CN116209535A

CN116209535A - Submerged arc welding method and submerged arc welding device for extremely narrow groove

Info

Publication number: CN116209535A
Application number: CN202180058879.3A
Authority: CN
Inventors: 中谷光良; 阿部洋平; 藤本贵大; 安部正光
Original assignee: Hitachi Zosen Corp
Current assignee: Hitachi Zosen Corp
Priority date: 2020-08-06
Filing date: 2021-07-07
Publication date: 2023-06-02
Also published as: JP2022029879A; WO2022030162A1; JP7481940B2

Abstract

An ultra-narrow groove submerged arc welding method and an ultra-narrow groove submerged arc welding device are based on an algorithm in an ultra-narrow groove SAW, wherein the algorithm controls welding conditions and aiming positions of a welding gun which do not generate welding defects aiming at the variation in welding. Measuring the width W of a weld bead obtained by performing a flat plate build-up welding on the same material as the welding object _B And a welding cross-section area A _R . Using welding heat input Q, bead width W _B And the distance L between the welding gun and the groove wall represents the heat input H to the groove wall during welding _G . Using the welding cross-section A _R And distance L represents the generalized distance R from the pool surface to the corner of the groove bottom at the weld gun sight position. At H _G On the R plane, the presence of fusion defects in groove welding determined by test is markedAnd displaying nothing, and drawing a judgment line based on the existence of fusion failure in the groove wall. And setting welding conditions so as to form a region free from fusion failure compared with the determination line, and performing groove welding.

Description

Submerged arc welding method and submerged arc welding device for extremely narrow groove

Technical Field

The invention relates to an ultra-narrow groove submerged arc welding method and an ultra-narrow groove submerged arc welding device.

Background

Submerged arc welding (Submerged arc welding: SAW) is commonly used for butt welding of thick and extremely thick plates in large-sized steel structures such as pressure vessels due to its high welding efficiency and high quality. When welding thick and extremely thick plates with SAW, in order to prevent welding defects such as fusion failure (LF), it is necessary to extend the groove angle to 30 °. However, if the bevel angle is wide, the necessary welding cross-sectional area increases, and a large amount of time is required until the welding ends due to the lamination of the weld beads.

In contrast, in the case of a narrow groove SAW in which the groove angle is 1 to 3 ° and the root width is narrowed, the necessary welding cross-sectional area is reduced, and a reduction in welding time can be expected. With respect to the narrow groove SAW, some research and development has been conducted so far. In recent years, a very narrow groove SAW in which a very thick plate to be welded is laminated in one layer from the initial layer to the final layer of a weld bead by setting the groove angle to be approximately 0 ° and the groove width to be 18mm or less has been studied.

In one-layer construction, it is necessary to melt both groove walls in one step, but the corners of the groove bottom are not easily melted due to the fact that they are not easily heated directly by arc plasma, heat is easily diffused, and fusion failure is easily generated. In addition, if the groove is narrowed, the slag does not peel off naturally after welding, and it becomes difficult to remove. If slag adheres to the groove wall in the event of undercut, slag can be trapped if it is not sufficiently removed. In order to prevent the above-described welding defect, it is necessary to select welding conditions under which a weld portion shape that does not cause undercut is formed in a state where both groove walls are melted. However, the range of welding conditions and aiming positions of the welding gun, that is, the range of appropriate welding conditions is narrow. Further, since the range of suitable welding conditions is narrow, the groove width and the aiming position of the welding gun may be changed by variations in welding (such as a change in groove width and a deviation in operation of the apparatus), and a defect may be generated suddenly under the welding conditions where the defect is not generated originally.

On the other hand, in recent years, a large-capacity welding power supply capable of digital waveform control has been developed, in which stability and reproducibility of output are improved as compared with the conventional movable iron core, and an output waveform can be controlled more precisely with respect to EN ratio, frequency, phase difference, and the like. For example, the welding cross-sectional area, which is the feeding speed of the wire, can be controlled by the EN ratio. In this way, in the digital waveform control power supply, the welding shape can be controlled by using parameters such as the EN ratio, and in the extremely narrow groove SAW, it is expected to prevent welding defects such as fusion failure and undercut.

On the other hand, as known techniques, JPS63-30175A (1988) and JPH6-75787B (1994) are disclosed. Among them, JPS63-30175a describes an apparatus for automatically performing left-right tracking and up-down tracking on a weld line. According to the device, aiming position of the welding gun can be automatically followed according to the change of the groove shape. JPH6-75787B discloses a welding method using an algorithm that formulates the weld bead shape at the time of lamination based on the weld bead cross-sectional height and the deposited cross-sectional area, determining the gun sight position for each layer.

However, according to the description of JPS63-30175a, since the welding conditions cannot be optimized for the variations in welding, welding defects occur in one-layer construction. According to JPH6-75787B, the welding conditions cannot be optimized for variations in welding because only the aiming position of the welding gun is determined for the inputted welding conditions without corresponding to one-layer construction.

Disclosure of Invention

Accordingly, an object of the present invention is to solve the above-described problems and to obtain a welding method and a welding apparatus based on an algorithm for controlling a welding condition and a gun sight position that do not cause a welding defect with respect to a variation in welding in an extremely narrow groove SAW.

In order to achieve the above object, the present invention provides an ultra-narrow groove submerged arc welding method, characterized in that a flat plate overlay welding is performed on the same raw material as a welding object under predetermined welding conditions, and a bead width W at the time of the flat plate overlay welding is measured _B And a welding cross-section area A _R A welding heat input Q is obtained from the welding conditions, and the welding heat input Q and the bead width W are used _B And the distance L between the welding gun and the groove wall represents the heat input H to the groove wall during welding _G Using the welding cross-sectional area A _R And the distance L between the welding gun and the groove wall represents a generalized distance R from the surface of the molten pool to the corner of the groove bottom at the aiming position of the welding gun, and the heat input H _G And H formed by distance R _G On the R plane, a display of the presence or absence of fusion failure at the time of groove welding obtained by the test is indicated, and a display of the presence or absence of fusion failure at the time of groove welding is indicated _G And drawing a judgment line based on the presence or absence of fusion failure in the groove wall on the R plane, and performing groove welding by setting welding conditions so that the judgment line becomes a region without fusion failure.

Thus, submerged arc welding with extremely narrow grooves can be performed without causing fusion failure.

The submerged arc welding method for extremely narrow grooves according to the present invention preferably uses a welding heat input Q and a bead width W _B And the difference between the welding gun and the groove wall L (W) _B -L) represents the heat input H to the bevel wall during welding _G 。

Furthermore, in the submerged arc welding method for extremely narrow grooves according to the present invention, the welding cross-sectional area A is preferably used _R Divided by the distance L between the welding gun and the groove wall (A) _R L), and the distance L between the welding gun and the groove wallAnd, the distance R from the surface of the molten pool to the corner of the groove bottom at the aiming position of the welding gun is shown.

Further, according to the ultra-narrow groove submerged arc welding method of the present invention, it is preferable that the welding conditions are set so that the measured distance L between the welding gun and the groove wall is within an appropriate range where no welding defect occurs, by measuring the distance L between the welding gun and the groove wall during groove welding.

Further, according to the submerged arc welding method for an extremely narrow groove of the present invention, at least one of EN ratio, welding current, voltage, and welding speed, which is a welding condition at the time of groove welding, is preferably controlled.

The submerged arc welding device with an extremely narrow groove is provided with a digital welding power source which can set and change the set values of EN ratio, welding current and voltage.

Thus, according to the method of the present invention, a device capable of performing welding without causing fusion failure can be obtained.

The submerged arc welding apparatus for an extremely narrow groove according to the present invention preferably includes a moving device that moves the welding gun in a direction orthogonal to the welding line direction to adjust the distance L between the welding gun and the groove wall.

Thus, when the aiming position of the welding gun deviates, the deviation can be corrected.

According to the present invention, even when the groove width varies during welding, submerged arc welding with an extremely narrow groove can be performed without causing fusion failure.

Drawings

Fig. 1 is a view showing a good molten state when submerged arc welding is performed on a narrow groove.

Fig. 2 is a view showing a state in which a welding failure occurs in a corner portion when submerged arc welding is performed on a narrow groove.

Fig. 3 is a view showing a state in which undercut is generated in a groove wall when submerged arc welding is performed on a narrow groove.

Fig. 4 is a diagram showing a test apparatus for observing the occurrence of a welding defect.

FIG. 5 shows the root width W _B Macro of weld section at the value of (2)And (5) observing a graph of the test result.

Fig. 6 is a diagram showing a relation between the bead height h and the penetration depth D.

FIG. 7 shows the root width W _R And the relation between the weld bead height h and the penetration depth D.

Fig. 8 is a graph showing the result of a macroscopic test of the cross section of the welded portion at each welding gun aiming position P.

Fig. 9 is a diagram illustrating a relationship among the gun sight position P, the bead height h, and the penetration depth D.

Fig. 10 is a diagram showing a relationship among the gun sight position P, the bead height h, and the penetration depth D.

Fig. 11 is a view showing a distance L between the welding gun and the groove wall.

FIG. 12 is a graph showing the distance L between the welding gun and the groove wall and the molten area A at the groove wall _G Is a graph of the relationship of (1).

FIG. 13 is a view showing the distance L between the welding gun and the groove wall and the melting width W at the groove wall _G Is a graph of the relationship of (1).

FIG. 14 is a graph showing "L+W" derived from FIG. 13 _G A graph of the relationship with "L".

FIG. 15 is a graph showing "L+W" derived from FIG. 13 _G Another plot of the relationship with "L".

FIG. 16 is a graph showing "L+W" derived from FIG. 13 _G A further graph of the relationship with "L".

FIG. 17 is a graph showing "L+W" derived from FIG. 13 _G Still another plot of the relationship with "L".

Fig. 18 is a view showing a state of formation of a molten pool in arc welding.

Fig. 19 is another view showing a state of formation of a molten pool in arc welding.

Fig. 20 is a further view showing a state of formation of a molten pool in arc welding.

Fig. 21 is a further view showing a state of formation of a molten pool in arc welding.

Fig. 22 is a diagram showing a state of heat input in submerged arc welding with an extremely narrow groove.

Fig. 23 is a view illustrating a distance from the surface of the molten pool to the corner of the groove bottom.

FIG. 24 shows heat input H to the groove wall _G Square r of distance ² And a diagram of a determination result of a fusion failure LF in groove welding.

Fig. 25 shows the heat input H to the groove wall _G Square r of distance ² A graph of the determination result of the fusion failure LF in groove welding is shown as a graph of the distance L between the welding gun and the groove wall.

FIG. 26 shows the heat input H to the groove wall _G Square r of distance ² A graph of the determination result of the fusion failure LF in groove welding indicates a distance L between the welding gun and the groove wall when the heat input amount Q changes.

Fig. 27 shows heat input H to the groove wall _G Square r of distance ² Weld bead width W is indicated on a graph of a determination result of fusion failure LF in groove welding _B And (3) a diagram of the distance L between the welding gun and the groove wall during change.

Fig. 28 shows the heat input H to the groove wall _G Square r of distance ² The welding cross-sectional area A is marked on the graph of the determination result of the fusion failure LF in groove welding _R And (3) a diagram of the distance L between the welding gun and the groove wall during change.

Fig. 29 shows a heat input H to the groove wall _G In the case where the horizontal axis is defined as the generalized distance R from the surface of the molten pool to the corner of the groove bottom and the vertical axis is defined as the generalized distance R, a diagram of an example of a poor fusion judgment model in the case of extremely narrow groove welding is shown.

Fig. 30 is a view showing a distance L between the welding gun and the groove wall in fig. 29.

Fig. 31 shows a welding cross-sectional area a in fig. 29 _R And (3) a diagram of the distance L between the welding gun and the groove wall during change.

Fig. 32 is a view showing a distance L between the welding gun and the groove wall when the heat input amount Q is changed in fig. 29.

Fig. 33 shows a bead width W in fig. 29 _B And (3) a diagram of the distance L between the welding gun and the groove wall during change.

Fig. 34 is a view showing an extremely narrow groove submerged arc welding apparatus according to an embodiment of the present invention.

Fig. 35 is a diagram showing a flow of a welding process using the welding apparatus of fig. 34.

Detailed Description

The present invention has been completed based on a test method. The present invention will be described in detail below with reference to this test method.

Fig. 1 to 3 show the submerged arc welding of a narrow groove. Here, groove wall 11, groove bottom 12, groove bottom corner 13, root width W of the groove are shown _R I.e. the distance between the walls 11, the melting tank 14. Among them, fig. 1 shows a good molten state. That is, the groove wall 11, the groove bottom 12, and the corner 13 are melted to an appropriate depth, respectively. In contrast, fig. 2 shows a state in which a fusion failure LF occurs in the corner portion 13. Fig. 3 shows a state in which undercut 15 is generated in groove wall 11 on the right side in the drawing.

(test)

The weld defects are expected to be received by the root width W shown in FIGS. 1-3 _R The aiming position P of the welding gun, namely the root width W _R The influence of the position of the welding torch in the direction of (a). Therefore, in order to evaluate the root width W _R And the effect of the change in the aiming position P of the welding gun on the welding defect, and groove welding is performed by a single welding gun. And judging welding defects under each welding condition, and measuring the welding bead height h and the penetration depth D. In addition, a flat plate overlay welding (bead on plate welding) is also performed in order to compare the shape of the welded portion with that at the time of groove welding. In order to produce a poor fusion judging model from the obtained result, a single welding gun and a tandem welding gun are adopted, and the welding bead width W is set _B And a welding cross-section area A _R Plate build-up welding was performed under varying welding conditions, and the bead width W was measured under each welding condition _B And a welding cross-section area A _R . Then, groove welding was performed under the welding conditions described above, and fusion failure was determined.

An outline of the test apparatus used is shown in fig. 4. Fig. 4 shows the configuration of the apparatus when the tandem welding gun performs the groove welding, and shows the

welding guns

16 and 17, the carriage 18 for moving the

welding guns

16 and 17, the feeder 19 for the welding wire, and the welding power source 20. The welding power supply 20 uses digital waveform controlAnd a power supply. The material of the test body 21 was 2 ¹ / ₄ Cr-1Mo steel. In order to simulate an extremely narrow groove in groove welding, 1 pair of materials having a length of 400mm×width of 70mm×thickness of 30mm were interposed between each other to form a test body 21, and an insert 24 having a length of 400×width w (a plurality of different sizes were prepared) ×thickness of 25mm was interposed therebetween to form a test body having a groove angle of 0 ° and a groove depth of 20 mm. A water-cooled copper plate 22 is provided on the side of the test body so that the bevel test body has a cooling rate equivalent to that of a large steel structural member. In addition, in order to suppress deformation at the time of welding, a positioning plate 23 is mounted. Arrow 25 indicates the welding direction. Preheating, the temperature between the channels is 200-250 ℃, and post heat treatment is not implemented. For the flat plate overlay welding, a flat plate test body having a length of 400mm×a width of 70mm×a plate thickness of 20mm was used. A wire and a flux corresponding to JIS Z3183S 642-2CM were used. Various test conditions were employed, but for easy understanding of the welding phenomenon, a single welding gun with a single electrode was used, with a welding gun angle of 0 ° (vertical). The welding conditions were "reference conditions" of rectangular wave having an EN ratio (negative current to alternating current ratio) of 0.5, welding current 600A, welding voltage 33V, welding speed 30cm/min, CTWD (Contact Tip to Work Distance: contact tip to work distance) of 30 mm. By varying the width W of the insert, the root width W is thereby made _R In W _R =8 to 18 mm. Regarding the welding gun aiming position P, the position of the center of the groove was set to 0mm, and varied in a range of 1 to 3mm in a direction orthogonal to the welding line direction.

In the test, a single welding gun or a tandem welding gun with 2 electrodes arranged in series was assumed in the operation. The electrode angle was set to 0 ° in the single welding gun, 0 ° in the tandem welding gun, and 15 ° in the rear electrode. The interval between the tandem welding guns was set to 15mm. The welding conditions are respectively changed according to the EN ratio of 0.0-1.0, the welding current of 400-800A, the voltage of 20-40V, the welding speed of 30-43 cm/min (single welding gun) and 60-81 cm/min (serial welding gun). CTWD was constant at 30mm. Root width W of groove test body _R The welding gun aiming position P was set to 0mm and 14 mm.

For each result of the plate build-up welding and the groove welding, a macroscopic test of a weld section for confirming the shape of the weld was performed, and the measurement was performedWidth W of weld bead _B And a welding cross-section area A _R . The test position is a position separated by 100mm or more from the welding start position and the end position as the welding stabilizing portion.

(test results)

To evaluate the root width W _R Effect of weld defects, root width W was set to the above reference conditions (EN ratio 0.5, welding current 600A, voltage 33V, welding speed 30 cm/min) _B Varying in the range of 8 to 18 mm. FIG. 5 shows the root width W _B Macroscopic test results of the weld section at the value of (2). The gun sight position was constant at p=0 mm. The results of the plate build-up under the same conditions are also shown in FIG. 5. At the root width W _R When 8mm, no fusion failure occurred, but both wall surfaces of the groove were largely melted, and undercut occurred. Slag adheres to the undercut and cannot be removed. At the root width W _R When 12 to 15mm, a good welded portion was obtained in which no undercut and no fusion failure occurred. At the root width W _R When =16 mm, the groove wall on one side (left side in the drawing) melts, while the groove wall on the opposite side (right side in the drawing) does not melt, and is a fusion failure, and slag cannot be removed. At the root width W _R When the thickness was 18mm, both wall surfaces were not melted, and the weld toe portions on both sides were not able to remove slag. At the root width W _R When the welding distance is 18mm, the welding distance is equal to the welding bead width W in the plate surfacing _B Root width W compared to (about 26.5 mm) _R Smaller (18 mm), but the groove wall did not melt.

Next, the height of the weld metal deposit from the bottom of the groove (bead height h) and the depth of penetration from the bottom of the groove into the base material (penetration depth D) at the welding gun aiming position P were evaluated. Their relationship is shown in fig. 6. Here, a welding gun 28 and a welding wire 29 are illustrated. Root width W _R The relationship between the bead height h and the penetration depth D is shown in fig. 7. The welding cross-sectional area is constant under the same welding conditions, but the width W of the root part _R When the width becomes wider, the bead height h becomes lower, at W _R When 12mm or more, the bead height h becomes substantially constant. On the other hand, the penetration depth D is the root width W _R Shallowest when=8mm, at rootWidth W of the part _R Become deeper when widened, at root width W _R When the length is=14 mm or more, the length becomes constant.

To evaluate the influence of the aiming position P of the welding gun on the welding defect, the width W of the root part without the welding defect is measured _R Test body=14 mm, and the gun sight position P was varied by 0 to 3mm under the above reference conditions. The results of the macroscopic test of the cross section of the weld at each gun sight P are shown in fig. 8. In the cross section of the welded portion shown in fig. 8, the direction from the center of the groove to the right is taken as the positive direction of the welding gun aiming position P. In the range of the gun sight position p=1 to 2mm, the shape of the welded portion is biased toward the sight shift direction (right side), but no welding defect occurs. On the other hand, when p=3 mm, the groove wall on the side far from the welding gun is not melted, and a fusion failure LF occurs. On the other hand, on the side where the welding gun 28 shown in fig. 6 approaches, the groove wall melts over a wide range, undercut is generated, and slag cannot be removed. Fig. 9 and 10 show the relationship among the gun sight position P, the bead height h, and the penetration depth D. The bead height h and penetration D are values directly below the gun sight position P. In the range of the welding gun aiming position p=0 to 2mm, even if the size of the welding gun aiming position P varies, the values of the welding bead height h and the penetration depth D do not change. In contrast, when the welding gun aiming position p=3 mm, both the weld bead height h and the penetration depth D become large.

(production of fusion failure determination model)

(conditions for the distance L between the welding gun and the groove wall for preventing welding defects)

As can be seen from the above test results, the welding defect is received by the root width W _R And the effect of the gun sight position P. If the root width W is _R And the value of the welding gun aiming position P is changed, the distance between the welding gun and the groove wall is changed. Namely, root width W _R The relationship with the gun sight position P can be expressed by the distance L between the gun and the groove wall shown in fig. 11. In fig. 5 and 8, since undercut is generated by excessive melting of the groove wall and gouging, it is considered that there is a correlation between the undercut and the melted area of the groove wall. Here, the molten area of the groove wall (when the cross-sections shown in fig. 5 and 8 are shownArea of appearance) is defined as A _G (see FIG. 12). As described above, the fusion defect LF of the groove welding is likely to occur at the corner 13 of the groove bottom. That is, it is considered that the welding condition in which the groove wall is melted greatly is more likely to prevent the poor welding LF. Here, the width (penetration) of the groove bottom from the corner 13 to the groove wall side is defined as W _G . FIG. 12 shows the melting width W at the groove wall under the above-mentioned reference conditions (EN ratio 0.5, welding current 600A, voltage 33V, welding speed 30 cm/min) _G And the melting area A is measured under the condition that the aiming position P of the welding gun is changed _G As a result of (a). FIG. 13 shows the measurement of the melting width W under the same conditions _G As a result of (a). The above measurement results each show the results of measurement at the left and right groove walls. Note that the difference was good (see), undercut (Δ) and poor LF (x). As shown in fig. 12, if the distance L between the welding gun and the groove wall becomes small, the molten area a _G The melting area A at the L=4mm position generating undercut is increased _G Up to 30mm ² The above. Further, as shown in FIG. 13, the melting width W at the groove wall _G Becomes maximum when the distance l=5 to 6mm between the welding gun and the groove wall, decreases when the distance L between the welding gun and the groove wall becomes further large, and becomes W _G A fusion failure LF was generated when=0 mm. As described above, if the distance L between the welding gun and the groove wall becomes small under the same welding conditions, undercut is likely to occur, and the fusion width W at the groove wall becomes large _G And (3) reducing. On the other hand, if the distance L between the welding gun and the groove wall is too large, the groove bottom cannot be sufficiently melted, and a poor fusion LF occurs. Namely, in the extremely narrow groove SAW under the above reference condition, the distance L between the welding gun and the groove wall for preventing the welding defect is in the range of 4 < L.ltoreq.7.5 mm.

(influencing factor on poor fusion LF)

As shown in fig. 13, the melting width W at the groove wall _G The distance l=5 to 6mm between the welding gun and the groove wall becomes extremely large, and L decreases as L becomes further large. Here, the width W of the weld bead during the build-up welding from the flat plate _B And the melting width W at the groove wall _G The effect of the groove wall on the weld shape is considered. FIGS. 14 to 17 show"L+W" derived from FIG. 13 _G Relationship with "L". As undercut is generated when L is less than or equal to 4mm, the L is more than or equal to 4 mm. In fig. 14, x is the occurrence of the fusion failure, which is no fusion failure LF. "L+W _G "is the width of the groove bottom and indicates how much the groove can be melted in the width direction of the groove. At L+W _G In the range of > L, a good weld portion with no fusion failure LF is obtained.

In fig. 14, the direction along the horizontal axis is divided into three regions, "region (a)", "region (b)", and "region (c)". Here, if the bead width W at the time of the plate build-up welding is considered _B Then the area (a) is W _B As shown in FIG. 15, the region of +2.ltoreq.L corresponds to the bead width W _B The distance L between the welding gun and the groove wall is larger, so the groove wall is far away from the aiming position P of the welding gun, and the welding bead width W is the same _B Is approximately the same as a flat plate overlay. Namely, L+W _G ＝W _B And/2, becomes a fusion failure LF. The area (b) is 7.5mm < L < W _B As shown in fig. 16, although the distance L between the welding gun and the groove wall is smaller than the bead width, the groove wall cannot be melted, and a fusion failure LF occurs. Compared with the plate overlaying, the heat in the groove welding is easy to diffuse, so that the groove wall is not easy to melt. The area (c) is an area with L being more than or equal to 4mm and less than or equal to 7.5mm, and the distance L between the welding gun and the groove wall is smaller. In this region, sufficient heat is transferred from the welding gun to the groove wall, so that the groove wall melts as shown in fig. 17. Thus, L+W _G > L, no fusion failure LF was generated.

However, as shown in fig. 13, when the distance between the welding gun and the groove wall is l=4 mm smaller than l=5 mm, the melting width W at the groove wall is _G And (3) reducing. L=4 mm is the root width W in fig. 7 _R Case=8 mm, and in fig. 10, case where the gun sight position p=3 mm. In either case, the bead height h increases and the penetration D decreases. On the other hand, the sum of the bead height h and the penetration depth D immediately below the aiming position of the welding gun is independent of the root width W _R And a gun sight position P.

In arc welding, as shown in fig. 18 and 19, arc 3 is used The arc force 32 of 1 balances the downward force of the molten pool 14 with the potential 33 of the molten metal due to gravity, thereby forming the molten pool 14. In a narrow groove having a narrow root width, the potential head 33 of the molten metal is larger than the arc force 32, and a preceding phenomenon of the molten metal (a phenomenon in which the molten metal greatly bulges on the surface of the molten pool immediately below the arc, and the heat input by the arc cannot reach the bottom of the groove) is likely to occur. In fig. 7 and 10, the width W at each root _R And the reason why no difference is observed in the sum of the bead height h and the penetration depth D at the gun sight position P is that the arc force 32, which is proportional to the square of the welding current, becomes strong. Therefore, if the bead height h increases immediately below the aiming position of the welding gun, the force of pressing down the molten pool 14 and the potential head 33 are balanced at a position higher than the groove bottom 12 of the groove (fig. 20 and 21). As a result, it is considered that the arc plasma is far from the groove wall (particularly, the corner 13 of the groove bottom), and therefore, the arc plasma cannot be sufficiently heated, and the melting width W at the groove wall is considered to be _G And (3) reducing. Therefore, in order to prevent the fusion failure LF, it is necessary to reduce the distance L between the welding gun 28 and the groove wall and the bead height h so that the distance between the welding gun and the corner 13 of the groove bottom does not become large.

(welding condition Range where welding defects are not generated)

(fusion failure determination model)

The range of the distance L between the welding torch and the groove wall (4 mm < L.ltoreq.7.5 mm) in FIGS. 11 to 13, in which no welding defect occurs, is the result of the above-mentioned reference conditions (EN ratio 0.5, welding current 600A, voltage 33V, welding speed 30 cm/min). In this regard, if the welding conditions are changed, the shape of the welded portion changes, and particularly, the poor fusion LF is susceptible to the welding conditions. In order to select a range of conditions for preventing the fusion failure LF for various welding conditions, it is generally necessary to conduct a very large number of experiments. However, in the present invention, a model for determining conditions for preventing fusion failure LF in a very narrow groove SAW was prepared based on the test results of the flat plate build-up welding.

That is, it is known from the above examination that the cause of the defective fusion LF in the extremely narrow groove SAW is a decrease in the amount of heat transferred from the arc to the groove wall. That is, it is important how much heat is input in the welding, and how much the heat input is delivered over a wide range. If welding current IA, welding voltage V, welding speed V cm/min are used, welding heat input Q kJ/mm is calculated from the following equation (1).

Q＝I×V×60/(v×10)×1/1000 (1)

Here, the weld bead width in the weld heat input is Q and the plate overlay is W _B In the case of the welding conditions of (2), the welding heat input Q can be considered to be applied to the bead width W _B Is not limited in terms of the range of (a). At this time, in the extremely narrow groove SAW under the same conditions, as shown in FIG. 22, considering the half-time heat input Q/2 of the welded portion, it is put on the one side W _B Range of/2. At this time, when the groove wall is located at a position separated from the arc plasma as a heat source by L (distance between the welding gun and the groove wall), the heat transferred to the groove wall is W _B 2-L. As heat input H to the groove wall _G [kJ/mm·mm]Is defined by the following expression (2). In this case, the heat input by the arc is gaussian, and the temperature of the molten pool is maximized immediately below the aiming position of the welding gun and becomes low as it goes toward the end of the molten pool.

H _G ＝Q/2(W _B /2-L) (2)

Another cause of the fusion failure is an increase in the bead height h. If the bead height h increases, the distance from the arc plasma to the corner of the groove bottom becomes longer, and the corner cannot be sufficiently heated. Here, the welding cross-sectional area a in the flat plate welding is used _R [mm ² ]And the distance L between the welding gun and the groove wall, the welding bead height h [ mm ] of the melting tank when the groove SAW is extremely narrow is expressed by the following expression (3) ]。

h＝A _R /2L (3)

If the molten pool surface at the aiming position of the welding gun is set as the origin, the distance from the origin to the corner of the groove bottom is represented by the following equation (4) using the welding track height h and the distance L between the welding gun and the groove wall ² (FIG. 23).

r ² ＝h ² +L ² (4)

H to be calculated by equation (2) _G And r calculated by the expression (4) ² As parameters that affect the generation of the fusion failure LF, a determination model was created. In order to make H _G And r ² Varying in bead width W _B And a welding cross-section area A _R Plate overlaying was performed under different welding conditions, and the bead widths W under each welding condition were measured _B And a welding cross-section area A _R . Then, groove welding was performed under these welding conditions, and the presence or absence of occurrence of fusion failure LF was determined. The test methods and the shape of the test body are as described above. Furthermore, root width W of groove test body _R The distance L between the welding gun and the groove wall is set to be constant, wherein the distance L is 14mm, the aiming position P is 0mm, and the distance L is 7 mm.

FIG. 24 shows the bead width W according to each welding condition _B And a welding cross-section area A _R Calculated heat input H to groove wall _G Sum of squares r of distance ² And a determination result of a fusion failure LF in groove welding. Note that there was no fusion failure (good), fusion failure at the groove wall on one side (o), and fusion failure at the groove wall on both sides (x). H representing the transverse axis _G The greater the value of (2), the greater the welding heat input to the groove wall and the r representing the longitudinal axis ² The greater the value of (c), the greater the distance between the heat source and the corner of the groove bottom. In FIG. 24, for example, at the same r ² ＝70mm ² H when comparing under left and right conditions _G When =0.8 kJ/mm·mm, a fusion failure LF is generated at the groove wall on both sides, and H _G Under the condition of =12.5 kJ/mm·mm or more, no fusion failure LF was generated. Namely, it can be said that H _G The larger the condition is, the more difficult the generation of the fusion failure LF is. In addition, at the same H _G When comparing under the condition of about 10 kJ/mm.mm, r ² ＝75mm ² A fusion failure LF is generated at the groove wall on one side, and r ² ＝63mm ² No fusion failure LF was generated at that time. That is, it can be said that the heat input H to the groove wall is for each _G There is a square r of the distance that does not generate a fusion failure LF ² Is not limited to the limit value of (2). As shown in fig. 24Bead width W obtained from plate build-up welding _B And a welding cross-section area A _R Deriving heat input H to groove wall _G Sum of squares r of distance ² The determination condition of the fusion failure LF can be obtained.

FIG. 25 shows the fusion width (penetration) W of the groove under each welding condition _G Is a measurement of (a). The darker the color of the mark, the lower the brightness, then the W is represented _G The larger. Width of fusion W here _G Is the average value at the two groove walls. The condition for the two sides to become a fusion failure LF is W _G =0mm, the condition that one side becomes a fusion failure LF is W _G A smaller value of =0.1 to 0.3 mm. On the other hand, the condition that no fusion failure LF is generated is W _G Values of =0.3 mm or more. Furthermore, if heat input H to the groove wall _G The square r of the distance becomes larger ² Becomes smaller, the melting width increases to W _G ＝0.9mm。

(distance L between welding gun and groove wall without causing poor fusion)

As described above, the range L between the welding torch and the groove wall, in which no welding defect occurs, can be determined (4 mm < L.ltoreq.7.5 mm) under the standard conditions (EN ratio 0.5, welding current 600A, voltage 33V, welding speed 30 cm/min). However, this is a range under the reference conditions, and if the welding conditions are changed, the range of the distance L between the welding gun and the groove wall, in which the welding defect does not occur, is also changed. Accordingly, the influence of the distance L between the welding gun and the groove wall is evaluated on a poor fusion judgment model, and the range of the distance L between the welding gun and the groove wall, in which poor fusion does not occur, is determined from the model.

Fig. 25 shows a distance L between the welding gun shown in fig. 13 and the groove wall. In fig. 25, the signs are good (+), undercut (+), poor fusion at one side of the groove (+), and poor fusion at both sides of the groove (x). Using the above formulas (2) and (4), 1/L in the range of L > 4mm ² Since the influence of the term is small, the shape of the model becomes a shape close to a substantially quadratic curve when L is changed on the determination model. In the above test, as shown in fig. 13, the melting width W is l=5 to 6mm _G =1.5 mm, becomes extremely large,in this case, no fusion failure occurred. However, as L becomes larger than the range, W _G When l=8mm, poor fusion occurs on one side of the groove, and when l=9mm, poor fusion occurs on both sides of the groove. In addition, although no fusion failure occurred when l=4mm, the melting width W _G And (3) reducing. If the test result is compared with the judgment model, r is the value when L=5-6 mm on the judgment model ² Becomes extremely small, marked at W _G The larger area was determined to be free from fusion failure. In contrast, as L becomes larger than the above range, heat input H to the groove wall _G Reduced, square r of distance ² Increase, indicated at W _G If l=8 mm or more in the smaller area, the fusion failure is determined. On the other hand, when the distance l=4mm between the welding gun and the groove wall, heat input H to the groove wall is performed _G Increasing, but correspondingly the square r of the distance ² Also increase, mark near W _G Smaller area (poor fusion side). As described above, the test result of changing L coincides with the result of the determination model. By using the produced determination model, the range of L in which no fusion failure occurs can be calculated.

The range of the distance L between the welding gun and the groove wall corresponding to the welding condition is determined by using the judging model. According to the test result, the weld bead width W is under the above reference condition _B 26.5mm, deposited cross-sectional area A _R ＝64.6mm ² . Further, according to the expression (1), the heat input amount q=4.0 kJ/mm. In arc welding, since the bead width and the deposited cross-sectional area are proportional to the welding heat input, it is difficult to change only the respective values. On the other hand, as described above, in the case of using the digital waveform control power source, the welding cross-sectional area a can be made constant in the state of welding heat input according to the EN ratio _R Varying by a degree of + -20%. Therefore, the digital waveform control power supply is used to control the heat input quantity Q and the weld bead width W _B Cross-sectional area A of welding _R The range of the individual change is set as + -20%, the shape of the welded part is changed from the reference condition, and the heat input H to the groove wall at the distance L between each welding gun and the groove wall is calculated _G Sum of squares r of distance ² Is a value of (2). FIGS. 26 to 28 show the resultsMarked on the decision model. In this case, the heat input amount Q or the bead width W _B Under the smaller condition, the whole curve is shifted to the left, and the range of L without generating poor fusion LF is reduced to be more than or equal to 5mm and less than or equal to 6mm. On the other hand, in the heat input quantity Q or the weld bead width W _B Under the larger condition, when the curve is shifted to the right side, the fusion defect does not occur when L is more than or equal to 4mm and less than or equal to 7.5mm (FIG. 26 and FIG. 27). At the welding cross-section area A _R Under the condition of smaller curve, the whole curve is displaced downwards, no poor fusion LF is generated when L is more than 4mm and less than or equal to 7.5mm, and the fusion area A is the same as that of the welding area _R Under large conditions, the entire curve is displaced upward, and fusion failure occurs at any L (fig. 28). As described above, by using the determination model, it is possible to obtain the weld bead width W and the heat input amount Q in the flat plate build-up welding _B Cross-sectional area A of welding _R An appropriate welding condition range in the extremely narrow groove SAW and a range of L corresponding to the welding condition range are determined. Further, if the heat input amount Q and the bead width W are increased _B Reducing the welding cross-sectional area A _R By shifting the curve downward to the right on the determination model, the range of the distance L between the welding gun and the groove wall, in which no fusion failure occurs, can be expanded.

(generalization)

The above expression (2) can be generalized and rewritten as follows.

H _G ＝C1×Q(C2×W _B -L)(2a)

Namely H _G Can use Q and (W) _B -L) product representation. In the formula (2 a), C1 is an arbitrary number, and C2 may be an arbitrary number within a range of 0.5.ltoreq.C2.ltoreq.1.

The above expression (4) can be substituted by expression (3) in a broad sense and rewritten as follows.

R＝(A _R /L) ^C3 +(L) ^C3 (4a)

R is a generalized distance from the surface of the molten pool to the corner of the groove bottom, and as shown in the formula (4 a), it is possible to use (A) _R The sum of the exponentiation of/L) and the exponentiation of (L). C3 may be any number in the range of 0 < C3 < 5.

FIG. 29 shows heat applied to the groove wallInput H _G An example of a poor fusion judgment model at the time of very narrow groove welding was set up with c1=1, c2=0.5, and c3=1 on the basis of the horizontal axis and the distance R from the surface of the molten pool to the corner of the groove bottom as the origin as the vertical axis. As in the case of fig. 24, if the fusion failure is lower than the determination line indicated by the broken line, the fusion failure is not generated, and if the fusion failure is higher than the determination line. In fig. 29, from the test results, the determination line was obtained by the least square method from the results of partial fusion failure and fusion failure. The determination line may be obtained by other suitable methods.

Repeating the above process to obtain the width W of the weld bead uniquely according to the welding conditions _B And a welding cross-section area A _R . In this case, the distance L between the welding gun and the groove wall may always change due to a change in welding. For example, the width W of the weld bead _B 26.5mm, deposited cross-sectional area A _R ＝64.6mm ² If only L is changed, the fusion failure determination model is shown by a solid line in fig. 30. Here, too, in the range of l=4 to 7.5mm, no fusion failure occurs, whereas in the case of L of 8mm or more, fusion failure occurs. In fig. 30, l=8mm is present substantially on the determination line, and thus becomes a fusion failure.

FIG. 31 shows that only the welding cross-sectional area A is changed under the above conditions _R And a state of defective fusion at the time of judgment. Here, in the welding cross-sectional area a _R ＝77.4mm ² In the range of l=4 to 7mm, and a is _R ＝64.6mm ² Under the condition of L=4 to 7.5mm, and then A _R ＝51.7mm ² Under the conditions of l=4 to 8mm, no fusion failure occurs.

In this way, by always controlling the welding conditions so that the distance L between the welding gun and the groove wall, which varies during welding, is lower than the determination line on the determination model, it is possible to reliably prevent fusion failure.

Fig. 32 similarly shows a state of the fusion failure determination under the welding condition in which only the heat input amount Q is changed. Here, it was determined that no fusion failure occurred in the range of l=4 to 8mm under the condition of q=4.8 kJ/mm, in the range of l=4 to 7.5mm under the condition of q=4.0 kJ/mm, and in the range of l=4 to 7mm under the condition of q=3.2 kJ/mm.

FIG. 33 shows the same after only the bead width W is changed _B And (3) a condition of defective fusion judgment under welding conditions. Here, W is _B In the range of l=4 to 9mm under the condition of=32.0 mm, in addition to W _B Under the condition of 26.5mm, the length is in the range of L=4 to 7.5mm, and further W is _B If the condition of =21.0 mm is in the range of l=4 to 6mm, it is determined that no fusion failure has occurred.

(welding device)

Fig. 34 shows an extremely narrow groove submerged arc welding apparatus according to an embodiment of the present invention. Here, a welding torch 42 having a single torch structure and a welding target 41 are shown. The welding torch 42 is mounted on the traveling carriage 43, and is movable in a welding direction 45 along a longitudinal direction of an extremely narrow groove 44 provided in the welding target 41. The welding gun 42 is mounted on a one-axis slider 46, so that the position of the welding gun can be adjusted in the width direction of the extremely narrow groove 44. The laser sensor 47 is integrated with the welding torch 42, and thereby moves in the width direction of the extremely narrow groove 44 together with the welding torch 42 by the one-axis slider 46. The laser sensor 47 recognizes the extremely narrow groove 44 at the front side of the welding site, and measures the current position of the welding gun 42 and the distance L from the welding gun 42 to the left and right groove walls ₁ 、L ₂ . In fig. 34, a digital welding power supply 48 and a control device (PC) 49 are shown. The control device 49 controls the width W of the weld bead under each welding condition _B And a welding cross-section area A _R The algorithm is stored as a database in advance, and is performed in the following

processes

1 and 2.

That is, in the process 1, the control device 49 is based on the measured distance L ₁ 、L ₂ A condition that does not become a fusion failure is selected from the fusion failure determination model, and the values of EN ratio, welding current, and voltage are instructed to the welding power supply 48, and the values of welding speed are instructed to the traveling carriage 43.

In process 2, the control device 49 sets the aiming position of the welding gun 42 to be the center of the groove (L ₁ ＝L ₂ ) And is also provided withL ₁ 、L ₂ The amount of movement Δl of the one-axis slider 46 to move the welding torch 42 is determined to be greater than 4 mm. That is, the control device 49 instructs the one-axis slider 46 of the difference between the current gun sight position and the target sight position as the movement amount, thereby controlling the gun sight position to be always appropriate.

It is appropriate that the welding conditions controlled by the digital welding power supply 48 be in the following ranges. Namely, EN ratio: 0.0 to 1.0, welding current: 400-800 [ A ], welding voltage: 20-40 [ V ], welding speed: 30 to 81[ cm/min ] is suitable.

(flow of welding)

A welding process using the welding apparatus of fig. 34 will be described with reference to the flowchart of fig. 35. If the process starts in step S11 in fig. 35, first, in step S12, data of the groove 44 of the welding target 41 is acquired by the laser sensor 47 in fig. 34. The acquired data acquired by the laser sensor 47 is transmitted to the control device 49, and the control device 49 acquires the distance L from the welding gun 42 to the left and right groove walls in step S13 ₁ 、L ₂ Is a data of (a) a data of (b). Then, in step S14, the control device 49 uses the above-described fusion failure determination model to obtain the distance L ₁ 、L ₂ And judging whether the fusion failure occurs under the condition of the data of (2).

When it is determined in step S14 that the fusion defect has occurred, in step S15, a new welding condition is selected as a welding condition change. Then, the selected result is received, and it is determined in step S16 whether or not the EN ratio to be set in the welding power supply 48 has been changed. When there is a change, the control device 49 controls the welding power supply 48 to change the set value of the EN ratio (step S17). If the set value of the EN ratio is not changed in step S16 and if the set value of the EN ratio is changed in step S17 in the welding power supply 48, it is then determined in step S18 whether or not there is a change in the welding current to be set in the welding power supply 48. If there is a change, the control device 49 controls the welding power source 48 to change the set value of the welding current (step S19). If the set value of the welding current is not changed in step S18 and if the set value of the current in the welding power supply 48 is changed in step S19, it is then determined in step S20 whether or not there is a change in the voltage to be set in the welding power supply 48. If there is a change, the control device 49 controls the welding power supply 48 to change the set value of the voltage (step S21). If the set value of the voltage is not changed in step S20 and if the set value of the voltage is changed in step S21, it is then determined in step S22 whether or not there is a change in the welding speed to be set in the traveling carriage 43. If there is a change, the control device 49 controls to change the set value of the movement speed of the traveling carriage 43, that is, the movement amount thereof (step S23).

In step S24, the control device 49 determines that no fusion failure has occurred based on the distance L obtained in step S13, in the case where there is no change in the welding speed in step S22, in the case where there is a change in the set value of the movement amount of the traveling carriage 43 in step S23, and in the case where it is determined that no fusion failure has occurred as a result of the determination in step S14 using the fusion failure determination model, as described above ₁ 、L ₂ Data determination L of (2) ₁ And L ₂ Whether equal. Upon judging as L ₁ And L ₂ If the steps are equal, the process returns to step S12, and the subsequent steps are repeated. Upon judging as L ₁ And L ₂ If the movement amounts are not equal, the control device 49 instructs the one-axis slider 46 to move the one-axis slider by the corresponding movement amount Δl so that L is equal in step S25 ₁ And L ₂ Equal. If the one-axis slider 46 moves the welding gun 42 by an amount ΔL such that L ₁ And L ₂ If the two steps are equal, the process returns to step S12 and the subsequent steps are repeated.

The influence of each of the above welding parameters will be described. If the EN ratio becomes large, the bead width W at the time of plate build-up welding _B Reduced welding cross-sectional area A _R And (3) increasing. Weld bead width W if welding current becomes large _B Cross-sectional area A of welding _R Are increased. If the voltage becomes high, the bead width W _B Increase the welding cross-section area A _R Is unchanged. Weld bead width W if welding speed becomes large _B Slightly reduced, depositedCross-sectional area A _R And (3) reducing.

Claims

1. A submerged arc welding method of an extremely narrow groove is characterized in that,

performing plate overlaying on the same raw material as the welding object under a preset welding condition, and measuring the welding bead width W during the plate overlaying _B And a welding cross-section area A _R ，

A welding heat input Q is determined from the welding conditions,

using the welding heat input Q and the welding bead width W _B And the distance L between the welding gun and the groove wall represents the heat input H to the groove wall during welding _G ，

Using the welding cross-section A _R And the distance L between the welding gun and the groove wall represents a generalized distance R from the surface of the molten pool to the corner of the groove bottom at the aiming position of the welding gun,

at the time of heat input H _G And H formed by distance R _G On the R plane, a display of the presence or absence of fusion failure at the time of groove welding obtained by the test is marked,

h indicating the presence or absence of fusion failure in the groove welding _G Drawing a determination line based on the presence or absence of fusion failure in the groove wall on the R plane,

welding conditions are set so that the determination line is a region free from fusion failure, and groove welding is performed.

2. The ultra-narrow groove submerged arc welding method according to claim 1, wherein the welding heat input Q and the bead width W are used _B And the difference between the welding gun and the groove wall L (W) _B -L) represents the heat input H to the bevel wall during welding _G 。

3. The submerged arc welding method of claim 1 or 2, wherein the welding cross-sectional area A is used _R Divided by the distance L between the welding gun and the groove wall (A) _R L), the sum of the exponentiation of the distance L between the welding gun and the groove wall,the distance R from the surface of the molten pool to the corner of the groove bottom at the aiming position of the welding gun is shown.

4. The ultra-narrow groove submerged arc welding method according to any one of claims 1 to 3, wherein the welding conditions are set so that the distance L between the welding gun and the groove wall is within an appropriate range that does not cause welding defects when the distance L between the welding gun and the groove wall is measured during groove welding.

5. The ultra-narrow groove submerged arc welding method according to any one of claims 1 to 4, characterized in that at least one of EN ratio, welding current, voltage and welding speed is controlled as a welding condition at the time of groove welding.

6. An ultra-narrow groove submerged arc welding apparatus for carrying out the ultra-narrow groove submerged arc welding method according to any one of claims 1 to 5, characterized in that,

The welding power supply is provided with a digital welding power supply, and the digital welding power supply can set and change the set values of the EN ratio, the welding current and the voltage.

7. The ultra-narrow groove submerged arc welding apparatus of claim 6, characterized by a moving means that moves the welding gun in a direction orthogonal to the welding line direction to adjust the distance L between the welding gun and the groove wall.

8. The ultra-narrow groove submerged arc welding apparatus according to claim 6 or 7, characterized by having a sensor for acquiring data of the groove before welding.