The use of nickel-iron-chromium alloy, which has high durability in carburizing, sulfidizing, and chlorinating environments, while also possessing 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 a nickel-iron-chromium alloy that has good high-temperature corrosion resistance in highly corrosive environments, such as environments that are carburizing, sulfidizing, and simultaneously chlorinating, and that has improved workability, particularly weldability.

[0002] Austenitic nickel-iron-chromium alloys with varying nickel, chromium, and iron content have long been used in furnace construction and the chemical and petrochemical industries. These applications require good high-temperature corrosion resistance in carburizing and sulfidizing environments, as well as good high-temperature strength.

[0003] In general, it should be noted that the high-temperature corrosion resistance of the alloys shown in Table 1 improves with increasing chromium content. All of these alloys form a chromium oxide layer (Cr2O3) and a somewhat closed silicon oxide layer beneath it. Adding small amounts of oxygen-affinity elements such as yttrium or cerium improves corrosion resistance. The chromium content is gradually consumed in the formation of a protective layer during 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 chromium content that forms the protective layer, the later it takes for the chromium content to fall below the critical value and for oxides other than Cr2O3 (such as iron-containing oxides or nickel-containing oxides) to form. Further improvements in high-temperature corrosion resistance can be achieved by adding silicon or aluminum. From a certain minimum content, these elements form a closed layer beneath the chromium oxide layer, thereby reducing the consumption of chromium.

[0004] In a carburizing environment (a mixture of CO, H2, CH4, CO2, and H2O), carbon penetrates into the material, which can lead to the formation of internal carbides. This causes a decrease in notched impact strength. A transformation process may also occur due to the depletion of chromium in the base material.

[0005] High carburizing resistance is achieved by materials with low carbon solubility and low carbon diffusion rates. Therefore, nickel alloys generally have higher carburizing resistance than iron-based alloys because nickel has lower carbon diffusion and carbon solubility than iron. Increasing the chromium content results in higher carburizing resistance due to the formation of a protective chromium oxide layer, except when the oxygen partial pressure in the gas is insufficient to form this protective chromium oxide layer. When the oxygen partial pressure is very low, materials that form layers of silicon oxide or even more stable aluminum oxide can be used, both of which can form protective oxide layers even with extremely low oxygen content.

[0006] In low oxygen partial pressure environments that promote carburization and sulfidation (mixtures of CO, H2, H2O, CO2, and H2S), sulfur penetrates the material, which can lead to the formation of sulfides. Furthermore, the melting point can drop to very low values ​​(635°C for Ni-Ni3S2 eutectic and 988°C for Fe-FeS eutectic). High-nickel nickel-iron-chromium alloys are often more sensitive to sulfidation environments than high-iron nickel-iron-chromium alloys. Here again, further improvements in high-temperature corrosion resistance can be achieved by adding silicon or aluminum.

[0007] In chlorinated environments with low oxygen partial pressure, volatile metal chlorides with high vapor pressure and / or low melting points can form, leading to high corrosion rates. Higher chromium and / or nickel content improves corrosion resistance.

[0008] German Patent No. 4130139 describes a hot-formable, heat-resistant austenitic nickel alloy comprising (in mass percent) 0.05–0.15% carbon, 2.5–3.0% silicon, 0.2–0.5% manganese, up to 0.015% phosphorus, up to 0.005% sulfur, 25–30% chromium, 20–27% iron, 0.05–0.15% aluminum, 0.001–0.005% calcium, 0.05–0.15% rare earth elements, 0.05–0.20% nitrogen, the remainder being nickel and ordinary impurities resulting from melting.

[0009] The alloy described in German Patent No. 4130139 is known by the names "NiCr28FeSiCe", alloy 45TM, Nicrofer 45TM, or material number 2.4889, and will be hereinafter referred to as "45TM".

[0010] Alloy 45TM is highly resistant to carburizing and sulfidizing media, making it suitable for use in waste incineration plants and coal gasification plants. Figure 1 shows the metallographically measured corrosion attack depth of various alloys against temperature after aging for 2100 hours in H2S-containing gas at the Fürstenhausen PRENFLO coal gasification pilot plant. Table 1 shows the composition of the alloys analyzed by prior art. High chromium and silicon content significantly reduces corrosion attack depth. A high silicon content of ≥2.5% allows for the formation of a silicon oxide layer beneath the protective chromium oxide layer, thereby increasing the corrosion resistance of the material. 45TM with 26-29% chromium and 2.5-3% silicon exhibits the shallowest corrosion attack depth at all temperatures, followed by AC66 with 26-28% chromium and up to 0.3% silicon.

[0011] However, alloy 45TM is extremely difficult to process. This is evident, for example, from the cracking that occurs during hot forming. Similarly, 45TM is prone to cracking during welding, making it impossible to perform specific welding (using filler material within the composition range of the material being welded), which is rational for corrosion prevention reasons, thus making the material difficult to use practically. In austenitic FeCrNi welds with primary austenite solidification, the formation of low-melting-point phases due to silicon accumulation at austenite grain boundaries (eutectic Fe-Fe2Si: 1212°C, eutectic NiSi-Ni3Si2: 964°C, and NiSi: 996°C) and the expansion of the solidification range are cited as causes of increased hot cracking.

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

[0013] In addition to carburizing and sulfiding conditions, the demands on materials become even higher when attacked by chlorine generated in coal gasification plants and waste incineration plants.

[0014] Materials used in carburizing, sulfidizing, and chlorinating environments, especially atmospheric environments, must be compromised in terms of composition.

[0015] High-temperature strength is improved, in particular, by increasing the carbon content. However, high-temperature strength is also improved by increasing the content of solid solution strengthening elements such as chromium, aluminum, silicon, molybdenum, and tungsten.

[0016] U.S. Patent No. 6,623,869 describes a metallic material containing, in mass percent, the following components: 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% to 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 remainder being substantially iron. In this case, the value of 40Si+Ni+5Al+40N+10(Cu+Co) is 50 or greater, 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 in furnace tubes, conduit systems, heat exchanger tubes, etc., in oil refineries and petrochemical plants. This can significantly improve the lifespan and safety of the plant.

[0017] U.S. Patent No. 3,833,358 describes an iron-based refractory alloy that provides high resistance to creep, thermal shock, thermal fatigue, and intercrystalline oxidation, as well as good weldability, and the alloy is substantially composed of the following elements (by weight): 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 to 2 Ta 0 to 0.3 Ti 0 to 1 Mo 0 to 0.5 Al 0 to 0.05 Pb 0 to 0.01 Sn 0 to 0.01 Zn 0 to 0.01 Cu 0 to 0.25 It consists of the above and the balance is substantially iron. Here, the weight ratios of the aforementioned elements are as follows: 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] U.S. Patent No. 3,865,581 describes a heat - resistant alloy having hot - formability, which mainly consists of C of 0.01 to 0.5%, Si of 0.01 to 2.0%, Mn of 0.01 to 3.0%, Ni of 22 to 80% and Cr of 10 to 40%, and contains one or both of B of 0.0005 to 0.20% and Zr of 0.001 to 6.0%, and further one or more of Ce of 0.001 to 0.5%, Mg of 0.001 to 0.2% and Be of 0.001 to 1.0%, together with the balance of iron and inevitable impurities. This is suitable for use in furnace construction (such as burner tips, protective housings, thermocouple protection tubes, etc.).

[0019] German Patent Application Publication No. 1024719 describes a method for adding cerium and / or lanthanum to a nickel-iron alloy. This is a hot-workable alloy characterized by the following composition: 0-0.5% carbon, 10-60% one or more elements from chromium, molybdenum, and tungsten (each of which does not exceed 30%), 0-73% iron, 0.02-1.10% cerium or lanthanum or both, and the remainder 4-70% nickel including impurities, provided 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] European Patent Application Publication No. 0812926 describes a nickel-based alloy that improves in strength upon use, comprising 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% aluminum, 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 remainder being iron and random impurities.

[0021] International Publication No. 2007 / 124996 describes a reaction vessel for use in the production of hydrogen sulfide by the reaction of sulfur and hydrogen, wherein some or all of the reaction vessel and optionally connecting conduits, fittings and measuring and control elements are made of an aluminum-containing material resistant to the reaction mixture. In particular, the material contains (in weight percent) 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-remainder% Fe, 1.0-5.0% Al, 0-2.5% Co, 0-1.5% Ti, 0-0.4% Y and up to 70% Ni.

[0022] German Patent Application Publication No. 102007005605 describes an iron-nickel-chromium-silicon alloy containing (in weight percent) 34-42% nickel, 18-26% chromium, 1.0-2.5% silicon, and 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, up to 0.01% sulfur, up to 0.005% boron, the remainder being iron and typical impurities resulting from the process. This alloy is used in heating elements.

[0023] U.S. Patent No. 5,021,215 states 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 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 remainder is Fe and random impurities. A high-strength, heat-resistant steel with improved deformability is disclosed, wherein the oxygen and nitrogen impurities are limited to 50 ppm or less and 200 ppm or less, respectively, and the austenite grain size is limited to 4 or higher.

[0024] Japanese Patent Publication No. 56-163244 describes the improvement of the hot workability and oxidation resistance of austenitic steel by adding specific amounts of C, Si, Mn, Ni, Cr, Al, B, rare earth elements, and Ca to austenitic steel. This is achieved by 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 an additional 0.0005-0.03% Mg as needed. The austenitic steel obtained therefrom is refined in a conventional steelmaking furnace, the molten steel is formed into billets, and then hot-rolled.

[0025] U.S. Patent No. 7,118,636 describes a nickel-iron-chromium alloy containing a solidified phase that can maintain a fine-grained structure during forging and machining of the alloy at high temperatures. Because the alloy contains sufficient amounts of titanium, zirconium, carbon, and nitrogen, fine titanium and zirconium nitrides are formed in the molten state of the alloy, even though it is close to its melting limit. When articles are manufactured from such alloys by thermomachining, a dispersion of fine titanium and zirconium carbonitride precipitates forms during the solidification of the molten material and remains in the alloy during subsequent (high-temperature) machining processes, preventing austenite grain growth. Nickel-iron-chromium alloys contain less than 0.05% by weight of niobium, at least 0.05% of zirconium, at least 0.05% of carbon, and at least 0.05% of nitrogen, where the weight ratio of carbon to nitrogen is at least 1:2 to less than 1:1, and contain sufficient amounts of titanium, zirconium, and / or aluminum to be chromium carbide-free, and the titanium, zirconium, carbon, and nitrogen are present in the molten state of the alloy as fine titanium and zirconium carbonitrides [(Ti x Zr 1-x )(C y N 1-y This is a sufficient amount to form a uniform dispersion of ). The nickel-iron-chromium alloy further consists of about 32% to 38% by weight of iron, about 22% to 28% by weight of chromium, about 0.10% to 0.60% of titanium, about 0.05% to 0.30% of zirconium, about 0.05% to 0.30% of carbon, about 0.05% to 0.30% of nitrogen, about 0.05% to 0.5% of aluminum, up to 0.99% of molybdenum, up to about 0.01% of boron, up to about 1% of silicon, up to about 1% of manganese, the remainder being nickel and random impurities.

[0026] Japanese Patent Publication No. 57-134544 describes how to improve the stress corrosion cracking resistance of oil well pipes by adding predetermined amounts of Mo, W, etc. to high-Cr-Ni steel as a pipe material. For this purpose, alloy steel 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 is used, and these are given by the following formula Cr(%) + 10 × Mo(%) + 5 × W(%) ≥ 70% 4% ≤ Mo(%) + 1 / 2W(%) < 8% The steel satisfies the following conditions. This steel is used for oil well tubing used in highly corrosive and harsh environments such as oil wells and natural gas wells. The alloy can be supplemented 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. This makes it possible to manufacture oil well tubing with excellent stress corrosion cracking resistance in the highly corrosive environments of oil wells containing H2S, CO2, and Cl.

[0027] The problem that forms the basis of this invention is, a) For example, in highly corrosive environments such as those that are carburizing, sulfidizing, and simultaneously chlorinating, it exhibits good high-temperature corrosion resistance comparable to alloy 45TM. b) Having sufficient workability, especially weldability, as close as possible to that of alloy AC66, and c) Possesses sufficient high-temperature strength at 500°C, equivalent to alloy AC66. The goal is to devise the use of a nickel-iron-chromium wrought alloy.

[0028] The problems that form the basis of this invention are as follows (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, Each contains 0.0001 to 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, Molybdenum less than 1.0%, less than 1.0% cobalt, Less than 0.5% copper, Tungsten less than 1.0%, The remainder is iron and normal impurities resulting from the process. The use of a nickel-iron-chromium alloy, which has exceptional high-temperature corrosion resistance, as a semi-finished product in a carburizing, sulfidizing, and simultaneously chlorinating environment, where the following relationship applies: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) The following conditions must be met, where Ni, Si, and Al are the concentrations of the elements in mass percent, which are resolved by use.

[0029] An advantageous development of the subject matter of the present invention can be obtained from the supplementary dependent claims.

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

[0031] The numerical range for chromium 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 to 1.50%. Preferably, the silicon content in the alloy can be adjusted within the following numerical range: ->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%, and here too, the preferred aluminum content can be adjusted as follows: ->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; it can be present in the alloy at a concentration of 0.0-1.0%. 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 to 0.20 or <0.20% - 0.005 or >0.005 to 0.10 or <0.10%.

[0035] Magnesium and / or calcium are also present in concentrations of 0.0001 to 0.05%. Preferably, these elements can be adjusted 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. Preferably, this can be adjusted within the following numerical ranges in the alloy: ->0.015~<0.12% - 0.03 or >0.03 to 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] This also applies to nitrogen elements present in concentrations of 0.001 to 0.150%. Preferred concentrations can be defined 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 in a content of 0.001 to 0.030%. The preferred content can be defined as follows: - 0.001~0.015%.

[0039] The alloy also contains oxygen in amounts of 0.0001 to 0.020%, particularly 0.0001 to 0.010%.

[0040] Sulfur is present in the alloy at a maximum concentration of 0.010%. Preferred concentrations can be defined as follows: - Maximum 0.008% sulfur.

[0041] Molybdenum is present in the alloy at a content of less than 1.0%. Furthermore, the molybdenum content can be limited 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] Furthermore, the alloy contains less than 1.0% cobalt. Additionally, the cobalt content can be limited 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] Furthermore, the alloy may contain less than 0.5% copper. The copper content can be further restricted 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%. Furthermore, the tungsten content can be limited as follows: - <1.0% W - Maximum 0.50% or <0.50% W - W up to 0.20 or <0.20% - Maximum 0.10% or <0.10% W - W up to 0.05 or <0.05% - Maximum 0.02% or <0.02% W.

[0045] The remainder of the alloy consists of iron and the usual impurities resulting from the manufacturing process. Furthermore, the iron content can 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 exists between nickel, silicon, and aluminum: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) The following conditions must be met, where Ni, Si, Al, and Si are the concentrations of the elements in mass percent.

[0047] The preferred range is 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) It can be adjusted like this.

[0048] The addition of oxygen-affinity elements such as cerium, lanthanum, yttrium, zirconium, and hafnium improves corrosion resistance. These elements do so by being incorporated into the oxide layer and blocking oxygen diffusion pathways at grain boundaries.

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

[0050] Preferably, if at least one of the elements cerium, lanthanum, yttrium, zirconium, and hafnium is present, 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] Selectively, when cerium and lanthanum are present together, cerium mischmetal (abbreviated as CeMM) can also be used in a content of 0.001-0.20%, but in that case, the FRE should be as follows: FRE=0.716×CeMM+1.124×Y+1.096×Zr+0.560×Hf≦0.10 (3a) The following changes must be made, where CeMM, Y, Zr, and Hf are the concentrations of the respective elements in mass percent.

[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 to 0.15 or <0.15% - 0.001 or >0.001 to 0.10 or <0.10% - 0.001 or >0.001 to 0.08 or <0.08% - 0.001 or >0.001 to 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 to 0.15 or <0.15% - 0.001 or >0.001 to 0.10 or <0.10% - 0.001 or >0.001 to 0.08 or <0.08% - 0.01 or >0.01 to 0.08 or <0.08% - 0.01 or >0.01 to <0.045%.

[0055] Selectively, titanium can be present in the alloy in a content of 0.0 to 0.50%. Preferably, titanium may be present in the alloy within the following numerical ranges: ->0.0~<0.50% ->0.0~0.50 or <0.50% - 0.001 or >0.001 to 0.20 or <0.20% - 0.001 or >0.001 to 0.15 or <0.15% - 0.001 or >0.001 to 0.10 or <0.10% - 0.001 or >0.001 to 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] The niobium content in the alloy can be selectively adjusted to 0.0-0.2%. Preferably, the niobium may be present 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 to 0.20 or <0.20% - 0.010 or >0.010~0.20 or <0.20%.

[0057] Selectively, 0.0–0.20% tantalum may also be included in the alloy. Preferred content can be defined as follows: ->0.0~<0.20% ->0.0~0.10 or <0.10% ->0.0~0.05 or <0.05%.

[0058] Selectively, boron may be present in the alloy in a content of 0.0001 to 0.008%. Preferred content can be defined as follows: - 0.0005~0.008% boron, - 0.0005~0.005% boron, - 0.0005-0.004% boron.

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

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

[0061] Furthermore, the element beryllium may be given as follows: Be is less than 0.001%.

[0062] The alloy according to the present invention is preferably melted openly and then treated in 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. In some cases, the precursor product is then annealed at a temperature of 900-1270°C for 0.1 to 70 hours. The alloy may also be remelted one or more times in an ESR (Electroslag Remelting Plant) and / or VAR (Vacuum Arc Remelting). The alloy is then formed into the desired semi-finished product form. For this purpose, it is annealed at a temperature of 800-1290°C for 0.1 to 70 hours as needed, followed by hot forming, which may involve intermediate annealing at a temperature of 800-1290°C for 0.05 to 70 hours. The surface of the material may be chemically and / or mechanically dematerialized for cleaning during and / or at the end of hot forming as needed (may be several times). Subsequently, if necessary, cold forming can be performed to the desired semi-finished form with a degree of formability up to 98%, which may be accompanied by intermediate annealing at 800-1250°C for 0.05 minutes to 70 hours, which may be performed under a shielding gas such as argon or hydrogen, if necessary, and then cooled in air, a fluid annealing atmosphere, or a water bath. Subsequently, solution annealing is performed at a temperature range of 800-1250°C for 0.05 minutes to 70 hours, which may be performed under a shielding gas such as argon or hydrogen, if necessary, and then cooled in air, a fluid annealing atmosphere, or a water bath. If necessary, chemical and / or mechanical cleaning of the material surface may be performed during and / or after the final annealing.

[0063] Semi-finished products manufactured by hot and / or cold rolling have a microstructure with an average particle size of 5 to 600 μm after solution annealing.

[0064] The alloy according to the present invention can be readily manufactured and used in semi-finished forms such as rods, plates, forged members, longitudinal seam welded pipes or seamless pipes, pipe fittings, valve components, and flanges. Various semi-finished forms can be assembled into necessary parts or attached to necessary parts.

[0065] The alloy according to the present invention can also be used for build-up welding of any type of metal part as needed.

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

[0067] [Figure 1] This figure shows the corrosion attack depth of various alloys against temperature after aging for 2100 hours in H2S-containing gas at the Prenflo pilot plant.

[0068] Examples: Test Implementation High-temperature corrosion resistance in carburizing, sulfidizing, and chlorinating environments was evaluated (using Dechema) by measuring the durability of the material in a fluid synthesis gas atmosphere with these properties at high temperatures.

[0069] For this purpose, 20 x 8 x 4 mm from the semi-finished products of each alloy. 3After cutting out samples of the dimensions, holes with a diameter of 3 mm were drilled, and then wet polishing was performed using SiC paper up to 1200 grit (particle size of approximately 15 μm). These samples were degreased and washed with isopropanol in an ultrasonic bath. In some cases, spalling corrosion products were captured, and each sample was suspended above the ceramic crucible using the aforementioned holes in the reaction vessel so that the mass of the spalling material could be determined by measuring the weight of the crucible containing the corrosion products. The sum of the mass of the spalling material 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. Regarding these, hereinafter, the specific pure mass change is m Netto and the specific total mass change is m Brutto , and the specific mass change of the spalling oxide is m spall are referred to as such.

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

[0071] In the following tests, after 1056 hours - A total mass increase of ≤ 2.0 mg / cm 2 (4) is considered to indicate that the alloy is durable in carburizing, sulfidizing, and chlorinating environments.

[0072] This corresponds to the case where the following relationship between nickel, silicon, and aluminum: Fc = -1.2 + 0.29×Ni - 4.6×Si - 4.4×Al ≤ 2.5 (1a) is satisfied, where Ni, Si, and Al and Si are the concentrations of the corresponding elements in mass% units.

[0073] Weldability is evaluated by the extent to which hot cracks occur during welding. The higher the risk of hot cracking, the worse the weldability of the material.

[0074] To quantify hot cracking susceptibility, various alloys were tested using the MVT (Modifizierten Varestraint Transvarestraint) test of the BAM (Bundesanstalt fuer Materialforschung und -pruefung). For this purpose, a sample measuring 100 mm × 40 mm × 10 mm was prepared from the alloy. In the MVT test, a TIG seam (TIG: tungsten inert gas) was applied longitudinally to the upper side of this sample by fully mechanized means at a constant feeding rate. A predetermined bending strain was applied to the sample as the arc passed through the center of the sample. In this case, the sample was bent longitudinally relative to the welding direction (varestraint mode). During this bending stage, hot cracking occurs in the localized test area of ​​the MVT sample.

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

[0076] For evaluation, the lengths of all solidification and remelting cracks visible in the sample are measured and summed using a 25x magnification optical microscope. Based on these results, each material can then be classified into "hot cracking resistance" (range 1), "increased tendency to hot crack" (range 2), and "hot cracking susceptibility" (range 3), as shown in Table 2.

[0077] In the following tests, alloys in range 1 ("Resistance to hot cracking") and range 2 ("Increased tendency to hot crack") in the MVT test are considered to be weldable well, because the weldable alloy AC66 according to prior art is in range 2. Alloys that are susceptible to hot cracking (range 3) are generally difficult to weld. In particular, welding with filler material of the same type (composition equivalent to the material being welded) is difficult or impossible.

[0078] high temperature strength Evaluation In a hot tensile test This was done. This is determined at the desired temperature by a tensile test in accordance with DIN EN ISO 6892-2. Here, the yield point R p0.2 , tensile strength R m The elongation at break A was determined. The test was performed on a circular sample with a measurement range diameter of 6 mm and an initial measurement length L0 of 30 mm. The yield point R at 500°C was determined. p0.2 Or tensile strength R m It should at least reach the minimum value of alloy AC66 according to prior art: - 500℃:R p0.2 ≥95MPa, or R m ≥115 MPa (5a, 5b).

[0079] It is desirable that these values ​​are superior to the minimum values ​​for alloy 45TM obtained from prior art.

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

[0081] The particle size is measured using the line section method.

[0082] manufacturing To verify the properties of parts manufactured from alloys, alloys melted in a laboratory-scale vacuum furnace were used.

[0083] Tables 3a and 3b show the analysis of batches melted at a laboratory scale and the analysis of prior art batches of AC66 (1.4877) and 45TM (2.4889) melted at a large scale for comparison. Prior art batches are denoted with T, and batches according to the present invention with E. Batches melted at a laboratory scale are denoted with L, and batches melted at a large scale with G.

[0084] Ingots of the alloys shown in Tables 3a and 3b, melted in a vacuum on a laboratory scale, 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 followed by further intermediate annealing at 900-1270°C for 0.1-1 hour. The resulting plates were then subjected to solution annealing at 800-1250°C for 1 hour. Samples necessary for measurement were prepared from these plates.

[0085] For alloys melted on a large scale, samples were obtained from the large-scale production of appropriately thick plates manufactured by companies. From these plates, the samples necessary for measurement were prepared.

[0086] The grain size of all alloy deformation forms was typically between 50 and 190 μm.

[0087] For the example batches in Tables 3a and 3b), the following characteristics were compared: - High-temperature corrosion resistance in carburizing, sulfidizing, and chlorinating environments. - Weldability by MVT test, - Creep resistance as determined by hot tensile testing.

[0088] The results are summarized in Table 4.

[0089] Table 4 shows the results of corrosion tests in the form of spalling and total mass change 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 alloys tested was approximately 27-28%. The prior art alloy AC66, which contains only 0.2% silicon, had a chromium content of 10.92 mg / cm³. 2 This shows an overwhelmingly large change in total mass. All prior art alloy 45TM containing 2.6% silicon, and all test batches melted on a laboratory scale with a silicon content exceeding 1.0%, showed a result of 2.0 mg / cm³. 2The following total mass changes are observed (2209, 250098, 250101, 250105, 250102, and 250107). Furthermore, if the aluminum content exceeds 0.40%, batches with a silicon content of 1.0% or less will also have a total mass change of 2.0 mg / cm if they simultaneously satisfy equation (1a) Fc ≤ 2.5. 2 The following is possible. This applies to batches 250084 (Si=0.59% and Al=0.95%), 250085 (Si=0.90% and Al=0.98%), 250106 (Si=0.98% and Al=0.80%), and 250108 (Si=0.70% and Al=0.86%).

[0090] Batches 250084, 250106, 250105, 250108, and 250107 conform to the present invention, but batch 2209, with a silicon content exceeding 1.50%, and batch 250098, with a nickel content of 44.0%, do not conform to the present invention. Batch 250098 (Si=1.20% and Al=0.85%) shows an equivalent or greater increase in total mass compared to batches 250106 (Si=0.98% and Al=0.80%) and 250101 (Si=1.01% and Al=0.75%), despite its significantly high silicon content of 1.2%. Batch 250098 (Ni=44.0%) has a significantly higher nickel content than batches 250106 (Ni=35.6%) and 250101 (Ni=38.2%). This indicates that corrosion worsens with increasing nickel content. Therefore, the upper limit for nickel is set at a maximum of 40%.

[0091] In contrast to batch 250101 (Ni=38.2%, Si=1.01%, and Al=0.75%), the total mass increase is 2.0 mg / cm³, which is not according to the present invention. 2 This is significantly higher (3.43 mg / cm³). 2 In batch 250100 (Ni=38.2%, Si=0.99%, and Al=0.43%), the aluminum content is slightly too low, so equation (1a) is not satisfied. This is not according to the present invention, but similarly, the total mass increase is 2.0 mg / cm³. 2 This is significantly higher (8.01 mg / cm³).2 Alternatively, 5.35 mg / cm³ 2 In batches 250103 (Ni=38.2%, Si=0.36%, and Al=0.82%) and 250099 (Ni=38.4%, Si=1.00%, and Al=0.20%), the silicon and aluminum content is outside the claimed limits and further fails to satisfy formula (1a).

[0092] Alloys 250084 and 250106 according to the present invention still exhibit spalling. Furthermore, when formula (1c)Fc ≤ 1.0 is also satisfied, these alloys no longer exhibit spalling (250107), and surprisingly, with a moderate silicon content, they further exhibit a silicon content of 1.0 mg / cm³, which is on the order of 45™ with 2.6% silicon and 0.16% aluminum. 2 It also exhibits extremely low total mass changes, which are significantly lower than those mentioned above.

[0093] Table 4 shows the classification of alloy weldability based on MVT testing. The weldable alloy AC66, according to prior art, falls into range 2. Alloy 45TM is classified into range 3 (hot crack susceptibility), meaning it has a strong tendency to crack, making welding difficult and potentially impossible with the same type of filler material.

[0094] Batches not according to the present invention (45TM, batches 2091, 2099, 2100, 2200, 2203, 2207, 2208, 2209) having a silicon content of 1.50% or more are all in range 3. Of the batches with a silicon content of approximately 1.4%, those with an aluminum content of less than 0.1% are in range 2 (batches 2093, 2101), and batches with a higher aluminum content are already in range 3 (batches 2103, 2096, 2097, 2098). Batches with a silicon content of less than 1.3% are all in range 1 or 2 (AC66, batches 2095, 2102, 250084~250108). All laboratory batches according to the present invention are in range 1 (batch 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 represent the yield point R of all alloys melted on a laboratory scale according to the present invention. p0.2 The tensile strength R of all alloys according to the present invention is 153 MPa or higher, and therefore clearly exceeds the minimum value of 95 MPa for AC66. These also exceed, though not by a large margin, the minimum value of 150 MPa for 45TM (see equations 5a and 6a). Similarly, the tensile strength R of all alloys according to the present invention m The strain was over 192 MPa, and therefore significantly higher than the minimum value of 115 MPa for AC66 (see Equation 5b). In hot tensile tests at 500°C, all showed strains exceeding 35%.

[0096] therefore, Limit values ​​as described in the claims of alloy "E" according to the present invention This can be substantiated in detail as follows: A relatively low nickel content (with a relatively high iron content (remainder)) is advantageous for low corrosion in carburizing, sulfidizing, and chlorinating environments. Therefore, 40% nickel content is the upper limit. If the nickel content is too low (with a high iron content (remainder)), the formation of the sigma phase is promoted, especially when the chromium and silicon content is high. Therefore, 35% nickel content is the lower limit.

[0097] Chromium improves corrosion resistance in carburizing, sulfidizing, and chlorinating environments. Too little chromium content means that when using the alloy in highly corrosive environments, the chromium concentration falls very rapidly below the critical limit, preventing the formation of a closed chromium oxide layer. Therefore, the lower limit for chromium content when used in carburizing, sulfidizing, and chlorinating environments is 26%. Too much chromium content promotes sigma phase formation in the alloy, especially at high chromium content. Therefore, 30% chromium should be considered 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, excessive silicon content impairs weldability, and particularly high chromium content promotes sigma phase formation. Therefore, the silicon content is limited to 1.50%.

[0099] A certain level of aluminum content 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 content impairs weldability, especially if the chromium and silicon content is high. Therefore, the aluminum content is limited to 1.30%.

[0100] Manganese is useful for improving processability. However, its content is limited to 1.0% because this element reduces high-temperature corrosion resistance.

[0101] Even with very low magnesium and / or calcium content, sulfur bonding improves workability, thereby avoiding the formation of low-melting-point NiS eutectic. Therefore, a minimum content of 0.0001% is required for magnesium and / or calcium. If the content is too high, intermetallic Ni-Mg or Ni-Ca phases may form, which also significantly worsens workability. Therefore, the magnesium and / or calcium content is limited to a maximum of 0.05%.

[0102] To achieve good creep resistance, a minimum carbon content of 0.015% is required. The carbon content is limited to a maximum of 0.12% because exceeding this level reduces workability due to the excessive formation of primary carbides.

[0103] A minimum nitrogen content of 0.001% is required, which improves the material's processability and high-temperature strength. Nitrogen is limited to a maximum of 0.150% because this element reduces processability by forming coarse carbonitrides.

[0104] The phosphorus content should preferably be 0.030% or less, because this surfactant impairs high-temperature corrosion resistance. Too low a phosphorus content increases costs. Therefore, the phosphorus content should be ≥0.001%.

[0105] To guarantee the manufacturability of the alloy, the oxygen content must be 0.020% or less. Too low an oxygen content increases costs. Therefore, the oxygen content must be ≥0.0001%.

[0106] It is desirable to adjust the sulfur content to be as low as possible, because this surfactant impairs high-temperature corrosion resistance. Therefore, the sulfur content is specified to a maximum of 0.010%.

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

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

[0109] Cobalt may be present in this alloy at a concentration of less than 1.0%. Higher concentrations will reduce its high-temperature corrosion resistance.

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

[0111] To provide sufficient durability in carburizing, sulfidizing, and chlorinating environments, the following relationship exists between nickel, silicon, and aluminum: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) The following conditions must be met, where Ni, Si, Al, and Si are the concentrations of the elements in mass percent. The limit of Fc is explained in detail in the text above.

[0112] If necessary, the addition of oxygen-affinity elements can further improve high-temperature corrosion resistance. These elements do so by being incorporated into the oxide layer and blocking the diffusion pathway of oxygen at the grain boundaries.

[0113] To achieve improved high-temperature corrosion resistance, a minimum content of 0.001% of one or more of the following elements is required: cerium, lanthanum, cerium mischmetal, yttrium, zirconium, and hafnium. For cost reasons, the upper limit for each element is set at 0.20%. In this case, the following formula applies: FRE=0.714×Ce+0.720×La+1.124×Y+1.096×Zr+0.560×Hf≦0.10 (2a) The following conditions must be met, where Ce, La, Y, Zr, and Hf are the concentrations of the element in mass percent. This formula limits the total content of elements such as cerium, lanthanum, yttrium, zirconium, and hafnium. Contents with FRE > 1.0 can again increase the corrosion rate and impair workability.

[0114] Titanium can be added as needed. Titanium increases high-temperature strength. Since exceeding 0.50% may worsen high-temperature corrosion behavior, 0.50% is the maximum value.

[0115] Niobium can also be added as needed to increase the high-temperature strength. However, increasing the niobium content significantly increases the cost. Therefore, the upper limit is set at 0.20%.

[0116] To improve high-temperature strength, tantalum can also be included in the alloy as needed. However, increasing the tantalum content significantly increases costs. Therefore, the upper limit is set at 0.20%. A minimum content of 0.001% is required to achieve the desired effect.

[0117] Boron can be added to alloys as needed to improve creep resistance. Therefore, a content of at least 0.0001% is desirable. At the same time, this surfactant element degrades high-temperature corrosion resistance. For this reason, the maximum content of boron is specified as 0.008%.

[0118] Vanadium is limited to a maximum of 0.50% if necessary, because this element reduces high-temperature corrosion resistance.

[0119] Lead is limited to a maximum of 0.002% where necessary, because this element reduces high-temperature corrosion resistance. The same applies to zinc and tin.

[0120] [Table 1]

[0121] [Table 2]

[0122] [Table 3]

[0123] [Table 4]

[0124] [Table 5]

Claims

1. (In mass percent) The following: 35.0-38% nickel, 26.0-30.0% chromium, > 0.7-1.50% silicon, 0.40-1.30% aluminum, 0.00-1.0% manganese, Each contains 0.0001 to 0.05% magnesium and / or calcium, 0.015-0.12% carbon, 0.001 to 0.150% nitrogen, 0.001-0.030% phosphorus, 0.0001 to 0.020% oxygen, Maximum 0.010% sulfur, Molybdenum less than 1.0%, Less than 1.0% cobalt, Less than 0.5% copper, Tungsten less than 1.0%, The remainder is iron and normal impurities resulting from the process. The use of a nickel-iron-chromium alloy, which has outstanding high-temperature corrosion resistance, as a semi-finished product in an environment that is carburizing, sulfidizing, and simultaneously chlorinating, where the following relationship applies: Fc=-1.2+0.29×Ni-4.6×Si-4.4×Al≦2.5 (1a) The following conditions must be met, where Ni, Si, and Al are the concentrations of the elements in mass percent.

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

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

4. The use according to claim 1, wherein the aluminum content is 0.50% to <1.30% or >0.50% to <1.30%.

5. The use according to claim 1, wherein the remaining iron content is 28.0% to 38.0% or >28.0% to 38.0%.

6. It contains one or more of the elements cerium, lanthanum, yttrium, zirconium, and hafnium in amounts of 0.001 to 0.20%, where the following formula applies: FRE=0.714×Ce+0.720×La+1.124×Y+1.096×Zr+0.560×Hf≦0.10 (2a) The use according to claim 1, wherein the following conditions must be met, where Ce, La, Y, Zr, and Hf are the concentrations of the elements in mass percent.

7. When cerium and lanthanum are present together, cerium mischmetal (abbreviated as CeMM) is also 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) The use according to claim 6 must be modified as follows, where CeMM, Y, Zr, and Hf are the concentrations of the elements in mass percent.

8. The use according to claim 1, wherein the titanium content is 0.0 to 0.50%.

9. The use according to claim 1, wherein the content of niobium and / or tantalum is 0.0 to 0.20% each.

10. The use according to claim 1, wherein the boron content is 0.0001 to 0.008%.

11. The use according to claim 1, further comprising up to 0.50% vanadium.

12. The use according to claim 1, wherein the impurities are adjusted to contain a maximum of 0.002% lead, a maximum of 0.002% tin, and a maximum of 0.002% zinc.

13. The use according to claim 1, wherein the semi-finished product is in the form of a strip, plate, wire, rod, forged member, longitudinal seam welded pipe, or seamless pipe.

14. The use of the claim according to Claim 1 as a semi-finished product in a component of the chemical industry.

15. The use of the claim according to Claim 1 as a semi-finished product in a component of a waste incineration plant or a waste pyrolysis plant.

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