Silver brazing material and joining method using the silver brazing material

Abstract

A silver brazing material containing silver, copper, zinc, manganese, nickel, and tin as indispensable constituent elements. The silver brazing material includes 35 mass % or more and 45 mass % or less silver, 18 mass % or more and 28 mass % or less zinc, 2 mass % or more and 6 mass % or less manganese, 1.5 mass % or more and 6 mass % or less nickel, and 0.5 mass % or more and 5 mass % or less tin, with the balance being copper impurities. Within these compositional ranges, a predetermined relation is set between the manganese content and the nickel content, whereby the silver brazing material can be provided with excellent characteristics also in terms of processability or wettability. In the silver brazing material of the present invention, the silver content is reduced, and also melting point reduction and the narrowing of the temperature difference between solidus temperature and liquidus temperature are attempted.

Claims

1. A silver brazing material comprising 35 mass % or more and 45 mass % or less silver, 18 mass % or more and less than 25 mass % zinc, 2 mass % or more and 6 mass % or less manganese, 1.5 mass % or more and 6 mass % or less nickel, and 0.5 mass % or more and 5 mass % or less tin, with the balance being copper and unavoidable impurities, wherein the silver brazing material has a manganese content (C.sub.Mn) and a nickel content (C.sub.Ni) represented by the following formula:
C.sub.Mn/C.sub.Ni≥0.9  [Equation 1] and wherein the contents of silver, copper, zinc, manganese, nickel, and tin are set to be within said ranges so that a temperature difference between solidus temperature and liquidus temperature of the material is 50° C. or less.

2. A joining method using the silver brazing material defined in claim 1, comprising the step of placing the silver brazing material at a brazing site of a member to be joined, and heating and melting the silver brazing material, wherein the silver brazing material is heated at a heating temperature of 725° C. or more and 825° C. or less.

3. A tool comprising two or more members joined through at least one joint, wherein said at least one joint includes the silver brazing material defined in claim 1.

4. The tool according to claim 3, wherein at least one of the members joined through a joint comprises any one of copper, copper alloys, carbon steel, tool steel, and stainless steel.

5. A tool comprising two or more members joined through at least one joint, wherein said at least one joint includes the silver brazing material defined in claim 1.

6. The silver brazing material according to claim 1, comprising 35 mass % or more and 45 mass % or less silver, 18 mass % or more and 24.8 mass % or less zinc, 2 mass % or more and 6 mass % or less manganese, 1.5 mass % or more and 6 mass % or less nickel, and 0.5 mass % or more and 5 mass % or less tin, with the balance being copper and unavoidable impurities.

7. The silver brazing material according to claim 1, comprising 35 mass % or more and 45 mass % or less silver, 18 mass % or more and 24.7 mass % or less zinc, 2 mass % or more and 6 mass % or less manganese, 1.5 mass % or more and 6 mass % or less nickel, and 0.5 mass % or more and 5 mass % or less tin, with the balance being copper and unavoidable impurities.

Description

DESCRIPTION OF EMBODIMENTS

(1) Hereinafter, an embodiment of the present invention will be described. In this embodiment, silver brazing materials (Ag—Cu-based alloys) of various compositions were produced by melt-casting, and their solidus temperatures and liquidus temperatures were measured. Then, each brazing material was evaluated for processability and wettability.

(2) In the production of evaluation samples of various silver brazing materials, first, high-purity materials of the constituent metals were mixed, and melted and cast in air, thereby producing a rod-like alloy ingot (18 mm in diameter). Next, the rod-like alloy ingot was sliced to cut out a 3-mm-thick sample. Then, the sample was rolled and cut into a chip-like sample. This sample was used for chemical analysis and X-ray fluorescence spectrometry to perform detailed composition analysis. In addition, from the cut-out sample, 0.1 g of a sample for thermometric analysis was further cut out, and the solidus temperature and liquidus temperature were measured.

(3) The measurement of solidus temperature and liquidus temperature was performed by differential scanning calorimetry (DSC). In this embodiment, measurement was performed by use of DSC3300 manufactured by Bruker AXS as the measurement device, in an Ar atmosphere, at temperature rise rate of 20° C./min, and in a measurement temperature range of room temperature to 1250° C. In the measured chart, tangents were drawn at relatively stable positions near the height of about 40 to 50% of the peak height of the peak during temperature rise (rising side and falling side), and also a tangent along the baseline was drawn. Then, the intersection between the tangent drawn on the rising side of the peak and the tangent of the baseline was defined as the solidus temperature (SL), while the intersection between the tangent drawn on the falling side of the peak and the tangent of the baseline was defined as the liquidus temperature (LL). In addition, based on the measured solidus temperature and liquidus temperature, the difference between the two was calculated.

(4) Table 1 shows the composition, the melting point (solidus temperature), and the liquidus temperature of each silver brazing materials of various compositions produced in this embodiment, together with the results of processability evaluation. Incidentally, in this embodiment, a silver brazing material of composition equivalent to “BAg-7”, which is a conventionally well-known silver brazing material, was produced and studied as “Conventional Example.”

(5) TABLE-US-00001 TABLE 1 Melting point (° C.) Composition (mass %) Temperature No. Ag Zn Mn Ni Sn Cu Solidus Liquidus difference 1 40.5 22.7 4.7 4.2 1.9 Balance 656 672 16 2 40.6 23.1 5.4 2.0 1.8 670 705 35 3 35.8 27.6 4.1 4.2 0.9 673 691 18 4 44.8 18.5 4.4 4.4 2.0 659 701 42 5 40.3 24.8 4.6 1.9 4.9 638 685 47 6 40.0 23.0 5.1 3.8 4.7 652 672 20 7 39.7 24.7 5.2 3.8 1.6 662 679 17 8 40.2 20.5 4.6 3.8 1.7 654 680 26 9 40.4 19.2 4.9 4.1 1.9 651 692 41 10 40.3 20.5 5.3 5.8 1.8 657 691 34 11 40.5 22.7 4.7 4.2 1.9 656 672 16 12 40.2 26.9 2.7 2.1 1.0 668 691 23 13 40.3 22.8 4.7 4.1 4.1 659 678 19 14 40.6 22.7 1.5 6.0 2.0 650 700 50 15 40.8 22.7 6.4 7.2 1.9 672 697 25 16 40.5 27.7 0.3 0.5 2.0 662 728 66 17 41.8 20.0 1.4 4.2 — 696 720 24 18 40.0 28.0 — 2.0 — 670 780 110 19 40.0 28.0 3.0 — — 675 720 45 20 25.0 33.0 2.0 2.0 — 705 800 95 21 50.2 21.7 5.3 3.8 1.8 655 750 95 22 43.6 17.1 3.8 2.0 2.0 645 699 54 23 30.8 30.8 3.7 3.2 7.3 617 710 93 Conventional 56.2 15.6 — — 5.1 620 650 30 Example

(6) As a result of studying the silver brazing materials of No. 1 to No. 15 in Table 1, it can be seen that addition of both manganese and nickel seems to be able to reduce melting point (i.e. liquidus temperature of 705° C. or less) and narrow the temperature difference between solidus temperature and liquidus temperature (50° C. or less).

(7) The brazing material of No. 16 is a silver brazing material close to the above silver brazing material described in Patent Document 1. In this silver brazing material, although manganese and nickel were added, because their amounts were too small, their effects were not exerted. As a result, the liquidus temperature was high, and the narrowing of the temperature difference between solidus temperature and liquidus temperature was also insufficient.

(8) The silver brazing material of No. 17 had a small amount of manganese and contained no tin, and thus the melting point was not satisfactory. The silver brazing materials of Nos. 18 and 19, to which manganese and nickel had not been added simultaneously, had high liquidus temperatures and were unsuitable. In addition, these silver brazing materials, to which tin had not been added, showed relatively high solidus temperatures. In the case where tin is added to such a material, the temperature difference from the liquidus temperature is expected to increase due to a decrease in the solidus temperature. The silver brazing material of No. 20 contains too little of silver, thereby the temperature difference between solidus temperature and liquidus temperature is large and the liquidus temperature is also high. Meanwhile, the silver brazing material of No. 21 contains too much of silver, and silver reduction is less significant. Further, the temperature difference between solidus temperature and liquidus temperature is also large. The silver brazing material of No. 22 contain small amount of zinc, so that the temperature difference between solidus temperature and liquidus temperature is more than 50° C.

(9) Then, the silver brazing material of No. 23 showed remarkably lowered melting point (solidus temperature) due to excessive addition of tin, the temperature difference from the solidus increased. In the present invention, although the addition of tin is indispensable, tin is believed to be an auxiliary additive element for melting point adjustment.

(10) Next, out of the silver brazing materials according to this embodiment described above, which satisfied conditions related to the melting point (No. 1 to No. 15 and Conventional Example), namely satisfied such criteria as that the liquidus temperature is 705° C. or less and the temperature difference between solidus temperature and liquidus temperature is 50° C. or less, some brazing materials (Nos. 1 to 4, 10, 14, 15, and Conventional Example) were subjected to processability and wettability evaluation tests.

(11) In the processability evaluation method, processability was judged from the possibility of plastic processing at the time when, in the production process of each of the silver brazing materials described above, a sample cut out from a rod-shaped ingot after melt-casting was rolled in a rolling mill. Rolling was performed at room temperature at a processing ratio of 10%. When processing was possible without cracks or the like, processability was rated as good (⊙), while when although small cracks were seen at the end of the rolled material, etc., processing was possible, processability was rated as fair (◯). Meanwhile, when notable cracks were formed in the rolled material, or rolling was not possible due to fracture, processability was rated as poor (x).

(12) In the wettability evaluation method, from each of the samples of various silver brazing materials cut out from rod-shaped ingots, 0.1 g of a silver brazing material for wettability evaluation was cut out.

(13) Next, three kinds of test metal plates made of carbon steel, a copper, and brass (dimension: 40 mm wide×50 mm long×1.2 mm thick) were prepared. Then, the brazing material was mounted on each metal plate, and, in order to set the heating time in the evaluation test, the brazing material in this state was heated with a burner from the back of the metal plate. The time until the silver brazing material reached 750° C. was measured and recorded.

(14) In the wettability evaluation test, after the above preparation, and after mounting the brazing material on each metal plate, for the prevention of oxidation during heating, a flux (TB610 manufactured by Tokyo Braze Co., Ltd.) was applied to the silver brazing material and the surface of the metal plate. Then, the metal plate was heated with a burner from the back to melt the brazing material. Burner heating was performed only for the time measured above and stopped after the passage of time, and the sample was allowed to cool in air. After cooling, the flux was washed, and the area of wetting/spreading of the molten/solidified silver brazing material was measured. As a method for area measurement, the lengths in two directions, width and length, of the area of the silver brazing material that wetted and spread were measured. Then, with respect to each length, the area of a hypothetical circle having the measured length as its diameter was determined, and the average of two determined areas was defined as the wetting/spreading area. Based on this method, each silver brazing material was tested on each metal plate three times, and the average was defined as the wetting/spreading area of the silver brazing material on the metal plate.

(15) Wettability was evaluated based on the wetting/spreading area of each silver brazing material measured above. First, the wettability on each metal plate was evaluated as follows relative to the wetting/spreading area of the silver brazing material. Carbon steel: 150 mm.sup.2 or more was rated as “excellent (⊙)”, 70 mm.sup.2 or more and less than 150 mm.sup.2 was rated as “fair (◯)”, and less than 70 mm.sup.2 was rated as “poor (x).” Copper: 150 mm.sup.2 or more was rated as “excellent (⊙)”, 70 mm.sup.2 or more and less than 150 mm.sup.2 was rated as “fair (◯)”, and less than 70 mm.sup.2 was rated as “poor (x).” Brass: 150 mm.sup.2 or more was rated as “excellent (⊙)”, 60 mm.sup.2 or more and less than 150 mm.sup.2 was rated as “fair (◯)”, and less than 60 mm.sup.2 was rated as “poor (x).”

(16) Then, of the evaluation results for the above three kinds of metal plates, when there was at least one “excellent (⊙)”, an overall wettability evaluation “excellent (⊙)” was given, when there was at least one “poor (x)”, an overall wettability evaluation “poor (x)” was given, and in other cases, an overall wettability evaluation “fair (◯)” was given.

(17) The above processability and wettability evaluation results are shown in Table 2.

(18) TABLE-US-00002 TABLE 2 Compositional Wettability Composition (mass %) ratio Low-carbon No. Ag Zn Mn Ni Sn Cu C.sub.Mn/C.sub.Ni Processability steel Copper Brass Overall 1 40.5 22.7 4.7 4.2 1.9 Balance 1.12 ◯ ◯ ◯ ◯ ◯ 2 40.6 23.1 5.4 2.0 1.8 2.77 ◯ ⊙ ⊙ ◯ ⊙ 3 35.8 27.6 4.1 4.2 0.9 0.98 ◯ ⊙ ◯ ◯ ⊙ 4 44.8 18.5 4.4 4.4 2.0 0.99 ◯ ◯ ◯ ◯ ◯ 10 40.3 20.5 5.3 5.8 1.8 0.91 ◯ ◯ ◯ ◯ ◯ 14 40.6 22.7 1.5 6.0 2.0 0.25 ◯ X X X X 15 40.8 22.7 6.4 7.2 1.9 0.89 ◯ ◯ X ◯ X Conventional 56.2 15.6 — — 5.1 — X ◯ ⊙ ⊙ ⊙ Example

(19) The silver brazing materials subjected to the evaluation test, except for the conventional example, contained all of the constituent elements of the silver brazing material according to the present invention (silver, zinc, manganese, nickel, tin, and copper). From the evaluation results shown in Table 2, the silver brazing material of No. 14 having a low manganese content/nickel content ratio (C.sub.Mn/C.sub.Ni) had poor wettability on all the materials evaluated herein, and was presumed to cause a huge obstacle to workability during brazing. In addition, in the silver brazing material of No. 15, from the fact that the manganese content and the nickel content were too high, and also they were out of balance, it is believed that the wettability was insufficient. In the case of this silver brazing material, the wettability on carbon steel and brass was “fair (◯).” In consideration of these results together with the composition of the silver brazing material of No. 14, with respect to composition, it was considered to be preferable to suppress the upper limits of the manganese content and the nickel content to about 6.0% of No. 14, and also make the value of their ratio a little higher than 0.89. With reference to the results of the silver brazing material of No. 10, it is believed to be suitable that the manganese content/nickel content ratio is 0.9 or more. In the present invention, from the above consideration, the upper limits of the manganese content and the nickel content, as well as their ratio, were set.

(20) Incidentally, the silver brazing material (BAg-7) of the conventional example similarly satisfied the standards related to the melting point, and the wettability was also excellent. From the viewpoint of reducing the melting point and ensuring workability while attempting silver reduction, the usefulness of the present invention that allows for the reduction of the silver content by 10 mass % or more is clear. In addition, the silver brazing material of the conventional example was inferior in terms of processability.

INDUSTRIAL APPLICABILITY

(21) As described above, the silver brazing material according to the present invention is a brazing material capable of achieving both silver reduction and improvement of the characteristics as a brazing material. The present invention is drawn to a silver brazing material that meets a conventional requirement for a silver brazing material, that is, melting point reduction, and also achieves the narrowing of the temperature difference between solidus temperature and liquidus temperature. In the silver brazing material of the present invention, the silver content is set within a predetermined range, and manganese and nickel are both added within appropriate ranges. At the same time, the relation between their contents is strictly set. As a result, a silver brazing material that satisfies the standards related to the melting point described above and also has excellent wettability can be obtained.

(22) The silver brazing material according to the present invention is suitable for braze-joining of copper or a copper alloy, braze-joining of metal materials for tools (ferrous materials, etc.) or steel such as stainless steel, and also braze-joining between different kinds of metal materials. Brazing by use of the silver brazing material according to the present invention enables the heating temperature that serves as the working temperature to be lowered, whereby an efficient brazing work can be performed without concerns about the liquation and the like.