A method for automatic welding of a circular tube

Abstract

The present application belongs to the field of welding, and specifically discloses a kind of automatic welding method of circular tube, the method comprises the following steps: the melting ring is fixed between two circular tubes, then adopts tungsten argon arc welding to weld;The material of the melting ring is same with the material of the circular tube;The tungsten argon arc welding adopts tungsten electrode as negative electrode;The welding step is carried out under the protection atmosphere;The protection atmosphere is argon or the mixed gas of argon and helium;The welding current is 61-92A, the welding voltage is 12.3-13.5V, and the welding speed is 150-180mm / min.Adopt the welding method in the present application to weld, can make the weld have higher mechanical strength, the weld formability is good, the weld quality is excellent, and the welding method in the present application is simple and easy to operate, the welding process is flexible, can realize the full automatic full position welding of small diameter circular tube.

Description

Technical Field

[0001] This invention belongs to the field of welding, and specifically relates to an automatic welding method for round pipes. Background Technology

[0002] With the rapid development of the nuclear power industry, the quality requirements for equipment such as steam generators and steam pipelines are becoming increasingly stringent. As a key piece of equipment in nuclear power plants, the performance of nuclear power heat exchangers directly impacts the economic benefits and safety of the entire plant. Due to limitations in casting technology, the multi-layered elongated tubes in nuclear power heat exchangers are generally extended from multiple short tubes using GTAW welding. This places extremely high demands on the quality and forming of the welded joints, requiring not only no obvious protrusions on the surface of the tube joints but also minimal internal collapse. Traditional manual arc welding struggles to control consistent quality output; therefore, the development and application of new processes for automated all-position welding of such small elongated tubes is urgently needed. Summary of the Invention

[0003] In order to overcome the problems existing in the prior art, one of the objectives of the present invention is to provide an automatic welding method for round tubes. After GTAW automatic welding, the joint is well formed, the joint quality is high, the joint appearance is flat, and the joint strength meets the usage requirements.

[0004] The second objective of this invention is to provide the application of the above-mentioned automatic welding method for circular tubes in the field of nuclear power heat exchangers.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The first aspect of the present invention provides an automatic welding method for round tubes, comprising the following steps:

[0007] The melting ring is fixed between the two round tubes, and then tungsten inert gas welding is used for welding.

[0008] The material of the melting ring is the same as the material of the circular tube;

[0009] The tungsten inert gas welding uses a tungsten electrode as the cathode electrode and a round tube as the anode.

[0010] The welding step is performed under a protective atmosphere; the protective atmosphere is argon, or a mixture of argon and helium;

[0011] The welding current is 61–92A, the welding voltage is 12.3–13.5V, and the welding speed is 150–180 mm / min.

[0012] This invention uses a fusion ring made of the same material as the round tube for cladding. After welding, the weld metal is entirely martensitic and no different phases are generated, resulting in excellent mechanical properties of the welded joint.

[0013] Preferably, the diameter of the tungsten electrode is 2-3 mm and the arc height is 2.5-3.5 mm.

[0014] Preferably, the welding current is a direct current positive current; more preferably, the welding current is a pulse current.

[0015] In this invention, the welding current is 61 to 92 A, for example, it can be selected from 61 A, 62 A, 63 A, 64 A, 65 A, 66 A, 67 A, 68 A, 69 A, 70 A, 71 A, 72 A, 73 A, 74 A, 75 A, 76 A, 77 A, 78 A, 79 A, ​​80 A, 81 A, 82 A, 83 A, 84 A, 85 A, 86 A, 87 A, 88 A, 89 A, 90 A, 91 A, 92 A.

[0016] In this invention, the welding voltage is 12.3 to 13.5V, for example, it can be selected from 12.3V, 12.4V, 12.5V, 12.6V, 12.7V, 12.8V, 12.9V, 13V, 13.1V, 13.2V, 13.3V, 13.4V, and 13.5V.

[0017] In this invention, the welding speed is 150-180 mm / min, for example, it can be selected from 150 mm / min, 152 mm / min, 154 mm / min, 156 mm / min, 158 mm / min, 160 mm / min, 162 mm / min, 164 mm / min, 166 mm / min, 168 mm / min, 170 mm / min, 172 mm / min, 174 mm / min, 176 mm / min, 178 mm / min, and 180 mm / min.

[0018] Preferably, the cross-sectional shape of the fusion ring is I-shaped, T-shaped, inverted T-shaped, or rectangular. A fusion ring with the above-mentioned structure exhibits good post-weld formation, with both the collapse and cladding amounts meeting testing standards. Compared to traditional welding wires, the weld joint is smooth and has a flat morphology.

[0019] Preferably, the material of the circular tube is P91 or P92. Both P91 and P92 are martensitic heat-resistant steels. P91 is composed of the following components by mass percentage: C 0.08-0.12wt%, Mn 0.30-0.60wt%, Si 0.20-0.50wt%, Cr 8.0-9.5wt%, Mo 0.85-1.05wt%, V 0.18-0.25%, Nb 0.06-0.1wt%, N 0.03-0.07wt%, Al≤0.04wt%, Ni≤0.4wt%, P≤0.02wt%, S≤0.01wt%, and Fe as the balance. P92 is composed of the following components by mass percentage: C 0.07–0.13 wt%, Mn 0.30–0.60 wt%, Si ≤0.50 wt%, Cr 8.5–9.5 wt%, Mo 0.30–0.60 wt%, V 0.15–0.25%, Nb 0.04–0.09 wt%, N 0.03–0.07 wt%, W 1.50–2.00 wt%, P ≤0.02 wt%, S ≤0.01 wt%, and Fe as the balance. Both P91 and P92 exhibit good weldability.

[0020] Preferably, the flow rate of the protective atmosphere is 10-15 L / min, for example, it can be selected from 10 L / min, 10.5 L / min, 11 L / min, 11.5 L / min, 12 L / min, 12.5 L / min, 13 L / min, 13.5 L / min, 14 L / min, 14.5 L / min, and 15 L / min.

[0021] Preferably, the diameter of the gas nozzle is 8-10 mm.

[0022] Preferably, the volume percentage of argon in the protective atmosphere is 60% to 100%, for example, it can be selected from 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, and 100%. Compared with pure argon, introducing a certain amount of helium into argon as a protective atmosphere can refine the grain size of the martensitic structure at the joint, improve the joint strength, and also increase the heat input during welding. More preferably, the volume percentage of argon in the protective atmosphere is 60-80%. After adding 20-40% helium to the protective atmosphere, the weld is wider and deeper, can completely penetrate the round tube, and the collapse meets the standard requirements, resulting in good weld formation.

[0023] Preferably, the tungsten inert gas (TIG) welding is performed by rotating the welding torch along the circumference of the tube at the joint between the melting ring and the tube using flat, vertical, and overhead welding methods. More preferably, the TIG welding is performed by rotating the welding torch 360°–720° vertically along the circumference of the tube at the joint between the melting ring and the tube using flat, vertical, and overhead welding methods. The welding torch can be clamped onto a preset circular rail of the automatic welding device using vises, with the nozzle of the welding torch perpendicular to the tangent of the tube, and the torch rotates 1–2 revolutions along the preset circular rail during welding.

[0024] Preferably, the flat welding parameters are: welding current of 81-92A, welding voltage of 13.1-13.5V, and welding speed of 145-155mm / min.

[0025] Preferably, the vertical welding parameters are: welding current of 61-72A, welding voltage of 12.3-12.7V, and welding speed of 165-175mm / min.

[0026] Preferably, the overhead welding parameters are: welding current of 81-92A, welding voltage of 13.1-13.5V, and welding speed of 145-155mm / min.

[0027] Preferably, the outer diameter of the circular tube is 10-20 mm, for example, it can be selected from 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, and 20 mm.

[0028] Preferably, the inner diameter of the circular tube is 10-16 mm; the outer diameter of the circular tube is 17-20 mm. For example, the inner diameter of the circular tube can be selected from 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, or 16 mm; the outer diameter of the circular tube can be selected from 17 mm, 18 mm, 19 mm, or 20 mm.

[0029] Preferably, the wall thickness of the circular tube is 1 to 4 mm, for example, it can be selected from 1 mm, 2 mm, 3 mm, or 4 mm.

[0030] Preferably, the width of the melting ring is 0.5 to 2 mm, for example, it can be selected from 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, and 2 mm.

[0031] Preferably, at least one boss is provided on both sides of the melting ring along the circumferential direction of the melting ring. In this invention, a boss refers to a protrusion that extends outward along the plane perpendicular to the melting ring.

[0032] Preferably, the thickness of the boss is 0.15 to 0.3 mm, for example, it can be selected from 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, and 0.3 mm.

[0033] Preferably, the boss is located at the inner diameter and / or outer diameter of the melting ring.

[0034] Preferably, when the boss is located at the outer diameter of the melting ring, the inner diameter of the boss is 0.15 to 0.3 mm smaller than the outer diameter of the circular tube. For example, it can be selected from 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, and 0.3 mm.

[0035] Preferably, when the boss is located at the inner diameter of the melting ring, the outer diameter of the boss is 0.15 to 0.3 mm larger than the inner diameter of the circular tube. For example, it can be selected from 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, and 0.3 mm.

[0036] Preferably, when the cross-sectional shape of the melting ring is I-shaped, T-shaped, or inverted T-shaped, the inner diameter of the melting ring is the same as the inner diameter of the circular tube, and the outer diameter of the melting ring is the same as the outer diameter of the circular tube.

[0037] Preferably, a boss is provided on both sides of the melting ring along the circumferential direction of the melting ring, and the two bosses are symmetrically arranged about the melting ring; when the boss is located at the inner diameter of the melting ring, the cross-sectional shape of the melting ring is inverted T-shaped. At this time, the outer diameter of the boss is 0.15-0.3 mm larger than the inner diameter of the circular tube. For example, it can be selected from 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, and 0.3 mm. When the boss is located at the outer diameter of the melting ring, the cross-sectional shape of the melting ring is T-shaped. At this time, the inner diameter of the boss is 0.15 to 0.3 mm smaller than the outer diameter of the circular tube. For example, it can be selected from 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, and 0.3 mm.

[0038] Preferably, two bosses are symmetrically provided on both sides of the melting ring along the circumferential direction of the melting ring. The two bosses on the same side of the melting ring are located at the inner and outer diameter positions of the melting ring, respectively, and the cross-sectional shape of the melting ring is I-shaped. The outer diameter of the boss located at the inner diameter position of the melting ring is 0.15 to 0.3 mm larger than the inner diameter of the circular tube. For example, it can be selected from 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, and 0.3 mm. The inner diameter of the boss located at the outer diameter of the melting ring is 0.15 to 0.3 mm smaller than the outer diameter of the circular tube. For example, it can be selected from 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, and 0.3 mm.

[0039] Preferably, the circular tube is provided with grooves. When the melting ring is I-shaped, two grooves are provided on the circular tube at the position where it contacts the melting ring to accommodate two bosses. When the melting ring is T-shaped or inverted T-shaped, a groove is provided on the circular tube at the position where it contacts the melting ring to accommodate a boss, thereby forming a stepped inlay structure between the circular tube and the melting ring.

[0040] Preferably, when the cross-sectional shape of the melting ring is rectangular, the inner diameter of the melting ring is 0.15 to 0.3 mm smaller than the inner diameter of the circular tube, and the outer diameter of the melting ring is 0.15 to 0.3 mm larger than the outer diameter of the circular tube. In this case, no boss is provided on the melting ring.

[0041] Preferably, the welding is performed 1 to 2 times.

[0042] The second aspect of the present invention provides the application of the automatic welding method for circular tubes described in the first aspect of the present invention in the field of nuclear power heat exchangers.

[0043] The beneficial effects of the present invention are: the welding method of the present invention can make the weld have high mechanical strength, good weld formability, and excellent weld quality. Moreover, the welding method of the present invention is simple and easy to operate, and the welding process is flexible, which can realize fully automatic and all-position welding of small diameter round pipes.

[0044] The welding method in this invention can be applied to the automatic welding of round tubes made of P91 or P92 martensitic heat-resistant steel. The resulting weld metal has a martensitic structure, which ensures excellent comprehensive mechanical properties, with a room temperature yield strength of 440-496 MPa, a room temperature tensile strength of 590-642 MPa, and an elongation of 26-47%. Attached Figure Description

[0045] Figure 1 This is a schematic cross-sectional view of the Type I martensitic heat-resistant steel melting ring workpiece in Examples 1 and 2.

[0046] Figure 2 This is a schematic diagram of the structure of the Type I martensitic heat-resistant steel melting ring workpiece in Examples 1 and 2.

[0047] Figure 3 This is a photograph of the actual circular tube welded using the welding method described in Example 1.

[0048] Figure 4 This is a schematic cross-sectional view of the T-shaped martensitic heat-resistant steel melting ring workpiece in Examples 3 and 4.

[0049] Figure 5 This is a schematic diagram of the structure of the T-shaped martensitic heat-resistant steel melting ring workpiece in Examples 3 and 4.

[0050] Figure 6 This is a schematic cross-sectional view of the inverted T-shaped martensitic heat-resistant steel melting ring workpiece in Examples 5 and 6.

[0051] Figure 7 This is a schematic diagram of the structure of the inverted T-shaped martensitic heat-resistant steel melting ring workpiece in Examples 5 and 6.

[0052] Figure 8This is a schematic cross-sectional view of the lamellar martensitic heat-resistant steel melting ring workpiece in Examples 7 and 8.

[0053] Figure 9 This is a schematic diagram of the structure of the lamellar martensitic heat-resistant steel melting ring workpiece in Examples 7 and 8. Detailed Implementation

[0054] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0055] The welding methods in the embodiments of the present invention all adopt automated welding equipment. The welding torch is fixed on a preset arc track along the circular tube by a clamp. The nozzle of the welding torch is perpendicular to the tangent of the circular tube. The welding uses a tungsten electrode as the cathode electrode and the circular tube as the anode electrode. The diameter of the tungsten electrode is 2.4 mm and the arc height is 3 mm. A DC pulse current is used during welding, and the diameter of the gas nozzle is 8-10 mm.

[0056] In this embodiment of the invention, the inner diameter of the circular tube is 14mm, the outer diameter is 18mm, and the circumference is 2mm.

[0057] Example 1

[0058] This example provides an automatic welding method for small-diameter circular pipes in all positions, which uses tungsten inert gas welding for welding filler.

[0059] Tungsten inert gas (TIG) welding uses a type I martensitic heat-resistant steel fusion ring as the weld filler. A schematic diagram of the structure of the type I martensitic heat-resistant steel fusion ring (i.e., the fusion ring) is shown below. Figures 1-2 As shown, the cross-sectional shape of the melting ring is I-shaped. The inner and outer diameters of the melting ring are the same as those of the circular tube. A 0.2mm boss is made 0.2mm inward from the edge of the inner and outer diameters of the melting ring, requiring symmetry along the centerline. The circular tube is embedded in the upper and lower recesses of the I-shaped martensitic heat-resistant steel melting ring workpiece. The inner diameter of the I-shaped martensitic heat-resistant steel melting ring workpiece is 14mm, the diameter of the lower boss is 14.4mm, the diameter of the upper boss is 17.6mm, the outer diameter is 18mm, the transverse width is 1.6mm, the ring width is 2mm, and the ring width of the circular tube is 2mm. The upper and lower parts of the melting ring extend inward by 0.2mm compared to the circular tube. The width of the upper and lower bosses of the melting ring is 0.2mm. The inner and outer radial recesses of the circular tube are 0.2mm, and the width of the recessed part is 0.2mm, forming a stepped embedded structure with the melting ring.

[0060] Tungsten inert gas (TIG) welding uses a 2.4mm diameter tungsten electrode; the shielding gas is 100% argon with a purity of 99.95%. The welding process parameters are divided into four parts:

[0061] (1) Flat welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0062] (2) Vertical (upper and lower) welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 61-72 A, welding voltage is 12.3-12.7 V, and welding speed is 170 mm / min.

[0063] (3) Overhead welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm, welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0064] During welding, two round tubes are inserted into the two ends of the I-type martensitic heat-resistant steel melting ring workpiece and aligned. The welding parameters are adjusted and controlled by the automated welding equipment at different welding positions. The welding torch is clamped on the fixture and runs along the preset arc track of the round tube. Automatic welding of the circumference of the round tube is achieved through three process parameters: flat welding, vertical (upper and lower) welding, and overhead welding. The nozzle of the welding torch is perpendicular to the tangent of the round tube. During welding, the welding torch first welds the weld seam at the left end of the melting ring and the round tube 1 to 2 times (i.e., the welding torch rotates 360° or 720°), and then welds the weld seam at the right end of the melting ring and the round tube 1 to 2 times (i.e., the welding torch rotates 360° or 720°), thus completing the tungsten inert gas welding filling.

[0065] Analysis of the microstructure and mechanical properties of the weld metal after welding using the method described in this example shows that the weld metal is entirely martensitic, with a room temperature yield strength of 454–467 MPa, a room temperature tensile strength of 610–624 MPa, and an elongation of 27–30%.

[0066] The actual image of the round tube welded using the welding method in this example is shown below. Figure 3 As shown, by Figure 3 It can be seen that the weld formed by the welding method in this example has good shape and is smooth and flat.

[0067] Example 2

[0068] This example provides an automatic welding method for small-diameter circular pipes in all positions, which uses tungsten inert gas welding for welding filler.

[0069] Tungsten inert gas welding uses a type I martensitic heat-resistant steel melting ring workpiece as the weld filler, and its structural diagram is shown below. Figures 1-2 As shown, the cross-sectional shape of the melting ring is I-shaped. The inner diameter of the melting ring is 14mm, the diameter of the lower boss is 14.4mm, the diameter of the upper boss is 17.6mm, the outer diameter is 18mm, the lateral width is 1.6mm, the ring width is 2mm, the width of the circular tube ring is 2mm, the upper and lower parts of the melting ring extend inward by 0.2mm compared to the circular tube, the width of the upper and lower bosses of the melting ring is 0.2mm, the inner and outer radial concave treatment of the circular tube is 0.2mm, the width of the concave part is 0.2mm, forming a stepped inlay structure with the melting ring.

[0070] Tungsten inert gas (TIG) welding uses a 2.4mm diameter tungsten electrode; the shielding gas is 60-80% argon + 20-40% helium, with a purity of 99.95%. The welding process parameters are divided into four parts:

[0071] (1) Flat welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0072] (2) Vertical (upper and lower) welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 61-72 A, welding voltage is 12.3-12.7 V, and welding speed is 170 mm / min.

[0073] (3) Overhead welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm, welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0074] During welding, two round tubes are inserted into the two ends of the I-type martensitic heat-resistant steel melting ring workpiece and aligned. The welding parameters are adjusted and controlled by the automated welding equipment at different welding positions. The welding torch is clamped on the fixture and runs along the preset arc track of the round tube. Automatic welding of the circumference of the round tube is achieved through three process parameters: flat welding, vertical (upper and lower) welding, and overhead welding. The nozzle of the welding torch is perpendicular to the tangent of the round tube. During welding, the welding torch first welds the weld seam at the left end of the melting ring and the round tube 1 to 2 times (i.e., the welding torch rotates 360° or 720°), and then welds the weld seam at the right end of the melting ring and the round tube 1 to 2 times (i.e., the welding torch rotates 360° or 720°), thus completing the tungsten inert gas welding filling.

[0075] Analysis of the microstructure and mechanical properties of the weld metal after welding using the welding method in this example shows that the weld metal is entirely martensitic, and the martensitic grains are finer than those under 100% argon gas. The room temperature yield strength is 482-496 MPa, the room temperature tensile strength is 633-642 MPa, and the elongation is 43-47%.

[0076] Example 3

[0077] This example provides an automatic welding method for small-diameter circular pipes in all positions, which uses tungsten inert gas welding for welding filler.

[0078] Tungsten inert gas welding uses a T-shaped martensitic heat-resistant steel melting ring workpiece as the weld filler, and its structural diagram is shown below. Figures 4-5 As shown, the cross-sectional shape of the melting ring is T-shaped. The inner and outer diameters of the melting ring are the same as those of the circular tube. A 0.2mm boss is made 0.2mm inward from the outer edge of the melting ring, requiring symmetry along the centerline. The circular tube is then embedded in the lower recess. Its inner diameter is 14mm, the diameter of the upper boss is 17.6mm, the outer diameter is 18mm, the lateral width is 1.6mm, the ring width is 2mm, and the ring width of the circular tube is 2mm. The upper part of the melting ring extends inward from the circular tube by 0.2mm. The upper boss of the melting ring is 0.2mm wide, and the outer diameter of the circular tube is recessed inward by 0.2mm, with a width of 0.2mm, forming a stepped embedding structure with the melting ring.

[0079] Tungsten inert gas (TIG) welding uses a 2.4mm diameter tungsten electrode; the shielding gas is 100% argon with a purity of 99.95%. The welding process parameters are divided into four parts:

[0080] (1) Flat welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0081] (2) Vertical (upper and lower) welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 61-72 A, welding voltage is 12.3-12.7 V, and welding speed is 170 mm / min.

[0082] (3) Overhead welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm, welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0083] During welding, two round tubes are inserted into the two ends of the T-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The welding parameters are adjusted and controlled by the automated welding equipment at different welding positions. The welding torch is clamped on the fixture and runs along the preset arc track of the round tube. Automatic welding of the circumference of the round tube is achieved through three process parameters: flat welding, vertical (upper and lower) welding, and overhead welding. The nozzle of the welding torch is perpendicular to the tangent of the round tube. During welding, the welding torch first welds the weld seam at the left end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), and then welds the weld seam at the right end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), thus completing the tungsten inert gas welding filling.

[0084] Analysis of the microstructure and mechanical properties of the weld metal after welding using the method described in this example shows that the weld metal is entirely martensitic, with a room temperature yield strength of 440–452 MPa, a room temperature tensile strength of 590–614 MPa, and an elongation of 26–28%.

[0085] Example 4

[0086] This example provides an automatic welding method for small-diameter circular pipes in all positions, which uses tungsten inert gas welding for welding filler.

[0087] Tungsten inert gas welding uses a T-shaped martensitic heat-resistant steel melting ring workpiece as the weld filler, and its structural diagram is shown below. Figures 4-5 As shown, the cross-sectional shape of the melting ring is T-shaped, with an inner diameter of 14 mm, a top boss diameter of 17.6 mm, an outer diameter of 18 mm, a transverse width of 1.6 mm, a ring width of 2 mm, and a circular tube ring width of 2 mm. The top of the melting ring extends inward by 0.2 mm from the circular tube. The top boss of the melting ring is 0.2 mm wide. The outer radial diameter of the circular tube is recessed inward by 0.2 mm, and the width of the recessed part is 0.2 mm, forming a stepped inlay structure with the melting ring.

[0088] Tungsten inert gas (TIG) welding uses a 2.4mm diameter tungsten electrode; the shielding gas is 60-80% argon + 20-40% helium, with a purity of 99.95%. The welding process parameters are divided into four parts:

[0089] (1) Flat welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0090] (2) Vertical (upper and lower) welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 61-72 A, welding voltage is 12.3-12.7 V, and welding speed is 170 mm / min.

[0091] (3) Overhead welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm, welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0092] During welding, two round tubes are inserted into the two ends of the T-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The welding parameters are adjusted and controlled by the automated welding equipment at different welding positions. The welding torch is clamped on the fixture and runs along the preset arc track of the round tube. Automatic welding of the circumference of the round tube is achieved through three process parameters: flat welding, vertical (upper and lower) welding, and overhead welding. The nozzle of the welding torch is perpendicular to the tangent of the round tube. During welding, the welding torch first welds the weld seam at the left end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), and then welds the weld seam at the right end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), thus completing the tungsten inert gas welding filling.

[0093] The microstructure and mechanical properties of the weld metal after welding using the welding method in this example were tested and analyzed. It can be seen that the weld metal is entirely martensitic, and the martensitic grains are finer than those of the microstructure under 100% argon gas. The room temperature yield strength is 470-481 MPa, the room temperature tensile strength is 610-625 MPa, and the elongation is 41-44%.

[0094] Example 5

[0095] This example provides an automatic welding method for small-diameter circular pipes in all positions, which uses tungsten inert gas welding for welding filler.

[0096] Tungsten inert gas welding uses an inverted T-shaped martensitic heat-resistant steel melting ring workpiece as the weld filler, and its structural diagram is shown below. Figures 6-7 As shown, the cross-sectional shape of the melting ring is an inverted T-shape. The inner and outer diameters of the melting ring are the same as those of the circular tube. A 0.2mm boss is made 0.2mm inward from the edge of the inner diameter of the melting ring, requiring symmetry along the centerline. The circular tube is then embedded in the upper recess. Its inner diameter is 14mm, the diameter of the lower boss is 14.4mm, the outer diameter is 18mm, the lateral width is 1.6mm, the ring width is 2mm, and the ring width of the circular tube is 2mm. The lower part of the melting ring extends inward 0.2mm from the circular tube. The lower boss of the melting ring is 0.2mm wide, and the inner radial recess of the circular tube is 0.2mm wide, forming a stepped embedding structure with the melting ring.

[0097] Tungsten inert gas (TIG) welding uses a 2.4mm diameter tungsten electrode; the shielding gas is 100% argon with a purity of 99.95%. The welding process parameters are divided into four parts:

[0098] (1) Flat welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0099] (2) Vertical (upper and lower) welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 61-72 A, welding voltage is 12.3-12.7 V, and welding speed is 170 mm / min.

[0100] (3) Overhead welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm, welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0101] During welding, two round tubes are inserted into the two ends of the inverted T-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The welding parameters are adjusted and controlled by the automated welding equipment at different welding positions. The welding torch is clamped on the fixture and runs along the preset arc track of the round tube. Automatic welding of the circumference of the round tube is achieved through three process parameters: flat welding, vertical (upper and lower) welding, and overhead welding. The nozzle of the welding torch is perpendicular to the tangent of the round tube. During welding, the welding torch first welds the weld seam at the left end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), and then welds the weld seam at the right end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), thus completing the tungsten inert gas welding filling.

[0102] The microstructure and mechanical properties of the weld metal after welding using the welding method in this example were tested and analyzed. It can be seen that the weld metal is entirely martensitic, with a room temperature yield strength of 451-463 MPa, a room temperature tensile strength of 598-619 MPa, and an elongation of 27-29%.

[0103] Example 6

[0104] This example provides an automatic welding method for small-diameter circular pipes in all positions, which uses tungsten inert gas welding for welding filler.

[0105] Tungsten inert gas welding uses an inverted T-shaped martensitic heat-resistant steel melting ring workpiece as the weld filler, and its structural diagram is shown below. Figures 6-7 As shown, the cross-sectional shape of the melting ring is an inverted T-shape, with an inner diameter of 14 mm, a diameter of 14.4 mm at the lower boss, an outer diameter of 18 mm, a transverse width of 1.6 mm, a ring width of 2 mm, a circular tube ring width of 2 mm, a melting ring extending inward 0.2 mm from the lower part of the circular tube, a boss width of 0.2 mm at the lower part of the melting ring, and a radial indentation of 0.2 mm in the inner part of the circular tube, with a width of 0.2 mm, forming a stepped inlay structure with the melting ring.

[0106] Tungsten inert gas (TIG) welding uses a 2.4mm diameter tungsten electrode; the shielding gas is 60-80% argon + 20-40% helium, with a purity of 99.95%. The welding process parameters are divided into four parts:

[0107] (1) Flat welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0108] (2) Vertical (upper and lower) welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 61-72 A, welding voltage is 12.3-12.7 V, and welding speed is 170 mm / min.

[0109] (3) Overhead welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm, welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0110] During welding, two round tubes are inserted into the two ends of the inverted T-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The welding parameters are adjusted and controlled by the automated welding equipment at different welding positions. The welding torch is clamped on the fixture and runs along the preset arc track of the round tube. Automatic welding of the circumference of the round tube is achieved through three process parameters: flat welding, vertical (upper and lower) welding, and overhead welding. The nozzle of the welding torch is perpendicular to the tangent of the round tube. During welding, the welding torch first welds the weld seam at the left end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), and then welds the weld seam at the right end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), thus completing the tungsten inert gas welding filling.

[0111] The microstructure and mechanical properties of the weld metal after welding using the welding method in this example were tested and analyzed: the weld metal was entirely martensitic, and the martensitic grains were finer than those under 100% argon gas. The room temperature yield strength was 482-493 MPa, the room temperature tensile strength was 624-637 MPa, and the elongation was 42-45%.

[0112] Example 7

[0113] This example provides an automatic welding method for small-diameter circular pipes in all positions, which uses tungsten inert gas welding for welding filler.

[0114] Tungsten inert gas welding uses a lamellar martensitic heat-resistant steel melting ring workpiece as the weld filler, and its structural diagram is shown below. Figures 8-9As shown, the cross-sectional shape of the melting ring is rectangular. The inner and outer diameters of the melting ring are 0.2 mm larger than those of the circular tube. The workpiece is required to be symmetrical along the centerline, and the inner and outer diameters of the circular tube are aligned with the same diameter of the melting ring. The inner diameter of the melting ring is 13.8 mm, the outer diameter is 18.2 mm, the transverse width is 1.6 mm, the ring width is 2.2 mm, and the ring width of the circular tube is 2 mm.

[0115] Tungsten inert gas (TIG) welding uses a 2.4mm diameter tungsten electrode; the shielding gas is 100% argon with a purity of 99.95%. The welding process parameters are divided into four parts:

[0116] (1) Flat welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0117] (2) Vertical (upper and lower) welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 61-72 A, welding voltage is 12.3-12.7 V, and welding speed is 170 mm / min.

[0118] (3) Overhead welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm, welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0119] During welding, two round tubes are inserted into the two ends of the plate-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The welding parameters are adjusted and controlled by the automated welding equipment at different welding positions. The welding torch is clamped on the fixture and runs along the preset arc track of the round tube. Automatic welding of the circumference of the round tube is achieved through three process parameters: flat welding, vertical (upper and lower) welding, and overhead welding. The nozzle of the welding torch is perpendicular to the tangent of the round tube. During welding, the welding torch first welds the weld seam at the left end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), and then welds the weld seam at the right end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), thus completing the tungsten inert gas welding filling.

[0120] The microstructure and mechanical properties of the weld metal after welding using the welding method in this example were tested and analyzed. It can be seen that the weld metal is entirely martensitic, with a room temperature yield strength of 439-450 MPa, a room temperature tensile strength of 587-611 MPa, and an elongation of 25-27%.

[0121] Example 8

[0122] This example provides an automatic welding method for small-diameter circular pipes in all positions, which uses tungsten inert gas welding for welding filler.

[0123] Tungsten inert gas welding uses a lamellar martensitic heat-resistant steel melting ring workpiece as the weld filler, and its structural diagram is shown below. Figures 8-9 As shown, the cross-sectional shape of the melting ring is rectangular. Its inner diameter is 13.8 mm, its outer diameter is 18.2 mm, its transverse width is 1.6 mm, its ring width is 2.2 mm, and the width of the circular tube ring is 2 mm.

[0124] Tungsten inert gas (TIG) welding uses a 2.4mm diameter tungsten electrode; the shielding gas is 60-80% argon + 20-40% helium, with a purity of 99.95%. The welding process parameters are divided into four parts:

[0125] (1) Flat welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0126] (2) Vertical (upper and lower) welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm. Welding current is 61-72 A, welding voltage is 12.3-12.7 V, and welding speed is 170 mm / min.

[0127] (3) Overhead welding process parameters: gas flow rate is 10-15 L / min, gas nozzle diameter is 8-10 mm, welding current is 81-92 A, welding voltage is 13.1-13.5 V, and welding speed is 150 mm / min.

[0128] During welding, two round tubes are inserted into the two ends of the inverted T-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The welding parameters are adjusted and controlled by the automated welding equipment at different welding positions. The welding torch is clamped on the fixture and runs along the preset arc track of the round tube. Automatic welding of the circumference of the round tube is achieved through three process parameters: flat welding, vertical (upper and lower) welding, and overhead welding. The nozzle of the welding torch is perpendicular to the tangent of the round tube. During welding, the welding torch first welds the weld seam at the left end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), and then welds the weld seam at the right end of the melting ring and the round tube 1-2 times (i.e., the welding torch rotates 360° or 720°), thus completing the tungsten inert gas welding filling.

[0129] The microstructure and mechanical properties of the weld metal after welding using the welding method in this example were tested and analyzed: the weld metal was entirely martensitic, and the martensitic grains were finer than those under 100% argon gas. The room temperature yield strength was 468-479 MPa, the room temperature tensile strength was 607-621 MPa, and the elongation was 39-42%.

[0130] In summary, the welding method of this invention enables fully automated welding, offers flexible welding processes, and simplifies and controls the welding technology. It achieves automated welding of circular pipes in all positions, resulting in high-strength, well-formed, and high-quality welds. Specifically, this invention employs an all-position automated tungsten inert gas (TIG) welding method to weld P91 or P92 martensitic heat-resistant steel. The resulting weld metal exhibits a martensitic structure, ensuring excellent comprehensive mechanical properties: Under 100% argon protection, the room temperature yield strength is 439–467 MPa, the room temperature tensile strength is 587–624 MPa, and the elongation is 25–30%. Under 60–80% argon + 20–40% helium protection, the room temperature yield strength is 468–496 MPa, the room temperature tensile strength is 607–642 MPa, and the elongation is 39–47%.

[0131] Compared to welding with a 100% argon shielding gas, welding with a shielding gas of 60-80% argon + 20-40% helium results in a wider and deeper weld that can completely penetrate the round pipe. The weld strength is higher, the collapse meets the standard requirements, and the weld formation is good.

[0132] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method of automatic welding of a circular pipe, characterized by: The method comprises the following steps: fixing the melting ring between two circular tubes and then welding by using tungsten argon arc welding; the material of the melting ring is the same as that of the circular tube; the tungsten argon arc welding uses a tungsten electrode as a cathode electrode and a circular tube as an anode; the welding step is carried out in a protective atmosphere which is a mixture of argon and helium; the welding current is 61-92 A, the welding voltage is 12.3-13.5 V, and the welding speed is 150-180 mm / min; in the protective atmosphere, the volume percentage of argon is 60-80% and the volume percentage of helium is 20-40%; the material of the circular tube is P91 or P92; the tungsten argon arc welding is carried out by rotating the circular tube in the circumferential direction of the circular tube in the ways of flat welding, vertical welding and overhead welding at the joint between the melting ring and the circular tube; the flat welding parameters are as follows: the welding current is 81-92 A, the welding voltage is 13.1-13.5 V, and the welding speed is 150-155 mm / min; the vertical welding parameters are as follows: the welding current is 61-72 A, the welding voltage is 12.3-12.7 V, and the welding speed is 165-175 mm / min; the overhead welding parameters are as follows: the welding current is 81-92 A, the welding voltage is 13.1-13.5 V, and the welding speed is 150-155 mm / min.

2. The automatic circular pipe welding method according to claim 1, characterized by: the cross-sectional shape of the melting ring is I-shaped, T-shaped, inverted T-shaped or rectangular.

3. The automatic circular pipe welding method according to claim 1, characterized by: the flow rate of the protective atmosphere is 10-15 L / min.

4. The automatic circular pipe welding method according to claim 1, characterized by: the outer diameter of the circular tube is 10-20 mm.

5. The automatic circular pipe welding method according to claim 1, characterized by: both sides of the melting ring are provided with at least one boss in the circumferential direction of the melting ring; the thickness of the boss is 0.15-0.3 mm; and the boss is arranged at the inner diameter and / or the outer diameter of the melting ring.

6. The application of the automatic circular tube welding method according to any one of claims 1-5 in the field of nuclear power heat exchangers.

Images