JPH0453921B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for brazing cemented carbide members used in various tools, printing wires, and the like.

[Prior Art] Conventionally, methods of brazing cemented carbide members have been used, but sufficient joint strength has not been obtained.

The reasons for this are as follows.

Ceramic particles such as tungsten carbide WC and titanium carbide TiC, which are hard components, appear on the surface of the cemented carbide member, and the brazing strength against these particles is extremely low.

Next, regarding surface cleaning, even if degreasing is done with a solvent such as thinner or trichloroethane, the oxide film of the binder metal (mainly cobalt) cannot be removed. Although flux is used in the brazing process, it is still difficult to remove the metal oxide film. Furthermore, even when a reducing flame was used to prevent oxidation during heating during brazing, it was difficult to completely remove this metal oxide film.

Furthermore, looking at the flow of molten wax, tungsten carbide WC, titanium carbide TiC,
The wettability of molten solder to ceramic carbide components such as tantalum carbide TaC is poor, and the wettability of molten solder to metal oxide films such as Co is also poor.

[Means for Solving the Problems] The present invention is intended to solve the problem of the bonding strength between the cemented carbide member and the base metal in the above-mentioned prior art. To provide a method for brazing cemented carbide members, in which sufficient joining strength by brazing can be obtained by plating with a metal that forms an alloy with a brazing material and has a lower melting point than the brazing material, and providing a metal plating layer. It is something.

[Example] In FIG. 2, the cemented carbide member has a structure in which cemented carbide components 1 of ceramic are connected with a binder 2.
The carbide component 1 is WC, TaC, TaC(Nb)C,
There are VCs, etc. As the binder 2, cobalt Co is usually used.

First, the surface of this carbide member is cleaned and degreased using thinner, trichloroethane, or the like.

Next, the carbide member is immersed in an etching solution to dissolve the exposed portion of the ceramic carbide component 1. As the etching solution, use potassium hydroxide aqueous solution, potassium ferricyanide aqueous solution, etc. at 50±2℃.
Soak for 10 minutes at a temperature of . As a result of the etching process removing the superhard component 1 on the surface, the surface becomes rich in Co as shown in the third figure and also has a surface roughening effect. After etching, the carbide member is washed with water and immediately plated.
By immediately proceeding to the plating process after etching, it is possible to prevent the formation of an oxide film on the Co surface of the binder. As for the type of metal plating, it is made of an alloy with the brazing material and is plated with a metal that has a lower melting point than the brazing material. If the brazing material is an alloy, plating with a metal that contains at least one of the alloy components and has a lower melting point than that alloy is effective. Also, it is preferable to use a metal that forms an alloy composition with the brazing material. The following is an example of the correspondence between the brazing material and the type of plating.

(Brazing material) (Type of plating) Ag-Cu-Zn system...Zn plating Ag-Cu system...Zn plating Cu-Ag-Sn system...Sn plating or Zn plating Au system...Au plating or Cu plating Sn-Pb system... Sn plating, Pb plating or solder plating If the plating thickness is too thin, there will be no surface protection effect, and if it is too thick, the brazing alloy composition of the brazed part will change and the strength will decrease, so it is desirable that the plating thickness is 1 to 30 μm.

As shown in the first figure, the metal plating layer 3 is formed by entering the recess formed by etching.

In the cemented carbide member made in this way, the binder (Co) surface is not exposed to the outside air and oxide film formation can be prevented. In addition, when brazing, it is basically desirable to braze in a reducing flame, but in the case of the present invention, since the carbide member is covered with the plating layer 3, good bonding can be achieved even when exposed to an oxidizing flame. Provides strength.

When the method for brazing cemented carbide members according to the present invention was used, the wettability of the molten solder to the joining members was very good, and the molten solder quickly uniformly covered the joining surface and its vicinity. Analysis of the cross section of the brazed part revealed that the plating layer was alloyed with the brazing material, and the boundary between the plating layer and the brazing material layer was not clear, and the composition changed continuously. A significant improvement in brazing productivity was also observed.

The bonding strength of the cemented carbide member brazing method according to the present invention will be compared with that of a conventional example. As a carbide member, the diameter is 0.35 mm as shown in Figure 4, and the hard component is
A wire 4 made of WC type binder Co was used and was brazed to the surface of a SUS steel base metal 5 having a plate thickness of 0.35 mm and a thickness of 2.00 mm. Silver brazing filler metal (Ag-Cu
−Zn diameter) was used. Zn plating was used for the plating layer of the cemented carbide member in the present invention. When we examined the tensile shear strength after brazing, we found that the average tensile shear strength of conventional cemented carbide members without any surface treatment was 13 kg. In contrast, those using the carbide member according to the present invention showed an average weight of 20 kg.

Next, when the method of the present invention was applied to the wire of a wire dot printer, the number of dots removed by brazing was compared between the conventional product and the wire using the present invention, which were brazed under the same conditions as above. It was as follows.

No treatment 30 to 40 million dots Sandblasting 50 to 60 million dots Etching only hard parts 50 to 60 million dots Using the present invention 300 million dots As is clear from the above, in the case of the present invention, the joint strength and durability of brazing are Improvement in sexual performance is observed. This is because the plating layer of the joining member and the brazing material constitute an alloy, so the wettability of the molten solder to the joining member is very good, which improves the joint strength. In addition, the carbide surface is Co-rich or This is due to the fact that Co (all) allows for a large brazing area, and the roughening effect of the carbide surface allows for better adhesion of the brazing material.

[Effects of the Invention] According to the method for brazing cemented carbide members according to the present invention, a metal that forms an alloy with the brazing material and has a lower melting point than the brazing material is used as the material for the metal plating layer on the cemented carbide member. As a result, the plating layer and the brazing material are alloyed during brazing, and the wettability of the molten solder to the joining members is very good, and it is possible to improve the joint strength and joint durability of the brazing.

[Brief explanation of the drawing]

1 to 4 show examples of the present invention, FIG. 1 is a cross-sectional explanatory diagram of a cemented carbide member plated, and FIGS. 2 and 3 are cross-sections of the carbide member shown in the order of processing steps. The explanatory drawing and FIG. 4 are perspective views when brazing the carbide member to the base metal. 1... Carbide component, 2... Hinder, 3... Metal plating layer, 4... Carbide member, 5... Base metal.

Claims (1)

[Claims] 1. A step of etching a cemented carbide member made of an alloy containing a binder and a ceramic carbide component, and dissolving the carbide component appearing on the surface; A method for brazing a cemented carbide member, comprising the steps of: plating with a metal that is an alloy with the metal and has a lower melting point than the brazing material; and brazing the cemented carbide member to a base metal.