JP4916264B2 - Electrodes for fusing welding - Google Patents

Description

  The present invention relates to an electrode for fusing welding using W or Mo or an alloy based thereon as a raw material.

  Conventionally, fusing welding has been used in a manufacturing process for joining an insulating coated conductor and a metal terminal (for example, see Non-Patent Document 1). In the mass production line, fusing welding is continuously performed. For this reason, the electrode for fusing welding is subject to repeated high heat and high load, and is easily deformed. Therefore, the material must be able to withstand deformation. In addition, it is required to have high electrical conductivity, high thermal conductivity, high strength, and high wear resistance, which are essential requirements for the fusing welding electrode.

Under such a background, a Cu alloy in which a hard alloy such as Al ₂ O ₃ is dispersed or a Cu alloy such as Cu—Cr or Cu—Cr—Zr is used as an electrode for fusing welding. Cu-Cr alloys are often used from a comprehensive viewpoint such as heat conduction characteristics, strength, and cost.
Recently, from the viewpoints of deformation resistance and heat resistance, W-based and Mo-based alloys, or alloys in which Ce oxide and Th oxide are dispersed have been used.
Patent Document 1 proposes a resistance welding electrode in which a W electrode is heat-treated to form an oxide film on the surface.
Seiwa Seisakusho HP (http://www.seiwamfg.co.jp/manu/top_fus_a.html) JP 2001-9574 A

By the way, the electrode introduced in Patent Document 1 is intended to provide a general resistance welding electrode capable of stabilizing welding quality by preventing welding conditions such as welding current and voltage from fluctuating. The above effect can be expected by forming an oxide film on the surface of the W electrode.
However, even with the same resistance welding electrode, the W or Mo fusing welding electrode used in a mode in which heating and pressurizing are repeatedly applied to the tip, the heating and pressurizing are repeated. There are cases where detachment wear and loss occur at the tip, and the electrode can no longer be used for a short time. For this reason, there has been a problem that the replacement frequency increases, resulting in an increase in cost.
The present invention has been devised to solve such a problem. As an electrode used for fusing welding, the present invention suppresses degranulation wear / deficiency on the use surface and stably improves the durability. Alternatively, an object is to provide an Mo-based fusing welding electrode at a low cost.

  In order to achieve the object, the fusing welding electrode of the present invention is made of W or Mo or an alloy based on them, has a cross-sectional average particle diameter of 50 μm or more, and an aspect ratio of 1.5 or more. It has the structure | tissue extended in the axial direction so that it may become. In particular, it is preferable that W or Mo or an alloy based on them is sintered and swaging processed, and then annealed to have a fibrous structure.

In the case of W or an alloy based on W, the hardness at normal temperature is preferably HV300 to 430. Moreover, in the case of Mo or an alloy containing Mo as a base material, the hardness at normal temperature is preferably HV180 to 260.
W or Mo or an alloy based thereon includes at least one selected from oxides, nitrides, carbides and borides of Group 2a, 4a, 5a, 6a or rare earth elements Fine particles may be dispersed. These fine particles preferably have a mean particle diameter of 2 μm or less dispersed in a proportion of 0.5 to 10% by mass in total.
The electrode for fusing welding of the present invention further has a double structure in which Cu or a Cu alloy is used as an electrode body, and W or Mo having the above characteristics or an alloy based on them is attached to the tip thereof. Is preferred.

  In the fusing welding electrode of the present invention, by performing further heat treatment on W or Mo produced through current sintering and subsequent swaging, or an alloy based thereon, during swaging The residual processing residual stress introduced is released, the aspect ratio of the crystal grains of the fibrous structure constituting the alloy is relatively small, and the cross-sectional average particle diameter is relatively large. For this reason, it becomes possible to provide the electrode for fusing welding whose durability was stably improved at low cost.

The inventors of the present invention have made various investigations on the causes of wear / defects occurring at the tip of the electrode and countermeasures when fusing welding using the W electrode. The same applies to the Mo electrode.
First, when observing the wear situation of the electrode tip during welding, as seen in FIG. 1, at the tip of the electrode, the crack extending in the vertical direction from the tip is connected to the crack extending in the radial direction of the electrode, It can be seen that particles on the tip surface of the electrode drop off and are lost.
By the way, W rods used for electrodes for fusing welding are usually manufactured through current sintering and subsequent swaging. For this reason, it has a fine fibrous structure. In addition, since strong processing such as swaging processing is performed in the manufacturing process, there is processing residual stress, which is very hard.

If the W bar is used for the electrode in this state, stress due to heating and pressurization is repeatedly applied to the tip of the electrode during welding, and a crack occurs from the initial stage of welding due to a synergistic effect with the residual stress. It is assumed that it will occur and gradually expand.
Therefore, in order to suppress the occurrence of wear and defects at the tip of the electrode, it is effective to suppress crack extension and crack connection, and it is effective to eliminate the initial residual stress as much as possible. Is done.

Usually, the residual stress in the metal material is removed by performing an annealing heat treatment. Therefore, even in the case of a W bar used for an electrode for fusing welding, a bar that has been subjected to annealing heat treatment on a bar that has been subjected to strong processing such as swaging is removed to remove the processing residual stress. It has been found that if a material is used, it is possible to suppress the occurrence of cracks generated from the initial stage of welding. In the case where a W material that has been actually heat-treated is used as an electrode material, the occurrence of cracks is small as seen in FIG.
By the way, the processing residual stress amount of the W bar used for the electrode for fusing welding can be roughly estimated by evaluating the hardness at normal temperature. The cross-sectional hardness of a W bar that has been subjected to strong processing such as swaging is usually about HV450, but after a sufficient annealing treatment, it becomes about HV300 or less.

A detailed description of the hardness that exhibits the proper annealing state will be given in the examples below. To suppress the occurrence of cracks that occur from the initial stage of welding and maintain the tip shape as an electrode, W or W In the case of using an alloy based on HV as an electrode material, it is preferably adjusted in the range of HV300 to 430.
When this value is exceeded, the residual stress is not sufficiently reduced, and cracks may occur at the electrode tip from a relatively early stage. On the other hand, if the electrode is annealed to below HV300, the tip diameter increases when used as an electrode, and the electrode life is reached in a relatively short time.
In addition, when using Mo or the alloy based on Mo as an electrode raw material, it is preferable to adjust similarly to the range of HV180-260.

The wear of the electrode tip during welding is greatly influenced not only by the processing residual stress but also by the distribution of crystal particles on the electrode tip surface, that is, by the metal structure.
That is, making the metal structure into a fibrous structure by swaging is extremely effective in terms of suppressing degranulation in order to make the extension direction of cracks more perpendicular. However, as described above, it causes a harmful effect due to a large processing residual stress. When the annealing heat treatment is applied, the fibrous structure is changed. When the fibrous structure disappears completely and becomes a granular structure, degranulation is likely to occur due to crack extension in the radial direction, and wear of the electrode tip portion increases. In addition, when annealing is performed, the crystal grains become larger.

A detailed description of the appropriate structure state after the annealing heat treatment will be given in the examples below, but in order to suppress the wear and loss of the core material, the major axis / minor axis ratio of the particles maintaining the fibrous structure, It is necessary that the so-called aspect ratio is 1.5 or more, and the average cross-sectional diameter of each particle is 50 μm or more.
If the aspect ratio is less than 1.5, detachment tends to occur at the electrode tip. On the other hand, if the average particle diameter of the cross section is less than 50 μm, the particles easily fall off and the electric resistance increases, resulting in severe electrode wear.

  Since the grain boundary is a portion where the bond strength between adjacent atoms across the grain boundary is weak, when the crystal grain size becomes small, the grain boundary area increases and the particles easily fall off. In particular, in the case of W or Mo or an alloy based on them, the influence is remarkable when the average particle diameter of the cross section is less than 50 μm, the particles are easily dropped by impact, and the electric resistance increases. Therefore, the average cross-sectional particle diameter is preferably 50 μm or more. Therefore, ideally, a single crystal having no grain boundary is preferable.

  When the core material of the fusing welding electrode of the present invention is manufactured by swaging while heating, the processing temperature is raised to the sintering temperature above the recrystallization temperature to increase the temperature for swaging. If the temperature of the tool can be equal to or higher than the recrystallization temperature and about the sintering temperature, W or Mo can grow and the average cross-sectional average particle diameter of the W or Mo particles can be increased without limit. However, in practice, processing at a high temperature close to the sintering temperature as described above cannot be performed, and the average cross-sectional particle diameter of W or Mo particles is limited to 3 mm. In consideration of the cost aspect, it is practical that the processing temperature is suppressed and the average cross-sectional particle diameter is about 300 μm.

  When the core material of the fusing welding electrode of the present invention is produced by swaging while heating, W or Mo has a body-centered cubic lattice crystal structure and is originally malleable ductility. It is not a material but a brittle material, it is difficult to perform plastic working, and even if it is processed at a temperature exceeding the brittle ductile transition temperature (about 400 ° C.), W or Mo particles cannot be extended, and the aspect ratio is cut in the middle. It can be processed only until 50. In consideration of the cost aspect, it is practical to suppress the processing temperature and set the aspect ratio to about 20 as an upper limit.

Further, when a W-based or Mo-based metal / alloy as in the present invention is used as a core material for a double electrode for fusing welding, the W-based or Mo-based metal / alloy causes an alloying reaction with a terminal metal. Sometimes. As the alloying reaction with the terminal metal proceeds, the tip shape of the core material is deformed, resulting in shortening of the electrode life.
In order to suppress the alloying reaction with the terminal metal, oxides, nitrides of 2a group elements, 4a group elements, 5a group elements, 6a group elements or rare earth elements in W-based or Mo-based metals and alloys, It is preferable to disperse at least one kind of fine particles selected from carbides and borides.
These fine particles have poor reactivity with terminal constituent components and terminal plating components such as Sn, Ag, Ni, Cu, Zn, Fe, Co, etc. Therefore, the W-based core material of the double electrode for fusing welding or It prevents the terminal metal from getting wet with the Mo-based metal / alloy, and suppresses the alloying reaction between the W-based or Mo-based metal / alloy and the terminal metal.

The fusing welding W-based or Mo-based metal / alloy of the present invention also includes oxides, nitrides, carbides and borides of 2a group elements, 4a group elements, 5a group elements, 6a group elements or rare earth elements. Dispersing at least one or more selected fine particles is also effective in suppressing fine cracking of the electrode.
Fine particles dispersed in W-based or Mo-based metal / alloys have the effect of pinning the propagation of cracks when the electrode is impacted, resulting in excellent impact resistance and suppressing cracking. To do.

In order to obtain the effect of addition, it is preferable to disperse the fine particles in an amount of 0.5% by mass or more. However, if it exceeds 10% by mass, the electrical conductivity is greatly reduced, and the electric resistance between the electrode and the material to be welded is increased, so Since it becomes difficult to pass a sufficient welding current between the materials, it becomes difficult to proceed with stable fusing welding.
Further, the particle diameter of the fine particles to be contained is preferably 2 μm or less. If fine particles exceeding 2 μm are contained, the core material tends to be broken due to the difference in thermal expansion coefficient.

Next, the manufacturing method of the electrode for fusing welding of this invention is demonstrated.
In general, a W-based or Mo-based metal / alloy is manufactured by a sintering method. The W-based or Mo-based metal / alloy of the present invention is also produced by a sintering method. It is preferable to employ an electric current sintering method.
In the case of W-based or Mo-based metals / alloys made of an electric current sintered body, about 10 to 200 ppm of K (potassium) is doped in the form of oxide, nitride, metal K, carbide or boride. What was done is used a lot. In this specification, it is added that W- or Mo-based metals / alloys include K-doped metals and alloys.

If necessary, W- or Mo-based metal / alloy oxide powder or metal powder with fine particles added is heat-treated in a reducing atmosphere, and the resulting powder is shaped into an appropriate shape, pre-sintered, and electrically sintered. Thereafter, swaging is applied to the sintered body to obtain a rod-like W-based or Mo-based metal / alloy.
The obtained rod-like metal / alloy is subjected to annealing heat treatment.
As for the conditions, in the case of W-based metals and alloys, treatment in a non-oxidizing atmosphere at 1400 to 3000 ° C. for 1 second or more and 1 hour or less is preferable. In the case of Mo-based metals and alloys, treatment in a non-oxidizing atmosphere at 980 to 2100 ° C. for 1 second or more and 1 hour or less is preferable. If the processing temperature is less than the above, or if the processing time is less than 1 second, the release of the processing residual stress introduced at the time of swaging processing is insufficient, and degranulation occurs at the tip surface during use, as an electrode, etc. The service life when used is shortened. Conversely, if the processing temperatures of W-based metals / alloys and Mo-based metals / alloys exceed 3000 ° C, 2100 ° C, or increase the processing time to exceed 1 hour, they are introduced during swaging. Recrystallization proceeds to the formed fibrous structure, the aspect ratio becomes small, the hardness decreases, and the life when used as an electrode or the like is shortened. Further, although the aspect ratio is maintained at 1.5 or more, the average particle diameter of the cross section cannot be increased to 50 μm or more because the recrystallization of the structure is relatively difficult to proceed. Conversely, if the processing temperature exceeds the above temperature, or if the processing time is increased to exceed 1 hour, recrystallization proceeds to the fibrous structure introduced during swaging, the aspect ratio becomes too small, Since the average particle diameter of the cross section is too large, the hardness is lowered and the life when used as an electrode or the like is shortened.

As described above, it is necessary to maintain a balance between the treatment temperature and the treatment time in the heat treatment in order to make the aspect ratio, the cross-sectional average particle diameter, and the prescribed value range of the core material.
When the core material of the double electrode for fusing welding of the present invention is produced by swaging while heating, in order to make the average particle diameter of the cross section to 50 μm or more, the grain is formed in the first swaging process. Growing to grow the cross-sectional average particle size to near 50 μm, and then the method of increasing the cross-sectional average particle size to 50 μm or more by heat treatment above the recrystallization temperature, even if the grain growth is not sufficient in swaging processing, The grains may be grown by a post-treatment heat treatment so that the average cross-sectional particle diameter is 50 μm or more. In order to effectively grow the grains to the required grain size, it is preferable to put a HIP (hot isostatic pressure) treatment before and after the swaging process. Factors of temperature, pressure, and time for giving recrystallization energy are effective for grain growth.
In addition, in order to increase the aspect ratio to 1.5 or more, the swaging process is performed at least at the ductile brittle transition temperature (about 400 ° C.), and the processing pressure is appropriately applied so that brittle fracture does not occur. It is preferable to implement.

The W- or Mo-based rod obtained above is cut into a predetermined length, and attached to the tip of an electrode body made of Cu or Cu alloy to produce a double electrode. In this case, the W-based or Mo-based rod is mounted so that one end is partially embedded in the electrode body and protrudes from the electrode body.
As the Cu or Cu alloy used for the electrode body, ordinary pure copper, Cu—Cr alloy, Cu—Cr—Zr alloy or the like is used.
As an aspect to be mounted on the electrode body, even if the rear end portion of the W-based or Mo-based rod body obtained above is press-fitted into the hole drilled in the tip portion of the electrode body in a rod state made of Cu or Cu alloy It may be good or may be inserted through a brazing material. Alternatively, shrink fitting may be performed, or cold forging may be performed after casting a W-based or Mo-based rod body with a copper material. If the W-based or Mo-based rod body and the Cu-based electrode main body are closely joined, there is no problem in terms of electrical conduction and thermal conduction.
After forming the double-structured electrode structure, it is sufficient to grind the tip and adjust it to the required shape as appropriate.

Example 1:
As test materials, a polyurethane-coated copper wire having a diameter of 1.5 mm and an Sn-plated crimp terminal were used. As the electrode, as shown in FIG. 3, a double structure electrode 3 was used in which the end of a φ4 mm × 13 mm tungsten core material 1 was embedded in a copper material 2 of φ8 mm × 22 mm and joined. As the tungsten core material 1, a 99.95% purity W powder was subjected to current sintering, swaging and centerless polishing were performed to obtain a diameter of 4 mm, a non-oxidizing atmosphere having a temperature range of 1400 to 3000 ° C. and 1 Heat treatment under various conditions varied in the range from 1 second to 1 hour was made to change the structure and hardness. The rear end of this tungsten core material 1 was embedded in the tip of Cu2, and a double-structure electrode 3 having a shape in which the tip of the tungsten core material 1 protruded from Cu2 was produced. In Table 2, the one described at the bottom is a comparative example in which the heat treatment is not performed and the centerless polishing is performed.
Continuous fusing welding was performed under the conditions shown in Table 1. Then, the continuity between the terminal and the conductive wire was checked, and the life of the electrode was determined as a poor weld if there was no continuity.
The results are shown in Table 2.

As can be seen from the results in Table 2, with an electrode having a core material in which the heat treatment conditions are appropriate, the core has an aspect ratio of 1.5 or more, and the average cross-sectional diameter is 50 μm or more, Fusing welding exceeding 5000 points could be performed without any problem.
On the other hand, if the heat treatment temperature is too low or the time is too short, the aspect ratio is maintained at 1.5 or higher, but the average cross-sectional particle diameter cannot be increased to 50 μm or more. When a core material was used, degranulation occurred at the tip surface, and fusing welding up to 5000 hit points could not be performed. In addition, if the processing temperature is too high or the processing time is too long, the aspect ratio tends to be too small or the average cross-sectional particle diameter tends to be too large, and using such a core material The hardness was lowered and the core material was greatly deformed, and the desired electrode life could not be obtained.

  In this example, a cylindrical shape was used as the shape of the core material, but the same result was obtained even in a prismatic shape or a polygonal shape. In this example, polyurethane was used as the insulating film of the insulating film-coated copper wire, but the same result was obtained even when polyimide or another insulating film was used. In this embodiment, Sn-plated products are used as the crimp terminals. However, Ag-plated products or other plated products may be used, and phosphor bronze, white, Kovar, or other materials may be used. It was.

Example 2:
As in Example 1, polyurethane-coated copper wires and Sn-plated crimp terminals were used as test materials. As the electrode, a double-structured electrode in which the end of a φ4 mm × 13 mm molybdenum core material was embedded in a φ8 mm × 22 mm copper material and joined was used. As a molybdenum core material, 99.95% pure Mo powder was energized and sintered, and then swaging and centerless polishing were performed to obtain a diameter of 6 mm. In a non-oxidizing atmosphere, a temperature range of 980 to 2100 ° C. and 1 second or more 1 What changed the structure | tissue by giving the heat processing of various conditions changed variously in the range below time was produced. The rear end of this molybdenum core material was embedded in the front end of Cu, and a double-structure electrode having a shape in which the front end of the molybdenum core material 1 protruded from Cu 2 was produced. In Table 3, the one shown at the bottom is a comparative example in which the heat treatment is not performed and the centerless polishing is performed.
Continuous fusing welding was performed under the same conditions as in Example 1, and the same evaluation as in Example was performed.
The results are shown in Table 3.

As can be seen from the results in Table 3, in the same manner as in Example 1, the heat treatment conditions were appropriate, the core had an aspect ratio of 1.5 or more, and the average cross-sectional diameter was 50 μm or more. With the electrode, fusing welding exceeding 5000 points could be performed without any problem.
On the other hand, if the heat treatment temperature is too low or the time is too short, the aspect ratio is maintained at 1.5 or higher, but the average cross-sectional particle diameter cannot be increased to 50 μm or more. When a core material was used, degranulation occurred at the tip surface, and fusing welding up to 5000 hit points could not be performed. In addition, if the processing temperature is too high or the processing time is too long, the aspect ratio tends to be too small or the average cross-sectional particle diameter tends to be too large, and using such a core material The hardness was lowered and the core material was greatly deformed, and the desired electrode life could not be obtained.

  In this example, a cylindrical shape was used as the shape of the core material, but the same result was obtained even in a prismatic shape or a polygonal shape. In this example, polyurethane was used as the insulating film of the insulating film-coated copper wire, but the same result was obtained even when polyimide or another insulating film was used. In this embodiment, Sn-plated products are used as the crimp terminals. However, Ag-plated products or other plated products may be used, and phosphor bronze, white, Kovar, or other materials may be used. It was.

Example 3:
The core material was W in which CeO ₂ powder having a particle diameter of 0.5 μm was dispersed at various blending ratios, and the influence of the CeO ₂ powder content and the width dimension ratio on the electrode life was investigated.
Except for containing CeO ₂ powder in the core material, the same as Example 1, with the heat treatment of the core material being 1600 ° C. × 30 minutes, the aspect ratio is 1.7, the average cross-sectional diameter is 100 μm, and the room temperature The core material characteristics were such that the hardness was HV380.

As can be seen from the results shown in Table 4, under the condition that the content of CeO ₂ powder was 0.5 to 10% by mass, an improvement effect was observed with an electrode life of 5000 or more striking points.
On the other hand, although the CeO ₂ powder content was less than 0.5% by mass, the electrode life was more than 5000 points due to the effect of the aspect ratio and the cross-sectional particle diameter, but a relatively large amount of plated metal was present at the tip of the core material. Was deposited. Further, when the CeO ₂ powder content exceeds 10% by mass, the life improvement action has disappeared. This is presumably because the amount of plating metal deposited on the tip of the electrode increases and the electrical resistance between the electrode and the material to be welded increases, resulting in insufficient welding.

  In this example, a cylindrical shape was used as the shape of the core material, but the same result was obtained even in a prismatic shape or a polygonal shape. In this example, polyurethane was used as the insulating film of the insulating film-coated copper wire, but the same result was obtained even when polyimide or another insulating film was used. In this embodiment, Sn-plated products are used as the crimp terminals. However, Ag-plated products or other plated products may be used, and phosphor bronze, white, Kovar, or other materials may be used. It was.

Example 4:
The life of the electrode was investigated using W in which 1% by mass of fine particles having various particle diameters and different materials were dispersed as a core material.
The core material characteristics and welding conditions are the same as in Example 3.
As can be seen from the results shown in Table 5, when fine particles having a particle size of 2 μm or less were dispersed in W, the electrode life was greatly extended. Improvement of the electrode life was effective regardless of the type of fine particles as long as it was a compound of 2a group element, 4a group element, 5a group element, 6a group element or rare earth element.
Further, when the particle diameter of the CeO ₂ fine particles was changed from 0.5 to 3 μm, the effect of improving the electrode life was observed when the particle diameter was 2 μm or less.

  In this example, a cylindrical shape was used as the shape of the core material, but the same result was obtained even in a prismatic shape or a polygonal shape. In this example, polyurethane was used as the insulating film of the insulating film-coated copper wire, but the same result was obtained even when polyimide or another insulating film was used. In this embodiment, Sn-plated products are used as the crimp terminals. However, Ag-plated products or other plated products may be used, and phosphor bronze, white, Kovar, or other materials may be used. It was.

The figure which illustrates typically the wear condition of the front-end | tip part of the core material in the electrode for conventional fusing welding The figure which illustrates typically the wear condition of the core material front-end | tip part in the electrode for fusing welding of this invention The figure explaining the structure (a) and the fusing welding situation (b) of a double structure embedded type fusing electrode

Claims (7)

  It is made of W or Mo or an alloy based on them, and has a cross-sectional average particle diameter of 50 μm or more and a structure extending in the axial direction so that the aspect ratio is 1.5 or more. Electrode for fusing welding.   The electrode for fusing welding according to claim 1, wherein the electrode has a fibrous structure that has been subjected to sintering and swaging, and thereafter annealing heat treatment.   The fusing welding electrode according to claim 1 or 2, comprising W or an alloy having W as a base material, and having a normal temperature hardness of HV300 to 430.   3. The fusing welding electrode according to claim 1, wherein the electrode is made of Mo or an alloy having Mo as a base material, and the hardness at normal temperature is HV180 to 260. 4.   In the alloy, 0.5 to 10% by mass of at least one kind of fine particles selected from oxides, nitrides, carbides and borides of Group 2a, 4a, 5a, 6a or rare earth elements The fusing welding electrode according to any one of claims 1 to 4, wherein the fusing welding electrode is dispersed in a proportion.   6. The fusing welding electrode according to claim 5, wherein the dispersed fine particles have an average particle diameter of 2 μm or less.   An electrode for fusing welding in which W or Mo according to any one of claims 1 to 6 or an alloy based on them is mounted as a core material at the tip of an electrode body made of Cu or a Cu alloy.

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