Efficient welding method for stainless steel pipe

Abstract

According to the efficient welding method for the stainless steel pipe, the stainless steel pipe to be welded is located on a rotating tire, the rotating tire drives the stainless steel pipe to be welded to automatically rotate, an automatic welding gun is located above the rotating tire, argon arc welding is adopted for bottoming of the stainless steel pipe, then CO2 welding is adopted for filling and capping, and a stainless steel pipe sealing head is used for assisting in the welding process; a to-be-welded stainless steel pipe adopts a V-shaped groove of 60 + / -5 degrees, the root gap is 3 + / -0.5 mm, argon arc welding is adopted during backing welding, and then CO2 welding is adopted for filling and capping. The welding efficiency of the stainless steel pipes is remarkably improved, aiming at stainless steel pipe butt welding seams, especially thick-wall pipes, through a layer temperature contrast test, after a CO2 automatic welding technology is adopted, compared with traditional welding, the welding construction efficiency can be improved by about more than three times, and for welding manufacturing of a large number of thick-wall stainless steel pipes in a maritime work module, the welding cost is greatly reduced. And a lot of welders and time cost can be saved.

Description

Technical Field

[0001] The present invention belongs to the field of shipbuilding and design, and particularly relates to an efficient welding method for stainless steel pipes. Background Art

[0002] Under the continuous influence of the global financial crisis, shipbuilding enterprises are facing difficulties in obtaining ship orders, low ship prices, and increasingly detailed quality requirements from shipowners and ship inspection authorities, resulting in increasingly fierce competition in the industry. Moreover, due to the rising and unstable labor costs. Under this dual pressure, we need to tap into internal potential and focus on researching the depth and breadth of new processes, new technologies, and the promotion of automatic and efficient welding, so as to improve the production efficiency of pipe processing and product quality, and reduce production costs.

[0003] The traditional process for welding stainless steel pipe fittings is to perform full welding using manual argon arc welding. This method is only applicable to the welding of stainless steel pipe fittings with relatively small specifications. In offshore projects, 316L (a stainless steel material grade) stainless steel pipes are widely used, with pipe wall thicknesses ranging from 20 mm to 73 mm. The welding workload is large and the welding quality requirements are high. If traditional full manual welding is still used, it will consume a large amount of labor costs and time costs. To solve the technical problems of stainless steel pipe welding, in-depth research on automatic and efficient welding process technologies is carried out. Summary of the Invention

[0004] To solve the above problems, the present invention provides an efficient welding method for stainless steel pipes, aiming to achieve the purpose of improving the welding efficiency of stainless steel pipes. The technical solution adopted is as follows:

[0005] An efficient welding method for stainless steel pipes, wherein the stainless steel pipe to be welded is located on a turning fixture, the turning fixture drives the stainless steel pipe to be welded to rotate automatically, an automatic welding torch is located above the turning fixture, the stainless steel pipe is welded with argon arc welding for the root pass, and then CO2 welding is used for filling and capping. During the welding process, a stainless steel pipe head is used for assistance.

[0006] The stainless steel pipe head is provided with two circular sealing plates. A rotatable central shaft is embedded in the center of one of the sealing plates. An inlet pipe and an outlet pipe are arranged on the central shaft. An airbag is circumferentially arranged on the edge of the sealing plate. The sealing plate is placed inside the stainless steel pipe to be welded, on both sides of the weld seam. Inflate the airbag, and the airbag bulges to clamp the sealing plate inside the stainless steel pipe to be welded.

[0007] The stainless steel pipe to be welded adopts a V-shaped groove with an angle of 60° ± 5°, and the root gap is 3 ± 0.5 mm. When welding the root pass, a GTS-316L argon arc welding wire with a diameter of 2.4 mm is used. The welding power supply adopts direct current straight polarity, the welding current is 45 - 80 amperes, the voltage is 12 - 14 volts, and the welding speed is 40 - 60 mm / minute; when welding the root pass, argon is filled into the inlet pipe, and the air inside the head is discharged from the outlet pipe. The argon gas flow rate is controlled at 10 - 15 liters / minute.

[0008] After the backing welding, water flows into the head through the inlet pipe and flows out through the outlet pipe, forming flowing circulating water in the head. CO2 welding is used for filling. A GFS-316LW dioxide wire with a diameter of 1.2 mm is used. The carbon dioxide gas flow rate is controlled at 20 - 25 liters per minute. The welding power supply uses DC reverse connection. The welding current is controlled at 160 - 240 amperes, the voltage is controlled at 30 - 38 volts, and the welding speed is controlled at 320 - 600 mm per minute.

[0009] After the filling welding, CO2 welding is used for surfacing. A GFS-316LW dioxide wire with a diameter of 1.2 mm is used. The carbon dioxide gas flow rate is controlled at 20 - 25 liters per minute. The welding power supply uses DC reverse connection. The welding current is controlled at 200 - 260 amperes, the voltage is controlled at 30 - 38 volts, and the welding speed is controlled at 320 - 600 mm per minute until the groove is completely filled.

[0010] For the above-mentioned high-efficiency welding method of stainless steel pipes, further, during the welding process, the interlayer temperature is controlled below 134 °C.

[0011] For the above-mentioned high-efficiency welding method of stainless steel pipes, further, during the backing welding, it is preferably welded for 2 - 3 layers.

[0012] For the above-mentioned high-efficiency welding method of stainless steel pipes, further, the turning fixture has two rollers with a distance between them, and the high-strength carbon steel pipe is placed between the two rollers.

[0013] For the above-mentioned high-efficiency welding method of stainless steel pipes, further, after the stainless steel pipes are welded, two non-destructive testing inspections of penetrant PT and radiographic RT are respectively carried out, and there are no welding defects in the welds.

[0014] For the above-mentioned high-efficiency welding method of stainless steel pipes, further, the angle of the welding torch is 90 ± 5 °.

[0015] For the above-mentioned high-efficiency welding method of stainless steel pipes, further, the rotation speed of the turning fixture matches the welding speed.

[0016] For the above-mentioned high-efficiency welding method of stainless steel pipes, further, the outer diameter of the stainless steel pipe divided by the pipe thickness is less than 20, and at the same time, the thickness of the stainless steel pipe is greater than 10 mm.

[0017] The beneficial effects of the present invention are:

[0018] 1) Significantly improve the welding efficiency of stainless steel pipes. For the butt welds of stainless steel pipes, especially thick-walled pipes with an outer diameter-to-wall thickness ratio of less than 20 and a wall thickness greater than 10 mm, it can be seen from the interlayer temperature comparison test that after adopting the CO2 automatic welding technology, compared with traditional welding, the welding construction efficiency can be increased by about more than 3 times. For the welding of a large number of thick-walled stainless steel pipes in offshore modules, a large number of welders and time costs can be saved.

[0019] 2) On the premise of ensuring welding quality, the use of automatic welding technology can effectively reduce the operation difficulty and labor intensity of welders.

[0020] 3) According to experience, even in the case where continuous welding cannot be used, it generally takes a lot of time for the interlayer temperature of general manual welding to cool to the qualified temperature. Therefore, the use of a cooling device can also significantly improve the welding production efficiency.

[0021] 4) For the welding of other similar materials, the application significance of the cooling device is greater. For example, for the welding of duplex stainless steel and super duplex stainless steel, the interlayer temperature has a greater impact on the weld quality and stricter requirements, generally not exceeding 80°C. The application of this technology will further improve the welding efficiency. Description of the Drawings

[0022] Figure 1 It is a schematic cross-sectional structure diagram when the stainless steel pipe head is located inside the stainless steel pipe to be welded;

[0023] Among them, 1 - stainless steel pipe to be welded, 2 - weld, 3 - sealing plate, 4 - central axis, 5 - inlet pipe, 6 - airbag, 7 - outlet pipe. Detailed Embodiment

[0024] The present invention will be further described in conjunction with the drawings.

[0025] An efficient welding method for stainless steel pipes. The stainless steel pipe to be welded is located on a rotating tire, and the rotating tire drives the stainless steel pipe to be welded to rotate automatically. The automatic welding torch is located above the rotating tire. The stainless steel pipe is welded with argon arc for backing, and then filled and covered with CO2 welding. During the welding process, a stainless steel pipe head is used for assistance.

[0026] As Figure 1 shown, the stainless steel pipe head is provided with two circular sealing plates. One of the sealing plates has a rotatable central axis embedded in the center. The central axis is provided with an inlet pipe and an outlet pipe. The periphery of the sealing plate is provided with airbags. The sealing plate is placed inside the stainless steel pipe to be welded, on both sides of the weld. The airbags are inflated, and the airbags bulge to clamp the sealing plate inside the stainless steel pipe to be welded.

[0027] The thickness of the stainless steel pipe to be welded is 16 mm, with a V-groove of 60°±5°. The root gap is 3±0.5 mm. When performing the root welding, a GTS-316L argon arc welding wire with a diameter of 2.4 mm is used. The welding power supply is direct current straight polarity. The welding current is 60 A, the voltage is 13 V, and the welding speed is 50 mm / min. When performing the root welding, argon is filled into the pipe, and the air inside the head is discharged through the outlet pipe. The argon gas flow rate is controlled at 10-15 L / min. The interlayer temperature is controlled below 134°C, and it is better to weld 2-3 layers.

[0028] After the root welding, water flows into the head through the inlet pipe and flows out through the outlet pipe, forming flowing circulating water inside the head. CO2 welding is used for filling. A GFS-316LW CO2 welding wire with a diameter of 1.2 mm is used. The carbon dioxide gas flow rate is controlled at 20-25 L / min. The welding power supply is direct current reverse polarity. The welding current is controlled at 200 A, the voltage is controlled at 36 V, and the welding speed is controlled at 450 mm / min.

[0029] After the filling welding, CO2 welding is used for surfacing. A GFS-316LW CO2 welding wire with a diameter of 1.2 mm is used. The carbon dioxide gas flow rate is controlled at 20-25 L / min. The welding power supply is direct current reverse polarity. The welding current is controlled at 245 A, the voltage is controlled at 35 V, and the welding speed is controlled at 460 mm / min until the groove is completely filled.

[0030] Welding layer temperature comparison

[0031] To verify the actual effect of the cooling device, under the same CO2 automatic welding conditions, two groups of tests were carried out to control the layer temperature by using circulating water cooling and natural cooling for comparison. Through the tests, it is obtained that when using natural cooling, the time required to complete welding is 467 minutes, and when using circulating water cooling, the time required to complete welding is 104 minutes. It can be seen from the line graph that the interval time between each pass. When using circulating water cooling, it is continuous welding, only with welding time and no cooling time. When using natural cooling, the interval time between two consecutive weld beads is mainly the waiting time for natural cooling to 150°C. Moreover, as the plate thickness increases, the required number of weld beads will necessarily increase, and the waiting time for subsequent weld beads will be longer.

[0032] Welding test

[0033] 1) Exploration and confirmation of welding parameters

[0034] To achieve the purpose of improving the welding efficiency of CO2 automatic welding and ensure the weld quality at the same time, through repeated tests and debugging, reasonable welding parameters have been explored, as shown in Table 1

[0035] Table 1 - Suitable parameter range for CO2 automatic welding

[0036]

[0037] 2) Tube welding flaw detection and verification of related mechanical properties

[0038] After overcoming the technical problems of high-efficiency automatic welding of stainless steel, a welding test plan for stainless steel tubes was prepared. According to the requirements of the test plan, tube welding was carried out. After tube welding, two non-destructive flaw detection inspections, namely penetrant testing (PT) and radiographic testing (RT), were performed respectively, and there were no welding defects in the weld. Subsequently, relevant mechanical property inspections were also carried out. The inspection items and quantities are shown in Table 2, and the test results of mechanical properties such as transverse tensile, impact tests at 4 positions, and bending are shown in Table 3. All the above inspection results meet the requirements.

[0039] Table 2 Inspection items and quantities of mechanical properties

[0040]

[0041] Table 3 Inspection results of mechanical properties

[0042]

Claims

1. An efficient welding method for stainless steel pipes, characterized in that, The stainless steel pipe to be welded is located on a rotary table, which drives the stainless steel pipe to be welded to rotate automatically. The automatic welding torch is located above the rotary table. The stainless steel pipe is welded with argon arc welding for backing, and then filled and capped with CO2 welding. During the welding process, a stainless steel pipe head is used for assistance; The stainless steel pipe head is equipped with two circular sealing plates. A rotatable central shaft is embedded in the center of one of the sealing plates. An inlet pipe and an outlet pipe are arranged on the central shaft. Air bags are circumferentially arranged at the edge of the sealing plate. The sealing plate is placed inside the stainless steel pipe to be welded, on both sides of the weld. Inflate the air bags, and the air bags bulge to clamp the sealing plate inside the stainless steel pipe to be welded; The stainless steel pipe to be welded uses a V-shaped groove with an angle of 60°±5°, and the root gap is 3±0.5mm. When performing backing welding, a GTS-316L argon arc welding wire with a diameter of 2.4 mm is used. The welding power supply uses DC straight polarity, the welding current is 45-80 amperes, the voltage is 12-14 volts, and the welding speed is 40-60 mm / minute; When performing backing welding, argon is filled into the inlet pipe, and the air inside the head is discharged from the outlet pipe. The argon gas flow rate is controlled at 10-15 liters / minute; After backing welding, water flows into the head through the inlet pipe and flows out through the outlet pipe. A flowing circulating water is formed inside the head. CO2 welding is used for filling. A GFS-316LW CO2 welding wire with a diameter of 1.2 mm is used. The carbon dioxide gas flow rate is controlled at 20-25 liters / minute. The welding power supply uses DC reverse polarity, the welding current is controlled at 160-240 amperes, the voltage is controlled at 30-38 volts, and the welding speed is controlled at 320-600 mm / minute; After filling welding, CO2 welding is used for capping. A GFS-316LW CO2 welding wire with a diameter of 1.2 mm is used. The carbon dioxide gas flow rate is controlled at 20-25 liters / minute. The welding power supply uses DC reverse polarity, the welding current is controlled at 200-260 amperes, the voltage is controlled at 30-38 volts, and the welding speed is controlled at 320-600 mm / minute until the groove is completely filled.

2. The high-efficiency welding method for a stainless steel pipe according to claim 1, characterized in that, During the welding process, the interlayer temperature is controlled below 134°C.

3. An efficient welding method for stainless steel pipes according to claim 1, characterized in that, When performing backing welding, it is better to weld 2-3 layers.

4. The high-efficiency welding method for stainless steel pipes according to claim 1, characterized in that, The rotary table is equipped with two rollers with a distance between them. The high-strength carbon steel pipe is placed between the two rollers.

5. A high-efficiency welding method for stainless steel pipes according to claim 1, characterized in that, After the stainless steel pipe is welded, two non-destructive testing inspections of penetrant PT and radiographic RT are respectively carried out, and there are no welding defects in the weld.

6. A high-efficiency welding method for stainless steel pipes according to claim 1, characterized in that, The welding torch angle is 90±5°.

7. The high-efficiency welding method for stainless steel pipes according to claim 1, characterized in that, The rotation speed of the rotary table matches the welding speed.

8. The high-efficiency welding method for stainless steel pipes according to claim 1, characterized in that, The outer diameter of the stainless steel pipe divided by the pipe thickness is less than 20, and at the same time the stainless steel pipe thickness is greater than 10 mm.

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