JPH0523876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a welded joint structure of clad steel for use in reactors such as pressure vessels.

(Prior art) When manufacturing pressure vessels, etc. using clad steel, which is a mixture of non-ferrous metals with excellent corrosion resistance such as titanium, zirconium, tantalum, aluminum, and steel, for a base material of carbon steel, Although it is necessary to join the steel to each other, titanium or zirconium becomes brittle when melted with carbon steel, so it cannot be directly welded to carbon steel, so a joint structure as shown in FIG. 5 is generally used.

In FIG. 5, base materials 21, 21 are butted against each other and joined by welding 22, and a scrap board 24 made of the same type of plywood or a material that can be welded is fitted into the removed portion of the composite material 23, and this scrap board 24 and A backing plate 25 of the same type or weldable as the composite material is overlapped over the composite material 23, and the corresponding plate 25 and the composite material 23 are welded 26, and the backing plates are welded 27 to each other.

In this case, the backing plate 25 is made of titanium or zirconium, and the base material 21 is carbon steel, so the thermal expansion coefficients are approximately 9×10 ^-6 /°C and 5.8× ^{10 -6} /°C, respectively.
℃, 12×10 ^-6 /℃, and a large thermal stress occurs in a titanium clad or zirconium clad pressure vessel used in batch operation, and the fillet welded part 26 of the fillet plate is From the state before use to the state after use shown in FIG. 6B, cracks 28, bead dents 29, and through defects 30 were caused due to low cycle fatigue failure, and there were defects that resulted in extremely short service life due to leakage.

Therefore, in the case of batch operation, the one shown in FIG. 7 is adopted. This is done by setting a backing plate 31 with a square cross section that fits into the removed portion of the composite material 23 and overlaps the composite material 23 on both sides of this removed portion.
This plate 31 is welded 32 to the composite material 23, a plate connecting plate 33 is stacked on the joint between the plates 31, and this plate connecting plate 33 is welded 34 to both the plate 31 and the composite material 23. It is something to do.

(Problems to be Solved by the Invention) By the way, the above-mentioned contact plate connecting plate 33 is connected to the contact plate joint portion 3.
Used for lap welding to enable sufficient welding of 5. In other words, since there is carbon steel (base metal) on the back side of the part where the composite material is removed in the joint part 35 of the contact plates, when directly welding the contact plates together, welding is at most about 1/2 of the thickness of the contact plate 31. Since we can only weld to the depth,
This requires lap welding of the connecting plate 33. Therefore, the contact plate joint 35 has a two-ply structure, and a reduction in thermal stress cannot be expected, and it is difficult to perform welding at the point indicated by arrow A in Fig. 7, and it is a part where stress is likely to concentrate. Therefore, even if the stress of the contact plate 31 is low, the lifespan as a whole is affected by the above-mentioned points, and there is a problem in that it is not possible to expect a life-extending effect as much as the left as a whole.

The present invention provides a clad steel welded joint structure that solves these problems.

(Means for Solving the Problems) The present invention, when joining composite materials on a base material, indents a band groove across both composite materials located on both sides of the composite material removed part. A backing metal of the same thickness as the groove depth is fitted into the band groove, and a backing plate made of a stepped molded product is placed on top of the backing metal so that the joint of these plates is positioned on the backing metal, but It is characterized by a welded joint structure of clad steel in which the backing plate is welded to both composite materials, and the joint between the backing plates is welded on the backing plate.

(Function) According to the present invention, since a stepped molded product with a corrugated cross section is used for the backing plate, sufficient flexibility can be given to the backing plate, and thermal stress is reduced compared to a straight-shaped backing plate. The stress decreases significantly (according to calculations, approximately 1/2), and therefore, under patch operating conditions, the cyclic stress becomes 1/2,
The estimated lifespan will be extended by approximately 10 times. That is, the occurrence of defects as shown in FIG. 6B is eliminated.

In addition, since the connections between the plates are made on the backing metal placed on the back side of these plates, highly reliable welding is possible, and welding defects such as the one shown by arrow A in Fig. 7 are likely to occur. , structures with high concentration of thermal stress can be eliminated.

The above-mentioned backing metal may be thin, and the length of the backing metal can be selected to be close to the width of the plate, so the rate of decrease in flexibility of the welded area between the plates can be significantly reduced compared to conventional methods. Thermal stress concentration in the weld is reduced.

(Example) An example of the present invention will be described below with reference to the drawings.

In Fig. 2, the base metals 1 and 1 made of carbon steel are beveled, and at the same time, the composite material 2 made of titanium or zirconium in this part is removed, and the base metals 1 and 1 are
are butted against each other and joined by welding 3.

Next, grooves 4 are formed in areas where welding of the plates, which will be described later, is unavoidable. This band groove 4 has a constant groove depth that spans the composite material removed portion 1a of the base material 1 and the composite material 2 on both sides thereof, and the backing metal 5 is appropriately fitted into this band groove 4. The backing plate 5 is a molded product made of the same material as the backing plate 6 and shaped to follow the back surface of the backing plate 6 (in the drawing, the shape is 〓), and its plate thickness is the same as the groove depth of the band groove 4. In the above-mentioned fitted state, the backing metal 5 is prevented from protruding from the band groove 4.

On the other hand, the contact plate 6 is manufactured from a stepped molded product having a square cross section as shown in the figure, and is fitted into the composite material removed portion 1a.
Each backing plate 6 is welded 7 to the composite material 2 with the backing plate 6a being set so as to overlap the composite material 2, 2, and the joint between the backing plates being positioned on the backing metal 5.
Then, the backing plates 6 and 6 are welded 8 together on the backing metal 5. This state is shown in FIG.

Note that the backing metal 5 is not welded to the composite material 2 and is left free so as not to impair the flexibility of the backing plate 6. In addition, the thickness of the backing metal 5 is made as thin as possible to the extent that it can function as a backing metal, so that the deterioration of the flexibility of the welded portion 8 is minimized. For example, the thickness of the backing plate 6 should be set to 2 to 3
mm, the thickness of the backing metal 6 is approximately 1 to 1.5 mm.

In addition, when welding 8 between the plates, the plates 6
Leave a gap of 2 to 4 mm between the joints and weld together with the backing metal 5.

Furthermore, the length of the backing metal 5 is the composite material removed portion 1a.
It is larger than the removal width of , and about 5 to 10 times larger than the width of the plate 6.
It is appropriate to make it close to the width of the contact plate by about mm shorter.

FIG. 3 shows a modified example, in which a scrap board 10 is fitted into the composite material removed portion 9a on the base material 9 in such a manner that it protrudes above the composite material 2 on both sides, and the scrap board 10 and the composite material 2 on both sides are fitted. A band groove is formed over the material 2, and a backing metal 11 is fitted into the groove, and the backing metal 11 and the backing plate 12 have a groove that is upside down from the waveform shape shown in Fig. 1. The one that has been prepared is used.

Figure 4 shows the results of a titanium design fatigue stress test on titanium clad steel, where point A is the 5th point.
The conventional structure shown in the figure, and the structure of the present invention shown in FIG.
This is an improvement of more than twice as much, proving the usefulness of the present invention.

(Effects of the Invention) As detailed above, according to the present invention, the cover plates have sufficient flexibility, the plates are welded together using a highly reliable backing method, and the welding Because the decline in the flexibility of the contact plate is kept to a minimum, it is made of tatin, zirconium, which is resistant to repeated stress.
It has a clad steel joint structure, which dramatically extends its lifespan. Therefore, it can be easily applied to equipment in which the liquid temperature pulsates even if it is not batch operated.

In addition, since the backing plate is fitted into the band groove, there are fewer protrusions and steps on the surface of the backing plate, making it difficult for slurry to adhere to the inner surface of the vessel when applied to pressure vessels, etc. .

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a welded joint structure showing an embodiment of the present invention, Fig. 2 is an exploded view thereof, Fig. 3 is a perspective view showing a modified example, and Fig. 4 is a design fatigue stress curve of titanium. . Figure 5 is a perspective view of a general welded joint structure, Figures 6A and B are diagrams for explaining defects in the structure shown in Figure 4, and Figure 7 is a conventional welded joint structure that is an improvement on the structure shown in Figure 4. FIG. 1, 9...base material, 2...mixture material, 4...band groove,
5, 11...Secret money, 6,12...Touch board.

Claims (1)

[Claims] 1. When joining composite materials on the base material, create a band groove across both composite materials located across the removed portion of the composite material, and apply a backing metal of the same thickness as the groove depth to this band groove. After fitting properly, a backing plate made of a stepped molded product is placed on top of the backing plate so that the joint of these plates is positioned on the backing metal, and the backing plate is welded to both composite materials. Clad steel welded joint structure in which the joints between plates are welded on the backing plate.