FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“CONTROLLING DISTORTION OF ONE OR MORE COMPONENTS WHEN JOINING”
APPLICANTS:

Name Nationality Address
BHARAT HEAVY ELECTRICALS LIMITED Indian BHEL HOUSE, SIRI FORT, NEW DELHI – 110049, INDIA., with one of its manufacturing units at
High Pressure Boiler Plant, Tiruchirapalli - 620014, Tamil Nadu

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-
TECHNICAL FIELD
[001] Embodiments herein relate to welding of components and, more particularly, to controlling of distortion which occurs in objects during welding and at least substantially reducing or eliminating requirement for correction of distortion after welding.

BACKGROUND
[002] Generally, components such as pipes, rods and other metal objects are widely used in the manufacturing of automobiles, boilers, and other structures. Typically, these structures require some of the components to be joined. Fabrication and joining of such components employ various methods such as welding, soldering and the like. Employing methods like welding, soldering and the like result in distortion and deformation of the objects due to the manner in which the methods are employed.
[003] Distortion occurs as a result of industrial metal working process that employs heat, such as welding. Distortion in welded objects is a result of non-uniform expansion and contraction of the weld and the surrounding base material, caused by the heating and cooling cycles of the welding process. Because the expansion and subsequent contraction of the material is restrained by the surrounding colder material, tensile stress is built up around the weld combined with simultaneously generated compressive stress in the rest of the material. The above mentioned stresses cause distortion if they reach a threshold level.
[004] Generally, distortion in a base component over which other component(s) are welded is corrected using cold bow correction process. In the cold bow correction process, the base component, which has been distorted during welding, is cold pressed so that the base component regains the shape it had before distortion. However, in certain situations correction by cold pressing may lead to cracks as a result of as-welded hardness of the material. Further, the configuration and shape of certain components welded on a base component may not allow carrying out correction procedure through cold pressing.
[005] Further, distortion occurred in the components that are welded can also be corrected using hot correction process. However, hot correction process is not recommended in certain situations, as any inadvertent heating at some spots of the distorted components above its transformation temperature can lead to micro-structural changes which can impair creep properties of the components, requiring additional heat-treatments to restore properties.
[006] In light of the foregoing, there is a need for a method and assembly for controlling distortion of components that occurs during welding. Further, the method and apparatus should at least substantially reduce the need for distortion correction after welding or substantially eliminate correction of distortion after welding.

STATEMENT OF INVENTION
[007] In view of the foregoing, an embodiment herein provides an assembly for controlling distortion in a component while welding the component to a base component. The assembly includes at least one fixture and at least a pair of setting stubs. The fixture defines at least one aperture for receiving the component which will be welded to the base component. Each of the pair of setting stubs has a first end engaged with the fixture and a second end engaged with the base component. The component received by the aperture is oriented towards a corresponding location on the base component, and the component and the base component are joined by welding.
[008] Further, a method for controlling distortion experienced by a base component while welding one or more components to the base component is provided. The method includes determining extent of distortion and direction in which the base component would distort when the components are welded to the base component. Subsequently, base component bent approximately to the determined extent in a direction opposite to the direction in which the base component would distort when the components are welded to the base component. Thereafter, components are welded to the base component.
[009] A method for controlling distortion while welding one or more components to a base component is provided. The method included bending the base component in a direction opposite to a direction in which the base component would be distorted when the components are welded to the base component. Further, a first end of each of a pair of setting stubs is engaged with a fixture comprising one or more apertures for receiving the component. A second end of each of the pair of setting stubs is engaged with the base component. The components are received through the apertures and welded to the base component.
[0010] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF THE FIGURES
[0011] Embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0012] FIG. 1a illustrates a base component, in accordance with an embodiment;
[0013] FIG. 1b illustrates a base component which has been distorted after welding, in accordance with an embodiment;
[0014] FIG. 1c illustrates a base component which is bent prior to welding, in accordance with an embodiment;
[0015] FIG. 1d illustrates a comparison between base component before it is bent and the base component after it is bent, in accordance with an embodiment;
[0016] FIG. 2a, 2b and 2c illustrates an assembly for controlling distortion in components while welding the components to a base component, in accordance with and embodiment; and
[0017] FIG. 3a, 3b and 3c illustrates a fixture defining plurality of apertures for receiving components, in accordance with an embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
[0018] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0019] The embodiments herein disclose an apparatus and a method for controlling distortion during welding. Referring now to the drawings, and more particularly to FIGS. 1 through 3, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0020] FIG. 1a illustrates a base component 102, in accordance with an embodiment. In an embodiment, the base component 102 is a metal component or an alloy component to which other metal or alloy components can be joined using welding process. The base component 102 can be a pipe, tube, rod, or plate, among others. The base component 102 illustrated in FIG. 1 is a pipe. Generally, when a prior known process is used to join components to the base component 102 using welding, the base component 102 gets distorted. FIG. 1b illustrates base component 102 which has been distorted after welding. In FIG. 1b, the components that are welded to the base component 102 are not illustrated. The base component 102 is distorted as a result of the welding carried out to join the components to the base component 102. In an embodiment, distortion experienced by base component 102 while welding one or more components to the base component 102 is controlled.
[0021] In an embodiment, distortion experienced by base component 102 while welding one or more components to the base component 102 is controlled by determining extent of distortion and direction in which the base component 102 would distort when the components are welded to the base component 102. Thereafter, the base component 102 is bent approximately to the determined extent in a direction opposite to the direction in which the base component 102 would get distorted when the components are welded to the base component 102. Thereafter, the components are welded to the base component 102.
[0022] In an embodiment, direction in which the base component 102 distorts after welding the components to the base component 102 will depend on locations on the base component 102 at which welding is performed to join the components to the base component 102.
[0023] In an embodiment, the extent of distortion experienced by the base component 102 when the components are welded to the base component 102 is determined by the following equation:
d = 0.35 * (q / v) * (? / c?) * (z/I) * L*2 / 8
Where,
d is the bending distortion of base component 102 in mm;
q is the heat input during welding process in watts;
v is the welding speed in mm / sec;
? is the coefficient of thermal expansion of base component 102 in mm / mm °C;
c? is the volumetric specific heat in J / mm °C;
c- Specific heat J/( KG °C)
?- Density (kg/ mm³ )
z is the neutral axis to weld axis distance in mm;
I is the moment of inertia of base component 102 in mm4;
L is the length of the base component in mm;
[0024] Subsequent to determination of extent of distortion and direction in which the base component 102 would get distorted when the components are welded to the base component 102, the base component 102 is bent in the opposite direction. FIG. 1c illustrates base component 102 that is bent prior to welding, in accordance with an embodiment. The base component 102 in FIG. 1c is bent in a direction opposite to the direction in which the base component 102 would get distorted when the components are welded to the base component 102. Further, the extent to which the base component 102 is bent in the opposite direction prior to welding is substantially equal to the extent to which the base component 102 would get distorted when the components are welded to base component 102. FIG. 1d illustrates a comparison between the base component 102 before it is bent and the base component 102 after it is bent, in accordance with an embodiment. At the centre of longitudinal axis 104, 106 (illustrated by dotted lines) of the base component 102, an offset of “d” is created between the longitudinal axis 104 of the base component 102 before bending and the longitudinal axis 106 of the base component 102 after bending. In an embodiment, “d” is calculated using the equation provided hereinabove.
[0025] Subsequent to bending the base component 102, the components are welded to the base component 102. The base component 102 gets distorted as a result of welding, thereby the offset “d” is reduced to approximately zero, thereby, at least substantially eliminating the need for distortion correction of the base component 102 after welding.
[0026] It has been observed that components that are welded to the base component 102 also experience distortion when prior known methods are employed. An embodiment provides an assembly for controlling distortion in a component while welding the component to the base component 102, as illustrated in FIG 2a, 2b and 2c. The assembly comprises, at least one fixture 206 and at least a pair of setting stubs 202a1 and 202a11. The fixture 206 has at least one aperture 208 for receiving at least one component 210 that will be welded to the base component 102. The component 210 that is received is oriented towards a corresponding location on the base component 102, where the component 210 and the base component 102 are joined by welding. First end of each of the setting stubs 202a1 and 202a11 are engaged with the fixture 206 and second end of each of the setting stubs 202a1 and 202a11 are engaged with the base component 102. The assembly illustrated in FIG 2a, 2b and 2c has four fixtures 206 (only one can be seen), and each of the fixture 206 is engaged with their respective pair of setting stubs 202a1 and 202a11, 202b1 and 202b11 (not shown), 202c1 and 202c11 (not shown), and 202d1 and 202d11(not shown). Each of the fixtures 206 has three apertures 208 for receiving three components 210 which will be welded to the base component 102. In an embodiment second end of each of the setting stubs 202 are directly engaged with the base component 102. In an embodiment, the second ends are welded to the base component 102. In another embodiment, the second ends of each of the setting stubs 202a1,202a11, 202b1, 202b11 (not shown), 202c1 202c11 (not shown), 202d1 and 202d11(not shown) are engaged with stub pad 204a1, 204a11, 204b1, 204b11 (not shown), 204c1, 204c11 (not shown), 204d1 and 204d11 (not shown), respectively. The stub pads 204 are in turn engaged with the base component 102. In an embodiment, the second end of each of the setting stubs 202 is welded to the stub pads 204, and the stub pads 204 are welded to the base component 102.
[0027] In an embodiment, the distance between adjacent fixtures 206 and adjacent setting stubs 202 are maintained by means of a pair of support fixtures 212a1 and 212a11.
[0028] The number of apertures 208 in the fixtures 206 depends on the number of components that need to be welded to the base component 102. Further, the cross section of the aperture 208 depends on the cross section of the component 210 that the aperture 208 is designed to accommodate. FIG. 3a, 3b, and 3c illustrate fixture 206 defining plurality of aperture 208 for receiving components 210, in accordance with an embodiment. As seen in FIG. 3a, 3b and 3c the cross section of the aperture 208 varies based on the cross section of the component that aperture 208 is designed to accommodate and the angle at which the component 210 has to be welded to the base component 102. Additionally, the distance between adjacent fixtures 206 depends on the desired layout of components 210 that are welded to the base component. Further, alignment of setting stubs 202 would vary based on welding layout of components 210 and base component 102.
[0029] Subsequent to engagement of the assembly with the base component 102, the components 210 are passed through their respective aperture 208. Thereafter the component 210 is welded to the base component 102. This arrangement controls the distortion experienced by the components 210 while the same is joined to the base component 102 by welding, thereby at least substantially reducing or eliminating correction of distortion in the components 210 after welding.
[0030] After completion of welding, the assembly is disengaged from the components 210 and the base component 102.
[0031] In an embodiment where the setting stubs 202 are welded to the base component 102, the setting stubs 202 are disengaged from the base component by grinding.
[0032] In another embodiment where stub pads 204 are welded to the base component 102, the setting stubs 202 which are welded to the stub pads 204 are removed by gas cutting. Further, any excess stub pads 204 material is flush ground.
[0033] In an embodiment, the base component 102 is a pipe made of SA335P91 material.
[0034] In an embodiment, the setting stubs 202 are SA213T22 tubes.
[0035] In an embodiment, the components 210 are of T91 tube materials.
[0036] In an embodiment, stub pads 204 are made of stainless steel material.
[0037] The various actions in disclosed method may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed may be omitted.
[0038] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

What is claimed is:
1. An assembly for controlling distortion in a component while welding the component to a base component, the assembly comprising:
a fixture defining at least one aperture for receiving the component; and
a pair of setting stubs each having a first end engaged with the fixture and a second end engaged with the base component, wherein the component received by the aperture is oriented towards a corresponding location on the base component, wherein the component and the base component are joined by welding.
2. The assembly according to claim 1, wherein the fixture has multiple apertures capable of receiving components to be welded to the base component.
3. The assembly according to claim 1, further comprising plurality of fixtures for receiving components to be welded to the base component.
4. The assembly according to claim 3, wherein each of the plurality of fixtures are engaged by a pair of setting stubs, wherein the first ends of each of corresponding pair of setting stubs are engaged with the corresponding fixture and the second ends of the setting stubs are engaged with the base component.
5. The assembly according to claim 3, wherein distance between adjacent fixtures and adjacent setting stubs are maintained by means of a pair of support fixtures.
6. The assembly according to claim 1, wherein the second end of each of the setting stubs is engaged with a stub pad which in turn is engaged with the base component.
7. The assembly according to claim 1, wherein the second end is welded to the stub pad and the stub pad is welded to the base component.
8. The assembly according to claim 1, wherein the base component is bent prior to engaging the assembly with the base component to compensate for the distortion experienced by the base component when the component is welded to the base component.
9. A method for controlling distortion experienced by a base component while welding one or more components to the base component, the method comprising:
determining extent of distortion and direction in which the base component would be distorted when the components are welded to the base component;
bending the base component approximately to the determined extent in a direction opposite to the direction in which the base component would be distorted when the components are welded to the base component; and
welding the components to the base component.
10. The method according to claim 9, wherein the extent to which the base component would distort when the components are welded to the base component is determined using the equation:
d=0.35 (q/v). (a/cp). (z/I). L2/8
Where d is bending distortion of the base component in mm, q is a heat input during welding process in watts, v is a welding speed in mm/sec, a is a coefficient of thermal expansion of the base component in mm/mm ?C, cp is a volumetric specific heat in J/mm ?C, z is a neutral axis to weld axis distance in mm, I is a moment of inertia of the base component in mm4, L is a length of the base component in mm.
11. A method for controlling distortion while welding one or more components to a base component, the method comprises:
bending the base component in a direction opposite to a direction in which the base component would be distorted when the components are welded to the base component;
engaging a first end of each of a pair of setting stubs with a fixture comprising one or more apertures for receiving the component;
engaging a second end of each of the pair of setting stubs with the base component;
receiving the components through the apertures; and
12. welding the components to the base component. An assembly for controlling distortion in a component while welding the component to a base component substantially as herein above described in the specification with reference to the accompanying drawings.
13. A method for controlling distortion experienced by a base component while welding one or more components to the base component substantially as herein above described in the specification with reference to the accompanying drawings.

Date this 11th August 2009

Mr. Nishant Kewalramani
Patent Agent