JPH0512073B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention effectively prevents oxides from remaining in the welding area, which tends to cause cracks, in a method of performing flash butt welding by butting plate-shaped materials to be welded, specifically steel plates, etc. This invention relates to a flash butt welding method for improving quality. The flash butt welding method is a butt welding method that utilizes the joule heat generated by the current flowing through the contact portion when the butt end surfaces of the welded materials come into contact, and the arc heat generated after the contact portion melts and scatters. The principle of the flash butt welding method will be explained in some detail below with reference to FIGS. 1a, b...e, which are explanatory views thereof. First, as shown in a, a pair of plate-shaped welded materials (steel plates) W,
After W' is clamped by a pair of upper and lower electrodes 1 attached to a fixed platen (not shown) and a pair of upper and lower electrodes 2 attached to a movable platen (not shown), both electrodes 1, A voltage is applied between 2 and the movable platen is advanced to advance the welded material W' clamped to the electrode 2 as shown in b. When the abutting end surfaces of the materials to be welded W and W' approach each other and make slight contact as shown in c, a short circuit current flows through the contact area, and the contact area melts due to the Joule heat generated in that area. scatter. Generally, the power supply circuit of a welding machine includes an inductance, so after the contact portion scatters, an arc is generated at that point. Due to the generation of this arc, molten metal flashes and scatters from the end faces of the welded materials W, W', and the electrical contact between the welded materials W, W' is broken. During this time, the movable platen continues to move forward, so after a short period of time, the end faces come into contact again, and after that contact portion melts and scatters, the same process as described above, in which an arc is generated, is repeated. In this way, the above-mentioned process is repeated many times over the entire butt surface of the welded materials W, W', thereby increasing the temperature near the end face and forming a molten layer on the entire end face surface (flashing process). ).
After that, as shown in d, the platens on both sides are rapidly moved to stop the occurrence of flashing, and the abutting portions are pressurized for a predetermined period of time with the entire end surfaces of the welded materials W and W' in close contact. , e, the welding is completed. (upset process). In the foregoing upsetting process, if oxides of manganese, silicon, chromium, etc., which are alloy components of the welded material, remain in the weld without being extruded, those oxides will be damaged when the weld is subjected to tensile stress or bending stress. Remaining of such oxides must be avoided as much as possible since it may cause cracking.
To avoid this, it is effective to some extent to select welding conditions appropriately, but
For example, in a welded material made of steel with a high silicon content, it is extremely difficult to prevent the oxide from remaining in the welded part simply by appropriately selecting welding conditions. In addition, a method has been proposed in which the area around the weld is shielded using an inert gas in order to prevent the oxides from remaining in the weld. Since this occurs frequently, there are problems in workability and operability, and it is difficult to implement. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a flash butt welding method that can easily shield the welded area to avoid the oxide remaining in the welded area. In the flash butt welding method according to the present invention, when flat butt welding is performed by butting plate-shaped materials to be welded, (a) a substance containing zinc or zinc powder (b) on at least the lower surface of the materials to be welded in the vicinity of the butt part; The method is characterized in that an alloy containing calcium or magnesium, an intermetallic compound, or any of its inclusions is deposited, and welding is performed while shielding the area around the welding part from the atmosphere by evaporation of this deposited material at the welding part. The method of the present invention will be explained below based on the drawings showing its implementation state. FIGS. 2 and 3 are schematic diagrams showing the implementation state of the method of the present invention, with FIG. 2 showing the state before welding and FIG. 3 showing the state during welding, respectively. Reference numerals 1 and 2 denote a pair of upper and lower electrodes similar to those explained in FIG. The electrodes 1 and 2 clamp a pair of plate-like welded materials (steel plates) W and W' that are butted against each other, respectively. That is,
One of the plate-shaped materials to be welded W is clamped by the electrode 1 on the fixed side, and the other plate-shaped material to be welded W' is clamped by the electrode 2 on the movable side. And both electrodes 1,
The movable platen is moved forward while applying a voltage between the electrodes 2 and the welded material W' clamped to the electrode 2 is moved forward. In this case, a substance 3 that generates gas during welding is attached in advance to the upper and lower surfaces of the welded materials W, W' in the vicinity of the abutting portions, respectively. The substance 3 that generates gas during welding turns into steam due to the heat during welding and generates gas, and from a practical standpoint, the following substances are used. (a) Substances containing zinc or zinc powder (b) Alloys or intermetallic compounds containing calcium or magnesium, or substances containing them. The methods for adhering these include the following methods. (i) A method in which each substance is made into a paste and applied with a brush, etc. (ii) A method in which a viscous liquid mixed with zinc powder, an alloy containing magnesium, etc. is dropped onto the surface to be adhered (iii) A method in which zinc powder or magnesium is applied (iv) A method of thermal spraying by spraying finely molten alloys containing zinc and magnesium onto the surface to be attached (v) Method of plating with zinc, etc. (vi) Method of using a material such as grease that can be coated The width from the end surface of the part to which the material 3 is attached (l ₁ and l ₂ in the figure) is particularly limited. Although it is not necessary, it is desirable that the adhered substance 3 exists at least until the moment when the upsetting process begins. Now, as mentioned above, when the abutting end surfaces of the welded materials W and W' to which the substance 3 is attached come close to each other and make slight contact, a short-circuit current flows through the contact area, and due to the Joule heat generated in that area, The contact portion is heated, and a portion of the heated portion melts and scatters. After it scatters, an arc is generated at that location as described above, and due to the arc generation, the molten metal becomes flashes and scatters from the end surfaces of the welded materials W, W', and the welded materials W, The electrical contact between W′ is broken. During this time, the moving platen continues to move forward, and after a short period of time, the end surfaces come into contact with each other again, and the same process as described above is repeated. After this flashing process, the platens on both sides are rapidly moved to stop the flashing, and the abutting portions are pressurized for a predetermined period of time to upset the welded materials W and W' with their entire end surfaces in close contact with each other. do. Welding is completed with this upset process. Now, in the above-mentioned flashing process, the adhered substance 3 easily turns into steam 4 as shown in FIG.
Since the oxidation of alloy components such as silicon and chromium is prevented, their oxides will not remain in the weld.
Therefore, the resulting welded part is excellent in that it does not crack or the like even when subjected to tensile stress or bending stress. In the example, the substance 3 that generates gas during welding is attached to the upper and lower surfaces of the welded materials W and W′ near the butt portions, respectively, but since the generated gas generally rises, Even if the substance 3 is attached only to the lower surface, the effect of the method of the present invention can be expected to be sufficient. Next, specific examples of the method of the present invention will be described. Consists of chemical components shown in Table 1, plate thickness: 3
A pair of steel plates having a diameter of 1 mm was used as the test material, and the test materials were butted together and flash butt welded under the welding conditions shown in Table 2. In this case, each substance shown in Table 3 was attached only to the lower surface of the welded materials near the butt.

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【table】

【table】

[Table] The resulting welded part is determined by dividing the length of the crack that occurs when the welded specimen is bent with the welded part in the center and transformed into a tightly flat state by the total length of the welded part. It was evaluated using the value multiplied by 100, that is, the defect occurrence rate. The results are shown in Table 3 above, and from the table it can be seen that the method of the present invention was not applied.
No. 1 had a defect incidence rate of 100%, whereas No. 2 to No. 6 to which the method of the present invention was applied had a defect incidence rate of 2.
9%, confirming the excellent effect of the method of the present invention. As detailed above, when flat butt welding is performed by butting plate-shaped materials to be welded using the method of the present invention, alloys containing zinc and magnesium, etc., are added to at least the lower surface of the materials near the butt portion during welding. Since welding is performed after a substance that generates a gas other than oxygen is attached to the material, the vapor pressure of the gas generated shields the area around the heated area from the atmosphere, preventing the oxidation of the alloy components in the welded material, and reducing the It is possible to prevent oxides from remaining in the welded area. Therefore, it can be said that the present invention provides a simple method for avoiding the oxides remaining in the welded portion and maintaining high welding quality.

[Brief explanation of the drawing]

FIGS. 1a, b, c, d, and e are explanatory diagrams of the principle of the flash butt welding method, and FIGS. 2 and 3 are schematic diagrams showing the implementation state of the method of the present invention. W, W'...material to be welded, 1, 2...electrode, 3...
...adhesive substance, 4...steam.

Claims (1)

[Scope of Claims] 1. When flat butt welding is performed by butting plate-shaped materials to be welded together, at least the lower surface of the materials to be welded in the vicinity of the butt part contains (a) a substance containing zinc or zinc powder; (b) calcium or A flash butt welding method characterized by depositing an alloy containing magnesium, an intermetallic compound, or a substance containing the same, and performing welding while shielding the periphery of the welded part from the atmosphere by evaporation of the deposited material during welding.