NI-CR-MO-NB ALLOY

Abstract

A Ni—Cr—Mo—Nb alloy consists of, in mass %, C: not more than 0.020%, Si: 0.02 to 1.0%, Mn: 0.02 to 1.0%, P: not more than 0.03%, S: not more than 0.005%, Cr: 18.0 to 24.0%, Mo: 8.0 to 10.0%, Al: 0.005 to 0.4%, Ti: 0.1 to 1.0%, Fe: not more than 5.0%, Nb: 2.5 to 5.0%, N: 0.002 to 0.02%, and at least one of W: 0.02 to 0.3% and V: 0.02 to 0.3%, and Ni as a remainder and inevitable impurities, in which an freely selected cross section of alloy, sum of number of particles of NbC carbide and (Ti, Nb)N nitride is 100 to 1000 particles/mm.sup.2, number of particles of the NbC carbide is not more than 40 particles/mm.sup.2, and number of particles of the (Ti, Nb)N nitride is 100 to 1000 particles/mm.sup.2.

Claims

1. A Ni—Cr—Mo—Nb alloy consisting of: in mass %, C: not more than 0.020%, Si: 0.02 to 1.0%, Mn: 0.02 to 1.0%, P: not more than 0.03%, S: not more than 0.005%, Cr: 18.0 to 24.0%, Mo: 8.0 to 10.0%, Al: 0.005 to 0.4%, Ti: 0.1 to 1.0%, Fe: not more than 5.0%, Nb: 2.5 to 5.0%, N: 0.002 to 0.02%, and at least one of W: 0.02 to 0.3% and V: 0.02 to 0.3%, and Ni as a remainder and inevitable impurities, wherein in a freely selected cross section of alloy, a sum of number of particles of NbC carbide and number of particles of (Ti, Nb)N nitride is 100 to 1000 particles/mm.sup.2, the number of particles of NbC carbide is not greater than 40 particles/mm.sup.2, and the number of particles of (Ti, Nb)N nitride is 100 to 1000 particles/mm.sup.2.

2. The Ni—Cr—Mo—Nb alloy according to claim 1, wherein Nb in the (Ti, Nb)N nitride is 5.0 to 40%.

3. The Ni—Cr—Mo—Nb alloy according to claim 1, wherein average particle diameter of the nitride is 0.10 to 3.00 μm.

4. The Ni—Cr—Mo—Nb alloy according to claim 1, wherein with respect to crystal grain diameter, 1 μm to less than 20 μm is not more than 10%, 20 μm to less than 40 μm is not more than 20%, 40 μm to less than 60 μm is not more than 30%, 60 μm to less than 80 μm is 15 to 40%, 80 μm to less than 100 μm is 15 to 40%, 100 μm to less than 120 μm is 10 to 90%, and not less than 120 μm is not more than 30%.

5. The Ni—Cr—Mo—Nb alloy according to claim 2, wherein average particle diameter of the nitride is 0.10 to 3.00 μm.

6. The Ni—Cr—Mo—Nb alloy according to claim 2, wherein with respect to crystal grain diameter, 1 μm to less than 20 μm is not more than 10%, 20 μm to less than 40 μm is not more than 20%, 40 μm to less than 60 μm is not more than 30%, 60 μm to less than 80 μm is 15 to 40%, 80 μm to less than 100 μm is 15 to 40%, 100 μm to less than 120 μm is 10 to 90%, and not less than 120 μm is not more than 30%.

7. The Ni—Cr—Mo—Nb alloy according to claim 3, wherein with respect to crystal grain diameter, 1 μm to less than 20 μm is not more than 10%, 20 μm to less than 40 μm is not more than 20%, 40 μm to less than 60 μm is not more than 30%, 60 μm to less than 80 μm is 15 to 40%, 80 μm to less than 100 μm is 15 to 40%, 100 μm to less than 120 μm is 10 to 90%, and not less than 120 μm is not more than 30%.

8. The Ni—Cr—Mo—Nb alloy according to claim 5, wherein with respect to crystal grain diameter, 1 μm to less than 20 μm is not more than 10%, 20 μm to less than 40 μm is not more than 20%, 40 μm to less than 60 μm is not more than 30%, 60 μm to less than 80 μm is 15 to 40%, 80 μm to less than 100 μm is 15 to 40%, 100 μm to less than 120 μm is 10 to 90%, and not less than 120 μm is not more than 30%.

Description

EXAMPLES

[0062] Hereinafter the present invention is explained further in detail by way of Examples.

[0063] In order to prepare alloys each having a chemical composition shown in Table 1, raw materials such as scrap, Ni, Cr, Mo and the like were melted in an electric furnace, and decarburization was performed by oxygen blowing by AOD (Argon Oxygen Decarburization) and/or VOD (Vacuum Oxygen Decarburization). After that, Al, limestone, and fluorite were added in order to form CaO—SiO.sub.2—Al.sub.2O.sub.3—MgO—F slag on melt alloy, so that deoxidation and desulfuration were performed. Furthermore, Nb, Ti were added, the composition was controlled, and the melt alloy was casted by a continuous casting apparatus, so that slabs each having a thickness 200 mm were obtained.

[0064] After that, each slab was hot rolled by a Steckel mill and was cold rolled, so as to produce a cold rolled plate. Table 1 shows chemical composition of each of the alloys, and Table 2 shows reduction of rolling, plate thickness, final annealing temperature, and evaluation result. It should be noted that the final annealing was performed for 4 minutes.

[0065] With respect to these sample materials, a cross section vertical to the rolled direction was cut out to have a thickness of 1 mm, the cross section was polished using a #800 polishing paper, and electrolytic polishing was performed for finishing. Each of the samples was evaluated by the following observations and measurements.

Number of Particles of NbC Carbide

[0066] First, by an energy dispersive X-ray spectroscopy (EDS) installed in a FE-SEM, NbC carbide existing was specified. Number of particles and particle size of NbC carbide specified in this way were obtained by FE-SEM, in a measurement in an area of 1 mm×1 mm.

Number of Particles of (Ti, Nb)N Nitride

[0067] First, by an energy dispersive X-ray spectroscopy (EDS) installed in a FE-SEM, (Ti, Nb)N nitride existing was specified. Number of particles and particle size of (Ti, Nb)N nitride specified in this way were obtained by FE-SEM, in a measurement in an area of 1 mm×1 mm

Nb Amount in (Ti, Nb)N Nitride

[0068] Nb amount in (Ti, Nb)N nitride was obtained by an energy dispersive X-ray spectroscopy (EDS) installed in a FE-SEM, in a measurement in a range of 1 mm×1 mm.

Crystal Grain Diameter Distribution

[0069] Crystal grain diameter distribution was obtained by electron beam backscatter diffraction (EBSD) installed in a FE-SEM, in a measurement at ten locations in a region of 1000 μm.sup.2.

Tensile Test

[0070] A flat tensile test piece as defined in Japanese Industrial Standards (JIS) No. 13B was cut out of the above cold rolled material in order for the tensile direction to be vertical to the rolled direction. Tensile tests were performed to obtain 0.2% proof stress.

[0071] Hereinafter Examples shown in Tables 1 and 2 are explained.

[0072] It should be noted that in the Tables, parentheses “( )” surround values not satisfying the range of the independent claim of the present invention, and brackets “[ ]” surround values satisfying the range of the independent claim, but not satisfying the range of the desirable dependent claims.

[0073] Since Nos. 1, 3, 4, 6 to 9, which are Examples of the present invention, all satisfy the desirable range of the present invention, they had appropriate microstructure, and they satisfied the range of 270 to 400 MPa of 0.2% proof stress by tensile tests. It should be noted that Nos. 2, 5, 10 to 13 to which*were added were almost good evaluation results; however, strictly speaking, since some of the properties were outside the range of the present invention, they were regarded as Reference Examples.

[0074] It should be noted that in the alloy of Example 3, Ti amount was high, but on the other hand, Nb amount was low and N amount was high. Therefore, number of particles of (Ti, Nb)N nitride was high, and Nb amount in (Ti, Nb)N nitride is out of the range, being 4%. Furthermore, particle size was large. As a result, crystal grain diameter distribution was shifted to being finer, and 0.2% proof stress was a relatively high value, being 385 MPa.

[0075] In the alloy of Example 5, since the C amount and N amount were low, number of particles of NbC was low and number of particles of (Ti, Nb)N nitride was also low. However, in total, not less than 100 particles/mm.sup.2, which is the lower limit value of the range, could be maintained. As a result, crystal grain diameter distribution was shifted to coarsening, and 0.2% proof stress was a relatively low value, being 272 MPa.

[0076] In the alloy of Example 9, the C amount was high, and in addition, the Ti amount was low and the Nb amount was high. Therefore, the number of particles of NbC formed was high; however, the number of particles of NbC was not so great as to affect the number of particles of (Ti, Nb)N, and an appropriate number of particles could be maintained. In addition, the Nb amount in (Ti, Nb)N nitride was out of the range, being 41%. As a result, crystal grain diameter distribution was shifted to being finer, and 0.2% proof stress was a relatively high value, being 391 MPa.

[0077] In the alloys of Examples 10 to 13, since the N amount was low, the number of particles of NbC was low and the number of particles of (Ti, Nb)N nitride was also low. However, in total, not fewer than 100 particles/mm.sup.2 which is the lower limit value of the range, could be maintained. As a result, crystal grain diameter distribution was shifted to coarsening, and 0.2% proof stress was a relatively low value, being 271 to 280 MPa.

[0078] Hereinafter Comparative Examples are explained.

[0079] In the alloy of Example 14, C amount was high, and the number of particles of NbC formed was far above the range. Therefore, the number of particles of (Ti, Nb)N was low, the Nb amount in (Ti, Nb)N was lower than the range and was outside of the present invention, the crystal grain diameter distribution was shifted to coarsening, and the 0.2% proof stress was below the range and was out of the range.

[0080] In the alloy of Example 15, since the Ti amount and the Nb amount were above the range and were out of the range, the number of particles of (Ti, Nb)N was higher than the range and was out of the range. Furthermore, Nb amount in (Ti, Nb)N was high, and sizes of nitride were below the range and were out of the range. Therefore, crystal grain diameter distribution was shifted to being finer, and 0.2% proof stress was higher than the range and was out of the range.

[0081] In the alloy of Example 16, since chemical composition Nb amount and was higher than the range and was out of the range, and heat treatment temperature was low, the number of particles of NbC was high, and the number of particles of (Ti, Nb)N was below the range and was out of the range. Furthermore, Nb amount in (Ti, Nb)N was high, and sizes of nitride were below the range and were out of the range. Therefore, crystal grain diameter distribution was shifted to coarsening, and 0.2% proof stress was below the range and was out of the range.

[0082] In the alloy of Example 17, N amount was low, number of particles of (Ti, Nb)N was below the range and was out of the range, crystal grain diameter distribution was shifted to coarsening, and 0.2% proof stress was below the range and was out of the range.

[0083] In the alloy of Example 18, since the Ti amount was lower and the Nb amount and the N amount were higher than the range and were out of the range, Nb amount in (Ti, Nb)N was higher than the range and was out of the range. Therefore, sizes of (Ti, Nb)N particles were below the range and were out of the range, and the number of particles of (Ti, Nb)N was higher than the range and was out of the range. As a result, crystal grain diameter distribution was shifted to being finer, and 0.2% proof stress was higher than the range and was out of the range.

[0084] In the alloy of Example 19, Nb amount and N amount were below the range and were out of the range. Furthermore, since annealing temperature was high, (Ti, Nb)N was coarse. Furthermore, number of particles of (Ti, Nb)N was below the range and was out of the range, crystal grain diameter distribution was shifted to coarsening, and 0.2% proof stress was below the range and was out of the range.

[0085] In the alloy of Example 20, since Ti amount was low, Nb amount in (Ti, Nb)N was higher than the range and was out of the range. Therefore, particle size of (Ti, Nb)N was below the range and was out of the range, and in addition, since C amount was relatively high, number of particles of NbC was higher and number of particles of (Ti, Nb)N was lower than the range and was out of the range. As a result, crystal grain diameter distribution was shifted to coarsening, and 0.2% proof stress was below the range and was out of the range.

[0086] In the alloy of Example 21, since Ti amount was high and Nb amount and N amount were low, Nb amount in (Ti, Nb)N was below the range and was out of the range. Size of (Ti, Nb)N particle was higher and its number of particles was below the range and was out of the range. Therefore, crystal grain diameter distribution was shifted to coarsening, and 0.2% proof stress was below the range and was out of the range.

[0087] In the alloy of Example 22, Nb amount and N amount were below the range and were out of the range, and number of particles of (Ti, Nb)N was below the range and was out of the range. As a result, crystal grain diameter distribution was shifted to coarsening, and 0.2% proof stress was below the range and was out of the range.

[0088] In the alloy of Example 23, since the N amount was higher than the range and was out of the range, the number of particles of (Ti, Nb)N was higher than the range and was out of the range. As a result, crystal grain diameter distribution was shifted to being finer, and 0.2% proof stress was higher than the range and was out of the range.

TABLE-US-00001 TABLE 1 Steel Chemical compositions mass % remainder Ni Division No. C Si Mn P S Cr Mo Al Ti Fe Nb N W V Examples  1 — 0.16 0.23 0.008 0.0008 23.06 8.32 0.120 0.68 4.33 3.11 0.012 0.08 0.02 * 2  0.012 0.12 0.13 0.012 0.0006 20.36 8.12 0.230 0.21 3.98 2.88 0.006 — —  3 0.011 0.22 0.31 0.023 0.0004 20.88 8.47 0.220 0.85 4.29 2.58 0.018 0.09 0.03  4 0.004 0.10 0.11 0.002 0.0001 22.19 9.12 0.009 0.18 3.52 3.25 0.008 — 0.10 * 5  0.009 0.15 0.12 0.003 0.0001 22.25 8.35 0.015 0.15 2.53 3.12 0.003 — —  6 0.015 0.18 0.10 0.005 0.0003 22.02 8.36 0.352 0.78 1.23 2.98 0.016 — 0.10  7 0.005 0.12 0.08 0.002 0.0004 18.89 9.28 0.238 0.34 1.35 3.02 0.009 0.02 —  8 0.006 0.14 0.09 0.011 0.0025 22.31 8.11 0.190 0.25 4.47 3.36 0.013 0.13 0.12  9 0.018 0.13 0.41 0.009 0.0004 21.98 8.09 0.260 0.12 4.67 4.81 0.012 0.06 0.09 * 10   0.007 0.15 0.12 0.003 0.0001 22.35 8.35 0.015 0.31 2.31 3.39 0.004 — — * 11   0.012 0.18 0.12 0.003 0.0002 22.25 8.36 0.019 0.41 3.61 2.91 0.002 — — * 12   0.011 0.15 0.14 0.004 0.0001 22.34 8.35 0.042 0.16 2.89 3.11 0.003 — — * 13   0.006 0.15 0.12 0.003 0.0001 22.19 8.35 0.022 0.19 2.31 3.28 0.005 — — Comparative 14 (0.025) 0.36 0.61 0.008 0.0005 23.72 8.11 0.160 0.89 4.23 3.21 0.011 0.06 0.03 Examples 15 — 0.21 0.08 0.007 0.0004 22.3 8.26 0.230 (1.52) 3.31 (5.52) 0.013 — — 16 0.019 0.15 0.10 0.006 0.0006 22.37 8.61 0.262 0.23 4.13 (5.23) 0.008 — — 17 0.005 0.13 0.09 0.012 0.0005 22.51 8.12 0.124 0.15 2.34 2.63 (0.001) 0.10 0.3 18 0.006 0.16 0.12 0.016 0.0005 22.91 8.31 0.271 (0.05) 3.82 (5.82) (0.035) — — 16 — 0.18 0.10 0.005 0.0003 22.02 8.36 0.352 0.85 1.23 (2.35) (0.001) — 0.10 20 0.017 0.13 0.11 0.024 0.0009 20.54 8.61 0.180 (0.09) 4.21 4.91 0.005 0.08 0.04 24 0.016 0.21 0.21 0.009 0.0007 21.98 8.21 0.250 (1.12) 4.95 (2.22) 0.005 — 0.01 22 — 0.15 0.33 (0.036) 0.0007 19.11 8.01 0.230 0.11 4.61 (2.30) (0.001) 0.04 0.02 23 — 0.14 0.22 0.019 0.0006 22.60 8.73 0.320 0.23 4.88 2.51 (0.029) 0.09 —

TABLE-US-00002 TABLE 2 Rolling Plate Annealing Sum of NbC Nb content in Particle Steel reduction thickness Temperature NbC (Ti, Nb)N and (Ti, Nb)N (Ti, Nb)N size Division No. % mm ° C. Particles/mm.sup.2 Particles/mm.sup.2 Particles/mm.sup.2 mass % μm Examples  1 98.0 4.0 1180  0 339  339 15 1.90 * 2  98.3 3.4 1190 19 246  265 19 1.70  3 99.0 2.0 1185 16 982  998  [4] [3.20]  4 98.5 3.0 1200  0 125  125 25 1.96 * 5  97.0 6.0 1195 10 (91) 101 38 1.50  6 97.9 4.2 1178 12 624  736  6 2.52  7 98.6 2.8 1160  0 689  689 28 2.30  8 98.3 3.4 1178  0 527  527 26 1.60  9 98.6 2.8 1185 35 511  546 [41] [0.09] * 10   98.0 4.0 1175  6 (98) 104 31 1.72 * 11   97.5 5.0 1190 28 (79) 107 18 2.33 * 12   97.5 5.0 1170 10 (90) 100 31 1.73 * 13   97.3 5.4 1180  8 (97) 105 33 1.31 Comparative 14 97.0 6.0 1175 (41) (58)  (99)  [3] [3.12] Examples 15 98.0 4.0 1180  0 (1182)  (1182)  [46] [0.06] 16 98.3 3.4 [1110] (48) (40)  (88) [42] 0.80 17 98.0 4.0 1180  0 (11)  (11) 39 1.60 18 98.7 2.6 1160 13 (2631)  (2644)  [65] [0.02] 19 97.9 4.2 [1250]  0  (3)  (3) 23 [4.50] 20 98.3 3.4 1170 (46) (43)  (89) [42] [0.03] 21 97.3 5.4 1180 16 (82)  (98)  [4] [3.30] 22 98.6 2.8 1176  0 (30)  (30) 16 1.60 23 98.6 2.8 1182  0 (2011)  (2011)  17 2.10 0.2% 1~20 20~40 40~60 60~80 80~100 100~120 120~ proof Steel (μm) (μm) (μm) (μm) (μm) (μm) (μm) stress Division No. % Mpa Examples  1 3 9 16 21 19 18 14 340 * 2  6 10  15 23 21 19  6 301  3 [12]  13  28 26 17  [4]  0 385  4 2 8 26 24 15 16  9 304 * 5  0 0 7 17 24 21 [31] 272  6 7 12  15 26 21 17  2 321  7 0 0 10 20 28 38  4 336  8 0 14  21 20 17 15 13 339  9 [12]  14  23 21 18 12  0 391 * 10   0 0 5 19 24 20 [32] 274 * 11   0 0 3 18 20 21 [38] 271 * 12   0 0 7 16 24 21 [32] 280 * 13   0 0 5 17 24 21 [33] 278 Comparative 14 0 0 8 17 18 23 [34] 267 Examples 15 [16]  [38]  28 18  [0]  [0]  0 435 16 0 0 7  [9] 16 26 [42] 250 17 0 0 0 [12] 19 26 [43] 248 18 [28]  [45]  21  [6]  [0]  [0]  0 481 19 3 6 7  [9] 19 22 [34] 251 20 0 5 8  [9] [11] 21 [46] 255 21 0 0 5 [13] 17 25 [40] 223 22 1 6 8 [10] [11] 21 [43] 266 23 [38]  [43]  13  [6]  [0]  [0]  0 443

[0089] The present invention can be used in industries having highly corrosive environments such as in chemical plants, natural gas plants, oil fields, and the like.