JPS58100995A - Low melting point brazing filler metal and its using method - Google Patents

Abstract

PURPOSE:To provide a low m. p. brazing filler metal which has a low m. p., and forms good fayed surfaces without showing any brittle layer in joining copper members by contg. P and Sn respectively at prescribed ratios and consisting of the balance Cu. CONSTITUTION:The above-described low m. p. brazing filler metal has the compsn. consisting of 3.0-6.5wt% P, 12-23wt% Sn, and the balance Cu and unavoidable impurities. To join copper members by using such low m. p. brazing filler metal, this brazing filler metal is inserted between a base material (Cu) and a base material (Cu), and at the point of the time when the temp. attains the selected value higher than the solidus line temp., upsetting pressure is loaded upon the materials. Then brittle compds., oxide films, etc. which are liquid phase part are discharged to the outside of the fayed surfaces and the copper materials are joined to each other by allowing only the alpha copper to remain in the fayed surfaces. This joining method is particularly effective for joining of copper to be used for pipes of room air conditions, car coolers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low melting point brazing material used for joining copper members and a method of using the same.

Since copper is a metal with the best thermal conductivity, it is difficult to centrally heat the joint to the melting temperature of copper in normal joining, making it difficult to obtain a reliable joint. Therefore, brazing is generally widely used for joining copper members. Silver solder and phosphorous copper solder are often used as brazing materials, but silver solder is silver 50
Phosphorous copper is often used because it is expensive due to its high content.

Phosphorus-copper solder is copper and phosphorus, or silver is added to this in a hypoeutectic structure, and its composition is a mixture of alpha copper and eutectic, which is different from conventional solder. The problem with this method was that the solder metal remained on the joint surface during the joint, making the joint more brittle than the base metal. The brazing temperature is 785°C to 925°C for Bout-1 and 705°C to 815°C for BOwp-5. Therefore,
The object of the present invention is to provide an excellent low melting point brazing material which solves the above-mentioned drawbacks, and to provide a method for joining copper parts using this brazing material.

That is, to summarize the present invention, the present invention contains phosphorus at 50 to 5% by weight, tin at 12 to 25% by weight,
The present invention relates to a low melting point brazing filler metal characterized in that the remainder consists of copper and unavoidable impurities.

The present inventors investigated the in-phase temperature for each composition of the brazing filler metal. Representative examples of the results are shown in FIGS. 1 and 2. 1st
The figure is a graph of the solidus temperature for each composition based on 0u-5chiP and varying the tin content from 10 to 30% by weight.The horizontal axis shows the tin content (weight%), and the vertical axis shows the tin content (weight%). Solidus temperature C
°C). Also, Figure 2 shows f:! This is a graph of the solidus temperature for each composition based on u-15%Sn and varying the phosphorus content from 1 to 8% by weight.The horizontal axis is the phosphorus content (weight%).
, and the vertical axis indicates the solidus temperature (°C). As can be seen from Figure 1, the range of solidus temperature below 550℃ is tin 11 to 23.
υ5 in weight% Even if it is less than or exceeds this range, the solidus temperature rapidly shifts to the high temperature side. Also, from Figure 2, it can be seen that the range where the solidus temperature is 550°C or less is 1 to 6.5% by weight of phosphorus.

The present inventors investigated brazing filler metals with combinations of seedlings. The brazing filler metal was manufactured by melting in an argon atmosphere a composition in which the balance was copper, the phosphorus needle was changed every 5% from 10 to 30% by weight, and the tin value was changed every 5% from 10 to 30% by weight. Using a brazing filler metal with this composition, a thin film (15 μm to 50 μm
μm) was manufactured. Bonding was performed using the brazing filler metal thus obtained on the bonding surfaces. An oxygen-free copper rod was used as the bonded sample at that time, and the size of the sample was a cylindrical test piece with a diameter of 8 mm and a length of 65 cm. The bonding was carried out using the apparatus shown in FIG. That is, FIG. 3 is a schematic diagram of a joining apparatus used in the method of the present invention, in which 1 indicates an oxygen-free steel rod as a base material, 2 a brazing filler metal, 3 a high-frequency coil, and 4 a ceramic jig for supporting 1.

Table 1 shows representative examples of the results.

Table 1 From the above results of Table 1 and the results of the solidus temperature, it was found that a brazing filler metal having a composition of 3 to 5% by weight of phosphorus and 12 to 23% by weight of tin exhibited the best properties.

That is, in the above five compositions, if the phosphorus content is less than 3% by weight, the self-solubility of the brazing filler metal is impaired, the wettability is significantly reduced, and the melting point is also increased, making it impossible to achieve the object of the present invention. Also, if phosphorus exceeds 65% by weight, 0u3P
A large amount of the compound crystallizes out, making it brittle and increasing its melting point, which is also not suitable for the purpose of the present invention.

If the amount of tin added is less than 12% by weight, the working melting point will not be lowered [it will not match unilaterally], and if it exceeds 23% by weight, it will become brittle, the melting point will rise, and the self-solubility of phosphorus will also decrease. It no longer serves the purpose.

The present invention also provides a method for joining copper members using the brazing filler metal, characterized in that the liquid phase generated in the brazing filler metal is pressurized and discharged to the outside of the bonding surface. Regarding.

For joining using the brazing filler metal of the present invention, an apparatus shown schematically in FIG. 3 is used. The process is carried out as shown in the joining process diagram of FIG. 4, and the pressure welding method is explained by the graph of the pressure welding process in FIG. In other words, the selected temperature (Tmax) at which the brazing filler metal is inserted between the base metal (Ou) and the base metal (Cu) is equal to or higher than the solidus temperature.
When this is reached, an upset pressure (P2) is applied to expel fragile compounds, oxide films, etc. from the bonding surface, leaving only the α-copper inside the bonding surface.

Note that the horizontal axis of the graph in FIG. 5 represents time (seconds), and the vertical axis represents temperature, pressure, and displacement.

A brittle intermetallic compound remains on the joint surface of conventional brazing, but no brittle layer is observed on the joint surface joined with the brazing material of the present invention, resulting in a good joint surface of 1°. The brazing filler metal and joining method of the present invention are particularly effective for joining steel used in room air conditioners, car cooler pipes, FFBs, and the like.

Examples and Comparative Examples of the present invention will be shown below, but the present invention is not limited thereto.

Example 1 A brazing filler metal having the composition shown in Table 2 was bonded to the bonding surface in the atmosphere without using flux. The bonded sample used was an oxygen-free copper rod, and the size of the sample was a cylindrical test piece with a diameter of 8 wn and a length of 35 m. Also, as a leakage resistance test piece for joints,
The joints were made using oxygen-free copper pipes with an outer diameter of 80%, an inner diameter of 6mm, and a length of 80mm. The results are shown in Table 2.

Table 2 FIG. 6 is a graph showing the mechanical properties in Table 2.

In the figure, the horizontal axis is the amount of phosphorus (wt%), and the vertical axis is the tensile strength, Kt.
i/wm2) and elongation (chi).

From Table 2 and FIG. 6 above, it can be seen that phosphorus amounts of 3 to 5% by weight give good results.

Example 2 The test piece shape was the same as in Example 1, and the joining method was also performed under the same conditions. The results are shown in Table 3+f-.

Table 3 FIG. 7 is a graph showing the mechanical properties in Table 3.

In the figure, the horizontal axis is the amount of tin (weight%), and the vertical axis is the tensile strength K
y/mn2) and elongation (%).

From Table 3 and FIG. 7, it can be seen that tin needles of 12 to 23% by weight give good results. Also, the upset pressure is 1
It can be seen that the optimum conditions are 9/τ2 or more and 4 Kg/am' or less.

That is, when the pressing force was less than I Kg/wn2, the melt inside the bonded surface was not discharged to the outside of the bonded surface, a brittle intermetallic compound layer remained, and the tensile strength was 15 to 9/2 or less, and the bond was broken. Moreover, if it exceeds 4 Kg/1an2, buckling deformation occurs, so the maximum pressing force is 4 K4/lrm2.

Fragments of brittle intermetallic compounds remain on the joint surfaces of conventional brazing filler metals. - No brittle layer was observed on the bonded surfaces bonded using the brazing material of the strength wood invention, and the bonded surfaces were good.

Therefore, the effects of the low melting point brazing filler metal of the present invention are particularly remarkable.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs showing solidus temperature, FIG. 3 is a schematic diagram of a bonding apparatus used in an embodiment of the method of the present invention,
FIG. 4 is a welding process diagram, FIG. 5 is a graph of the pressure welding process, and FIGS. 6 and 7 are graphs showing the mechanical strength of the bonded portions bonded by the bonding method of the present invention. 1: base metal oxygen-free copper rod, 2: brazing filler metal, 3: high frequency coil, 4: ceramic jig that supports 1. Fig. 4 Fig. 111q M 0fj-) Fig. 6 Fig. 7 Fig. 5rr (%)

Claims (1)

[Scope of Claims] 1. A low melting point brazing material characterized by comprising 50% to 6.5% by weight of phosphorus, 12% to 25% by weight of tin, and the remainder copper and unavoidable impurities. Z Phosphorus is 50% by weight ~ & 5% by weight, tin is 12% by weight
In a method of joining copper members using a low melting point brazing filler metal consisting of ~23% by weight, the balance being copper and unavoidable impurities, the heating temperature is equal to or higher than the in-phase line temperature, and the liquid phase part that forms in the brazing filler metal at the above heating temperature. A method for joining steel members, characterized in that the material is discharged from the joining surface by applying pressure.