WO2013179614A1

WO2013179614A1 - Laser-arc hybrid welding method

Info

Publication number: WO2013179614A1
Application number: PCT/JP2013/003278
Authority: WO
Inventors: 博幸角
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2012-05-29
Filing date: 2013-05-23
Publication date: 2013-12-05
Also published as: JPWO2013179614A1; CN104349863A; KR20140133935A

Abstract

By the present invention, in order to suppress cold cracking, consumable electrode type arc welding is placed at the preceding side and laser welding is placed at the succeeding side with respect to the direction of weld progress, using a high-strength steel sheet having a tensile strength of at least 780 MPa as the welding subject, the distance between the position at which a welding wire for arc welding is aimed and the position of laser beam irradiation is set to a range of 3-5 mm, the electrode angle for arc welding is set to a sweepback angle in the range of 20-60° toward the direction of weld progress, and the incidence angle of the laser beam for laser welding is set to an angle in the range of 0-30° in the direction of weld progress from the vertical direction.

Description

Laser-arc hybrid welding method

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

Since laser welding can obtain a high energy density, deep penetration can be performed and high speed welding is expected, which is expected as a high-efficiency welding method. Moreover, since it becomes very local fusion | 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 with 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 with different energy densities, the welding speed is increased, the dimensional accuracy of the groove gap is reduced, It is known to be 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 (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 gap resistance (high-speed weldability) are achieved by performing welding with an arc preceding, laser following, and placing the laser and 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, the arc is preceded and the 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 the weld line and arranging the tips of the electrodes. By irradiating a laser beam through the gap between the arc electrodes in a state inclined in the welding progress direction, a high-quality welded joint can be obtained even if 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.

JP-A-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 with a tensile strength of 780 MPa or more which is easy to harden, cold cracking of the weld metal (weld metal) is low. There is concern about the occurrence of (cold cracking).

In general, the causes of cold cracking include (a) diffusible hydrogen of weld metal, (b) HAZ (welded heat-affected zone), hardened microstructure of weld metal, and (c) welding. There are three types of restraint stress of the joint, 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 Patent Documents 1 to 3 described above, the 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 that 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 problems, the present inventor measured the amount of diffusible hydrogen in the weld metal part of laser / arc hybrid welding under conditions in which the arrangement of the laser and the arc was variously changed, and the welding condition (welding condition). 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, when the electrode angle of the preceding arc welding (angle of electrode) is inclined so as to be a sweepback angle with respect to the welding progress direction side, the finding that the effect of reducing the amount of diffusible hydrogen is large Also got. Furthermore, it was also found that the effect of reducing the amount of diffusible hydrogen is small unless the distance between the welding wire target position (wire aim position) and laser beam irradiation position (laser beam irradiation position) of arc welding is within a certain range.

The present invention has been made based on 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 The distance between the laser beam irradiation position and the laser beam irradiation position is set to a range of 3 to 5 mm, and the arc welding electrode angle is set to a receding angle of 20 to 60 ° in the welding progress direction. A laser-arc hybrid welding method characterized in that the incidence is set to an angle in the range of 0 to 30 ° from the vertical direction to the 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 the laser power of the laser welding (laser power) 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 (but welding) 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 showing a situation when butt welding of materials to be welded is seen from the side in the welding progress direction in one 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 toward the welding direction. 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 target position of the welding wire for 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, if 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 air increases and diffusible hydrogen is mixed. It becomes easy. Therefore, the distance X between the welding wire target 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 20-60 °. 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 in the range of 30 to 45 °.

Furthermore, 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 for laser welding is set in the range of 0 to 30 °. More preferably, it is in the range of 0 to 15 °.

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 amount of deposition of the welding wire 3 (volume of deposit 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 becomes difficult to obtain the deep penetration expected by laser-arc hybrid welding of thick plates. In addition, when the melting of the base material by laser welding (dilution ratio) is reduced, the effect of reducing diffusible hydrogen is difficult to obtain because it approaches that of arc welding alone. Therefore, the laser output of laser welding is preferably 3 kW or more.

In addition, as the 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).

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

For example, electrodes such as MAG welding (metal active gas welding) using CO ₂ gas or a mixed gas of Ar and CO ₂ and MIG welding (metal inert gas welding) using an inert gas such as Ar or He are continuously melted. In this case, the welding electrode type (consumable electrode type) welding that wears out is suitable.

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

The test method shown in JIS Z 3118 is generally used as a method for measuring the amount of hydrogen in a steel weld for arc welding. Therefore, in the measurement of diffusible hydrogen in laser-arc hybrid welding, basic matters such as the shape of the test piece, the collection of diffusible hydrogen, and the 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 In the range of 3 to 5 mm, 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 1, 3, 4, and 7, the welding current for arc welding is set to 300 A or less, and the laser output for laser welding is set to 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 the “hydrogen amount per mass of deposited metal” generally used for evaluation in arc welding, but “per unit 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. In addition, the collection conditions (collecting conditions) of diffusible hydrogen were 45 degreeC x 72 hours, and the amount of hydrogen was measured with the gas chromatograph method (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 high-strength steel can be improved.

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

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 in the range of 3 to 5 mm, the electrode angle of arc welding is set to a receding angle of 20 to 60 ° in the welding progress direction, 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.