PROCESS AND DEVICE FOR MULTIPLE-ROD INTERNAL WELDING OF SPIRALLY SEAMED WELDED PIPES

METHODE ET DISPOSITIF DE SOUDAGE INTERNE A BAGUETTES MULTIPLES DE TUYAUX A SOUDURE HELICOIDALE

English Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides a process for multiple-
rod internal welding for the production of spirally seamed
welded pipes having small diameters of approximately 20 to 30"
in which both the welding and the strip forming are effected at
an angle .alpha.' to the vertical median plane of the pipe which is in
an approximate range between 5 and 30° and that guide motion
of the pipe occurs in a plane, which is inclined by an angle a
in the same range as the angle .alpha.' with respect to the horizontal.
The present invention also provides a device for multiple-rod
internal welding for the production of spirally seamed welded
pipes having small diameters of approximately 20 to 30" compris-
ing forming roll sets and internal welding point which are
located in a plane at an angle .alpha. in the approximate range from
5 to 30° with respect to the vertical median plane of the pipe
and a pipe-swinging device having a fulcrum disposed at an angle
.alpha. in the same range as the angle .alpha.' with respect to the horizontal.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for multiple-rod internal welding for
the production of spirally seamed welded pipes having small
diameters of approximately 20 to 30" in which both the welding
and the strip forming are effected in a plane at an angle .alpha.' to
the vertical median plane of the pipe which is in an approximate
range between 5 and 30° and guide motion of the pipe occurs in
a plane, which is inclined by an angle .alpha. with respect to the
horizontal, which is in the same range as the angle .alpha.'.
2. A process as claimed in Claim 1, in which the angle
is from 5 to 15°.
3. A device for multiple-rod internal welding for the
production of spirally seamed welded pipes having small diameters
of approximately 20 to 30" comprising forming roll sets and an
internal welding point which are located at an angle .alpha.' in the
approximate range from 5 to 30° with respect to the vertical
median plane of the pipe and a pipe-swinging device having a
fulcrum disposed at an angle .alpha. with respect to the horizontal,
which is in the same range as the angle .alpha.'.
4. A device as claimed in Claim 3, in which the angle
.alpha.' is in the range 5 to 15°.

Description

S3~
The present invention relates to a process for multiple-
rod internal welding of spirally seamed welded pipes, particul-
arly, of pipes having small diameters of approximately 20 to 30"
and to a device for carrying out the process.
As is known, the selection of a suitable welding
position for internal welding of spirally seamed welded pipes
results in optimum multiple-rod welding. The welding position
is chosen so that on solidification of the layer of weld the weld
attains an optimum shape. The zone of solidification of the
molten bath is obtained froM the welding parameters welding-arc
voltage, current and velocity. If this ~one lies in the region
of the ascending pipe wall, then the welding puddle recedes, the
internal weld will be broad, flat and inclined at the centre and t
has a small depth of penetration. This phenomenon is evident
particularly in the case of pipes of small diameter of approx-
imately 20 to 30" since the curvature of the pipe surface is
greater and since the solidifying zone passes into the steeper
region earlier.
In order to avoid this form of weld, the welding point
~20 is allowed to move into the descending region of the pipe wall.
In particular welding is as far as possible, carried out in a
region between 5 and 30, preferably between 5 and 15 as seen
from the lowest point of the pipe circumference.
This method has the following disadvantages: -`
lo The strip edge and -the pipe edge move relative to
one another until they enter the region of the spar roll since
on enterin~ by way of the front forming roll set the strip is ;
first bent in the opposite direction. The more closely spaced
the lower forming roll sets, i.e., the smaller the pipe diameter,
the greater will be this relative motion. `~
2. The point about which the pipe is swung during the
;
guide motion lies theore-tically exactly at the lower dead center.
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3~136
Howeve.r, the fulcrum should lie ahead of the welding point, if .-
possible, in order to prevent the layer of weld from being torn :-
up again during guiding. :
With pipes of small diameter the above disadvantages
are exactly diametrically opposed -to the necessity of welding in ~:
the range oE angles specified hereinbefore.
The present inven-tion provides a process by means of
which an optimum weld form can be obtained even for pipes of
small diameter and a device for carrying out said process. ..
According to the present invention there is provided a
process for multiple~rod internal welding in the production of
spirally seamed welded pipes having small diameters of approximat~
ely 20 to 30" in which both the welding and the strip forming are
carried out in a plane at an angle ~' to the vertical medium
plane of the pipe approximately in the range between 5 and 30,
preferably between 5 and 15, the guide motion of the pipe being
carried out in a plane which is inclined by an angle ~ which is
in the same range as the angle ' with respect to the horizontal.
For carrying out the process according to the invention
a device is provided in which the forming roll sets, the inter- :~
nal welding and the fulcrum of the pipe-swinging device are
disposed at an angle ~ approximately in a range between 5 and
30, preferably between 5 and 15. ~ '
In accordance with the present invention the zone of
solidification of t'ne molten bath and thus the zone of the reced-
ing molten bath is so favourably influenced that the interal
weld has no detrimental features with respect to the shape of the :.
depth of penetration. Accordingly, the device according to the . :
invention can also be used for equipment in which the strip inlet
can be swung while the pipe outlet is fixed.
The present invention will be further illustrated by
way of the accompanying drawings in which:

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Figure 1 is a schematic representation plane of a
device according to one embodiment of the present invention on
a reduced scale for use in multiple rod internal welding of
spirally seamed pipes.
Figure 2 shows a top plan view of Figure 1.
As illustrated in Figure 1 the horizontal strip 5,
bent by the forming roll sets 1 and 2, is welded at the internal
welding point 3, which lies approximately at an angle ~' with t
respect to the vertical median plane of the pipe 6. The pipe 6
is guided in the plane 4 about the fulcrum 7 which lies ahead
of the welding point 3, the plane 4 being approximately at an
angle ~ of from 5 to 30 with respect to the horizontal strip ;-5, which angle ~ is in the same range as the angle ~'. The
position of the welding point 3 and of that the fulcrum 7 are
shown in Figure 2 in top plan view.
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