JPH06277872A - Brazing method for metallic member having nitrided layer on surface and brazing filler metal for welding used therefor - Google Patents

Abstract

PURPOSE:To inexpensively improve joining strength in a brazed product of the metallic member having the nitrided layer on the surface having high wear resistance. CONSTITUTION:Brazing filler metal added with Al or Cr or Al and Cr by 0.5-3% at the weight rate on brazing filler metal consisting essentially of Ag-Cu or Ag-Cu-Zn is produced. The other member to be joined (printed wire) 2 is brazed on the metallic member (printed lever) 1 having the nitrided layer 1a on the surface by using this brazing filler metal. Since Al or Cr easily combines with Ni in the nitrided layer and molten brazing filler metal 3 is improved on wettability for the nitrided layer, this is stuck to the surface of the metallic member extending over the wide range. The nitrided layer which has been executing a cohesion suppressing function between the metallic member and the molten brazing filler metal is extinguished by using this brazing filler metal and a layer where a compound of N in the nitrided layer with Al or N with Cr is diffused is produced. As a result, an affinity between the metallic member and the molten brazing filler metal becomes higher, bubbles in the molten brazing filler metal are removed and strong joined surface is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing method for a metal member having a nitride layer on the surface thereof such as a printing lever of a wire dot printer and another member to be joined such as a printing wire, and a brazing material for welding used therefor. It is about.

[0002]

2. Description of the Related Art Recently, the printing speed of wire dot printers has been remarkably improved and the printing density has been increased. Therefore, the printing lever and the printing wire constituting the printing head have high strength and high abrasion resistance. There is a demand for something with the characteristics.

In response to these requirements, the material of the printing lever is carbon tool steel, special tool steel, maraging steel, etc., which is heat-treated, and the surface of which is plated with Ni.

Similarly, a high strength piano wire or a special tool steel material is used as a printing wire material, and a cemented carbide material or the like is used as a high-grade product.

[0005] And, for joining the print lever and the print wire, a high-strength silver solder mainly containing silver-copper (Ag-Cu) or silver-copper-zinc (Ag-Cu-Zn) is used. The brazing method is adopted.

Further, since the portion where the return spring comes into contact with the print lever is greatly worn, it has been attempted to employ a print lever having a nitride layer formed on the surface thereof, which has high wear resistance and is low in cost. There is.

[0007]

However, a metal member having a nitride layer on its surface has a high abrasion resistance, but on the other hand, it has an action of suppressing the adhesion of reaction products generated near the surface of the member. For this reason, during brazing, the surface tension of the molten braze is increased, the wettability, which is the most important factor in brazing, is lowered, and the strength at the joint is lowered.

More specifically, as shown in FIG.
A print wire 1 which is a member to be joined to the end of the print lever 11.
Molten brazing material 13 in which silver brazing material is melted in the state where 2 is brought close to each other 13
Even if the metal is deposited, the brazing surface 14 does not undergo a diffusion reaction or the like between the nitride layer 11a and the molten braze 13, and the nitride layer remains in that state. Further, if the diffusion reaction is not carried out on the brazing surface 14, there is a problem that the bubbles 13a generated at the time of heating cannot be completely removed from the melting brazing and the bubbles 13a remain in the fusion brazing. The presence of the bubbles 13a in the fusion brazing reduces the strength of the joint because it reduces the area of the joint accordingly. Further, in the brazing surface 14, since the diffusion reaction is not performed, the molecular bond in the joint surface is very weak, which causes the strength of the joint surface to decrease. Therefore, it is difficult to obtain a joined product such as a print lever as a metal member having a nitride layer on the surface and a print wire as a joined member.

Thus, it is difficult to obtain a brazed product of an inexpensive metal member having a nitride layer having high wear resistance and another member to be joined, but this problem is caused by the joining of the printing lever and the printing wire. It is not only a problem of strength but also a problem applicable to general brazing of members having a nitrided layer. This should be solved by making it possible to braze these members using a brazing material having high wettability to the nitrided layer.

Therefore, an object of the present invention is to braze a metal member having a nitride layer on its surface to another member to be joined,
It is an object of the present invention to provide a brazing material capable of improving the wettability, and at the same time to improve the bonding strength by brazing a metal member having a nitride layer on its surface and another member to be bonded.

[0011]

In order to achieve the above object, Ag as a brazing filler metal for brazing a metal member having a nitride layer on its surface and another member in the present invention is used.
A brazing filler metal containing Cu, Ag, Cu, Zn, and Zn as the main components was added with 0.5 to 3% by weight of Al or Cr or both Al and Cr, respectively.

By using the above brazing material, a metal member having a nitride layer on the surface and another member to be joined are brazed to obtain a joined portion having high joining strength.

[0013]

By the above means, Al, Cr or A
By adding 0.5 to 3% by weight of both 1 and Cr, respectively, when brazing another joining member to a metal member having a nitrided layer on the surface, Al and Cr form a molten braze and a nitrided layer. To increase the affinity and reduce the effect of suppressing the adhesion of reaction products on the surface of the nitrided layer, so that the wettability of the brazing filler metal for welding is improved.

When a metal member having a nitride layer on its surface and another member to be joined are brazed using the above brazing material, Al or Cr in the brazing material reacts with N in the nitride layer at the joining surface. This promotes the diffusion action, thereby improving the wettability, suppressing the bubbles remaining in the molten brazing material, and improving the bonding strength.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, as shown in FIG. 2, as a metal member having a nitride layer on the surface, the tip of a print lever 1 which constitutes a print head of a wire dot printer is provided near the one end of a print wire 2. Take the case of brazing the molten metal through the molten braze 3.

The print lever 1 is formed by nitriding a nitriding steel material having a predetermined shape and forming a nitriding layer 1a having high wear resistance on the surface. Also, the printing wire 2
Uses a cemented carbide material.

As a brazing material, BAg-24, which has the highest wettability among silver brazing materials with respect to general metal members.
A composition having the same composition as (JIS Z 3261) to which Al was added in an amount of 1 to 3% by weight was adopted.

In the brazing operation, the print lever 1 and the print wire 2 are attached to a brazing jig and arranged as shown in FIG. 1, and a high frequency heating device is used to set the temperature to about 750 ° C.
Then, the tip of the print lever 1 is joined to the vicinity of the end of the print wire 2.

Since Al added to the silver solder has the property of easily combining with N in the nitride layer on the surface of the print lever,
While the brazing material is at a high temperature, a vigorous chemical reaction occurs between the molten brazing material 3 adhering to the print lever 1 and the nitride layer 1a to form a compound such as AlN. Therefore, the joining surface 4 is in a state where the nitride layer 1a disappears and the base material Fe, the brazing material 3 and this compound are mixed. As a result, the structure of the joint surface is, in order from the inside of the printing lever 1, the base metal containing Fe as the main component, the structure of the brazing filler metal containing the compound of AlN in the base metal, and then Ag-Cu. -Zn
The structure of the brazing filler metal whose main component is is gradually distributed. Since the joint surface has such a structure, the nitride layer does not suppress the adhesion,
The affinity between the print lever 1 and the molten solder 3 is increased. Further, since the chemical reaction is actively carried out, no bubbles remain in the molten brazing material, so that a strong joint can be obtained.

The printing wire 2 does not have a nitride layer,
Since a cemented carbide material with good wettability is used, no problem in joining strength occurs.

As described above, when a brazing filler metal (BAg-24) containing 1% of Al is used and a metal member having a nitride layer on the surface is brazed and joined, no Al is added. Bonding strength of about 1.5 times is obtained as compared with brazing with a brazing material (BAg-24).

The brazing filler metal (BAg-2) used in this embodiment.
In addition to Al added to 4), Al can be added to other brazing materials containing Ag and Cu or Ag, Cu and Zn as the main components, and the wettability to the nitride layer can be similarly enhanced. is there.

In addition to Al, Cr is also effective as an additive material because it is easy to form a compound with N. In the brazing material of the present invention, instead of Al, Cr, which easily combines with N in the nitride layer, is added. The same result can be obtained by adding both Al, Cr and Cr. However, the bonding strength can be increased only when the addition amount of these is 0.5 to 3% by weight. If the amount of Al or Cr added is 0.5% or less, the improvement of the wettability is insufficient, and if it is 3% or more, Ag-Cu (α-
[beta]) or Ag-Cu-Zn ([alpha]-[beta]-[gamma]) in the solid solution segregates Al and Cr, which results in weakening the bonding strength.

In this embodiment, the brazing temperature is 750 ° C.
However, it is necessary to appropriately set the optimum brazing temperature according to the properties of the joining base material and the brazing material. Further, the printing wire or the like as the member to be joined is not limited to the cemented carbide material, but the same joining strength can be obtained even if it is made of a piano wire or a special tool steel wire.

The present invention is not limited to the brazing of the printing lever and the printing wire, but is applicable to general brazing of metal members having a nitride layer.

[0027]

As described above, according to the present invention, Ag and C are used.
Brazing a metal member having a nitride layer on its surface and another member to be joined by adding a small amount of Al or Cr or Al and Cr into a brazing material containing u or Ag, Cu and Zn as main components. It is possible to obtain a brazing filler metal capable of improving the wettability during the welding and preventing the bubbles from remaining in the fusion brazing solder.

By brazing another member to be joined to a metal member having a nitride layer on the surface using the above brazing material, a brazed product having a very high joint strength can be obtained. For this reason, it is possible to use inexpensive nitriding-treated members as means for imparting wear resistance, so that it is possible to reduce the cost of brazing products used under harsh conditions such as joining parts of the printing lever and the printing wire. Can be obtained at.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing a brazing state in the present invention.

FIG. 2 is an explanatory diagram showing a state in which a print wire is brazed to the tip of the print lever.

FIG. 3 is an enlarged cross-sectional view showing a brazing state in a conventional example.

[Explanation of symbols]

 1 Metal member 1a Nitrided layer 2 Joined member 3 Brazing material

Claims (2)

[Claims] 1. A brazing material containing Ag and Cu or Ag, Cu and Zn as main components, and Al or Cr or Al and C.
A brazing filler metal for welding, characterized in that both of r are added in a weight ratio of 0.5 to 3%. 2. A metal member having a nitride layer on the surface, which comprises brazing a metal member having a nitride layer on the surface and another member to be joined by using the brazing material according to claim 1. Brazing method.