JP3205449B2 - Filler wire for laser welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filler wire for laser welding for welding using a laser as a heat source, and more particularly to a filler wire capable of obtaining a good bead shape, workability and a sound weld. It is.

[0002]

2. Description of the Related Art Laser welding is known as one of the laser processing techniques, in which light having a uniform wavelength and phase (coherent) generated by a laser oscillator is narrowed down by a lens or a mirror to be welded. This is a method of joining by heating and melting by absorbing the light to the material to be welded. The feature of this welding method is that it does not attenuate in the atmosphere with a high energy density more than 1000 times that of a welding arc, has submicrometer fineness, and has high controllability in which the beam can be freely manipulated by an optical system. For this reason, high-speed welding can be performed, and it is used for butt welding and lap welding of thin plates. Lasers used for welding include a CO ₂ laser which is a gas laser and a YAG laser which is a solid laser. Furthermore, since a vacuum processing chamber is not required unlike electron beam welding, laser welding is becoming widespread as cost performance increases.

[0003]

Conventionally, in laser welding, a method of welding without using a filler material and a method of using a solid wire containing Si or Mn with a relatively medium carbon content as a filler material have been adopted. It had been. In general, joints used for laser welding are often I-shaped butt joints without special beveling, but when using no filler material like the former,
There was a problem that the tolerance of the gap between the base materials and the gap was small and that blow holes and pits were easily formed.

On the other hand, when a filler metal is used as in the latter case, since the cooling rate is high in laser welding, the hardness of the weld metal becomes too high and the hardness difference from the base metal is large, so that there is a problem as a weld joint. There were many. When welding a surface-treated steel sheet such as a galvanized steel sheet, for example,
There was a problem that blowholes frequently occurred.

As means for solving such problems, for example, Japanese Patent Laid-Open Publication No.
There is a technology described in Japanese Patent Application Laid-Open No. 22280/22 and Japanese Patent Application Laid-Open No. 5-185280, and a technology described in Japanese Patent Application Laid-Open No. 3-230880 using a flux-cored wire as a filler wire. These technologies use a filler metal during laser welding, expand the tolerance for misalignment and gaps in the base metal, limit some wire components, make the hardness difference between the base metal and the weld metal relatively small, and improve the toughness. Improvements have been made to improve pits and blow holes generated during welding of galvanized steel sheets. However, when a wire is used for laser welding, a good bead shape and workability cannot always be obtained in practical use.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a C: 0.0% by weight (the same applies hereinafter).
5 to 0.15%, Si: 0.30 to 1.50%, Mn:
0.90 to 2.20%, Ti: 0.05 to 0.40%,
P: 0.02 to 0.08%, S: 0.01 to 0.06%
And a balance consisting of Fe and unavoidable impurities.

[0007]

In order to solve the above-mentioned problems, the present inventors have conducted many experiments and studies on a filler wire capable of obtaining a sound weld in laser welding using a filler wire. It was able to do. Hereinafter, the present invention will be described in detail.

First, the reasons for limiting the components of the filler wire of the present invention will be described. C has the effect of securing strength and stabilizing the structure. However, if it exceeds 0.15%, the cooling rate during laser welding is high, so that the hardening of the weld metal is promoted, and hot cracking resistance and workability after welding are improved. 0.1
5%. Further, if the content is less than 0.05%, the microstructure of the weld metal cannot be stabilized and the lower limit is set to 0.05%.
And

[0009] Si is an effective component as a deoxidizing agent, and is added to a steel material in an appropriate amount depending on the purpose. The Si added to the filler wire of laser welding acts as a deoxidizing agent in the molten metal to obtain a clean welded portion and has an effect of suppressing the occurrence of blow holes. Further, the viscosity of the molten metal is adjusted to improve the bead shape. However, Si is also C
Is an element that promotes the hardening of the welded portion as in 1.50.
%, The difference in hardness between the weld metal and the base metal increases, and the workability deteriorates. Therefore, the upper limit is set to 1.50%.
On the other hand, if it is less than 0.30%, deoxidation at the time of welding becomes insufficient and blowholes are generated, and the viscosity of the weld metal becomes insufficient to deteriorate the bead shape. Therefore, the lower limit is set to 0.30%. The amount of Si added to the filler wire is 0.30 to 1.5.
When it is in the range of 0%, a weld metal excellent in workability can be obtained under a wide range of welding conditions.

Mn is a component effective as a deoxidizing agent like Si, and is widely used in steel materials for the purpose of improving strength, securing a fine microstructure, and improving toughness.
Further, Mn added to the filler wire acts as a deoxidizing agent to obtain a clean welded portion and has an effect of suppressing the occurrence of blow holes. However, Mn is also an element that promotes the hardening of the welded portion, like Si and C. If it exceeds 2.20%, the difference in hardness between the weld metal and the base metal increases, the workability deteriorates, and excess deoxidation occurs. Therefore, the upper limit is set to 2.20% because pits and blowholes are easily generated. Also, 0.
If it is less than 90%, deoxidation at the time of welding becomes insufficient and blow holes are generated. Therefore, the lower limit is set to 0.90%. If the amount of Mn added to the filler wire is in the range of 0.90 to 2.20%, a weld metal having excellent workability can be obtained.

Ti is a component effective as a strong deoxidizer,
It has the effect of suppressing the occurrence of pits and blowholes. In addition, by forming an oxide (TiO ₂ ), it becomes a nucleus for grain refinement, has a fine microstructure, and has an effect of improving toughness. To obtain these effects, 0.05% or more is required. However, if it exceeds 0.40%, solid solution Ti increases and the hardening of the welded portion is promoted, so that the difference in hardness between the weld metal and the base metal increases, and the formability deteriorates. Furthermore, since the amount of oxides or nitrides becomes too large and the toughness is impaired, the amount of Ti added to the filler wire is set in the range of 0.05 to 0.40%.

Further, a feature of the present invention is that the effects of P and S, which have been regarded as impurities, have been found, and they have been positively incorporated into filler wires for laser welding.

[0013] P is generally contained in steel as an impurity, and efforts have been made to keep it as low as possible in steel because it deteriorates mechanical properties. However, when P is added to the filler wire of the laser welding, the viscosity of the molten metal is adjusted during welding, the wettability with the base material is improved, and a smooth weld bead can be obtained. P in filler wire is 0.0
If it is less than 2%, the effect of improving the bead shape is not sufficient, and if P in the filler wire exceeds 0.08%, the embrittlement of the weld metal becomes severe. Therefore, the P content is set to 0.02 to 0.08%.

S is generally contained as an impurity in steel materials except for free-cutting steel and the like. In order to promote deterioration of mechanical properties and high-temperature cracking during welding, efforts have been made to keep S as low as possible in steel. However, when S is added to the filler wire of laser welding, the melting point of the molten metal is reduced during welding, and a smooth weld bead can be obtained, and the wettability with the base material is improved, and particularly, the toe shape is excellent. A weld bead can be obtained. If S in the filler wire is less than 0.01%, the effect of improving the bead shape is not sufficient, and if S in the filler wire is more than 0.06%, a brittle structure due to segregation of S is precipitated in the weld metal and hot cracking is likely to occur. Become. For this reason, the S content is set to 0.01 to 0.06%.

The filler wire according to the present invention has a laser beam type (eg, a gas laser, a solid laser, etc.), a beam mode (eg, a single mode, a multi mode, a ring mode, etc.), a beam diameter, an output, a welding speed, and a welding target. There is no limitation on the material of the material, its base material surface treatment method, plate thickness, and the like. The filler wire diameter is not particularly limited, but is preferably smaller than the laser beam diameter, and the filler wire diameter is preferably 2 mm or less.

[0016]

Next, examples of the present invention will be described. As the laser welding conditions, the CO ₂ laser shown in FIG. 1 was used, the output was 4 KW, the mode was multi-mode, and the welding speed was 2.
The test was performed at 0 m / min and the feed speed was 2.0 m / min using the test filler wires shown in Table 1. Ar
Gas (flow rate 10 liter / min) is used as an assist gas, the welding joint is a butt joint and the gap is 0 mm
And The base material is a 0.8 mm thick SPCC material (JIS G
3141), a welding experiment was conducted, and the bead shape, internal soundness, and workability were investigated. In FIG. 1, 1 is a laser oscillator, 2 is a torch, 3 is a filler wire, 4 is a base material, 5 is a welding bead, and 6 is an assist gas.

The bead shape was visually inspected, and a bead having a constant bead width and bead height and having no weld defect such as undercut or overlap at the bead toe portion was determined to be good.
The internal soundness is determined by conducting an X-ray transmission test in accordance with JIS Z3104 (radiation transmission test method for steel welded parts and classification method of transmission photograph). Is 20% of the total bead length
Good for the following (symbols in the table; ○), and poor for more than 20% (same;
X). In addition, all weld defects such as cracks observed other than blowholes were regarded as defective. Table 1 shows the results.

[0018]

[Table 1]

Further, a macro test piece was taken from the center of the joint, and the hardness Hv (load 200
g) was investigated, and a difference ΔH in hardness between the base metal and the weld metal was obtained as a determination of workability. From the conventional knowledge, the difference ΔH in hardness (= hardness of the weld metal−hardness of the base metal) is good when Hv100 or less (symbol in the table; 、), and poor when Hv100 or more (same as above).
X).

As is clear from Table 1, good results were obtained in the bead shape, internal soundness, and workability of the welded portion in the range of the present invention. In contrast, Comparative Example N
o. Nos. 11, 13 and 15 have good workability, but N
o. In No. 11, the amounts of C and P were less than the range of the present invention.
In No. 13, cracks occurred because the S content exceeded the range of the present invention. In No. 15, since the amount of P exceeded the range of the present invention and the amount of S was less than the range of the present invention, the bead shape and the internal soundness were poor.

In addition, No. Nos. 12, 14, and 16 had good bead shapes, but no. In No. 12, the Si content was less than the present invention and the Ti content exceeded the present invention. 1
No. 6 has a C and Mn content exceeding the range of the present invention and a Ti content below the range of the present invention. No. 14 has a C content exceeding the range of the present invention and Mn
Since the amount was less than the range of the present invention, internal soundness and workability were poor. Comparative Example No. In No. 17, the bead shape and internal soundness were good, but the workability was poor because the amount of Si exceeded the range of the present invention. In addition, No. 18
Although the internal soundness and workability are good,
Since P and S were less than the range of the present invention, the bead shape was poor.

No. 2 without filler wire. In No. 19, the bead shape became concave, the number of blow holes was large, and the internal soundness and workability were poor.

[0023]

As described above, according to the filler wire for laser welding of the present invention, a welded joint excellent in bead shape, internal soundness and workability can be obtained, and application in this field can be expanded. This can greatly contribute to cost reduction.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the procedure of laser welding.

[Explanation of symbols]

 Reference Signs List 1 laser oscillator 2 torch 3 filler wire 4 base material 5 welding bead 6 assist gas

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yasunobu Miyazaki 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (56) References JP-A-6-106381 (JP, A) JP-A-3-221280 (JP, A) JP-A-62-248594 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 35/30 B23K 26/00

Claims (1)

(57) [Claims] (1) C: 0.05 to 0.15% by weight,
Si: 0.30 to 1.50%, Mn: 0.90 to 2.2
0%, Ti: 0.05 to 0.40%, P: 0.02
A filler wire for laser welding, comprising 0.08%, S: 0.01 to 0.06%, the balance being Fe and unavoidable impurities.