JPH07108383A - Manufacture of welding tube stock for aluminum wheel - Google Patents

Abstract

PURPOSE:To provide the manufacture of an aluminum alloy welding tube stock for a wheel, by which a satisfactory welded joint can be attained by DC butt welding. CONSTITUTION:After butting a tube stock for an aluminum wheel, when performing pressure welding, after increasing a welding current to a regular current, as a first stage, an electric current is applied between at least 8 cycles or more and 30 cycles or less. Next, as a second stage, the electric current is decreased between 80& or less and 50% or more of the regular current to perform DC butt welding. In a working after welding, forming workability, especially spinning workability is excellent, and a welded joint with high welding strength, can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy base pipe for a wheel of an automobile or the like, and particularly by a DC butt welding method, it is excellent in forming workability, particularly spinning workability in post-welding processing, and is highly welded. The present invention relates to a welding method capable of obtaining strength.

Here, the DC butt welding is a method for welding and joining by applying pressure while applying a DC current to the joining surface, and conventionally, an AC current is applied and flashing is performed in a range of 5 to 1.
In principle, this is a method different from the method of performing pressure bonding while generating for 0 seconds.

[0003]

2. Description of the Related Art In recent years,
Aluminum wheels are widely used due to the demand for weight reduction of automobiles. Various methods are used for manufacturing the aluminum wheel. Among these, as a method for manufacturing a wheel by welding aluminum plate materials, 50
There is a welding method in which an aluminum alloy rectangular plate material of 00 series is rolled into a cylindrical shape, the end faces thereof are abutted against each other, and current is applied to generate heat and melt due to the contact resistance of the joint end faces while simultaneously performing pressure welding.

[0004] However, this DC butt welding is a method with high productivity, in which flash does not occur at the time of welding and the welding time is short, and it is used for welding of iron wheels. Partial application has begun.

This is because it is very difficult to evenly generate heat in the welded portion, a roaring noise is likely to occur at the same time as welding, and poor fusion occurs, so that it is difficult to obtain a good welded joint.

Under the circumstances, the present invention has an object to provide a method for producing an aluminum alloy welded raw pipe for a wheel, which can obtain a good welded joint by DC butt welding. .

[0007]

Under the above-mentioned background, the present inventors have previously made an aluminum alloy base pipe for wheels by the same method as the DC butt welding method of 5000 series and 6000 series aluminum alloys for wheels. A manufacturing technique was proposed (Japanese Patent Application Laid-Open No. 4-365831, Japanese Patent Application No. 4-30931).
No. 2).

This welding method is performed by setting a condition range such as welding current, welding time, pressure or the like, or by setting an initial current time, a welding speed and an initial electrode interval according to the conductivity of aluminum. The welding method is to make a good weld joint.

However, the inventors of the present invention have conducted extensive studies in order to further improve the stability of the welding conditions, and as a result, adjust the welding current time and current value at the time of main welding by abutting the aluminum tube base pipes. By doing so, it was found that a sound welded joint can be obtained under more stable conditions than the above method, and the present invention has been made here.

That is, according to the present invention, at the time of pressure welding after abutting the aluminum tube base pipes, the welding current is increased to the main current and then at least 8 cycles or more 30
Energize in cycles or less, then 80% or less of this current 5
The gist is a method for manufacturing a welded raw pipe for an aluminum wheel, which is characterized in that a DC butt welding is performed by reducing a current to 0% or more.

The present invention will be described in more detail below.

[Action]

The present invention is, in short, that after welding the aluminum-tube base pipes and then increasing the welding current to the main current during pressure welding, the first step is to energize at least 8 cycles and 30 cycles or less. Then, as the second step, the DC butt welding is a two-step method in which the current is reduced to 80% or more and 50% or more of the main current, welding is performed for a predetermined time, and then the current is interrupted. FIG. 1 shows an example of welding conditions, and the difference between the conventional method (dotted line) and the method of the present invention (solid line) can also be seen from this example.

First, the reasons for limiting the welding current and time, which are the most important welding conditions in the present invention, will be shown.

Regarding the welding time, good welding is possible even if the total welding time is kept at a high current, but the stability is low and abnormal heat generation is likely to occur due to a slight change in the welding condition. In addition, a roaring noise is generated due to the scattering of the molten metal, and defects such as defective fusion may easily occur. Therefore, the welding time of the main current in the first stage is set to 30 cycles or less.

On the other hand, if the welding time is less than 8 cycles, the joint interface may not be completely melted due to insufficient heat input for welding, and defects such as entrainment may occur. For this reason,
The welding time must be at least 8 cycles or longer. Therefore, when the welding time of the main current in the first stage is 8 cycles or more and 30 cycles or less, it is necessary to reduce the welding current.

Next, regarding the setting of the welding current in the second stage, when the current exceeds 80% of the main current, a roaring noise is generated due to the scattering of the molten metal due to excessive heat input, and defects such as defective fusion occur. May easily occur. On the other hand, when the electric current is less than 50% of the main electric current, the joint interface cannot be sufficiently melted, defects such as defective fusion occur, and a stable joint cannot be obtained. Therefore, the current of the second stage is 80% of this current.
It is necessary to set below 50%.

The welding conditions other than the above are not particularly restricted in the present invention, but the following conditions are desirable.

First, although there is no particular limitation on the first stage main welding current (main current), as shown in FIG.
At a current density in the range of up to 400 A / mm ² , and at point A (current density: 100 A / mm ² , squeeze pressure: 30 N / mm ² ),
Point B (current density: 400 A / mm ² , squeeze pressure: 40 N
/ Mm ² ), point C (current density: 100 A / mm ² , squeeze pressure: 100 N / mm ² ), point D (current density: 100 A / mm ² ,
Squeeze pressure: 100 N / mm ² ) Weld in a predetermined welding cycle (8 cycles or more and 30 cycles or less) under the squeeze pressure in the diagonal line surrounded by 100 N / mm ² (the first stage), and then further apply this squeeze pressure. It is recommended to apply an upset pressure of 0 to 150 N / mm ² and weld at a predetermined current (second stage).

The initial current time (up slope) up to the main welding current (main current) is, as shown in FIG. 3, point A (conductivity: 25%, up slope: 3 cycles), point B (conductivity). Rate: 25%, upslope: 20 cycles), point C
(Conductivity: 60%, upslope: 120 cycles),
It is recommended to carry out within the diagonal line surrounded by point D (conductivity: 60%, upslope: 10 cycles) and point E (conductivity: 35%, upslope: 120 cycles).

Further, after the upslope, in the main welding, the moving speed of the butt material at the time of upsetting is 100 mm / sec.
It is recommended that the above welding be performed, the initial electrode spacing is set to 30 to 15 mm, and the final electrode spacing is set to 15 to 5 mm, and then welding is performed.

The time for interrupting the current after the second stage welding (see FIG. 1) is not particularly limited, either.
Desirably, the cycle is 10 cycles or less, and when it is more than 10 cycles, the melting amount of the welded portion is increased, a roaring noise is easily generated due to the scattering of the molten metal due to excessive heat input, and the excess amount is easily increased. Further, when shutting off, in order to prevent defects inside the weld and adjust the excess amount, not only the current is cut in one step, but the method may be divided into 2 to 3 steps and the time may be gradually decreased by 2 to 3 cycles.

Further, as the material of the aluminum alloy,
The 5000 series and 6000 series alloys for wheels are not particularly limited as an example. Especially 51 of 5000 series alloy
When applied to Al-Mg based materials containing 2 to 4% of Mg, such as 54, 5052, 5454 alloys, the effect is greater. Mg
If the amount is less than 2%, the strength after welding is low, and if it exceeds 4%, the corrosion resistance is poor and it becomes difficult to use it as a wheel.

Thus, when the DC butt welding of the method of the present invention is applied to the production of an aluminum alloy weld tube, the weld element for a wheel of a welded joint which is excellent in mechanical properties and bendability as well as in 180 ° bending. A tube is obtained.

Next, examples of the present invention will be described.

[Example 1]

5454 series Al alloy 4.5mmt × 198mm
After performing ring processing on a plate having a size of w × 1030 mm1, direct current butt welding was performed under the conditions shown in Table 1 (see FIG. 1 for the condition symbols in the table). After that, the excess at the time of welding was deleted, and various properties such as mechanical properties, bendability, and welding defects of the welded part were investigated. The results are shown in Table 2.

The 180 ° bending test is based on JIS Z 2
It carried out based on the 248 push-bending method. The test piece was sampled in the manner shown in FIG. 4 and had a size of 4.5 mmt × 30 mmw × 180 mml.
The sample having the size of ∘ was used and evaluated by ○ (no crack), Δ (crack of 2 mm or less), and × (break).

Further, the tensile test was conducted in accordance with JIS Z 3121 using a test piece taken in the manner shown in FIG.
The case of fracture at the weld was indicated by "melt", and the case of material fracture was indicated by "mother". Weld defects (fusion state, winding, extra-height shape, etc.) are ○ (no defect in the sheet width direction (Fig. 5)), △
(Defects were generated on a partial cross section in the plate width direction) and x (defect) was evaluated. The overall judgment was made by ○ (can be used as a wheel tube) and × (cannot be used as a wheel tube).

As is clear from Table 2, all of the examples of the present invention in which DC butt welding was performed under the conditions according to the method of the present invention,
High welding strength, excellent bendability (formability), 1
Excellent welded joints are obtained even at 80 ° bending.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

As described in detail above, according to the present invention,
By DC butt welding, a good welded joint of an aluminum alloy base pipe for a wheel can be obtained. Stable welding can be performed, and welding workability is also good.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of welding conditions.

FIG. 2 is a diagram showing a relationship between a first stage main welding current and a pressing force.

FIG. 3 is a diagram showing an initial current time (up slope) up to a main welding current (main current).

4A and 4B are diagrams showing a collection procedure of a bending test piece and a tensile test piece, in which FIG. 4A is a perspective view and FIG. 4B is a view seen from above.

5 (a) and 5 (b) are views for explaining an evaluation site of a welding defect and a defect example.

Claims (1)

[Claims] 1. When the aluminum pipes for aluminum wheels are butted against each other and pressure welded, the welding current is increased to the main current, and then the current is applied for at least 8 cycles and 30 cycles or less, and then 80% of the main current is applied. A method for producing a welded base pipe for an aluminum wheel, which comprises direct current butt welding with a current reduced to 50% or more.