Two-electrode submerged arc welding method and welding equipment

Abstract

A two-electrode submerged arc welding method capable of improving the quality of welded joints is provided. [Solution] A two-electrode submerged arc welding method includes distributing a cut wire within a groove of a base material (2), outputting current from a power source via a leading electrode (3) to energize a leading welding wire (4) and generating an arc (A) between the base material (2) and the leading welding wire (4) within the groove, and energizing a trailing electrode (6) from the power source to supply a heated filler wire (7) to a molten pool (P) formed behind the arc (A) while welding is proceeding, without generating an arc, wherein the leading electrode (3) is inclined toward the welding direction (X) at a predetermined sweepback angle (θ) with respect to an axis (Z) perpendicular to the welding direction (X) and the base material (2).

Description

[Technical Field]

[0001] The present disclosure relates to a two-electrode submerged arc welding method, a welded joint, and a welding device. For example, the present disclosure relates to a submerged arc welding method, and more particularly to a method of performing submerged arc welding by supplying a heated filler wire (hot wire) to a molten pool (molten metal) formed by an arc of a preceding welding wire without passing an electric current through it to generate an arc. [Background technology]

[0002] Submerged arc welding is a method of welding in which a welding wire is fed into granular flux dispersed at the weld area and an arc is generated between the welding wire in the flux and the base material, and is widely used, for example, when welding steel decks for road bridges. For example, Patent Document 1 discloses a submerged arc welding method using a hot wire that enables one-pass welding in grooves with plate thicknesses up to 19 mm, thereby enabling high-quality and efficient welding, thereby shortening the welding time and reducing welding defects. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7470837 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional technology described in Patent Document 1 had room for improvement in terms of optimizing the shape of the "ura-nami" (a bead (protrusion) of penetration that appears on the back side of the welded base material) and improving the quality of the welded joint.

[0005] An object of the present disclosure is to provide a two-electrode submerged arc welding method, a welded joint, and a welding device that can improve the quality of a welded joint. [Means for solving the problem]

[0006] A two-electrode submerged arc welding method according to a first aspect for solving the above problems comprises: Distributing a cut wire within the groove of the base material; outputting a current from a power source through a leading electrode to energize a leading welding wire, thereby generating an arc between the base metal and the leading welding wire within the groove; a welding process is carried out while supplying a heated filler wire to a molten pool formed behind the arc by applying current from the power source through a trailing electrode without generating an arc; Including, The leading electrode is inclined toward the welding direction at a predetermined sweepback angle with respect to an axis perpendicular to the welding direction and the base metal.

[0007] A welded joint according to a second aspect of the present invention is obtained by welding the base materials together via a weld metal portion using the two-electrode submerged arc welding method described above.

[0008] A welding apparatus according to a third aspect for solving the above problems comprises: a leading electrode that outputs a current from a power source to energize a leading welding wire and generate an arc between the base metal and the leading welding wire within a groove of the base metal; the leading welding wire supported by the leading electrode; a trailing electrode that supplies a filler wire heated by energizing the power source without generating an arc to a molten pool formed behind the arc while proceeding with welding; a filler wire supported by the trailing electrode; Equipped with The leading electrode is inclined toward the welding direction at a predetermined sweepback angle with respect to an axis perpendicular to the welding direction and the base metal. [Effects of the Invention]

[0009] According to a two-electrode submerged arc welding method, a welded joint, and a welding device according to an embodiment of the present disclosure, it is possible to improve the quality of the welded joint. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a first explanatory diagram of a two-electrode submerged arc welding method according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a second explanatory diagram of a two-electrode submerged arc welding method according to an embodiment of the present disclosure. [Figure 3A] FIG. 3 is a first diagram for explaining an example of an effect achieved by the welding device of FIG. 2. [Figure 3B] FIG. 3B is an enlarged view of a part of FIG. 3A. [Figure 4A] FIG. 3 is a second diagram for explaining an example of an effect achieved by the welding device of FIG. [Figure 4B] FIG. 4B is an enlarged view of a part of FIG. 4A. [Figure 5] FIG. 4 is a graph showing test results of a welded joint obtained using a two-electrode submerged arc welding method according to an embodiment. [Figure 6A] FIG. 2 is a first schematic diagram for explaining test results of a welded joint obtained using a two-electrode submerged arc welding method according to an embodiment. [Figure 6B] FIG. 2 is a second schematic diagram for explaining test results of a welded joint obtained using a two-electrode submerged arc welding method according to an embodiment. [Figure 7A] FIG. 4 is a schematic diagram showing an example of the state of the groove on the leading side of the weld metal portion obtained under the first condition. [Figure 7B] FIG. 4 is a schematic diagram showing an example of the state of the groove on the trailing side of the weld metal portion obtained under the first condition. [Figure 8A] FIG. 10 is a schematic diagram showing an example of the state of the groove on the leading side of the weld metal portion obtained under the second condition. [Figure 8B]FIG. 10 is a schematic diagram showing an example of the state of the groove on the trailing side of the weld metal portion obtained under the second condition. [Figure 9A] FIG. 10 is a schematic diagram showing an example of the state of the groove on the leading side of the weld metal portion obtained under the third condition. [Figure 9B] FIG. 10 is a schematic diagram showing an example of the state of the groove on the trailing side of the weld metal portion obtained under the third condition. [Figure 10] FIG. 3 is a third schematic diagram for explaining test results of a welded joint obtained using a two-electrode submerged arc welding method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following mainly describes one embodiment of the present disclosure with reference to the accompanying drawings. The following description of the welding device 1 also applies to a two-electrode submerged arc welding method performed by the welding device 1 to which the present disclosure is applied, and to a welded joint in which base materials 2 are welded together via a weld metal portion using the two-electrode submerged arc welding method. In the present disclosure, the "base material 2" includes, for example, a steel plate having a thickness of 16 mm.

[0012] FIG. 1 is a first explanatory diagram of a two-electrode submerged arc welding method according to an embodiment of the present disclosure. FIG. 1 is a schematic diagram showing the relative positional relationship of a leading electrode 3 and a trailing electrode 6 used to perform the two-electrode submerged arc welding method. FIG. 2 is a second explanatory diagram of a two-electrode submerged arc welding method according to an embodiment of the present disclosure. FIG. 2 is a configuration diagram of a welding apparatus 1 for performing the two-electrode submerged arc welding method. The welding apparatus 1 has a leading electrode 3, a leading welding wire 4, a trailing electrode 6, and a filler wire 7.

[0013] The leading electrode 3 outputs current supplied from a power supply (not shown) to energize the leading welding wire 4, generating an arc A between the base metal 2 and the leading welding wire 4 in the groove of the base metal 2. The leading electrode 3 has an electrode member made of, for example, a copper alloy or a highly heat-resistant material. The leading electrode 3 outputs current supplied from a welding power supply (not shown) to energize the leading welding wire 4. As a result, an arc A is formed between the leading welding wire 4 and the base metal 2 in the groove of the base metal 2. The arc A generates high temperatures, reaching several thousand degrees, and functions as the main heat source for efficiently melting the joint end of the base metal 2 and the tip of the leading welding wire 4 and forming a predetermined molten pool P. The leading electrode 3 is required to have stable formation of the arc A and high current resistance, so a material with good thermal conductivity and durability may be selected.

[0014] The leading welding wire 4 is supported by the leading electrode 3. The leading welding wire 4 is mechanically and electrically supported by the leading electrode 3, and is fed toward the base material 2 while being held in a predetermined attitude and position. The leading welding wire 4 is made of, for example, a material that is suitable for the base material 2 to be welded, and is selected so as to exhibit the desired welding performance. As a result of the above, a stable arc A is formed between the base material 2 and the leading welding wire 4, and a uniform molten pool P can be generated.

[0015] The trailing electrode 6 receives current from a power source (not shown) and supplies the heated filler wire 7 to a molten pool P formed behind the arc A without generating an arc, thereby progressing the welding. The trailing electrode 6 has an electrode member made of, for example, a copper alloy or a highly heat-resistant material. The trailing electrode 6 preheats the filler wire 7 to a predetermined temperature and then supplies it to the molten pool P formed behind the arc A, thereby progressing the welding. The trailing electrode 6 is configured to output a current value that achieves stable heating while suppressing arc generation, based on the relationship between the diameter, feed speed, and extension length of the filler wire 7. As described above, the trailing electrode 6 improves melting efficiency and suppresses excessive heat input, contributing to stabilizing welding quality.

[0016] The filler wire 7 is supported by the trailing electrode 6. The filler wire 7 is mechanically and electrically supported by the trailing electrode 6, and is fed toward the molten pool P while being held in a predetermined posture and position. The filler wire 7 is made of, for example, a material that is compatible with the base material 2 to be welded, and is selected so as to exhibit the desired deposition performance. As a result, the heated filler wire 7 is efficiently supplied to the molten pool P formed behind the arc A, improving the deposition rate and welding quality of the weld.

[0017] 1 , the leading electrode 3 is inclined toward the welding direction X at a predetermined sweep angle θ with respect to an axis Z perpendicular to the welding direction X and the base metal 2. The sweep angle θ is greater than 0°. The sweep angle θ may be within a range of preferably greater than 0° and not greater than 45°, more preferably greater than 5° and not greater than 20°, more preferably greater than 5° and not greater than 10°, more preferably greater than 0° and not greater than 20°, more preferably greater than 0° and not greater than 10°, and even more preferably greater than 0° and not greater than 5°.

[0018] The trailing electrode 6 is inclined at a predetermined angle R in the opposite direction to the welding direction X with respect to an axis Z perpendicular to the welding direction X and the base material 2. The angle R with respect to the axis Z may be, for example, within a range of 30° or more. Therefore, the trailing electrode 6 is inclined at an inter-electrode angle (R+θ) with respect to the leading electrode 3, facing the opposite side of the axis Z from the leading electrode 3.

[0019] The inter-electrode angle (R+θ) is the inclination angle of the second combination of the trailing electrode 6 and the filler wire 7 relative to the first combination of the leading electrode 3 and the leading welding wire 4. The first combination and the second combination maintain a V-shape with the inter-electrode angle (R+θ) as the central angle, even when they move in the welding direction X during welding.

[0020] The two-electrode submerged arc welding method performed by the welding apparatus 1 can avoid various problems by optimizing the welding conditions. For example, the electrode gap D, which is the distance between the tip 4a of the preceding welding wire 4 and the tip 7a of the filler wire 7 before welding begins, may be set to 10 to 14 mm. The diameter of the preceding welding wire 4 may be 4.8 mm. The diameter of the filler wire 7 may be 1.2 mm or 1.4 mm.

[0021] The extension length L of the filler wire 7 from the trailing electrode 6 may be set to 35 to 40 mm. In the present disclosure, the "extension length L" refers to, for example, the amount of extension from the tip 6a of the trailing electrode 6 to the tip 7a of the filler wire 7 before the start of welding.

[0022] The leading electrode 3 has AC polarity. Therefore, the leading electrode 3 outputs AC current to the leading welding wire 4. This generates an arc A between the leading welding wire 4 and the base material 2, and the arc A forms a molten pool P. By using AC polarity for the leading electrode 3, the deposition rate is increased and the occurrence of magnetic arc blow is suppressed compared to when DC positive polarity is used. Additionally, the amount of oxygen in the weld metal is reduced, improving the mechanical properties of the metal. Furthermore, the flux consumption rate is reduced, resulting in excellent workability and cost efficiency. Due to these effects, the welding device 1 stably forms an arc A and generates a molten pool P with the leading electrode 3, and can achieve high-quality welding in coordination with the supply of the subsequent filler wire 7.

[0023] The polarity of the trailing electrode 6 is negative DC. Therefore, the trailing electrode 6 outputs a negative DC current to the filler wire 7. This supplies electrons in a fixed direction to the filler wire 7, enabling stable resistance heating without generating an arc. With negative DC polarity, heat is generated when electrons are emitted from the tip of the filler wire 7, increasing the heating efficiency of the filler wire 7 itself. As a result, the amount of wire melted and the amount of deposition are increased. Therefore, the welding device 1 can stabilize the melting performance of the filler wire 7 even when the filler wire 7 is fed into the molten pool P at a high feed rate. In a welding device 1 where arc generation must be avoided on the trailing electrode 6 side, control using a negative DC current is more effective. Additionally, by using a DC power source, the welding device 1 can precisely control the current value output from the trailing electrode 6, ensuring consistent heating.

[0024] A two-electrode submerged arc welding method according to one embodiment of the present disclosure will be described with reference mainly to Figure 2. In the two-electrode submerged arc welding method according to one embodiment, a filler wire 7 heated by electrical conduction is used as a hot wire, and the filler wire 7 is inserted into the molten pool P of the leading welding wire 4 from behind in order to obtain a large deposition amount while minimizing an increase in heat input.

[0025] The two-electrode submerged arc welding method first includes distributing a cut wire within the groove of the base metal 2. Because the base metal 2 includes, for example, a steel plate with a thickness of 16 mm, the fill height of the cut wire may be 16 mm or more. The cut wire may be made of a metallic material of the same type as the base metal 2 or a similar composition. This ensures intermetallic consistency and weldability during welding in the two-electrode submerged arc welding method. In addition, by distributing the cut wire uniformly within the groove of the base metal 2, the occurrence of voids during melting is suppressed, contributing to the formation of a sound weld metal joint.

[0026] The two-electrode submerged arc welding method includes outputting current from a power source via a leading electrode 3, energizing a leading welding wire 4, and generating an arc A between the base material 2 and the leading welding wire 4 in a groove in the base material 2. For example, as shown in FIG. 2 , current is applied from a power source to the leading welding wire 4 while a constant amount of granular flux 5 is continuously supplied from the vicinity of the leading electrode 3 toward below the leading electrode 3, and an arc A is generated between the base material 2 and the leading welding wire 4. Then, the leading electrode 3 and the trailing electrode 6 are moved at a predetermined speed in the traveling direction X. As a result, a molten pool P is formed behind the arc A.

[0027] The two-electrode submerged arc welding method involves passing current from a power source through the trailing electrode 6, heating the filler wire 7 without generating an arc, and supplying the heated filler wire 7 to a molten pool P formed behind the arc A while welding proceeds. For example, in the trailing electrode 6, current is passed from a power source to the filler wire 7 to heat it, and the filler wire 7 is fed from a filler wire feeder (not shown) to the trailing electrode 6 at a predetermined speed. Welding proceeds while the filler wire 7 is fed to the molten pool P formed behind the arc A. The above-mentioned "predetermined speed" is, for example, within a range of 16 m / min or less.

[0028] Weld metal 9 is formed further rearward of molten pool P. Slag 8 is formed on the surface of weld metal 9, while molten slag 10 is disposed in front of the surface so as to cover the groove of base metal 2. Flux 5 is positioned on the farthest side from base metal 2 so as to further cover the entire surface.

[0029] A current of the upper limit of the range that does not generate an arc is output from the trailing electrode 6 to the filler wire 7, taking into account the relationship between the diameter, feed speed, and extension length L of the filler wire 7. For example, when the feed speed of the filler wire 7 is 16 m / min or less and the extension length L of the filler wire 7 is 35 to 40 mm, and when a filler wire 7 with a diameter of 1.2 mm is used, the upper limit may be 230 to 290 A. When a filler wire 7 with a diameter of 1.4 mm is used under the same conditions of the feed speed and extension length L, the upper limit may be 330 to 390 A.

[0030] The two-electrode submerged arc welding method as described above is performed on only one surface, either the front or back surface, of the base metal 2. However, the method is not limited to this, and the two-electrode submerged arc welding method may be performed on each of both surfaces of the base metal 2.

[0031] When the welding device 1 performs submerged arc welding under the above conditions while supplying the filler wire 7 to the molten pool P, it can stably melt the filler wire 7 without causing problems such as poor melting. As a result, the welding device 1 can obtain a sufficient deposition amount and can perform welding in one pass without exceeding the heat input limit, even when welding a steel plate with a thickness of 16 mm.

[0032] In addition to the effects of single-pass welding as described above, the welding apparatus 1 can improve the quality of the welded joint. As will be understood by comparing Figures 3A and 3B (described later) with Figures 4A and 4B, the welding apparatus 1 can more appropriately shape the "back bead," which refers to the penetration bead that appears on the back surface of the welded base metal 2. For example, the welding apparatus 1 can smoothly form the back bead in the weld metal portion of the welded joint by inclining the leading electrode 3 toward the welding advance direction X at a predetermined sweep angle θ with respect to an axis Z perpendicular to the welding advance direction X and the base metal 2.

[0033] The welding apparatus 1 can improve the durability of the welded metal portion by smoothly forming a back rib in the weld metal portion of a welded joint. For example, as shown in FIGS. 4A and 4B, when the back rib corners are formed with a large curvature and a sharp shape, stress concentration is likely to occur, and even a small force may lead to fracture. On the other hand, as shown in FIGS. 3A and 3B, when the back rib corners are formed with a small curvature and a smooth shape, stress is dispersed, and fracture is reduced even with a relatively large force. Therefore, the welding apparatus 1 enables the realization of a welded joint with excellent back rib formability and high fatigue durability.

[0034] A welded joint according to one embodiment is formed by welding two base materials 2 together via a weld metal portion using the two-electrode submerged arc welding method. In the welded joint, the weld metal portion contains, by mass%, 0.02 to 0.05% of Ti, 0.01 to 0.05% of Mo, and 0.0005% to 0.0010% of B.

[0035] The weld metal part has tensile properties of 0.2% proof stress: 320 MPa or more and tensile strength: 490 MPa or more, and impact toughness of absorbed energy: 27 J or more in a Charpy impact test, or the weld metal part has tensile properties of 0.2% proof stress: 400 MPa or more and tensile strength: 570 MPa or more, and impact toughness of absorbed energy: 27 J or more in a Charpy impact test. [Example]

[0036] Below, a two-electrode submerged arc welding method, a welded joint, and a welding device 1 according to an embodiment of the present disclosure will be described in more detail using examples, but the present disclosure is not limited to the following examples. The numerical values ​​described in the examples are merely examples and do not limit the scope of the present disclosure. The scope of the present disclosure should be determined solely based on the claims. Below, components similar to those in the embodiment will be assigned the same reference numerals, and duplicate explanations will be omitted.

[0037] Using a steel plate with a plate thickness of 16 mm as the base material 2, a two-electrode submerged arc welding method according to one embodiment of the present disclosure was performed in a bead-on-plate manner on one side of the base material 2 on which a groove was formed, and various characteristics of the weld metal portion of the welded joint were verified. In addition, as a comparative example, a single-electrode submerged arc welding method was performed under similar conditions as necessary.

[0038] (Welding conditions) Leading electrode 3 current: 720A-33V Leading welding wire 4 feed speed: 35cm / min Diameter of leading welding wire 4: 4.8mm Filler wire diameter: 1.2mm, 1.4mm Distance D: 10mm Filler wire 7 feed speed: 10~16m / min Filler wire 7 protrusion length L: 40 mm Current of trailing electrode 6: 230~390A Angle R: 30°

[0039] Fig. 3A is a first diagram for explaining an example of an effect achieved by the welding apparatus 1 of Fig. 2. Fig. 3B is an enlarged view of a portion of Fig. 3A. Figs. 3A and 3B show an example of the appearance of a weld metal portion of a welded joint formed by the welding apparatus 1 according to the embodiment using a two-electrode submerged arc welding method. In Figs. 3A and 3B, the sweep angle θ is 5°, as an example.

[0040] Fig. 4A is a second diagram for explaining an example of an effect achieved by the welding apparatus 1 of Fig. 2. Fig. 4B is an enlarged view of a portion of Fig. 4A. Figs. 4A and 4B show an example of the appearance of a weld metal portion of a welded joint formed using a two-electrode submerged arc welding method according to Comparative Example 1 in which the sweep angle θ is set to 0° and the leading electrode 3 is not inclined, in comparison with the welding apparatus 1 according to an embodiment of the present disclosure.

[0041] 4A and 4B, the back bevels were formed in a pointed shape in the weld metal part formed using the two-electrode submerged arc welding method according to Comparative Example 1. In this case, the curvature radius of the corner of the back bevel, i.e., the toe radius, was 0.14 mm, and the curvature, which is the reciprocal of this radius, was a relatively large value.

[0042] 3A and 3B, the weld metal joint formed using the two-electrode submerged arc welding method according to the embodiment has a smooth back bead. The radius of curvature of the back bead corner, i.e., the toe radius, is 15 mm, and the curvature, which is its reciprocal, is a relatively small value.

[0043] Tables 1 to 4 show various test results when the conditions were changed for each of the Example and Comparative Example 2, with a submerged arc welding method using a single electrode being Comparative Example 2. Table 1 shows multiple conditions for each of Comparative Example 2 and the Example. In Tables 1 to 4, Nos. 1 to 3 respectively indicate the test specimen numbers for the multiple conditions of Comparative Example 2. Nos. 4 and 5 respectively indicate the test specimen numbers for the multiple conditions of the Example. The test results shown in Tables 1 to 4 were obtained using base metal 2 having a tensile strength of 490 MPa class.

[0044] [Table 1]

[0045] In Nos. 1 to 3 of the submerged arc welding method using a single electrode according to Comparative Example 2, filler wire 7, which was used as a hot wire in the two-electrode submerged arc welding method according to the Example, was not used. Meanwhile, in each of Nos. 1 to 3 of the submerged arc welding method using a single electrode according to Comparative Example 2, a cut wire was also used. In Nos. 1 and 3, wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YK-D was used as the cut wire. In No. 2, wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YK-DM was used as the cut wire. In all of Nos. 1 to 3, wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YD was used as the welding wire. Additionally, a flux manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YF-15A was used in combination.

[0046] In both Examples 4 and 5, the cutting wire used was a wire manufactured by Nippon Steel Welding Co., Ltd. under the brand name YK-D. The filler wire 7, or hot wire, was a wire manufactured by Nippon Steel Welding Co., Ltd. under the brand name YM-26. In both Examples 4 and 5, the preceding welding wire 4 used was a wire manufactured by Nippon Steel Welding Co., Ltd. under the brand name YD. In addition, a flux manufactured by Nippon Steel Welding Co., Ltd. under the brand name YF-15A was used in combination. In Example 4, the hot wire feeding speed was 14 m / min, while in Example 5, the hot wire feeding speed was 16 m / min.

[0047] Table 2 shows the test results of round bar tensile tests conducted using the weld metal parts of the welded joints obtained under each of the conditions of No. 1 to No. 5. In Table 2, "yield point" corresponds to "0.2% proof stress."

[0048] [Table 2] In both Nos. 4 and 5, which are the results of the example shown in Table 2, the values ​​of each parameter are generally equal to or greater than the values ​​of Nos. 1 to 3, which are the results of Comparative Example 2. In both Nos. 4 and 5, which are the results of the example, it can be seen that the weld metal zone has tensile properties of 0.2% proof stress: 320 MPa or more and tensile strength: 490 MPa or more.

[0049] Table 3 shows the results of chemical composition analysis of the weld metal of the welded joints obtained under each of the conditions No. 1 to No. 5.

[0050] [Table 3] It can be seen that both Nos. 4 and 5, which are the results of the examples shown in Table 3, contain a larger amount of Ti than Comparative Example 2.

[0051] Table 4 shows the results of Charpy impact tests performed using the weld metal of the welded joints obtained under each of the conditions No. 1 to No. 5. In Table 4, "TP No." is an identification number used to distinguish each individual test piece actually used in the Charpy impact test. "Notch position" indicates the location of the notch on the test piece. "DEPO" indicates that the notch is located in the weld metal itself. "HAZ" indicates that the notch is located in an area where the base metal 2 has not melted but where the properties have changed due to the heat of welding. The Charpy impact test was performed by immersing the test piece in 0°C alcohol and maintaining the temperature of the test piece at 0°C.

[0052] [Table 4] In Nos. 4 and 5, which are the results of the examples listed in Table 4, the absorbed energies under the "DEPO" condition were 47 and 44, respectively. These values ​​are generally larger than the absorbed energies of 24, 38, and 45 obtained under the "DEPO" condition for Nos. 1 to 3, which are the results of Comparative Example 2 listed in Table 2. It can be seen that in both Nos. 4 and 5, which are the results of the examples, the weld metal joint has impact toughness with an absorbed energy of 27 J or more in the Charpy impact test.

[0053] FIG. 5 is a graph showing test results of welded joints obtained using a two-electrode submerged arc welding method according to an embodiment. FIG. 5 shows test results of welded joints obtained using two-electrode submerged arc welding methods according to two embodiments, Example 1 and Example 2, compared to Comparative Example 2, which used a single electrode. For example, FIG. 5 shows the temperature dependence of absorbed energy (J) in a Charpy impact test conducted using the weld metal portion of a welded joint. In FIG. 5, the combination of black circles and a solid line indicates the experimental results of Example 1. The combination of white circles and a dashed line indicates the experimental results of Example 2. The combination of crosses and a dotted line indicates Comparative Example 2.

[0054] In Example 1, wire with a brand YD manufactured by Nippon Steel Welding Co., Ltd. was used as the preceding welding wire 4. In addition, a flux with a brand YF-15A manufactured by Nippon Steel Welding Co., Ltd. was used in combination. Wire with a brand YK-D manufactured by Nippon Steel Welding Co., Ltd. was used as the cutting wire. Wire with a brand YM-26 manufactured by Nippon Steel Welding Co., Ltd. was used as the hot wire, which was the filler wire 7. In Example 2, wire with a brand YD manufactured by Nippon Steel Welding Co., Ltd. was used as the preceding welding wire 4. In addition, a flux with a brand YF-15A manufactured by Nippon Steel Welding Co., Ltd. was used in combination. Wire with a brand YK-DM manufactured by Nippon Steel Welding Co., Ltd. was used as the cutting wire. Wire with a brand YM-55C manufactured by Nippon Steel Welding Co., Ltd. was used as the hot wire, which was the filler wire 7. In Comparative Example 2, wire with a brand YD manufactured by Nippon Steel Welding Co., Ltd. was used as the welding wire. In addition, a flux with a brand YF-15A manufactured by Nippon Steel Welding Co., Ltd. was used in combination. The cut wire used was a wire manufactured by Nippon Steel Welding Co., Ltd., with the brand name YK-DM.

[0055] 5, it can be seen that for each of Example 1 and Example 2, the absorbed energy value is higher over a wider temperature range than the value for Comparative Example 2. For Example 2, the absorbed energy value is significantly higher than the value for Comparative Example 2 over the entire temperature range.

[0056] Tables 5 to 8 show various test results when the combination of the cut wire and the hot wire was changed in the two-electrode submerged arc welding method according to the embodiment. Table 5 shows several conditions for the combination of the cut wire and the hot wire. In Tables 5 to 8, Nos. 6 to 11 respectively show the test specimen codes under several conditions for the combination of the cut wire and the hot wire. The test results shown in Tables 5 to 8 were obtained using base metal 2 having a tensile strength of 490 MPa.

[0057] [Table 5]

[0058] In all of the two-electrode submerged arc welding methods No. 6 to No. 11 according to the examples, wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YD was used as the preceding welding wire 4. In addition, a flux manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YF-15A was used in combination. As the cutting wire, wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YK-D or YK-DM was used. As the hot wire, wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YM-26, YM-55C, or YM-28 was used.

[0059] Table 6 shows the test results of the round bar tensile tests carried out using the weld metal parts of the welded joints obtained under the conditions of each of Nos. 6 to 11. In Table 6, "yield point" corresponds to "0.2% proof stress."

[0060] [Table 6] Referring to Nos. 6 to 11, which are the results of the examples listed in Table 2, the values ​​of each parameter change depending on the combination of the cutting wire and the hot wire. For example, when YK-DM is used as the cutting wire, the strength of the weld metal joint tends to increase. In all of Nos. 6 to 11, which are the results of the examples, it can be seen that the weld metal joint has tensile properties of 0.2% proof stress: 320 MPa or more and tensile strength: 490 MPa or more.

[0061] Table 7 shows the results of chemical composition analysis of the weld metal of the welded joints obtained under each of the conditions of Nos. 6 to 11.

[0062] [Table 7] It can be seen that Ti is contained most abundantly in No. 9, which is the result of an example listed in Table 7. It can be seen that Nos. 6 and 8, which are the result of an example listed in Table 7, contain, in mass%, Ti: 0.02 to 0.05%, Mo: 0.01 to 0.05%, and B: 0.0005% to 0.0010%.

[0063] Table 8 shows the results of Charpy impact tests performed using the weld metal of the welded joints obtained under each of the conditions No. 6 to No. 11. In Table 8, "TP No." is an identification number used to distinguish each individual test piece actually used in the Charpy impact test. "Notch position" indicates the location of the notch on the test piece. "DEPO" indicates that the notch is located in the weld metal itself. "HAZ" indicates that the notch is located in an area where the base metal 2 has not melted but where the properties have changed due to the heat of welding. The Charpy impact tests were performed by immersing the test piece in 0°C alcohol and maintaining the temperature of the test piece at 0°C.

[0064] [Table 8] In No. 9, which is the result of an example shown in Table 8, the absorbed energy was 101 under the "DEPO" condition, which was the highest. It can be seen that in No. 9, which is shown to have the highest Ti and Mo contents in Table 7, the absorbed energy also became the highest in accordance with the respective contents of Ti and Mo. It can be seen that in all of Nos. 6 to 11, which are the result of an example, the weld metal part had impact toughness of 27 J or more absorbed energy in a Charpy impact test.

[0065] Unlike the test results up to now, Tables 9 and 10 were obtained using a base material 2 having a tensile strength of 570 MPa. In the two-electrode submerged arc welding method according to the examples, wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name Y-DM was used as the preceding welding wire 4. In addition, a flux manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YF-15B was used in combination. Wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YK-DM was used as the cutting wire. Wire manufactured by Nippon Steel Welding Industry Co., Ltd. under the brand name YM-60C was used as the hot wire.

[0066] [Table 9] It can be seen that the weld metal zone obtained by the two-electrode submerged arc welding method according to the example has tensile properties of 0.2% proof stress: 400 MPa or more and tensile strength: 570 MPa or more.

[0067] [Table 10] It can be seen that the weld metal part obtained by the two-electrode submerged arc welding method according to the example has impact toughness of 27 J or more in absorbed energy in a Charpy impact test.

[0068] The above are test results relating to single-sided welding. Below, test results relating to double-sided welding of the base material 2 will be explained, which differ from the test results up to now.

[0069] Fig. 6A is a first schematic diagram for explaining test results of a welded joint obtained using a two-electrode submerged arc welding method according to an embodiment. Fig. 6B is a second schematic diagram for explaining test results of a welded joint obtained using a two-electrode submerged arc welding method according to an embodiment. Fig. 6A is a diagram showing two base materials 2 to be double-sided welded as viewed from above. Fig. 6B is a diagram showing two base materials 2 to be double-sided welded as viewed from a side.

[0070] Each of the two base materials 2 is a steel plate having a width of 500 mm and a thickness of 28 mm. The two arranged base materials 2 have a total depth of 400 mm. Where the two base materials 2 are butted together, a groove is formed on both sides. For example, a groove is formed on both the leading BP (Back Pass) side and the trailing FP (Face Pass) side.

[0071] The groove has an 80° groove angle on the leading BP side and a 50° groove angle on the trailing FP side, creating an X-shaped groove with no root face. On the leading BP side, the first layer is sealed using CO2 welding, and then submerged arc welding is performed. On the trailing FP side, the first layer, which was created by CO2 welding, is removed by gouging, and then submerged arc welding is performed in the same way.

[0072] Submerged arc welding was performed under three conditions. The first condition includes a condition in which the welding wire feed rate was 45 cm / min in the submerged arc welding method using a single electrode according to Comparative Example 2. The second condition includes a condition in which the welding wire feed rate was 35 cm / min in the submerged arc welding method using a single electrode according to Comparative Example 2. The third condition includes a condition in which the welding wire feed rate was 35 cm / min in the two-electrode submerged arc welding method according to the example.

[0073] 7A is a schematic diagram showing an example of the state of the groove on the leading BP side of the weld metal part obtained under the first condition. FIG. 7B is a schematic diagram showing an example of the state of the groove on the trailing FP side of the weld metal part obtained under the first condition. In the groove on the leading BP side of the weld metal part, a first layer is sealed by CO2 welding, and then a fourth layer is formed by four passes of submerged arc welding. In the groove on the trailing FP side of the weld metal part, the first layer formed by CO2 welding is removed by gouging, and then a seventh layer is formed by seven passes of submerged arc welding.

[0074] 8A is a schematic diagram showing an example of the state of the groove on the leading BP side of the weld metal part obtained under the second condition. FIG. 8B is a schematic diagram showing an example of the state of the groove on the trailing FP side of the weld metal part obtained under the second condition. In the groove on the leading BP side of the weld metal part, the first layer is sealed by CO2 welding, and then three layers are further formed by three passes of submerged arc welding. In the groove on the trailing FP side of the weld metal part, the first layer formed by CO2 welding is removed by gouging, and then a fifth layer is further formed by five passes of submerged arc welding.

[0075] The welding wire feed speed under the second condition is slower than that under the first condition, and as a result, the number of passes is reduced on both the leading BP side and the trailing FP side.

[0076] 9A is a schematic diagram showing an example of the state of the groove on the leading BP side of the weld metal part obtained under the third condition. FIG. 9B is a schematic diagram showing an example of the state of the groove on the trailing FP side of the weld metal part obtained under the third condition. In the groove on the leading BP side of the weld metal part, a first layer is sealed by CO2 welding, and then a second layer is formed by one pass of two-electrode submerged arc welding. In the groove on the trailing FP side of the weld metal part, the first layer formed by CO2 welding is removed by gouging, and then a third layer is formed by three passes of two-electrode submerged arc welding.

[0077] In the third condition, the two-electrode submerged arc welding method according to the embodiment is used, and therefore the number of passes is reduced on both the leading BP side and the trailing FP side compared to the first and second conditions. On the leading BP side, welding is achieved by one pass of two-electrode submerged arc welding.

[0078] 10 is a third schematic diagram for explaining test results of a welded joint obtained using a two-electrode submerged arc welding method according to an embodiment. The test results of the angular distortion measurement test performed under each of the first to third conditions will be explained with reference to FIGS. 6A to 10.

[0079] In this measurement test, the amount of angular distortion was the average value at three locations, 100 mm, 250 mm, and 400 mm along the weld line direction. Measurements were conducted on both the leading BP side and the trailing FP side. As shown in Figure 10, the amount of angular distortion was coded with a positive direction representing upward deformation and a negative direction representing downward deformation. An example of the measurement results is shown in Table 11.

[0080] [Table 11] For example, under the first condition, the angular distortion after welding the leading BP side was +14.5° and after welding the trailing FP side was +1.6°. Under the second condition, the angular distortion after welding the leading BP side was +15.8° and after welding the trailing FP side was +4.4°. On the other hand, under the third condition, the angular distortion after welding the leading BP side was +8.3° and after welding the trailing FP side was -0.8°. In either case, under the third condition, the angular distortion value was smaller than the values ​​under the first and second conditions and was closer to zero.

[0081] Table 12 shows the test results of the round bar tensile tests conducted using the weld metal parts of the welded joints obtained under each of Conditions 1 to 3. In Table 12, "yield point" corresponds to "0.2% proof stress."

[0082] [Table 12] In the results of the example under the third condition shown in Table 12, the values ​​of the yield point and tensile strength are greater than those in the results of Comparative Example 2 under the first and second conditions. The results of the example show that the weld metal part has tensile properties of 0.2% proof stress: 320 MPa or more and tensile strength: 490 MPa or more.

[0083] Table 13 shows the results of chemical composition analysis of the weld metal of the welded joints obtained under each of the first to third conditions.

[0084] [Table 13] In the results of the example under the third condition shown in Table 13, it can be seen that the Ti content is significantly increased compared to the first and second conditions.

[0085] Table 14 shows the results of Charpy impact tests conducted using the weld metal portions of the welded joints obtained under each of the first to third conditions. In Table 14, "Notch Position" indicates the location of the notch in the test specimen. "DEPO" indicates that the notch is located in the weld metal portion itself. "HAZ" indicates that the notch is located in an area where the base material 2 has not melted but where the properties have changed due to the heat of welding. The Charpy impact tests were conducted by immersing the test specimen in 0% alcohol and maintaining the temperature of the test specimen at 0°C.

[0086] [Table 14] In the results of the examples under the third condition shown in Table 14, the brittle fracture rate was the highest at 60 under the "DEPO" condition. In the results of the examples under the third condition, it can be seen that the weld metal part has impact toughness with absorbed energy of 27 J or more in a Charpy impact test.

[0087] (Variation) It will be apparent to those skilled in the art that the present disclosure may be embodied in other specific forms other than the above-described embodiments without departing from the spirit or essential characteristics thereof. Therefore, the foregoing description is illustrative and not limiting. The scope of the disclosure is defined not by the foregoing description but by the appended claims. All modifications within the range of equivalents of any modifications are intended to be embraced therein.

[0088] For example, the shape, pattern, size, arrangement, orientation, type, and number of each of the above-described components are not limited to those described above and illustrated in the drawings, and may be arbitrarily configured as long as the function can be realized.

[0089] In the above embodiment, the polarity of the leading electrode 3 is AC and the polarity of the trailing electrode 6 is DC negative, but this is not limiting. The polarity of the leading electrode 3 may be other than AC. The polarity of the trailing electrode 6 may be other than DC negative.

[0090] In the above embodiment, the filling height of the cutting wire is described as 16 mm or more, but is not limited thereto, and may be less than 16 mm.

[0091] In the above embodiment, the diameter of the preceding welding wire 4 is described as 4.8 mm, but is not limited to this. The diameter of the preceding welding wire 4 may have other values.

[0092] In the above embodiment, the weld metal portion of the weld joint is described as containing, by mass%, Ti: 0.02 to 0.05%, Mo: 0.01 to 0.05%, and B: 0.0005% to 0.0010%, but is not limited thereto. The weld metal portion of the weld joint may be configured under other conditions.

[0093] In the above embodiment, the weld metal portion of the welded joint has tensile properties of 0.2% proof stress: 320 MPa or more and tensile strength: 490 MPa or more, and impact toughness of absorbed energy: 27 J or more in a Charpy impact test, but is not limited thereto. The weld metal portion of the welded joint may be configured under other conditions.

[0094] In the above embodiment, the weld metal part has been described as having tensile properties of 0.2% proof stress: 400 MPa or more, tensile strength: 570 MPa or more, and impact toughness of absorbed energy: 27 J or more in a Charpy impact test, but is not limited thereto. The weld metal part of the weld joint may be configured under other conditions.

[0095] Some embodiments of the present disclosure will be described below as examples, however, it should be noted that the embodiments of the present disclosure are not limited to these examples. [Appendix 1] Distributing a cut wire within the groove of the base material; outputting a current from a power source through a leading electrode to energize a leading welding wire, thereby generating an arc between the base metal and the leading welding wire within the groove; a welding process is carried out while supplying a heated filler wire to a molten pool formed behind the arc by applying current from the power source through a trailing electrode without generating an arc; Including, the leading electrode is inclined toward the welding direction at a predetermined sweepback angle with respect to an axis perpendicular to the welding direction and the base metal; Two-electrode submerged arc welding method. [Appendix 2] 2. A two-electrode submerged arc welding method according to claim 1, The sweepback angle is in the range of greater than 0° and less than or equal to 5°. Two-electrode submerged arc welding method. [Appendix 3] A two-electrode submerged arc welding method according to appendix 1 or 2, the polarity of the preceding electrode is alternating; The polarity of the trailing electrode is DC negative. Two-electrode submerged arc welding method. [Appendix 4] A two-electrode submerged arc welding method according to any one of appendices 1 to 3, performed on each of the two surfaces of the base material; Two-electrode submerged arc welding method. [Appendix 5] A two-electrode submerged arc welding method according to any one of appendices 1 to 4, The filling height of the cut wire is 16 mm or more; Two-electrode submerged arc welding method. [Appendix 6] A two-electrode submerged arc welding method according to any one of appendices 1 to 5, The diameter of the preceding welding wire is 4.8 mm; Two-electrode submerged arc welding method. [Appendix 7] A welded joint in which the base materials are welded together via a weld metal portion by the two-electrode submerged arc welding method described in any one of appendices 1 to 6. [Appendix 8] 8. The welded joint of claim 7, The weld metal portion contains, by mass%, Ti: 0.02 to 0.05%, Mo: 0.01 to 0.05%, and B: 0.0005% to 0.0010%. Welded joints. [Appendix 9] A welded joint according to appendix 7 or 8, The weld metal part has tensile properties of 0.2% proof stress: 320 MPa or more and tensile strength: 490 MPa or more, and impact toughness of absorbed energy: 27 J or more in a Charpy impact test. Welded joints. [Appendix 10] A welded joint according to appendix 7 or 8, The weld metal part has tensile properties of 0.2% proof stress: 400 MPa or more and tensile strength: 570 MPa or more, and impact toughness of absorbed energy: 27 J or more in a Charpy impact test. Welded joints. [Appendix 11] a leading electrode that outputs a current from a power source to energize a leading welding wire and generate an arc between the base metal and the leading welding wire within a groove of the base metal; the leading welding wire supported by the leading electrode; a trailing electrode that supplies a filler wire heated by energizing the power source without generating an arc to a molten pool formed behind the arc while proceeding with welding; a filler wire supported by the trailing electrode; Equipped with the leading electrode is inclined toward the welding direction at a predetermined sweepback angle with respect to an axis perpendicular to the welding direction and the base metal; Welding equipment. [Explanation of symbols]

[0096] 1. Welding equipment 2 Base material 3 Leading electrode 3a tip 4. Pre-welding wire 4a tip 5. Flux 6 Trailing electrode 6a tip 7 Filler Wire 7a tip 8. Slug 9 Weld Metal 10 Molten slag A Arc D Between poles L protrusion length P molten pool R angle X Direction of travel Z-axis θ Sweeping angle

Claims

1. Distributing a cut wire within the groove of the base material; outputting a current from a power source through a leading electrode to energize a leading welding wire, thereby generating an arc between the base metal and the leading welding wire within the groove; a welding process is carried out while supplying a heated filler wire to a molten pool formed behind the arc by applying current from the power source through a trailing electrode without generating an arc; Including, the leading electrode is inclined toward the welding direction at a predetermined sweepback angle with respect to an axis perpendicular to the welding direction and the base metal; The method further includes welding the base materials together via a weld metal portion, The toe radius of the back wave formed in the weld metal portion is 15 mm when the sweepback angle is 5°. Two-electrode submerged arc welding method.

2. 2. The two-electrode submerged arc welding method according to claim 1, The sweepback angle is in the range of greater than 0° and less than or equal to 5°. Two-electrode submerged arc welding method.

3. 2. The two-electrode submerged arc welding method according to claim 1, the polarity of the preceding electrode is alternating; The polarity of the trailing electrode is DC negative. Two-electrode submerged arc welding method.

4. A two-electrode submerged arc welding method according to any one of claims 1 to 3, performed on each of the two surfaces of the base material; Two-electrode submerged arc welding method.

5. A two-electrode submerged arc welding method according to any one of claims 1 to 3, The filling height of the cut wire is 16 mm or more. Two-electrode submerged arc welding method.

6. A two-electrode submerged arc welding method according to any one of claims 1 to 3, The diameter of the preceding welding wire is 4.8 mm. Two-electrode submerged arc welding method.

7. A two-electrode submerged arc welding method according to any one of claims 1 to 3, The weld metal portion contains, in mass%, Ti: 0.02 to 0.05%, Mo: 0.01 to 0.05%, and B: 0.0005% to 0.0010%. Two-electrode submerged arc welding method.

8. A two-electrode submerged arc welding method according to any one of claims 1 to 3, The weld metal part has tensile properties of 0.2% proof stress: 320 MPa or more and tensile strength: 490 MPa or more, and impact toughness of absorbed energy in a Charpy impact test: 27 J or more. Two-electrode submerged arc welding method.

9. A two-electrode submerged arc welding method according to any one of claims 1 to 3, The weld metal part has tensile properties of 0.2% proof stress: 400 MPa or more and tensile strength: 570 MPa or more, and impact toughness of absorbed energy in a Charpy impact test: 27 J or more. Two-electrode submerged arc welding method.

10. a leading electrode that outputs a current from a power source to energize a leading welding wire and generate an arc between the base metal and the leading welding wire within a groove of the base metal; the leading welding wire supported by the leading electrode; a trailing electrode that supplies a filler wire heated by energizing the power source without generating an arc to a molten pool formed behind the arc while proceeding with welding; a filler wire supported by the trailing electrode; Equipped with the leading electrode is inclined toward the welding direction at a predetermined sweepback angle with respect to an axis perpendicular to the welding direction and the base metal; When the base materials are welded and joined via a weld metal portion, the toe radius of the back wave formed in the weld metal portion is 15 mm when the sweepback angle is 5°. Welding equipment.

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