JPS6025229B2 - Flash welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to flash welding methods, and more particularly to improving the quality of flash weld joints.

Currently, the flashing welding method is used in a wide range of fields, but in recent years, the application of the flash welding method to materials having a particularly large cross-sectional area has been considered due to its characteristics of short time and high efficiency.

However, in flash welding of such large cross-sectional area materials, welding defects generally occur frequently, which is a major problem to be solved.

In order to eliminate flash welding defects, it is necessary to generate flash uniformly over the entire end face of the welded material during flashing, which is the heating process, and to ensure that the temperature of the end face of the welded material is sufficiently high to the melting temperature just before the final welding process, which is pressurization (upsetting). It is necessary that a molten metal layer is formed by reaching the end surface, that the end surface is kept clean without causing oxidation, or that the end surface has few irregularities. However, thin sheet wide medium wood,
When flash welding materials with a large cross-sectional area, such as large-diameter pipes or large round pipes, it is difficult to generate flash uniformly over the entire end face, which may result in uneven overflow on the end face. Also, welding defects are likely to occur due to increased unevenness on the end face. If such defects exist in the welded portion, they will adversely affect the properties of the joint, such as mechanical properties, grain hardness, and fatigue. In order to solve these problems, various measures have been taken to prevent the occurrence of defects, such as lowering the conventionally applied flash voltage, lowering the impedance of the welding machine, examining various control methods, and examining the upset pressure force. I've been trying. However, even with these methods, fundamental solutions could not be achieved, and there were limits to the prevention of defects. In view of the above-mentioned points, the present invention aims to prevent defects in flash welds and to improve the quality of welded joints.

That is, the present invention is a flash welding method characterized in that an auxiliary material is provided on the side surface adjacent to the abutting ends of the materials to be welded, and these materials are flashed.

A detailed explanation will be given below according to the drawings.

As shown in Figure 1, in the flash welding method, a voltage (flash voltage) is applied between the welded materials 1 fixed to an electrode 2, and the end surfaces of the welded materials 1 are brought into light contact with each other (this process is called flashing). ) Both end faces are heated, and when the end faces reach a sufficient melting temperature, pressure is rapidly applied between both end faces to complete the welding (this process is called upset). During flushing, both end faces partially come into contact, but a large short-circuit current flows through this contact area, and the contact area quickly reaches the melting temperature of the welded material and is instantly burned out. (Occurrence of flash) At this time, the molten metal formed at the contact portion of the welded material 1 is scattered in all directions due to the magnetic force due to the short circuit current or the pressure due to the arc generated following the contact.
Most of this scattered molten base metal is removed from between the end faces of the welded material, but some only moves on the end face.
There are cases where the molten metal remains on the end face or the scattered molten metal adheres to other places on the end face again. As a result of detailed observation of the scattering phenomenon of molten metal during flash welding, the present inventors have found that this scattering phenomenon can be actively utilized to improve the properties of the end surface of the welded material.
We thought that this might reduce welding defects and conducted various studies.

As a result, adjacent to the butt ends of the materials to be welded, a metal or alloy that has the effect of improving the end surface properties of the materials to be welded is installed as an auxiliary material, and during flash welding, flash is also generated from the auxiliary material. It has been found that it is possible to add the auxiliary material metal to the end face of the welded material by generating .

Now, this phenomenon will be explained based on Figs. 2 and 3. In the figures, 1 is the material to be welded, and 4 is the thickness b as described later.
, medium a, auxiliary material having a length of 1, 3 indicates a welding transformer, and in particular, as shown in FIG. 6 reaches the melting temperature in a short time due to the large short circuit current, and the magnetic field caused by the short circuit current or the arc that follows the short circuit causes a sudden temperature rise, and the resulting explosive force causes the molten metal to reach the melting temperature like 5. It scatters in the form of particles or moves on the end surface.

Such scattering or movement of the molten metal occurs equally on both the end face of the material to be welded 1 and the end face of the auxiliary material 4, and a part of the molten metal of the auxiliary material that has been scattered or moved reaches the end face of the material to be welded 1. As the flash process progresses, the molten metal layer 7 containing the auxiliary material components is partially formed on the end face of the welded material due to the scattering or movement of the auxiliary molten metal. Of course, a part of this molten metal layer 7 is also scattered due to the contact of the end surface of the welded material, but due to the flywheel action with the molten metal of the welded material, in the latter half of the flashing process, the molten metal layer 7 containing the auxiliary material components covers the entire end surface of the welded material. A metal layer is formed,
This results in a smooth metal or alloy layer that is effective in preventing defects. Next, the arrangement of auxiliary materials used in the present invention,
, describes the law.

As is clear from the above description of the present invention, it is necessary that the auxiliary material be installed on the side surface adjacent to the end of the welded material and flushed together with the welded material. In this case, the auxiliary material does not necessarily need to be pressurized (upset). Furthermore, in the present invention, providing an auxiliary material on adjacent side surfaces does not necessarily mean that the auxiliary material and the material to be welded are in close contact with each other, but there may be a gap between them. According to the studies conducted by the present inventors so far, the auxiliary materials used in the present invention are attached to two sides of the welded material 1 as shown in FIG. 2 when the welded material 1 is a flat plate, or as needed. When the material to be welded 1 is a round bar or a pipe, the auxiliary material 4 is applied to the entire side surface adjacent to the butt end of the material to be welded 1, as shown in FIGS. 6 and 7. Generally, better results can be obtained in terms of preventing air entrainment or adding alloying elements by arranging it over the inner and outer surfaces. That is, flash welding is normally performed in air, but when welding is performed in the atmosphere, welding defects are less likely to occur than in arc welding.

This is said to be because the occurrence of flash prevents air from being drawn into the end face of the welded material. If flashes occur continuously, less air will be trapped and fewer defects will occur. Therefore, by placing the auxiliary material as mentioned above on the side surface adjacent to the butt end of the welded material, the occurrence of flash at the auxiliary material will prevent air from being drawn into the end surface of the welded material, thereby preventing the occurrence of weld defects. It has the function of suppressing In addition, when the purpose of using an auxiliary material is to add alloying elements, if a sufficient effect can be obtained, one adjoining part of the butt weave of the material to be welded may be used as shown in Figure 4 or 5. The auxiliary material 4 may be placed adjacent only to the side surface.

However, according to the observation, it seems that the weld metal scatters strongly in two directions, moving from the transformer 3 side to the opposite side. It seems that the method shown in FIG. 5, which is installed on the same surface, is more effective in adding alloying elements. In the present invention, it goes without saying that the number of auxiliary materials is not limited to one type, and several types of auxiliary materials can be appropriately combined and used at the same time depending on the purpose.

For example, as shown in FIGS. 8 and 9, it is possible to add two or more types of alloying elements by variously combining two or more types of auxiliary materials 4, 8, and 9. Further, as for the dimensions of the auxiliary material used in the present invention, for example, when the material to be welded is a flat plate, it has the same length 1 as the inside of the material to be welded 1, as shown in FIG. It is sufficient if it is equal to or greater than the flashing distance on one side of the welding material.

The thickness b of the auxiliary material may be selected depending on the thickness of the material to be welded 1, and when the material to be welded 1 is thick, better results can be obtained by making the auxiliary material thicker as well. It goes without saying that when the material to be welded 1 is a round bar or pipe as shown in FIGS. 6 and 7, the size and shape of the auxiliary material may be appropriately selected depending on the cross-sectional shape of the material to be welded. In the flash welded joint shape obtained by the method of the present invention, if the thickness of the auxiliary material is thinner than that of the welded material, as shown in FIG. , it is deformed outward by the material to be welded 1, so that no upset portion is generated and the shape is separated from the material to be welded 1.

Therefore, the auxiliary material 4 can be easily removed after flash welding, and does not pose a problem when using the welded joint. Next, referring to the effects brought about by the present invention, first of all,
By using the auxiliary material, it becomes possible to add alloying elements to the end face of the welded material.

That is, in general, the flash welding phenomenon is greatly influenced by the components of the material to be welded, such as the melting temperature or viscosity of the material to be welded, but according to the method of the present invention, alloying elements can be added to the end surface of the material to be welded by using an auxiliary material. This makes it possible to change the composition of the molten metal or its physical properties such as melting temperature and viscosity.

If the composition or amount of the added element is selected according to the material to be welded, it is possible to generate a uniform and fine flash, resulting in a smooth end surface of the material to be welded.
Defect-free flash welded joints can be obtained. In particular, when a material that lowers the melting temperature of the welded material is used as an auxiliary material, a sufficiently thick molten metal layer is formed on the end surface of the welded material, and even if the end surface of the welded material has irregularities, it will not work during upsetting. This is smoothed out, resulting in a welded joint free of weld defects. It is also possible to use a material that causes oxidation and contains a dark element as an auxiliary material to temporarily prevent oxidation of the end face of the welded material. Furthermore, as an auxiliary material, a single-element material consisting of an element that is effective in improving the mechanical properties, rutting resistance, corrosion resistance, and fatigue properties of flash welded joints, or an alloy material consisting of two or more elements may be used. Accordingly, these elements can be added to the end face of the welded material, and the above-mentioned properties of the flash welded joint can be improved. In addition, if a material is selected that causes a particularly large number of flashes to occur, the effect of preventing air from being drawn into the end face of the welded material will be even greater. Furthermore, if a material with a high vapor pressure is selected as the auxiliary material, the effect of protecting the end face of the welded material from oxidation by metal vapor will be greater, and a joint with fewer defects can be obtained. As described above, according to the method of the present invention, various effects can be obtained by using auxiliary materials, and as a result, it is possible to eliminate welt defects and obtain a welded joint with excellent properties. .

The method of the present invention can be widely applied to materials having various cross-sectional shapes, as well as to the aforementioned thin plates, pipes, and round bars. Furthermore, the method of the present invention can be applied to flash welding not only of general various steels including stainless steel, but also of nonferrous metal materials such as copper, aluminum, and alloys thereof. Finally, the present invention will be explained in more detail with reference to Examples.

Example 1 The material to be welded was an SM5 female with a plate thickness of 12.7 mm, a medium diameter of 300 mm, and a length of 20 mm.As an auxiliary material, a material having the components shown in Table 1 was used.

The dimensions of the auxiliary material were board thickness 3.0 mm, medium 30 mm, length 100 mm, and the pupils were as shown in Figure 2. The second welding condition
Shown in the table. Table 3 shows the defect occurrence rates by the method of the present invention and the conventional method.

The conventional method is a case in which flash welding is performed using only the materials to be welded without using an auxiliary material as in the method of the present invention. Table 1: Chemical composition of sample material (wt%) Table 2: Flash welding conditions Table 3 shows the defect rate of welds in the method of the present invention and the conventional method.

The defect rate is the area rate of defects on the fractured crack surface in a bending test after removing threads after welding. Table 3
Defect rate of the present invention method and conventional method As shown in Table 3, according to the present invention method, the defect rate is lower than that of the conventional method,
The effects of the present invention are obvious.

Note that the mechanical properties of the welded joint obtained by the method of the present invention were sufficient. Example 2 As a material to be welded, a flat plate having the chemical composition shown in Table 4 and having a thickness of 12.7 cm, a middle 30 mound and a length of 20 mboard was used.

As an auxiliary material, plate thickness 3 having the chemical components shown in Table 4 is used.
The materials having the dimensions of the side, the middle 30 mounds, and the low side were arranged as shown in FIG. 2, respectively. Welding conditions are shown in Table 2. Table 4: Chemical composition of sample materials Table 5 shows the results of Charpy impact tests on welded parts using the method of the present invention and the conventional method.

The notch position was set at the joint surface. As shown in Table 5,
While the conventional method has an impact value of around 1 skin of lk9, the method of the present invention shows an impact value of 2k9 1 skin or more, and the effect of the present invention is clear. Table 5 Sialby impact test results (JIS No. 4 2-piece Vnotte Nyarpy, test temperature 0
℃) The other mechanical properties of the welded joint obtained by the method of the present invention were also satisfactory.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of flash welding using the conventional method;
The figure shows an example of the method of the present invention, Figure 3 is a schematic diagram of the end face situation in the method of the present invention, and Figures 4 and 5 show an example in which the auxiliary material is placed only on one side in the method of the present invention. 6 is a diagram showing an example in which the material to be welded is a round bar in the method of the present invention, FIG. 7 is a diagram showing an example in which the material to be welded is a pipe in the method of the present invention, Figure 9 shows an example of using two or more types of auxiliary materials in the method of the present invention, and Figure 10 shows
FIG. 3 is a diagram showing a cross-sectional shape of a welded part obtained by the present invention. 1; Material to be welded, 2: Electrode, 3: Welding transformer, 4, 8, 9
auxiliary material, 5: scattered particles, 6: end surface shark portion, 7: auxiliary material molten metal layer, 10: upset portion. Figure 1 Figure 2 Figure 4 Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] 1. A flash welding method characterized by providing an auxiliary material on the side surface adjacent to the butt ends of the materials to be welded and flashing these materials simultaneously.