Use of shaped bodies for the storage and transport of liquid hydrogen

Abstract

Use of shaped bodies for storing or transporting liquid hydrogen, characterized in that the shaped bodies are produced by a process for producing shaped bodies comprising the following steps: (a) Melting an alloy consisting of: Si 2.50 to 4.50% Cr 10.50 to 19.00% Ni 13.50 to 20.00% Mn 0.50 to 1.50% Co 1.00 to 2.00% Mon 0.50 to 1.50% and the remainder is iron and unavoidable impurities, the levels of C, P, S and Cu as unavoidable impurities being as follows: C not more than 0.050% P not more than 0.030% S not more than 0.030% Cu not more than 1.5% where all quantities are given in weight percent based on the total mass of the alloy, (b) Pouring the molten metal into a mold, (c) Performing a solution annealing treatment of the resulting shaped body at a temperature in the range of 950 °C to 1150 °C, wherein the alloy has a Charpy impact strength of at least 27 J / cm² at -253 °C 2 exhibits.

Description

Introduction

[0001] The present invention relates to the use of shaped bodies for storing or transporting liquid hydrogen. The shaped bodies consist of stainless steel with a high silicon content, produced by casting, and are used with liquid hydrogen (-253 °C). State of the art

[0002] The debate surrounding global warming caused by carbon dioxide emissions has led to increased interest in new forms of energy generation and storage. One form of energy storage being considered is the storage of energy in the form of hydrogen. Hydrogen can be produced through electrolysis or from hydrocarbons. Its energy can be harnessed, for example, through combustion and in fuel cells. Storing hydrogen is one of the challenges facing the further development of hydrogen technology. Due to its low density, hydrogen can only be stored in larger quantities under high pressure or as a liquid. Liquid hydrogen is stored at approximately -253 °C. Materials used in systems for storing or utilizing liquid hydrogen must therefore possess the necessary mechanical properties at these temperatures.Critical parameters include the yield strength, tensile strength, elongation at break, reduction of area (as a measure of ductility), hardness, toughness and especially fracture toughness at -253 °C.

[0003] For applications involving liquid hydrogen, conventional high-alloy austenitic stainless steels, such as SUS 304 with a nickel content of approximately 8 to 10.5 percent by weight and approximately 18 to 20 percent by weight, have been used for decades. High nickel content promotes strength and prevents embrittlement of the steel caused by hydrogen. SUS 316 and SUS 316L are better suited. These steels additionally contain molybdenum, which further reduces embrittlement and improves toughness. However, all these steels generally have to be used as forged products with thick walls because their physical properties, especially their hardness, are insufficient. Some steels specifically developed for use with liquid hydrogen contain nickel in amounts of 12 percent by weight and more.JP 2018-104793 A describes an austenitic steel with 12.5 to 15.4 wt% nickel and less than 1 wt% chromium, which is particularly suitable for use in liquid hydrogen tanks. Corresponding steel variants with chromium contents of 21.5 to 23.5 wt% for use in liquid hydrogen pipelines are also known under the trade name HRX19. However, a problem with all these steels is that they can only be given properties suitable for use with liquid hydrogen through forging. As cast steels, they exhibit insufficient hardness and / or fracture toughness. Cast components for valves or similar applications therefore have a short service life. Manufacturing such components from forged parts using subtractive processes is, in turn, very complex. Such processes are hardly suitable for mass production.Therefore, there is a need to further develop hydrogen technology in this area. US Patent Application No. 2004 / 0042926 A1 describes high-silicon steels. These steels contain 2 to 5% silicon, 8 to 25% chromium, 4 to 16% nickel, and no more than 0.01% carbon. These steels exhibit high corrosion resistance, high heat resistance, and high wear resistance. They also have good machinability and castability. Object of the present invention

[0004] The object of the present invention was to provide cast components suitable for the storage and transport of liquid hydrogen. These components can be valves or parts thereof. The components should exhibit sufficient hardness and fracture toughness at -253 °C. Description of the invention

[0005] A first object of the present invention relates to the use of shaped bodies for storing or transporting liquid hydrogen, characterized in that the shaped bodies are produced by a process for producing shaped bodies which includes the following steps: (a) Melting an alloy consisting of: Si 2.50 to 4.50% Cr 10.50 to 19.00% Ni 13.50 to 20.00% Mn 0.50 to 1.50% Co 1.00 to 2.00% Mon 0.50 to 1.50% and the remainder is iron and unavoidable impurities, the levels of C, P, S and Cu as unavoidable impurities being as follows: C not more than 0.050% P not more than 0.030% S not more than 0.030% Cu no more than 1.5% where all quantities are given in weight percent based on the total mass of the alloy, (b) Pouring the molten metal into a mold; (c) Performing a solution annealing treatment of the resulting shaped body at a temperature in the range of 950 °C to 1150 °C.

[0006] In this description, all percentage values ​​refer to the proportion of the respective element in the total alloy by weight.

[0007] Currently, SUS316L stainless steel is used as the standard material for liquid hydrogen. The present invention demonstrates that a high-silicon stainless steel, exhibiting strength, low-temperature toughness, hardness, corrosion resistance, and good abrasion properties, is suitable for use with liquid hydrogen. The present invention makes it possible to use cast steel instead of forged steel. The steel of the present invention contains 2.50 to 4.50% silicon, 10.50 to 19.00% chromium, and 13.50 to 20.00% nickel as its main constituents. It is a high-silicon stainless steel. Therefore, its structure and properties are not primarily due to the presence of carbon, as is the case with conventional steels, but rather to the high silicon content.Although conventional steel contains carbon, it is not necessary in the present invention and does not contribute to the essential properties of the molded parts. The alloys of the molded parts are nevertheless referred to herein, among other things, as steel or stainless steel, since they exhibit similar properties to steel. silicon

[0008] The alloys of the present invention contain a large amount of silicon. The silicon creates a specific metallographic structure that imparts strength to the alloys. This makes carbon unnecessary. Si also gives the alloys high fracture toughness at -253 °C, oxidation resistance, corrosion resistance, heat resistance, and resistance to softening at high temperatures. Si further lowers the melting point of the alloys, increases the flowability of their melts, and thereby improves castability. If its content is below 2.5%, its effect with regard to the aforementioned properties is insufficient. A higher silicon content increases the castability of the melt and leads to more balanced properties of the resulting molded part. Therefore, the silicon content is preferably at least 3.0%, more preferably at least 3.3%, and most preferably at least 3.5%.A lower limit of 3.7% is most preferred. However, since silicon is a strong ferrite-forming element, an excessive amount disrupts the fundamental structural equilibrium of the alloys. The upper limit is therefore set at 4.5%. If, however, high fracture toughness at a temperature of -253 °C is desired, it is preferred that the silicon content not exceed 3.5%, more preferably not exceeding 3.0%, and most preferably in the range of 2.5% to 2.9%. chrome

[0009] Chromium is a component that ensures the fundamental properties of the alloys used in the present invention, namely corrosion resistance (in particular, resistance to hydrogen embrittlement), heat resistance, and oxidation resistance of stainless steel. In combination with nickel, chromium imparts the desired microstructure (single-phase structure consisting of austenite or two-phase structure consisting of austenite and ferrite) to the steel matrix and thus the desired properties. Furthermore, chromium counteracts hydrogen embrittlement. If the chromium content is less than 10.5%, the effect against hydrogen embrittlement is insufficient. A content of at least 17.0% is preferred to obtain a good microstructure and to increase the effect against hydrogen embrittlement. At chromium contents above 19%, the chromium equivalent Craq defined below becomes large, and the austenite content increases.It is therefore difficult to obtain the desired mechanical properties. However, in some uses of the present invention, where alloys with high fracture toughness at -253 °C are desired, it is preferred that the chromium content does not exceed 15%. nickel

[0010] Nickel imparts good low-temperature toughness, corrosion resistance, oxidation resistance, and heat resistance to steel. Furthermore, in combination with chromium, it gives the steel matrix the desired microstructure (single-phase structure consisting of austenite or two-phase structure consisting of austenite and ferrite). Nickel has a particularly significant influence on impact toughness at ultra-low temperatures. To achieve high impact toughness at around -253 °C, a nickel content in the range of 13.50% to 20.00% is required. A nickel content in the range of 13.50% to 18.00% is preferred, a content of 13.50% to 15.00% is particularly preferred, and a content in the range of 13.50% to 14.50% is most preferred. Like silicon and chromium, nickel also provides increased resistance to hydrogen embrittlement. For this purpose, it is desirable for nickel to be present in large quantities.Especially when only small amounts of silicon and chromium are used, the nickel content is preferably in the range of 14 to 20%, particularly in the range of 15 to 20%. Manganese, cobalt and molybdenum

[0011] The alloy of the present invention further contains manganese, cobalt, and molybdenum in small amounts. Manganese acts as a deoxidizing agent and is also an austenite-forming element, thus counteracting hydrogen embrittlement. However, at excessively high proportions, it reduces corrosion resistance and negatively impacts mechanical properties. Therefore, the manganese content is in the range of 0.50 to 1.50%. Cobalt is also an element that promotes austenite formation. It also increases strength (hardness) and corrosion resistance. These effects become significant at 0.50% and above, and increase with rising content. However, cobalt is expensive. Therefore, it is used in the range of 1.00 to 2.00%. Molybdenum contributes to improved toughness and wear resistance. It also increases the corrosion resistance of steel as well as its strength at elevated temperatures.To ensure these effects to a sufficient degree, a content of at least 0.50% is desirable. However, since molybdenum is a ferrite-forming element, an excessive content leads to an undesirable structure. Furthermore, molybdenum is expensive. Therefore, the molybdenum content should not exceed 1.50%. Contaminants

[0012] Carbon, phosphorus, sulfur, and copper have a negative impact on the properties of the alloy of the present invention and are preferably not included therein. However, they are often introduced into alloys through an unavoidable presence in commercially available metals. Their content must be kept within narrow limits.

[0013] Carbon is an element that increases the strength of steel, and generally, high-strength steels contain a certain amount of carbon as an essential component. The present invention contains a large amount of silicon, which makes the use of carbon unnecessary. Carbon reduces the toughness of steel and adversely affects its machinability, oxidation resistance, and corrosion resistance. Therefore, the carbon content should be as low as possible. The amount of carbon in the alloy of the present invention should not exceed 0.050%, preferably not exceeding 0.030%. The carbon content of the alloy of the present invention is particularly preferably 0.020% or less, most preferably 0.010% or less.

[0014] Phosphorus is a typical harmful impurity in stainless steel. It segregates within the steel and impairs its mechanical properties, machinability, and corrosion resistance. Therefore, its content should be limited to 0.030% and reduced to the lowest possible level. 0.015% is preferred, and 0.010% is most preferred.

[0015] Sulfur is also a harmful impurity. It causes red brittleness in steel, thereby reducing its hot formability. It impairs the purity of the steel through sulfide inclusions and deteriorates mechanical properties such as fatigue strength and dielectric strength. It also reduces corrosion resistance. Therefore, the sulfur content should be limited to 0.030%, preferably not exceeding 0.020%, and particularly preferably, and especially in the case of steel intended for the production of thin wires with a diameter not greater than 0.1 mm, the sulfur content should be limited to 0.005% or less.

[0016] Copper is frequently introduced into alloys through recycled steel and other ingredients. It impairs the hot formability of steel. Furthermore, it reduces toughness at -253 °C. The negative impact of copper is relatively minor up to an amount of 1.5%. The present alloy should therefore contain no more than 1.5% copper, preferably no more than 1.0%, particularly preferably no more than 0.70%, and most preferably no more than 0.30%. Other unavoidable impurities that the alloy used in the present application may contain are aluminum, tungsten, nitrogen, oxygen, or hydrogen. The alloy used in the present process preferably contains no more than 0.01% aluminum, no more than 0.5% tungsten, no more than 0.03% nitrogen, no more than 0.002% oxygen, and no more than 0.0002% hydrogen. Hydrogen embrittlement

[0017] The alloy used in the present process is particularly suitable for shaped parts intended for use with liquid hydrogen. Hydrogen causes hydrogen embrittlement in conventional steels. In the present alloy, however, hydrogen embrittlement is suppressed by a high content of silicon, nickel, chromium, and other alloying elements. The ability of the elements contained in the alloy to suppress hydrogen embrittlement is expressed by a nickel equivalent yH. The alloy used in the application according to the invention preferably has a nickel equivalent yH of at least 24%, wherein the nickel equivalent is calculated according to formula (1): yH=0.35*Si(%)+0.65*Cr(%)+1.0*Ni(%)+1.05*Mn(%)+0.98*Mo(%)+12.6*C(%), wherein Si(%), Cr(%), Ni(%), Mn(%), Mo(%) and C(%) represent the content of these elements in the alloy in weight percent, each based on the total amount of the alloy. In the uses according to the invention, the alloys preferably have a nickel equivalent yH of at least 26.9%. Alloys with a nickel equivalent yH of at least 28.5% are particularly preferred. They exhibit practically no hydrogen embrittlement. Most preferably, the nickel equivalent yH is at least 29%.

[0018] In a preferred embodiment of the use according to the invention, the alloy has the following composition: Si 2.50 to 3.50% Cr 10.50 to 19.00% Ni 13.50 to 20.00% Mn 0.50 to 1.50% Co 1.00 to 2.00% Mon 0.50 to 1.50% and the remainder is iron and unavoidable impurities, with the levels of C, P, S and Cu as impurities being as follows: C not more than 0.030% P not more than 0.030% S not more than 0.030% Cu not more than 1.00% where all quantities are given as weight percent based on the total mass of the alloy. Such alloys exhibit high fracture toughness and low hydrogen embrittlement. This is particularly true when the chromium content in this alloy is 15% or less and the nickel content is 14% or more, especially 15% or more. In this embodiment as well, the carbon content is preferably 0.030% or less and the copper content 1.00% or less. In a further preferred embodiment of the use according to the invention, the alloy has the following composition: Si 3.70 to 4.50% Cr 17.00 to 19.00% Ni 13.50 to 14.50% Mn 0.50 to 1.50% Co 1.00 to 2.00% Mon 0.50 to 1.50% and the remainder is iron and unavoidable impurities, with the levels of C, P, S and Cu as impurities being as follows: C not more than 0.030% P not more than 0.030% S not more than 0.030% Cu not more than 1.00% where all quantities are given as weight percent based on the total mass of the alloy. Such an alloy has a nickel equivalent yH of at least 26.9% and is therefore particularly preferred for hydrogen applications. Even more preferred is an alloy of such composition with a nickel equivalent yH of at least 28.5%, and most preferred is an alloy of such composition with a nickel equivalent yH of at least 29%.

[0019] In the present process, casting is preferably carried out under protective gas and otherwise preferably according to known procedures with the usual protective devices. Solution annealing

[0020] Solution annealing at a temperature of 1050 to 1150 °C imparts a single-phase structure comprising fine austenite or a two-phase structure comprising fine austenite and ferrite to the molded parts according to the invention. This gives the molded parts the necessary hardness and overall improved mechanical properties. This structure confers high fracture toughness at extremely low temperatures, particularly at -253 °C, and is especially resistant to hydrogen embrittlement. At temperatures below 950 °C, solid solution formation is insufficient and the retained austenite content is too high, which counteracts the increase in strength. Conversely, at temperatures above 1150 °C, the crystal grains become coarse and the toughness decreases. Solution annealing generally yields the best results at temperatures in the range of 1050 to 1150 °C.It is therefore preferred that the solution annealing treatment be carried out in this temperature range. The temperature ranges for the solution annealing treatment of 950 to 1150 °C and of 1050 to 1150 °C can be applied equally to all processes and all alloys of the present invention.

[0021] The solution annealing treatment typically lasts 10 to 60 minutes, preferably 20 to 40 minutes. The best mechanical properties are obtained under these conditions. For larger molded parts, the heating time can be estimated at 1 to 2 hours per 2.54 cm (1 inch) of molded part thickness. The optimal solution annealing treatment time can be determined through preliminary tests to achieve the desired properties, particularly the desired hardness and / or fracture toughness of the molded part.

[0022] The cooling method after solution annealing is not particularly limited. Cooling can be achieved, for example, by water cooling, oil cooling, or gas cooling. Water cooling, oil cooling, and cooling with liquid nitrogen are preferred. Water cooling is particularly preferred. The molded parts can simply be immersed in water. However, cooling to a temperature in the range of 10 to 50 °C is always sufficient. The minimum temperature to which the molded parts must be cooled can be determined by preliminary tests. The temperature at which the properties have reached the required values ​​is sufficient. Cooling with water, oil, or gas is normally sufficient to achieve the required cooling rate. For larger molded parts, oil cooling or water cooling may be necessary to obtain the required cooling rate.Immersion in water or oil at approximately 20 °C is usually sufficient to achieve the necessary cooling rate, even for larger molded parts. The required cooling rate can also be determined through preliminary tests.

[0023] Precipitation hardening is not necessary for the alloys used in the present invention.

[0024] Fig.This figure shows metallographic structures of alloys rich in silicon, nickel, and chromium that, after casting, were subjected to a solution heat treatment at 1050 °C for 30 minutes and subsequently water-cooled. The y-axis shows the nickel equivalent Niaq, according to the formula Niaq = Ni(%) + 30 * C(%) + 0.5 * Mn(%) + 0.1 * Co(%), where Ni(%), C(%), Mn(%), and Co(%) represent the content of these elements in the alloy in weight percent, based on the total amount of the alloy. The x-axis shows a chromium equivalent Craq plotted according to the formula Craq = Cr(%) + 0.3 * Mo(%) + 1.5 * Si(%) + 0.5 * Nb(%), where Cr(%), Mo(%), Si(%) and Nb(%) represent the content of these elements in the alloy in weight percent, each based on the total amount of the alloy. Fig.This shows how the metallographic structures of the alloys change depending on the nickel equivalent Niaq and the chromium equivalent Craq. The letters A, F, and M in Fig. Austenite, ferrite, and martensite denote the phases that are dominant. They indicate the regions where each structure is predominant, optionally with approximate quantities for the proportion of each phase. Niobium (Nb) may only be present in the alloys used according to the invention as an unavoidable impurity. Its content in the alloys should generally be 0% or close to 0%. Depending on the composition, the alloys contain predominantly austenite phases (A), optionally with small amounts of ferrite phases (F), and preferably without martensite phases (M). The structure of the alloys used in the present invention is ideal if they correspond to the diagram shown. Fig.on or above line a and on or above line c. Line a corresponds to the formula Nieq = 25.40 - 0.80 * Creq and line c corresponds to the formula Nieq = -8.48 + 1.03 * Creq. A preferred use of the present invention is therefore characterized in that the composition of the alloy obeys the following conditions: Niaq>=25.40−0.80*Craq and Niaq>=−8.48+1.03*Craq

[0025] Alloys that meet these conditions exhibit a suitable microstructure, i.e., a large proportion of austenite phases, which gives the alloys the necessary properties, such as high fracture toughness at -253 °C and low hydrogen embrittlement. Line b corresponds to the formula Niaq = 19.20 - 0.81 * Craq and line D corresponds to the formula Niaq = -5 + 0.5 * Craq. Lines b and d describe regions that lie outside the alloys used in the applications of the invention and are therefore irrelevant to the present invention.

[0026] A particularly critical property of steels used at low temperatures is fracture toughness. Japanese regulations stipulate that steels used for components of liquid hydrogen plants must have a fracture toughness of at least 27 J / cm². 2The fracture toughness required by this patent application is determined according to a Charpy impact test (Charpy impact strength). Cast components made from steels conventionally used for such systems, such as SUS316L, cannot meet these requirements or can only do so with a small safety margin. Furthermore, components cast from such steels, for example, those used in valves, have short service lives, necessitating frequent and costly system maintenance. Therefore, even complex components for such systems are often machined from forged steel using subtractive processes. This is labor-intensive and results in very large components. Consequently, it incurs high costs and is hardly suitable for mass production.The processes described herein enable the production of cast components that exhibit sufficient fracture toughness even at extremely low temperatures. The alloy has a Charpy impact strength of at least 27 J / cm². 2 The impact strength is measured according to the Charpy test in accordance with JIS Z 2242 and at a temperature of -253 °C, using a cuboid test specimen with a height and width of 10 mm and a V-shaped notch of 2 mm, with the force being applied on the opposite side of the notch. Alloys exhibiting a fracture toughness of at least 40 J / cm² under these conditions are particularly preferred. 2 , especially preferred by at least 60 J / cm² 2 and most preferred by at least 80 J / cm² 2 have. Molded body

[0027] The molded parts produced by the method described herein can be any type of molded part. Preferably, the molded parts are selected from the group consisting of valves, parts of valves, pumps, parts of pumps, turbines, parts of turbines, fittings, parts of fittings, pipes, distributors, connectors, bolts, screws, and nuts. Valves or parts thereof are particularly preferred. Molded parts for use in systems where liquid hydrogen is stored, transported, or processed are also preferred. For the purposes of the present invention, systems where liquid hydrogen is stored, transported, or processed include, in particular, pipelines, the associated equipment and other piping systems, and hydrogen refueling stations and their associated equipment.

[0028] The manufacturing process for molded parts described herein is versatile. It makes all possible shapes accessible through casting, even in mass production. Since the alloy used in the process described herein contains a high proportion of silicon, the melt of this alloy is very fluid. This makes it possible to cast even very thin molded parts down to a thickness of only 1 mm. The molded parts for the applications according to the invention are versatile, particularly for apparatus used at low and extremely low temperatures. Since the steels used for the molded parts for the applications according to the invention also exhibit high strength, the molded parts can also be used for apparatus operating under high pressure.

[0029] A further aspect of the present invention is the use of a molded body characterized in that at least parts of the molded body have temperatures below -200 °C, preferably -252 °C or below. Use in the range of -252 °C to -259 °C, i.e., in the range where hydrogen is liquid at normal pressure, is also preferred. A use according to the invention is also preferred in that at least parts of the molded body, for example, the valves, are in contact with liquid hydrogen (H₂).

[0030] Another embodiment of the present invention is the use of the molded bodies described herein as valves, parts of valves, pumps, parts of pumps, turbines, parts of turbines, fittings, parts of fittings, pipes, distributors, connectors, bolts, screws and nuts for storing or transporting liquid hydrogen.

[0031] Hydrogen embrittlement is a problem in many specialized applications. The molded parts of the present invention are suitable for all such applications. For example, bolts for certain onshore wind turbines are manufactured from the aluminum alloy SCM435. Hydrogen embrittlement is one of the problems encountered here. Bolts manufactured according to the method described herein do not exhibit any relevant hydrogen embrittlement. The use of bolts manufactured according to the method described herein in wind turbines is therefore a further embodiment of the present invention. Brief description of the image: Fig. shows the metallographic structure of the steel described herein. Examples: Measurement methods:

[0032] Tensile tests: A round bar according to JIS No. 14A is subjected to a tensile test according to JIS Z 2241:2011 on a test machine according to JIS B 7721 at 25 °C. Yield strength, tensile strength, elongation at break, and area of ​​reduction at break are determined. After the measurement, the area of ​​reduction at break is determined according to JIS G 3199:2009.

[0033] Hardness: Round bars with a diameter of 20 mm and a thickness of 10 mm were cast and, after high-gloss polishing, the hardness was determined on a Rockwell hardness tester.

[0034] Notched impact strength (fracture strength): V-notched specimens were manufactured according to JIS No. 4A, and the Charpy impact strength was determined according to JIS Z 2242 at 20 °C, -196 °C, and -253 °C using a device according to JIS B 7722. Nitrogen cooling was used for measurements at -196 °C, and liquid helium cooling for measurements at -253 °C. Cuboid specimens with a height and width of 10 mm and a V-shaped notch of 2 mm were used, with the impact force applied on the opposite side of the notch. For the forged alloys, specimens were manufactured according to the same specifications, and the Charpy impact strength was determined at -253 °C using the same specifications and the same device. Production of the molded parts

[0035] A series of molded parts were produced from six alloys according to the procedure described herein. The alloys were cast into the desired shape and cooled to 25 °C. They were then solution annealed for 30 minutes at 1050 °C. The molded parts were cooled to 25 °C by immersion in water. Tables 1a and 1b show the composition of the alloys. Table 1a: element Alloy No. Si Cr Ni Mn Co Mon 1 2,79 10,7 14,6 0,93 1,50 0,97 2 2,85 12,0 14,5 0,84 1,50 0,90 3 2,87 13,2 14,6 0,91 1,50 0,89 4 3,00 14,4 16,9 0,91 1,50 0,89 5 2,96 12,6 15,7 0,93 1,50 0,90 6 2,99 18,0 12,1 0,97 1,50 1,40 Table 1b (continuation of Table 1a): element Alloy No. C P S Cu Note V Al W 1 0,003 0,02 0,01 0,59 0,20 0,04 0,004 0,030 2 0,006 0,02 0,01 0,57 0,20 0,05 0,004 0,022 3 0,047 0,02 0,01 0,58 0,17 0,04 0,004 0,029 4 0,010 0,02 0,02 0,55 0,18 0,05 0,004 0,027 5 0,003 0,02 0,01 0,57 0,20 0,05 0,005 0,021 6 0,023 0,03 0,01 0,26 0,02 0,07 0,002 0,602

[0036] All elements in Table 1a are necessary for the present invention. All elements in Table 1b are unavoidable impurities whose presence is not necessary for the present invention. All values ​​in Tables 1a and 1b are measured values, except for the cobalt content. For cobalt, the weighted content is given. The measurements were performed using a Thermo Fisher Scientific Inc. ARL iSpark 8820 solid-state emission spectrometer, Waltham, MA, USA. Mechanical properties

[0037] The following Table 2 shows the results of the Charpy impact strength measurements in J / cm². 2 The impact strength of the manufactured molded parts is given at 20 °C, -196 °C, and -253 °C. For comparison, the Charpy impact strength of the corresponding forged molded parts is given at -253 °C. Table 2: Impact strength according to Charpy in [J / cm2] Alloy No. cast steel Forged steel 20°C -196°C -253 °C -253 °C 1 258 126 105 173 2 200 104 60 224 3 244 125 98 176 4 146 139 44 370 5 87 121 36 179 6 201 62 38 60

[0038] As can be seen, the impact strength according to Charpy at -253 °C is significantly above 27 J / cm² for all alloys. 2 This is unusually high for a cast steel. In particular, alloys 1, 2, and 3 exhibit a Charpy impact strength of approximately 100 J / cm² at -253 °C. 2 . or 60 J / cm² 2 These values ​​are so far from the required minimum value of 27 J / cm². 2 removed that molded parts made from these alloys have a sufficient safety margin with regard to Charpy impact strength and a long service life.

[0039] As expected, Table 2 also shows that the Charpy impact strength decreases with temperature. Only for alloy 5, which exhibits a particularly low Charpy impact strength at 20 °C, does the Charpy impact strength initially increase to -196 °C, before dropping sharply to -253 °C. Table 2 also shows that the corresponding forged steel made from the same alloy exhibits a higher Charpy impact strength at -253 °C. This corresponds to the behavior of conventional steel.

[0040] Table 3 shows further mechanical properties of the molded parts described herein. All values ​​were measured at 20 °C. Table 3: Tensile strength, elongation, ductility Alloy No. Yield strength Tensile strength Elongation at break fracture constriction [N / mm2] [N / mm2] [%] 10 / 01 1 148 330 52,1 43,8 2 183 417 44,7 39,9 3 157 193 13,4 16,4 4 194 462 57,2 29,5 5 212 421 36,1 13,9 6 307 549 23,7 24,5

Claims

[1] Use of shaped bodies for storing or transporting liquid hydrogen, characterized by that the shaped bodies are produced by a process for producing shaped bodies comprising the following steps: (a) Melting an alloy consisting of: Si 2.50 to 4.50%, Cr 10.50 to 19.00%, Ni 13.50 to 20.00%, Mn 0.50 to 1.50%, Co 1.00 to 2.00%, Mon 0.50 to 1.50%, and the rest is iron and unavoidable impurities, with the contents of C, P, S and Cu as unavoidable impurities being as follows: C not more than 0.050%, P not more than 0.030%, S not more than 0.030%, Cu not more than 1.5%, where all quantities are given in percentages by weight based on the total mass of the alloy, (b) pouring the melt into a mold, (c) carrying out a solution heat treatment of the shaped body thus obtained at a temperature in the range of 950 °C to 1150 °C, wherein the alloy has a Charpy impact toughness of at least 27 J / cm 2 has. [2] Use according to claim 1, characterized by that the alloy has the following composition: Si 2.50 to 3.50%, Cr 10.50 to 19.00%, Ni 13.50 to 20.00%, Mn 0.50 to 1.50%, Co 1.00 to 2.00%, Mon 0.50 to 1.50%, and the rest is iron and unavoidable impurities, with the contents of C, P, S and Cu as unavoidable impurities being as follows: C not more than 0.050%, P not more than 0.030%, S not more than 0.030%, Cu not more than 1.50%. [3] Use according to one of claims 1 or 2, characterized by that the solution annealing treatment is carried out at a temperature in the range of 1050 to 1150 °C. [4] Use according to one of claims 1 to 3, characterized by that the shaped bodies are selected from the group consisting of valves, parts of valves, pumps, parts of pumps, turbines, parts of turbines, fittings, parts of fittings, pipes, distributors, connectors, bolts, screws and nuts. [5] Use according to one of the preceding claims, characterized by that the molded bodies are valves. [6] Use according to one of the preceding claims, characterized by that the molded bodies are parts of valves.

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