Bilateral double-layer inner side bending nozzle device and narrow gap welding method thereof

Abstract

This invention discloses a double-sided, double-layered, inner-bent nozzle device and its narrow-gap welding method. The nozzle device consists of an outer layer of front and rear nozzle tubes and an inner layer of front and rear nozzle tubes arranged vertically. Each nozzle tube is formed by connecting an upper connecting section, a middle vertical section, and a lower bent section. The middle vertical section and the lower bent section extend into the narrow-gap welding groove and can be used at the full groove depth. The lower bent sections of the inner front nozzle tube and the inner rear nozzle tube are bent inward and aligned with the lower section of the welding torch contact tip from the front and rear sides, respectively. The lower bent sections of the outer front nozzle tube and the outer rear nozzle tube are bent inward and aligned obliquely downward from the front and rear sides with the welding arc zone in the groove, respectively. The gas flow rate of the inner / outer nozzles is vectorized to protect the high-temperature welding zone and directly cool the contact tip, thereby protecting the contact tip and the lower end face of the welding torch body from the impact of the high-temperature welding gas flow, thus improving the narrow-gap welding quality and the service life of the welding torch contact tip.

Description

Technical Field

[0001] This invention belongs to the field of high-efficiency welding and automated welding technology, specifically relating to a nozzle device and welding method suitable for narrow-gap gas shielded metal arc welding. Background Technology

[0002] Narrow-gap gas metal arc welding (GMAW) is a high-efficiency arc welding method suitable for thick plates, typically performed automatically. Narrow-gap GMAW often employs I-shaped or U-shaped narrow-gap grooves, with a groove gap generally ranging from 8 to 16 mm. For ultra-narrow-gap welding, the groove gap can be reduced to 4 to 5 mm. To address the challenge of poor sidewall fusion in narrow-gap grooves, ultra-narrow-gap GMAW, rocking / oscillating arc GMAW, rotating arc narrow-gap GMAW, and double-pass narrow-gap GMAW processes have been developed.

[0003] In narrow-gap GMAW, the narrow bevel gap and limited welding space make the issues of welding nozzle cooling and welding gas protection particularly prominent. In fact, narrow-gap welding nozzles are consumables requiring frequent replacement and cannot be directly water-cooled; especially during oscillating / rotating arc welding, the conductor rod and nozzle experience oscillating / rotating motion relative to the torch body, rendering water cooling ineffective. Accordingly, to extend nozzle lifespan, gas cooling is the only possible effective method, requiring nozzle structure design for implementation. On the other hand, to address the gas protection issue in narrow-gap welding, external nozzle devices and extended-type nozzle devices have been developed. For shallow bevels (30mm or less), external sleeve-type welding gas nozzles can be used; for deeper bevels (over 30mm), extended-type welding gas nozzles are necessary to provide effective gas protection for the arc welding area deep within the narrow-gap bevel.

[0004] Extending nozzles come in two forms: sleeve-type nozzles and side-mounted nozzles. Chinese patent application number 202010914110.4, entitled "Sleeve-shaped Flat Nozzle Device for Narrow Gap Welding and its Usage Method," discloses a sleeve-shaped flat nozzle device that can extend into narrow gap welding bevels. The flat nozzle is fitted around the outside of a conductive rod, and the welding shielding gas it emits provides direct gas cooling to the conductive tip connected to the lower end of the conductive rod, improving the service life of the conductive tip. Its disadvantage is that the sleeve-shaped flat nozzle needs to be fitted around the outside of the conductive rod, increasing the nozzle thickness and consequently increasing the allowable bevel gap, which significantly reduces the efficiency of narrow gap welding.

[0005] Chinese patent application number 200610038184.6, entitled "A Gas Protection Device for Narrow Gap Welding with Rotating Arc", discloses a side-mounted nozzle device that can extend into a narrow gap welding groove. It has an inwardly curved flat nozzle symmetrically arranged on both sides of the welding torch conductor rod, forming a double-sided single-layer nozzle device. The nozzle thickness can be no greater than the diameter of the welding torch conductor rod, which is suitable for narrow grooves of 12mm and below and has high welding efficiency. Its disadvantages are: the two welding shielding gas streams ejected from the double-sided inwardly curved flat nozzles converge in the high-temperature welding zone to generate an upward high-temperature hot gas stream, which directly impacts the lower end face of the welding torch body and the conductive nozzle connected to the lower end of the welding torch conductive rod. This results in: ① the conductive nozzle softening under the continuous impact of the high-temperature hot gas stream, significantly shortening its service life and reducing its practicality; ② the lower end face of the welding torch body being severely heated, requiring strong water cooling, increasing the complexity of the welding torch structure and reducing its practicality; ③ the welding fumes carried in the upward high-temperature hot gas stream easily entering the interior of the welding torch body, increasing the welding torch failure rate.

[0006] Chinese Patent Application No. 202011546613.7, entitled "A Narrow Gap Welding Gun", discloses a narrow gap welding gun including a primary air intake mechanism and a secondary air intake mechanism. The secondary air intake mechanism includes a protective gas cover for protecting several layers of weld beads on the surface. The primary air intake mechanism includes two sets of air blowing pipes located on both sides of the conductive nozzle for protecting the weld beads deep in the narrow gap bevel. The end cut of the inner air blowing pipe faces inward to protect the intermediate arc and molten pool, and the end cut of the outer air blowing pipe faces outward to prevent external air from being drawn in and to protect the surface of the welded high-temperature weld. Its disadvantages include: ① The inner air blowing pipe is a straight pipe, and the gas it blows out generally flows downwards, which cannot directly cool the conductive nozzle. Furthermore, the two airflows on either side of the conductive nozzle converge in the arc and molten pool areas, generating an upward high-temperature hot airflow that directly impacts the conductive nozzle and the secondary protective gas shield, affecting their service life; ② The end of the inner air blowing pipe has an inward-facing bevel, making it easier for the two inner airflows to flow inwards after reaching the bottom of the bevel, thus promoting the formation of an upward high-temperature hot airflow; ③ The inner and outer air blowing pipes share the same air chamber, resulting in the same outlet airflow velocity for both pipes, which cannot be independently adjusted. The section causes the airflow from the inner air pipe, which is located at a higher position, to have a lower velocity when it reaches the bottom of the bevel. This allows the faster airflow from the outer air pipe to partially converge along the bottom of the bevel towards the arc area, promoting the formation of an upward high-temperature hot airflow. ④ The beveled cut at the end of the air pipe increases the cross-sectional area of ​​the air pipe outlet, thereby reducing the outlet velocity and stiffness of the welding shielding gas and reducing the welding gas shielding effect. ⑤ The water cooling of the conductive rod is required to indirectly cool the conductive nozzle. This indirect cooling not only has a poor cooling effect but also complicates the welding torch mechanism and reduces its practicality.

[0007] In summary, when the nozzle is inserted into a narrow-gap groove, the sleeve-type nozzle, fitted onto the outside of the conductive rod, provides direct air cooling to the contact tip, extending its lifespan. However, because its nozzle thickness is significantly greater than the diameter of the conductive rod, it results in a larger permissible groove gap and reduced welding efficiency. Existing single-layer or double-layer side-mounted nozzles, with a nozzle thickness not exceeding the diameter of the conductive rod, are suitable for narrower grooves and offer high welding efficiency. However, the two welding shielding gas streams ejected from the two nozzles cannot directly cool the contact tip. Furthermore, their convergence in the high-temperature welding zone generates an upward-flowing hot gas stream that directly impacts the welding torch contact tip, significantly shortening its lifespan. In other words, current technology has failed to effectively resolve the trade-off between narrow-gap arc welding efficiency and contact tip lifespan. Summary of the Invention

[0008] The purpose of this invention is to address the prominent problems of limited practicality in existing technologies and the mutual constraint between welding efficiency and the service life of the welding torch contact tip in narrow-gap GMAW welding. This invention proposes a double-sided, double-layer, inner-bent nozzle device and its narrow-gap welding method suitable for narrow bevels, with good contact tip cooling effect and high practicality. This improves both the welding efficiency and the welding quality of narrow-gap GMAW welding, as well as the service life of the welding torch contact tip.

[0009] To achieve the above-mentioned objectives, the narrow gap welding method of the present invention is implemented using the following technical solution:

[0010] A narrow-gap welding method uses a welding torch comprising a torch body, a torch conductor mechanism, and a nozzle device, wherein the nozzle device includes an outer rear nozzle tube and an outer front nozzle tube, as well as an inner rear nozzle tube and an inner front nozzle tube, and includes the following steps:

[0011] ① Setting up the nozzle device: The upper ends of the four nozzle tubes, namely the outer rear nozzle tube, the outer front nozzle tube, the inner rear nozzle tube, and the inner front nozzle tube, are all fixed to the welding torch body. Each nozzle tube is composed of an upper connecting section, a middle vertical section, and a lower curved section connected together. The lower parts of the inner front nozzle tube and the inner rear nozzle tube are bent inward and aligned with the lower section of the conductive nozzle in the lower part of the welding torch conductive rod mechanism from the front and rear sides, respectively. The lower parts of the outer front nozzle tube and the outer rear nozzle tube are bent inward and aligned with the welding arc area in the narrow gap welding groove from the front and rear sides, respectively.

[0012] ② Set the welding shielding gas flow rate: Connect each nozzle tube to the gas chamber or directly to the gas source, so that the outlet gas flow rate of the inner layer rear nozzle tube is not less than the outlet gas flow rate of the outer layer rear nozzle tube, and the outlet gas flow rate of the inner layer front nozzle tube is not less than the outlet gas flow rate of the outer layer front nozzle tube; or, it also includes making the outlet gas flow rate of the inner layer rear nozzle tube not less than the outlet gas flow rate of the inner layer front nozzle tube, and / or the outlet gas flow rate of the outer layer rear nozzle tube not less than the outlet gas flow rate of the outer layer front nozzle tube.

[0013] ③ Welding method for each layer: The welding wire is fed obliquely from the welding torch conductive rod mechanism. The rotation mechanism in the welding torch body drives the welding torch conductive rod mechanism, causing the electric arc at the end of the welding wire to rotate or swing in an arc within the narrow gap welding groove. Alternatively, the welding wire is fed straight down from the welding torch conductive rod mechanism along the center line of the welding torch. The pre-formed welding wire drives the electric arc at its end to rotate or swing left and right within the narrow gap welding groove. At the same time, the welding torch and the electric arc move relative to the workpiece along the welding direction. The middle vertical section and the lower curved section of each nozzle tube extend into the narrow gap welding groove accordingly, thereby forming a narrow gap weld under the action of the welding shielding gas sprayed from the four nozzle tubes.

[0014] ④ Multi-layer welding method: As the number of narrow gap weld layers increases, the welding torch along with the four nozzle tubes moves upward together to maintain a constant distance between the lower end of the four nozzle tubes and the bottom of the groove, until the gas outlet on either side of the inner layer rear nozzle tube and the inner layer front nozzle tube is exposed above the upper surface of the narrow gap weld groove, or by setting a gas storage groove above the narrow gap weld groove, the nozzle device is used until the narrow gap weld groove is fully welded, thus realizing multi-layer narrow gap welding.

[0015] Preferably, in step ①, when the lower curved sections of the inner rear nozzle tube and the inner front nozzle tube are aligned with the lower section of the conductive nozzle from the front and rear sides respectively, the center line of the lower curved section of the inner rear nozzle tube and the center line of the lower curved section of the inner front nozzle tube 302 intersect at a point on the center line of the lower section of the conductive nozzle. At this time, the center line of the lower curved section of the nozzle tube and the center line of the lower section of the conductive nozzle are on the same plane.

[0016] Alternatively, it may include aligning the intersection of the center lines of the lower curved sections of the inner rear nozzle tube and the inner front nozzle tube with the center point of the end of the conductive nozzle; or it may include making the distance from the center of the end of the lower curved section of the inner rear nozzle tube to the center point of the end of the conductive nozzle equal to the distance from the center of the end of the lower curved section of the inner front nozzle tube to the center point of the end of the conductive nozzle.

[0017] Preferably, in steps ① and ③, when the lower curved sections of the outer left nozzle tube and the outer right nozzle tube are respectively aligned obliquely downward from the front and rear sides with the welding arc area within the narrow gap welding groove, the center line of the lower curved section of the outer rear nozzle tube and the center line of the lower curved section of the outer front nozzle tube intersect at a point on the workpiece surface. The intersection point is located on the welding torch center line, or on the center line of the extended section of the welding wire when it is obliquely fed forward or backward along the welding direction. At this time, the center line of the lower curved section of the nozzle tube is on the same longitudinal plane as the welding torch center line or the center line of the extended section of the welding wire; or, it further includes making the distance from the center of the end of the lower curved section of the outer rear nozzle tube to the intersection point equal to the distance from the center of the end of the lower curved section of the outer front nozzle tube to the intersection point.

[0018] Specifically, when the intersection point is located on the center line of the welding torch, the welding wire is fed obliquely and the arc at the end of the welding wire rotates, or the welding wire is fed straight down along the center line of the welding torch and the pre-formed welding wire causes the arc at its end to rotate or swing left and right; or, when the intersection point is located on the center line of the extended section of the obliquely fed welding wire, the arc at the end of the welding wire swings in an arc shape.

[0019] Preferably, in step ④, once the gas outlet of either the inner rear nozzle pipe or the inner front nozzle pipe of the inner layer nozzle is exposed on the upper surface of the narrow gap welding groove, a left process plate and a right process plate are placed on the upper surface of the left and right walls of the narrow gap welding groove before welding, so that the left process plate and the right process plate form a gas storage groove. The depth of the gas storage groove h3 is not less than (h1+(h2-h1)), where h1 is the nozzle height, h2 is the height of the upper end of the inner layer nozzle, and (h2-h1) is the height difference between the inner layer nozzle and the outer layer nozzle, so that the nozzle device is used until the narrow gap welding groove 7 is fully welded, thus realizing the full groove depth use of the nozzle device.

[0020] To achieve the above-mentioned objectives, the double-sided double-layer inner-bent nozzle device for the narrow-gap welding method of the present invention is implemented using the following technical solution:

[0021] The device consists of four nozzles arranged vertically: an outer rear nozzle, an outer front nozzle, an inner rear nozzle, and an inner front nozzle. The center plane of each nozzle is on the same longitudinal center plane as the center plane of the welding torch conductive rod mechanism. The outer rear nozzle and the inner rear nozzle are located on the rear side of the welding torch conductive rod mechanism, while the outer front nozzle and the inner front nozzle are located on the front side of the welding torch conductive rod mechanism. The inner rear nozzle is inside the outer rear nozzle, and the inner front nozzle is inside the outer front nozzle.

[0022] Each nozzle tube is composed of an upper connecting section, a middle vertical section, and a lower curved section connected together. The upper ends of the upper connecting sections of the four nozzle tubes are fixed to the welding torch body through nozzle connectors. The middle vertical sections of the outer front nozzle tube and the outer rear nozzle tube are symmetrical with respect to the center line of the welding torch. The middle vertical sections of the inner front nozzle tube and the inner rear nozzle tube are symmetrical with respect to the center line of the welding torch. The lower curved sections of the inner front nozzle tube and the inner rear nozzle tube are bent inward and aligned with the lower section of the conductive nozzle in the lower part of the welding torch conductive rod mechanism from the front and rear sides respectively. The lower curved sections of the outer front nozzle tube and the outer rear nozzle tube are bent inward and aligned with the welding arc zone in the narrow gap welding groove from the front and rear sides respectively.

[0023] Preferably, the cross-sections of the inner rear nozzle tube and the inner front nozzle tube are smaller than the cross-sections of the outer rear nozzle tube and the outer front nozzle tube.

[0024] Preferably, the upper connecting section of the outer rear nozzle tube and the outer front nozzle tube is a flat tube or a transitional body with a round upper section and a flat lower section, and the middle vertical section and the lower curved section are flat tubes.

[0025] Preferably, the upper connecting section of the inner rear nozzle tube and the inner front nozzle tube is a round tube, a flat tube, or a transitional body that is round at the top and flat at the bottom, and the middle vertical section and the lower curved section are round tubes or flat tubes.

[0026] Furthermore, the thickness of the flat tube or the outer diameter of the round tube is not greater than the outer diameter of the conductive rod in the upper part of the welding torch conductive rod mechanism.

[0027] Optionally, the inner side of the outer rear nozzle tube is connected to the outer side of the inner rear nozzle tube to form an integrated dual-air-path rear nozzle body, and the inner side of the outer front nozzle tube is connected to the outer side of the inner front nozzle tube to form an integrated dual-air-path front nozzle body.

[0028] Compared with existing similar technologies, the main advantages and beneficial effects of this invention are:

[0029] 1) The nozzle device of the present invention consists of two sets of inner and outer curved nozzles arranged on both sides of the welding torch conductive rod. The outer nozzle is curved toward the welding arc area to protect the high-temperature area of ​​the narrow gap welding, while the inner nozzle is curved toward the conductive tip to directly cool the conductive tip and suppress the upward flow of high-temperature airflow in the welding area. By vectorizing the airflow of the inner / outer nozzles, the flow rate of the welding shielding gas before and after the arc is reasonably distributed, so as to improve the narrow gap welding efficiency, the narrow gap welding quality and the service life of the welding torch conductive tip.

[0030] Therefore, compared with the invention patent with Chinese patent application number 200610038184.6 entitled "A Rotating Arc Narrow Gap Welding Gas Protection Device" which uses a double-sided single-layer nozzle, the two sets of inner and outer curved nozzles in this invention are not necessarily symmetrically distributed on both sides of the arc, but are arranged separately for the welding arc and the conductive nozzle, thus providing protection for both the welding arc and the conductive nozzle. This allows the conductive nozzle and the lower end face of the welding torch body to avoid being impacted by continuous high-temperature hot airflow. As a result, this invention not only improves the service life of the conductive nozzle, but also avoids high-temperature heat damage to the welding torch body.

[0031] Furthermore, in the invention patent application No. 202011546613.7 entitled "A Narrow Gap Welding Gun," both the inner and outer air pipes are vertically aligned straight pipes. The purpose of the inner air pipe's end being higher than the outer air pipe's end is to prevent welding spatter from clogging the inner air pipe's outlet. The inward-facing cut of the inner air pipe's end is solely for broadly protecting the intermediate arc and molten pool, while the outward-facing cut of the outer air pipe's end is solely to prevent external air from being entrained and to protect the surface of the already welded high-temperature weld. Compared to the nozzle structure of this inner and outer air pipe, the two sets of nozzles in this invention employ a lower inward-bending structure, and the objects aligned with the inward bend are different, resulting in different working principles and therefore different functions.

[0032] 2) This invention provides direct gas cooling to the welding torch's contact tip through the airflow from a side-mounted inner-layer curved nozzle. By ensuring the airflow velocity in the inner nozzle is no less than that in the outer nozzle, the upward flow of high-temperature airflow, primarily originating from the welding arc and molten pool, is suppressed. This effectively reduces the operating temperature at the tip of the contact tip and the bottom surface of the welding torch body, significantly improving the service life of the narrow-gap welding contact tip and the welding torch. Furthermore, by ensuring that the thickness of both the inner and outer nozzles is no greater than the diameter of the contact rod, a narrow welding bevel is achieved, resulting in high welding efficiency. Thus, while improving narrow-gap welding efficiency through the side-mounted nozzle, the direct gas cooling effect of the inner nozzle effectively extends the service life of the narrow-gap welding contact tip and the welding torch, creatively solving the problem of the mutual constraint between narrow-gap arc welding efficiency and contact tip service life, thereby enhancing the nozzle's practicality.

[0033] 3) By making the cross-sectional area of ​​the inner nozzle tube smaller than that of the outer nozzle, the present invention can help the inner nozzle obtain a faster outlet airflow velocity without increasing the airflow consumption of the inner nozzle, so as to more effectively suppress the upward rush of high temperature airflow in the welding area; it can also set the nozzle tube of the inner nozzle as a cylindrical body without increasing the bevel gap, so as to facilitate the manufacturing and installation of the inner nozzle.

[0034] 4) This invention increases the gas flow rate of the inner and / or outer nozzles behind the arc, thereby increasing the gas velocity of the shielding gas behind the arc. It can vectorically adjust the distribution of the welding shielding gas flow rate between the front and rear of the arc, allowing more shielding gas to flow towards the welding direction. While improving the gas protection effect in the welding arc area, it also directs more welding fumes towards the front of the welding, resulting in a bright and high-quality weld formation and improving welding quality.

[0035] 5) By setting an air-storing bevel on the upper surface of the narrow gap bevel, the present invention enables the side-mounted nozzle to be used until the bottom of the nozzle is exposed on the upper surface of the two side walls of the narrow gap bevel. This allows the side-mounted nozzle to be used at the full bevel depth within the narrow gap welding bevel, thus eliminating the need for an external protective gas shield or an external sleeve-shaped nozzle to protect several layers of weld beads near the bevel surface. This simplifies the nozzle mechanism design and improves the practicality of the side-mounted nozzle. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the double-sided double-layer inner curved nozzle device for narrow gap welding according to the present invention. Figure 1 In the diagram, 1—welding torch body; 201—outer layer rear nozzle tube; 202—outer layer front nozzle tube; 301—inner layer rear nozzle tube; 302—inner layer front nozzle tube; 4—welding torch conductive rod mechanism; 5—welding wire; 6—electric arc; 9—welding torch centerline; V 2a —Outlet airflow velocity of the outer rear nozzle tube; V 2b —Outlet airflow velocity of the outer front nozzle tube; V 3a —Inner layer rear nozzle outlet airflow velocity; V 3b —Inner layer front nozzle tube outlet airflow velocity.

[0037] Figure 2 This is a schematic diagram of the arc's rocking / rotating motion. Figure 2 In the diagram, 10—rotational motion; 11—circular rocking motion; 12—center line of the arc motion trajectory; 13—welding direction; r—arc rocking / rotation radius; O—projection point of the welding torch center line 9 on the workpiece surface; M—midpoint of the arc rocking motion.

[0038] Figure 3 This is a schematic diagram showing the positional relationship of the outer nozzle tube in Example 1 of the outer nozzle. Figure 3 In the diagram, 201a—center line of the lower curved section of the outer rear nozzle tube; 202a—center line of the lower curved section of the outer front nozzle tube; 704—workpiece surface; O4—center of the end of the lower curved section of the outer rear nozzle tube; O5—center of the end of the lower curved section of the outer front nozzle tube.

[0039] Figure 4 This is a schematic diagram showing the positional relationship of the outer nozzle tube in Example 2 of the outer nozzle. Figure 4In the diagram, O1 is the intersection of the center line of the welding wire extending obliquely forward or backward along the welding direction and the surface of the workpiece.

[0040] Figure 5 This is a schematic diagram showing the positional relationship of the inner nozzle tube in Example 1 of the inner nozzle. Figure 5 In the diagram, 401—first conductive rod; 402—first conductive nozzle; d1—outer diameter of conductive rod; d2—outer diameter of circular nozzle tube; O2—center point of the end of the first conductive nozzle; O6—center point of the end of the lower curved section of the inner layer rear nozzle tube; O7—center point of the end of the lower curved section of the inner layer front nozzle tube.

[0041] Figure 6 This is a schematic diagram showing the positional relationship of the inner nozzle tube in Example 2 of the inner nozzle. Figure 6 In the diagram, 403 represents the second conductive rod; 404 represents the second conductive nozzle; and O3 represents the center point of the end of the second conductive nozzle.

[0042] Figure 7 This is a photograph showing one working state of the nozzle device of the present invention. Figure 7 In the middle, 403a—bent conductive rod; 404a—center hole conductive nozzle.

[0043] Figure 8 This is a schematic diagram of the cross-section when the outer and inner nozzles extend into the narrow gap welding groove. Figure 8 In the diagram, 7—narrow gap welding bevel; 701—left side wall; 702—right side wall; 703—weld; 8—gas storage bevel; 801—left process plate; 802—right process plate; d—thickness of flat tube nozzle.

[0044] Figure 9 for Figure 8 A right-view longitudinal section diagram of the outer and inner nozzles extending into the narrow gap welding groove. Figure 9 In the diagram, h1 is the nozzle height; h2 is the height of the upper end of the inner nozzle; and h3 is the depth of the gas storage bevel. Detailed Implementation

[0045] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0046] The orientation of the nozzle device of the present invention is specified as follows: See Figure 8 and Figure 9As shown, the location of the left wall 701 on the cross-section of the narrow gap welding groove 7 is "left", and the location of the right wall 702 on the opposite side is "right"; the location of the electric arc 6 is "down", and the location of the welding torch conductive rod mechanism 4 is "up"; the location of the outer layer rear nozzle tube 201 on the longitudinal section of the narrow gap welding groove 7 is "rear", moving forward along the welding direction 13, and the location of the outer layer front nozzle tube 202 is "front"; the welding torch centerline 9 is the center, the direction closer to the welding torch centerline 9 is "inner", and the direction farther from the welding torch centerline 9 is "outer".

[0047] like Figure 1 As shown, the present invention provides a double-sided double-layer inner-bent nozzle device for narrow gap welding, which consists of four nozzle tubes. These four nozzle tubes are arranged in the vertical direction. The upper ends of the four nozzle tubes are fixedly connected to the welding torch body 1 for narrow gap welding, and the lower sections of the four nozzle tubes are bent inward. The four nozzle tubes are the outer rear nozzle tube 201, the outer front nozzle tube 202, the inner rear nozzle tube 301, and the inner front nozzle tube 302. The outer rear nozzle tube 201 and the inner rear nozzle tube 301 are located behind the welding torch conductive rod mechanism 4, while the outer front nozzle tube 202 and the inner front nozzle tube 302 are located in front of the welding torch conductive rod mechanism 4. The inner rear nozzle tube 301 is inside the outer rear nozzle tube 201, and the inner front nozzle tube 302 is inside the outer front nozzle tube 202. The inner front nozzle tube 302 and the inner rear nozzle tube 301 form the inner nozzle layer, and the outer front nozzle tube 202 and the outer rear nozzle tube 201 form the outer nozzle layer. The center planes of the four nozzles are on the same longitudinal center plane as the center plane of the welding torch conductive rod mechanism 4.

[0048] All four nozzle tubes are hollow tubular bodies. Each nozzle tube consists of an upper connecting section, a middle vertical section, and a lower curved section connected continuously. They can be manufactured as a single piece or assembled from sections. The upper ends of the upper connecting sections of all four nozzle tubes are connected by nozzle connectors. Figure 1 (omitted from drawing) is fixedly connected to the welding torch body 1. The middle vertical section and the lower curved section of each nozzle tube can extend into the narrow gap welding groove 7 (see...). Figure 8 and Figure 9 ).

[0049] Four nozzle tubes work in conjunction with the torch body 1 and the torch conductive rod mechanism 4 to form a narrow-gap welding torch. The torch conductive rod mechanism 4 includes a conductive rod and a conductive nozzle. The upper end of the conductive rod is connected to the torch body 1 along the torch centerline 9, and the lower end is connected to the conductive nozzle. The conductive rod can be a straight conductive rod or a curved conductive rod, and the conductive nozzle can be a center-hole conductive nozzle, an eccentric conductive nozzle, or a bent conductive nozzle. When a straight conductive rod is used with an eccentric conductive nozzle or a bent conductive nozzle, or when a curved conductive rod is used with a center-hole conductive nozzle, the welding wire 5 extends obliquely downward from the torch conductive rod mechanism 4, such as... Figure 1As shown; when the straight conductive rod is equipped with a center-hole conductive nozzle, the welding wire 5 is fed straight downwards along the center line 9 of the welding torch. Figure 1 (The text is omitted as it is not drawn.)

[0050] The upper connecting sections of the outer rear nozzle tube 201 and the outer front nozzle tube 202 are flat tubes or transitional bodies with a round upper section and a flat lower section, while the middle vertical section and the lower curved section are flat tubes. The upper connecting sections of the inner rear nozzle tube 301 and the inner front nozzle tube 302 are round tubes, flat tubes, or transitional bodies with a round upper section and a flat lower section, while the middle vertical section and the lower curved section are round tubes or flat tubes. The lower curved sections of the inner rear nozzle tube 301 and the inner front nozzle tube 302 are both bent inwards, aligning with the lower section of the conductive nozzle inside the welding torch conductive rod mechanism 4 from the front and rear sides, respectively. This is used to directly cool the conductive nozzle and suppress the upward flow of high-temperature gas in the welding center area (including the arc zone and the molten pool zone). The lower curved section of the outer rear nozzle tube 201 and the lower curved section of the outer front nozzle tube 202 are both bent inward, and are respectively aligned with the welding arc area in the narrow gap welding groove 7 from the front and rear sides. This is used to protect the high temperature area of ​​narrow gap welding, including the electric arc, the molten pool and the solidified high temperature weld, thus forming a double-sided double-layer inner curved nozzle device.

[0051] Preferably, the middle vertical sections of the outer nozzle and the inner nozzle are symmetrically arranged on both sides of the welding torch centerline 9, that is, the middle vertical sections of the outer front nozzle tube 202 and the outer rear nozzle tube 201 are structurally symmetrical with respect to the welding torch centerline 9, and the middle vertical sections of the inner front nozzle tube 302 and the inner rear nozzle tube 301 are structurally symmetrical with respect to the welding torch centerline 9.

[0052] Optionally, the inner side of the outer rear nozzle tube 201 is connected to the outer side of the inner rear nozzle tube 301 to form an integral dual-air-path rear nozzle body; similarly, the inner side of the outer front nozzle tube 202 is connected to the outer side of the inner front nozzle tube 302 to form an integral dual-air-path front nozzle body; the dual-air-path front nozzle body and the dual-air-path rear nozzle body can each be formed by bending a dual-channel hollow tubular body.

[0053] Preferably, the cross-sectional area of ​​the inner nozzle tube is smaller than that of the outer nozzle tube. This allows the inner nozzle to achieve a faster outlet airflow velocity V without increasing its airflow consumption. 3a and V 3b This suppresses the upward flow of high-temperature airflow, which mainly comes from the welding arc and molten pool area. It also allows the nozzle tube of the inner nozzle to be set as a round tube without increasing the bevel gap, so as to facilitate the manufacturing and installation of the inner nozzle.

[0054] Preferably, the thickness of the flat tube of each nozzle is no greater than the outer diameter of the conductive rod in the upper part of the welding torch conductive rod mechanism 4; when the inner nozzle tube is a circular tube, its outer diameter is no greater than the outer diameter of the conductive rod. For example, when the diameter of the conductive rod is 8mm, the thickness of the flat tube and the outer diameter of the circular tube of each nozzle can both be no greater than 8mm. This allows for the use of the narrowest possible bevel gap, for example, narrowing the bevel gap of narrow-gap welding to 10-13mm to improve welding efficiency.

[0055] Optionally, the nozzle device of the present invention further includes a gas chamber, which may be provided with a gas screen. The gas chamber is provided between the nozzle connector and the welding torch body 1. The gas chamber is fixedly connected to the welding torch body 1 through the nozzle connector and is connected to and communicates with each nozzle tube. The gas chamber includes a rear gas chamber that is connected to the upper connecting section of both the outer rear nozzle tube 201 and the inner rear nozzle tube 301, and a front gas chamber that is connected to the upper connecting section of both the outer front nozzle tube 202 and the inner front nozzle tube 302. Alternatively, the gas chamber includes a rear outer gas chamber connected to the upper connecting section of the outer rear nozzle tube 201, a rear inner gas chamber connected to the upper connecting section of the inner rear nozzle tube 301, a front outer gas chamber connected to the upper connecting section of the outer front nozzle tube 202, and a front inner gas chamber connected to the upper connecting section of the inner front nozzle tube 302. By setting up a gas chamber, the welding shielding gas supplied from an external gas source (gas pipe) can be calmed and rectified, making the gas flow from each nozzle pipe more stable and orderly, thereby improving the welding protection effect.

[0056] The nozzle device of the present invention is suitable for welding wire 5 fed obliquely downward from the welding torch conductive rod mechanism 4 in narrow gap welding with a rocking arc or rotating arc, or for welding wire 5 fed straight downward along the welding torch center line 9 in narrow gap welding with a rotating arc or swaying arc, or for welding wire 5 fed straight downward along the welding torch center line 9 or obliquely downward from the welding torch conductive rod mechanism 4 in narrow gap welding without rocking, swaying or rotating arc. The pre-formed welding wire includes cable welding wire, twisted welding wire, bent welding wire or corrugated welding wire.

[0057] In use, the welding wire 5 extends obliquely downward from the welding torch conductive rod mechanism 4 (see...). Figure 1 (not shown) or extends straight downwards along the centerline 9 of the welding torch. When the welding wire 5 extends straight downwards from the welding torch conductive rod mechanism 4 along the centerline 9 of the welding torch, the welding wire 5 is a straight welding wire or a pre-formed welding wire. The pre-formed welding wire can drive the arc at the end of the welding wire to rotate unidirectionally or oscillate left and right between the two walls of the narrow gap welding groove, so as to increase the penetration depth of the groove sidewall. Thus, under the protection of the welding gas provided by the nozzle device, the pre-formed welding wire rotating arc or oscillating arc narrow gap welding of each single-pass weld can be realized. When the welding wire 5 extends obliquely downwards from the welding torch conductive rod mechanism 4, such as Figure 1 and Figure 2As shown, the rotary motion mechanism in the welding torch body 1 can drive the welding torch conductive rod mechanism 4, causing the electric arc 6 at the end of the welding wire 5 to rotate unidirectionally around the welding torch centerline 9, or to reciprocate in a circular arc shape around the shaking midpoint M relative to the welding torch centerline 9, at which time the radius of the electric arc shaking or rotation is r. The projection point O of the welding torch centerline 9 on the plane of the electric arc motion trajectory and the shaking midpoint M are located on the centerline 12 of the electric arc motion trajectory. After the welding torch and the electric arc 6 move relative to the workpiece along the welding direction 13, the shaking arc or rotating arc narrow gap welding of each single-pass weld can be realized in the narrow gap welding groove 7 under the protection of the welding gas provided by the nozzle tube. The direction of arc rotation can be clockwise or counterclockwise. When the welding wire 5 extends obliquely from the welding torch conductive rod mechanism 4, it can also be biased towards one side of the narrow gap welding groove. Thus, under the protection of the welding gas provided by the nozzle tube, narrow gap welding of each double-pass weld can be achieved without shaking, swaying, or rotating the arc. The welding shielding gas can be CO2 gas, argon gas, or an argon-rich mixture.

[0058] In the nozzle device of this invention, the inner nozzle provides direct gas cooling to the conductive tip in the lower part of the welding torch conductive rod mechanism 4, and suppresses the upward flow of high-temperature gas mainly from the welding arc and molten pool area. This effectively reduces the working temperature of the welding conductive tip end and the bottom end face of the welding torch body 1, improving the service life of the conductive tip and the reliability of the welding torch. By ensuring that the thickness of both the side-mounted inner and outer nozzles is no greater than the diameter of the conductive rod, a narrow bevel gap can be used to achieve high welding efficiency. Thus, while improving the welding efficiency of narrow gaps, the service life of the conductive tip and the reliability of the narrow gap welding torch are effectively improved, solving the problem of the mutual constraint between the welding efficiency of narrow gap arc welding and the service life of the conductive tip, and improving practicality.

[0059] See Figure 3 The structure of Embodiment 1 of the outer nozzle shown has the following configuration: the center line 201a of the lower curved section of the outer rear nozzle tube 201 and the center line 202a of the lower curved section of the outer front nozzle tube 202 intersect at the same point, O, on the workpiece surface 704 within the narrow gap welding groove 7. Point O is also the projection point of the welding torch centerline 9 onto the workpiece surface 704. At this time, the center lines 201a and 202a of the lower curved sections of the outer nozzle tube are on the same longitudinal plane as the welding torch centerline 9. Preferably, the distance from the center O4 of the lower curved section end of the outer rear nozzle tube 201 to the intersection point O is equal to the distance from the center O5 of the lower curved section end of the outer front nozzle tube 202 to the intersection point O, thereby obtaining two symmetrical welding shielding gas flows about both sides of the welding torch centerline 9 to improve arc stability. Embodiment 1 of the outer nozzle is suitable for rotating arc narrow gap welding when the welding wire 5 extends obliquely downwards (see...). Figure 3), or applicable to narrow gap welding of straight welding wire or pre-formed welding wire when welding wire 5 is fed straight down along the center line 9 of welding torch (omitted and not shown); among them, when using pre-formed welding wire, it is possible to realize narrow gap welding of rotating arc through cable welding wire or twisted welding wire, or to realize narrow gap welding of left and right swinging arc through bent welding wire or corrugated welding wire.

[0060] See Figure 4 The structure of the outer nozzle in Embodiment 2 shown has the following configuration: the center line 201a of the lower curved section of the outer rear nozzle tube 201 and the center line 202a of the lower curved section of the outer front nozzle tube 202 intersect at point O1 on the workpiece surface 704 within the narrow gap welding groove. Simultaneously, point O1 is located directly in front of the workpiece along the welding direction 13 (see...). Figure 4 The center line of the extended section of the welding wire 5 when it extends obliquely to the rear (not shown) is on the same longitudinal plane as the center line of the welding torch 9 and the center line of the extended section of the obliquely extended welding wire 5. Preferably, the distance from the center O4 of the lower curved section of the outer rear nozzle tube 201 to the intersection point O1 is equal to the distance from the center O5 of the lower curved section of the outer front nozzle tube 202 to the intersection point O1, so that the narrow gap welding arc can obtain two welding shielding gas flows that are basically symmetrical on both sides, thereby improving the arc stability. Embodiment 2 of the outer nozzle is suitable for rocking arc narrow gap welding when the welding wire 5 extends obliquely downward. At this time, the welding wire 5 drives the welding arc to rock symmetrically on both sides about the welding direction 13 (see Figure 2 Alternatively, it can be used for narrow-gap welding where the welding wire 5 extends obliquely downwards without shaking, waving, or rotating the arc. In this case, the welding wire 5 does not shake, waving, or rotate, and preferably the welding wire 5 is biased towards one side of the narrow-gap welding groove.

[0061] See Figure 5 The structure of the inner nozzle in Embodiment 1 shown includes a welding torch conductive rod mechanism 4 comprising an upper first conductive rod 401 and a lower first conductive nozzle 402. The first conductive rod 401 is a straight conductive rod, and the first conductive nozzle 402 is an eccentric conductive nozzle or a central hole conductive nozzle. The center lines of the first conductive rod 401 and the first conductive nozzle 402 are both located on the welding torch center line 9. The upper end of the first conductive rod 401 is connected to the welding torch body 1, and the lower end is connected to the first conductive nozzle 402. The welding wire 5 passes through the central hole of the first conductive rod 401 and is then obliquely fed downwards from the eccentric hole of the eccentric conductive nozzle (see...). Figure 5 ), or it can be fed straight down from the center hole of the conductive tip ( Figure 5(omitted from the drawing); The center line 301a of the lower curved section of the inner layer rear nozzle tube 301 intersects the center line 302a of the lower curved section of the inner layer front nozzle tube 302 at a point located on the center line of the lower section of the first conductive nozzle 402. At this time, the center lines 301a and 302a of the lower curved sections of the two nozzle tubes of the inner layer nozzle are on the same longitudinal plane as the welding torch center line 9.

[0062] Preferably, both the inner rear nozzle tube 301 and the inner front nozzle tube 302 are circular nozzle tubes, and their outer diameter d2 is not greater than the outer diameter d1 of the conductive rod. Additionally, the intersection of the center lines 301a and 302a of the lower curved section can be made to coincide with the end center point O2 of the first conductive nozzle 402, or the distance from the end center O6 of the lower curved section of the inner rear nozzle tube 301 to the end center point O2 of the first conductive nozzle 402 can be equal to the distance from the end center O7 of the lower curved section of the inner front nozzle tube 302 to the end center point O2 of the first conductive nozzle 402, thereby improving the cooling effect at the end of the conductive nozzle. Embodiment 1 of the inner nozzle is suitable for narrow-gap welding of the rocking arc or rotating arc when the welding wire 5 extends obliquely downwards, or suitable for welding when the welding wire 5 is fed straight downwards along the center line 9 of the welding torch. Figure 5 Narrow gap welding using straight welding wire or pre-formed welding wire (not shown in the image).

[0063] See Figure 6 The structure of the inner nozzle in Embodiment 2 shown includes a welding torch conductive rod mechanism 4 comprising a second conductive rod 403 and a second conductive nozzle 404. The second conductive rod 403 is either a curved or straight conductive rod, and the second conductive nozzle 404 is either a central hole conductive nozzle or a curved conductive nozzle. The upper end of the second conductive rod 403 is connected to the welding torch body 1, and the lower end is connected to the second conductive nozzle 404. The welding wire 5 passes through the central hole of the second conductive rod 403 and is then obliquely fed downwards from the central hole of the second conductive nozzle 404. The center line 301a of the lower curved section of the inner rear nozzle tube 301 intersects the center line 302a of the lower curved section of the inner front nozzle tube 302 at a single point. When the center lines 301a and 302a of the lower curved sections of the two nozzle tubes of the inner nozzle are on the same longitudinal plane as the center line of the second conductive nozzle 404, their intersection point is exactly located on the center line of the lower section of the second conductive nozzle 404.

[0064] Preferably, both the inner rear nozzle tube 301 and the inner front nozzle tube 302 are circular nozzle tubes, and their outer diameter d2 is not greater than the outer diameter d1 of the conductive rod. Furthermore, when the center lines 301a and 302a of the lower curved sections of the two inner nozzle tubes are in the same plane as the center line of the second conductive nozzle 404, the intersection of the center lines 301a and 302a of the lower curved sections can coincide with the end center point O3 of the second conductive nozzle 404; or, the distance from the end center O6 of the lower curved section of the inner rear nozzle tube 301 to the end center point O3 of the second conductive nozzle 404 can be equal to the distance from the end center O7 of the lower curved section of the inner front nozzle tube 302 to the end center point O3 of the second conductive nozzle 404, thereby improving the cooling effect at the end of the conductive nozzle. Example 2 of the inner nozzle is suitable for narrow gap welding with a shaking arc when the welding wire 5 extends obliquely downwards, or for narrow gap welding with a non-shaking, non-oscillating, and non-rotating arc when the welding wire 5 extends obliquely downwards.

[0065] like Figure 7 As shown, in the nozzle device of the present invention, the welding torch conductive rod mechanism 4 is composed of a bent conductive rod 403a and a central hole conductive nozzle 404a. The outer rear nozzle tube 201 and the outer front nozzle tube 202 are both formed by bending and pressing a round tube, and the inner rear nozzle tube 301 and the inner front nozzle tube 302 are both formed by bending a round tube. During welding, the inner front and rear nozzle tubes are aligned obliquely downward from the front and rear sides of the bent conductive rod 403a with the lower section of the central hole conductive nozzle 404a, and the outer front and rear nozzle tubes 202 and 201 are aligned obliquely downward from the sides of the bent conductive rod 403a with the arc at the end of the welding wire 5. Among them, the cross-sections of the inner two nozzle tubes 301 and 302 are smaller than the cross-sections of the outer two nozzle tubes 201 and 202. The middle vertical sections of the inner and outer front and rear nozzle tubes are symmetrically arranged about the center line 9 of the welding torch on both sides, while the lower nozzle tube bending section is asymmetrical. The bending section of the inner nozzle tube is not parallel to the bending section of the outer nozzle tube on the same side. It is suitable for narrow gap welding with shaking arc or non-shaking arc when the welding wire 5 is fed obliquely downward.

[0066] like Figure 8 , Figure 9 and Figure 1 As shown, taking the narrow gap welding application of the shaking arc / rotating arc as an example, when the nozzle device of the present invention is used, Figure 8 This is a schematic diagram of the cross-section when the outer and inner nozzles extend into the narrow gap welding groove 7. Figure 9 This is a right-view longitudinal section diagram showing the outer and inner nozzles extending into the narrow gap welding groove 7. Preferably, the welding torch centerline 9 is perpendicular to the workpiece surface 704, and the thickness d of the flat tubular nozzle of the outer nozzle is the same as the outer diameter of the conductive rod in the welding torch conductive rod mechanism 4.

[0067] Before welding, set the welding shielding gas flow rate for the four nozzle tubes of the nozzle device, including the outer and inner nozzles. When the four nozzle tubes of the outer and inner nozzles are used within the narrow gap welding groove 7, such as... Figure 8 and Figure 9 As shown, the welding wire 5 is fed obliquely downward from the welding torch conductive rod mechanism 4. The rotational motion mechanism in the welding torch body 1 drives the welding torch conductive rod mechanism 4, causing the electric arc 6 at the end of the welding wire 5 to rotate unidirectionally 10 or reciprocate in an arc-shaped motion 11 within the narrow gap welding groove 7. At the same time, the welding torch, together with the electric arc 6, moves relative to the workpiece along the welding direction 13, thereby forming a narrow gap weld 703 under the protection of the welding gas ejected from the four nozzle tubes of the outer and inner nozzles.

[0068] As the number of layers in the narrow-gap weld 703 increases, the welding torch, along with the nozzle assembly, moves upward to maintain a constant distance between the lowest point of the nozzle assembly and the bottom of the bevel 7 (which is also the workpiece surface 704), i.e., the nozzle height h1 remains constant. Figure 9 As shown. During the welding process, the nozzle device can be used until the gas outlet on either side of the inner rear nozzle tube 301 and the inner front nozzle tube 302 in the inner nozzle is exposed on the upper surface of the narrow gap welding groove 7. Then, an external sleeve nozzle can be used until the narrow gap welding groove 7 is fully welded.

[0069] Alternatively, once the gas outlet on either side of the inner rear nozzle pipe 301 and the inner front nozzle pipe 302 in the inner nozzle layer is exposed on the upper surface of the narrow gap welding groove 7, a process plate is placed on the upper surface of the left wall 701 and the right wall 702 of the narrow gap welding groove 7 before welding. That is, the left process plate 801 and the right process plate 802 are placed accordingly, so that the left process plate 801 and the right process plate 802 form a gas storage groove 8 (see...). Figure 8 The depth h3 of the gas storage slope 8 (see...) Figure 9 The depth h3 of the gas storage bevel 8 is not less than (h1 + (h2 - h1)), where h1 is the nozzle height, h2 is the height of the upper end of the inner nozzle, and (h2 - h1) is the height difference between the inner and outer nozzles. Since the depth h3 of the gas storage bevel 8 is not less than the sum of the nozzle height h1 and the height difference (h2 - h1) between the inner and outer nozzles, the nozzle device can be used until the narrow gap welding bevel 7 is fully welded, thus achieving full bevel depth utilization of the nozzle device.

[0070] Optionally, the outlet gas velocity V of the inner layer rear nozzle pipe 301 can be adjusted by setting the welding shielding gas flow rate before welding. 3a The outlet airflow velocity V of the outer rear nozzle tube 201 shall not be less than 2a This causes the outlet airflow velocity V of the inner front nozzle pipe 302 to be... 3b The outlet airflow velocity V is not less than that of the outer front nozzle tube 202. 2b,like Figure 1 As shown. Thus, through the airflow of the inner nozzle, while providing direct gas cooling to the welding torch contact tip, it can more effectively suppress the upward rush of high-temperature airflow mainly from the welding arc and molten pool area, thereby reducing the working temperature of the welding contact tip end and the bottom end face of the welding torch body, improving the service life of the contact tip and the reliability of the welding torch operation.

[0071] Optionally, the outlet gas velocity V of the inner layer rear nozzle pipe 301 can be adjusted by setting the welding shielding gas flow rate before welding. 3a The outlet airflow velocity V is not less than that of the inner front nozzle tube 302. 3b And / or make the outlet airflow velocity V of the outer rear nozzle tube 201 2a The outlet airflow velocity V is not less than that of the outer front nozzle tube 202. 2b See Figure 1 Therefore, by increasing the gas flow rate of the inner and / or outer nozzles behind the arc, the shielding gas velocity behind the arc can be increased, and the distribution of the welding shielding gas flow rate between the front and rear of the arc can be vectorized, allowing more shielding gas to flow in the welding direction 13 (see...). Figure 9 This method enhances the protective effect of welding gas and directs more welding fumes towards the welding front, resulting in a bright and high-quality weld joint and thus improving welding quality.

[0072] Furthermore, there are many specific methods and approaches to implement this invention, and the above description is only a preferred embodiment of this invention. It should be noted that those skilled in the art can make several equivalents, improvements, and modifications without departing from the principle of this invention, and these equivalents, improvements, and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in the embodiments of this invention can be implemented using existing technology.

Claims

1. A narrow gap welding method, characterized in that... Includes the following steps: ① The upper ends of the outer front and rear nozzle tubes (202, 201) and the inner front and rear nozzle tubes (302, 301) are fixed on the welding torch body. Each nozzle tube is composed of an upper connecting section, a middle vertical section and a lower curved section connected together. The lower part of the inner front and rear nozzle tubes (302, 301) bends inward and is aligned with the lower part of the conductive nozzle in the lower part of the welding torch conductive rod mechanism from the front and rear sides respectively. The lower part of the outer front and rear nozzle tubes (202, 201) bends inward and is aligned with the welding arc area in the narrow gap welding groove from the front and rear sides respectively. ② Connect each nozzle tube to the gas chamber or to the gas source. The outlet gas velocity of the inner rear nozzle tube (301) is not less than the outlet gas velocity of the outer rear nozzle tube (201), and the outlet gas velocity of the inner front nozzle tube (302) is not less than the outlet gas velocity of the outer front nozzle tube (202). The outlet gas velocity of the inner rear nozzle tube (301) is not less than the outlet gas velocity of the inner front nozzle tube (302), and / or the outlet gas velocity of the outer rear nozzle tube (201) is not less than the outlet gas velocity of the outer front nozzle tube (202), so that more welding fumes are directed to the front of the welding. ③ The welding wire is fed obliquely, and the electric arc at the end of the welding wire rotates or swings in an arc within the narrow gap welding groove. Alternatively, the welding wire is fed straight down along the center line of the welding torch, and the pre-formed welding wire drives the electric arc at its end to rotate or swing left and right within the narrow gap welding groove. At the same time, the welding torch and the electric arc move relative to the workpiece along the welding direction. The vertical section in the middle and the curved section at the bottom of each nozzle tube extend into the narrow gap welding groove, forming a narrow gap weld under the action of the welding shielding gas. ④ As the number of narrow gap weld layers increases, the welding torch and four nozzle tubes move upward together, maintaining a constant distance from the lower end of each nozzle tube to the bottom of the groove, until the gas outlet on either side of the inner front and rear nozzle tubes (302, 301) is exposed above the narrow gap weld groove. By setting a gas storage groove (8) above the narrow gap weld groove, the nozzle device is used until the narrow gap weld groove is fully welded, thus achieving multi-layer narrow gap welding; the nozzle device consists of the outer rear nozzle tubes (20) arranged in the vertical direction. 1) The four nozzles are composed of the outer front nozzle pipe (202), the inner rear nozzle pipe (301) and the inner front nozzle pipe (302); the gas storage bevel (8) is formed by placing a process plate on the upper surface of the left wall (701) and the right wall (702) of the narrow gap welding bevel (7) before welding, that is, placing the left process plate (801) and the right process plate (802) respectively, so that the left process plate (801) and the right process plate (802) form a gas storage bevel (8).

2. The narrow gap welding method according to claim 1, characterized in that: In step ①, when the lower curved sections of the inner rear nozzle tube (301) and the inner front nozzle tube (302) are aligned with the lower section of the conductive nozzle from the front and rear sides respectively, the center line (301a) of the lower curved section of the inner rear nozzle tube (301) and the center line (302a) of the lower curved section of the inner front nozzle tube (302) intersect at a point on the center line of the lower section of the conductive nozzle. At this time, the center lines (301a, 302a) of the lower curved section of the nozzle tube and the center line of the lower section of the conductive nozzle are on the same plane. Alternatively, it may include aligning the intersection of the center lines (301a, 302a) of the lower curved sections of the inner rear nozzle tube (301) and the inner front nozzle tube (302) with the center point of the end of the conductive nozzle; or, it may include aligning the distance from the center of the end of the lower curved section of the inner rear nozzle tube (301) to the center point of the end of the conductive nozzle with the distance from the center of the end of the lower curved section of the inner front nozzle tube (302) to the center point of the end of the conductive nozzle.

3. The narrow gap welding method according to claim 1, characterized in that: In steps ① and ③, when the lower curved sections of the outer rear nozzle tube (201) and the outer front nozzle tube (202) are respectively aligned obliquely downward from the front and rear sides with the welding arc area within the narrow gap welding groove, the center line (201a) of the lower curved section of the outer rear nozzle tube (201) and the center line (202a) of the lower curved section of the outer front nozzle tube (202) intersect at a point on the workpiece surface. The intersection point is located on the welding torch centerline (9) or on the direction of welding. On the center line of the extended section of the welding wire (5) when it is obliquely fed out from the front or rear, the center line (201a, 202a) of the lower curved section of the nozzle tube is on the same longitudinal plane as the center line (9) of the welding torch or the center line of the extended section of the welding wire (5); or, it also includes making the distance from the center of the lower curved section of the outer rear nozzle tube (201) to the intersection point equal to the distance from the center of the lower curved section of the outer front nozzle tube (202) to the intersection point; When their intersection is located on the center line (9) of the welding torch, the welding wire (5) is fed out obliquely and the arc at the end of the welding wire (5) rotates, or the welding wire (5) is fed straight down along the center line (9) of the welding torch and the pre-formed welding wire (5) drives the arc at its end to rotate or swing left and right; or, when their intersection is located on the center line of the extended section of the obliquely fed welding wire (5), the arc at the end of the welding wire (5) swings in an arc shape.

4. The narrow gap welding method according to claim 1, characterized in that: The inner nozzle is composed of an inner front nozzle tube (302) and an inner rear nozzle tube (301). In step ④, once the gas outlet of either the inner rear nozzle tube (301) or the inner front nozzle tube (302) of the inner nozzle is exposed on the upper surface of the narrow gap welding groove (7), a left process plate (801) and a right process plate (802) are placed on the upper surface of the left side wall (701) and the right side wall (702) of the narrow gap welding groove (7) before welding, so that the left process plate (801) and the right process plate (802) form a gas storage groove (8). The depth of the gas storage groove h3 is not less than (h1+(h2-h1)), where h1 is the nozzle height, h2 is the height of the upper end of the inner nozzle, and (h2-h1) is the height difference between the inner nozzle and the outer nozzle, so that the nozzle device is used until the narrow gap welding groove (7) is fully welded, and the nozzle device is used at the full groove depth.

5. A double-sided, double-layer, inner-bent nozzle device for implementing the narrow-gap welding method according to any one of claims 1-4, characterized in that: The device consists of four nozzles arranged in the vertical direction: an outer rear nozzle (201), an outer front nozzle (202), an inner rear nozzle (301), and an inner front nozzle (302). The center plane of each nozzle is on the same longitudinal center plane as the center plane of the welding torch conductive rod mechanism (4). The outer rear nozzle (201) and the inner rear nozzle (301) are located on the rear side of the welding torch conductive rod mechanism (4), the outer front nozzle (202) and the inner front nozzle (302) are located on the front side of the welding torch conductive rod mechanism (4), the inner rear nozzle (301) is inside the outer rear nozzle (201), and the inner front nozzle (302) is inside the outer front nozzle (202). Each nozzle tube is composed of an upper connecting section, a middle vertical section and a lower curved section connected together. The upper ends of the upper connecting sections of the four nozzle tubes are fixed to the welding torch body (1) through nozzle connectors. The middle vertical sections of the outer front nozzle tube (202) and the outer rear nozzle tube (201) are symmetrical with respect to the welding torch centerline (9). The middle vertical sections of the inner front nozzle tube (302) and the inner rear nozzle tube (301) are symmetrical with respect to the welding torch centerline (9). The lower curved sections of the inner front nozzle tube (302) and the inner rear nozzle tube (301) are bent inward and aligned with the lower section of the conductive nozzle in the lower part of the welding torch conductive rod mechanism (4) from the front and rear sides respectively. The lower curved sections of the outer front nozzle tube (202) and the outer rear nozzle tube (201) are bent inward and aligned with the welding arc area in the narrow gap welding groove from the front and rear sides respectively.

6. The dual-sided, double-layer, inner-bend nozzle device according to claim 5, characterized in that: The cross-sections of the inner rear nozzle tube (301) and the inner front nozzle tube (302) are smaller than the cross-sections of the outer rear nozzle tube (201) and the outer front nozzle tube (202).

7. The dual-sided, double-layer, inner-bend nozzle device according to claim 5, characterized in that: The upper connecting section of the outer rear nozzle tube (201) and the outer front nozzle tube (202) is a flat tube or a transitional body with a round upper section and a flat lower section, while the middle vertical section and the lower curved section are flat tubes.

8. The dual-sided, double-layer, inner-bend nozzle device according to claim 5, characterized in that: The upper connecting sections of the inner rear nozzle tube (301) and the inner front nozzle tube (302) are round tubes, flat tubes, or transitional bodies with a round upper section and a flat lower section, while the middle vertical section and the lower curved section are round tubes or flat tubes.

9. The dual-side-mounted, double-layered, inner-bend nozzle device according to claim 7 or 8, characterized in that: The thickness of the flat tube or the outer diameter of the round tube shall not be greater than the outer diameter of the conductive rod in the upper part of the welding torch conductive rod mechanism (4).

10. The dual-side-mounted, double-layered, inner-bend nozzle device according to claim 5, characterized in that: The inner side of the outer rear nozzle tube (201) is connected to the outer side of the inner rear nozzle tube (301) to form an integrated dual-air-path rear nozzle body. The inner side of the outer front nozzle tube (202) is connected to the outer side of the inner front nozzle tube (302) to form an integrated dual-air-path front nozzle body.

Images