JPS5829197B2 - Joining method by arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a method for arc welding of items such as steel ingot gripping tongs and rolls used in hot conditions, where cracks have occurred or are likely to occur in the surface layer due to thermal and mechanical fatigue. This relates to a joining method.

Cracks in welded joints usually tend to occur at the boundary between the base material to be welded and the deposited metal.

Furthermore, most of the cracks originate from the surface, and cracks that occur on the surface progress to the inside, leading to large cracks that can damage the body.

Therefore, the purpose of this application is to provide a method for obtaining a welded product in which the crack source generated on the surface of the material is difficult to proceed inside. This is a joining method using arc welding, which is characterized by welding the grooves formed in the parts to be joined in multiple stages. Further effects can be obtained by making the grooves wavy or by making the end face of the uppermost groove wavy.

In the figure, 1 indicates the base material to be welded, 2 indicates the weld metal, and 3 indicates the end face of the uppermost groove.

Note that this method is applied to joining objects whose surfaces have deteriorated or are likely to deteriorate, so if only one of the objects to be joined has deteriorated, this method should be applied to only that one side. (See Figure 1), or both (See Figure 2).

The method of the present invention will be described in detail with reference to the drawings showing one embodiment of the method. Due to the multi-stage groove, a crack source (a in the figure) occurs near the boundary between the base material and the weld metal on the surface. ), even if the crack progresses along the boundary layer, the tip of the crack contacts the base metal at point β, so it is difficult for the crack to progress beyond this point. .

Therefore, cracks only occur in the thin part of the surface layer, and the entire base material does not crack.

In consideration of actual workability, it is preferable to make the groove shape wider toward the top.

That is, it is easier to weld the lower part.

Furthermore, by making the end face of the groove at the top step wavy (including a zigzag shape), the boundary line between the base material and the weld metal on the surface can be made into the wavy shape, which reduces the possibility of cracks occurring on the surface. Since the source crack lines can be made disjoint or discontinuous in their directions, it is possible to prevent the cracks from growing into large cracks.

This is because the small crack lines generated on the surface run in different directions, so even if they go inside, it is difficult to concentrate them into one single crack line.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing the main parts of a bonded product showing one embodiment of the method of the present application, and FIG. 2 is a partially cutaway perspective view showing the main parts of a bonded product according to another example. In the diagram, 1... Base material to be welded, 2... Weld metal, 3...
End face of the uppermost groove, α...Crack source, β...Point where the crack progression line contacts the base metal.

Claims (1)

[Scope of Claims] 1. A joining method by arc welding, which is characterized in that when joining objects whose surfaces have deteriorated or are likely to deteriorate, welding is performed by forming grooves in multiple stages on the parts to be joined. 2. The joining method by arc welding according to claim 1, wherein the width of the groove increases as the groove approaches the upper level. 3. A joining method by arc welding according to claim 1 or 2, in which the end surface of the uppermost groove is wavy.