JP3783975B2 - Brazing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for brazing refractory metal Mo (molybdenum), Mo alloy, W (tungsten), or W alloy used for high-temperature members, and particularly in the atmosphere, which has been impossible with these metal materials. It relates to the brazing method.
[0002]
[Prior art]
Mo, Mo alloy, W or W alloy, which is a refractory metal, is used, for example, as a member for a high temperature vessel, a rotating anode for an X-ray tube, a cathode ray tube cathode, etc., and is widely used as a high temperature member. Further, brazing is adopted as the joining method.
[0003]
Brazing is also referred to as brazing, and melts a metal filler metal (brazing material) having a melting point lower than that of the base material without melting the base material, and uses capillarity to go to the gap between the joint surfaces. This is a method of joining by spreading. Therefore, it does not cause embrittlement due to crystal grain coarsening and intermetallic compound generation due to melting and solidification of the base material, and it can suppress thermal stress because the construction temperature is low, and there is no structural change of the base material, There are advantages such as low residual stress. Furthermore, brazing is suitable for materials that require high energy for melting the base material, such as hardly fusible metals, or materials that are prone to cracking during solidification.
[0004]
However, Mo, Mo alloys, W or W alloys, which are high temperature members, have a drawback that oxidation occurs rapidly at high temperatures. Therefore, it is necessary to perform brazing of Mo, Mo alloy, W, or W alloy, which are high melting point metals, in a vacuum, a reducing atmosphere, or an inert gas atmosphere.
[0005]
This also applies to other joining methods such as TIG, laser, electron beam welding, diffusion joining, and rivet joining.
[0006]
[Problems to be solved by the invention]
Therefore, in order to maintain a brazing environment in a vacuum, reducing, or inert gas atmosphere, a vacuum device, an airtight chamber, a reducing gas or inert gas supply facility, an expensive reducing gas or inert gas is required. . Further, when large metal members are brazed, it is difficult to form the hermetic chamber itself, and the size that can be manufactured is limited by the size of the hermetic chamber.
[0007]
The present invention has been made in consideration of the above-described circumstances, and provides a brazing method capable of joining Mo, Mo alloy, W, or W alloy members in the atmosphere without requiring a vacuum facility or an airtight chamber. There is.
[0008]
[Means for Solving the Problems]
The brazing method of the present invention that solves the above-described problem is the brazing method in which at least one of the metal members to be joined is Mo, Mo alloy, W, or W alloy. A brazing material in which boron is contained in the Ru—Mo eutectic alloy is applied to the fillet portion between them , and the back side of the brazing material application surface that is not directly exposed to the flame or the side surface of one metal member is 1600 in the atmosphere. ° C. was heated at to 2000 ° C. in a high temperature flame, to melt the brazing material, and forming a molten brazing metal layer.
[0009]
After attaching the backing plate so as to cover both of the metal members to be joined, a brazing material is applied to the groove formed by both metal members and the backing plate, and from the back side of the backing plate. You may make it heat.
[0010]
Further, after applying the brazing material to at least one of the metal members to be joined and superimposing them, the back surface side of the brazing material application surface or the side surface of one of the metal members may be heated.
[0013]
The Ru-Mo eutectic alloy may further contain nickel.
[0016]
[Action]
By doing so, the oxide of the metal member to be brazed has high volatility, so that oxidation occurs during heating and the oxide volatilizes, and a fresh metal surface is constantly exposed, and further, the metal surface is melted into the molten brazing material. A covered oxide layer is not formed, and good brazing can be performed even in the atmosphere.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The brazing material used in the present invention is not limited as long as it does not cause problems such as embrittlement and evaporation at the use temperature and use atmosphere of the brazing joint.
[0018]
For example, a Ru-Mo eutectic alloy brazing material can be used for Mo and W, but this brazing material has a high melting point of 1955 ° C., resulting in a decrease in strength and construction problems due to embrittlement of the Mo and W materials. There are also many. On the other hand, it was experimentally found that the melting point can be lowered to 1600 ° C. by adding 2.8% by weight of B (boron) to the Ru—Mo eutectic alloy brazing material.
[0019]
The composition range of the base Ru—Mo brazing material can be 33.5 to 49.5 wt% in terms of Ru amount. The Ru—Mo brazing material has a Ru—Mo eutectic structure in this range, and 43 wt% Ru-57 wt% Mo which is the eutectic point is desirable. By adding 2.8% by weight of boron B to the Ru—Mo eutectic alloy brazing material, the brazing temperature is lowered and the brazing material can withstand 1500 ° C. and can be used in a reducing and inert atmosphere.
[0020]
In the present invention, a brazing material of preferably 41.7% by weight Ru-55.5% by weight Mo-2.8% by weight B is used.
[0021]
Furthermore, the wettability of the brazing material can be further improved by adding 0.3 wt% to 10 wt% of Ni (nickel) to the brazing material. Here, the reason why Ni is 0.3% by weight or more is that the addition of less than 0.3% by weight cannot be expected to improve the wettability of the brazing material. Further, the reason why Ni is limited to 10% by weight or less is that when it exceeds 10% by weight, the formation of fragile Mo—Ni intermetallic compounds becomes remarkable and the strength is lowered.
[0022]
In the present invention, a high-temperature gas burner or high-frequency heating can be used as a heating source, and the product temperature to be heated, that is, the temperature of the heated part is preferably 1600 to 2000 ° C. By heating the material and the entire brazing material from the back surface of the brazing joint with a heating source such as a high-temperature gas burner, brazing can be performed in the atmosphere.
[0023]
In addition, in the case of burner heating, if brazing material powder is applied to the joint and heated from the surface of the joint, the brazing material is scattered by the gas pressure, and brazing is not preferable. In this case, even when a brazing material paste-formed with a binder is used, brazing becomes impossible.
[0024]
Therefore, Mo or W is used for the base material 1, the base material 2, and the backing plate 3, and in the combined state as shown in FIG. 1, the gap between the base material 1 and the base material 2, that is, the ends of the base materials 1 and 2 A brazing material 4 in which a brazing filler metal powder is pasted with a binder is applied to a groove formed by the portion and the backing plate 3, and heated in the atmosphere using a high-temperature gas burner from the back of the joint, that is, the backing plate 3 side. As a result, as shown in FIG. 2, the brazing material spreads over the abutting portion and the entire overlapping surface, and the brazing material was not scattered and good brazing was obtained. Involvement of oxygen was not recognized at the interface between the brazing material and the material of either Mo or W and inside the brazing material. Here, isobutyl methacrylate is used as the binder, but similar results can be obtained if other binders, such as paraffin, are usually used for powder molding of Mo and W.
[0025]
Furthermore, the molybdenum base material and the backing plate may be a lanthanum-containing molybdenum plate (for example, disclosed in Japanese Patent Publication No. 2-38659). This lanthanum-containing molybdenum is composed of lanthanum or lanthanum oxide less than 0.1 to 1.0% by weight and the remainder molybdenum, and exhibits an interlocking structure that is recrystallized by extending substantially in a certain direction. It is a molybdenum alloy excellent in workability and high temperature deformation resistance characterized by having crystal grains. By using this lanthanum-containing molybdenum as a high temperature member, the amount of deformation at a high temperature can be made smaller than when pure molybdenum is used.
[0026]
In general, the oxide on the surface of the material adversely affects the wettability of the brazing material, resulting in poor wetting such as voids and reduced strength. In the present invention, the detailed mechanism for obtaining a good braze joint is unknown. However, in the case of Mo, for example, the oxide of Mo is highly volatile, so that oxidation occurs when heated and the oxide volatilizes. The metal surface of Mo is constantly exposed, and the metal surface is covered with a melted brazing material using as a main component a Ru—Mo eutectic system excellent in bondability with Mo, and no oxide layer is generated. it is conceivable that. However, the Mo surface that is not covered with the brazing material is naturally oxidized, but its thickness is thin and can be removed by a normal blast treatment because of the high volatility of the oxide.
[0027]
In W, it is considered that brazing in the atmosphere is possible by the same mechanism.
[0028]
Originally, in a TIG welding torch or the like, it is very difficult to stably maintain a gas seal with an inert gas, and the seal is incomplete. In the brazing method of the present invention, such an incomplete gas seal is used. A heating means such as a TIG welding torch that can only be used can be employed.
[0029]
FIG. 3 shows an example in which the base materials 1 and 2 are partially overlapped and joined to each other at the corner (filled portion) formed by the end portion of the overlapped base material 1 and the upper surface of the base material 2. The material 4 is applied and heated from the side surface and the back surface side of the base material 2. In this case, by heating, the brazing material 4 in the fillet portion penetrates between the base materials 1 and 2, thereby forming a molten metal brazing layer between the base materials 1 and 2.
[0030]
4 and 5 show examples in which the entire surfaces of the base materials 1 and 2 are overlapped and joined. After the brazing material 4 is applied to one of the base materials 1 and 2 to be overlapped, the base materials 1 and 2 are overlapped. In addition, heating is performed from the side surface and the back surface side of the base material 2.
[0031]
As can be understood from the above description, in the brazing method according to the present invention, the brazing material is applied either before or after the base materials 1 and 2 and the backing plate 3 are combined in a predetermined state. It may be done.
[0032]
【Example】
Example 1
In the joint portion shown in FIG. 1, Mo is used for the base material 1, the base material 2, and the backing plate 3, and the gap between the base material 1 and the base material 2 is 41.7 wt% Ru-55.5 wt% Mo—. 2.8 wt% B brazing filler metal powder made of isobutyl methacrylate paste was applied, and then heated in the atmosphere using the oxygen-acetylene burner and TIG welding torch from the back of the joint, that is, the backing plate 3 side. Bonding was performed.
[0033]
In this case, since the gas flux hits from the back of the joint and does not directly hit the brazing filler metal part by any heating method using an oxygen-acetylene burner or a TIG welding torch, good brazing was obtained without scattering of the brazing filler metal. The presence of an oxide layer and voids were not observed at the joint interface and the brazing material, and a very good joint was obtained.
[0034]
Comparative Example 1
In the joint portion shown in FIG. 1, Mo is used for the base material 1, the base material 2, and the backing plate 3, and the gap between the base material 1 and the base material 2 is 41.7 wt% Ru-55.5 wt% Mo—. After preparing a joint in which a brazing material in which 2.8 wt% B brazing filler metal powder was pasted with isobutyl methacrylate was applied, the surface, that is, the brazing filler metal side was used with an oxygen-acetylene burner and a TIG welding torch in the atmosphere. Heating and bonding were performed.
[0035]
In this case, in both heating methods, the gas flux hits the surface of the joint and directly hits the brazing filler metal part, so that the brazing filler metal was scattered by the gas flux and brazing was impossible.
[0036]
Example 2
In the joint portion shown in FIG. 1, lanthanum-containing molybdenum (disclosed in Japanese Examined Patent Publication No. 2-38659) is used for the base material 1, the base material 2, and the backing plate 3, and the gap between the base material 1 and the base material 2 is 41.7. Wt% Ru-55.5 wt% Mo-2.8 wt% B After brazing filler metal powder was coated with isobutyl methacrylate, the oxygen-acetylene burner was applied from the back of the joint, that is, the backing plate 3 side. And using the TIG welding torch, it heated and joined in air | atmosphere.
[0037]
In this case, the gas flux hits from the back of the joint in any of the heating methods and does not directly hit the brazing material portion, so that the brazing material was not scattered and good brazing was obtained. Existence of an oxide layer and voids were not observed at the joint interface and the brazing material, and a very good joint was obtained.
[0038]
Example 3
In the joint portion shown in FIG. 1, W is used for the base material 1, the base material 2 and the backing plate 3, and 41.7% by weight Ru-55.5% by weight Mo-- is formed in the gap between the base material 1 and the base material 2. 2.8 wt% B brazing filler metal powder made of isobutyl methacrylate paste was applied, and then heated in the atmosphere using the oxygen-acetylene burner and TIG welding torch from the back of the joint, that is, the backing plate 3 side. Bonding was performed.
[0039]
In this case, in any of the heating methods, the gas flux hits from the back of the joint and does not directly hit the brazing material portion, so that the brazing material was not scattered and good brazing was obtained. Existence of an oxide layer and voids were not observed at the joint interface and inside the brazing material, and a very good joint was obtained.
[0040]
Example 4
In the joint portion shown in FIG. 1, Mo is used for the base material 1, the base material 2, and the backing plate 3, and the gap between the base material 1 and the base material 2 is 40.5 wt% Ru-53.8 wt% Mo—. 2.7 wt% B-3.0 wt% Ni brazing powder powder was coated with a brazing material made of isobutyl methacrylate, then the oxygen-acetylene burner and TIG welding torch from the back of the joint, that is, the backing plate 3 side Was used for heating and bonding in the atmosphere.
[0041]
In this case, in any of the heating methods, the gas flux hits from the back of the joint and does not directly hit the brazing material portion, so that the brazing material was not scattered and good brazing was obtained. The presence of an oxide layer and voids were not observed at the joint interface and the brazing material, and a very good joint was obtained.
[0042]
Example 5
As shown in FIG. 6 and FIG. 7, 41.7 wt% Ru-55.5 wt% Mo-2.8 wt% B brazing filler metal powder is pasted with isobutyl methacrylate on one end face of a D10 mm Mo round bar 2 ′. After the brazing material 4 is applied, the end surfaces of the same size Mo round bar 1 'are overlapped, and then the side surface of the brazing material application surface is heated in the atmosphere using a TIG welding torch. Bonding was performed. After brazing, the brazing material flowing out from the joint was removed and subjected to a room temperature tensile test. As a result, a tensile strength of 220 Mpa was obtained. Further, as a result of observing the cross section, no trace of voids was observed in the brazing filler metal part, and a very good joint was obtained.
[0043]
Similar results were obtained when the Mo round bar was used as a lanthanum-containing molybdenum bar (for example, disclosed in JP-B-3-22460).
[0044]
【The invention's effect】
As described above, according to the present invention, at least one of the metal members to be joined, which is a refractory metal, can be brazed in the atmosphere in the brazing of Mo, Mo alloy, W or W alloy. The vacuum equipment and hermetic chamber required by the brazing method are not required. In addition, there is no need for reducing gas or inert gas supply equipment, expensive reducing gas or inert gas, and it is possible to braze with an incomplete seal even when a gas seal such as inert gas is used. Become.
[0045]
In addition, when a large metal member is brazed, an airtight chamber is not required, so that the manufacturable size is not limited, and for example, brazing can be performed on site.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a bonding method of the present invention.
FIG. 2 is a cross-sectional view showing a state in which base materials are joined to each other as shown in FIG.
FIG. 3 is a cross-sectional view showing an example in which base materials are partially overlapped and joined.
FIG. 4 is a cross-sectional view showing an example in which the entire surfaces of base materials are overlapped and joined.
5 is a cross-sectional view showing a state in which the base materials are joined to each other as shown in FIG.
FIG. 6 is a perspective view showing an example in which round bars are butt-joined.
7 is a perspective view showing a state in which round bars are joined to each other as shown in FIG. 6;
[Explanation of symbols]
1, 2, Base material 3 Backing plate 4 Brazing material 1 ', 2' Round bar

Claims (4)

At least one of the metal members to be joined is a brazing of Mo, Mo alloy, W or W alloy ,
The fillet portion between at least one or metallic member surface to be bonded of the metallic member is coated with a brazing material that contains boron in the Ru-Mo eutectic alloy,
The back surface of the brazing material coating surface that is not directly exposed to flame or the side surface of one metal member is heated in the atmosphere with a high temperature flame of 1600 ° C to 2000 ° C ,
A brazing method comprising melting the brazing material to form a molten metal brazing layer.   In the brazing method according to claim 1, after attaching the backing plate so as to cover both of the metal members to be joined, a brazing material is applied to the groove formed by both the metal members and the backing plate, A brazing method comprising heating from the back side of the backing plate. The brazing method according to claim 1, wherein after the brazing material is applied to and superposed on at least one of the metal members to be joined, the back surface side of the brazing material application surface or the side surface of one of the metal members is heated. Characteristic brazing method. The brazing method according to any one of claims 1 to 3, wherein the brazing material further contains nickel .

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