High-strength, high-toughness, anti-corrosive welding method for TKY joints for deep water jackets

Abstract

The present invention discloses a high-strength, high-toughness, corrosion-resistant welding method for TKY joints for deep water jackets. [Solution] A T / K / Y joint is preheated at a predetermined temperature according to the wall thickness of the base material, different welding parameters are set for different welding processes, root welding is performed on the preheated T / K / Y joint by a shielded metal arc welding process, then build-up welding is performed by a gas shielded metal arc welding process, and finally, finish welding is performed by a gas shielded metal arc welding process, in which a corresponding welding rod is used for root welding, a welding wire is selected according to the under-match principle for finish welding, and a welding wire is selected according to the even-match principle for build-up welding, and the diffusible hydrogen content of any welding rod and any welding wire is equal to or less than the predetermined diffusible hydrogen content.

Description

[Technical field]

[0001] The present invention relates to the technical field of welding, and more particularly to a high-strength, high-toughness, corrosion-resistant welding method for TKY joints for deep water jackets. [Background technology]

[0002] Fixed jacket platform for offshore petroleum engineering is the most commonly used structural form in the extraction of oil and gas resources in deep water areas. The cross joint of large pipes (TKY joint) is the most major welded structure. As the main load-bearing structure in offshore engineering, the TKY joint generates high stress concentration at the connection point of the main pipe and the branch pipe due to the self-weight of the structure and equipment, waves, storms, and other extreme loads, and the interaction of alternating load and seawater corrosion makes it easy for corrosion, fatigue, and fracture damage to occur at the welded part. Therefore, in order to meet the long-term use of offshore platforms, it is required that the TKY joint has excellent low-temperature toughness, air corrosion resistance, and seawater corrosion resistance. The welding quality of high-strength steel directly affects the performance of the TKY joint. Unreasonable welding may cause low-temperature cracking or a decrease in toughness. Due to the action of the welding heat cycle, the structure and properties of the base material on both sides of the welded part will change significantly, and the welded heat-affected zone will soften or embrittle, resulting in a decrease in the performance of the TKY welded joint. Current research on commonly used welding methods mainly focuses on controlling the welding heat input and optimizing the welding thermal cycle to reduce the adverse effects on the weld heat affected zone. In addition, due to the action of the filler metal composition and the welding thermal cycle, the weld metal is usually the weak area of ​​the joint, especially at the location of the weld root, where its composition changes significantly due to the dilution of the base metal, which can easily cause localized embrittlement of the weld metal.

[0003] In the field of marine engineering, gas shielded welding and submerged arc welding are the most widely used welding methods. For example, Chinese patent CN108453340B discloses a welding method for steel structure TKY joints, the focus of which is on the formation of welds and solving defects. CN112935601A discloses a thick plate multi-layer multi-pass welding method for low alloy high strength steel, which solves the problem of insufficient strength of welds by combining gas shielded welding and submerged arc welding. CN109128550B discloses a gas shielded welding process for high tensile strength bridge steel, which combines two different welding wires and CO2 gas shielded welding process to ensure that the whole welded joint has high plastic toughness. CN116765665A discloses a welding process for 500MPa-grade weathering steel, which combines flux-cored wire and cold metal transition welding process to improve the low temperature impact performance of the welded joint. The above prior art has optimized the welding process of high-strength steel according to various purposes and improved the performance of the weld to a certain extent, but it is difficult to optimize the welding process of steel for offshore platform structures using the above methods. The failure of the welded joint of high-strength steel caused by the improper welding process or substandard weld performance will have a serious impact on the safety of deepwater platforms.

[0004] Therefore, in the complex marine environment, a welding process is required that can ensure that the tensile strength of the entire weld meets the standards, and that the root and cap of the weld have high toughness and high corrosion resistance, while ensuring that the welded thick-wall structure of the TKY joint has the comprehensive performance of unstable fracture resistance and high corrosion resistance. Summary of the Invention

[0005] In response to the deficiencies of the prior art, the objective of the present invention is to provide a high-strength, high-toughness, corrosion-resistant welding method for TKY joints for deepwater jackets, thereby solving the problems that the welding process of TKY joints for deepwater platform jackets results in low toughness, poor corrosion resistance, and easy low-temperature cracking of the welded joints.

[0006] To achieve the above object, the present invention provides a high-strength and high-toughness anti-corrosion welding method for TKY joints for deep-water jackets, including the following steps. S1: Preheat the T / K / Y joint at a predetermined temperature according to the wall thickness of the base material. S2: Set different welding parameters for different welding processes. S3: Perform root welding on the preheated T / K / Y joint by the covered arc welding process and welding rod, then perform build-up welding by the gas shielded metal arc welding process and welding wire, and finally perform finish welding by the gas shielded metal arc welding process. Here, for root welding, select the welding rod according to the under-match principle, for finish welding, select the first welding wire according to the under-match principle, for build-up welding, select the second welding wire according to the even-match principle, and the diffusible hydrogen content of the welding rod, the first welding wire, and the second welding wire is all below a predetermined diffusible hydrogen content.

[0007] Furthermore, when the wall thickness W of the base material satisfies 38 mm < W ≤ 50 mm, the preheating temperature is in the range of 65°C to 150°C.

[0008] Furthermore, when the wall thickness W of the base material satisfies 50 mm < W ≤ 80 mm, the preheating temperature is in the range of 110°C to 150°C.

[0009] Furthermore, the predetermined diffusible hydrogen content is 5.0 ml / 100 g, and preferably, the diffusible hydrogen content of the welding rod, the first welding wire, and / or the second welding wire may be the same or different.

[0010] Furthermore, the diameter of the first welding wire and / or the second welding wire is 1 mm or 1.2 mm.

[0011] Furthermore, the dry extension of the first welding wire and / or the second welding wire is 10 to 12 times their respective diameters.

[0012] Furthermore, the first welding wire and the second welding wire may have the same or different yield strength, tensile strength, and / or impact toughness.

[0013] Furthermore, in step S3, the shielding gas used when performing build-up welding and / or finish welding is composed of 82% Ar and 18% CO2, and preferably, the flow rate of the shielding gas when welding is 20 L / min to 25 L / min.

[0014] In addition, the welding parameters corresponding to different welding processes are set such that the interlayer distance of adjacent welding layers is 3mm to 5mm, and the interlayer temperature of adjacent welding layers is less than 250°C.

[0015] Furthermore, when performing root welding by a shielded metal arc welding process, the corresponding welding parameters are: welding current: 90A to 120A, arc voltage: 20V to 23V, welding speed: 65mm / min to 90mm / min.

[0016] Furthermore, when build-up welding and finish welding are performed by the gas shielded metal arc welding process, the build-up welding welding voltage is 18V to 24V, the welding current is 160A to 190A, the welding speed is 300mm / min to 500mm / min, and the wire feed speed is 6m / min to 9m / min.

[0017] Furthermore, when finishing welding is performed by a gas shielded metal arc welding process, the corresponding welding parameters are: welding voltage: 22V to 24V, welding current: 175A to 190A, welding speed: 300mm / min to 500mm / min, wire feed speed: 8m / min to 9m / min.

[0018] Furthermore, when performing build-up welding and / or finish welding, the welding equipment oscillates at an oscillation frequency of 2.5Hz-4Hz and an oscillation amplitude of 1mm-2mm.

[0019] The technical solutions of the present invention have the following advantages over the prior art: In the present invention, the KTY joint to be welded is preheated at high temperature, the root welding is performed by SMAW (shielded metal arc welding), the build-up welding and finish welding are performed by GMAW (gas shielded metal arc welding), the welding rod is selected according to the undermatch principle in the root welding, the corresponding first welding wire is used according to the undermatch principle in the finish welding, the second welding wire is used according to the even match principle in the build-up welding, and the diffusible hydrogen content of the corresponding welding wire and welding rod used in each welding pass is all equal to or less than the predetermined diffusible hydrogen content, so that the toughness of the whole weld is improved by the different alloying strategy and the occurrence of cold cracking is prevented.

[0020] In the present invention, by combining low heat input parameters corresponding to different welding processes, the width of the heat-affected zone in the weld is further reduced, which is favorable for reducing the dilution of the base metal to the weld, and the occurrence of hard and brittle phases in the weld metal due to the action of thermal cycles is avoided, and the occurrence of localized embrittlement is reduced.

[0021] The present invention uses low hydrogen, high toughness and high corrosion resistance welding rods or wires with different performances such as yield strength, tensile strength and impact toughness in the root / capping pass and filling pass based on the combination of high preheat and low welding heat input, that is, different alloying strategies are used to complete high performance welding of deepwater TKY jacket joints, which prevents and reduces the occurrence of cold cracking, improves the toughness of the entire weld, and the strength of the entire weld meets the standard, and the root and cap parts of the weld have high strength, high toughness and high corrosion resistance. By combining the two methods, the thick-walled structure of high strength steel for deepwater platform has high comprehensive performance of unstable fracture resistance and corrosion resistance. [Brief description of the drawings]

[0022] [Figure 1] 1 is a flow chart of a high-strength, high-toughness, corrosion-resistant welding method for a TKY joint for a deep water jacket provided in an embodiment of the present invention. [Diagram 2] 1 is a schematic diagram of a welded joint structure of a TKY joint for deep water jacket provided in an embodiment of the present invention.

[0023] Explanation of symbols 1 - root weld, 2 - 1st pass build up weld, 3 - 2nd pass build up weld, 4 - 3rd pass build up weld, 5 - 4th pass build up weld, 6 - 5th pass build up weld, 7 - 1st pass finish weld, 8 - 2nd pass finish weld. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In order to make the objectives, technical means and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the drawings and examples. The specific examples described in this specification are merely illustrative of the present invention and are not intended to limit the present invention.

[0025] The present invention provides a high-strength, high-toughness, corrosion-resistant welding method for deep-water jacket TKY joints, which includes the following steps: S1: Preheat the T / K / Y joints at a specific temperature according to the wall thickness of the base metal. S2: Setting different welding parameters for different welding processes. S3: Root welding the preheated T / K / Y joint with a covered metal arc welding process and a welding rod, then build-up welding with a gas shielded metal arc welding process and a welding wire, and finally finish welding with a gas shielded metal arc welding process, using different alloyed welding wires, where the root welding uses a welding rod with high toughness and high corrosion resistance according to the "undermatch principle", the finish welding uses a first welding wire with high toughness and high corrosion resistance according to the "undermatch principle", and the build-up welding uses a second welding wire with strength close to that of the base material according to the "even match principle", thereby ensuring that the strength of the entire weld meets the standard, and the diffusible hydrogen content of the welding rod, the first welding wire, and the second welding wire are all equal to or less than the predetermined diffusible hydrogen content.

[0026] In this embodiment, the wall thickness of a general medium-thickness base material is 38 mm - 80 mm. When the wall thickness W of the base material satisfies 38 mm < W ≤ 50 mm, the preheating temperature is within the range of 65°C to 150°C. For example, when W is 45 mm, the preheating temperature is 80°C or higher, and when W is 50 mm, the minimum preheating temperature is 100°C.

[0027] In this embodiment, when the wall thickness W of the base material satisfies 50 mm < W ≤ 80 mm, the preheating temperature is within the range of 110°C to 150°C. When W is 65 mm, the preheating temperature is 115°C or higher, and when W is 80 mm, the minimum preheating temperature is 140°C.

[0028] In this embodiment, the diffusible hydrogen content of the welding rod, the first welding wire, and the second welding wire is all 5.0 ml / 100 g or less. For example, it is 5.0 ml / 100 g, 4.0 ml / 100 g, 3.0 ml / 100 g, 2.0 ml / 100 g, etc. Specifically, the diffusible hydrogen content of the welding rod, the first welding wire, and / or the second welding wire may be the same or different.

[0029] In this embodiment, the diameter of the first welding wire and / or the second welding wire is 1 mm or 1.2 mm. For example, for the first welding wire, the diameter of the first welding wire is 1.2 mm, and the diameter of the second welding wire is 1 mm.

[0030] In this embodiment, the dry extension of the first welding wire and / or the second welding wire is 10 to 12 times the diameter of each welding wire. For example, when the diameter of the corresponding welding wire is 1 mm, its dry extension is 11 mm or 12 mm, and when the diameter of the corresponding welding wire is 1.2 mm, its dry extension is 12 mm or 14.4 mm. If it is too long, the arc voltage will decrease, there will be too much weld metal, the formation of the welded joint will be poor, the penetration depth will be small, the arc will be unstable, and the spatter will be large. If it is too short, the contact tip will be burned by the arc, and the nozzle will be easily clogged by metal spatter.

[0031] In this embodiment, the first welding wire and the second welding wire may have the same or different yield strength, tensile strength, and / or impact toughness. For example, the first welding wire and the second welding wire have different yield strength, tensile strength, and impact toughness. Also, for example, the first welding wire and the second welding wire have the same yield strength, tensile strength, and impact toughness. Furthermore, for example, the first welding wire and the second welding wire have different yield strength and tensile strength but the same impact toughness.

[0032] In this embodiment, the yield strength, tensile strength, and impact toughness of any one of the above welding rods are different from the yield strength, tensile strength, and impact toughness of any one of the welding wires (the first welding wire and the second welding wire), respectively.

[0033] In this embodiment, the shielding gas used when performing build-up welding and / or finish welding in step S3 is composed of 82% Ar and 18% CO2. Specifically, the flow rate of the shielding gas during welding is 20 L / min to 25 L / min, and for example, the gas flow rate may be 20 L / min, 21 L / min, 22 L / min, 23 L / min, 24 L / min, or 25 L / min. In this case, a stable welding environment and relatively high welding quality can be ensured.

[0034] In this embodiment, with the welding parameters corresponding to different welding processes, the interlayer distance is between 3mm and 5mm, and the interlayer temperature (i.e., interpass temperature) is below 250°C, which ensures that the welding quality of each pass is acceptable.

[0035] In this embodiment, when performing root welding by the shielded metal arc welding process, the corresponding welding parameters are set as follows: welding current is 90A to 120A, for example, 90A, 100A, 110A, 120A, etc., arc voltage is 20V to 23V, for example, 20V, 21V, 22V, 23V, etc., welding speed is 65mm / min to 90mm / min, for example, 65mm / min, 70mm / min, 75mm / min, 80mm / min, 85mm / min, 90mm / min, etc.

[0036] In this embodiment, when build-up welding and finish welding are performed by the gas shielded metal arc welding process, the welding voltage of the build-up welding is 18V to 24V, for example, 18V, 20V, 22V, 23V, 24V, etc., the welding current is 160A to 190A, for example, 160A, 170A, 180A, 190A, etc., the welding speed is 300mm / min to 500mm / min, for example, 300mm / min, 350mm / min, 400mm / min, 450mm / min, 500mm / min, etc., and the wire feed speed is 6m / min to 9m / min, for example, 6m / min, 7m / min, 8m / min, 9m / min, etc.

[0037] In this embodiment, when finishing welding is performed by gas shielded metal arc welding process, the corresponding welding parameters are as follows: welding voltage is 22V to 24V, for example, 22V, 23V, 24V, etc., welding current is 175A to 190A, for example, 175A, 180A, 185A, 190A, etc., welding speed is 300mm / min to 500mm / min, for example, 300mm / min, 350mm / min, 400mm / min, 450mm / min, 500mm / min, etc., wire feed speed is 8m / min to 9m / min, for example, 8m / min, 8.5m / min, 9m / min, etc.

[0038] By welding with a combination of low heat input parameters corresponding to the different welding processes, the width of the heat affected zone of the welded joint is reduced, which is advantageous for reducing the dilution of the base metal with respect to the welded joint, and a decrease in welding strength is avoided.

[0039] In this embodiment, when performing surfacing welding and / or finishing welding, the welding equipment oscillates at an oscillation frequency of 2.5 Hz - 4 Hz and an oscillation amplitude of 1 mm - 2 mm. For example, the oscillation frequency may be 2.5 Hz, 3 Hz, 3.5 Hz, 4 Hz, etc., and the oscillation amplitude may be 1 mm, 1.5 mm, 2 mm, etc.

[0040] To better explain the implementation details of the present invention, the present invention will be described below by way of examples. The following examples are merely the optimal embodiments and do not limit the protection scope of the present invention.

[0041] Example 1 Taking the steel D36 for TKY joint where pipe members intersect as an example, this material has a yield strength of 355 MPa and a tensile strength of 490 - 630 MPa. The specific welding steps include the following. Step 1: According to the wall thickness and diameter of the D36 base metal, perform beveling and assembly strictly in accordance with the parameters such as the bevel form, root face, and welding gap of the joint specified in the American Welding Society standard AWS D1.1, and plan the welding path with the bevel and welding pass shown in Figure 2.

[0042] Step 2: Arrange welding equipment such as a welding torch, welding power source, cooling water tank, and gas cylinder.

[0043] Step 3: Preheat the TKY joint structure. When the wall thickness is 38 mm < W ≤ 50 mm, the preheating temperature is 65°C or higher; when the wall thickness is 50 mm < W ≤ 80 mm, the preheating temperature is 110°C or higher.

[0044] Step 4: Set different welding parameters according to the specific bevel size, match the welding wire, and perform welding. When welding the root pass 1 (root pass) by SMAW, the welding parameters are set as follows: welding current is set to 90A-120A, arc voltage is set to 20V-23V, welding speed is set to 65mm / min-90mm / min, and the matched welding rod has a yield strength of 390MPa, a tensile strength of 470MPa, and an impact toughness of 100J (-50℃). When welding passes 2 to 6 by GMAW to form the first to fifth filling passes, the welding parameters are set as follows: when welding the filling passes 2 to 4, the welding voltage is set to 18V-20V, the welding current is set to 160A-170A, the wire feed speed is set to 6m / min-7m / min, and the welding speed is set to 300mm / min-500mm / min, and when welding the filling passes 5 to 6, the welding voltage is set to 20-24V, the welding current is set to 170-180A, the wire feed speed is set to 7-9m / min, and the welding speed is set to 300-500mm / min. When welding the filling passes 2 to 6, the oscillation frequency of the welding torch is set to 2.5HZ-4HZ, and the oscillation width is set to 1mm, and the matched second welding wire has a yield strength of 495MPa, a tensile strength of 575MPa, and an impact toughness of 105J (-20℃).

[0045] When finishing welding the welding pass (capping pass) 7-8 by GMAW, the welding voltage is set to 22V-24V, the welding current is set to 175A-190A, the wire feed speed range is 8m / min-9m / min, the welding speed is set to 300mm / min-500mm / min, the oscillation frequency is set to 2.5HZ-4HZ, the oscillation width is set to 2mm, and the yield strength of the matched first welding wire is 390MPa, the tensile strength is set to 470MPa, and the impact toughness is set to 100J (-50℃).

[0046] In step 4, the amount of diffusible hydrogen in the deposited metal of the welding rod, the first welding wire, and the second welding wire used in each pass is 5.0 ml / 100 g or less. The first welding wire and the second welding wire have different yield strengths, tensile strengths, and impact toughnesses, and the first welding wire and the second welding wire have diameters of 1.0 mm or 1.2 mm, the dry extensions are 10-12 times the diameters of the first welding wire and the second welding wire, respectively, the shielding gas is 82% Ar and 18% CO2, and the gas flow rate is 20 L / min-25 L / min.

[0047] The specific welding parameters of the welds of each pass should be selected such that the interlayer distance is 3mm-5mm and the interlayer temperature is not more than 250℃. After the welding of each layer is completed, the slag removal treatment should be carried out in a timely manner.

[0048] Example 2 In this embodiment, the base material is the same as that in embodiment 1, the yield strength of the material is 355 MPa, the tensile strength is 490-630 MPa, the welding steps and corresponding welding parameters are also basically the same, but the welding wire used is different. When welding root pass 1 by SMAW, the matched welding rod has a yield strength of 390 MPa, a tensile strength of 470 MPa, an impact toughness of 100 J (-50 °C), a diameter of 1.0 mm, a dry extension of 11 mm, and the diffusible hydrogen content of the welding rod is 4.0 ml / 100 g. When welding the first filling pass 2 to the sixth filling pass 6 by GMAW, the second welding wire matched according to the even match principle has a yield strength of 495 MPa, a tensile strength of 575 MPa, an impact toughness of 105 J (-20°C), a diameter of 1.2 mm, a dry extension of 12 mm, and the amount of diffusible hydrogen in the deposited metal of the second welding wire is 5.0 ml / 100 g. When welding capping pass 7-8 by GMAW, the first welding wire used according to the undermatch principle has a yield strength of 390 MPa, a tensile strength of 470 MPa, an impact toughness of 100 J (-50 °C), a diameter of 1 mm, a dry extension of 11 mm, and the amount of diffusible hydrogen in the deposited metal of the welding wire is 4.0 ml / 100 g.

[0049] In any one of the above embodiments, based on the combination of low hydrogen welding wire, high preheat, and low welding heat input, different alloying strategies for root / capping pass and filling pass are used to complete high performance welding of deep water TKY jacket joint, which prevents and reduces the occurrence of cold cracking and improves the toughness of the entire weld. Through the different alloying strategies for root / capping pass and filling pass, the strength of the entire weld meets the standard, and the root and cap (welding surface) areas have high strength, high toughness, and high corrosion resistance. By combining the two methods, the thick-walled structure of high strength steel for deep water platform has high comprehensive performance of unstable fracture resistance and corrosion resistance.

[0050] In the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying a relative importance or number of the technical features depicted. Thus, features qualified as "first" and "second" may explicitly or implicitly include one or more of those features. In this specification, "plurality" means two or more, unless otherwise expressly qualified.

[0051] The above description is only a preferred embodiment of the present invention, and does not limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength, high-toughness, corrosion-resistant welding method for a deep-water jacket TKY joint, comprising the following steps S1 to S3: S1: Preheat the T / K / Y joint at a predetermined temperature according to the wall thickness of the base material, where the wall thickness of the base material is greater than 38 mm; S2: Set different welding parameters for different welding processes, where when the wall thickness W of the base metal satisfies 38 mm < W ≦ 50 mm, the preheating temperature is 65 ° C to 150 ° C, and when the wall thickness W of the base metal satisfies 50 mm < W ≦ 80 mm, the preheating temperature is 110 ° C to 150 ° C; S3: Root welding is performed on the preheated T / K / Y joints by a shielded metal arc welding process, then filling welding is performed by a gas shielded metal arc welding process, and finally capping welding is performed by a gas shielded metal arc welding process. wherein for root welding, a welding rod is selected according to the undermatch principle, the welding current is 90A to 120A, the arc voltage is 20V to 23V, and the welding speed is 65mm / min to 90mm / min; for finish welding, a first welding wire is selected according to the undermatch principle, the welding current is 175A to 190A, the welding voltage is 22V to 24V, the welding speed is 300mm / min to 500mm / min, and the wire feed speed is 8m / min to 9m / min; for build-up welding, a second welding wire is selected according to the even-match principle, the welding current is 160A to 190A, the welding voltage is 18V to 24V, the welding speed is 300mm / min to 500mm / min, and the wire feed speed is 6m / min to 9m / min; In step S3, the diffusible hydrogen amounts of the welding rod, the first welding wire, and the second welding wire are all equal to or less than a predetermined diffusible hydrogen amount, and the shielding gas used when performing build-up welding and / or finish welding is 82% Ar and 18% CO. ２ and a flow rate of the shielding gas during welding is 20 L / min to 25 L / min.

2. 2. The welding method according to claim 1, wherein the predetermined amount of diffusible hydrogen is 5.0 ml / 100 g.

3. The welding method according to claim 2 , wherein the diffusible hydrogen amounts of the welding rod, the first welding wire and / or the second welding wire may be the same or different.

4. The welding method according to claim 1 , wherein the first welding wire and / or the second welding wire has a diameter of 1 mm or 1.2 mm.

5. 5. The method of claim 4, wherein the dry extension of the first welding wire and / or the second welding wire is 10 to 12 times the diameter of each of the first and second welding wires.

6. The welding method according to claim 1 , wherein the first welding wire and the second welding wire have different yield strengths, tensile strengths, and / or impact toughnesses.

7. 2. The welding method according to claim 1, wherein the welding parameters corresponding to different welding processes are set such that the interlayer distance of adjacent welding layers is 3mm to 5mm, and the interlayer temperature of adjacent welding layers is less than 250°C.

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