JPS61165284A - High-energy density welding method of low melting metallic material - Google Patents

Abstract

PURPOSE:To obtain beautiful weld beads having no defects on both front and rear surfaces in the stage of subjecting low melting metallic materials to high- energy density welding by subjecting said materials to penetration welding at the energy density at which a backing strip made of copper or copper alloy does not melt. CONSTITUTION:The low melting metallic materials consisting of an Al alloy, Mg alloy, etc. are used as materials to be welded and are subjected to the penetration welding of high-energy density by using the backing strip made of the copper or copper alloy. The welding conditions under which the backing strip does not melt are set in this stage from the relation between the value ab obtd. by dividing the distance D0 from the center of the focusing coil 2 of an energy beam 1 to the surface of the work 3 by the distance DF from the center of the coil 2 to the beam focus 4 and the beam current. The good weld beads having no defects on both the front and rear surfaces are thus obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for high-energy density welding of low-melting metal materials such as aluminum, aluminum alloys, magnesium, and magnesium alloys, particularly thin-walled metal materials, and more particularly to Specifically, the present invention relates to a penetrating high-energy density welding method that is free from surface defects such as underfill and can form good beads on both sides of a base material.

[Conventional technology]

High energy density welding such as electron beam welding and laser welding has many advantages such as higher welding efficiency and the ability to set the welding position extremely accurately compared to ordinary arc welding, etc. It is beginning to be widely used for welding of precision equipment and welding of precision equipment. On the other hand, aluminum, magnesium, and their various alloys are lighter than steel materials, so their field of use is rapidly expanding as they meet the demands for smaller size and lighter weight. The number of cases in which high energy density welding is applied is gradually increasing. However, since the above-mentioned light metals generally have a low melting point, various problems arise when attempting to apply the above-mentioned high energy density welding to these light metals. The biggest problem among these problems is the occurrence of underfill defects on the bead surface, as shown schematically in FIG. 9, and it is extremely difficult to improve these defects by selecting welding conditions. has been done. Therefore, 10th to 12th
Measures to prevent underfill have been taken as shown in the figure, but as shown below, they are not necessarily satisfactory. That is, in Fig. 10 (4), @ is the backing material 2 which is the same as the base material 1.
This method uses partial penetration welding to eliminate underfill defects, but since the backing material 2 is integrally welded to the back side of the welded part, it is difficult to remove the backing material 2. .

Figure 11 (4) @ is a method in which the groove surface of the base metal 1 is formed into a convex shape and welding is performed, but the process involves cutting the convex part after welding and cutting the back bead that protrudes greatly on the back side. It takes a lot of work. Figure 12 (3) and (3) are methods in which filler metal 8 is placed on top of the underfill defect that has occurred and decorative welding is performed, but work efficiency is low because welding has to be performed twice. Moreover, since the back bead protrudes greatly, the removal work is also complicated.

On the other hand, in various welding processes such as submerged arc welding and electroslag welding, the technology of using water-cooled copper dowels to support molten metal has been known for quite some time. This takes advantage of the fact that copper has extremely high thermal conductivity, and if it is water-cooled, it will not melt even if it comes into direct contact with molten metal such as steel.

However, in high energy density welding as mentioned above, the energy density of the electron beam, etc. is 1
02 to 105 times, which is extremely high, so if a copper dowel is placed on the back side of the weld, the electron beam, etc. that penetrates the material to be welded will reach the copper dowel and melt it, causing the copper to enter the weld metal. A problem arises in that the mechanical properties and corrosion resistance are deteriorated by contamination. For these reasons, electron beam welding and the like do not employ a method of welding by directly applying a copper dowel to the back surface.

[Problem that the invention seeks to solve]

Under these circumstances, the present invention aims to provide a high energy density welding method that can obtain a beautiful weld bead with no defects on both sides with simple operations for low melting point metals such as those mentioned above. In particular, we have made it possible to effectively utilize the copper dowels used in ordinary level energy welding for high energy density welding, thereby solving the above-mentioned problems that occur in high energy density welding of low melting point metal materials. This is what we are trying to resolve.

[Means for solving problems]

The high energy density welding method according to the present invention uses a low melting point metal material as the material to be welded, and performs penetration welding using a backing material made of copper or copper alloy under an energy density that does not melt the backing material. The main points are as follows.

[Effect]

In the present invention, as will be made clear in the examples below, low-melting point metals such as aluminum, aluminum alloys, magnesium, and magnesium alloys are to be welded, and a backing metal made of copper or copper alloy is brought into contact with the back surface of the welding target, and an electron beam or Welding is performed by irradiating a heating source with a high energy density such as a laser (hereinafter referred to as an electron beam), and in this welding, the irradiated electron beam etc. penetrates the material to be welded and does not damage the backing metal. Control the energy density so that it does not melt. As a result, the molten metal on the back side is supported by the backing metal, so the back bead is beautifully finished and the bead has an appropriate amount of excess on the surface, making it possible to completely eliminate underfill defects. can. Moreover, during welding, the energy density is controlled so that the backing metal does not melt, so it can be easily removed after welding, and workability including post-processing can be significantly improved.

〔Example〕

The structure and effects of the present invention will be further clarified by following the details of the experiment below.

First, the inventors selected steel materials, magnesium alloys, and aluminum alloys, and conducted basic experiments to clarify the critical output value of the electron beam required to melt these materials. The results were obtained. That is, the accelerating voltage of the electron beam was set to 120 KV, the work distance was set to 650 KV, the focal point was positioned so that it was on the work surface, and the work material was an aluminum alloy (508 KV).
8: Fig. 1), a magnesium alloy (AZ81C: Fig. 2), and copper (CI220: Fig. 8), and the meltability was investigated when the beam current and welding speed were changed. The result is the first
As shown in Figure 8, aluminum alloys and magnesium alloys melt with a beam current as low as 1 to 8 mA, but copper does not melt even with a beam current of 10 mA. Fig. 4 is a graph showing the influence of beam current and a value on the meltability of a copper workpiece when the focal position of the electron beam is shifted in the thickness direction of the copper workpiece. When the beam is moved away from the workpiece surface, the diameter of the beam increases and the energy density drops sharply, making it possible to keep the copper workpiece in an unmolten state even when the beam current is increased to 25 mA, for example.

It is easily assumed that when the accelerating voltage is changed, the limit of the beam current at which the surface of the plate material does not melt changes.

The value a shown in FIG. 4 is the distance (Do) from the center of the focusing coil 2 of the beam 1 to the surface of the workpiece 8, as shown schematically in FIG. It is the value divided by the distance fi (DF).

In general, as a condition for obtaining good Uranami in electron beam welding, there is a constant between the amount of beam required to penetrate the entire thickness of the workpiece and the amount of beam scattered to the back side of the workpiece. It is said that there is a ratio of 10 to 2596, which is the amount of beam required for the beam to penetrate the thickness of the workpiece, for the amount of beam scattered on the back side of the workpiece. .

Considering these characteristics of the electron beam and the melting properties of copper, aluminum alloy, magnesium alloy, etc., by appropriately adjusting the beam current and focus position, it is possible to penetrate the aluminum alloy and prevent the copper material placed on the back side from melting. Various welding conditions can be obtained. For example, when the energy density of the beam penetrating the back side of the workpiece is high, the beam current can be kept to about 10 mA or less, and when the energy density is low, the beam current can be kept to about 25 mA or less. The object to be welded can be reliably welded over the entire thickness without melting. Furthermore, if the thickness of the material to be welded is kept to about 15 mm or less, the above-mentioned appropriate beam welding conditions can be easily obtained.

6 to 8 are schematic explanatory diagrams illustrating welding modes according to the present invention, and in FIG. 6 (4), @ is a copper dowel 5 with a flat top surface placed on the bottom surface of the workpiece 1.1. In this example, the back surface of the bead is formed to be flush with the back surface of the workpiece 1 to be welded. Also, Fig. 7 (A),
Q3) shows an example of welding by arranging a copper dowel 5 with a groove 6 for forming a back bead on the upper surface. It is also possible to form a moderate excess bead by adjusting. Figure 8 (@) is an example that is adopted when welding and manufacturing box materials, etc. A copper dowel 5 is attached to the back corner of the welded materials 1, 1 assembled at approximately right angles, and high energy is applied from the outside side. An example of density welding is shown. In any of these welding examples, since the molten metal is supported by the copper dowel 5, it does not flow out to the back side, and an appropriate amount of excess metal is ensured on the front bead. In addition, when forming an extra bead on the back side as in the example shown in Figures 7 and 8, if the extra bead is too large, the overall amount of molten metal will be relatively insufficient, resulting in insufficient extra bead on the bead surface. However, in such cases, it is sufficient to replenish an appropriate amount of filler metal from the surface side during welding. In addition, if the welding time is short and the heat capacity of the copper dowel is sufficiently large, a simple rectangular copper dot may be used, but if the welding time is long or the heat capacity of the copper dot is small, It is preferable to use a water-cooled structure for the copper dowel to prevent temperature rise.

Table 1 shows the results of high energy density welding experiments of the present invention using magnesium alloy (A281C) and aluminum alloy (5088), and as is clear from this table, copper was used as the backing material. By adjusting the energy density and beam current of the electron beam so that the copper material does not melt, the material to be welded can be reliably welded over the entire thickness without melting the copper material. Furthermore, beautiful beads can be obtained on both sides without any underfill or the like.

However, if a copper dowel is not used, underfill defects will occur, and if a steel whose meltability when irradiated with an electron beam is similar to that of the material to be welded is used as a backing material, part of the backing material will be damaged by the electron beam. It will melt due to As is clear from the results in Table 1, when implementing the present invention, the energy density (including beam current and AB value), welding speed, etc. must be adjusted appropriately depending on the type and thickness of the material to be welded. need to be controlled.

11' [Effects of the Invention] The present invention is constructed as described above, and the copper dowel can be applied to high-energy density welding of low-melting point metal materials, thereby eliminating underfill defects, which have been considered a problem in the past. It is possible to reliably eliminate this problem, and to obtain a healthy and beautiful weld bead on both the front and back sides. Moreover, in the present invention, by simply arranging the copper backing material on the back side and appropriately adjusting the energy density of the electron beam, etc., there is no need for any other groove processing or complicated post-processing after welding. This is an extremely excellent method in terms of workability and welding efficiency.

[Brief explanation of the drawing]

Figures 1 to 3 are graphs of experimental results showing the melting state when beam current and welding speed are changed for aluminum alloy, magnesium alloy, and copper. A graph showing the influence of
Figures 6 to 8 are schematic sectional views showing welding examples of the present invention, Figure 9 is a schematic sectional view showing underfill defects that occur in conventional examples, and Figures 10 to 12 show known examples of underfill prevention welding. It is a schematic sectional view. 1... Material to be welded, 2... Backing material.

Claims (1)

[Claims] In high-energy-density welding of low-melting-point metal materials, welding is performed using a backing material made of copper or copper alloy at an energy density that does not melt the backing material. High energy density welding method for melting point metal materials.