WO2015122047A1 - One-side submerged arc welding method for multielectrode and method for producing welded product - Google Patents

Abstract

A welding device (1) performs one-side submerged arc welding of a steel plate by using a first welding unit (10) which uses a first wire (110), a second welding unit (20) which uses a second wire (120), a third welding unit (30) which uses a third wire (130), and a fourth welding unit (40) which uses a fourth wire (140). When doing so, the first welding unit (10) controls the feeding speed of the first wire (110) so as to be a constant speed by using a first feeding device (11), and supplies power to the first wire (110) by using a first welding power source (12) for which the power-supply method is set to DC and the external properties are set to a constant voltage. As a result, it is possible to reduce faults in the appearance of a penetration bead obtained by the one-side submerged arc welding of a multielectrode.

Description

Multi-electrode single-sided submerged arc welding method, method of manufacturing weldment

The present invention relates to a multi-electrode single-sided submerged arc welding method and a method of manufacturing a weldment.

As one type of consumable electrode type arc welding, a flux composed of powder metal, artificial oxide or mineral is dispersed on the surface of the groove provided on the steel plate, and the flux deposited on the groove of the steel plate is used. In particular, a submerged arc welding method is known in which an electrode wire and a steel plate are melt mixed and integrated by supplying an electric current to the electrode wire being fed to generate an arc from the electrode wire. Compared with other arc welding methods such as clad arc welding, Tig arc welding and gas shielded arc welding, this submerged arc welding method has the advantage of deep penetration and high efficiency because it can use a large current.

Here, Patent Document 1 discloses that, in the submerged arc welding method, power is supplied to the electrode wire using a welding power source having a drooping characteristic or a constant current characteristic as an external characteristic, and the welding voltage setting signal and the welding voltage feedback signal It is described to control the electrode wire delivery rate by the magnitude of the difference signal.

Further, in Patent Document 2, a plurality of electrode wires are arranged from the front surface side to the back surface side of the steel plate by arranging a plurality of electrode wires along the groove and arranging a backing material on the back surface side of the steel plate. A multi-electrode single-sided submerged arc welding process has been described which welds in a single pass using. In this multi-electrode single-sided submerged welding method, the entire thickness of the steel plate can be completely penetrated in one run (this is called one run), and there is no need to reverse the steel plate. It is widely used.

Japanese Patent Laid-Open No. 2000-117442 JP 2007-268551 A

In the multi-electrode single-sided submerged arc welding described above, a back wave bead is formed on the back surface side of the steel plate mainly by the electrode wire (leading electrode) to be welded first to the steel plate among the plurality of electrode wires.

However, it is possible to supply power to the electrode wire of the leading electrode using a welding power source having a drooping characteristic or a constant current characteristic, and to obtain a back surface obtained by adopting a configuration in which the feeding speed is feedback controlled based on the arc voltage. Poor appearance may occur in the wave bead.

An object of the present invention is to reduce appearance defects of a back wave bead obtained by multi-electrode single-sided submerged arc welding.

The present invention is a multi-electrode single-sided submerged arc welding method using a leading electrode and a trailing electrode following the leading electrode, wherein each of the leading electrode and the trailing electrode uses a wire having a diameter of 2.4 mm or more. The feed method and external characteristics of the power supply for feeding each wire, and the speed control method of the feed speed of each wire; in the leading electrode, the feed method is DC, the external characteristic is constant voltage characteristics, The speed control method is set to constant speed control, and in the trailing pole,
(A) the feeding method is DC, the external characteristic is a constant voltage characteristic, the speed control method is constant speed control (b) the feeding method is AC, the external characteristic is constant voltage characteristic, and the speed control method is constant speed control (C) the feeding method is alternating current, the external characteristic is a constant current characteristic, the speed control method is voltage feedback control based on an arc voltage (d) the feeding method is alternating current, the external characteristic is a drooping characteristic, the speed control method is Voltage feedback control based on arc voltage (e) The power supply system is set to either direct current, the external characteristic is constant current characteristics, and the speed control system is voltage feedback control based on arc voltage.
In such a multi-electrode single-sided submerged arc welding method, the trailing electrode includes a plurality of electrodes following the leading electrode, and each of the plurality of electrodes constituting the trailing electrode includes the feeding method. The external characteristics and the speed control method may be set to any one of (a) to (e).
In the final pole located on the rearmost side with respect to the leading pole among the plurality of electrodes constituting the trailing pole, the power feeding method, the external characteristic, and the speed control method are either (c) or (c) It can be characterized by being set to the above (d).
Furthermore, when using the power supply having the constant voltage characteristic, the differential value dV / dI, which is the slope of the voltage with respect to the current at the operating point, is characterized by being −12.0 × 10 ⁻³ (V / A) or more. It can be done.
Furthermore, when using the power supply having the constant current characteristic or the drooping characteristic, the differential value dV / dI, which is the slope of the voltage with respect to the current at the operating point, is -24.0 × 10 ^-3 (V / A) or less Can be characterized.
From another point of view, the present invention is a method of manufacturing a weldment formed by welding a base material by single-sided submerged arc welding using a leading electrode and a trailing electrode following the leading electrode. The feeding electrode and the external characteristic of the power supply for feeding each wire using the wire having a diameter of 2.4 mm or more in the leading electrode and the trailing electrode respectively, and the speed control method of the feeding speed of each wire In the leading electrode, the feeding method is set to DC, the external characteristic is set to constant voltage characteristics, and the speed control method is set to constant speed control, and in the trailing electrode,
(A) the feeding method is DC, the external characteristic is a constant voltage characteristic, the speed control method is constant speed control (b) the feeding method is AC, the external characteristic is constant voltage characteristic, and the speed control method is constant speed control (C) the feeding method is alternating current, the external characteristic is a constant current characteristic, the speed control method is voltage feedback control based on an arc voltage (d) the feeding method is alternating current, the external characteristic is a drooping characteristic, the speed control method is Voltage feedback control based on arc voltage (e) The power supply system is set to either direct current, the external characteristic is constant current characteristics, and the speed control system is voltage feedback control based on arc voltage.

ADVANTAGE OF THE INVENTION According to this invention, the appearance defect of the back wave bead obtained by multiple electrode single-sided submerged arc welding can be reduced.

It is a figure showing a schematic structure of a welding device concerning an embodiment of the invention. It is a figure for demonstrating the structure of the welding power supply in each of a 1st welding unit-a 4th welding unit, and a feeder. (A)-(c) is a figure for explaining the external characteristic of welding power supply. It is a figure for demonstrating the structure of the experimental apparatus in a 1st Example and a 1st comparative example. It is a figure for demonstrating the structure of the experimental apparatus in 2nd Example and a 2nd comparative example. It is a figure for demonstrating the structure of the experimental apparatus in 3rd Example and a 3rd comparative example. (A) shows the dimensions of each steel plate and groove in the first embodiment and the first comparative example, (b) shows the dimensions of each steel plate and groove in the second embodiment and the second comparative example, and (c) shows it It is a figure for demonstrating each dimension of each steel plate and groove in 3rd Example and a 3rd comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.
FIG. 1 is a view showing a schematic configuration of a welding apparatus 1 according to the present embodiment. The welding device 1 performs single-sided submerged arc welding (4-electrode single-sided submerged arc welding) on a work (not shown) made of steel plate using four electrodes (wires).

The welding apparatus 1 performs welding using a first welding unit 10 that performs welding using a first wire 110, a second welding unit 20 that performs welding using a second wire 120, and a third wire 130. A third welding unit 30 and a fourth welding unit 40 for welding using the fourth wire 140 are provided. In addition, welding apparatus 1 carries bogie 90 mounted on first to fourth welding units 10 to 40 and traveling along moving direction A from right to left in the figure, and bogie drive device 50 for driving bogie 90. And a control device 60 for controlling the operation of the first welding unit 10 to the fourth welding unit 40 and the carriage driving device 50. The welding apparatus 1 further includes a first flux supply device 70 and a second flux supply device 80 that accommodate a front flux (not shown) therein and supply the front flux downward in the drawing. In this example, the control device 60, the first flux supply device 70, and the second flux supply device 80 are also mounted on the carriage 90.

Among them, the first welding unit 10 includes a first feeding device 11 having a first feeding roller 11a for feeding the first wire 110 along a feeding direction B which is directed downward from above in the drawing, A first welding power source 12 connected to a first contact tip 12a for supplying a welding current (first welding current) in contact with the supplied first wire 110 is provided. The first welding unit 10 further includes a reel (not shown) around which the first wire 110 is wound and which is a supply source of the first wire 110.

In addition, the second welding unit 20 is fed by a second feeding device 21 provided with a second feeding roller 21 a that feeds the second wire 120 along a feeding direction B which is directed downward from above in the drawing. And a second welding power source 22 connected to a second contact tip 22a for supplying a welding current (second welding current) in contact with the coming second wire 120. The second welding unit 20 further includes a reel (not shown) around which the second wire 120 is wound and which is a supply source of the second wire 120.

Furthermore, the third welding unit 30 is fed with a third feeding device 31 provided with a third feeding roller 31a that feeds the third wire 130 along the feeding direction B from the upper side to the lower side in the drawing. And a third welding power source 32 connected to a third contact tip 32a for supplying a welding current (third welding current) in contact with the coming third wire 130. The third welding unit 30 further includes a reel (not shown) around which the third wire 130 is wound and which is a supply source of the third wire 130.

Furthermore, the fourth welding unit 40 includes a fourth feeding device 41 having a fourth feeding roller 41a that feeds the fourth wire 140 along the feeding direction B from the upper side to the lower side in the drawing, And a fourth welding power source 42 connected to a fourth contact tip 42a for supplying a welding current (fourth welding current) in contact with the fourth wire 140. In addition, the fourth welding unit 40 further includes a reel (not shown) around which the fourth wire 140 is wound and which is a supply source of the fourth wire 140.

In the welding apparatus 1 of the present embodiment, the first welding power source 12, the second welding power source 22, the third welding power source 32, and the fourth welding power source 42 are mounted on the carriage 90, and the first welding together with the carriage 90. Although the power source 12 to the fourth welding power source 42 are configured to travel, the present invention is not limited to this. For example, the first welding power source 12 to the fourth welding power source 42 are fixed to the outside of the carriage 90 and disposed, and the respective components on the first welding power source 12 to the fourth welding power source 42 and the carriage 90 using cables etc. And may be connected.

Further, the first flux supply device 70 is provided with a first flux supply port 70a for supplying the front flux accommodated inside toward the lower side in the drawing. Then, the amount of front flux supplied by the first flux supply device 70 is adjusted by a valve (not shown) provided in the first flux supply device 70.

Furthermore, the second flux supply device 80 is provided with a second flux supply port 80a for supplying the front flux contained therein toward the lower side in the drawing. The amount of front flux supplied by the second flux supply device 80 is adjusted by a valve (not shown) provided in the second flux supply device 80.

In the welding device 1, the first wire 110 which is the first electrode at the most downstream side with respect to the movement direction A is a second wire 120 whose second electrode is the second electrode at the upstream side of the first wire 110. A third wire 130 serving as the third electrode is disposed upstream of 120 and a fourth wire 140 serving as the fourth electrode downstream of the third wire 130 and on the most upstream side. Further, in the welding device 1, the first flux supply device 70 is downstream of the first wire 110 in the moving direction A, and the second flux supply device 80 is upstream of the second wire 120 in the moving direction A. And it arrange | positions downstream of the 3rd wire 130, respectively. When the welding apparatus 1 is viewed from above in the drawing, the first flux supply port 70a, the first wire 110, the second wire 120, the second flux supply port 80a, the third wire 130, and the fourth wire 140 move Along the straight line along the direction A, they are arranged in this order.

Further, in the welding device 1, as the first wire 110 to the fourth wire 140, those having a diameter of 2.4 mm or more and 6.4 mm or less are used. Here, all four of the first to fourth wires 110 to 140 may have the same diameter, or three may have the same diameter, while one may have a different diameter, or two may be the same. The diameter may be two while the same may be the same diameter, or all four may be different diameters.

Furthermore, each of the first wire 110 to the fourth wire 140 used in the welding device 1 is basically composed of a solid wire having no flux. However, one or more of these may be made of flux cored wire.

In the following description, the first welding unit 10 including the first wire 110 may be referred to as a "leading electrode". In addition, the second welding unit 20 including the second wire 120, the third welding unit 30 including the third wire 130, and the fourth welding unit 40 including the fourth wire 140 may be collectively referred to as a "following electrode". . Furthermore, the second welding unit 20 including the second wire 120 is a “first intermediate pole”, the third welding unit 30 including the third wire 130 is a “second intermediate pole”, and a fourth welding unit including a fourth wire 140 40 may be referred to as the "last pole".

2 shows welding power sources (first welding power source 12 to fourth welding power source 42) and feeding devices (first feeding device 11) in each of the first welding unit 10 to fourth welding unit 40 constituting welding apparatus 1. FIG. 7 is a diagram for explaining the configuration of the fourth to fourth feeding devices 41). Here, FIG. 2 shows the relationship between each welding unit, the power supply system and external characteristics in each welding power source, and the wire speed control system in each feeder.

First, the first welding unit 10 will be described.
The first welding power source 12 constituting the first welding unit 10 is a DC power source adopting DC (Direct Current) as a power feeding method, and the external characteristic thereof is a constant voltage characteristic. Further, the first feeding device 11 performs constant speed control for feeding the first wire 110 at a constant speed as a wire speed control method.

Next, the second welding unit 20 will be described. In the present embodiment, the second welding unit 20 is configured by any one of the five combinations (first configuration to fifth configuration) described below.

(A) First Configuration The second welding power source 22 in the first configuration is a DC power source adopting DC (Direct Current) as a power feeding method, and the external characteristic thereof is a constant voltage characteristic. In addition, the second feeding device 21 in the first configuration performs constant speed control for feeding the second wire 120 at a constant speed as a wire speed control method. Thus, the first configuration is the same combination as the first welding unit 10.

(B) Second Configuration The second welding power source 22 in the second configuration is an AC power source adopting AC as a power feeding method, and its external characteristic is a constant voltage characteristic. Further, the second feeding device 21 in the second configuration performs constant speed control for feeding the second wire 120 at a constant speed as a wire speed control method.

(C) Third Configuration The second welding power source 22 in the third configuration is an AC power source adopting AC as a power feeding method, and its external characteristic is a constant current characteristic. In addition, the second feeding device 21 in the third configuration performs voltage FB (Feed Back) shift control to sequentially feed the second wire 120 at an appropriate speed by feedback control based on arc voltage as a wire speed control method. .

(D) Fourth Configuration The second welding power source 22 in the fourth configuration is an AC power source adopting AC as a power feeding method, and its external characteristic is a drooping characteristic. In addition, the second feeding device 21 in the fourth configuration performs voltage FB shift control that feeds the second wire 120 at an appropriate speed sequentially by feedback control based on an arc voltage as a wire speed control method.

(E) Fifth Configuration The second welding power source 22 in the fifth configuration is a DC power source adopting DC as a power feeding method, and the external characteristic thereof is a constant current characteristic. Moreover, the 2nd sending apparatus 21 in 5th structure performs voltage FB shift control which feeds the 2nd wire 120 one by one at an appropriate speed one by one by feedback control based on arc voltage as a wire speed control system.

Further, as with the second welding unit 20, the third welding unit 30 and the fourth welding unit 40 are configured by any one of the first configuration (a) to the fifth configuration (e) described above. be able to. Here, all three of the second welding unit 20, the third welding unit 30, and the fourth welding unit 40 may have the same configuration, or two may have the same configuration and one may have a different configuration. And all three may be configured differently.

The feed speed of the first wire 110 to the fourth wire 140 can be determined based on the moving speed (welding speed) of the carriage 90 in the moving direction A. For example, in the case of constant speed control, the operator determines the reference value of the feed speed based on the welding speed, and performs constant speed control so as to maintain the reference value of the feed speed. Further, for example, in the case of voltage FB shift control, the operator determines the reference value of the feed speed with reference to the welding speed, and performs the shift control by feeding back the arc voltage to the reference value of the feed speed.

Next, the external characteristics of the above-described welding power sources will be described.
FIG. 3 is a diagram for explaining the external characteristics of the welding power source. Here, FIG. 3 (a) illustrates a constant voltage characteristic, FIG. 3 (b) illustrates a constant current characteristic, and FIG. 3 (c) illustrates a drooping characteristic. Further, in each of FIGS. 3A to 3C, the horizontal axis is the output current I (A), and the vertical axis is the output voltage V (V). The external characteristic curve moves (changes) in accordance with the indication of the current or voltage input to the welding power source. In FIG. 3 (a), an external characteristic curve corresponding to four steps of indicator voltages is illustrated, and in each of FIGS. 3 (b) to (c), an external characteristic curve corresponding to four stages of indicator currents is illustrated. There is. In the case of a welding power source, the output current I corresponds to the welding current, and the output voltage V corresponds to the sum of the arc voltage plus other voltage loss factors (consumption in the cable, contact resistance, etc.).

First, the constant voltage characteristics shown in FIG. 3A will be described.
In the case of the constant voltage characteristic, the fluctuation of the output voltage V is smaller than the fluctuation of the output current I.

Next, the constant current characteristics shown in FIG. 3B will be described.
In the case of the constant current characteristic, the fluctuation of the output voltage V is large relative to the fluctuation of the output current I. From the opposite point of view, in the constant current characteristic, even if the output voltage V fluctuates significantly, the fluctuation of the output current I is small.

Subsequently, the drooping characteristic shown in FIG. 3C will be described.
In the case of the drooping characteristic, as in the case of the constant current characteristic, the fluctuation of the output voltage V is large relative to the fluctuation of the output current I. However, in the case of the drooping characteristic, the fluctuation of the output voltage V is gentler than that of the constant current characteristic, and changes depending on the current value.

Here, FIGS. 3 (a) to 3 (c) show arc characteristics for generating an arc of arc length L, as well as the respective external characteristics. In each of them, an operating point P at which a point of intersection of the curve of any external characteristic and the curve of the arc characteristic generates an arc of a desired arc length L (a specific output current I and a corresponding specific output voltage V ). In the following description, the inclination of the voltage with respect to the current at the operating point P for generating an arc of the target arc length L is referred to as a differential value dV / dI.

Here, a welding power source having a drooping characteristic and a constant current characteristic is considered to have little variation in penetration depth, and is suitable for submerged arc welding. However, in a welding power supply having a drooping characteristic and a constant current characteristic, since the arc voltage is easily changed, it is generally combined with the feeding of the wire by the voltage FB shift control. When combining welding power source having drooping characteristics and constant current characteristics with voltage FB shift control, if the arc length L becomes short, the arc length L is lowered by decreasing the wire feeding speed according to the decrease of the arc voltage. Is returned to the original length, and when the arc length L is increased, the arc length L is returned to the original length by increasing the wire feeding speed according to the increase of the arc voltage.

On the other hand, a welding power source having a constant voltage characteristic is considered to be suitable for mag welding or mig welding using a small diameter wire. Also, a welding power source having constant voltage characteristics may be used for submerged arc welding using a wire of 2.0 mm or less in diameter. However, in welding power sources having constant voltage characteristics, welding current is likely to change, so it is generally combined with wire feeding by constant speed control. When welding power source having constant voltage characteristics and constant speed control are combined, if the arc length L becomes short, the welding current automatically increases and the arc length L returns to the original length, while, If the arc length is increased, the welding current is automatically reduced, whereby the arc length L returns to the original length.

Here, the features of the welding conditions in the multi-electrode single-sided submerged arc welding method of the present embodiment will be described.

<About the diameter of each wire>
In the single-sided submerged arc welding method, it is necessary to melt the groove with a strong arc force to form a back wave bead. However, it does not mean that the welding current is simply high, but if a lot of wires are melted by high-speed feeding, a pool will be formed directly under the arc, which will buffer the arcing force itself and reduce the penetration. Therefore, it is desirable to increase the welding current, but not to increase the wire melting amount, and it is desirable to meet this condition at low current density (A / mm ² ), that is, increase the wire diameter and slow the wire It is preferable to feed. In the case of gas shielded arc welding, generally, a thin wire having a diameter of 1.6 mm or less is used, but for single sided submerged arc welding, a wire having a diameter of 2.4 mm or more is preferable. More preferably, it is desirable to use a wire having a diameter of 3.2 mm or more, and further, a diameter of 4.8 mm or more. There is no particular technical limitation in setting the upper limit, but a diameter of 6.4 mm or less is practical from the viewpoint of wire feedability and cuttability.

<About the number of electrodes>
The leading electrode has a function to melt the groove deeply to form a molten pool and a back wave bead, and since the welding conditions are specialized in this role, the thickness of the base material is thin, for example, the molten pool is the base material Even if the surface is reached, the surface bead appearance is not good with a single electrode. On the other hand, since the final pole mainly plays a role in adjusting the appearance of the front bead, welding conditions are different from those of the leading pole. As described above, in the single-sided submerged arc welding, since it is necessary to share roles, it is essential to form a plurality of electrodes using two or more wires. Generally, the number of wires increases as the thickness of the steel plate increases. There is no particular technical limitation in which an upper limit is imposed on the number of electrodes, but for single-sided welding, for example, a 4-electrode system shown in FIG. 1 has been put to practical use.

An appropriate distance is provided between the respective electrodes. The thickness and welding speed, and various controls of the welding machine and the wire feeding used are not uniform but are appropriately adjusted. Depending on the distance between the electrodes, a flux supply port (a first flux supply port 70a and a second flux supply port 80a shown in FIG. 1) may be provided.

<About wire speed control method at the leading electrode, external characteristics and power supply method>
[About wire speed control method at leading electrode]
In multi-electrode single-sided submerged arc welding, the leading electrode is mainly used to form a back bead. The inventors of the present invention found that in back wave welding, the driving force of penetration significantly affects the back wave quality, and is likely to result in excess or lack of back wave beads. Then, the present inventors repeated experiments on the driving force of penetration, and it is correct in current and voltage factors in general joints, but not in single-sided welding, the wire feeding speed has the largest influence. I found it.

That is, if the wire feeding speed is excessive, the wire easily depresses the molten pool supported mainly by the surface tension on the back surface of the steel plate to form an excess back wave. Furthermore, if the feed speed is high, the wire may break through the molten pool.

Conversely, if the wire feeding speed is insufficient, the molten pool will not be pushed from the back surface of the steel plate, resulting in a back wave shortage. In principle, these phenomena should not occur if the wire feed speed reacts without time loss and the arc length L can be returned to the inevitable change in the arc length L. However, in practice, the wire motor that feeds the wire is an industrial product, and the reaction is delayed to some extent. With respect to the delay of the reaction time, the height of the back bead is not robust and is easily influenced by the change.

In view of this problem, the leading electrode that affects the formation of the back wave welding does not affect the feeding speed even if the current or voltage changes, and controls to make the feeding speed constant (constant speed control) Revealed that it is desirable. As described above, in the large diameter submerged arc welding, the wire feed constant control is a control method which has hitherto been unsuitable. The reason for this is that the large diameter wire is difficult to melt uniformly across the entire cross section, and as a result, the wire melting rate becomes unstable, and consequently the stabilization of the arc length L can not be expected either. However, only in the case of forming the back wave bead by single-sided welding, the feed speed stabilization has a higher shape stabilization effect than the stabilization of the arc length L.

[On the external characteristics of the leading electrode]
Next, regarding the external characteristics of the leading electrode, the drooping characteristics are common sense in the prior art. As described above, the drooping characteristics show small variation in current value with respect to variation in voltage value. A movable iron core movable welding machine that uses leakage reactance without using electronic elements as a welding machine structure that has a simple structure, is inexpensive, and easy to maintain, has been used since old times, but with this method only drooping characteristics could be made There are also historical circumstances of that.

In the application to non-sing wave welding where the current value most affects the penetration depth, it is effective for penetration stabilization, while for the shape stabilization of the back wave bead in the back wave welding, the fluctuation of the current value is It is not high rank as an influence factor. On the other hand, although the arc length L also has less influence on back wave stabilization than the fluctuation of the feeding speed, an excessive sudden change of the arc length L brings an adverse effect. For example, if the arc length L is zero, that is, the arc disappears, the welding itself stops or the arc is generated explosively at the time of reignition, so that the back bead can not be formed normally by the force. On the other hand, if the arc length L becomes excessive, the arc can not be maintained, the arc disappears immediately after that, or the arc force per unit area decreases, and the back wave bead can not be formed.

In addition, defects such as irregularities in the shape of the weld bead, meandering affected by the magnetic blow, and undercuts that sweep the base material occur. That is, stabilization control of the arc length L is necessary.

Assuming that the feed speed is constant for back wave stabilization, a control target other than feed speed control is required as a means for stabilizing the arc length L. It is known that the melting rate of the consumable electrode type welding wire is expressed by the equation (1), and it is suggested that the current value (welding current I) which is a square has the largest influence.

Mw = K1 · I + K2 · I ² · ・ · L (1)
Mw: wire melting rate I: welding current :: electrical resistivity L: wire protrusion length K1, K2: constant

From this, it is effective to actively change the welding current I as a means for stabilizing the arc length L on the assumption that the feed speed is constant. For example, if the arc length L becomes short, the wire melting speed Mw decreases by rapidly raising the welding current I, and the arc length L returns to the original state. On the other hand, if the arc length L is increased, the wire melting speed Mw is increased by rapidly reducing the current, and the arc length L is also returned. This phenomenon is generally referred to as the arc length self-control function. The self-control function of the arc length requires a sharp change in current, and the external characteristic to realize this is only the constant voltage characteristic. Therefore, in order to realize the constant wire feeding speed necessary to stabilize back wave welding, it is necessary as an indirect factor that the external characteristics of the welding power source corresponding to the leading electrode be constant voltage characteristics.

Such a combination of “wire speed control: constant speed” and “external property: constant voltage property” is used in a gas shielded arc welding method using a thin wire having a diameter of 1.6 mm or less. This is because the wire is thin and the meltability is excellent, so the self-control action of the arc length is very effective. However, in a wire with a diameter of 2.4 mm or more, the meltability is inferior to a wire thinner than this, so when used for non-single-sided welding, the self-control function of the arc length does not act quickly and arc and bead shapes It causes instability.

[About the feeding method at the leading electrode]
Then, although it is a feed system of a leading electrode, direct current is essential for the leading electrode of single-sided welding. In alternating current, current zero, that is, an arc extinguishing state occurs periodically. In the case of the trailing electrode in non-single-sided welding or single-sided welding, that is, after the second electrode, short-time arc disappearance has a slight effect on the welding quality, but in the leading electrode strongly influences the stabilization of the back wave. Cause destabilization. If the arc does not reignite quickly, the solid wire depresses the molten pool, resulting in a backwash excess.

For the above reasons, the leading electrode adopts a combination of “wire speed control: constant speed”, “external characteristic: constant voltage characteristic” and “feed method: direct current”.

In addition, the high current submerged arc welding machine which is most popular at present is an alternating current machine by an inexpensive iron core operation type. In this method, the external characteristics inevitably become drooping characteristics. On the other hand, if a thyristor element is used to generate direct current, a large current direct current can be obtained, and the external characteristics can also be made constant voltage characteristics. Furthermore, recently, inverter welding machines which are weak to heat and difficult to produce large current outputs have also been developed which are characterized by large current outputs, and if this is used, very excellent DC characteristics can be obtained.

<About wire speed control method, external characteristics and power supply method at trailing electrode>
Although not visible in multi-electrode single-sided submerged arc welding, the molten pool formed in the surface flux deposited on the steel plate is basically a large one called "one pool" where all molten metal wires are connected Liquid metal. As described above, although the leading pole has the largest influence on the shape of the back wave bead, in the case of one pool, although the degree of influence is relatively small, the shape of the trailing bead is also the shape of the back wave bead Will affect the For example, even if a back wave bead in a liquid state in a good shape can be formed by the first electrode that is the leading electrode, the molten pool formed by the first electrode by the second and subsequent electrodes that become the trailing electrode is pushed out to the back side. If so, the final solidified back bead will be irregular. Therefore, the same “wire speed control: constant speed” and “external characteristic: constant voltage characteristic” can be applied to the second and subsequent electrodes. Here, although it is desirable that the feeding method is direct current as in the leading electrode, the degree of influence of polarity in the second and subsequent electrodes is relatively small with respect to the first electrode, so that alternating current is also practical.

On the other hand, when the plate thickness of the steel plate becomes thick and the number of electrodes increases, even if the pressure in the molten pool formed by the trailing electrode changes slightly even in one pool, it is on the back side of the molten pool far in distance Will have no major impact. In such a case, “wire speed control: voltage FB shift control” and “external characteristic: droop characteristic” which are conventionally used can also be applied. It is self-evident that there is no problem in using a welding power source of “external characteristics: constant current characteristics” in which the target characteristics are the same instead of the drooping characteristics. The trailing electrode needs to adjust the shape of the front bead as a role, and for this purpose it may be more effective to stabilize by giving priority to the current value and arc length L even if the feed speed changes . To meet such requirements, “Wire speed control: Voltage FB shift control”, “External characteristics: drooping characteristics or constant current characteristics”, and arc mutual interference and deflection by magnetic blow are less likely to occur. A combination of

<Others>
[About backing]
Grooved copper or solid oxide backings are generally used in single-sided welding to receive the back bead. The solid oxide specifically corresponds to ceramic or glass. In the case of glass, generally, a tape-shaped one in which glass fibers are woven is used. If there is no backing material, the molten pool will fall when excessive arcing force acts on the primary layer, the arc will disappear and welding will not be able to continue. If you use any backing material, you can prevent such a worst case.

If the base of the steel plate that is the base material is in close contact, the shape of the back wave bead should stabilize even if the arc force is unstable, but in fact the large steel plate is not flat but slightly curved or wavy They are not always in close contact because they often Therefore, in order to fill the gap between the bottom of the steel plate and the backing material which inevitably occurs, the backing flux may be dispersed in advance. Then, it becomes possible to prevent the dripping of the molten pool on the back side to some extent. Furthermore, there is also a method of pushing up the backing flux by spraying a thick backing flux without injecting a backing material and injecting a gas into an air hose laid under the backing material to improve adhesion. In this case, the backing flux may have a powder laminated structure with a curable resin in order to prevent the molten pool from falling off.

[Table Flux]
There is no need to explain in particular because it is the minimum basic configuration as submerged arc welding, but the flux is a container with a hose under it called a hopper (the first flux feeder 70 and the second flux feeder 80 shown in FIG. 1) As the welding progresses, it is sprayed at a constant speed from the flux supply port of the hose tip provided between the electrodes immediately before the leading electrode or as required.

[About groove filling material]
When powdery steel or steel alloy is dispersed in the groove, it melts at the time of welding to form a part of the molten metal. In addition to the effect of high efficiency, when the route gap is partially excessive, it is difficult for the back wave to escape. Furthermore, there is also an effect of suppressing the quality deterioration of the base metal heat affected zone by increasing the cooling rate in the vicinity of the weld. Moreover, in back wave welding, it is effective in reducing the wire feeding of the trailing electrode after the first electrode and arc instability. However, if the application rate is too high, it may not melt and remain solid, which may cause defects, so excessive application should not be performed. Determine the optimum amount by the balance of current and groove shape. As a material of a powder, what is called iron powder with a so-called fine particle size, and what made the grain of a welding wire small diameter and was made coarse is used.

[Differential value of welding voltage having constant voltage characteristics]
Generally, specifications are described under the name of a constant voltage characteristic, a drooping characteristic, a constant current characteristic, etc. in a welding machine, so the user side is less likely to scrutinize the characteristic. However, the names of these external characteristics are conceptual and do not have quantitative definitions. Recently, there are models that allow users to adjust external characteristics. The slope of the voltage-current characteristic desired as the constant voltage characteristic at the operating point current, that is, the differential value dV / dI is more horizontal than −12.0 × 10 ⁻³ (V / A). In other words, the desirable differential value dV / dI is -12.0 × 10 ^-3 (V / A) or more. If the differential value dV / dI is -12.0 × 10 ^-3 (V / A) or more, the current largely changes according to the change of the arc length L, and the self-control function of the arc length L is effectively effective. Desirable to work. More preferably, if the differential value dV / dI is −8.0 × 10 ⁻³ (V / A) or more, the back wave shape is more stabilized. It should be noted that, as the characteristic of the external characteristics in general including the constant voltage characteristic, the positive side can not be a slope, so that the differential value dV / dI has a practical upper limit of 0.

[Differential value of welding voltage having constant current characteristic or drooping characteristic]
The constant current characteristics and the drooping characteristics are also not defined quantitatively. It can be said that the constant current characteristics and the drooping characteristics are different from whether they are generated using a rectifying element or the leakage flux due to the operation of an iron core, but in terms of aiming constant current even if the arc length L changes. It is the same. The slope of the desirable voltage-current characteristics common to the constant current characteristics and the drooping characteristics, that is, the differential value dV / dI at the operating point current is more vertical than -24.0 × 10 ^-3 (V / A) In other words, the desired differential value dV / dI is less than -24.0 × 10 ^-3 (V / A). If the characteristic of differential value dV / dI is -24.0 × 10 ^-3 (V / A) or less and voltage feedback control of feed speed are combined, the change of arc voltage is caught sensitively and the feed speed is changed By doing this, the arc length L can be stabilized, which contributes to the stabilization of the front bead shape. (-Infinity) is a practical lower limit, since the positive side can not have a slope as a general property of the external characteristics including the constant current characteristics and the drooping characteristics.

Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples unless the gist is exceeded.

First Example and First Comparative Example
FIG. 4 is a diagram for explaining the configuration of the experimental apparatus in the first embodiment and the first comparative example. The basic configuration of the experimental apparatus shown in FIG. 4 is the same as that of the welding apparatus 1 shown in FIG. Here, FIG. 4 shows a work 200 including the first steel plate 201 and the second steel plate 202, a front flux 300 supplied to the front side of the work 200, and a backing disposed on the back side of the work 200 together with the experimental apparatus. A portion 400 shows a weld metal 500 formed on the work 200 along with welding.

FIG. 7A shows the dimensions of the steel plates and the grooves in the first embodiment and the first comparative example. In this example, each of the first steel plate 201 and the second steel plate 202 was subjected to an open end surface treatment using a tensile strength 490 MPa grade carbon steel plate having a thickness of 35 mm and a width of 500 mm × length 3000 mm to form butt joints. The groove shape was 45 ° V-shaped to 29 mm from the surface, and the remaining plate thickness of 6 mm was vertical as the root face. Although the root gap was set to 0 mm where both steel plates contact at the shortest part, there was a point where a gap of up to 2 mm was inevitably generated due to distortion of the steel plate. Each wire (the first wire 110 to the fourth wire 140) is a JIS Z3351 YS-S6 equivalent product, and the front flux 300 is a JIS Z3352 SACI1 equivalent product. The surface flux 300 is automatically and continuously sprayed with an appropriate amount before the first electrode (leading electrode) and between the second electrode and the third electrode.

As a backing portion 400, a grooved backing copper plate 402, to which a small amount of a backing flux 401 was dispersed, was pressed against the steel plate groove back side. Also, for each electrode, independent welding power sources were connected between the contact tips and the steel plates corresponding to each electrode. Each wire is fed to the weld by a feed roller provided immediately above each contact tip.

Then, a test of the four-electrode single-sided submerged arc welding method was performed using the experimental apparatus shown in FIG. More specifically, wire diameter, power feeding method, external characteristics, wire speed control, welding current, and arc voltage were changed for each electrode using the test apparatus shown in FIG. In the experimental apparatus shown in FIG. 4, the distance between the tip of the first wire 110 and the tip of the second wire 120 is 40 mm, the distance between the tip of the second wire 120 and the tip of the third wire 130 is 120 mm, The distance between the tip of the third wire 130 and the tip of the fourth wire 140 is 30 mm. And the welding speed in this example was made common at 44 (cm / min).

Moreover, as a test result, the back wave bead shape, the front bead shape, and the internal defect were evaluated. The back bead shape should ideally be 10 mm or more in width and 2 mm to 6 mm in back wave height, and those with small meanders and small variations in width may be regarded as very good A, and these evaluations may be inferior. Those not present were rejected as B, and those requiring repair due to the back bead shape defect were rejected as C. Also for the front bead shape, the same evaluation criteria as the back wave bead shape were used. With regard to internal defects, those with no defects found by the ultrasonic flaw test and the cross section macro cut test were regarded as “none”, and those with poor fusion confirmed as “present”.

The manufacturing conditions and the test results in the first example and the first comparative example are shown in Table 1 and Table 2. Here, no. 1-1 to No. 1-5 is a 1st Example, and No. 1 shown in Table 2 is. 1-6 to No. 1-11 is a first comparative example.

In the feeding methods shown in Tables 1 and 2, "AC" means alternating current, "DC (EP)" is direct current, and means "Electrode Plus" with the wire, that is, the electrode side as the positive electrode, "DC (EN)" means "Electrode Negative" which is direct current and has a wire, ie, the electrode side as a negative electrode. This notation is the same in Tables 3 to 6 described later.

First, the first embodiment will be described.
No. 1-1 uses direct current, constant voltage characteristics, constant speed control for the first electrode, and uses the conventional alternating current, drooping characteristics, and voltage FB shift control for the second and subsequent electrodes, but good back bead The shape is obtained. On the other hand, the front bead shape is also very good because the fourth electrode, which is the final pass, is subjected to the AC / droop characteristic / voltage FB shift control.

No. 1-2 is no. This is the case where the differential value dV / dI of the external characteristics in the welding power source of the first electrode is smaller than that of 1-1, that is, the constant voltage characteristic is weakened, and accordingly, the arc length of the first electrode in the first layer welding Since the control action is weakened and destabilized, the back wave bead shape is No. It is slightly inferior to 1-1. However, since direct current and constant speed control are adopted, a back wave bead shape that is within an acceptable range is obtained.

No. No. 1-3 is No. Similar to 1-1, but the power supply polarity of the first electrode is DC positive polarity, that is, the electrode side-(minus). In general, although the power supply polarity in direct current often adopts direct current reverse polarity, that is, the electrode side + (plus), there is no problem in the welding quality, and it is shown that either can be used in the present construction method.

No. In 1-4, all electrodes have DC / constant voltage characteristics / constant speed control, and by incorporating control to reduce the pressure change of the molten pool also after the second electrode, a very good back bead shape is obtained. ing. However, although it is within the allowable range, the shape of the front bead is slightly inferior to the case of adopting alternating current when adopting direct current that is susceptible to inter-arc interference and magnetic blow.

No. In 1-5, all the electrodes have constant voltage characteristics and constant speed control, and only the first electrode is direct current, while the others are alternating current. By adopting the alternating current on the trailing electrode side, the arc is less susceptible to the magnetic blow effect, and as a result, not only the back wave bead shape but also the front bead shape becomes very good.

Subsequently, the first comparative example will be described.
No. 1-6 are typical used now. AC, droop characteristics, and voltage FB shift control are adopted for all electrodes. Fluctuations in the feed rate and periodical arc loss caused by alternating current cause instability in the backwave molten pool, and although internal defects and front bead shapes are not particularly problematic, they are not suitable for backwave welding and backwaves. Poor bead shape was remarkable.

No. 1-7 is no. Although constant voltage characteristics and constant speed control are applied to the fourth electrode with respect to 1-6, even if control to reduce the pressure change of the molten pool for only the fourth electrode, which is the final electrode, is added, the contribution rate Was lower than that of the first electrode, so that the back bead shape did not improve.

No. 1-8 is No. Similar to 1-7, constant voltage characteristics and constant speed control are applied to the second electrode instead of the fourth electrode. However, in the second electrode which is the first intermediate electrode, the stabilizing contribution of the pressure applied to the molten pool forming the back wave bead is lower than that of the first electrode, and the improvement effect of the back wave bead shape is not obtained.

No. In 1-9, wire feeding is controlled at constant speed while the welding power source of the conventional alternating current and drooping characteristics is kept as it is for both the first electrode and the second electrode. In the drooping characteristics, in principle, the arc length stabilization must be achieved by wire feed control, but since the speed is constant, the arc length stabilization function does not work at all. Therefore, the arc length always fluctuated significantly and stable welding could not be performed. As a result, both the back wave bead shape and the front bead shape were greatly roughened and unstable, and a fusion failure also occurred inside.

No. In the configuration 1-10, the first electrode has a direct current and a constant current characteristic, and on the other hand, the wire speed control is constant speed controlled. The welding power source with direct current and constant current characteristics is generally a non-electrode type, that is, a power source system used in TIG welding and plasma welding that generates an arc from a non-consumable tungsten electrode, not from consumable wire. The same control as that of the drooping characteristic is necessary for the control of the electrode. Even if this power source is used as the electrode type, in the case of constant speed control of the wire, the long stabilization action of the arc does not work at all. Therefore, no. As in 1-9, the arc length always fluctuated significantly, and stable welding was not possible. Both the back wave bead shape and the front bead shape were greatly roughened and unstable, and a fusion failure also occurred inside.

No. 1-11 is replaced with DC, constant current characteristics, and voltage FB shift control from AC, drooping characteristics, and voltage FB shift control for all the conventional electrodes, but the first electrode has constant voltage characteristics and constant speed control The back wave bead shape was not stabilized because it had not been. With regard to the front bead shape, constant current characteristics and voltage FB shift control acted, and it was an allowable range of those in which instability due to arc mutual interference peculiar to direct current was observed.

Second Example and Second Comparative Example
FIG. 5 is a diagram for explaining the configuration of the experimental apparatus in the second embodiment and the second comparative example. The basic configuration of the test apparatus shown in FIG. 5 is obtained by removing the fourth welding unit 40 from the welding apparatus 1 shown in FIG. Here, FIG. 5 shows a work 200 including the first steel plate 201 and the second steel plate 202, a front flux 300 supplied to the front side of the work 200, and a backing disposed on the back side of the work 200 together with the experimental apparatus. A portion 400 shows a weld metal 500 formed on the work 200 along with welding.

Moreover, FIG.7 (b) has shown the dimension of each steel plate and groove in 2nd Example and 2nd comparative example. In this example, the first steel plate 201 and the second steel plate 202 were subjected to open tip surface treatment using a tensile strength 400 MPa class carbon steel plate having a thickness of 30 mm and a width of 500 mm × length 3000 mm, respectively, to form butt joints. The groove shape was 45 ° V-shaped to 25 mm from the surface, and the remaining plate thickness of 5 mm was vertical as the root face. Although the root gap was set to 0 mm where both steel plates contact at the shortest part, there was a point where a gap of up to 2 mm was inevitably generated due to distortion of the steel plate. Each wire (the first wire 110 to the third wire 130) is a JIS Z3351 YS-S6 equivalent product, and the front flux 300 is a JIS Z3352 SACI1 equivalent product. The surface flux 300 is automatically continuously dispersed in an appropriate amount before the first electrode (leading electrode) and between the second and third electrodes.

A backing flux 412 containing a curable resin component is dispersed in a small amount on the underlaying flux 411 without using a molded solid such as a copper plate or a ceramic plate as the backing portion 400 on the back side of the steel sheet groove back The backing flux 412 was pressed against the back surface of the steel sheet by injecting a gas from an air hose 413 passed through the inside. Also, for each electrode, independent welding power sources were connected between the contact tips and the steel plates corresponding to each electrode. Each wire is fed to the weld by a feed roller provided immediately above each contact tip.

And the test of the 3-electrode single-sided submerged arc welding method was done using the experimental apparatus shown in FIG. More specifically, wire diameter, power feeding method, external characteristics, wire speed control, welding current, welding voltage were changed for each electrode using the test apparatus shown in FIG. 5, and the influence was confirmed. In the experimental apparatus shown in FIG. 5, the distance between the tip of the first wire 110 and the tip of the second wire 120 is 40 mm, and the distance between the tip of the second wire 120 and the tip of the third wire 130 is 120 mm. And the welding speed in this example was made common at 47 (cm / min).

As a test result, the back wave bead shape, the front bead shape, and the internal defect were evaluated. The back bead shape should ideally be 9 mm or more in width and 2 mm to 5 mm in back wave height, and those with small meanders and small variations in width may be regarded as very good A, although these evaluations may be inferior Those not present were rejected as B, and those requiring repair due to the back bead shape defect were rejected as C. Also for the front bead shape, the same evaluation criteria as the back wave bead shape were used. With regard to internal defects, those with no defects found by the ultrasonic flaw test and the cross section macro cut test were regarded as “none”, and those with poor fusion confirmed as “present”.

Tables 3 and 4 show the manufacturing conditions and the test results in the second example and the second comparative example. Here, no. 2-1 to No. 2-4 is a 2nd Example, and No. 4 shown in Table 4 is. 2-5 to No. 2-10 is a second comparative example.

First, the second embodiment will be described.
No. 2-1 uses DC, constant voltage characteristics, and constant speed control for the first electrode, and uses the conventional AC, droop characteristics, and voltage FB shift control for the second and subsequent electrodes, but good back bead The shape is obtained. In addition, the appearance of the front bead shape is also very good by setting the third electrode, which is the final pass, to AC / droop characteristics / voltage FB shift control.

No. 2-2 is no. This is the case where the differential value dV / dI of the external characteristic in the welding power source of the second and third electrodes is larger than that of 2-1, ie, the constant current characteristic is weakened. When the constant current characteristic weakens, the arc voltage also becomes difficult to change, and feedback control of the arc length also becomes difficult to be effective. Therefore, although within the allowable range, the stability of the arc length degrades the front bead shape which has a greater effect than the back wave bead shape. That is, it is suggested that the voltage FB shift control with a small differential value dV / dI is more preferable in order to make the front bead shape good.

No. 2-3 has all the electrodes as direct current / constant voltage characteristics / constant speed control, and by incorporating control to reduce the pressure change of the molten pool also after the second electrode, a very good back bead shape Is obtained. On the other hand, although within the allowable range, the front bead shape is slightly disturbed by the inter-arc interference caused by the alignment of the direct current, so it is slightly inferior to the case of adopting the alternating current.

No. For 2-4, DC, constant voltage characteristics and constant speed control are adopted for the 1st electrode, while 2nd electrode is DC, constant current characteristics and voltage FB shift control, and 3rd electrode is AC, constant current characteristics and voltage FB It is gearshift control. Since inter-arc interference occurs due to the direct current being lined up between the first and second electrodes, the back bead shape is slightly inferior although it is within the allowable range. On the other hand, by adopting a constant current characteristic which is further excellent in constant current characteristic than the drooping characteristic to the trailing electrode forming the surface layer side, the arc length is more stabilized and an excellent surface bead shape is obtained. .

Subsequently, a second comparative example will be described.
No. No. 2-5 is No. In contrast to 2-1, the first electrode is not direct current but alternating current. Although constant voltage characteristics and constant speed control are in the category of the present invention, since alternating current is used, periodical arc disappearance peculiar to alternating current causes instability of back wave molten pool and obtains stable back wave bead shape. I could not.

No. 2-6 is a typical used today. AC, droop characteristics, and voltage FB shift control are adopted for all electrodes. Although there is no particular problem with the internal defects and the front bead shape, both the alternating current and the shift control are unsuitable for back wave welding, and a defect occurs in the back wave bead shape.

No. 2-7 is a first electrode, and the third electrode is a category of the present invention, but the second electrode is a combination of AC / droop characteristics / current FB shift control. Since the drooping characteristic is that the current does not move much with the movement of the arc length, the feedback control monitoring the current is inferior to the arc voltage feedback as an arc length control means. As the control of the arc length did not work well and the wire feeding was not constant, not only the back bead shape defect but also the internal defect of the fusion defect and the defect of the front bead shape occurred.

No. 2-8 is a combination of constant current characteristics and current FB speed control in which constant current characteristics are further enhanced with respect to the drooping characteristics for all electrodes. Since the control of the arc length does not work well and the wire feeding is not constant, not only defects in the back wave bead shape but also internal defects in the fusion failure and defects in the front bead shape occur. The overall quality was even worse than 2-7.

No. 2-9 is a combination of constant voltage characteristics and voltage FB shift control as the first electrode. Since the constant voltage characteristic does not move the voltage much with respect to the movement of the arc length, the feedback control monitoring the voltage has low performance as an arc length control means, and the first electrode forming the back wave bead has a wire feeding speed Since it is most important for shape stabilization that C. is constant, a good back bead shape can not be obtained in this configuration. In addition, due to the significant instability of the first layer by the first electrode, fusion failure also occurs at the junction with the second electrode.

No. 2-10 combines DC, constant current characteristics, and constant speed control as the first electrode, but in this combination, the arc length stabilization control does not work, so the welding is unstable and the back bead shape is defective Not only that, but also due to the significant instability of the primary layer by the first electrode, fusion failure also occurs at the junction with the second electrode.

Third Example and Third Comparative Example
FIG. 6 is a diagram for explaining the configuration of the experimental apparatus in the third embodiment and the third comparative example. The basic configuration of the experimental apparatus shown in FIG. 6 is obtained by removing the third welding unit 30, the fourth welding unit 40, and the second flux supply apparatus 80 from the welding apparatus 1 shown in FIG. Here, FIG. 6 shows a work 200 including the first steel plate 201 and the second steel plate 202, a front flux 300 supplied to the front side of the work 200, and a backing disposed on the back side of the work 200 together with the experimental apparatus. A portion 400, a weld metal 500 formed on the work 200 along with welding, and a groove filling material 600 previously supplied to the groove are shown together.

Moreover, FIG.7 (c) has shown the dimension of each steel plate and groove in 3rd Example and a 3rd comparative example. In this example, each of the first steel plate 201 and the second steel plate 202 was subjected to an open end surface treatment using a plate thickness 14 mm and a width 500 mm × length 3000 mm of a 520 MPa grade carbon steel plate, to form butt joints. The bevel shape was a 50 ° V-shape without a root face. Although the root gap was set to 0 mm where both steel plates contact at the shortest part, there was a point where a gap of up to 2 mm was inevitably generated due to distortion of the steel plate. Each wire (the first wire 110 and the second wire 120) is a JIS Z3351 YS-S6 equivalent product, and the front flux 300 is a JIS Z3352 SACI1 equivalent product. The surface flux 300 is automatically and continuously sprayed with an appropriate amount prior to the first electrode (leading electrode). Further, separately from the front flux 300, a bevel filler 600 made of iron powder was manually sprayed in advance in the bevel. The filling height of the groove filling material 600 was controlled at 3 mm from the surface position of the steel plate. The groove filling material 600 is melted together with each wire and front flux 300 at the time of welding to form a molten pool.

Attach a soft backing material 421 called glass tape made by weaving glass fibers to a few mm thickness without using a molded solid or backing flux such as a copper sheet or ceramic sheet as the backing part 400 on the back side of the steel sheet groove end The Because the glass tape is soft, it can be adhered to the back without being affected by the corrugation of the steel plate. At the time of welding, the vicinity of the arc melts, but the non-melted part acts as a cushion to prevent excessive melting of the back wave. Also, for each electrode, independent welding power sources were connected between the contact tips and the steel plates corresponding to each electrode. Each wire is fed to the weld by a feed roller provided immediately above each contact tip.

Then, using the experimental apparatus shown in FIG. 6, a test of the two-electrode single-sided submerged arc welding method was conducted except for a part (No. 3-8 described later). More specifically, wire diameter, feeding method, external characteristics, wire speed control, welding current, and arc voltage were changed for each electrode using the test apparatus shown in FIG. 6, and the influence was confirmed. In the experimental apparatus shown in FIG. 6, the distance between the poles of the tip of the first wire 110 and the tip of the second wire 120 was 70 mm. And although the welding speed in this example was constant in each manufacturing condition, it was made to differ according to manufacturing conditions. No. 3-8 is a test by the single electrode single-sided submerged arc welding method using only the first wire 110.

As a test result, the back wave bead shape, the front bead shape, and the internal defect were evaluated. The back bead shape should ideally be 6 mm or more in width and 1 mm to 4 mm in back wave height, and those with small meanders and small variations in width may be regarded as very good A, and these evaluations may be inferior. Those not present were rejected as B, and those requiring repair due to the back bead shape defect were rejected as C. Also for the front bead shape, the same evaluation criteria as the back wave bead shape were used. With regard to internal defects, those with no defects found by the ultrasonic flaw test and the cross section macro cut test were regarded as “none”, and those with poor fusion confirmed as “present”.

Tables 5 and 6 show the manufacturing conditions and the test results in the third example and the third comparative example. Here, no. 3-1 to No. 3-4 is a 3rd Example, No. shown in Table 6 3-5 to No. 3-14 is a third comparative example.

First, the third embodiment will be described.
No. 3-1 uses direct current, constant voltage characteristics, constant speed control for the first electrode, and the second electrode uses the conventional alternating current, drooping characteristics, and voltage FB shift control, but it has a good back bead shape and surface The bead shape is obtained.

No. 3-2 is no. Although the first electrode was a direct current on the electrode side with respect to 3-1, no. The same quality as 3-1 is obtained.

No. In 3-3, both electrodes are used on the electrode side: DC, constant voltage characteristics and constant speed control. No. 3-1 and No. As in 3-2, the constant speed control is better than the second pole shift control, although the stability of the back bead shape is originally excellent. However, by using the groove filling material 600, so much There was no influence on back wave bead shape. On the other hand, in the case of the two-electrode method, the second electrode, which is the final pole, is a controlling electrode in the form of a front bead, and thus within the allowable range, shape stability Slightly inferior.

No. In 3-4, both electrodes have constant voltage characteristics and constant speed control, and the first electrode is DC and the second electrode is AC. The feed control of the wire that most strongly affects the back bead shape is constant, and the first electrode is a direct current without periodic arc breakage, while the second electrode governing the front bead shape is inter-arc interference Since the alternating current was not affected by the magnetic blow or the magnetic blow, the best front and back quality in the third example was obtained.

Subsequently, a third comparative example will be described.
No. 3-5 is a typical used today. AC, droop characteristics, and voltage FB shift control are adopted for both poles. Although internal defects and the shape of the front bead have no particular problem, both the alternating current and the shift control are unsuitable for back wave welding, and the back bead shape is notable. In addition, since the thickness of the steel plate was smaller than those in Examples 1 and 2 described above, the defect in the back wave bead shape also affected the front bead shape and slightly deteriorated.

No. Although the combination of alternating current, constant current characteristics, and constant speed control is used as the first electrode 3-6 in this combination, in this combination, not only the periodic arc breakage peculiar to the alternating current adversely affects the back wave bead shape, but also the arc length Since stabilization control does not work, welding is unstable, and not only defects in back bead shape, but also significant instability of the first layer by the first electrode causes fusion failure at the junction with the second electrode. did. If the number of electrodes is large as in the first embodiment and the second embodiment, a defect in the back bead shape due to the first electrode has little effect on the front bead shape, but since this example has two electrodes, Instability of the back wave bead shape affected the front bead shape and caused deterioration.

No. The combination of the first electrode at constant voltage characteristics and constant speed control is a category of the present invention in 3-7, but the wire diameter is as thin as 2.0 mm. As a result, a back wave bead could not be formed, and a dent was generated on the back surface side of the steel plate. In order to form the back wave bead, it is necessary to have both the strong arc force and the thickness reduction of the molten pool which does not disturb it. In order to fit this combination, it is effective to reduce the current density, and the larger the wire diameter, the more advantageous. That is, it can be said that the wire diameter of 2.0 mm is insufficient.

No. 3-8 is a combination of constant voltage characteristics and constant speed control within the scope of the present invention, but it is a challenge to simultaneously finish back wave bead formation and front bead formation with only one electrode. However, although a good shape could be obtained for the back wave bead, it was not possible to make the front bead shape good. Since the role of the first electrode is specialized in forming the back wave bead, the welding conditions are limited, and the front bead shape has to be a narrow convex shape. If there are two or more electrodes, the thin and convex molten pool shape formed by the leading electrode can be arranged using welding conditions for making the front bead shape better in the trailing electrode (especially the final electrode). (1) Since this role can not be shared in electrode construction, it is unsuitable for back wave welding.

No. 3-9 adopts alternating current, constant current characteristics, and voltage FB shift control as the leading electrode. Although internal defects and the shape of the front bead are not particularly problematic, the AC and shift control are not suitable for back wave welding, and defects in the back wave bead shape were remarkable.

No. No. 3-10 leading electrode; 3-11, no. Although the trailing electrode of 3-12 is constant voltage characteristics / voltage FB shift control, the constant voltage characteristics do not move much with respect to the movement of the arc length regardless of direct current or alternating current, so the voltage monitored feedback Since the control has low performance as an arc length control means, welding is unstable, and appearance defects occur in both the back wave bead shape and the front bead shape, and a fusion failure also occurs in the meeting portion.

No. 3-13, no. Although the trailing electrode of 3-14 has constant current characteristics and constant speed control, regardless of direct current and alternating current, welding stabilization is not possible because arc length stabilization control does not work in this combination, so back bead shape In addition, appearance defects occurred in both the front bead shape, and fusion defects also occurred in the meeting portion.

In the first embodiment, the case where the backing flux 401 and the backing copper plate 402 are used as the backing part 400 in the four-electrode single-sided submerged arc welding has been described. In the second embodiment, the case where the underlaying flux 411, the backing flux 412 and the air hose 413 are used as the backing portion 400 in the three-electrode single-sided submerged arc welding has been described. Furthermore, in the third embodiment, the case of using the soft backing material 421 as the backing part 400 in the two-electrode single-sided submerged arc welding has been described. However, the number of electrodes in multi-electrode single-sided submerged welding and the configuration of the backing portion 400 are not limited to the combinations described above, and the combinations may be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 ... Welding apparatus, 10 ... 1st welding unit, 11 ... 1st feeding apparatus, 12 ... 1st welding power supply, 20 ... 2nd welding unit, 21 ... 2nd feeding apparatus, 22 ... 2nd welding power supply, 30 ... third welding unit, 31 ... third feeding device, 32 ... third welding power source, 40 ... fourth welding unit, 41 ... fourth feeding device, 42 ... fourth welding power source, 50 ... truck driving device, 60 ... control device 70 first flux supply device 80 second flux supply device 90 carriage 110 first wire 120 second wire 130 third wire 140 fourth wire 200 Workpiece, 201: first steel plate, 202: second steel plate, 300: front flux, 400: backing portion, 500: weld metal, 600: groove filling material

Claims (6)

1. A multi-electrode single-sided submerged arc welding method using a leading electrode and a trailing electrode following the leading electrode,
   In each of the leading electrode and the trailing electrode, a wire having a diameter of 2.4 mm or more is used,
   The power supply method and external characteristics of the power supply that supplies power to each wire, and the speed control method of each wire supply speed,
   In the leading electrode, the power feeding method is set to DC, the external characteristic is constant voltage characteristics, and the speed control method is set to constant speed control.
   At the trailing pole,
   (A) the feeding method is DC, the external characteristic is a constant voltage characteristic, the speed control method is constant speed control (b) the feeding method is AC, the external characteristic is constant voltage characteristic, and the speed control method is constant speed control (C) the feeding method is alternating current, the external characteristic is a constant current characteristic, the speed control method is voltage feedback control based on an arc voltage (d) the feeding method is alternating current, the external characteristic is a drooping characteristic, the speed control method is Voltage feedback control based on arc voltage (e) Multi-electrode characterized in that the feeding method is set to DC, the external characteristics are constant current characteristics, and the speed control method is set to voltage feedback control based on arc voltage. Single-sided submerged arc welding method.
2. The trailing electrode includes a plurality of electrodes following the leading electrode,
   The feeding method, the external characteristic, and the speed control method are set to any one of (a) to (e) in each of the plurality of electrodes constituting the trailing electrode. The multi-electrode single-sided submerged arc welding method according to Item 1.
3. Among the plurality of electrodes constituting the trailing electrode, the last method of the feeding method, the external characteristic, and the speed control method is the (c) or the (c) at the last electrode located on the rearmost side with respect to the leading electrode. A method according to claim 2, characterized in that it is set to d).
4. When using the power supply having the constant voltage characteristic, a differential value dV / dI which is a slope of a voltage with respect to a current at an operating point is −12.0 × 10 ⁻³ (V / A) or more. The multi-electrode single-sided submerged arc welding method according to any one of claims 1 to 3.
5. When using the power supply having the constant current characteristic or the drooping characteristic, the differential value dV / dI, which is the slope of the voltage relative to the current at the operating point, is -24.0 × 10 ^-3 (V / A) or less The multi-electrode single-sided submerged arc welding method according to claim 1, characterized in that
6. A method for producing a weldment comprising welding a base material by single-sided submerged arc welding using a leading electrode and a trailing electrode following the leading electrode,
   In each of the leading electrode and the trailing electrode, a wire having a diameter of 2.4 mm or more is used,
   The power supply method and external characteristics of the power supply that supplies power to each wire, and the speed control method of each wire supply speed,
   In the leading electrode, the power feeding method is set to DC, the external characteristic is constant voltage characteristics, and the speed control method is set to constant speed control.
   At the trailing pole,
   (A) the feeding method is DC, the external characteristic is a constant voltage characteristic, the speed control method is constant speed control (b) the feeding method is AC, the external characteristic is constant voltage characteristic, and the speed control method is constant speed control (C) the feeding method is alternating current, the external characteristic is a constant current characteristic, the speed control method is voltage feedback control based on an arc voltage (d) the feeding method is alternating current, the external characteristic is a drooping characteristic, the speed control method is Arc-voltage-based voltage feedback control (e) A weldment characterized in that the feeding method is DC, the external characteristics are constant-current characteristics, and the speed control method is arc-voltage-based voltage feedback control. Manufacturing method.

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