JP5385951B2 - Silver brazing material - Google Patents

Description

  The present invention relates to a silver brazing material used for brazing (brazing), for example, a cemented carbide member and another member.

  Cemented carbide is generally a composite material obtained by sintering tungsten carbide (WC) powder using cobalt (Co) as a binder, and has high hardness and excellent wear resistance, and is widely used in cutting tools and the like. However, it is very expensive since it contains a rare metal such as tungsten as a main component.

  For this reason, for example, in cutting tools such as drills, the amount of cemented carbide used is reduced by reusing the shank. For example, only a worn blade portion of a used tool is removed, and a new blade portion is brazed to the remaining cemented carbide shank portion to be reused as a tool.

  By the way, conventionally, for example, a silver (Ag) brazing material disclosed in Patent Document 1 is used for brazing between the blade portion and the shank portion.

JP 2001-121288 A

  However, as a result of various studies, the present inventors have found that Co, which is a binder in the cemented carbide, diffuses into the brazing layer (brazing material) when brazing the cemented carbide with the conventional silver brazing material. Thus, it was found that Co in the cemented carbide near the bonding interface is deficient and breakage easily occurs.

  That is, when the brazing layer portion of the brazed joint has a certain level of strength, fracture occurs in the cemented carbide (the Co-deficient region where Co is deficient), and the size of this Co-deficient region depends on the strength of the joint. I found that it has a big influence.

  The present invention solves the above-mentioned problems, and provides a silver brazing material excellent in practicality that can exhibit excellent bonding strength even when used in bonding cemented carbide members. is there.

  The gist of the present invention will be described with reference to the accompanying drawings.

A silver brazing material composed of silver (Ag), copper (Cu), zinc (Zn), and cobalt (Co), wherein the content of each component is Ag: 48.0 to 54.0 mass%, Cu: The present invention relates to a silver brazing material characterized by being 19.0 to 23.0 mass%, Zn: 13.0 to 30.0 mass%, and Co: 0.1 to 2.3 mass%.

The silver brazing material is made of silver (Ag), copper (Cu), zinc (Zn), cobalt (Co), and tin (Sn), and the content of each component is Ag: 48.0 to 54. 0.0 mass%, Cu: 19.0 to 23.0 mass%, Zn: 13.0 to 30.0 mass%, Co: 0.1 to 2.3 mass%, Sn: 10.0 to 12.0 The present invention relates to a silver brazing material characterized by being in mass%.

The silver brazing material is made of silver (Ag), copper (Cu), zinc (Zn), cobalt (Co), and nickel (Ni), and the content of each component is Ag: 48.0 to 54. 0.0 mass%, Cu: 19.0 to 23.0 mass%, Zn: 13.0 to 30.0 mass%, Co: 0.1 to 2.3 mass%, Ni: 2.1 to 2.2 The present invention relates to a silver brazing material characterized by being in mass%.

Further, in the silver brazing material according to any one of claims 1 to 3 , when the silver brazing material is brazed using the silver brazing material, the brazing layer portion of the joint contains a high concentration of Co. A Co-rich phase is formed, and the hardness of the Co-rich phase is related to a silver brazing material characterized by being 280 HV or higher.

The silver brazing material according to any one of claims 1 to 4 , wherein the silver brazing material joins a cemented carbide member mainly composed of tungsten carbide (WC) and Co and another member. The present invention relates to a silver brazing material characterized by being used in

6. The silver brazing material according to claim 5 , wherein the other member is the cemented carbide member .

The silver brazing material according to any one of claims 5 and 6 , wherein the silver brazing material is formed at a joint interface between the cemented carbide member and the silver brazing material when joined to the cemented carbide member. The present invention relates to a silver brazing material characterized in that the width of the Co-deficient region is 1 μm or less.

  Since the present invention is configured as described above, it becomes a silver brazing material having excellent practicality that can exhibit excellent bonding strength even when used when bonding cemented carbide members.

It is a table | surface which shows the chemical composition and liquidus line of the used brazing material. It is a schematic explanatory drawing of a brazing apparatus. It is a SEM photograph which shows the mode of Co deficiency in the cemented carbide alloy of the joining interface vicinity. It is a graph which shows the bending strength of the coupling using the conventional silver brazing material. It is a photograph which shows the mode of the fracture surface after a bending test. It is a graph which shows the relationship between the addition amount of Co to BAg0, and bending strength. It is a photograph which shows the mode of the fracture surface after a bending test. It is a SEM photograph which shows the mode of Co deficiency in the cemented carbide alloy of the joining interface vicinity. It is a SEM photograph which shows the structure | tissue of a brazing layer part. It is a table | surface which shows the chemical composition and Vickers hardness of each phase of a brazing layer part. It is a SEM photograph which shows the brazing | waxing layer part structure | tissue of the joint by BAg0-2Co. It is a SEM photograph which shows the fracture | rupture path | route of the joint by BAg0-2Co. It is a graph which shows the relationship between the addition amount of Co to BAg-24-0Ni, and bending strength. It is a photograph which shows the mode of the fracture surface after a bending test. It is a SEM photograph which shows the mode of Co deficiency in the cemented carbide alloy of the joining interface vicinity. It is a SEM photograph which shows the structure | tissue of a brazing layer part. It is a table | surface which shows the chemical composition and Vickers hardness of each phase of a brazing layer part. It is a SEM photograph which shows the brazing layer part structure | tissue of the joint by BAg-24-0Ni-2Co. It is a graph which shows the relationship between the addition amount of Co to BAg-24, and bending strength. It is a photograph which shows the mode of the fracture surface after a bending test. It is a SEM photograph which shows the mode of Co deficiency in the cemented carbide alloy of the joining interface vicinity. It is a SEM photograph which shows the structure | tissue of a brazing layer part. It is a table | surface which shows the chemical composition of each phase of a brazing layer part.

  An embodiment of the present invention which is considered to be suitable will be briefly described with reference to the drawings showing the operation of the present invention.

  Since Co is contained in the silver brazing material in advance, for example, when brazing a cemented carbide member (with Co as a binder), the silver brazing material in the vicinity of the bonding interface between the cemented carbide member and the silver brazing material This prevents the diffusion of Co. Accordingly, the width of the Co-deficient region in the vicinity of the bonding interface between the cemented carbide member and the silver brazing material can be reduced as much as possible, and the cemented carbide member is less likely to break and has a high bonding strength. Excellent brazing can be performed.

  Specific embodiments of the present invention will be described with reference to the drawings.

  This example is a silver brazing material mainly composed of Ag, Cu, Zn, and Co. The content of each component is Ag: 48.0 to 54.0% by mass, Cu: 19.0. It is set to 23.0 mass%, Zn: 13.0-30.0 mass%, Co: 0.1-2.3 mass%.

  The range of numerical limitations such as the content of each component in this example is derived based on experimental examples described later. First, an outline of this example will be described.

This embodiment, for example, is used when the brazing cemented carbide members What happened mainly composed of WC and Co. In addition, you may use when brazing a cemented carbide member and members other than a cemented carbide member, and you may use when brazing members other than a cemented carbide member.

  In addition, this example has a Co-rich phase containing Co at a high concentration, and the Co content is such that the hardness of the Co-rich phase is 280 HV or more, more preferably 300 HV or more. Is set. This is because when there is no hardness of 280 HV or more, the effect of improving the bonding strength due to the inclusion of Co is not sufficiently exhibited.

  Further, in this example, when the brazing filler metal and the cemented carbide member are joined, the width of the Co-deficient region formed at the joining interface between the cemented carbide member and the silver brazing material is 1 μm or less. The content of Co is set in This is because if there is a Co deficient region exceeding 1 μm, the effect of improving the bonding strength due to the inclusion of Co is not sufficiently exhibited. The Co-deficient region is a region where the amount of Co in the cemented carbide member is smaller than other regions. In this embodiment, the length in the direction perpendicular to the bonding interface is the width of the Co-deficient region. The width of this Co-deficient region can be confirmed, for example, by elemental surface analysis using an energy dispersive X-ray spectrometer (EDS) mounted on a scanning electron microscope (SEM). For example, in FIGS. 3, 8 and 15, the vicinity of the bonding interface is observed so that the cemented carbide member is arranged on the left side of each photograph and the brazing layer portion is arranged on the right side. The amount of Co is shown, and the higher the line in each photograph, the larger the amount of Co, so that the width of the Co-deficient region is obtained from this line. Specifically, when the Co amount of the cemented carbide member is measured by surface analysis in a region where one side is 40 times or more the WC grain size, and the averaged line is expressed in a direction orthogonal to the bonding interface, The area from the point where the averaged line starts to fall toward the junction interface (the amount of Co begins to decrease) to the junction interface is defined as the Co deficiency region, and the width is obtained.

  Moreover, 10.0 to 12.0 mass% of tin (Sn) may be added to the said structure, or 2.1 to 2.2 mass% of nickel (Ni) may be added. Also in this case, it is possible to obtain a good silver brazing material.

  If the content of each component is set so that the melting point (liquidus) is 700 ° C. or less, the heating temperature at the time of brazing can be lowered accordingly, improving workability and energy saving in the brazing process. Can be realized.

  Since the present embodiment is configured as described above, when brazing a cemented carbide member having Co as a binder by previously containing Co in the silver brazing material, the silver brazing material of the cemented carbide member and Co diffusion to the silver brazing material in the vicinity of the bonding interface is prevented. Accordingly, the width of the Co-deficient region in the vicinity of the bonding interface between the cemented carbide member and the silver brazing material can be reduced as much as possible, and the cemented carbide member is less likely to break and has a high bonding strength. Excellent brazing can be performed.

  Therefore, the present embodiment is extremely practical in that it can exhibit excellent bonding strength even when used when bonding cemented carbide members.

  Hereinafter, experimental examples supporting the effects of the present embodiment will be described in detail.

  As a test material, a 6 mm diameter cemented carbide (WC-9.2 mass% Co-0.8 mass% Cr-0.4 mass% V, bending strength: about 3990 MPa) round bar was used. In addition, “mass%” and “mass%”, which are units indicating the content, have the same meaning, and are used together in this specification. The average particle size of WC is about 0.2 μm. The length of the test piece for joining was 50 mm, and the joining end face was finished to a mirror surface with diamond paste (average surface roughness: Ra≈0.05 μm), and then subjected to joining by ultrasonic cleaning in acetone.

  The brazing material used is a silver brazing material (BAg-24-0Ni) excluding Ni in the composition of BAg-24 and BAg-24 used for brazing of cemented carbide, and developed by the present inventors. The silver brazing material (BAg0) according to Japanese Patent No. 4093322 and the silver brazing material to which Co is added (Example). The chemical composition and liquidus of the silver brazing material used are shown in FIG. The amount of Co added is as shown in the leftmost column of FIG. 1 as “−0.1Co”, “−1Co”, etc. (the unit is mass%). The liquidus was measured by differential thermal analysis (DTA). Japanese Patent Laid-Open No. 63-317290 discloses a silver brazing material to which Co is added, but uses and purposes for adding Co are different. In addition, since the silver brazing material for cemented carbide does not contain Zn, it is difficult to join the cemented carbide with the silver brazing alloy. Therefore, it is difficult to join the cemented carbide described in JP-A-63-317290. Silver brazing material is not applicable for brazing of cemented carbide.

  The outline of the brazing apparatus used for joining is shown in FIG. Brazing was performed in the atmosphere, and heating was performed by high frequency induction heating. A commercially available flux is applied to the joining surfaces of two joining test pieces (super-hard alloy members) arranged vertically, and a flaky wax having a mass of about 0.05 g is inserted, followed by a heating rate of 10 ° C./s. (This temperature is referred to as the bonding temperature). After holding at the bonding temperature for 30 s, it was air-cooled. The bonding temperature was 650 ° C. or 750 ° C., depending on the solder used. The temperature of the test piece was measured with an R thermocouple attached at a location about 1 mm away from the joint end face. In addition, as shown in FIG.2 (b), the 0.1 mm diameter tungsten wire was inserted in the joining surface of the upper side test piece, and the clearance was hold | maintained at 0.1 mm. During the joining, a load of about 90 N was applied in the axial direction of the cemented carbide round bar (joint specimen).

  The brazed joint is processed into a center part of 4 mm in diameter and a parallel part length of 5 mm, and then subjected to a three-point bending test (distance between fulcrums: 25 mm, test speed: 0.1 mm / min) to measure the bending strength. did. This bending strength was defined as the joint strength of the joint. Further, the structure and fracture path of the brazing layer portion (the brazing material in the brazed state) were observed with a scanning electron microscope (SEM), and elemental analysis and the like were performed with an energy dispersive X-ray spectrometer (EDS). The hardness test of the brazing layer part structure was performed using a dynamic ultra-micro hardness meter, and the Vickers hardness was obtained at a test time of 10 s.

  Next, experimental results will be described.

  Fig. 3 shows BAg-24, which has been conventionally used for brazing cemented carbide, BAg-24-0Ni excluding Ni from this, and cemented carbide near the joint interface of joints brazed using BAg0. The state of medium Co deficiency is shown. The bonding temperature is 750 ° C. when BAg-24, BAg-24-0Ni is used, and 650 ° C. when BAg0 is used. It can be seen that the width of the Co-deficient region of the joint made of BAg-24, which has been conventionally used for brazing for cemented carbide, is relatively wide. This is considered to be because Co in the cemented carbide is easily diffused into the brazing layer portion due to the influence of Ni contained in the brazing component in a solid solution with Co. Further, when the junction temperature is low, the Co-deficient region is narrowed. This is probably because Co is difficult to diffuse into the brazing layer because the junction temperature is low.

  The bending strength of the joint brazed using each silver solder is shown in FIG. When BAg-24 and BAg-24-0Ni were compared, the bending strength was higher in BAg-24-0Ni where the Co-deficient region in the cemented carbide was narrow. However, the bending strength of the joint by BAg0 having the narrowest Co-deficient region showed the lowest value.

  Next, the state of the fracture surface after the bending test of each joint by silver brazing is shown in FIG. 5. The fracture of the joint using BAg-24 and BAg-24-0Ni is shown in FIGS. Most of the fractures occurred in the cemented carbide as shown in FIG. In addition, as shown in FIG. 5 (c), the fracture of the joint due to BAg0 occurred mainly in the brazing layer. From this, the bending strength of the joint by BAg-24-0Ni was higher than that of BAg-24 because the Co-deficient region in the cemented carbide was narrow and it was difficult for fracture in the cemented carbide to occur. Is considered to be the cause. The reason why the bending strength of the joint by BAg0 was low is considered to be that the brazing layer portion was weak.

  Next, the influence of Co addition to BAg0 was investigated. As described above, since the fracture of the joint due to BAg0 occurs in the brazing layer portion, it is necessary to strengthen the brazing layer portion in order to improve the bending strength. Further, although the Co-deficient region in the cemented carbide is narrow because the bonding temperature is low, it is fully conceivable that this deficient region becomes a problem due to the strengthening of the brazing layer portion. Therefore, by adding Co to the silver brazing in advance, the diffusion of Co from the cemented carbide was suppressed, and at the same time, the brazing layer portion was expected to be strengthened by solid solution strengthening of Co. FIG. 6 shows the bending strength of a joint made of silver solder with BAg0 and Co added thereto. By adding a small amount of Co, the bending strength of the joint was improved, and the maximum bending strength was shown at an addition amount of 0.5 mass%. Moreover, when the addition amount was further increased, the bending strength of the joint due to the addition amount tended to decrease. FIG. 7 shows the state of the fracture surface after the bending test. When a silver brazing alloy containing 0.5 mass% of Co was used, the fracture partially occurred in the cemented carbide. From this, it is expected that the brazing layer portion is not easily broken by the addition of Co. In addition, when a silver brazing alloy containing 2 mass% of Co is used, the fracture at the brazing layer portion is almost all, and it is expected that the brazing layer portion is weakened by adding Co excessively. .

  FIG. 8 shows the state of Co deficiency in the cemented carbide near the joint interface of a joint brazed using BAg0 and BAg0-0.5Co. It can be seen that the addition of 0.5 mass% Co reduced the Co deficient region in the cemented carbide. From this, it can be considered that the addition of Co makes it difficult for the joint made thereby to break in the cemented carbide. Next, the brazing layer structure of the joint brazed using BAg0 and BAg0-0.5Co is shown in FIG. The solidification structure of normal silver brazing is mainly composed of primary crystals of α-Cu phase (copper solid solution containing Zn and a little Ag), α1-Ag phase (silver solid solution containing Zn and a little Cu), and eutectics thereof. In this experimental example, it is considered that the same organization is formed. That is, the phase indicated by W is considered to be a silver solid solution phase, the phase indicated by D is considered to be a copper solid solution phase, the portion indicated by E is considered to be a eutectic structure of W and D, and these structures were observed in any brazing layer portion. . In addition, when a silver solder added with Co was used, a Co-rich phase indicated by B was observed. The definition of the Co rich phase will be described later.

  The chemical composition and Vickers hardness of each phase are shown in FIG. In addition, since the Co-rich phase was very small and it was difficult to measure the hardness, the hardness of the phase having almost the same composition formed in the brazing layer portion of the joint using BAg0-2Co described later is regarded as the hardness of this phase. . It can be seen that in both the silver solid solution phase and the copper solid solution phase, the amount of Co contained increases, and the hardness increases accordingly. From the above, it is considered that the improvement of the bending strength of the joint using BAg0-0.5Co is due to the reduction of the Co deficient region in the cemented carbide near the joining interface and the solid solution strengthening of the brazing layer.

  The structure of the brazing layer portion of the joint using BAg0-2Co is shown in FIG. The phase formed in the brazing layer portion was the same as that of the joint made of BAg0-0.5Co, but there were many Co-rich phases indicated by B, which were coarse. Further, the Vickers hardness of this phase was as hard as 390 HV. This hardness is the average hardness of the Co-rich phase, but it was 300 HV or higher even if the hardness was low. FIG. 12 shows the fracture path of the joint with BAg0-2Co. The fracture occurred around the hard Co-rich phase. From this, it is considered that the bending strength decreased when the amount of Co added was increased due to an increase in Co-rich phase and coarsening.

  Next, the influence of Co addition to BAg-24-0Ni was examined.

  FIG. 13 shows the bending strength of a joint brazed using BAg-24-0Ni and a silver brazing alloy with Co added thereto. By adding a small amount of Co, the bending strength of the joint was improved, and the maximum bending strength was shown at an addition amount of 0.5%. Moreover, when the addition amount was increased, the bending strength of the joint due to it increased. This was the same result as when Co was added to BAg0. FIG. 14 shows the state of the fracture surface after the bending test. Most of the fractures of the joints using BAg-24-0Ni and BAg-24-0Ni-0.5Co were fractures of cemented carbide. . In the case of the joint using BAg-24-0Ni-2Co, many fractures at the brazing layer portion were observed.

  FIG. 15 shows the state of Co deficiency in the cemented carbide near the joint interface of a joint brazed using BAg-24-0Ni, BAg-24-0Ni-0.5Co, and BAg-24-0Ni-2Co. It can be seen that the Co-deficient region is reduced by adding Co. Further, there was almost no difference between the Co addition amount of 0.5 mass% and 2.0 mass%. From this, it is considered that the fracture in the cemented carbide is less likely to occur by adding Co, as in the case of adding Co to BAg0.

  The structure of the brazing layer portion of the joint brazed using BAg-24-0Ni and BAg-24-0Ni-0.5Co is shown in FIG. Although it differs greatly from the structure formed in the brazing layer portion of the joint by BAg0 shown in FIG. 9, the appearing phases are considered to be the same, and when silver solid solution, copper solid solution, their eutectic structure, and Co are added Showed a Co-rich phase that looked black. Moreover, the chemical composition and Vickers hardness of each phase are shown in FIG. As in the case of BAg0 described above, the Co-rich phase was very small and it was difficult to measure the hardness, so that the composition of almost the same composition formed in the brazing layer portion of the joint using BAg-24-0Ni-2Co described later was used. The hardness of the phase is the hardness of this phase. Similar to the case of adding Co to BAg0, the amount of Co dissolved in each phase increased by adding Co, and the hardness increased accordingly. From this, the reason why the bending strength is improved by adding Co to BAg-24-0Ni is due to the reduction of the Co deficient region in the cemented carbide near the bonding interface and the strengthening of the solid solution of Co. This is considered to be because the hard alloy and the brazing layer portion are less likely to break. The brazing layer structure of the joint made of BAg-24-0Ni-2Co is shown in FIG. Many Co-rich phases that appear black are coarse. As the amount of Co increases, the bending strength of the joint decreases due to the fact that the braze layer portion easily breaks due to this hard and coarse Co-rich phase, as in the case of adding Co to BAg0. Conceivable.

  Next, the influence of Co addition to BAg-24 was examined.

  FIG. 19 shows the bending strength of a joint brazed using BAg-24 and a silver braze added with Co. As in the case of BAg-24-0Ni described above, the bending strength of the joint was improved by adding Co, but the bending strength of the joint by silver brazing with Co added to BAg-24-0Ni was improved. Compared to a low value. Further, even when the amount of Co added was increased, no apparent decrease in bending strength was observed. FIG. 20 shows the state of the fracture surface after the bending test. Most of the fractures of the joints with BAg-24 and BAg-24-0.5Co occurred in the cemented carbide. Further, when the amount of Co added was increased, the fracture of the joint caused by that increased in the brazing layer. FIG. 21 shows a state of Co deficiency in the cemented carbide near the joint interface of the joints of BAg-24, BAg-24-0.5Co, and BAg-24-2Co. When Co was added to BAg0 or BAg-24-0Ni, as shown in FIGS. 8 and 15, respectively, the addition amount was 0.5 mass%, but almost no Co deficiency was observed (Co deficient region). When 0.5 mass% of Co was added to BAg-24, the cemented carbide Co-deficient region near the joint interface of the joint was still wide. This is because Ni and Co contained in the silver brazing are elements that are solid-solved at a total rate, and it is considered that diffusion from the cemented carbide to the brazing layer occurs when a small amount of Co is added. When 2 mass% of Co was added, a Co-deficient region near the junction interface was hardly seen. Next, the joint structure of the joint made of BAg-24, BAg-24-0.5Co, and BAg-24-2Co is shown in FIG. A phase considered to be a silver solid solution and a copper solid solution was observed at each joint. Further, a Co-rich phase that looks black was observed in the brazing layer portion of the joint using the silver brazing added with Co. The chemical composition of each phase is shown in FIG. 23. Unlike the case where Co was added to BAg0 or BAg-24-0Ni, the Co-rich phase contained a small proportion of Co and contained a little more Ni. . There was some variation in the Co content, but the smallest content was about 58 at%. From this result, the Co-rich phase was defined as a phase containing 55 at% or more of Co. Moreover, the Co concentration increased as the amount added increased. From this fact, it is considered that when the amount of Co added is increased, breakage at the brazing layer portion is likely to occur, and breakage at the brazing layer portion is increased. However, since Ni is an element that dissolves Co at a total rate, when the brazing component contains Ni, the Co-rich phase has a lower Co concentration than when it does not contain Ni, It is considered that since the coarsening hardly occurs, no obvious decrease in the bonding strength was observed. However, it is predicted that the bonding strength gradually decreases when the amount of added Co is further increased.

  From the above, for any of BAg-24, BAg-24-0Ni, and BAg0, the bending strength (joining strength) is improved when brazing cemented carbide members by adding an appropriate amount of Co. We were able to confirm that

Claims (7)

A silver brazing material composed of silver (Ag), copper (Cu), zinc (Zn), and cobalt (Co), wherein the content of each component is Ag: 48.0 to 54.0 mass%, Cu: A silver brazing material comprising 19.0 to 23.0 mass%, Zn: 13.0 to 30.0 mass%, and Co: 0.1 to 2.3 mass%. A silver brazing material composed of silver (Ag), copper (Cu), zinc (Zn), cobalt (Co), and tin (Sn), and the content of each component is Ag: 48.0 to 54.0. Mass%, Cu: 19.0 to 23.0 mass%, Zn: 13.0 to 30.0 mass%, Co: 0.1 to 2.3 mass%, Sn: 10.0 to 12.0 mass% Silver brazing material characterized by being. A silver brazing material composed of silver (Ag), copper (Cu), zinc (Zn), cobalt (Co) and nickel (Ni), and the content of each component is Ag: 48.0 to 54.0. % By mass, Cu: 19.0-23.0% by mass, Zn: 13.0-30.0% by mass, Co: 0.1-2.3% by mass, Ni: 2.1-2.2% by mass Silver brazing material characterized by being. The silver brazing material according to any one of claims 1 to 3 , wherein when the silver brazing material is brazed using the silver brazing material, a Co rich material containing Co at a high concentration in the brazing layer portion of the joint. A silver brazing material in which a phase is formed and the hardness of the Co-rich phase is 280 HV or more. The silver brazing material according to any one of claims 1 to 4 , wherein the silver brazing material is used when joining a cemented carbide member mainly composed of tungsten carbide (WC) and Co and another member. Silver brazing material characterized in that it is made. 6. The silver brazing material according to claim 5 , wherein the other member is the cemented carbide member . 7. The silver brazing material according to claim 5 , wherein the silver brazing material is formed at a joint interface between the cemented carbide member and the silver brazing material when joined to the cemented carbide member. A silver brazing material characterized in that the width of the Co-deficient region is 1 μm or less.