High energy keyhole welding method and pipe assembly therefrom

Abstract

The present invention relates to a high-energy keyhole welding method comprising: a primary welding step of filling a weld portion of two base materials in which a groove is formed in at least one base material with filler material; and a secondary welding step of using high-energy keyhole welding on the weld portion filled with filler material. In addition, the present invention also discloses a pipe assembly joined by a keyhole welding method.

Description

Technology Field

[0001] The present invention relates to a high-energy keyhole welding method and a pipe assembly according thereto, and more specifically, to a high-energy keyhole welding method and a pipe assembly according thereto in which butt joints are welded in a high-energy keyhole manner, wherein at least one base material has a groove formed thereon. Background Technology

[0002] Generally, piping refers to the installation of pipes, tubes, and hoses for the purpose of transporting fluids such as liquids, gases, and powders, or for protecting wiring, and the term also refers to the pipes themselves. Piping used in the plant industry plays a role in supplying and controlling various fluids or gases. Since these pipes are primarily exposed to various environments such as high temperature, high pressure, and chemical corrosion, they are made of various materials such as stainless steel, carbon steel, low-alloy steel, non-ferrous metals, and PVC suitable for each specific application, and are manufactured in various diameters and thicknesses depending on the intended use.

[0003] Meanwhile, piping installed in large-scale factories requires connecting standardized pipes of specified sizes and / or shapes to extend them to the required length or bend them in the required direction. These pipe connections are primarily achieved by welding.

[0004] Generally, Tungsten Inert Gas (TIG) welding or Gas Tungsten Arc Welding (GTAW) technology began in the 1940s and is still widely used today in places requiring high-quality welding. Almost 100% of semiconductor piping is welded using TIG welding.

[0005] However, conventional TIG welding has the disadvantage that, because it uses low energy, the welding heat does not sufficiently penetrate from the surface of the base material to the core to melt it; therefore, to form excellent inner and outer beads in a single weld, it can typically only be applied up to a maximum thickness of 3 mm. Consequently, to weld a base material (pipe) with a thickness of 3 mm or more, a preliminary step must be taken to form a groove (e.g., a bevel groove) that opens the upper surface of the butting base materials to expose them down to the bottom surface. As shown in Fig. 1, when a groove is formed, the process cannot be completed in a single weld, so two or more welds must be performed; consequently, the welding time required is long, resulting in low productivity.

[0006] In addition, in the case of butt welding with improved welds, there was a problem in that it was difficult to automate conventional manual TIG welding because a perfect weld result must be achieved through the skill of a skilled welder who adjusts welding parameters (weld head movement, gap, speed, current, etc.) in response to step variations and minute gap variations caused by the difference in diameter and thickness between the two base materials.

[0007] Meanwhile, this technology, developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) of the Australian government in the 1980s to solve the problem of low productivity in conventional manual TIG welding, implemented keyhole welding in GTAW welding, which was previously only possible through plasma, laser welding, or electron beam welding, and was named High Energy Keyhole TIG Welding (also named 'K-TIG'). High Energy Keyhole TIG Welding technology is a technology that performs TIG welding with a current of 300 to 1,000 A, which is much larger than the welding current of 50 to 300 A mainly used in manual TIG welding.

[0008] High-energy keyhole TIG technology effectively cools the welding head by equipping it with a water cooling system, thereby preventing damage to the head due to overheating. It also effectively cools the tungsten electrode and concentrates energy only on the tip portion of the electrode, increasing the density and penetration power (Arc Pressure) of the welding arc. This allows for welding base materials with a thickness of 3mm to 16mm in a single pass, significantly improving productivity. Furthermore, since keyhole TIG welding can be performed even when the base material is vertically cut and butted without forming grooves in the base material, automation becomes simple and easy.

[0009] However, because high-energy keyhole TIG welding uses high energy, there is a disadvantage in that the welding quality is affected by the mounting condition of the base material, such as when the gap between the butt joints of two base materials prepared by vertical cutting is uneven, or when grooves are formed on one or both sides of the base material, resulting in uneven thickness of the weld area. In such cases, the allowable range of parameter settings for the keyhole welding process is drastically reduced, which can lead to welding defects such as 'burn-out' (over-welding) or 'insufficient penetration' (insufficient welding). For example, when welding with a welding current of 400A, there is a problem where excessive heat is generated in a specific area causing burn-out, and if the energy is lowered to 350A to prevent this, there is insufficient heat in other areas causing insufficient penetration.

[0010] Meanwhile, so-called "elbow pipes," which are curved pipes supplied by piping material suppliers for the fabrication of piping assemblies, are manufactured and delivered under the assumption that they will be welded manually by a welder using conventional low-energy TIG welding machines. Consequently, most of these elbow pipes are received with their ends machined at a specific angle (similar to a "correction" in the welding process). In this case, to apply high-energy keyhole TIG welding, the ends of the elbow pipes must be cut vertically again. While this facilitates high-energy keyhole TIG welding, it cannot be applied to low-energy manual TIG welding. Consequently, there is a problem in that flexibility between low-energy manual TIG welding and high-energy TIG welding operations cannot be ensured to suit on-site conditions. The problem to be solved

[0011] The present invention was devised to solve the problems of the prior art and aims to provide a high-energy keyhole welding method with improved workability and a pipe assembly based thereon, so that defects such as burn-through or insufficient penetration do not occur when keyhole TIG welding technology is applied to actual welding.

[0012] In addition, the present invention aims to provide a high-energy keyhole welding method and a piping assembly based thereon, which can expand the range of welding conditions such as current, speed, wire feed, and base material spacing by performing keyhole TIG welding as a primary welding (pre-welding) and a secondary welding (high-energy welding) to primarily fill or compensate for welds with irregular spacing or welds with improved spacing.

[0013] The present invention aims to solve the existing disadvantages occurring in high-energy keyhole TIG welding and to provide a welding method that forms sound inner and outer beads. means of solving the problem

[0014] A high-energy keyhole welding method according to one embodiment of the present invention for achieving the above objective comprises: a first welding step of filling a weld portion of two base materials in which a groove is formed in at least one base material with filler material; and a second welding step of using high-energy keyhole welding on the area of ​​the weld portion filled with filler material.

[0015] Preferably, the first welding step uses arc welding to melt the filler material and fill the weldment.

[0016] Preferably, the arc welding includes gas tungsten arc welding (GTAW), covered metal arc welding (SMAW), gas metal arc welding (GMAW), or flux-cored arc welding (FCAW).

[0017] Preferably, the primary welding step utilizes the Melt-In Mode of arc welding.

[0018] Preferably, the melt-in mode is performed as a primary welding step under conditions in which the filler material is melted and filled into the weld using a low-energy welding method with a current ranging from 50A to 250A.

[0019] Preferably, the secondary welding step uses high-energy TIG welding in which the welding arc completely penetrates the base materials and the filler material in a single weld to create a keyhole and melts up to the opposite surface of the base materials.

[0020] Preferably, the secondary welding step utilizes plasma arc welding (PAW) or laser welding.

[0021] Preferably, the plasma arc welding or laser welding is performed at an energy range capable of forming a back bead by melting the opposite surface to form a keyhole.

[0022] Preferably, the primary welding step includes a step of filling a portion of the volume of the weld with the filler material so that insufficient penetration and burn-through do not occur in the secondary welding step.

[0023] Preferably, in the primary welding step, a back bead may or may not be formed.

[0024] Preferably, the angle of improvement is 5˚ to 85˚.

[0025] Preferably, the angle of improvement is 30˚.

[0026] Preferably, the root gap between the base materials is 4.0 mm or less.

[0027] Preferably, improvements are formed on both of the two base materials to form the weldment.

[0028] Preferably, the root gap between the base materials is 4.0 mm or less.

[0029] Preferably, each of the above-mentioned base materials has an improved portion in which an improvement is formed and a non-improved portion in which an improvement is not formed.

[0030] Preferably, the improvement is linear, curved, or a combination of linear and curved types.

[0031] Preferably, one of the above base materials is a straight metal pipe and the other is a metal elbow-type fitting or another straight metal pipe.

[0032] The aforementioned objective of the present invention can be achieved by a pipe assembly joined by the keyhole welding method mentioned above.

[0033] In addition, the present invention includes a primary welding step of filling the weldment of two base materials to be welded with filler material using low energy; and a secondary welding step of welding the weldment filled with filler material using high-energy keyhole welding. Effects of the invention

[0034] The high-energy keyhole welding method and the piping assembly according to the present invention have the following effects.

[0035] First, pre-fill welding prior to the high-energy welding stage can resolve the disadvantages that occurred in the conventional high-energy keyhole TIG welding process.

[0036] Second, it can be applied to pipes of all sizes and ensures stability during the high-energy welding stage.

[0037] Third, since both the pipes and elbows can be used as they are without processing, the cost and time required to machine the elbows vertically to create a square groove shape can be saved.

[0038] Fourth, flexibility can be secured to apply manual TIG or high-energy TIG depending on the site conditions.

[0039] Fifth, it is possible to secure welding quality and a wide range of welding conditions depending on the gap of the weld joints of the base materials. Brief explanation of the drawing

[0040] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. Figure 1 is a process diagram for schematically explaining a conventional low-energy manual TIG welding process. FIG. 2 is a conceptual diagram schematically illustrating the primary welding step of a high-energy keyhole welding method according to one embodiment of the present invention. FIG. 3 is a conceptual diagram schematically illustrating the state in which two base materials have been first welded by a first welding step according to one embodiment of the present invention. FIG. 4 is a photograph of two base materials before (a) and after (b) the completed welding state by a primary welding step according to one embodiment of the present invention. FIG. 5 is a conceptual diagram schematically illustrating the process of performing secondary welding on base materials that have completed primary welding according to a preferred embodiment of the present invention. FIG. 6 is a conceptual diagram (a) and actual photograph (b) schematically illustrating base materials that have been welded through a secondary welding step of a high-energy keyhole welding method according to another embodiment of the present invention. FIG. 7 is a graph showing the relationship between welding current and high-energy welding speed before (a) and after (b) pre-welding application according to a preferred embodiment of the present invention. FIG. 8 is a photograph comparing the welding quality according to the keyhole welding method according to one embodiment of the present invention with the welding quality according to the prior art. FIG. 9 is a conceptual diagram schematically illustrating the state in which base materials are mounted to which a high-energy keyhole welding method according to another embodiment of the present invention is applied. Figure 10 is a conceptual diagram illustrating the state in which the filler material is molten after undergoing the primary welding step in the weld of Figure 9. Figure 11 is a conceptual diagram schematically illustrating the process of performing a secondary welding step in the state of Figure 10. FIG. 12 is a conceptual diagram schematically illustrating the state in which base materials are mounted to which a keyhole welding method according to another embodiment of the present invention is applied. Figure 13 is a conceptual diagram illustrating the state in which the filler material is melted after undergoing the primary welding step in the weld of Figure 12. Figure 14 is a conceptual diagram schematically illustrating the process of performing a secondary welding step in the state of Figure 12. Specific details for implementing the invention

[0041] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, and should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely one preferred embodiment of the present invention and do not represent all of the technical spirit of the present invention; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0042] In the drawings, the size of each component or specific part constituting the component is exaggerated, omitted, or schematically depicted for convenience and clarity of explanation. Accordingly, the size of each component does not entirely reflect its actual size. If it is determined that a specific description of related known functions or configurations could unnecessarily obscure the essence of the invention, such description shall be omitted.

[0043] As used herein, the terms “joining,” “mounting,” “fixing,” or “connecting” include not only cases where one member and another member are directly joined, mounted, fixed, or connected, but also cases where one member is indirectly joined, mounted, fixed, or connected to another member through an intermediate member.

[0044] Additionally, this specification uses terms indicating direction such as up, down, left, right, front, back, etc., but these directions may vary depending on the direction in which the object is placed and the direction of observation.

[0045] In one embodiment of the method of the present invention, each step has been described as a step combined in a specific order for the purpose of explanation; however, a person skilled in the art will understand that in other embodiments, one or more steps, or parts thereof, may be performed in a different order, overlap in time, be performed in series or in parallel, be omitted, or one or more additional steps may be added, or the method may be modified in several combinations.

[0046] FIG. 2 is a conceptual diagram schematically illustrating the mounting state of base materials for the primary welding step of a high-energy keyhole welding method according to one embodiment of the present invention.

[0047] Referring to FIG. 2, a first base material (12) is prepared in which no groove is formed at the end of one base material (12) to be welded, such as a straight pipe, that is, the longitudinal direction of the base material (12) and the end surface are orthogonal to each other. Additionally, a second base material (14) is prepared in which a groove is formed at the end of another base material (14) to be welded, such as a straight pipe or an elbow, that is, the longitudinal direction of the base material (14) and the groove surface (15) have a predetermined groove angle (β) (e.g., in the range of approximately 5˚ to approximately 85˚, preferably approximately 30˚).

[0048] In one embodiment, the improved surface (15) may have a straight shape, a curved shape that is convex or concave toward the base material, or a mixed shape of straight and curved shapes. FIG. 2 illustrates the improved surface (15) being straight.

[0049] Next, the first base material (12) and the second base material (14) are attached. Then, the root gap (G) between the first base material (12) and the second base material (14) becomes approximately 4.0 mm, the bevel angle (β) becomes approximately 30˚, and a weld (16) is formed between the end surface of the first base material (12) and the bevel surface (15) of the second base material (14). An attachment shape like that shown in FIG. 2 can be named a 'bevel groove' or a 'half V bevel'.

[0050] Next, as illustrated in FIG. 3, in the primary welding step or pre-welding step, filler material (18) is filled into the weld (16) formed by the first base material (12) and the second base material (14).

[0051] In one embodiment, the primary welding step may use arc welding to melt the filler material (18) and fill the weld (16). Additionally, the arc welding method used in the primary welding step may vary, and for example, gas tungsten arc welding (GTAW), shielded metal arc welding (SMAW), gas metal arc welding (GMAW), or flux-cored arc welding (FCAW) may be used.

[0052] In one embodiment, the primary welding step may utilize the Melt-In Mode of arc welding. The Melt-In Mode may be performed under welding conditions that melt and fill the weld with a low-energy welding method using a current ranging from 50A to 250A, for example. After undergoing this primary welding step, the filler material (18) is melted into the weld (16) between the first base material (12) and the second base material (14), as illustrated in FIGS. 3 and 4.

[0053] In one embodiment, the first welding step is preferably filled with a portion (approximately 10 to 90%) of the total volume of the weld (16) with filler material (18) so that insufficient penetration and burn-through do not occur in the second welding step described later.

[0054] In one embodiment, during the first welding step, a back bead (penetration bead) may or may not be formed. FIG. 3 illustrates a state in which no back bead is formed.

[0055] FIG. 5 is a conceptual diagram schematically illustrating the process of performing secondary welding on base materials that have completed primary welding according to a preferred embodiment of the present invention.

[0056] Referring to FIG. 5, when the filler material (18) is melted and hardened in the weldment (16) between the first base material (12) and the second base material (14), high-energy keyhole welding is performed on the area of ​​the weldment (16) filled with the filler material (18).

[0057] In one embodiment, the secondary welding step may utilize high-energy TIG welding in which, in one pass, the welding arc completely penetrates a portion of the end of the first base material (12), a portion of the end of the second base material (14), and the filler material (18) to create a keyhole and melt up to the opposite side of the base materials (12, 14). In other embodiments, the secondary welding step may utilize plasma arc welding (PAW) or laser welding. In FIG. 5, reference numeral 11 illustrates an electrode.

[0058] In the above-described embodiment, plasma arc welding or laser welding is performed at an energy range capable of forming a back bead by melting the opposite surface to form a keyhole.

[0059] According to the present embodiment, when a secondary welding step is performed, a keyhole portion (13) that is generally wider at the top and narrower at the bottom can be formed from the upper surface to the lower surface of the first base material (12) and the second base material (14), as shown in FIG. 6(a). FIG. 6(b) is a cross-sectional photograph of the actual object.

[0060] FIG. 7 is a graph showing the relationship between welding speed and welding current, where part (a) represents the prior art and part (b) represents the present invention. In addition, FIG. 8 is a photograph comparing welding quality (a) according to the prior art with welding quality (b) according to an embodiment of the present invention. FIG. 7a and FIG. 8a are examples where a conventional high-energy welding method is applied to a square groove where no improvement is formed, and FIG. 7b and FIG. 8b are examples where a welding part of a bevel groove undergoes a primary welding step and is finished with a secondary welding step according to an embodiment of the present invention.

[0061] As illustrated in FIG. 7a, according to the prior art, local gaps may occur depending on the shape of the base material, and the size of the keyhole exit changes depending on the gap of the square groove, causing the arc shape to waver and the arc to become unstable. Furthermore, due to the difference in gaps, the range of welding variables such as usable current, welding speed, and tip-to-tip distance becomes very narrow. In addition, as illustrated in FIG. 8a, according to the prior art, welding quality changes, and in severe cases, there is a high possibility of burn-through or insufficient penetration occurring.

[0062] However, as illustrated in FIGS. 7b and FIGS. 8b, according to an embodiment of the present invention, the keyhole welding method allows the arc to be stably managed by filling the weld area in the first welding step, thereby keeping the size of the keyhole exit constant in the second welding step. Consequently, it can be confirmed that the surface quality of the weld area after the second welding is improved and the range of usable current and welding speed is widened compared to the welding quality according to the prior art.

[0063] FIG. 9 is a conceptual diagram schematically illustrating the state in which base materials are mounted to which a keyhole welding method according to another embodiment of the present invention is applied, FIG. 10 is a conceptual diagram illustrating the state in which the filler material is melted after undergoing a first welding step in the weld of FIG. 9, and FIG. 11 is a conceptual diagram schematically explaining the process of performing a second welding step in the state of FIG. 10.

[0064] Referring to FIGS. 9 to 11, the keyhole welding method according to the present embodiment is named "V Groove" or "V groove" because both the first base material (22) and the second base material (24) have grooves formed therein and each has grooved surfaces (23, 25), and the weld portion (26) formed by the grooved surfaces (23, 25) exhibits a 'V' shape. Additionally, it is preferable that the root gap (G) between the first base material (22) and the second base material (24) during installation is a maximum of 4.0 mm. Compared to the "bevel groove" of the previously described embodiment, the angle formed by the weld portion is 2β, and the filler material (28) forms an approximately parallelogram shape. The remaining first welding step and second welding step are identical to those of the previously described embodiment, so a detailed description is omitted. Reference numeral 27 indicates the keyhole portion.

[0065] FIG. 12 is a conceptual diagram schematically illustrating the state in which base materials are mounted to which a keyhole welding method according to another embodiment of the present invention is applied, FIG. 13 is a conceptual diagram illustrating the state in which the filler material is melted after undergoing a first welding step in the welded part of FIG. 12, and FIG. 14 is a conceptual diagram schematically explaining the process of performing a second welding step in the state of FIG. 12.

[0066] Referring to FIGS. 12 to 14, the first base material (32) and the second base material (34) each have a reinforced portion (33a) in which a reinforcement is formed and a non-reinforced portion (33b) in which no reinforcement is formed, and the weld portion (36) is named "Y reinforcement" in that it has an overall "Y" shape, which is different from the previously described "V reinforcement" embodiment, and the remaining parts are identical to the "V reinforcement" embodiment, so a detailed description thereof is omitted. Reference numeral 38 indicates a filler material, and reference numeral 37 indicates a keyhole portion. In this embodiment, during the first welding step, the filler material (38) is filled into a part of the reinforced portion (33a) and a part of the non-reinforced portion (33b).

[0067] In another embodiment, the keyhole welding method of the present invention may include a primary welding step in which the two base materials to be welded have no improvement so that the weldment forms a square groove (straight line shape) and filler material is filled into such a weldment using low energy, and then a secondary welding step in which the weldment filled with filler material is main welded using high-energy keyhole welding.

[0068] Preferred embodiments of the present invention have been described above with reference to the accompanying drawings. However, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention; therefore, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application. Explanation of the symbols

[0069] 12, 22, 32... 1st base material 14, 24, 34... Second base material 13, 27, 37... Keyhole 15, 23, 25... Improvement surface 16, 26, 36... welds 18, 28, 38... Dragon crayfish

Claims

Claim 1 A high-energy keyhole welding method comprising: a primary welding step of filling a weld joint of two base materials to be welded using low energy; and a secondary welding step of welding the weld joint filled with the filler using high-energy keyhole welding. Claim 2 In claim 1, the primary welding step is a high-energy keyhole welding method in which the filler material is melted using arc welding to fill the weld. Claim 3 In claim 2, the arc welding comprises a high-energy keyhole welding method including gas tungsten arc welding (GTAW) or covered metal arc welding (SMAW) or gas metal arc welding (GMAW) or flux-cored arc welding (FCAW). Claim 4 In claim 2, the primary welding step is a high-energy keyhole welding method using the Melt-In Mode of arc welding. Claim 5 In claim 4, the high-energy keyhole welding method is performed under welding conditions in which the melt-in mode is a low-energy welding method using a welding current in the range of 50A to 250A to melt and fill the filler material in the weld. Claim 6 In claim 1, the secondary welding step is a high-energy keyhole welding method using high-energy TIG welding in which the welding arc completely penetrates the base materials and the filler material in a single welding pass to create a keyhole and melts up to the opposite surface of the base materials. Claim 7 In claim 1, the secondary welding step is a high-energy keyhole welding method using plasma arc welding (PAW) or laser welding. Claim 8 In claim 7, the plasma arc welding or the laser welding is performed in an energy range capable of forming a keyhole to melt the opposite surface and form a back bead, a high-energy keyhole welding method. Claim 9 A high-energy keyhole welding method in claim 1, wherein the first welding step comprises the step of filling a portion of the volume of the weld with the filler material so as not to cause insufficient penetration and burn-through in the second welding step. Claim 10 In claim 1, the primary welding step is a high-energy keyhole welding method in which a back bead is formed or not formed. Claim 11 A high-energy keyhole welding method in claim 1, wherein the angle of improvement between the base materials is 5˚ to 85˚. Claim 12 A high-energy keyhole welding method in claim 11, wherein the angle of improvement is 30˚. Claim 13 A high-energy keyhole welding method in claim 11, wherein the root gap between the base materials is 4.0 mm or less. Claim 14 A high-energy keyhole welding method in claim 1, wherein improvements are formed on both of the two base materials to form the weld. Claim 15 A high-energy keyhole welding method in claim 14, wherein the root gap between the base materials is 4.0 mm or less. Claim 16 A high-energy keyhole welding method in claim 14, wherein the base materials all have a grooved portion in which a groove is formed and a non-grooved portion in which a groove is not formed. Claim 17 A high-energy keyhole welding method in claim 1, wherein the improvement between the base materials is straight, curved, or a mixture of straight and curved. Claim 18 A high-energy keyhole welding method in claim 1, wherein one of the base materials is a straight metal pipe and the other is a metal elbow-type fitting or another straight metal pipe. Claim 19 A pipe assembly joined by the high-energy keyhole welding method of any one of claims 1 to 18. Claim 20 delete

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