JPH0220677A - Welding method for super head alloy thin wire - Google Patents

Abstract

PURPOSE:To improve the joining strength without generating such a defect as a void, etc. by irradiating the vicinity of a weld zone by a laser beam in a state that a super hard alloy thin wire is allowed to abut on a base metal, and wrapping the super hard alloy thin wire by a generated fillet. CONSTITUTION:A printing wire 2 of a super hard alloy thin wire is fitted and allowed to abut on a recessed part 4a which is formed on the tip of an armature 4 being a base metal. In such a state, a laser beam 14 radiates from the back side of the armature 4 to a joint part from a laser device 13. By such laser irradiation, the armature 4 is melted and coagulated locally and a fillet part 15 which has wrapped in the printing wire 2 is formed. In such a way, the base metal and the super hard alloy thin wire can be coupled with high welding strength without being accompanied with such a defect as generation of a void, etc. of the super hard alloy thin wire caused by using jointly a flux, which is generated in a conventional brazing method.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applied to, for example, a wire dot printer head, and combines an armature made of a ferromagnetic material incorporated into the printer head and a printing wire as a thin cemented carbide wire. The present invention relates to a welding method for welding and joining between.

[Conventional technology]

First, the structure of the above-mentioned wire dot printer head, which is an object of the present invention, will be explained with reference to FIG. In the figure, 1 is a funnel-shaped printer head housing, and 2 is a guide frame 3 with its tip facing the top open end of the housing 1.
Cemented carbide fine wire (diameter 0.2 to 0.35
+++ m) printing wire, 4 is an armature welded to the printing wire for each printing wire 2, 5 is a leaf spring supporting the armature 4, 6 is a magnet for driving the armature assembled integrally with the housing l. It is a road.

Here, the armature 4 is a small block piece made of a ferromagnetic material such as silicon iron, and the above-described printing wire 2 is brazed to the tip thereof as indicated by the symbol W. Further, the armature 4 is overlapped with the free end side of the leaf spring 5 and spot welded. On the other hand, the magnetic path 6 includes a disk-shaped base yoke 7, a ring-shaped permanent magnet 8 laminated around the outer periphery of the yoke 7, yokes 9 and 10, and a magnetic path 6 installed in the base yoke 7 facing the lower surface of the armature 4. The degaussing coil 11 is assembled with the core 12 of the equipment, and the leaf spring 5
is sandwiched between yokes 9 and 10 and integrally fastened to housing 1 with bolts 13.

The operation of such a wire dot printer head is well known; when the demagnetizing coil 11 is de-energized, the armature 4 resists the spring force of the leaf spring 5 due to the magnetomotive force of the permanent magnet 8, as shown by the dotted line in FIG. and is adsorbed to the core 12. On the other hand, if the degaussing coil 11 is excited in response to the print signal,
The magnetic flux passing through the core 12 is canceled by the magnetomotive force of the permanent magnet 8, and the magnetic attraction force disappears, and as a result, the armature 4 is biased upward by the spring restoring force of the leaf spring 5, as shown by the solid line in the fifth example. At the same time, the tip of the printing wire 2 protrudes forward from the housing 1, and printing is performed by the dot matrix method.

[Problem to be solved by the invention]

By the way, in the wire dot printer head mentioned above,
During each printing operation, the armature 4 swings between the solid line and dotted line positions in FIG. Move up and down while being forcibly guided,
During this process, the tip of the printing wire 2 collides with the object to be printed. For this reason, when brazing the printing wire 2 and the armature 4, repetitive bending moments are applied intensively to the joint in the positive and negative directions for each printing operation, and as a result, during long-term use, the brazing joint becomes fatigued. There is a risk of cracking or fatigue failure.

On the other hand, in the above-mentioned wire dot printer, as mentioned above, the printing wire 2 usually employs a thin cemented carbide wire such as high-speed steel, and the armature 4 is made of a ferromagnetic material such as silicon iron. Furthermore, silver solder is used as a brazing material for brazing the printing wire 2 to the armature 4, which is a base metal, and a flux agent is used in combination for brazing.

However, on the surface of cemented carbide, ceramic particles such as tungsten carbide WC and titanium carbide TiC, which are hard components, appear on the surface, and the strength of brazing to these particles is extremely low (and the strength of brazing materials is extremely low). It is also known that the brazing material has low wettability with respect to the metal oxide film of cobalt (cobalt) contained as a binder metal, and it is extremely difficult to braze thin cemented carbide wires as it is. be.

As a countermeasure for this, attempts have been made to increase the heating temperature during brazing to precipitate cobalt as a binder metal and improve wettability with the brazing metal, but the cobalt precipitation causes thin wires to form. In this case, the sensitivity of the notch effect increases and the strength of the printing wire itself decreases. There is also a known method in which the surface of the printing wire is etched and then metal plated, and then the wire is brazed to the armature, but this method increases the cost of the pretreatment.

In this way, when the printing wire 2 made of a fine cemented carbide wire is joined to the alloy armature 4 by brazing, sufficient bonding strength cannot be obtained to withstand the stress concentration caused by the repetition of the printing operation described above. . In addition, if the flux used in brazing is not completely removed, rust will occur and the strength of the joint will decrease.In addition, in wire dot printers, if the amount of brazing material attached is large, the moving parts This increases the weight of the printer, which has a negative impact on the high-speed printing function.

The present invention has been made in view of the above points, and is intended for the above-mentioned wire dot printers, etc., by replacing the conventional brazing method with a method that does not cause defects such as voids in the thin cemented carbide wire itself. It is our promise to provide a welding method that can join cemented carbide thin wires to alloys with high joint strength.

(Means for Solving Problem 1) In order to solve the above problem, the welding method of the present invention irradiates a laser beam near the welding part on the base metal side with the cemented carbide thin wire in contact with the alloy. Here, the fillet of the alloy metal produced by melting and solidification wraps the thin cemented carbide wire and joins the thin cemented carbide wire and the alloy.

[Effect]

As in the above method, by irradiating the laser beam near the weld on the base metal side with the cemented carbide thin wire in contact with the alloy, a part of the alloy metal is melted by the laser irradiation heat, and this melt The metal fills the gap between the alloy and the cemented carbide wire,
Furthermore, in a flowing state that envelops the thin wire, it solidifies by cooling to form a fillet. In addition, during this process, the ceramic component of the cemented carbide also diffuses into the base metal, resulting in a welded joint with high joint strength.

In addition, especially in the wire dot printer mentioned above, during the welding process using laser irradiation, the cobalt oxide film as a binder metal formed on the surface of the fine cemented carbide wire is removed from the silicon component contained in the ferromagnetic material of the armature. Since it is removed by the deoxidizing action of , it works to increase the wettability between the fillet and the ceramic particle components of the cemented carbide. Moreover, since the laser beam is not directly irradiated onto the cemented carbide thin wire during the welding process, there is no risk of defects such as voids caused by the evaporation and scattering of the components of the cemented carbide due to laser irradiation.
This prevents a decrease in the strength of the cemented carbide thin wire itself due to this defect.

On the other hand, it has been confirmed that good results can be obtained by welding using a YAG laser device as a laser beam source, with an irradiation voltage of 350 to 360 cm, and a defocus amount of about 4 to 5 mff1 to the irradiated surface. ing. Note that if the laser irradiation conditions are below the above range, the fillet will not wrap the cemented carbide fine wire insufficiently, and if it exceeds the above range, the molten metal will evaporate and scatter, making it impossible to form a sufficient fillet. Furthermore, if the laser beam directly touches a thin cemented carbide wire, cobalt, which is the main component of the cemented carbide, will evaporate and scatter, creating voids on the surface of the thin wire, so care must be taken.

〔Example〕

Fig. 1 is an explanatory diagram of the welding method according to the present invention for joining an armature and a printing wire in a wire dot printer, Fig. 2 is a side view of Fig. 1, and Fig. 3 is an explanatory diagram of the welding method according to the present invention for joining an armature and a printing wire in a wire dot printer. 4 shows a cross-sectional view of a welded joint of a sample welded to the same material. In the figure, the same members corresponding to those in FIG. Note that a recess 4a is previously formed at the tip of the armature 4 made of an alloy, and a printing wire 2 (diameter of about 0.2 to 0.3511 In+) made of a fine cemented carbide is fitted into this recess 4a. It is welded and joined like this. Note that the recess 4a described above is not necessarily necessary, and the printing wire 2 may be directly brought into contact with the wall surface on the armature 4 side for welding.

Here, in order to weld between the printing wire 2 and the armature 4, first the printing wire 2 is welded to the recess 4a of the armature 4.
In this state, a laser beam 14 is irradiated from the YAG laser device 13 toward the joint from the back side of the armature 4. Here, set the irradiation voltage to 350 to 36
By performing laser irradiation under the conditions of 0 V and defocus amount of 4 to 5 I, the armature 4 is locally melted and solidified in a dotted area with a diameter of 0.3 to 0.5 mm, forming a fillet that wraps around the printing wire 2. 15 is formed. The welding point is preferably located at the center of the armature 4 in order to alleviate the bending moment applied to the welding point during the printing operation described in FIG. 5.

On the other hand, the Vickers hardness of the bonded portion of the printing wire 2 was determined based on a sample in which the printing wire 2 and the armature 4 were actually bonded using the laser welding method and the conventional brazing method described above.
When we actually measured the fatigue strength, we found that brazing has a hardness value of Hv according to the law.
(1) is 150-200, whereas in the laser welding method it is 500-600, and the fatigue strength is 11 K
gf/n+m” (conventional method) to 65 Kgf/r1m”
It was confirmed that this could be improved. Furthermore, when the cross section of the welded joint of the sample was analyzed using an electron microscope, no defects such as voids were observed in the joint, and the printing wire 2 showed that tungsten, which is a ceramic component of the cemented carbide, was found in the armature 4. It was observed that it was well diffused into the alloy region.

It is clear that this allows the bonding strength between the printing wire 2 and the armature 4 to be significantly improved compared to the conventional brazing method.

Although the above description has been made regarding the connection between the armature of a wire dot printer head and the printing wire, it is needless to say that the present invention is not limited to this and can be applied to other fields as well.

〔Effect of the invention〕

As explained above, in the welding method of the present invention, a laser beam is irradiated near the welding part on the base metal side while the cemented carbide fine wire is in contact with the alloy, and the wire is melted there.

By wrapping the cemented carbide thin wire with the fillet of the solidified alloy metal to bond the cemented carbide thin wire and the alloy, the following effects are achieved.

In other words, conventional brazing can firmly weld the cemented carbide wire and the alloy with high bonding strength without causing defects in the cemented carbide wire due to the use of flux as seen in conventional brazing methods. can. In addition, by applying it to areas where repeated bending moments are concentrated during each printing operation, such as the joint between the armature and printing wire in a wire dot printer head, it increases the fatigue strength of the joint and improves the reliability and durability of the printer head. can significantly improve sex.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the welding method of the present invention, which is applied to the joint between the armature and printing wire of a wire dot printer head, FIG. 2 is a side view of FIG. Sectional view of the welded joint of the sample carried out, No. 4
The figure is a sectional view of the structure of the wire dot blink head, and FIG. 5 is an explanatory diagram of the operation of the main parts in FIG. 4. In each figure, 2: printing wire (carbide thin wire), 4: armature (base metal), 13: laser device, 14: laser beam,
15: Fillet. Figure 2 Figure 4 Figure 3 Figure 5

Claims (1)

[Claims] 1) A method of welding a cemented carbide fine wire to a base metal, the method comprising:
With the thin cemented carbide wire in contact with the base metal, a laser beam is irradiated near the welded part on the base metal side, and the fillet of the base metal that is melted and solidified is formed to wrap around the thin cemented carbide wire to form a super A method for welding a thin cemented carbide wire, characterized by joining the thin hard metal wire and a base metal.