High Cr Ni-based alloy welding wire, shielded metal arc welding rod, and weld metal formed by shielded metal arc welding

Abstract

Provided is a high Cr Ni-based alloy welding wire with which tensile strength and weld cracking resistance of a welded portion, the integrity of the microstructure of a welded metal, and inhibition of scale generation are improved. The high Cr Ni-based alloy welding wire is configured to have an alloy composition comprising, by mass, C: 0.04% or less, Mn: 7% or less, Fe: 1 to 12%, Si: 0.75% or less, Al: 0.01 to 0.7%, Ti: 0.01 to 0.7%, Cr: 25.0 to 31.5%, Ta: 1 to 10%, and Mo: 1 to 6%, and as inevitable impurities, Ca+Mg: less than 0.002%, N: 0.1% or less, P: 0.02% or less, O: 0.01% or less, S: 0.0015% or less, H: 0.0015% or less, Cu: 0.08% or less, and Co: 0.05% or less, and the balance: Ni. Then, the high CrNi-based alloy welding wire is configured such that the contents of S, Ta, Al, and Ti satisfy the following relation (1) and the contents of Ta, Mo, and N satisfy the following relation (2):
12000S+0.58Ta2.6Al2Ti19.3(1)
Ta+1.6Mo+187N.sup.35.7(2).

Claims

1. A high Cr Ni-based alloy welding wire comprising, by mass, C: 0.006% to 0.04%, Mn: 0.05% to 7%, Fe: 1 to 12%, Si: 0.05% to 0.75%, Al: 0.01 to 0.7%, Ti: 0.01 to 0.7%, Cr: 25.0 to 31.5%, Ta: 1 to 10%, Nb: 0%, and Mo: 1 to 6%, and as inevitable impurities, Ca+Mg: less than 0.002%, N: 0.1% or less, P: 0.02% or less, O: 0.01% or less, S: 0.0015% or less, H: 0.0015% or less, Cu: 0.08% or less, and Co: 0.05% or less, and the balance: Ni, contents of S, Ta, Al, and Ti satisfying the following relation (1) and contents of Ta, Mo, and N satisfying the following relation (2):
12000S+0.58Ta2.6Al2Ti19.3(1)
Ta+1.6Mo+187N5.7(2).

2. The high Cr Ni-based alloy welding wire according to claim 1, wherein the content of Al is 0.26 to 0.7 mass %.

3. The high Cr Ni-based alloy welding wire according to claim 1, wherein the content of Ti is 0.36 to 0.7 mass %.

4. The high Cr Ni-based alloy welding wire according to claim 1, further comprising, by mass, at least one element selected from B, Zr, and rare earth elements: 0.0065% to 0.02%.

5. The high Cr Ni-based alloy welding wire according to claim 1, wherein the content of Ca+Mg is 0.0016% or less.

6. A high Cr Ni-based alloy welding wire comprising, by mass, C: 0.006% to 0.04%, Mn: 0.05% to 7%, Fe: 1 to 12%, Si: 0.05% to 0.75%, Al: 0.01 to 0.7%, Ti: 0.01 to 0.7%, Cr: 25.0 to 31.5%, Ta: 1 to 10%, Nb: 0%, and Mo: 1 to 6%, and as inevitable impurities, N: 0.1% or less, P: 0.02% or less, O: 0.01% or less, S: 0.0015% or less, H: 0.0015% or less, Cu: 0.08% or less, and Co: 0.05% or less, and the balance: Ni, wherein Ca and Mg are not present in detectable amounts, contents of S, Ta, Al, Ti, Mo, and N satisfying the following relations (1) and (2):
12000S+0.58Ta2.6Al2Ti19.3(1)
Ta+1.6Mo+187N5.7(2).

7. The high Cr Ni-based alloy welding wire according to claim 6, wherein the content of Al is 0.26 to 0.7 mass %.

8. The high Cr Ni-based alloy welding wire according to claim 6, wherein the content of Ti is 0.36 to 0.7 mass %.

9. The high Cr Ni-based alloy welding wire according to claim 6, further comprising, by mass, at least one element selected from B, Zr, and rare earth elements: 0.001% to 0.02%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A includes photographs each showing a result of a dye penetrant test conducted on a build-up welded portion formed on a SUS 304 plate by TIG welding using an embodiment (Example 2) of the present invention.

(2) FIG. 1B includes photographs each showing a result of the dye penetrant test conducted in a similar manner using a comparative example (Comparative Example 12) of the present invention.

(3) FIG. 1C is a photograph enlarging a portion of FIG. 1B (portion indicated by an arrow).

(4) FIG. 1D is a sectional view showing the groove surface of the SUS 304 plate used in FIGS. 1A and 1B.

(5) FIG. 2A is a plan view of a welded joint for a restraint weld cracking test of a thick plate (thick structural member) for evaluating weld cracking resistance.

(6) FIG. 2B is a front view of FIG. 2A.

(7) FIG. 3A is a graph showing a relationship between the content of Nb and a result of the dye penetrant test of a build-up welded portion on the SUS 304 plate formed by the TIG welding.

(8) FIG. 3B is a graph showing a relationship between the content of Ta and the result of the dye penetrant test.

(9) FIG. 4 is a graph showing a relationship between the content of S in a welding wire and a result of a side bend test conducted on a portion of the thick plate (thick structural member) restraint-welded by the TIG welding.

(10) FIG. 5A is a structure photograph of a section of a welded metal formed by using the embodiment (Example 1) of the present invention taken by an optical microscope at a magnification of approximately 200.

(11) FIG. 5B is a structure photograph of a section of a welded metal formed by using a comparative example (Comparative Example 8) to the present invention taken by the optical microscope under the condition same as 5A.

(12) FIG. 6A is a photograph of a weld bead surface of Comparative Example 12 of the present invention taken by a scanning electron microscope (SEM) at a magnification of approximately 400.

(13) FIG. 6B is a graph showing a result of qualitative analysis of the weld bead surface using a scanning electron microscope-energy dispersive X-ray analysis (SEM-EDX).

MODE FOR CARRYING OUT THE INVENTION

(14) An embodiment of a high Cr Ni-based alloy welding wire of the present invention will be described below. Table 2 shows alloy compositions of high Cr Ni-based alloy welding wires in the embodiment of the present invention and alloy compositions of Comparative Examples for confirming an effect of the present invention.

(15) TABLE-US-00002 TABLE 2 Chemical Compositions of Welding Wires (Mass %) Wire C Mn Fe P S Si Cu Ni Al Ti Cr Nb Ta Symbol (%) (%) (%) (ppm) (ppm) (%) (%) (%) (%) (%) (%) (%) (%) Example 1 Y1 0.023 1.26 10.2 60 6 0.25 0.03 Rem. 0.12 0.25 27.8 1.1 Example 2 Y2 0.022 0.45 8.5 20 7 0.71 0.005 Rem. 0.15 0.25 25.5 0.15 2.2 Example 3 Y3 0.021 3.28 9.2 10 5 0.86 0.003 Rem. 0.31 0.36 28.9 0.23 1.2 Example 4 Y4 0.02 0.15 9.5 100 5 0.26 0.05 Rem. 0.32 0.36 29.6 1.05 Example 5 Y5 0.016 0.09 7.1 50 6 0.21 0.04 Rem. 0.17 0.22 30.0 2.5 Example 6 Y6 0.016 0.35 6.56 110 4 0.32 0.02 Rem. 0.32 0.41 29.5 0.01 2.3 Example 7 Y7 0.031 6.68 3.5 50 6 0.51 0.06 Rem. 0.21 0.32 30.1 5.8 Example 8 Y8 0.025 0.69 3.2 20 8 0.46 0.01 Rem. 0.29 0.20 25.2 6.2 Example 9 Y9 0.015 2.51 1.2 60 4 0.21 0.005 Rem. 0.16 0.42 26.2 9.2 Example 10 Y10 0.021 0.45 8.4 30 8 0.15 0.02 Rem. 0.26 0.37 29.5 0.41 2.2 Example 11 Y11 0.032 0.38 8.4 40 4 0.26 0.01 Rem. 0.28 0.40 29.8 0.32 3.0 Example 12 Y12 0.015 0.74 9.2 20 5 0.25 0.02 Rem. 0.09 0.12 29.2 1.3 Example 13 Y13 0.022 0.9 9.8 50 10 0.26 0.03 Rem. 0.41 0.49 30.2 0.09 1.15 Example 14 Y14 0.029 1.1 6.5 60 10 0.32 0.02 Rem. 0.56 0.64 30.6 0.07 2.8 Example 15 Y15 0.016 1.2 7.4 80 12 0.28 0.01 Rem. 0.68 0.65 29.1 0.01 2.2 Example 16 Y16 0.035 0.75 2.4 40 7 0.52 0.07 Rem. 0.16 0.23 31.2 5.7 Comparative Y17 0.009 0.03 9.32 30 10 0.11 0.12 Rem. 0.32 0.41 30.6 Example 1 Comparative Y18 0.01 0.36 0.01 80 8 0.07 0.01 Rem. 0.22 0.31 28.71 0.10 10.5 Example 2 Comparative Y19 0.021 0.45 9.9 100 15 0.36 0.05 Rem. 0.15 0.25 29.3 0.83 0.01 Example 3 Comparative Y20 0.03 0.36 11.5 80 6 0.25 0.03 Rem. 0.007 0.008 30.1 0.03 1.2 Example 4 Comparative Y21 0.025 0.48 6.3 50 5 0.42 0.04 Rem. 0.71 0.73 29.3 3.3 Example 5 Comparative Y22 0.023 0.9 6.22 40 20 0.09 0.06 Rem. 0.11 0.24 30.06 0.10 2.3 Example 6 Comparative Y23 0.011 0.26 8.2 80 17 0.12 0.01 Rem. 0.63 0.51 28.9 0.03 3.7 Example 7 Comparative Y24 0.026 0.24 11 30 20 0.18 0.06 Rem. 0.70 0.52 28.96 0.01 Example 8 Comparative Y25 0.006 0.81 11.8 100 10 0.03 0.08 Rem. 0.078 0.18 29.33 0.97 Example 9 Comparative Y26 0.007 0.81 10.5 50 10 0.02 0.09 Rem. 0.081 0.18 28.93 1.2 Example 10 Comparative Y27 0.02 0.26 10 50 5 0.26 0.04 Rem. 0.07 0.21 23.8 0.78 Example 11 Comparative Y28 0.02 0.31 8.79 40 5 0.11 0.05 Rem. 0.13 0.18 29.5 2.51 0.01 Example 12 Mo Co O N H Ca + Mg B Zr REM Relations (%) (%) (ppm) (%) (ppm) (ppm) (ppm) (ppm) (ppm) (1) (3) (2) (4) Example 1 1.2 0.03 45 0.016 8 7.0 6.0 Example 2 3.2 0.01 30 0.02 7 17 9.1 11.6 Example 3 1.3 0.04 15 0.021 7 10 5.7 8.1 Example 4 1.5 0.02 20 0.02 9 10 20 15 30 5.1 7.2 Example 5 5.0 0.04 30 0.015 9 10 50 7.8 13.3 Example 6 4.2 0.03 50 0.005 13 10 50 60 4.5 10.0 Example 7 3.2 0.01 20 0.015 12 60 9.4 13.7 Example 8 2.5 0.02 30 0.012 11 12.0 12.4 Example 9 1.6 0.03 25 0.028 8 10 8.9 17.0 Example 10 2.1 0.01 90 0.016 10 19 7.9 10.5 Example 11 3.2 0.02 70 0.026 7 17 5.7 14.2 Example 12 1.5 0.005 40 0.03 5 18 6.3 9.3 Example 13 2.4 0.03 20 0.025 7 10.8 10.0 Example 14 3.4 0.005 25 0.008 11 11.0 10.0 Example 15 3.4 0.03 15 0.033 7 12.6 13.8 Example 16 4.5 0.04 15 0.025 7 10.6 17.6 Comparative 0.05 10 0.023 10 10 10.3 4.3 Example 1 Comparative 10.5 0.03 69 0.009 8 14.7 29.4 Example 2 Comparative 0.02 0.03 50 0.01 10 18.9 5.1 Example 3 Comparative 1.3 0.01 60 0.03 9 7.9 9.0 Example 4 Comparative 3.1 0.02 40 0.03 7 4.6 13.9 Example 5 Comparative 3.1 0.06 31 0.01 10 11 24.8 9.5 Example 6 Comparative 3.4 0.01 20 0.009 10 15 20.0 10.9 Example 7 Comparative 0.01 0.03 55 0.008 25 16 21.1 1.5 Example 8 Comparative 0.02 0.02 30 0.007 10 30 10 12.0 2.3 Example 9 Comparative 0.02 0.04 45 0.02 25 25 20 20 10 12.1 5.0 Example 10 Comparative 0.02 0.02 22 0.011 7 5.9 2.9 Example 11 Comparative 3.51 0.01 28 0.006 7 90 20 10.6 16.3 Example 12 Relations: (1) 12000S + 0.58Ta 2.6Al 2Ti 19.3 (2) Ta + 1.6Mo + 187N 5.7 (3) 12000S + 0.58Ta + 2.1Nb 2.6Al 2Ti 19.3 (4) Ta + 3.8Nb + 1.6Mo + 187N 5.7

(16) Examples 1 to 16 in Table 2 show the alloy compositions of the welding wires in this embodiment. The welding wire in each of Example 1 to 16 comprises, by mass, C: 0.04% or less, Mn: 7% or less, Fe: 1 to 12%, Si: 0.75% or less, Al: 0.01 to 0.7%, Ti: 0.01 to 0.7%, Cr: 25.0 to 31.5%, Ta: 1 to 10%, and Mo: 1 to 6%, and as inevitable impurities, P: 0.02% or less, O: 0.01% or less, N: 0.1% or less, S: 0.0015% or less, H: 0.0015% or less, Cu: 0.08% or less, and Co: 0.05% or less, and the balance: Ni. The contents of S, Ta, Al, Ti, Mo, and N in each of Examples 1, 5, 6, 7, 8, 9, 12, 15, and 16 satisfy the following relations (1) and (2):
12000S+0.58Ta2.6Al2Ti19.3(1)
Ta+1.6Mo+187N.sup.35.7(2).

(17) Further, the content of Nb in each of Examples 2, 3, 4, 10, 11, 13, and 14 satisfies a condition of 0.5 mass % or less, and the contents of S, Ta, Nb, Al, Ti, Mo, and N in each of Examples 2, 3, 4, 10, 11, 13, and 14 satisfy the following relations (3) and (4).
12000S+0.58Ta+2.1Nb2.6Al2Ti19.3(3)
Ta+3.8Nb+1.6Mo+187N5.7(4).

(18) Further, the content of Al in each of Examples 3, 4, 6, 8, 10, 11, 13, 14, and 15 satisfies a condition of 0.26 to 0.7 mass %. The content of Ti in each of Examples 3, 4, 6, 9, 10, 11, 13, 14, and 15 satisfies a condition of 0.36 to 0.7 mass %.

(19) The content of Nb in each of Examples 2, 4, 9, 10, 11, and 12 satisfies the condition of 0.5 mass % or less, and the total content of Ca and Mg as an inevitable impurity satisfies a condition of less than 0.002 mass %.

(20) The content of at least one kind of element selected from B, Zr, and rare earth elements in each of Examples 3 to 7 further satisfies a condition of 0.02 mass % or less.

(21) Table 3 shows evaluation results obtained by conducting a tensile test on a weld metal, a dye penetrant test on a build-up welded portion, a side bend test on a welded metal portion of a thick structural member, a check test of a microstructure (presence or absence of a microvoid in the structure of a welded metal) in the section of the welded metal, and a test for checking presence or absence of scale generation on the build-up surface (weld bead surface) of multiple layers on a carbon steel plate resulting from build-up welding. The weld metal is formed by using each of the high Cr Ni-based alloy welding wires of the various alloy compositions shown in Table 2.

(22) TABLE-US-00003 TABLE 3 Evaluation of Welding Wire Characteristics Tensile Strength Result of Side Bend Test (MPa) on Welded Portion of Thick Presence or Test Temperature Result of Structural Member Presence of Absence of Scale ( C.) Penetration Test Total Absence of Generation on Room on Build-Up Cracking No. of Microvoid in Welded Welded Metal Temp. 350 Portion Length (mm) Defects Pass/Fail* Metal Structure Structure Example 1 634 501 No Indication of 1.2 3 Pass None None Defect Example 2 712 551 No Indication of 3.3 5 Pass None None Defect Example 3 702 505 No Indication of 0.5 1 Pass None None Defect Example 4 645 515 No Indication of 0 0 Pass None None Defect Example 5 720 558 No Indication of 0 0 Pass None None Defect Example 6 719 555 No indication of 0 0 Pass None None Defect Example 7 734 564 No indication of 1.8 2 Pass None None Defect Example 8 752 575 No Indication of 3.1 7 Pass None None Defect Example 9 760 578 No Indication of 4.4 7 Pass None None Defect Example 10 707 552 No Indication of 4.0 5 Pass None None Defect Example 11 724 557 No Indication of 1.4 3 Pass None None Defect Example 12 660 525 No Indication of 0 0 Pass None None Defect Example 13 677 524 No Indication of 4.4 7 Pass None None Defect Example 14 720 556 No indication of 4.0 6 Pass None None Defect Example 15 705 553 No indication of 5.5 8 Pass None None Defect Example 16 751 572 No Indication of 4.6 6 Pass None None Defect Comparative 570 460 Indication of 7.7 11 Fail None None Example 1 Defect Comparative 810 576 No Indication of 12.5 14 Fail None None Example 2 Defect Comparative 572 460 Indication of 13.0 13 Fail None None Example 3 Defect Comparative 660 510 No Indication of 7.5 11 Fail None None Example 4 Defect Comparative 722 562 No indication of 0 0 Pass None Present Example 5 Defect Comparative 705 553 Indication of 22.1 25 Fail None None Example 6 Defect Comparative 725 562 Indication of 17.5 20 Fail None None Example 7 Defect Comparative 571 444 Indication of 23.1 16 Fail Present None Example 8 Defect Comparative 620 470 No Indication of 4.9 6 Pass None Present Example 9 Defect Comparative 623 482 Indication of 6.5 9 Pass Present Present Example 10 Defect Comparative 580 446 No Indication of 0.5 1 Pass None None Example 11 Defect Comparative 727 575 Indication of 5.2 9 Pass None Present Example 12 Defect *Notes (Ministerial Ordinance No. 81): (1) A crack should not exceed 3 mm in length (except those occurring at edge corners of a test (2) The total length of cracks having a length of 3 mm or less should not exceed 7 mm. (3) The number of cracks and/or blowholes should not exceed 10.

(23) In the tensile test, tensile strengths of the weld metal at room temperature and at 350 C. were measured, based on JIS G 0202. When the tensile strength measured at the room temperature is included in a range of 610 to 780 MPa and the tensile strength measured at 350 C. is included in a range of 485 MPa or more, the measured tensile strength resulting from the tensile test was evaluated to be good. The reason why the appropriate ranges of the tensile strength are set to such numerical value ranges is as follows. When the tensile strength is less than 610 MPa at the room temperature or less than 485 MPa at 350 C., a satisfactory strength characteristic of the weld metal cannot obtained. When the tensile strength exceeds 780 MPa at the room temperature, reduction of ductility or an excessive increase in the residual stress of the welded portion may be caused.

(24) Evaluation of high-temperature cracking susceptibility using the dye penetrant test was conducted at the build-up welded portion of the groove surface of a SUS 304 thick-walled plate, as a preparatory step for production of a welded joint of a thick structure member for a restraint weld cracking test shown in FIGS. 2A and 2B that will be described later. In the dye penetrant test, build-up welding of three to six layers was performed on the groove surface with a groove width of approximately 60 mm and a groove length of approximately 250 mm by TIG welding (see FIGS. 1A to 1D). Then, a process surface obtained by deleting an excess metal portion was formed by machining to achieve a predetermined groove shape. The dye penetrant test was conducted on this process surface, based on JIS Z 2343-1, and then presence or absence of a weld cracking was visually checked (see FIGS. 1A to 1C).

(25) The side bend test was conducted, based on JIS Z 3122. A bend test piece of a shape with a plate thickness of 10 mm was taken from the welded joint of the thick structure member, and a guided bend test method using jigs of a male type and a female type was carried out on the bent test piece. The male type jig was pressed against the female type jig so that the test piece is bent to form a U-character shape. The curvature radius (R) of the surface of the test piece in that case was set to twice the plate thickness, or R was set to be equal to 20 mm. After the test, the bent surface was observed by a magnifying glass, and the number of cracks (or blowholes) produced at the welded portion and the length of the cracks were measured. Based on the ministerial ordinance (No. 81) defining technical standards for welding of an electrical work piece, evaluation of the side bend test was made according to the following requirements (1), (2), and (3):

(26) (1) The length of a crack (except the one that occurs at an edge corner of the bend test piece) should not exceed 3 mm.

(27) (2) The total length of cracks that satisfy the above requirement (1) should not exceed 7 mm.

(28) (3) The number of cracks and/or blowholes should not exceed 10 pieces.

(29) The bend test piece that has satisfied all of the above requirements (1) (2) and (3) was evaluated to have passed the side bend test. The bend test piece that does not satisfy one of the above requirements (1) to (3) was evaluated not to have passed the side bend test.

(30) In the check test of the microstructure, the section of the welded metal of the thick structural member (SS 400) shown in FIGS. 2A and 2B was magnified to about 15 to 400 times its original size, using an optical microscope to check presence or absence of a microvoid. As a test piece of observation by the optical microscope, the test piece obtained by the following process was used. The welded metal cut out from the thick structural member was embedded in a resin, and a baffed finish was applied to the embedded welded metal. Electrolytic etching is then applied to this resulting metal using 10 percent oxalic acid as an etching solution, thereby yielding the microstructure. The test piece in which the microstructure has been yielded by the above-mentioned process was used. The structure photograph that has been taken is shown in FIG. 5 which will be described later in detail.

(31) In the test of welding performance, presence or absence of scale generation on the bead surface of the welded metal on the thick structural member (SS400) shown in FIGS. 2A and 2B was visually checked.

(32) The effect of this embodiment will be specifically described, based on each test result shown in Table 3. In each of Comparative Examples 1, 3, 8, 9, and 11, the content of Ta is less than 1 mass % that is the lower limit, and in Comparative Example 10 the content of Mo is also less than 1 mass % that is the lower limit. Thus, the tensile strength of each of Comparative Examples 1, 3, 8, 9, 10 and 11 at 350 C. was less than 485 MPa. In Comparative Example 2, the content of Ta exceeds 10 mass %, and the content of Mo exceeds 6 mass % that is the upper limit. Thus, the tensile strength of Comparative Example 2 at the room temperature exceeded 800 Mpa. On contrast therewith, the contents of Ta and Mo in each of Examples 1 to 16 meet composition requirements of the present invention. Thus, a good characteristic of tensile strength that exceeded 610 MPa at the room temperature and exceeded 485 Mpa at 350 C. was obtained. Specifically, a good tensile strength was obtained in the range of the content of Ta: 1 to 10 mass % and in the range of the content of Mo: 1 to 6 mass %, as shown in Tables 2 and 3.

(33) FIG. 3 graphically shows dye penetrant test results of many welding materials of Ni-based alloy 690 including Examples of the present invention and Comparative Examples, by sensitivity analysis using a neural network. FIG. 3A shows a relationship between Nb and the number of cracks, while FIG. 3B shows a relationship between Ta and the number of cracks. The number of cracks indicates the number of defects detected by the dye penetrant test. Referring to FIGS. 3A and 3B, the number of cracks on the build-up surface increases with an increase in the content of Nb, as shown in FIG. 3A. On contrast therewith, even if the content of Ta is increased, the number of cracks does not increase, as shown in FIG. 3B. This tendency shown in FIGS. 3A and 3B agrees with the fact that, although a defect has occurred in Comparative Example 3 (having the condition that the content of Nb exceeds 0.5 mass % and the content of Ta is less than 1 mass %), no defect has occurred in each of Examples 1 to 16 (having the condition that the content of Nb is 0.5 mass % or less and the content of Ta is 1 to 10 mass %).

(34) The content of S in each of Comparative Examples 6 to 8 exceeds 0.0015 mass % (15 ppm) that is the upper limit. In each of Comparative Examples 6 to 8, consequently, the number of cracks exceeds 10 pieces, and the total length of the cracks in each of Comparative Examples 6 to 8 exceeds 7 mm in the side bend test. Thus, Comparative Examples 6 to 8 do not satisfy the technical standards for welding (defined in the ministerial ordinance No. 81). On contrast therewith, under the condition of the content of S: 0.0015 mass % or less as shown in Examples 1 to 16, good weld cracking resistance was obtained.

(35) FIG. 4 is a graph where the dye penetrant test results of the lot of welding materials of the Ni-based alloy 690 including Examples of the present invention and Comparative Examples are outlined, by the sensitivity analysis using the neural network. This FIG. 4 shows a relationship between the content of S in each welding wire formed by the TIG welding and cracks detected by the side bend test. Referring to FIG. 4, it has been found that the number of cracks tends to transitionally increase when the content of S is in the range of 0.001 mass % (10 ppm) to 0.002 mass % (20 ppm). Thus, preferably, the content of S is set to be 15 ppm or less.

(36) The content of Al is less than 0.01 mass %, and the content of Ti is less than 0.01 mass % in Comparative Example 4. Thus, the content of Al and the content of Ti do not satisfy the composition requirements of the present invention. Consequently, a remarkable cracking has occurred in the side bend test of the welded portion of the thick structural member, which does not satisfy the technical standards for welding (defined in the ministerial ordinance No. 81). In Comparative Example 5, the content of Al exceeds 0.7 mass %, and the content of Ti exceeds 0.7 mass %, and the content of Al and the content of Ti do not satisfy the composition requirements of the present invention. Thus, a scale was generated on the weld bead surface, as shown in Table 3. On contrast therewith, in each of Examples 1 to 16, the content of Al is in the range of 0.1 to 0.7%, and the content of Ti is in the range of 0.1 to 0.7%, and there is no scale generation on the weld bead surface (with good welding performance). Further, good weld cracking resistance was obtained.

(37) The content of H exceeds 0.0015 mass % (15 ppm) in each of Comparative Examples 8 and 10, and does not therefore satisfy the composition requirement of the present invention. Thus, a microvoid as shown in FIG. 5B is generated, thereby impairing the integrity of the microstructure. On contrast therewith, the content of H is 0.0015 mass % (15 ppm) or less in each of Examples 1 to 16. Thus, it has been confirmed that the integrity of the microstructure of the welded metal is maintained, as shown in FIG. 5A. H is mixed into the welding wire when the welding wire is drawn as well as when the welding wire is melted. That is, when a lubricant is attached to the welding wire at the time of drawing the welding wire, the content of H remarkably increases. Thus, the lubricant must be fully washed away after the welding wire has been drawn. Comparative Example 12 is a welding wire that satisfies the conditions described in Patent Document 6 which is the related art. However, the content of Nb in Comparative Example 12 is high, and does not therefore satisfy the composition requirement of the present invention. Thus, a weld cracking was generated in the dye penetrant test of the build-up welded portion of the groove surface of the thick-walled plate, as shown in FIGS. 6A and 6B.

(38) Though Ca+Mg as the inevitable impurity is not added to each of Examples 1 to 16 in Table 2, the content of Ca+Mg is reduced to be less than 0.002 mass % (20 ppm) in each of Examples 2 and 4 and Examples 9 to 12. When such an alloy composition is employed, scale generation on the bead surface may be remarkably inhibited, in addition to improvement in the tensile strength and weld cracking resistance of the welded portion and improvement in the integrity of the microstructure of the welded metal. The content of Ca+Mg in each of Comparative Examples 9, 10, and 12 exceeds 0.002 mass % (20 ppm), and does not therefore satisfy the composition requirement of the present invention. Consequently, a scale was generated on the build-up surface (weld bead surface) of multiple layers, as shown in FIG. 6A. Analysis of the chemical composition of this scale has shown that this scale is an oxide mainly comprising Mg, as shown in FIG. 6B. On contrast therewith, no scale was generated on the build-up surface of multiple layers in each of Examples 1 to 16. That is, in order to inhibit scale generation on the bead surface, preferably, Ca+Mg is not added, as in Examples 1 to 16, and the content of Ca+Mg is reduced to be less than 0.002 mass % (20 ppm).

(39) An alloy composition where the content of Cu is 0.08 mass % or less, and the content of Co is 0.05 mass % or less is employed in each of Examples 1 to 16, as shown in Table 2. Assume that such an alloy composition is employed, and build-up welding is performed on the carbon steel plate. Then, weld cracking susceptibility does not increase due to reduction of the content of Cu, even if the dilution ratio has increased and a considerable amount of Fe is included in the build-up welded metal. Further, due to reduction of the content of Co, a radioactivity level in a working environment may be reduced when a periodic inspection or the like is carried out. On contrast therewith, the content of Cu in each of Comparative Examples 1 and 10 exceeds 0.08 mass %. Thus, when build-up welding is performed on the carbon steel plate and then the dilution ratio increases, weld cracking susceptibility cannot be reduced. The content of Co exceeds 0.05 mass % in Comparative Example 6. Thus, a radioactivity level in the working environment cannot be reduced when the periodic inspection or the like is carried out.

(40) As shown in Table 2, each of Examples 3 to 7 has an alloy composition further including at least one kind of elements of B, Zr, and rare-earth elements (REM) of 0.02 mass % (200 ppm) or less in the alloy composition in each of Examples 1 and 2 and Examples 8 to 16 described above. With such an alloy composition is employed, an effect of further increasing the weld cracking resistance at the welded port ion of the thick structural member may be obtained. On contrast therewith, each of Comparative Examples 1 to 8 and Comparative Example 11 does not include at least one kind of elements of B, Zr, and the rare-earth elements (does not include any of B, Zr, and the rare-earth elements). Thus, the effect of further increasing the weld cracking resistance like that in each of the examples 3 to 7 cannot be obtained.

(41) When the high Cr Ni-based alloy welding wire in each of Examples 1 to 16 as described above is employed, the tensile strength and the weld cracking resistance of the welded portion, the integrity of the microstructure of the welded metal, and the welding performance (inhibition of scale generation) may be increased.

(42) Next, an embodiment of a high Cr Ni-based shielded metal arc welding rod of the present invention will be described. Table 4 shows alloy compositions of welding wires used for high Cr Ni-based shielded metal arc welding rods of the present invention and alloy compositions of Comparative Examples for confirming an effect of the present invention.

(43) TABLE-US-00004 TABLE 4 Chemical Compositions of Wires for Shielded Metal Arch Welding Rods (Mass %) Wire C Mn Fe P S Si Cu Ni Al Ti Cr Symbol (%) (%) (%) (ppm) (ppm) (%) (%) (%) (%) (%) (%) Comparative S1 0.008 5.21 8.27 50 10 0.06 0.02 Rem. 0.56 0.65 27.5 Example 13 Comparative S2 0.008 5.25 7.76 60 7 0.12 0.01 Rem. 0.52 0.40 27.6 Example 14 Comparative S3 0.011 3.55 7.65 60 5 0.05 0.02 Rem. 1.22 0.45 27.7 Example 15 Comparative S4 0.012 1.30 8.84 60 6 0.05 0.04 Rem. 0.65 1.31 29.6 Example 16 Example 6 Y6 0.016 0.35 8.58 110 4 0.32 0.02 Rem. 0.32 0.41 29.5 Example 10 Y10 0.021 0.45 8.43 30 6 0.15 0.02 Rem. 0.26 0.37 29.5 Example 11 Y11 0.032 0.38 8.41 40 4 0.26 0.01 Rem. 0.28 0.40 29.8 Example 13 Y13 0.022 0.93 9.84 50 10 0.26 0.03 Rem. 0.41 0.49 30.2 Example 14 Y14 0.029 1.12 6.54 60 10 0.32 0.02 Rem. 0.56 0.64 30.6 Example 15 Y15 0.016 1.22 7.42 80 12 0.28 0.01 Rem. 0.68 0.65 29.1 Example 17 S5 0.010 5.34 5.41 50 5 0.05 0.02 Rem. 0.52 0.82 29.1 Example 18 S6 0.011 2.11 2.13 60 6 0.06 0.03 Rem. 0.31 0.75 29.7 Example 19 S7 0.010 5.36 2.34 50 7 0.05 0.01 Rem. 0.29 0.97 27.5 Example 20 S8 0.012 1.22 2.66 70 10 0.04 0.04 Rem. 0.95 0.38 30.2 Example 21 S9 0.010 5.22 1.11 50 4 0.03 0.01 Rem. 0.72 0.40 27.5 Example 22 S10 0.012 3.06 5.32 30 8 0.06 0.02 Rem. 0.71 0.73 28.3 Nb Ta Mo Co O N H Ca + M B Zr REM (%) (%) (%) (%) (ppm) (%) (ppm) (ppm) (ppm) (ppm) (ppm) Comparative 3.11 0.50 0.31 0.01 20 0.009 7 Example 13 Comparative 0.10 3.57 0.35 0.03 6 0.013 8 10 Example 14 Comparative 0.35 0.55 1.11 0.01 10 0.017 9 Example 15 Comparative 1.75 2.58 5.88 0.04 13 0.014 7 Example 16 Example 6 0.01 2.33 4.20 0.03 50 0.005 13 10 50 60 Example 10 0.41 2.21 2.11 0.01 90 0.018 10 19 Example 11 0.32 2.94 3.23 0.02 70 0.026 7 17 Example 13 0.09 1.15 2.45 0.03 20 0.025 7 Example 14 0.07 2.84 3.43 0.005 25 0.008 11 Example 15 0.01 2.29 3.42 0.03 15 0.033 7 Example 17 1.50 2.51 1.77 0.02 20 0.011 7 10 Example 18 1.72 0.01 2.51 0.01 10 0.018 10 Example 19 2.55 0.10 4.13 0.01 9 0.015 8 Example 20 0.51 2.45 3.64 0.02 12 0.017 7 Example 21 0.87 2.97 5.96 0.01 12 0.012 6 10 Example 22 1.70 2.94 4.55 0.02 12 0.011 8

(44) Referring to Table 4, each of Examples 6, 10, 11, 13 to 15, and 17 to 22 shows an example of the welding wire used for the high Cr Ni-based shielded metal arc welding rod of the present invention. Referring to Table 4, Examples 6, 10, 11, and 13 to 15 are obtained by selecting a part of the high Cr Ni-based welding wires of various alloy compositions shown in Table 2, as the wires for the shielded metal arc welding rods. Each of the examples shown in Table 4 has a composition comprising, by mass, C: 0.04% or less, Mn: 7% or less, Fe: 1 to 12%, Si: 0.75% or less, Al: 0.26 to 1.0%, Ti: 0.36 to 1.0%, Cr: 25.0 to 31.5%, Nb: 3.0% or less, Ta: 3.0% or less, and Mo: 1 to 6%, and as inevitable impurities, P: 0.02% or less, O: 0.01% or less, N: 0.1% or less, S: 0.0015% or less, H: 0.0015% or less, Cu: 0.08% or less, and Co: 0.05% or less, and the balance: Ni. By selecting a welding work condition whereby weld cracking susceptibility is reduced, the welding wire of the present invention may also be used for the TIG welding.

(45) Table 5 shows results of welding performance tests of the shielded metal arc welding rods produced with the welding wires for the high Cr Ni-based alloy welding rods of various alloy compositions shown in Table 4. In the welding performance tests, each item of stability of an arc, spatter generation, slag encapsulation, slag detachability, slag burning, bead shape, and comprehensive evaluation of these items were evaluated with one of marks of (good), (passable), and X (bad).

(46) TABLE-US-00005 TABLE 5 Wires Used for Shielded Metal Arc Welding Rods and Result of Welding Performance Test* Wire Flux Arc Spatter Slag Slag Slag Bead Comprehensive Symbol Type Stability Generation Encapsulation Detachability Burning Shape Evaluation Comparative S1 Lime X X Example 13-1 Comparative S2 Lime X X Example 14-1 Comparative S3 Lime X X Example 15-1 Comparative S4 Lime X X Example 16-1 Example Y6 Lime 6-1 Example Y10 Lime 10-1 Example Y11 Lime 11-1 Example Y13 Lime 13-1 Example Y14 Lime 14-1 Example Y15 Lime 15-1 Example S5 Lime 17-1 Example S6 Lime 18-1 Example S7 Lime 19-1 Example S8 Lime 20-1 Example S9 Lime 21-1 Example S10 Lime 22-1 *Note: Good Passable X Bad

(47) Each of Examples 6-1, 10-1, 11-1, 13-1 to 15-1, and 17-1 to 22-1 in Table 5 shows a result of the welding performance test of the shielded metal arc welding rod produced with the welding wire in this embodiment for the high Cr Ni-based alloy welding rod in Table 4 described above.

(48) The high Cr Ni-based alloy shielded metal arc welding rods in Examples 6-1, 10-1, 11-1, and 13-1 to 15-1 were respectively produced with the wires in Examples 6, 10, 11, and 13 to 15 in Table 4. The high Cr Ni-based alloy shielded metal arc welding rods in Examples 17-1 to 22-1 were respectively produced with the wires in Examples 17 to 22 in Table 4. As shown in Tables 4 and 5, a lime-type flux was used in each of these examples (Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1 to 22-1), for the reason that will be described later in detail.

(49) The content of Nb in the wire in Comparative Example 13-1 exceeds 3.0 mass %, and does not therefore satisfy the composition requirement of the present invention. The content of Ta in the wire in Comparative Example 14-1 exceeds 3.0 mass %, and does not therefore satisfy the composition requirement of the present invention. Consequently, in the welding performance test for each of the shielded metal arc welding rods (in Comparative Examples 13-1 and 14-1) using the wires of Comparative Examples 13 and 14, slag burned on the bead surface of a welded portion. This burning may cause a defect in welding and may make it difficult to perform good welding, thus reducing welding performance. The content of Al in the wire of Comparative Example 15-1 exceeds 1.0 mass %, and does not therefore satisfy the composition requirement of the present invention. The content of Ti in the wire of Comparative Example 16-1 exceeds 1.0 mass %, and does not therefore satisfy the composition requirement of the present invention. Consequently, in the welding performance test for each of the shielded metal arc welding rods (in Comparative Examples 15-1 and 16-1) using the welding wires of Comparative Examples 15 and 16, slag detachability was bad, thus posing a great problem for efficiently performing a welding work. Slag also burned a little bit (which was evaluated with the mark of ). On contrast therewith, Examples 6-1, 10-1, 11-1, 13-1 to 15-1, and 17-1 to 22-1 respectively show the shielded metal arc welding rods using the wires (of Examples 6, 10, 11, 13 to 15, and 17 to 22) that satisfy the composition requirements of the present invention and whose welding performances were good (were evaluated with the marks of ).

(50) Table 6 shows alloy compositions of weld metals of the examples formed by the high Cr Ni-based alloy shielded metal arc welding rods produced with the welding wires of the various alloy compositions and alloy compositions of Comparative Examples for confirming the effect of the present invention.

(51) TABLE-US-00006 TABLE 6 Combinations of Wires and Flux Types Used for Shielded Metal Arc Welding Rods and Chemical Compositions of Weld Metals (Mass %) Wire Flux C Mn Fe P S Si Cu Ni Al Ti Cr Symbol Type (%) (%) (%) (ppm) (ppm) (%) (%) (%) (%) (%) (%) Comparative S1 Lime 0.030 4.32 8.32 60 15 0.27 <0.01 Rem. 0.13 0.12 28.09 Example 13-1 Comparative S2 Lime 0.031 4.33 7.68 60 20 0.30 0.01 Rem. 0.11 0.11 28.27 Example 14-1 Comparative S3 Lime 0.032 3.81 9.10 60 20 0.22 0.02 Rem. 0.35 0.25 28.41 Example 15-1 Comparative S3 Lime- 0.019 3.21 9.10 60 60 0.41 0.05 Rem. 0.20 0.02 28.21 Example Titania 15-2 Comparative S4 Lime- 0.021 4.28 8.84 60 20 0.45 0.04 Rem. 0.06 0.03 29.86 Example Titania 16-2 Comparative Y22 Lime- 0.034 2.32 8.50 50 60 0.26 0.09 Rem. 0.08 0.15 29.65 Example Titania 17-2 Example 6-1 Y6 Lime 0.031 2.10 8.34 80 10 0.25 0.03 Rem. 0.20 0.13 29.30 Example Y10 Lime 0.034 0.81 8.14 50 45 0.15 0.02 Rem. 0.08 0.08 29.80 10-1 Example Y11 Lime 0.039 0.69 8.25 40 10 0.25 0.02 Rem. 0.09 0.08 29.22 11-1 Example Y13 Lime 0.031 0.91 8.81 40 10 0.25 0.02 Rem. 0.08 0.08 29.27 13-1 Example Y14 Lime 0.034 1.81 7.22 70 10 0.26 0.02 Rem. 0.10 0.11 29.13 14-1 Example Y15 Lime 0.030 2.65 5.03 50 20 0.24 0.02 Rem. 0.13 0.12 30.25 15-1 Example S5 Lime 0.030 4.45 6.13 40 15 0.11 0.03 Rem. 0.10 0.15 29.18 17-1 Example S5 Lime 0.031 4.32 6.22 50 15 0.13 0.04 Rem. 0.14 0.16 29.45 17-2 Example S10 Lime 0.032 3.12 5.95 30 10 0.14 0.01 Rem. 0.14 0.16 28.77 22-1 Nb Ta Mo Co O N H Ca + Mg B Zr REM (%) (%) (%) (%) (%) (%) (ppm) (ppm) (ppm) (ppm) (ppm) Comparative 2.77 0.40 0.58 0.02 0.07 0.020 10 Example 13-1 Comparative 0.37 2.87 0.55 <0.01 0.06 0.018 12 Example 14-1 Comparative 0.21 0.48 1.21 <0.01 0.07 0.022 15 Example 15-1 Comparative 0.15 0.33 1.09 0.04 0.07 0.020 22 Example 15-2 Comparative 2.54 4.45 6.31 0.04 0.07 0.018 25 Example 16-2 Comparative 0.75 2.17 3.87 0.06 0.07 0.018 23 Example 17-2 Example 6-1 0.56 3.51 4.20 0.01 0.07 0.035 15 20 20 10 Example 1.11 3.30 5.63 0.01 0.07 0.015 12 20 10-1 Example 0.15 2.61 2.93 0.02 0.08 0.033 15 10 11-1 Example 0.03 1.80 3.92 0.02 0.08 0.033 15 13-1 Example 0.75 2.04 3.12 0.03 0.07 0.033 15 14-1 Example 0.95 3.30 2.77 0.03 0.07 0.025 10 15-1 Example 1.71 1.93 1.36 0.02 0.07 0.021 15 10 17-1 Example 1.22 2.21 3.51 0.01 0.07 0.034 10 17-2 Example 1.33 0.52 4.03 0.01 0.07 0.02 10 22-1

(52) Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1 in Table 6 show the alloy compositions of the weld metals of high Cr Ni-based alloys formed by shielded metal arc welding in this embodiment. The high Cr Ni-based alloy weld metals formed by the shielded metal arc welding in Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1 were formed by the shielded metal arc welding rods produced with the wires (in Examples 6, 10, 11, 13 to 15, 17, and 22) selected from among the welding wires for the high Cr Ni-based shielded metal arc welding rods in Table 4 described above. The weld metals in the examples shown in FIG. 6 each comprises, by mass, C: 0.04% or less, Mn: 7% or less, Fe: 1 to 12%, Si: 0.75% or less, Al: 0.01 to 0.7%, Ti: 0.01 to 0.7%, Cr: 25.0 to 31.5%, Nb+Ta: 1.8 to 4.5%, Mo: 1 to 6%, and as inevitable impurities, Ca+Mg: less than 0.002%, P: 0.02% or less, S: 0.005% or less, H: 0.002% or less, N: 0.1% or less, O: 0.1% or less, Cu: 0.08% or less, and Co: 0.05% or less, and the balance: Ni.

(53) Table 7 shows evaluation results obtained after execution of tests of welding performances of the high Cr Ni-based alloy shielded metal arc welding rods of various alloy compositions shown in Table 6, tensile tests of the weld metals, side bend tests of welded metal portions of thick structural members, and check tests of microstructures of welded metals.

(54) TABLE-US-00007 TABLE 7 Evaluation of Characteristics of Shielded Metal Arc Welding Rods Tensile Strength (MPa) Test Presence of Comprehensive Temperature Result of Side Bend Test on Welded Portion Absence of Evaluation of ( C.) of Thick Structural Member Microvoid in Welding Room Total Cracking Welded Metal Performance* Temp. 350 Length (mm) No. of Defects Pass/Fail** Structure Comparative Example 13-1 X 612 484 7.8 11 Fail None Comparative Example 14-1 X 600 481 6.5 9 Pass None Comparative Example 15-1 X 577 466 6.5 7 Pass None Comparative Example 15-2 X 575 465 17.1 20 Fail Present Comparative Example 16-2 X 808 580 21.3 24 Fail Present Comparative Example 17-2 728 558 18.9 23 Fail Present Example 6-1 731 565 3.3 5 Pass None Example 10-1 755 578 6.9 10 Pass None Example 11-1 702 551 1.0 2 Pass None Example 13-1 646 516 1.8 3 Pass None Example 14-1 715 554 2.2 4 Pass None Example 15-1 741 566 4.2 5 Pass None Example 17-1 718 559 4.3 5 Pass None Example 17-2 729 560 4.9 7 Pass None Example 22-1 633 510 3.2 5 Pass None *Note: Good Passable X Bad **Notes (Ministerial Ordinance No. 81): (1) A crack should not exceed 3 mm in length (except those occurring at edge corners of a test piece). (2) The total length of cracks having a length of 3 mm or less should not exceed 7 mm. (3) The number of cracks and/or blowholes should not exceed 10.

(55) The welding wires (in Comparative Examples 13, 14, 15, and 16 shown in Table 4) used for producing the welding rods in Comparative Examples 13-1 to 15-1 and Comparative Examples 15-2 and 16-2 do not satisfy the composition requirements of the present invention. Thus, there is a problem of degradation of the welding performances of Comparative Examples 13-1 to 15-1 and Comparative Examples 15-2 and 16-2 (see Table 5).

(56) The content of Nb+Ta in the weld metal in each of Comparative Examples 15-1 and 15-2 is low, and does not therefore satisfy the composition requirement of the present invention. The content of Mo in each of Comparative Examples 13-1 and 14-1 is low, and does not therefore satisfy the composition requirement of the present invention. Consequently, tensile strength at 350 C. in each of Comparative Examples 13-1, 14-1, 15-1, and 15-2 was less than 485 MPa. That is, as compared with Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1 that compositely include Nb+Ta and Mo, a satisfactory tensile characteristic cannot obtained from Comparative Examples 13-1, 14-1, 15-1, and 15-2.

(57) The content of Nb+Ta in Comparative Example 16-2 exceeds 4.5 mass %, and does not therefore satisfy the composition requirement of the present invention. For that reason, the total length of cracks exceeded 7 mm and the number of the cracks exceeded 10 pieces in the side bend test of the welded metal portion of the thick structural member in Comparative Example 16-2. Thus, preferably, the weld metal in Comparative Example 16-2 includes Nb to of 1.8 to 4.5 mass % or less and Mo of 1 to 6 mass %, as in each of Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1.

(58) The content of S in each of Comparative Examples 15-2 and 17-2 exceeds 0.005 mass % (50 ppm), and does not therefore satisfy the composition requirement of the present invention. For that reason, the total length of cracks exceeded 7 mm and the number of cracks exceeded 10 pieces in the side bend test of the welded metal portion of the thick structural member. The total length of cracks and the number of cracks do not satisfy the technical standards for welding (defined in the ministerial ordinance No. 81). On contrast therewith, each of Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1 whose content of S is 0.005 mass % or less (50 ppm) satisfies the technical standards for welding (defined in the ministerial ordinance No. 81). Thus, preferably, the content of S in the weld metal formed by using the shielded metal arc welding rod of the present invention is set to 0.005 mass % (50 ppm) or less as in Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1.

(59) As described above, the influence of a flux and presence of Mn need to be taken into consideration in the case of shielded metal arc welding. For that reason, the content of S in the weld metal (in each of Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1) formed by using the shielded metal arc welding rod in this embodiment is 0.005 mass % (50 ppm) or less, while the content of S in each of the welding wires (in Examples 1 to 16 and Examples 17 to 22) described above is 0.0015 mass % (15 ppm) or less. Accordingly, the content of S acts on the total length of cracks generated in the side bend test for the welded portion of the thick structural member differently from the action shown in FIG. 4 indicating the case of the TIC welding.

(60) The content of H in each of Comparative Examples 15-2, 16-2, and 17-2 exceeds 0.002 mass 1 (20 ppm), and does not therefore satisfy the composition requirement of the present invention. Thus, a microvoid was generated in the welded metal. In addition, the number of cracks exceeded 10 pieces in the side bend test of the welded metal portion of the thick structural member in each of Comparative Examples 15-2, 16-2, and 17-2, and does not therefore satisfy the technical standards for welding (defined in the ministerial ordinance No. 81). As described above, moisture absorbed by the flux in the shielded metal arc welding generates hydrogen. Thus, the content of H in a welded metal formed by the shielded metal arc welding tends to be higher than that formed by the TIG welding. Generally, as flux types for a high Cr Ni-based alloy shielded metal arc welding rod, a lime-titania type mainly comprising TiO.sub.2, CaCO.sub.3, and CaF.sub.2 and a lime-type mainly comprising CaCO.sub.3 and CaF.sub.2 are present. Out of these flux types, the lime-type flux was used for the shielded metal arc welding rod of the present invention. The reason for the use of the lime-type flux is that the partial pressure of H decreases due to a gas component such as CO.sub.2 to be generated from CaCO.sub.3 at a time of welding, so that the content of H in the welded metal decreases more than with the other flux type. The CaF.sub.2 component of the flux is melted into a molten slag during the welding, and then reacts with a molten metal, thereby controlling an increase of S and the like. Thus, the use of the lime-type flux is also effective for increasing weld cracking resistance.

(61) The lime-titania type flux was used in Comparative Examples 15-2, 16-2, and 17-2. The content of H in each of Comparative Examples 15-2, 16-2, and 17-2 using such a lime-titania type flux exceeds 0.002 mass % (20 ppm), as described above. Thus, the microvoid was generated in the welded metal. For this reason, preferably, the lime-type flux is used, as in Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1, thereby controlling the content of H to be 0.002 mass % or less.

(62) The content of Cu in Comparative Example 17-2 exceeds 0.08 mass %. Thus, weld cracking susceptibility cannot be reduced when the dilution ratio increases after build-up welding has been performed on a carbon steel plate. The content of Co in Comparative Example 17-2 exceeds 0.05 mass %. Thus, a radioactivity level in the working environment cannot be reduced when the periodic inspection or the like is carried out.

(63) The welding performance of the high Cr Ni-based alloy shielded arc welding rod having the alloy composition in each of Examples 6-1, 10-1, 11-1, 13-1 to 15-1, 17-1, 17-2, and 22-1 is good. In the welded metal formed by each of these welding rods, tensile strength and weld cracking resistance of the welded portion and the integrity of the microstructure of the welded metal may be increased all together.

INDUSTRIAL APPLICABILITY

(64) According to the present invention, the tensile strength characteristic and the weld cracking resistance of a welded portion and the integrity of the microstructure of a welded metal may be increased by configuring a high Cr Ni-based alloy welding wire to have an alloy composition comprising, by mass, C: 0.04% or less, Mn: 7% or less, Fe: 1 to 12%, Si: 0.75% or less, Al: 0.01 to 0.7%, Ti: 0.01 to 0.7%, Cr: 25.0 to 31.5%, Ta: 1 to Mo: 1 to 6%, and N: 0.1% or less, and as inevitable impurities, P: or less, O: 0.01% or less, S: 0.0015% or less, H: 0.0015% or less, Cu: 0.08% or less, and Co: 0.05% or less, and the balance: Ni, and by configuring such that the contents of S, Ta, Al, Ti, Mo, and N to satisfy the following relations (1) and (2):
12000S+0.58Ta2.6Al2Ti19.3(1)
Ta+1.6Mo+187N5.7(2).