JPWO2013179614A1 - Laser-arc hybrid welding method - Google Patents

Abstract

In order to suppress the occurrence of cold cracking, high strength steel sheets with a tensile strength of 780 MPa or more are to be welded, consumable electrode type arc welding is preceded in the welding progress direction, laser welding is arranged downstream, and arc The distance between the welding wire target position and the laser beam irradiation position is in the range of 3 to 5 mm, and the electrode angle of arc welding is set to a receding angle in the range of 20 to 60 mm on the welding direction side. The incident angle is set to an angle in the range of 0 to 30 mm from the vertical direction to the welding progress direction. [Selection] Figure 1

Description

The present invention relates to a laser and arc hybrid welding method in which laser welding and consumable electrode arc welding are used in combination, and in particular, tensile strength. High strength steel sheet with high strength of 780 MPa or more
or plate) and a laser-arc hybrid welding method.

  Since laser welding can obtain a high energy density, deep penetration and high speed welding are possible, and it is expected as a high-efficiency welding method. Moreover, since it becomes very local melting, the influence of the heat added to a base material is also small, and a high quality welded joint (weld joint) with a small distortion and a deformation | transformation can be obtained.

  On the other hand, arc welding, which has been widely used conventionally, can be handled more easily than laser welding, and the apparatus is inexpensive and versatile. However, compared to laser welding, the penetration depth is small and the welding speed is also slow.

  Therefore, in order to utilize the advantages of both, laser / arc hybrid welding combining laser welding and arc welding has been proposed. Since laser-arc hybrid welding uses two heat sources having different energy densities, the welding speed is increased, the groove gap is dimensional accuracy reduced, It is known that it is effective in increasing the penetration depth, improving the characteristics of the welded joint (specifically, improving the toughness of the weld metal, etc.), and suppressing weld defects.

  Incidentally, as a laser-arc hybrid welding method, for example, those described in Patent Documents 1 to 3 below are known.

  In Patent Document 1, a laser is disposed in advance and an arc is disposed in the subsequent direction, and the root gap of the material to be welded is set to a range of 10% or more of the plate thickness to a laser beam diameter or less. Thus, a laser-arc hybrid welding method capable of achieving high penetration welding with deep penetration has been disclosed.

  In Patent Document 2, high-speed weldability and high gap resistance (high speed weldability) are achieved by performing welding with an arc preceding, a laser following, and placing the laser and the arc on the same weld line. A technique relating to a laser-arc hybrid welding method excellent in gap tolerance) is disclosed.

  In Patent Document 3, an arc is preceded and a laser is moved backward, and arc welding is performed by arranging a pair of arc electrodes (also referred to as torches) on both sides of a welding line and arranging their tips. A laser beam (laser beam) is irradiated through the gap between the arc electrodes in a state tilted in the welding progress direction, so that a high-quality welded joint can be produced even when a large gap exists between the members to be welded. A technique relating to a laser-arc hybrid welding method that can be formed by the following method is disclosed.

Japanese Patent Laid-Open No. 10-216972 JP 2006-224130 A JP 2011-147944 A

  By the way, since the cooling rate after welding of laser-arc hybrid welding is higher than that of arc welding, particularly in high strength steel having a tensile strength of 780 MPa or more which is easy to harden, low temperature cracking of weld metal (weld metal). There is concern about the occurrence of (cold cracking).

  In general, the causes of cold cracking include (a) diffusible hydrogen of weld metal, (b) welded-heated zone (HAZ), hardened microstructure of weld metal, and (c) welding. The joint stress of the joint is three, and it is said that cold cracking occurs when these conditions are met. Immediately after the end of welding, hydrogen is often dissolved in a supersaturated state in the weld metal, and it is considered that these diffuse into high stress points and accumulate to crack.

  However, in the above-mentioned Patent Documents 1 to 3, the main focus is on achieving both gap tolerance and high-speed welding, and no consideration is given to prevention of cold cracking. In particular, in the case of laser-arc hybrid welding, diffusible hydrogen, which is considered to be mixed from the welding wire or the atmosphere in the arc welding process, cannot be ignored.

  The present invention has been made in view of the circumstances as described above, and is a low-temperature crack prevention technique that is considered to be a problem in applying laser-arc hybrid welding to a high-strength steel sheet having a tensile strength of 780 MPa or more. For establishment, an object is to provide a laser-arc hybrid welding method capable of reducing the amount of diffusible hydrogen in a weld metal.

In order to solve the above-mentioned problems, the present inventor measured the amount of diffusible hydrogen in the weld metal part of laser-arc hybrid welding under various conditions of changing the arrangement of the laser and the arc, and welding conditions (welding conditions). The effects of selenium on the amount of diffusible hydrogen have been investigated. As a result, the amount of diffusible hydrogen tends to decrease when welding with an arc in the front and a laser in the succeeding case and welding with the laser in the preceding and the arc in the following. I found out. In addition, the electrode angle of the preceding arc welding (angle of)
It was also found that the effect of reducing the amount of diffusible hydrogen is large when the electrode is inclined so as to have a sweepback angle with respect to the welding progress direction side. Furthermore, it has also been found that the effect of reducing the amount of diffusible hydrogen is small unless the distance between the welding wire aiming position (wire aim position) and the laser beam irradiation position (laser beam irradiation position) of arc welding is within a certain range.

  The present invention has been made on the basis of the above knowledge and has the following features.

  [1] A high strength steel sheet having a tensile strength of 780 MPa or more is to be welded, consumable electrode type arc welding is preceded and laser welding is followed in the welding progress direction, and the welding wire target position for arc welding And the laser beam irradiation position within a range of 3 to 5 mm, the arc welding electrode angle is set to a receding angle of 20 to 60 ° in the welding direction, and the laser welding incident angle (angle of) A laser-arc hybrid welding method, characterized in that the incidence is set to an angle in a range of 0 to 30 ° from a vertical direction to a welding direction.

  [2] The laser / arc hybrid welding method according to [1], wherein a welding current of the arc welding is 300 A or less.

  [3] The laser-arc hybrid welding method according to [1] or [2], wherein a laser power of the laser welding is 3 kW or more.

  According to the present invention, in performing laser-arc hybrid welding of a high strength steel plate having a tensile strength of 780 MPa or more, the amount of diffusible hydrogen in the weld metal can be reduced, and a high strength steel plate having a tensile strength of 780 MPa or more. It is possible to improve the low temperature cracking resistance.

FIG. 1 is a schematic side view of a situation in which butt welding of materials to be welded is seen from the side in the welding direction in one embodiment of the present invention. FIG. 2 is a schematic view of a test piece used for measuring the hydrogen amount in the example of the present invention.

  A laser-arc hybrid welding method according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic side view of a situation when butt welding of materials to be welded is viewed from the side in the welding progress direction in an embodiment of the present invention. In FIG. 1, 1 is a material to be welded, 2 is an arc welding electrode, 3 is a welding wire, 4 is a laser welding head, 5 is a laser beam, 6 is a weld bead, and arrow A is welding. Each direction is shown. Also, let X be the distance between the target position of the arc welding wire and the laser beam irradiation position. Further, the inclination angle (that is, the receding angle) of the arc welding electrode 2 with respect to the vertical direction is θa, and the incident angle of the laser beam of laser welding is θb. In addition, the welding wire target position of arc welding means the point where the extension line of a welding wire cross | intersects the steel plate surface. The laser beam irradiation position refers to the center of the beam diameter of the irradiated laser beam on the steel plate surface.

  First, in this embodiment, arc welding is preceded and laser welding is arranged downstream, and the electrode angle θa of arc welding is set to a receding angle on the welding progress direction side. This is because diffusible hydrogen brought in from the atmosphere is reduced by welding the arc welding with a sweepback angle method, thereby reducing the width of the weld bead and reducing the area of the molten metal in contact with the atmosphere. This is because it can be reduced. Therefore, considering the handling of the arc welding electrode 2 and the laser welding head 4, arc welding is the preceding arrangement.

  In addition, the distance X between the welding wire aiming position of the arc welding and the laser beam irradiation position is defined as a range of 3 to 5 mm. When X is less than 3 mm, the laser beam 5 directly hits the welding wire 3 due to the fluctuation of the welding wire 3, and the welding tends to become unstable. Also, when X exceeds 5 mm, the molten pool formed by arc welding and the molten pool by laser welding are separated, so the surface area where the molten metal comes into contact with the atmosphere increases and diffusible hydrogen is mixed. It becomes easy. Therefore, the distance X between the welding wire aiming position of the arc welding and the laser beam irradiation position is set in the range of 3 to 5 mm.

  And the receding angle θa of arc welding is defined as a range of 20 to 60 °. If the receding angle θa is less than 20 °, the width of the weld bead of arc welding is not significantly narrowed, so it is difficult to obtain the effect of reducing the diffusible hydrogen of the weld metal, and if the receding angle θa exceeds 60 °, the arc The weld bead shape becomes unstable and the penetration depth decreases. Therefore, the receding angle θa for arc welding is set in the range of 20 to 60 °. More preferably, it is the range of 30-45 degrees.

  Further, the incident angle θb of the laser beam 5 is defined as a range of 0 to 30 ° from the vertical direction to the welding progress direction. When the incident angle θb of the laser beam 5 is less than 0 °, the laser welding head 4 and the arc welding torch 2 are inclined to the same side as the welding direction, and only interfere with each other in position. In addition, there is no effect obtained. On the other hand, when the incident angle θb of the laser beam 5 exceeds 30 °, the penetration depth decreases. Therefore, the incident angle θb of the laser beam 5 of laser welding is set in the range of 0 to 30 °. More preferably, it is the range of 0-15 degree.

  And it is preferable that the welding current of arc welding shall be 300 A or less. The laser output of laser welding is preferably 3 kW or more.

  That is, when the arc welding current exceeds 300 A, the welding amount of the welding wire 3 (volume of deposition metal) increases, so that diffusible hydrogen mixed from the welding wire 3 also increases. Therefore, the welding current for arc welding is preferably 300 A or less.

  On the other hand, if the laser output is less than 3 kW, it is difficult to obtain the deep penetration expected in laser-arc hybrid welding of thick plates. In addition, when the melting of the base material by laser welding (dilution ratio) becomes small, it becomes closer to the case of arc-only welding, and it is difficult to obtain the effect of reducing diffusible hydrogen. Therefore, the laser output of laser welding is preferably 3 kW or more.

  In addition, as laser welding used in the present invention, laser beams using various forms of oscillators can be used.

For example, a gas _{(e.g., CO 2 (carbon dioxide gas)} , helium - neon (helium-neon), argon (argon would be), nitrogen (Pnitrogen), iodine (iodine) or the like) gas laser (gas laser) used as the medium, A solid laser using a solid (for example, YAG doped with rare earth elements) as a medium, a fiber laser using a fiber instead of a bulk as a laser medium A disk laser or the like is preferable. Or you may use a semiconductor laser (semiconductor laser).

  Moreover, as the arc welding used in the present invention, gas shielded arc welding can be used in which welding is performed while shielding the arc and the weld metal from the atmosphere with a shielding gas.

For example, MAG welding using a CO ₂ gas or a mixed gas of Ar and CO ₂ (metal
Electrode welding (consumable electrode type), in which electrodes are continuously melted and consumed, such as active gas welding) and MIG welding (metal inert gas welding) using an inert gas such as Ar or He, is preferable.

  The present invention will be described more specifically with reference to examples of the amount of diffusible hydrogen in the weld metal portion of the laser-arc hybrid weld joint.

  The test method shown in JIS Z 3118 is generally used as a method for measuring the hydrogen content of steel welds intended for arc welding. Accordingly, in the measurement of diffusible hydrogen in laser-arc hybrid welding, basic matters such as the shape of the test piece, collection of diffusible hydrogen, and a method for measuring the amount of hydrogen were performed in accordance with JIS (Japan Industrial Standards). That is, from an HT780 grade steel plate used as a test steel, a test plate 1A having a plate thickness of 12 mm × width of 25 mm × length of 40 mm and an end tab (end tab of 12 mm thick × 25 mm wide × 45 mm long) as shown in FIG. ) 1B was prepared, and the amount of diffusible hydrogen in the welds with various laser-arc hybrid welding conditions varied was measured.

  Table 1 shows the laser-arc hybrid welding conditions.

Note that a YAG laser welding machine was used for laser welding, and the laser shielding gas was pure Ar. On the other hand, HT780 grade MAG welding solid wire (1.2 mm diameter) was used for arc welding, and 80 vol% Ar-20 vol% CO ₂ was used as the shielding gas. The welding speed was set to 0.5 m / min to prevent penetration of the test plate 1A having a thickness of 12 mm.

  In the present invention examples (joints No. 1, 3, 4, 6, 7, and 8) in Table 1, the arc welding is preceded by the laser welding, and the distance X between the welding wire target position of the arc welding and the laser beam irradiation position Is an example in which the electrode angle θa of arc welding is set to a receding angle of 20 to 60 ° and the incident angle θb of the laser beam is set to 0 to 30 °. In addition, the joint No. In Nos. 1, 3, 4, and 7, the welding current for arc welding is 300 A or less, and the laser output for laser welding is 3 kW or more. 6, the welding current of arc welding is set to 320 A, which exceeds 300 A, and the joint No. In No. 8, the laser output of laser welding is 2.5 kW, which is less than 3 kW.

  On the other hand, among the comparative examples (joints No. 2, 5, 9, 10, 11) in Table 1, the joint No. No. 2 is an example in which laser welding precedes arc welding. No. 5 is an example in which the distance X between the target position of the welding wire for arc welding and the laser beam irradiation position is 1 mm which is less than 3 mm. No. 9 is an example in which the distance X between the target position of the welding wire for arc welding and the laser beam irradiation position is 6 mm, which is more than 5 mm. No. 10 is an example in which the incident angle θb of the laser beam is 45 ° which is more than 30 °. 11 is an example in which the arc welding torch angle θa is set to a receding angle of 70 °, which exceeds 60 °.

  Table 2 shows the results of measurement of the amount of diffusible hydrogen in these laser-arc hybrid welds.

  Here, as an evaluation index of the amount of diffusible hydrogen, not “amount of hydrogen per mass of deposited metal” generally used for evaluation in arc welding, but “amount per mass of weld metal” “Hydrogen amount” was used. The reason for this is that in the case of laser-arc hybrid welding, the melting (dilution ratio) of the base metal is higher than that of arc-only welding due to the effect of high-energy density laser welding. This is because it was deemed appropriate. The collecting conditions for diffusible hydrogen were 45 ° C. × 72 hours, and the amount of hydrogen was measured by gas chromatographic measurement.

  As is apparent from Table 2, in the present invention example, the “hydrogen amount per mass of the weld metal” was 0.40 ml / 100 g or less. On the other hand, the “hydrogen amount per mass of weld metal” in the comparative example was a value exceeding 0.60 ml / 100 g. That is, according to the present invention, the “hydrogen amount per mass of the weld metal” can be almost halved.

  According to the present invention, since the amount of diffusible hydrogen in the laser-arc hybrid weld can be reduced, the low temperature cracking resistance of the high strength steel can be improved, and thus an industrially significant effect is achieved.

1 Work Material 1A Test Plate 1B End Tab 2 Arc Welding Electrode 3 Welding Wire 4 Laser Welding Head 5 Laser Beam 6 Welding Bead

Claims (3)

  A high strength steel plate with a tensile strength of 780 MPa or more is the object to be welded. Consumable electrode type arc welding is preceded and laser welding is arranged downstream of the welding direction, and the welding wire target position and laser beam of arc welding are arranged. The distance of the irradiation position is set to a range of 3 to 5 mm, the electrode angle of arc welding is set to a receding angle of 20 to 60 ° on the welding progress direction side, and the laser beam incidence angle of laser welding is progressed from the vertical direction. A laser-arc hybrid welding method characterized in that the angle is in the range of 0 to 30 ° to the direction.   The laser-arc hybrid welding method according to claim 1, wherein a welding current of the arc welding is 300 A or less. The laser-arc hybrid welding method according to claim 1 or 2, wherein the laser output of the laser welding is 3 kW or more.

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