JPH03476A - Tig welding method - Google Patents

Abstract

PURPOSE:To obtain an uniform weld bead by setting the arc length in the region where the arc length is longer than the region where the arc length is in proportion to the depth of penetration and the depth of penetration is not changed by the arc length. CONSTITUTION:Nonconsumable electrode arc welding is performed by using a welding power source having an almost constant-current characteristic. The arc length is then set in the second region where the arc length is longer than the first region where the arc length is approximately in inverse proportion to the depth of penetration and the depth of penetration is hardly changed by the arc length. In addition, the arc length is set in the third region where the arc length is longer than the second region and the depth of penetration is approximately in proportion to the arc length. By this method, a drop of a welding current due to resistance heat generation of an electrode is suppressed and fine welding is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a TIG welding method, and particularly to a method suitable for AC TIG welding of aluminum or aluminum alloys.

[Conventional technology]

The formula expressing the influence of welding conditions on the penetration depth in arc welding is given by Yasutoshi and Hase, "Welding Arc Phenomena" expanded edition, Sanpo Publishing (1967), p. 368-36.
According to the Jackson O formula published in 9, penetration depth = ki, l'i and π = 8, where k: constant determined by the welding method; welding current V: welding speed Vmi arc voltage is widely known. , and the smaller the current ■, the welding speed V
The faster the arc voltage V, (arc length) is, the higher the arc voltage V (arc length) is (
(long) indicates that the penetration depth decreases.

Regarding the influence of welding conditions on the penetration depth, see, for example, Yokoo, Mita, Watanabe, "Introduction to TIG Welding", Sanpo Publishing (1986), p. 80-83, edited by the Light Metals Association of Japan, "Aluminum It is also described in Handbook JRt) Light Metals Association (1981) p. 115-116.

In other words, when welding with constant welding current and welding speed,
It is said that the longer (higher) the arc length (arc voltage), the shallower the penetration depth.

[Problem to be solved by the invention]

Conventionally, in TIG welding, welding conditions were set within the range where Jackson's equation holds true, and welding was performed with a relatively short arc length (approximately 3 ms for welding aluminum and aluminum alloys). In the area, the penetration depth changes due to changes in the arc length due to camera shake, making it difficult to obtain a uniform weld bead. In addition, when it is difficult to get the torch close to the welding line in a narrow space or deep groove, the electrode protrusion length is increased to keep the arc length short. becomes low, and the welding current value is limited. Further, in the conventional method, there is a limit to the penetration depth that can be obtained even if the welding current is increased.

The purpose of the present invention is to provide a method for solving the above problems by utilizing the previously unknown relationship between arc length and penetration depth, and improving workability and welding quality for arc welding of aluminum, aluminum alloys, etc. It's about doing.

[Means to solve the problem]

In non-consumable electrode arc welding using a welding current with approximately constant current characteristics, when the welding current and welding speed are kept constant and the arc length is varied, the relationship between the arc length and arc voltage is as shown in Figure 2. holds true. Also, since the heat input to the base metal by the arc is [current × voltage × efficiency], when the welding current is constant, the heat input to the base metal changes as the arc length changes. It changes as shown in the figure.

On the other hand, the arc pressure applied to the base metal decreases as the arc length increases, as shown in FIG.

The penetration depth of the base metal in arc welding is considered to be determined by the heat input applied to the base metal and the force that excavates the base metal, that is, the arc pressure. Therefore, penetration depth PD
Using the above heat input W and arc pressure P, P D = a W, + b P, + c (a, b, c
: constant determined by welding conditions, etc.), and the third
From Fig. 4 and Fig. 4, there is a difference between arc length and penetration depth.
The relationship shown in the figure will be established. That is, in addition to the well-known region A (first region) where the arc length and penetration depth are approximately inversely proportional, there is also a region B (second region) where the penetration depth hardly changes depending on the arc length and the penetration depth. There is a region C (third region) where the arc length and the arc length are approximately proportional.

Based on such new knowledge, the invention according to claim 1 sets the arc length in a second region B, which has a longer arc length than the first region A and whose penetration depth hardly changes depending on the arc length. It is characterized by

Further, the invention according to claim 2 provides a third region having a longer arc length than the second region B, and in which the penetration depth and the arc length are approximately proportional.
The arc length is set in region C of .

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 5 and 6.

Figure 5 shows a welding power source with approximately constant current characteristics (no-load voltage 40V).
), welding current 100A, welding speed 300mu/
m t n % shielding gas A r ・10 II
This figure shows the relationship between arc length and penetration depth when AC TIG welding is performed on aluminum alloy A 5052 with a plate thickness of 3. In this example, the arc length is 4
In the case of n or less, the penetration depth decreased as the arc length increased, but when the arc length was set to about 4 to 5 cranes, the penetration depth hardly changed. Also, the arc length is 6
When f1 or more, the penetration depth increases as the arc length increases, and it was possible to obtain deeper penetration than in the known region where arc length and penetration depth are approximately inversely proportional.

Figure 6 shows a welding current of 20% using the same welding power source as above.
OA, welding speed 250m5/min, shielding gas A
r・1! Aluminum Al1 with M/win plate thickness of 5 dragons
2 shows the relationship between arc length and penetration depth when AC TIG welding is performed. In this example, as well as the example shown in Fig. 5, the penetration depth hardly changes when the arc length is about 4 to 6 fl, and when the arc length is 6 fl or more, the penetration depth increases as the arc length increases. It was possible to obtain deeper penetration than the known range (arc length of 41 cm or less).

In the above examples, the area where the penetration depth hardly changes depending on the arc length is the area where the arc length is 4 to 61 m, but it goes without saying that this value varies depending on the plate thickness and welding conditions. .

Furthermore, although the above embodiments are based on the case where the AC frequency used for welding is a commercial frequency (50 Hz), the present invention is not limited to this, and even if a higher or lower frequency is adopted, the effect of the present invention can still be achieved. It won't be damaged.

Note that the relationship between arc length and penetration depth shown in FIG. 1 approximately holds true not only in AC TIG welding but also in DC TIG welding. The base metal heat input and therefore the arc length required to obtain a predetermined penetration depth vary depending on the base material W (melting point), but if a welding power source with a no-load voltage corresponding to the welding power source is used, aluminum or The present invention can also be applied to DC TIG welding for materials other than aluminum alloys.

〔Effect of the invention〕

According to the invention set forth in claim 1, it is possible to perform welding in which the penetration depth hardly changes even if the arc length changes slightly.
A uniform weld bead can be obtained without being affected by camera shake or changes in the base metal position.

On the other hand, according to the invention described in claim 2, it is possible to perform welding in which the penetration depth increases as the arc length becomes longer, so it is possible to obtain deeper penetration than conventionally, and it is difficult to bring the torch close to the weld line. Even in this case, there is no need to increase the protruding length of the electrode as in the conventional method, and therefore the reduction in fusing current due to resistance heating of the electrode can be suppressed, resulting in good welding.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between arc length and penetration depth in the TIG welding method of the present invention, Figs. 2 to 4 are diagrams for explaining the present invention in detail, and Figs. FIG. 6 is a diagram showing an embodiment of the present invention. l...Arc length, ■1...Arc voltage, W3...
Base metal heat input, P... arc pressure, PD... penetration depth, A, B, C... area indicating the classification of the relationship between l and PD, a, b, c... PD A constant that determines. Figure 1 Figure 2

Claims (1)

[Claims] 1. In non-consumable electrode arc welding performed using a welding power source with substantially constant current characteristics, the arc length is longer than the first region where the arc length and penetration depth are substantially inversely proportional, and the penetration depth is A TIG welding method characterized in that the arc length is set in a second region where the depth hardly changes depending on the arc length. 2. In non-consumable electrode arc welding performed using a welding power source with approximately constant current characteristics, a third region where the arc length is longer than the second region and where the penetration depth and arc length are approximately proportional,
A TIG welding method characterized by setting the arc length.