Claims:1) A fixture (400) to eliminate root oxidation in a welding process comprising:
a case (402) of hollow cylindrical shape provided with an integrally machined extending base (402(a)) at its bottom portion 5 to receive a tube of a pipe to tube joint and a pipe (602) of said pipe to tube joint inserted into said case (402) to mate against said tube, said case (402) provided with one opening (402(b)) along its wall thickness for inlet of an inert gas and another threaded opening (402(c)) along its wall thickness to receive a bolt (404) to 10 firmly held said pipe (602) in mating position with said tube; and
said welding process carried out in the inert gas environment by inserting a TIG torch into said pipe (602) up to said pipe to tube joint.
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2) The fixture (400) as claimed in claim 1, wherein said pipe (602) and said tube are made of Inconel 617 alloy.
3) The fixture (400) as claimed in claim 1, wherein any excess inert gas in said case (402) escapes through a gap (502) created between 20 said case (402) and said pipe (602). , Description:FIELD OF THE INVENTION:
The present invention relates to the field of fixtures used in a welding process. Particularly, the present invention relates to a fixture to eliminate root oxidation in a full penetration welding process.
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BACKGROUND OF THE INVENTION:
For the development of Advanced Ultra Super Critical boiler (AUSC) technology in the country, one of the gap areas which has been identified is the manufacture of a super heater header. The candidate material which has been selected for the supercritical header is alloy 617 which can operate satisfactorily under the 10 conditions of 710-degree C operating temperature and 310 ata pressure. The manufacturing of such as thick walled component made of alloy 617 was expected to pose great challenges mainly due to the material characteristics and the adoption of a relatively new welding technology. This Inconel 617 pipe to tube welding is the first of its kind, where we had adopted the full penetration joint, 15 which requires welding from the either side the vertical tube i.e., welding from inner side of the tube (autogenous TIG welding) followed by filling the groove from outer side. A special purpose TIG (Tungsten Inert Gas) torch has designed to do the autogenous welding from inner side but due to atmospheric air, the root is getting oxidized and penetration is not uniform or acceptable. 20
Referring to the figure 1(a), there is provided a pipe to tube joint 100 comprising a pipe 102 and a tube 104 placed adjoining to each other with a groove 106 in between therein.
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Referring to the figure 1(b), a TIG torch 200 is inserted into the pipe 102 to reach a mating location 103 of the pipe 102 and the tube 104 and a welding operation is performed therein at the mating location 103. This kind of welding operation results in the oxidation at the pipe to tube joint 100.
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None of the prior art disclosed a fixture which eliminate root oxidation during welding of the pipe to tube joints.
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Therefore, there is felt a need for development of a fixture to eliminate root oxidation in a welding process.
OBJECTS OF THE INVENTION:
An object of the present invention is to provide a fixture to eliminate root 5 oxidation in a full penetration welding process.
Another object of the present invention is to provide a fixture which facilitates in increasing the strength of the weld.
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One more object of the present invention is to provide a fixture which facilitates in uniform penetration at the root joint in a welding process.
Still another object of the present invention is to provide a fixture which facilitates in providing inert gas environment in a welding process. 15
Further another object of the present invention is to provide a fixture which acts a purging case in a welding process.
Yet another object of the present invention is to provide a fixture which helps in 20 achieving good quality weld at the pipe to tube joints, without any defects.
SUMMARY OF THE INVENTION:
In accordance with the present invention, a fixture to eliminate root oxidation in a welding process is provided, the fixture comprising a case to accommodate a tube 25 and a pipe mated against each other. The case is provided with one opening for inlet of an inert gas and another threaded opening to receive a bolt to firmly hold the pipe in mating position with the tube. The welding process is carried out in the inert gas environment by inserting a TIG torch into the pipe up to the mating position of the pipe and the tube. 30
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BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described with reference to the accompanying drawings in which:
Figure 1(a) illustrates a perspective view of a pipe to tube joint according to the 5 prior art;
Figure 1(b) illustrates a cross-sectional view of a pipe to tube joint of figure 1(a) and a method of welding thereof;
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Figure 2(a) illustrates a perspective view of a fixture in accordance with the present invention;
Figure 2(b) illustrates a cross-sectional view of a fixture of figure 2(a); and
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Figure 3 illustrates a perspective view of a fixture of figure 2(a) holding a pipe to tube joint for welding purposes in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
A preferred embodiment will now be described in detail with reference to 20 accompanying drawings. The preferred embodiment does not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.
Referring to fig 2(a) and 2(b), In accordance with the present invention, there is 25 provided a fixture 400 comprising a case 402 and a bolt 404. The case 402 is typically a hollow cylinder provided with an integrally machined extending base 402(a) at its bottom portion. The case 402 is also provided with one opening 402(b) along its wall thickness for inlet of an inert gas and another threaded opening 402(c) along its wall thickness to accommodate the bolt 404. 30
Referring to fig 3, the pipe to tube joint comprises a pipe 602 and a tube (not shown in the figure). The tube is inserted into the case 402 to rest against the
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integrally machined extending base 402(a) (not shown in the figure) followed by the insertion of the pipe 602 into the case 402 to mate against the tube. The pipe 602 is firmly held in mating position with the tube by means of engaging the bolt 404 against the pipe 602. An inert gas, typically argon is allowed to enter into the case 402 through the opening 402(a) and thereby surrounds the pipe 602 and the 5 tube. Any excess inert gas in the case 402 escapes through a gap 502 created between the case 402 and the pipe 602. A TIG torch is inserted into the pipe 602 to reach the mating position of the pipe 602 and the tube and welding operation is performed therein at the mating position in the inert gas environment thereby achieving a good quality weld without any defects. 10
Typically, the diameter of said fixture 400 depends on the diameter of said pipe 602 and said tube.
TECHNICAL ADVANCEMENTS: 15
A fixture to eliminate root oxidation in a welding process has several technical advantages including but not limited to the realization of:
? a fixture to eliminate root oxidation in a full penetration welding process;
? a fixture which facilitates in increasing the strength of the weld;
? a fixture which facilitates in uniform penetration at the root joint in a 20 welding process;
? a fixture which facilitates in providing inert gas environment in a welding process;
? a fixture which acts a purging case in a welding process; and
? a fixture which helps in achieving good quality weld at the pipe to tube 25 joints, without any defects.
Although the invention has been described herein above with reference to the embodiments of the invention, the invention is not limited to the embodiments described herein above. It is to be understood that modifications and variations of the embodiments can be made without departing from the spirit and scope of the 30 invention.