Automatic circular pipe welding method

Abstract

The invention belongs to the field of welding, and particularly discloses an automatic circular tube welding method which comprises the following steps: fixing a melting ring between two circular tubes, and then welding by adopting argon tungsten-arc welding; the material of the melting ring is the same as that of the circular pipe; the argon tungsten-arc welding adopts a tungsten electrode as a negative electrode; the welding step is carried out in a protective atmosphere; the protective atmosphere is argon or mixed gas of argon and helium; the welding current ranges from 61 A to 92A, the welding voltage ranges from 12.3 V to 13.5 V, and the welding speed ranges from 150 mm / min to 180 mm / min. When the welding method is adopted for welding, a weld joint can have high mechanical strength, the formability of the weld joint is good, the quality of the weld joint is excellent, the welding method is simple and easy to operate, the welding process is flexible, and full-automatic all-position welding of the small-diameter round pipe can be achieved.

Description

Technical Field

[0001] The invention belongs to the field of welding, and in particular relates to an automatic round pipe welding method. Background Art

[0002] With the rapid development of the nuclear power industry, the quality requirements for steam generators, steam pipes and other equipment are getting higher and higher. As a key equipment in a nuclear power plant, the performance of the nuclear power heat exchanger directly affects the economic benefits and safety of the entire nuclear power plant. Due to the limitations of casting technology, the multi-layer long round tubes in the nuclear power heat exchanger are generally extended by welding multiple short round tubes using GTAW. This places very high requirements on the quality and forming of the welded joints, requiring not only that there should be no obvious protrusions on the surface of the round tube joints, but also that the internal collapse of the round tube joints should be small. However, it is difficult to control uniform quality output with traditional manual arc welding, so new process development and application are urgently needed for the automatic full-position welding of such small long round tubes. Summary of the invention

[0003] In order to overcome the problems existing in the above-mentioned prior art, one of the purposes 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 smooth, and the joint strength meets the use requirements.

[0004] A second object of the present invention is to provide an application of the above-mentioned round tube automatic welding method in the field of nuclear power heat exchangers.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A first aspect of the present invention provides a round tube automatic welding method, comprising the following steps:

[0007] The melting ring is fixed between two round tubes and then welded by tungsten inert gas welding;

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

[0009] The tungsten inert gas arc welding adopts a tungsten electrode as a cathode electrode and a round tube as an anode;

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

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

[0012] The present invention adopts the same melting ring as the round tube material for cladding, and the weld metal after welding is all martensitic structure, and different phases will not be generated, and the weld joint has excellent mechanical properties.

[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; further preferably, the welding current is a pulse current.

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

[0016] In the present invention, the welding voltage is 12.3-13.5V, 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 the present invention, the welding speed is 150-180 mm / min, for example, 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, 180 mm / min.

[0018] Preferably, the cross-sectional shape of the melting ring is I-shaped, T-shaped, inverted T-shaped or rectangular. The melting ring with the above structure is well formed after welding, and the collapse amount and the cladding amount both meet the inspection standards. Compared with traditional welding wires, the welding joint is smooth and the morphology is flat.

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

[0020] Preferably, the flow rate of the protective atmosphere is 10 to 15 L / min, for example, 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, 15 L / min.

[0021] Preferably, the gas nozzle has a diameter of 8 to 10 mm.

[0022] Preferably, the volume percentage of argon in the protective atmosphere is 60-100%, 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%, 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 position, improve the joint strength, and in addition, can also increase the heat input during welding. Further 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, the round tube can be completely welded through, the collapse amount meets the standard requirements, and the weld is well formed.

[0023] Preferably, the tungsten inert gas arc welding is performed by rotating the welding gun along the circumference of the round tube by using flat welding, vertical welding and overhead welding at the joint of the melting ring and the round tube; further preferably, the tungsten inert gas arc welding is performed by rotating the welding gun 360° to 720° vertically along the circumference of the round tube by using flat welding, vertical welding and overhead welding at the joint of the melting ring and the round tube. The welding gun can be clamped on the preset circular track of the automatic welding device by a jaw clamp, the muzzle of the welding gun is perpendicular to the tangent of the round tube, and the welding gun is rotated 1-2 circles along the preset circular track during welding.

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

[0025] Preferably, the vertical welding parameters are: welding current is 61-72A, welding voltage is 12.3-12.7V, and welding speed is 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 round tube is 10 to 20 mm, for example, 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 round tube is 10-16 mm, and the outer diameter of the round tube is 17-20 mm. For example, the inner diameter of the round tube can be selected from 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, and the outer diameter of the round tube can be selected from 17 mm, 18 mm, 19 mm, 20 mm.

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

[0030] Preferably, the width of the melting ring is 0.5-2 mm, for example, 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, 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. The boss in the present invention refers to a protrusion extending outward in a direction perpendicular to the plane where the melting ring is located.

[0032] Preferably, the thickness of the boss is 0.15-0.3 mm, for example, 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, 0.3 mm.

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

[0034] Preferably, when the boss is arranged 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 round 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 arranged 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 round 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 an inverted T shape. At this time, 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. 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 arranged on both sides of the melting ring along the circumferential direction of the melting ring, and the two bosses on the same side of the melting ring are respectively located at the inner diameter and outer diameter of the melting ring, and the cross-sectional shape of the melting ring is I-shaped. The outer diameter of the boss located at the inner diameter 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, 0.3 mm. The inner diameter of the boss located at the outer diameter position of the melting ring is 0.15 to 0.3 mm smaller than the outer diameter of the round 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, and when the melting ring is I-shaped, two grooves for accommodating two bosses are provided at the position of the circular tube in contact with the melting ring; when the melting ring is T-shaped or inverted T-shaped, a groove for accommodating the boss is provided at the position of the circular tube in contact with the melting ring, so that the circular tube and the melting ring form a stepped mosaic structure.

[0040] Preferably, when the cross-sectional shape of the melting ring is rectangular, the inner diameter of the melting ring is 0.15-0.3 mm smaller than the inner diameter of the circular tube, and the outer diameter of the melting ring is 0.15-0.3 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 times are 1 to 2 times.

[0042] The second aspect of the present invention provides application of the round tube automatic welding method 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 as follows: the welding method of the present invention is used for welding, so that the weld has higher mechanical strength, good weld formability, and excellent weld quality; the welding method of the present invention is simple and easy to operate, the welding process is flexible, and fully automatic and full-position welding of small-diameter round tubes can be realized.

[0044] The welding method of the present invention can be applied to the automatic welding of round tubes made of P91 or P92 martensitic heat-resistant steel. The weld metal formed is a martensitic structure, which ensures excellent comprehensive mechanical properties. The room temperature yield strength is 440-496 MPa, the room temperature tensile strength is 590-642 MPa, and the elongation is 26-47%. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the cross-sectional structure of the I-type martensitic heat-resistant steel melting ring workpiece in Examples 1 and 2.

[0046] Figure 2 Schematic diagram of the structure of the I-type martensitic heat-resistant steel melting ring workpiece in Examples 1 and 2.

[0047] Figure 3 This is a physical picture of the round tube after welding by the welding method in Example 1.

[0048] Figure 4 Schematic diagram of the cross-sectional structure of the T-type martensitic heat-resistant steel melting ring workpiece in Examples 3 to 4.

[0049] Figure 5 Schematic diagram of the structure of the T-type martensitic heat-resistant steel melting ring workpiece in Examples 3 to 4.

[0050] Figure 6 Schematic diagram of the cross-sectional structure of the inverted T-shaped martensitic heat-resistant steel melting ring workpiece in Examples 5 to 6.

[0051] Figure 7 Schematic diagram of the structure of the inverted T-shaped martensitic heat-resistant steel melting ring workpiece in Examples 5 to 6.

[0052] Figure 8It is a schematic diagram of the cross-sectional structure of the lamellar martensitic heat-resistant steel melting ring workpiece in Examples 7 to 8.

[0053] Fig. 9 Schematic diagram of the structure of the lamellar martensitic heat-resistant steel melting ring workpiece in Examples 7 to 8. DETAILED DESCRIPTION

[0054] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

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

[0056] The circular tube used in the embodiment of the present invention has an inner diameter of 14 mm, an outer diameter of 18 mm, and a ring width of 2 mm.

[0057] Example 1

[0058] This example provides a full-position automatic welding method for small-diameter round pipes, which uses tungsten inert gas arc welding for welding and filling.

[0059] Tungsten inert gas arc welding uses a type I martensitic heat-resistant steel melting ring workpiece as a weld filler. The structural schematic diagram of the type I martensitic heat-resistant steel melting ring workpiece (i.e., melting ring) is as follows: Figure 1-2 As shown, the cross-sectional shape of the melting ring is I-shaped, and the inner and outer diameters of the melting ring are the same as those of the round tube. A 0.2mm boss is made 0.2mm inward from the inner and outer diameter edges of the melting ring, and it is required to be symmetrical along the center line, and the round tube is embedded in the upper and lower recesses of the I-type martensitic heat-resistant steel melting ring workpiece. The I-type martensitic heat-resistant steel melting ring workpiece has an inner diameter of 14mm, a diameter of 14.4mm at the lower boss, a diameter of 17.6mm at the upper boss, an outer diameter of 18mm, a lateral width of 1.6mm, a ring width of 2mm, and a round tube ring width of 2mm. The upper and lower parts of the melting ring extend inward by 0.2mm compared to the round tube, and the upper and lower boss widths of the melting ring are 0.2mm. The inner and outer radial directions of the round tube are recessed by 0.2mm, and the width of the recessed part is 0.2mm, forming a stepped inlay structure with the melting ring.

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

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

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

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

[0064] During welding, two round tubes are respectively inserted into the two ends of an 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 gun is clamped on the fixture and runs along the preset circular arc track of the round tube. The three process parameters of flat welding, vertical (upper and lower) welding and overhead welding are used to realize automatic welding of the round tube in all positions around the circumference. The muzzle of the welding gun is perpendicular to the tangent of the round tube. During welding, the welding gun first welds the left end weld of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and then welds the right end of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), thus completing the tungsten inert gas arc welding filling.

[0065] The microstructure and mechanical properties of the weld metal after welding using this welding method were tested and analyzed, and it was found that the weld metal was 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 picture of the round tube after welding using the welding method in this example is as follows Figure 3 As shown by Figure 3 It can be seen that the weld formed by the welding method in this example has good formability and is flat and smooth.

[0067] Example 2

[0068] This example provides a full-position automatic welding method for small-diameter round pipes, which uses tungsten inert gas arc welding for welding and filling.

[0069] Tungsten inert gas welding uses type I martensitic heat-resistant steel melting ring workpiece as weld filler. Its structural diagram is shown in the figure below. Figure 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 circular tube ring width is 2mm, the upper and lower parts of the melting ring extend inward by 0.2mm compared with the circular tube, the upper and lower boss width of the melting ring is 0.2mm, the inner and outer radials of the circular tube are recessed by 0.2mm, the width of the recessed part is 0.2mm, and a stepped inlaid structure is formed with the melting ring.

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

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

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

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

[0074] During welding, two round tubes are respectively inserted into the two ends of an 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 gun is clamped on the fixture and runs along the preset circular arc track of the round tube. The three process parameters of flat welding, vertical (upper and lower) welding and overhead welding are used to realize automatic welding of the round tube in all positions around the circumference. The muzzle of the welding gun is perpendicular to the tangent of the round tube. During welding, the welding gun first welds the left end weld of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and then welds the right end of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), thus completing the tungsten inert gas arc welding filling.

[0075] The microstructure and mechanical properties of the weld metal after welding using this welding method were tested and analyzed, and it was found that the weld metal was entirely martensitic, and the martensitic grains were finer than those of the structure under 100% argon. The room temperature yield strength was 482-496 MPa, the room temperature tensile strength was 633-642 MPa, and the elongation was 43-47%.

[0076] Example 3

[0077] This example provides a full-position automatic welding method for small-diameter round pipes, which uses tungsten inert gas arc welding for welding and filling.

[0078] Tungsten inert gas welding uses a T-shaped martensitic heat-resistant steel melting ring workpiece as the weld filler. Its structural diagram is shown in the figure below. Figure 4-5 As shown, the cross-sectional shape of the melting ring is T-shaped, and the inner and outer diameters of the melting ring are the same as those of the round tube. A 0.2mm boss is made 0.2mm inward from the outer diameter edge of the melting ring, and it is required to be symmetrical along the midline, and the round tube is 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 round tube is 2mm. The upper part of the melting ring extends 0.2mm inward from the round tube, the boss width above the melting ring is 0.2mm, the outer diameter of the round tube is recessed 0.2mm inward, and the width of the recessed part is 0.2mm, forming a stepped embedded structure with the melting ring.

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

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

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

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

[0083] During welding, two round tubes are respectively inserted into the two ends of a 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 gun is clamped on the fixture and runs along the preset circular arc track of the round tube. The three process parameters of flat welding, vertical (upper and lower) welding and overhead welding are used to realize automatic welding of the round tube in all positions around the circumference. The muzzle of the welding gun is perpendicular to the tangent of the round tube. During welding, the welding gun first welds the left end weld of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and then welds the right end of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and the tungsten inert gas arc welding filling is completed.

[0084] The microstructure and mechanical properties of the weld metal after welding using this welding method were tested and analyzed, and it was found that the weld metal was 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 a full-position automatic welding method for small-diameter round pipes, which uses tungsten inert gas arc welding for welding and filling.

[0087] Tungsten inert gas welding uses a T-shaped martensitic heat-resistant steel melting ring workpiece as the weld filler. Its structural diagram is shown in the figure below. Figure 4-5 As shown, the cross-sectional shape of the melting ring is T-shaped, with an inner diameter of 14mm, an upper boss diameter of 17.6mm, an outer diameter of 18mm, a lateral width of 1.6mm, a ring width of 2mm, a circular tube ring width of 2mm, the upper part of the melting ring extends 0.2mm inward compared to the circular tube, the boss width above the melting ring is 0.2mm, the outer diameter of the circular tube is recessed inward by 0.2mm, the width of the recessed part is 0.2mm, and a stepped inlaid structure is formed with the melting ring.

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

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

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

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

[0092] During welding, two round tubes are respectively inserted into the two ends of a 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 gun is clamped on the fixture and runs along the preset circular arc track of the round tube. The three process parameters of flat welding, vertical (upper and lower) welding and overhead welding are used to realize automatic welding of the round tube in all positions around the circumference. The muzzle of the welding gun is perpendicular to the tangent of the round tube. During welding, the welding gun first welds the left end weld of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and then welds the right end of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and the tungsten inert gas arc welding filling is completed.

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

[0094] Example 5

[0095] This example provides a full-position automatic welding method for small-diameter round pipes, which uses tungsten inert gas arc welding for welding and filling.

[0096] Tungsten inert gas arc welding uses an inverted T-shaped martensitic heat-resistant steel melting ring workpiece as the weld filler. Its structural diagram is shown in the figure below. Figure 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 round tube. A 0.2mm boss is made 0.2mm inward from the inner diameter edge of the melting ring. It is required to be symmetrical along the midline, and the round tube is 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 round tube is 2mm. The lower part of the melting ring extends 0.2mm inward from the round tube. The width of the boss below the melting ring is 0.2mm. The inner diameter of the round tube is recessed 0.2mm, and the width of the recessed part is 0.2mm, forming a stepped embedding structure with the melting ring.

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

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

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

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

[0101] During welding, two round tubes are respectively inserted into the two ends of an inverted T-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The automated welding equipment adjusts and controls the welding parameters at different welding positions. The welding gun is clamped on the fixture and runs along the preset circular arc track of the round tube. The three process parameters of flat welding, vertical (upper and lower) welding and overhead welding are used to realize automatic welding of the round tube in all positions around the circumference. The muzzle of the welding gun is perpendicular to the tangent of the round tube. During welding, the welding gun first welds the left end weld of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and then welds the right end of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and the tungsten inert gas arc welding filling is completed.

[0102] The microstructure and mechanical properties of the weld metal after welding using this welding method were tested and analyzed. It was found that the weld metal was 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 a full-position automatic welding method for small-diameter round pipes, which uses tungsten inert gas arc welding for welding and filling.

[0105] Tungsten inert gas arc welding uses an inverted T-shaped martensitic heat-resistant steel melting ring workpiece as the weld filler. Its structural diagram is shown in the figure below. Figure 6-7 As shown, the cross-sectional shape of the melting ring is an inverted T shape, with an inner diameter of 14mm, a diameter of 14.4mm at the lower boss, an outer diameter of 18mm, a lateral width of 1.6mm, a ring width of 2mm, a circular tube ring width of 2mm, the lower part of the melting ring extends 0.2mm inward than the circular tube, the width of the boss below the melting ring is 0.2mm, the inner diameter of the circular tube is recessed 0.2mm, the width of the recessed part is 0.2mm, and a stepped inlaid structure is formed with the melting ring.

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

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

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

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

[0110] During welding, two round tubes are respectively inserted into the two ends of an inverted T-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The automated welding equipment adjusts and controls the welding parameters at different welding positions. The welding gun is clamped on the fixture and runs along the preset circular arc track of the round tube. The three process parameters of flat welding, vertical (upper and lower) welding and overhead welding are used to realize automatic welding of the round tube in all positions around the circumference. The muzzle of the welding gun is perpendicular to the tangent of the round tube. During welding, the welding gun first welds the left end weld of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and then welds the right end of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and the tungsten inert gas arc welding filling is completed.

[0111] The microstructure and mechanical properties of the weld metal after welding using this welding method were tested and analyzed: the weld metal was entirely martensitic, and the martensitic grains were finer than those under 100% argon, 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 a full-position automatic welding method for small-diameter round pipes, which uses tungsten inert gas arc welding for welding and filling.

[0114] Tungsten inert gas welding uses a sheet of martensitic heat-resistant steel melting ring workpiece as the weld filler. Its structural diagram is shown in the figure below. Figure 8-Figure 9As shown, the cross-section of the melting ring is rectangular, and the inner and outer diameters of the melting ring are 0.2mm larger than the inner and outer diameters of the round tube. The workpiece is required to be symmetrical along the center line, and the inner and outer diameters of the round tube are aligned with the same diameter of the melting ring. The inner diameter of the melting ring is 13.8mm, the outer diameter is 18.2mm, the horizontal width is 1.6mm, the ring width is 2.2mm, and the ring width of the round tube is 2mm.

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

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

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

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

[0119] During welding, two round tubes are respectively inserted into the two ends of a lamellar martensitic heat-resistant steel melting ring workpiece and aligned. The automated welding equipment adjusts and controls the welding parameters at different welding positions. The welding gun is clamped on the fixture and runs along the preset circular arc track of the round tube. The three process parameters of flat welding, vertical (upper and lower) welding and overhead welding are used to realize automatic welding of the round tube in all positions around the circumference. The muzzle of the welding gun is perpendicular to the tangent of the round tube. During welding, the welding gun first welds the left end weld of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and then welds the right end of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and the tungsten inert gas arc welding filling is completed.

[0120] The microstructure and mechanical properties of the weld metal after welding using this welding method were tested and analyzed. It was found that the weld metal was 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 a full-position automatic welding method for small-diameter round pipes, which uses tungsten inert gas arc welding for welding and filling.

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

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

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

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

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

[0128] During welding, two round tubes are respectively inserted into the two ends of an inverted T-shaped martensitic heat-resistant steel melting ring workpiece and aligned. The automated welding equipment adjusts and controls the welding parameters at different welding positions. The welding gun is clamped on the fixture and runs along the preset circular arc track of the round tube. The three process parameters of flat welding, vertical (upper and lower) welding and overhead welding are used to realize automatic welding of the round tube in all positions around the circumference. The muzzle of the welding gun is perpendicular to the tangent of the round tube. During welding, the welding gun first welds the left end weld of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and then welds the right end of the melting ring and the round tube 1 to 2 times (that is, the welding gun rotates 360° or 720°), and the tungsten inert gas arc welding filling is completed.

[0129] The microstructure and mechanical properties of the weld metal after welding using this welding method were tested and analyzed: the weld metal was entirely martensitic, and the martensitic grains were finer than those of the structure under 100% argon. 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 the present invention can realize full-automatic welding, the welding process is flexible, the welding process is simple and easy to control, and the automatic welding of round tubes in all positions is realized. The weld strength after welding is high, the weld shaping is good, and the weld quality is high. Specifically, the present invention adopts a full-position automatic tungsten inert gas argon arc welding method to weld P91 or P92 martensitic heat-resistant steel, and the weld metal formed is a martensitic structure, which ensures excellent comprehensive mechanical properties: the room temperature yield strength is 439-467MPa under 100% argon protection, the room temperature tensile strength is 587-624MPa, and the elongation is 25-30%. The room temperature yield strength is 468-496MPa under 60-80% argon + 20-40% helium protection, the room temperature tensile strength is 607-642MPa, and the elongation is 39-47%.

[0131] Compared with welding under 100% argon shielding gas, welding with 60-80% argon + 20-40% helium shielding gas results in wider and deeper welds, which can completely penetrate the round pipe, higher weld strength, and the amount of collapse meets standard requirements, and the weld is well formed.

[0132] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A round tube automatic welding method, characterized in that: The following steps are involved: The melting ring is fixed between two round tubes and then welded by tungsten inert gas welding; The material of the melting ring is the same as that of the round tube; The tungsten inert gas arc welding adopts a tungsten electrode as a cathode electrode and a round tube as an anode; The welding step is carried out under a protective atmosphere; the protective atmosphere is argon gas, or a mixture of argon gas and helium gas; The welding current is 61-92A, the welding voltage is 12.3-13.5V, and the welding speed is 150-180mm / min.

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

3. The automatic round tube welding method according to claim 1, characterized in that: The material of the round tube is P91 or P92.

4. The automatic round tube welding method according to claim 1, characterized in that: The flow rate of the protective atmosphere is 10 to 15 L / min.

5. The round tube automatic welding method according to claim 1 or 4, characterized in that: The volume percentage of argon in the protective atmosphere is 60-100%.

6. The automatic round tube welding method according to claim 1, characterized in that: The tungsten inert gas arc welding is performed by rotating along the circumferential direction of the round tube by adopting the methods of flat welding, vertical welding and overhead welding at the joint of the melting ring and the round tube.

7. The automatic round tube welding method according to claim 6, characterized in that: The flat welding parameters are: welding current is 81-92A, welding voltage is 13.1-13.5V, and welding speed is 145-155mm / min; And / or, the vertical welding parameters are: welding current is 61-72A, welding voltage is 12.3-12.7V, welding speed is 165-175mm / min; And / or, the overhead welding parameters are: welding current is 81-92A, welding voltage is 13.1-13.5V, and welding speed is 145-155mm / min.

8. The round tube automatic welding method according to claim 1, characterized in that: The outer diameter of the round tube is 10 to 20 mm.

9. The round tube automatic welding method according to claim 8, characterized in that: At least one boss is provided on both sides of the melting ring along the circumferential direction of the melting ring; the thickness of the boss is 0.15-0.3 mm; the boss is arranged at the inner diameter and / or outer diameter of the melting ring.

10. Application of the round tube automatic welding method according to any one of claims 1 to 9 in the field of nuclear power heat exchangers.

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