Claims:We claim:
1. A method (400) for repairing damaged part (4) of a base material (1), the method (400) comprising:
removing (402) damaged portion (4) of the base material (1) completely to form a vacant repair area (4);
repairing (404) the vacant repair area (4) by depositing a plurality of layers of repair material (3) by a welding process to form a welded repair area (5); and
heating (406) the welded repair area (5) upto a predetermined temperature to form a uniform penetration of the repair material.

2. The method (400) as claimed in claim 1, wherein the base material (1) is copper material.

3. The method (400) as claimed in claim 1, wherein the welding process is high frequency pulse TIG welding.

4. The method (400) as claimed in claim 1, wherein the heating (406) is done by local torch heating process to avoid formation of crack in the welded repair area (5) by thermal stress.

5. The method (400) as claimed in claim 1, wherein the predetermined temperature is in range from 150o C to 250o C to form uniform penetration.

6. The method (400) as claimed in claim 1, wherein the number of layers in the welded vacant repair area depends on the depth of the vacant repair area (2).

7. The method (400) as claimed in claim 1, wherein the repair material is copper alloy.

8. The method (400) as claimed in claim 1, wherein the plurality of layers of repair material (3) is deposited by high frequency pulse TIG welding process.

9. The method (400) as claimed in claim 1, wherein the repair material is decided upon material of the base material, wherein the repair material is an alloy of the base material with high physical and chemical properties.
, Description:A NEW APPROACH FOR REPAIR WELDING OF COPPER USED IN PIPE BENDING BY HIGH FREQUENCY GAS TUNGSTEN ARC WELDING PROCESS
FIELD OF INVENTION:
[001] The present subject matter described herein, relates to welding process, and, in particular, to a new approach for repair welding of copper used in pipe bending by high frequency gas tungsten arc welding. More particularly, the present subject matter relates to a method also entailing a localized pre-heat technique that is applied to a limited intermediate region of the weld repair prior to completion of the weld repair, and avoids a full post heat of the component.
BACKGROUND AND PRIOR ART:
[002] Copper and copper alloys offer a unique combination of material properties that makes them advantageous for many manufacturing environments. They are widely used because of their excellent electrical and thermal conductivities, outstanding resistance to corrosion, ease of fabrication, and good strength and fatigue resistance. Other useful characteristics include spark resistance, metal-to-metal wear resistance, low-permeability properties, and distinctive color.
[003] In manufacturing, copper is often joined by welding. The arc welding processes are of primary concern. Arc welding can be performed using shielded metal arc welding (SMAW), gas-tungsten arc welding (GTAW), gas-metal arc welding (GMAW), plasma arc welding (PAW), and submerged arc welding (SAW). Copper and most copper alloys can be joined by arc welding. Welding processes that use gas shielding are generally preferred. Gas-tungsten arc welding is well suited for copper and copper alloys because of its intense arc, which produces an extremely high temperature at the joint and a narrow Heat-Affected Zone (HAZ).
[004] In welding the copper and the more thermally conductive copper alloys, the intensity of the arc is important in completing fusion with minimum heating of the surrounding the highly conductive base metal. A narrow HAZ is particularly desirable in the welding of copper alloys that have been precipitation hardened.
[005] Many of the standard tungsten or alloyed tungsten electrodes can be used in GTAW of copper and copper alloys. The selection factors normally considered for tungsten electrodes apply in general to the copper and copper alloys. Except for the specific classes of copper alloys, thoriated tungsten (usually EWTh-2) is preferred for its better performance, longer life, and greater resistance to contamination.
[006] Consequently, weld repair techniques have been proposed using filler materials that do not require post-weld heat treatment. However, such techniques are generally limited to temporary repairs and some noncritical applications, because weld repairs that undergo post-weld heat treatment generally exhibit superior properties. Other alternatives for making weld repairs without post-weld heat treatment include various temper bead welding techniques, in which a carefully controlled welding sequence provides some degree of tempering by superimposing a suitable temperature region of the HAZ from the weld bead being deposited on a hard portion of a HAZ from a previously deposited weld bead. Such techniques have been performed in an attempt to provide beneficial softening of hard metallurgical structures in the HAZ.
[007] United States Patent 4460659 titled “Copper alloy welding filler and method of use” discusses a copper alloy welding filler for use in arc welding copper to produce sound welds with good mechanical strength and high electrical conductivity is disclosed. The filler consists essentially of a zirconium-boron copper alloy filler metal wherein the concentration ratio of zirconium to boron is at least about 4 to 1; the minimum concentration of boron is about 300 PPM; and the concentration of zirconium is a maximum of about 6000 PPM. The minimum level of about 300 PPM boron on a weight basis eliminates porosity in the weld; while zirconium below about 6000 PPM is effective to eliminate weld cracking without having a detrimental effect on the electrical conductivity.
[008] Japanese Patent JPH071086 titled “Method for repairing copper-made casting mold” discusses to restore the inner wall surface in a mold to an original flattened surface by applying masking treatment to the part except worn parts, dipping the mold in a copper-plating bath and executing electroplating to it. On the inner wall surface of the copper-made casting mold 1, worn parts 2 are in existence. By applying the material free from erosion in the copper-plating bath and having, at the same time, electric insulation property on the surface of the mold 1 except the worn parts 2, the masking layer 3 is formed. Successively, the mold 1 is dipped into the copper-plating bath 4 and connected to a negative pole of a DC electric source 5. Further, a consumable electrode 6 is arranged opposite the worn parts 2 without contact so as to cover the whole of the worn parts 2 and connected to a positive pole. By this method, the thickness in the worn parts 2 is restored according to progress of the electroplating.
[009] German Patent DE4314275 titled “Method of welding copper pipes” discusses a method of joining thin-walled copper pipes in pipeline construction which enables a metallic joint to be made between copper pipes without foreign metals such as silver being incorporated in the joint and so that definable stability of the joint is obtained, it is proposed to increase the material thickness in the joining area of the copper pipes and to make the metal joint by arc welding.
[0010] Accordingly, what is needed is a reliable weld repair technique with high frequency gas tungsten arc welding process for copper alloys used to form induction heating that produces a long-lasting weld repair without resorting to post-weld heat treatment of the repaired component and without causing distortion of the component.
OBJECTS OF THE INVENTION:
[0011] The principal objective of the present invention is to provide a reliable weld repair technique with high frequency gas tungsten arc welding process for copper alloys used to form induction heating in pipe bending applicaitons.
[0012] Another object of the present subject matter is to provide a long-lasting weld repair without resorting to post-weld heat treatment of the repaired component and without causing distortion of the component.
[0013] Another object of the present subject matter is to provide a welding method for repairing copper tubes/pipes in bending by high frequency gas tungsten arc welding.
[0014] Yet another object of the present subject matter a method for entailing a localized pre-heat technique that is applied to a limited intermediate region of the weld repair area prior to completion of the weld repair, and avoids a full post heat of the component.
[0015] Yet another object of the present subject matter is provide narrow Heat-Affected Zone (HAZ) and locally heating the HAZ to avoid complete pre heating of the component.
SUMMARY OF THE INVENTION:
[0016] The subject matter disclosed herein relates to a method for repairing welding of copper used in pipe bending by high frequency gas tungsten arc welding. In the present the method, damaged portion of the base material completely removed to form a vacant repair area. The base material is copper material. The vacant repair area is bigger in size and area as compared to initial crack. The vacant repair area is covered by depositing a plurality of layers of repair material by a welding process. The repair material is a copper alloy. Further, the repair material is decided upon material of the base material, wherein the repair material is an alloy of the base material with high physical and chemical properties. The plurality of layers of repair material can be deposited one by one in the vacant repair area. Further, number of layers in the vacant repair area depends on the depth of the vacant repair area. If depth is more, number of layers is more. The welding process is high frequency pulse TIG welding in which heat input is very much controlled so that a controlled and uniform penetration can be achieved. Once the layer of the repair material is deposited, the deposited layer is pre-heated with localized pre-heat technique which is applied on the limited intermediate region of the weld repair area. The heating of the welded vacant repair area upto a predetermined temperature to form a uniform penetration of the repair material. The heating is done by local torch heating process to avoid formation of crack in the welded vacant repair area by thermal stress. The local torch heating process is localized pre heat technique which heated the limited intermediate region upto 150o C to 250o C to avoid formation of Heat-Affected Zone (HAZ). The local torch heated the limited region and avoids full post heating of the component upon completion of the work.
[0017] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0019] Fig. 1 illustrates schematic cross section of the copper alloy material having crack defect, in accordance with an embodiment of the present subject;
[0020] Fig. 2 illustrates cross section of the copper alloy material, wherein a crack defect has been ground for repair structure, in accordance with an embodiment of the present subject;
[0021] Fig. 3 illustrates schematic cross section of the copper alloy material where the weld repairing is finished by high frequency gas tungsten arc welding, in accordance with an embodiment of the present subject; and
[0022] Fig. 4 illustrates a method for repairing the copper base material by avoid HAZ, in accordance with an embodiment of the present subject.
[0023] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0024] The subject matter disclosed herein relates to a method for repairing welding of copper used in pipe bending by high frequency gas tungsten arc welding. More particularly, the present subject matter relates to a method for entailing a localized pre-heat technique that is applied to a limited intermediate region of the weld repair prior to completion of the weld repair, and avoids a full post heat of the component. In the present the method, damaged portion of the base material completely removed to form a vacant repair area. The base material is copper material. The vacant repair area is bigger in size and area as compared to initial crack. The vacant repair area is covered by depositing a plurality of layers of repair material by a welding process. The repair material is a copper alloy. Further, the repair material is decided upon material of the base material, wherein the repair material is an alloy of the base material with high physical and chemical properties. The plurality of layers of repair material can be deposited one by one in the vacant repair area. Further, number of layers in the vacant repair area depends on the depth of the vacant repair area. If depth is more, number of layers is more. The welding process is high frequency pulse TIG welding in which heat input is very much controlled so that a controlled and uniform penetration can be achieved. Once the layer of the repair material is deposited, the deposited layer is pre/post-heated with localized pre/post-heat technique which is applied on the limited intermediate region of the weld repair area. The heating of the welded vacant repair area upto a predetermined temperature to form a uniform penetration of the repair material. The heating is done by local torch heating process to avoid formation of crack in the welded vacant repair area by thermal stress. The local torch heating process is localized pre heat technique which heated the limited intermediate region upto 150o C to 250o C to avoid formation of Heat-Affected Zone (HAZ). The local torch heated the limited region and avoids full post heating of the component upon completion of the work.
[0025] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0026] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0027] Figure 1, 2, and 3 illustrate cross section of the crack or damaged portion in the copper base material, removing of damaged potion and depositing layers of repair material in the damaged portion to repair the base material. FIG. 1 shows a base material 1 which has a damaged portion 4. As shown in figure 3, a weld repair 3 has been built up to restore the base material to its original dimensions after a damaged portion has been ground 2 removed. The weld repair 3 generally includes one or more weld repair layers that have been deposited on the surface of the base material 1 to yield a surfacing weld repair.
[0028] Fig. 4 illustrates a method for repairing the copper base material by avoiding HAZ, in accordance with an embodiment of the present subject. Figure 1, 2, and 3 are taken to explain the method. In the present the method 400, damaged portion 4 of the base material is identified by known methods. Once the damaged portion 4 is identified, the damaged portion 4 of the base material 1 is completely removed to form a vacant repair area 2 (as shown in figure 2) at step 402. The base material 1 is copper material. The vacant repair area 2 is bigger in size and area as compared to initial crack 4 (as shown in figure 1). The vacant repair area 2 is repaired by depositing a plurality of layers of repair material 3 by a welding process, at step 404. The repair material 3 is a copper alloy. Further, the repair material 3 can be decided upon material of the base material 1, wherein the repair material 3 is an alloy of the base material 1 with high physical and chemical properties. The plurality of layers of repair material 3 can be deposited one by one in the vacant repair area 2. Further, number of layers in the vacant repair area 2 depends upon the depth of the vacant repair area 2. If depth is more, number of layers is more.
[0029] The welding process is high frequency pulse Tungsten Inert Gas (TIG) welding in which heat input is very much controlled so that a controlled and uniform penetration can be achieved. In manufacturing, copper is often joined by welding. The Arc welding can be performed using Shielded Metal Arc Welding (SMAW), Gas-Tungsten Arc Welding (GTAW), Gas-Metal Arc Welding (GMAW), Plasma Arc Welding (PAW), and Submerged Arc Welding (SAW). Copper and most copper alloys can be joined by arc welding. Welding processes that use gas shielding are generally preferred. Gas-tungsten arc welding GTAW or TIG welding is well suited for copper and copper alloys because of its intense arc, which produces an extremely high temperature at the joint and a narrow Heat-Affected Zone (HAZ).
[0030] In welding the copper and the more thermally conductive copper alloys, the intensity of the arc is important in completing fusion with minimum heating of the surrounding the highly conductive base metal. A narrow HAZ is particularly desirable in the welding of copper alloys that have been precipitation hardened.
[0031] At step 406, once the layer of the repair material is deposited in the vacant repair area and forms welded repair area. The deposited layer of the welded repair area is pre-heated with localized pre-heat technique which is applied on the limited intermediate region of the welded repair area. The heating of the welded repair area upto a predetermined temperature to form a uniform penetration of the repair material. The heating is done by local torch heating process to avoid formation of crack in the welded vacant repair area by thermal stress. The local torch heating process is localized pre heat technique which heated the limited intermediate region upto 150o C to 250o C to avoid formation of Heat-Affected Zone (HAZ). The local torch heated the limited region and avoids full post heating of the component upon completion of the work.
[0032] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.