JP4707949B2 - Multi-electrode single-sided submerged arc welding method - Google Patents

Description

  The present invention relates to a highly efficient single-sided submerged arc welding method that uses three or four electrodes.

  Conventionally, as a high-efficiency welding method for thick steel plates, a single-sided submerged arc welding method has been actively applied mainly to shipbuilding. In recent years, the demand for further efficiency has increased, and a technique has been developed that enables welding at a high speed of 100 cm / min or more using three or more electrodes using a flux as a backing. For example, in Japanese Patent Application Laid-Open No. 6-254683, a direct current is passed through the first electrode to concentrate the arc as a low voltage, and the voltage of the second electrode is increased to form a stable and sound back bead. In JP-A-8-99178, the back bead is formed by high-speed welding by limiting the wire diameter of each electrode, the welding current of the first electrode and the second electrode, the distance between the electrodes, the spreading thickness and the bulk density of the backing flux. A smooth back bead with a stable width and height is obtained. Furthermore, Japanese Patent Application Laid-Open No. 5-337651 discloses a sound defect with four electrodes, with the wire diameter of each electrode, the welding current of each electrode, the distance between the electrodes, the back flux component, the front flux component, and the C amount of the wire being limited. There is a disclosure of a technique for obtaining a weld metal having no crack.

  However, there has been a demand for higher efficiency due to the recent intensification of international competitiveness in shipbuilding, and there is a problem in achieving higher efficiency by further increasing the welding speed with the above-described technology. In other words, when the welding current is increased, the back bead becomes excessive and the bead becomes non-uniform, and the solidification of the weld metal is fast due to the cooling from the backing copper plate. As shown in the macro structure conceptual diagram of FIG. The metal 21 has a structure in which dendrites (dendritic crystals) are associated with each other at the center of the bead width. Therefore, it is impossible to increase the speed further, and an improvement in efficiency from other means is desired.

1A and 1B are cross-sectional views showing examples of the single-sided submerged arc welding method referred to here. In Fig.1 (a), the back flux 4 spread | diffused in the layer form on the copper metal 2 is pressed on the back surface of the to-be-welded material 1 by the raising mechanism, such as the air hose 5, from the back surface of the to-be-welded material 1 which faced | matched. Then, submerged arc welding is performed from the surface using the wire 3 and the surface flux 6. Further, in FIG. 1 (b), copper backing is not used, and the back flux 4 housed in the fireproof canvas 7 is pressed against the back surface of the workpiece 1 by a push-up mechanism such as an air hose 5. By these methods, weld beads are simultaneously formed on the front side and the back side of the workpiece 1.
Japanese Patent Laid-Open No. 6-254683 JP-A-8-99178 Japanese Patent Laid-Open No. 5-337651

  An object of the present invention is to provide a welding method for obtaining a sound weld metal with high efficiency in single-sided submerged arc welding in which the entire thickness of a steel plate is welded in one run using three or four electrodes. .

The gist of the present invention is that in a single-sided submerged arc welding method in which granular or powdery flux is used as a backing, and the entire plate thickness is made in one run using three or four electrodes, the groove of the workpiece is welded. The angle is set to a V-shaped groove having no root surface of 35 to 60 °, and steel grains or iron powder is filled in the groove from 1/3 of the thickness of the material to be welded to the height of the surface of the material to be welded. wire diameter of each electrode at least 4.8 mm, the current of the first electrode (I1) and 1200～2000A, and the current of the second electrode (I2) and the third electrode current (I3) is I1> I2 ≧ In the case of I3 and I1 + I2 of 2450 to 3400A, the distance between the first electrode and the second electrode of 20 to 70 mm, and the distance between the second electrode and the third electrode of 3 electrode welding is 100 to 150 mm, In the case of 4-electrode welding, it is 150-300mm In multielectrode one side submerged arc welding method, characterized in that contact.
Further, the current (I4) of the fourth electrode is also characterized by being not more than the current (I3) of the third electrode (I3 ≧ I4).

  According to the multi-electrode single-sided submerged arc welding method of the present invention, by setting the groove shape of the material to be welded to a V-shaped groove, it is possible to omit one step of the groove processing step of the welding pretreatment, and within the groove. By filling steel grains or iron powder and making the wire diameter, welding current and interelectrode distance of each electrode appropriate, it is possible to obtain a sound weld metal with high efficiency.

  As a result of various investigations such as processes before and after the welding process, welding conditions, and the like, the inventors have obtained the following knowledge in the multi-electrode single-sided submerged arc welding method.

  The submerged arc welding of the present invention is performed with three electrodes or four electrodes, but the first and second electrodes and the third and subsequent electrodes are welded under the conditions of forming another pool as will be described in detail later. As a result, as shown in the conceptual diagram of the macrostructure of the welded portion by the method of the present invention in FIG. 2, the weld metal 22 by the third and subsequent electrodes solidifies after the weld metal 22 by the first and second electrodes solidifies. Become an organization. For this reason, the dendrite has a shape that grows upward as shown in FIG. 2, and unlike the structure in which the dendrite is associated at the center of the bead width as shown in FIG. In submerged arc welding, the solidified weld metal is covered with slag. It will not be an obstacle.

  The welding method of the present invention welds the entire thickness of the steel sheet in one run, but can be applied to a thickness of about 10 mm to about 40 mm. Whether welding with three electrodes or four electrodes is sufficient up to a plate thickness of about 20 mm, the welding speed can be increased by using four electrodes. Further, when the plate thickness is larger than about 20 mm, it is preferable to cope with an increase in the amount of metal to be deposited by using four electrodes and to prevent the occurrence of insufficient surplus of the front bead.

The present invention is characterized in that a V-shaped groove having no root surface is adopted as the groove shape of the material to be welded. That is, a Y-shaped groove has been adopted as the groove shape of the material to be welded in the conventional multi-electrode single-sided submerged arc welding method because of the ease of temporary assembly and the wide range of welding conditions. In the following description, the V groove, the V-shaped groove, and the V-shaped groove are those having no root surface, and are distinguished from the Y groove in this respect. 4 (a) and 4 (b) are diagrams for explaining a groove working step located in the pre-process of the temporary assembly step, where FIG. 4 (a) shows a Y groove and FIG. 4 (b) shows a V groove. In the figure, reference signs A, B, and C respectively indicate the directions of the cutting torch. As shown in FIG. 4A, in the case of a Y-shaped groove, the end of the welded material is cut perpendicularly to the A direction so as to have a target plate width, and then the B direction so that a predetermined groove angle is obtained. It is necessary to perform two cutting steps for one end face. On the other hand, by adopting the V-shaped groove, as shown in FIG. 4B, the plate width can be determined and the groove can be cut only by cutting once in the C direction.

  However, when the V-shaped groove is adopted, unlike the Y-shaped groove, the groove has no root surface 24 (FIG. 4A). There was a problem that the butt portion shifted up and down. Therefore, by using the two plate relative positioning devices described in Japanese Patent No. 3215312 and Japanese Patent No. 3215313 previously proposed by the present inventors, the groove surface of the welded material does not shift. The temporary assembly welding became easy.

  When the V-shaped groove is used as described above, there is no root surface, so in the conventional submerged arc welding method, the back bead is excessively uneven and the bead becomes non-uniform, and the welding conditions at low current and low speed are unavoidable. Is done. In the present invention, since the steel grain or iron powder is filled in the groove from 1/3 of the thickness of the material to be welded to the height of the surface of the material to be welded, the allowable range of welding conditions can be widened. In this case, if the filling thickness of the steel grains or iron powder in the groove is less than 1/3 of the plate thickness, the back bead is excessively formed and the bead becomes non-uniform. For this reason, when trying to make the width and height of the back bead uniform, low-current and low-speed welding conditions are adopted, resulting in poor efficiency. On the contrary, when the filling thickness of the steel grains or iron powder in the groove exceeds the surface of the material to be welded, the back bead is hardly produced. For this reason, when high current and high speed welding conditions are adopted, the back bead is non-uniform and the weld metal is rapidly solidified, and the weld metal becomes a structure in which the dendrite is associated at the center of the bead width, so that it is easily cracked.

  The particle size distribution of the steel grains or iron powder is preferably 1.5 mm or less from the viewpoint of improving the arc stability and the shape of the back bead. In addition, the component is mainly composed of Fe, but C is preferably 0.10% by mass or less, and S and P are preferably 0.020% by mass or less from the viewpoint of crack resistance, and the other components take into account the strength and toughness of the weld metal. Si, Mn, Mo, and other deoxidizing agents and alloying agents can be contained. If the above particle size and components are satisfied, a granular body obtained by cutting steel wires of various sizes may be used.

  The groove angle of the V-shaped groove is 35 to 60 ° because it affects the formation of the back and front beads, the penetration shape, and the amount of welding. If the groove angle is less than 35 °, the point where the arc is generated becomes high, so that the back bead cannot be stably formed. Further, since the weld metal has a structure in which the dendrite is associated at the center of the bead width, the weld metal is easily broken. On the other hand, when the groove angle exceeds 60 °, the groove cross-sectional area is large, and it is necessary to reduce the welding speed in order to secure the amount of deposited metal, resulting in poor welding efficiency. The root interval of the V groove is basically zero, that is, the ends of the diagonally cut plates are brought into contact with each other, but up to about 3 mm is allowable.

  Next, the preferable range about welding construction conditions is demonstrated. First, the wire diameter of each electrode is set to 4.8 mm or more. In the present invention, a sound back bead is formed by the first electrode and the second electrode under high-current welding conditions in order to weld a material to be welded on one side with high efficiency without slowing the welding speed. If it is less than 8 mm, the arc concentrates, the back bead becomes convex, and undercut occurs. Therefore, in order to widen the back bead by softening the arc, the wire diameter is set to 4.8 mm or more. The third electrode and the fourth electrode used as necessary prevent the occurrence of internal defects such as cracks, poor fusion and slag entrainment defects, and provide the amount of welding necessary to form a moderately large surface bead. Secure. When the wire diameters of the third electrode and the fourth electrode are less than 4.8 mm, the arc is not concentrated and spreads, and the weld metal becomes a structure in which the dendrite is associated at the center of the bead width, so that it is easy to break. Further, poor fusion may occur, or the amount of welding may be insufficient, resulting in insufficient surface bead accumulation.

The current (I1) of the first electrode is 1200 to 2000 A in order to form a healthy back bead. If the current (I1) of the first electrode is less than 1200 A, the back bead cannot be formed stably. On the other hand, if it exceeds 2000 A, the back bead is excessively produced and the bead becomes non-uniform. The current (I2) of the second electrode and the current (I3) of the third electrode are set such that I1> I2 ≧ I3 and I1 + I2 are 2450 to 3400A based on the current (I1) of the first electrode. The current (I2) of the second electrode is less than the current (I1) of the first electrode in order to control the formation of the back bead. When the current (I2) of the second electrode is equal to or greater than the current (I1) of the first electrode (I1 ≦ I2), the back bead is excessively formed and the bead becomes non-uniform.

  FIG. 6 is a diagram showing the arrangement of the electrodes in the weld line direction. The distance 12 between the first electrode 8 and the second electrode 9 is 20 to 70 mm in order to control the back bead shape. If the inter-electrode distance 12 between the first electrode 8 and the second electrode 9 is less than 20 mm, the back bead becomes excessive. Conversely, if it exceeds 70 mm, the back bead does not spread and undercut occurs.

  After the third electrode, internal defects such as poor fusion and slag entrainment are prevented, the necessary amount of welding is secured, and at the same time, the weld metal formed by the first electrode and the second electrode is melted, as shown in FIG. In addition, the weld metal dendrite is controlled to grow upward to prevent hot cracking. If the current (I3) of the third electrode exceeds the current (I2) of the second electrode (I2 <I3) contrary to the conditions described above, the amount of welding increases but the penetration becomes deeper, and the weld metal has a bead width. It becomes easy to break because it becomes an organization where dendrites meet in the center.

  Moreover, when the third electrode is arranged in the molten pool (pool) formed by the first electrode and the second electrode, a so-called one pool is formed, the arc by the third electrode reaches the back bead, the back bead is excessively discharged and welding is performed. The metal becomes a structure in which dendrites are associated with each other at the center of the bead width, and is easily broken. Therefore, as shown in FIG. 6, the inter-electrode distance 13 between the second electrode 9 and the third electrode 10 is 100 to 150 mm in the case of three-electrode welding, and 150 to 300 mm in the case of four-electrode welding. If the distance between the second electrode 9 and the third electrode 10 is less than 100 mm in the case of three-electrode welding and less than 150 mm in the case of four-electrode welding, the molten pool becomes one pool, and the back bead is excessively ejected and the dendrite is at the center of the bead width. Becomes a meeting organization and is easy to break. Conversely, if the inter-electrode distance 13 between the second electrode 9 and the third electrode 10 is more than 150 mm in the case of three-electrode welding and more than 300 mm in the case of four-electrode welding, the melting generated in the first electrode 8 and the second electrode 9 The slag is completely solidified, the arc becomes unstable, the surface bead shape becomes poor, and poor fusion and slag entrainment defects occur. The interelectrode distances 12, 13, and 14 in the present invention refer to the distance between the centers of the wires on the groove bottom surface 15.

  When the fourth electrode is used, the current (I4) of the fourth electrode is equal to or lower than the current (I3) of the third electrode (I3 ≧ I4). The fourth electrode compensates for the insufficient amount of welding at the third electrode, and widens the front bead to suppress the occurrence of undercut. When the current (I4) of the fourth electrode exceeds the current (I3) of the third electrode (I3 <I4), the front bead becomes convex and an undercut occurs. In addition, it is preferable that the interelectrode distance 14 of the 3rd electrode 10 and the 4th electrode 11 is 20-70 mm in order to expand the width | variety of a surface bead.

  Steel materials (material JIS SM400) shown in Table 1 are cut into V-shaped grooves and shown in Tables 5 and 6 using the wires shown in Table 2, the back flux shown in Table 3, and the front flux shown in Table 4. Under welding conditions, single-sided submerged arc welding with a welding length of 2000 mm was performed with the apparatus shown in FIG. In addition, the steel grains filled in the groove have components of C: 0.05% by mass, Si: 0.01% by mass, Mn: 1.51% by mass, P: 0.008% by mass, S: 0.006. A steel wire having a diameter of 1 mm with a mass% cut to a length of 1 mm was used.

  Test No. shown in Table 5 1-4 are examples of the present invention, and the test Nos. Shown in Table 6 were performed. 5 to 8 are comparative examples. About each test example, after investigating the external appearance of the back bead and front bead after welding, the presence or absence of the internal defect of a weld metal was investigated by the X-ray penetration test. The results are also summarized in Table 5 and Table 6, respectively.

  Test No. which is an example of the present invention. For 1-4, the V-shaped groove angle and the steel grain filling thickness in the groove are appropriate, so that the back bead and the front bead have a good and uniform bead shape and are also defective inside the weld metal. The result was very satisfactory, with high efficiency welding.

Test No. in Comparative Examples. In No. 5, since the filling height of the steel grains in the groove was low with respect to the plate thickness, the back bead was excessively formed and the bead was not uniform.
Test No. In No. 6, the back bead did not come out because the steel grain filling height in the groove was higher than the plate thickness.
Test No. Since No. 7 has a wide groove angle, the groove cross-sectional area is large and the weld metal deposition amount is insufficient.
Test No. In No. 8, since the groove angle was narrow, there were places where the back bead did not come out, and some hot cracks also occurred.

  The steel materials shown in Table 1, which are the same as those used in Example 1, were cut into V-shaped grooves, and the wires shown in Table 2, the back flux shown in Table 3, and the front flux shown in Table 4 were used. Single-sided submerged arc welding with a weld length of 2000 mm was performed with the apparatus shown in FIG. The steel grains filled in the groove are the same as those used in Example 1. As shown in Tables 7 to 9, the welding conditions were performed under the welding conditions in which the wire diameter, the welding current of each electrode, and the distance between the electrodes were changed.

  Test No. shown in Table 7 9 to 12 are examples of the present invention, and the test numbers shown in Table 8 and Table 9 were obtained. 13 to 20 are comparative examples. The investigation for each test example was performed in the same manner as in Example 1. The results are also summarized in Tables 7 to 9.

  Test No. which is an example of the present invention. 9 to 12 are all V-shaped groove angles, steel grain filling thicknesses in the grooves, wire diameters of the respective electrodes, currents of the first electrodes, current balances of the respective electrodes, the first electrode and the second electrode The inter-electrode distance and the inter-electrode distance between the second electrode and the third electrode are appropriate, so that the back bead and the front bead have a good and uniform bead shape, and there are no defects inside the weld metal, enabling high-efficiency welding. It was a very satisfactory result.

Test No. in Comparative Examples. In No. 13, since the wire diameter of the first electrode was thin, the back bead became convex and undercut occurred.
Test No. In No. 14, since the wire diameter of the third electrode was thin, poor fusion and hot cracking occurred in the weld metal.

Test No. No. 15 was uneven because the welding current of the first electrode was high and the back bead was excessive.
Test No. No. 16 was non-uniform because there was no back bead because the current of the first electrode was low. Further, since the distance between the second electrode and the third electrode was long, the shape of the front bead was poor and slag entrainment defects were also generated.

Test No. In No. 17, since the current of the second electrode was equal to or greater than the current of the first electrode, the back bead was excessive and non-uniform. Further, since the distance between the second electrode and the third electrode was long, the shape of the front bead was poor and slag entrainment defects were also generated.
Test No. No. 18 was hot cracked because the current of the third electrode exceeded the current of the second electrode. Further, since the distance between the first electrode and the second electrode was long, the back bead did not spread and undercut occurred.

Test No. In No. 19, since the distance between the first electrode and the second electrode was short, the back bead appeared too much and was not uniform.
Test No. In No. 20, since the current of the fourth electrode exceeded the current of the third electrode, the front bead became convex and undercut occurred. Further, since the distance between the second electrode and the third electrode was short, the back bead was excessively formed and further hot cracking occurred.

(A), (b) is sectional drawing which shows the example of a single-sided submerged arc welding method, respectively Conceptual diagram of the macrostructure of the weld by the method of the present invention Conceptual diagram of the macro structure of the welded part by the conventional method It is a figure explaining a groove process, Comprising: (a) The figure is a Y groove, (b) The figure is a V groove Groove cross-sectional view explaining the deviation of the steel plate position Diagram showing the arrangement of electrodes in the weld line direction

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Material to be welded 2 Copper metal 3 Wire 4 Back flux 5 Air hose 6 Front flux 7 Fire-resistant canvas 8 1st electrode 9 2nd electrode 10 3rd electrode 11 4th electrode 12 Between electrode of 1st electrode and 2nd electrode Distance 13 Distance between second electrode and third electrode 14 Distance between third electrode and fourth electrode 15 Groove bottom 21 Weld metal 22 Weld metal by first and second electrodes 23 By electrodes after third electrode Weld metal 24 Route surface

Claims (2)

In a single-sided submerged arc welding method in which granular or powdery flux is used for the backing and the entire plate thickness is made in one run using three or four electrodes, the groove angle of the workpiece is 35 to 60 °. the root face is opened destination without V shape, the steel grains or iron powder was filled from 1/3 of workpieces thickness to the height of the workpieces surface in the open destination, wire diameter of each electrode 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, and I1 + I2 is 2450 to 3400A, 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 to four in the case of four-electrode welding. Features to be welded at 300mm Multielectrode sided submerged arc welding method according to. Current of the fourth electrode (I4) is a multi-electrode single-sided submerged arc welding method according to claim 1, characterized in that the current of the third electrode (I3) hereinafter (I3 ≧ I4).

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