The invention relates to an austenitic corrosion-resistant steel with high resistance to hydrogen-induced embrittlement over the entire temperature range (−253° C. to at least +100° C.), in particular between −100° C. and room temperature (+25° C.). The proposed steel is suited for all metallic components which are in contact with hydrogen such as, for example, hydrogen tanks, valves, pipes, fittings, bosses, liners, springs, heat exchangers or bellows.
Steel which is exposed to mechanical stress in a hydrogen atmosphere over a longer period of time is subjected to hydrogen embrittlement. Austenitic stainless steels with high nickel content such as material no. 1.4435, X2CrNiMo18-14-3 constitute an exception. In case of such austenitic steels, a nickel content of at least 12.5 percent by mass is considered to be necessary in order to achieve sufficient resistance to hydrogen embrittlement over the entire temperature range from −253° C. to at least +100° C. and pressure range from 0.1 to 100 MPa. However, like molybdenum, nickel is a very expensive alloying element so that cost-effective, hydrogen-resistant steels are especially missing for the mass production of, for example, tank components in the motor vehicle sector.
It is therefore the object of the invention to provide a cost effective steel which is resistant to hydrogen-induced embrittlement over the entire temperature range, in particular in the range of maximum hydrogen embrittlement between room temperature and −100° C., which is resistant to corrosion and which has good hot and cold forming and welding capabilities.
According to the invention, this is achieved with an austenitic steel having the following composition:
According to the invention, an austenitic steel has the following composition:
The steel according to the invention can be produced with or without the addition of molybdenum. If molybdenum is added, the molybdenum content of the steel can, for example, be 0.5 to 3 percent by mass. That is to say that it can contain up to 0.3 percent by mass of aluminum as a smelting-related steel companion element. The same applies to nitrogen. In addition, molybdenum can be contained in the steel only as a smelting-related steel companion element.
The smelting-related steel companion elements comprise further conventional production-related elements (e.g. sulfur and phosphorus) as well as further nonspecifically alloyed elements. Preferably, the phosphorus content is <0.05 percent by mass, the sulfur content ≦0.4 percent by mass, in particular ≦0.04 percent by mass. The content of all smelting-related steel companion elements is at most 0.3 percent by mass per element.
Among the micro-alloying elements, (a) yttrium, scandium, lanthanum, cerium and (b) zirconium and hafnium are of particular relevance.
The alloy according to the invention may have an yttrium content of 0.01 to 0.2 percent by mass, in particular to 0.10 percent by mass, wherein yttrium can fully or partly be replaced by one of the elements scandium, lanthanum or cerium. Preferably, the hafnium content and the zirconium content are in each case 0.01 to 0.2 percent by mass, in particular to 0.10 percent by mass, wherein hafnium or zirconium can fully or partly be replaced by 0.01 to 0.2 percent by mass, in particular to 0.10 percent by mass of titanium.
Due to the reduction of the nickel content to 4 to 12.5 percent by mass, in particular at most 9 percent by mass, and the low or even missing molybdenum content, the costs of the alloy according to the invention can be reduced.
Despite the reduction of the nickel content and the low molybdenum content or the absence of molybdenum (i.e. without the addition of molybdenum), the steel according to the invention has very good mechanical properties in a hydrogen atmosphere over the entire temperature range from −253° C. to at least +100° C. and pressure range from 0.1 to 100 MPa.
For example; in a tensile test carried out at a test temperature of −50° C., a gas pressure of hydrogen of 40 MPa and a strain rate of 5×10-5 l/s, the steel according to the invention has, in the solution-annealed condition, a relative reduction area (RRA) (=reduction of area Z in air or helium/reduction of area Z in hydrogen×100%) of at least 90%. The corresponding relative tensile strength R_Rm, relative yield strength R_Rp0.2 and relative elongation at break R_A5 are likewise at least 90%. In addition, the high yield strength of the steel from 300 to 400 MPa is of significant importance.
The steel according to the invention may be solution annealed (AT). In addition, it can be used when being cold formed, in particular cold drawn or cold rolled.
The steel provides very good weldability as well as good resistance to corrosion.
The steel according to the invention has a high resistance to hydrogen embrittlement over the entire temperature range from −253° C. to at least +100° C. and pressure range from 0.1 to 100 MPa.
Thus, the steel according to the invention is a cost-effective, hydrogen-resistant material for use in hydrogen technology.
That is to say that the steel can be used for devices and components of systems for the generation, storage, distribution and application of hydrogen, in particular in cases where the devices and/or components come into contact with hydrogen. This applies, in particular, to pipes, control devices, valves and other shut-off devices, containers, fittings, bosses and liners, heat exchangers, pressure sensors, etc., including parts of said devices, for example springs and bellows.
The invention relates, in particular, to steels for hydrogen technology in motor vehicles. A (high-)pressure tank, a cryogenic (high-)pressure tank or a liquid hydrogen tank made of the steel according to the invention can be used for the storage of hydrogen.
In addition, the steel is suited for applications outside of motor vehicle technology which require excellent austenitic stability, in particular after cold forming.
The following steels according to the invention with the following composition (as a mass percentage):
Due to the relatively low nickel content of at most 9 percent by mass and the absence of molybdenum, both steels are very cost-effective.
As shown in case of Steel No. 1, the steel according to the invention can also be tungsten-free.
Thus, the steel according to the invention having a stable austenitic structure is a cost-effective, hydrogen-resistant material for use in hydrogen technology.
The examples below showing steels according to the invention serve the purpose of further explaining the invention.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
Number | Date | Country | Kind |
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10 2012 104 260.8 | May 2012 | DE | national |
This application is a continuation of PCT International Application No. PCT/EP2013/060084, filed May 15, 2013, which claims priority under 35 U.S.C. §119 from German Patent Application No. 10 2012 104 260.8, filed May 16, 2012, the entire disclosures of which are herein expressly incorporated by reference.
Number | Date | Country | |
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Parent | PCT/EP2013/060084 | May 2013 | US |
Child | 14541420 | US |