JP2018051606A - Friction stirring joining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a large swollen part of a joint part having a rivet shape, and form a large swollen part even when a member to be joined has a prepared hole with a large diameter, in friction stirring joining.CONSTITUTION: In a friction stirring joining method using a friction stirring tool having a projection part on the tip flat surface part of a cylindrical columnar shape, there are carried out the following steps of: (a) bringing a plate-like joining material into contact with the upper surface of a plate-like member to be joined having a prepared hole bored, and bringing a molding die into contact with the lower surface thereof; and (b) while rotating the friction stirring tool, lowering it, moving it in a prescribed horizontal direction, and pressing it into the joining material to perform friction stirring. Thereby, the joining material caused to flow is deformed and filled into the cavity part of the molding die to form a joint part having a rivet shape, thereby mechanically joining the joining material to the plate-like member to be joined.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a friction stir welding method.

Conventionally, by rotating the tip contact surface in the direction perpendicular to the axis of the rotary tool that rotates about the axis, contact the bonding material, generate frictional heat, and stir in the heated state, in a non-molten state. There is known a friction stir welding method in which plastic flow is generated and mechanically joined to a material to be joined (for example, Patent Document 1).
According to this friction stir welding method, for example, as described in Patent Document 1, the uneven portion formed on the surface portion of the material to be joined is used as a molding die, and the joining material plastically flowed into the uneven portion is allowed to flow to join. It is supposed to be possible.

  In recent years, a rivet-shaped joint is obtained by flowing a joint material plastically flowed by friction stir into a prepared hole that has been previously opened in the material to be joined, and bulging it up to a mold recess on the back of the prepared hole. Has also been proposed (Non-Patent Documents 1 and 2).

  By the friction stir welding method as described above, unlike conventional metallurgical joining methods, mechanical joining is possible, so that various materials to be joined such as steel, glass, CFRP, etc. can be selected. Thus, characteristics such as no problem of weight increase compared to the conventional method using fasteners such as rivets are realized.

Japanese Patent No. 4646421

Journal of Manufacturing Process 15 (2003) 616-624 Journal of Manufacturing Science and Engineering OCTOBER 2015, Vol.137 051018-1−051018-9

  However, although improvements and devices have been attempted in recent years, even when a soft material such as aluminum is used as the bonding material, the plastic flow is increased to increase the rivet-like shape as in Non-Patent Documents 1 and 2. It is not always easy to form a large head and make the joining more reliable. Even if the rotational speed of the rotary tool is increased and the pressing force on the bonding material is increased, it is not easy to form a large bulge.

  Moreover, it is not easy to reliably form the rivet-like bulge portion as required as the diameter of the prepared hole of the material to be joined becomes larger.

  For this reason, in the conventional friction stir welding method, it has been difficult to simply realize fastener (rivet) -less joining that can maintain the actually required strength.

  Further, in the conventional method, there is a difficulty in preventing deformation of the material to be joined even when a mold is used.

  Therefore, the present invention is based on the progress of the friction stir welding method by improvement and contrivance so far, and solves the problems with the conventional method, forming a large rivet-shaped bulge, and reducing the diameter of the pilot hole. It is an object of the present invention to provide a new friction stir welding method that makes it easy to reliably form a large bulge of a bonding material even in a large case, and can also effectively suppress deformation of the material to be bonded. .

The friction stir welding method of the present invention is a friction stir welding method using a friction stir tool having a protrusion on a cylindrical tip flat portion in order to solve the above-described problem, and includes the following steps:
(A) A plate-shaped joining material is brought into contact with the upper surface of a plate-shaped material to be joined with a pilot hole, and a molding die is brought into contact with the lower surface;
(B) Rotating the friction stir tool with respect to the joining material, lowering it, sending it in a predetermined horizontal direction, press-fitting and friction stirring, thereby flowing the joined material into the mold The cavity portion is deformed and filled to form a rivet-like joint portion, and the joining material is mechanically joined to the plate-like joined material.

  Further, in the above-described invention method, a plurality of joint portions are formed while being fed in a predetermined horizontal direction, or the molding die has a spacer and a contact plate, and the spacer can be divided so that the cavity portion is formed. It is also preferable that the friction stir tool is shifted to the forward rotation side and sent in a predetermined horizontal direction.

  According to the present invention, in the friction stir welding method, the rivet-shaped bulge portion is formed to be large, and it is ensured that a large bulge portion is formed even in the case of a material to be joined having a large diameter of the pilot hole, and Can be easy.

  Moreover, according to this invention, the technical means which suppresses a deformation | transformation of a to-be-joined material effectively is provided.

It is the general | schematic front sectional drawing (a) and side sectional drawing (b) which illustrated embodiment. It is the general | schematic side sectional view illustrated about the other form of the joint part bulging part. It is the general | schematic side sectional view illustrated about the form different from FIG. It is the schematic which illustrated the friction stirring tool. It is the top view which illustrated setting of the amount of offset about feed of a tool. It is the general | schematic side sectional view which illustrated embodiment of the metal mold | die which consists of a split type | mold spacer and a backing plate. It is an experiment photography figure illustrated about the case where a tool is sent in the horizontal direction (A) and the case where it does not send (B) about formation of a bulging part.

  1A and 1B are schematic views illustrating an embodiment of the present invention. 1A shows a front sectional view, and FIG. 1B shows a side sectional view.

In the method of the present invention, for example, the friction stir welding method is performed using the friction stir tool 1 having the projection 1c on the tip flat portion 1b of the cylindrical shape 1. In this method, the following steps:
(A) The plate-shaped bonding material 3 is brought into contact with the upper surface of the plate-shaped material 2 having the pilot hole 2a and the molding die 4 is brought into contact with the lower surface,
(B) While rotating the friction stir tool 1 with respect to the joining material 3 (direction α) and feeding it in a predetermined horizontal direction (direction β), press-fitting and friction stir.
As a result, the fluidized bonding material 3 is deformed and filled in the cavity portion 4a of the molding die 4 to form a bulge of the rivet-shaped joint portion 5, and the bonding material is applied to the plate-shaped workpiece. Join mechanically.

  The material 2 to be joined here may be various materials, for example, a hard steel plate, glass, CFRP, or the like. The prepared hole 2a in the material to be joined 2 can be opened by various means, for example, by a press shearing process using a drill or a holed packing plate. The thickness of the material to be joined 2 and the diameter of the pilot hole 2a can also be determined as appropriate. The inclination of the wall surface of the prepared hole due to sag when press shearing may be used as a rivet-like joint.

  The bonding material 3 may be a relatively soft material such as aluminum, and the thickness thereof may be appropriate.

The area of the tip flat portion 1b of the rotating friction stir tool 1, the volume of the protrusion 1c, the rotational speed, the lowering (direction α), the horizontal direction (direction β), the pressing force and the press-fitting amount during press-fitting, Regarding the feed force and feed speed in the horizontal direction: 1) Type and thickness of joining material 3 2) Diameter and thickness of pilot hole 2a of material 2 to be joined 3) Shaft length of rivet joint 5 and bulging head Size 4) Softening temperature of the joining material 5) It can be determined in consideration of the generation status of the flash generated at the contact portion between the outer edge of the friction stir tool 1 and the joining material. The volume of the joining material displaced by the press-fitting and movement of the friction stir tool 1 is determined by the outer diameter of the tip flat portion 1b of the friction stir tool 1, the volume of the protrusion 1c, and the amount of press-fitting. The volume of the rivet-like joint portion is determined by subtracting the volume of the joining material to be worn and the volume necessary for backfilling the movement trace of the protrusion 1c of the friction stirring tool when the friction stirring tool moves. Regardless of whether or not the friction stir tool 1 is moved, increasing the diameter of the protrusion 1c is effective in increasing the volume of the rivet-shaped joint in terms of increasing the volume of the joining material that can be pushed, On the other hand, if the area of the tip flat portion 1b is reduced thereby, the amount of heat input due to frictional heat per unit time is reduced, and the effect of softening the material by friction stirring is remarkably reduced, which is caused in the joining material by thermal stress. Since the compression molding force is reduced, the reverse effect is obtained. Therefore, it adjusts so that it may not become excessive, or the outer diameter of the front end plane part 1b may be enlarged simultaneously.

  At the same time, the outer diameter of the tip flat portion 1b, the rotational speed, the lowering (direction α), while feeding in the horizontal direction (direction β), the pressing force and the amount of press-fitting and the feeding speed in the horizontal direction are The compression molding force generated in the joining material by the rotation, press-fitting and movement of the stirring tool 1 acts on the joining material by the prepared hole 2a of the material to be joined 2 and the wall surface of the cavity portion 4a of the molding die 4. Considering that the frictional force resists and the bonding material is deformed as a result of the subtraction and fills the cavity 4a, the compression molding force sufficient for filling and the softening temperature of the bonding material are determined. The frictional force acting on the bonding material by the prepared hole 2a wall surface of the material to be bonded 2 increases as the hole diameter decreases. On the other hand, if the compression molding force and the softening temperature of the joining material are excessive, a flash develops at the outer edge of the tip flat surface portion 1b of the friction stir tool 1 and the contact portion of the joining material, so that adjustment is made so as not to be excessive. By increasing the area of the tip flat portion 1b of the friction stir tool 1, the amount of heat input by frictional heat per unit time is increased, the material is softened more, and the compression molding force generated in the joining material by thermal stress is increased. If the feed rate of the friction stir tool 1 is slowed, the heat input time can be increased to increase the total heat input and to make the material softer. By increasing the pressing force and the horizontal feed force when the friction stir tool 1 is press-fitted, it is possible to adjust so as to increase the compression molding force generated in the joining material.

  In the above method, the prepared hole 2a of the material to be bonded 2 has a circular cross section as well as the shape of the cavity portion 4a of the mold 4 and a polygonal cross section, for example, a side cross sectional view of FIG. It is good also as the slit shape 21a so that the rib-shaped coupling part 51 may be formed.

  In order to further increase the bonding strength, various embodiments such as forming the joint portion 52 as the pilot hole 22a having an inclined surface as illustrated in FIG. 3 are considered.

In any embodiment, in the friction stir welding method of the present invention,
<A> As shown in FIG. 1 and FIG. 4 as the friction stir tool 1, the tip flat portion 1 b of the columnar shape 1 a has a protrusion 1 c. <B> The friction stir tool 1 is rotated and joined. It is characterized by being sent in the horizontal direction β while being press-fitted into the material 3, and is essential.

  By the above features <A> and <B>, it is possible to make the flow of the material to be joined 3 by friction stirring efficient and generate a larger flow amount. As a result, the bulging portions of the rivet-shaped joint portions 5, 51, 52 are formed to be large, and it is possible to reliably and easily form a large bulge even if the prepared material has a large diameter or opening. can do.

  In the friction stir tool 1 of the feature <A>, the shape of the protrusion 1c may be a disk shape, a columnar shape, a conical shape, or the like. Further, the tip flat surface portion 1b provided with the protrusion 1c may be provided with the inclination angle θ as a whole or partially within about 5 °, for example, as necessary.

  This inclination angle θ facilitates the downward movement of the material in the joining material (direction toward the cavity 4a of the molding die 4) and the horizontal feeding of the friction stir tool 1 when the feature <B> is performed. Also.

  With respect to the magnitude of the inclination angle θ, the feed force in the horizontal direction of the friction stir tool 1, the filling of the material to be joined to the cavity 4 a of the molding die 4, the occurrence of flash, the movement trace of the friction stir tool 1 (tool It is preferable to determine the aesthetic appearance of the mark.

  The friction stir tool 1 is preferably considered to be formed of a heat-resistant alloy that is hard and has high heat resistance. In addition to heat resistance, the molding die 4 is preferably considered to be formed of stainless steel gold or the like having a low thermal conductivity in order to keep the material to be joined warm.

  In order to more smoothly advance the feature <B> in the horizontal direction (β) and more effectively form the joint portion at a predetermined position, as illustrated in FIG. It is also effective to set the offset amount by shifting the friction stir tool 1 toward the rotational advance side with respect to the position direction and to send it in the horizontal direction. Of the volume of the joining material that is pushed away by the press-fitting and movement of the friction stir tool 1, the joining material volume on the rotation advance side of the friction stir tool 1 is the volume of the joining material that wears due to the volume of the rivet joint and the occurrence of flash. Although the volume is converted only to the volume, the joining material volume on the rotation and retreat side is also converted to backfill of the movement trace of the protrusion 1c of the friction stir tool. Therefore, by moving the friction stir tool 1 to the rotational advance side within a range in which the position direction of the predetermined pilot hole 2a is within the projected area of the front end flat portion 1b, the movement trace of the friction stir tool from the volume of the rivet joint portion. The backfilling of the material makes it difficult to deprive the volume of the bonding material.

  The setting of the offset amount is particularly preferably considered when forming joint portions in the plurality of pilot holes 2a as illustrated in FIG. The magnitude of such an offset amount can be determined in consideration of the diameter of the tip flat portion 1b of the friction stir tool 1 and the diameter and volume of the protrusion 1c.

  FIG. 6 is a side sectional view illustrating another embodiment of the present invention. In this embodiment, the molding die 4 is constituted by a spacer 4A and a backing plate 4B, the spacer 4A is separable, and the cavity portion 4a is variable within a predetermined range.

  With such a configuration, it is possible to effectively suppress unnecessary deformation of the material to be joined 2 in the implementation of the method of the present invention. The prepared hole 2a of the workpiece 2 is supported.

  The spacer 4A may be two pieces as a split type, or three or more pieces. Further, the cavity 4a may have a cross-sectional shape other than a circle as long as it can support the pilot hole 2a.

  FIG. 7 shows the feature <A> <B>, the diameter of the columnar shape 1a of the tool 1 of FIG. 4 is 15 mm, the diameter of the disk-shaped protrusion 1c is 5 mm, the height is 2.5 mm, and the inclination angle θ is as follows. Compared with the case where the tool 1 is fed in the horizontal direction at 50 mm / min in joining a 3 mm thick aluminum plate and a 0.8 mm thick CFRP plate using a 5 ° one (Fig. 7 (a)) Therefore, the case where the tool is only press-fitted into the center of the pilot hole without sending it (FIG. 7B) shows the degree of bulging of aluminum according to the diameter of the pilot hole. The rotational speed of the tool 1 is 1240 rpm, and the press-fitting depth is 27. mm.

  When the tool 1 is fed in the horizontal direction as shown in FIG. 7A, the amount of bulging that forms the joint portion is large even when the pilot hole diameter is large, whereas FIG. It can be seen that the amount of bulging is small when () is not sent. It can be seen that the method of the present invention for feeding the tool 1 is effective when the pilot hole diameter is large.

  In fact, when the tool is fed in the horizontal direction by combining with the mold cavity, the bulge head is firmly and securely formed even if the pilot hole diameter is large, and the rivet-like joint is securely Confirmed to be composed. On the other hand, when it was not sent, it was confirmed that the joint portion was poorly formed and was not at a practical level.

DESCRIPTION OF SYMBOLS 1 Friction stirring tool 2 Joined material 2a Pilot hole 3 Joining material 4 Mold 4a Cavity part 5 Joint part

Claims (4)

A friction stir welding method using a friction stir tool having a protrusion on a cylindrical tip flat portion, the following steps:
(A) A plate-shaped joining material is brought into contact with the upper surface of a plate-shaped material to be joined with a pilot hole, and a molding die is brought into contact with the lower surface;
(B) While rotating the friction stir tool with respect to the joining material, it is lowered, and while being fed in a predetermined horizontal direction, press-fit and friction stir,
By deforming and filling the fluidized bonding material into the cavity of the molding die to form a rivet-shaped joint, and mechanically bonding the bonding material to the plate-shaped workpiece Friction stir welding method characterized.   The friction stir welding method according to claim 1, wherein a plurality of joint portions are formed while being fed in a predetermined horizontal direction.   3. The friction stir welding method according to claim 1, wherein the molding die has a spacer and a backing plate, and the spacer is separable to form a cavity portion.   The friction stir welding method according to any one of claims 1 to 3, wherein the friction stir tool is shifted to the forward rotation side and sent in a predetermined horizontal direction.