JPH0580315B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a deformation prevention method applied to welding surface deposits of stainless steel pipes used in nuclear power plants.

<Conventional technology> Conventionally, nozzle stubs and
Support members, hanging tools, branch pipes, etc. are attached by welding. During this welding, deformation caused by tensile stress is corrected by attaching reinforcing materials, applying reverse strain, and press forming.

<Problems to be Solved by the Invention> By the way, when attaching stainless steel nozzles and branch pipes by welding, 12 to 15 bead build-ups are performed, but the temperature of the layered pipe for this welding is determined to be 177°C or less. (This is due to the deterioration of the stainless steel material.) In the conventional method, when 3 to 4 beads are stacked, the temperature exceeds 177°C, so it takes time to reach 177°C.

Furthermore, in the conventional method, a strain of 10 to 15/1000 is generated, and in extreme cases, the tube axis springs up and the inner diameter of the steel tube drops due to the shrinkage effect of the welding heat around the welded portion.

For this reason, reinforcing materials and reverse strain must be attached or applied at the initial stage, and corrections must be made using a press molding machine to remove the strain, which takes a lot of effort. 10~15/100
If the amount of 0 strain that occurs must be reduced to 3/1000 or less, it will not be approved according to the regulations.

FIGS. 3 and 4 generally show the amount of deformation (λ) of the main pipe due to welding. In FIG. 3, 1 is a main pipe, and 6 is a branch pipe welded to the main pipe 1. Further, in the figure, g is the amount of welding (mm ³ ), l is the deformed length (mm), t is the wall thickness of the main tube 1, and D is the outer diameter of the main tube 1 (mm).

However, despite the above correction work, the amount of deformation of the base material 1 is the amount of welding (g),
Currently, it is not possible to make appropriate corrections because it is not constant due to factors such as heat input and base material strength.

The present invention has been made in view of the above-mentioned current situation, and is intended to enable welding without being affected by welding deformation when attaching attachments such as nozzles and branch pipes to a stainless steel main pipe. The purpose is to

<Means for Solving the Problems> In the present invention, the amount of deformation of the main pipe due to welding is determined by the amount of welding,
As a result of examining the factors that do not become constant due to factors such as heat input and base metal strength, we focused on the direction of dispersing and absorbing heat, and by using the in-pipe water cooling method, welding heat is Distributed by
The deformation amount of the main pipe is made constant by absorbing the shrinkage force and reducing the contractile force. In the case of branch pipes, in order to butt weld the pipes together (Uranami welding method), after welding the first layer, both ends of the stainless steel pipe are sealed, a rootstock is laid on one side of the stainless steel pipe, and the stainless steel pipe is tilted. Fill the stainless steel pipe with water with the welding area facing upward, and in the case of branch pipes, water is filled up to the welding area, and air is vented on one side for welding.

<Function> According to the method for preventing deformation during welding according to the present invention, when welding a branch pipe, nozzle stub, support, etc. to be attached to a stainless steel pipe, by tilting the stainless steel pipe and the water in the stainless steel pipe, the welding is prevented. At that time, the heat is transferred to the water, and when the water has heat, it circulates, so it can disperse and absorb the amount of heat compared to the amount of heat input, and the contractile force of the main tube decreases, causing deformation inside the tube, and the spring of the tube shaft. It is possible to prevent climbing.

<Example> FIG. 1 shows a schematic diagram of the present invention, and FIG. 2 shows the amount of deformation of a main pipe due to welding according to the present invention.

After only the first layer welding of the branch pipe 6 to be welded to the stainless steel pipe 1 is completed, both ends of the stainless steel pipe 1 are sealed with a polyethylene cap 3 and seal tape 4, and then one end of the stainless steel pipe 1 is attached to the bottom with the welded surface facing upward. Stainless steel pipe 1 with rootstock 10
Tilt. Water 2 is filled into the stainless steel pipe 1 from a polyethylene hose 5 provided on one polyethylene cap 3, and especially at the welded portion of the branch pipe 6, the water 2 is filled up to the upper part of the welded portion as shown in the figure. After that, the polyethylene hose 5 shall be used as an air vent, and when the branch pipe 6 is welded, the surrounding water 2
As the water is loosened, it begins to move to a higher place, and cold water comes in. Water 2 circulates and dissipates the heat in the welding area, so the interlayer temperature does not reach 40 to 60℃ or higher, and the second As shown in Figure 2, the amount of deformation of the main tube 1 is 2/1000, which is within the specified value.

If the nozzle stub 7, pad 8, and support 9 are welded in the same manner, the amount of deformation can be kept within the specified value.

<Effects of the Invention> According to the method for preventing deformation during welding according to the present invention, pre-strain work before welding, distortion removal after welding, and deformation correction work are unnecessary, and welding heat input management can be unified.
Not only can work efficiency be improved, but also the amount of deformation can be predicted.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the amount of deformation according to the present invention, and FIGS. 3 and 4 are diagrams and diagrams illustrating the amount of deformation according to the conventional method. In the drawing, 1 is the main pipe, 2 is water, 3 is polyethylene cap, 4 is tape, 5 is polyethylene hose, 6 is branch pipe, 7 is nozzle stand, 8 is pad, 9 is support, 10 is rootstock .

Claims (1)

[Claims] 1. When attaching attachments such as nozzle stands and branches to the outer surface of a stainless steel pipe by welding, seal both ends of the stainless steel pipe, install a rootstock at the bottom of one end of the stainless steel pipe, and tilt the stainless steel pipe. A method for preventing deformation of deposits on the surface of a stainless steel pipe during welding, the method comprising: filling water into the stainless steel pipe with the deposit as the top surface; and filling the water up to the welded part of the deposit welded in the first layer.