Method for girth welding of pressure pipelines

Abstract

The present application relates to a welding method, and discloses a transverse seam welding method for pressure pipelines, comprising the following steps: 1) forming two blunt edges with different lengths by pairing the workpieces to be welded, and the length of the blunt edge of the lower workpiece is greater than that of the upper workpiece, and then performing backing welding by K-TIG welding under the protection of a shielding gas; 2) performing filler layer welding on the bevel area by MIG welding; and 3) performing cover layer welding on the bevel area by MIG welding. According to the present application, the two workpieces are paired, and the length of the blunt edge of the lower workpiece is set to be greater than that of the upper workpiece, so as to support the molten pool generated during welding, which is beneficial to achieving the relative balance between the arc pressure generated during welding and the surface tension of the molten metal, thereby effectively slowing down the flow trend of the liquid molten pool and forming a stable keyhole.

Description

Technical Field

[0001] The invention relates to a welding method, in particular to a transverse seam welding method for a pressure-bearing pipeline. Background Art

[0002] In the oil, gas, and chemical industries, pipeline welding is essentially the same as other welding projects, but there are some differences in the pipeline structure. Compared to common grid and beam structures, oil pressure pipelines are significantly different and are subject to both external and internal pressure. Therefore, they have higher requirements for tightness, strength, and toughness.

[0003] Normally, in order to ensure the quality of the root foundation, the welding of pressure-bearing process pipelines generally adopts the welding method of manual argon arc welding and arc welding. This welding method is limited by the process of ordinary tungsten inert gas welding, and the welding of pressure-bearing process pipelines is different from the welding of flat plates. When welding flat plates, the flat plates can be placed on a horizontal surface so that the formed molten pool is relatively stable and will not move. When welding pipelines, most of the welding is carried out on the side of the pipeline, resulting in an unstable molten pool, and the welding groove is generally V-shaped with a groove angle of 60°. Figure 1 As shown, since the groove angle is too large, the required welding filling amount is also very large, resulting in relatively low welding efficiency. Summary of the Invention

[0004] The main problem to be solved by the present invention is to provide a transverse seam welding method for pressure pipelines, which can prevent the molten pool from flowing and improve the welding efficiency.

[0005] In order to solve the above technical problems, the present invention also provides a transverse seam welding method for a pressure-bearing pipeline, comprising the following steps:

[0006] 1) Pair the workpieces to be welded, so that the two blunt edges are of different lengths and the blunt edge of the lower workpiece is longer than the blunt edge of the upper workpiece, and perform root welding by K-TIG welding under shielding gas;

[0007] 2) Use MIG welding to weld the filler layer in the groove area;

[0008] 3) Use MIG welding to perform cover layer welding on the groove area.

[0009] Preferably, the bevel angle formed by the bevel edge of the upper workpiece is greater than the bevel angle formed by the bevel edge of the lower workpiece.

[0010] Further preferably, the bevel angle of the sloped edge of the lower workpiece is 10°-15°, and the bevel angle of the sloped edge of the upper workpiece is 30°-35°.

[0011] Through the above-mentioned preferred technical solution, the groove angle formed by the slope of the upper workpiece is set to be greater than the groove angle formed by the slope of the lower workpiece, so as to support the molten pool formed by MIG welding and prevent the molten pool from flowing downward quickly, thereby affecting the welding effect of the filling layer.

[0012] Preferably, the workpiece is medium-thick plate carbon steel and / or stainless steel.

[0013] Further preferably, the sloped edges of the upper and lower workpieces and the two blunt edges form a Y-shaped groove. According to this preferred technical solution, the Y-shaped groove is formed by combining the sloped edges of the upper and lower workpieces with the two blunt edges, and the groove surface of the Y-shaped groove is simple to process.

[0014] Preferably, the MIG welding is used for filling at least three times.

[0015] Further preferably, the length of the blunt edge of the upper workpiece is 3-6 mm, and the length of the blunt edge of the lower workpiece exceeds the blunt edge of the upper workpiece by 1-2 mm. During KTIG welding, the heat input at the lower edge of the groove is greater than the heat input at the upper edge, resulting in the lower groove being easier to melt than the upper groove, resulting in poor surface stability of the liquid molten pool and failure to form a stable keyhole effect. Therefore, increasing the length of the blunt edge of the lower groove and reducing the melting rate of the molten pool on the lower groove are more conducive to the formation of a keyhole effect of deep penetration welding. Through this preferred technical solution, the length of the blunt edge of the lower workpiece is greater than the length of the blunt edge of the upper workpiece, so that the blunt edge of the lower workpiece can support the high-temperature liquid molten pool formed during K-TIG welding, which is conducive to achieving a relative balance between the arc pressure and the surface tension of the molten workpiece.

[0016] Preferably, in step 1), the welding current when the K-TIG welding is used for bottom welding is 500-520A, and the welding speed is 150mm / min-300mm / min.

[0017] Preferably, in step 2), when the MIG welding is used for filling welding, the welding current is 280-320A, the welding voltage is 30-33V, and the welding speed is 300mm / min-450mm / min.

[0018] Preferably, in step 3), when the MIG welding is used for cap welding, the welding current is 250-300 A, the welding voltage is 28-30 V, and the welding speed is 300 mm / min-350 mm / min.

[0019] Through the above technical solution, the present invention provides a transverse seam welding method for pressure pipelines, which supports the molten pool generated during welding by assembling two workpieces and setting the blunt edge length of the lower workpiece to be greater than the blunt edge length of the upper workpiece. This is beneficial to achieve a relative balance between the arc pressure generated during welding and the surface tension of the molten metal, thereby effectively slowing down the flow trend of the liquid molten pool and forming a stable keyhole.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the groove structure of ordinary TIG welding;

[0022] Figure 2 Schematic diagram of the groove structure of K-TIG welding;

[0023] Figure 3 This is a groove welding sequence diagram of K-TIG welding of the present invention.

[0024] Reference numerals

[0025] 1 Upper workpiece 2 Lower workpiece

[0026] 3 Upper workpiece blunt edge 4 Lower workpiece blunt edge

[0027] 5 Upper workpiece slope 6 Lower workpiece slope DETAILED DESCRIPTION

[0028] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0029] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "installed," and "connected" should be understood broadly. For example, the term "connected" may refer to a fixed connection, a detachable connection, or an integral connection; it may refer to a direct connection or an indirect connection through an intermediate medium; it may refer to internal communication between two components or an interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0030] An embodiment of the transverse seam welding method for a pressure pipeline of the present invention comprises the following steps: 1) pairing workpieces to be welded, forming two blunt edges of unequal lengths, with the blunt edge 4 of the lower workpiece being longer than the blunt edge 3 of the upper workpiece, and performing a root pass welding by K-TIG welding under a shielding gas;

[0031] 2) Use MIG welding to weld the filler layer in the groove area;

[0032] 3) Use MIG welding to perform cover layer welding on the groove area.

[0033] The present invention adopts deep penetration tungsten inert gas arc welding (K-TIG) for base welding and MIG welding for combined welding of the filling layer and the cover layer. K-TIG welding is used to weld the groove compared with ordinary TIG welding. Since K-TIG welding has a higher energy density, this welding process is based on traditional TIG welding and forms a smaller keyhole to achieve deep penetration welding by increasing the current (>300A). Therefore, when K-TIG welding is used in a flat welding position, the high-temperature liquid molten pool generated will not have a tendency to flow along the slope of the workpiece, and the keyhole generated is more stable than the keyhole generated by ordinary TIG welding. However, when welding in a horizontal position, because the volume of the high-temperature liquid molten pool formed per unit time by K-TIG welding is larger, the high-temperature liquid molten pool formed is prone to flowing downward along the slope of the lower workpiece 2 under the action of gravity. Therefore, when we assemble the two workpieces to be welded, we set the length L2 of the lower workpiece blunt edge 4 to be greater than the length L1 of the upper workpiece blunt edge 3, so that the lower workpiece blunt edge 4 can provide a certain support for the high-temperature liquid molten pool, preventing the high-temperature liquid molten pool from flowing downward during welding, thereby affecting the welding forming state. In addition, the use of unequal blunt edges is conducive to achieving a relative balance between the arc pressure generated during welding and the surface tension of the liquid metal in the molten state, thereby forming a stable deep-penetration welding keyhole.

[0034] like Figure 2 As shown, in one embodiment of the transverse seam welding method for pressure-bearing pipelines of the present invention, the groove angle formed by the upper workpiece bevel 5 is greater than the groove angle formed by the lower workpiece bevel 6. By setting the groove angle of the lower workpiece bevel 6 smaller, the high-temperature liquid molten pool generated during welding can be supported to a certain extent when welding in a horizontal position, effectively slowing the downward sliding rate of the high-temperature liquid molten pool. Preferably, the groove angle of the lower workpiece bevel 6 is set to 10°-15°, and the groove angle of the upper workpiece bevel 5 is set to 30°-35°. Compared with the welding method of conventional arc welding, the groove angle required for conventional welding is too large. The excessive groove angle will inevitably lead to excessively large filler and cover layers required for welding, thereby affecting the overall welding efficiency. In addition, due to the excessive groove angle, the high-temperature liquid molten pool generated during horizontal welding will slide rapidly along the groove formed by the lower workpiece 2, thereby affecting the overall welding effect and aesthetics.

[0035] Compared with the traditional TIG welding method, the groove angle of the traditional TIG welding groove is set to about 60°, and the groove angles of the upper workpiece 1 and the lower workpiece 2 are equal, and the blunt edge lengths on the upper workpiece 1 and the lower workpiece 2 are also equal. In the traditional welding procedure, in order to ensure the quality of the root base, a welding method of manual argon arc welding + stick arc welding is generally adopted. However, the root welding using this method usually requires welding wire for supplementary welding, and direct welding cannot be performed. The K-TIG welding method used in the present invention does not require welding wire for welding. Before welding, it is only necessary to align the two workpieces and position them. After positioning, the two blunt edges of the upper workpiece 1 and the lower workpiece 2 can be self-melted by the large current of K-TIG without adding welding wire, thereby reducing the cost of welding wire.

[0036] like Figure 3 As shown, in an embodiment of a transverse seam welding method for a pressure pipeline according to the present invention, the upper workpiece 1 and the lower workpiece 2 can be made of medium-thick plate carbon steel and / or stainless steel. The upper workpiece 1 and the lower workpiece 2 are assembled, and the upper workpiece bevel 5 and the lower workpiece bevel 6 are combined with the blunt edges of the upper workpiece 1 and the lower workpiece 2 to form a Y-shaped groove. The Y-shaped groove is welded using a combination of K-TIG and MIG welding. The welding process includes the following steps:

[0037] The first step is bottom welding:

[0038] K-TIG welding is used for base welding at the upper workpiece 1 and the blunt edge 4 of the lower workpiece, with a welding current of 500-520A and a welding speed of 150mm / min-300mm / min.

[0039] The second step is filling layer welding:

[0040] On the basis of K-TIG welding, MIG welding is used for filling layer welding. The welding current is controlled at 280-320A, the welding voltage is controlled at 30-33V, and the welding speed is controlled at 300mm / min-450mm / min.

[0041] The third step is cover welding:

[0042] On the basis of the filling layer welding, MIG welding is used again for the cover welding. The current of the cover welding is controlled at 250-300A, the welding voltage is controlled at 28-30V, and the welding speed is controlled at 300mm / min-350mm / min.

[0043] Among them, when welding the filling layer of the groove, the filling times are at least 3 times. It should be noted that the groove refers to a groove of a certain collective shape processed and assembled with a welding part of the workpiece, generally including X-type, K-type, V-type, U-type and other shapes, and is not limited to the Y-type groove used in the present invention.

[0044] like Figure 3 As shown, an embodiment of the transverse seam welding method for pressure pipelines of the present invention, the blunt edge length of the upper workpiece 1 is 3-6 mm, and the blunt edge 4 of the lower workpiece exceeds the length of the upper blunt edge by 1-2 mm. During KTIG welding, the heat input at the lower edge of the groove is greater than the heat input at the upper edge, which causes the lower groove to melt more easily than the upper rupture, resulting in poor surface stability of the liquid molten pool and failure to form a stable keyhole effect. Therefore, increasing the length of the blunt edge of the lower rupture and reducing the melting rate of the molten pool on the lower rupture are more conducive to forming a keyhole effect of deep fusion welding. In addition, by setting the length of the lower blunt edge slightly longer to support the high-temperature liquid molten pool, the high-temperature liquid molten pool can be prevented from continuously flowing downward.

[0045] In addition, when performing the bottom welding of the transverse seam welding method for pressure pipelines of the present invention, the K-TIG welding used directly performs group welding on the upper workpiece 1 and the lower workpiece 2, and there is no need to perform supplementary welding on the welds that have been K-TIG welded after welding, thereby effectively improving the welding efficiency. For traditional welding methods, the welds need to be submerged arc welded again after welding, and when performing submerged arc welding, the current of the submerged arc welding needs to be accurately controlled to prevent excessive current from welding through the welds, thereby affecting the overall welding effect.

[0046] It should be noted that in the production of pipelines and pressure vessel products, medium and thick carbon steel and stainless steel plates are usually welded. The most commonly used welding processes are submerged arc welding, argon arc welding and plasma welding. However, these three welding processes have great limitations. Among them, submerged arc welding: it is impossible to achieve single-sided welding and double-sided forming, and the back side must be air-planed to clean the root, which has low production efficiency; argon arc welding: shallow penetration, low coverage rate, and must open grooves and multiple layers and multiple passes for welding, resulting in low production efficiency; plasma welding: high equipment requirements, high requirements for workpiece assembly, narrow surface welds, and low system cost performance.

[0047] Therefore, in response to the limitations of the above-mentioned traditional processes, K-TIG deep penetration argon arc welding was developed. The penetration keyhole process of K-TIG deep penetration argon arc welding has a penetration rate 8 times that of GTAW, enabling it to perform X-ray quality welding in materials with a thickness of 16mm in a single pass without the need for edge chamfering. The resulting welding speed is up to 10 times that of traditional TIG / GTAW welding, gas consumption is reduced by more than 90%, and power consumption is reduced by more than 90%. The physical characteristics of the keyhole process of K-TIG welding produce high energy density in the welding arc, thereby opening and completely penetrating the material to be welded and welding at high speed. The combination of the surface energy associated with the keyhole geometry and the relatively unrestricted outlet of the arc gas produces a very stable and benign molten pool.

[0048] K-TIG deep-penetration argon arc welding is designed to convert a high-current arc into a plasma jet, which completely penetrates the material and forms a high-surface-tension molten pool at the bottom of the material. By controlling the surface tension, the molten metal in the pool is prevented from falling from the root surface into the pool, affecting the dynamic balance of the pool. K-TIG deep-penetration argon arc welding can also maintain and stabilize the weight of the molten material during welding. During this process, the penetration ability of K-TIG deep-penetration argon arc welding varies depending on the material. For example, it can achieve full penetration single-pass welding on austenitic stainless steel with a thickness of 13 mm, and it can also achieve full penetration single-pass welding on 16 titanium alloy. No edge chamfering or joint gap is required; all that is required is a simple square joint. Furthermore, K-TIG deep-penetration argon arc welding maintains a dynamic balance within the molten pool through the arc force generated by the current and the static pressure and surface tension of the liquid metal. This dynamic balance is key to the advantages of the K-TIG welding process, and the process is well-suited for use with materials with low thermal conductivity, such as stainless steel, nickel-based alloys, titanium alloys, zirconium alloys, and cobalt alloys. These more expensive metals require higher weld quality and formability. K-TIG deep-penetration argon arc welding offers higher quality and faster processing than traditional TIG welding. Its welds are 100% matrix, free of multiple fusion lines, completely eliminating slag inclusions, porosity, and other common weld defects. Furthermore, the ripple-free weld pool of K-TIG deep-penetration argon arc welding ensures ultra-high-quality capping and base layers, eliminating the need for back cleaning, surface polishing, or grinding.

[0049] In addition, when K-TIG welding is used for welding pressure process pipelines, single-sided welding and double-sided forming are achieved in 16mm titanium, 14mm zirconium, 13mm austenitic stainless steel, Hastelloy, nickel-chromium-iron alloy and various nickel-cobalt alloys and 9mm conductive materials (such as ferrite and carbon steel), thereby greatly saving the time and energy required for back welding. When the K-TIG welding speed is 250-300mm / min, stainless steel below 14mm can be welded through in one go, thereby significantly improving welding efficiency. In addition, this application adopts a composite welding method of K-TIG and MIG welding for welding. Due to the high cladding efficiency of MIG welding, the overall welding efficiency can be further improved.

[0050] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," or "an implementation" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In the present invention, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0051] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention may be subjected to various simple modifications, including combining the specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A transverse seam welding method for a pressure-bearing pipeline, characterized in that: The following steps are involved: 1) Pairing workpieces to be welded, forming two blunt edges of unequal lengths, with the blunt edge of the lower workpiece being longer than the blunt edge of the upper workpiece, the blunt edge of the upper workpiece being 3-6 mm long, and the blunt edge of the lower workpiece being 1-2 mm longer than the blunt edge of the upper workpiece, and performing root welding by K-TIG welding under shielding gas; 2) Use MIG welding to weld the filler layer in the groove area; 3) Use MIG welding to weld the cover layer of the groove area.

2. The transverse seam welding method for pressure pipelines according to claim 1, characterized in that: The groove angle formed by the sloped edge of the upper workpiece is greater than the groove angle formed by the sloped edge of the lower workpiece.

3. The transverse seam welding method for pressure pipelines according to claim 2, characterized in that: The bevel angle of the slope edge of the lower workpiece is 10°-15°, and the bevel angle of the slope edge of the upper workpiece is 30°-35°.

4. The transverse seam welding method for pressure pipelines according to claim 1, characterized in that: The workpiece is medium-thick plate carbon steel and / or stainless steel.

5. The transverse seam welding method for pressure pipelines according to claim 1, characterized in that: The sloped edges of the upper workpiece and the lower workpiece and the two blunt edges form a Y-shaped groove.

6. The transverse seam welding method for pressure pipelines according to claim 1, characterized in that: The MIG welding is used for filling at least three times.

7. The transverse seam welding method for a pressure pipeline according to any one of claims 1 to 6, characterized in that: In step 1), the welding current when the K-TIG welding is used for the root welding is 500-520A, and the welding speed is 150mm / min-300mm / min.

8. The transverse seam welding method for a pressure pipeline according to any one of claims 1 to 6, characterized in that: In step 2), when the MIG welding is used for filling welding, the welding current is 280-320A, the welding voltage is 30-33V, and the welding speed is 300mm / min-450mm / min.

9. The transverse seam welding method for a pressure pipeline according to any one of claims 1 to 6, characterized in that: In step 3), when the MIG welding is used for cap welding, the welding current is 250-300 A, the welding voltage is 28-30 V, and the welding speed is 300 mm / min-350 mm / min.

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