Method for producing a component from the semi-finished product of an nickel-chromium-aluminium alloy

Abstract

The invention relates to a method for producing a component, partially or entirely formed from a semi-finished product of a nickel-chromium-aluminium alloy, with (in wt.%) greater than 18 to 33% chromium, 1.8 to 4.0% aluminium, 0.01 to 7.0% iron, 0.001 to 0.50% silicon, 0.001 to 2.0% manganese, 0.00 to 0.60% titanium, respectively 0.0 to 0.05% magnesium and / or calcium, 0.005 to 0.12% carbon, 0.0005 to 0.050% nitrogen, 0.0001 to 0.020% oxygen, 0.001 to 0.030% phosphorus, max. 0.010% sulphur, max. 2.0% molybdenum, max. 2.0% tungsten, with the rest being greater than or equal to 50% nickel and the usual method-related impurities, wherein the component contains weld seams of the same type and / or the component is partially or entirely provided with weld seams of the same type for installation in a system, wherein, and after the welding operation, only the weld seams of the same type and the heat-affected zones undergo annealing between greater than 980 and 1250 °C for times of 0.05 minutes up to 24 hours in order to homogenise the weld seams and / or reduce stress, followed by cooling in inert protective gas or air, moving (blown) protective gas or air, with the result that the creep strength and the creep ductility of the weld seams are improved with this annealing operation, wherein the following conditions must be fulfilled: (1a): Cr + AI ≥ 28; and (2a): Fp ≤ 39.9, with (3a): Fp = Cr + 0.272*Fe + 2.36*AI + 2.22*Si + 2.48*Ti + 0.374*Mo + 0.538*W - 11.8*C, wherein Cr, Fe, AI, Si, Ti, Mo, W and C are the concentrations of the respective elements in wt.%.

Description

[0001] Process for producing a component from a semi-finished product of a nickel-chromium-aluminium alloy

[0002] The invention relates to a method for producing a component from the semi-finished product of a nickel-chromium-aluminium wrought alloy with excellent high-temperature corrosion resistance, good creep resistance and good processability.

[0003] Austenitic nickel-chromium-aluminum wrought alloys with varying nickel, chromium, and aluminum contents have long been used in furnace construction and in the chemical and petrochemical industries. These applications require good high-temperature corrosion resistance, even in carburizing atmospheres that generate metal dusting, as well as good high-temperature strength / creep resistance.

[0004] In general, it should be noted that the high-temperature corrosion resistance of the alloys listed in Table 1 increases with increasing chromium content. All of these alloys form a chromium oxide layer (Cr20s) with an underlying, more or less continuous, aluminum oxide layer (Al2O3) at the corresponding aluminum contents. Small additions of elements with a strong oxygen affinity, such as yttrium or cerium, improve oxidation resistance. The chromium content is slowly consumed over the course of use in the application to build up the protective layer. Therefore, a higher chromium content increases the service life of the material, since a higher content of the element chromium, which forms the protective layer, delays the point in time at which the chromium content falls below the critical limit and oxides other than pure chromium oxides (Cr20s), which can be, for example, iron- and nickel-containing oxides, form.High-temperature corrosion resistance can be further increased by adding aluminum and silicon. Above a certain minimum concentration, these elements form a continuous layer beneath the chromium oxide layer, thus reducing chromium consumption. In carburizing atmospheres (CO, H2, CH4, CO2, H2O mixtures with possibly other process-related non-oxidizing components), carbon can penetrate the material, potentially leading to the formation of internal carbides. These cause a loss of notched impact toughness. The melting point can also drop to very low values ​​(down to 350°C), and transformation processes can occur due to chromium depletion of the matrix.

[0005] High resistance to carburization is achieved by materials with low carbon solubility and a low carbon diffusion rate. Nickel alloys are therefore generally more resistant to carburization than iron alloys because both carbon diffusion and carbon solubility are lower in nickel than in iron. Increasing the chromium content results in greater carburization resistance through the formation of a protective chromium oxide layer, unless the oxygen partial pressure in the gas is too low to form this protective chromium oxide layer. At very low oxygen partial pressures, silicon- or aluminum-containing materials can be used, which form a layer of silicon oxide or the even more stable aluminum oxide, respectively. These form at even lower oxygen partial pressures than chromium oxide.

[0006] If the carbon activity is greater than 1 (i.e., the gas is not in equilibrium), "metal dusting" can occur in nickel, iron, or cobalt alloys. Upon contact with the gas, the alloys can absorb large amounts of carbon. The demixing processes occurring in the carbon-supersaturated alloy lead to material destruction. The alloy decomposes into a mixture of metal particles, graphite, carbides, and / or oxides. This type of material destruction occurs in the temperature range of approximately 500 to 750°C.

[0007] Typical conditions for the occurrence of metal dusting are highly carburizing CO, H2, and / or CFU gas mixtures, such as those found in ammonia synthesis, methanol plants, metallurgical processes, and also hardening furnaces. Resistance to metal dusting tends to increase with increasing nickel content of the alloy, although nickel alloys are not resistant to metal dusting.

[0008] The chromium and aluminum content have a significant influence on corrosion resistance under metal dusting conditions (see Figure 2). Nickel alloys with a low chromium content, such as Alloy 600 (N06600) (see Table 1), show comparatively high corrosion rates under metal dusting conditions. The nickel alloys Alloy 602 CA (N06025) with a chromium content of 25% and an aluminum content of 2.3%, and Alloy 690 (N06690) with a chromium content of 30% are significantly more resistant (Hermse, CGM and van Wortei, JC: Metal dusting: relationship between alloy composition and degradation rate. Corrosion Engineering, Science and Technology 44 (2009), pp. 182 - 185). Resistance to metal dusting increases with the sum of chromium and aluminum (Cr + AI).

[0009] The high-temperature strength or creep strength at the specified temperatures (approximately 500 to 750°C) is improved, among other things, by a high carbon content. High contents of solid-solution strengthening elements such as chromium, aluminum, silicon, molybdenum, and tungsten also improve the high-temperature strength or creep strength. In the range from 500 to 900°C, additions of aluminum, titanium, and / or niobium can improve the strength by precipitation of the γ' and / or γ" phases.

[0010] State-of-the-art examples of these alloys are listed in Table 1.

[0011] Alloys such as Alloy 602 CA (N06025), Alloy 693 (N06693), or Alloy 603 (N06603) have long been known for their excellent corrosion resistance compared to Alloy 600 (N06600) or Alloy 601 (N06601) due to their high aluminum content of more than 1.8%. Alloy 602 CA (N06025), Alloy 693 (N06693), Alloy 603 (N06603), and Alloy 690 (N06690) exhibit excellent carburization resistance or metal dusting resistance due to their high chromium and / or aluminum contents. At the same time, alloys such as Alloy 602 CA (N06025), Alloy 693 (N06693), or Alloy 603 (N06603) exhibit excellent high-temperature strength and creep resistance due to their high carbon and aluminum content, respectively, in the temperature range in which metal dusting occurs. Alloy 602 CA (N06025) and Alloy 603 (N06603) still exhibit excellent high-temperature strength and creep resistance even at temperatures above 1000°C. However,The high aluminum content impairs workability, with the impairment becoming more pronounced the higher the aluminum content (Alloy 693 - N06693). The same applies to a greater extent to silicon, which forms low-melting phases with nickel. In Alloy 602 CA (N06025) or Alloy 603 (N06603), cold formability is particularly limited by a high proportion of primary carbides.

[0012] WO 2013 / 182177 A1 discloses (in weight %) 24 to 33% chromium, 1.8 to 4.0% aluminum, 0.10 to 7.0% iron, 0.001 to 0.50% silicon, 0.005 to 2.0% manganese, 0.00 to 0.60% titanium, 0.0002 to 0.05% each magnesium and / or calcium, 0.005 to 0.12% carbon, 0.001 to 0.050% nitrogen, 0.0001 - 0.020% oxygen, 0.001 to 0.030% phosphorus, max. 0.010% sulfur, max. 2.0% molybdenum, max. 2.0% tungsten, balance nickel and the usual process-related impurities, where the following relationships must be met: must:

[0013] Cr + AI > 28 (2a) and

[0014] Fp < 39.9 with (3a)

[0015] Fp = Cr + 0.272*Fe + 2.36*AI + 2.22*Si + 2.48*Ti + 0.374*Mo + 0.538*W 11.8*C (4a) where Cr, Fe, AI, Si, Ti, Mo, W, and C are the concentrations of the respective elements in mass%. This nickel-chromium-aluminum alloy exhibits excellent high-temperature corrosion resistance in highly corrosive conditions, such as excellent metal dusting resistance, good corrosion resistance in air, good phase stability, good high-temperature strength, and good creep resistance, while maintaining good processability. US 6623869 B1 discloses a metallic material consisting of not more than 0.2% C, 0.01 - 4% Si, 0.05 - 2.0% Mn, not more than 0.04% P, not more than 0.015% S, 10 - 35% Cr, 30 - 78% Ni, 0.005 - 4.5% Al, 0.005 - 0.2% N, and one or both of 0.015 - 3% Cu and 0.015 - 3% Co, with the remainder being 100% iron.The value of 40Si+Ni+5AI+40N+10(Cu+Co) is not less than 50, where the element symbols represent the content of the corresponding elements in mass%. The material exhibits excellent corrosion resistance in environments where metal dusting may occur and can therefore be used for furnace pipes, piping systems, heat exchanger tubes, and similar components in petroleum refineries or petrochemical plants, significantly improving the service life and safety of the equipment.

[0016] EP 0 508 058 A1 discloses an austenitic nickel-chromium-iron alloy consisting of (in weight %) C: 0.12 - 0.3%, Cr: 23 - 30%, Fe: 8 - 11%, Al: 1.8 - 2.4%, Y: 0.01 - 0.15%, Ti: 0.01 - 1.0%, Nb: 0.01 - 1.0%, Zr: 0.01 - 0.2%, Mg: 0.001 - 0.015%, Ca: 0.001 - 0.01%, N: max. 0.03%, Si: max. 0.5%, Mn: max. 0.25%, P: max. 0.02%, S: max. 0.01%, Ni: remainder including unavoidable impurities resulting from the melting process.

[0017] Alloys for furnace construction and the petrochemical industry must be weldable for the manufacture of individual components of a plant. The individual components must also be weldable during installation into the plant. Due to their microstructure, weld seams often exhibit lower creep rupture strength and / or are prone to cracking. Heat treatment of the weld seam can improve creep rupture strength and reduce the tendency to cracking. Some examples are listed in the following state of the art.

[0018] EP 0 234 200 A1 discloses a method and apparatus for heat treating longitudinally welded pipes made of austenitic, ferritic, or austenitic-ferritic stainless steels. The pipes are annealed after welding the longitudinal seam. The method is characterized in that the pipes are solution-annealed only partially in the area of ​​the weld seam and the heat-affected zone, while the remaining areas are heat-treated at a lower temperature. For high-alloy molybdenum-containing steels, annealing is carried out at a temperature greater than 1100°C, preferably greater than 1250°C, with the annealing temperature being maintained for longer than 5 seconds, preferably approximately 25 seconds.

[0019] US 3865639 A discloses a method for producing a welded assembly whose welded parts withstand operating temperatures in the range of approximately 900 to 1050°C, wherein the parts consist of at least one high-alloy austenitic steel alloyed with chromium, nickel, and / or cobalt and containing less than 60% by weight of iron, up to 0.5% by weight of carbon, and small concentrations of additional elements such as manganese and silicon. Here, the specified parts are subjected to welding, wherein the welding results in the formation of at least one weld seam having a solidification front corresponding to a physical and chemical discontinuity in the seam. The weld seam is also made of a high-alloy austenitic steel and is then treated so that the solidification front becomes chemically homogeneous.whereby the carbides of the weld are present to a maximum extent and according to a fine, uniform distribution in the precipitated state, which results in the creep rupture strength and tensile strength of the weld being increased to values ​​that are at least approximately equal to those of the non-welded parts, by subjecting at least the weld and the adjacent areas of the welded parts to a homogenization heat treatment at a temperature between approximately 1100 to 1200°C for a period of several minutes to several hours, after which at least the weld and the adjacent areas are cooled to approximately 800°C at a temperature decrease rate of approximately 100°C / h and then by air cooling to room temperature. US 3046167 A describes a process for the heat treatment of welded, age-hardenable chromium-nickel stainless steels,to impart a high degree of ductility and toughness in the hardened state, the process comprising the successive steps of welding and converting the welded products by annealing to a structure that is essentially martensitic but contains some ferrite, followed by restoring the steel to a structure that is essentially austenitic, although it contains some ferrite. This is achieved by annealing at a temperature and for a time sufficient to re-austenitize the martensite and ferrite and to break down the original cast structure of the weld. This is followed by converting the metal back to a structure that is essentially martensitic, along with very little ferrite, and finally hardening the metal by a suitable heat treatment to a state that is essentially fully martensitic. In the processing of age-hardenable chromium-nickel stainless steel products,selected from the group of steels with an analysis of approximately 17% chromium, 7% nickel, 1% aluminum, and the balance iron; approximately 17% chromium, 4% nickel, 3% copper, and the balance iron; approximately 15% chromium, 7% nickel, 2% molybdenum, 1% aluminum, and the balance iron; and approximately 12% chromium, 8% nickel, 6% molybdenum, 1% aluminum, and the balance iron, wherein the process comprises first welding the products in a shielding gas, then converting the welded products by heating to about 760 to 954.4°C and cooling to about room temperature to -73.3°C, subsequently tempering the converted products at about 1065.6°C, then converting the products by heating and cooling as described above, and finally age hardening by heating to about 482.2 to 593.3°C.

[0020] US 4168190 A describes a method and apparatus for the local solution treatment of austenitic stainless steel which has been partially sensitized, for example, by a local temperature increase, without creating a sensitized structure at the thermal boundaries between the locally treated portion and the rest of the material, comprising the steps of: (a) rapidly heating the sensitized portions of the material to a temperature at which the carbides go into solution; and (b) rapidly quenching the heated material.

[0021] The object underlying the invention is to design a method for producing a component from the semi-finished product of a nickel-chromium-aluminium wrought alloy, wherein the component contains weld seams and / or the installation of this component in a system is carried out partially or entirely with weld seams.

[0022] This object is achieved by a method for producing a component, partially or completely from a semi-finished product of a nickel-chromium-aluminium alloy, with (in mass %) greater than 18 to 33% chromium, 1.8 to 4.0% aluminium, 0.01 to 7.0% iron, 0.001 to 0.50% silicon, 0.001 to 2.0% manganese, 0.00 to 0.60% titanium, 0.0 to 0.05% each of magnesium and / or calcium, 0.005 to 0.12% carbon, 0.0005 to 0.050% nitrogen, 0.0001 - 0.020% oxygen, 0.001 to 0.030% phosphorus, max. 0.010% sulphur, max. 2.0% molybdenum, max.2.0% tungsten, balance nickel, greater than or equal to 50% and the usual process-related impurities, whereby the component contains welds of the same type and / or the component is provided partially or completely with welds of the same type for installation in a system, whereby «ad after welding only the welds of the same type and the heat-affected zones are subjected to annealing between greater than 980 and 1250°C for times of 0.05 minutes up to 24 hours to homogenise the welds and / or to reduce stresses, followed by cooling in static shielding gas or air, moving (blown) shielding gas or air, with the result that the creep strength and creep ductility of the welds are improved by this annealing, whereby the following relationships must be satisfied:.

[0023] Cr + AI > 28 (1 a) and Fp < 39.9 with (2a)

[0024] Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti

[0025] + 0.374*Mo + 0.538*W - 11.8*C (3a) where Cr, Fe, AI, Si, Ti, Mo, W and C are the concentrations of the respective elements in mass%.

[0026] Advantageous further developments of the subject matter of the invention can be found in the associated subclaims.

[0027] Semi-finished metal products are semi-finished products such as sheets, strips, bars, forgings, pipes and wires.

[0028] A component can be assembled from two or more machined semi-finished products and / or other components. Joining can be achieved using a fusion welding process, possibly with additional filler metal. A filler metal can be added during welding, for example, via welding rods or wires.

[0029] A welding consumable of the same type has a comparable composition to one of the adjacent semi-finished products and / or components being processed. A welding consumable of the same type can also, with appropriate weld geometry, consist of a component of at least one of the adjacent semi-finished products to be welded.

[0030] The nickel-chromium-aluminum wrought alloy used in this invention, abbreviated here to Alloy NiCrAl-H, is preferably melted open in an electric furnace or arc furnace, followed by treatment in a VOD (vacuum, oxidizing, deoxidizing) or VLF (vacuum ladle furnace) system. However, melting and pouring in a vacuum is also possible. The alloy is then poured into blocks, electrodes, or as a continuous cast to form a precursor. If necessary, the precursor is then annealed at temperatures between 900 and 1270°C for 0.1 to 70 hours. Furthermore, it is possible to remelt the alloy one or more times using ESR (electro-slag remelting) and / or VAR (vacuum arc remelting). The alloy is then formed into the desired semi-finished product. For this purpose, annealing may take place at temperatures between 900 and 1270°C for 0.1 hours to 70 hours, followed by hot forming, if necessary.with intermediate annealing between 900 and 1270°C for 0.05 hours to 70 hours. If necessary, the surface of the material can be chemically and / or mechanically removed for cleaning (even several times) in between and / or after the end of the hot forming. This can then be followed by cold forming with a degree of deformation of up to 98% into the desired semi-finished product shape, if necessary with intermediate annealing between 800 and 1250°C for 0.05 minutes to 70 hours, if necessary under a protective gas such as argon or hydrogen, followed by cooling in air, in a moving annealing atmosphere or in a water bath. If necessary, this can then be followed by solution annealing in the temperature range 800 to 1250°C for 0.05 minutes to 70 hours, if necessary under a protective gas such as argon or hydrogen, followed by cooling in air, in a moving annealing atmosphere or in a water bath. If necessary, chemical and / or mechanical cleaning of the material surface can be carried out in between and / or after the final annealing.

[0031] Solution annealing preferably takes place between the following temperatures:

[0032] 1000 or > 1000 to 1200°C or < 1200°C

[0033] 1000 or > 1000 to 1175°C or < 1175°C

[0034] 025 or > 1025 to 1150°C or < 1150°C 1050 or > 1050 to 1130°C or < 1130°C 1080 or > 1080 to 1130°C or < 1130°C

[0035] Solution annealing preferably takes place in the following time ranges:

[0036] 0.05 minutes to 24 hours

[0037] 0.05 minutes to 8 hours 0.05 minutes to 4 hours 0.1 minutes to 1 hour 1 minute to 1 hour 5 minutes to 1 hour The nickel-chromium-aluminum wrought alloy (Alloy NiCrAI-H) used in this invention can be easily manufactured and used in the semi-finished forms of strip, sheet, bar, forgings, wire, longitudinally welded tube and seamless tube.

[0038] These semi-finished products are manufactured with an average grain size of 30 to 600 pm. Preferred ranges are:

[0039] 40 pm to 300 pm.

[0040] 60 pm to 300 pm.

[0041] 75 pm to 200 pm.

[0042] The parts required for the component are cut or separated from the semi-finished product, machined accordingly and then joined using a fusion welding process under protective gas.

[0043] Optionally, the fusion welding process can be one of the following processes, for example:

[0044] Tungsten inert gas welding (TIG)

[0045] Metal inert gas welding (MIG)

[0046] Metal active gas welding (MAG)

[0047] Plasma welding

[0048] Electron beam welding

[0049] Laser beam welding

[0050] Gas welding or autogenous welding

[0051] Electrode welding / manual arc welding

[0052] The protective gas can preferably be argon or argon and hydrogen or argon and nitrogen.

[0053] But submerged arc welding and other processes are also conceivable.

[0054] The welding consumable of the same type is preferably a nickel-chromium-aluminium alloy with (in mass-%) greater than 18 to 33% chromium, 1.8 to 4.0% aluminium, 0.01 to 7.0% iron, 0.001 to 0.50% silicon, 0.001 to 2.0% manganese, 0.00 to 0.60% titanium, 0.0 to 0.05% each magnesium and / or calcium, 0.005 to 0.12% carbon, 0.0005 to 0.050% nitrogen, 0.0001 - 0.020% oxygen, 0.001 to 0.030% phosphorus, max. 0.010% sulphur, max. 2.0% molybdenum, max. 2.0% tungsten, balance nickel greater than or equal to 50% and the usual process-related impurities, where the following relationships must be fulfilled:

[0055] Cr + AI > 28 (1 a) and Fp < 39.9 with (2a)

[0056] Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti

[0057] + 0.374*Mo + 0.538*W - 11.8*C (3a) where Cr, Fe, AI, Si, Ti, Mo, W and C are the concentration of the respective elements in mass%.

[0058] The following further developments of the subject matter of the invention with regard to the composition are advantageous both for the nickel-chromium-aluminium alloy Alloy NiCrAI-H from which the semi-finished product is manufactured and for the welding filler material of the same type.

[0059] The spread range for the element chromium is between 18 and 33%, with preferred ranges being set as follows:

[0060] 20 or 20 to 33 or 33%

[0061] 22 or 22 to 33 or 33%

[0062] 24 or 24 to 33 or 33%

[0063] 24 or 24 to 32 or 32%

[0064] 25 or 25 to 32 or 32%

[0065] 26 or 26 to 32 or 32%

[0066] 27 or 27 to 32 or 32%

[0067] 28 or 28 to 32 or 32%

[0068] 28 or 28 to 31 or 31%

[0069] 28 or 28 to 30 or 30% 29 or > 29 to 31 or < 31%

[0070] The aluminum content is between 1.8 and 4.0%, whereby, depending on the application of the alloy, preferred aluminum contents can be set as follows:

[0071] 1.8 or > 1.8 to < 4.0%

[0072] 1.8 or > 1.8 to 3.2 or < 3.2%

[0073] 2.0 or > 2.0 to 3.2 or < 3.2%

[0074] 2.0 or > 2.0 to 3.0 or < 3.0%

[0075] 2.0 or > 2.0 to 2.8 or < 2.8%

[0076] 2.0 or > 2.2 to 2.8 or < 2.8%

[0077] 2.0 or > 2.2 to 2.6 or < 2.6%

[0078] The iron content is between 0.01 and 7.0%, whereby, depending on the application, preferred contents can be set within the following ranges:

[0079] 0.01 to 4.0 or < 4.0%

[0080] 0.01 to 3.0 or < 3.0%

[0081] 0.01 to 2.5 or < 2.5%

[0082] 0.1 to 2.0 or < 2.0%

[0083] 0.1 to 1.0 or < 1.0%

[0084] The silicon content is between 0.001 and 0.50%. Si can preferably be adjusted within the alloy's range as follows:

[0085] 0.001 - 0.20 or < 0.20%

[0086] 0.001 - 0.10 or < 0.10%

[0087] 0.001 - 0.05 or < 0.05%

[0088] The same applies to the element manganese, which can be present in the alloy at 0.001 to 2.0%. Alternatively, the following range is also conceivable:

[0089] 0.005 to 0.50 or < 0.20%

[0090] 0.005 to 0.20 or < 0.20% 0.001 to 0.20 or < 0.20%

[0091] 0.005 to 0.10 or < 0.10%

[0092] 0.005 to 0.05 or < 0.05%

[0093] The titanium content is between 0.00 and 0.60%. Preferably, Ti can be adjusted within the alloy's range as follows:

[0094] 0.001 to 0.60 or < 0.60%

[0095] 0.001 to 0.50 or < 0.50%

[0096] 0.001 to 0.30 or < 0.30%

[0097] 0.001 to 0.25 or < 0.25%

[0098] 0.001 to 0.10 or < 0.10%

[0099] 0.001 to 0.02 or < 0.02%

[0100] 0.01 to 0.10 or < 0.10%

[0101] Magnesium and / or calcium are also present in concentrations of 0.00 to 0.05%. These elements can preferably be adjusted in the alloy as follows:

[0102] 0.00 to 0.03 or < 0.03%

[0103] 0.00 to 0.02 or < 0.02%

[0104] The alloy contains 0.005 to 0.12% carbon. This can preferably be adjusted within the alloy's spread range as follows:

[0105] 0.01 to < 0.12%

[0106] 0.01 to 0.10 or < 0.10%

[0107] 0.01 to 0.08 or < 0.08%

[0108] 0.01 to 0.05 or < 0.05%

[0109] 0.02 to 0.10 or < 0.10%

[0110] 0.03 to 0.10 or < 0.10%

[0111] This also applies to the element nitrogen, which is present in concentrations between 0.0005 and 0.05%. Preferred concentrations can be as follows:

[0112] 0.001 - 0.04%. The alloy also contains oxygen in concentrations between 0.0001 and 0.020%, particularly 0.0001 to 0.010%.

[0113] The alloy also contains phosphorus in concentrations between 0.001 and 0.030%. Preferred concentrations can be as follows:

[0114] 0.001 - 0.020%

[0115] The element sulfur is present in the alloy as follows: max. 0.010 %

[0116] Molybdenum and tungsten are present individually or in combination in the alloy at a maximum content of 2.0% each. Preferred contents can be as follows:

[0117] Mo max. 1.0%

[0118] W max. 1 .0 %

[0119] Mo max. < 1.0%

[0120] W max. < 1 .0 %

[0121] Mo max. < 0.50%

[0122] W max. < 0.50%

[0123] Mo max. < 0.10%

[0124] W max. < 0.10%

[0125] Mo max. < 0.05%

[0126] W max. < 0.05%

[0127] Nickel is the remainder. Preferably, the remainder can be specified as follows:

[0128] > 50% or > 50%

[0129] > 55% or > 55%

[0130] > 60% or > 60%

[0131] > 65% or > 65%

[0132] > 67 % or > 67 % For highly corrosive conditions, but especially for good metal dusting resistance, it is advantageous if the following relationship between Cr and Al is fulfilled:

[0133] Cr + AI > 28 (1 a) where chromium and aluminium represent the concentration of the respective elements in

[0134] Mass%. Preferred ranges can be set with:

[0135] Cr + AI > 29 (1 b)

[0136] Cr + Al > 30 (1 c)

[0137] Cr + AI > 31 (1 d)

[0138] In addition, the following relationship must be fulfilled to ensure sufficient phase stability:

[0139] Fp < 39.9 with (2a)

[0140] Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti

[0141] + 0.374*Mo + 0.538*W - 11.8*C (3a) where Cr, Fe, AI, Si, Ti, Mo, W and C are the concentrations of the respective elements in mass%.

[0142] Preferred ranges can be set with: Fp < 38.4 (2b)

[0143] Fp < 36.6 (2c)

[0144] Optionally, the element niobium can be adjusted in the alloy in contents of 0.0 to 1.10%. Preferably, niobium can be adjusted in the alloy within the spread range as follows: 0.001 to < 1.10% 0.001 to 1.0 or < 1.0% 0.001 to 0.70 or < 0.70% 0.001 to 0.50 or < 0.50% 0.001 to 0.30 or < 0.30% 0.01 to 0.30 or < 0.30% If niobium is present in the alloy, formula (3a) must be supplemented by a term with niobium as follows:

[0145] Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti

[0146] + 1 ,26*Nb + 0.374*Mo + 0.538*W - 11 ,8*0 (3b) where Cr, Fe, AI, Si, Ti, Nb, Mo, W and C are the concentrations of the respective elements in mass%.

[0147] The zirconium content can optionally be between 0.0 and 0.20%. Preferably, zirconium can be adjusted within the alloy's range as follows:

[0148] 0.0 to 0.15 or < 0.15%

[0149] 0.0 to 0.10 or < 0.10%

[0150] 0.001 to 0.07 or < 0.07%

[0151] 0.001 to 0.04 or < 0.04% 0.01 to 0.04 or < 0.04%

[0152] Optionally, the element yttrium can be adjusted in the alloy in contents of 0.0 to 0.20%. Preferably, yttrium can be adjusted in the alloy within the spread range as follows: 0.0 to 0.15 or < 0.15% 0.0 to 0.10% or < 0.10% 0.0 to 0.08 or < 0.08% 0.001 to < 0.045% 0.01 to 0.04 or < 0.04%

[0153] Optionally, the element lanthanum can be adjusted in the alloy in contents of 0.0 to 0.20%. Preferably, lanthanum can be adjusted in the alloy within the spread range as follows: 0.0 to 0.15 or < 0.15% 0.0 to 0.10 or < 0.10% 0.0 to 0.08 or < 0.08% 0.001 to 0.04 or < 0.04% 0.01 to 0.04 or < 0.04%

[0154] Optionally, the element cerium can be adjusted in the alloy in amounts ranging from 0.0 to 0.20%. Preferably, cerium can be adjusted in the alloy within the range as follows:

[0155] 0.0 to 0.15 or < 0.15%

[0156] 0.0 to 0.10% or < 0.10%

[0157] 0.0 to 0.08 or < 0.08%

[0158] 0.001 to 0.04 or < 0.04%

[0159] 0.01 to 0.04 or < 0.04%

[0160] Optionally, cerium mischmetal can also be used with simultaneous addition of cerium and lanthanum in concentrations of 0.0 to 0.20%. Preferably, cerium mischmetal can be adjusted within the alloy's spread range as follows:

[0161] 0.0 to 0.15 or < 0.15%

[0162] 0.0 to 0.10% or < 0.10%

[0163] 0.0 to 0.08 or < 0.08%

[0164] 0.001 to 0.04 or < 0.04%

[0165] 0.01 to 0.04 or < 0.04%

[0166] Optionally, the element hafnium can be added to the alloy in amounts ranging from 0.0 to 0.20%. Hafnium can preferably be added to the alloy within the range as follows:

[0167] 0.0 to 0.15 or < 0.15%.

[0168] 0.0 to 0.10 or < 0.10%.

[0169] 0.001 to 0.07 or < 0.07%.

[0170] 0.001 to 0.04 or < 0.04%

[0171] 0.01 to 0.04 or < 0.04%.

[0172] Optionally, the alloy may also contain 0.001 to 0.60% tantalum. Preferred tantalum contents can be as follows: 0.001 to 0.50 or < 0.50%

[0173] 0.001 to 0.40 or < 0.40%

[0174] 0.001 to 0.30 or < 0.30%

[0175] 0.001 to 0.20 or < 0.30%

[0176] 0.001 to 0.10 or < 0.10%

[0177] 0.01 to 0.10 or < 0.10%

[0178] Optionally, the element boron can be included in the alloy as follows:

[0179] Boron 0.0001 - 0.008%

[0180] Preferred levels can be as follows:

[0181] Boron 0.0005 - 0.008%

[0182] Boron 0.0005 - 0.004%

[0183] Furthermore, the alloy can contain between 0.0 and 5.0% cobalt, which can be further limited as follows:

[0184] 0.01 to 5.0 or < 5.0%

[0185] 0.01 to 2.0 or < 2.0%

[0186] 0.1 O to 2.0 or < 2.0%

[0187] 0.01 to 0.5 or < 0.5%

[0188] 0.01 to 0.1 or < 0.1%

[0189] Furthermore, the alloy can optionally contain a maximum of 0.5% copper.

[0190] The copper content can also be limited as follows:

[0191] Cu max. < 0.20 or 0.20%

[0192] Cu max. < 0.10 or 0.10%

[0193] Cu max. < 0.05 or 0.05%

[0194] Cu max. < 0.015%

[0195] If copper is present in the alloy, the formula (3a) must be supplemented with a copper term as follows: Fp = Cr + 0.272*Fe + 2.36*AI + 2.22*Si + 2.48*Ti

[0196] + 0.477*Cu + 0.374*Mo + 0.538*W - 11.8*C (3c) where Cr, Fe, Al, Si, Ti, Cu, Mo, W and C are the concentrations of the respective elements in mass%.

[0197] If niobium and copper are present in the alloy, formula (3a) must be supplemented with a term containing niobium and a term containing copper as follows:

[0198] Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti

[0199] + 1 ,26*Nb + 0.477*Cu + 0.374*Mo + 0.538*W - 11 ,8*C (3d) where Cr, Fe, AI, Si, Ti, Nb, Cu, Mo, W and C are the concentrations of the respective elements in mass%.

[0200] Furthermore, the alloy can optionally contain a maximum of 0.5% vanadium.

[0201] The vanadium content can also be limited as follows:

[0202] V max. < 0.10%

[0203] Finally, the elements lead, zinc and tin may be present as impurities in the following amounts:

[0204] Lead max. 0.002%

[0205] Zinc max. 0.002%

[0206] Tin max. 0.002%

[0207] Weld seams and heat-affected zones can be annealed using heating mats, infrared radiators, lasers, or inductive electrical heating, among other methods. Optionally, parts of the remaining structure can be cooled simultaneously.

[0208] It is also possible, after welding, to subject the entire component with the identical welds to annealing at between 980 and 1250°C for periods of 0.05 minutes to 24 hours in order to homogenise the welds and / or to reduce stresses, followed by cooling in static shielding gas or air, moving (blown) shielding gas or air, with the result that this annealing (if necessary after solution annealing of the semi-finished product) improves the creep strength and creep ductility of the identical welds.

[0209] Furthermore, after welding and homogenizing the welds of the same type, it is possible to repeat this annealing either by annealing the entire component, including the welds, or by annealing only the welds of the same type and the heat-affected zones. This can be done either by annealing the entire component, including the welds of the same type, or by annealing only the welds of the same type and the heat-affected zones. The order of partial annealing of only the welds of the same type and the heat-affected zones and the annealing of the entire component is arbitrary.

[0210] Annealing after welding preferably takes place between the following temperatures:

[0211] 1000 or > 1000 to 1200 or < 1200 °C

[0212] 1000 or > 1000 to 1175 or < 1175 °C

[0213] 1025 or > 1025 to 1150 or < 1150 °C

[0214] 1050 or > 1050 to 1130 or < 1130 °C

[0215] 1080 or > 1080 to 1130 or < 1130 °C

[0216] Annealing after welding preferably takes place in the following time ranges: 0.05 minutes to 16 hours 0.05 minutes to 8 hours 0.05 minutes to 4 hours 0.1 minutes to 1 hour 1 minute to 1 hour

[0217] 5 minutes to 1 hour The shielding gas for annealing after welding can preferably consist of the following gases, if not in air:

[0218] argon

[0219] Argon-air mixtures

[0220] hydrogen

[0221] Argon - hydrogen mixtures

[0222] Argon-nitrogen mixtures

[0223] The improvement in creep strength and creep ductility of the same type of welds occurs particularly in the area of ​​the y'-joint, which covers the temperature range less than or equal to 750°C.

[0224] After annealing the component with the same type of welds, or after annealing only the same type of welds and the heat-affected zones of the component, or the same type of welds and the heat-affected zones from installation in the system, the surface can be cleaned or machined by brushing, pickling, blasting, grinding, turning, peeling, and / or milling. One or more of these processes can optionally be performed after welding. Material-removing machining after the final annealing by grinding, turning, peeling, or milling improves the corrosion resistance, particularly the metal dusting resistance, of the annealed surfaces, especially the welds and heat-affected zones.

[0225] After grinding the weld seam and the heat-affected zone, it is advantageous to achieve roughness values ​​Ra of 0.01 to 15 pm, as this improves the corrosion resistance and in particular the metal dusting resistance and brings it almost to the value of the base material.

[0226] The components manufactured according to the invention are preferably intended for use in areas where highly corrosive conditions prevail, such as highly carburizing conditions and atmospheres that generate metal dusting, such as components in the petrochemical industry. They are also suitable for furnace construction.

[0227] Examples:

[0228] Manufacturing a component from semi-finished product

[0229] Figure 1a on the left shows sketches of the semi-finished products in the form of sheet metal (1), strip (2), bar (3), tube (4), wire or welding filler in wire form (5) in plan view and cross-section. Figure 1a on the right shows an example of how a product or preliminary product (7) is created, for example by cutting out and chamfering two components (1a, 1b) from the semi-finished sheet metal (ii) and then joining them by fusion welding (iii) with a welding filler in the form of wire (5) by means of a V-seam (6a) (iv). Figure 1b on the left shows a further example of the creation of a product or preliminary product (7), for example by cutting out and chamfering two tube components (4a, 4b) from the semi-finished tube (ii) and then joining them by fusion welding (iii) with a welding filler in the form of wire (5) by means of a V-seam (6b) (iv). Figure 1 b middle shows another example of the creation of a product or pre-product (7), in which a sheet metal semi-finished product ora hole is milled (ii) into a sheet metal component (1c), a semi-finished pipe or a pipe component (3c) is inserted into this hole and is inserted (iv) by fusion welding (iii) with a welding filler in the form of wire (5) by means of a fillet weld (6c). Figure 1b right shows a further example of the creation of a product or a pre-product (7), in which two strip sections (2a, 2b) (ii) cut out of the semi-finished strip, which have been machined to fit with the edges, are butt-joined (6d) (iv) by fusion welding (iii) with part of the edges as a welding filler (9).

[0230] Tests performed:

[0231] The equilibrium phases occurring for the various alloy variants were calculated using Thermotech's JMatPro program. The Thermotech TTNI7 database for nickel alloys was used as the data basis for the calculations.

[0232] Creep strength is determined in a continuous uniaxial creep test with strain measurement under tensile stress according to DIN EN ISO 204. For this purpose, the specimen is mounted in a creep testing machine and loaded with a constant test force. The fracture time tu and the creep elongation Au are measured. b The fracture time is a measure of creep strength, and the creep elongation is a measure of creep ductility. The tests were carried out on round specimens with a diameter of 10 mm in the measuring range and an initial reference length L r o of 50 mm. Sampling was carried out transversely to the forming direction of the semi-finished product.

[0233] Description of the properties

[0234] The nickel-chromium-aluminum alloy Alloy NiCrAI-H used in this invention has, in addition to excellent corrosion resistance in highly corrosive conditions, for example, excellent “metal dusting” resistance, good phase stability and creep resistance.

[0235] Phase stability

[0236] In the nickel-chromium-aluminum-iron system with additions of titanium and / or niobium, depending on the alloy content, various embrittling TCP phases (topologically closed packed phases) can form, such as the Laves, sigma, or p-phase, or even the embrittling r| or s-phase. Calculations of the equilibrium phase fractions as a function of temperature, e.g., for N06690, batch 111389 (see Table 2 for the compositions used here), mathematically show the formation of α-chromium (BCC phase in Figure 3) in large quantities below 720°C (Ts BCC). Since this phase is analytically very different from the base material, its formation is generally hampered. However, if the formation temperature Ts BCC of this phase is very high, it can certainly occur, as described, for example, in “E. Slevolden, JZ Albertsen. II. Fink, “Tjeldbergodden Methanol Plant: Metal Dusting Investigations,” Corrosion / 2011 , paper no. 11144 (Houston, TX: NACE 2011 ), p.15" for a variant of Alloy 693 UNS 06693. Figure 4 and Figure 5 show the phase diagrams of the Alloy 693 variants (from US 4882125; Table ) Alloy 3 and Alloy 10 from Table 2 respectively. This phase is brittle and leads to undesirable embrittlement of the material. Alloy 3 has a formation temperature TS BCC of 1079°C and Alloy 10 of 939°C. In "E. Slevolden, JZ Albertsen. U. Fink, Tjeldbergodden Methanol Plant: Metal Dusting Investigations," Corrosion / 2011 , paper no. 11144 (Houston, TX: NACE 2011 ), p. 15" does not describe the exact analysis of the alloy in which a-chromium (BCC) occurs. However, it can be assumed that a-chromium (BCC phase) can form among the examples or analyses listed in Table 2 for Alloy 693, which mathematically have the highest formation temperatures TS BCC (such as Alloy 10). In a corrected analysis (with a reduced formation temperature Ts BCC), "E. Slevolden, JZ Albertsen. U.Fink, Tjeldbergodden Methanol Plant: Metal Dusting Investigations," Corrosion / 2011, paper no. 11144 (Houston, TX: NACE 2011), p. 15" a-chromium is then only observed near the surface. To avoid the occurrence of such an embrittling phase, the formation temperature Ts BCC for the nickel-chromium-aluminum alloy (Alloy NiCrAl-H) used in this invention should be less than or equal to 939°C - the lowest formation temperature Ts BCC among the examples for Alloy 693 in Table 2 (from US 4882125 Table 1).

[0237] This is especially the case if the following formula is fulfilled:

[0238] Fp < 39.9 with (2a)

[0239] Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti +1.26*Nb + 0.477*Cu

[0240] + 0.374*Mo + 0.538*W - 11.8*C (3d) where Cr, Al, Fe, Si, Ti, Nb, Cu, Mo, W, and C are the concentrations of the respective elements in mass%. Table 2 with the alloys shows that Fp is greater than 39.9 for Alloy 8, Alloy 3, and Alloy 2, and exactly 39.9 for Alloy 10. For all other alloys, TS BCC is less than 939°C, and thus Fp < 39.9. Example of the production of welded components and their properties

[0241] Tables 3a and 3b show the analyses of industrially melted batches of Alloy NiCrAl-H alloys used in this invention, from which sheets and welding rods were manufactured. These batches satisfy the formula (2a) Al + Cr > 28, thus meeting the requirement for metal dusting resistance. For the compositions in Tables 3a and 3b, the Fp value was also calculated according to formula (3a). Fp is less than 39.9, as required.

[0242] These batches were open-melted in quantities of 16 t, followed by treatment in a VOD plant. Electrodes were then cast and ESR remelted. The alloy was then annealed at temperatures between 900 and 1270°C for 0.1 to 70 hours and hot-formed, with intermediate annealings between 900 and 1270°C for 0.1 to 70 hours. Hot-rolled sheets with thicknesses of 25 and 16 mm were produced from batch 319144. Hot-rolled wire was produced from batch 318385. After hot rolling, the sheets were solution-annealed at 1100°C for 40 minutes and then cooled in air. They were then blasted, pickled, and ground to remove the oxide layer. The 25 mm thick sheets had a grain size of approximately 89 pm, while the 16 mm thick sheets had a grain size of approximately 82 pm. The 25 mm and 16 mm sheets therefore have a comparable grain size.The wire rod was also blasted, pickled, and ground, and then cold drawn to final thickness with intermediate annealings between 800 and 1250°C for 0.05 minutes to 70 hours. The wire is then solution annealed in hydrogen in the temperature range of 800 to 1250°C for 0.05 minutes to 70 hours and processed into welding rods with diameters of 2.0 and 2.4 mm.

[0243] Sheet sections were cut from the 25 mm thick solution-annealed semi-finished sheet, which were then annealed at 980°C for 3 hours, followed by air cooling. Samples for creep rupture tests were made from the solution-annealed and additionally annealed sheets or sheet sections, respectively, in a transverse direction. The results of the creep rupture tests according to DIN EN ISO 204 are shown in Table 5.

[0244] Sheet sections measuring 150 x 500 mm were cut from the 16 mm thick semi-finished sheet. Two sections each were welded with a 70° V-seam using manual TIG welding under pure argon, using 2.0 and 2.4 mm thick filler metals from batch 318385 as filler metal, and the welding parameters specified in Table 4. The weld seam and the heat-affected zone were brushed immediately after welding. Some sections of the welded sheets produced in this way were annealed at 980°C for 3 hours followed by air cooling, others at 1100°C for 40 minutes followed by air cooling, and still others at 1100°C for 3 hours followed by air cooling. Some were not annealed. Seams or seam sections were also produced that were ground or not post-treated at all. From the welded sheets or the welded and annealed sheets orSamples for creep tests were prepared from sheet sections perpendicular to the weld seam. The results of the creep tests according to DIN EN ISO 204 are shown in Table 5.

[0245] Table 5 shows that in creep tests at 600°C, an additional annealing at 980°C for 3 hours followed by air cooling (specimen 19 45B or 19 46B) of a solution-annealed sheet results in a reduction in the fracture time tu compared to the solution-annealed sheet only (specimen 19 23B or 19 7B). A creep test (specimen 302W or 303W) across the weld seam without further annealing (state of the art T) also shows a significantly reduced fracture time tu compared to a creep test on the solution-annealed sheet only. An additional annealing of the welded section from which the creep rupture specimens are made at 980°C for 3 hours followed by air cooling (specimen 247W and 249W) has no noticeable effect on the fracture time tu, but reduces the creep elongation Au bIn contrast, an additional annealing according to the invention of the welded section from which the creep rupture specimens are made at 1100°C for 40 minutes followed by air cooling (specimen 250W and 503W) produces a significant increase in the fracture time tu by a factor of approximately 3 as well as an increase in the creep elongation Au b partially exceeds the value of the samples not annealed after welding (specimen 302W and 303W, respectively). In particular, an additional annealing according to the invention of the welded section from which the creep rupture specimens are made at 1100°C for 3 hours followed by air cooling (specimen 511W and 506W, respectively) produces a further increase in the fracture time tu and an increase in the creep rupture strain Au. b almost to the value of the creep test on the only solution-annealed non-welded sheet (sample 19 23B or 19 7B).

[0246] At 700°C, a creep test (sample 306W) across the weld seam without further annealing (state of the art T), as at 600°C, shows a reduced fracture time tu compared to the creep test on the only solution-annealed sheet (sample 30 34B). An additional annealing of the welded section from which the creep rupture specimens are made at 980°C for 3 hours followed by air cooling (sample 248W) again produces a slight reduction in the fracture time tu compared to the sample 306W, which was not annealed after welding. In contrast, an additional annealing according to the invention of the welded section from which the creep rupture specimens are made at 1100°C for 40 minutes followed by air cooling (sample 251W) produces an increase in the fracture time tu by a factor of approximately 2 as well as an increase in the creep elongation Au. bsignificantly higher than the value of the sample not annealed after welding (306W). In particular, an additional annealing according to the invention of the welded section from which the creep rupture specimens are made at 1100°C for 3 hours followed by air cooling (sample 253W) produces a further increase in the fracture time tu beyond the fracture time of the creep test on the solution-annealed sheet only. At 800°C, an additional annealing at 980°C for 3 hours followed by air cooling (sample 19 49B) of a solution-annealed sheet produces a similar fracture time tu compared to the solution-annealed sheet only (sample 19 22B). A creep test (sample 309W) across the weld seam without further annealing (state of the art T) also has a similar fracture time tu compared to the creep test on the only solution annealed sheet (sample 19 22B).An additional annealing of the welded section from which the creep rupture specimens are made at 1100°C for 40 minutes followed by air cooling (sample 519W) also produces a similar fracture time tu compared to the creep rupture test on the only solution annealed sheet (sample 19 22B).

[0247] This means that heat treatment of the weld seam after welding at 1100°C for at least 40 minutes significantly improves the fracture time and creep rupture elongation of a creep test specimen perpendicular to the weld seam at temperatures of 600 and 700°C, and thus in the y'-formation range. At higher temperatures above the y'-solvus temperature, the unannealed weld seam has a similar to better fracture time tu compared to the solution-annealed sheet. Annealing the weld seam of the same type only has an insignificant effect on the fracture time at service temperatures above the y'-solvus temperature.

[0248] The claimed limits for the process and the nickel-chromium-aluminium alloy Alloy NiCrAI-H used in this invention can therefore be justified in detail as follows:

[0249] If the chromium content is too low, the chromium concentration below the oxide layer drops very quickly below the critical limit when the alloy is used in a corrosive atmosphere, meaning that a continuous chromium oxide layer can no longer form. 18% chromium is therefore the lower limit for chromium. Excessively high chromium contents impair the phase stability of the alloy, particularly at high aluminum contents of > 1.8%. 33% chromium is therefore the upper limit. The formation of an aluminum oxide layer below the chromium oxide layer reduces the oxidation rate. Below 1.8% aluminum, the aluminum oxide layer is too patchy to be fully effective. Excessively high aluminum contents impair the processability of the alloy. An aluminum content of 4.0% is therefore the upper limit.

[0250] The cost of the alloy increases with a reduction in iron content. Below 0.01%, costs increase disproportionately, as special starting materials are required. Therefore, 0.01% iron is considered the lower limit for cost reasons. As the iron content increases, phase stability (formation of embrittling phases) decreases, especially at high chromium and aluminum contents. Therefore, 7% iron is a reasonable upper limit to ensure phase stability of the alloy according to the invention.

[0251] Silicon is required in the production of the alloy. Therefore, a minimum content of 0.001% is required. Excessively high levels impair processability and phase stability, especially with high aluminum and chromium contents. The silicon content is therefore limited to 0.50%.

[0252] A minimum manganese content of 0.001% is required to improve processability. Manganese is limited to 2.0% because this element reduces oxidation resistance.

[0253] Titanium increases high-temperature strength. Oxidation resistance can deteriorate at 0.60% and above, which is why 0.60% is the maximum value.

[0254] Even very low magnesium and / or calcium contents improve processing by binding sulfur, thus preventing the formation of low-melting NiS eutectics. At excessively high contents, intermetallic Ni-Mg or Ni-Ca phases can occur, which significantly impair processability. The magnesium and / or calcium content is therefore limited to a maximum of 0.05%. A minimum carbon content of 0.005% is necessary for good creep resistance. Carbon is limited to a maximum of 0.12%, as above this content, this element reduces processability due to the excessive formation of primary carbides.

[0255] A minimum nitrogen content of 0.0005% is required, which improves the material's processability. Nitrogen is limited to a maximum of 0.05% because this element reduces processability by forming coarse carbonitrides.

[0256] The oxygen content must be < 0.020% to ensure the alloy's manufacturability. Too low an oxygen content increases costs. Therefore, the oxygen content should be > 0.0001%.

[0257] The phosphorus content should be less than or equal to 0.030%, as this surfactant impairs oxidation resistance. Too low a phosphorus content increases costs. Therefore, the phosphorus content should be > 0.001%.

[0258] Sulfur levels should be kept as low as possible, as this surfactant impairs oxidation resistance. Therefore, a maximum of 0.010% sulfur is specified.

[0259] Molybdenum is limited to a maximum of 2.0%, as this element

[0260] Oxidation resistance reduced.

[0261] Tungsten is limited to a maximum of 2.0%, as this element

[0262] Oxidation resistance is also reduced.

[0263] Nickel is the remaining element. Too little nickel reduces phase stability, especially with high chromium contents. Therefore, nickel must be greater than or equal to 50%. For highly corrosive conditions, but especially for good metal dusting resistance, it is advantageous if the following relationship between Cr and Al is met:

[0264] Cr + Al > 28 (1 a) where Cr and Al are the concentrations of the respective elements in mass%. Only then is the content of oxide-forming elements high enough to ensure sufficient metal dusting resistance.

[0265] In addition, the following relationship must be fulfilled to ensure sufficient phase stability:

[0266] Fp < 39.9 with (2a)

[0267] Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti

[0268] + 0.374*Mo + 0.538*W - 11.8*C (3a) where Cr, Fe, Al, Si, Ti, Mo, W, and C are the concentrations of the respective elements in mass%. The limits for Fp and the possible inclusion of additional elements have been explained in detail in the previous text.

[0269] If necessary, oxidation resistance can be further improved by adding oxygen-affine elements such as yttrium, lanthanum, cerium, cerium mischmetal, zirconium, and hafnium. These elements are incorporated into the oxide layer and block the oxygen diffusion pathways at the grain boundaries.

[0270] Yttrium increases oxidation resistance. The upper limit is determined by

[0271] For cost reasons, the rate is set at 0.20%.

[0272] Lanthanum increases oxidation resistance. The upper limit is determined by

[0273] For cost reasons, the rate is set at 0.20%.

[0274] Cerium increases oxidation resistance. The upper limit is set at 0.20% for cost reasons. Cerium Mischmetall increases oxidation resistance. The upper limit is set at 0.20% for cost reasons.

[0275] Niobium can be added if necessary, as it also increases high-temperature strength. Higher contents significantly increase costs. The upper limit is therefore set at 1.10%.

[0276] If necessary, the alloy can also contain tantalum, as tantalum also increases high-temperature strength and oxidation resistance. Higher contents significantly increase costs. The upper limit is therefore set at 0.60%. A minimum content of 0.001% is required to achieve an effect.

[0277] If desired, the alloy can also contain zirconium. Zirconium increases high-temperature strength and oxidation resistance. For cost reasons, the upper limit is set at 0.20% zirconium.

[0278] If desired, the alloy can also contain hafnium. Hafnium increases high-temperature strength and oxidation resistance. For cost reasons, the upper limit is set at 0.20% hafnium.

[0279] If necessary, boron can be added to the alloy, as it improves creep resistance. Therefore, a minimum content of 0.0001% should be present. At the same time, this surfactant impairs oxidation resistance. Therefore, a maximum of 0.008% boron is specified.

[0280] Cobalt can be present in this alloy in up to 5.0%. Higher contents significantly reduce oxidation resistance.

[0281] Copper is limited to a maximum of 0.5% because this element reduces oxidation resistance. Vanadium is limited to a maximum of 0.5% because this element reduces oxidation resistance.

[0282] Lead is limited to a maximum of 0.002% because this element reduces oxidation resistance. The same applies to zinc and tin.

[0283] Grain sizes that are too small, less than 30 pm, lead to poor creep resistance at higher temperatures. Grain sizes that are too large, greater than 600 pm, lead to very low creep ductility at temperatures in the γ' formation range.

[0284] Homogenization of similar welds and / or to reduce stresses by further annealing between greater than 980 and 1250°C for times from 0.05 minutes up to 24 hours, followed by cooling in static shielding gas or air, moving (blown) shielding gas or air, improves the creep strength and creep ductility of the welds in the y' formation area. At a temperature that is less than or equal to 980°C, the temperature is too low, so that homogenization cannot be carried out economically due to the long times required. At a temperature significantly above solution annealing, noticeable grain growth occurs, which reduces the high-temperature strength at low temperatures as well as the elongation in the creep rupture test in the y' formation area. Short times below 0.05 minutes are insufficient even at very high temperatures. Times longer than 24 hours are uneconomical, especially for larger components.

[0285] Annealing under protective gas reduces oxidation of the material during annealing and thus material loss.

[0286] Fig. 1 a: Left: Sketches in plan view and cross section of the semi-finished forms sheet 1 , strip 2, rod 3 tube 4, and wire or welding filler in wire form 5. Right: Example of production of a component 7 by chamfering two sheets 1a, 1 b and joining by fusion welding with a welding filler in wire form 5 by means of a V-seam 6a.

[0287] Fig. 1 b: Example of the production of components 7. Left: Chamfering of two pipes at one end 4a, 4b and joining by fusion welding with a wire-shaped welding filler metal 5 using a V-seam 6b. Middle: Milling of a hole in a sheet 1 c and inserting and joining of a pipe 4c by fusion welding with a wire-shaped welding filler metal 5 using a fillet weld 6c. Right: Joining of two strip sections 2a, 2b with the edges machined to fit with a part of the edges as welding filler metal 9 butt-jointed by fusion welding 6d.

[0288] Fig. 2: Metal loss due to metal dusting as a function of the aluminum and

[0289] Chromium content in a highly carburizing gas with 37% CO, 9% H2O, 7% CO2, 46% H2 and the following activities a c = 163 and p(Ü2) = 2.5 10- 27. (from (Hermse, CGM and van Wortei, JC: Metal dusting: relationship between alloy composition and degradation rate. Corrosion Engineering, Science and Technology 44 (2009), p. 182 - 185).

[0290] Fig. 3: Quantitative proportions of the phases in thermodynamic equilibrium in

[0291] Temperature dependence of Alloy 690 (N06690) using batch 111389 as an example.

[0292] Fig. 4: Quantitative proportions of the phases in thermodynamic equilibrium in

[0293] Dependence on temperature of Alloy 693 (N06693) using Alloy 3 from Table 2 as an example. Fig. 5: Quantities of the phases in thermodynamic equilibrium in

[0294] Temperature dependence of Alloy 693 (N06693) using Alloy 10 as an example from Table 2.

[0295] Table 1: Some alloys according to ASTM B 168-11. All values ​​in mass%.

[0296] Table 2: Compositions of some alloys according to ASTM B 168-11. All values ​​are in mass %.

[0297] *) Alloy composition from patent US 4,88,125 Table 1.

[0298] Table 3a: Composition of the industrially melted batches (G) of the nickel-chromium-aluminum alloy Alloy NiCrAl-H used in this invention, Part 1. All values ​​are in mass %. (H: Examples of the nickel-chromium-aluminum alloy Alloy NiCrAl-H used in this invention, G: industrially melted)

[0299] Table 3b: Composition of the industrially melted batches (G) of the nickel-chromium-aluminium alloy Alloy NiCrAI-H, Part 2, used in this invention. All values ​​are in mass% (for all alloys: Pb: max. 0.002%, Zn: max. 0.002%, Sn: max. 0.002%; meaning of H, G: see Table 3a).

[0300] Table 4: Welding parameters for welding the 16 mm thick sheets (batch 319144) with welding rods from batch 318385, the nickel-chromium-aluminium alloy Alloy NiCrAI-H used in this invention.

[0301] Table 5: Results of the creep tests according to DIN EN ISO 204 on i) 25 mm thick solution-annealed sheets (1100°C / 40 min / LK, grain size 89 pm) of batch 319144 (BM) and ii) 16 mm thick solution-annealed sheets (1100°C / 40 min / LK, grain size 82 pm) of batch 319144 (S) welded with welding rods from batch 318385. LK

[0302] = Air cooling.*) Fracture at the shoulder, not measurable. **) Testing is still in progress. E = According to the invention; T = State of the art.

Claims

Patent claims 1. A process for manufacturing a component, produced partly or entirely from a semi-finished product of a nickel-chromium-aluminum alloy, with (in mass %) greater than 18 to 33% chromium, 1.8 to 4.0% aluminum, 0.01 to 7.0% iron, 0.001 to 0.50% silicon, 0.001 to 2.0% manganese, 0.00 to 0.60% titanium, 0.0 to 0.05% magnesium and / or calcium each, 0.005 to 0.12% carbon, 0.0005 to 0.050% nitrogen, 0.0001 to 0.020% oxygen, 0.001 to 0.030% phosphorus, max. 0.010% sulfur, max. 2.0% molybdenum, max.2.0% tungsten, balance nickel greater than or equal to 50% and the usual process-related impurities, wherein the component contains identical welds and / or the component is partially or completely provided with identical welds for installation in a system, wherein after welding only the identical welds and the heat-affected zones are subjected to annealing between greater than 980 and 1250°C for periods of 0.05 minutes up to 24 hours for the purpose of homogenizing the welds and / or reducing stresses, followed by cooling in stationary shielding gas or air, moving (blown) shielding gas or air, with the result that this annealing improves the creep resistance and creep ductility of the welds, wherein the following relationships must be satisfied: Cr + Al > 28 (1 a) and Fp < 39.9 with (2a) Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti + 0.374*Mo + 0.538*W - 11 ,8*C (3a) where Cr, Fe, Al, Si, Ti, Mo, W and C are the concentrations of the elements concerned in mass-%.

2. The method according to claim 1, wherein the component contains welds of the same type, and after welding the entire component with the welds is homogenized and / or reduced by The weld is subjected to stresses of annealing at temperatures between 980 and 1250°C for periods ranging from 0.05 minutes to 24 hours, followed by cooling in static protective gas or air, moving (blown) protective gas or air, or in water, resulting in improved creep resistance and creep ductility of the welds. A method according to claims 1 and 2, wherein, after grinding the weld and the heat-affected zone, it is advantageous to achieve roughness values ​​Ra of 0.01 to 15 pm, as this improves corrosion resistance and, in particular, metal dusting resistance, bringing it approximately to the value of the base material of the component. A method according to one or more of claims 1 to 3, wherein the semi-finished product has a grain size of 30 to 600 pm. A method according to one or more of claims 1 to 4, with a chromium content of 20 to 33%.A process according to one or more of claims 1 to 5, with an aluminum content of 1.8 to 3.2%. A process according to one or more of claims 1 to 6, with an iron content of 0.01 to 4.0%. A process according to one or more of claims 1 to 7, with an optional additional niobium content of 0.0 to 1.1%, wherein formula (43a) is supplemented by a term with Nb. Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti + 1.26*Nb + 0.374*Mo + 0.538*W - 11.8*C (3b) and Cr, Fe, Al, Si, Ti, Nb, Mo, W and C are the concentrations of the elements concerned in mass %. A process according to one or more of claims 1 to 8, optionally with a zirconium content of 0.0 to 0.20%. A process according to one or more of claims 1 to 9, optionally with a yttrium content of 0.001 to 0.20%. A process according to one or more of claims 1 to 10, optionally with a lanthanum content of 0.001 to 0.20%. A process according to one or more of claims 1 to 11, optionally with a cerium content of 0.001 to 0.20%. A process according to one or more of claims 1 to 12, optionally with a cerium mischmetal content of 0.001 to 0.20%. A process according to one or more of claims 1 to 13, optionally with a hafnium content of 0.001 to 0.20%. A process according to one or more of claims 1 to 14, optionally with a tantalum content of 0.001 to 0.60%.A process according to one or more of claims 1 to 15, optionally comprising a boron content of 0.0001 to 0.008%. A process according to one or more of claims 1 to 16, optionally further comprising 0.0 to 5.0% cobalt. Method according to one or more of claims 1 to 17, optionally further comprising a maximum of 0.5% copper, wherein formula (4a) is supplemented by a term with Cu: Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti + 0.477*Cu + 0.374*Mo + 0.538*W- 11.8*C (3c) and Cr, Fe, Al, Si, Ti, Cu, Mo, W and C are the concentrations of the respective elements in mass %. Process according to one or more of claims 1 to 18, optionally further containing a maximum of 0.5% vanadium. Process according to one or more of claims 1 to 19, wherein the impurities are adjusted to levels of max. 0.002% Pb, max. 0.002% Zn, max. 0.002% Sn. Use of the process according to one or more of claims 1 to 20 in the petrochemical industry.

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