JP2005262244A - Method for joining metallic member by pulse energization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for joining difficultly joinable metallic materials (hard-to-join materials) by pulse energization without an intermediate material such as a brazing filler metal. <P>SOLUTION: When joining two or more conductive metallic members by pulse energization, while pressurizing the joint faces of the metallic members in a state that the faces are abutted, a temperature raising/lowering operation, in which the temperature of the metallic members is raised by applying a pulse current to the members and then lowered under the temperature of their transformation point or solid solution treatment, is repeated a plurality of times. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for joining metal members by pulse energization.

In recent years, a joining method based on pulse energization is used for joining various metal members to a joining method such as brazing.
In particular, when joining metal members having different melting points by pulse energization, it is sufficient for the first time by increasing the frequency of the pulse current (see, for example, Patent Document 1) or sandwiching a brazing material between the materials to be joined. Joining became possible.

  However, in metal materials that are difficult to bond (hardly-bonded metal materials), such as SUS420J2 alloys (pre-hardened steel) such as STAVAX (registered trademark owned by Woodeholm Co., Ltd.), brazing material is intervened even when joining by pulse energization It was impossible to join them without using them.

JP 2002-103049 A (2nd page, etc.)

  The present invention eliminates such conventional problems and provides a method of strongly joining a metal material that is difficult to join (hardly-joined metal material) by pulse energization without inclusions such as a brazing material. It is the purpose.

The present inventor has intensively studied to achieve the above object.
As a result, the present inventor repeats a temperature raising / lowering operation for a metal material other than “a nickel-based heat-resistant alloy containing at least chromium” by energizing a pulse current and then lowering the temperature across the transformation point a plurality of times. Thus, it has been found that a metal material that is difficult to join (hardly-joined metal material) can be firmly joined by pulse energization without inclusions such as a brazing material. On the other hand, for "a nickel-base heat-resistant alloy containing at least chromium" that does not have a transformation point, the temperature is raised by energizing a pulsed current, and then the temperature is lowered and lowered with the solution treatment temperature interposed therebetween, by repeating multiple times. The present inventors have found that it can be firmly joined by pulse energization without inclusions such as brazing material.
The present inventor has completed the present invention based on these findings.

According to the first aspect of the present invention, when two or more metal members that can be energized are joined by energization of a pulse current, the temperature is raised by energizing the pulse current while applying pressure while the joining surfaces of the metal members are in contact with each other. Then, a method for joining metal members by pulse energization is provided, in which a temperature raising / lowering operation of lowering the temperature with the transformation point or solution treatment temperature interposed therebetween is repeated a plurality of times.
The present invention according to claim 2 provides the joining method according to claim 1, wherein the metal member is a hard-to-join alloy containing at least chromium.
The present invention according to claim 3 provides the joining method according to claim 1 or 2, wherein the lowest temperature when the temperature is lowered after the temperature rise is 900 ° C. or lower.
The present invention according to claim 4 provides the joining method according to any one of claims 1 to 3, wherein a maximum temperature at the time of temperature rise is 1030 ° C or higher.

  According to the first to fourth aspects of the present invention, a metal material that is difficult to bond (hardly-bonded metal material) can be firmly bonded by pulse energization without inclusions such as a brazing material.

Embodiments of the present invention will be described below.
The present invention according to claim 1 relates to a method of joining metal members by pulse energization. When joining two or more metal members that can be energized by energization of a pulse current, pressurization is performed with the joining surfaces of the metal members abutting each other. While raising and lowering the temperature by energizing the pulse current and then lowering the temperature with the transformation point or solution treatment temperature sandwiched, the temperature raising and lowering operation is repeated a plurality of times.

  Here, the number of metal members to be joined is not limited to two, and two or more metal members can be joined at the same time. In the case of a rod-shaped metal member, a plurality of joint surfaces can be joined at the same time by applying pressure in a state where a plurality of the metal members are butted in series. Further, if a plurality of metal members joined in series in this way are arranged in parallel and are simultaneously pressurized and energized, a larger number of joints can be performed simultaneously.

The metal member that can be joined is not particularly limited as long as it can be energized. For example, examples of metal members that can be joined include steel materials such as high-speed tool steel (high-speed steel), die steel (SKD), and stainless steel (SUS); non-ferrous metals such as copper, aluminum, zinc, and non-ferrous alloys; Nickel-based heat-resistant alloys, shape memory alloys, heat-resistant alloys, vibration-proof alloys, sound-proof alloys, shield materials, and other special alloys; sintered metals such as discharge plasma sintered bodies and hot-press sintered bodies; exhibit conductivity at high temperatures Materials such as ceramics; semiconductors; single crystal materials and the like.
In particular, the present invention is suitable for joining metal materials that are difficult to join (hardly-joined metal materials).
As such a difficult-to-join metal material, for example, as described in claim 2, a difficult-to-join alloy containing at least chromium is cited.
Specifically, an iron-based (Fe-based) alloy containing at least chromium, a nickel-based (Ni-based) alloy containing at least chromium, or the like can be given.
More specifically, examples of the Fe-based alloy containing at least chromium include SKD11, SKD61, SUS420J2, SNCM420, and SKH51 defined by JIS. These are all Fe-based alloys containing at least 3% chromium.
More specifically, examples of Ni-based alloys containing at least chromium include precipitation effect Ni-based alloys Inconel 718 and matrix-reinforced Ni-based alloys Inconel 600.

  The metal member to be joined is not particularly limited as long as it can be energized as described above, but it is preferable to use a member subjected to dimensional processing with extremely high accuracy. In addition, it is desirable that both surfaces or one surface of the metal member to be bonded be cleaned in advance to remove dirt, deposits, and the like. Specifically, for example, it is desirable to wash both surfaces or one surface of the metal member to be joined using an ultrasonic solvent or the like and an organic solvent such as isopropanol. Alternatively, the both surfaces or one surface of the metal member to be bonded may be cleaned by sputtering, cleaning liquid, or the like, and the foreign material, oxide film, passive film, or the like at the bonding interface may be removed for bonding. Furthermore, interface modification by plasma treatment under an argon atmosphere or plasma irradiation treatment under atmospheric pressure may be performed on both surfaces or one surface of the metal members to be joined. By performing such interface modification by plasma treatment in an argon atmosphere, the oxide film and the like at the interface can be removed, and the bonding can be facilitated.

Furthermore, as a metal member to join, the thing to which the mirror surface thru | or smoothing process was given to both surfaces or one side of the joining surface is preferable. Examples of a method for applying a mirror surface or a smoothing treatment to both surfaces or one surface of the joint surface include known methods such as polishing and buffing. It is desirable to finish the surface roughness of the joining surface to a mirror surface or a smooth surface of 0.5 μm or less by this treatment.
In joining by pulse energization, the metal member to be joined may be accurately positioned using a V block or the like as necessary.

In the present invention, two or more kinds of metal members can be joined at the same time with respect to the various metal members as described above, and the same kind of metal members or different kinds of metal members can be joined together.
Specifically, joining of steel materials, joining of steel materials and non-ferrous metals and special alloys, joining of non-ferrous metals (such as aluminum and copper), and joining of special alloys can be performed.
It can also be used to join members having different characteristics such as a combination of shape memory alloy, magnetic material, non-magnetic material and the like.
Furthermore, a processing groove having an arbitrary shape is formed on both surfaces or one surface of the joint surface, and a fluid passage including a straight line and a curve, a narrow hole, a slit, a pool, and the like can be formed by joining.

  The present invention includes various molds with built-in heat exchange channels, manifolds with built-in curved passages for liquid gas materials, turbine blades, engine valves, piston heads, fuel cell cooling plates, fuel injection nozzles, fiber material injection nozzles, semiconductor heating unit cooling plates It can be applied to a hydraulic solenoid, an ultra-fine punch type with a fine hole slit, an optical fiber connector and terminal part, a cooling pipe joint such as a rocket engine combustion part, and a sensor electromagnetic valve by a magnetic material non-magnetic material joint.

The shape of the metal members to be joined is not particularly limited, and may be, for example, a bulk shape (solid), a thin plate shape of about 1 mm or less, a pipe shape, a corrugated plate shape, or the like. The present invention can be used for joining various shapes of metal members having the same shape or different shapes.
The joining surface may be flat or a curved surface so long as no gap is formed between the joining surfaces.
Further, the joint surface can be processed into a complementary joint surface shape so that the joint surface of the first metal member and the joint surface of the second metal member are in close contact with each other. For example, when the joint surface of one metal member is a convex curved surface, a concave curved surface that is in close contact with the metal member can be adopted as the shape of the joint surface of the other metal member.

According to the first aspect of the present invention, when two or more metal members that can be energized are joined by energization of a pulse current, the pulse current is energized while applying pressure while the joining surfaces of the metal members are in contact with each other. The temperature raising / lowering operation of raising the temperature and then lowering the temperature across the transformation point or the solution treatment temperature is repeated a plurality of times.
When energizing the pulse current, first, the metal member is abutted and pressurized in the abutted state.
More specifically, after both surfaces or one surface of the bonding surface is processed as described above as necessary, the bonding surfaces are butted against each other, and pressure is applied so that the butted bonding surfaces are brought into close contact with each other.

The pressure applied to the joint surface varies depending on the inherent hardness, pressure resistance, etc. of the metal member, but is generally in the range of 1 to 700 MPa, preferably in the range of 10 to 200 MPa. The pressing direction can be applied not only from a single axis direction but also from a multi-axis direction such as an orthogonal direction or an oblique direction.
The electrode direction and the bonding interface pressing direction may be different or the same.
The shape of the electrode in contact with the bonding member may be a disk shape, a roller shape that can be energized, or may be engraved according to the shape of the bonding member. The electrode sandwiching the bonding member may be a carbon material or a molybdenum material, but a carbon material is more preferable.

In the present invention according to claim 1, a pulse current is applied while applying pressure in a state where the joint surfaces of two or more metal members are in contact with each other.
More specifically, the bonding surfaces of two or more metal members are abutted with each other, and a pair of electrodes are applied to any direction of the metal members to be bonded while pressurizing at a predetermined pressure so that the abutted bonding surfaces are brought into close contact with each other. Only the metal member to be pulsed is energized.

Here, “pulsed current is applied only to the metal member to be joined” means that a material other than the metal member to be joined is not used. In other words, it is generally used in the discharge plasma sintering method. This means that a carbon mold surrounding the metal members to be joined is not used.
By not using an energizable carbon mold that surrounds a metal member other than the metal member to be joined between the electrodes, it is possible to prevent a decrease in current density due to the use of an energizable carbon mold, and to Enables direct temperature control to achieve efficient bonding, and eliminates the shape restrictions of bonded metal members that could only be made in the shape of a disk or cylinder in the carbon mold so far. It became possible, and the joining range was dramatically expanded.
In the present invention according to claim 1, the current density is increased by energizing only the metal member to be joined without using the carbon mold surrounding the metal member to be joined as described above, and a pulse current is generated between the joining interfaces. By performing the flow, a bonding process by pulse energization is performed.

At this time, it is possible to energize the vicinity of the butted joint surfaces while forcibly heating from the outside. Thereby, a long member etc. can be joined efficiently in a short time.
There are no particular restrictions on the means for forcibly heating from the outside, but direct heating methods such as nichrome wire, or induction heating methods such as microwave induction heating, millimeter wave induction heating, submillimeter wave induction heating are most preferable. . In addition, high-frequency heating and the like can be mentioned, and one of these can be used alone, or two or more can be used in combination.
The heating time for forcibly heating from the outside may generally be 60 minutes or less.
Moreover, in order to prevent the heat | fever divergence of the metal member to join and to prevent temperature nonuniformity, a single to multiple | multiplex reflection board can be installed in the metal member outer periphery to join.

  The pulse current bonding is usually performed in a vacuum or an inert gas atmosphere. That is, it is desirable to perform a pulse energization bonding in a vacuum atmosphere, but it may be performed in an inert gas atmosphere such as nitrogen gas or argon gas.

The pulse current can be either a direct current pulse current or an alternating current pulse current, but a direct current pulse current is usually used. The pulse current may be energized within a frequency range of 3 to 160 Hz.
In the present invention according to claim 1, the current density is increased by energizing only the metal member to be joined without using the carbon mold surrounding the metal member to be joined as described above, and the duty ratio is increased between the joining interfaces. That is, it is preferable to flow a pulse current having a pulse ON / OFF ratio (ON / ON + OFF) of 50 to 99% (pulse ON: OFF ratio = 1: 1 to 99: 1).
The duty ratio of the pulse current is effective for all energizable metal members within the above range, but there is a more appropriate duty ratio range depending on the type of metal member.
For example, when carbon steel S45C is used as the metal member, the duty ratio of the pulse current is preferably a pulse ON: OFF ratio = 75: 25 to 99: 1, but a more preferable range is 90: A range of 10-98: 2 is recommended.
It is preferable that a pulse current having a high ON time ratio of such a pulse is supplied, the temperature of the entire member is gradually increased by self-heating, and the temperature of the entire member is increased as uniformly as possible.
Moreover, as a pulse current, the thing of the range of 100-50000A, Preferably 300-30000A is used, The voltage is about 100V or less to about 1v, However, It is not restrict | limited to this.

In the present invention according to claim 1, such a pulse current is energized to raise the temperature, and then the temperature raising / lowering operation for lowering the temperature across the transformation point or the solution treatment temperature is repeated a plurality of times, that is, repeated two or more times. It is necessary. More specifically, it is necessary to repeat the temperature raising / lowering operation with the transformation point or solution treatment temperature of the metal member to be joined in between.
Here, “transformation point or solution treatment temperature” is used because “Ni-based heat-resistant alloy containing at least chromium” does not have a transformation point. Instead of “point”, “solution treatment temperature” recognized as corresponding to this transformation point is used.
The maximum temperature at the time of temperature rise and the minimum temperature at the time of temperature fall differ depending on the type of metal member to be joined and it is difficult to uniquely determine, but usually the maximum temperature at the time of temperature rise is 950 ° C. or more, Further, the minimum temperature when the temperature is lowered after the temperature rise is 900 ° C. or lower.
For example, when the metal member is an Fe-based alloy that is a difficult-to-bond material, particularly an Fe-based alloy containing chromium, the maximum temperature at the time of temperature rise needs to be 1000 ° C. or higher.
In the case of a hard-to-join alloy containing at least chromium as described in claim 2, it is particularly effective to repeat this temperature raising / lowering operation, and the maximum temperature at the time of temperature rise needs to be 1030 ° C. or higher. In particular, when the metal member is a Ni-base heat-resistant alloy containing at least chromium, it is desirable that the maximum temperature at the time of temperature rise be 1100 ° C. or higher.
Here, the maximum temperature at the time of temperature rise may be reached at least once during the temperature raising / lowering operation.
On the other hand, for example, when the metal member is an Fe-based alloy containing at least chromium, the minimum temperature when the temperature is lowered after the temperature rise needs to be 900 ° C. or less, preferably 780 ° C. or less. Further, when the metal member is a Ni-base heat-resistant alloy containing at least chromium, it is desirable that the minimum temperature when the temperature is lowered after the temperature rise is 800 ° C. or less.
If the maximum temperature at the time of temperature rise and the minimum temperature when the temperature is lowered after the temperature rise are out of the above range, the object of the present invention cannot be achieved.
The temperature lowering may be performed by stopping the pulse current and naturally cooling, or may be performed by blowing an inert gas such as argon gas onto a metal member to be joined and forcibly cooling. The minimum temperature when the temperature is lowered after the temperature rise is not higher than the transformation point of the metal member to be joined or not higher than the solution treatment temperature.
It should be noted that the structural change can be caused to contribute to the bonding strength by preferably performing the cooling rate in the range of 30 ° C./min to 400 ° C./min. This is done by passing the transformation point or solution treatment temperature of the joining member as soon as possible, fixing the transient phenomenon of the structure, and promptly causing a systematic change of the joint interface when the temperature rises again. This is because can be made stronger.
Thereafter, the pulse current is supplied again to raise the temperature of the metal member, and the metal member is joined by repeating such a temperature raising / lowering operation a plurality of times.

In addition, the temperature here is the value which measured the temperature at the time of joining, inserting the thermocouple 6 in the metal member center part to join, as shown in FIG.
FIG. 1 is a conceptual diagram of a metal member joining apparatus using pulse energization. In FIG. 1, reference numeral 1 denotes a metal member to be joined, and reference numeral 2 denotes an electrode such as a carbon electrode. Reference numeral 3 represents a pulse current generator, and reference numeral 4 represents a pressurizing means (for example, an air cylinder or a hydraulic cylinder) for pressurizing the electrode. Further, in FIG. 1, reference numeral 2A denotes an upper ram electrode, and reference numeral 2B denotes a lower ram electrode. However, the upper and lower ram electrodes may be integrated with the upper and lower electrodes 2, respectively. Reference numeral 5 denotes a vacuum chamber that can be evacuated. The vacuum chamber is not limited to a vacuum atmosphere, but can be an inert gas atmosphere as necessary.

As another method for measuring the temperature, there is a method of measuring the heat generation state of the surfaces of the metal members to be joined with a radiation thermometer. However, in this case, the temperature may be higher or lower than when measured with a thermocouple. For example, when a thermocouple is inserted into a metal member made of SKD11 (a Fe-based alloy containing at least chromium) and measured, the temperature is 940 ° C., and at this time, the radiation thermometer indicates 1030 ° C. Even if the ε value of the radiation thermometer is set to an appropriate value according to the type of the metal member, the displayed temperature is considerably different between the thermocouple and the radiation thermometer.
This is because the method of the present invention is self-heating due to the pulse current, so there is a difference between the current density flowing through the surface of the metal member and the current density flowing through the center, and there is a difference between the internal temperature and the external surface temperature. is there. This is because, in the case of self-heating due to a pulse current, the temperature rises rapidly on the outer surface at an early stage, and then the temperature rises quickly on the inside, so that a phenomenon that cannot be imagined by a heat transfer mechanism from external heating occurs.
For this reason, in the method of the present invention, the measured value when the thermocouple is almost inserted into the metal member to be joined is used as the temperature display when joining.

In the present invention according to claim 1, such a pulse current is energized to raise the temperature, and then the temperature raising / lowering operation for lowering the temperature across the transformation point or the solution treatment temperature is repeated a plurality of times, that is, repeated two or more times. When such a temperature raising / lowering operation is performed only once, it is impossible to firmly bond a difficult-to-join metal material by pulse energization without inclusions such as a brazing material. The object of the invention cannot be achieved. FIG. 2 is a graph showing a pattern when such a temperature raising / lowering operation is performed only once, and is a conceptual diagram of a joining program for performing the temperature raising / lowering operation only once. In this case, the temperature increasing / decreasing pattern by the temperature increasing / decreasing operation indicates one mountain.
In this way, when the temperature raising / lowering operation is performed only once, if a low melting point metal such as brazing material is not interposed, for example, SUS420J2 alloy (prehardened steel) such as STAVAX (registered trademark owned by Woodeholm Corporation), In difficult-to-join metal materials such as stainless steel alloy steel and chromium heat-resistant steel containing 3% or more of chromium, it is difficult to directly join metal materials to be joined.

On the other hand, as in the present invention according to claim 1, when a temperature increase / decrease operation in which a pulse current is energized to raise the temperature and then the temperature is lowered across the transformation point or the solution treatment temperature is repeated a plurality of times. In addition, it is possible to firmly bond a difficult-to-join metal material by pulse energization without inclusions such as a brazing material. FIG. 3 is a graph showing a pattern when such a temperature raising / lowering operation is repeated twice, and is a conceptual diagram of a joining program in which the temperature raising / lowering operation is repeated twice. In this case, the temperature increasing / decreasing pattern by the temperature increasing / decreasing operation indicates two peaks.
The principle by which the strength of bonding is remarkably improved by a plurality of temperature raising and lowering operations with the transformation point or solution treatment temperature in between is not exactly known, but the preheating effect on the metal member to be joined together with the metal member to be joined. The repetitive changes in the structure due to the temperature increase / decrease operation across the transformation point or the solution treatment temperature may have the effect of lowering the energy level or the bonding barrier at the bonding interface such as the oxide nonconducting film. Imagine.
That is, by preheating the metal members to be joined in a sense, there is little loss of pulse current applied to the metal members to be joined, and it can be used as energy to break the joining barrier, transformation point or solution treatment It is considered that the oxide layer generated at the bonding interface diffuses and disappears in the metal member to be bonded due to the change of the structure due to the temperature raising and lowering operation with the temperature interposed therebetween.
However, since the technique of the present invention is new, the principle has not yet been elucidated.

In the present invention according to claim 1, after the temperature raising / lowering operation is repeated a plurality of times as described above, heat diffusion is performed in a vacuum or an inert gas atmosphere to perform interdiffusion to further strengthen the bonding. be able to. This is because a part where bonding is not completed in time can be bonded more completely by performing interdiffusion only by bonding by pulse energization.
In particular, depending on the material of the metal member to be joined, it may be possible that the joint is not completely joined by one interdiffusion joining process. Therefore, the interdiffusion joining process may be performed not only once but multiple times. .
In the past, so-called tempering treatment has been performed after sintering, so that joining in a solid state has been performed, but this and this interdiffusion joining treatment are completely different. No other interdiffusion bonding process in pulse energization has been found so far.
During bonding by pulse energization, the temperature is raised to a predetermined temperature by self-heating, but since the heat treatment is not due to pulse energization, it is necessary to raise the temperature by external heating to the predetermined temperature.
Such an interdiffusion bonding process can be performed at 70% or more and less than 90% of the melting point of the bonding member.
When this interdiffusion bonding process is performed, no pulse current flows. Further, although pressurization is not particularly necessary, pressurization from the previous stage may be performed as it is.

In the present invention according to claim 1, after performing the joining process by pulse energization by repeating the temperature raising / lowering operation a plurality of times as described above, the interdiffusion joining process in which heat treatment is subsequently performed under a predetermined condition is performed. It is preferable to perform a mutual diffusion bonding process after performing a bonding process by energization to obtain a liquid phase state.
The interdiffusion bonding process after the liquid phase state is used refers to the mutual diffusion bonding process after the liquid phase state in pulse energization, and is different from the conventionally known liquid phase diffusion bonding. The conventionally known liquid phase diffusion bonding refers to a phenomenon that occurs when a low melting point member is inserted between the bonding surfaces, and clearly differs from the mutual diffusion bonding processing after the liquid phase state described here. However, it has been found that such diffusion in the liquid phase state occurs even in pulse energization. In addition, this “interdiffusion bonding treatment after being in a liquid phase state” is “solid phase diffusion” in which it is not melted but diffused in a solid phase state in that it is melted and then liquid phase state is allowed to cause mutual diffusion. Are clearly different.

  According to the heat treatment (interdiffusion bonding treatment) after making the liquid phase state in such pulse energization, a strong bonding enough to be recognized as having the same characteristics as the base material in an impact test or the like is obtained, The metal members to be joined can be joined extremely firmly and reliably in a short time and at low cost.

  The present invention is as described above. Thus, according to the present invention, metal materials that are difficult to join, such as an Fe-based alloy or a Ni-based alloy that is a heat-resistant alloy, can be firmly joined by pulse energization without inclusions such as a brazing material. . In addition, after completion of joining, desired various known heat treatments can be performed.

EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not restrict | limited at all by these.
Example 1
(1) Joining Pulse energization joining apparatus as shown in FIG. 1, that is, a pair of electrodes 2 for supplying a pulse current to the metal member 1 to be joined, a pulse current generator 3 for energizing the electrode 2 with a pulse current, FIG. 3 is a conceptual diagram of a joining program that includes a pressurizing means 4 for pressurizing the electrode 2, and further uses a pulse energizing joining device equipped with a vacuum chamber 5 to repeat the temperature raising and lowering operation twice as shown in FIG. 3. Based on the conditions shown in Table 1, joining by pulse energization was performed. As the electrode 2, a carbon electrode was used.
Note that, as a duty ratio of the pulse current, a pulse current of 3 Hz was used at a pulse ON: OFF ratio of 98: 2.
The metal member 1 to be joined has a surface roughness of 1.0 μm or less and is made of the material shown in Table 1, and a test piece having a diameter of 16 mm and a length of 42 mm was used, and two of them were abutted and joined. .
The metal member 1 was first cleaned with isopropanol using ultrasonic waves.
Next, the metal members 1 are brought into contact with each other, and with a load of 200 kg (10 MPa) applied thereto, a pair of electrodes are applied to both ends of the metal member 1 so that only the metal member 1 is energized to increase the current density. Then, a pulse current (900 A) having a pulse ratio of 98: 2 was allowed to flow between the bonding interfaces to perform bonding (first-stage bonding) processing by pulse energization. At this time, the temperature of the joint measured by the thermocouple 6 rose to a maximum of 1010 ° C. The pulse current was 900A.
During the above operation, the atmosphere was kept at a vacuum of 10 Pa or less.
Thereafter, the supply of the pulse current is stopped, and after spontaneous cooling, the temperature is lowered below the transformation point of the metal member 1, and then again applied to both ends of the metal member 1 with a load of 200 kg (10 MPa) applied thereto. By applying a pair of electrodes and energizing only the metal member 1 to increase the current density, a pulse current (1000 A) having a pulse ratio of 98: 2 is caused to flow between the bonding interfaces, thereby joining by pulse energization (second stage). ). At this time, the temperature of the joint measured by the thermocouple 6 rose to a maximum of 1060 ° C. The pulse current was 1000A.
At this time, the reflector was wrapped around the joining member 1 in a single layer and covered.

Thereafter, pulse energization was stopped, and heat treatment (interdiffusion bonding treatment) was performed at a temperature of 1030 ° C. by external heating.
During the above operation, the atmosphere was kept at a vacuum of 5 Pa or less.
In this way, a joined product was manufactured.

(2) Breaking energy measurement test With respect to the test piece (tensile test piece parallel part: diameter 8 mm) cut out from the joined product thus obtained, the breaking energy according to JIS Z2242 (metal material impact test method). Was measured. The results are shown in Table 1.

The breaking energy is obtained from the following equation.
・ Fracture energy (E) = M (cosβ-cosα)
Here, M = W · r (W is the load due to the mass of the hammer (unit: N), and r is the distance (unit: m) from the center of the rotation axis of the hammer to the center of gravity).
Further, α is a hammer lifting angle, and β is a hammer swing-up angle after the test piece is broken.
In addition, as a test apparatus of this time, the apparatus with the maximum generated impact energy as follows was used. Therefore, it is possible to measure up to 9.7 KJ as the breaking energy.
W = 10.78KN
r = 0.9m
M = W · r = 9.702KN · m≈9.7KJ

  According to the results in Table 1, it can be seen that the hard-to-join metal material can be firmly joined by repeating the temperature raising / lowering operation a plurality of times as in the present invention.

  According to the present invention, since a difficult-to-join metal material can be firmly joined by pulse energization without inclusions such as a brazing material, it can be effectively used for joining metal materials.

It is a conceptual diagram of the joining apparatus of the metal member by pulse electricity supply. It is a conceptual diagram of the joining program which performs temperature raising / lowering operation only once. It is a conceptual diagram of the joining program which repeats temperature raising / lowering operation twice. It is a partially notched explanatory drawing which shows the pattern which measures temperature with a thermocouple.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal member 2 Electrode 2A Upper ram electrode 2B Lower ram electrode 3 Pulse current generator 4 Pressurizing means 5 Vacuum chamber 6 Thermocouple

Claims (4)

  When joining two or more metal members that can be energized by energizing a pulse current, the pulse current is energized and the temperature is raised while applying pressure while the joining surfaces of the metal members are in contact with each other, and then the transformation point or solution treatment A method for joining metal members by pulse energization, wherein a temperature raising / lowering operation for lowering the temperature across the temperature is repeated a plurality of times.   The joining method according to claim 1, wherein the metal member is a hard-to-join alloy containing at least chromium.   The joining method according to claim 1 or 2, wherein the lowest temperature when the temperature is lowered after the temperature rise is 900 ° C or lower. The joining method according to claim 1, wherein a maximum temperature at the time of temperature rise is 1030 ° C. or higher.

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