Single-tungsten high-current high-frequency double-pulse double-heating-wire surfacing method

Abstract

The invention belongs to the technical field of welding, and particularly relates to a single-tungsten high-current high-frequency double-pulse double-hot-wire surfacing method. The high-frequency double-pulse current is adopted as the main welding current for welding, meanwhile, the pulse frequency of the large pulse current stage and the pulse frequency of the small pulse current stage are limited to be larger than or equal to 5000 Hz, the arc pressure can be reduced along with increase of the pulse current frequency, and therefore large-current welding can be carried out when the arc voltage is controlled to be smaller than or equal to 25 V; therefore, the occurrence of hump welding beads in high-speed welding is reduced. According to the method, high-frequency double-pulse current is adopted, the distance between molten pools can be effectively reduced, and therefore the incomplete fusion defect is not prone to occurring; and meanwhile, the high-frequency double-pulse current can cause molten pool oscillation, and the effects of refining crystal grains and reducing air holes are achieved. Compared with single-path wire feeding, two-path wire feeding is adopted, the cladding rate is higher, the dilution rate is lower, and practical significance is achieved for surfacing application.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a single tungsten extremely large current high frequency double pulse double hot wire surfacing method. Background Art

[0002] At present, in the nuclear power, petrochemical, offshore and other industries, the corrosion-resistant cladding layer of the inner wall of small-diameter pipelines, flange end faces and other large-diameter pipeline inner walls is basically made by single tungsten electrode single DC hot wire process. The single tungsten electrode single DC hot wire process is very mature, but the welding efficiency is still relatively low. In actual production, the welding speed is generally 200-300mm / min and the wire feeding speed is 1.5-2m / min.

[0003] In order to improve welding efficiency, the double tungsten electrode single hot wire process has been developed in recent years. Although the double tungsten electrode single hot wire process has a relatively high welding efficiency, the welding speed in actual production is generally 500-1000mm / min and the wire feeding speed is 3-8m / min, but the welding process window of this method is narrow and is very susceptible to fluctuations in welding wire quality. Moreover, since double tungsten electrodes are used, arc interference between the currents of the two tungsten electrodes and the hot wire current of the welding wire needs to be avoided during welding. Therefore, the control of the welding equipment is relatively complicated and difficult to promote.

[0004] Therefore, the single tungsten electrode single direct current hot wire process is still more widely used. In order to improve the welding efficiency of the single tungsten electrode single direct current hot wire process, people try to use the standard tungsten electrode high current high speed welding process, but the high current high speed welding process is prone to hump welds and defects such as lack of fusion and porosity. Summary of the invention

[0005] The purpose of the present invention is to provide a single tungsten extremely large current high-frequency double-pulse double-hot wire surfacing method. The surfacing method provided by the present invention has the advantages of stable welding process, high cladding efficiency, low dilution rate, etc., and can well overcome the defects such as hump welds, lack of fusion, and pores that are prone to occur during high current and high speed welding.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a single tungsten extremely large current high frequency double pulse double hot wire surfacing method, comprising the following steps:

[0008] In the flowing welding protective gas atmosphere, the arc is started with a tungsten electrode. After the arc starting current rises to the main welding current, the welding wire is fed into the molten pool, and then the welding workpiece starts to rotate for welding.

[0009] The main welding current is a double-pulse current, which includes a number of repeated pulse units, and the pulse unit includes a large pulse current stage and a small pulse current stage in sequence. The peak current of the large pulse current stage is 400-600A, the base current is 300-500A, and the pulse frequency of the large pulse current stage is ≥5000Hz; the peak current of the small pulse current stage is 200-500A, the base current is 100-400A, and the pulse frequency of the small pulse current stage is ≥5000Hz; the welding wire is two-way; the wire feeding speed of a single-way welding wire is ≥2m / min; the arc voltage of the welding is ≤25V.

[0010] Preferably, the duty cycle of the large pulse current stage is 30-60%, and the pulse frequency of the large pulse current stage is 5000-20000 Hz; the duty cycle of the small pulse current stage is 30-60%, and the pulse frequency of the small pulse current stage is 5000-20000 Hz.

[0011] Preferably, in the pulse unit: the duration of the large pulse current stage is 0.01 to 0.1 second; the duration of the small pulse current stage is 0.01 to 0.1 second.

[0012] Preferably, the hot wire current of the single-path welding wire is alternating current, and the hot wire current is 50-100A; the wire feeding speed of the single-path welding wire is 2-8m / min; the total wire feeding speed of the two-path welding wire is 4-16m / min.

[0013] Preferably, the arc voltage of the welding is 15-25V; the welding speed is 800-1500mm / min.

[0014] Preferably, the initial arc starting current is 100-250A, and the time for the initial arc starting current to rise to the main welding current is 0.1-3 seconds.

[0015] Preferably, the diameter of the tungsten electrode is 6.4 mm; the front end of the tungsten electrode is a cone with a platform, the front end angle of the tungsten electrode is 30 to 90°, but not 90°, and the diameter of the platform is 0.5 to 3 mm.

[0016] Preferably, the welding shielding gas is argon, the purity of the argon is ≥99.99%, and the flow rate of the welding shielding gas is 25-35 L / min; before the arc starting, it also includes: pre-gas supply using the welding shielding gas, and the pre-gas supply time is 3-6 seconds.

[0017] Preferably, when the arc current rises to the main welding current, the welding wire is fed to the molten pool after a delay of 0.5 to 2 seconds;

[0018] When the welding wire is fed into the molten pool, the workpiece to be welded starts to rotate for welding after a delay of 0.1 to 0.5 seconds; the rotation is self-rotation, and the linear speed of the rotation is 800 to 1500 mm / min; the welding obtains multiple closed welds, and the multiple closed welds are continuously welded.

[0019] Preferably, the arc is extinguished after the welding obtains multiple closed welds; the arc extinguishing includes: attenuating the main welding current to a decaying current, and the arc starting power supply is turned off after the decaying current is maintained for 0.1 to 5 seconds, and the decaying current is 50 to 120A; the welding wire stops feeding after a delay of 0 to 1 second when the main welding current starts to decay, and the power supply of the hot wire current is turned off after the wire feeding stops; the welding workpiece stops rotating after a delay of 0 to 10 seconds when the main welding current starts to decay; after the arc starting power supply is turned off, the power supply of the hot wire current is turned off, and the welding workpiece stops rotating, the welding protective gas is stopped after 25 to 50 seconds.

[0020] The invention provides a single tungsten large current high frequency double pulse double hot wire surfacing method, comprising the following steps: in a flowing welding protective gas atmosphere, arcing is started by using a tungsten electrode, and after the arcing current is increased to a main welding current, a welding wire is fed into a molten pool, and then welding is performed when the workpiece to be welded starts to rotate; the main welding current is a double pulse current, and the double pulse current includes a plurality of repeated pulse units, and the pulse units include a sequential large pulse current stage and a small pulse current stage, the peak current of the large pulse current stage is 400-600A, the base current is 300-500A, and the pulse frequency of the large pulse current stage is ≥5000Hz; the peak current of the small pulse current stage is 200-500A, the base current is 100-400A, and the pulse frequency of the small pulse current stage is ≥5000Hz; the welding wire is two-way; the wire feeding speed of the single-way welding wire is ≥2m / min; the arc voltage of the welding is ≤25V. The present invention has found that when a standard tungsten electrode with a large current is used for welding, a hump weld defect is very likely to occur due to the increase in arc pressure. The present invention adopts a high-frequency double-pulse current as the main welding current for welding, and at the same time limits the pulse frequency of the large pulse current stage and the small pulse current stage to ≥5000Hz, so that the arc pressure can be reduced as the pulse current frequency increases, so that the present invention can control the welding of a large current when the arc voltage is ≤25V, thereby reducing the occurrence of a high-speed welding hump weld. Furthermore, the present invention adopts a high-frequency double-pulse current, which can effectively reduce the spacing of the molten pool, so that unfused defects are not likely to occur; at the same time, the high-frequency double-pulse current can cause the molten pool to oscillate, which has the effect of refining grains and reducing pores. Compared with a single-channel wire feeding, the present invention adopts two-way wire feeding, and its cladding rate is higher and the dilution rate (the meaning of the dilution rate is: the parent material will also melt during welding, so the parent material will be mixed in the weld, so the filling wire is diluted by the parent material) is lower, which has practical significance for surfacing applications. Therefore, the single tungsten extremely large current high frequency double pulse double hot wire surfacing method provided by the present invention can improve the welding efficiency and effectively overcome the defects such as hump weld, lack of fusion, and porosity that are easy to occur in the process of high current and high speed welding.

[0021] Furthermore, in the present invention, the hot wire current of the single-channel welding wire is alternating current. The present invention has found that when the DC hot wire current exceeds 100A, it will interfere with the main arc, thereby affecting the quality of the cladding. The present invention uses an AC hot wire, which can effectively avoid arc interference and arc blow. At the same time, the deposition rate is improved by controlling the hot wire current to 50-100A.

[0022] In summary, the present invention adopts a single tungsten extremely large current high-frequency double-pulse double AC hot wire high-speed cladding method, the welding current (large pulse current peak current) reaches 400A~600A, the welding speed is 800~1500mm / min, and the sum of the two wire feeding speeds is 4~16m / min. It has the advantages of stable welding process, high cladding efficiency, and low dilution rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A physical picture of a welded part obtained by the single tungsten extremely large current high frequency double pulse double hot wire surfacing method provided in an embodiment of the present invention;

[0024] Figure 2 This is a double pulse current variation curve diagram used in an embodiment of the present invention;

[0025] Figure 3 This is a physical picture of the welding product of comparative example 1 of the present invention containing unfused defects. DETAILED DESCRIPTION

[0026] The present invention provides a single tungsten extremely large current high frequency double pulse double hot wire surfacing method, comprising the following steps:

[0027] In the flowing welding protective gas atmosphere, the arc is started with a tungsten electrode. After the arc starting current rises to the main welding current, the welding wire is fed into the molten pool, and then the welding workpiece starts to rotate for welding.

[0028] The main welding current is a double-pulse current, which includes a number of repeated pulse units, and the pulse unit includes a large pulse current stage and a small pulse current stage in sequence. The peak current of the large pulse current stage is 400-600A, the base current is 300-500A, and the pulse frequency of the large pulse current stage is ≥5000Hz; the peak current of the small pulse current stage is 200-500A, the base current is 100-400A, and the pulse frequency of the small pulse current stage is ≥5000Hz; the welding wire is two-way; the wire feeding speed of a single-way welding wire is ≥2m / min; the arc voltage of the welding is ≤25V.

[0029] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0030] The workpiece to be welded that is applicable to the single tungsten extremely large current high-frequency double-pulse double-hot-wire surfacing method provided by the present invention preferably includes a pipe or a flange end face. In a specific embodiment of the present invention, the workpiece to be welded is preferably a pipe, and the inner diameter of the pipe is 250 mm. Before welding the workpiece to be welded using the single tungsten extremely large current high-frequency double-pulse double-hot-wire surfacing method provided by the invention (before pre-supplying of welding shielding gas), the present invention preferably cleans the workpiece to be welded. The cleaning preferably includes: removing the oxide scale from the area to be welded of the workpiece to be welded, and then cleaning the workpiece to be welded from which the oxide scale has been removed. The present invention has no special requirements for the method for removing the oxide scale. The reagent used for the cleaning is preferably alcohol or acetone.

[0031] In the present invention, the welding shielding gas is preferably argon, and the purity of the argon is preferably ≥99.99%. Before the arc is started, the present invention preferably further comprises: pre-gasing with the welding shielding gas, and the pre-gasing time is preferably 3 to 6 seconds; the flow rate of the welding shielding gas during the pre-gasing is preferably 25 to 35 L / min, and more preferably 30 L / min.

[0032] The present invention uses a tungsten electrode to start the arc in a flowing welding shielding gas atmosphere. In the present invention, the diameter of the tungsten electrode is preferably 6.4 mm; the front end of the tungsten electrode is preferably a cone (truncated cone) with a platform, and the angle of the front end (truncated cone) of the tungsten electrode is preferably 30 to 90°, and is not 90°, and is more preferably 45°. The diameter of the platform (the top platform of the truncated cone) is preferably 0.5 to 3 mm, and is more preferably 1 mm. The flow rate of the welding shielding gas during the arc starting is preferably 25 to 35 L / min, and is more preferably 30 L / min. The initial current of the arc starting is preferably 100 to 250 A, and is specifically preferably 100 A.

[0033] The present invention increases the arc starting current to the main welding current. In the present invention, the time from the initial arc starting current to the main welding current is preferably 0.1 to 3 seconds, more preferably 2 seconds. The main welding current is a double pulse current, and the double pulse current includes a plurality of repeated pulse units, and the pulse unit includes a large pulse current stage and a small pulse current stage in sequence. In each of the pulse units: the duration of the large pulse current stage is preferably 0.01 to 0.1 seconds, and more preferably 0.02 seconds; the duration of the small pulse current stage is preferably 0.01 to 0.1 seconds, and more preferably 0.02 seconds. Both the large pulse current stage and the small pulse current stage are preferably rectangular waves. The peak current of the large pulse current stage is 400-600A, preferably 450-550A, and specifically preferably 450A; the base current is preferably 300-500A, more preferably 350-450A, and specifically preferably 350A; the duty cycle of the large pulse current stage is preferably 30-60%, more preferably 40-55%, and specifically preferably 50%; the pulse frequency of the large pulse current stage is ≥5000Hz, preferably 5000-20000Hz, and specifically preferably 10000Hz. The peak current of the small pulse current stage is preferably 200-500A, more preferably 250-450A, and specifically preferably 350A; the base current is preferably 100-400A, more preferably 200-350A, and specifically preferably 250A; the duty cycle of the small pulse current stage is preferably 30-60%, more preferably 40-55%, and specifically preferably 50%; the pulse frequency of the small pulse current stage is ≥5000Hz, preferably 5000-20000Hz, and specifically preferably 10000Hz.

[0034] In the present invention, when the arc current rises to the main welding current, the present invention preferably delays 0.5 to 2 seconds before feeding the welding wire to the molten pool, and more preferably delays 0.5 seconds.

[0035] The present invention feeds the welding wire into the molten pool, and then the workpiece to be welded starts to rotate for welding. In the present invention, the material of the welding wire is preferably stainless steel or nickel-based welding wire, preferably nickel-based welding wire. In a specific embodiment of the present invention, the material of the welding wire is preferably nickel-based 625 welding wire. The diameter of the welding wire is preferably 1.2 mm.

[0036] In the present invention, the welding wire is two-way; both welding wires preferably have an AC hot wire function. The hot wire current of the single-way welding wire is preferably AC. The hot wire current is preferably 50-100A, more preferably 55-85A, and specifically preferably 60A. The wire feeding speed of the single-way welding wire is ≥2m / min, preferably 2-8m / min, more preferably 3-6m / min, further preferably 4-5m / min, and specifically preferably 4.2m / min. The sum of the wire feeding speeds of the two-way welding wires is preferably 8-16m / min.

[0037] In the present invention, when the welding wire is fed to the molten pool, the present invention preferably delays 0.1 to 1 second before the workpiece to be welded starts to rotate for welding, preferably 0.1 to 0.5 seconds, and specifically preferably 0.1 seconds. The rotation is preferably self-rotation, and the linear speed of the rotation is preferably 800 to 1500 mm / min, more preferably 900 to 1400 mm / min, and specifically preferably 1200 mm / min. The arc voltage of the welding is ≤25V, preferably 15 to 25V. The present invention preferably detects the arc voltage during the welding process to ensure that the arc voltage is maintained at a set value, thereby ensuring that the arc length is consistent and avoiding defects such as lack of fusion. The welding speed is preferably 800 to 1500 mm / min, more preferably 900 to 1400 mm / min, and specifically preferably 1200 mm / min. In the present invention, the linear speed of the rotation is the welding speed. The welding obtains multiple closed welds, and the multiple closed welds are continuously welded. In a specific embodiment of the present invention, when the welding torch used for welding completes a circle of 360° welding, it starts to switch to the next weld.

[0038] In the present invention, the arc is extinguished after the welding obtains multiple closed welds; the arc extinguishing preferably includes: the main welding current is decayed to the decay current, the decay current is preferably maintained for 0.1 to 5 seconds and then the arc starting power supply is turned off (i.e., the arc is turned off), the decay current is preferably 50 to 120A, more preferably 60 to 100A; the decay time is preferably 0.1 to 5 seconds. When the main welding current decays, it is preferably delayed by 0 to 1 second before the wire feeding stops, and after the wire feeding stops, the power supply of the hot wire current is preferably turned off. When the main welding current decays, it is preferably delayed by 0 to 10 seconds before the welding workpiece stops rotating. After the arc starting power supply is turned off, the power supply of the hot wire current is turned off, and the welding workpiece stops rotating, the welding shielding gas is preferably maintained for 25 to 50 seconds before the gas supply stops.

[0039] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] Example 1

[0041] (1) First, remove the oxide scale on the inner surface of the pipe with an inner diameter of 250 mm and clean it with alcohol or acetone.

[0042] (2) A single tungsten electrode with high current and high frequency double pulse surfacing method was used, with a tungsten electrode diameter of 6.4 mm, a front end angle of 45°, and a platform diameter of 1 mm.

[0043] (3) The welding shielding gas is high-purity argon with a purity of ≥99.99% and an argon flow rate of 30 L / min. The arc is started at high frequency after 3 to 6 seconds of pre-gas supply.

[0044] (4) The arc starting current is 100A, and then rises to the main welding current within 2 seconds.

[0045] (5) The main welding current used in the high-frequency double-pulse surfacing method includes repeated pulse units, each pulse unit is a sequence of large pulse current and small pulse current, and the current change curve is as follows: Figure 2 As shown, both the large pulse current stage and the small pulse current stage are rectangular waves. In one pulse unit: the duration of the large pulse current stage is 0.02 seconds; the duration of the small pulse current stage is 0.02 seconds. The large pulse peak current is 450A, the base current is 350A, the duty cycle is 50%, the pulse frequency is 10000Hz; the small pulse peak current is 350A, the base current is 250A, the duty cycle is 50%, the pulse frequency is 10000Hz, and the arc voltage is 20±0.2V.

[0046] (6) After the arc starting current rises to the main welding current, wait for 0.5 seconds to start two-way wire feeding. Both welding wires have AC hot wire function, each hot wire current is 60A, and the double wire feeding speed is 4.2m / min each.

[0047] (7) 0.1 second after the welding wire is fed into the molten pool, the workpiece starts to rotate at a linear speed of 1200 mm / min.

[0048] (8) During the welding process, the arc voltage is tracked and detected according to the set arc voltage value (20±0.2V) to ensure that the arc voltage is maintained at 20±0.2V to ensure consistent arc length and avoid defects such as lack of fusion. When the welding gun completes a 360° welding circle, it starts to switch to the next weld.

[0049] (9) When the entire weld is completed, the arc closure stage begins: the current decays from the high-frequency double pulse to the decay current within 3 seconds, the decay current is 60A, and the decay current is directly turned off after being maintained for 0.2 seconds. The wire feeding is delayed for 0.2 seconds from the moment the high-frequency pulse current decays, and then the hot wire current is turned off. The rotation is delayed for 1 second from the moment the high-frequency pulse current decays, and the lagging shielding gas is maintained for 20 seconds before being turned off.

[0050] Figure 1 The actual picture of the welded part obtained by the single tungsten high current high frequency double pulse double hot wire surfacing method provided in this embodiment is shown in FIG. Figure 1 It can be seen that the surfacing method provided in this embodiment can improve the welding efficiency and effectively overcome defects such as hump welds, lack of fusion, and pores that are prone to occur during high-current and high-speed welding.

[0051] Comparative Example 1

[0052] (1) First, remove the oxide scale on the inner surface of the pipe with an inner diameter of 250 mm and clean it with alcohol or acetone.

[0053] (2) A single tungsten electrode with high current and high frequency double pulse surfacing method was used, with a tungsten electrode diameter of 6.4 mm, a front end angle of 45°, and a platform diameter of 1 mm.

[0054] (3) The welding shielding gas is high-purity argon with a purity of ≥99.99% and an argon flow rate of 30 L / min. The arc is started at high frequency after 3 to 6 seconds of pre-gas supply.

[0055] (4) The arc starting current is 100A, and then rises to the main welding current within 2 seconds.

[0056] (5) Ordinary single pulse process is adopted: peak current is 400A, base current is 300A, peak time is 100ms, base time is 100ms, arc voltage is 20±0.2V.

[0057] (6) After the arc starting current rises to the main welding current, wait for 0.5 seconds to start two-way wire feeding. Both welding wires have AC hot wire function, each hot wire current is 60A, and the double wire feeding speed is 4.2m / min each.

[0058] (7) 0.1 second after the welding wire is fed into the molten pool, the workpiece starts to rotate at a linear speed of 800 mm / min.

[0059] (8) During the welding process, the arc voltage is tracked and detected according to the set arc voltage value (20±0.2V) to ensure that the arc voltage is maintained at 20±0.2V to ensure consistent arc length and avoid defects such as lack of fusion. When the welding gun completes a 360° welding circle, it starts to switch to the next weld.

[0060] (9) When the entire weld is completed, the arc closure stage begins: the current decays from the high-frequency double pulse to the decay current within 3 seconds, the decay current is 60A, and the decay current is directly turned off after being maintained for 0.2 seconds. The wire feeding is delayed for 0.2 seconds from the moment the high-frequency pulse current decays, and then the hot wire current is turned off. The rotation is delayed for 1 second from the moment the high-frequency pulse current decays, and the lagging shielding gas is maintained for 25 seconds before being turned off.

[0061] Figure 3 This is a physical picture of the welding product of Example 1. Figure 3 It can be seen that, since Comparative Example 1 adopts a single-pulse process, the distance between the molten pools is relatively large, so it is easy to form unfused defects. Figure 3 There are multiple unfused welding defects in the products.

[0062] From the above embodiments, it can be seen that the single tungsten extremely large current high-frequency double-pulse double AC hot wire high-speed cladding method provided by the present invention has a welding current of 400-600A, a welding speed of 800-1500mm / min, and a total of two wire feeding speeds of 4-16m / min. It has the advantages of stable welding process, high cladding efficiency, and low dilution rate.

[0063] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A single tungsten extremely large current high frequency double pulse double hot wire surfacing method, characterized in that: The following steps are involved: In the flowing welding protective gas atmosphere, the arc is started with a tungsten electrode. After the arc starting current rises to the main welding current, the welding wire is fed into the molten pool, and then the welding workpiece starts to rotate for welding. The main welding current is a double-pulse current, which includes a number of repeated pulse units, and the pulse unit includes a large pulse current stage and a small pulse current stage in sequence. The peak current of the large pulse current stage is 400-600A, the base current is 300-500A, and the pulse frequency of the large pulse current stage is ≥5000Hz; the peak current of the small pulse current stage is 200-500A, the base current is 100-400A, and the pulse frequency of the small pulse current stage is ≥5000Hz; the welding wire is two-way; the wire feeding speed of a single-way welding wire is ≥2m / min; the arc voltage of the welding is ≤25V.

2. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1 is characterized in that: The duty cycle of the large pulse current stage is 30-60%, and the pulse frequency of the large pulse current stage is 5000-20000 Hz; the duty cycle of the small pulse current stage is 30-60%, and the pulse frequency of the small pulse current stage is 5000-20000 Hz.

3. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1 or 2, characterized in that: In the pulse unit: the duration of the large pulse current stage is 0.01 to 0.1 seconds; the duration of the small pulse current stage is 0.01 to 0.1 seconds.

4. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1 is characterized in that: The hot wire current of the single-path welding wire is alternating current, and the hot wire current is 50-100A; the wire feeding speed of the single-path welding wire is 2-8m / min; the total wire feeding speed of the two-path welding wire is 4-16m / min.

5. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1 or 4, characterized in that: The arc voltage of the welding is 15-25V; the welding speed is 800-1500mm / min.

6. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1 is characterized in that: The initial arc starting current is 100-250A, and the time from the initial arc starting current to the main welding current is 0.1-3 seconds.

7. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1 or 6, characterized in that: The diameter of the tungsten electrode is 6.4 mm; the front end of the tungsten electrode is a cone with a platform, the front end angle of the tungsten electrode is 30-90°, and is not 90°, and the diameter of the platform is 0.5-3 mm.

8. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1 is characterized in that: The welding shielding gas is argon gas, the purity of the argon gas is ≥99.99%, and the flow rate of the welding shielding gas is 25-35 L / min; Before the arc is struck, the method further includes: pre-supplying welding shielding gas, wherein the pre-supplying time is 3 to 6 seconds.

9. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1 is characterized in that: When the arc current rises to the main welding current, the welding wire is fed to the molten pool after a delay of 0.5 to 2 seconds; When the welding wire is fed into the molten pool, the workpiece to be welded starts to rotate for welding after a delay of 0.1 to 0.5 seconds; the rotation is self-rotation, and the linear speed of the rotation is 800 to 1500 mm / min; the welding obtains multiple closed welds, and the multiple closed welds are continuously welded.

10. The single tungsten extremely large current high frequency double pulse double hot wire surfacing method according to claim 1, 4 or 9, characterized in that: After the welding obtains multiple closed welds, the arc is extinguished; the arc extinguishing includes: attenuating the main welding current to the attenuation current, and the arc starting power supply is turned off after the attenuation current is maintained for 0.1 to 5 seconds, and the attenuation current is 50 to 120A; the welding wire is stopped from being fed after a delay of 0 to 1 second at the beginning of the attenuation of the main welding current, and the power supply of the hot wire current is turned off after the wire feeding is stopped; the welding workpiece stops rotating after a delay of 0 to 10 seconds at the beginning of the attenuation of the main welding current; after the arc starting power supply is turned off, the power supply of the hot wire current is turned off, and the welding workpiece stops rotating, the welding protective gas is stopped after 25 to 50 seconds.

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