JPS59225899A - Welding method of tab plate in production of uo steel pipe - Google Patents

Abstract

PURPOSE:To arc-weld tab plates with a good bead shape in the stage of welding the tab plates to four corners of a plate prior to pressing in production of a UO steel pipe by disposing solid materials having specific quality on both sides of the tab plates. CONSTITUTION:A plate 1 for producing a UO steel pipe is formed by C, U, O forming to a tubular shape and after the joint is tack-welded, the joint is subjected to regular welding from the inside and outside. Tab plates 2 for regular welding are preliminarily arc-welded to four corners of the plate 1 in such a case. Solid materials 4 formed of materials, such as copper, graphite, etc. which do not weld with the steel plate 1 and the tab plates 2 are placed on both ends of the plates 2 in the stage of arc-welding the plates 2 to the plate 1 with the weld bead having high weld strength. The arc is started in the position 5 apart slightly from the material 4 and the arc welding is performed at prescribed welding current and speed. After the arc is stopped just before 5 the other material 4, both materials 4 are removed. The plates 2 are welded to the plate 1 with the good weld bead over the entire transverse length thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used to manufacture UO steel pipes by arc welding tab plates to the four corners of a steel plate. Regarding the tab & welding method when using the attaching method.

In the manufacturing process of UO steel pipes, a steel plate is beveled and then formed into a tubular shape by C, U, and O forming. After the pipe is tack-welded at the joint 1, it is subjected to welding (generally submerged arc welding) from the inner and outer surfaces.

When performing main +j welding, tab plates are required at both tube ends to improve the quality of the tube ends. There are several ways to attach this tab plate, such as (a) attaching it after tack welding, and (b) attaching it to the four corners of the steel plate before beveling. (B)
Compared to method (a), method (a) has advantages such as improving the quality of tack welding of the tube end.

Here, we will discuss the case where the previous method is adopted.

FIG. 1 fa) is a plan view showing tab plates attached to the four corners of a steel plate, and FIG. 1 b is a sectional view thereof. The size of the tab plate 1 is width (Wl = 50-200 mm, length L) = 1
00 to 400 cities are often used. The tab plate attached to the steel plate is subjected to external forces during the subsequent processes (bevel processing and press forming), so when attaching the tab plate, sufficient strength must be taken to prevent it from falling even if subjected to these external forces. The tab plate also has the role of restraining thermal deformation of the tube end weld during number welding, so it is necessary to ensure sufficient mounting strength.

As a method for attaching the tab plate, there is a method of attaching the tab plate by arc welding, which can ensure sufficient attachment strength and is easy to perform. In this method, the tab plate is beveled in 11 directions, and M
This is a method of welding by IG welding or carbon dioxide arc welding.

However, when welding both ends of the tab plate, molten metal runs off and good welding cannot be achieved. FIG. 2(a) is an example of a cross-sectional view of the central portion of the tab plate when the method described in 2 is carried out. (b) is an example of a cross-sectional view of the end of the tab plate. As shown in Figure 2 (b), the molten metal flows at the tab plate end, resulting in a weld bead. This may cause defects.

A possible method for alleviating the above problems is a method of welding in several steps (multi-layer welding method), but it is not possible to completely prevent the flow of molten steel. Furthermore, since the welding time is very long, there are efficiency problems.

The present invention aims to provide a tab plate welding method in which a good bead shape is formed over the entire length of the tab plate when attaching several tab plates to the four corners of a steel plate by arc welding in the manufacture of UOzhf pipes. This is the purpose.

That is, in the present invention, when attaching a tab plate to a steel plate for manufacturing UO steel pipes by arc welding, a solid material that does not bond with the tab plate is applied to the start and end portions of the tangent line of the tab, and when welding the tab plate, The arc starts from a position where the solid material is not damaged by the arc start, and at the same time the molten metal hits the solid material and fills the groove, the welding torch is moved, and the welding torch is moved in the same way to the front of the solid material at the welding end. This is a tab plate welding method for manufacturing UO steel pipes, which is characterized by stopping the welding torch at , and stopping the arc after the molten metal hits the solid material and fills the groove.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 3(a) shows a plan view when the tab plate is welded. (b) shows its cross-sectional view. ] is a steel plate, 2 is a tab plate, and 4 is a solid material that prevents molten metal from flowing. The solid material 4 is preferably made of copper, graphite, solid flux, or the like. In short, any material may be used as long as it does not weld to the steel plate or tab plate.

Welding torch 5 performs welding in the direction of the arrow.

The arc start and stop are performed at a position slightly away from the solid material 4 in order to prevent damage to the solid material 4. FIG. 4 is a graph showing changes in welding speed and welding current from arc start to arc stop. Next, a specific welding procedure will be explained.

First, the solid material 4 is applied to both ends of the tab plate 2, and then the arc is started at a position a little 7 inches away from the solid material 4. ARCSTAR 1 The temporary welding current is lowered to a predetermined current value, and 1-5 is stopped for the time necessary to fill the groove at the end of the tab plate with molten steel. After that, welding is performed at a predetermined welding speed and current, and at a position slightly away from the other solid material 4, the welding current is lowered in the same way as when starting the arc, and the groove at the end of the tab plate is filled with molten steel. Arc stop is performed after stopping the torch 5 for the required time. After the molten steel solidifies, the solid material 4 is removed.

FIG. 5 is a cross-sectional view of a bead when the method of the present invention is used. FIG. 5(a) is an example of a cross-sectional view of the central part of the tab plate,
(b) is an example of a cross-sectional view of the end of the tab plate. Figure 5 (b
), it can be seen that there is no bead irregularity due to the flow of molten steel at the end of the tab plate (), and a good bead shape can be obtained.

As described above, the present invention is a tab plate welding method that can prevent the flow of molten steel near the end of the tab plate and can obtain a good bead over the entire length of the tab plate 1J.

[Brief explanation of the drawing]

Figure 1 fa) is a plan view showing the tab plates at the four corners of the steel plate.
(b) is a cross-sectional view of the tab plate, FIG. Figure (a) is a plan view of one embodiment of the method of the present invention, (b) is a cross-sectional view thereof, Figure 4 is a graph showing the pattern of welding speed, bath and contact current in one embodiment of the method of the present invention, and Figure 5 Figure (a) is a cross-sectional view of the central portion of the tab plate when the tab plate is gripped by the method of the present invention, and (b) is a cross-sectional view of the vicinity of the end of the tab plate. 1: Steel plate 2: Tab plate 3: Welding bead /I: Solid material 5: Welding torch Fig. 3 (α) Fig. 4 1114Igl 5th (υ)

Claims (1)

[Claims]] When attaching a tab plate to a steel plate for UO steel pipe production by arc bath welding, a solid material that is not welded to the tab is applied to the start and end portions of the tab plate welding line, and the tab plate is welded in the tab plate bath. At the time of contact, the arc starts from a position where the solid material is not damaged by the arc start, and at the same time as the molten metal hits the solid material and fills the groove, the bath welding 1.-- is transferred to the bath tangent line.
At the welding end, the welding torch is similarly stopped in front of the solid material, and the arc is stopped when the molten metal hits the solid material and fills the groove.Tab plate welding in UO pipe manufacturing. Method. 2. The tab plate welding method for UOe4tJr pipe manufacturing according to claim 1, in which the welding current is lowered from a predetermined current at arc start and arc stop to fill the groove with molten metal.