JPH0671436A - Enclosed arc welding of rail - Google Patents

Abstract

PURPOSE:To form a sound welding bead by welding with directing welding torch to both welding proceeding and its opposite directions, gradually moving to the welding proceeding direction and stopping welding arc after welded with directing the welding torch between a backing and weld zone until the oval shape of crater becomes semicircle. CONSTITUTION:After completing joint welding from the leg part to belly part of facing rails 1, 1 with arranging groove, the enclosed arc multi layer welding of the head part of the rail 1 is executed with butting a backing 2 along the contour shape of head side of the rail 1. The arc of covered electrode 4 is directed to the opposite direction of the welding proceeding direction to weld, moving to the crater part in melted state generated near bead's end, moving in the welding proceeding direction, welding until the oval shape of crater becomes semicircle with butting welding arc between the weld zone and backing and then stopping the welding arc. This welding method is repeated for each layer to weld the head part of the rail 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for enclosed arc welding of rails used for transportation of railways and industrial machines.

[0002]

2. Description of the Related Art Conventionally, rail welding methods include a flash butt welding method in which end surfaces are heated and pressed by a spark generated by energizing the rails to be joined and energized between them, and an oxygen-acetylene flame or Others such as gas pressure welding method that heats and presses at high temperature with a gas flame such as oxygen-propane flame, and thermite welding method that uses the high temperature reaction heat generated by igniting a mixture of fine aluminum and iron oxide In addition, the enclosed arc welding method is used.

This enclosed arc welding method is also introduced in Japanese Patent Publication No. 56-4350 as a welding method that has been widely used conventionally. FIG. 2 shows a plan view (A) and a side surface (B) of a conventional rail closed-arc welding method. The rails 1 and 1 to be joined and the outer shape of the rail are shown in FIG. Abutment 2 that abuts along
Is a joining method in which the covered arc welding rod 4 is added to the joint welding portion 3 formed in 1) and multi-layer welding is performed in a downward posture to form a welding bead, and the reliability of various welding characteristics compared to other welding methods. Because of its high advantages, it is commonly used as a field welding method.

However, the high-carbon steel quality enclosed arc welding method such as rails, which is required to have wear resistance, fatigue damage resistance, and static high strength, has a composition as shown in Table 1.

[Table 1] JIS Z3212 low-alloy high-strength steel coated arc welding rod is used, and it is constructed in a downward arc welding posture.
However, the C component in the weld metal formed in the joint is 0.
Since it is contained in a high amount of about 3%, the difference in the solidification temperature resulting from the difference in the C content between the weld metal and the base material such as the rail, that is, the solidification temperature of the weld metal is 1530 ° C. Due to the difference of 1470 ° C, near the melting boundary of the base metal (H
AZ) had a problem of frequent hot cracking. In order to reduce this crack, a high-temperature stress relief annealing treatment is performed after welding, but this method also has a problem that an annealing device must be always provided at the welding site.

More recently, as one of the in-situ welding methods by which hot cracking due to the C content can be eliminated and stress relief annealing can be omitted depending on the characteristics required for the welded joint, for example, Japanese Patent Laid-Open No. 63-160799. As introduced in the official gazette, a welding method applying a high carbon coated arc welding rod containing C: 0.4 to 1.0% has been developed. Such a high carbon welding rod also remarkably improves the wear resistance and fatigue damage resistance required for rails, for example.

[0006]

However, in the downward multi-layer welding method of rails, in which a groove is provided and welding is performed while applying a metal to the side faces of the welded joints of the rails facing each other,
High-carbon welding rods, like austenitic stainless welding rods, have shrinkage (contraction holes) and solidification cracks (crater cracks) at the weld bead end crater (molten pool).
There was a problem that is likely to occur. Crater cracking is a phenomenon that occurs in the crater part when one covered arc welding rod finishes welding.The size depends on the magnitude of the tensile stress during crater or solidification shrinkage. It may cause a decrease in static strength and fatigue strength of the joint.

In particular, the downward-facing multi-layered welded portion of the head in the enclosed arc welding method of the rail is surrounded by a metal shell, and the weld end portion cannot be processed outside as an extra deposit outside the rail end surface. The department must be sound. Generally, in order to keep the crater portion of the weld end sound, the size of the crater is reduced by igniting (the arc is applied once or several times to the crater portion instantaneously), and at the same time the amount of deposited metal in the crater portion is increased. Method is used. However, in the case of high-C weld metal, the crater is unlikely to become small due to ignition, and shrinkage and crater cracking are likely to occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rail welding method that prevents the shrinkage and crater cracks that are likely to occur in the conventional rail enclosed arc welding methods as described above.

[0009]

In order to achieve the above object, the present invention has the following structure, that is, the welding of joints from the leg portions of the rails facing each other to the abdomen portion is completed by providing a groove. After that, in the enclosed arc multi-layer welding of the rail head that welds by contacting the metal to the side surface of the head, for each layer,
Weld the welding arc in the direction opposite to the welding direction,
At the bead end crater in the molten state that occurred, the welding arc is gradually moved in the welding progress direction, and finally, the welding arc is applied between the metal and the weld until the ellipse shape of the crater becomes a semi-circular shape. After that, it is the rail's enclosed arc welding method that stops the welding arc.

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a welding method of the present invention in plan view (A) and side view (B) in the order of steps (a), (b) and (c). After finishing the welding of the abdomen from the leg portions of the rails 1 and 1 to be joined facing each other with a groove provided, the dowel 2 is abutted along the outer shape of the rail head side view. In the enclosed arc multi-layer welding of the rail head to be welded, first, as shown in (a), the arc of the coated welding rod 4 is welded in the opposite direction different from the welding progress (arrow) direction, and then (b) figure. As shown in FIG. 5C, the welded arc is moved to the welding advancing direction while gradually turning the coated welding rod 4 as shown in FIG. While applying a welding arc to the gold 2, welding is performed until the elliptical shape of the crater becomes a semicircular shape, and then the welding arc is stopped. The head of the rail is welded by performing the layer-by-layer welding in which such a welding method is repeated for each layer. In the figure, 5 indicates a lower welding layer.

According to the present invention as described above, the size of the crater is reduced, and the solidification rate is increased by directly contacting the crater portion with the copper metal having a high cooling rate. Therefore, the shrinkage and the crater portion are cracked. Can be prevented. INDUSTRIAL APPLICABILITY According to the present invention, when the crater cannot be brought out of the rail cross section like the welding of the rail head in the enclosed arc welding of the rail, the shrinkage and crack of the weld end crater portion which are a concern in the high C type weld metal are caused. It is possible to prevent and form a healthy crater.
Next, examples of the present invention will be described.

[0012]

EXAMPLES Table 2 shows a method of the present invention as shown in FIG. 1 in which a metal plate is brought into contact with a side surface of a head of a 60K rail, which has been welded to the abdomen from a leg of a 60K rail facing each other with a gap of 13 mm. The rail head is covered with a 4mmΦ coated welding rod (C: 0.60%, Si:
(0.30%, Mn: 0.70%), and the welding current and the rail head when the multi-layer welding is performed by the existing welding method which is conventionally performed as shown in FIG. 2 in the comparison method. The external appearance is shown. As is clear from the results shown in the table, according to the present invention, a sound welded joint having no shrinkage and no crater was obtained.

[0013]

[Table 2]

[0014]

As described above, according to the present invention, in the enclosed arc welding using the coated arc welding rod of the high-strength rail, it is possible to prevent cavities and cracks in the crater portion of the bead end, and form a very sound bead. be able to.

[Brief description of drawings]

1A and 1B are a plan view and a side view showing a welding method of the present invention, which are shown in the order of steps of (a), (b), and (c).

2A and 2B are a plan view and a side view showing a conventional welding method.

[Explanation of symbols]

 1 Rail 2 Metal 3 Joint weld 4 Covered welding rod 5 Lower weld layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Sugino 1-1 Tobahata-cho, Tobata-ku, Kitakyushu City, Fukuoka Prefecture Inside Nippon Steel Co., Ltd. Yawata Works (72) Inventor Ken-ichi Karine 20 Shintomi, Futtsu-shi, Chiba Prefecture -1 Inside Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Katsuyoshi Ueyama 2-8-8, Mitsumachi, Kokubunji, Tokyo 38 Inside Railroad Technical Research Institute (72) Inventor, Mitsumasa Tatsumi Ichimitsu, Kokubunji, Tokyo 2-8, Machi 38 Inside the Railway Technical Research Institute

Claims (1)

[Claims] 1. In an enclosed arc multi-layer welding of a rail head, in which a groove is provided and joint welding of the abdomen is completed from the leg portions of the rails facing each other, and then a metal is brought into contact with the side surface of the head for welding. , For each layer, the welding arc is welded in the direction opposite to the welding advancing direction, the welding arc is gradually transferred to the welding advancing direction at the bead end crater portion in the molten state that has occurred, and finally the metal and the welding portion Enclosed arc welding method for rails, characterized in that welding is performed until the elliptical shape of the crater becomes a semicircular shape while applying a welding arc in between, and then the welding arc is stopped.