Metal fusion bonding – Process – Using dynamic frictional energy
Reexamination Certificate
2001-05-29
2003-01-28
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Using dynamic frictional energy
C228S002100
Reexamination Certificate
active
06510975
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a friction agitation joining tool used for welding joining members made of metal such as aluminum or its alloy, and also relates to a friction agitation joining method using the aforementioned joining tool.
2. Description of Related Art
A friction agitation joining method is classified into a solid-phase welding method, and has advantages such that the method can be applied to any kinds of metallic materials and that the method causes fewer thermal strain due to joining. Thus, recently, the friction agitation joining method is used at various assembling sites of structures, such as vessels, automobiles, railroad cars and panel structures.
FIG. 5
shows two plate-shaped metal joining members which are being butt-joined by a friction agitation joining method.
In
FIG. 5
, the reference numerals
101
and
102
denote plate-shaped metal joining members. Both the joining members
101
and
102
have the same thickness, and are disposed in a butted state. The reference numeral
110
denotes a friction agitation joining tool. The joining tool
110
is equipped with a column-shaped rotor
111
and a pin-shaped probe
112
having a diameter smaller than a diameter of the probe. The pin-shaped probe
112
is projected from a part of the end face
111
a
of the rotor
111
. In order to efficiently agitate and mix the materials of both the joining members
101
and
102
to soften by frictional heat, agitating projections (not shown) are formed on the peripheral surface of the entire length of the probe
112
.
When joining both the joining members
101
and
102
in a butted state with the aforementioned joining tool
110
, the probe
112
is rotated in accordance with the rotation of the rotor
111
. Then, the rotating probe
112
is inserted into the butted portion
103
of both the joining members
101
and
102
, and the end face
111
a
of the rotating rotor
111
is forced to be pressed on the surface of both the joining members
101
and
102
. While keeping this state, the probe
112
is advanced relative to both the joining members
101
and
102
along the butted portion
103
.
As a result, a portion of both the joining members
101
and
102
where the probe
112
contacts and its vicinity will be softened by the frictional heat generated due to the rotation of the probe
112
and the contact between the end face
111
a
of the rotor
111
and the surface of the joining members
101
and
102
. In accordance with the advancing movement of the probe
112
, the softened and agitated materials of the joining members
101
and
102
are plastically fulidized to go around the probe
112
and to fill up a groove formed behind the probe
112
as it moves. Then, the materials will be cooled and solidified by the immediate loss of such friction heat. This phenomenon will be repeated with the advancing movement of the probe
112
, which causes the joining members
101
and
102
to be integrally joined along the entire length of the butted portion
103
. The reference numeral
109
denotes the joined portion of the joining members
101
and
102
.
FIG. 6
shows the stacked two joining members joined by the aforementioned joining tool
110
.
In
FIG. 6
, the reference numerals
105
and
106
denote plate-shaped metal joining members, respectively. Both joining members
105
and
106
are stacked one on top of the other. The reference numeral
107
denotes the superposed interface of the joining members
105
and
106
.
When both the joining members
105
and
106
are joined in a stacked state with the aforementioned joining tool
110
, the following problems will arise.
As mentioned above, the probe
112
is provided with the aforementioned agitating protrusions on the peripheral surface of the entire length thereof. When the rotating probe
112
is inserted into both the joining members
105
and
106
from the upper surface of the upper joining member
105
, the materials of the upper and lower joining members
105
and
106
softened by the frictional heat will be stirred up by the agitating protrusions. Thereby, the upper surface of the upper joining member
105
swells. On the other hand, the upper surface of the upper joining member
105
is pressed down by the end face
111
a
of the rotor
111
to be flattened. Consequently, the thickness of the joined portion
109
of the upper joining member
105
and its vicinity decreases. This deteriorates the strength of the joined members.
Furthermore, since natural-oxidation films
105
a
and
106
a
are usually formed in the superposed interface of the joining member
105
and
106
as shown in
FIG. 7A
, the natural-oxidation films
105
a
and
106
a
will be stirred up by the agitating protrusions at the time of joining. Thus, as shown in
FIG. 7B
, the natural-oxidation films near the joined portion
109
will be raised. This causes an easy generation of fatigue cracks, resulting in a deterioration of fatigue strength of the obtained stacked joint.
SUMMARY OF INVENTION
The object of the present invention is to provide a friction agitation joining tool which can prevent a deterioration of strength of the joined members, such as a deterioration of joined strength and fatigue strength, to obtain a joined member having strength reliability, and also to provide a friction agitation joining method using such a joining tool.
Other purpose of the present invention will become apparent from the following embodiments.
According to a first aspect of the present invention, a friction agitation joining tool includes a rotor and a probe to be inserted into joining members, wherein the probe has a diameter smaller than a diameter of the rotor and is provided at a part of an end surface of the rotor, wherein the probe is provided with a groove formed on a peripheral surface of at least a longitudinal middle portion of the probe, the groove extending in an axial direction of the probe.
With this joining tool, at the time of joining, the probe is inserted into two pieces of metal joining members stacked one on top of the other such that the probe crosses both of the joining members. Thereby, the groove is disposed generally perpendicular to the superposed interface of the stacked joining members. For this reason, the natural-oxidation films formed on the superposed interface of each joining member will be ground minutely with the edge of the groove. Consequently, the standup of the natural-oxidation film which may occur near the joined portion will be suppressed, which enhances the fatigue strength of the obtained stacked joint.
In the aforementioned groove, it is preferable that the groove is formed such that a width of the groove becomes gradually narrow toward a basal end of the probe. With this preferred embodiment, it is possible to minimize the phenomenon that the materials of the joining members entered in the groove is conveyed outside the joining members through the groove during joining. This can prevent a deterioration of joining strength due to shortage.of materials.
Furthermore, in the aforementioned preferred embodiment, it is preferable to set a width W of the groove so as to satisfy the following inequality:
5/100≦(
W
1
−W
2)/(2
t
0)≦15/100,
where W
1
is a width of one end of the groove at a tip end side of the probe, W
2
is a width of the other end of the groove at a basal end side of the probe, and t
0
is a total thickness of joining members. By setting the width W as mentioned above, it becomes possible to assuredly prevent a deterioration of the joining strength due to shortage of materials.
In the aforementioned joining tool according to the first aspect of the present invention, it is preferable to set a width W of the groove so as to satisfy the following inequality:
1/20
≦W/D
2≦1/8,
where D
2
is a diameter of the probe. This enables the natural-oxidation film to be completely ground into fine particles.
In the aforementioned joining tool according to the first aspect of the present invention, it is preferable to set a
Dunn Tom
Showa Denko K.K.
Stoner Kiley
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