JP6607677B2 - Four-electrode single-sided single-layer submerged arc welding method - Google Patents

Description

  The present invention relates to a four-electrode single-sided single-layer submerged arc welding method for performing single-sided single-layer welding using four electrodes.

  Multi-electrode single-sided submerged arc welding is a high-efficiency welding method that is applied to a wide range of fields, mainly shipbuilding as joint welding. Various welding methods have been disclosed as such a multi-electrode single-sided submerged arc welding method with high efficiency.

For example, in Patent Document 1, in a single-sided submerged arc welding method in which a flux is used as a backing and a three-electrode or four-electrode electrode is used, a groove shape of a workpiece to be welded has a V shape of 25 to 60 °. A multi-electrode single-sided submerged arc welding method characterized by filling and welding steel grains or iron powder in the groove from 1/5 of the thickness of the material to be welded to the height of the surface of the material to be welded Is disclosed.
In this welding method, the wire diameter of each electrode is 4.8 mm or more, the first electrode current (I1) is 1200 to 2000A, the second electrode current (I2) and the third electrode current (I3) are I1. > I2 ≧ I3, the distance between the first electrode and the second electrode is 20 to 70 mm, the distance between the second electrode and the third electrode is 100 to 150 mm in the case of three-electrode welding, and 150 in the case of four-electrode welding. It is characterized by welding at ˜300 mm.

For example, in Patent Document 2, four electrodes are used, the wire diameter of the first electrode is 4.8 mmφ, the wire diameter of the second to fourth electrodes is 6.4 mmφ, and the current of the first electrode is I ₁ ( A), the current of the second electrode is I ₂ (A), the current of the third electrode is I ₃ (A), the current of the fourth electrode is I ₄ (A), the welding speed is S (cm / min), When the thickness of the welded steel sheet is t (mm), 60 ≦ S ≦ 200, 1000 ≦ St ≦ 4000, 1100 ≦ I ₁ ≦ 2400, 900 ≦ I ₂ ≦ 2100, 1000 ≦ I ₃ + I ₄ ≦ 4200, 2. A multi-electrode single-sided submerged arc welding method characterized by using a firing type front and back flux with an inter-electrode distance of 125 to 250 mm between the third electrodes is disclosed.

JP-A-2005-319507 Japanese Patent Laid-Open No. 5-337651

However, the following problems exist in the prior art.
In the technique described in Patent Document 1, since the distance between the second electrode and the third electrode is long, the penetration of the third electrode is shallow, and the weld metal generated between the electrodes of the first electrode and the second electrode There is a problem that it is not possible to remove cracks.
Further, depending on the protruding length of the wire, there is a problem that the slag generated in the first electrode and the second electrode adheres to the chips of the third electrode and the fourth electrode, and the appearance of the front bead becomes poor.

In the technique described in Patent Literature 2, there is a possibility that cracks may occur in the weld metal depending on the distance between the second electrode and the third electrode and the setting of the current of the third electrode.
Further, depending on the protruding length of the wire, there is a problem that the slag generated in the first electrode and the second electrode adheres to the chips of the third electrode and the fourth electrode, and the appearance of the front bead becomes poor.

Also, in single-sided single-layer submerged arc welding, the bead shape tends to be a so-called “none type” as the steel plate to be welded becomes thicker, and the incidence of hot cracking increases. Therefore, in order to reduce the rate of occurrence of cracks in the thick plate, it has been necessary to employ conditions that sacrifice the bead shape.
In single-sided single-layer submerged arc welding, it is also necessary to suppress the occurrence of poor fusion in the weld metal.

  Accordingly, the object of the present invention is to provide a four-electrode single-sided single-layer submerged arc welding method in which the occurrence rate of hot cracks is small even in a thick metal plate, the bead shape is good, and the occurrence of poor fusion is suppressed. There is to do.

The four-electrode single-sided single-layer submerged arc welding method (hereinafter referred to as “submerged arc welding method” or “welding method” as appropriate) according to the present application is a four-electrode single-sided single-layer submerged arc welding in which one-sided single-layer welding is performed using four electrodes. A distance between electrodes of the first electrode and the second electrode: 25 to 65 mm; a distance between electrodes of the second electrode and the third electrode: 100 to 149 mm; and a distance between the third electrode and the fourth electrode Distance: 40 to 80 mm, wire diameter of first electrode: more than 3.2 mmφ and less than 6.4 mmφ, wire diameter of second electrode: more than 3.2 mmφ, wire diameter of third electrode and fourth electrode: 4.8 mmφ The wire protrusion length of the third electrode and the fourth electrode: 40 mm or more, the current of the fourth electrode: 1050 to 1400 A, the current of the third electrode is I3 (A), and the thickness of the welded steel sheet is t (mm) ) And when The welding is performed under the condition of the following formula (1) I3 ≧ 7 × (distance between the second electrode and the third electrode (mm)) + 12.5t−350 (1).

  According to such a welding method, in a predetermined electrode, the distance between the electrodes, the wire diameter, and the wire protruding length are defined, and by satisfying Expression (1), occurrence of poor fusion is suppressed, The back bead is stable and the hot cracking resistance is improved.

In the welding method of the present invention, the current of the third electrode is preferably 750 to 1600A.
According to this welding method, the arc of the third electrode is more stable and the bead shape is better.

In the welding method of the present invention, the wire diameter of the second electrode is preferably 4.8 mmφ.
According to such a welding method, the back bead is more stable, the bead width is likely to be wider, and the hot crack resistance is more likely to be improved.

Moreover, the welding method of this invention can make the plate | board thickness of the said to-be-welded steel plate into 10-40 mm.
According to this welding method, even if it is a thick plate, while being able to suppress a favorable hot crack, a favorable bead shape can be obtained.

In the welding method of the present invention, it is preferable that the wire diameter of the first electrode is 4.0 to 4.8 mmφ.
According to this welding method, the back bead is more stable.

In the welding method of the present invention, it is preferable that the wire diameters of the third electrode and the fourth electrode are 6.4 mmφ.
According to such a welding method, the hot crack resistance is more easily improved by setting the wire diameter of the third electrode to a preferable value. In addition, the front bead is more stable by setting the wire diameter of the fourth electrode to a preferable value.

  The four-electrode single-sided single-layer submerged arc welding method of the present invention can suppress hot cracking even in a thick plate of a weld metal and obtain a good bead shape. Furthermore, occurrence of poor fusion of weld metal is suppressed.

It is sectional drawing of the welding apparatus used for the 4 electrode single-sided single layer submerged arc welding method of this invention. It is a top view of the steel plate welded with the 4 electrode single-sided single layer submerged arc welding method of the present invention. It is sectional drawing of the steel plate periphery which shows a mode at the time of performing 4 electrode single-sided single layer submerged arc welding. It is sectional drawing of the steel plate periphery which shows a mode at the time of performing 4 electrode single-sided single layer submerged arc welding. It is sectional drawing for demonstrating the distance between electrodes and the wire protrusion length in the 4 electrode single-sided single layer submerged arc welding method of this invention. It is sectional drawing of the steel plate periphery for demonstrating the high temperature crack resistance in an Example.

Hereinafter, embodiments of the present invention will be described in detail.
The four-electrode single-sided single-layer submerged arc welding method of the present invention is a four-electrode single-sided single-layer submerged arc welding method that welds one single-sided layer using four electrodes. And the welding method of this invention prescribes | regulates the relationship between the distance between electrodes, the wire diameter of an electrode, the wire protrusion length of an electrode, the electric current, the distance between electrodes, and the plate | board thickness of a to-be-welded steel plate.

First, the outline of the main part of the welding apparatus used in the welding method of the present invention and the steel plate will be described.
(Welding equipment)
As shown in FIG. 1, the welding apparatus 100 mainly includes a gantry frame 11, a welder 12, and a welder beam 13.

The gantry frame 11 is formed so as to exhibit a concave shape in cross-section, with a steel square frame, and the upper part is opened, and the backing device 50a or the backing device 50b shown in FIGS. Has been. The steel plate 20 is placed on the backing copper plate 55 of the backing device 50a or the fireproof canvas 56 of the backing device 50b.
The welder beam 13 moves the welder 12 along the longitudinal direction of the steel plate 20.
The welding machine 12 is disposed above the gantry frame 11 (above the steel plate 20), and welds the steel plate 20 from the front side of the welding groove portion M (see FIG. 2) of the steel plate 20. Here, the welding machine 12 includes four electrodes (welding torches) 15. The welder 12 welds the steel plate 20 by single-sided submerged arc welding with the electrode 15 from the front side of the welding groove portion M while moving along the welder beam 13 at a predetermined speed.

  Here, the multi-electrode single-sided submerged arc welding method to which the present application belongs, as shown in FIGS. 3 and 4, is a backing flux 52 spread in layers on the backing copper plate 55 from the back surface of the abutted steel plates 20 and 20. Alternatively, the backing flux 52 accommodated in the fireproof canvas 56 is pressed by a lifting mechanism such as an air hose 59 and welded. In the multi-electrode single-sided submerged arc welding method, submerged arc welding is performed from the front side of the steel plate 20 using the front flux 51, and beads are simultaneously formed on the front and back surfaces of the steel plate 20. 3 is for the FCB (Flux Copper Backing) (registered trademark) system, and the description for FIG. 4 is for the RF (Resin Flux) (registered trademark) system. 3 and 4, reference numeral 53 is slag, reference numeral 54 is a weld metal, reference numeral 57 is a heat-resistant cover, and reference numeral 58 is an underlay flux.

(steel sheet)
Examples of the steel plate 20 include a steel plate for shipbuilding, and the length thereof is, for example, 10 to 30 m. As shown in FIG. 2, this steel plate 20 is subjected to intermittent in-plane provisional contact at the position of the weld groove portion M by abutting the steel plates 20 together.
Tabs 21 and 22 for processing craters are attached to the start end 31 and the end end 32 of the steel plate 20.

  In the welding method of the present invention, the distance between the first electrode and the second electrode: 25 to 65 mm, the distance between the second electrode and the third electrode: 100 to 149 mm, the third electrode and the fourth electrode. The distance between the electrodes: 20 to 80 mm, the wire diameter of the first electrode: more than 3.2 mmφ and less than 6.4 mmφ, the wire diameter of the second electrode: more than 3.2 mmφ, and the wire diameters of the third electrode and the fourth electrode : Exceeding 4.8 mmφ, wire protruding length of the third electrode and the fourth electrode: 40 mm or more, when the current of the third electrode is I3 (A), and the thickness of the steel plate to be welded is t (mm), Welding is performed under the condition of the following formula (1) I3 ≧ 7 × (distance between second electrode and third electrode (mm)) + 12.5t−350 (1).

  In the submerged arc welding, a solid wire is mainly used, and the wire diameter is limited to a specific nominal diameter such as 4.8 mmφ or 6.4 mmφ. The actual diameter is generally widely interpreted as including an error range. Here, in JIS Z 3200: 2005, the tolerance of the solid wire for submerged arc welding (3.2 mmφ, 4.0 mmφ, 4.8 mmφ, 6.4 mmφ) is ± 0.06 mm. Therefore, the wire diameter defined in the present invention includes an error of ± 0.06 mmφ as the actual diameter. That is, for example, a wire diameter of 4.8 mmφ means “4.8 mmφ ± 0.06 mmφ” as an actual diameter, and a wire diameter of 6.4 mmφ means “6.4 mmφ ± 0.06 mmφ”. Shall.

As shown in FIG. 5, the welding machine has four electrodes, a first electrode 15a, a second electrode 15b, a third electrode 15c, and a fourth electrode 15d, in this order from the welding progress direction (the direction indicated by the arrow in the figure). Electrode. The inter-electrode distances B1 to B3 are the distances between the reference lines when the reference lines are drawn perpendicularly to the tips of the wires 16a to 16d of the electrodes 15a to 15d in the arrangement of the electrodes when performing welding. The horizontal distance.
Further, the wire protruding lengths A1 to A4 refer to the center of the tips of the tips 17a to 17d, that is, from the contact points between the tips of the tips 17a to 17d and the wires 16a to 16d in the arrangement of the electrodes when welding. The vertical length to the reference line when the reference line is drawn horizontally with respect to the tips of 16a to 16d. When the tips of the wires 16a to 16d are in contact with the steel plate 20, the wire protrusion lengths A1 to A4 are perpendicular to the steel plate 20 from the contact points between the tips of the tips 17a to 17d and the wires 16a to 16d. It becomes length.
Hereinafter, each condition will be described.

(Distance between the first electrode and the second electrode: 25 to 65 mm)
If the interelectrode distance B1 between the first electrode 15a and the second electrode 15b is 25 to 65 mm, the arcs hardly interfere with each other, the arcs of the first electrode and the second electrode are stabilized, and the back bead is stabilized. When the interelectrode distance B1 is less than 25 mm, the arcs interfere with each other and the arc becomes unstable, and the back bead becomes unstable. On the other hand, when the interelectrode distance B1 exceeds 65 mm, the molten metal pool becomes unstable and the back bead becomes unstable. Therefore, the interelectrode distance B1 between the first electrode 15a and the second electrode 15b is set to 25 to 65 mm. From the viewpoint of further stabilizing the back bead, the interelectrode distance B1 is preferably 30 mm or more, and more preferably 35 mm or more. From the viewpoint of further stabilizing the back bead, the interelectrode distance B1 is preferably 60 mm or less, more preferably 55 mm or less.

(Distance between the second electrode and the third electrode: 100 to 149 mm)
If the inter-electrode distance B2 between the second electrode 15b and the third electrode 15c is 100 to 149 mm, the back bead is stabilized and the hot crack resistance is improved. When the inter-electrode distance B2 is less than 100 mm, the back bead becomes unstable. On the other hand, when the inter-electrode distance B2 exceeds 149 mm, the third electrode 15c is not sufficiently melted and the hot cracking resistance is deteriorated. Therefore, the interelectrode distance B2 between the second electrode 15b and the third electrode 15c is 100 to 149 mm. From the viewpoint of further stabilizing the back bead, the interelectrode distance B2 is preferably 110 mm or more, more preferably 115 mm or more. Further, from the viewpoint of further improving the hot cracking resistance, the inter-electrode distance B2 is preferably 145 mm or less, more preferably 140 mm or less.

(Distance between the third electrode and the fourth electrode: 20 to 80 mm)
If the inter-electrode distance B3 between the third electrode 15c and the fourth electrode 15d is 20 to 80 mm, the arc bead is reduced even with a large current, and the surface bead is stabilized. When the inter-electrode distance B3 is less than 20 mm, the influence of arc interference becomes large, and the surface bead becomes unstable. On the other hand, when the inter-electrode distance B3 exceeds 80 mm, the front bead becomes unstable. Therefore, the interelectrode distance B3 between the third electrode 15c and the fourth electrode 15d is 20 to 80 mm. In addition, from the viewpoint of further stabilizing the front bead, the inter-electrode distance B3 is preferably 40 mm or more, and more preferably 50 mm or more. Further, from the viewpoint of further stabilizing the front bead, the interelectrode distance B3 is preferably 70 mm or less, more preferably 65 mm or less.

(Wire diameter of the first electrode: more than 3.2 mmφ and less than 6.4 mmφ)
If the wire diameter of the first electrode 15a is more than 3.2 mmφ and less than 6.4 mmφ, stable penetration is realized and the back bead is stabilized. When the wire diameter is 3.2 mmφ or less, the arc becomes unstable and the back bead becomes unstable. On the other hand, when the wire diameter is 6.4 mmφ or more, the penetration becomes shallow and the back bead becomes unstable. Therefore, the wire diameter of the first electrode 15a is more than 3.2 mmφ and less than 6.4 mmφ. From the viewpoint of further stabilizing the back bead, the wire diameter of the first electrode 15a is preferably 4.0 mmφ or more. Further, from the viewpoint of further stabilizing the back bead, the wire diameter of the first electrode 15a is preferably 4.8 mmφ or less, more preferably 4.8 mmφ.

(The wire diameter of the second electrode: over 3.2 mmφ)
If the wire diameter of the second electrode 15b exceeds 3.2 mmφ, the back bead is stable, the bead width is widened, and the hot crack resistance is improved. When the wire diameter is 3.2 mmφ or less, the arc becomes unstable and the back bead becomes unstable. Therefore, the wire diameter of the second electrode 15b exceeds 3.2 mmφ. On the other hand, if the wire diameter is 6.4 mmφ or less, the bead width is widened, and the hot crack resistance is easily improved. Therefore, the wire diameter of the second electrode 15b is preferably 6.4 mmφ or less. That is, the wire diameter of the second electrode 15b can be any of 4.0 mmφ, 4.8 mmφ, and 6.4 mmφ. In addition, the wire diameter of the second electrode 15b is preferably 4.8 mmφ or more from the viewpoint of making the back bead more stable, making the bead width wider, and making it easier to improve hot cracking resistance. Is 4.8 mmφ.

(The wire diameter of the third electrode: over 4.8 mmφ)
If the wire diameter of the third electrode 15c exceeds 4.8 mmφ, the penetration becomes deep and the hot crack resistance is improved. When the wire diameter is 4.8 mmφ or less, the arc is concentrated and poor fusion occurs. Therefore, the wire diameter of the third electrode 15c exceeds 4.8 mmφ. On the other hand, if the wire diameter is 6.4 mmφ or less, the penetration becomes deep and the hot cracking resistance is easily improved. Therefore, the wire diameter of the third electrode 15c is preferably 6.4 mmφ or less. Note that, from the viewpoint of further improving the hot cracking resistance, the wire diameter of the third electrode 15c is preferably 6.4 mmφ.

(Wire diameter of the fourth electrode: over 4.8 mmφ)
If the wire diameter of the fourth electrode 15d exceeds 4.8 mmφ, the front bead is stabilized. When the wire diameter is 4.8 mmφ or less, the surplus is high, overlap occurs, and the surface bead becomes unstable. Accordingly, the wire diameter of the fourth electrode 15d exceeds 4.8 mmφ. On the other hand, when the wire diameter is 6.4 mmφ or less, the bead width is not widened, the central portion is difficult to be convex, and the front bead is easily stabilized. Therefore, the wire diameter of the fourth electrode 15d is preferably 6.4 mmφ or less. Note that, from the viewpoint of further stabilizing the front bead, the wire diameter of the fourth electrode 15d is preferably 6.4 mmφ.

(The wire protruding length of the third electrode: 40 mm or more)
If the wire protruding length A3 of the third electrode 15c is 40 mm or more, the front bead is stabilized. If the wire protrusion length A3 is less than 40 mm, slag adheres to the third electrode 15c, and this slag falls into the molten pool during welding. Therefore, the front bead becomes unstable. Therefore, the wire protruding length of the third electrode is set to 40 mm or more. In addition, from the viewpoint of further stabilizing the front bead, the wire protrusion length A3 is preferably 45 mm or more, more preferably 50 mm or more. The upper limit is not particularly defined, but from the viewpoint of further stabilizing the front bead, the electric wire protrusion length A3 is preferably 80 mm or less, more preferably 75 mm or less.

(The wire protrusion length of the fourth electrode: 40 mm or more)
If the wire protrusion length A4 of the fourth electrode 15d is 40 mm or more, the front bead is stabilized. If the wire protrusion length A4 is less than 40 mm, slag adheres to the fourth electrode 15d, and this slag falls into the molten pool during welding. Therefore, the front bead becomes unstable. Therefore, the wire protrusion length of the fourth electrode is 40 mm or more. In addition, from the viewpoint of further stabilizing the front bead, the wire protrusion length A4 is preferably 45 mm or more, more preferably 50 mm or more. The upper limit is not particularly defined, but from the viewpoint of further stabilizing the front bead, the electric wire protruding length A4 is preferably 80 mm or less, more preferably 75 mm or less.

(I3 ≧ 7 × (distance between second electrode and third electrode + 12.5t−350))
As a result of intensive studies, the present inventors have found that the hot crack resistance can be improved by mutually adjusting the current, the distance between the electrodes, and the plate thickness. That is,
When the current of the third electrode 15c is I3 (A) and the thickness of the steel plate 20 to be welded is t (mm), the following formula (1) “I3 ≧ 7 × (electrode between the second electrode and the third electrode) If the distance (mm) + 12.5t−350 (1) ”is satisfied, the hot cracking resistance is improved. If the formula (1) is not satisfied, the third electrode 15c is not sufficiently melted and the high temperature resistance is increased. Therefore, “I3 ≧ 7 × (distance between second electrode and third electrode (mm) + 12.5t−350”. This relational expression is derived from an experiment. It is.

  The current (I3) of the third electrode 15c is preferably 750 to 1600A. If the current (I3) of the third electrode 15c is 750 A or more, a better bead can be obtained. Further, if the current (I3) of the third electrode 15c is 1600 A or less, a better bead can be obtained.

  The plate | board thickness of the steel plate 20 can be 10-40 mm, for example. With the welding method of the present invention, it is possible to suppress good hot cracking and obtain a good bead shape even with a thick plate of 25 mm or more.

  The current values of the first electrode 15a, the second electrode 15b, and the fourth electrode 15d are not particularly limited. The current of the first electrode 15a can be set to 1100 to 1700A, the current of the second electrode 15b can be set to 750 to 1400A, for example, and the current of the fourth electrode 15d can be set to 750 to 1400A, for example. Thereby, a better bead shape can be obtained.

As a welding method, for example, welding is performed by a FCB (Flux Copper Backing) method (see FIG. 3) using a bond flux for a steel plate 20 whose groove shape is a Y-shaped groove. Thereby, a better bead shape can be obtained.
However, the present invention is not limited to this, and may be a V-shaped groove steel plate. Further, welding using a molten flux may be used, and welding may be performed using an RF (Resin Flux) method (see FIG. 4).

Next, an outline of four-electrode single-sided single-layer submerged arc welding using the welding method of the present invention will be described with reference to FIGS.
(Preparation process)
In the preparation step, first, the steel plates 20 and 20 to which the tabs 21 and 22 are attached and intermittently or continuously in-plane temporarily attached are prepared. Next, the backing flux 52 is supplied to the upper surface of the backing copper plate 55 of the backing device 50a by a flux supply means (not shown). Alternatively, the underlay flux 58 is supplied to the upper surface of the heat-resistant cover 57 in the fireproof canvas 56 of the backing device 50b by a flux supply means (not shown), and the backing flux 52 is further supplied thereon. And the steel plates 20 and 20 are set to the welding apparatus 100, and the welding groove part M formed with the steel plates 20 and 20 is arrange | positioned above the backing device 50a or the backing device 50b. Then, fine adjustment is performed by operating a driving device (not shown) so that the backing copper plate 55 or the fire-resistant canvas 56 is positioned directly below the welding groove portion M. Next, compressed air is introduced into the air hose 59, the air hose 59 is expanded, the backing copper plate 55 or the underlay flux 58 is pressed against the back side of the welding groove portion M, and the backing flux 52 is applied to the back surface of the welding groove portion M. Press down.

(Electrode adjustment process)
In the electrode adjusting step, the four inter-electrode distances B1 to B3 are adjusted, and the wire protruding lengths A1 to A4 are adjusted. Moreover, the current value of each electrode 15a-15d is set. Thereby, it adjusts so that it may become the prescription | regulation of the welding method of this invention. Note that the order of the preparation step and the electrode adjustment step is not particularly defined, and either step may be performed first or may be performed simultaneously.

(Welding process)
In the welding process, first, the welding machine 12 of the welding apparatus 100 is moved to the welding start position. Next, an electric current is supplied to the electrode 15 so that it may become the regular electric current value of this invention, and the welding machine 12 is operated. Then, the steel plates 20 and 20 are welded while supplying the surface flux 51 while moving the welding machine 12 at a predetermined speed along the welder beam 13 from the start end 31 to the end end 32 of the steel plate 20.

  Hereinafter, examples that fall within the scope of the present invention will be described in comparison with comparative examples that depart from the scope of the present invention.

About two steel plates with slopes formed on the end faces, the end faces face each other and abut each other to form a Y-shaped groove. This Y-shaped groove has a groove angle of 45 °, 50 °, 60 °, a root face of 3 to 6 mm, and a root gap of 0 mm. In this example, the length of the steel plate was 1.2 m, and the thickness of the steel plate was 12 to 40 mm. The groove angle is 60 ° when the plate thickness is 12 mm, 50 ° when 25 mm, and 45 ° when 40 mm.
The composition of this steel sheet, the composition of the wire used, and the composition of the flux are shown in Table 1 below.

About this steel plate, the submerged arc welding of the single side | surface was performed on the conditions shown in Tables 2-4, and the following evaluation was performed.
A welding apparatus having a backing device 50a shown in FIG. 3 or a backing device 50b shown in FIG. 4 was used, and a high-temperature sintered flux was used as the front flux and a sintered flux was used as the back flux. The conditions other than those shown in Tables 2 to 4 are conventionally known conditions, and all are the same conditions. In addition, what does not satisfy the scope of the present invention is indicated by underlining the numerical values.

(Bead shape)
The bead shape was evaluated by visually observing the front and back beads. The front bead and the back bead have an extra height of 2 to 4 mm, and the extra height and the bead width are almost uniform (）), the extra height is 2 to 4 mm, and Those with a slightly uniform overfill height and bead width were evaluated as good (◯). Also, the front bead and the back bead are defective if the overfilling is too small or excessive, undercutting occurs frequently, the bead width is uneven, or the bead appearance is poor (× ).

(High temperature crack resistance)
As shown in FIG. 6, the weld metal formed by this welding method includes a weld metal 60 formed by the first electrode (L pole) and the second electrode (T1 pole), a third electrode (T2 pole), and It consists of a weld metal 61 formed by a fourth electrode (T3 pole). In the structure of the weld metal 60 generated at the first electrode and the second electrode, the dendrite grows right side, and high temperature cracking is likely to occur. Therefore, the weld metal generated in the third electrode is deeply melted, and the fragile structure is melted to improve the hot crack resistance. Therefore, the penetration depth T of the third electrode and the fourth electrode was measured and evaluated from the cross-sectional macrostructure. When the thickness of the steel plate 20 is t, the penetration depth T of the weld metal 61 formed by the third electrode and the fourth electrode from the surface (upper surface) of the steel plate 20 is “4 / 4t> T ≧ 3 / 4t. In the case where the relationship of “3 / 4t> T” and “T ≧ 4 / 4t” is determined as poor (×).

(Poor fusion)
The fusion failure was evaluated by an X-ray transmission test. The weld metal was evaluated as good (）) if there was no defect, and was determined as poor (x) if there was a defect.
These results are shown in Tables 5-7.

As shown in Table 5, No. 1 satisfying the scope of the present invention or being a reference example . 1-41 was favorable in all the evaluation items.
On the other hand, as shown in Tables 6 and 7, No. 1 does not satisfy the scope of the present invention. 42 to 113 gave the following results.

  No. No. 42 had a bad back bead shape because the wire diameter of the first electrode was less than the lower limit. No. No. 43 had a bad back bead shape because the wire diameter of the first electrode exceeded the upper limit. No. No. 44 had a bad back bead shape because the wire diameter of the second electrode was less than the lower limit. No. No. 45 had a bad back bead shape because the wire diameter of the second electrode was less than the lower limit.

  No. No. 46 was poorly fused because the wire diameter of the third electrode was less than the lower limit. No. In No. 47, the wire diameter of the fourth electrode was less than the lower limit value, so the surface bead shape was poor. No. No. 48 had a bad back bead shape because the distance between the first electrode and the second electrode was less than the lower limit. No. No. 49 had a bad back bead shape because the distance between the first electrode and the second electrode exceeded the upper limit.

  No. In No. 50, the back bead shape was poor because the distance between the second electrode and the third electrode was less than the lower limit. No. No. 51 was inferior in hot crack resistance because the distance between the second electrode and the third electrode exceeded the upper limit. No. No. 52 had a bad surface bead shape because the distance between the third electrode and the fourth electrode was less than the lower limit. No. 53, the inter-electrode distance between the third electrode and the fourth electrode exceeded the upper limit value, so the surface bead shape was poor. No. No. 54 had a bad back bead shape because the distance between the first electrode and the second electrode was less than the lower limit. No. No. 55 had a bad back bead shape because the distance between the first electrode and the second electrode exceeded the upper limit.

  No. No. 56 had a bad back bead shape because the distance between the second electrode and the third electrode was less than the lower limit. No. No. 57 was inferior in hot cracking resistance because the distance between the second electrode and the third electrode exceeded the upper limit and did not satisfy the formula (1). No. No. 58 had a bad surface bead shape because the wire protrusion length of the third electrode was less than the lower limit. No. No. 59 had a bad bead shape because the wire protrusion length of the third electrode was less than the lower limit.

  No. No. 60 had a bad bead shape because the wire protruding length of the fourth electrode was less than the lower limit. No. No. 61 had a bad surface bead shape because the wire protrusion length of the fourth electrode was less than the lower limit. No. No. 62 had a poor surface bead shape because the distance between the third electrode and the fourth electrode was less than the lower limit. No. In No. 63, the inter-electrode distance between the third electrode and the fourth electrode exceeded the upper limit value, so the surface bead shape was poor. No. Since 64 does not satisfy Formula (1), it was inferior in hot cracking resistance. No. Since 65 did not satisfy the formula (1), it was inferior in hot cracking resistance.

  No. No. 66 had a bad back bead shape because the wire diameter of the first electrode was less than the lower limit. No. No. 67 had a bad back bead shape because the wire diameter of the first electrode exceeded the upper limit. No. No. 68 had a bad back bead shape because the wire diameter of the second electrode was less than the lower limit. No. No. 69 had a bad back bead shape because the wire diameter of the second electrode was less than the lower limit.

  No. No. 70 was poorly fused because the wire diameter of the third electrode was less than the lower limit. No. No. 71 had a bad bead shape because the wire diameter of the fourth electrode was less than the lower limit. No. No. 72 had a bad back bead shape because the distance between the first electrode and the second electrode was less than the lower limit. No. No. 73 had a bad back bead shape because the interelectrode distance between the first electrode and the second electrode exceeded the upper limit.

  No. No. 74 had a bad back bead shape because the distance between the second electrode and the third electrode was less than the lower limit. No. No. 75 was inferior in hot cracking resistance because the interelectrode distance between the second electrode and the third electrode exceeded the upper limit and did not satisfy the formula (1). No. No. 76 had a bad surface bead shape because the distance between the third electrode and the fourth electrode was less than the lower limit. No. In No. 77, the inter-electrode distance between the third electrode and the fourth electrode exceeded the upper limit value, so the surface bead shape was poor. No. In No. 78, the back bead shape was poor because the distance between the first electrode and the second electrode was less than the lower limit. No. In No. 79, the back bead shape was poor because the interelectrode distance between the first electrode and the second electrode exceeded the upper limit.

  No. No. 80 had a bad back bead shape because the distance between the second electrode and the third electrode was less than the lower limit. No. No. 81 was inferior in hot cracking resistance because the distance between the second electrode and the third electrode exceeded the upper limit. No. No. 82 had a bad surface bead shape because the wire protrusion length of the third electrode was less than the lower limit. No. In No. 83, the surface bead shape was poor because the wire protrusion length of the third electrode was less than the lower limit.

  No. No. 84 had a bad surface bead shape because the wire protruding length of the fourth electrode was less than the lower limit. No. No. 85 had a poor surface bead shape because the wire protrusion length of the fourth electrode was less than the lower limit. No. No. 86 had a poor bead shape because the distance between the third electrode and the fourth electrode was less than the lower limit. No. No. 87 had a bad surface bead shape because the distance between the third electrode and the fourth electrode exceeded the upper limit. No. Since 88 did not satisfy | fill Formula (1), it was inferior to hot cracking resistance. No. Since 89 did not satisfy Formula (1), it was inferior in hot cracking resistance.

  No. No. 90 had a bad back bead shape because the wire diameter of the first electrode was less than the lower limit. No. No. 91 had a bad back bead shape because the wire diameter of the first electrode exceeded the upper limit. No. No. 92 had a bad back bead shape because the wire diameter of the second electrode was less than the lower limit. No. No. 93 had a bad back bead shape because the wire diameter of the second electrode was less than the lower limit.

  No. No. 94 was poorly fused because the wire diameter of the third electrode was less than the lower limit. No. No. 95 had a poor bead shape because the wire diameter of the fourth electrode was less than the lower limit. No. No. 96 had a bad back bead shape because the distance between the first electrode and the second electrode was less than the lower limit. No. No. 97 had a bad back bead shape because the distance between the first electrode and the second electrode exceeded the upper limit.

  No. No. 98 had a bad back bead shape because the distance between the second electrode and the third electrode was less than the lower limit. No. No. 99 was inferior in hot cracking resistance because the distance between the second electrode and the third electrode exceeded the upper limit. No. No. 100 had a poor surface bead shape because the distance between the third electrode and the fourth electrode was less than the lower limit. No. In 101, the inter-electrode distance between the third electrode and the fourth electrode exceeded the upper limit value, so the surface bead shape was poor. No. No. 102 had a bad back bead shape because the distance between the first electrode and the second electrode was less than the lower limit. No. No. 103 had a bad back bead shape because the distance between the first electrode and the second electrode exceeded the upper limit.

  No. In 104, the back bead shape was poor because the distance between the second electrode and the third electrode was less than the lower limit. No. No. 105 was inferior in hot cracking resistance because the distance between the second electrode and the third electrode exceeded the upper limit and did not satisfy the formula (1). No. No. 106 had a bad bead shape because the wire protrusion length of the third electrode was less than the lower limit. No. In No. 107, the wire protruding length of the third electrode was less than the lower limit value, so the surface bead shape was poor.

  No. For No. 108, the wire protruding length of the fourth electrode was less than the lower limit value, so the surface bead shape was poor. No. In No. 109, the wire protruding length of the fourth electrode was less than the lower limit value, so the surface bead shape was poor. No. No. 110 was inferior in hot cracking resistance because the inter-electrode distance between the third electrode and the fourth electrode was less than the lower limit value, so the surface bead shape was poor, and the formula (1) was not satisfied. No. No. 111 had a bad surface bead shape because the distance between the third electrode and the fourth electrode exceeded the upper limit. No. Since 112 does not satisfy the formula (1), it was inferior in hot cracking resistance. No. Since 113 did not satisfy Formula (1), it was inferior in hot cracking resistance.

  The present invention has been described in detail with reference to the embodiments and examples. However, the gist of the present invention is not limited to the above-described contents, and the scope of right is widely interpreted based on the description of the claims. Must. Needless to say, the contents of the present invention can be widely modified and changed based on the above description.

DESCRIPTION OF SYMBOLS 11 Mount frame 12 Welding machine 13 Welding machine beam 15 Electrode 15a 1st electrode 15b 2nd electrode 15c 3rd electrode 15d 4th electrode 16a-16d Wire 17a-17d Tip 20 Steel plate 21, 22 Tab 31 Start end 32 End 50a, 50b Back Equipment 51 Front flux 52 Backing flux 53 Slag 54 Weld metal 55 Backing copper plate 56 Fireproof canvas 57 Heat resistant cover 58 Underlay flux 59 Air hose 60 Weld metal formed by the first and second electrodes 61 Weld metal formed with 4 electrodes 100 Welding device A1 to A4 Wire protruding length B1 to B3 Distance between electrodes T Penetration depth of weld metal formed with 3rd electrode and 4th electrode t Thickness

Claims (6)

A four-electrode single-sided single-layer submerged arc welding method for welding one-sided single layer using four electrodes,
Distance between the first electrode and the second electrode: 25 to 65 mm
The distance between the second electrode and the third electrode: 100 to 149 mm
Interelectrode distance between the third electrode and the fourth electrode: 40 to 80 mm
Wire diameter of first electrode: over 3.2 mmφ and less than 6.4 mmφ Wire diameter of second electrode: over 3.2 mmφ Wire diameter of third electrode and fourth electrode: over 4.8 mmφ Third electrode and fourth Wire protrusion length of electrode: 40 mm or more Current of fourth electrode: 1050-1400 A
When the current of the third electrode is I3 (A) and the thickness of the steel plate to be welded is t (mm), the following formula (1)
I3 ≧ 7 × (distance between the second electrode and the third electrode (mm)) + 12.5t−350 (1)
A four-electrode single-sided single-layer submerged arc welding method, wherein welding is performed under the following conditions:   The current of the said 3rd electrode is 750-1600A, The 4 electrode single-sided single layer submerged arc welding method of Claim 1 characterized by the above-mentioned.   The wire diameter of said 2nd electrode is 4.8 mmphi, The 4 electrode single-sided single layer submerged arc welding method of Claim 1 or Claim 2 characterized by the above-mentioned.   The plate thickness of the said to-be-welded steel plate is 10-40 mm, The 4 electrode single-sided single layer submerged arc welding method as described in any one of Claims 1-3 characterized by the above-mentioned.   The four-electrode single-sided single-layer submerged arc welding method according to any one of claims 1 to 4, wherein the wire diameter of the first electrode is 4.0 to 4.8 mmφ.   The wire diameter of the said 3rd electrode and a 4th electrode is 6.4 mmphi, The 4 electrode single-sided single layer submerged arc welding method as described in any one of Claims 1-5 characterized by the above-mentioned.

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