Submerged arc welding process, welding wire and application for manufacturing induction heated bent pipe mother pipe

Abstract

The application relates to the technical field of submerged-arc welding, and particularly discloses a submerged-arc welding process, welding wire and application for manufacturing an induction heating elbow mother pipe, wherein the welding wire comprises the following components in mass ratio: C 0.05-0.09%, Si 0.20-0.25%, Mn 1.55-1.75%, P 0.0010%, S 0.005-0.007%, Al 0.01%, Ni 2.0-4.5%, Cr 0.35-0.45%, Cu 0.45-0.75%, V 0.03%, Nb 0.025%, Mo 0.15-0.3%, Ti 0.01%, and B 0.0005%, wherein Ceq of the alloy is 0.4-0.95%, and Pcm of the alloy is 0.27-0.31%. The welding seam welded by the welding wire and the welding process exhibits strong heat-resistant processing performance and can withstand various types of heat treatment.

Description

Technical Field

[0001] This invention relates to the field of submerged arc welding technology, specifically to a submerged arc welding process, welding wire, and application for manufacturing induction heating bent pipe main tubes. Background Technology

[0002] The main pipe for bend production is the primary raw material, including submerged arc welded steel pipes, high-frequency resistance welded steel pipes, and seamless steel pipes. Hot-bent bends for natural gas pipelines mainly use submerged arc welded steel pipes, especially straight-seam submerged arc welded steel pipes, as the main pipe material. The weld seam is the weakest point of the entire steel pipe; therefore, improving the quality of the submerged arc weld seam in the bend main pipe and its adaptability to the hot-bent bend manufacturing process are key measures to improve the overall quality of the bend. Summary of the Invention

[0003] Based on this, the present invention proposes a straight seam submerged arc welding wire, a submerged arc welding method and its application. The weld produced by using this welding wire and welding method exhibits strong heat-resistant processing performance and can withstand various types of heat treatment.

[0004] According to a first aspect of the present invention, a straight seam submerged arc welding wire is provided, comprising an alloy of the following components in a mass ratio:

[0005] The alloy comprises: C 0.05-0.09%, Si 0.20-0.25%, Mn 1.55-1.75%, P 0.0010%, S 0.005-0.007%, Al 0.01%, Ni 2.0-4.5%, Cr 0.35-0.45%, Cu 0.45-0.75%, V 0.03%, Nb 0.025%, Mo 0.15-0.3%, Ti 0.01%, and B 0.0005%, wherein the Ceq of the alloy is 0.4-0.95%, and the Pcm of the alloy is 0.27-0.31%.

[0006] According to a second aspect of the present invention, an application of a straight seam submerged arc welding wire in the welding process of a bend main pipe of X60 and above steel grade is provided.

[0007] According to a third aspect of the present invention, a method for welding steel pipes using straight seam submerged arc welding wire is provided, comprising:

[0008] Root welding is performed using the first welding wire;

[0009] The welding wire described in claim 1 for manufacturing induction heating bent pipe mother tube is used as the second welding wire for filling;

[0010] Use a third welding wire for the cover;

[0011] or

[0012] The first welding wire, the welding wire for manufacturing induction heating bent pipe mother tube as described in claim 1, and the third welding wire are used for simultaneous welding. They are concentrated on the same machine head, with the first welding wire for large bottom penetration, the second welding wire for filling, and the third welding wire for covering.

[0013] The welding bevel for submerged arc welding is: double-sided V-shaped, single-sided angle 25-65°, and blunt edge 4-10mm. The welding process parameters for submerged arc welding are: current 500-1250A, voltage 30-50V, welding extension 55-85mm, and welding speed 1.2-2m / min.

[0014] According to an embodiment of the present invention, the welding wire must be used in conjunction with an alkaline flux with a basicity B > 1.5.

[0015] According to an embodiment of the present invention, the first welding wire is an H08C welding wire.

[0016] According to an embodiment of the present invention, the third welding wire is H08MnMoTiB welding wire.

[0017] According to a fourth aspect of the present invention, an induction-heated bend header pipe of X60 and above steel grade is provided, which is manufactured using the straight seam submerged arc welding wire of claim 1.

[0018] As can be seen from the above technical solutions, the straight seam submerged arc welding wire, submerged arc welding method, and application provided by the present invention have the following beneficial effects:

[0019] This invention provides a submerged arc welding process that is highly adaptable to the manufacturing process of induction heating pipe bending. The weld seam of the steel pipe (main pipe) produced by the submerged arc welding process of this invention exhibits strong heat-resistant processing properties. It can withstand various types of heat treatment (including quenching, tempering, normalizing, and quenching and tempering) and repeated heat treatments while maintaining excellent strength and toughness. It is well-suited to the manufacturing process of induction heating pipe bending and is suitable for the manufacture of hot-bent pipes for high-pressure, long-distance oil and gas pipelines.

[0020] This invention overcomes the problem that the toughness and plasticity of the submerged arc weld of the main pipe of the bend decrease sharply due to the transformation of the microstructure and the coarsening of the grains after undergoing the heat treatment required by the bend manufacturing process. The grain size of the weld metal is not lower than grade 9, and at the same time, it ensures that the strength of the weld metal after heat treatment is not lower than the strength requirements of the corresponding steel grade steel pipe in ISO 3183 or GB / T 9711.

[0021] The weld seam of the bent pipe produced according to this invention, after undergoing heat treatments such as quenching, normalizing, tempering, annealing, and quenching and tempering, exhibits an average value greater than 115 J and a minimum value greater than 95 J in an impact toughness test at -45°C; furthermore, the weld seam strength is not lower than that of the steel pipe base material. The weld metal retains excellent strength and toughness after heat treatment, demonstrating good heat workability and excellent adaptability to induction heating bending pipe manufacturing processes.

[0022] This invention employs a welding method that increases the weld bevel angle from the original 60° to 80°. This technique increases the transition angle at the fusion line, making the transition at that location smoother, significantly reducing stress concentration, and facilitating slag removal during the welding process, thus reducing welding defects. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the welding angle in an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0025] According to a first aspect of the present invention, a straight seam submerged arc welding wire is provided, comprising an alloy of the following components in a mass ratio:

[0026] The alloy comprises: C 0.05-0.09%, Si 0.20-0.25%, Mn 1.55-1.75%, P 0.0010%, S 0.005-0.007%, Al 0.01%, Ni 2.0-4.5%, Cr 0.35-0.45%, Cu 0.45-0.75%, V 0.03%, Nb 0.025%, Mo 0.15-0.3%, Ti 0.01%, and B 0.0005%, wherein the Ceq of the alloy is 0.4-0.95%, and the Pcm of the alloy is 0.27-0.31%.

[0027] In the chemical composition of the welding wire of this invention, the total alloy content of C and alloying elements such as Mn, Mo, Ni, Cu, and Nb, calculated by carbon equivalent (Ceq), must be greater than 0.40%, with the C content being greater than 0.05%. This ensures that the weld metal has good hardenability and high strength before and after heat treatment, and guarantees that the weld obtains a uniform, fine-grained acicular ferrite structure after heat treatment and cooling. To further ensure that the weld and heat-affected zone have high low-temperature impact resistance after heat treatment, the Ni and Cu contents are significantly increased, while the B content is strictly controlled. This ensures that the weld has good heat workability, improves the toughness and plasticity of the weld metal, and lowers the low-temperature embrittlement transition temperature of the weld metal. Specifically, the Ni content must not be less than 2.0%, the Cu content must not be less than 0.45%, and the B content must not be greater than 0.0005%. However, considering the weldability of the welding wire, its total alloy content, calculated by carbon equivalent (Ceq), must be less than 0.95%, of which the C content must be less than 0.09%, the Ni content must be no more than 4.5%, and the Cu content must be no more than 0.75%.

[0028] According to a second aspect of the present invention, an application of a straight seam submerged arc welding wire in the welding process of a bend main pipe of X60 and above steel grade is provided.

[0029] According to a third aspect of the invention, such as Figure 1 As shown, a method for welding steel pipes using straight seam submerged arc welding wire is provided, comprising:

[0030] Root welding is performed using the first welding wire;

[0031] The welding wire described in claim 1 for manufacturing induction heating bent pipe mother tube is used as the second welding wire for filling;

[0032] Use a third welding wire for the cover;

[0033] or

[0034] The first welding wire, the welding wire for manufacturing induction heating bent pipe mother tube as described in claim 1, and the third welding wire are used for simultaneous welding. They are concentrated on the same machine head, with the first welding wire for large bottom penetration, the second welding wire for filling, and the third welding wire for covering.

[0035] The welding bevel for submerged arc welding is: double-sided V-shaped, single-sided angle 25-65°, and blunt edge 4-10mm. The welding process parameters for submerged arc welding are: current 500-1250A, voltage 30-50V, welding extension 55-85mm, and welding speed 1.2-2m / min.

[0036] According to an embodiment of the present invention, the welding wire must be used in conjunction with an alkaline flux with a basicity B > 1.5.

[0037] According to embodiments of the present invention, the alkaline flux with basicity B > 1.5 comprises the following components:

[0038]

[0039] According to an embodiment of the present invention, the first welding wire is an H08C welding wire.

[0040] According to an embodiment of the present invention, the third welding wire is H08MnMoTiB welding wire, comprising the following components:

[0041] welding wire C Mn Yes P S B You Mo I will H08MnMoTiB 0.07 1.64 0.22 0.013 0.003 0.0048 0.06 0.35 0.03

[0042] The welding wire in this invention must be used in conjunction with an alkaline flux with a basicity B > 1.5 to ensure that the weld metal has higher low-temperature impact toughness before and after heat treatment, and exhibits good adaptability to the heat treatment process.

[0043] According to a fourth aspect of the present invention, an induction-heated bend header pipe of X60 and above steel grade is provided, which is manufactured using the straight seam submerged arc welding wire of claim 1.

[0044] The technical solution of the present invention will be described in detail below through preferred embodiments. It should be noted that the specific embodiments in the following text are for illustrative purposes only and are not intended to limit the present invention.

[0045] Example 1

[0046] Using the welding wire composition listed in Table 1, welding was performed on the Φ508×16mm bend base pipe of X60 steel grade. First, a first quenching was performed at 920℃ using medium-frequency induction heating. Then, the entire pipe was heated to 920℃ in a heat treatment furnace. After removal, it was quickly immersed in a 6%-8% brine solution at a temperature not exceeding 35℃ (the time from furnace removal to immersion in water should not exceed 120 seconds) for a second quenching. Finally, a stress-relief annealing heat treatment was performed at 620℃ in a heat treatment furnace to produce the hot-bent bend. The welding process parameters for the X60 steel grade base pipe are shown in Table 2, and the performance test results of the bend weld are shown in Table 3. The performance met the technical specifications for X60 steel grade bend pipes.

[0047] Table 1. Chemical composition of welding wire

[0048] C Yes Mn P S Al 0.06％ 0.20％ 1.55％ 0.001％ 0.007％ 0.01％ Nor Cr I will V Nb Mo 4.0％ 0.35％ 0.55％ 0.03％ 0.025％ 0.15％ You B Ceq PCM 0.01％ 0.0003％ 0.73％ 0.27％

[0049] Table 2. Welding process parameters for X60 grade steel main pipe

[0050]

[0051] Table 3 shows the performance test results of the bend weld. The performance meets the technical specifications for X60 steel grade bends.

[0052]

[0053] Example 2:

[0054] Using the welding wire composition listed in Table 4, the Φ610×20mm bend base pipe of X60 steel grade was welded, and then the bend was produced by quenching at 920℃ and tempering at 520℃ after medium-frequency induction heating. The welding process parameters of the X60 steel grade base pipe are shown in Table 5, and the performance test results of the bend weld are shown in Table 6. The performance meets the technical indicators specified for X60 steel grade bend pipes.

[0055] Table 4. Chemical composition of welding wire

[0056] C Yes Mn P S Al 0.06％ 0.20％ 1.55％ 0.001％ 0.007％ 0.01％ Nor Cr I will V Nb Mo 4.0％ 0.35％ 0.55％ 0.03％ 0.025％ 0.15％ You B Ceq PCM 0.01％ 0.0003％ 0.73％ 0.27％

[0057] Table 5. Welding process parameters for X60 grade steel main pipe

[0058]

[0059]

[0060] Table 6 shows the performance test results of the bend weld. The performance meets the technical specifications for X60 steel grade bends.

[0061]

[0062] Example 3:

[0063] Using the welding wire composition listed in Table 7, a Φ1016×30.2mm bent pipe of X70 steel grade was welded. The pipe was then subjected to medium-frequency induction heating at 980℃ for quenching and stress-relieving annealing at 580℃ to produce a hot-bent pipe. The welding process parameters for the X70 steel grade pipe are shown in Table 8, and the performance test results of the bent pipe weld are shown in Table 9. The performance meets the technical specifications for X60 steel grade bent pipes.

[0064] Table 7. Chemical composition of welding wire

[0065] C Yes Mn P S Al 0.065％ 0.23％ 1.65％ 0.001％ 0.005％ 0.01％ Nor Cr I will V Nb Mo 4.0％ 0.45％ 0.65％ 0.03％ 0.025％ 0.25％ You B Ceq PCM 0.01％ 0.0003％ 0.80％ 0.30％

[0066] Table 8. Welding process parameters for X70 grade steel main pipe

[0067]

[0068]

[0069] Table 9. The performance test results of the bend weld are as follows, and the performance meets the technical specifications specified for X70 steel grade bends.

[0070]

[0071] Example 4:

[0072] Using the welding wire composition listed in Table 10, a Φ1422×35.2mm bent pipe of X80 steel grade was welded. The pipe was then heat-treated by medium-frequency induction heating at 1100℃ and normalizing at 980℃ to produce a hot-bent pipe. The welding process parameters for the X80 steel grade pipe are shown in Table 11, and the performance test results of the bent pipe weld are shown in Table 12. The performance meets the technical specifications for X60 steel grade bent pipes.

[0073] Table 10. Chemical composition of welding wire

[0074] C Yes Mn P S Al 0.07％ 0.25％ 1.75％ 0.001％ 0.005％ 0.01％ Nor Cr I will V Nb Mo 4.0％ 0.45％ 0.7％ 0.03％ 0.025％ 0.3％ You B Ceq PCM 0.01％ 0.0003％ 0.83％ 0.31％

[0075] Table 11. Welding process parameters for X80 grade steel main pipe

[0076]

[0077] Table 12. The performance test results of the bend weld are as follows, and the performance meets the technical specifications specified for X80 steel grade bends.

[0078]

[0079] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A welding wire for manufacturing induction-heated bent pipe mother tubes, characterized in that, Alloys comprising the following components by mass ratio: The alloy comprises: C 0.05-0.09%, Si 0.20-0.25%, Mn 1.55-1.75%, P 0.0010%, S 0.005-0.007%, Al 0.01%, Ni 2.0-4.5%, Cr 0.35-0.45%, Cu 0.45-0.75%, V 0.03%, Nb 0.025%, Mo 0.15-0.3%, Ti 0.01%, and B 0.0005%, wherein the Ceq of the alloy is 0.4-0.95%, and the Pcm of the alloy is 0.27-0.31%.

2. The application of the welding wire of claim 1 for manufacturing induction heating bend header pipe in the welding process of bend header pipe of X60 and above steel grade.

3. A submerged arc welding process for manufacturing induction-heated bent pipe main tubes using the welding wire described in claim 1, characterized in that, The welding process employs high wire extension hot wire welding technology, including: Root welding is performed using root welding wire; The welding wire described in claim 1 for manufacturing induction heating bent pipe mother tube is used as the first welding wire for filling; Cover welding wire is used for cover welding; or The root welding wire, the welding wire for manufacturing induction heating bent pipe mother tube as described in claim 1, and the cover welding wire are used for simultaneous welding, and they are concentrated on the same machine head. The root welding wire is used for large bottom penetration, the first welding wire is used for filling, and the cover welding wire is used for covering. The welding bevel for submerged arc welding is: double-sided V-shaped, single-sided angle 40-80°, and blunt edge 4-10mm. The welding process parameters for submerged arc welding are: current 500-1250A, voltage 30-50V, welding extension 55-85mm, and welding speed 1.2-2m / min.

4. The submerged arc welding process according to claim 3, characterized in that, Root welding is performed using root welding wire; The welding wire used in claim 1 for manufacturing induction heating bent pipe mother tubes is used as the first welding wire and the second welding wire for filling; Cover welding wire is used for cover welding; or The root welding wire, the welding wire for manufacturing induction heating bent pipe mother tube as described in claim 1, and the cover welding wire are used for simultaneous welding, and they are concentrated on the same machine head. The root welding wire is used for large bottom penetration, the first welding wire and the second welding wire are used for filling, and the cover welding wire is used for covering.

5. The submerged arc welding process according to claim 4, characterized in that, The first and second welding wires must be used with an alkaline flux with a basicity B > 1.

5.

6. The submerged arc welding process according to claim 3 or 4, characterized in that, The root welding wire is H08C or H08MnMoTiB welding wire.

7. The submerged arc welding process according to claim 4, characterized in that, The first welding wire, or the first and second welding wires, is the submerged arc welding wire for the mother tube as described in claim 1.

8. The submerged arc welding process according to claim 3 or 4, characterized in that, The cover welding wire is H08MnMoTiB welding wire.

9. An induction-heated bend header pipe of X60 and above steel grade manufactured using the straight seam submerged arc welding wire of claim 1.

Images