Title of Invention

AN APPARATUS FOR MAKING ROOT PASS WELDING USING SUBMERGED ARC WELDING PROCESS

Abstract The invention provides an apparatus for single pass and root pass welding using submerged arc welding process which consists of a main support plate (1) being fastened to a bottom support plate (2) via a first fastening means (3) when the bottom surface of the main support plate (1) attached to a biasing means (8, 9) via a second fastening means (10). A water-cooled copper shoe (4) is provided with a plurality of support pins (7) designed corresponding to the sleeves (8) of the biasing means (8, 9). The copper shoe (4) being mounted on the bottom support plate (2) enables the copper shoe (4) to be in firm contact with the root weldable component (14). An inlet water tube (5) is prOVided for supplying cooled water. An outlet tube (6) is connected to a water hose (11) for draining the hot water from the channel (12). The main support plate is attachable and detachable to the submerged arc welding machine. The water cooled copper shoe (4) and a biasing means (7, 8, 9) moves in synchronization with the movement of submerged arc welding head when the copper shoe (4) is disposed with a cooling channel (12) for extracting heat during welding, wherein the welding head oscillates for filling the root gap effectively and for avoiding direct contact of arc with copper.
Full Text FIELD OF INVENTION
The invention relates to the single" pass welding and root pass welding in a multi-layer welding application. More particularly, the invention relates to an apparatus for making the root pass welding using submerged arc welding processes.
BACKGROUND OF THE INVENTION
Headers used in thermal power plants and process industries are produced from plate section. The headers generally constitute a tabular section formed from plate structure. The following manufacturing process is adopted:
As a first step, plates are bent to the required diameter. Both the edges of the plates are gas cut with an angle prior to bending and subsequently machined after bending. Then the edges of the preformed plates are joined together using Submerged Arc Welding (SAW) or a combination of submerged arc welding and Gas Metal Arc Welding (GMAW). In the first instance, for example, in the SAW-process, a steel backing plate is fitted with the joint to support the molten metal during root pass

-3-
welding; root and subsequent welding passes are made by submerged arc welding process; the steel backing plate is removed by machining method; and final machining is carried-out to arrive at the exact dimensions, wherever necessary. This process involves recurring cost of steel backing and subsequent machining leading to longer manufacturing cycle time. In the second method, the root pass is made with Gas Metal Arc Welding process and subsequent filling passes made with submerged arc welding process. The disadvantages of higher cost and higher manufacturing cycle time is equally applicable in this method too, for the similar reasons involved in the first alternative method described herein above. In a possible deviation of the process steps, for example in the second method, the edges may be cut after forming/bending. However, a suitable root joint configuration for root welding is still not feasible without permanent/temporary backing. Thus, the disadvantages still persist.
To produce hull structures in ships, long plates are joined together using either Submerged Arc Welding or Gas Metal Arc Welding process, after due edge preparation using conventional machining method. The length of the joints shall in most cases exceed 10meters of length and they need to be welded continuously. Due to this

-4-
requirement, it is difficult to maintain the gap between the plates and it is bound to vary between 2 to 15mm or more. For welding in such situations, backing in the root pass is a must, to take care of the varying root gaps. Backing can be either of a temporary type, like ceramic or flux backing, or a permanent type, for example, the same composition of the steel plate that is being welded. However, permanent steel backing is not desirable in such applications. The cost of temporary backing and the subsequent disposal of the backing debris are the disadvantage of the above method.
Canadian patent CA1171916 titled " Method and apparatus for forming a root bead by a submerged arc welding process" describes a method wherein the welding electrode is moved parallel to, and closely adjacent the gap, and the welding current is altered between a background current and the peak current. Variation in current levels facilitates forming the weld bead without burn-back through out the root. This invention is based on electrical input modification only and does not have a solution for wider root gap filling in thick section welding application based on mechanical innovation.

-5-
US patent no. 5590829 describes a mobile backing method for welding of box structures. In this invention, the mobile backing, mounted on a wheeled carriage and placed at the bottom of the joint, is separately powered and made to synchronize with the speed of welding head mounted on top of the joint. In this method, an elaborate control is needed to exactly synchronize and to overcome any obstruction that may come in the traversing path of the mobile backing or head at any given point during the welding operation. This invention cannot be used for general purpose applications involving other than box type structures. Hence, simplification of this invention with a possibility for general purpose applications could be one of the possible solutions to the existing problems.
US patent no. 6713710 describes an apparatus with a movable backing for flux cored wire plasma arc welding process for single pass welding. In this invention, the welding head is integrated with a spring loaded tracking roller arrangement. This can be used for single pass welding only, since the movable backing and the spring loaded tracking arrangement has to be detached, for using this set-up in a multi layer welding applications. In this design, the detachment of the apparatus will be cumbersome and time consuming. Also, this

-6-
arrangement due to difficulty in positioning of guide shaft rollers, is not suitable for welding of thick section pipes, which forms major part of Submerged Arc welding applications. The invention uses a roller for joint tracking. This arrangement is not suitable for Submerged Arc welding, since the groove/root gap will be filled with granulated flux materials and does not allow proper movement of the tracking roller. The integrated weld head and the tracking means, obstruct accessibility to the welding head during operation, including cleaning and maintenance. Although, the invention is suitable for root gaps between 3 to 10mm only, the same is not recommended for most of the applications using Submerged Arc welding process in which the root gap variations are from 8 to 15mm. More over, this invention does not take into account the effect of oscillation of the welding head to cover wider root gap variations.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an apparatus for making the root pass welding using submerged arc welding process for components of thickness above 6mm, with a root gap between 8 to 15mm.

-7-
Another object of the invention is to propose an apparatus for making the root pass welding using submerged arc welding process which can be attached to and detached from the Submerged Arc welding machine easily and quickly.
Yet another object of the invention is to propose an apparatus for making the root pass welding using submerged arc welding process, which enables making the root joints with gas cut edges including machined edges.
A further object of the invention is to propose an apparatus for making the root pass welding using submerged arc welding process, which is capable of providing a uniform under bead surface even with unevenness and offset in joint design.
A still further object of the invention is to propose an apparatus for making the root pass welding using submerged arc welding process, which is capable of covering a wide and varying root gaps, generated due to head oscillation in SAW.

-8-
A still another object of the invention is to propose an apparatus for making the root pass welding using submerged arc welding process, which is capable of avoiding the generation of disposable debris/slag on the rear side of the weld during root pass submerged arc welding. The description, which follows, is to be understood as only illustrative of a particular form of this invention. However, such a particular form is only an exemplary embodiment and invention is not intended to be taken restrictively to the example alone.
SUMMARY OF INVENTION
Accordingly there is provided
The apparatus is fitted on to a main support plate, which is having a provision for a simple mechanical fastening means at its top portion for integrating with the submerged arc welding machine. A water-cooled copper shoe/ backing plate is connected with a bottom support plate, thus enabling a synchronized movement of the assembly with the head of the submerged arc welding machine while welding. The cooper backing is held under pressure towards a bottom side of the joint with the help of a biasing means comprising sleeves and spring .

-9-
The apparatus of the invention is adaptable for single pass butt welding and root pass welding in a multilayer welding application using submerged arc welding process, which basically consists of a
movable water-cooled copper backing assembly including a spring

support mechanism to keep a water-cooled copper shoe firmly against the bottom surface of the joint. The proposed apparatus is suitable for making the root pass on a low cost gas cut edges and also machined grooves. The root pass is carried out with the same submerged arc welding machine, which is to be further used for laying filler layers in a multilayer application to complete the welding. For laying subsequent filling layers, the apparatus is simply detached or rotated at 90 degrees in the opposite direction to the weld direction. The apparatus is capable to compensate the effect of unevenness and offset in joint edges with the automatic tilting of copper shoe enabled by the spring mechanism. By adapting the apparatus single pass butt welds can be made including root pass submerged arc welding with root gaps between 5 to 8mm without oscillation of the welding head. Root gaps beyond 8mm and up to
15mm can be root pass welded using submerged are welding process

-10-
with the apparatus, by synchronizing the oscillation of the submerged arc welding head to cover the wide root gap with weld metal. The apparatus enables root pass welding without the need for back gouging operation prior to subsequent filling up passes after root welding. The apparatus is very simple to attach on to the submerged arc welding machine and detach with simple mechanical fastening. The operation of the apparatus is simple and accurate, since the apparatus is synchronized with the welding head. The apparatus can be also adapted to Gas Metal Arc Welding, Gas Tungsten and Plasma welding processes.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 of the invention illustrates the cross sectional view of the proposed apparatus for root submerged arc welding of plates and plate formed pipes according to the present invention.
Figure 2, shows the cross section of the water-cooled copper assembly of the apparatus as per the present invention.

-11-
Figure 3, shows the arrangement of the movable water cooled copper backing assembly of the apparatus placed on a plate formed pipe joint for root Submerged Arc welding according to the invention.
Figure 4, shows the schematic representation of the root bead formed using the apparatus of the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
As shown in Fig.-l, a main support plate (1) is prepared with a length depending on the provision for attaching with the head of the submerged arc welding, usually more than 500mm length and is fixed on to the submerged arc welding head with a simple mechanical fastening means. The detachment and attachment of the apparatus on to the Submerged Arc welding machine takes not more than a minute. The thickness and width of the main support plate (1) has the required rigidity to hold a water-cooled copper shoe (4), and a biasing means (7,8,9) during their movement in synchronization

-12-
with the movement of submerged arc welding head (not shown in the figure). The main support plate (1), is attached to a bottom support plate (2) via a first fastening means (3) which holds the water-cooled copper assembly (4,7,8,9), when pressurized against the bottom side (figure 3) of the proposed joint. The cooling water through an inlet water tube (5) is supplied via a flexible water hose (11) to a cooling channel (12) of the copper shoe (4) to enable extraction of heat energy during root welding operation. The outlet water is drained through the flexible water hose (11) which is further connected to the copper shoe (4) via an outlet tube (6). These tubes (5,6) are made of copper.
The copper shoe (4) is mounted on the bottom support plate (2). A plurality of sleeves (8) for providing support to a spring element (9) is mounted on the bottom support plate (2). The copper shoe (4) is provided with a plurality of support pins (7). The bottom surface of the plate (1) is attached to the spring client (9) via a second fastening means (10). This enables the copper shoe (4) to be in firm contact with the bottom surface of the plate (1) or plate formed pipe to be root welded (14). Also, the continuous heat extraction through the water channels (6,12) keeps the temperature of the copper shoe

-13-
(4)/backing as low as possible in order to avoid inadvertent melting of copper surface and sticking on to the surface of the plate/pipe component. The pressure exerted by the spring element (9) towards the bottom surface of the weld root (14), enables to nullify the effect of unevenness and offset in joint edges with the possibility of automatic tilt of the copper shoe (4) to ensure firm contact. For root gaps wider than 8mm, oscillation of the welding head to be used to fill the root gap effectively and to avoid direct contact of arc with copper. In order to obtain adequate root penetration and a good under bead, a groove (13) is provided on the copper shoe (4).
The process of root Submerged Arc welding, on a grooved joint design with movable water-cooled copper backing is observed to achieve adequate side wall penetration (15).

WE CLAIM
1. An apparatus for root pass welding using submerged arc welding process
comprising:
- a main support plate (1) being fastened to a bottom support plate (2) via
a first fastening means (3), the bottom surface of the main support plate
(1) attached to a biasing means (8, 9) via a second fastening means (10);
- a water-cooled copper shoe (4) provided with a plurality of support pins
(7) designed corresponding to the sleeves (8) of the biasing means (8, 9);
- the copper shoe (4) being mounted on the bottom support plate (2)
enabling the copper shoe (4) to be in firm contact with the root-weldable
component (14);
- an inlet water tube (5) for supplying cooled water;
- an outlet tube (6) connected to water hose (11) for draining the hot water
from the channel (12);
characterized in that,
the said main support plate is attachable and detachable to the submerged
arc welding machine, wherein the said water-cooled copper shoe (4) and a
biasing means (7, 8, 9) moves in synchronization with the movement of
submerged arc welding head when the copper shoe (4) is disposed with a
cooling channel (12) for extracting heat during welding, wherein the
welding head oscillates for filing the root gap effectively and for avoiding
direct contact of arc with copper.
2. The apparatus as claimed in claim 1, wherein the thickness of the
weldable components (14) is above 6 mm and width of the root gap is
between 8 to 15 mm.
3. The apparatus as claimed in claim 1, wherein the inlet and outlet tubes
(5, 6) are made of copper.
4. The apparatus as claimed in claim 1, wherein the copper shoe is provided
with at least one groove (13) for obtaining adequate root penetration.
5. The apparatus as claimed in claim 1, wherein the movable water-cooled
copper shoe (4) is capable of enabling higher side wall penetration (15).


The invention provides an apparatus for single pass and root pass welding using
submerged arc welding process which consists of a main support plate (1) being
fastened to a bottom support plate (2) via a first fastening means (3) when the
bottom surface of the main support plate (1) attached to a biasing means (8, 9)
via a second fastening means (10). A water-cooled copper shoe (4) is provided
with a plurality of support pins (7) designed corresponding to the sleeves (8) of
the biasing means (8, 9). The copper shoe (4) being mounted on the bottom
support plate (2) enables the copper shoe (4) to be in firm contact with the root
weldable component (14). An inlet water tube (5) is prOVided for supplying
cooled water. An outlet tube (6) is connected to a water hose (11) for draining
the hot water from the channel (12). The main support plate is attachable and
detachable to the submerged arc welding machine. The water cooled copper
shoe (4) and a biasing means (7, 8, 9) moves in synchronization with the
movement of submerged arc welding head when the copper shoe (4) is disposed
with a cooling channel (12) for extracting heat during welding, wherein the
welding head oscillates for filling the root gap effectively and for avoiding direct
contact of arc with copper.

Documents:

00281-kol-2007 correspondence-1.1.pdf

00281-kol-2007 form-18.pdf

0281-kol-2007-abstract.pdf

0281-kol-2007-assignment.pdf

0281-kol-2007-claims.pdf

0281-kol-2007-correspondence others.pdf

0281-kol-2007-description (complete).pdf

0281-kol-2007-drawings.pdf

0281-kol-2007-form1.pdf

0281-kol-2007-form2.pdf

0281-kol-2007-form3.pdf

281-KOL-2007-(19-09-2011)-CORRESPONDENCE.pdf

281-KOL-2007-ABSTRACT 1.1.pdf

281-KOL-2007-AMANDED CLAIMS.pdf

281-KOL-2007-CORRESPONDENCE-1.1.pdf

281-kol-2007-correspondence.pdf

281-KOL-2007-DESCRIPTION (COMPLETE) 1.1.pdf

281-KOL-2007-DRAWINGS 1.1.pdf

281-KOL-2007-EXAMINATION REPORT REPLY RECIEVED.pdf

281-kol-2007-examination report.pdf

281-KOL-2007-FORM 1 1.1.pdf

281-kol-2007-form 18.pdf

281-KOL-2007-FORM 2 1.1.pdf

281-kol-2007-form 3.1.pdf

281-KOL-2007-FORM-27.pdf

281-kol-2007-gpa.pdf

281-kol-2007-granted-abstract.pdf

281-kol-2007-granted-claims.pdf

281-kol-2007-granted-description (complete).pdf

281-kol-2007-granted-drawings.pdf

281-kol-2007-granted-form 1.pdf

281-kol-2007-granted-form 2.pdf

281-kol-2007-granted-letter patent.pdf

281-kol-2007-granted-specification.pdf

281-KOL-2007-OTHERS-1.1.pdf

281-KOL-2007-OTHERS.pdf

281-kol-2007-reply to examination report.pdf


Patent Number 247422
Indian Patent Application Number 281/KOL/2007
PG Journal Number 14/2011
Publication Date 08-Apr-2011
Grant Date 06-Apr-2011
Date of Filing 26-Feb-2007
Name of Patentee BAHARAT HEAVY ELECTRICALS LIMITED
Applicant Address BHARAT HEAVY ELECTRICALS LIMITED REGIONAL OPERATIONS DIVISION (ROD) PLOT NO:9/1,DJBLOCK 3RD FLOOR,KARUNAMOYEE, SALT LAKE CITY,KOLKATA-700091 HAVING ITS REGISTERED OFFICE AT BHEL HOUSE,SIRI FORT NEW DELHI-110049
Inventors:
# Inventor's Name Inventor's Address
1 GENGUSAMY NAIDU BUVANASHEKARAN WELDING RESEARCH INSTITUTE, BHARAT HEAVY ELECTRICALS LIMITED, TIRUCHIRAPPALLI-620 014 TAMIL NADU INDIA
2 MANNAR SAMY RAMAKRISHNAN WELDING RESEARCH INSTITUTE, BHARAT HEAVY ELECTRICALS LIMITED, TIRUCHIRAPPALLI-620 014 TAMIL NADU INDIA
3 KRISHNASAMY PADMANABAN WELDING RESEARCH INSTITUTE, BHARAT HEAVY ELECTRICALS LIMITED, TIRUCHIRAPPALLI-620 014 TAMIL NADU INDIA
PCT International Classification Number B23K9/18,35/12,35/02
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA