CN117754086A

CN117754086A - Pipeline welding system and pipeline welding method

Info

Publication number: CN117754086A
Application number: CN202410035721.XA
Authority: CN
Inventors: 黄巍; 李理想; 周昀
Original assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2024-01-09
Filing date: 2024-01-09
Publication date: 2024-03-26

Abstract

A K-TIG welding gun includes a welding electrode, a welding power source outputs a pulsed current having a pulse frequency at a pipe section to be welded, wherein the pulsed current has a plurality of peak current portions and a plurality of base current portions, and the pipe section to be welded remains stationary. Welding defects such as molten damage caused by sagging and collapse of a welding pool are reduced while the penetration is ensured, and the fixed full-position welding of the pipeline is realized.

Description

Pipeline welding system and pipeline welding method

Technical Field

The application belongs to the field of pipeline welding, and relates to a pipeline welding system and a pipeline welding method. In particular to a method combining K-TIG welding and high-frequency pulse argon arc welding.

Background

TIG welding (Tungsten Inert Gas Welding, also known as Tungsten Inert Gas (TIG)) uses the large amount of heat generated by the arc formed between the tungsten electrode and the workpiece to melt the part to be welded, and the filler wire is added to obtain a strong weld joint. For such welding, it is very critical to ensure penetration of the weld (weld joint). However, TIG welding is often suitable for welding thin plates having a thickness of less than 3mm, since the electrode has limited current carrying capacity and excessive welding current can cause the tungsten electrode to melt. If TIG welding is used on substrates that are more than 3mm thick, the joint must be beveled (grooved) to ensure good penetration. The number of welds has to be increased due to the presence of grooves. And groove machining and increased welds can result in reduced welding efficiency.

K-TIG is a non-consumable electrode inert gas shielded welding of a deep-melting lockhole, and belongs to the high-current TIG welding technology. The dynamic balance of a molten pool is kept by the arc pressure formed by high current, the gravity and the surface tension of liquid metal, so that small holes with stable geometric forms are formed, and the single-sided welding and double-sided forming of the medium plate can be realized. K-TIG is capable of welding materials (such as ferritic stainless steel, austenitic stainless steel, duplex stainless steel, titanium alloy, zirconium alloy, and the like) with a thickness of less than 16mm at a speed 100 times faster than conventional TIG welding techniques without the need for wire filling or beveling. The above welding method is more suitable for flat welding (flat position wielding). When the workpiece has a curved surface (e.g., pipe welding), it is desirable to keep the pipe rotating and the welding gun stationary. Otherwise, the vertical or overhead welding is more prone to forming welding defects such as droops (pendant drop), or fusion (melding down) caused by collapse of the weld puddle. In production practice, the pipeline can not rotate and can only be kept still, so that the satisfactory welding effect is difficult to achieve by adopting the method.

For pipe welding, the root thickness required to maintain the mechanical integrity of the welded joint also makes the root pass a critical step in the process. Some studies have shown that keyhole or keyhole (keyhole) technology provides a method that helps to achieve a complete root pass and defect-free filling. In the small hole technique, the arc must pass through the substrate, forming a through hole at the joint. The through hole is closed by means of solidification of the additional material fed behind the arc when the welding gun is moved. The diameter of the selected tungsten electrode is above 6mm (the common diameter is 6.3-6.5 mm), the welding current is 600-650A, the arc voltage is 16-20V, under the action of such high standard parameters, the electromagnetic shrinkage force of the arc is greatly improved, and the macroscopic appearance is that the arc straightening degree, the arc force and the penetrating power are obviously enhanced. During welding, the electric arc is deeply penetrated into the base material, and molten metal is extruded to the side wall around the molten pool to form a keyhole. The pores will exist stably if the arc pressure, the vapor reaction force from the evaporation of the metal on the side walls of the pores, and the liquid metal surface tension and the liquid metal internal pressure reach a dynamic balance. As the arc advances, the molten pool metal bridges behind the arc and cools to solidify into a weld.

In order to achieve the required penetration and to achieve full position welding of fixed pipes without machining joint bevels (joint balls) or automatic wire feeding, the present application combines the methods of high frequency pulse tungsten inert gas (high frequency pulsed current TIG, HFPC TIG) and small Kong Wuji inert gas (keyhole tungsten inert gas welding, K-TIG).

Disclosure of Invention

In order to overcome the technical problems in the fixed welding of the pipeline, the welding defects of drop, fusion damage caused by collapse of a welding pool and the like are reduced while the penetration is ensured, and the pipeline welding system and the pipeline welding method are provided. The purpose is to provide a welding device and a method which can obtain stable penetration bead when small hole welding is carried out, and full penetration full position welding is realized by K-TIG welding once.

To achieve the above object, a first aspect of the present application discloses a pipe welding system, including:

the K-TIG welding gun comprises a welding electrode;

a welding power source that outputs a pulsed current having a pulse frequency at a pipe section to be welded, wherein the pulsed current has a plurality of peak current portions and a plurality of base current portions; and

a pipe section to be welded, wherein the pipe section remains stationary.

Further, the peak current range is 500-1000A.

Further, the pulse frequency is set in the range of 10000-15000 Hz.

Further, a pulse peak period (T _p ) The duty cycle in each pulse time ranges from 30% to 35%.

Further, the thickness of the pipe section ranges from 3 to 6mm.

Further, the pipe welding system employs a gas selected from the group consisting of: argon and/or hydrogen.

Further, the shielding gas includes 10% or less by volume of hydrogen, and preferably 5% or less by volume of hydrogen.

In a second aspect of the present application, there is provided a method of pipe welding employing the pipe welding system of the first aspect, comprising the steps of:

(1) Abutting the edges of the pipe sections to be welded;

(2) Performing K-TIG welding on the two butted edges, wherein the pipeline section is kept stationary;

(3) Dividing a pipeline section into at least one partition, starting an arc at a 0-degree position by a K-TIG welding gun, forming a first welding point in a first arc starting time, and performing arc extinction after the K-TIG welding gun moves a first distance along the circumference;

(4) After the first arc extinguishing time, the K-TIG welding gun is started, and in the second arc extinguishing time, a second welding point is formed, and the K-TIG welding gun is started after moving a second distance along the circumference;

(5) And (3) repeating the step (3) and the step (4) until the K-TIG welding gun finishes all-position welding.

Further, a pulse current is provided in the first arcing time and/or the second arcing time, and the duty ratio of the pulse peak period of the pulse current in each pulse time ranges from 30% to 35%.

Further, the first distance and the second distance are equal.

Compared with the prior art, the technical scheme provided by the application has the following advantages:

1. the present application uses a pulse current as a welding current, and controls the pulse frequency of the pulse current to a frequency required for a molten pool on the back side of a base material at the time of welding. Thus, a stable penetration bead without sagging can be reliably obtained during keyhole welding.

2. In the pipeline fixing and welding process, joint inclined planes (joint ends) are not required to be machined, wire feeding is not required, high-thickness all-position welding can be achieved, cost is saved, and welding efficiency is improved.

Drawings

The advantages and spirit of the present application may be further understood by reference to the following detailed description of the invention and the accompanying drawings.

FIG. 1 is an exemplary version of a welding system provided by embodiments of the present application;

FIG. 2 is a schematic diagram of pulse currents for arc starting and extinguishing times provided by embodiments of the present application;

FIG. 3 is a schematic view of a partition of a pipe section provided by an embodiment of the present application;

fig. 4a and 4b are photographs of a pipe provided in an embodiment of the present application after welding.

Detailed Description

Specific embodiments of the present application are described in detail below with reference to the accompanying drawings. However, the present application should be understood not to be limited to such an embodiment described below, and the technical idea of the present application may be implemented in combination with other known technologies or other technologies having functions identical to those of the known technologies.

In the following description of the specific embodiments, for the sake of clarity in explaining the structure and operation of the present application, description will be given by way of directional terms, but words of front, rear, left, right, outer, inner, outer, inner, axial, radial, etc. are words of convenience and are not to be construed as limiting terms.

In the following description of the specific embodiments, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, merely to facilitate description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operate in a specific orientation, and are therefore not to be construed as limiting the present application.

The terms "upward", "downward", "above" and "below" are made with reference to the central longitudinal axis of the tube. Thus, the terms "upward" and "downward" should be understood to refer to directions away from and toward the longitudinal axis. Furthermore, when a first structure is described as being positioned "above" or "below" a second structure, this should be understood to mean that the first structure is positioned further or closer to the longitudinal axis.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not intended to be limiting with respect to time sequence, number, or importance, but are not to be construed as indicating or implying a relative importance or implicitly indicating the number of features indicated, but merely for distinguishing one feature from another in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly specified otherwise. Likewise, the appearances of the phrase "a" or "an" in this document are not meant to be limiting, but rather describing features that have not been apparent from the foregoing. Likewise, unless a particular quantity of a noun is to be construed as encompassing both the singular and the plural, both the singular and the plural may be included in this disclosure. Likewise, modifiers similar to "about" and "approximately" appearing before a number in this document generally include the number, and their specific meaning should be understood in conjunction with the context.

It should be understood that in this application, "at least one" means one or more, and "a plurality" means two or more. "and/or" is used to describe association relationships of associated objects, meaning that there may be three relationships, e.g., "a and/or B" may mean: only a, only B and both a and B are present, wherein a, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (one) of a, b or c may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.

In this application, the terms "mounted," "connected," "secured," and the like are to be construed broadly, unless otherwise specifically indicated and defined. For example, the two parts can be fixedly connected, detachably connected or integrated; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements or interaction relationship between the two elements. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be. "fixedly connected" or "non-movably connected" is understood to mean that the connection between two or more structural members is not configured to provide relative movement. An example of a fixed connection is a welded connection or a bolted connection, and in some cases a welded seam and a bolted connection. "movably connected" or "movable" or "mobile connection" is understood to mean a connection between two or more structural members that allows for horizontal and/or vertical relative movement between the members under extreme dynamic loads. Such a connection typically does not allow movement under static or generally dynamic loads (e.g., as applied from light/medium wind).

The terms "unit", "article", "module" and "module" described in the present specification mean a unit for processing at least one function and operation, and may be implemented by hardware components or software components and combinations thereof.

The welding power supply is used for applying a welding voltage between the electrode and the substrate to cause a welding current to flow. The welding current may be a pulsed current. One skilled in the art can set the output circuit in the welding power supply as required by the pulse current.

Welding as used herein will refer to the deposition of molten material by operation of an arc (including, but not limited to, submerged arc welding, GMAW welding, MAG welding MIG welding, TIG welding) or by operation of any arc used with a pipe welding system.

Each aspect or embodiment defined herein may be combined with any other aspect or embodiment unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Description of the terms

Welding as used herein includes, but is not limited to, submerged arc welding, GMAW welding, MAG welding, MIG welding, TIG welding. A welding power supply refers to any device capable of powering such operations as welding when power is applied thereto (including, but not limited to, transformer-rectifiers, inverters, converters, resonant power supplies, quasi-resonant power supplies, switch-mode power supplies, etc.), as well as control circuitry and other auxiliary circuitry associated therewith.

Those skilled in the art will appreciate that an industrial robot, welding carriage, etc. may be used to achieve a certain speed and path movement of the welding gun, and the present invention is not limited.

As used herein, 5G welding, all-position welding, or pipe welding may all refer to pipe horizontal fixed welding. Typically the pipe is held stationary and the gun is moved circumferentially to weld to achieve an all position (all position) weld.

In general, a filler metal (wire) may be added to a molten pool to perform K-TIG welding, depending on the purpose. In the K-TIG welding of the present embodiment, the joint gap can be filled by melting the base materials without using a filler metal. However, pulse K-TIG welding may also be performed using filler materials.

As used herein, the tungsten electrode may be provided with a material, an electrode diameter, and a tip shape which are generally used in K-TIG welding.

The thickness of the substrate of the pipe is not particularly limited, and is, for example, 3mm to 6mm, preferably 3mm to 5.5mm.

Specific embodiments of the present application are described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the tip in the K-TIG welding gun covers the tungsten electrode. A high frequency generator (not shown) generates a pilot arc 102 between the tungsten electrode and the tip. A shielding gas containing argon gas and hydrogen gas is supplied to the welding tip, and the welding portion is shielded from the atmosphere by the shielding gas, thereby maintaining welding quality. Hydrogen is an active gas, and generates a thermal shrinkage effect (thermal shrinkage effect). Therefore, when a mixed gas of argon and hydrogen is used as the shielding gas, the arc converges, and the directivity of the arc can be improved to suppress the swing of the arc.

The shielding gas supply provides an inert gas, such as argon, to the welding gun. The shielding gas supply may comprise a container, such as a gas cylinder, the delivery of shielding gas via appropriate tubing being controlled by a corresponding controller.

To achieve full penetration, the present application combines the K-TIG welding technique with the high frequency pulse technique. Using the K-TIG welding technique, we can increase the welding current to be high enough (1000A) and the arc pressure to overcome the surface tension of the puddle, forming a keyhole 103 inside the weld puddle. A molten pool is formed along the length direction of the pipe 101 on the inner side thereof and behind the hole welding direction. The molten pool melts the substrate by the heat emitted from the welding gun.

The pulse current is used as welding current, and the pulse frequency of the pulse current is controlled to be the frequency required by a molten pool on the inner side of a base material during welding. The pulse frequency control of the pulsed current helps to obtain a reliable, sagging-free, stable penetration bead.

The peak current and the base current of the pulse current are controlled together with the pulse frequency of the pulse current. In the pulse welding process, the basic value stage mainly plays a role of arc maintenance, and the peak value stage is a process of mainly outputting power supply heat and melting welding wires to form a molten pool. By adopting the high-frequency pulse welding technology, the pulse frequency can be increased to be high enough (15000 Hz), the electric arc is further contracted, and the welding penetration is increased.

It is known to those skilled in the art that a cooling system may be configured in a K-TIG torch to cool a tungsten rod. The high temperature region of the cathode region tungsten tip is limited to an extremely narrow region. The current density of the cathode region is thus increased, which further enhances the arc contraction by electromagnetic effects, which may also increase the weld penetration.

Meanwhile, in order to prevent welding defects such as overhang (pendant drop) and melting (melting down) caused by collapse of a molten pool, it is very critical to control the size of the molten pool as small as possible.

The welding substrate used in this example was 304L stainless steel tubing. It has a thickness of 5mm and a diameter of 108mm. In Ar and 5%H ₂ As shielding gas (shielding gas), argon gas (purging gas) is used for protecting the weld joint from oxidation.

The cathode of the welding electrode was a tungsten electrode with a diameter of 6.4mm and was sharpened 30 °.

As discussed in detail below, the edges of adjacent pipe sections to be welded are butted, and the joint may be "I" shaped. The gap size of the joint ranges from 0 to 0.5mm. At least one seam may be formed at the interface of each pair of adjacent pipe sections to hold the pipe sections together.

The welding process of the present embodiment consists of a cycle comprising a plurality of arc starting phases and arc extinguishing phases. The parameter setting adopts zonal control of welding current and pulse frequency.

As shown in fig. 2, full penetration can be achieved during the arcing phase, while the quenching phase rapidly cools the molten pool at zero current to prevent collapse of the pool. The arcing stage adopts a high-frequency pulse current mode, the pulse frequency is set at 10000-15000 Hz, the peak current range is 500-1000A, and the base value current is set at 5A. By adjusting the balance value of the peak current time and the base current time in the arcing stage, different average current control weld penetration and weld pool size can be obtained. By adjusting the cycle time of the arc quenching phase, the bath temperature and cooling time can be controlled. An exemplary pulse frequency in this embodiment is 15000Hz with a peak current of 1000A. The duration of the arcing phase may be referred to as the arcing time. The arcing time is related to the diameter of the pipe section to be welded.

As shown in fig. 2, a rectangular or trapezoidal current wave is manufactured with a pulse current and the shape is made to repeat. Setting the time of the upper bottom part of the rectangle or trapezoid as the pulse peak period T _p The time of the bottom part is the pulse base period T _b The respective current is pulse peak current I _p And pulse base current I _b . Wherein T is _p The duty cycle during each pulse time is about 30% to 35%. It should be noted that fig. 2 is a schematic diagram of pulse current for the above-mentioned arcing time and extinguishing time, not as T _p 、T _b Or I _p 、I _b Is expressed by specific numerical values of (a).

As shown in fig. 3, the welding position of the pipe section is divided into three regions. The welding gun is initially at the top, i.e. is set in an arc at 0 ° and is rotated in a counter-clockwise direction for welding, moving between 0 ° and 15 °. And then proceeds upwards to a vertical position, between 15 ° and 135 °, ending in a horizontal position (flat position), between 135 ° and 180 °. Each location area is associated with an associated welding parameter to ensure penetration and no collapse of the puddle. The welding parameters at the above positions are shown in table 1. Taking a position between 0 and 15 as an example, a first weld is formed within one arcing time, i.e. 0.8 s; the welding gun moves for 2mm, after 3s of arc extinguishing time, the welding gun executes the arc starting operation to form a second welding point, and the cycle is performed.

Table 1 welding parameters for each welding position

The welding gun can form a plurality of welding points at the welding position. Taking a position between 0 ° and 15 ° as an example, the distance between the center position of the first welding point and the center position of the second welding point (i.e., the first distance), the distance between the center position of the second welding point and the center position of the third welding point may be equal. The distance between adjacent welds is related to factors such as the speed of the weld gun, the diameter of the pipe section, the thickness of the weld bead, etc.

As an example, the distance between the center position of the first welding point and the center position of the second welding point is different from the distance between the center position of the second welding point and the center position of the third welding point.

The pipes welded by the method are identified by X-ray inspection along the length of the weld and the thickness of the weld bead, as shown in FIG. 4a and FIG. 4b, and no weld defects are found in the welds obtained at all welded joints.

The scheme of the invention can be used for all-position welding of various fixed pipelines, such as oil and gas pipelines and the like. The butt welding of thicker pipelines can realize full penetration without processing grooves or wire feeding. Therefore, compared with other welding technologies, the welding quality is ensured and the cost is saved.

The preferred embodiments of the present application are described in this specification, which are intended to be illustrative of the technical aspects of the present application and not limiting. All technical solutions that can be obtained by logic analysis, reasoning or limited experiments according to the conception of the present application by a person skilled in the art are within the scope of the present application.

Claims

1. A pipe welding system, the pipe welding system comprising:

the K-TIG welding gun comprises a welding electrode;

a pipe section to be welded, wherein the pipe section remains stationary.

2. The pipe welding system of claim 1, wherein the peak current is in the range of 500-1000A.

3. A pipe welding system according to claim 1 or 2, wherein the pulse frequency is set in the range 10000-15000 Hz.

4. A pipe welding system according to claim 1 or 2, characterized in that the duty cycle during the pulse peak of the pulse current is in the range of 30-35% per pulse time.

5. A pipe welding system according to claim 1 or 2, wherein the thickness of the pipe section is in the range 3-6 mm.

6. A pipe welding system according to claim 1 or 2, characterized in that the pipe welding system employs as shielding gas a gas selected from the group consisting of: argon and/or hydrogen.

7. A pipe welding system according to claim 6, wherein the shielding gas comprises 10% or less hydrogen by volume, preferably 5% or less hydrogen by volume.

8. A method of pipe welding, characterized in that the method employs a pipe welding system according to any one of claims 1 to 7, comprising the steps of:

(1) Abutting the edges of the pipe sections to be welded;

9. The method according to claim 8, characterized in that during the first and/or second arcing time, a pulsed current is provided, the duty cycle during the pulse peak of the pulsed current being in the range of 30-35% per pulse time.

10. The method of claim 8, wherein the first distance and the second distance are equal.