JPH0381071A - Nonconsumable electrode arc welding method for aluminum alloy - Google Patents

Abstract

PURPOSE:To narrow a bead width and to deepen penetration by applying a reverse polarity current having a specified crest value of a welding current and the specified weld time when a nonconsumable electrode is in the positive polarity and applying a straight polarity current having a specified crest value of a welding current and the specified weld time when the nonconsumable electrode is in the negative polarity. CONSTITUTION:The nonconsumable electrode with the tip 1a having an inclined flat shape on both sides is arranges in the direction where the long side directions L1 and L2 of the electrode tip are coincident with the weld line directions. When the nonconsumable electrode is in the positive polarity, the reverse polarity current having 300-500A crest value of the welding current and 0.5-3mus weld time is applied. When the nonconsumble electrode is in the negative polarity, the straight polarity current having 150-500A crest value of the welding current and 9-15mus weld time is applied to perform welding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a non-consumable electrode arc welding method for obtaining deep penetration in a single pass of a medium-thick aluminum alloy plate.

[Prior Art] Conventionally, as a non-consumable electrode arc welding method for obtaining a deep penetration welding result of aluminum alloy, the first method is to mechanically or chemically remove the oxide film of the aluminum alloy before welding. This method uses direct current positive polarity TIG welding. Although this method can achieve a certain degree of deep penetration, it requires an extra step of removing the oxide film before welding, and The oxide film formed after the work gets caught up in the molten metal and often causes welding defects.

In addition, the second method is a method of appropriately adjusting the energization time ratio of positive and negative polarity of the alternating current, the a-current ratio, or both using a rectangular wave alternating current pulse current.
Although it is possible to remove the oxide film on the aluminum surface and achieve a certain degree of deep weld penetration, the bead width increases, the heat-affected area expands, and the electrode tip wears out considerably. Must be interrupted often.

Furthermore, the third method is AC plasma welding, but although deep penetration can be achieved with this method, series arcs are likely to occur when the current is large, so in practice it is recommended that the plate thickness be 8 [mm]. ] or below, and it was difficult to use thicker plates.

Furthermore, the tip of the non-consumable electrode is cut into a flat shape and rotated or oscillated around the electrode axis to increase the directivity of the arc and obtain melt penetration in the groove wall. Although this combination is used to prevent undercuts and improve defective beads, the bead width has become wider.

[Problems to be Solved by the Invention] None of the conventional welding methods for medium-thick aluminum alloy plates can sufficiently remove the oxide film on the aluminum alloy surface to obtain a defect-free weld. However, there are problems in that the bead width is narrow and deep penetration cannot be obtained, or the tip of the non-consumable electrode is severely worn out, and these problems have not been solved at the same time.

[Means for Solving the Problems] The method of non-consumable electrode arc welding of aluminum alloys of the present invention includes: (1) securing an appropriate leaning width, (2) narrowing the bead width, and (2) increasing the penetration depth. To do,■
In order to reduce electrode wear and satisfy the above four requirements at the same time, A. A non-consumable electrode whose tip has a flat shape with both sides inclined is made such that the long side direction of the electrode tip coincides with the direction of the welding line. B. In order to narrow the bead width, deepen the penetration depth, and reduce electrode wear, the peak value Is of the positive welding current is set to a predetermined value. C. In order to obtain the same effect as in B above, the conduction time Ts of the positive welding current should be set to a predetermined value or more. D. After ensuring an appropriate leaning width, narrow the bead width. , In order to minimize the consumption of the electrode, the conduction time Tr of the reverse polarity welding current is set to a predetermined value as small as possible; E. With the same effect as above, the peak value Ir of the reverse polarity welding current is set to an appropriate value. F. The above B should be set so that the above-mentioned ■ to ■ are satisfied at the same time.
A method for non-consumable electrode arc welding of aluminum alloys by examining the interrelationships of the parameters in sections E to E and within the appropriate range of the four parameters [Function and Examples (Explanation of Figures 2 to 6)] The welding current applied in the non-consumable electrode arc welding method for aluminum alloys of the invention is a rectangular wave alternating current, and the four parameters of this rectangular wave alternating current are determined by the non-consumable electrode as shown in FIG. When the polarity is positive (hereinafter,
The peak value of the welding current when the electrode is of negative polarity (hereinafter referred to as positive polarity) is Ir, the energization time is Tr, and the peak value of the welding current when the electrode is of negative polarity (hereinafter referred to as positive polarity) is Is.

Let the energization time be Ts.

When these four parameters are changed, the four items that are particularly desired to be satisfied in the welding method of the present invention are: ■ penetration depth, ■ bead width, ■ cleaning width, and ■ extent of electrode wear. The results of the study are shown in Table 1, and the shape of the tip 1a of the non-consumable electrode 1 used in the welding method of the present invention below is as shown in FIG.
The figure (A) is a front view, the figure (B) is a side view, and the figure (C) is a plan view seen from the direction of the tip of the electrode. C) arrow, L2
It is arranged so that the long side direction shown in the direction coincides with the welding line direction shown in FIG. 4, which will be described later. That is, the electrode tip 1
The spread of the arc 4 generated from a to the objects 3 and 4 to be welded is as shown in FIGS. 4(A) and 4(B), and as a result,
In relation to the appropriate values of the above four parameters, the bead width is 8! in the conventional method shown in FIG. 5(A). From the same figure (B)
82 of the method of the invention shown in FIG. Similarly, the penetration depth is as shown in (A) and (B) in the same figure.
It increases from Pl to Pl. Note that the bead shape in Fig. 5 is made of aluminum alloy (A505) with a plate thickness of 10 mm.
2) at a welding current of 350 [A] and a welding speed of 50 [cm/
(A) shows the case of welding at Ts
This is a conventional welding method using sine waves of -10 and Tr-6 [ms], and the figure (B) shows l5-350 [A]
, Ts-10[ms ko, Ir-350
[A] and the case of the welding method of the present invention using a rectangular wave of Tr~1 [ms] is shown. In addition, FIG. 6 shows that l5=
350 [A.

Ts-10 [mS Co, I r-350 [A] and T
After repeating a rectangular wave current of r-1 [ms] for 10 minutes, pausing for 5 minutes, and turning on the current again, these cycles were repeated a total of 6 times and welded for 1 hour, as shown in the same figure (B). However, the electrode tip was only worn to the extent that it was slightly rounded. On the other hand, for comparison, we used a non-consumable electrode (hereinafter referred to as a round pointed electrode) whose electrode tip shape before welding started was a circular pointed cross section (not shown). The effective value of polarity current is 350 [A], and the conduction time of positive polarity and reverse polarity current is 10 [ms] each.
When welding for 1 hour using a sine wave of 6 [ms], the shape of the electrode tip was completely melted and consumed, and the tip became rounded, making it extremely difficult to restart the arc, as shown in Figure (C). It has become.

(Explanation of Fig. 7) Next, Fig. 7 shows the welding current of 15-400 when the electrode is negative (positive polarity) among the above four parameters.
A, its energization time TsmlO [ms], and the welding current Ir-400 [A] when the electrode is positive (reverse polarity) are set to constant values, and the energization time Tr of the reverse polarity current is set to 0.
It is a diagram showing the melt penetration depth P [mml (vertical axis) when changing from 5 [ms] to 6 [ms] (horizontal axis). The welding conditions of this example are that the material to be welded is a magnesium-containing aluminum alloy with a plate thickness of 10 mm, the welding speed is 50 cm/ml, and the flat electrode of the welding method of the present invention is shown by the solid line. The penetration depth P when using the welding method is larger than that when welding is performed under the same conditions as above using the conventional method of pointed round electrode shown by the dotted line.

(Explanation of Figure 1) Figure 1 shows that among the four parameters mentioned above, the conduction time Ts of the positive polarity welding current is about 10 [ms], the conduction time Tr of the reverse polarity welding current is 1 [msl], and the welding speed is 50 [msl]. [cm/m
in], and when the positive welding current Is and the reverse polarity current Ir (horizontal axis), which is equal to the positive current, are changed, the ratio P/W of penetration depth P and bead width W (vertical axis ). In the figure, in the shaded area where the positive polarity current or the reverse polarity current is less than 290 [A1], the cleaning action is not performed sufficiently because the reverse polarity current is small, so the oxide film gets caught up in the weld metal. However, good weld metal can be obtained with 290[A3 or higher]. In addition, the solid line in the figure shows the ratio P/W of penetration depth to bead width when using the flat electrode used in the welding method of the present invention, and the dotted line shows the ratio P/W of the conventional pointed round electrode. A larger P/W value can be obtained than when using it.

(Appropriate Welding Condition Range) In the welding method of the present invention, the reason for limiting the range of appropriate welding conditions will be explained.

Positive polarity current Is Reverse polarity current conduction time T r = 3 [ms]
, when the peak value Is of the positive polarity current becomes less than 150[A1] when the peak value of the welding current reaches 1r-500[:A], the cooling effect of the electrode tip due to electron emission becomes small, and the electrode melts away. Therefore, the positive polarity current is
It is necessary to make it 150 [A3 or more.

Current application time Ts of positive polarity and reverse polarity welding current.

T "In the welding method of the present invention, the frequency is 50 to 100 [
Hzl provides good weld penetration and arc stability, and within this range, shallow penetration and arc breakage do not occur. Outside this range, the weld penetration becomes shallow and arc breakage tends to occur.

Further, when the reverse polarity time Tr is set to 0.5 to 3 [ms], the peak value Ir of the reverse polarity current can be increased to 500 [A], and the wear of the electrode can be reduced. Further, by setting the normal time of the positive polarity current a to 9 to 15 [ms], the current can be made larger than the reverse polarity current, and a melt-in shape similar to that of a non-consumable electrode using a normal direct current can be obtained.

Reverse polarity current Ir Since the reverse polarity current conduction time is set to 0.5 to 3 [ms], the peak value of the reverse polarity current is 300 [ms] in order to ensure the leaning width necessary for welding aluminum alloys.
A3 or higher is required.

[Effects of invention The welding method of the present invention has the following effects.

A. [By arranging a non-consumable electrode with a flat gutter tip so that its long side direction matches the welding line direction,
A deep melt-in shape with a narrow bead width can be obtained.

B. By setting the peak value Is of the positive welding current to 150 [A3 or more, the cooling effect of the electrode tip due to electron emission is promoted and the wear and tear of the electrode is prevented.

The application time Ts of the C6 positive polarity welding current is 9 to 15 [ms].
], and by making the conduction time Tr of the reverse polarity welding current larger than 0.5 to 3 [ms], the conduction time Tr of the reverse polarity welding current necessary for cleaning can be minimized and the wear of the electrode can be reduced. At the same time, it is possible to obtain the same deep weld penetration shape as in the case of direct current positive polarity.

D. The conduction time Tr of the reverse polarity welding current is 0.5 to 3 [m
s], and the peak value Ir of the reverse polarity welding current can be increased to 500 [A], and even though the conduction time Tr of the reverse polarity current is short, the leaning width can be sufficiently maintained. can be secured.

E. As mentioned above, the conduction time Tr of the reverse polarity current is set to 0.
Since it is set to a short time of 5 to 3 [ms], the peak value of the reverse polarity welding current! r is required to be 300 [A], thereby ensuring the cleaning effect.

F. As mentioned above, the positive polarity current conduction time is 9 to 15[
ms] and the conduction time of the reverse polarity current to 0.5
The frequency of the alternating current is set to 5 for a short time of 3 [ms].
By setting the frequency to 0 to 100 [Hz], it is possible to increase the penetration of the welded part and improve the stability of the arc.

As described above, the welding conditions of the present invention are such that the above conditions are related to each other and work together to: 1) ensure an appropriate leaning width, 2) have a narrow bead width, and 2) prevent weld penetration. Deep ■Can minimize electrode wear.

[Brief explanation of drawings]

FIG. 1 shows the peak values Is of positive polarity and reverse polarity welding currents when welding by the welding method of the present invention. It is a figure which shows the relationship between Ir (horizontal axis) and ratio P/W (vertical axis) of melt penetration depth P and bead width W (vertical axis). FIG. 2 is a diagram illustrating the definition of four parameters, the peak value of the welding current and the current application time, used in the welding method of the present invention. FIG. 3 shows an electrode whose tip used in welding according to the present invention has a flat shape with both sides inclined; FIG.
B) is a side view, and (C) is a plan view seen from the direction of the electrode tip. FIGS. 4A and 4B are diagrams showing the spread of an arc generated from the tip of the electrode shown in FIG. 2, and show a front view and a side view, respectively. FIGS. 5A and 5B are diagrams illustrating the cross-sectional shape B of the bead when welded by the conventional method and the method of the present invention, respectively. FIG. 6(A) is a diagram showing the shape of the tip of the flat electrode before welding starts, and FIG. Diagram (C)
FIG. 2 is a diagram showing a state of change in the tip shape of a conventional pointed round electrode after 1 hour of aWS for comparison with the welding method of the present invention. Figure 7 shows the penetration depth P when the current application time Tr of the reverse polarity current is changed in the case of a flat electrode used in the welding method of the present invention (solid line) and a pointed round electrode for comparison. It is a diagram shown about the case (dotted line). 1... Non-consumable electrode with electrode tip 1a having a flat shape with both sides inclined, Ll, L2... Long side direction, L... Welding line, Ir.
...The peak value Tr of the welding current when the electrode has positive polarity (reverse polarity)...The application time Is of the welding current when the electrode has positive polarity (reverse polarity)...The electrode has negative polarity (positive polarity) The peak value Ts of the welding current when the electrode is negative polarity (positive polarity) the welding current conduction time

Claims (1)

[Claims] 1. In a non-consumable electrode arc welding method for aluminum alloy, a non-consumable electrode whose tip has a flat shape with both sides inclined is arranged in a direction in which the long side direction of the electrode tip and the direction of the welding line coincide. Then, a substantially rectangular alternating current is supplied between the non-consumable electrode and the aluminum alloy, and when the non-consumable electrode has positive polarity, the peak value Ir of the welding current is 300 to 5.
00 [A] and the current application time Tr is 0. A reverse polarity current of 5 to 3 [ms] is applied, and when the non-consumable electrode has negative polarity, the peak value Is of the welding current is 150
to 500 [A] and the current application time Ts is 9 to 15 [m
A non-consumable electrode arc welding method for aluminum alloys, which involves welding by applying a positive current of [s].