阅读说明：本技术 水下全位置局部干法脉冲mig焊接系统及焊接方法 (Underwater all-position local dry pulse MIG welding system and welding method ) 是由 王振民 陈浩宇 张芩 徐孟嘉 吴祥淼 于 2021-07-29 设计创作，主要内容包括：本发明提供了一种一种水下全位置局部干法脉冲MIG焊接系统及焊接方法；其中系统包括工控机、水下机器人、SiC焊接电源、潜水送丝装置、气体装置和送丝罩；工控机、水下机器人、SiC焊接电源和潜水送丝装置均通过总线进行连接；送丝罩与水下机器人机械手连接；送丝罩包括带有焊接定位腔的罩体；焊接定位腔的腔口形成与工件目标焊接区域平面贴合的贴合平面；焊接定位腔的腔壁分别设有送丝口、送气口和排水阀；送气口与气体装置连接；焊接定位腔中设有与送丝口连通的送丝导管；焊接定位腔中还设有用于定位的爪状定位模块。该系统具备局部强排水功能,可为水下焊接提供干燥空间且焊接空间气流场稳定,具备宽工艺适应性。(The invention provides an underwater all-position local dry pulse MIG welding system and a welding method; the system comprises an industrial personal computer, an underwater robot, a SiC welding power supply, a diving wire feeding device, a gas device and a wire feeding cover; the industrial personal computer, the underwater robot, the SiC welding power supply and the diving wire feeding device are all connected through a bus; the wire feeding cover is connected with the underwater robot manipulator; the wire feeding cover comprises a cover body with a welding positioning cavity; a joint plane jointed with the plane of the target welding area of the workpiece is formed at the opening of the welding positioning cavity; the cavity wall of the welding positioning cavity is respectively provided with a wire feeding port, a gas feeding port and a drain valve; the gas supply port is connected with a gas device; a wire feeding guide pipe communicated with the wire feeding port is arranged in the welding positioning cavity; and a claw-shaped positioning module for positioning is also arranged in the welding positioning cavity. The system has a local strong drainage function, can provide a drying space for underwater welding, is stable in a welding space airflow field, and has wide process adaptability.)

1. The utility model provides an underwater full position local dry method pulse MIG welding system which characterized in that: the method comprises the following steps:

the industrial personal computer is used for monitoring;

an underwater robot for working under water;

a SiC welding power supply for providing energy for a welding process;

the diving wire feeder is used for providing filling wires for the welding process and adjusting the wire feeding speed in real time;

a gas device for providing a draining gas for the welding process;

and a wire feeding cover for covering the target welding area of the workpiece to provide a dry welding space;

the industrial personal computer, the underwater robot, the SiC welding power supply and the diving wire feeding device are all connected through a bus; the wire feeding cover is connected with the underwater robot manipulator;

the wire feeding cover comprises a cover body with a welding positioning cavity; the opening of the welding positioning cavity forms a joint plane jointed with the plane of the target welding area of the workpiece, so that the welding positioning cavity is relatively closed when the cover body is jointed with the plane of the target welding area of the workpiece; the cavity wall of the welding positioning cavity is respectively provided with a wire feeding port, a gas feeding port and a drain valve; the gas supply port is connected with a gas device so as to input drainage gas into the welding positioning cavity; a wire feeding guide pipe communicated with the wire feeding port is arranged in the welding positioning cavity so as to introduce the wire output by the diving wire feeding device into the welding positioning cavity; the outlet at the tail end of the wire feeding guide pipe corresponds to the position of the cavity opening of the welding positioning cavity, so that a wire can extend out of the outlet at the tail end of the wire feeding guide pipe after passing through the wire feeding guide pipe and can be contacted with the plane of a target welding area of a workpiece at the cavity opening of the welding positioning cavity to realize welding; a claw-shaped positioning module for positioning is also arranged in the welding positioning cavity; the claw-shaped positioning module forms a positioning space, and the central axis of the positioning space is coaxial with the central axis of the welding positioning cavity.

2. The underwater full position partial dry pulse MIG welding system of claim 1 further comprising: the SiC welding power supply comprises a main circuit for converting three-phase alternating current into welding current as output and a control circuit for controlling the welding power supply; and one output pole of the main circuit is used for connecting a wire, and the other output pole of the main circuit is used for connecting a workpiece.

3. The underwater full position partial dry pulse MIG welding system of claim 2 further comprising: a conductive nozzle is arranged at the outlet of the tail end of the wire feeding guide pipe; the main circuit is used for connecting the output electrode of the wire material with the contact tip.

4. The underwater full position partial dry pulse MIG welding system of claim 2 further comprising: the main circuit comprises:

the three-phase rectification filter circuit is used for converting three-phase alternating current into direct current bus voltage;

the SiCMOS ultrahigh frequency inverter circuit is used for converting the direct current bus voltage into alternating current square waves;

the transformer is used for converting the high-voltage small current of the alternating-current square wave into the low-voltage large current;

and a full wave rectification filter circuit for rectification and filtering;

the three-phase rectification filter circuit, the SiCMOS ultrahigh frequency inverter circuit, the transformer and the full-wave rectification filter circuit are sequentially connected.

5. The underwater full position partial dry pulse MIG welding system of claim 2 further comprising: the control circuit comprises a core module, an ultrahigh frequency driving module, a load voltage and current sampling module, an isolating switch control module and a communication module.

6. The underwater full position partial dry pulse MIG welding system of claim 1 further comprising: the wire feeding guide pipe comprises a first pipe section connected with the wire feeding port and a second pipe section connected to one end of the first pipe section, which is close to the mouth of the welding positioning cavity; the second pipe section and the central axis of the welding positioning cavity form an included angle; a height interval is reserved between the tail end of the second pipe section and the mouth of the welding positioning cavity; and the extension line of the second pipe section passes through the cavity opening of the welding positioning cavity.

7. The underwater full position partial dry pulse MIG welding system of claim 1 further comprising: the claw-shaped positioning module is detachably arranged in the welding positioning cavity;

the claw-shaped positioning module comprises at least three positioning claws; a positioning space for positioning the cylindrical part in the workpiece is formed between the positioning claws.

8. The underwater full position partial dry pulse MIG welding system of claim 1 further comprising: the cover body comprises an upper cover body and a lower cover body; the upper cover body and the lower cover body are detachably connected; the wire feeding port, the air feeding port and the drain valve are respectively positioned at the top end of the upper cover body; the lower cover body is gradually reduced when extending from one side close to the upper cover body to one side far away from the lower cover body.

9. A welding method, characterized by: for use in the underwater full position localized dry pulse MIG welding system of any one of claims 1 to 8; the method comprises the following steps:

s1, the industrial personal computer sends motion trail parameters to the underwater robot, and the underwater robot moves to the position near a workpiece target welding area according to the motion trail parameters; the industrial personal computer sends the multi-axis motion parameters to the underwater robot, and the underwater robot drives the wire feeding cover to align to the welding starting point according to the multi-axis motion parameters, so that the mouth of the welding positioning cavity of the wire feeding cover is attached to the plane of the target welding area of the workpiece, and the welding positioning cavity is relatively closed;

s2, starting the SiC welding power supply, and sending welding process parameters to the SiC welding power supply by the industrial personal computer; the SiC welding power supply starts the gas device to work and output the drainage gas, and the water in the welding positioning cavity of the wire feeding cover is drained; the submersible wire feeder conveys wires, and the SiC welding power supply outputs pulse welding current; during the period that the SiC welding power supply outputs the pulse welding current, the wire feeding cover rotates along the central shaft of the welding positioning cavity to realize arc-shaped, belt-shaped or annular welding seam welding;

and S3, after welding, stopping the work of the SiC welding power supply, the diving wire feeding device and the gas device, sending a new motion trail parameter to the underwater robot by the industrial personal computer, moving the underwater robot to a new area to be welded, and repeating the S2 welding process until the welding task is finished.

10. The welding method of claim 9, wherein: when the target welding area of the workpiece is provided with a cylindrical part, in the step S1, in the process of attaching the welding positioning cavity opening of the wire feeding cover and the target welding area plane of the workpiece, the cylindrical part is clamped by the claw-shaped positioning module of the wire feeding cover to realize positioning.

Technical Field

The invention relates to the technical field of welding equipment, in particular to an underwater all-position local dry pulse MIG welding system and a welding method.

Background

Metal Inert Gas (MIG) welding is used as an effective means for land metal material connection, has the characteristics of mature process, relatively low cost, convenient maintenance and good flexibility, and is popularized and applied to underwater welding repair at present. The underwater local dry welding provides a local gas phase space for electric arcs through a small device, can ensure reliable fusion of welding seams and workpieces compared with wet welding, is lower in equipment cost compared with a dry method, has certain welding stability and convenience, and is an important development direction for underwater welding repair.

However, in the process of repairing underwater structures such as submarine pipelines, nuclear reactor core plates and pressure vessels, besides horizontal welding, vertical welding, horizontal welding, overhead welding and other welding at various positions are often required, under these conditions, the stress balance state of a molten pool is easily broken, and metal of the molten pool is easily caused to flow down and separate from a welding line under the action of surface tension and gravity; and the unstable gas phase space of the welding area further aggravates the unbalanced stress condition of the molten pool, so that the welding has quality problems.

In addition, the pulse MIG welding has flexible electric arc blowing force adjusting capacity, and the electric arc force-gravity-surface tension stress balance of the overhead welding molten pool can be realized through the combined regulation and control of technological parameters such as pulse frequency, peak ratio, peak size and the like, so that a better welding effect is achieved. The invention of China, namely a pulse MIG welding power supply (publication number CN110744173A), provides a pulse MIG welding power supply with the inversion frequency of 80kHz, however, as Si-IGBT is adopted as a main power device, key indexes such as radiation resistance, inversion frequency, response speed, electric energy conversion efficiency and the like of the Si-IGBT still have great defects, and the Si-IGBT is difficult to adapt to complex working conditions of underwater welding. Compared with the prior art, the new generation pulse MIG welding power supply based on the SiC power device realizes comprehensive surpassing in the aspects of dynamic characteristics, energy fine adjustment capability and the like, can ensure a stable welding power supply-underwater welding arc system under the conditions of underwater undercurrent disturbance, water film wetting and strong cooling, and improves the stability of underwater welding.

In order to meet the welding requirements of various positions of horizontal welding, vertical welding, overhead welding and the like of an underwater structure, the development of an underwater all-position local dry pulse MIG welding system and a welding method is urgently needed.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide an underwater all-position local dry pulse MIG welding system and a welding method; the system has a local strong drainage function, can provide a drying space for underwater welding, is stable in a welding space airflow field, and has wide process adaptability.

In order to achieve the purpose, the invention is realized by the following technical scheme: the utility model provides an underwater full position local dry method pulse MIG welding system which characterized in that: the method comprises the following steps:

the industrial personal computer is used for monitoring;

an underwater robot for working under water;

a SiC welding power supply for providing energy for a welding process;

the diving wire feeder is used for providing filling wires for the welding process and adjusting the wire feeding speed in real time;

a gas device for providing a draining gas for the welding process;

and a wire feeding cover for covering the target welding area of the workpiece to provide a dry welding space;

the industrial personal computer, the underwater robot, the SiC welding power supply and the diving wire feeding device are all connected through a bus; the wire feeding cover is connected with the underwater robot manipulator;

the wire feeding cover comprises a cover body with a welding positioning cavity; the opening of the welding positioning cavity forms a joint plane jointed with the plane of the target welding area of the workpiece, so that the welding positioning cavity is relatively closed when the cover body is jointed with the plane of the target welding area of the workpiece; the cavity wall of the welding positioning cavity is respectively provided with a wire feeding port, a gas feeding port and a drain valve; the gas supply port is connected with a gas device so as to input drainage gas into the welding positioning cavity; a wire feeding guide pipe communicated with the wire feeding port is arranged in the welding positioning cavity so as to introduce the wire output by the diving wire feeding device into the welding positioning cavity; the outlet at the tail end of the wire feeding guide pipe corresponds to the position of the cavity opening of the welding positioning cavity, so that a wire can extend out of the outlet at the tail end of the wire feeding guide pipe after passing through the wire feeding guide pipe and can be contacted with the plane of a target welding area of a workpiece at the cavity opening of the welding positioning cavity to realize welding; a claw-shaped positioning module for positioning is also arranged in the welding positioning cavity; the claw-shaped positioning module forms a positioning space, and the central axis of the positioning space is coaxial with the central axis of the welding positioning cavity.

Preferably, the SiC welding power supply includes a main circuit for converting three-phase alternating current into welding current as an output, and a control circuit for controlling the welding power supply; and one output pole of the main circuit is used for connecting a wire, and the other output pole of the main circuit is used for connecting a workpiece.

Preferably, the outlet at the tail end of the wire feeding conduit is provided with a contact nozzle; the main circuit is used for connecting the output electrode of the wire material with the contact tip.

Preferably, the main circuit comprises:

the three-phase rectification filter circuit is used for converting three-phase alternating current into direct current bus voltage;

the SiCMOS ultrahigh frequency inverter circuit is used for converting the direct current bus voltage into alternating current square waves;

the transformer is used for converting the high-voltage small current of the alternating-current square wave into the low-voltage large current;

and a full wave rectification filter circuit for rectification and filtering;

the three-phase rectification filter circuit, the SiCMOS ultrahigh frequency inverter circuit, the transformer and the full-wave rectification filter circuit are sequentially connected.

Preferably, the control circuit comprises a core module, an ultrahigh frequency driving module, a load voltage and current sampling module, an isolating switch control module and a communication module.

Preferably, the wire feeding conduit comprises a first pipe section connected with the wire feeding port and a second pipe section connected to one end of the first pipe section, which is close to the mouth of the welding positioning cavity; the second pipe section and the central axis of the welding positioning cavity form an included angle; a height interval is reserved between the tail end of the second pipe section and the mouth of the welding positioning cavity; and the extension line of the second pipe section passes through the cavity opening of the welding positioning cavity.

Preferably, the claw-shaped positioning module is detachably arranged in the welding positioning cavity;

the claw-shaped positioning module comprises at least three positioning claws; a positioning space for positioning the cylindrical part in the workpiece is formed between the positioning claws.

Preferably, the cover comprises an upper cover and a lower cover; the upper cover body and the lower cover body are detachably connected; the wire feeding port, the air feeding port and the drain valve are respectively positioned at the top end of the upper cover body; the lower cover body is gradually reduced when extending from one side close to the upper cover body to one side far away from the lower cover body.

A welding method, characterized by: the underwater all-position local dry pulse MIG welding system is used for the underwater all-position local dry pulse MIG welding system; the method comprises the following steps:

s1, the industrial personal computer sends motion trail parameters to the underwater robot, and the underwater robot moves to the position near a workpiece target welding area according to the motion trail parameters; the industrial personal computer sends the multi-axis motion parameters to the underwater robot, and the underwater robot drives the wire feeding cover to align to the welding starting point according to the multi-axis motion parameters, so that the mouth of the welding positioning cavity of the wire feeding cover is attached to the plane of the target welding area of the workpiece, and the welding positioning cavity is relatively closed;

s1, the industrial personal computer sends motion trail parameters to the underwater robot, and the underwater robot moves to the position near a workpiece target welding area according to the motion trail parameters; the industrial personal computer sends the multi-axis motion parameters to the underwater robot, and the underwater robot drives the wire feeding cover to align to the welding starting point according to the multi-axis motion parameters, so that the mouth of the welding positioning cavity of the wire feeding cover is attached to the plane of the target welding area of the workpiece, and the welding positioning cavity is relatively closed;

s2, starting the SiC welding power supply, and sending welding process parameters to the SiC welding power supply by the industrial personal computer; the SiC welding power supply starts the gas device to work and output the drainage gas, and the water in the welding positioning cavity of the wire feeding cover is drained; the submersible wire feeder conveys wires, and the SiC welding power supply outputs pulse welding current; during the period that the SiC welding power supply outputs the pulse welding current, the wire feeding cover rotates along the central shaft of the welding positioning cavity to realize arc-shaped, belt-shaped or annular welding seam welding;

and S3, after welding, stopping the work of the SiC welding power supply, the diving wire feeding device and the gas device, sending a new motion trail parameter to the underwater robot by the industrial personal computer, moving the underwater robot to a new area to be welded, and repeating the S2 welding process until the welding task is finished.

Preferably, when the target welding area of the workpiece has a cylindrical part, in the step S1, in the process of the planar fitting of the welding positioning cavity opening of the wire feeding cover and the target welding area of the workpiece, the cylindrical part is clamped by the claw-shaped positioning module of the wire feeding cover to realize positioning.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the invention has the function of local strong drainage and can provide a drying space for underwater welding; the welding device can be used for all-position welding of a plane welding area, including vertical welding, transverse welding, overhead welding and the like, and has wide process adaptability; the drain valve is convenient for the falling and flowing of welding slag and residual moisture in the overhead welding process, and can improve the welding stability;

2. according to the invention, the central axis of the welding positioning cavity of the wire feeding cover does not displace in the welding process, so that the stability of an airflow field in the welding positioning cavity is ensured, and the problem of unstable gas phase space of arc, strip and annular welding seams in the traditional welding process is solved;

3. the wire feeding cover adopted by the invention has the characteristics of small volume and good flexibility, can be well matched and compatible with an underwater robot, can fully exert the advantages of the motion precision and the flexibility of the robot, has good accessibility to underwater welding operation in a narrow space, and can meet the welding repair requirements of underwater complex components such as an underwater oil-gas pipeline, the interior of a nuclear spent fuel pool and an underwater steel structure of an ocean platform;

4. the SiC welding power supply adopts a wide bandgap power device SiCSMOSFET to establish a full-bridge inversion topology, can increase the inversion frequency to more than 200kHz, is about 10 times of the prior industrial welding power supply technology, and provides a power basis for fine regulation and control of arc energy; the flexible configuration and accurate control of pulse current waveforms can be realized by combining a full digital control circuit, flexible and rapid electric arc regulation and control capability is provided, and the stress balance of a molten pool in the full-position welding process is ensured by using electric arc force;

5. the invention can realize the automation of underwater all-position welding, realize the information interaction and digital cooperation of an industrial personal computer, an underwater robot, a SiC welding power supply and other peripheral equipment based on bus communication, further ensure the accuracy of the automatic operation of each flow of the underwater all-position welding, and have the advantages of strong anti-interference capability, good repeatability, high efficiency and good safety.

Drawings

FIG. 1 is a system block diagram of an underwater full position partial dry pulse MIG welding system of the present invention;

FIG. 2 is a schematic diagram of a SiC welding power supply for the underwater full position partial dry pulse MIG welding system of the present invention;

FIG. 3 is a schematic perspective view of a wire feed hood of the underwater full position partial dry pulse MIG welding system of the present invention;

FIG. 4 is a schematic top view of a wire feed hood of the underwater full position partial dry pulse MIG welding system of the present invention;

FIG. 5 is a cross-sectional view taken along line A-A of FIG. 4;

FIG. 6 is a schematic bottom view of a wire feed hood of the underwater full position partial dry pulse MIG welding system of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Examples

The underwater all-position local dry pulse MIG welding system shown in FIG. 1 includes:

the industrial personal computer is used for monitoring;

an underwater robot for working under water;

a SiC welding power supply for providing energy for a welding process;

the diving wire feeder is used for providing filling wires for the welding process and adjusting the wire feeding speed in real time;

a gas device for providing a draining gas for the welding process;

and a wire feeding cover for covering the target welding area of the workpieces to provide a dry welding space.

The industrial personal computer, the underwater robot, the SiC welding power supply and the diving wire feeding device are all connected through a bus.

As shown in fig. 2, the SiC welding power supply includes a main circuit for converting three-phase alternating current into welding current as an output, and a control circuit for controlling the welding power supply; and one output pole of the main circuit is used for connecting a wire, and the other output pole of the main circuit is used for connecting a workpiece.

The main circuit comprises a three-phase rectification filter circuit, a SiCMOS ultrahigh frequency inverter circuit, a transformer and a full-wave rectification filter circuit which are connected in sequence. The input rectification filter circuit is connected with three-phase alternating current in the forward direction and converts the three-phase alternating current into direct current bus voltage, the SiCMOS high-frequency inverter circuit converts the direct current bus voltage into alternating current square waves and applies the alternating current square waves to the primary side of the transformer, the transformer converts primary side high-voltage small current into secondary side low-voltage large current, and flexible regulation output current is obtained through the output rectification filter circuit, so that accurate regulation of arc force is realized.

The control circuit comprises a core module, an ultrahigh frequency driving module, a load voltage and current sampling module, an isolating switch control module and a communication module.

The core module preferably adopts a 32-bit DSC chip, an 8M crystal oscillator circuit and a 3.3V direct current power supply circuit to ensure the normal operation of a control system, provides rich on-chip peripherals such as PWM, CAN, ADC and GPIO, and also embeds a FreeRTOS light-weight real-time operating system in the DSC chip to ensure that task scheduling, sampling data processing and control signal generation are orderly carried out.

The front end of the driving module is connected with a PWM interface of the DSC chip to amplify the PWM signal, and the rear end of the driving module is connected with and drives the ultrahigh frequency inverter circuit to alternately conduct M1, M4, M2 and M3, so that the arc energy regulation and control of 200kHz level is completed. The front end of the current sampling module is connected with the output end of the full-wave rectification filter circuit and samples the injected current, and the rear end of the current sampling module is connected with an ADC (analog-to-digital converter) interface of the DSC chip; the main control module takes voltage signals of 0-3.3V sampled by the ADC as feedback, and adjusts the PWM duty ratio by using an incremental digital PID algorithm to realize current and voltage regulation of the main circuit. The isolating switch control module adopts a chip PC817 to realize optical coupling isolation, converts high and low levels sent by GPIO into switching signals and transmits the switching signals to the gas device, and realizes the logic control of the delivery of the drainage gas. The communication module is connected with the CAN interface and the CAN bus of the DSC chip to realize data transmission between the SiC welding power supply and external equipment. The ultrahigh frequency driving module, the load voltage and current sampling module and the isolating switch control module can all adopt the prior art.

The SiC welding power supply adopts the SiC MOSFET as a power switch, can increase the inversion frequency to more than 200kHz, has the maximum output current of 600A, has a wide regulation range, and has the pulse frequency of 900Hz, and benefits from a full digital control method, the SiC welding power supply has the capacity of short-time fine regulation of electric arc energy, can fully ensure the self weight, surface tension and electric arc force balance of a molten pool at different welding positions, prevents molten metal from flowing downwards, and is favorable for improving the process stability and process adaptability of underwater welding.

The wire feeding cover is connected with the underwater robot manipulator and is clamped by the underwater robot manipulator.

As shown in fig. 3 to 6, the wire feed cover includes a cover body 1; the cover body 1 comprises an upper cover body and a lower cover body; the upper cover body and the lower cover body are detachably connected; the lower cover body becomes smaller when extending from the side close to the upper cover body to the side far away from the lower cover body.

The cover body 1 is provided with a semi-closed welding positioning cavity 1.1; a joint plane jointed with the plane of the target welding area of the workpiece is formed at the opening of the welding positioning cavity 1.1, so that the welding positioning cavity 1.1 is relatively closed when the cover body 1 is jointed with the plane of the target welding area of the workpiece; the top end of the upper cover body is provided with a wire feeding port 2, a gas feeding port 4 and a drain valve 5 respectively, wherein the wall of the welding positioning cavity 1.1 is provided with a wire feeding port; the gas feed 4 is connected to a gas device for feeding water-draining gas into the welding-position chamber 1.1.

A wire feeding conduit 7 communicated with the wire feeding port 2 is arranged in the welding positioning cavity 1.1. The wire feeding guide pipe 7 comprises a first pipe section connected with the wire feeding port 2 and a second pipe section connected to one end of the first pipe section, which is close to the mouth of the welding positioning cavity 1.1; the second pipe section forms an included angle with the central axis of the welding positioning cavity 1.1; a height interval is reserved between the tail end of the second pipe section and the opening of the welding positioning cavity 1.1; the extension line of the second pipe section penetrates through the orifice of the welding positioning cavity 1.1 to realize that the tail end outlet corresponds to the orifice of the welding positioning cavity 1.1, so that the wire 8 extends out of the tail end outlet after passing through the wire feeding guide pipe 7 and is in contact with the target welding area plane of the workpiece at the orifice of the welding positioning cavity 1.1 to realize welding.

The second pipe section and the central axis of the welding positioning cavity 1.1 form an included angle, so that the wire feeding at an inclined angle is realized; the wire 8 is fed along the first pipe section and the second pipe section, and then a welding point is formed at the intersection point of the extension line of the second pipe section and the plane of the opening of the welding positioning cavity 1.1; and a height interval is reserved between the tail end of the second pipe section and the opening of the welding positioning cavity 1.1, so that the second pipe section can be prevented from being burnt out by welding energy, and the service life is prolonged. The first pipe section and the second pipe section are preferably in smooth transition through an arc section. The outlet at the tail end of the pipe section II is provided with a conductive nozzle; the main circuit is used for connecting the output electrode of the wire material with the contact tip.

And a claw-shaped positioning module 6 for positioning is also arranged in the welding positioning cavity 1.1. The claw-shaped positioning module 6 comprises at least three positioning claws; a positioning space for positioning the cylindrical part in the workpiece is formed between the positioning claws; the central axis of the positioning space is coaxial with the central axis of the welding positioning cavity 1.1.

The working principle of the wire feeding cover is as follows: the cover body 1 is clamped by an underwater robot manipulator; when the welding positioning cavity 1.1 works, the cavity opening of the welding positioning cavity 1.1 is attached to the plane of a target welding area of a workpiece, and the welding positioning cavity 1.1 forms a relatively closed space. When welding around the cylindric position of work piece, fix a position on cylindric position through claw form orientation module 6 card, ensure that the work piece is accurate centering. The gas supply port 4 is connected with a gas device and inputs drainage gas into the welding positioning cavity 1.1; draining water in the welding positioning cavity 1.1 from the drain valve 5 by using drainage gas to provide a stable gas phase space in the welding positioning cavity 1.1; the welding torch moves according to the welding seam path plan so as to drive the wire feeding cover to move; the wire 8 is fed by the wire feeder, is input into the wire feeding guide pipe 7 from the wire feeding port 2 and is conveyed along the extending direction of the wire feeding guide pipe 7, and then extends out of the tail end outlet of the wire feeding guide pipe 7 to be contacted with the target welding area of the workpiece at the cavity port of the welding positioning cavity 1.1. In the welding process, the wire feeding guide pipe 7 and the wires 8 in the wire feeding guide pipe rotate along with the rotation of the cover body 1, so that the movement of a welding path is realized; the central axis of the welding positioning cavity 1.1 does not generate displacement, thereby ensuring the stability of the gas flow field in the welding positioning cavity 1.1 and solving the difficult problem of unstable gas phase space of arc-shaped, strip-shaped and annular welding lines in the traditional welding process. In addition, the wire feed hood of the present invention may also be used in welding applications, such as straight and curved welds.

When the wire 8 is contacted with the workpiece, because the wire 8 and the workpiece are respectively connected to the two sides of the output of the welding power supply, the wire 8 is in short circuit with the workpiece when in contact, electric energy is converted into heat energy, and metal is instantly melted to realize welding. In the welding process, the water discharge valve 5 can continuously discharge water drops falling back due to gravity, and the gas phase space and the electric arc combustion are stable.

The wire feeding cover has small volume, easy installation and flexible movement; the gas phase space stability of the underwater welding process is well guaranteed, the problem of water flow falling back under the action of gravity can be solved, the welding device is suitable for welding of various positions such as vertical welding, transverse welding and overhead welding, and the all-position welding advantage is achieved.

The claw-shaped positioning module 6 is detachably arranged in the welding positioning cavity 1.1 through the connecting piece 3; the accessible is changed the claw form orientation module 6 of different models, obtains the location space of equidimension not to the cylindric position that matches the variation in size welds.

The welding method of the underwater all-position local dry pulse MIG welding system comprises the following steps of:

s1, the industrial personal computer sends motion trail parameters to the underwater robot, and the underwater robot moves to the position near a workpiece target welding area according to the motion trail parameters; the industrial personal computer sends the multi-axis motion parameters to the underwater robot, the underwater robot drives the wire feeding cover to align to the welding starting point according to the multi-axis motion parameters, so that the mouth of the welding positioning cavity of the wire feeding cover is attached to the plane of the target welding area of the workpiece, and the welding positioning cavity is relatively closed. When the target welding area of the workpiece is provided with a cylindrical part, the cylindrical part is clamped by the claw-shaped positioning module of the wire feeding cover to realize positioning in the process of attaching the welding positioning cavity opening of the wire feeding cover and the target welding area plane of the workpiece.

S2, starting the SiC welding power supply, and sending welding process parameters to the SiC welding power supply by the industrial personal computer; the SiC welding power supply starts the gas device to work through the isolating switch control module to output the drainage gas, and the moisture in the welding positioning cavity of the wire feeding cover is drained, so that the drying of a gas phase space is ensured; the submerged wire feeder conveys wires according to a set wire feeding speed, the SiC welding power supply outputs pulse welding current according to preset parameters, and the stable molten drop transition and the stress balance of a molten pool are ensured through corresponding electric arc force; and during the period that the SiC welding power supply outputs the pulse welding current, the wire feeding cover rotates along the central shaft of the welding positioning cavity to realize arc-shaped, belt-shaped or annular welding seam welding.

And S3, after welding, stopping the work of the SiC welding power supply, the diving wire feeding device and the gas device, sending a new motion trail parameter to the underwater robot by the industrial personal computer, moving the underwater robot to a new area to be welded, and repeating the S2 welding process until the welding task is finished.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.