JP3217138B2 - Laser welding wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire used for welding using a laser as a heat source.

[0002]

2. Description of the Related Art Laser welding is a joining method using a laser having a high energy density, a light energy that does not attenuate in the atmosphere, and the like as a heat source. For example, a CO ₂ laser or a YAG laser is used. For this reason, high-speed welding can be performed, and it is used for butt welding and lap welding of thin plates. Further, since a vacuum processing chamber is not required unlike electron beam welding and multi-processing is possible, it is being adopted as a welding method replacing electron beam welding.

Conventionally, two types of laser welding methods have been adopted: a method using no filler metal and a method using a filler material (wire) containing Si or Mn having a relatively high carbon content. I was However, in the case of laser welding without using a wire as in the former case, there are problems in that the base material is misaligned, the allowable range for the gap is narrow, and blowholes and pits are easily generated. Further, when the carbon equivalent of the base material is high, there is also a problem that the weld metal is hard and the toughness cannot be obtained.

[0004] On the other hand, in the latter laser welding using a wire, a wire having a relatively medium carbon content is used.
Although the problems such as the allowable range for the gap can be solved, there is a disadvantage that the hardness of the weld metal is high. Therefore, it has been attempted to use a wire having a relatively low carbon content and containing Si or Mn. According to this, the hardness of the weld metal can be reduced even though the base metal is diluted,
Since the cooling rate is high, there is a problem that baking easily occurs and the toughness is not high.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a welding material capable of improving the toughness of a weld joint in laser welding using a wire.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventors have studied the relationship between the composition of the wire and the toughness when a steel sheet having a relatively medium carbon equivalent is used as the base material. As a result, they have found that this is possible by using a wire having a low carbon equivalent and a complex addition of B and Ti or Zr, and have completed the present invention.

That is, according to the present invention, C: 0.10% or less, Si: 0.50% or less, Mn: 1.50% or less, and B:
0.0016-0.010%, and Ti: 0.01
又 は 0.10% and Zr: 0.01 to 0.10%
The gist of the present invention is a laser welding wire containing a seed and a balance of Fe and impurities.

Hereinafter, the present invention will be described in more detail.

[0009]

[Action]

[0010] The wire of the present invention is a wire having a specific component composition in which B and Ti or Zr are added at a low carbon equivalent as described above. Since the carbon equivalent of the wire is low, it is easy to make the structure ferritic even if the weld metal is quenched,
Moreover, by fixing O and N with Ti or Zr, B
In addition to preventing oxidation and nitriding of B, making B into a solid solution state to refine the crystal grains, and using oxides of Ti and Zr as nuclei for the refinement, the toughness of the welded portion can be improved.
When B, Ti, and Zr are added to the wire, C, Si,
There is also an effect that wire rigidity can be obtained as compared with the case of only Mn, and the effect is particularly large when Ti is added. The reasons for limiting the components of the wire will be described below.

C: As described above, conventionally, a steel wire having a relatively medium carbon content has been used as a filler metal because a steel wire having a carbon content substantially equal to that of a steel plate as a base material has been selected. At least C content in the wire is 0.10%
That was all. For this reason, the weld metal was quenched, and martensite and bainite were formed and hardened, and no toughness was obtained. In the present invention, the carbon content in the wire is also reduced,
In order to easily generate ferrite even when the weld metal is quenched, the amount of carbon in the wire is preferably regulated to 0.005% or less. If the carbon content is more than 0.005%, it becomes difficult to make the weld metal have a ferrite-rich structure. Needless to say, when the base material is medium-high carbon steel (C content of 0.18% or more), the C content in the wire must be kept as low as possible, but the C content is 0.18%.
Even in the case of the following steel sheets, the amount of ferrite in the weld metal may not always be 100%. Even in such a case, according to the component-based wire of the present invention, the C content of the wire is set to 0.1%. By regulating the content to 10% or less, a weld metal having a high toughness value can be obtained. Therefore, the C content in the wire is set to 0.10% or less, and preferably 0.005% or less.

Si, Mn: Since the contents of Si and Mn also affect the hardening action by the rapid cooling described above, it is preferable that Si and Mn are also low Si and low Mn, respectively. Specifically, the amount of Si in the wire is 0.30% or less, and the amount of Mn is 0.50.
% Or less. However, when an active gas such as CO ₂ or O ₂ is mixed and used as a shielding gas or an assist gas,
Since the yield into the weld metal is reduced, it is necessary to consider this yield in advance. Further, it is necessary to add a certain amount of Si in order to improve the conformity of the weld metal fusion zone to the base material during laser irradiation and reduce defects. Mn does not contribute much to the hardenability as much as C. Rather, a combination of a wire component system within the scope of the present invention and a base material having a low carbon equivalent may provide higher toughness in some cases. Therefore, the Si content is set to 0.50% or less and the Mn content is set to 1.50% or less.

B: B has the effect of lowering the ferrite formation temperature by keeping it in a solid solution state in the weld metal, suppressing the formation of grain boundary ferrite and ferrite side plates, and promoting the formation of acicular ferrite. And fine ferrite can be obtained, and the toughness can be improved by the effect of refining the crystal grains. For this purpose, it is necessary to add B to the wire in an amount of 0.0016% or more. However, 0.0
If it exceeds 10%, on the contrary, the toughness deteriorates, which is not preferable. Therefore, the amount of B in the wire is 0.0016 to 0.010.
% Range. The preferred amount of B depends on the amount of Ti or Zr and the amount of oxygen, but is 0.0020 to 0.0060%.

Ti, Zr: B alone is oxidized or nitrided only by adding B alone, so that the above-described effect of solid solution B to refine the crystal grains cannot be obtained. Therefore, by adding Ti to the wire, Ti is oxidized or nitrided, thereby fixing O and N, preventing oxidation or nitridation of B, and keeping B in a solid solution state. Ti is an oxide (TiO ₂ )
By forming a nucleus, it becomes a nucleus for fine graining and has an effect of making crystal grains fine. To obtain these effects, the Ti amount should be 0.0.
1% or more is required. However, when the content exceeds 0.10%, the amount of oxides or nitrides becomes too large and the toughness is impaired. Therefore, the Ti amount in the wire is 0.01 to 0.1.
The range is 0%. Since Zr has the same effect as Ti,
The amount of Zr in the wire is in the range of 0.01 to 0.10%.
However, it is sufficient to add either Ti or Zr, but the same effect can be obtained by adding both.

The impurities in the wire should be as small as possible. Oxygen (O) is required as a nucleus for refining the ferrite structure, for example, in the above-mentioned oxide of Ti and Zr, in order to secure the effect of refining crystal grains, a minimum amount is necessary. is there. That is, 0.000 in the wire
It is preferable that the oxygen content is 1% or more. However, if the content is more than 0.05%, pores are likely to be generated, and it is difficult to obtain a sound weld. However, if an active gas such as CO ₂ or O ₂ is mixed in the shielding gas and / or the assist gas, Even if O (oxygen) in the wire is higher, generation of pores can be suppressed. Its tolerance is 0.20%.

The main conditions for laser welding include the type of laser beam, beam mode, output, welding speed, etc., but these are not particularly limited. Gas laser (eg, CO ₂ laser) or solid-state laser
(Eg, a YAG laser), but a CO ₂ laser capable of obtaining a large output is desirable, and a YAG laser is also possible. The laser beam mode includes a single mode, a multi mode, a ring mode, and the like. The single mode has the highest power density, but the multimode and the ring mode are desirable from the viewpoint of the penetration characteristics and gap. Further, a shielding gas such as Ar may be supplied as an assist gas for preventing oxidation, preventing sputtering, and the like. Welding while reciprocating the laser beam left and right using a beam scanner is effective for gap tolerance, aiming, etc., and also has the effect of reducing blowholes because the molten metal pool is agitated. The wire diameter is preferably smaller than the laser beam diameter, and is preferably 2 mm or less.

The base material is a steel plate having a medium carbon equivalent as in the prior art, but is not particularly limited. For example, the present invention can be applied to a low carbon equivalent steel sheet such as a TMCP steel sheet. TMCP steel sheet has low carbon equivalent (Ceq), 0.34 to 0.38% of non-water-cooled TMCP steel sheet, water-cooled TMCP steel sheet
It is said to be 0.30 to 0.36% in steel sheet ("Journal of the Shipbuilding Society of Japan" No. 726 (December 1989) pp. 797-80
8).

Next, an embodiment of the present invention will be described.

[0019]

Example 1 A medium carbon steel sheet (sheet thickness 12 mm) having the composition shown in Table 1 was used as a base material, and a butt joint shown in FIG.
2 mm and a depth of 6 mm were formed, and wires (diameter: 1.2 mm) having various component compositions shown in Tables 2, 3 and 4 were used.
A laser welding test was performed using a CO ₂ laser according to the welding procedure shown in FIG. The other components in the wire are C:
0.003%, Si: 0.08%, and Mn: 0.19%.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

The welding conditions were as follows: output: 10 KW, welding speed:
1m / min, wire feeding speed: 4m / min, lens diameter: 7.
5in, Burn pattern diameter: 2mm, Assist gas: Ar (2
0 l / min).

An impact test piece (2 mm V side notch) was sampled from the obtained weld, and the impact value was examined. The result is
As shown in Tables 2, 3, and 4, excellent toughness was obtained by using a wire having a component composition within the range of the present invention.

[0026]

Example 2 TMCP having the component composition shown in Table 5 as a base material
Using a steel plate (plate thickness: 12 mm), a groove having a width of 1.2 mm and a depth of 6 mm is formed with a butt joint shown in FIG. 1, and wires (diameter: 1.2 mm) of various component compositions shown in Table 6 are used. A laser welding test was performed using a CO ₂ laser according to the welding procedure shown in FIG.

[0027]

[Table 5]

[0028]

[Table 6]

The welding conditions were as follows: output: 10 KW, welding speed:
1m / min, wire feeding speed: 4m / min, lens diameter: 7.
The shield gas and the assist gas (20 l / min) shown in Table 6 were used with a 5 inch burn pattern diameter of 2 mm.

An impact test piece (2 mm V side notch) was sampled from the obtained welded portion, and the impact value was examined. The result is
As shown in Table 6, excellent toughness was obtained by using a wire having a component composition in the range of the present invention.

[0031]

As described in detail above, the laser welding wire of the present invention is a wire in which B and Ti or Zr are added at a low carbon equivalent, so that a sound welded joint having excellent toughness can be obtained. Can be

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a shape dimension (mm) and a groove shape of a base steel plate, (a) is a plan view, and (b) is a cross-sectional view showing a welded joint portion.

FIG. 2 is a diagram illustrating a welding procedure.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-64486 (JP, A) JP-A-63-126683 (JP, A) JP-A-62-279092 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B23K 35/30 B23K 26/00

Claims (3)

(57) [Claims] 1. C. 0.10% by weight (hereinafter the same)
Hereinafter, Si: 0.50% or less, Mn: 1.50% or less, B: 0.0016 to 0.010%, and Ti: 0.5%.
A laser welding wire comprising one or two of 0.01 to 0.10% and 0.01 to 0.10% of Zr, the balance being Fe and impurities. 2. The method according to claim 1, wherein the wire is O (oxygen): 0.0001 or more.
The laser welding wire according to claim 1, wherein the wire contains 0.20%. 3. When the wire diameter is smaller than the beam diameter,
3. The laser welding wire according to claim 1 , wherein the diameter is 2 mm or less. 4.