JPH0592271A - Welding method for aluminum material improved in weld crack - Google Patents

Abstract

PURPOSE:To prevent a fine crack on a heat-afected zone of weld by controlling the width of a cleaning area to the specified length. CONSTITUTION:When a pulse current to change over the polarity of a TIG welding electrode and Al material 1 to the positive and negative is impressed, the cleaning widths W can be regulated within 3mm from deposited metal part toes 3a by setting an EN ratio to about 70-95%. Consequently, stress generated based on imbalance of structure in the solidification process of the heat- affected zone and a deposited metal part 3 is minimized. In addition, since bubbles and foreign matters are mixed at the time of welding and defective appearance is caused when the cleaning width is diminished to zero, the cleaning width is preferably regulated to 0.1-1mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method used for manufacturing vehicles, ships, tanks, and other welded structures made of aluminum, and more particularly to a welding method for producing a cleaning action during welding such as TIG welding. The present invention relates to a method for welding an aluminum material with improved weld cracking in the affected area.

[0002] In this specification, the term aluminum is used to include its alloy.

[0003]

2. Description of the Related Art Generally, AC is used for welding aluminum materials.
-TIG welding or the like is used. This is because the presence of an oxide film poses a problem in the welding of aluminum materials, but in TIC welding or the like, a cleaning action occurs during welding and the oxide film around the welded metal portion is removed, resulting in a beautiful surface.

[0004]

However, when the aluminum material is subjected to TIG welding or the like as described above, minute cracks sometimes occur in the weld heat affected zone (HAZ portion). In particular, when the aluminum material is an extruded shape material having a coarse surface recrystallization reaching a thickness of, for example, 100 μm or more, the welding heat input is particularly large and the joint shape has heat like T-shaped fillet. The structure in which stress is easily applied to the affected area has a drawback that microcracks are likely to occur. In most cases, these microcracks were generated in the cleaning area 1 to 2 mm from the weld metal toe to the base material side.

The present invention has been made in order to solve the above drawbacks, and prevents even minute cracks in the heat-affected zone of the welding even if the aluminum material is an extruded shape material having coarse surface recrystallization. The purpose is to provide a method for welding the obtained aluminum material.

[0006]

To achieve the above object, the inventors of the present invention have earnestly studied and as a result, when the cleaning area is expanded in TIG welding or the like, the range of microcracks in the heat affected zone is increased
The inventors have found that fine cracks in the heat-affected zone can be prevented by controlling the width of the cleaning area (hereinafter referred to as the cleaning width) within a certain range, and the present invention has been completed based on such knowledge.

[0007] That is, the gist of the present invention is to refer to the reference numerals of the drawings.

Incidentally, (4) shown in FIG. 1 is an oxide film.

The cleaning action generally occurs in bar-plus (base metal cathode) welding using argon as the shielding gas. The specific type of welding may be TIG or any other type as long as it produces such a cleaning action. Here, the cleaning width (W) is the weld metal part (3).
The reason for being regulated within 3 mm from the toe (3a) is as follows. That is, it is presumed that the cracking in the heat-affected zone is caused by the stress caused by the imbalance of the structure in the solidification process after welding between the heat-affected zone and the deposited metal portion. Therefore, when the cleaning width (W) is wide, the heat-affected zone is also wide, and microcracks are likely to occur in the heat-affected zone.
This is because when the cleaning width (W) is 3 mm or less, the heat-affected zone is also narrowed and fine cracks are suppressed. However, the case where the cleaning width is 0, that is, the cleaning action is not included, is not included in the scope of the present invention. This is because if there is no cleaning action, air bubbles and foreign matter are mixed in during welding, resulting in poor appearance. It is particularly preferable to regulate the cleaning width to 0.1 to 1 mm.

The cleaning width (W) is set to the welded metal portion (3).
The specific method for controlling within 3 mm from the toe (3a) is not particularly limited, but the following method may be used, for example.
That is, the most preferable method is the EN ratio (Electrod) of the current applied between the electrode and the aluminum material (1).
e Negative ratio).
Here, the EN ratio is 1 as shown in FIG. 2 with the electrode rod of the TIG welding machine or the like as the + side and the aluminum material (1) as the-side.
When a repetitive pulse current is applied in which the aluminum material is positive and the electrode rod is negative during the time T1 of the cycle, and the electrode material is positive and the aluminum material is negative during the time T2, EN ratio = {T1 / A ratio expressed by (T1 + T2)} × 100 (%). The EN ratio is conventionally set to about 50% in general, but by setting this EN ratio to about 70 to 95%, the cleaning width (W) should be restricted within 3 mm from the weld metal toe (3a). You can EN
If the ratio is less than 70%, the cleaning width may exceed 3 mm, and if it exceeds 95%, the cleaning width may become zero.

Although the cleaning width (W) varies depending on the shield gas flow rate and the welding current, depending on the size of the base material, the cleaning width can be controlled by limiting the shield gas flow rate and the welding current within a certain range. You may regulate within 3 mm. Specifically, the shield gas flow rate is 3 to 1
It is better to set it to about 0 l / min. If it is less than 3 l / min, the appearance of the welded portion may be poor, and if it exceeds 10 l / min, the cleaning width may exceed 3 mm.
The welding current may be set to about 50 to 150A. If it is less than 50 A, there is a risk of poor penetration of the welded portion, and if it exceeds 150 A, the cleaning width may exceed 3 mm. Further, the EN ratio, the shield gas flow rate, and the welding current may be controlled together.

[0012]

[Example] A5083P-O, 4.0 t x 100 w x 3
A groove was formed on the surface of the aluminum base material made of 001 (mm), and the groove was welded using an AC-TIG inverter control welding machine. Here, as a filler material, A518
1.5 m from the toe of the weld metal by using 3 BY; 2.4φ (mm) and appropriately combining the welding conditions such as EN ratio, Ar shield gas flow rate, and welding current as shown in Table 1.
Various cleaning widths of m, 2.0 mm, 3.0 mm and 4.0 mm were formed.

[0013]

[Table 1]

Next, in order to examine the relationship between the cleaning width and the weld crack in the heat affected zone of the obtained welded product, J
The crack was confirmed by a penetrant flaw detection test specified in IS, and the length of the crack was measured.

And for each cleaning width,
A value of (crack length / cleaning width) × 100% was calculated and both values were shown in a graph. The result is as shown in FIG.

From the above results, it is understood that the welding cracks in the heat affected zone can be suppressed by limiting the cleaning width within 3 mm from the weld metal toe.

Further, the same aluminum base material, filler material, and welding machine as described above are used, and the weld metal portion is obtained when the EN ratio is changed under the conditions of welding current: 150 A and shield gas flow rate: 10 l / min. When the cleaning width from the toe was measured, it was as shown in the graph in FIG. From this graph, it is understood that the cleaning width from the weld metal toe can be regulated within 3 mm by setting the EN ratio to about 70% or more. It can also be seen that the cleaning width rapidly approaches 0 when the EN ratio exceeds 95%.

Also, using the same aluminum base material, filler material, and welding machine, welding current: 150 A, EN ratio: 7
When the cleaning width from the toe of the deposited metal portion when the Ar shield gas flow rate was changed was measured under the condition of 0%, it was as shown in the graph in FIG. From this graph, it is understood that the cleaning width can be regulated within 3 mm by setting the shield gas flow rate to about 10 l / min or less. In addition, the shield gas flow rate is 3 l
If it is less than / min, the appearance of the welded part is poor.

Also, when the same aluminum base material, filler metal, and welding machine are used, the welding current is variously changed under the conditions of EN ratio: 70% and shield gas flow rate: 10 l / min. When the cleaning width from the toe of the welded metal portion was measured, it was as shown in FIG. From this graph, by setting the welding current to about 150A or less,
It can be seen that the cleaning width can be regulated within 3 mm. Further, when the welding current was less than 50 A, poor penetration of the welded portion occurred.

[0020]

According to the present invention, when welding an aluminum material that causes a cleaning action, the cleaning width is restricted to within 3 mm from the weld metal toe, so that the aluminum material has a large thickness of about 100 to 150 μm. Even in the case of extruded profiles having surface recrystallization and welding such profiles, it is possible to suppress welding cracks in the heat-affected zone that have occurred in the past, and a high-quality weld structure without welding cracks. It is possible to produce and provide things.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an aluminum material after welding.

FIG. 2 is a waveform diagram showing an example of a current applied between an electrode rod of a welding machine and an aluminum material, with the electrode rod as a + side.

FIG. 3 is a graph showing the relationship between cleaning width and weld cracking.

FIG. 4 is a graph showing a relationship between an EN ratio and a cleaning width.

FIG. 5 is a graph showing the relationship between the shield gas flow rate and the cleaning width.

FIG. 6 is a graph showing the relationship between welding current and cleaning width.

[Explanation of symbols]

 1 ... Aluminum material 3 ... Weld metal part 3a ... Weld metal toe W ... Cleaning width

Claims (1)

[Claims] 1. A method for welding an aluminum material (1) in which a cleaning zone (2) is formed during welding, wherein a width (W) of the cleaning zone (2) is defined as a toe (3a) of a weld metal part (3). The method for welding an aluminum material with improved weld cracking is characterized in that it is controlled within 3 mm.