JPH03234393A - Welding method utilizing laser beam - Google Patents

Abstract

PURPOSE:To obtain a sound welded joint with high efficiency by supplying metal powder consisting of low C, low Si, low Mn and the balance Fe substantially as filler metal. CONSTITUTION:The laser beam is oscillated from a laser beam oscillator 1 and a bead 4 is formed on base metals 3 to perform welding by using a torch 2. At that time, the metal powder consisting of low C, low Si, low Mn and the balance Fe substantially is supplied from a powder feeder 5. The powder contains <=0.30wt.% C and 0.5-9.5% deoxidizer mainly composed of Si and Mn. As necessary, the powder further contains >=1 kind of, by wt.%, 0.01-0.15% Ti, 0.01-0.15% Nb, 0.025-0.15% P and 0.01-0.15% Zr. Consequently, a filler metal component can be easily changed.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a laser welding method, and more particularly to a laser welding method using powder as a filler metal. (Prior Art and Problems to be Solved) Laser welding is known as one of laser processing techniques. Laser welding is a joining method that uses a laser as a heat source, which has features such as high energy density, no attenuation in the atmosphere, and optical energy, and CO2 laser, YAG laser, etc. are used. For this reason, high-speed welding is possible and it is used for butt welding and lap welding of thin plates. Furthermore, unlike electron beam welding, it does not require a vacuum processing chamber and multi-processing is possible, so it is being adopted as a welding method in place of electron beam welding. Conventionally, two methods have been adopted for laser welding: a method without using a filler metal, and a method using a wire-shaped filler metal containing Si and Mn with a relatively medium carbon content. However, in the case of laser welding that does not use a filler metal as in the former case, there are problems in that the tolerance range for misalignment of base metals and gaps is narrow, and blowholes and pits are likely to appear. On the other hand, in the latter case, laser welding using a wire-shaped filler metal has the following problems. First, we need to check the groove accuracy during welding, the bending of the groove, and the plume (
If there are various fluctuations such as changes in the amount of ultra-fine powder (ultra-fine powder in the base metal) generated, the response is poor and it is not possible to take appropriate measures immediately, resulting in the wire buckling and welding to continue. things become difficult. Especially when the welding speed is 3~
This is likely to occur at high speeds such as 4m/win. In addition, it goes without saying that the composition of the weld metal is greatly influenced by the filler metal composition, but if it is made into a wire, it is determined by the wire, and if a slight change in composition is required, a different type can be used. You need to prepare the wire. In addition, wire-shaped filler metal is normally fed diagonally as in T-G welding, but with this feeding, it is difficult to set the aiming point of the wire, and the wire is affected by the laser beam, which travels in a straight line. Therefore, there was a problem in efficiently welding. Furthermore, conventional wires have been made of steel wires that have a relatively medium carbon content and contain Si and Mn; There is a large difference in strength, which causes many problems as welded joints, and when galvanized steel sheets are welded, there is also the problem of frequent defects such as blowholes and bits. The present invention solves the above-mentioned problems of the prior art, allows for immediate adjustments to be made in response to fluctuations in the number of factors during welding, allows for easy change of filler metal composition, and provides a sound welded joint. The purpose of this invention is to provide a laser welding method that is highly efficient. (Means for Solving the Problems) In order to solve the above problems, the present inventor has conducted extensive research on the properties, component composition, feeding mode, etc. of filler metals, and as a result, the present inventor has developed a powder as a filler metal. We have discovered that this is possible by supplying the following, and have hereby made the present invention. That is, the present invention is characterized in that when performing welding using a laser as a heat source, a metal powder containing low C1, low Si, and low Mn, with the remainder substantially consisting of iron, is supplied as a filler metal. In addition, in another aspect of the present invention, when welding using a laser as a heat source, the filler metal is 1% by weight (the same applies hereinafter), and C: 0.
．． Ti: 30% or less and a deoxidizing agent mainly composed of Si and Mn = 5 to 30%, and if necessary, Ti: 0.0
1 to 0.15%, Nb: 0. Ol~0.15%, P:0
．． 025-0615% and Zr: 0.01-0.15
The invention is characterized in that it provides a deoxidizing agent-containing powder containing one or more of %. The present invention will be explained in more detail below. ('Function) First, the reason why powder is supplied as an embodiment of the filler material in the present invention will be explained. First, if the filler metal is in powder form, problems such as poor response, buckling, and continuity of welding associated with wire feeding are eliminated. Second, when changing the composition of the wire, it is necessary to prepare wires with various compositions, but when used in powder form, you only need to change the necessary components of the powder components to be mixed. The ingredients can be easily adjusted. By appropriately mixing a slag forming agent and iron powder into the powder, it is possible to improve the cleanliness of the weld metal and the efficiency of welding. Of course, the problem of the difference in strength between the welded joint and the base metal can also be solved by appropriately adjusting the powder components. Thirdly, when the filler metal is in powder form, it is less likely to be shadowed by a laser beam that travels in a straight line, as is the case with wire.
Rather, since the absorption ability due to laser beam scattering can be improved, the thermal efficiency to the welded part can be improved and efficient welding can be performed. Further, the powder can also be supplied from the same axis as the laser beam. In addition, in welding using a laser as a heat source, there is a method of placing flux on the base material in order to obtain a shielding effect (see Japanese Patent Application Laid-Open No. 62-21479). Since this method does not directly supply the laser beam to the laser beam, it is not a method that can solve the problems of the present invention. In addition, a method of placing alloyed powder on a mother plate in laser deposition (Japanese Patent Laid-Open No. 62-38789
No. 38792), but this is also not a method that can solve the problems of the present invention. Next, the reasons for limiting the components of the powder in the present invention will be explained. (1) When the filler metal is a low C metal powder: C: Since conventional wires have a relatively medium carbon content, there was a problem that the weld metal was rapidly cooled and hardened too much.
In the present invention, such a problem can be solved because the carbon content in the powder is made low, such as 0.10% or less. Preferably, C≦0°005%. Si, Mn: Since the Si and Mn contents also affect the hardening effect due to the aforementioned rapid cooling, the Si and Mn contents are set to be low. Preferably, SiS is 2.30% and MnS is 2.50%. As other components, elements (Afl, Zr, etc.) that have a deoxidizing effect and do not contribute to an increase in the strength of the weld metal can be included as appropriate. The remainder is essentially iron powder. Such metal powder may be prepared as a mixture of individual powders of each component, or as an appropriate alloy powder. The particle size, supply amount, etc. of the metal powder are also determined as appropriate. (2) When the filler material is a powder containing a deoxidizing agent: Si, Mn (deoxidizing agent): The deoxidizing agent is used to adjust the viscosity of the molten metal and the amount of slab generation, especially in the case of galvanized steel sheets. Controls the growth, floating, and release of zinc vapor into the atmosphere, suppresses the formation of pores such as blowholes and pits, and improves welding workability such as the appearance and shape of the bead, and the strength and toughness of the weld metal. Mechanical performance can be controlled within a range that does not cause any practical problems. For that purpose, 0.5 to 9.5% of a deoxidizing agent is contained. 0.5
If it is less than 9.5%, such an effect cannot be obtained, and if it is more than 9.5%, the strength of the weld metal becomes too high, resulting in a decrease in toughness, especially in the base metal and HAZ (heat affected zone). This is not desirable because the difference in strength between the Typical deoxidizers include Si, Mn, and the like. Even if these are used alone, they can also be used as Fe-8L, Fe-M
It may be used as a compound such as n, FeFe-8i-, Fe-8i-Zr. C: C can be contained at 0.30% or less. C generates GO or CO2 gas in the molten metal,
It has the effect of stirring the molten pool, and particularly when welding galvanized steel sheets, it promotes the floating and release of zinc vapor in the molten metal to the atmosphere, reducing the number of pores. However, C
If C is more than 0.30%, the amount of CO and CO2 gas generated will increase, which will actually lead to the generation of pores. It may be added in the form of Ti, Zr, Nb: Also, Ti, Zr, and Nb can be contained as alloying elements, with Ti: 0.01 to 0.15%, Zr: 0.
It is preferable to contain one or more of Nb: 0.01 to 0.15% and Nb: 0.01 to 0.15%. Especially when welding galvanized steel sheets, these Ti, Zr, and Nb have effects such as forming compounds with zinc and increasing the viscosity of molten metal, and have a remarkable effect of reducing pits and blowholes. Note that if the amount is less than the lower limit, the pore prevention effect cannot be obtained, and if the amount is more than the upper limit, the mechanical performance of the weld metal such as crack resistance, elongation, and toughness is reduced. Ti, Zr, and Nb can be used alone or in compounds or other Fe-Zr-5i, Fe-Zr, Fe-Ti,
It may be used in a form contained in raw materials such as Fe-Nb. As other components, Fa, P, etc. can be included as appropriate. Fe can improve welding efficiency. In addition, particularly in the case of welding galvanized steel sheets, it has the effect of reducing the amount of slag generated and promoting the release of zinc vapor from the molten pool to the atmosphere. For that purpose, the Fe content is preferably 65 to 90%. Particularly when welding galvanized steel sheets, P is a compound that is stable with zinc at temperatures above the melting point of zinc (P-Zn series,
This has the effect of reducing the amount of zinc vapor generated and suppressing the generation of pores. For that purpose, it is contained in an amount of 0.025 to 0.15%. P may be used alone or may be contained in other raw materials such as Fa-P. Any suitable slag forming agent can be used, and it is desirable to contain it in an amount of 3.5% or less. Note that the appropriate size of the powder is about 1 to 200 μm in diameter. If it is less than 1 μm, there will be a lot of fume, the yield will be reduced, and it will be easily oxidized, and if it is more than 200 μm, it will be difficult to dissolve. Powder having such a component composition may be supplied into a laser beam using a powder supply pipe as shown in FIG. At that time, a carrier gas (such as Ar) can also be used. In addition, Ar is used to prevent oxidation, spatter, etc.
, He or the like may be used as the assist gas. By sending argon gas into the powder feeding nozzle at high speed, it is possible to obtain the effect of assist gas (gas for plume removal), and the structure is also simplified. Of course,
The feeding nozzle and the assist gas nozzle may be separate. The main conditions for laser welding include the type of laser beam, beam mode, output, welding speed, etc., but these are not particularly limited. Types of laser light include gas lasers (for example, CO2 lasers) and solid-state lasers (for example, YAG lasers), but CO2 lasers that can provide a large output are desirable. Laser beam modes include single mode, multimode, ring mode, etc. Single mode has the highest power density, but multimode and ring mode are preferable from the viewpoint of penetration characteristics and gap tolerance. The practical range of output, welding speed, etc. is 1 to 5.
KW, welding speed is 1.0-5. On/llll1n. Note that welding while using a beam scanner to move the laser beam back and forth from side to side is effective for improving gap tolerance, aiming, etc., as well as stirring the molten metal pool, which has the effect of reducing blowholes, etc. . Needless to say, the present invention is suitable for butt welding and lap welding of thin plates, and is also capable of welding galvanized steel plates, as there are no restrictions on the material of the base material, the plate thickness, etc. (Example) Next, an example of the present invention will be shown. Stall'' 12 According to the welding procedure shown in Fig. 1, C<0.005%, Si<0.0↓%, Mn:0.
A laser welding test was conducted by supplying steel powder containing 0.063%, P: 0.005%, and 4% S:O, OO. As for the laser welding conditions, a CO2 laser was used, the output was varied in the range of 2.5 to 3 KW, the mode was set to multimode, and the welding speed was varied in the range of 200 to 300 ■/■in. Flow rate 50 using Ar gas as assist gas
Used in Q/win. In addition, the welded joints are butt joints, and the base material is 1.2-■ thick 5 pcc material (JIS G
3141) was used. Further, as a comparative example, a laser welding test was conducted using a conventional wire under the same conditions. The hardness of the weld metal was measured, and weld defects (pores) were investigated using an X-ray transmission test. The results are shown in Table 1. As is clear from Table 1, in the case of the comparative example, the hardness of the weld metal is too high, and the difference in strength from the base metal is large. In addition, in the case of the comparative example, the welding speed was so fast that the wire feeding could not follow it in some cases.On the other hand, in the case of the inventive example, the difference in hardness between the weld metal and the base metal (v50, and this difference in hardness corresponds to a difference in tensile strength of about 15 kgf/am", and a better joint was obtained compared to the comparative example. (Note) The hardness is n== A slag-forming agent-containing metal powder having the composition shown in Table 2 was prepared.The raw material powder in this case was FeMn-C, FeMn-C, FeMn-C, FeMn-C,
-Mn-C is used, P is Fe-P, Zr is Fe-
Zr or Fe-Zr-8i or Zr is used, Ti is Fe-Ti or Ti, Nb is Fe-Nb or Nb
The components were adjusted using iron powder as Fe, and an iron alloy of Si and Mn as the deoxidizing agent. Compounds of alkali metals were mainly used as the slag forming agent. Next, a laser welding test was conducted using this powder under the same conditions as in Example 1. However, the welding speed is 80
~200 cod/Uain, the assist gas flow rate was 20Q/min, and the base material was 2.3
A galvanized steel sheet with a thickness of mm and a zinc coating weight of 90/90 g/m2 was used. Further, as a comparative example, a laser welding test was conducted using a conventional wire under the same conditions. Table 2 shows the results of investigating the occurrence of blowholes. As is clear from Table 2, the occurrence of blowholes was not observed in any of the examples of the present invention, whereas the occurrence of many blowholes was observed in the case of the comparative example.

[Left below]

(Effects of the Invention) As detailed above, according to the present invention, powder of a specific composition is supplied as filler metal in laser welding, so even if various factors change during welding, adjustments can be made immediately. At the same time, the filler metal components can be easily changed, and a welded joint with good joint strength, pores, etc. can be obtained with high efficiency.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the procedure for laser welding according to the present invention. DESCRIPTION OF SYMBOLS 1... Laser oscillator, 2... Torch, 3... Base material, 4... Bead, 5... Powder supply device.

Claims (2)

[Claims] (1) A welding method using a laser, which is characterized in that when performing welding using a laser as a heat source, a metal powder with low C, low Si, and low Mn and the remainder substantially consisting of iron is supplied as a filler metal. (2) The powder contains C: 0.30 wt% or less and a deoxidizing agent mainly composed of Si and Mn: 0.5 to 9.5 wt%.
Contains Ti: 0.01 to 0.15 if necessary.
wt%, Nb: 0.01-0.15 wt%, P: 0.0
25-0.15wt% and Zr: 0.01-0.15w
The method according to claim 1, which is a deoxidizing agent-containing powder containing one or more types of t%.