WO2023169629A1

WO2023169629A1 - Method for producing a component made of a nickel-chromium-aluminium alloy and provided with weld seams

Info

Publication number: WO2023169629A1
Application number: PCT/DE2023/100170
Authority: WO
Inventors: Heike Hattendorf; Benedikt NOWAK
Original assignee: Vdm Metals International Gmbh
Priority date: 2022-03-10
Filing date: 2023-03-03
Publication date: 2023-09-14
Also published as: DE102022105659A1

Abstract

The invention relates to a method for producing a component with one or more weld seams and/or for installing a component into a system with one or more weld seams consisting 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 partially or entirely consists of semi-finished products of this nickel-chromium-aluminium wrought alloy, and after the welding operation, only the weld seams made of this nickel-chromium-aluminium wrought alloy and the heat-affected zones surrounding the weld seams 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

Process for producing a welded component from a nickel-chromium-aluminum alloy

The invention relates to a method for producing a component provided with weld seams from a nickel-chromium-aluminum wrought alloy with excellent high-temperature corrosion resistance, good creep resistance and good processability.

Austenitic nickel-chromium-aluminum wrought alloys with different nickel, chromium and aluminum contents have long been used in furnace construction and in the chemical and petrochemical industries. For this use, good high-temperature corrosion resistance, even in carburizing atmospheres that produce metal dusting, and good high-temperature strength/creep resistance are required.

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 closed, aluminum oxide layer (AI2O3) with the corresponding aluminum contents. Small additions of elements with a strong affinity for oxygen, such as yttrium or cerium, improve the oxidation resistance. The chromium content is slowly consumed over the course of use in the area of application to build up the protective layer. Therefore, a higher chromium content increases the lifespan 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 is below the critical limit and oxides other than pure chromium oxides (Cr20s) form, which is, for example, iron - and nickel-containing oxides. A further increase in high-temperature corrosion resistance can be achieved by adding aluminum and silicon. Above a certain minimum content, these elements form a closed layer beneath the chromium oxide layer and thus reduce the consumption of chromium. In carburizing atmospheres (CO, H2, CH4, CO2, H2O mixtures with possibly other process-related non-oxidizing components), carbon can penetrate into the material, which can lead to the formation of internal carbides. These cause a loss of notched impact strength. The melting point can also drop to very low values (up to 350°C) and conversion processes can occur due to chromium depletion of the matrix.

High resistance to carburization is achieved by materials with low carbon solubility and low carbon diffusion rates. 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 by forming 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, materials containing silicon or aluminum can be used, which form a layer of silicon oxide or the even more stable aluminum oxide, which forms at significantly lower oxygen partial pressures compared to chromium oxide.

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. In contact with the gas, the alloys can absorb large amounts of carbon Segregation processes that take place on carbon-supersaturated alloys lead to material destruction. The alloy breaks down 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.

Typical conditions for the occurrence of “metal dusting” are strongly carburizing CO, H2 and/or CFU gas mixtures, such as those that occur in ammonia synthesis, in methanol plants, in metallurgical processes, but also in hardening furnaces. The resistance to “metal dusting” tends to increase as the nickel content of the alloy increases, although nickel alloys are not resistant to “metal dusting” either.

The chromium and aluminum content have a significant influence on the corrosion resistance under “metal dusting” conditions (see Figure 2). Nickel alloys with low chromium content, such as the alloy 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, C.G.M. and van Wortei, J.C.: Metal dusting: Relationship between alloy composition and degradation rate. Corrosion Engineering, Science and Technology 44 (2009), pp. 182 - 185). The resistance to “metal dusting” increases with the sum of chromium and aluminum (Cr + AI).

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

Prior art examples of these alloys are listed in Table 1.

Alloys such as Alloy 602 CA (N06025), Alloy 693 (N06693) or Alloy 603 (N06603) have long been recognized for their excellent corrosion resistance compared to Alloy 600 (N06600) or Alloy 601 (N06601) due to the high aluminum content of more than 1 .8% known. Alloy 602 CA (N06025), Alloy 693 (N06693), Alloy 603 (N06603) and Alloy 690 (N06690) show due to their high Chromium and/or aluminum content ensures excellent carburization resistance or “metal dusting” resistance. At the same time, alloys such as Alloy 602 CA (N06025), Alloy 693 (N06693) or Alloy 603 (N06603) show excellent high-temperature strength or creep resistance in the temperature range in which “metal dusting” occurs due to the high carbon or aluminum content. Alloy 602 CA (N06025) and Alloy 603 (N06603) still have excellent high-temperature strength and creep resistance even at temperatures above 1000°C. However, the processability is impaired, among other things, by the high aluminum content, with the impairment becoming greater the higher the aluminum content is (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), the cold formability in particular is limited by a high proportion of primary carbides.

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, the balance nickel and the usual process-related impurities, whereby the following relationships must be met: Cr + Al > 28 (2a) and

Fp < 39.9 with (3a)

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

+ 0.374*Mo + 0.538*W 11 .8*C (4a) where Cr, Fe, Al, Si, Ti, Mo, W and C are the concentration of the relevant elements in mass%. This nickel-chromium-aluminum alloy shows 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. The 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 rest being 100% iron. The value of 40Si+Ni+5AI+40N+10(Cu+Co) is not less than 50, where the symbols of the elements mean the content of the corresponding elements in mass%. The material has excellent corrosion resistance in an environment where metal dusting can occur and can therefore be used for stovepipes, pipe systems, heat exchanger tubes, etc. used in petroleum refineries or petrochemical plants and can significantly improve the lifespan and safety of the plant.

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%, AI 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 caused by melting.

Alloys for furnace construction and the petrochemical industry must be able to be welded to produce the individual components of a system. The individual components must also be able to be welded when installed in the system. Due to their structure, weld seams often show lower creep strength and/or tend to crack. By heat treating the weld seam, the creep strength can be improved and the tendency to cracking can be reduced. Some examples are listed in the following prior art.

EP 0 234 200 A1 discloses a method and a device for the heat treatment of longitudinally welded pipes made of austenitic, ferritic or austenitic-ferritic stainless steels, the pipes being annealed after the longitudinal seam has been welded. The procedure is through characterized in that the pipes are only partially solution annealed 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 s, preferably approx. 25 s.

The US 3865639 A discloses a method for producing a welded assembly, the welded parts of which withstand operating temperatures in the range of approximately 900 to 1050 ° C, the parts consisting of at least one high-alloy austenitic steel alloyed with chromium, nickel and / or cobalt and contains less than 60% iron by weight, up to 0.5% carbon by weight and low concentrations of additional elements such as manganese and silicon. Here, the specified parts are subjected to welding, the welding leading to the formation of at least one weld seam which has a solidification front corresponding to a physical and chemical discontinuity in the seam, the weld seam also consisting of a high-alloy austenitic steel and then being treated in such a way that that the solidification front becomes chemically homogeneous, whereby the carbides of the weld are present in the precipitated state to a maximum extent and in a fine, uniform distribution, with the result that the creep strength and the tensile strength of the weld are increased to values similar to those of the non-welded parts all are at least approximately the same by subjecting at least the seam and the adjacent areas of the welded parts to a homogenization heat treatment at a temperature between about 1100 to 1200 ° C for a period of several minutes to several hours, after which at least the seam and the adjacent areas to to about 800 ° C at a temperature decrease rate of about 100 ° C / h and then cooled to room temperature with air cooling. The US 3046167 A describes a process for the heat treatment of welded, hardenable chrome-nickel stainless steels in order to then give them 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 a structure which is essentially martensitic but contains some ferrite, subsequently restoring the structure of the steel which is essentially austenitic although it contains some ferrite. This is done by annealing at a temperature and for a time sufficient to re-austenitize the martensite and ferrite and break up the original cast structure of the weld. This is followed by converting the metal back into a structure that is substantially martensitic, along with very little ferrite, and finally hardening the metal by appropriate heat treatment to a state that is substantially fully martensitic. When processing 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 rest iron; and approximately 12% chromium, 8% nickel, 6% molybdenum, 1% aluminum and balance iron, the process comprising first welding the products under inert 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, then annealing the converted products at about 1065.6°C, then converting the products by heating and cooling as described above and finally curing by heating to about 482.2 to 593 , 3°C.

US 4168190 A describes a method and apparatus for local solution annealing of austenitic stainless steel that has been partially sensitized, for example, by a local temperature increase, without producing a sensitized structure at the thermal boundaries between the locally treated portion and the rest of the material, comprising the Steps: (a) rapid heating of the sensitized parts of the material to a temperature at which the carbides go into solution; and (b) rapid quenching of the heated material.

The object on which the invention is based is to design a method for producing a component with weld seams from a nickel-chromium-aluminum wrought alloy, the component partly consisting of a nickel-chromium-aluminum wrought alloy and/or for installing this component in a system with one or more weld seams.

This object is achieved by a method for producing a component with one or more weld seams and / or for installing a component in a system with one or more weld seams, which consist 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% 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% sulfur, max. 2.0% molybdenum, max. 2.0% tungsten, rest nickel greater than or equal to 50% and the usual process-related impurities, whereby the component consists partly or entirely of semi-finished products of this wrought nickel-chromium-aluminum alloy , and after welding only the weld seams made of this nickel-chromium-aluminum wrought alloy and the heat-affected zones surrounding the weld seams to homogenize the weld seams and / or to reduce stresses of an annealing between greater than 980 and 1250 ° C for times of 0.05 minutes to 24 hours, followed by cooling in static protective gas or air, moving (blown) protective gas or air, with the result that this annealing improves the creep strength and creep ductility of the weld seams, the following relationships being satisfied must:

Cr + AI > 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 relevant elements in mass%.

Advantageous developments of the subject matter of the invention can be found in the associated subclaims.

Metal semi-finished products are semi-finished products, such as sheet metal, strip, bar, forgings, seamless or longitudinally welded pipe or wire.

A component can be assembled from two or more machined semi-finished products and/or other components. Joining can be done, for example, using a fusion welding process, if necessary with extra welding filler. A welding filler metal can be supplied during welding, for example via welding rods or wires. A welding filler can also consist of a part of at least one of the adjacent semi-finished products to be welded, provided the weld seam geometry is designed accordingly.

The nickel-chromium-aluminum wrought alloy mentioned in this invention, abbreviated here as Alloy NiCrAI-H, is preferably melted openly in an electric furnace or an arc furnace, followed by treatment in a VOD (Vacuum, Oxidizing, Deoxidizing) or VLF (Vacuum Ladle Furnace) facility. But melting and casting in a vacuum is also possible. The alloy is then cast in blocks, electrodes or as continuous casting to form a preliminary product. If necessary, the preliminary product is then annealed at temperatures between 900 and 1270 ° C for 0.1 hour to 70 hours. Furthermore, it is possible to additionally remelt the alloy one or more times using ESU (electro-slag remelting plant) and/or VAR (vacuum arc remelting). The alloy is then shaped into the desired semi-finished product shape. For this purpose, annealing may be carried out at temperatures between 900 and 1270°C for 0.1 hour to 70 hours, then 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 (even several times) in between and/or after the end of hot forming for cleaning. Afterwards, if necessary, cold forming with degrees of deformation up to 98% into the desired semi-finished product shape, possibly with intermediate annealing between 800 and 1250 ° C for 0.05 minutes to 70 hours, if necessary under protective gas, such as argon or hydrogen, followed by a Cooling takes place in air, in the moving annealing atmosphere or in a water bath. Then solution annealing takes place in the temperature range from 800 to 1250 ° C for 0.05 minutes to 70 hours, if necessary under protective gas, such as. B. Argon or hydrogen, followed by cooling in air, in the 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 last annealing.

Solution annealing preferably takes place between the following temperatures:

1000 or > 1000 to 1200°C or < 1200°C 1000 or > 1000 to 1175°C or < 1175°C 1025 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

Solution annealing preferably takes place in the following time ranges:

0.05 minutes to 24 hours

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 wrought nickel-chromium-aluminum alloy (Alloy NiCrAl-H) used in this invention can be easily manufactured and used in the semi-finished forms of strip, sheet, bar, forgings, wire, longitudinally welded pipe and seamless pipe. These semi-finished molds are manufactured with an average grain size of 30 to 600 pm. Preferred areas are:

40pm to 300pm.

60pm to 300pm.

75pm to 8pm.

The parts required for the component are cut or separated from the semi-finished product, processed accordingly and then connected using a fusion welding process under inert gas.

Optionally, the fusion welding process may be, for example, one of the following processes:

Tungsten inert gas welding (TIG)

Metal inert gas welding (MIG)

Metal active gas welding (MAG)

Plasma welding

Electron beam welding

Laser beam welding

Gas welding or oxyfuel welding

Electrode welding / manual arc welding

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

But submerged arc welding and other processes are also conceivable.

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

20 or > 20 to 33 or < 33%

22 or > 22 to 33 or < 33%

24 or > 24 to 33 or < 33%

24 or > 24 to 32 or < 32% 25 or > 25 to 32 or < 32%

26 or > 26 to 32 or < 32%

27 or > 27 to 32 or < 32%

28 or > 28 to 32 or < 32%

28 or > 28 to 31 or < 31%

28 or > 28 to 30 or < 30%

29 or > 29 to 31 or < 31%

The aluminum content is between 1.8 and 4.0%, although here too, depending on the area of application of the alloy, preferred aluminum contents can be set as follows:

1.8 or > 1.8 to < 4.0%

1.8 or > 1.8 to 3.2 or < 3.2%

2.0 or > 2.0 to 3.2 or < 3.2%

2.0 or > 2.0 to 3.0 or < 3.0%

2.0 or > 2.0 to 2.8 or < 2.8%

2.0 or > 2.2 to 2.8 or < 2.8%

2.0 or > 2.2 to 2.6 or < 2.6%

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

0.01 to 4.0 or < 4.0%

0.01 to 3.0 or < 3.0%

0.01 to 2.5 or < 2.5%

0.1 - 2.0 or < 2.0%

0.1 - 1.0 or < 1.0%

The silicon content is between 0.001 and 0.50%. Si can preferably be set in the alloy within the spread range as follows:

0.001 - 0.20 or < 0.20%

0.001 - 0.10 or < 0.10% 0.001 - 0.05 or < 0.05%

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

0.005 to 0.50 or < 0.20%

0.005 to 0.20 or < 0.20%

0.001 to 0.20 or < 0.20%

0.005 to 0.10 or < 0.10%

0.005 to 0.05 or < 0.05%

The titanium content is between 0.00 and 0.60%. Ti can preferably be set in the alloy within the spread range as follows:

0.001 to 0.60 or <0.60%

0.001 to 0.50 or < 0.50%

0.001 to 0.30 or < 0.30%

0.001 to 0.25 or < 0.25%

0.001 to 0.10 or < 0.10%

0.001 to 0.02 or < 0.02%

0.01 to 0.10 or < 0.10%

Magnesium and/or calcium is also contained in levels of 0.00 to 0.05%. It is preferably possible to set these elements in the alloy as follows:

0.00 to 0.03 or < 0.03%

0.00 to 0.02 or < 0.02%

The alloy contains 0.005 to 0.12% carbon. This can preferably be set in the alloy within the spread range as follows:

0.01 to < 0.12%

0.01 to 0.10 or < 0.10%

0.01 to 0.08 or < 0.08%

0.01 to 0.05 or < 0.05% 0.02 to 0.10 or < 0.10%

0.03 to 0.10 or < 0.10%

This also applies to the element nitrogen, which is contained in levels between 0.0005 and 0.05%. Preferred contents can be as follows: 0.001 - 0.04%.

The alloy also contains oxygen in levels between 0.0001 and 0.020%, in particular 0.0001 to 0.010%.

The alloy also contains phosphorus in levels between 0.001 and 0.030%. Preferred contents can be as follows: 0.001 - 0.020%

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

Molybdenum and tungsten are contained individually or in combination in the alloy with a maximum content of 2.0% each. Preferred contents can be given as follows:

Mon max. 1.0%

W max. 1.0%

Mo max. < 1.0%

W max. < 1.0%

Mon max. < 0.50%

W max. < 0.50%

Mon max. < 0.10%

W max. < 0.10%

Mon max. < 0.05%

W max. < 0.05%

Nickel is the remainder. The remainder can preferably be specified as follows: > 50% or > 50%

> 55% or > 55%

> 60% or > 60%

> 65% or > 65%

> 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 met:

Cr + AI > 28 (1 a) where chromium and aluminum are the concentration of the relevant elements in

Mass% are. Preferred areas can be set with:

Cr + AI > 29 (l b)

Cr + AI > 30 (l c)

Cr + AI > 31 (l d)

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

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 relevant elements in mass%.

Preferred areas can be set with:

Fp < 38.4 (2b)

Fp < 36.6 (2c)

Optionally, the element niobium can be set in the alloy in contents of 0.0 to 1.10%. Niobium can preferably be adjusted in the alloy within the expansion 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 contained in the alloy, the formula (3a) must be supplemented with a term containing niobium as follows:

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) where Cr, Fe, Al, Si, Ti, Nb, Mo, W and C are the concentrations of the relevant elements in mass%.

Optionally, the zirconium content can be between 0.0 and 0.20%. Zirconium can preferably be set in the alloy within the expansion range as follows:

0.0 to 0.15 or < 0.15%

0.0 to 0.10 or < 0.10%

0.001 to 0.07 or < 0.07%

0.001 to 0.04 or < 0.04%

0.01 to 0.04 or < 0.04%

The element yttrium can optionally be set in contents of 0.0 to 0.20% in the alloy. Yttrium can preferably 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% Optionally, the element lanthanum can be set in the alloy in contents of 0.0 to 0.20%. Lanthanum can preferably 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%

Optionally, the element cerium can be set in the alloy in contents of 0.0 to 0.20%. Cerium can preferably 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%

If cerium and lanthanum are added at the same time, cerium mixed metal can optionally be used in contents of 0.0 to 0.20%. Cerium mixed metal can preferably be set in the alloy within the expansion 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%

Optionally, the element hafnium can be set in the alloy in contents of 0.0 to 0.20%. Hafnium can preferably be adjusted in the alloy within the spreading range as follows:

0.0 to 0.15 or <0.15%. 0.0 to 0.10 or <0.10%.

0.001 to 0.07 or <0.07%.

0.001 to 0.04 or < 0.04%

0.01 to 0.04 or <0.04%.

Optionally, the alloy can also contain 0.001 to 0.60% tantalum.

Preferred tantalum contents can be as follows:

0.001 to 0.50 or < 0.50%

0.001 to 0.40 or < 0.40%

0.001 to 0.30 or < 0.30%

0.001 to 0.20 or < 0.30%

0.001 to 0.10 or < 0.10%

0.01 to 0.10 or < 0.10%

The element boron can optionally be contained in the alloy as follows:

Boron 0.0001 - 0.008%

Preferred contents can be given as follows:

Boron 0.0005 - 0.008%

Boron 0.0005 - 0.004%

Furthermore, the alloy can contain between 0.0 and 5.0% cobalt if necessary, which can also be limited as follows:

0.01 to 5.0 or < 5.0%

0.01 to 2.0 or < 2.0%

0.1 O to 2.0 or < 2.0%

0.01 to 0.5 or < 0.5%

0.01 to 0.1 or < 0.1%

Furthermore, the alloy can contain a maximum of 0.5% copper if necessary. The copper content can also be limited as follows:

Cu max. < 0.20 or 0.20%

Cu max. < 0.10 or 0.10% Cu max. < 0.05 or 0.05% Cu max. < 0.015%

If copper is contained in the alloy, the formula (3a) must be supplemented with a copper term as follows:

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) where Cr, Fe, Al, Si, Ti, Cu, Mo, W and C are the concentrations of the relevant elements in mass%.

If niobium and copper are contained in the alloy, the formula (3a) must be supplemented by a term with niobium and a term with copper as follows:

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

+ 1.26*Nb + 0.477*Cu + 0.374*Mo + 0.538*W - 11.8*C (3d) where Cr, Fe, Al, Si, Ti, Nb, Cu, Mo, W and C are the concentrations of relevant elements are in mass%.

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

The vanadium content can also be limited as follows:

V max. < 0.10%

Finally, the elements lead, zinc and tin can also be present in levels as follows:

Lead max. 0.002%

Zinc max. 0.002%

Tin max. 0.002% The annealing of the weld seams and the heat-affected zones can be done, for example, using heating mats, infrared radiators, lasers or inductive electrical heating. Optionally, parts of the rest of the structure can be cooled at the same time.

It is also possible, after welding, to subject the entire component with the weld seams to annealing between 980 and 1250 ° C for times of 0.05 minutes to 24 hours, followed by cooling, in order to homogenize the weld seams and / or to reduce stresses in stationary protective gas or air, moving (blown) protective 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 weld seams.

Furthermore, it is possible, after welding and homogenizing the weld seams, either by annealing the entire component containing the weld seams or by annealing only the weld seams and the heat-affected zones, to repeat this annealing, optionally by annealing the entire component containing the weld seams or by annealing only the weld seams and heat-affected zones. The order of partial annealing of only weld seams and heat-affected zones and the annealing of the entire component is arbitrary.

Annealing after welding preferably takes place between the following temperatures:

1000 or > 1000 to 1200 or < 1200 °C

1000 or > 1000 to 1175 or < 1175 °C

1025 or > 1025 to 1150 or < 1150 °C 1050 or > 1050 to 1130 or < 1130 °C 1080 or > 1080 to 1130 or < 1130 °C

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

5 minutes to 1 hour

The protective gas for annealing after welding can preferably consist of the following gases, if not in air:

argon

Argon - air mixtures

hydrogen

Argon - hydrogen mixtures

Argon - nitrogen mixtures

The improvement in the creep strength and creep ductility of the weld seams takes place particularly in the area of y' formation, which includes the temperature range less than or equal to 750 ° C.

After annealing the component with the weld seams or after annealing only the weld seams and the heat-affected zones of the component, or the weld seams and the heat-affected zones from installation in the system, the surface can be optionally cleaned by brushing, pickling, blasting, grinding, turning, peeling and/or milling can be cleaned or processed. One or more such processing operations can optionally take place after welding. In particular, material-removing processing after the final annealing by grinding, turning, peeling and milling improves the corrosion resistance, especially the “metal dusting” resistance, of the annealed surfaces, especially the weld seams and the heat-affected zones.

After grinding the weld seam and the heat-affected zone, it is advantageous if roughness values Ra of 0.01 to 15 pm are achieved, as this is the Corrosion resistance and in particular the metal dusting resistance is improved and increased almost to the value of the base material.

The components produced according to the invention should preferably be used in areas in which highly corrosive conditions, such as heavily carburizing conditions, atmospheres that produce “metal dusting” prevail, such as components in the petrochemical industry. In addition, they are also suitable for oven construction.

Examples:

Manufacture of a component from semi-finished products

Figure 1a on the left shows sketches of the semi-finished products in the form of sheet metal (1), strip (2), rod (3), tube (4), wire or welding filler in wire form (5) in top view and cross section. Figure 1 a on the right shows an example of how a product or preliminary product (7) is created by, for example, cutting out and chamfering (ii) two components (1 a, 1 b) from the semi-finished sheet metal and then shaping them by fusion welding (iii) with a welding filler metal of wire (5) can be joined using a V-seam (6a) (iv). Figure 1 b on the left shows another example of the creation of a product or preliminary product (7), in which, for example, two pipe components (4a, 4b) are cut off and chamfered (ii) from the semi-finished pipe and then by fusion welding (iii) with a welding filler in the form of wire (5) using a V-seam (6b) (iv). Figure 1 b middle shows another example of the creation of a product or preliminary product (7), in which a hole is milled (ii) through a semi-finished sheet metal product or a sheet metal component (1 c), into which a semi-finished pipe product or a pipe component (1 3c) is used and is inserted by fusion welding (iii) with a welding filler in the form of wire (5) by means of a fillet weld (6c) (iv). Figure 1 b on the right shows another example of the creation of a product or a preliminary product (7), in which two strip sections (2a, 2b) (ii) cut out of the semi-finished strip and with the edges made to fit Fusion welding (iii) with part of the edges as a welding filler (9) butt-joined (6d) (iv).

Accomplished tests:

The phases occurring in equilibrium were calculated for the different alloy variants using the JMatPro program from Thermotech. The TTNI7 database for nickel alloys from Thermotech was used as the database for the calculations.

The creep strength is determined in a non-interrupted uniaxial creep test with strain measurement under tensile stress according to DIN EN ISO 204. To do this, the sample is installed in a creep testing machine and loaded with a constant test force. The rupture time tu and the time rupture elongation Au ^b are determined. The rupture time is a measure of the creep strength and the time rupture elongation is a measure of the creep ductility. The tests were carried out on round samples with a diameter of 10 mm in the measuring range and an initial reference length L _r o of 50 mm. The sampling was carried out transversely to the forming direction of the semi-finished product.

Description of properties

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

Phase stability

Depending on the alloy content, various embrittling TCP phases (Topologically Closed Packed phases) such as: B. form the Laves, Sigma, or p phase or the embrittling r| or s phase. The calculation of the Equilibrium phase proportions depending on the temperature, for example for N06690, batch 111389 (see Table 2 for the compositions used here), show mathematically the formation of a-chromium (BCC phase in Figure 3) below 720 ° C (Ts BCC) in large proportions. Since this phase is analytically very different from the base material, the formation of this phase is generally made more difficult. However, if the formation temperature Ts BCC of this phase is very high, it can certainly occur, as 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 is described. 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”, the exact analysis of the alloy in which a-chromium (BCC) occurs is not described. However, it can be assumed that a-chromium (BCC phase) can form under the examples or analyzes 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 reduced formation temperature Ts BCC) in “E. Slevolden, JZ Albertsen. U. Fink, Tjeldbergodden Methanol Plant: Metal Dusting Investigations," Corrosion/2011, paper no. 11144 (Houston, TX: NACE 2011), p. 15" a-chrome was then only observed near the surface. In order to avoid the occurrence of such an embrittling phase, in the nickel-chromium-aluminum alloy (Alloy NiCrAl-H) used in this invention, the formation temperature Ts BCC should be less than or equal to 939 ° C - the lowest formation temperature Ts BCC among the alloy examples 693 in Table 2 (from US 4882125 Table 1).

This is particularly the case when the following formula is met:

Fp < 39.9 with (2a) Fp = Cr + 0.272*Fe + 2.36*Al + 2.22*Si + 2.48*Ti

+1.26*Nb + 0.477*Cu + 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 relevant elements are 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 therefore Fp < 39.9.

Example of the production of components with welds and their properties

Tables 3a and 3b show the analyzes of industrially melted batches of Alloy NiCrAl-H alloys used in this invention from which sheets and welding rods (welding filler in the form of wire) were manufactured. For these batches, the formula (2a) AI + Cr > 28 is met and thus the requirement for “metal dusting” resistance is met. For the compositions in Tables 3a and 3b, the value for Fp was also calculated according to formula (3a). Fp is less than 39.9 as required.

These batches were open smelted in quantities of 16 tonnes, followed by treatment in a VOD plant. Electrodes were then cast and ESU was remelted. The alloy was then annealed at temperatures between 900 and 1270 ° C for 0.1 to 70 hours and hot formed with intermediate annealing between 900 and 1270 ° C for 0.1 to 70 hours. Hot-rolled sheets with a thickness 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, stained and sanded to remove the oxide layer. The 25 mm thick sheets had a grain size of around 89 pm, the 16 mm thick sheets had a grain size of around 82 pm. The 25 mm sheet and the 16 mm sheet therefore have a comparable grain size. The wire rod was also blasted, pickled and ground and then cold drawn to final thickness with intermediate annealing between 800 and 1250 ° C for 0.05 minutes to 70 hours. Then the Wire is solution annealed under hydrogen in the temperature range from 800 to 1250°C for 0.05 minutes to 70 hours and processed into welding rods with a diameter of 2.0 and 2.4 mm.

Sheet metal sections were cut from the 25 mm thick solution-annealed semi-finished sheet metal, which were annealed at 980 ° C for 3 hours with subsequent air cooling. Samples for creep tests transverse to the rolling direction were manufactured from the only solution annealed and the additionally annealed sheets or sheet sections. The results of the creep tests according to DIN EN ISO 204 are shown in Table 5.

Sheet metal sections measuring 150 x 500 mm were cut from the 16 mm thick semi-finished sheet metal. Two pieces each were welded with a 70° V-seam using TIG manual welding under pure argon using the 2.0 and 2.4 mm thick welding rods from batch 318385 as welding filler with the welding parameters given in Table 4. The weld seam and 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 with subsequent air cooling, others with 1100 ° C for 40 minutes with subsequent air cooling and others with 1100 ° C for 3 hours with subsequent air cooling. Some received no annealing. Seams or seam sections were also produced that were sanded or not treated at all. Samples for creep tests were made from the welded sheets or the welded and annealed sheets or sheet sections transversely to the weld seam. The results of the creep tests according to DIN EN ISO 204 are shown in Table 5.

From Table 5 it can be seen that in creep tests at 600 ° C, an additional annealing at 980 ° C for 3 hours followed by air cooling (sample 19 45B or 19 46B) of a solution-annealed sheet reduces the fracture time tu compared to the only solution-annealed one sheet metal (sample 19 23B or 19 7B). A creep test (sample 302W or 303W) transverse to 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 sheet metal that was only solution annealed. An additional annealing of the welded section from which the creep samples are made at 980 ° C for 3 hours followed by air cooling (sample 247W or 249W) has no noticeable effect on the rupture time tu, but noticeably reduces the rupture elongation Au ^b . In contrast, an additional annealing according to the invention of the welded section from which the creep samples are made, at 1100 ° C for 40 minutes followed by air cooling (sample 250W or 503W), produces a significant increase in the fracture time tu by approximately a factor of 3 and a Increase in the elongation at break Au ^b partially exceeds the value of the samples that were not annealed after welding (sample 302W or 303W). In particular, an additional annealing according to the invention of the welded section from which the creep samples are made at 1100 ° C for 3 hours followed by air cooling (sample 511W or 506W) produces a further increase in the rupture time tu and an increase in the rupture elongation Au ^b fast on the value of the creep test on only solution-annealed, non-welded sheet metal (sample 19 23B or 19 7B).

At 700°C, a creep test (sample 306W) transverse to the weld seam without further annealing (state of the art T) also shows, as at 600°C, a reduced fracture time tu compared to the creep test on sheet metal that has only been solution-annealed (sample 30 34B). Additional annealing of the welded section from which the creep specimens are made at 980°C for 3 hours followed by air cooling (sample 248W) again produces a slight reduction in fracture time tu compared to sample 306W, which was not annealed after welding. On the other hand, an additional annealing according to the invention of the welded section from which the creep samples are made at 1100 ° C for 40 minutes followed by air cooling (sample 251 W) produces an increase in the fracture time tu by a factor of approximately 2 as well as an increase in the time fracture elongation Au ^b significantly higher than the value of the sample that was not annealed after welding (306W). In particular, an additional annealing according to the invention of the welded section from which the creep samples 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 only solution-annealed sheet.

At 800°C, 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) transverse to the weld seam without further annealing (state of the art T) also has a similar fracture time tu compared to the creep test on sheet metal that has only been solution-annealed (sample 19 22B). Additional annealing of the welded section from which the creep samples 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 test on the solution-annealed sheet only (sample 19 22B).

This means that heat treatment of the weld seam after welding at 1100 ° C for at least 40 minutes improves, according to the invention, the fracture time and the rupture elongation of a creep test transverse to the weld seam at temperatures of 600 and 700 ° C and thus significantly in the area of y 'formation. 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 metal. Annealing the weld seam only has a negligible effect on the fracture time at operating temperatures above the y'-solvus temperature.

The claimed limits for the process and the nickel-chromium-aluminum alloy NiCrAl-H used in this invention can therefore be justified in detail as follows:

Too low a chromium content means that the chromium concentration below the oxide layer increases very quickly when the alloy is used in a corrosive atmosphere falls below the critical limit so that a closed chromium oxide layer can no longer form. Therefore, 18% chromium is the lower limit for chromium. Chromium contents that are too high impair the phase stability of the alloy, especially with high aluminum contents of > 1.8%. Therefore, 33% chromium is to be regarded as the upper limit.

The formation of an aluminum oxide layer beneath the chromium oxide layer reduces the oxidation rate. Below 1.8% aluminum, the aluminum oxide layer is too patchy to fully develop its effect. Too high aluminum contents impair the processability of the alloy. Therefore, an aluminum content of 4.0% is the upper limit.

The cost of the alloy increases as the iron content is reduced. Below 0.01% the costs increase disproportionately because special raw materials have to be used. Therefore, 0.01% iron is to be viewed as the lower limit for cost reasons. As the iron content increases, the phase stability decreases (formation of embrittling phases), especially with high chromium and aluminum contents. Therefore, 7% iron is a sensible upper limit to ensure the phase stability of the alloy according to the invention.

Silicon is required in the production of the alloy. A minimum content of 0.001% is therefore necessary. Contents that are too high, in turn, affect the processability and phase stability, especially with high aluminum and chromium contents. The silicon content is therefore limited to 0.50%.

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

Titanium increases high temperature strength. From 0.60% the oxidation behavior can deteriorate, which is why 0.60% is the maximum value. Even very low magnesium contents and/or calcium contents improve processing by binding sulfur, which prevents the occurrence of low-melting NiS eutectics. If the content is too high, intermetallic Ni-Mg phases or Ni-Ca phases can occur, which significantly worsen the processability. The magnesium content 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 level this element reduces processability due to the excessive formation of primary carbides.

A minimum nitrogen content of 0.0005% is required, which improves the processability of the material. Nitrogen is limited to a maximum of 0.05% because this element reduces processability through the formation of coarse carbonitrides.

The oxygen content must be <0.020% to ensure the alloy can be manufactured. Too low an oxygen content increases costs. The oxygen content is therefore > 0.0001%.

The phosphorus content should be less than or equal to 0.030%, as this surface-active element impairs oxidation resistance. Too low a phosphorus content increases costs. The phosphorus content is therefore > 0.001%.

Sulfur contents should be kept as low as possible since this surface-active element impairs oxidation resistance. A maximum of 0.010% sulfur is therefore specified.

Molybdenum is limited to a maximum of 2.0% as this element reduces oxidation resistance. Tungsten is limited to a maximum of 2.0% as this element also reduces oxidation resistance.

Nickel is the remaining element. Too low a nickel content reduces phase stability, especially at high chromium contents. Nickel must therefore be greater than or equal to 50%.

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

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 relevant elements in mass%. The limits for Fp and the possible inclusion of further elements were explained in detail in the previous text.

If necessary, the oxidation resistance can be further improved with the addition of oxygen-affinous elements such as yttrium, lanthanum, cerium, cerium mixed metal, zirconium, hafnium. They do this by being incorporated into the oxide layer and blocking the diffusion paths of oxygen on the grain boundaries.

Yttrium increases oxidation resistance. The upper limit is set at 0.20% for cost reasons. Lanthanum increases oxidation resistance. The upper limit is set at 0.20% for cost reasons.

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

Cerium mixed metal increases oxidation resistance. The upper limit is set at 0.20% for cost reasons.

If necessary, niobium can be added, as niobium also increases high-temperature strength. Higher salaries increase costs significantly. The upper limit is therefore set at 1.10%.

If necessary, the alloy can also contain tantalum, since tantalum also increases high-temperature strength and oxidation resistance. Higher salaries increase costs significantly. The upper limit is therefore set at 0.60%. A minimum level of 0.001% is required to have an effect.

If necessary, 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.

If necessary, 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.

If necessary, boron can be added to the alloy because boron improves creep resistance. Therefore there should be a content of at least 0.0001%. At the same time, this surface-active element impairs the oxidation resistance. A maximum of 0.008% boron is therefore specified. Cobalt can be contained in this alloy up to 5.0%. Higher contents noticeably reduce the oxidation resistance.

Copper is limited to a maximum of 0.5% as this element reduces resistance to oxidation.

Vanadium is limited to a maximum of 0.5% as this element reduces oxidation resistance.

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

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 range of y' formation.

Homogenization of the weld seams and/or to reduce stresses by annealing between greater than 980 and 1250°C for times of 0.05 minutes up to 24 hours, followed by cooling in stationary protective gas or air, moving (blown) protective gas or air , improves the creep strength and creep ductility of the weld seams in the area of y' formation. If the temperature 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 well above solution annealing, noticeable grain growth occurs, which reduces the high-temperature strength at low temperatures as well as the elongation in the creep test in the area of Y' formation. Short times below 0.05 minutes are not sufficient even at very high temperatures. Times longer than 24 hours are uneconomical, especially for larger components.

Annealing under inert gas reduces oxidation of the material during annealing and thus material loss. Character description

Fig. 1 a: Left: Sketches in plan and cross section of the semi-finished shapes sheet metal (, strip 2, rod 3 tube 4, and wire or welding filler in wire form 5. Right: exemplary production of a component 7 by chamfering two sheets 1 a, 1 b and joining by fusion welding with a welding filler in wire form 5 using a V-seam 6a.

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

Fig. 2: Metal loss through “metal dusting” as a function of aluminum and

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).

Fig. 3: Quantities of the phases in thermodynamic equilibrium in

Dependence on the temperature of Alloy 690 (N06690) using the example of batch 111389.

Fig. 4: Quantities of the phases in thermodynamic equilibrium in

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

Dependence on the temperature of Alloy 693 (N06693) using the example of Alloy 10 from Table 2.

Table 1: Some alloys according to ASTM B 168-11. All information in mass%.

Table 2: Compositions of some alloys according to ASTM B 168-11. All information in mass%.

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

Table 3a: Composition of the industrially melted batches (G) of the nickel-chromium-aluminum alloy NiCrAl-H used in this invention, part 1. All information in mass%. (H: Examples of the nickel-chromium-aluminum alloy NiCrAl-H used in this invention, G: melted on an industrial scale)

Table 3b: Composition of the industrially smelted batches (G) of the nickel-chromium-aluminium alloy NiCrAI-H used in this invention, part 2. All information in mass% (applies to all alloys: Pb: max. 0.002%, Zn : max. 0.002%, Sn: max. 0.002%; meaning of H, G: see Table 3a).

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

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) from batch 319144 (BM) and ii) 16 mm welded with welding rods from batch 318385 thick, solution-annealed sheets (1100°C / 40 min/LK, grain size 82 pm) from batch 319144 (S). LK

= air cooling.*) Break on the shoulder, not measurable, **) Test is still running. E = According to the invention; T = state of the art.

Claims

Patent claims

1. Process for producing a component with one or more weld seams and / or for installing a component in a system with one or more weld seams, which consist 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% 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% sulfur , max. 2.0% molybdenum, max. 2.0% tungsten, the rest nickel greater than or equal to 50% and the usual process-related impurities, whereby the component consists partly or entirely of semi-finished products of this wrought nickel-chromium-aluminum alloy, and after Weld only the weld seams made of this wrought nickel-chromium-aluminum alloy and the heat-affected zones surrounding the weld seams to homogenize the weld seams and/or to reduce stresses during annealing between greater than 980 and 1250 ° C for times of 0.05 minutes up to 24 hours, followed by cooling in static shielding gas or air, moving (blown) shielding gas or air, with the result that this annealing improves the creep strength and creep ductility of the weld seams, whereby the following relationships must be satisfied:

Cr + AI > 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 relevant elements in mass%. Method according to claim 1, wherein the component contains welds, and after welding the entire component with the welds to homogenize the weld and / or to reduce stresses of a further annealing between greater than 980 and 1250 ° C for times of 0.05 minutes to is subjected to 24 hours, followed by cooling in static protective gas or air, moving (blown) protective gas or air or in water, with the result that the creep strength and creep ductility of the weld seams is improved. Method according to claims 1 to 2, wherein after a grinding process of the weld seam and the heat-affected zone it is advantageous if roughness values Ra of 0.01 to 15 pm are achieved, as this improves the corrosion resistance and in particular the “metal dusting” resistance and approximates it Increases the value of the base material. 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. Method according to one or more of claims 1 to 4, with a chromium content of 20 to 33%. Method according to one or more of claims 1 to 5, with an aluminum content of 1.8 to 3.2%. Method according to one or more of claims 1 to 6, with an iron content of 0.01 to 4.0%. Method according to one or more of claims 1 to 7, if necessary with a niobium content of 0.0 to 1.1%, the formula (4a) being 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 relevant elements in mass % . Method according to one or more of claims 1 to 8, optionally with a zirconium content of 0.0 to 0.20%. Method according to one or more of claims 1 to 9, optionally with an yttrium content of 0.001 to 0.20%. Method according to one or more of claims 1 to 10, optionally with a lanthanum content of 0.001 to 0.20%. Method according to one or more of claims 1 to 11, optionally with a cerium content of 0.001 to 0.20%. Method according to one or more of claims 1 to 12, optionally with a cerium mixed metal content of 0.001 to 0.20%. Method according to one or more of claims 1 to 13, optionally with a hafnium content of 0.001 to 0.20%. Method according to one or more of claims 1 to 14, optionally with a tantalum content of 0.001 to 0.60%. Method according to one or more of claims 1 to 15, optionally with a boron content of 0.0001 to 0.008%. Method according to one or more of claims 1 to 16, further optionally containing 0.0 to 5.0% cobalt. Method according to one or more of claims 1 to 17, further optionally containing a maximum of 0.5% copper, the formula (4a) being 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 relevant elements in mass %. Method according to one or more of claims 1 to 18, further optionally containing a maximum of 0.5% vanadium. Method according to one or more of claims 1 to 19, wherein the impurities are set in contents of max. 0.002% Pb, max. 0.002% Zn, max. 0.002% Sn. Use of the method according to one or more of claims 1 to 20 in the petrochemical industry.