JP2015083315A - Mig arc brazing wire, mig arc brazing method and mig arc brazing joint body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an MIG arc brazing wire, MIG arc brazing method and MIG arc brazing joint body which achieve a good joint.SOLUTION: The MIG arc brazing wire is a wire for joining a joint material comprising a base material comprising carbon steel and copper by MIG arc brazing, with silicon (Si) content being 2.0-5.0 mass% and manganese (Mn) content being 0.5-2.0 wt.%, and with the balance being Cu and inevitable impurities.

Description

  Embodiments described herein relate generally to a MIG arc brazing wire, a MIG arc brazing method, and a MIG arc brazing joint.

  A valve-type water turbine generator is a generator in which a generator is built in an egg-shaped structure called a valve. The valve is composed of an inner cylinder and an outer cylinder, and the outer cylinder incorporates a generator. Further, the outer cylinder is formed so as to surround the inner cylinder with the inner cylinder and the central axis being coaxial. Both the inner cylinder and the outer cylinder are made of carbon steel, and a plurality of copper heat transfer fins joined to the outer cylinder are provided between the inner cylinder and the outer cylinder. The heat inside the valve is released to the outside through the heat transfer fins.

  A cask (shielding container) for storing spent nuclear fuel is provided with an inner cylinder for storing the spent nuclear fuel, and an outer cylinder surrounding the inner cylinder with the inner cylinder and the central axis as the same axis. The outer cylinder is configured to absorb external impacts. Both the inner cylinder and the outer cylinder are made of carbon steel, and a plurality of copper heat transfer fins are joined to the outer circumference of the inner cylinder and the inner circumference of the outer cylinder. The heat of the spent nuclear fuel is radiated to the outside through the heat transfer fins.

  TIG welding and arc brazing are used for joining different materials of copper and carbon steel as described above. As the arc brazing, for example, plasma MIG arc brazing is used. Plasma MIG arc brazing is a technique in which the material to be joined is heated to such an extent that it is not melted by the plasma arc, and MIG arc brazing is performed in the plasma arc. However, in plasma MIG arc brazing, there is a problem that the welding apparatus and torch are enlarged and it is difficult to join the narrow portion, and manual joining is difficult.

  Arc brazing may be used in joining stainless steel and carbon steel other than joining copper and carbon steel. For example, an arc brazing method using a shielding gas containing 5 to 22% by volume of carbon dioxide gas and the balance of argon, helium, or a mixed gas of argon and helium in combination with a low heat input welding power source is known. In particular, the low heat input welding power source has the advantage that the amount of spatter can be reduced, and various proposals have been made for the low heat input welding power source used for arc brazing.

JP 2008-82906 A

  However, when copper and carbon steel are joined by MIG arc brazing using a low heat input welding power source, the amount of spatter generated increases because carbon dioxide is contained in the shield gas when the conventional shield gas is used. easy. In addition, because copper and carbon steel have greatly different thermal conductivities, when MIG arc brazing is performed using a low heat input welding power source, the droplet transfer is not stable, and the weld bead shape is meandering. This is likely to occur. Also, with MIG arc brazing of copper and carbon steel, the arc is also likely to become unstable. Thus, in the MIG arc brazing using the low heat input welding power source, the optimal wire and shield gas composition according to the material to be joined has not been known.

  The problem to be solved by the present invention is to provide a wire for MIG arc brazing, a MIG arc brazing method, and a MIG arc brazing joined body capable of achieving good joining in joining copper and carbon steel.

  The wire for MIG arc brazing of the embodiment is a wire for joining a base material made of carbon steel and a material to be joined made of copper by MIG arc brazing, and has a silicon (Si) content of 2.0 to 5 0.0 mass%, manganese (Mn) content is 0.5 to 2.0 wt%, and the balance consists of Cu and inevitable impurities.

It is sectional drawing which shows schematically the MIG arc brazing joined body of embodiment. It is a figure showing roughly the MIG arc brazing device of an embodiment. It is a schematic block diagram which shows the positional relationship of the test body and welding torch by the MIG arc brazing method of embodiment. It is sectional drawing which shows schematically the valve turbine generator of embodiment. It is AA sectional drawing of the valve water turbine generator (FIG. 4) of embodiment. It is sectional drawing which shows roughly an example of the radioactive storage container of embodiment. It is sectional drawing which shows roughly the junction part of the radioactive containment container of FIG. 6 is a schematic configuration diagram showing a positional relationship between a test body and a welding torch according to a MIG arc brazing method of Example 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, devices having common functions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a cross-sectional view showing a MIG arc brazing joined body 1 formed by the MIG arc brazing method using the MIG arc brazing wire of the present embodiment. In the MIG arc brazing joined body 1, a plate-like base material 2 made of carbon steel and a plate-like joined material 3 made of copper are joined by a bead 4. The base material 2 and the material to be joined 3 are combined in a substantially T shape with a joining angle θ of preferably θ = 90 to 135 °. This is to form a good bead 4 with no overlap or undercut. Note that the bonding angle θ is an angle formed by the plate surfaces on which the beads 4 are formed in the base material 2 and the bonded material 3.

  The MIG arc brazing joined body 1 is formed by subjecting the base material 2 and the material to be joined 3 to MIG arc brazing using a wire and shield gas having a specific composition and using a low heat input welding power source.

  The base material 2 is made of carbon steel. The carbon steel as the base material 2 has a thermal conductivity of preferably 50 to 70 W / mK, more preferably 55 to 60 W / mK. As the base material 2, for example, low carbon steel, medium carbon steel, and high carbon steel having a carbon (C) content of 0.02 to 2% in mass% are preferably used.

  On the other hand, the material 3 to be joined in the present embodiment is made of copper. Copper which is the material to be bonded 3 preferably has a thermal conductivity of 350 to 450 W / mK, more preferably 360 to 420 W / mK. For example, pure copper such as deoxidized copper, oxygen-free copper, and tough pitch copper is preferably used as the material to be bonded 3. According to the MIG arc brazing method of the present embodiment, good bonding can be achieved using the base material 2 and the material to be bonded 3 having different thermal conductivities as described above. Moreover, the shape of the base material 2 and the to-be-joined material 3 is not specifically limited, Shapes other than plate shape may be sufficient. In this case, it is preferable that the surfaces on which the MIG arc brazing is applied in the base material 2 and the material to be joined 3 are substantially flat.

  The wire of this embodiment contains 2.0-5.0 mass% silicon (Si), 0.5-2.0 mass% manganese (Mn), and the balance consists of copper (Cu) and inevitable impurities. Solid wire. The reasons for limiting the components of the MIG arc brazing wire of the present invention will be described below.

  With respect to arc stability in MIG arc brazing, it is important that Si and Mn are included in the wire. When the arc is not stable, bonding defects and defects such as a shape defect of the bead 4 and spatter are likely to occur. In order to stabilize the arc, it is important that the arc spot of the arc is stably formed. However, when an oxide is present on the cathode side, the cathode spot is more easily generated. Since Si and Mn generate oxides that are the source of cathode spots, the stability of the arc is improved.

  Si has the effect of improving the arc stability and improving the shape of the bead 4. Here, when Si is less than 2.0% by mass, the arc generated at the wire tip is not stable, and the shape of the bead 4 becomes a meandering shape with respect to the MIG arc brazing direction. Moreover, when Si exceeds 5.0 mass%, an arc will be stabilized, but the shape of the bead 4 will become convex. In any case, since it is difficult to obtain a bead 4 having a good shape, the Si content is 2.0 to 5.0 mass%, preferably 3.0 to 4.0 mass%.

  Mn has the effect of improving the arc stability and improving the fluidity of the molten base material 2 and the material 3 to be joined and smoothing the droplet transfer. When Mn is less than 0.5% by mass, droplet transfer becomes insufficient, and the droplet becomes a form of short-circuit transfer. On the other hand, if it exceeds 2.0% by mass, the fluidity of the droplet becomes too large and the droplet becomes large, resulting in a globular transition. In any case, since the amount of sputtering tends to increase, the content of Mn is 0.5 to 2.0% by mass, preferably 0.7 to 1.5% by mass.

  Inevitable impurities include nickel (Ni), chromium (Cr), molybdenum (Mo), boron (B) and the like derived from the wire manufacturing raw material, and the total content is less than 0.0001% by mass. is there.

  In this embodiment, helium (He) is 50 to 80% by volume of the shielding gas, and the balance is made of Ar and inevitable impurities. Hereinafter, the reasons for limiting the components of the shielding gas will be described.

  He has the effect of spreading and stabilizing the arc during MIG arc brazing. Since He has a higher potential gradient than argon gas, the arc voltage during welding is increased, and heating of the base material 2 is promoted. Further, since the heating amount of the base material 2 is increased, the generation of metal vapor effective in improving the arc stability from the molten pool in which the base material 2 is melted is also promoted, so that the arc stability is improved.

  When He is less than 50%, the arc generated at the tip of the tungsten electrode is not stable, and the bead 4 has a meandering shape with respect to the MIG arc brazing direction. Further, when the He exceeds 80%, the arc is stabilized, but the shape of the bead 4 becomes convex and a good bead shape cannot be obtained. Therefore, He is 50 to 80% by volume, preferably 65 to 75% by volume.

Inevitable impurities include oxygen (O ₂ ) and hydrogen (H ₂ ) present in the atmosphere, and the total content thereof is less than 0.0001% by volume.

  Next, the formation method of the MIG arc brazing joined body 1 of this embodiment is demonstrated. FIG. 2 is a schematic configuration diagram showing an example of the MIG arc brazing apparatus 100 in the present embodiment. In FIG. 2, the welding torch 10 includes a gas nozzle 5 and a contact tip 6. The contact chip 6 is provided with a cavity, and a wire 7 is inserted into the cavity. When the MIG arc brazing is started, the low heat input welding power source 11 applies a voltage between the wire 7 and the base material 2 to generate an arc. At the same time, the shield gas is supplied from the gas supply device 9 to the gas nozzle 5 and flows out from the tip of the gas nozzle 5 so as to cover the periphery of the wire 7. The wire 7 is automatically and continuously fed by the wire feeder 8 while forming a bead by the generated arc.

  FIG. 3 is a schematic view showing the MIG arc brazing method of the present embodiment. First, in the arranging step, the base material 2 and the material to be joined 3 are combined into a T shape having a joining angle θ = 90 °. The base material 2 is inclined from the horizontal, preferably α = 45 to 55 °, and is arranged so that the bisector of the joint angle θ of the base material 2 and the joint material 3 is in the vertical direction. Next, the MIG arc brazing of this embodiment is performed in the joining process. At this time, the inclination angle β of the thermal spraying torch 10 from the vertical direction is preferably β = ± 5 °. Thereby, since the arc can be stabilized and the droplet transfer can be performed stably, the bead 4 having a good shape can be formed and the MIG arc brazing joined body 1 which is well joined can be obtained.

  The flow rate of the shielding gas is not particularly limited and is, for example, 10 to 30 liters / minute. When the shielding gas flow rate is less than 10 liters / minute, the molten metal part is not properly shielded, and pores may be generated. When the shielding gas flow rate exceeds 30 liters / minute, air entrainment may occur and pores may be generated. As the low heat input welding power source 9, it is preferable to use a CMT (Cold Metal Transfer) power source. Further, since the heat input is effective for preventing deformation of the base material, it is preferably 10 to 200 kJ / cm.

  As described above, according to the MIG arc brazing method of the present embodiment, since the arc stability and the shape of the bead 4 are excellent and joining with reduced spatter generation is possible, MIG arc brazing having excellent joining properties is achieved. The MIG arc brazing joined body 1 which is achieved and is well joined can be obtained.

  Next, an application example of the MIG arc brazing method of the present embodiment will be described. FIG. 4 is a schematic configuration diagram showing the valve turbine generator 20. The valve turbine generator 20 includes an inner cylinder 21 and a generator 27, and is joined to the inner cylinder 21 and the outer cylinder 22 that coaxially surrounds the inner cylinder 21 with the central axis as the center axis, and the inner surface of the outer cylinder 22. A plurality of heat transfer fins 23 for radiating heat generated by the generator 27 are provided. The inner cylinder 21 and the outer cylinder 22 are made of carbon steel, and the conductive fins 23 are made of copper. A rotary shaft 24 is provided through the center of the outer cylinder 22 of the valve turbine generator 20. One end of the rotating shaft 24 outside the outer cylinder 22 is provided with a runner (not shown) that rotates by receiving a water flow, and the other end of the rotating shaft 24 is provided with a generator rotor 25. . A generator stator 26 is held on the inner wall surface of the outer cylinder 23 facing the generator rotor 25, and a current is generated in the generator stator 26 by rotating the generator rotor 25. It has become.

  FIG. 5 is a cross-sectional view of the valve turbine generator 20 taken along the line AA. In the valve turbine generator 20, the MIG arc brazing joined body 1 similar to that shown in FIG. 1 is formed on the outer cylinder 22 by joining heat transfer fins 23 with beads 28. The bead 28 is formed by performing the MIG arc brazing of the present embodiment from one side of the joint surface of the outer cylinder 22 and the heat transfer fin 23. Thereby, the stability of the arc and the shape of the bead 28 are excellent, and joining with reduced spatter generation is possible. Therefore, the MIG arc brazing joined body 1 in which the outer cylinder 22 and the heat transfer fins 23 are well joined can be obtained.

  Next, another application example of the MIG arc brazing method of the present embodiment will be described. FIG. 6 is a cross-sectional view schematically showing a part of the radioactive nuclear fuel storage container 30. 6 includes an inner cylinder 31 that stores spent nuclear fuel, an outer cylinder 32 that coaxially surrounds the inner cylinder 31 and a central axis that is coaxial with the inner cylinder 31, and an inner cylinder 31 and an outer cylinder 32. A plurality of heat transfer fins 33 are provided. The radioactive nuclear fuel is accommodated in a space defined by the inner cylinder 31, the outer cylinder 32, and the heat transfer fins 33, and heat generated by the radioactive nuclear fuel is released to the outside through the heat transfer fins 33. The inner cylinder 31 and the outer cylinder 32 are made of carbon steel, and the conductive fins 33 are made of copper. FIG. 7 is an enlarged view of the joint 40 in FIG. The joint portion 40 is formed by joining the inner cylinder 31 and the heat transfer fins 33, and the outer cylinder 32 and the heat transfer fins 33 by the beads 34. The bead 34 is formed by performing the MIG arc brazing of this embodiment from one side of the joint 40. Thereby, the stability of the arc and the shape of the bead 34 are excellent, and joining with reduced spatter generation is possible. Therefore, the MIG arc brazing joined body 1 in which the inner cylinder 31 and the heat transfer fins 33, the outer cylinder 32, and the heat transfer fins 33 are well bonded can be obtained.

  In the present embodiment, the MIG arc brazing method has been described in which the outer cylinder 22 and the heat transfer fins 23 of the valve turbine generator and the inner cylinder 31 and the outer cylinder 32 of the radioactive nuclear fuel storage container and the heat transfer fins 33 are joined. The present invention is not limited to this. In other words, the MIG arc brazing of the present embodiment can be applied as long as it is a joining of a carbon steel material and a copper material.

Next, the present invention will be described in more detail using examples.
(Examples 1-4, Comparative Examples 1-7)
In FIG. 3, a carbon steel plate having a thickness of 16 mm simulating the outer cylinder 22 of the valve turbine generator 20 is used as the base material 2, and a copper plate having a thickness of 2.5 mm simulating the heat transfer fins 23 is used as the material to be joined 3. Thus, a test body of the MIG arc brazing joined body 1 was produced. The test body is arranged so that the copper plate has a T-shape with a bonding angle θ = 90 ° with respect to the carbon steel plate, and the carbon steel plate in the test body of the MIG arc brazing bonded body 1 is inclined at α = 45 ° from the horizontal plane. Then, they were joined with the same MIG arc brazing apparatus as shown in FIG. The welding torch had an inclination angle β = 0 ° from the vertical direction, and the power source was a CMT power source. Wires and shield gas having the configurations shown in Table 1 were prepared, and a test was performed by combining them.

[MIG arc brazing conditions]
Welding equipment: CMT welding power source (Flounias)
Test material (carbon steel plate): JIS G 3101 (2004) SS400 (plate thickness 16 mm)
Test material (copper plate): JIS H 3100 (2000) C1020 (plate thickness 2.5 mm)
Wire feeding speed: 6m / min Wire diameter: φ1.2mm
Brazing speed: 45 cm / min Shield gas flow rate: 15-20 liter / min Heat input: about 10-15 kJ / cm

  Visual evaluation was performed with respect to the stability of the arc during MIG arc brazing, the amount of spatter generated, and the bead shape. The results are shown in Table 1. The evaluation in Table 1 is as follows.

[Arc stability]
The stability of the arc was evaluated. The case where there was no arc wobbling was marked with ○, and the case where arc wobbling was seen was marked with x.

[Spatter generation amount]
The amount of spatter generated was observed. The case where there was no spatter adhesion in the vicinity of the bead was marked with ◯, and the case where spatter adhered was marked with ×.

[Bead shape]
The shape of the bead was observed. The case where there was no meandering of the beads was marked with ◯, and the case where the beads meandered and an overlap occurred at the toe end of the bead.

  From Table 1, the Si content in the wire is 2.0 to 5.0% by weight, the Mn content is 0.5 to 2.0% by weight, and the He in the shielding gas is 50 to 80% by volume. It can be seen that good results are obtained.

(Examples 5-8, Comparative Examples 8-14)
FIG. 8 is a schematic configuration diagram showing the MIG arc brazing method of the present embodiment. In this example, a test body was prepared using a carbon steel plate 12 having a thickness of 20 mm simulating the outer cylinder 31 of the radioactive nuclear fuel storage container shown in FIG. As shown in FIG. 8, the copper plate 13 is arranged with respect to the carbon steel plate 12 so that the joining angle θ = 135 °, and the carbon steel plate 12 is inclined at α = 55 ° from the horizontal plane, as shown in FIG. 2. It joined by the same MIG arc brazing apparatus. The welding torch had an inclination angle β = 0 ° from the vertical direction, and the power source was a CMT power source. Wires and shield gases having the compositions shown in Table 2 were prepared, and these were combined for testing.

[MIG arc brazing conditions]
Welding equipment: CMT welding power source (Flounias)
Test material (carbon steel plate 11): JIS G 3101 (2004) SS400 (plate thickness 20 mm)
Test material (copper plate 12): JIS H 3100 (2000) C1020 (plate thickness 6 mm)
Wire feed speed: 10m / min Wire diameter: φ1.2mm
Brazing speed: 45 cm / min Shield gas flow rate: 15-20 liter / min Heat input: about 10-15 kJ / cm

  The evaluation was performed for visual stability in the same manner as in Example 1 with respect to the stability of the arc during MIG arc brazing, the amount of spatter generated, and the bead shape. The test results are shown in Table 2.

  From Table 2, the Si content in the wire is 2.0 to 5.0% by weight, the Mn content is 0.5 to 2.0% by weight, and the He in the shielding gas is 50 to 80% by volume. It can be seen that good results can be obtained.

  As mentioned above, according to embodiment described, favorable joining can be achieved in the joining of copper and carbon steel.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Bonded body, 2, 12 ... Base material, 3, 13 ... Joined material, 4, 28, 34 ... Bead, 5 ... Gas nozzle, 6 ... Contact chip, 7 ... Wire, 8 ... Wire feeder, 9 ... Gas supply device, 10 ... welding torch, 11 ... low heat input welding power source, 20 ... valve turbine generator, 21, 31 ... inner cylinder, 22, 32 ... outer cylinder, 23, 33 ... heat transfer fin, 24 ... rotating shaft , 25 ... generator rotor, 26 ... generator stator, 27 ... generator, 30 ... radioactive nuclear fuel storage container, 40 ... junction, 100 ... MIG arc brazing device.

Claims (5)

A wire for joining a base material made of carbon steel and a material to be joined made of copper by MIG arc brazing,
The silicon (Si) content is 2.0 to 5.0% by mass, the manganese (Mn) content is 0.5 to 2.0% by weight, and the balance is made of Cu and inevitable impurities. MIG arc brazing wire. A MIG arc brazing method for joining a base material made of carbon steel and a material to be joined made of copper,
An arrangement step of arranging the base material and the material to be joined at a predetermined joining angle θ;
The silicon (Si) content is 2.0 to 5.0 mass% and the manganese (Mn) content is 0.5 to 2.0 wt% on one side of the joining surface of the base material and the material to be joined. And the tip of the thermal spraying torch for feeding a wire made of Cu and inevitable impurities is positioned,
A helium (He) content is 50 to 80% by volume so as to cover the tip of the thermal spraying torch, and the balance is supplied with a shielding gas composed of Ar and inevitable impurities,
While applying a voltage between the wire and the base material by a low heat input welding power source to generate an arc and forming a bead, the wire is fed from the tip of the spraying torch to supply the base material and the workpiece. A MIG arc brazing method comprising: a bonding step of bonding a bonding material. The base material is carbon steel having a thermal conductivity of 50 to 70 W / mK,
The MIG arc brazing method according to claim 2, wherein the material to be joined is copper having a thermal conductivity of 350 to 450 W / mK.   The MIG arc brazing method according to claim 2 or 3, wherein the base material and the material to be joined are joined at a joining angle θ of 90 to 135 °.   A MIG arc brazing joined body, wherein a base material made of carbon steel and a material to be joined made of copper are joined by the MIG arc brazing method according to any one of claims 2 to 4.

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