JPS6216895A - Welding deformation preventing method - Google Patents

Abstract

PURPOSE:To eliminate a straightening work after welding, and to shorten the work time by giving a distortion of quantity which is balanced with a welding distortion, by heating by keeping pace with a welding work, to a position which is considered to be balanced structural with a welding deformation. CONSTITUTION:In a weld zone 2 of a material to be welded 1, a distortion is generated by heating and cooling. By giving a distortion which is balanced by heating a position 3 which is balanced structurally with said distortion, both distortions are balanced and a welding deformation is suppressed. For instance, when a build-up welding 2 is executed to the center part of a plate 1a, heating 3 is applied to this plate 1a from the rear side of the weld zone. By executing this heating simultaneously with welding, an angular deformation generated by welding and an angular deformation generated by heading are balanced, and the plate 1a is not brought to an angular deformation. According to such a constitution, a straightening work after welding can be omitted.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to preventing welding deformation of goo in a boiler.

[Conventional technology]

In structures where deformation caused by welding is a problem, the current practice is to correct the welding deformation after the welding operation is completed.

(Problems to be Solved by the Invention) Conventionally, welding deformation is corrected after the welding work is completed, which increases the number of man-hours and lengthens the working time due to the post-process strain relief work.

[Failure to solve the problem]

During the welding work, in parallel with the welding work, as shown in Figure 1, the position of the material to be welded 1 that is structurally balanced with the shape of the weld 2 is heated 3 under conditions that give an amount of strain that balances the welding deformation.
do. This allows deformation caused by welding to be suppressed in-process during welding work.

[Effect]

Generally, distortion as shown in FIG. 2 occurs in the welded part of the material to be welded 1 due to heating and cooling during welding.

Here, this strain is referred to as "specific strain." Therefore,
By applying an amount of inherent strain 2b that balances structurally the inherent strain 2α caused by welding, the deformation caused by both inherent strains will be balanced, and welding deformation will be suppressed. For example, when overlay welding 2 is performed at the center of the flat plate lOL, the flat plate lα undergoes angular deformation as shown in FIG.

If this plate is heated 3 from the back side of the welded part as shown in FIG. 4, this angular deformation will disappear after cooling. Therefore, if heating is performed at the same time as welding to balance the angular deformation caused by welding and the angular deformation caused by heating, the flat plate ILL will not be angularly deformed.

Furthermore, as shown in FIG. 5, when two welds are present on the cylindrical shell 1b, the inherent strain generated in the welds causes a deflection as shown in the figure. In this case, the deflection of the cylindrical shell 1b can be suppressed by heating 3 a position 180° symmetrical to the welding position at the same time as welding, as shown in FIG. 6, to balance the inherent strain caused by both. Heating conditions in this case (
(heating temperature, time, etc.) are selected in advance through experiments or the like to produce deformation equivalent to that caused by welding.

〔Example〕

A model test was conducted to apply the present invention to prevention of welding deformation of a goo IC in a boiler. Since a small diameter nozzle 4 with an outer diameter of about 50 m is welded 2 to the boiler goo IC (outer diameter 200 to 600 m), welding deformation occurs as shown in FIG. 7. In the model test, a small model test body with typical dimensions used in the actual machine was used. Dimensions are outer diameter 216xyrr
, wall thickness 24 mm, length 61 (hna). Weld the nozzle 4 with an outer diameter of 50.8 m to this header model, and in parallel, position the welding position 180° symmetrically as shown in Figure 8. Gas heating 3. Nozzle 4 is 110.8 in the axial direction of Hegu IC.
Welded 2 in 5 places with the same spacing (as the spacing on the actual machine). The specific method was to first weld two nozzles 4 from the ends, and then gas heat 3 the 180° symmetrical positions of the first grain. From now on, nozzle 4
A method was adopted in which each time one welded, a 180° symmetrical position behind the weld was heated. The reason why the 2nd welding position and the 3rd heating position were shifted was to take into consideration the influence of the heating length on the welding work. The gas heating conditions were determined through experiments to obtain deformation equivalent to that obtained by welding. After welding, go to IC
When the deflection distribution was measured, the results shown in FIG. 9 were obtained. In this figure, the vertical axis shows the amount of deflection of the hegu IC, and the horizontal axis shows the position in the axial direction. The measurement position is 45xyn from the center of the nozzle stand 4. In the figure, the * mark represents the deflection of the welded joint, and the O mark represents the result when this welding deformation prevention method is applied. From this figure, it can be seen that the present welding deformation prevention method suppresses the deflection of the hege.

It is also believed that this method can be applied to robot welding of small-diameter header nozzles currently in use.

〔Effect of the invention〕

According to the present invention, by suppressing the deformation caused by welding in-process, it is possible to omit strain relief work after welding, and it is possible to significantly reduce the number of man-hours and shorten the construction period.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the basic idea of the present invention, Figure 2 is a diagram explaining the strain that occurs in the welded part, and Figure 3 is a diagram showing the deformation of a flat plate when overlay welding is performed on the flat plate. Figure 4 shows how the deformation explained in Figure 3 is resolved by heating, and Figure 5 shows the deformation of the cylindrical shell when there is a welded part on the cylindrical shell. Figure 6 is a diagram explaining a method for suppressing welding deformation when there is a welded part on a cylindrical shell, and Figure 7 is a diagram explaining the deformation that occurs when the nozzle head is welded to the boiler. Figure 8 is a diagram explaining the method for suppressing deformation that occurs when welding the nozzle stub to the boiler joint, and Figure 9 is a diagram showing the application of the welding deformation prevention method of the present invention to a model test piece of the boiler joint. This figure shows the results. l... Material to be welded 2... Welding 3... Heating 1α... Flat plate 1b... Cylindrical shell
1c...Go to the boiler 4...Manufacturer's sub-agent Patent attorney 2 persons outside of important documents Figure 1 Figure 3 To 3 Figure 5

Claims (1)

[Claims] In order to prevent welding deformation of a structure, by applying a strain that balances the welding strain at a position that is considered to be structurally balanced with the deformation caused by welding by heating in parallel with the welding operation. , a welding deformation prevention method characterized by preventing welding deformation.