JPH066229B2 - Arc welding method for Al-Li alloy - Google Patents

Description

TECHNICAL FIELD The present invention relates to an arc welding method for an Al—Li alloy that eliminates defects such as blowholes generated in a welded portion.

[Prior Art] Conventionally, as a welding method of this kind, as shown in FIG.
Using a weld metal material of the same quality as the plate material for the plate material 1 of the Al-Li alloy, by TIG welding or MIG welding, that is, an arc 4 is generated between the electrode 3a of the welding machine (torch) 3 and the welding portion 2. A method of performing welding while spraying an inert gas is known.

[Problems to be Solved by the Invention] However, in the above welding method, LiOH and Li in the alloy
Due to H and H ₂ absorbed in the metal during welding, defects such as blowholes often occur in the peripheral portions of the back beat portion 2a and the toe portion 2b of the welded portion 2. Therefore, the welded portion There was a case where the mechanical strength of was reduced and the reliability was impaired.

Further, as shown in FIGS. 9 (B) and 9 (C), by welding the thick plate material 1 and laminating the welded portions 2 by a plurality of built-up portions, the back beat portion 2a and the stoppers are similarly formed. Defects such as blow holes occur at the end 2b.

The present invention has been made to solve the above-mentioned problems of the prior art, and does not cause defects such as blowholes on the back side of the welded portion, and arc welding of an Al-Li alloy having improved reliability of the welded portion. The purpose is to provide a method.

[Means for Solving Problems] The present invention made to achieve the above object is to cut both sides of a plate material made of an aluminum alloy containing Li,
After the plate material is subjected to the inert gas arc welding from the front side, the inert gas and the arc are sprayed from the back side of the welded portion of the plate material so as to melt the surface of the welded portion.

Here, the aluminum alloy containing Li means an aluminum alloy containing 0.1 wt% to 30 wt% of Li, and if necessary, Mg 0.1 wt% to 15 wt%, M
n 0.1% by weight to 15% by weight, other Fe, Ni, Zr
Including those containing such components, spraying an inert gas and an arc means that the surface of the weld is heated to a high temperature by the arc while spraying an inert gas with a TIG welding machine, etc., and a part of the surface is slightly melted. It means to let.

[Operation] Unlike other aluminum alloys that do not contain Li, the Al-Li alloy targeted by the present invention is very susceptible to defects such as blowholes due to arc welding.

In other words, in the welding of aluminum alloy that does not contain Li,
Blowholes hardly occur except when welding an alloy that has been left for a long time. On the other hand, an Al-Li alloy containing active Li contains water vapor and H when it is left during casting or after casting. ₂ may be absorbed to form inclusions such as LiOH and LiH inside the alloy, which may cause blowholes in the welded portion. Also, A
The l-Li alloy absorbs water vapor, H _{2 and the} like during welding, which may cause blowholes.

Therefore, when welding such an Al-Li alloy, inert gas arc welding such as TIG welding or MIG welding is performed. According to this inert gas arc welding, it is possible to suppress the generation of blowholes in the welded portion sprayed with the inert gas by the cleaning action of the spray activated gas sprayed at the time of welding.

However, even in the case of performing such an inert gas arc welding in the Al-Li alloy, when the weld reaches the back side of the member (plate material or the like) to be welded, the blow hole is blown by the back side (that is, the arc is blown). The problem is that it occurs on the opposite side of the welded surface). That is, A
Since the l-Li-based alloy is an active alloy as described above, even on the back side of the welded portion, LiOH and L contained in the alloy can be used.
Many blowholes may be generated due to iH, water vapor and H ₂ absorbed during welding.

Therefore, in the present invention, first, both surfaces of the alloy plate material are cut to remove LiOH, LiH, etc. that cause blowholes, and this plate material is subjected to inert gas arc welding from the front side. Therefore, on the front side of the welded portion, it is possible to prevent the generation of blowholes by cutting the surface and cleaning the inert gas. Then, after this arc welding, an inert gas and an arc are blown from the back side of the weld to slightly melt the surface on the back side of the weld. Therefore, even on the back side of the welded part, defects such as blowholes generated on the back side can be eliminated by surface cutting before welding and melting of the surface after welding.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1 (A), first, 0.8% Li, 4.
Both surfaces 1a, 1b of the plate material 1 made of 7% Mg-the balance Al
The thickness T (about 0.3 mm) is cut and polished by a scraper or the like. Then, as shown in FIG. 1 (B), the plate material 1
After the groove is formed, an alloy material having substantially the same material as the plate material is used as a welding member, and an arc 4 is generated from the electrode 3a of the welding machine 3 to perform TIG welding or MIG welding. At this time, as a welding method, for example, AC. Single-layer butt welding by TIG arc welding was used, and the conditions were as follows: welding current 70A, welding speed 18 cm / min, Ar gas flow 12 /
Set to minutes.

Then, as shown in FIG. 1 (C), a welding machine 3 is installed below the back beat portion 2a to generate an arc 4 on the lower surface of the welding portion 2 to perform so-called arc cleaning.
The conditions at this time are: current 50A, moving speed 20 cm / min,
The Ar gas flow rate is set to 12 / min. As a result, the surface temperature of the welded portion 2 is about 7
The temperature is set to 00 to 800 ° C. By the above cleaning operation, a part of the surface of the back beat portion 2a is slightly melted and the blow hole disappears, and the welded portion 2 having no defect as shown in the photograph of FIG. 2 is obtained (see FIG. 5). ).

In addition, if the so-called weaving is performed while swinging the arc left and right with respect to the traveling direction in the cleaning work, defects such as blow holes can be removed over a wide range.

Table 1 shows the results of the above-mentioned examples in Table 1, and Comparative Example 1 in which the arc cleaning work is performed only by cutting and Comparative Example 2 in which neither cutting nor arc cleaning work is performed. According to this, in Comparative Examples 1 and 2, as shown in the photographs of FIG. 3 and FIG. 4 (see FIG. 6 and FIG. 7), the welded portion 2 was formed on the back beat portion 2a and the toe portion 2b. Reveals that blowholes still remain. As Comparative Example 3, an Al alloy containing no Li (4.5% Mg-remainder Al) was welded in the same manner as in Comparative Example 2, but in this case, no blowhole was generated in the welded portion (Table 1). reference).

Therefore, according to the above-mentioned embodiment, the cleaning work by the arc can completely eliminate the blowholes on the back side of the welded portion, and when it is desired to eliminate the blowholes over a wide area around the welded portion, It is effective to add a step of cutting the surface of the plate material.

Further, as shown in FIG. 8, in the case of welding a plate material 1 made of a thick plate, and in the method of laminating the welded portions 2 in a number of built-up portions, it is opposite to the last welded built-up portion. Defects such as blowholes are likely to occur in the back beat portion 2a on the side. Therefore, as shown in FIG. 8 (B), after welding is completed by the generation of an arc from above the welded portion 2, as shown in FIG. 8 (C), cleaning by the arc from the back beat portion 2a side is performed. The blowholes can be eliminated by carrying out the same as in the method shown in FIG.

[Effects of the Invention] As described above, according to the present invention, both sides of a plate material are cut, and after welding, an inert gas and an arc are blown from the back side of the welded portion to blowholes on the backside of the welded portion. It is possible to improve the reliability of the welded portion by eliminating the defect of No.

[Brief description of drawings]

FIG. 1 is an explanatory view showing steps of a welding method according to an embodiment of the present invention, FIG. 2 is a photograph showing a state of a metal structure of a welded portion according to the same embodiment, and FIGS. 3 and 4 are according to a comparative example. Photos showing the state of the metallographic structure of the welded portion, FIGS. 5 to 7 are explanatory views for explaining the photographs of FIGS. 2 to 4, and FIG. 8 is an illustration showing the steps of the welding method according to another embodiment. FIG. 9 and FIG. 9 are explanatory views showing defects caused by the conventional welding method. DESCRIPTION OF SYMBOLS 1 ... Plate material 2 ... Welding part 2a ... Back beat part 2b ... Toe part 3 ... Welding machine 3a ... Electrode 4 ... Arc

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-19078 (JP, A) JP-A-53-29245 (JP, A) JP-B-40-4325 (JP, B1)

Claims (1)

[Claims] 1. A plate material made of an aluminum alloy containing Li is cut on both sides, and after the plate material is subjected to an inert gas arc welding from the front side, the surface of the welded portion is melted from the back side of the welded portion of the plate material. An arc-welding method for an Al-Li alloy, characterized in that an inert gas and an arc are sprayed onto the alloy.