JP7364543B2 - Dissimilar material joining method and dissimilar material joined body - Google Patents

Description

The present invention relates to a dissimilar material joining method and a dissimilar material joined body.

2. Description of the Related Art In response to recent global environmental problems caused by exhaust gas, efforts are being made to improve fuel efficiency by reducing the weight of transport vehicles such as automobiles. For example, in order to increase safety in the event of a collision without hindering the reduction of the weight of the car body, some of the steel materials traditionally used have been replaced with lighter and more energy-absorbing materials. are also being replaced by superior light alloy materials such as aluminum alloy materials.

Unless all parts of the vehicle body are made of aluminum alloy materials, these aluminum alloy materials are inevitably used in combination with steel materials such as steel plates or shaped steel that are originally commonly used in normal automobile bodies. It is necessary to join dissimilar metals (dissimilar metal joining) between wood and steel.

Patent Document 1 discloses a technique for joining steel materials and aluminum alloy materials using steel rivets. Further, as a technique applying this joining using rivets, Patent Document 2 discloses a technique for joining a plurality of aluminum materials using aluminum rivets.

Japanese Patent Application Publication No. 2010-207898 JP2018-79476A

However, when resistance spot welding an aluminum rivet and an aluminum material, the welding current is larger (approximately three times) than resistance spot welding of steel materials, and the heat input at the contact point between the steel material and the aluminum material is significantly large. Become. Therefore, a phenomenon occurs in which molten aluminum, in which the rivet and the aluminum material are melted, flows out of the joint (dust generation), resulting in a reduction in the nugget size and a decrease in joint strength.

Therefore, the present invention provides a method for joining dissimilar materials and a joined body of dissimilar materials, which can suppress the outflow of molten aluminum near the welding area and achieve a good joint when resistance spot welding is performed using aluminum rivets to join dissimilar materials. The purpose is to provide.

The present invention consists of the following configuration.
(1) Attaching an annular collar having a higher melting point than aluminum to the shaft of an aluminum rivet having a head and a shaft,
Driving the shaft portion of the rivet to which the collar is attached into a steel material to penetrate it;
arranging the steel material and the aluminum material so that the tip of the shaft of the rivet of the steel material faces the aluminum material,
The rivet and the aluminum material are sandwiched between a pair of electrodes, and resistance spot welding is performed while applying pressure between the electrodes to join the aluminum material and the steel material.
Method for joining dissimilar materials.
(2) Attach the shaft portion of an aluminum rivet having a head and a shaft portion to the through hole of the steel material provided with the through hole through an annular collar having a higher melting point than aluminum;
arranging the steel material and the aluminum material so that the tip of the shaft of the rivet of the steel material faces the aluminum material,
The rivet and the aluminum material are sandwiched between a pair of electrodes, and resistance spot welding is performed while applying pressure between the electrodes to join the aluminum material and the steel material.
Method for joining dissimilar materials.
(3) A dissimilar material joined body in which a steel material and an aluminum material overlapped with each other are joined by an aluminum rivet having a shaft portion and a head,
An annular collar having a higher melting point than aluminum is arranged between the steel material and the rivet,
A nugget formed by melting and solidifying the rivet and the aluminum material is formed on the inner diameter side of the collar.
Joined body of different materials.

According to the present invention, when resistance spot welding is performed using aluminum rivets to join dissimilar materials, it is possible to suppress the outflow of molten aluminum near the welding part and achieve good joining.

FIG. 1 shows a rivet with a collar attached, in which (A) is a perspective view of the rivet as seen from the head side, and (B) is a perspective view of the rivet as seen from the shaft side. FIG. 2 is an axial cross-sectional view of the rivet and collar shown in FIG. FIG. 3 is an exploded perspective view of the rivet and collar. FIG. 4 is a step-by-step process diagram (A) to (C) showing the process of driving a rivet into a steel material. FIG. 5 is a process explanatory diagram showing how a steel material with a collar and a rivet driven therein is stacked on an aluminum material. FIG. 6 is a process explanatory diagram showing resistance spot welding of a steel material and an aluminum material using rivets. FIG. 7 is an explanatory diagram showing steps (A) to (C) of the process from applying pressure between the electrodes to applying electricity. FIG. 8 is a process explanatory diagram showing another procedure for fixing a rivet to a steel material. FIG. 9 is a process explanatory diagram showing another procedure for fixing a rivet to a steel material. FIG. 10 is a cross-sectional photograph of the joint.

Embodiments of the present invention will be described in detail below with reference to the drawings.
In the dissimilar metal joining method of the present invention, when aluminum rivets are used to resistance spot weld steel and aluminum materials, the rivet shaft is covered with an annular collar to prevent molten aluminum from flying out. ing.

<Rivet composition>
FIG. 1 shows a rivet with a collar attached, in which (A) is a perspective view of the rivet as seen from the head side, and (B) is a perspective view of the rivet as seen from the shaft side. FIG. 2 is an axial cross-sectional view of the rivet and collar shown in FIG. FIG. 3 is an exploded perspective view of the rivet and collar.

The rivet 11 has a head 13 and a shaft portion 15, as shown in FIGS. 1 and 2. The head 13 has a disk shape with a larger diameter than the shaft 15, and the shaft 15 has a substantially cylindrical shape and projects from the head 13 along the central axis L of the rivet 11. The shaft end surface 15a has a conical protrusion 17 serving as a projection, but is not limited to a projection, and may be a curved surface protruding with a predetermined radius of curvature, or may be a flat surface. The rivet 11 is made of aluminum, and as shown in FIG. 3, a collar 21 is attached to the shaft portion 15 to cover the outer periphery of the shaft portion.

The collar 21 includes a cylindrical portion 23 and an annular flange portion 25 extending radially outward from one axial end of the cylindrical portion 23 . The inner peripheral surface 23a of the cylindrical portion 23 has a circular cross section orthogonal to the central axis L, and covers the shaft outer peripheral surface 15b of the rivet 11. The rivet-side annular surface 25a and the insertion-side annular surface 25b of the flange portion 25, which face each other, are both formed as flat surfaces parallel to each other. The material of the collar 21 only needs to have a higher melting point than aluminum, which is the material of the rivet 11, and steel can be used.

This collar 21 is attached to the rivet 11 by inserting the shaft portion 15 of the rivet 11 into the inner periphery of the cylindrical portion 23. It is preferable that the shaft outer circumferential surface 15b of the rivet 11 and the inner circumferential surface 23a of the collar 21 are in close contact with each other without any gap. By fitting the shaft outer circumferential surface 15b and the inner circumferential surface 23a to each other, it is possible to prevent the collar 21 from falling off and improve handling performance. Further, the end surface 23c on the opposite flange side of the cylindrical portion 23 of the collar 21 is formed to be equal to or lower than the outer peripheral edge 15c of the shaft end surface 15a in the axial direction of the shaft portion 15 of the rivet 11. be done. In other words, it is preferable that the collar 21 is attached to the rivet 11 without the cylindrical portion 23 protruding from the outer circumferential edge 15c of the shaft end surface 15a of the shaft portion 15. Moreover, it is preferable that the flange portion 25 be in close contact with the back surface 13a of the head of the rivet 11.

<Materials of steel and aluminum>
Examples of the steel used here include high-tensile steel, galvanized steel, and stainless steel. This steel material can be a plate material, a shaped material, a cast material, a press-formed product of a plate material, a hot stamped product, or the like.
Examples of the aluminum material include aluminum and aluminum alloys (JIS standard 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, or 7000 series). From the viewpoint of weldability, aluminum alloys of 5000 series, 6000 series, and 7000 series are particularly preferred. This aluminum material is not limited to a plate material, and may be an extruded member (a pipe material, a hollow, solid, or irregular cross-sectional shape material), or a forged material (a plate material, a ribbed material). Further, the surface of the aluminum material 37 may be subjected to various surface treatments such as blasting, etching, and brush polishing as a preliminary treatment. In that case, organic matter on the surface of the aluminum material is removed, improving bonding quality.

<Steps for joining different materials>
Next, a procedure for joining aluminum and steel to dissimilar materials using the rivet 11 described above will be described.

(Drive-in process)
FIG. 4 is a step-by-step explanatory diagram showing the process of driving the rivet 11 into the steel material 33 in steps (A) to (C).
As shown in FIG. 4A, a plate-shaped steel material 33 is placed on a die 31 having a cylindrical upper part, and a rivet 11 with a collar 21 attached thereto is placed above the die 31. Then, the head 13 of the rivet 11 is pushed down with the punch 35.

As shown in FIG. 4B, when the punch 35 descends, the shaft portion 15 of the rivet 11 and the collar 21 are driven into the steel material 33. Then, the steel material 33 is punched out between the die 31 and the cylindrical portion 23 of the collar 21 and the shaft portion 15, and this punched portion (blank) 33A falls inside the die 31.

In this way, as shown in FIG. 4C, the rivet 11 with the collar 21 inserted therein is fitted into the steel material 33. At this time, the shaft portion 15 of the rivet 11 is caulked and fixed to the steel material 33, and the flange portion 25 of the collar 21 is sandwiched between the head back surface 13a of the rivet 11 and the steel material 33, and the head back surface 13a and the rivet The side annular surface 25a is in close contact with the side annular surface 25a.

In other words, the outer circumferential surface 15b of the shaft portion of the rivet 11 and the inner circumferential surface 23a of the collar 21 are in close contact with each other without any gaps, and the outer circumferential surface 23b of the collar 21 and the inner circumferential surface of the through hole 34 formed in the steel material 33 are in close contact with each other without any gaps. It is closely attached. Further, the shaft portion 15 of the rivet 11 that has passed through the steel material 33 has its shaft portion tip end surface 15a exposed on the lower surface of the steel material 33.

The driving of the rivet 11 equipped with such a collar 21 may be performed simultaneously with the press forming process (trimming process) of the steel material 33, for example. That is, when press forming the steel material 33, a punch is installed in the press die, or the press die itself is used instead of the punch, and the rivet 11 is punched out at the same time as the press die is lowered. Thereby, the rivet 11 is caulked and fixed to the steel material 33. In this state, when the steel material 33 is transported to the resistance spot welding line, the rivet 11 is caulked and fixed to the steel material 33, so the rivet 11 does not fall during the transportation process, and the workability of the joint can be improved. .

(Resistance spot welding process)
FIG. 5 is a process explanatory diagram showing how a steel material 33 with a collar 21 and a rivet 11 driven therein is stacked on an aluminum material 37.
In performing resistance spot welding, the steel material 33 to which the rivet 11 is attached is placed so as to overlap the aluminum material 37 to be joined, with the tip of the shaft portion 15 of the rivet 11 facing the aluminum material 37.

FIG. 6 is a process explanatory diagram showing how the steel material 33 and the aluminum material 37 are resistance spot welded using the rivet 11.
A set of plate materials made by overlapping a steel material 33 with a rivet 11 attached thereto and an aluminum material 37 is sandwiched between a pair of electrodes 43 and 45 at the position of the rivet 11. Then, while applying pressure between the electrodes 43 and 45 using a pressurizing device (not shown), current is applied between the electrodes (current I) using a power source device (not shown). Then, a nugget is formed between the shaft end surface 15a of the rivet 11 and the aluminum material 37.

Here, the process up to the formation of the nugget 47 by applying current between the electrodes will be described in detail.
FIG. 7 is an explanatory diagram showing steps (A) to (C) of the process from applying pressure between the electrodes to applying electricity.

As shown in FIG. 7A, the tip end surface 15a of the shaft portion of the rivet 11 is pressed against the aluminum material 37 by sandwiching the electrodes 43 and 45. As shown in FIG. Then, by applying electricity between the electrodes 43 and 45, the tip end surface 15a of the shaft portion and the aluminum material 37, which are in close contact with each other near the central axis L, are heated by the electricity and melted, and a nugget 47 is formed.

As shown in FIG. 7B, the nugget 47 formed by energization grows from the central axis L as a starting point, and the molten aluminum reaches the inner circumferential surface 23a of the collar 21. At this time, the end surface 23c of the cylindrical portion 23 of the collar 21 on the side opposite to the flange is strongly pressed against the aluminum material 37 due to the pressure applied from the electrodes 43 and 45, and is brought into close contact with the aluminum material 37. In other words, the collar 21 functions as an annular corona bond, and the molten aluminum is prevented from spilling out.

Then, as shown in FIG. 7C, the nugget 47 that has reached the collar 21 continues to grow, but the radially outward growth of the nugget 47 is dammed by the cylindrical portion 23 of the collar 21. Furthermore, since the flange portion 25 of the collar 21 is in close contact with the head back surface 13a of the rivet 11, the molten aluminum of the nugget 47 is prevented from scattering radially outward from between the head back surface 13a and the steel material 33. Ru.

As described above, when the rivet 11 with the collar 21 attached to the shaft portion 15 is resistance spot welded to the aluminum material 37 with the steel material 33 in between, the molten aluminum between the rivet 11 and the aluminum material 37 spreads more than the aluminum. It is blocked by a collar 21 made of a material with a high melting point. Thereby, it is possible to suppress molten aluminum from flowing out from the joint between the rivet 11 and the aluminum material 37, and it is possible to join the steel material 33 and the aluminum material 37 well and with high strength. In addition, since the rivet 11 can be placed in an appropriate posture without tilting with respect to the steel material 33, in other words, the shaft portion 15 of the rivet 11 can be regulated in the normal direction of the plate surface of the steel material 33, so that the rivet 11 and the aluminum Resistance spot welding with the material 37 can be performed evenly and with high precision.

Further, since the collar 21 has the flange portion 25 that is in close contact with the back surface 13a of the head of the rivet 11, it is possible to reliably prevent molten aluminum from flowing out from between the head 13 of the rivet 11 and the steel material 33. In particular, if the collar 21 is made of steel, it has a higher melting point than aluminum, so it is less susceptible to the effects of molten aluminum, and its load-bearing properties are improved, making it possible to form a strong corona bond, making it possible to securely hold molten aluminum. can be dammed up. In addition, since the collar 21 is in close contact with the rivet 11 and the steel material 33 without any gaps, it can contribute to improving the joint strength of the dissimilar material joined body.

<Other examples of rivet fixing procedures>
In the above example, the rivet 11 with the collar 21 attached is driven into the steel material 33 to caulk and fix the rivet 11 to the steel material 33, but the procedure for fixing the rivet 11 to the steel material 33 is not limited to this.

FIG. 8 is a process explanatory diagram showing another procedure for fixing the rivet 11 to the steel material 33.
As shown in FIG. 8, a through hole 34 serving as a pilot hole is provided in a portion of the steel material 33 where the rivet 11 is to be provided. Further, a collar 21 is attached to the rivet 11. In this state, the shaft portion 15 of the rivet 11 with the collar 21 attached thereto is pushed into the through hole 4 using a press or the like, and the rivet 11 is caulked and fixed to the steel material 33.

In this case, since the rivet 11 and the collar 21 can be handled as one unit, the handling properties of the rivet 11 and the collar 21 are improved, and the workability of resistance spot welding can be improved.

FIG. 9 is a process explanatory diagram showing another procedure for fixing the rivet 11 to the steel material 33.
As shown in FIG. 9, a through hole 34 serving as a pilot hole is provided in the portion of the steel material 33 where the rivet 11 is to be provided, and the cylindrical portion 23 of the collar 21 is fitted or bonded into the through hole 34 to attach the collar 21 to the steel material 33. Attach it. Then, the shaft portion 15 of the rivet 11 is inserted into the cylindrical portion 23 of the collar 21 using a press or the like, and the shaft portion 15 of the rivet 11 is passed through the through hole 34 of the steel material 33 to which the collar 21 is attached. Thereby, the rivet 11 is caulked and fixed to the steel material 33.

In this case, since the rivet 11 is attached to the steel material 33 by itself, the same rivet supply mechanism as in the case where the normal collar 21 is not used can be used.

In addition, in these other fixing procedures, caulking the rivet 11 to the steel material 33 by pressing may be performed during the press forming process of the vehicle body, for example, when the steel material 33 is an automobile body structural material. . Moreover, separately from such a press forming process, it may be performed in a process before or after the press forming process, for example, in a manufacturing process of the steel material 33.

A steel material with a rivet attached thereto and an aluminum material were overlapped via a collar, and the rivet and aluminum material were resistance spot welded, and the cross section of the joint was observed and evaluated.
The steel materials, aluminum materials, rivets, collars, and welding conditions are as follows.

(material)
Steel material: Galvanized steel plate thickness 1.2mm
Aluminum material: 6000 series aluminum alloy plate, thickness 0.8mm
Rivet: Made of aluminum, head diameter 12mm, shaft diameter 8mm
Color: Made of steel, cylindrical part inner diameter 8mm, flange part outer diameter 12mm, thickness 0.5mm

(Welding conditions)
Welding current: 28-34kA
Energization time: 4cycles
Pressure force: 6.0kN

(Evaluation results)
FIG. 10 is a cross-sectional photograph of the joint.
The nugget 47 generated at the joint was formed over a wide area and reached the collar 21, but did not reach the outside of the joint. That is, the molten aluminum produced by resistance spot welding was dammed up by the cylindrical part 23 of the collar 21 interposed between the shaft part 15 of the rivet 11 and the through hole 34 of the steel material 33. Furthermore, since the flange portion 25 of the collar 21 is in close contact with the head back surface 13a of the head 13 of the rivet 11, the molten aluminum of the nugget 47 is absorbed from between the head back surface 13a of the rivet 11 and the steel material 33. Outflow was also suppressed.

As described above, the present invention is not limited to the embodiments described above, and those skilled in the art can combine the configurations of the embodiments with each other, modify and apply them based on the description of the specification and well-known techniques. It is also contemplated by the present invention to do so, and is within the scope for which protection is sought.

As mentioned above, the following matters are disclosed in this specification.
(1) Attaching an annular collar having a higher melting point than aluminum to the shaft of an aluminum rivet having a head and a shaft,
Driving the shaft portion of the rivet to which the collar is attached into a steel material to penetrate it;
arranging the steel material and the aluminum material so that the tip of the shaft of the rivet of the steel material faces the aluminum material,
The rivet and the aluminum material are sandwiched between a pair of electrodes, and resistance spot welding is performed while applying pressure between the electrodes to join the aluminum material and the steel material.
Method for joining dissimilar materials.
According to this dissimilar metal joining method, by resistance spot welding the rivet and the aluminum material, the spread of the molten rivet and the molten aluminum of the aluminum material is dammed by a collar made of a material with a higher melting point than aluminum. . This makes it possible to prevent molten aluminum from flowing out from the joint. Therefore, the rivet can be satisfactorily resistance spot welded to the aluminum material to join the steel material and the aluminum material with good quality and high strength. Furthermore, since the collar allows the rivet to be placed in an appropriate posture without tilting relative to the steel material, resistance spot welding between the rivet and the aluminum material can be performed with high precision by eliminating nugget bias.

(2) Attach the shaft portion of an aluminum rivet having a head and a shaft portion to the through hole of the steel material provided with the through hole through an annular collar having a higher melting point than aluminum;
arranging the steel material and the aluminum material so that the tip of the shaft of the rivet of the steel material faces the aluminum material,
The rivet and the aluminum material are sandwiched between a pair of electrodes, and resistance spot welding is performed while applying pressure between the electrodes to join the aluminum material and the steel material.
Method for joining dissimilar materials.
According to this dissimilar metal joining method, by resistance spot welding the rivet and the aluminum material, the spread of the molten rivet and the molten aluminum of the aluminum material is dammed by a collar made of a material with a higher melting point than aluminum. . This makes it possible to prevent molten aluminum from flowing out from the joint. Therefore, the rivet can be satisfactorily resistance spot welded to the aluminum material to join the steel material and the aluminum material with good quality and high strength. In addition, the process of inserting the rivet into the pilot hole of the steel material can be performed at any time during the press forming process of the steel material, or separately from the press forming process, or before or after the press forming process, improving the degree of freedom in the process. .

(3) The method for joining dissimilar materials according to (2), wherein the shaft portion of the rivet with the collar attached thereto is fitted into the through hole of the steel material to attach the rivet to the steel material.
According to this dissimilar material joining method, a rivet equipped with a collar can be easily attached to a steel material, and workability can be improved.

(4) Fitting the collar into the through hole of the steel material, passing the shaft through the inner peripheral surface of the collar fitted into the through hole, and attaching the rivet to the steel material; (2) The method for joining dissimilar materials described in .
According to this dissimilar material joining method, by fitting the collar into the pilot hole of the steel material, handling of the rivet becomes easier and workability can be improved.

(5) The collar is integrally formed with a cylindrical portion disposed between the shaft portion of the rivet and the steel material, and a flange portion disposed between the head of the rivet and the steel material. The method for joining dissimilar materials according to any one of (1) to (4).
According to this dissimilar metal joining method, the molten aluminum can be effectively dammed up by the cylindrical part of the collar, and the flange part integrated with the cylindrical part allows the molten aluminum to flow from between the rivet head and the steel material. It is possible to suppress aluminum from flowing out.

(6) The method for joining dissimilar materials according to any one of (1) to (5), wherein the collar is made of steel.
This method of joining dissimilar materials has a higher melting point than aluminum, so it is less susceptible to the effects of molten aluminum, and it also has improved load-bearing properties, making it possible to form a strong corona bond and more reliably damming up molten aluminum. be able to.

(7) A dissimilar material joined body in which a steel material and an aluminum material stacked on top of each other are joined by an aluminum rivet having a shaft portion and a head,
An annular collar having a higher melting point than aluminum is arranged between the steel material and the rivet,
A nugget formed by melting and solidifying the rivet and the aluminum material is formed on the inner diameter side of the collar.
Joined body of different materials.
According to this dissimilar material joined body, the spread of the molten aluminum of the molten rivet and aluminum material is dammed by the collar, and a structure can be achieved in which the outflow (dust) of the molten aluminum from the joint portion to the outside is suppressed. Therefore, the steel material and the aluminum material can be joined with high strength.

(8) The collar is integrally formed with a cylindrical portion disposed between the shaft portion of the rivet and the steel material, and a flange portion disposed between the head of the rivet and the steel material. The dissimilar material joined body according to (7).
According to this dissimilar material joined body, since the space between the rivet and the steel material is covered with the collar without any gap, the adhesion is improved and the joining between the rivet and the steel material is improved.

(9) The dissimilar material joined body according to (7) or (8), wherein the collar is made of steel.
According to this joined body of dissimilar materials, the steel collar improves the load resistance and further improves the joint strength.

11 Rivet 13 Head 15 Shaft 21 Collar 23 Cylindrical part 25 Flange 33 Steel material 34 Through hole 37 Aluminum material 43, 45 Electrode

Claims (9)

Attaching an annular collar having a higher melting point than aluminum to the shaft of an aluminum rivet having a head and a shaft,
Driving the shaft portion of the rivet to which the collar is attached into a steel material to penetrate it;
arranging the steel material and the aluminum material so that the tip of the shaft of the rivet of the steel material faces the aluminum material,
The rivet and the aluminum material are sandwiched between a pair of electrodes, and resistance spot welding is performed while applying pressure between the electrodes to join the aluminum material and the steel material.
Method for joining dissimilar materials. The shaft portion of an aluminum rivet having a head and a shaft portion is attached to the through hole of the steel material provided with the through hole through an annular collar having a higher melting point than aluminum,
arranging the steel material and the aluminum material so that the tip of the shaft of the rivet of the steel material faces the aluminum material,
The rivet and the aluminum material are sandwiched between a pair of electrodes, and resistance spot welding is performed while applying pressure between the electrodes to join the aluminum material and the steel material.
Method for joining dissimilar materials. The method for joining dissimilar materials according to claim 2, wherein the rivet is attached to the steel material by fitting the shaft portion of the rivet fitted with the collar into the through hole of the steel material. 3. The rivet is attached to the steel material by fitting the collar into the through hole of the steel material, and passing the shaft through the inner peripheral surface of the collar fitted into the through hole. Method for joining dissimilar materials. The collar is integrally formed with a cylindrical part disposed between the shaft part of the rivet and the steel material, and a flange part disposed between the head of the rivet and the steel material. The method for joining dissimilar materials according to any one of claims 1 to 4. The method for joining dissimilar materials according to any one of claims 1 to 5, wherein the collar is made of steel. A dissimilar material joined body in which a steel material and an aluminum material stacked on top of each other are joined by an aluminum rivet having a shaft portion and a head,
An annular collar having a higher melting point than aluminum is arranged between the steel material and the rivet,
A nugget formed by melting and solidifying the rivet and the aluminum material is formed on the inner diameter side of the collar.
Joined body of different materials. The collar is integrally formed with a cylindrical part disposed between the shaft part of the rivet and the steel material, and a flange part disposed between the head of the rivet and the steel material. , The dissimilar material joined body according to claim 7. The dissimilar material joined body according to claim 7 or 8, wherein the collar is made of steel.

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