JPWO2014132335A1 - Friction stir welding apparatus and joining method - Google Patents

Abstract

In friction stir welding, a friction stir welding apparatus is provided that can increase the effect of reducing tensile residual stress due to rapid cooling immediately after joining by increasing the amount of heat input to the welded portion. The cooling device (3) is provided on the opposite side to the traveling direction of the rotor (1), and the surface (5) to be joined immediately after the rotor (1) passes by the coolant (4) is cooled. is doing. Furthermore, a donut-shaped heat input means (6) is provided outside the rotor (1). The heat input means (6) is in contact with the surface of the bonded portion (5) at the processed surface (6a) for machining the bonded portion, and is pressed by the reaction force of the pressing mechanism (6b). The pressing mechanism (6b) is fixed by a pressing plate (6c). Furthermore, since the heat input means (6) is fixed to the rotor (1) by the holder (6d), it rotates with the rotation of the rotor (1).

Description

  The present invention relates to a friction stir welding apparatus and a joining method using the same.

  Friction Stir Welding (FSW) is a joining method that joins members by agitating the periphery of the welded part by plastic flow by pressing the cylindrical tool against the welded part with a strong force while rotating it. It is. FSW is a joining method characterized by low heat input and low thermal deformation compared to other welding methods because it does not melt the members to be joined. Conventionally, FSW has been used for joining thin plate members with a soft material such as aluminum, such as a railway vehicle structure.

  In recent years, with the development of tool materials, it has become possible to join steel materials and thick plate members using FSW. Therefore, in the future, FSW is expected to be widely applied to the joining of materials used in corrosive environments such as stainless steel.

  On the other hand, in FSW bonding of steel materials, heat input is larger than that of soft materials such as aluminum. Therefore, even with FSW, there is concern about the generation of tensile residual stress due to bonding. The tensile residual stress is known to cause so-called stress corrosion cracking (SCC) in a corrosive environment, and therefore needs to be sufficiently considered.

  As a conventional technique, Patent Document 1 describes a method for reducing tensile residual stress by quenching a joint immediately after welding in general welding such as arc welding. Patent Document 2 describes the reduction of residual stress by cooling the joint in FSW.

JP 2004-167575 A JP 2004-148350 A

  In the case of FSW, the method for reducing residual stress by rapid cooling immediately after welding may not always provide a sufficient residual stress reduction effect. Here, the reduction of the residual stress due to rapid cooling immediately after welding occurs due to the difference in temperature between the surface of the bonded portion and the inside and the difference in thermal expansion due to this temperature difference. In the method for reducing residual stress by rapid cooling immediately after welding, a temperature difference is generated only by frictional heat with a cylindrical tool, so that there is a problem that a sufficient residual stress reduction effect cannot be obtained. Therefore, it is necessary to appropriately increase the amount of heat input to the joint and increase the temperature difference between the surface and the inside during cooling.

  In view of this, an object of the present invention is to increase the amount of heat input to the welded portion appropriately in FSW and increase the effect of reducing the tensile residual stress due to rapid cooling immediately after joining.

  The friction stir welding apparatus according to the present invention includes a cooling device that cools the joint through which the rotor has passed in friction stir welding using a rotor, and at a position facing the joint on the outer periphery of the rotor. It has the heat input means rotated with a rotor, It is characterized by the above-mentioned.

  According to the friction stir welding apparatus of the present invention, the temperature difference between the surface and the inside during cooling becomes large, and the effect of reducing the tensile residual stress after construction can be increased.

The schematic diagram which shows the friction stir welding apparatus concerning Example 1 of this invention. The schematic diagram which shows the temperature distribution of the thickness direction of the to-be-joined part explaining the principle of this invention. The perspective view in FIG. The schematic diagram which shows the friction stir welding apparatus concerning Example 2 of this invention. The schematic diagram which shows the friction stir welding apparatus concerning Example 3 of this invention. The schematic diagram which shows the friction stir welding apparatus concerning Example 4 of this invention.

  The present invention will be described below with reference to the drawings.

  Example 1 of the present invention will be described below. FIG. 1 is a schematic diagram of a friction stir welding apparatus according to Example 1 of the present invention. In the friction stir welding apparatus shown in FIG. 1, the rotor 1 includes a probe 2, and the probe 2 is press-fitted into the joined portion. The attachment portion of the probe 2 has a shoulder 11 for integrating a plurality of members by plastic flow around the joint portion and kneading. Moreover, the cooling device 3 is provided on the opposite side to the traveling direction of the rotor 1, and the surface 5 to be joined immediately after the rotor 1 passes by the coolant 4 is cooled. Furthermore, a donut-shaped heat input means 6 is provided outside the rotor 1. The heat input means 6 is in contact with the surface 5 to be bonded at a processing surface 6a for machining the bonded portion, and is pressed by the reaction force of the pressing mechanism 6b. The pressing mechanism 6b is fixed by a pressing plate 6c. Furthermore, since the heat input means 6 is fixed to the rotor 1 by the holder 6d, it rotates with the rotation of the rotor 1. Here, the heat input means 6 is a tool that heats the processed surface 6a by frictional heat generated by rotation. The heat input means 6 is preferably polished with a large frictional heat, but does not exclude other processing tools such as cutting.

  According to this apparatus, as the rotor 1 rotates, the surface 5 to be welded is machined by the machining surface 6a, and the frictional heat of machining is generated, so that the conventional friction without the heat input means 6 is generated. Compared with a stir welding apparatus, the temperature of the to-be-joined part surface 5 can be raised.

FIG. 2 is a schematic diagram showing the temperature distribution in the plate thickness direction of the bonded portion for explaining the principle of the present invention. The temperature distribution 7a in the plate thickness direction before quenching by the present apparatus becomes higher on the surface of the joint due to frictional heat than the temperature distribution 7b in the plate thickness direction before quenching by the conventional method using no heat input means. When cooled by the coolant 4 from this state, the temperature of the surface 5 to be joined decreases, so the temperature distribution immediately after quenching by this apparatus is like the temperature distribution 8a in the thickness direction immediately after quenching by this apparatus. In addition, the temperature distribution immediately after the rapid cooling by the conventional method is the temperature distribution 8b in the thickness direction immediately after the rapid cooling by the conventional method. At this time, in the present apparatus, the temperature difference ΔT ₁ between the surface and the interior is larger than ΔT ₂ by the conventional method. As a result, since the difference in thermal expansion between the surface and the interior becomes large, in this apparatus, the tensile residual stress after FSW construction can be greatly reduced as compared with the conventional method.

  FIG. 3 is a perspective view of FIG. In this apparatus, not only the bead 5a by normal joining but the processing mark 5b by the heat input means 6 appears. That is, the shape of the bead 5a is smoothed by the heat input means 6 as compared with the conventional method. Therefore, this apparatus can be expected not only to improve the residual stress but also to improve the fatigue strength and the like by smoothing the bead 5a and reducing the stress concentration.

  Thus, according to the present invention, the tensile residual stress after the FSW construction can be reduced as compared with the conventional method, and the bead shape can be smoothed.

  Next, FIG. 4 shows a schematic diagram of the friction stir welding apparatus according to the second embodiment. In the following, description of the same symbols as those in the first embodiment is omitted. Example 2 is an example in the case where the rotor 1 is constructed while being inclined with respect to the surface 5 to be joined. Even when the rotor 1 is tilted, the processed surface 6a of the heat input means 6 is formed in advance at a predetermined angle that matches the tilt angle of the rotor 1, so that the surface 5 to be joined at the rear in the traveling direction. Can be processed by the processing surface 6a.

  Therefore, the improvement effect of the residual stress by cooling can be heightened because the temperature of the surface of a junction part rises.

  FIG. 5 is a schematic diagram of the friction stir welding apparatus according to the third embodiment. The third embodiment has a heat input control device 9 that controls heat input by the heat input means 6. The heat input control mechanism 9 includes a force plate 9a, a rolling part 9b, an electric actuator 9c, a load measuring device 9d, a thermocouple 9e, and a controller. The heat input control device 9 is fixed at the position of the load measuring device 9d, does not rotate, and is in contact with the rotating heat input means 6 via the rolling portion 9b. In Example 3, the temperature behind the traveling direction is always measured by the thermocouple 9e. Furthermore, the contact force of the processing surface 6a can be controlled by adjusting the pushing amount of the electric actuator 9c. That is, it can be controlled by the controller so that the temperature of the surface 5 to be joined becomes the optimum temperature before quenching that has been obtained in advance.

  Thus, according to the present invention, the tensile residual stress after FSW construction can be reduced more appropriately than in the conventional method, and the bead shape can be smoothed.

  FIG. 6 is a schematic diagram of a friction stir welding apparatus according to a fourth embodiment. In the fourth embodiment, the heat input control device 9 has a heater 10. The heater 10 is provided inside a box-shaped force plate. In Example 4, the heat input means 6 is heated by the heater 10, so that the heat input from the heat input means 6 to the surface 5 to be joined can be increased.

  The present invention is suitable for joining stainless steel or the like, which is a material used in a corrosive environment and in which SCC due to tensile residual stress is a problem. Further, it is suitable for joining thick members that are easily deformed and easily generate tensile residual stress.

  In addition, the material of the heat input means of the present invention is preferably a material having a large heat capacity and difficult to escape heat, such as stainless steel. Further, the processing method of the heat input means of the present invention is preferably polishing with large frictional heat, but does not exclude other processing methods such as cutting. Moreover, although the example which used the coil-type spring for the pressing mechanism of the processing tool was shown in said Example, you may use the other mechanism in which reaction force generate | occur | produces, such as a leaf | plate spring.

DESCRIPTION OF SYMBOLS 1 ... Rotor 2 ... Probe 3 ... Cooling device 4 ... Coolant 5 ... Surface to be joined 5a ... Bead 5b ... Processing mark 6 ... Heat input means 6a ... Processed surface 6b ... Pressing mechanism 6c ... Presser plate 6d ... Holder 7a ... Temperature distribution in the thickness direction before quenching by this apparatus 7b ... Plate before quenching by conventional method Temperature distribution 8a in the thickness direction ... Temperature distribution 8b in the thickness direction immediately after quenching by this apparatus ... Temperature distribution 9 in the thickness direction immediately after quenching by the conventional method 9 ... Heat input controller 9a ... Force plate 9b ... rolling part 9c ... electric actuator 9d ... load measuring device 9e ... thermocouple 10 ... heater 11 ... shoulder

Claims (8)

In a friction stir welding apparatus using a rotor,
While having a cooling device that cools the joint through which the rotor has passed,
A friction stir welding apparatus comprising heat input means that rotates together with the rotor at a position facing the joint on the outer periphery of the rotor. In the friction stir welding apparatus according to claim 1,
The friction stir welding apparatus according to claim 1, wherein a surface of the heat input means facing the joint is formed so that the thickness of the heat input means decreases toward the outside of the heat input means. In the friction stir welding apparatus according to claim 1 or 2,
A friction stir welding apparatus having a pressing mechanism for pressing the heat input means against the surface of the bonded portion. In the friction stir welding apparatus according to any one of claims 1 and 3,
A temperature measurement unit for measuring the temperature of the surface of the joint,
A friction stir welding apparatus comprising a heat input control device that controls a heat input to the welded portion by controlling a pressing force of the heat input means based on a measurement result of the temperature measuring portion. In the friction stir welding apparatus according to any one of claims 1 to 4,
A friction stir welding apparatus comprising a heater for heating the heat input means. In the friction stir welding method using a rotor,
A friction stir welding method, wherein the joint through which the rotor has passed is cooled, and a rotor is provided at a position facing the joint on the outer periphery of the rotor to input heat. In the friction stir welding method according to claim 6,
A friction stir welding method characterized in that the temperature of the joint surface is measured, and the heat input to the weld is controlled by controlling the pressing force of the heat input means based on the measurement result. In the friction stir welding method according to claim 6 or 7,
The friction stir welding method, wherein the heat input means is heated.

Images