sandwiching the metal material between a pair of electrodes and maintaining the pair of electrodes in the same position with respect to the metal material. A welding apparatus for a metal material for heating an area, wherein the first heating means is connected to a pair of electrodes and applies power of a first frequency to the metal material to heat a predetermined area, and is connected to the pair of electrodes. Energization control for independently controlling the second heating means for applying power of the second frequency to the metal material to heat the area different from the predetermined area, and the first heating means and the second heating means, respectively. And a section.
In the above configuration, the inside of the predetermined region of the metal material is heated by the first heating unit, the vicinity of the predetermined region of the metal material is heated by the second heating unit, the heating by the first heating unit and the second heating unit Heating by the heating means may be controlled independently by the energization control unit.
The first heating means is a heating means for heating the inside of the circle in which the axial cross section of the electrode is projected on the metal material, and the second heating means is along a circle in which the axial cross section of the electrode is projected on the metal material. It is a heating means which heats the area | region which makes a ring shape, and the heating by a 1st heating means and the heating by a 2nd heating means may be independently controlled by the electricity supply control part.
The first frequency may be lower than the second frequency, and the circular interior may be welded by supplying power of the first frequency to the metal material. The second frequency is higher than the first frequency, and when the power of the second frequency is applied to the metal material, the ring-shaped region is resistance-heated, or resistance heating and high-frequency induction heating are performed. Also good.

  In order to achieve the above object, a metal material welding apparatus according to the present invention includes a pair of electrodes arranged so as to sandwich the metal material, a welding power source for supplying welding power to the pair of electrodes, and a pair of electrodes. A high-frequency power source for supplying high-frequency power, a welding power source and a high-frequency power source are respectively connected in parallel to the pair of electrodes, and a current blocking inductance is connected between the welding power source and the pair of electrodes. A current blocking capacitor is connected between the power source and the pair of electrodes, and the current blocking inductance prevents the high frequency current supplied from the high frequency power source to the pair of electrodes from flowing into the welding power source, thereby blocking the current. The capacitor is characterized in that current supplied from the welding power source to the pair of electrodes is prevented from flowing into the high frequency power source side.

  According to the above configuration, the power supply for spot welding connected via the current blocking inductance and the high frequency power supply connected to the pair of electrodes via the current blocking capacitor are provided. Thus, a welding apparatus capable of supplying each power to the metal material is obtained. For this reason, a high frequency voltage can be applied through a pair of electrodes for spot welding, and the metal material can be heated by direct energization of the outer periphery of the electrodes.

  Further, the metal material welding apparatus may include a gun arm, and a spot welding power source and a high-frequency power source may be connected to the pair of electrodes via the gun arm. You may provide the electricity supply control part which controls an output time and an output current with respect to the power supply for welding and a high frequency power supply, respectively. The welding power source may be a low frequency power source. This low-frequency power source can be configured by being connected to a pair of electrodes via a transformer, and a bypass capacitor being connected in parallel to the winding on the pair of electrodes of the transformer.

  The welding power source may be a DC power source. A series resonance circuit can be constituted by the current blocking capacitor and the current blocking inductance. A parallel resonance circuit may be configured by the current blocking inductance and the parallel resonance capacitors connected to the upper and lower portions of the gun arm. The stray inductance of the gun arm can be used as the current blocking inductance. The high-frequency power source may be fed directly to the electrode side through a current blocking capacitor, or may be fed from the gun arm side root.

  According to the said structure, while performing spot welding according to the material of a metal material, the direct heating by the high frequency power supply can be efficiently and quickly performed for the nugget outer periphery formed by the spot welding of the metal material.

  According to the present invention, a high-frequency power source is connected to an electrode of a metal welding apparatus with a simple apparatus configuration, the outer periphery of the electrode can be heated via the same electrode, and the heat treatment of the spot-welded nugget periphery is performed. It is possible to provide a metal material welding apparatus capable of performing the above in a short time. Furthermore, free heat treatment can be performed by changing the frequency of the high frequency.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Metal welding equipment)
FIG. 1 is a diagram schematically illustrating an example of a configuration of a metal welding apparatus 1 according to an embodiment of the present invention.
A metal welding apparatus 1 includes an electrode arm 2, an electrode support 3 having one end connected to the upper part 2 </ b> A and the lower part 2 </ b> B of the electrode arm 2, and a pair connected to the other end of each electrode support 3. Electrode 4, welding power source 6 connected to electrode arm 2 via inductance 5, high frequency power source 8 connected to electrode arm 2 via capacitor 7, welding power source 6 and high frequency power source 8. And an energization control unit 10 that performs output control.
Although not shown, the metal welding apparatus 1 is a fixed base that supports the electrode arm 2, a drive mechanism that drives the electrode arm 2, and a pressing mechanism that pushes one electrode 4 out of the electrode support portion 3 (not shown). Etc.). The pressing mechanism is used for pressurizing the metal material 9 to be a welded member, which will be described later, with the electrodes 4 and 4.

  The electrode arm 2 includes an upper portion 2A and a lower portion 2B, and is connected to the electrodes 4 and 4 via the electrode support portions 3, respectively. The electrode arm 2 is also called a gun arm. The gun arm 2 shown in the figure has a so-called C-shape and is called a C-type gun arm. In a portable type or robot type welding apparatus, an X type gun or the like is used in addition to the C type gun arm 2. Any shape of the electrode arm 2 can be applied, but in the following description, the C-type gun arm 2 is assumed.

  The pair of electrodes 4 and 4 are opposed to each other with a gap, and two steel plates 9 are inserted as metal materials 9 into the gap. The electrode 4 is made of, for example, a copper material, and has a circular or elliptical shape or a rod shape.

FIG. 2 is an electric circuit diagram of the metal material welding apparatus 1 shown in FIG.
As shown in FIG. 2, the electric circuit of the metal material welding apparatus 1 includes a welding circuit portion 1A and a welding portion 1B surrounded by a dotted line. The welding circuit unit 1 </ b> A includes a welding power source 6, a high frequency power source 8, an inductance 5, a capacitor 7, and an electric circuit such as an energization control unit 10 that performs output control of the welding power source 6 and the high frequency power source 8. The welded portion 1B is a circuit that is electrically connected to the welding circuit portion 1A, and is a metal sandwiched between the gun arm 2, the pair of electrodes 4, 4 that are electrically connected to the gun arm 2, and the pair of electrodes 4, 4. It is comprised from the material 9.
The welding power source 6 is a low-frequency power source. For example, the commercial power source 12 having an output frequency of 50 Hz or 60 Hz, the low-frequency power source control unit 14 connected to one end of the commercial power source 12, and the other end of the commercial power source 12 are low. A welding transformer 16 connected to the output end of the frequency power supply control unit 14. Both ends of the secondary winding of the welding transformer 16 are connected to the left end of the upper part 2A and the left end of the lower part 2B of the C-type gun arm 2, respectively. The low frequency power supply control unit 14 includes a power control semiconductor element such as a thyristor, a gate drive circuit, and the like, and performs energization control from the commercial power supply 12 to the electrode 4.

  A bypass capacitor 11 is connected in parallel to the C-type gun arm 2 side of the welding transformer 16, that is, the secondary winding 16A. The bypass capacitor 11 has a low capacitive impedance with respect to the frequency of the high frequency power supply 8. For this reason, the voltage by which the high frequency voltage from the high frequency power supply 8 is applied to the secondary winding 16A can be minimized, and the high frequency induced voltage to the primary side of the welding transformer 16 can be lowered.

  The high-frequency power source 8 includes an oscillator 18 and a matching transformer 20 connected to the output terminal of the oscillator 18. One end of the matching transformer 20 is connected to the upper part 2 </ b> A of the C-type gun arm 2. The other end of the matching transformer 20 is connected to the lower part 2 </ b> B of the C-type gun arm 2 via the capacitor 7. The capacitor 7 can also serve as a matching capacitor for a series resonance circuit described later. The capacitance value of the capacitor 7 depends on the oscillation frequency of the oscillator 18 and the stray inductance 5 of the C-type gun arm 2. The oscillator 18 includes an inverter using various transistors, and controls the energization power of the high frequency power supply 8 to the electrode 4.

  As shown in FIG. 2, the path from the C-type gun arm 2 connected to the secondary winding of the welding transformer 16 to the electrodes 4 and 4 has an inductance 5. As the inductance 5, a stray inductance formed by the C-type gun arm 2 can be used.

  When the capacitor 7 also serves as a matching capacitor, a series resonance circuit may be configured by the matching capacitor 7 and the inductance 5.

(Modification 1 of metal material welding apparatus)
FIG. 3 is an electric circuit diagram showing Modification 1 of the metal material welding apparatus.
In the electric circuit of the metal welding apparatus 25 shown in FIG. 3, the high frequency power supply 8 is connected to the electrodes 4 and 4 via the C-type gun arm 2 in the electric circuit of the metal welding apparatus 1 shown in FIG. On the other hand, it is directly connected to the pair of electrodes 4 and 4 without using the C-type gun arm 2. The high frequency power supply 8 may be connected to the base of the electrodes 4 and 4 via the capacitor 7. The other circuit configuration is the same as that of the electric circuit shown in FIG.

(Variation 2 of metal material welding apparatus)
FIG. 4 is an electric circuit diagram showing a second modification of the metal material welding apparatus.
The electric circuit of the metal material welding apparatus 30 shown in FIG. 4 is different from the metal material welding apparatus 1 shown in FIG. 2 in that a capacitor 32 for parallel resonance is connected in parallel between the pair of electrodes 4 and 4. Yes. That is, the capacitor 32 for parallel resonance is connected in parallel to the upper part 2A and the lower part 2B of the C-type gun arm 2. Accordingly, the parallel resonance capacitor 32 and the inductance 5 constitute a parallel resonance circuit. In this case, the capacitor 7 has a function of blocking a low frequency current from the low frequency power source 6. The other circuit configuration is the same as that of the circuit shown in FIG.

(Separation of low frequency power supply 6 and high frequency power supply 8)
The relationship between the low frequency power supply 6 and the high frequency power supply 8 will be described.
An inductance 5 and a capacitor 7 are connected between the low-frequency power source 6 and the high-frequency power source 8, and an inductive reactance X _L (X _L = 2πf _L ) due to the inductance 5 (L) at a low frequency (f _L ). L, where f _L is the frequency of the low frequency power supply 6 and L is the value of the inductance 5.) is small at low frequencies.
On the other hand, the capacitive reactance X _C (X _C = 1 / (2πf _L C)) due to the capacitor 7 (C) becomes a large value at a low frequency (f _L ). Therefore, current leakage to the high-frequency power source 8 of the low-frequency power source 6 is blocked by the large capacitive reactance X _C of the capacitor 7 at low frequency (f _L). That is, the capacitor 7 serves as a low frequency current blocking capacitor.

Of the impedance when the low-frequency power source 6 is viewed from the high-frequency power source 8, the capacitive reactance X _C (X _L = 1 / (2πf _H C) of the high frequency (f _H ), where f _L is the high-frequency power source 8. Is a small value at high frequencies.
On the other hand, at a high frequency, the inductive reactance X _L (X _L = 2πf _H L, where f _H is the frequency of the high frequency power supply 8) due to the inductance 5 becomes a large value. Therefore, current leakage to the low-frequency power source 6 of the high-frequency power source 8 is blocked by the large inductive reactance X _L of the inductance 5 at high frequency (f _H). That is, the inductance 5 is a high frequency current blocking inductance.

  In the metal welding apparatuses 1, 25, 30, the capacitor 7 acts as a current blocking capacitor from the low frequency power supply 6 to the high frequency power supply 8, and the inductance 5 is a current blocking inductance from the high frequency power supply 8 to the low frequency power supply 6. That is, it acts as a choke coil.

The C-type gun arm 2 has various shapes depending on the size of the steel plate 9 to be spot welded. Therefore, if the floating inductance 5 of the C-type gun arm 2 is not large, in the welding apparatus 1,25,30 of the metal material, for high-frequency current blocking to a predetermined inductive reactance X _L at high frequency inductance 13 May be further added. This external inductance 13 can be connected to the secondary winding side of the welding transformer 16 on the low frequency power source 6 side, for example.

  The features of the metal welding apparatus 1, 25, 30 of the present invention are that the low frequency power supply 6 and the high frequency power supply 8 are separated by the inductance 5 and the capacitor 7, and the low frequency power supply 6 and the high frequency are provided on the electrode 4. Two power sources having different frequencies from the power source 8 can be simultaneously applied.

(Current distribution in the steel sheet)
FIG. 5 is a cross-sectional view schematically showing a current distribution generated in the steel sheet 9 when power is simultaneously applied to the two superposed steel sheets 9 from the low frequency power source 6 and the high frequency power source 8. It is a figure which shows the heating state of 9.
In FIG. 5, the solid line represents the high-frequency current 22 from the high-frequency power supply 8, and the dotted line represents the low-frequency current 24 from the low-frequency power supply 6. The electrode 4 is made of copper, has a diameter of 6 mm, and the frequency of the low frequency power supply 6 is 50 Hz. The thickness of one steel plate 9 is 2 mm, and the frequency of the high-frequency power supply 8 is 40 kHz. The low frequency current 24 flows through the entire inside of the electrodes 4 and 4, and the steel plate 9 is energized with a cross-sectional area width of approximately the nugget diameter.

  FIG. 6A is a plan view showing a heating region of the steel plate 9 by only the low frequency current 24, and a circular interior 9A obtained by projecting the axial cross section of the electrode 4 onto the steel plate 9 is a main heating region. 6B is a temperature distribution in the XX direction of FIG. 6A. In the steel plate 9, a circular interior 9A obtained by projecting the axial cross section of the electrode 4 onto the steel plate 9 is intensively heated.

On the other hand, the high-frequency current 22 is concentrated on the surface of the electrode 4 and the outer peripheral region of the nugget. The difference between the low frequency current 24 and the high frequency current 22 is related to the so-called skin thickness.
FIG. 6C is a plan view showing a heating region of the steel plate 9 by only the high-frequency current 22, and the outer circumference of the electrode 4 projected on the steel plate 9 and the vicinity of the outer circle, that is, a circular outer shape forming a ring shape. The ring-shaped neighboring region 9B becomes the main heating region. 6D is a temperature distribution in the XX direction of FIG. 6C, and in the steel plate 9, an outer circumferential circle obtained by projecting the axial cross section of the electrode 4 onto the steel plate 9, and a substantially ring-shaped region 9B in the vicinity of the outer circumferential circle. Is heated by resistance. In this case, the heating by the high frequency current 22 includes a region where the adjacent steel plate 9 is induction heated by the high frequency current 22 flowing on the surface of the electrode 4. This induction heating is different from normal induction heating using an induction heating coil. Accordingly, the projected outer circumference circle projected onto the steel plate 9 by the high-frequency current 22 and the ring-shaped region 9B in the vicinity of the outer circumference circle are heated by resistance heating by the high-frequency current 22 or heating in which the high-frequency induction heating is superimposed with this resistance heating. It can be carried out.

  In FIG. 6D, the width of the ring-shaped region 9B can be changed by further changing the operating frequency of the high-frequency power source 8. In fact, when spot welding was performed by applying the low frequency current 24, it was confirmed that the width of the high temperature region of the nugget outer peripheral region was changed when the operating frequency of the high frequency power source 8 was changed. Accordingly, the outer circumferential circle projected onto the steel plate 9 by the high-frequency current 22 and the ring-shaped region 9B in the vicinity of the outer circumferential circle are heated by resistance heating by the high-frequency current 22 or heating in which the high-frequency induction heating is superimposed with this resistance heating. Can do.

  Therefore, when electric power is simultaneously applied from the low frequency power source 6 and the high frequency power source 8 to the two stacked steel plates 9, the heating region of the steel plate 9 is a passage region of the low frequency current 24 as shown in FIG. The circular interior 9 </ b> A and the ring-shaped region 9 </ b> B that becomes the region through which the high-frequency current 22 passes are superimposed. Further, the temperature distribution of the steel sheet 9 generated by these currents 22 and 24 is as follows. As shown in FIG. 6F, the temperature distribution by the low-frequency current 24 (see FIG. 6B) and the temperature distribution by the high-frequency current 22 (see FIG. 6 (D)) is superimposed. That is, in the steel plate 9, the circular interior 9 </ b> A in which the axial cross section of the electrode 4 is projected onto the steel plate 9, the outer circumference circle in which the axial cross section of the electrode 4 is projected onto the steel plate 9, and the ring-shaped region 9 </ b> B near the outer circumference circle are heated. .

(Skin thickness)
The skin thickness (δ) is expressed by the following equation (1).
δ = 503.3 × (ρ / (μ × f)) ^1/2 (m) (1)
Here, ρ is the resistivity (Ω · m) of the material, μ is the relative permeability of the material, and f is the frequency (Hz).
The skin thickness changes with the power of 1/2 of the frequency. Therefore, the lower the frequency, the thicker the material, and the thinner the higher the frequency. In general, since the power source for spot welding is 50 Hz or 60 Hz, if the electrode has a diameter of about 6 mm, the current flows through the entire electrode.

On the other hand, the frequency of the high frequency power supply 8 when heating only the surface of the steel plate 9 can be set so as to have a predetermined skin thickness according to the above equation (1). Therefore, the frequency may be set in order to select the heating width of the nugget outer peripheral region.
That is, by changing the frequency of the high-frequency current 22, the heating width of the nugget outer peripheral region can be changed, and the ring-shaped region 9B can be subjected to heat treatment such as tempering. Therefore, when the steel plate 9 uses a relatively soft material, for example, an S20C annealed material, the ring-shaped region 9B can be softened.
In the material, the magnitude of the high-frequency current 22 at the depth of the skin thickness is 1 / e of the outermost surface (where e is a natural logarithm), that is, about 1/3. The skin thickness of the steel plate 9 is about 9.3 mm at a frequency of 50 Hz, and about 0.3 mm at a frequency of 40 kHz.

(Frequency selection of high frequency power supply)
The frequency of the high-frequency power supply 8 is determined by the inductance 5 connected to the secondary winding side of the welding transformer 16, the inductance 13 further inserted as necessary, and the capacity of the matching capacitor 7. When the stray inductance of the gun arm 2 is used as the inductance 5, the inductance 5 is determined by the shape of the gun arm 2. For this reason, the value of the matching capacitor 7 determines the frequency. When the frequency is increased, the heating pattern in the outer peripheral region becomes local due to the skin effect, and the heating width becomes narrower. However, since the inductance 5 (ωL) of the gun arm 2 is proportional to the frequency, the voltage of the matching capacitor 7 also increases. A circuit in which the electrodes 4 and 4 are viewed from the high-frequency power supply 8 is a series resonance circuit. At the series resonance frequency, the voltage of the inductance 5 and the voltage of the matching capacitor 7 are the same. Therefore, if the voltage of the matching capacitor 7 is increased, it becomes difficult to synthesize the two frequencies of the low frequency and the high frequency. 13 is required. The large current blocking inductances 5 and 13 also affect the low frequency current 24, and the secondary voltage of the conventional spot welder needs to be significantly increased.

Conversely, when the series resonance frequency is lowered, the heating pattern of the temperature increase pattern in the nugget outer peripheral region becomes wide, but the voltage of the matching capacitor 7 becomes low, so that the two-frequency synthesis becomes easy.
Further, it is necessary to mount a welding transformer 16, a bypass capacitor 11, and a current blocking inductance 13 as necessary on the gun arm 2. Among these, the weight of the welding transformer 16 is the heaviest. The weight of the welding transformer 16 is inversely proportional to the frequency. Considering the above, the operating frequency is optimally 5 kHz to 40 kHz. However, this is not the case when the gun arm 2 is not mounted on a welding apparatus such as a welding robot. Further, the difference in frequency between the low frequency and the high frequency is preferably 10 times or more from the viewpoint of the two-frequency synthesis circuit.

(Heat treatment using metal welding equipment)
The spot welding and heat treatment by the metal material welding apparatus 1, 25, 30 of the present invention will be described.
The metal material 9 is welded by sandwiching the metal material 9 between the pair of electrodes 4 and 4 and heating the metal material 9 by energization. As an example, the first step of heating a predetermined region of the metal material 9 by the first energization of the pair of electrodes 4 and 4 and the position of the pair of electrodes 4 and 4 sandwiching the metal material 9 are the same as the first step. A second step of heating a region different from the first step by second energization of the pair of electrodes 4 and 4 while maintaining the position may be provided. Here, the heating time of the first step and the second step can be controlled independently. When the first energization is energization from the low-frequency power source 6, the predetermined heating region of the metal material 9 by the first energization is the circular interior 9A described above. When the second energization is the energization from the high frequency power supply 8, the predetermined heating region of the metal material 9 by the first energization is the ring-shaped region 9B described above. The above first step and second step may be combined.

7 to 9 are diagrams schematically illustrating waveforms of currents flowing through the pair of electrodes 4 and 4. 7 to 9, the horizontal axis represents time (arbitrary scale), and the vertical axis represents current waveforms 22 and 24 (arbitrary scale) applied from the low-frequency power source 6 and the high-frequency power source 8.
FIG. 7 is a diagram showing a heating waveform when spot welding and heat treatment are simultaneously performed by the power from the low-frequency power source 6 and the power from the high-frequency power source 8.
As shown in FIG. 7, the entire nugget formed by welding is heated by the electric power from the low-frequency power source 6, and the nugget outer peripheral region is simultaneously heated by the electric power from the high-frequency power source 8. Here, the whole nugget corresponds to a circular interior 9 </ b> A obtained by projecting the axial cross section of the electrode 4 onto the steel plate 9. The nugget outer peripheral region corresponds to an outer peripheral circle obtained by projecting the axial cross section of the electrode 4 onto the steel plate 9 and a ring-shaped region 9B in the vicinity of the outer peripheral circle.

  According to the metal material welding apparatus 1, 25, 30 of the present invention, spot welding between steel plates 9 is performed by the low frequency power source 6 from the current distribution when the power from the low frequency power source 6 and the high frequency power source 8 are simultaneously applied. In addition, the electrode outer peripheral surface of the region not in contact with the electrode 4 of the two steel plates 9 can be heated by the high frequency power source 8.

FIG. 8 is a diagram illustrating a heating waveform when power from the high-frequency power source 8 is applied after power from the low-frequency power source 6 is applied.
As shown in FIG. 8, when power is applied from the low-frequency power source 6 and then is stopped, and then power is applied from the high-frequency power source 8, the steel plates 9 are spot welded together by power application from the low-frequency power source 6. The surface of the area | region which is not in contact with the electrode 4 of the nugget outer peripheral area | region of the two steel plates 9 is heated by power application from the high frequency power supply 8 after that.
Thereby, according to the welding apparatus 1,25,30 of the metal material of this invention, the outer periphery of the nugget formed by spot welding by applying electric power from the high frequency power supply 8 after applying electric power from the low frequency power supply 6 Heat treatment of the region (sometimes referred to as annealing) can be performed. By adjusting the temperature and heating time of this heat treatment, it can be applied to a heat treatment such as a tempering treatment of the steel plate 9 or the like.

FIG. 9 is a diagram showing a heating waveform in the case of performing preheating using the high frequency power supply 8 before applying power from the low frequency power supply 6.
As shown in FIG. 9, when power is applied from the low-frequency power source 6 after power is applied from the high-frequency power source 8, the surface of the region where the steel plates 9 are not spot-welded first, that is, the copper electrode 4 is contacted. A nearby region that is not heated is heated. Two steel plates 9 are spot-welded by applying electric power from the low-frequency power source 6 after this preheating.
Thereby, according to the metal material welding apparatus 1, 25, 30 of the present invention, by applying power from the low-frequency power source 6 after applying power from the high-frequency power source 8, It can also be pre-heated before being welded. By adjusting the preheating temperature and heating time, quenching caused by spot welding can be prevented.

(Modification of heat treatment using metal welding equipment)
Still another heating method by the metal welding apparatus 1 will be described.
FIGS. 10-12 is a figure which shows an example of the current waveform sent through a pair of electrode. The horizontal axis represents time (arbitrary scale), and the vertical axis represents current waveforms 22 and 24 (arbitrary scale) applied to the pair of electrodes from the low-frequency power source 6 and the high-frequency power source 8.
FIG. 10 is a diagram showing a heating waveform in the case where preheating using the high-frequency power supply 8, heating using the low-frequency power supply 6, and post-heating using the high-frequency power supply 8 are continuously performed. The term afterheating is used to mean heating after the preheating. That is, the post-heat indicates a heat treatment after the steel plate 9 is spot welded using the low frequency power source 6.
When the power from the low frequency power source 6 is applied after the power from the high frequency power source 8 is applied, the surface of the region where the steel plates 9 are not spot welded is first heated. The two steel plates 9 are spot welded by application of electric power from the low-frequency power source 6 after this preheating. Furthermore, the heat treatment of the outer peripheral region of the nugget formed by spot welding can be performed by the post-heating by the electric power from the high-frequency power source 8. By adjusting the temperature and heating time of this heat treatment, it can be applied to a heat treatment such as a tempering treatment of the steel plate 9 or the like.

FIG. 11 is a diagram showing a heating waveform in the case where preheating is performed using the high frequency power source 8 and partial simultaneous heating is performed using the high frequency power source 8 and the low frequency power source 6.
As shown in FIG. 11, the power from the high frequency power supply 8 is applied for a preheating time and a predetermined time immediately after the application time of the power from the low frequency power supply 6. That is, power is superimposed from the high frequency power supply 8 only in the initial period of application of power from the low frequency power supply 6. The effect of preheating is the same as that of the heating method of FIG. Moreover, since the electric power from the low frequency power source 6 and the high frequency power source 8 is partially superimposed and applied to the steel plate 9, spot welding is performed in the same manner as in the simultaneous heating method of FIG. The outer peripheral surface of the electrode 4 in a region not in contact with 4 can be heated by the electric power from the high frequency power supply 8.

FIG. 12 shows a heating waveform in the case where heating using the low frequency power source 6 and post-heating using the high frequency power source 8 are performed, and partial simultaneous heating is performed using the low frequency power source 6 and the high frequency power source 8. FIG.
As shown in FIG. 12, the power from the high frequency power supply 8 is applied for a predetermined time before the application of the low frequency power supply 6 is finished and for a time after heat. Since the power from the low-frequency power source 6 and the high-frequency power source 8 is partially superimposed, the electrode 4 in the region that is not in contact with the electrodes 4 of the two steel plates 9 while performing spot welding similarly to the heating waveform of FIG. Can be heated by a high-frequency power source 8. The effect of post-heating is the same as that of the heating method of FIG.

  Since the heating time of the steel plate 9 by the high-frequency power source 8 can be controlled by the energization control unit 10, it is possible to raise the temperature only at the spot welded portion of the steel plate 9 or the like to be spot-welded, thereby reducing the power consumption required for heating. be able to.

(Variation 3 of metal material welding apparatus)
Next, Modification 3 of the metal material welding apparatus will be described.
FIG. 13 is an electric circuit diagram showing a third modification of the metal material welding apparatus. The metal material welding apparatus 35 shown in FIG. 13 differs from the metal material welding apparatus 1 shown in FIG. 2 in that the spot welding power source 6 uses a DC power source 36 instead of a low frequency power source. The DC power source 36 is constituted by a DC power source using an inverter or the like, and the magnitude of the DC current, the energization time, and the like are controlled by the energization control unit 10. Since the other structure is the same as that of the metal welding apparatus 1, description is abbreviate | omitted.

(Variation 4 of metal material welding apparatus)
Next, Modification 4 of the metal material welding apparatus is shown.
FIG. 14 is an electric circuit diagram showing a fourth modification of the metal material welding apparatus. The metal material welding apparatus 40 shown in FIG. 14 is different from the metal material welding apparatus 30 shown in FIG. 4 in that the low frequency power source 6 is a DC power source 36. The DC power source 36 is constituted by a power source using an inverter or the like, and the magnitude of the DC current, the energization time, and the like are controlled by the energization control unit 10. Since the other structure is the same as that of the metal welding apparatus 30, description is abbreviate | omitted.

  Also in the metal welding apparatuses 35 and 40, the capacitor 7 acts as a current blocking capacitor from the DC power source 36 to the high frequency power source 8, and the inductance 5 is a current blocking inductance from the high frequency power source 8 to the DC power source 36, that is, Acts as a choke coil.

  According to the metal welding apparatuses 35 and 40, spot welding is performed by applying a direct current to the electrodes 4 and 4, and unlike the case where the low frequency power source 6 is used, there is no skin effect. Can be selected according to the workpiece 9.

(Heating method when a DC power source is used as the power source for welding)
Also in the metal welding apparatuses 35 and 40 using the DC power source 36 as the welding power source 6, the same heating method as that of the metal welding apparatuses 1, 25 and 30 can be employed.
FIGS. 15-19 is a figure which shows the heating waveform of the welding apparatuses 35 and 40 of a metal material. In each figure, the horizontal axis indicates time (arbitrary scale), and the vertical axis indicates current waveforms 26 and 22 (arbitrary scale) applied from the DC power source 36 and the high frequency power source 8.
FIG. 15 is a diagram illustrating a heating waveform of simultaneous heating using the DC power source 36 and the high frequency power source 8. The effect of simultaneous heating is the same as the effect of simultaneous heating using the low frequency power source 6 and the high frequency power source 8 shown in FIG.

  FIG. 16 is a diagram illustrating a heating waveform in which the high-frequency power source 8 is used for post-heating. The effect of after-heating using the high-frequency power source 8 is the same as the effect of after-heating using the high-frequency power source 8 shown in FIG.

  FIG. 17 is a diagram illustrating a heating waveform in which the high-frequency power source 8 is used for preheating. The effect of preheating of the high frequency power supply 8 is the same as the effect of preheating using the high frequency power supply 8 shown in FIG.

  FIG. 18 is a diagram showing a heating waveform in the case where preheating using the high-frequency power supply 8, heating using the DC power supply 36, and post-heating using the high-frequency power supply 8 are continuously performed. The heating effect in this case is the same as the effect of the heating method shown in FIG.

  FIG. 19 is a diagram showing a heating waveform in the case where preheating is performed by the high frequency power supply 8 and partial simultaneous heating is performed using the high frequency power supply 8 and the DC power supply 36. In this case, the high frequency power supply 8 is used for preheating, and the high frequency power supply 8 is applied for a predetermined time immediately after the application time of power from the DC power supply 36. That is, power is superimposed from the high frequency power supply 8 only in the initial period of application of power from the low frequency power supply 6. The effect of preheating is the same as the heating method of FIG.

  FIG. 20 is a diagram showing a heating waveform when partial heating is performed partially using the high frequency power supply 8 and the DC power supply 36 and afterheating is performed by the high frequency power supply 8. In this case, the high frequency power supply 8 is applied for a predetermined time immediately after the application of power from the DC power supply 36 is completed. That is, power is superimposed from the high frequency power supply 8 immediately before the application time of power from the low frequency power supply 6 ends. The effect of preheating is the same as the heating method of FIG.

  Since the heating time of the steel plate 9 by the high-frequency power source 8 can be controlled by the energization control unit 10, it is possible to raise the temperature only at the spot welded portion of the steel plate 9 or the like to be spot-welded, thereby reducing the power consumption required for heating. be able to.

  According to the present invention, by heating the high-frequency power supply 8 to the work 9 via the electrodes 4 and 4 of the metal welding apparatuses 1, 25, 30, 35, and 40, partial heating is performed in the non-contacting region. Can do. A method of performing high-frequency heating of the workpiece 9 before or after application of power from the low-frequency power source 6 or the DC power source 36 or simultaneously with application of the low-frequency power source 6 or the DC power source 36 can be selected.

  In the metal welding apparatuses 1, 25, 30, 35, and 40, the steel sheet 9 is quenched by rapid cooling after welding. In this case, the cooling direction includes heat radiation from the horizontal direction on the steel plate 9 (see FIG. 7) and heat transfer from the vertical direction of the electrodes 4 and 4. The heat transfer in the vertical direction from the electrodes 4 and 4 is significant because the electrodes 4 and 4 are water-cooled. As a specific example of the heat storage, high-frequency energization is performed after spot welding, a heat storage is formed in the nugget outer peripheral region, and the nugget is cooled by heat transfer in the vertical direction of the electrodes 4 and 4. As a result, the heat transfer in both the vertical and horizontal directions that occurs when high-frequency energization is not performed is only in the vertical direction, so that the structure formation during solidification of the steel sheet 9 can be controlled.

  In the conventional spot welder, the temperature rise profile of the steel plate 9 is the highest in the region where the steel plates 9 overlap in the central region where the electrodes 4, 4 and the steel plate 9 are in contact. It is formed. That is, in the conventional spot welder, the region immediately below the electrodes 4 and 4 is heated. However, when the high-frequency current 22 is applied to the electrodes 4 and 4, the high-frequency current 22 is concentrated on the surfaces of the electrodes 4 and 4 due to the skin effect, and when the high-frequency current 22 contacts the steel plate 9, the surface of the steel plate 9 is affected by the skin effect. Flowing. By this current path, the region where the temperature of the steel plate 9 is highest is the outer periphery of the electrodes 4, 4, that is, the nugget outer periphery region.

  In this way, partial heating of only the outer peripheral region of the nugget can be performed by energizing the electrodes 4 and 4 with the high-frequency current 22 supplied from the high-frequency power source 8, and this partial heating range is the range where the temperature is most increased. Moreover, it becomes a more efficient heating method than heating the whole directly under the electrodes 4 and 4 by restricting the partial heating range. Since the high-frequency current can be heated by the outer circumference of the electrodes 4 and 4, a well state can be formed thermally. For this reason, since it can be made to melt and solidify in the state which suppressed the heat removal in the plate surface of the steel plate 9, welding is possible for a short time.

  Thus, by selectively heat-treating the nugget outer peripheral region that determines the welding region strength by high-frequency energization, it is possible to make a spot-welded joint with sufficient strength even in a short time even if the carbon content of the steel plate is high. .

  According to the metal welding apparatus 1, 25, 30, 35, 40, the electric power from the spot welding power source 6 is mainly used to form the melt-solidified portion of the steel sheet 9 by conducting two frequencies. Heating using the high-frequency power source 8 can be used to intensively heat the circular portion of the nugget outer peripheral region that determines the strength. For this reason, the welding location of the steel plate 9 can be heated intensively and independently, and desired spot welding quality can be obtained in an overwhelmingly short time that cannot be obtained by conventional spot welding.

  In spot welding using a conventional thyristor phase control system, there is a portion where the current is interrupted, which is not preferable in terms of welding quality. However, according to the metal welding apparatuses 1, 25, 30, 35, and 40, the amplitude of the high-frequency current 22 Since the control is performed, the high-frequency current 22 is not interrupted, and the quality of spot welding of the steel plate 9 can be improved.

(Work that can be used in the present invention)
In the above description, the metal material 9 to be spot-welded is, for example, the steel plate 9, but any material may be used as long as the metal material 9 is used. Further, the shape of the work 9 is not limited to a plate, and may be any shape. Moreover, although the steel plate 9 showed the example which carries out the spot welding of 2 sheets, the welding of a some board may be sufficient.

  Further, the spot-welded metal material 9 may be spot welding of different metal materials.

Hereinafter, a specific example in which the steel plate 9 is spot-welded by the metal material welding apparatus 1 of the present invention will be described in detail.
Spot welding of two steel plates 9 was performed. FIG. 21 is a diagram schematically illustrating power application from the low frequency power supply 6 and the high frequency power supply 8. The conditions of the steel plate 9, the low frequency power supply 6, the high frequency power supply 8, etc. used are shown below.
Steel plate 9: thickness 2 mm, size 5 cm × 15 cm
Low frequency power supply 6: 50 Hz, electrode 4 is made of copper and has a diameter of 6 mm, power supply capacity 50 kVA
Energizing time of the low-frequency power source 6: 0.3 to 0.5 seconds High-frequency power source 8: 30 kHz, 50 kW output Energizing time of the high-frequency power source 8: 0.3 to 0.6 seconds

  The composition of the steel plate 9 contains 0.19 to 0.29% by weight of C (carbon) as a component other than iron.

First, as shown in FIG. 21, preheating was performed for 0.3 seconds with electric power from the high-frequency power source 8. The high frequency input power was changed from 4.9 kW to 37 kW.
Next, power was applied from the low frequency power source 6 to perform welding. As shown in FIG. 18, the low-frequency power source 6 was turned on by two stages of energization of the first current and the second current. The rise of the first current is one cycle, the first energization is two cycles, and the first current value is 11 kA. After cooling for one cycle, set the second current value to 8. A current was supplied for 16 cycles as kA. The two-stage energization by the low-frequency power source 6 was 20 cycles including cooling, and the welding time was 0.4 seconds.

  In Example 2, the power from the high frequency power source 8 was applied for 0.3 seconds simultaneously with the power from the low frequency power source 6. The high frequency input power was changed from 2.7 kW to 39.9 kW. The energization of power from the low frequency power source 6 is the same as that in the first embodiment.

  In Example 3, the power from the high frequency power source 8 was applied for 0.3 seconds immediately after the end of energization of the power from the low frequency power source 6. The high frequency input power was changed from 2.7 kW to 39.9 kW. The energization of the low frequency power source 6 is the same as that in the first embodiment.

(Comparative example)
As a comparative example for Examples 1 to 3, welding was performed by energizing the low frequency power supply 6 without applying the high frequency power supply 8. That is, normal spot welding was performed.

A cross tension test was performed on the weld samples of Examples and Comparative Examples to determine the breaking load. Table 1 shows the high-frequency energization pattern, the high-frequency input power, the breaking load, and the average breaking load of the welding samples of Examples and Comparative Examples.

  In Example 1, the number of samples of the weld specimen in which the high frequency input power is 4.9 kW is three. The fracture loads of the weld samples were 19.54 kN, 18.46 kN, and 20.28 kN, respectively. The fracture loads of the weld samples with high-frequency input powers of 8.6 kW, 20.9 kW, 28.5 kW, and 37 kW were 21.26 kN, 19.59 kN, 17.98 kN, and 19.58 kN, respectively. From this, it was found that the average breaking load of the weld sample of Example 1 that was pre-heated by high-frequency energization and then spot-welded with the low-frequency power source 6 was 19.5 kN.

  In Example 2, the number of samples of the weld specimen in which the high frequency input power was 2.7 to 3.8 kW was two, and the breaking loads were 15.97 kN and 17.70 kN, respectively. The fracture loads of the weld samples with high frequency input powers of 22.8 to 25 kW and 33.3 to 39.9 kW were 20.5 kN and 21.05 kW, respectively. From this, it was found that the average breaking load of the weld specimen of Example 2 in which spot welding was performed using the low-frequency power source 6 while simultaneously applying high-frequency energization was 18.8 kN.

  In Example 3, the fracture loads of the weld samples with high frequency input powers of 4.2 kW, 8.6 kW, 30.8 kW, and 39.9 kW were 18.7 kN, 18.35 kN, 17.94 kN, and 19.73 kN, respectively. there were. From this, it was found that the average breaking load of the weld specimen of Example 3 to which high-frequency current was applied after welding using the low-frequency power source 6 was 18.7 kN.

  The number of samples of the weld sample of the comparative example was two, and the breaking loads were 12.47 kN and 12.88 kN, respectively. From this, it was found that the average breaking load of the welding sample subjected to the conventional spot welding by the two-stage energization of the comparative example was 12.7 kN.

The average breaking loads obtained from the weld samples subjected to the preheating of Example 1, the simultaneous heating of Example 2, and the post-heating of Example 2 are 1.54 times 1 for the average breaking load of the comparative example, respectively. .48 times and 1.47 times the size. Therefore, it was found that the average breaking load obtained with the weld samples of Examples 1 to 3 was improved by about 50% as compared with the case of spot welding with only the low frequency power source 6. In Examples 1 to 3, although high-frequency energization has a difference between preheating, simultaneous and after-heating, any heating method can significantly increase the breaking load compared to spot welding using only the low-frequency power source 6 of the comparative example. I was able to.
In addition, if the carbon content of the steel plate 9 was in the range of about 0.19 wt% to 0.26 wt%, the breaking load could be significantly increased as compared with the comparative example.

  In order to confirm the heating effect of the high frequency power source 8 alone, the chromium molybdenum steel 9 was quenched using the same metal welding apparatus 1 as in Example 1. The used chromium molybdenum steel 9 is SCM435 and has the same dimensions as the steel plate of Example 1. The energization for 0.3 second was performed from the high frequency power source 8 at the same frequency as in Example 1 to perform the quenching treatment.

FIG. 22 is a diagram showing the hardness distribution of the surface of the chromium molybdenum steel (SCM435) 9 subjected to the quenching process of Example 4. The horizontal axis in the figure indicates the position of the electrode 4 on the surface of chromium molybdenum steel (SCM4359) in the axial cross-sectional direction, and also indicates the position of the electrode 4 and its outer diameter. The vertical axis in the figure represents Vickers hardness (HV).
As is clear from FIG. 22, the hardness corresponding to the outermost periphery of the electrode 4 of the chromium molybdenum steel (SCM435) of Example 4 is the highest, about 670 HV, and the hardness of the unquenched region is about 370 HV. It was found that the hardness was higher than that. Thus, it has been found that only the ring-shaped region in the outer peripheral region of the electrode 4 can be quenched in the chromium molybdenum steel (SCM435) by applying power from the high-frequency power source 8.

  A chrome molybdenum steel (SCM435) having been hardened in advance and having a hardness of about 620 HV was heated using the same metal welding apparatus 1 as in Example 1 to perform a tempering treatment. A tempering process was performed by energizing for 0.3 seconds from the high-frequency power source 8 at the same frequency as in Example 1.

FIG. 23 is a diagram showing the hardness distribution of the surface of the chromium molybdenum steel (SCM435) 9 subjected to the tempering process of Example 5. The horizontal and vertical axes in FIG. 23 are the same as those in FIG.
As apparent from FIG. 23, the hardness of the region corresponding to the outermost periphery of the electrode 4 of the chromium molybdenum steel (SCM435) 9 of Example 5 is the lowest, about 550 HV, which is higher than the hardness before tempering (about 620 HV). It was found that the hardness was low. As a result, it has been found that only the ring-shaped region in the outer peripheral region of the electrode 4 in the chromium molybdenum steel (SCM435) 9 can be tempered by applying power from the high-frequency power source 8.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Absent. The shape of the gun arm 2 and the electrode 4 and the values of the inductance 5 and the capacitor 7 in the above-described embodiment can be appropriately designed according to the type and shape of the work 9.

It is a figure which shows typically an example of a structure of the welding apparatus of the metal material which concerns on embodiment of this invention. It is an electric circuit diagram of the welding apparatus of the metal material shown in FIG. It is an electric circuit diagram which shows the modification 1 of the welding apparatus of a metal material. It is an electric circuit diagram which shows the modification 2 of the welding apparatus of a metal material. It is sectional drawing which shows typically the electric current distribution which arises in a steel plate when electric power is simultaneously applied to two laminated steel plates from a low frequency power supply and a high frequency power supply. It is a figure which shows the heating state of a steel plate. It is a figure which shows the heating waveform in the case of performing spot welding and heat processing simultaneously with the electric power from a low frequency power supply, and the electric power from a high frequency power supply. It is a figure which shows the heating waveform in the case of applying the electric power from a high frequency power supply, after applying the electric power from a low frequency power supply. It is a figure which shows the heating waveform in the case of performing the preheating using a high frequency power supply, before applying electric power from a low frequency power supply. It is a figure which shows the heating waveform in the case of performing preheating using a high frequency power supply, heating using a low frequency power supply, and post-heating using a high frequency power supply continuously. It is a figure which shows a heating waveform at the time of performing partial simultaneous heating using a high frequency power supply and a low frequency power supply while performing preheating using a high frequency power supply. It is a figure which shows the heating waveform in the case of performing the heating using a low frequency power supply and the post-heating using a high frequency power supply, and also performing partial simultaneous heating using a low frequency power supply and a high frequency power supply. It is an electric circuit diagram which shows the modification 3 of the welding apparatus of a metal material. It is an electric circuit diagram which shows the modification 4 of the welding apparatus of a metal material. It is a figure which shows the heating waveform of simultaneous heating using DC power supply and high frequency power supply. It is a figure which shows the heating waveform which used the high frequency power supply for after-heating. It is a figure which shows the heating waveform which used the high frequency power supply for preheating. It is a figure which shows the heating waveform in the case of performing preheating using a high frequency power supply, heating using a DC power supply, and post-heating using a high frequency power supply continuously. It is a figure which shows a heating waveform at the time of performing partial simultaneous heating using a high frequency power supply and DC power supply while performing preheating with a high frequency power supply. It is a figure which shows a heating waveform in the case of performing partial heating simultaneously using a high frequency power supply and a DC power supply, and performing post-heating by a high frequency power supply. It is a figure which illustrates typically the electric power application from a low frequency power supply and a high frequency power supply. It is a figure which shows hardness distribution of the chromium molybdenum steel (SCM435) surface which the hardening process of Example 4 was carried out. It is a figure which shows the hardness distribution of the chromium molybdenum steel (SCM435) surface which performed the tempering process of Example 5. FIG. It is sectional drawing which shows the spot welding of steel plates typically. It is a top view of the sample used for the tension test for investigating the spot weld strength of a high-tensile steel plate, (A) shows the sample of a superposition joint, and (B) shows the sample of a cross joint.

Explanation of symbols

1, 25, 30, 35, 40: Metal welding apparatus 1A, 25A, 30A, 35A, 40A: Welding circuit section 1B, 25B, 30B, 35B, 40B: Welding section of welding apparatus 2: Gun arm 2A: Upper part of gun arm 2B: Upper part of gun arm 3: Electrode support part 4: Electrode 5: Floating inductance 6: Low frequency power supply 7: Matching capacitor 8: High frequency power supply 9: Work piece 9A: Circular interior 9B: Ring-shaped region 10: Energization Control unit 11: Bypass capacitor 12: Commercial power supply 13: High frequency current blocking inductance 14: Low frequency power supply control unit 16: Welding transformer 18: Oscillator 20: Matching transformer 22: High frequency current 24: Low frequency current 26: DC current 36: DC Power supply

Claims (16)

A metal material welding apparatus that sandwiches a metal material between a pair of electrodes and energizes the metal material while maintaining the pair of electrodes in the same position to heat different regions of the metal material,
A first heating unit connected to the pair of electrodes and applying a first frequency power to the metal material to heat a predetermined region;
A second heating unit that is connected to the pair of electrodes and applies power of a second frequency to the metal material to heat a region different from the predetermined region;
An energization control unit for independently controlling the first heating unit and the second heating unit;
A metal material welding apparatus comprising: The inside of the predetermined region of the metal material is heated by the first heating means,
The vicinity of the predetermined region of the metal material is heated by the second heating means,
The metal material welding apparatus according to claim 1, wherein heating by the first heating means and heating by the second heating means are controlled independently by the energization control unit. The first heating means is a heating means for heating a circular interior obtained by projecting an axial cross section of the electrode onto the metal material,
The second heating means is a heating means for heating a ring-shaped region along a circle obtained by projecting the axial cross section of the electrode onto the metal material,
The metal material welding apparatus according to claim 2, wherein heating by the first heating means and heating by the second heating means are controlled independently by the energization control unit.   The said 1st frequency is lower than the said 2nd frequency, The said circular inside is welded by supplying the electric power of this 1st frequency to the said metal material, The Claim 3 characterized by the above-mentioned. Metal material welding equipment.   The second frequency is higher than the first frequency, and when the power of the second frequency is applied to the metal material, the ring-shaped region is resistance-heated, or resistance heating and high-frequency induction heating are performed. The metal material welding apparatus according to claim 3, wherein the metal material welding apparatus is a metal material welding apparatus. A pair of electrodes arranged so as to sandwich a metal material, a welding power source for supplying welding power to the pair of electrodes, and a high frequency power source for supplying high frequency power to the pair of electrodes,
The welding power source and the high-frequency power source are connected in parallel to the pair of electrodes,
A current blocking inductance is connected between the welding power source and the pair of electrodes,
A current blocking capacitor is connected between the high-frequency power source and the pair of electrodes,
The current blocking inductance prevents a high frequency current supplied from the high frequency power source to the pair of electrodes from flowing into the welding power source,
The metal current welding apparatus, wherein the current blocking capacitor blocks current supplied from the welding power source to the pair of electrodes from flowing into the high frequency power source side.   The metal material welding apparatus according to claim 6, further comprising a gun arm, wherein the spot welding power source and the high-frequency power source are connected to the pair of electrodes via the gun arm. .   The metal material welding apparatus according to claim 4, further comprising an energization control unit that controls an output time and an output current for the welding power source and the high-frequency power source, respectively.   The metal welding apparatus according to any one of claims 6 to 8, wherein the welding power source is a low-frequency power source.   10. The metal according to claim 9, wherein the low-frequency power source is connected to the pair of electrodes via a transformer, and a bypass capacitor is connected in parallel to the winding on the pair of electrodes side of the transformer. Material welding equipment.   The metal welding apparatus according to any one of claims 6 to 8, wherein the welding power source is a DC power source.   The metal material welding apparatus according to claim 6, wherein the current blocking capacitor and the current blocking inductance constitute a series resonance circuit.   The metal material welding apparatus according to claim 6 or 7, wherein the current blocking inductance and a parallel resonance capacitor connected to an upper portion and a lower portion of the gun arm constitute a parallel resonance circuit.   The metal material welding apparatus according to claim 6, wherein the current blocking inductance is a floating inductance of the gun arm.   The metal material welding apparatus according to claim 6, wherein the high-frequency power source is directly fed to the electrode side through the current blocking capacitor.   The metal material welding apparatus according to claim 6 or 7, wherein the high-frequency power source is fed from the base of the gun arm via the current blocking capacitor.

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