JPH0224638B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for strengthening welded metal such as welded joints and molten pipes. When constructing pressure-resistant shells for use at ultra-high pressures for 2,000m deep-sea diving research vessels or 6,000m deep-sea diving research vessels, it may be necessary to perform inset welding of penetrating metal fittings to the ultra-high tensile strength steel that composes these pressure shells. These welded joints are not allowed to be thickened or cut after welding, and the appearance quality is also strict.They are still welded by the normal number of passes, and the specified strength (0.2% yield strength ≥ 90 kg) is not allowed.
f/mm ² ). These welding methods generally include shielded arc welding or TIG welding, and depending on the plate thickness, multilayer build-up welding as shown in FIG. 1 is often performed. In FIG. 1, 0 indicates the base material and 1 to 10 indicate the weld metal, and each number corresponds to a welding pass. If the material is to be used after being quenched and then tempered or aged, if welding requires 10 passes as shown in Figure 1, the intermediate passes equivalent to passes 1 to 9 will consist of passes 2 to 10, respectively. The welding heat produces a tempering or aging effect, resulting in a strength level comparable to that of steel that has been quenched and tempered or quenched and aged. However, in the 10th and final pass, this effect cannot be obtained, and the strength level falls to the same level as steel that has only been quenched. for example,
0.2% yield strength of NS80, NS90, 10Ni−80Co steel, etc. is 80~
140Kgf/mm In class ² high tensile strength steel, the 0.2% yield strength of the weld metal in the 10th pass is lower by ^about 10 to 20Kgf/mm2 compared to the 0.2% yield strength of other welded metals. For this reason, conventionally in actual welded joints, the thickness of the joint part is increased in advance to take into account the reduction in reinforcement at the final pass part. In addition to the number of passes required to form the regular reinforcement shape, an additional layer is laminated to increase the strength. We have no choice but to take measures such as increasing the number of high-level parts, but even with these measures, the shape of the joint after welding becomes significantly uneven, resulting in cutting off the thickened part or excess part after welding. There are also cases where it is necessary to do so. It is an object of the present invention to eliminate the drawbacks of the above-mentioned prior art and to provide a method for strengthening the weld metal in the final pass portion without increasing the plate thickness or adding additional layers. For this reason, the present invention applies high-density energy such as arc, electron beam, laser light, or plasma to the surface of the deposited metal corresponding to the final pass of welding or melting in a method for manufacturing a pressure hull for an underwater ship that involves a welding or melting process. Manufacture of a pressure-resistant shell for an underwater ship characterized by moving high-density energy in the direction of the weld line while irradiating, irradiating the surface of the welded metal multiple times, and reducing the amount of irradiation heat each time the irradiation is repeated. It became law. Note that laser beams are often used in the atmosphere, electron beams are used in a vacuum, and plasma and arc are often used in an inert gas atmosphere. Furthermore, irradiation of weld metal with arc, etc. means that it is necessary to irradiate at least the weld metal corresponding to the final pass.
Other weld metals may also be irradiated. Arc, electron beam, laser light and plasma all have high energy density,
For example, with a gas flame or the like with low energy density, the heat diffusion is large and the temperature rise is insufficient, and an improvement in 0.2% proof stress could not be expected, so the above limitations were made. Furthermore, the alloys targeted by the present invention are not limited to the ultra-high tensile strength steel shown in this example, but include Al alloys,
This includes all metal materials that undergo heat treatment, such as copper alloys and Ti alloys, but the higher the strength of the material, the more remarkable the effect. Hereinafter, the method for strengthening weld metal of the present invention will be explained using Examples. As an example, we will explain the test results of a welding material assuming a pressure hull of a 2000m deep-sea submersible research vessel. FIG. 2 shows a schematic cross-sectional view of the groove shape of the joint welded in this example. In Figure 2, the plate thickness of the through-fitting joint (H groove) in a is 30 mm, and b
The equatorial joint (U groove) has a plate thickness of 40 mm, and both joints have a groove angle of φ12° and a groove radius of R6 mm. The base material has a 0.2% yield strength of 90Kgf/with the composition shown in Table 1.
mm ² Level quenched and tempered steel NS90 was used, and the wire corresponding to the weld metal was a co-metallic wire with the composition shown in Table 2.
Automatic TIG welding was performed downward using TN ₈ . The welding conditions are shown in Table 3. That is, after the sixth pass, which is the final pass, the feeding of the welding wire is stopped, and the weld metal is irradiated with arc twice while the arc current is slightly lowered. In addition, here, the current value of the first pass of irradiation is 200~
300 A, the current value of the second irradiation pass is 150 to 250 A, and the current value of the lower irradiation passes is preferably 200 A or less in terms of heat treatment effect and workability. JISZ3111A-
A No. 2 tensile test piece was taken and subjected to a tensile test. The results are shown in Table 4. In addition, in Fig. 3a and b, the test piece sampling position t ₁ of the surface layer A and the test piece sampling position t ₂ of the plate thickness center part B are respectively 4 mm from the base material surface.
7.5mm, and the specimen sampling position of surface layer C
t ₃ and the test piece sampling position t ₄ of the mid-thickness section D are 5 mm and 20 mm, respectively. As shown in the results in Table 4, in conventional joints that do not apply arc heating to the surface layer,
0.2% yield strength of plate thickness center part B and D is 98~100Kgf/
mm ² is a sufficiently high value, but in surface areas A and C it is 80 to 85 Kgf/mm ² which is lower than the target value of 90 Kgf/mm ²
Only a low yield strength of 0.2% can be obtained. At the center of the plate thickness, the weld metal of each pass is affected by heat and tempered compared to the weld metal of the next pass, resulting in a high yield strength, but the weld metal of the final pass is not tempered, so the yield strength remains low. It has become. On the other hand, in the joint of the present invention in which the surface layer is irradiated with an arc, the weight of the surface layer A and C is 98 to 100 kg.
f/mm ² and a high yield strength equivalent to those in the middle of the plate thickness B and D. In this example, after welding, the same welding equipment can be used as is, and heating can be done by simply stopping the wire feed and lowering the arc current, so no special equipment or preparation work is required, and it is simple and quick. It has the advantage of being able to work. In addition, there is no need to take the trouble to feed the wire for heat treatment.
The bead shape does not rise unnaturally, and there is no need to cut the excess portion. As detailed above, according to the strengthening method of the present invention, it is possible to strengthen the weld metal of materials that require aging or tempering using a heating element with high energy density, and the shape of the joint after welding is uniform. Therefore, there is no need to cut the excess portion. Therefore, the method of the present invention can be applied to all welded parts of materials that undergo quenching, tempering, or aging, but is particularly applicable to welding of pressure shells of deep-sea research vessels, submarines, etc., and bridge penstocks, which require severe processing accuracy. This method is suitable for strengthening joints.

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【table】 [Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of a welded joint, Fig. 2 is a schematic cross-sectional view of a welded joint for explaining the groove shape, and Fig. 3 is a schematic cross-sectional view of a welded joint for explaining the test piece sampling position.
indicates H-shaped development, and b indicates U-shaped groove. 0... Base material, 1-10... Weld metal.

Claims (1)

[Claims] 1. In a manufacturing method for pressure hulls for underwater ships that involves welding or melting processes, the surface of the deposited metal corresponding to the final pass of welding or melting is irradiated with high-density energy such as arc, electron beam, laser light, or plasma. A method for manufacturing a pressure shell for an underwater ship, characterized by moving high-density energy in the direction of the welding line, irradiating the surface of the welded metal multiple times, and reducing the amount of irradiation heat each time the irradiation is repeated.