KR20230151699A - Method of electro gas arc welding - Google Patents

Abstract

The present invention is an electro gas arc welding method, comprising the steps of placing a welding torch on a welding base material; And performing electro gas arc welding by moving the welding torch circularly at least once, wherein the circular movement is centered at 1/2 point based on the thickness direction of the welding base material. It may be characterized as rotating along a circular orbit.

Description

{Method of electro gas arc welding}

The present invention relates to an electro gas arc welding method, and more specifically, to an electro gas arc welding method that can improve the microstructure of a weld zone.

Electro gas arc welding (EGW) has a larger heat input than general welding methods. In particular, EGW has the characteristic of ensuring excellent productivity and economic efficiency as it can complete production with only single-pass welding even in the welding process of thick plates, such as the ship manufacturing process.

During EGW welding, relatively thin plates of approximately 20 mm can be welded using the arc generated at a fixed position. However, when the thickness of the plate becomes thicker than about 50 mm, the operator controls the welding from the front to the back through oscillation of the electrode, as described in Korean Patent No. 10-1994008. do.

However, due to the nature of the process, EGW welding uses a copper shoe through which coolant flows on the front part, and the copper shoe plays the biggest role in the cooling and solidification behavior of the weld zone. In terms of welding metallurgy, solidification always progresses from the surface to the center in the fusion zone during welding. At this time, during the nucleation and growth process, diffusion of atoms causes segregation in the direction of cooling. This segregation had the problem of acting as the main factor causing a decrease in mechanical properties, especially in the center of the weld zone.

Korean Patent No. 10-1994008

The present invention is intended to solve various problems including the problems described above, and its purpose is to provide an electro gas arc welding method that can improve the microstructure of the weld zone during EGW welding. However, these tasks are illustrative and do not limit the scope of the present invention.

According to one embodiment of the present invention, an electro gas arc welding method is provided. The electro gas arc welding method includes placing a welding torch on a welding base material; And performing electro gas arc welding by moving the welding torch circularly at least once, wherein the circular movement is centered at 1/2 the point based on the thickness direction of the welding base material. It can rotate along a circular orbit.

Additionally, according to the present invention, the circular motion can rotate so that the radius gradually increases outward from the center of the circular orbit.

Additionally, according to the present invention, the circular motion can rotate from the outside of the circular orbit to the center so that the radius becomes gradually smaller.

Additionally, according to the present invention, the radius of the circular orbit can satisfy Equation 1 below.

[Formula 1]

r≤ 0.5T - 5

(where r is the radius of the circular orbit, and T is the thickness of the welding base material)

Additionally, according to the present invention, the radius of the circular orbit can satisfy Equation 2 below.

[Formula 2]

(Here, r is the radius of the circular orbit, R is the distance between base materials (root gap) on the back surface, T is the thickness of the weld base material, and θ is the angle of improvement formed by the weld base material)

Additionally, according to the present invention, the electro gas arc welding can be performed only by circular motion of the welding torch.

Additionally, according to the present invention, the circular orbit may be set to be spaced apart from the improved surface, the back surface, and the front surface of the weld base material by a predetermined distance.

Additionally, according to the present invention, the predetermined distance may be 5 mm to 10 mm.

Additionally, according to the present invention, the rotation speed of the welding torch during the circular motion may be 30 rpm to 240 rpm.

According to an embodiment of the present invention made as described above, an electro gas arc welding method capable of improving the microstructure of the welded portion during EGW welding can be implemented. Of course, the scope of the present invention is not limited by this effect.

1 is a diagram schematically illustrating the structure of an electrogas arc welding device according to an embodiment of the present invention.
Figure 2 is a diagram illustrating an electrogas arc welding method according to an embodiment of the present invention.
Figure 3 is a diagram showing an electro gas arc welding method according to a comparative example of the present invention.
Figure 4 is a schematic diagram for explaining an electro gas arc welding method according to an embodiment of the present invention.
Figures 5 and 6 are diagrams showing the microstructure of the welded area analyzed with an optical microscope after electrogas arc welding according to an experimental example of the present invention.
Figure 7 is a diagram schematically illustrating how electro gas arc welding is performed according to an embodiment of the present invention.

Hereinafter, various preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples may be modified into various other forms, and the scope of the present invention is as follows. It is not limited to the examples. Rather, these embodiments are provided to make the present disclosure more faithful and complete and to fully convey the spirit of the present invention to those skilled in the art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will now be described with reference to drawings that schematically show ideal embodiments of the present invention.

Figure 7 is a diagram schematically illustrating how electro gas arc welding is performed according to an embodiment of the present invention. Referring to FIG. 7, the backing material 60 and the copper dip 70 are positioned to face each other in the thickness direction of the weld base material 80, and the welding torch 10 is placed between the backing material 60 and the copper dip 70. ) is placed so that welding is performed along the traveling direction.

1 is a diagram schematically illustrating the structure of an electrogas arc welding device according to an embodiment of the present invention.

Referring to FIG. 1, the electro gas arc welding device 100 according to an embodiment of the present invention includes a welding torch 10, a feeding unit 20, a driving unit 30, a laser sensor 40, and a control unit 50. ) includes. In addition, in order to perform welding, the backing material 60 and the copper immersion plate 70 are positioned to face each other in the thickness direction of the weld base material 80.

In general, electro gas arc welding (hereinafter referred to as EGW) requires setting various process conditions such as copper immersion/cooling method/back support method/welding material. The above conditions can be modified to suit each situation, and vertical upward welding is performed by receiving welding material from an electrode tip located at the top of the weld zone.

Specifically, the electro gas arc welding device 100 according to an embodiment of the present invention includes a welding torch 10 equipped with a welding wire at the tip, and a wire feeding unit 20 that supplies the welding wire to the welding torch 10. Includes. In order to perform vertical butt welding, the welding torch 10 includes a drive unit 30 that moves the welding base material 80 in the thickness direction or moves the welding torch 10 in the vertical direction to perform upward welding. do.

In addition, the electro gas arc welding device 100 is formed within the welding torch 10 and includes a laser sensor 40 capable of measuring distance information between improved surfaces of the welding base material 80 and distance information between improved surfaces of the welding base material 80. It includes a control unit 50 that calculates welding conditions corresponding to and controls the amount of heat input by adjusting welding current and voltage conditions according to the welding conditions and the location of the area to be welded. The electro gas arc welding device 100 may further include a power supply unit (not shown) that supplies welding current conditions, voltage conditions, and power to each device through operator manipulation.

The welding torch 10 is a torch used in EGW and functions to supply and energize welding wire. The welding torch 10 is driven to rotate in the thickness direction of the welding base material 80 by the drive unit 30. A laser sensor 40 is provided inside the welding torch 10. The laser sensor 40 can accurately measure the distance between improved surfaces of the weld base material 80.

The melting point base material 80 is provided as a vertical iron plate with a thickness of 10 mm to 100 mm, and has a 'V' shape when viewed from the top, as shown in FIG. 2. Here, the laser sensor 40 is used to measure the distance between the improved surfaces formed by the welding base materials 80. A backing material 60 is installed on the back side (hereinafter, the back side) of the weld base material 80, and a copper immersion plate 70 is installed on the front side (hereinafter, the front side) of the weld base material 80. Here, the backing material 60 can support the molten metal during the welding process and cool it to form a weld bead. The copper immersion 70 supports the molten metal and can perform a cooling function using a water-cooled hose (not shown) and supply a protective gas. This copper immersion 70 can be moved up and down by the driving unit 30 together with the welding torch 10.

The driving unit 30 may weave the welding torch 10 in the thickness direction (arrow direction shown in FIG. 2) of the welding base material 80. The drive unit 30 may use a commercially available motor to control the weaving speed and position.

The control unit 50 sets the welding start and end points before starting or during welding, and controls the position of the welding torch 10 through settings such as weaving speed and width. At this time, the welding current and voltage conditions are controlled while driving the welding torch 10, and in order to accurately control the conditions, the welding base material 80 is improved using the laser sensor 40 provided in the welding torch 10. Measure the interplanar distance (P) at each location. The control unit 50 can control the current and voltage by calculating the amount of heat input for each welding position based on the measured distance (P) information between the improved surfaces.

The EGW welding method using the EGW welding device 100 having these configurations may include the following steps.

and disposing the welding torch (10). The welding torch 10 is disposed at the welding portion of the welding base material 80 to be vertically butt welded. At this time, the backing material 60 and the copper dip 70 are installed on the back side and the front side of the weld base material 80, respectively. The welding torch 10 supplies wire from the wire feeding unit 20 and generates an arc using a protective gas such as carbon dioxide.

Thereafter, the control unit 50 controls the welding torch 10 to weave in the thickness direction of the welding base material 80, forms the melting portion 82 on the welding base material 80, and performs welding. Here, the welding heat input must be controlled by adjusting the welding current and voltage conditions according to the location of the welding area. First, in order to perform EGW welding, a step of basically applying input values for each position of the welding torch 10 can be performed. The input value means a value set by the welding torch 10 based on the back surface of the welding base material 80.

Afterwards, a step of measuring real-time current, voltage, and width for each position of the welding torch 10 can be performed. In the above step, information on the distance between improved surfaces of the welding base material 80 can be measured using the laser sensor 40 provided in the welding torch 10. Here, information on the distance between improved surfaces of the weld base material 80 means the width. EGW welding can be performed by calculating the heat input per unit length (area) for each position of the welding torch 10 based on the measured data.

In order to control the welding conditions, information on the distance between the improved surfaces of the weld base material 80 must be measured in at least three areas. One of the three or more areas must be an area corresponding to the center in the thickness direction of the weld base material. In addition, for another of the three or more areas, distance information between the area closest to the back surface of the weld base material 80 and the area furthest from the back surface of the weld base material 80 are also required.

For example, when assuming that the area closest to the back surface of the weld base material 80 is P1, the central area of the weld base material 80 can be assumed to be P2, and the area furthest from the back surface is P3. It can be assumed. At this time, while the welding torch 10 sequentially moves through P1, P2, and P3, the laser sensor 40 can measure the distance between the improved surfaces of the welding base material 80 at each position.

At the reference points P1, P2, and P3, the initial voltage, current, and heat input are set at P2, that is, the center area of the welding base material 80 as the basic position. Thereafter, the welding torch 10 moves along the thickness direction of the welding base material 80, measures the distance information between improvement surfaces in real time, and reflects this in the welding conditions.

Here, the reason for setting P1 and P3 theoretically means a threshold value that can be located on a part of the welding base material 80 due to the shape of the welding torch 10 itself. For example, if the welding torch 10 is placed at a shorter distance from the back surface than P1 set in the drawing, the welding torch 10 may be damaged by physically contacting the backing material 60. Alternatively, if the welding torch 10 is placed so that the distance from the back surface is longer than P3 set in the drawing, the welding torch 10 may be damaged by physically contacting the copper immersion metal 70.

In addition, since the P1 and P3 positions may be closer to the center than the above-mentioned threshold during actual EGW welding, the actual P1 and P3 positions are directly measured by the welding torch 10 before performing EGW welding. At this time, before starting EGW welding, the minimum (min) and maximum (Max) values of the distance between the welding base materials 80 can be measured through oscillation and reflected in the recording and calculation.

In the present invention, the thickness (T) of the weld base material 80 is limited to 20 mm to 55 mm. This refers to the thickness range of the sheet to which a single torch torch is applied. If EGW welding is performed on a sheet thicker than this, welding must be performed using a tandem type torch. On the other hand, for sheets whose thickness is thinner than the above range, there is no need to measure the distance between improvement surfaces because oscillation does not cause a significant difference. Additionally, when using a tandem type torch, the circular motion of each electrode can be controlled individually, making it possible to design more complex convection than a single type torch.

Figure 2 is a diagram showing an electro gas arc welding method according to an embodiment of the present invention, Figure 3 is a diagram showing an electro gas arc welding method according to a comparative example of the present invention, and Figure 4 is an embodiment of the present invention This is a schematic diagram for explaining the electro gas arc welding method according to the embodiment.

First, referring to FIG. 3, EGW welding generally uses oscillation between the base material 80 and the base material 80 arranged in a V shape, that is, a welding torch (in the area where EGW welding is performed) After placing 10), EGW welding was performed by reciprocating the welding torch 10 in the thickness direction (arrow shown as M) of the base material 80. For example, for general plates, welding progresses by generating an arc from an electrode at a fixed position. In addition, for thick materials, welding was performed throughout the entire plate by accompanying oscillation. However, it is difficult to prevent segregation that occurs in the molten part 82 during EGW welding using such oscillation. Since segregation can deteriorate the mechanical properties at the center of the weld, a method was needed to prevent the creation of segregation as much as possible.

To solve this problem, as shown in FIG. 2, EGW welding according to an embodiment of the present invention introduces oscillation motion and dash circular motion driving to activate convection in the weld zone. . As an example, in the present invention, EGW welding can be performed only by circular movement of the welding torch 10. As another example, to maximize the welding effect, oscillation motion and circulation motion may be used simultaneously.

The reason for driving the circulation motion in the present invention is that the amount of convection in the molten zone can be extremely increased, and segregation of the molten zone is eliminated through control of the radius of the circular orbit and welding speed during circular motion during the EGW welding process, The microstructure of the weld zone can be refined and complicated.

For example, EGW welding according to an embodiment of the present invention includes the steps of placing the welding torch 10 on the welding base material 80 and circularly moving the welding torch 10 at least once to perform electro gas arc welding (electro gas arc welding). It includes the step of performing arc welding. Here, the circular motion may rotate along a circular orbit centered on a 1/2 point based on the thickness direction of the welding base material 80.

The circular motion may rotate so that the radius gradually increases outward from the center of the circular orbit. Alternatively, the circular motion may rotate from the outside to the center of the circular orbit so that the radius becomes gradually smaller. The direction of the circular motion can be driven either clockwise or counterclockwise.

Meanwhile, when performing EGW welding while moving the welding torch 10 in a circular motion, the radius of the circular orbit is a very important factor that must be considered. The radius of the circular orbit must simultaneously satisfy Equations 1 and 2 below.

[Formula 1]

r ≤ 0.5T - 5

(where r is the radius of the circular orbit, and T is the thickness of the welding base material)

[Formula 2]

(Here, r is the radius of the circular orbit, R is the distance between base materials (root gap) on the back surface, T is the thickness of the weld base material, and θ is the angle of improvement formed by the weld base material)

The reason why the radius r of the circular orbit is important is because the radius r means the maximum distance that the welding torch 10 can move during EGW welding. Referring to FIG. 4, due to the structure of the welding torch 10, the circular orbit can be set to be spaced a predetermined distance from the improved surface, the back surface, and the front part of the welding base material 80. At this time, the predetermined distance may be 5 mm to 10 mm. In general, due to the structural characteristics of the welding torch 10, EGW welding is performed at a distance of about 5 mm from the back portion where the backing material 60 is disposed and the front portion where the copper immersion plate 70 is disposed. At this time, during EGW welding, the predetermined distance can be controlled up to 10 mm depending on the rotation speed and number of rotations of the welding torch 10.

For example, as shown in Figure 4, assuming that the distance from the back surface is a, the distance from the front part is b, and the distance from the weld base material 80 is c, a, b, and c are each 5 mm. It can be strong. At this time, the center point

Meanwhile, the rotation speed of the welding torch 10 during the circular motion may be 30 rpm to 240 rpm. If the rotation speed is less than 30 rpm, the convection phenomenon in the molten zone caused by the rotation of the welding torch 10 is not applied, so the structure of the welded zone may not be refined. On the other hand, if the rotation speed exceeds 240 rpm, defects may occur due to severe eddy currents in the weld zone. Therefore, the rotation speed of the welding torch 10 must satisfy 30 rpm to 240 rpm, and this must be maintained appropriately while EGW welding is performed.

As another example, the rotational speed of the welding torch 10 may be controlled to become increasingly faster or gradually slower within the above range.

Hereinafter, the EGW welding method of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and should not be construed as limiting the present invention in any way.

As an example sample of the present invention, EGW welding was performed on a marine carbon steel plate with a thickness of 50 mm. At this time, the welding conditions were controlled to a current of 300 to 400 A, a voltage of 30 to 40 V, and a heat input of 150 to 250 KJ/cm, and the welding torch 10 was moved in a circular motion at a rotation speed of 60 to 80 rpm to prepare an example sample. At this time, the radius during circular motion was controlled to 15 mm.

Meanwhile, in order to compare with the example sample, EGW welding was performed using the same base material and only oscillating the welding torch 10 without circular motion. At this time, the driving speed of the welding torch 10 was controlled to 500 mm/s to prepare a comparative sample.

Afterwards, the microstructure of the weld zone of the two welded samples was analyzed using an optical microscope, and the impact toughness at the weld zone was measured three times. The impact toughness data is summarized in Table 1 below. The impact toughness values summarized in Table 1 refer to the average value after measuring the impact toughness of the welded zone three times repeatedly.

Sample Impact toughness (J) Example 61 Comparative example 45

Figures 5 and 6 are diagrams showing the microstructure of the welded area analyzed with an optical microscope after electrogas arc welding according to an experimental example of the present invention.

Referring to Table 1, in the case of the example sample of the present invention, it was confirmed that the impact toughness (mechanical properties) was improved by about 36% from 45J to 61J compared to the comparative example sample. This improvement in properties is due to the rotation of the welding torch 10, so that the solidification structure of the weld part in the example sample (FIG. 5) becomes relatively finer than the solidification structure of the weld part in the comparative example sample (FIG. 6), and complexity increases. It is believed that this is because it was done.

As described above, the EGW welding method according to the embodiment of the present invention performs welding while moving the welding torch 10 in a circular motion, thereby eliminating segregation that occurs in the molten zone during EGW welding, and the resulting microstructure. As complexity increases, there is an effect of being able to proactively respond to the increase in the size of ships.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the attached patent claims.

10: welding torch
20: Delivery unit
30: drive unit
40: Laser sensor
50: control unit
60: Backing material
70: Copper deposit
80: Base material
82: melting portion
100: Electro gas arc welding device

Claims (9)

Placing a welding torch on a welding base material; and
Comprising: performing electro gas arc welding by circularly moving the welding torch at least once,
The circular motion is characterized in that it rotates along a circular orbit centered on 1/2 the point based on the thickness direction of the weld base material,
Electro gas arc welding method. According to claim 1,
The circular motion is characterized in that it rotates so that the radius gradually increases outward from the center of the circular orbit.
Electro gas arc welding method. According to claim 1,
The circular motion is characterized in that the radius rotates from the outside to the center of the circular orbit so that the radius gradually decreases.
Electro gas arc welding method. According to claim 1,
The radius of the circular orbit satisfies Equation 1 below,
Electro gas arc welding method.
[Formula 1]
r≤ 0.5T - 5
(where r is the radius of the circular orbit, and T is the thickness of the welding base material) According to claim 4,
The radius of the circular orbit satisfies Equation 2 below,
Electro gas arc welding method.
[Formula 2]

(Here, r is the radius of the circular orbit, R is the distance between base materials (root gap) on the back surface, T is the thickness of the weld base material, and θ is the angle of improvement formed by the weld base material) According to claim 1,
The electro gas arc welding is performed only with circular motion of the welding torch,
Electro gas arc welding method. According to claim 1,
Characterized in that the circular orbit is set to be spaced apart from the improved surface, back surface, and front surface of the weld base material by a predetermined distance, respectively.
Electro gas arc welding method. According to claim 7,
The predetermined distance is 5 mm to 10 mm,
Electro gas arc welding method. According to claim 1,
The rotation speed of the welding torch during the circular motion is 30 rpm to 240 rpm,
Electro gas arc welding method.