USE OF A TITANIUM-FREE NICKEL-CHROMIUM-IRON-MOLYBDENUM ALLOY

Abstract

An alloy with the composition (in mass-%): C: max. 0.02%; S: max. 0.01%; N: max. 0.03%; Cr: 20.0-23.0%; Ni: 39.0-44.0%; Mn: 0.4-<1.0%; Si: 0.1-<0.5%; Mo: >4.0-<7.0%; Nb: max. 0.15%; Cu: >1.5-<2.5%; Al: 0.05-<0.3%; Co: max. 0.5%; B: 0.001-<0.005%; Mg: 0.005-<0.015%; Fe: the rest, as well as smelting related impurities, is further processed as an alloyed solid in the form of wire, strip, rod or powder via the molten phase and is used in the field of wet corrosion applications in the oil and gas as well as the chemical industry.

Claims

1. A method comprising: providing an alloy with the composition (in mass-%) C max. 0.02% S max. 0.01% N max. 0.03% Cr 20.0-23.0% Ni 39.0-44.0% Mn 0.4-<1.0% Si 0.1-<0.5% Mo >4.0-<7.0% Nb max. 0.15% Cu >1.5-<2.5% Al 0.05-<0.3% Co max. 0.5% B 0.001-<0.005% Mg 0.005-<0.015% Fe the rest, as well as smelting related impurities, further processing the alloy as an alloyed solid in the form of wire, strip, rod or powder via the molten phase and using the processed alloy in the field of wet corrosion applications in the oil and gas industry or the chemical industry.

2. The method according to claim 1 with the alloy having the composition (in mass-%) C max. 0.015% S max. 0.005% N max. 0.02% Cr 21.0-<23.0% Ni >39.0-<43.0% Mn 0.5-0.9% Si 0.2-<0.5% Mo >4.5-6.5% Nb max. 0.15% Cu >1.6-<2.3% Al 0.06-<0.25% Co max. 0.5% B 0.002-0.004% Mg 0.006-0.015% Fe the rest, as well as smelting related impurities.

3. The method according to claim 1 with the alloy having the composition (in mass-%) C max. 0.010% S max. 0.005% N max. 0.02% Cr 22.0-<23% Ni >39.0-<43.0% Mn 0.55-0.9% Si 0.2-<0.5% Mo >5.0-6.5% Nb max. 0.15% Cu >1.6-<2.2% Al 0.06-<0.20% Co max. 0.5% B 0.002-0.004% Mg 0.006-0.015% Ti max. 0.10% P max. 0.025% W max. 0.50% Fe min. 22% as well as smelting related impurities.

4. The method according to claim 1, wherein the material is used as wire-like or rod-like weld filler metal for the buildup welding by means of arc or laser process.

5. The method according to claim 1, wherein the material is used as wire-like or rod-like weld filler metal for the joint welding for base metals, such as Alloy 825 or Alloy 825 CTP.

6. The method according to claim 1, wherein the material is used as wire-like or rod-like weld filler metal for the joint welding for superaustenitic steels and/or nickel-base alloys.

7. The method according to claim 1, wherein the material is processed by means of additive manufacturing by the arc, laser or electron beam welding process with the use of welding wire.

8. The method according to claim 1, wherein the material is used in the form of powder for the so-called plasma powder welding method.

9. The method according to claim 1, wherein the material is used in the form of powder for so-called additive manufacturing printing method for the manufacture of structural parts.

10. The method according to claim 1, wherein the material is used in the form of strip for the so-called electroslag and/or submerged arc welding for buildup welding or for joint welding.

11. The method according to claim 1, wherein the material is used in the form of powder for thermal spraying processes, especially the flame spraying.

12. The method according to claim 1, wherein the material is used in the form of a coated rod electrode.

13. The method according to claim 1, wherein the material is used in the form of cored wire electrodes.

Description

[0037] This objective is accomplished by the use of a titanium-free alloy with the following composition (in mass-o): [0038] C max. 0.02% [0039] S max. 0.01% [0040] N max. 0.03% [0041] Cr 20.0-23.0% [0042] Ni 39.0-44.0% [0043] Mn 0.4-<1.0% [0044] Si 0.1-<0.5% [0045] Mo >4.0-<7.0% [0046] Nb max. 0.15% [0047] Cu >1.5-<2.5% [0048] Al 0.05-<0.3% [0049] Co max. 0.5% [0050] B 0.001-<0.005% [0051] Mg 0.005-<0.015% [0052] Fe the rest, [0053] as well as smelting related impurities, [0054] which is further processed as an alloyed solid in the form of wire, strip, rod or powder via the molten phase and is used in the field of wet corrosion applications in the oil and gas as well as the chemical industry.

[0055] Advantageous further developments of the subject matter of the invention can be inferred from the dependent claims

[0056] The suitability of the Alloy 825 CTP as a weld filler metal is not described in DE 10 2014 002 402 A1 and the product forms of welding wire, welding strip and powder (for additive manufacturing, for example) are not mentioned. The new area of application is characterized in that the material is basically processed via the molten phase.

[0057] The element carbon is present as follows in the alloy: [0058] max. 0.02%

[0059] Alternatively, carbon may be limited as follows: [0060] max. 0.015% [0061] max. 0.01% [0062] <0.01%

[0063] The Chromium content lies between 20.0 and 23.0%. Preferably, Cr may be adjusted within the range of values as follows in the alloy: [0064] 20.0 to 22.0% [0065] 21.0 to 23.0% [0066] 20.5 to 22.5% [0067] 22.0 to 23.0%

[0068] The nickel content lies between 39.0 and 44.0%, wherein preferred ranges may be adjusted as follows: [0069] 39.0 to <42.0% [0070] 39.0 to <41.0% [0071] 39.0 to <40.0%

[0072] The molybdenum content lies between >4.0 and <7.0%, wherein here, depending on service area of the alloy, preferred molybdenum contents may be adjusted as follows: [0073] >5.0 to <7.0% [0074] >5.0 to <6.5% [0075] >5.5 to <6.5% [0076] >6.0 to <7.0%

[0077] The material may preferably be used for the following applications: [0078] as wire-like or rod-like weld filler metal for the joint welding for the base metal Alloy 825 or Alloy 825 CTP, [0079] as wire-like or rod-like weld filler metal for the joint welding for superaustenitic steels or nickel-base alloys, [0080] for the application known as wire arc additive manufacturing (WAAM)in other words, the manufacture of structural parts by means of arc-welding processes with the use of welding wire, [0081] in the form of powder for the so-called plasma powder welding method, [0082] in the form of powder for the so-called additive manufacturing printing method for the manufacture of structural parts, [0083] in the form of strip for the so-called electroslag and/or submerged arc welding for buildup welding or joint welding, [0084] in the form of powder for thermal spraying processes, such as flame spraying, [0085] in the form of a coated rod electrode, [0086] in the form of cored wire electrodes.

[0087] In performed hot cracking investigations, in welding tests and modeling considerations, it was surprisingly found that the hot cracking safety, i.e. the resistance of a material to the formation of solidification and remelting cracks during a molten processing of the above-mentioned material, is dramatically better than with welding wire FM 825.

[0088] The investigations by means of the Modified Varestraint Transvarestraint (MVT) hot cracking test reveal the advantages of the FM 825 CTP compared with the FM 825 due to the following result:

[0089] The MVT test is an externally stressed hot cracking test, with which specimens of the material FM 825 CTP material and specimens of the FM 825 were tested successively with an elongation energy of 7.5 kJ/cm and 14.5 kJ/cm at applied total bending strains of the respective specimens of 1%, 2% and 4%. The evaluation was based on the length of hot cracks located on the surface of the specimen in the weld metal and heat-affected zone after the test procedure. The values of the test series were then presented comparatively in a diagram, in which materials can basically be divided into three hot-cracking classes according to the determined test values (FIG. 1). Specimens of pure weld metal were used for the conducted investigations.

[0090] According to these MVT results, FM 825 welded with an elongation energy of 7.5 kJ/cm with the respective applied total bending strains of 1%, 2% and 4% lies, with the measured hot crack values (total hot crack length), in sector 2 with the interpretation tendency to hot cracking and in sector 3 with the interpretation in jeopardy of hot cracking. In the MVT tests conducted in the same way with the FM 825 CTP, all hot crack values (total hot crack lengths) lie in sector 1, which classifies the material as safe from hot cracking. Thus the MVT investigations show an unexpectedly good weldability in the form of the high hot cracking resistance of the FM 825 CTP.

[0091] The surprising results of the MVT investigations were checked, in that two plates of the Alloy 825 CTP with the batch number 130191 were welded together in the butt joint by means of the plasma welding method, wherein the following set of welding parameters was used: welding current=220 A, welding voltage=19.5 V, welding speed=30 cm/min, plasma gas flow rate=1 L/min, shielding gas flow rate=20 L/min, working distance=5 mm.

[0092] FIG. 2 shows a transverse macrosection of the welded joint. No hot cracks were found in the welded seam.

[0093] J-Mat Pro calculations were carried out for further investigation of the surprisingly good weldability. FIG. 3 shows a comparison of the solidification intervals of FM 825 CTP and of FM 825 as a function of the cooling rate. In the model, the solidification interval is an indicator of the hot-cracking susceptibility of a material and in the ideal case (for example, in the case of a pure material) is equal to 0. Since the cooling rate in welding varies greatly depending on method, structural part thickness, welding parameters, etc., the consideration not only of an individual cooling rate but also the consideration of a range of cooling rates from 0 C./s to 50 C./s is particularly informative. It is evident in FIG. 3 that a solidification interval lower by 40 C. to 70 C. was modeled for the FM 825 CTP than for the FM 825 in the entire investigated cooling rate range.

[0094] The Alloy 825 or FM 825 CTP has been melted in the following compositions:

TABLE-US-00001 Element in wt-% Mg Ca in in C S N Cr Ni Mn Si Mo Ti Nb Cu Fe Al B ppm ppm Ref 825 0.002 0.0048 0.006 22.25 39.41 0.8 0.3 3.27 0.8 0.01 2 R 0.14 0 LB2181 0.002 0.004 0.006 22.57 39.76 0.8 0.3 3.27 0.4 0.01 2.1 R 0.12 0 LB2182 0.006 0.003 0.052> 22.46 39.71 0.8 0.3 3.27 0.01 2 R 0.11 0 LB2183 0.002 0.004 0.094> 22.65 39.61 0.8 0.3 3.28 0.01 1.9 R 0.1 0 LB2218 0.005 0.0031 0.048 22.50 39.59 0.8 0.3 3.27 0.01 2 R 0.12 0.01 100 LB2219 0.005 0.0021 0.043> 22.71 39.99 0.8 0.3 4.00> 0.01 2 R 0.10 0.01 100 LB2220 0.004 0.00202 0.042> 22.56 39.84 0.8 0.33 4.93> 0.01 2 R 0.11 0 100 LB2221 0.004 0.0022 0.038> 22.43 39.66 0.8 0.3 3.74> 0.01 1.9 R 0.11 0 10 LB2222 0.003 0.0033 0.042> 22.5 39.62 0.8 0.3 3.66> 0.01 2 R 0.18 0 20 LB2223 0.002 0.0036 0.041> 22.4 39.78 0.7 0.3 3.65> 0.01 2.00 R 0.27> 0 20 LB2234 0.003 0.005 0.007 22.57 39.77 0.8 0.3 3.26 0.01 2.1 R 0.15 0 80 10 LB2235 0.003 0.0034 0.006 22.56 39.67 0.8 0.3 3.28 0.01 2.1 R 0.12 0 150 12 LB2236 0.002 0.004 0.006 22.34 39.46 0.8 0.3 3.27 0.01 2 R 0.11 0 30 42 LB2317 0.001 0.0025 0.030 22.48 40.09 0.8 0.3 4.21 0.01( 2 R 0.16 0 100 5 LB2318 0.002 0.0036 0.038> 22.76 39.77 0.8 0.3 5.20> 0.01 2.1 R 0.15 0 100 4 LB2319 0.002( 0.0039 0.043> 22.93> 39.79 0.8 0.3 6.06 0.01 2.2 R 0.12 0 100 3 LB2321 0.002 0.0051 0.040> 22.56 40.23> 0.7 0.3 6.23 0.01 2.1 R 0.10 0 100 4 132490 0.002 0.002 0.015 22.39 39.37 0.69 0.26 5.76 0.02 2.02 R 0.11 0.002 90 130191 0.005 0.002 0.032 22.28 39.19 0.71 0.27 5.88 0.06 0.02 2.05 R 0.09 0.002 110 100 169801 0.012 0.002 0.013 22.53 39.36 0.75 0.22 5.67 0.07 0.03 1.92 R 0.11 0.002 140 100 121253 0.010 0.002 0.031 22.31 39.19 0.65 0.30 5.66 0.07 0.02 1.95 R 0.18 0.002 80 100 119829 0.004 0.002 0.023 22.39 39.98 0.76 0.25 5.64 0.06 0.09 1.96 R 0.14 0.002 80 100 133253 0.005 0.002 0.222 26.69 31.49 1.44 0.01 6.46 0.01 0.01 1.21 R 0.07 0.002 20 100 116616 0.005 0.002 0.029 22.59 39.28 0.69 0.26 5.66 0.07 0.03 2.10 R 0.11 0.003 80 100

[0095] The material FM 825 CTP has been melted on a large scale as weld filler metal and has been further processed to weld filler metal, among other alternatives as welding wire with a diameter of 1.00 mm.

[0096] With the wire of the batch 132490, fully mechanized buildup welds were executed on S 355 carbon steel by means of the metal inert gas welding process (MIG method) using the pulsed arc, as illustrated in principle in FIG. 4. The following were used as the welding parameter: welding current=170 A, welding voltage=24 V, wire speed=7.4 m/min, welding speed=55 cm/min, and pure argon was used as shielding gas. The buildup welding was executed partly in 2 layers. It was shown both by means of visual inspection and by means of dye penetrant inspection that neither macroscopic nor microscopic hot cracks could be detected on the weld metal surface.

[0097] The results prove the following new findings: [0098] the FM 825 CTP may be used for the buildup welding, for example for the ends of mechanically clad pipes, [0099] the FM 825 CTP may be used as a joint welding material for the joining of Alloy 825 and/or Alloy 825 CTP structural parts, [0100] the FM 825 CTP may be used as a material for the shape-imparting buildup welding (WAAM) and in the process is more easily reprocessable than corresponding additive-manufactured structural parts of FM 625, for example, [0101] the FM 825 CTP may be used in the form of powder for the field of additive manufacturing and in the process may represent a more cost-effective, resource-saving and better mechanically post-processable alternative to FM 625, [0102] in contrast to FM 825, the titanium in FM 825 CTP is not an alloying element. Therefore shielding gases containing nitrogen (proportions) are possible for the welding and/or printing instead of the otherwise used inert gases, which reduces manufacturing costs.

LIST OF REFERENCE SYMBOLS

[0103] FIG. 1: MVT diagram with empirical sectors for evaluation of the hot cracking safety

[0104] FIG. 2: Metallographic transverse section of the plasma weld seam

[0105] FIG. 3: Solidification intervals of FM 825 CTP (Alloy 825 CTP) and FM 825 (Alloy 825) in comparison as a function of the cooling rate

[0106] FIG. 4: Schematic diagram of the test of weldability of FM 825 CTP by means of buildup welding