JPS6123580A - Welding method of al or al-based alloy member - Google Patents

Abstract

PURPOSE:To allow through and rigid welding under fine welding workability by applying an interim member of medium thickness in connecting a thick aluminium member with a thin aluminium member. CONSTITUTION:Fillet welding is performed from the side as shown by an arrow A in the circumferential direction by forming a comparatively thin boss section 3 (of which inner radius is slightly larger than outer radius of a thin pipe 1) at the inner peripheral side of a thick flange 2 and by inserting the thin pipe 1 into the boss section 3. In this case, thickness t3 of the boss section 3 shall be made smaller than thickness t2 of the flange body. From the above, there will be not much difference in melting amount between the thin pipe 1 and the boss section 3, allowing the welding areas of both thin pipe 1 and boss section 3 to be heated almost evenly and thus leading to through and rigid fusion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for welding members made of Al or an Al-based alloy (hereinafter simply referred to as Al), and particularly relates to a method for welding members made of Al or Al-based alloys (hereinafter simply referred to as Al), and in particular, a method for welding members made of Al or Al-based alloys (hereinafter simply referred to as Al), and in particular, a method for welding members made of Al or Al-based alloys (hereinafter simply referred to as Al), and in particular, a thick-walled member made of Al (for example, a flange) and The present invention relates to a method for firmly welding thick-walled ceramic members (for example, thin-walled pipes) with excellent welding workability.

[Conventional technology]

Since Al is lightweight and has excellent strength and corrosion resistance, it is used in a wide range of applications including automobile parts. In particular, the demand for Al for use in fluid piping for car coolers, car air conditioners, etc. is rapidly increasing as the demand for lower fuel consumption through lighter vehicle bodies increases.

By the way, when Al is used for fluid piping, it is often necessary to join a connecting flange to the tip of the Al pipe, and as a joining method, chloride (NaC11CaC1
2, KCl, etc.) and fluorides (NaF.

A brazing method using a flux containing CaF2, etc.) or a vacuum brazing method is employed. However, the brazing method using 7lux has the following problems: ■ Pollution problems caused by chlorides and fluorides in the flux; ■ Corrosion caused by flux remaining in the joint; ■ The complexity required to remove the flux and the associated cost increase; ■ There are many problems such as a decrease in strength caused by high-temperature heating of the entire joint, and there is an opportunity to reconsider the brazing method itself.

[Problem that the invention seeks to solve]

Under these circumstances, attempts have been made to join the Al pipe and the Al7 flange by welding, but they have not been put to practical use for the reasons explained below. That is, Al
When welding aluminum pipes, it is considered effective to use AC or DC reverse polarity power supply characteristics that can have a cleaning effect on the oxide film. Mere application will not yield satisfactory results. When we investigated the reason, we came to the following conclusion.

That is, as shown in FIG. 12, for example, the wall thickness t1 of the Al pipe 1 is generally considerably thinner than the wall thickness t2 of the flange 2 joined to the tip thereof, and the heat capacity of the Al pipe 1 is smaller than that of the seven flange 2. It's extremely small.

Moreover, since the thermal conductivity of Al is extremely good, for example, when fillet welding is to be performed from the direction of the arrow, since the Al pipe 1 is thin, the heat applied to the welded part is not dissipated by conduction. As a result, the welding point quickly becomes hot, but since 7 lange 2 is within the thickness, the welding heat is conducted to the periphery of the welding point. Poor fusion defects are likely to occur due to insufficient heat.

Also, if the temperature of the flange z side is sufficiently raised, All
If the pipe side becomes overheated, it may cause excessive melting or burn-through of the pipe wall. Particularly under alternating current or direct current reverse polarity welding conditions that are expected to have a cleaning effect on the oxide film, the penetration is small due to the characteristics of the power source, so as mentioned above, sufficient penetration is provided to the joint of the flange 2, which has a large heat capacity. In order to do this, the area around the welding part must be sufficiently preheated, but since the Al tube side is also preheated accordingly, problems such as the above-mentioned burn-through are more likely to occur. Moreover, as circumferential welding progresses, welding heat accumulates on the side of the Al tube, which has a smaller heat capacity, so that the above problem is further exacerbated and the strength of the joint becomes unstable and low.

This kind of problem is not limited to welding thin-walled Al pipes to thick-walled flanges, but also when welding thin-walled aluminum pipes with small heat capacity.
・J AlI parts (tubes, plates, etc.) and thick Al# with large heat capacity! This is considered to be a problem that inevitably arises when attempting to weld members.

Under these circumstances, the present invention has been developed to provide a thick ceramic member A made of aluminum.
The purpose of this invention is to provide a technique that can reliably weld thick ceramic members without causing welding defects.

[Means for solving problems]

In the present invention, when joining a thick aluminum ceramic member and a small-thick aluminum cracked member, the thick aluminum ceramic member is integrally formed in advance at the joint portion of the thick aluminum ceramic member, and the aluminum Welding a thick ceramic member made of aluminum to a thick ceramic member has a similar purpose.

[Effect]

Hereinafter, the present invention will be described in detail by taking as an example the case of welding to a large-walled aluminum flange on a thick-walled ceramic pipe made of aluminum. 1st
The figure is a vertical cross-sectional view showing a small-walled Al1lll pipe 1 to be welded and a 7-walled aluminum ceramic flange 2 facing each other, and a relatively thin boss portion 3 on the inner peripheral edge joining side of the large-walled 7-walled flange 2. (The inner diameter is also slightly larger than the outer diameter of the small-walled pipe 1), and the boss part 3 is formed as shown in FIG.
Insert the small-walled pipe 1 into the tube and perform fillet welding in the circumferential direction from the direction indicated by the arrow. In this case, the wall thickness ta of the boss portion 3 (the thickness at the top is shown in the figure) is smaller than the wall thickness t of the flange main body, and is preferably equal to the wall thickness t of the small-walled pipe 1. or slightly larger). By doing this, there will be no large difference in heat capacity between the small-walled pipe 1 and the boss part 3, so the welding heat can be used to heat and raise the temperature of both the small-walled pipe 1 and the welded part of the boss part 30 almost equally, and the boss part The two sides can be fused together soundly and firmly without causing insufficient heating on the 3rd side, resulting in poor fusion, or overheating on the 1st side of the small-walled pipe, resulting in burn-through. Third
(see figure).

As is clear from the above explanation, the wall thickness, shape, etc. of the boss portion 3 are designed to make its heat capacity smaller than that of the main body of the flange 2, so that it approaches the heat capacity of the small-walled pipe 1. However, in order to make more effective use of the above purpose, the wall thickness t of the boss portion 3 should be the same as the wall thickness t of the small-walled pipe 1.

0.5 to 1.5t1) preferably O,S
t.

It is preferable to set it in the range of ~1.3t. Also, boss part 3
The protrusion height H (see Fig. 2) is also not particularly limited, but in order to maintain good welding workability, formability of the boss portion 3, and integrity after joining, the wall thickness of the small-walled pipe 1 is important. t for t□
, to 6t□, preferably t1 to 4t. In setting the wall thickness t of the boss portion 3, it should be determined strictly based on the wall thickness of the line welded portion (T' in Fig. 3), but it should be determined strictly based on the wall thickness of the line welded portion (T' in Fig. 3). By setting the wall thickness within the above-mentioned preferred range, the purpose of the present invention can be fully utilized.

Furthermore, in the examples shown in FIGS. 1 to 3, the boss portion 3 was formed integrally with the flange 2 main body, but for example, as shown in FIG. 4,
Of course, the 72-inch 2 may be a short tube-shaped boss member 3' formed as a printing material and fixed by welding to the tube-joining side of the flange 2.

Incidentally, since the difference in heat capacity between the boss member 3' and the flange 2 is smaller than the difference in heat capacity between the pipe 1 and the flange 2, there is no particular problem when welding them together.

FIG. 5 is an explanatory cross-sectional view of a main part showing still another embodiment of the present invention, in which the inner diameter of the boss portion 3 is larger than the inner diameter of the main body of the flange 2 by an amount equivalent to the wall thickness of the pipe 1. It is preferable that the inner surface of the joint be made flush with the welding plate, since it is possible to eliminate pressure loss at the joint when fluid flows.

By the way, it is best that the inner diameter of the boss part 3 has a size that allows it to fit tightly into the small-walled pipe 1, but even if there is a slight gap, welding is performed while filling the gap by TIG welding or the like using a welding rod. It doesn't matter because I can do it. However, if this gap is too large, even if a welding rod is used, it will not be possible to sufficiently fill the gap G with the deposited metal M, and a healthy joint will not be obtained. It is preferable to keep the thickness to about the same level or less as the wall thickness t1 of the thick pipe, usually about 1 mm or less.

Next, the welding method may be TIG welding or MIG welding, but in the present invention, where Al is to be welded, AC or DC reverse polarity which has a cleaning action on the oxide film is used. A welding method should be used, and if the gap G of the welding part is narrow, welding can be performed without using a welding rod. However, if the gap G is wide, a welding rod or consumable electrode should be used to secure a sufficient amount of weld metal to fill the gap G, and even if the gap G is extremely narrow, a sufficient amount of additional weld metal should be used. It is desirable to use an L welding rod in combination to form a bond and obtain a sound bond. In addition, the inventors have confirmed in other experiments that even though constant current welding is used, it is better to use a pulse welding method in which high and low currents are alternately applied.
Good results were obtained in both welding workability and joint performance.

In the above illustrations, the case where the small-walled pipe 1 and the seven flange 2 are joined together has been explained, but the present invention is of course not limited to such a joining example.
Welding of plate materials and large-walled aluminum plates, large-walled A] The same can be considered for welding of small-walled aluminum pipes to main binding pipes and containers, etc., and welding of large-walled aluminum members with large heat capacity. By welding a small-thickness Al member with a small heat capacity to the joint side via a medium-thickness Al member with a small heat capacity as well as the large-thickness Al member, it is possible to prevent fusion failure on the large-thickness Al member side. Welding can be performed in a very sound manner with good welding workability without causing burn-through due to overheating on the small-thickness Al member side.

〔Example〕

A boss part (M: 1.5m+n or 3mm, R:
3ff1m% H: 2.5mm or 5. ) is formed in advance, and an Al pipe (A3003, outer diameter 12.7
mmφ, wall thickness 25mm), insert the welding rod (A5356
Pulse alternating current TIG welding was performed at a circumferential speed of 20 cm/min using a BY2.4Mφ).

As a result, welding can be carried out smoothly without fusion failure on the 72-inch side or burn-through on the tube side, and the corrosion resistance, airtightness, and pressure resistance of the resulting welded part are improved. When we compared the joints obtained by brazing with the joints obtained by the brazing method, we found that there was no inferiority, and rather good results were obtained. FIG. 8 shows an example of a fragmentary structure of a welded part. Figure 9 shows the relationship between the distance from the center of the joint and the hardness of the joint, in comparison with those joined by the brazing method. It can be seen that the width of the softened region is also extremely narrow compared to the joint obtained in .

Example 2 The shape and dimensions of the boss part are as shown in Fig. 10) (W: 2, 5
An, W': 3 mm or 5 mm, H: 3 mm), except that the circumferential welding with the Al pipe was carried out in exactly the same manner as in Example 1, and good results were obtained in terms of welding workability and joint performance. It was done.

Embodiment 3 The boss portion 3 having the shape shown in FIG. 11 has a basic shape, and the height H
2.5 theory or 5 bleaching, the wall thickness t8 of the Al pipe 1 was set to 2.5M, and the wall thickness Wt of the boss portion 3 - the wall thickness t of the Al pipe 1 was changed at various ratios. The welding properties and the shape of the weld bead were investigated in the same manner as in Example 1.

The results are shown in Table 1 below).
0.5t for the wall thickness t1 of the t-Al pipe 1.

~1.5t1, preferably 0.8t, ~1.5t1.
If it is set within the range of 3t1, excellent welding workability and bead shape can be reliably obtained.

◎: Very good ○: Good △: Welding is possible, but it is difficult to control the bead shape, etc. [Effects of the invention] The present invention is configured as described above, but the point is that a large-walled aluminum member and a small-walled member are used. When joining thick members, the difference in heat capacity is reduced by interposing a medium-thickness member at the joint, so even when welding is applied, fusion failure may occur on the large-thickness side, resulting in It is possible to achieve a very sound and strong joint with good welding workability without causing any burn-through or the like on the small wall thickness side.As a result, the welding method can be used instead of the conventional brazing method. It became possible to hire.

[Brief explanation of the drawing]

Figures 1 to 5 are cross-sectional explanatory diagrams of main parts showing embodiments of the present invention, Figure 6 is a cross-sectional view of main parts showing the situation in which welding defects occur when the gap between the boss and the pipe is too wide, and Figure 7 Figure 8 is an explanatory diagram showing the shape of the seven flange used in the experiment, Figure 8 is a schematic vertical cross-sectional diagram showing an example of the cross-sectional shape of the welded part obtained by the present invention, and Figure 9 is a graph showing the relationship between the hardness of the welded part. , Figure 10.11 is a cross-sectional view of the main part showing the shape of the boss part adopted in the experiment, and Figure 12 shows the problem when attempting to weld a small-walled Al pipe and a large-walled 7-lange using the normal method. It is an explanatory diagram for pointing out a point. 1... Al ceramic thick walled tube 2... Al%7 lange 3.
-Al boss part

Claims (1)

[Claims] When joining a small-thick Al or Al-based alloy small-thickness member to a large-thickness Al or Al-based alloy member, a medium-thickness Al or Al-based alloy medium-thickness member is attached in advance to the joint of the large-thickness Al or Al-based alloy member. A method for welding an Al or Al-based alloy member, the method comprising integrally forming a small-thick Al or Al-based alloy member to a medium-thick Al or Al-based alloy member.