Metal fusion bonding – Process – Using dynamic frictional energy
Reexamination Certificate
2001-02-26
2003-05-06
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Using dynamic frictional energy
C228S002100
Reexamination Certificate
active
06557746
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a friction stir welding method.
DESCRIPTION OF THE RELATED ART
A friction stir welding method is a technique in which a round shaft (called a rotary tool) is rotated and inserted into the joint between members to be welded, and the rotating rotary tool is moved along the junction line of the joint, thereby heating, mobilizing and plasticising the material in the welding region, so as to effect a solid-phase welding of the members. The rotary tool comprises a large-diameter portion and the small-diameter portion at the leading end thereof. The welding is performed by inserting the small-diameter portion into the joint between the members to be bonded, such that the end surface of the large-diameter portion comes into contact with the aforementioned members. A screw thread is formed an the small-diameter portion. The end surface of the large-diameter portion on the screw thread side has a concave shape. Moreover, friction stir welding may be performed by positioning members to be bonded between two large-diameter portions of the rotary tool. This technique is disclosed in Japanese Patent No. 2,712,838 (U.S. Pat. No. 5,460,317), and Japanese Patent National Publication of PCT Application No. 9-508073 (EP 0752926B1).
SUMMARY OF THE INVENTION
A case of friction stir welding the abutting region formed between two extruded members
10
,
20
made of aluminum alloy will be considered with reference to
FIG. 4. A
trapezoidal concave portion
12
is provided at the end surface of the face plate
11
of the member
10
, and a trapezoidal convex portion
22
is provided at the end surface of the face plate
21
of the member
20
. The convex portion
22
is inserted into the concave portion
12
when the two members
10
,
20
are abutted. The concave portion
12
and the convex portion
22
have a trapezoidal shape to simplify insertion. Also, the end portions of the members
10
,
20
are provided with raised portions
13
,
23
projecting upwardly. In the case where the members
10
,
20
are used to form a car body of a railway car, the length of the members
10
,
20
is approximately 20 m. Therefore, the members
10
,
20
at the abutting region may each tend to constitute a substantially different plane. In order to prevent such situation, the end surfaces of the abutting region are provided with the concave portion
12
and the convex portion
22
and are fitted against each other.
In such a state, friction stir welding is performed by rotating and inserting a small-diameter portion
51
of a rotary tool
50
from above into the welding joint until the end surface of a large-diameter portion
53
(end surface on the small-diameter portion
51
side) is inserted slightly into the raised portions
13
,
23
. The rotating rotary tool
50
is then moved along the welding joint in the abutting region, as is illustrated in FIG.
9
. Reference number
100
indicates a bed for fixing the members
10
,
20
.
The rotary tool
50
used for welding is shown in FIG.
10
. The rotary tool
50
has a small-diameter portion
51
attached to the leading end of the large-diameter portion
53
. The small-diameter portion
51
has a tapered shape with a larger diameter portion located towards the leading end. This is to stir the material in the abutting region of the concave portion
12
and the convex portion
22
sufficiently. The tapered surface of the small-diameter portion
51
is provided with a male screw thread. The end surface
53
h
of the large-diameter portion
53
is contoured so as to be concave towards the large-diameter portion
53
.
The small-diameter portion
51
in the vicinity of the large-diameter portion
53
(the small-diameter portion
51
on the base end side) is not provided with a screw thread. This is because it is difficult to provide the screw thread on the small-diameter portion
51
close to the base end side due to the fact that the small-diameter portion
51
is tapered.
As seen in
FIG. 9
, during welding, the region of the small-diameter portion
51
without the screw thread is placed at the position of the upper slopes (called sides)
12
b
,
22
b
of the trapezoidal concave portion
12
and the trapezoidal convex portion
22
. Therefore, the stirring in this region tends to be insufficient. When stirring is insufficient, this is considered to have an undesirable influence on the strength of the weld. In the case where the material to be welded is an aluminum alloy, the surfaces of the members
10
,
20
tend to be oxidized. When stirring is insufficient, it is considered that such metal oxide has a bad influence on the strength of the weld.
An object of the present invention is to provide a friction stir welding method that is capable of providing good welding at the abutting region with the concave portion and convex portion fitted together.
The present invention is characterized by the face that friction stir welding is performed by positioning a screw thread on the rotary tool in the fitted region of the concave portion and the convex portion.
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US 2001/0007717A1 Ezumi et al. (Jul. 12. 2001).
Ezumi Masakuni
Fukuyori Kazushige
Matsunaga Tetsuya
Antonelli Terry Stout & Kraus LLP
Dunn Tom
Hitachi , Ltd.
Stoner Kiley
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