Use of nickel-iron-chromium alloys that have high durability in carburizing, sulfidizing and chlorinating environments while at the same time having good workability and strength

Abstract

The following (in mass percent): 35.0-38% nickel, 26.0-30.0% chromium, >0.7-1.50% silicon, 0.40-1.30% aluminum, 0.00-1.0% manganese, 0.0001-0.05% magnesium and / or calcium, 0.015-0.12% carbon, 0.001-0.150% nitrogen, 0.001-0.030% phosphorus, 0.0001-0.020% oxygen, maximum 0.010% sulfur, less than 1.0% molybdenum, and less than 1.0% iron. 1. Use of a nickel-iron-chromium alloy having outstanding high temperature corrosion resistance, containing 0.01% cobalt, less than 0.5% copper, less than 1.0% tungsten, the balance iron and normal process impurities, as a semi-finished product in a carburizing, sulfiding and simultaneously chlorinating environment, in which the following relationship must be satisfied: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al<2.5(1a), where Ni, Si and Al are the concentrations of the respective elements in mass%.

Description

[Technical field]

[0001] The present invention relates to the use of nickel-iron-chromium alloys having good high temperature corrosion resistance in highly corrosive environments, such as carburizing, sulfidizing and simultaneously chlorinating environments, and improved workability, especially weldability.

[0002] Austenitic nickel-iron-chromium alloys with different nickel, chromium and iron contents have been used for a long time in furnace construction and in the chemical and petrochemical industries, where good high-temperature corrosion resistance, even in carburizing and sulfidizing environments, is required, as well as good high-temperature strength.

[0003] In general, it should be noted that the hot corrosion resistance of the alloys shown in table 1 increases with increasing chromium content. All these alloys form a chromium oxide layer (Cr2O3) and a more or less closed silicon oxide layer underneath. The addition of small amounts of elements with a strong oxygen affinity, such as yttrium or cerium, improves the corrosion resistance. The chromium content is gradually consumed in the formation of the protective layer during the course of use in the application area. Therefore, the higher the chromium content, the longer the service life of the material. This is because the higher the content of the chromium element forming the protective layer, the later the time when the chromium content falls below the critical value and oxides other than Cr2O3 (such as iron-containing or nickel-containing oxides) are formed. A further improvement in hot corrosion resistance can be achieved by the addition of silicon and aluminum. From a certain minimum content, these elements form a closed layer underneath the chromium oxide layer, thereby reducing the consumption of chromium.

[0004] In carburizing environments (CO, H2, CH4, CO2, H2O mixtures), carbon penetrates into the material, which can lead to the formation of internal carbides. This causes a decrease in notched impact strength. Transformation processes can also occur due to the depletion of chromium in the base material.

[0005] High carburization resistance is achieved by materials with low carbon solubility and low carbon diffusion rates. Nickel alloys are therefore generally more resistant to carburization than iron-based alloys, because of both the lower carbon diffusivity and solubility in nickel compared to iron. Increasing the chromium content provides higher carburization resistance due to the formation of a protective chromium oxide layer, unless the oxygen partial pressure in the gas is insufficient to prevent this. At very low oxygen partial pressures, materials can be used that form silicon oxide or the more stable aluminum oxide layers, both of which are able to form protective oxide layers even at significantly lower oxygen contents.

[0006] In carburizing and sulfidic environments (CO, H2, H2O, CO2, H2S mixtures) with low oxygen partial pressure, sulfur penetrates into the material, which can lead to the formation of sulfides. The melting point can also be reduced to very low values ​​(635 °C for Ni-Ni3S2 eutectic and 988 °C for Fe-FeS eutectic). Nickel-iron-chromium alloys with a high nickel content are often more sensitive in sulfidic environments than nickel-iron-chromium alloys with a high iron content. Here too, further improvement of the high-temperature corrosion resistance can be achieved by the addition of silicon and aluminum.

[0007] In chlorinated environments with low oxygen partial pressure, high corrosion rates can occur because volatile metal chlorides with high vapor pressures and / or low melting points can be formed. High chromium and / or nickel content improves corrosion resistance.

[0008] DE 4130139 describes a hot-formable, heat-resistant, austenitic nickel alloy that contains (in mass%) 0.05-0.15% carbon, 2.5-3.0% silicon, 0.2-0.5% manganese, max. 0.015% phosphorus, max. 0.005% sulfur, 25-30% chromium, 20-27% iron, 0.05-0.15% aluminium, 0.001-0.005% calcium, 0.05-0.15% rare earths, 0.05-0.20% nitrogen, the balance being nickel and the usual impurities resulting from melting.

[0009] The alloy described in DE 41 30 139 C1 is known under the name "NiCr28FeSiCe", Alloy 45™, Nicrofer 45™ or material number 2.4889 and will be referred to hereinafter as "45™".

[0010] Alloy 45TM is highly resistant to carburizing and sulfidizing media and is therefore suitable for use in waste incineration and coal gasification plants. Figure 1 shows the metallographically determined corrosion attack depth of various alloys after 2100 hours of aging in H2S-containing gas at the PRENFLO coal gasification pilot plant in Fürstenhausen versus temperature for various alloys. Table 1 shows the composition of the analyzed alloys according to the prior art. A high chromium content and a high silicon content significantly reduce the corrosion attack depth. A high silicon content of ≥ 2.5% can lead to the formation of a silicon oxide layer below the protective chromium oxide layer, which makes the material more corrosion resistant. 45TM with 26-29% chromium and 2.5-3% silicon has the lowest corrosion attack depth at all temperatures, followed by AC66 with 26-28% chromium and up to 0.3% silicon.

[0011] However, alloy 45TM is very difficult to process, which is evident, for example, by cracking during hot forming. When welding, 45TM is similarly prone to cracking, which precludes proper welding (using filler metal within the compositional range of the welded material), which is reasonable for corrosion protection reasons, and makes the material difficult to use in practical applications. In austenitic FeCrNi weldments with primary austenitic solidification, the formation of low-melting phases due to silicon accumulation at the austenite grain boundaries (eutectic Fe-Fe2Si: 1212 °C, eutectic NiSi-Ni3Si2: 964 °C, and NiSi: 996 °C) and an expanded freezing range are cited as reasons for the increased hot cracking.

[0012] On the other hand, alloy AC66 (see Table 1 for composition) has sufficient weldability and workability, but as Figure 1 shows, it has poor corrosion resistance in coal gasification plants.

[0013] Carburizing and sulfiding conditions, as well as chlorine attack, such as occurs in coal gasification and waste incineration plants, place even greater demands on materials.

[0014] Materials used in carburizing, sulfidizing and chlorinating environments, especially atmospheres, must make compromises with regard to composition.

[0015] High temperature strength is improved by increasing the carbon content, among other things, but also by increasing the content of solution strengthening elements such as chromium, aluminum, silicon, molybdenum and tungsten.

[0016] US Patent No. 6,623,869 describes a metallic material containing the following components in mass percent: 0.2% or less carbon, 0.01-4% silicon, 0.05-2% manganese, 0.04% or less phosphorus, 0.015% or less sulfur, 10-35% chromium, 30-78% nickel, 0.005% or more but less than 4.5% aluminum, 0.005-0.2% nitrogen, and one or both of 0.015-3% copper and 0.015-3% cobalt, with the balance being substantially iron. In this case, the value of 40Si+Ni+5Al+40N+10(Cu+Co) is 50 or more, and the element symbols represent the alloy content of each element. This metallic material has excellent corrosion resistance in environments where metal dusting may occur, and can be used for furnace tubes, ducting systems, heat exchanger tubes, etc. in oil refineries and petrochemical plants. This makes it possible to significantly improve the life and safety of the plant.

[0017] U.S. Pat. No. 3,833,358 describes an iron-based refractory alloy that provides high resistance to creep, thermal shock, thermal fatigue and intercrystalline oxidation and good weldability, the alloy essentially consisting of the following elements (in weight proportions): C 0.05~0.20 Ni 30~40 Cr 20~30 Nb 0.2~2 N 0.04~0.2 Mn 0.6~2 Si 0.6~2 Ta 0~0.3 Ti 0~1 Mo 0~0.5 Al 0~0.05 Pb 0~0.01 Sn 0~0.01 Zinc 0~0.01 Cu 0~0.25 and the remainder being essentially iron, wherein the weight ratios of the aforementioned elements are expressed by the following formula: 30×C%+Ni%+0.5×Mn%+16×N%=Cr%+0.5×(Nb+1 / 2Ta)%+3.5×Ti%+1.5×Si%+Mo%+(11+ / -2)% A=B+ / -20% where A = 30 × C% and B = 2 × Ti% + 6 × (Nb + 1 / 2Ta)%.

[0018] US Patent No. 3,865,581 describes a heat-resistant alloy having hot formability, mainly composed of 0.01-0.5% C, 0.01-2.0% Si, 0.01-3.0% Mn, 22-80% Ni and 10-40% Cr, together with one or both of 0.0005-0.20% B and 0.001-6.0% Zr, and further one or more of 0.001-0.5% Ce, 0.001-0.2% Mg and 0.001-1.0% Be, with the balance being iron and unavoidable impurities. It is suitable for use in furnace construction (burner tips, protective housings, thermocouple protection tubes, etc.).

[0019] DE 1024719 A1 describes the addition of cerium and / or lanthanum to a nickel-iron alloy, which is a hot-workable alloy characterized by the following composition: 0-0.5% carbon, 10-60% of one or more of the elements chromium, molybdenum and tungsten (the amount of each of these elements not exceeding 30%), 0-73% iron, 0.02-1.10% cerium and / or lanthanum, the balance being 4-70% nickel including impurities, with the proviso that the content of the rare earth metals is adapted to the nickel content as follows: Nickel % Cerium or Lanthanum or both % 4 Approx. 0.02~1.10 10 Approx. 0.02~1.05 20 Approximately 0.02~0.90 30 Approx. 0.02~0.75 40 Approx. 0.02~0.60 50 approx. 0.02~0.45 60 approx. 0.02~0.30 70 Approximately 0.02~0.15.

[0020] EP 0 812 926 A1 describes a nickel-base alloy that has improved strength in use and is composed of 0.06-0.14% carbon, 35-46% nickel, 22.5-26.5% chromium, 0-1.5% manganese, 0.5-2% silicon, 0.1-1% titanium, 0.05-2% aluminium, 1-3% molybdenum, 0.2-1% niobium, 0.1-1% tantalum, 0-0.3% tungsten, 0-0.008% boron, 0-0.05% zirconium, and the balance iron and random impurities.

[0021] WO 2007 / 124996 describes a reaction vessel for use in the production of hydrogen sulfide by reaction of sulfur with hydrogen, the reaction vessel and optionally the connecting conduits as well as some or all of the fittings and measuring and control elements being made of an aluminium-containing material which is resistant to the reaction mixture, in particular the material containing (in % by weight) 0-0.3% C, 0-2.5% Si, 0-2.5% Mn, 0-0.1% P, 0-0.3% S, 15.0-28.0% Cr, 0-1.0% Cu, 0-balance % Fe, 1.0-5.0% Al, 0-2.5% Co, 0-1.5% Ti, 0-0.4% Y and up to 70% Ni.

[0022] DE 102007005605 A1 describes an iron-nickel-chromium-silicon alloy containing (in % by weight) 34-42% nickel, 18-26% chromium, 1.0-2.5% silicon, 0.05-1% Al, 0.01-1% Mn, 0.01-0.26% lanthanum, 0.0005-0.05% magnesium, 0.01-0.14% carbon, 0.01-0.14% nitrogen, max. 0.01% sulfur, max. 0.005% boron, the balance being iron and normal process impurities. This alloy is used for heating elements.

[0023] U.S. Pat. No. 5,021,215 describes substantially the following (in weight percent): C: 0.05~0.30%, Si: 3.0% or less, Mn: 10% or less, Cr: 15~35%, Ni: 15-50%, Mg: 0.001-0.02%, B:0.001~0.01%, Zr:0.001~0.10%, At least one element selected from the group consisting of Ti: 0.05-1.0%, Nb: 0.1-2.0%, and Al: 0.05-1.0%; Mo: 0-3.0%, W: 0-6.0%, (Mo+1 / 2W≦3.0%) The balance is Fe and random impurities In the present disclosure, the impurities oxygen and nitrogen are limited to 50 ppm or less and 200 ppm or less, respectively, and the austenite grain size is limited to 4 or more.

[0024] JP 56-163244 A describes the improvement of the hot workability and oxidation resistance of austenitic steels by adding specific amounts of C, Si, Mn, Ni, Cr, Al, B, rare earth elements and Ca to the austenitic steels. This is achieved by an austenitic steel having the following composition (in weight percent): <0.2% C, 1.5-3.5% Si, <2% Mn, 8-35% Ni, 15-30% Cr, <2% Al, 0.0005-0.005% B, 0.005-0.1% rare earth elements and 0.0005-0.02% Ca, or 0.0005-0.03% Mg, with further additions if necessary. The austenitic steel obtained from this is refined in a conventional steelmaking furnace and the molten steel is formed into billets and then hot rolled.

[0025] US Patent No. 7,118,636 describes a nickel-iron-chromium alloy that contains a solidification phase that allows the alloy to maintain a fine grain structure during forging and processing at high temperatures. The alloy contains sufficient amounts of titanium, zirconium, carbon and nitrogen to form fine titanium and zirconium nitrides in the molten state of the alloy, even though they are close to their solubility limits. When articles are made from such alloys by thermomechanical processing, a dispersion of fine titanium and zirconium carbonitride precipitates forms during solidification of the melt and remains in the alloy during subsequent (high temperature) processing steps, preventing austenite grain growth. The nickel-iron-chromium alloy contains less than 0.05 weight percent niobium, at least 0.05% zirconium, at least 0.05% carbon, at least 0.05% nitrogen, where the weight ratio of carbon to nitrogen is at least 1:2 to less than 1:1, and contains sufficient titanium, zirconium and / or aluminum to be free of chromium carbides, where the titanium, zirconium, carbon and nitrogen are sufficient to form fine titanium and zirconium carbonitrides [(Ti x Zr 1-x )(C y N 1-y The nickel-iron-chromium alloy further comprises about 32% to about 38% by weight iron, about 22% to about 28% by weight chromium, about 0.10% to about 0.60% titanium, about 0.05% to about 0.30% zirconium, about 0.05% to about 0.30% carbon, about 0.05% to about 0.30% nitrogen, about 0.05% to about 0.5% aluminum, up to 0.99% molybdenum, up to about 0.01% boron, up to about 1% silicon, up to about 1% manganese, the balance being nickel and random impurities.

[0026] Japanese Patent Application Laid-Open No. 57-134544 describes the improvement of the stress corrosion cracking resistance of oil well tubular goods by adding a predetermined amount of Mo, W, etc. to high Cr-Ni steel as a pipe material. For this purpose, alloy steels having a composition of <0.10% C, <1.0% Si, <2.0% Mn, <0.030% P, <0.005% S, <0.5% Al, 22.5-30% Cr, 25-60% Ni and Mo and / or W are used, which are represented by the following formula: Cr(%)+10×Mo(%)+5×W(%)≧70% 4%≦Mo(%)+1 / 2W(%)<8% The steel satisfies the above requirements. The steel is used for oil well tubular goods used in highly corrosive and harsh environments such as oil wells and natural gas wells. The alloy can be added with <1% Cu and / or <2% Co and / or <0.10% of one or more rare earth elements, <0.20% Y, <0.10% Mg, <0.10% Ca and <0.5% Ti. The steel can be produced with excellent stress corrosion cracking resistance in the highly corrosive environment of oil wells containing H2S, CO2 and Cl.

[0027] The object of the present invention is to a) have good high temperature corrosion resistance comparable to that of Alloy 45™ in highly corrosive environments, such as carburizing, sulfidizing and simultaneously chlorinating environments; b) have sufficient workability, especially weldability, as close as possible to that of alloy AC66; and c) It has sufficient high-temperature strength at 500°C equivalent to that of alloy AC66. The aim of the present invention is to devise the use of nickel-iron-chromium wrought alloys.

[0028] The object of the present invention is to provide a method for producing a composition comprising the steps of: 35.0-38% nickel, 26.0-30.0% chromium, >0.7~1.50% silicon, 0.40-1.30% aluminum, 0.00-1.0% manganese, 0.0001-0.05% each of magnesium and / or calcium, 0.015-0.12% carbon, 0.001-0.150% nitrogen, 0.001-0.030% phosphorus, 0.0001~0.020% oxygen, Maximum 0.010% sulfur, Less than 1.0% molybdenum, Cobalt less than 1.0% less than 0.5% copper, Less than 1.0% tungsten, The remainder is iron and normal process impurities. 2. Use of a nickel-iron-chromium alloy having outstanding high-temperature corrosion resistance, comprising: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) must be satisfied, where Ni, Si and Al are the concentrations of the respective elements in mass %, as resolved by use.

[0029] Advantageous developments of the subject matter of the invention can be taken from the accompanying dependent claims.

[0030] The nickel content is 35.0-38.0%, and the preferred content can be adjusted within the following numerical ranges: - 35 or >35.0~<38.0% - 35 or >35.0–37 or <37.0%.

[0031] The numerical range of chromium element is 26.0-30.0%, and the preferred range can be adjusted as follows: - >26.0~<30.0% - 27.0 or >27.0-30.0 or <30.0% - 28.0 or >28.0–30.0 or <30.0%.

[0032] The silicon content is >0.7-1.50%. Preferably, silicon can be adjusted in the alloy within the following numerical ranges: - >0.70~<1.50% - 0.80 or >0.80~1.50 or <1.50% - 0.90 or >0.90~1.50 or <1.50% - 0.80 or >0.80~1.50 or <1.50% - 0.80 or >0.80~1.45 or <1.45%.

[0033] The aluminum content is 0.40-1.30%, where again the preferred aluminum content can be adjusted as shown below: - >0.40~<1.30% - 0.50 or >0.50~1.30 or <1.30% - 0.50 or >0.50~1.20 or <1.20% - 0.50 or >0.50~1.10 or <1.10% - 0.60 or >0.60-1.10 or <1.10%.

[0034] The same applies to manganese, which may be present in the alloy at 0.0 to 1.0%. The following numerical ranges are also possible: - >0.0~<1.00% - >0.0~0.50 or <0.50% - >0.0~0.05 or <0.05% - 0.005 or >0.005~0.20 or <0.20% - 0.005 or >0.005~0.10 or <0.10%.

[0035] Magnesium and / or calcium are also included with contents between 0.0001 and 0.05%. Preferably, there is the possibility to adjust these elements in the alloy as follows: - 0.0001~0.030% - 0.0001~0.020% - 0.0002~0.015% - 0.0010~0.010%.

[0036] The alloy contains 0.015 to 0.12% carbon, which can preferably be adjusted in the alloy within the following numerical ranges: - >0.015~<0.12% - 0.03 or >0.03~0.10 or <0.10% - 0.04 or >0.04~0.10 or <0.10% - 0.05 or >0.05~0.10 or <0.10% - 0.05 or >0.05-0.09 or <0.09%.

[0037] The same applies to the nitrogen element, which is contained in a content of 0.001 to 0.150%. The preferred content can be specified as follows: - >0.001~<0.150% - 0.010 or >0.010~0.140 or <0.140% - 0.020 or >0.020~0.140 or <0.140% - 0.050 or >0.050~0.140 or <0.140%.

[0038] The alloy also contains phosphorus with a content of 0.001 to 0.030%. The preferred contents can be defined as follows: - 0.001~0.015%.

[0039] The alloy also contains oxygen with a content of 0.0001 to 0.020%, in particular 0.0001 to 0.010%.

[0040] The element sulfur is provided in the alloy at a maximum content of 0.010%. The preferred contents can be defined as follows: - Maximum 0.008% Sulfur.

[0041] Molybdenum is present in the alloy at a content of less than 1.0%. The molybdenum content may be further restricted as follows: - Maximum 0.50 or <0.50% Mo - Maximum 0.20 or <0.20% Mo - Maximum 0.10 or <0.10% Mo - Maximum 0.05 or <0.05% Mo - Maximum 0.02 or <0.02% Mo.

[0042] In addition, the alloy contains less than 1.0% cobalt. The cobalt content may be further restricted as follows: - Maximum 0.50 or <0.50% Co - Maximum 0.20 or <0.20% Co - Maximum 0.10 or <0.10% Co - Maximum 0.05 or <0.05% Co - Maximum 0.015 or <0.015% Co.

[0043] Additionally, the alloy may contain less than 0.5% copper. Additionally, the copper content may be limited as follows: - Maximum 0.30 or <0.30% Cu - Maximum 0.10 or <0.10% Cu - Maximum 0.05 or <0.05% Cu - Maximum 0.015 or <0.015% Cu.

[0044] Tungsten is present in the alloy at a maximum content of 1.0%. Further tungsten content may be restricted as follows: - <1.0% W - Maximum 0.50 or <0.50% W - Maximum 0.20 or <0.20% W - Maximum 0.10 or <0.10% W - Maximum 0.05 or <0.05% W - Maximum 0.02 or <0.02% W.

[0045] The balance of the alloy consists of iron and normal impurities resulting from manufacturing. Additionally, the iron content may be limited as follows: - 28.0 or >28.0–38.0% - 29.0 or >29.0–38.0% - 30.0 or >30.0–38.0 or <38.0%.

[0046] To provide sufficient durability in carburizing, sulfidizing and chlorinating environments, the following relationship must be observed between nickel, silicon and aluminum: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) must be satisfied, where Ni, Si and Al and Si are the concentrations of the respective elements in mass %.

[0047] The preferred ranges are as follows: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦1.5 (1b) Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦1.0 (1c) can be adjusted as follows.

[0048] The addition of oxygen-affinity elements such as cerium, lanthanum, yttrium, zirconium and hafnium improves corrosion resistance by incorporating these elements into the oxide layer where they block oxygen diffusion paths at the grain boundaries.

[0049] Optionally, the alloy may contain 0.001-0.20% each of one or more of the elements cerium, lanthanum, yttrium, zirconium and hafnium, where the elements have the following formula: FRE=0.714×Ce+0.720×La+1.124×Y+1.096×Zr+0.560×Hf≦0.10 (2a) must be satisfied, where Ce, La, Y, Zr and Hf are the concentrations of the respective elements in mass %.

[0050] Preferably, when at least one of the elements cerium, lanthanum, yttrium, zirconium and hafnium is present, the FRE can be set as follows: FRE=0.714×Ce+0.720×La+1.124×Y+1.096×Zr+0.560×Hf≦0.075 (2b) FRE=0.714×Ce+0.720×La+1.124×Y+1.096×Zr+0.560×Hf≦0.065 (2c).

[0051] Alternatively, when cerium and lanthanum are present simultaneously, cerium mischmetal (abbreviated as CeMM) can also be used in a content of 0.001-0.20%, in which case the FRE is as follows: FRE=0.716×CeMM+1.124×Y+1.096×Zr+0.560×Hf≦0.10 (3a) where CeMM, Y, Zr and Hf are the concentrations of the respective elements in mass %.

[0052] Preferably, when cerium mischmetal is added, the FRE can be set as follows: FRE=0.716×CeMM+1.124×Y+1.096×Zr+0.560×Hf≦0.075 (3b) FRE=0.716×CeMM+1.124×Y+1.096×Zr+0.560×Hf≦0.065 (3c).

[0053] Preferably, cerium, lanthanum, cerium mischmetal, zirconium and hafnium may be present in the alloy within the following numerical ranges: - >0.001~<0.20% - 0.001 or >0.001~0.15 or <0.15% - 0.001 or >0.001~0.10 or <0.10% - 0.001 or >0.001~0.08 or <0.08% - 0.001 or >0.001~0.05 or <0.05% - 0.001 or >0.001~0.04 or <0.04% - 0.01 or >0.01-0.04 or <0.04%.

[0054] Preferably, yttrium may be present in the alloy within the following numerical ranges: - >0.001~<0.20% - 0.001 or >0.001~0.15 or <0.15% - 0.001 or >0.001~0.10 or <0.10% - 0.001 or >0.001~0.08 or <0.08% - 0.01 or >0.01~0.08 or <0.08% - 0.01 or >0.01~<0.045%.

[0055] Alternatively, the element titanium may be present in the alloy in a content of 0.0-0.50%. Preferably, titanium may be contained in the alloy in the following numerical ranges: - >0.0~<0.50% - >0.0~0.50 or <0.50% - 0.001 or >0.001~0.20 or <0.20% - 0.001 or >0.001~0.15 or <0.15% - 0.001 or >0.001~0.10 or <0.10% - 0.001 or >0.001~0.05 or <0.05% - 0.001 or >0.001~0.04 or <0.04% - 0.005 or >0.005~0.20 or <0.20%, - 0.010 or >0.010~0.20 or <0.20%.

[0056] Optionally, the niobium element can be adjusted to a content of 0.0-0.2% in the alloy. Preferably, niobium can be contained in the alloy within the following numerical ranges: - >0.0~<0.20% - >0.0~0.15 or <0.15% - >0.0~0.10 or <0.10% - >0.0~0.05 or <0.05% - >0.0~0.02 or <0.02% - 0.001 or >0.001~0.20 or <0.20% - 0.010 or >0.010~0.20 or <0.20%.

[0057] Optionally, 0.0 to 0.20% tantalum may also be included in the alloy. The preferred contents can be defined as follows: - >0.0~<0.20% - >0.0~0.10 or <0.10% - >0.0~0.05 or <0.05%.

[0058] Optionally, the boron element may be contained in the alloy in a content of 0.0001 to 0.008%. The preferred content can be defined as follows: - 0.0005-0.008% boron, - 0.0005 to 0.005% boron, - 0.0005-0.004% Boron.

[0059] Additionally, the alloy may contain up to 0.50% vanadium. - <0.50% V - V max 0.40 or <0.50% - V max 0.20 or <0.20% - V max 0.08 or <0.10% - V max 0.05 or <0.05%.

[0060] Finally, as impurities the elements lead, zinc and tin may still be present in the following contents: Pb max. 0.002%, Zn max. 0.002%, Sn max. 0.002%.

[0061] Additionally, the element beryllium may be given as: Less than 0.001% Be.

[0062] The alloy according to the invention is preferably melted in the open and then processed in a VOD (vacuum, oxidation, decarburization) or VLF (vacuum ladle furnace). However, smelting and casting in a vacuum are also possible. The alloy is then cast into ingots or electrodes or cast as a continuous casting to form a precursor product. Optionally, the precursor product is then annealed at a temperature of 900-1270 ° C for 0.1 h to 70 h. It is also possible to further remelt the alloy one or more times in an ESR (electroslag remelting plant) and / or VAR (vacuum arc remelting). The alloy is then brought into the desired semi-finished product form. For this, it is optionally annealed at a temperature of 800-1290 ° C for 0.1 h to 70 h and then hot forming, optionally with an intermediate annealing at a temperature of 800-1290 ° C for 0.05 h to 70 h. The surface of the material can be subjected to chemical and / or mechanical material removal processes (possibly several times) for cleaning during and / or at the end of the hot forming. Thereafter, if necessary, cold forming to the desired semi-finished product form with a degree of forming of up to 98% can be performed, optionally with an intermediate annealing at 800-1250 ° C for 0.05 min to 70 h, optionally under a shielding gas such as argon or hydrogen, followed by cooling in air, in a fluidized annealing atmosphere or in a water bath. Then, a solution annealing is performed at a temperature range of 800-1250 ° C for 0.05 min to 70 h, optionally under a shielding gas such as argon or hydrogen, followed by cooling in air, in a fluidized annealing atmosphere or in a water bath. If necessary, chemical and / or mechanical cleaning of the material surface can be performed during and / or after the final annealing.

[0063] The semi-finished products produced by hot and / or cold rolling have a microstructure with an average grain size of 5-600 μm after solution annealing.

[0064] The alloy according to the invention can be successfully manufactured and used in semi-finished forms such as bars, plates, forgings, longitudinal seam welded or seamless pipes, pipe fittings, valve parts, flanges, etc. The various semi-finished forms can be assembled into or attached to the required parts.

[0065] The alloy according to the invention can likewise be used for overlay welding of any kind of metal parts, if required.

[0066] The alloy according to the invention is particularly suitable as a component in the field of use with carburizing, sulfidizing and chlorinating environments, especially atmospheres. Due to the good high-temperature corrosion resistance and good deformation workability and weldability, the alloy according to the invention is suitable for use as a component in waste incineration plants, pyrolysis plants, smelting furnaces, chemical industry, coal gasification plants and industrial furnace construction, activated carbon filters, waste pyrolysis and precious metal recovery. [Brief description of the drawings]

[0067] [Figure 1] Depth of corrosion attack versus temperature for various alloys after aging for 2100 hours in H2S-containing gas at the Prenflo pilot plant.

[0068] Working Example: Testing An evaluation of high temperature corrosion resistance in carburizing, sulfidizing and chlorinating environments was carried out (at Dechema) by endurance of materials possessing these properties in a flowing synthetic gas atmosphere at high temperatures.

[0069] For this purpose, a 20 x 8 x 4 mm piece of semi-finished material from each alloy was cut. 3After cutting out the samples with dimensions of , a hole of 3 mm diameter was drilled and then wet polished with SiC paper up to 1200 grit (grain size about 15 μm). The samples were degreased and cleaned with isopropanol in an ultrasonic bath. Each sample was suspended above a ceramic crucible in a reaction vessel using said hole so that the spalled corrosion products could be captured and the mass of the spalls determined by weighing the crucible containing the corrosion products. The sum of the mass of the spalls and the mass change of the sample is the total mass change of the sample. The specific mass change is the mass change per unit surface area of ​​the sample. In the following, the specific net mass change is referred to as m Netto , the specific total mass change is m Brutto , the specific mass change of the spalled oxide is m spall It is called.

[0070] A gas mixture consisting of 60% CO, 30% H2, 4% CO2, 1% H2S, 0.05% HCl and 3.95% H2O was flowed into the reaction vessel space. This mixture has carburizing (60% CO), sulfidizing (1% H2S) and chlorinating (0.05% HCl) effects. The tests were carried out at 500 °C. The test duration was 1056 h each, divided into 11 cycles of 96 h each. For each test, there were two specimens of each alloy. The values ​​given are the average values ​​of these two specimens.

[0071] In the following test, after 1056 hours - ≦2.0mg / cm 2 (4) Total mass increase are considered to be durable in carburizing, sulfiding and chlorinating environments.

[0072] This means that the following relationship exists between nickel, silicon and aluminum: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) where Ni, Si and Al and Si are the concentrations of the respective elements in mass%.

[0073] Weldability is rated based on the extent to which hot cracking occurs during welding. The higher the risk of hot cracking, the poorer the weldability of the material.

[0074] To quantify the hot-cracking susceptibility, various alloys were tested in the MVT (Modifizierten Varestraint Transvarestraint) test at the Bundesanstalt für Materialforschung und -pruefung (BAM). For this purpose, specimens with dimensions 100 mm x 40 mm x 10 mm are prepared from the alloys. In the MVT test, a fully mechanical TIG seam (TIG: tungsten inert gas) is applied longitudinally at a constant feed rate to the upper side of this specimen. When the arc passes through the center of the specimen, a defined bending strain is applied to the specimen. In this case, the specimen is bent longitudinally relative to the welding direction (varestraint mode). During this bending phase, hot cracks are generated in the localized test area of ​​the MVT specimen.

[0075] The tests were carried out at a bending strain of 4%, a die speed of 2 mm / s, and an energy per unit length of 7.5 kJ / cm, each under 4.8 pure argon.

[0076] For the evaluation, the lengths of all solidification and remelt cracks visible in the sample are measured and summed under an optical microscope at 25x magnification. Based on these results, each material can then be classified as "hot cracking resistant" (range 1), "increased hot cracking tendency" (range 2) and "hot cracking susceptible" (range 3) as shown in Table 2.

[0077] In the following tests, alloys in range 1 (hot cracking resistant) and range 2 (increased tendency to hot crack) on the MVT test are considered to be well weldable because the prior art weldable alloy AC66 is in range 2. Alloys in range 3 that are hot cracking susceptible are generally difficult to weld, especially with filler metal of the same composition as the welded material.

[0078] high temperature strength Rating Hot tensile test This is determined at the desired temperature in a tensile test according to DIN EN ISO 6892-2, where the yield point R p0.2 , tensile strength R m and the breaking elongation A are determined. The test was carried out on a circular specimen with a measurement area diameter of 6 mm and an initial measurement length L0 of 30 mm. The yield point R at 500 °C p0.2 Or tensile strength R m should reach at least the minimum values ​​for alloy AC66 according to the prior art: - 500℃:R p0.2 ≧95MPa or R m ≧115MPa (5a, 5b).

[0079] Desirably, these are better than the prior art Alloy 45™ minimums.

[0080] - 500℃:R p0.2 ≧150MPa or R m ≧500MPa (6a, 6b).

[0081] The particle size is measured by the line intercept method.

[0082] manufacturing To characterize the components manufactured from the alloys, the alloys were melted in a vacuum furnace on a laboratory scale.

[0083] Tables 3a and 3b show the analysis of the batches melted on a laboratory scale and on a larger scale of prior art batches of AC66 (1.4877) and 45TM (2.4889) used for comparison. Prior art batches are marked with a T and the batches according to the invention with an E. Laboratory scale melted batches are marked with an L and large scale melted batches with a G.

[0084] Ingots of the alloys of Tables 3a and 3b melted on a laboratory scale in vacuum were annealed at 900-1270°C for 8 hours and then hot rolled to a final thickness of 13 or 6 mm by hot rolling and a further intermediate annealing at 900-1270°C for 0.1-1 hour. The plates thus produced were subjected to solution annealing at 800-1250°C for 1 hour. The samples required for the measurements were produced from these plates.

[0085] For alloys melted on a large scale, samples were obtained from large-scale production of plates of appropriate thickness made by the industry. From these plates, the specimens required for the measurements were manufactured.

[0086] The grain size for all alloy variations was typically between 50 and 190 μm.

[0087] The following properties were compared for the example batches of Table 3a and b): - High temperature corrosion resistance in carburizing, sulfidizing and chlorinating environments; - Weldability by MVT test, - Creep resistance by hot tensile test.

[0088] The results are listed in Table 4.

[0089] Table 4 shows the results of corrosion tests in the form of total mass change and spalling at 500 °C after 1056 hours in an atmosphere consisting of 60% CO, 30% H2, 4% CO2, 1% H2S, 0.05% HCl and 3.95% H2O. The chromium content of all the tested alloys was about 27-28%. The prior art alloy AC66, which contains only 0.2% silicon, has a chromium content of 10.92 mg / cm3. 2 The prior art Alloy 45™ containing 2.6% silicon and all laboratory melted test batches containing more than 1.0% silicon show a total mass change of 2.0 mg / cm 2The following total mass changes are shown (2209, 250098, 250101, 250105, 250102 and 250107). Furthermore, when the aluminum content is more than 0.40%, the batches with a silicon content of 1.0% or less also have a total mass change of 2.0 mg / cm3 if they simultaneously satisfy the formula (1a) Fc ≦ 2.5. 2 This is the case for batches 250084 (Si=0.59% and Al=0.95%), 250085 (Si=0.90% and Al0.98%), 250106 (Si=0.98% and Al0.80%) and 250108 (Si=0.70% and Al=0.86%).

[0090] Batches 250084, 250106, 250105, 250108 and 250107 are according to the invention, whereas batch 2209 with a silicon content of more than 1.50% and batch 250098 with a nickel content of 44.0% are not according to the invention. Despite the significantly higher silicon content of 1.2%, batch 250098 (Si=1.20% and Al=0.85%) shows a similar or higher total mass gain compared to batches 250106 (Si=0.98% and Al=0.80%) and 250101 (Si=1.01% and Al=0.75%). Batch 250098 (Ni=44.0%) has a significantly higher nickel content compared to batches 250106 (Ni=35.6%) and 250101 (Ni=38.2%). This shows that the higher the nickel content, the worse the corrosion. Therefore, the nickel content is capped at a maximum of 40%.

[0091] In contrast to batch 250101 (Ni=38.2%, Si=1.01% and Al=0.75%), which is not according to the invention, the total mass gain is 2.0 mg / cm 2 Much higher than (3.43 mg / cm 2 ) Batch 250100 (Ni=38.2%, Si=0.99% and Al=0.43%) has a slightly too low aluminum content, so that equation (1a) is not satisfied. It is not according to the invention and also has a total mass gain of 2.0 mg / cm 2 significantly higher than (8.01 mg / cm2 or 5.35 mg / cm 2 ) Batches 250103 (Ni=38.2, Si=0.36% and Al=0.82%) and 250099 (Ni=38.4%, Si=1.00% and Al=0.20%) have silicon and aluminum contents outside the claimed limits and also do not satisfy equation (1a).

[0092] The alloys 250084, 250106 according to the invention still show spalling. Moreover, when the formula (1c) Fc≦1.0 is also fulfilled, these alloys no longer show spalling (250107) and, surprisingly, even at a moderate silicon content, it is of the order of 1.0 mg / cm for 45TM with 2.6% silicon and 0.16% aluminum. 2 It also has a very low total mass change, significantly below .

[0093] Table 4 shows the weldability classification of alloys according to MVT testing. Prior art weldable alloy AC66 is in range 2. Alloy 45TM is in range 3 (hot-cracking susceptible), which means it has a high tendency to crack, is difficult to weld, and is difficult or impossible to weld with the same type of filler metal.

[0094] Batches not according to the invention with a silicon content of 1.50% or more and above 1.50% (45TM, batches 2091, 2099, 2100, 2200, 2203, 2207, 2208, 2209) are all in range 3. Among the batches with a silicon content of about 1.4%, those with an aluminum content of less than 0.1% are in range 2 (batches 2093, 2101), and those with a higher aluminum content are already in range 3 (batches 2103, 2096, 2097, 2098). All batches with a silicon content of less than 1.3% are in range 1 or 2 (AC66, batches 2095, 2102, 250084 to 250108). All laboratory batches according to the invention are either range 1 (batches 250084, 250106, 250105, 250108 and 250107) or range 2 (batch 250102).

[0095] The results of the hot tensile tests at 500°C in the table show that the yield points R of all alloys melted on a laboratory scale according to the present invention are p0.2 are greater than or equal to 153 MPa, thus clearly exceeding the minimum value of 95 MPa for AC66. They also exceed, although not significantly, the minimum value of 150 MPa for 45TM (see Eqs. 5a and 6a). Similarly, the tensile strengths R m are greater than 192 MPa and thus also significantly above the minimum value of 115 MPa for AC66 (see Eq. 5b). Hot tensile tests at 500°C all showed strains greater than 35%.

[0096] therefore, The claimed limits for the alloy "E" according to the invention This can be justified in detail as follows: A relatively low nickel content (with a relatively high iron content (balance) at the same time) favors low corrosion in carburizing, sulfidizing and chlorinating environments. A content of 40% is therefore the upper nickel limit. Too low a nickel content (with a too high iron content (balance) at the same time) promotes the formation of sigma phases, especially in the presence of high chromium and silicon contents. A nickel content of 35% is therefore the lower limit.

[0097] Chromium improves the corrosion resistance in carburizing, sulfiding and chlorinating environments. Too little chromium means that when the alloy is used in highly corrosive environments, the chromium concentration falls below the critical limit very quickly, so that a closed chromium oxide layer can no longer form. Therefore, the lower chromium limit for use in carburizing, sulfiding and chlorinating environments is 26% chromium. Too much chromium promotes the formation of sigma phase in the alloy, especially at high chromium contents. Therefore, 30% chromium should be considered as the upper limit.

[0098] Silicon improves corrosion resistance in carburizing, sulfidizing and chlorinating environments. Therefore, a minimum content of 0.40% is required. On the other hand, too much silicon impairs weldability and promotes sigma phase formation, especially at high chromium contents. Therefore, the silicon content is limited to 1.50%.

[0099] A certain amount of aluminum improves corrosion resistance in carburizing, sulfidizing and chlorinating environments. Therefore, a minimum content of 0.40% is necessary. On the other hand, too much aluminum impairs weldability, especially when the chromium and silicon contents are high. Therefore, the aluminum content is limited to 1.30%.

[0100] Manganese is useful for improving workability. Manganese is limited to 1.0% because this element reduces high-temperature corrosion resistance.

[0101] Even very low magnesium and / or calcium contents improve workability by binding sulfur, thereby avoiding the occurrence of low-melting NiS eutectic. Therefore, a minimum content of 0.0001% for magnesium and / or calcium is required. Too high a content can result in the occurrence of intermetallic Ni-Mg or Ni-Ca phases, which also significantly impair workability. Therefore, the magnesium and / or calcium content is limited to a maximum of 0.05%.

[0102] A minimum carbon content of 0.015% is necessary to obtain good creep resistance. Carbon is limited to a maximum of 0.12%, because above this content this element reduces workability due to the excessive formation of primary carbides.

[0103] A minimum content of 0.001% nitrogen is required, as it improves the workability and high temperature strength of the material. Nitrogen is limited to a maximum of 0.150%, as this element reduces workability by forming coarse carbonitrides.

[0104] The phosphorus content is preferably less than 0.030%, because this surface active element impairs high temperature corrosion resistance. Too low a phosphorus content will increase the cost. Therefore, the phosphorus content is ≧0.001%.

[0105] To ensure the manufacturability of the alloy, the oxygen content must be less than 0.020%. Too little oxygen content will increase the cost. Therefore, the oxygen content is ≥ 0.0001%.

[0106] It is desirable to keep the sulfur content as low as possible, since this surface active element impairs high temperature corrosion resistance, so sulfur is specified at a maximum of 0.010%.

[0107] Molybdenum is limited to less than 1.0% since this element reduces high temperature corrosion resistance.

[0108] Tungsten is limited to less than 1.0% since this element also reduces high temperature corrosion resistance.

[0109] Cobalt may be present in this alloy in amounts up to 1.0%, as higher contents reduce the high temperature corrosion resistance.

[0110] Copper is limited to less than 0.5% since this element reduces the high temperature corrosion resistance.

[0111] To provide sufficient durability in carburizing, sulfidizing and chlorinating environments, the following relationship must be observed between nickel, silicon and aluminum: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) must be satisfied, where Ni, Si and Al and Si are the concentrations of the respective elements in mass %. The limits for Fc are explained in detail in the preceding text.

[0112] If necessary, the high temperature corrosion resistance can be further improved by the addition of oxygen-affinity elements, which do so by being incorporated into the oxide layer where they block the diffusion paths of oxygen at the grain boundaries.

[0113] To obtain the effect of improving the hot corrosion resistance, a minimum content of one or more of the elements cerium, lanthanum, cerium mischmetal, yttrium, zirconium and hafnium of 0.001% each is required. The upper limit for each element is set at 0.20% for cost reasons. In this case, the following formula: FRE=0.714×Ce+0.720×La+1.124×Y+1.096×Zr+0.560×Hf≦0.10 (2a) must be satisfied, where Ce, La, Y, Zr and Hf are the concentrations of the respective elements in mass%. This formula limits the total content of elements such as cerium, lanthanum, yttrium, zirconium and hafnium. A content of FRE>1.0 again increases the corrosion rate and may impair workability.

[0114] Titanium can be added if necessary. Titanium increases high temperature strength. Above 0.50%, high temperature corrosion behavior may deteriorate, so 0.50% is the maximum value.

[0115] Niobium can also be added as needed to increase high-temperature strength. If the content is too high, the cost becomes very high. Therefore, the upper limit is set at 0.20%.

[0116] If desired, the alloy may also contain tantalum, as it also improves high temperature strength. Higher contents are very cost-prohibitive. Therefore, an upper limit of 0.20% is specified. A minimum content of 0.001% is required to be effective.

[0117] Boron can be added to the alloy if necessary, since it improves creep resistance. Therefore, it is desirable for it to have a content of at least 0.0001%. At the same time, this surface active element deteriorates high-temperature corrosion resistance. Therefore, boron is specified to a maximum of 0.008%.

[0118] Vanadium is limited by necessity to a maximum of 0.50% since this element reduces high temperature corrosion resistance.

[0119] Where necessary, lead is limited to a maximum of 0.002% since this element reduces high temperature corrosion resistance, as do zinc and tin.

[0120] [Table 1]

[0121] [Table 2]

[0122] [Table 3]

[0123] [Table 4]

[0124] [Table 5]

Claims

1. The following (in mass %): 35.0 to 38% nickel, 26.0 to 30.0% chromium, >0.7-1.50% silicon, 0.40 to 1.30% Aluminum, 0.00 to 1.0% manganese, 0.0001-0.05% each of magnesium and / or calcium, 0.015 to 0.12% carbon, 0.001 to 0.150% nitrogen, 0.001 to 0.030% phosphorus, 0.0001 to 0.020% oxygen, Maximum 0.010% sulfur, less than 1.0% molybdenum, less than 1.0% Cobalt, less than 0.5% copper, less than 1.0% tungsten, The remainder is iron and normal process impurities.

2. Use of a nickel-iron-chromium alloy having outstanding high-temperature corrosion resistance, comprising: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) must be satisfied, where Ni, Si and Al are the concentrations of the respective elements in mass %.

2. 2. Use according to claim 1, wherein the nickel content is >35.0 to <38%.

3. 3. Use according to claim 1 or 2, wherein the chromium content is >26.0-30.0%.

4. 4. Use according to any one of claims 1 to 3, wherein the aluminum content is ≧0.50% or >0.50% to <1.30%.

5. 5. Use according to any one of claims 1 to 4, wherein the remaining iron content is 28.0 or >28.0-38.0%.

6. One or more of the elements cerium, lanthanum, yttrium, zirconium and hafnium are included at 0.001 to 0.20% each, where the following formula is satisfied: FRE=0.714×Ce+0.720×La+1.124×Y+1.096×Zr+0.560×Hf≦0.10 (2a) 6. The use according to claim 1 , wherein Ce, La, Y, Zr and Hf are the concentrations of the elements in mass %.

7. When cerium and lanthanum are present simultaneously, cerium mischmetal (abbreviated as CeMM) is also used with a content of 0.001 to 0.20%, in which case FRE is defined as follows: FRE=0.716×CeMM+1.124×Y+1.096×Zr+0.560×Hf≦0.10 (3a) 7. Use according to any one of claims 1 to 6, wherein CeMM, Y, Zr and Hf are the concentrations of the respective elements in mass%.

8. Use according to any one of claims 1 to 7, optionally with a titanium content of 0.0 to 0.50%.

9. 9. Use according to any one of claims 1 to 8, optionally with a niobium and / or tantalum content of 0.0 to 0.50% each.

10. 10. Use according to any one of claims 1 to 9, optionally with a boron content of 0.0001 to 0.008%.

11. 11. Use according to any one of claims 1 to 10, further optionally comprising up to 0.50% vanadium.

12. 12. Use according to any one of claims 1 to 11, characterized in that the impurities are controlled with a content of max. 0.002% lead, max. 0.002% tin, max. 0.002% zinc.

13. 13. Use according to any one of the preceding claims, characterized in that the semi-finished products are in the form of strips, plates, wires, bars, forged parts, longitudinal seam welded pipes and seamless pipes.

14. 14. Use according to any one of claims 1 to 13 as or in parts of the chemical industry.

15. 14. Use according to any one of claims 1 to 13 as a semi-finished product in a waste incineration plant or waste pyrolysis plant or as a semi-finished product in a part of a waste incineration plant or waste pyrolysis plant.

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