FIELD OF INVENTION
The invention relates to a friction welding process for welding of carbon steel
valve body to carbon steel yoke components.
BACKGROUND OF THE INVENTION
Joining of carbon steel valve body to carbon steel yoke components can be done
directly by fusion welding. But it takes a long cycle time which often produces
defective welds. Friction welding is an automated solid state welding process
suitable for mass production. The process achieves high productivity due to its
less flash generation as compared to other arc welding process for example,
shielded metal arc welding, gas metal arc welding and flux cored arc welding.
Thus, the friction welding process is normally used for production of jobs for
example, axle cases, engine exhaust valves, and other similar components.
Currently joining of carbon steel valve body to carbon steel yoke components is
done by SMAW, GMAW & GTAW process but the quality of joint does not
generally meet the code requirement. Further, if the code requirement is to be
met without failure, the process like GTAW, GMAW or SMAW exhibit lower
productivity.
The conventional fusion welding process need consumables and power source.
The fusion weld exhibits defects like slag inclusion, cracks, under-cut. In macro
structure, the heat affected zone is found to be higher. In the friction welded
joint according to the invention, the heat affected zone is found to be
substantially small, and without any defects like slag inclusion, under-cut etc.
The economy of a welding process largely depends on a factor namely, flash,
which constitutes a difference of the length of a work piece before and after the
welding process. In order to maintain economy of a welding process, it is
important to maintain the flash as low as possible. This requires optimization of
the important welding parameters to maintain a minimum flash.
United States Patent 6532655B1 to Hew Nam Ahn, Young Seop Yoon et al.
discloses a method for using friction welding to manufacture a hollow piston for
variable displacement swash plate compressors of air conditioning system. This
method produces a desired hollow piston by separately forming a body and a cap
and by simply machining the body and the cap prior to welding the body and the
cap together in to a single structure through a frictional welding process. The
term "friction welding" as used in this description, is considered to include both
direct drive friction welding as well as inertia welding.
United States patent 4850772 to John CJenkins, Lorain, Ohio et. al. describes a
method for using a friction weldable stud. The stud includes an elongated body
having a collar or skirt located around the body and extending outwardly there
from. The collar has a first surface facing in one direction towards an end of the
body, with the surface having an engagable configuration for engagement by a
corresponding configured chuck of a welding tool. The tool can there by rotate
the stud and also apply an axial force to it through the chuck and collar load. The
collar and body can be made by friction welding technique.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a friction welding
process in a friction welding machine for producing a butt joint between a valve
body and a yoke made one of carbon steel, stainless steel and dissimilar
combination material.
Another, object of the present invention to propose a friction welding process in
a friction welding machine for producing a butt joint between a valve body and a
yoke made one of carbon steel, stainless steel and dissimilar combination
material which eliminates wastage of consumables including reduces the cycle
time.
A still another object of the present invention to propose a friction welding
process in a friction welding machine for producing a butt joint between a valve
body and a yoke made one of carbon steel, stainless steel and dissimilar
combination material, which provides weld-chemistry of the produced weld
according to the codes.
SUMARY OF THE INVENTION
Accordingly, there is provided a friction welding process for welding of valve
body to yoke components comprising of steps of joining together a first end
piece of a carbon steel valve body and a yoke of hollow section to produce a
butt joint, the length of the yoke and valve body pieces being selected to be
longer than a final required length and determined considering the length of
each joinable material equal to their required final length, plus a length
cushioned for the expected weld flush or burnoff loss; and applying at least one
flash interlayer material at predetermined locations with controlled thickness to
provide a datum reference.
According to the invention the friction welding was chosen. Initially carbon steel
tube to carbon steel tube butt joint was friction welded. The joint integrity was
tested by pedal test. Carbon steel valve body to carbon steel yoke but joint was
friction welded and tested for the soundness of the joint the combination of
carbon steel valve body to carbon steel yoke having done first. A special fixture
was made to main the perpendicularity between the valve body to yoke.
Removal of flash in and out the joint was carried out in the machine itself.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 - a schematic representation of a valve body to yoke butt joint
produced through the inventive process.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
According to the invention, as shown in FIG - 1 a valve body end piece of a
carbon steel 1 and a second end piece of an yoke (3), are joined together to
form an integral joint by using the procedure of friction welding. The end pieces
(1, 3) are selected as hollow sections shaped with corresponding round cross-
section.
A first end of a carbon steel valve body (1) and the yoke 3, both being typically
longer than required as per the final dimensions , are conventionally cut to a
length equal to their final required length, including a length for the expected
weld flush or burnoff loss.
The forged carbon steel valve body (1), is machined in circular shape in the front
side, and further machined into substantially round shape and dimension, with a
base circle dimension equal the diameter of the opposing component (the
diameter of the end pieces), so that it will form a flush on the machine chuck.
Required torque during the weld process is applied by connecting the holder to a
friction welding machine. The yoke is shown as circular cross-section piece (3).
The actual cross-section of the yoke piece (3) a complex and that is to say, the
cross, as long as section should allows a sufficient grip to hold it securely for
either spinning or holding during the welding operation.
Friction welding is used to weld the carbon steel end piece (1). The yoke piece
(3) is preferably held in a stationary clamping device, producing a controlled
dimension flash, ready for further machining. A plurality of protruding flash
interlayer material (2) when disposed at desired location, provide a datum
reference position for further machining.
According to the invention, while implementing a valve body to yoke joint,
having same diameter, 90% weld upset (loss of length) occurs in the diameter
part including associated length tolerance in the valve body (1) and the yoke (3)
and the thickness of the flash material (2) is precisely controlled. When the base
circle dimension of the valve body (1) and yoke pieces (3) are same, same
burnoff occurs. According to the invention, the thickness and diameter of the
valve body (1) and yoke pieces (3) are selected to be close to the desired
thickness of the final dimensions, plus the expected burnoff.
WE CLAIM
1. A friction welding process for welding of valve body to yoke components
comprising of steps of:
- joining together a first end piece of a carbon steel valve body and a yoke
of hollow section to produce a butt joint, the length of the yoke and valve
body pieces being selected to be longer than a final required length and
determined considering the length of each joinable material equal to their
required final length, plus a length cushioned for the expected weld flush
or burnoff loss; and
- applying at least one flash interlayer material at predetermined locations
with controlled thickness to provide a datum reference.
2. A process as claimed in claim 1 wherein the similar/dissimilar material
combination and wherein an hollow valve body to carbon steel to yoke
components is joined with joint integrity.
3. A process as claimed in claim 1 wherein, the required mechanical
properties is produced in the weld joint.
4. A process as claimed in claim 1 wherein welding the similar / dissimilar
material combination with configuration such as a hollow carbon steel
valve body and carbon steel of yoke components is possible.
5. A process as claimed in claim 4 wherein the welded assembly can be
further machined to form a valve body yoke assembly.
6. A friction welding process for welding of carbon steel valve body to yoke
components, as herein described and illustrated with reference to the
accompanying drawing.

The invention relates to a friction welding process for welding of valve body
to yoke components comprising of steps of joining together a first end piece
of a carbon steel valve body and a yoke of hollow section to produce a butt
joint, the length of the yoke and valve body pieces being selected to be
longer than a final required length and determined considering the length of
each joinable material equal to their required final length, plus a length
cushioned for the expected weld flush or burnoff loss; and applying at least
one flash interlayer material at predetermined locations with controlled
thickness to provide a datum reference.