FIELD OF THE INVENTION
The present invention relates filling up of the terminal hole producing during the
end of friction stir welding. More particularly, the invention relates to a method
of plugging holes created on a product welded in a friction stir welding machine.
BACKGROUND OF THE INVENTION
Friction stir welding is a solid state welding process in which plasticized material
is processed to form a weld. Friction stir welding involves heat generation
through friction process between a rotating tool plunged inside the materials
being welded, which creates a zone of plasticized material with the tool
traversing along the weld joint. The plasticized material flows along the tool to its
rear side and get consolidated to the form of a weld. At the end of the weld, the
tool is withdrawn from the material creating a blind hole which corresponds to
the profile of the tool pin. For critical application, this hole needs to be filled in.

US 6,213,379B1 discloses a Friction plug welding (FPW) which is advantageous
for friction stir welding (FSW) hole close-out and weld repairs in Al-Cu-Li fusion
or friction stir welds. The known fusion welding methods of Al-Cu-Li produces
weld containing defects. These defective areas are found by non-destructive
examination after welding and proof testing. The existing techniques for
repairing typically small defects weaken the weldment, heavily dependent on
welder's skilly and are costly. In contrast thereof, the technique of friction plug
welding repairs, increases strength ductility and resistance to cracking over initial
weld quality without requiring much time or operator skill. In the friction plug
welding, pulling the plug is advantageous because all hardware for performing
the weld can be placed at a single location available on the side of the
workpiece.
The prior art friction stir welding requires plugs with special contours for plug
welding. The prior art further requires special tooling/fixtures for carrying out the
weld. This technique can be used for the hole produced during butt welding. It is
not suitable for plugging of holes produced during friction stir welding of T joints.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a method of plugging holes
created on a product produced in a friction stir welding machine.
Another object of the invention is to propose a method of plugging holes created
on a product produced in a friction stir welding machine, which adapts plugs with
simple configuration.
A still another object of the invention is to propose a method of plugging holes
created on a product produced in a friction stir welding machine, in which the
plug is formed of same materials that of the product.
A further object of the invention is to propose a method of plugging holes
created on a product produced in friction stir welding machine, in which the tool
and fixtures to plug the hole are selected to be adaptable for friction stir welding
process.

SUMMARY OF THE INVENTION
Accordingly, there is provided a method of plugging holes generated on a
product produced in a friction stir welding machine. According to the invention,
the plug is fitted into the hole by applying a pressure on the plug, and then
carrying out seal-welding on the top edge of the plug with base material by
friction process.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 schematically shows insertion of a plug inside a hole by applying pressure
on top of the plug.
Fig. 2 shows completion of seal welding of the plug after the plug is fitted into
the hole.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in Fig. 1, a top plate (4) and a bottom plate (5) is welded to form a T
joint in a friction stir welding machine. After withdrawal of the welding tool (1)

from the components (4,5) being welded, a hole (3) is created on the product
having a size same as that of the pin tool. A plug (2) made of the same material
is placed on the hole (3) and the plug (2) is inserted by the pin tool (1) by
applying a pressure. After full insertion the tool is rotated in an orbital motion on
the surface of the base materials (see Fig. 2), so that the plug seal is welded
with the base material. Unlike the prior art using taper plug. The invention
adapts a cylindrical plug of same material. The size of the hole altogether
corresponds to the size of the plug, the plug height is however marginally higher
than the thickness of the top plate (4). Substantially low power is require
performing the weld and a sound weld metal property is produced as
experimented by plug welding of 16 mm to 18 mm aluminum plate in a T joint
configuration. A flash (6) after completion of the process is produced such that
the hole gets filled permanently.

WE CLAIM:
1. A method of plugging holes created on a product welded in a friction stir
welding machine, comprising the steps of:
providing a first plate (4) over a second plate (5);
welding the plates (4,5) to form a T-joint in a friction stir welding
process adapting a friction stir welding machine having a tool pin
(1), the withdrawal of the tool pin (1) on completion of the welding
process creates a hole (3) on the welded product (4,5);
providing a plug (3) on the hole (3), placing the tool pin (1) on the
plug (3), and applying a vertically downward pressure on the tool
pin (1) so as to fully insert the plug (3) into the hole (2); and
rotating the tool pin (2) in an orbital motion on the surface of the
base material (4,5) such that the plug (3) is seal-welded with the
base material,
characterized in that the plug (3) is formed with material same as that of the
base material, in that the plug (3) is cylindrically shaped, and in that the height
of the plug (3) is marginally higher than the thickness of the first plate (4).

2. The method as daimed in claim 1, wherein on completion of the seal-
welding, a flash (6) Is generated to fill the hole permanently.

A method of plugging holes created on a product welded in a friction stir welding
machine, comprising the steps of: providing a first plate (4) over a second plate
(5); welding the plates (4,5) to form a T-joint in a friction stir welding process
adapting a friction stir welding machine having a tool pin (1), the withdrawal of
the tool pin (1) on completion of the welding process creates a hole (3) on the
welded product (4,5); providing a plug (3) on the hole (3), placing the tool pin
(1) on the plug (3), and applying a vertically downward pressure on the tool pin
(1) so as to fully insert the plug (3) into the hole (2); and rotating the tool pin
(2) in an orbital motion on the surface of the base material (4,5) such that the
plug (3) is seal-welded with the base material, characterized in that the plug (3)
is formed with material same as that of the base material, in that the plug (3) is
cylindrically shaped, and in that the height of the plug (3) is marginally higher
than the thickness of the first plate (4).