JPH04237576A - Aluminum alloy plate having excellent spot weldability - Google Patents

Abstract

PURPOSE:To improve an electrode life and to improve the stability of the quality of a weld zone by applying iron plating consisting of iron as its essential constituting component on at least the surface of the aluminum alloy plate, which surface faces the electrode. CONSTITUTION:The iron plating consisting of the iron as its essential constituting component is applied on the aluminum alloy plate, by which the formation of an aluminum oxide at the end of the electrode is suppressed. The iron plating essentially consisting of the iron as its essential component refers to the plating of single layer or lamination of >=2 layers of iron plating, iron/zinc alloy plating, etc. Means for plating may be any means including electroplating, vapor deposition plating or cladding, etc., and are not particularly limited. The effect of the plating surface is exhibited when the plating is applied on the surface facing the electrode. The frequencies of the exchange of the electrode at the time of spot welding, etc., or shaping of a front end shape by dressing are decreased in this way and the productivity is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy plate mainly used as a lightweight material for automobiles, and particularly to an aluminum plate or aluminum alloy plate having excellent spot resistance weldability.

0002

[Prior Art] The weight reduction of automobiles is being actively promoted from the viewpoint of energy conservation and global environmental problems caused by CO2, but among these, aluminum or aluminum alloys are being used in terms of material reliability, workability, recycling, etc. has been in the spotlight and is being used more frequently in recent years.

However, when assembling these aluminum alloy plates into automobile bodies, most of them are spot resistance welded, but aluminum alloy plates have extremely poor spot resistance welding properties, especially electrode life, compared to steel plates, so it is difficult to assemble automobile bodies. The current situation is that this has led to a significant decline in production efficiency. In other words, in spot resistance welding of aluminum alloy plates, the number of welding points that can produce a proper nugget with the same electrode is extremely short, so it is necessary to adjust the electrode shape by dressing or replace it with a new electrode before a proper nugget can no longer be obtained. The frequency of welding has increased, and this has a significant impact on welding efficiency and, by extension, on the production efficiency of automobile bodies.

[0004] Aluminum alloys have only recently been put to practical use in mass-produced products such as automobiles by spot resistance welding, so there are no proposals or appropriate means to solve the above problems. The current situation is that we are still producing with this problem.

[0005]

[Problems to be Solved by the Invention] The present invention has the advantage that the electrode life during spot resistance welding, that is, the continuous dot performance, is significantly improved compared to conventional aluminum or aluminum alloy plates, and that the welding process can be easily and stably performed industrially. Moreover, it is an object of the present invention to provide an aluminum plate or an aluminum alloy plate that can be manufactured economically.

[0006]

[Means for solving the problem] Aluminum plate or aluminum alloy plate (hereinafter referred to as aluminum alloy plate)
When spot resistance welding is performed repeatedly using the same copper-based electrode, the current-carrying diameter at the tip of the electrode expands along with the welding point, and the nugget diameter decreases due to the accompanying decrease in current density in the plate. Regarding the electrode life, the aluminum alloy plate was characterized by a significantly higher rate of expansion of the electrode tip diameter than the steel plate.

[0007] Therefore, we paid attention to such a phenomenon, and as a result of intensive investigation into its causes, we found that in the case of continuous dot welding of aluminum alloy plates, aluminum adheres to the current-carrying part of the electrode tip, and its oxide is deposited along with the dots. They discovered that this forms an insulating layer that eventually causes sparks between the electrode and this insulating layer, causing the electrode to become damaged in a moth-like manner. It was discovered that this phenomenon peculiar to aluminum alloy plates promoted the expansion of the electrode tip diameter, resulting in an extremely shortened electrode life.

[0008] Based on this knowledge, the present invention has been completed as a result of intensive studies in order to suppress aluminum oxide formed at the tip of the electrode when the aluminum alloy plate is welded. That is, the present invention suppresses the formation of aluminum oxide at the tip of the electrode and significantly improves the life of the electrode by applying iron-based plating containing iron as a main component to at least the surface of the aluminum alloy plate facing the electrode. It is something.

[0009]

[Function] In the present invention, iron-based plating whose main component is iron refers to iron plating, iron-zinc alloy plating, iron-nickel alloy plating, or other iron alloy plating in a single layer or a stack of two or more layers. refers to something done. Further, the plating method may be any method such as electroplating, vapor deposition plating, or cladding, and the method is not particularly limited. Further, as described above, the effect is exhibited by applying the plating to the surface facing the electrode, but of course, the effect is not inhibited even if other surfaces are plated.

[0010] When applying the above iron-based plating to the surface of an aluminum or aluminum alloy plate and expecting the effect of improving the electrode life during continuous spot resistance welding, it is sufficient that the iron weight in the iron-based plating is less than 1 g/m2. Furthermore, even if the iron weight exceeds 100 g/m2, no further effect can be expected, and it also results in economical waste of raw materials and energy, so the preferred method of iron-based plating is Weight is 1 to 100g/m based on the weight of iron in plating
It is 2.

[0011]

[Example] Next, an example of the present invention will be described. A1100 (pure Al
The present invention was electroplated using iron plating, iron-zinc plating, and iron-nickel plating using A5052 (Al--Mg-based) and A5052 (Al--Mg-based) materials. Further, the electrode life was evaluated using an inverter DC welding machine under the following electrodes and welding conditions.

[0012] Electrode shape: Conical cone (CF) type tip diameter
: 5.0mmφ Material: Cr-Cu Welding conditions Pressure force: 150kgf Initial pressurization time: 20/50 seconds Current application time: 6/50 seconds Holding time: 5/50 seconds Welding current: 15kA Electrode life nugget diameter is 4√ Judgment is made by the number of dots below t (t: plate thickness) Examples and comparative examples of the present invention are summarized in Table 1 along with their implementation details and effects. Example 1 of the present invention
It can be seen that in No. 16, the electrode life was significantly improved compared to Comparative Examples 1 to 6.

[0013]

[0014]

As explained above, according to the present invention, by applying iron-based plating to the surface of an aluminum plate or aluminum alloy, the life of the electrode during spot resistance welding is significantly improved. This significantly reduces the frequency of changing electrodes or shaping the tip shape by dressing during spot welding at production sites, leading to a significant increase in productivity, and at the same time dramatically improving the stability of the quality of welded parts. You can also expect good results.

Claims (1)

[Claims] 1. An aluminum alloy plate with excellent spot resistance weldability, characterized in that at least the surface of the aluminum alloy plate facing an electrode is coated with iron-based plating containing iron as a main component.