Seamless Austenitic Steel Tubes for Cryogenic Hydrogen Cracking Resistance
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Solution Overview
Problem
Existing systems for transmitting liquid hydrogen face challenges such as hydrogen embrittlement, risk of cracking in welded tubes, and the need for materials that can withstand extreme conditions like low temperatures and high pressures, which can lead to explosions due to gaseous hydrogen accumulation.
Innovation Solution
A system utilizing seamless tubes made of austenitic stainless steel, specifically 21-6-9 stainless steel, which are manufactured through extrusion, hot forming, cooling, and cold pilger milling or cold drawing to reduce wall thickness and enhance mechanical strength, while minimizing the risk of cracking and weight, thereby improving safety and efficiency in liquid hydrogen transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If welded tubes are used for liquid hydrogen transmission, then manufacturing is easier and cost is lower, but the risk of cracking increases and reliability decreases
Solution Approach 1:
The invention extracts and eliminates the weld seam from the tube structure by using seamless tubes. This removes the vulnerable zone where cracks typically initiate and propagate, directly resolving the reliability issue while maintaining manufacturing feasibility through continuous extrusion processes.
Solution Approach 2:
The invention segments the tube into multiple seamless sections joined by mechanical connections rather than welding. This avoids creating continuous weld zones that are susceptible to cracking, while still achieving the necessary length through assembly of multiple segments.
2Strength
If tube wall thickness is increased to resist hoop stresses, then strength increases, but weight increases
Solution Approach 1:
The invention changes the material parameters by using austenitic stainless steel with specific alloy compositions (high Mn: 8-10%, Cr: 19-21.5%, Ni: 5.5-7.5%, N: 0.15-0.40%) that provide exceptional strength-to-weight ratio. This allows achieving required strength with reduced wall thickness compared to conventional materials.
Solution Approach 2:
The invention uses composite alloying strategy combining multiple elements (Mn, Cr, Ni, N, Mo) that work synergistically to enhance mechanical properties. The specific composition creates a material with superior strength characteristics that enables weight reduction while maintaining or improving hoop stress resistance.
3Ease of manufacture
If conventional austenitic stainless steel is used, then manufacturing is easier, but resistance to hydrogen embrittlement and extreme conditions is insufficient
Solution Approach 1:
The invention modifies the chemical composition parameters of austenitic stainless steel by significantly increasing Mn content (8-10%) and N content (0.15-0.40%), and adjusting Cr (19-21.5%) and Ni (5.5-7.5%). These parameter changes enhance resistance to hydrogen embrittlement and extreme conditions while maintaining manufacturability through established extrusion processes.
Solution Approach 2:
The invention creates a composite alloy system where Mn, Cr, Ni, N, and Mo work together to provide enhanced resistance to hydrogen embrittlement. The specific composition ratios create synergistic effects that improve material performance in cryogenic hydrogen service while keeping the austenitic structure and manufacturing processes conventional.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The seamless tubes provide increased lifetime, reduced weight, and improved resistance to hoop stresses, allowing for higher pressure applications and safer handling of liquid hydrogen, reducing the risk of explosions and enhancing storage densities.
Implementation Method 1
Another issue which occurs when using hydrogen is known as hydrogen embrittlement. This effect is relevant every time hydrogen is in contact with a metal surface because individual hydrogen atoms will diffuse through the metal.
Implementation Method 2
Welded tubes bear the risk of cracking within the weld zone. In addition, if there would be a crack in the tube transmitting liquid hydrogen, because of the low boiling temperature, hydrogen would immediately change into a gaseous state.
Implementation Method 3
The seamless tubes provide increased lifetime, reduced weight, and improved resistance to hoop stresses, allowing for higher pressure applications
Data Source
Figure 1~3
AI summary
The present disclosure relates to a system for transmission of liquid hydrogen with a liquid hydrogen transmitting equipment, a liquid hydrogen receiving equipment, and a conduit in fluid communication with the liquid hydrogen transmitting equipment and with the liquid hydrogen receiving equipment for guiding liquid hydrogen between the liquid hydrogen transmitting equipment and the liquid hydrogen receiving equipment. So far tubes made of an austenitic stainless steel comprising this composition of ingredients are welded. A major problem of tubes used for liquid hydrogen applications is the risk for cracking. Especially when they are used under extreme conditions. Therefore there is a need to provide a tube made of an austenitic stainless which at least overcomes one of the foresaid problems. According to the present disclosure it is thus suggested to provide a system for transmission of liquid hydrogen, wherein at least a section of the conduit is provided by a seamless tube made of an austenitic stainless steel comprising, in weight%, C < 0.080, 8.00 < Mn < 10.00, Si < 1.00, P < 0.030, S < 0.030, 19.00 < Cr < 21.50, 5.50 < Ni < 7.50, 0.15 < N < 0.40, Mo < 0.75, Cu < 0.75, which is balanced by Fe and normally occurring impurities.