Development of New High Strength Austenitic Stainless Steels for Large Lightweight Storage Applications

Partners

• Centro Sviluppo Materiali SPA – Project Coordinator
• Acerinox Europa
• TU Bergakademie Freiberg
• University of Oulu

Official webpage

www.austrong.eu

Abstract

Austenitic stainless steels possess excellent corrosion resistance, reasonable weldability as well as high toughness at very low temperatures. However, their low yield strength limits their use in large storage structures such as tanks for liquid hydrogen, water, biogas and alike. Project AUSTRONG aims at addressing this issue by envisaging concomitant enhancement of strength and toughness in austenitic stainless steels using the innovative concept of thermomechanically controlled processing (TMCP), which is expected not only to permit lightweighting of such storage structures, but will also promote elimination of solution annealing step in plate manufacture, thus contributing to both reduced carbon footprint as well as production and usage costs. The expected results will be new weldable austenitic stainless steels possessing high yield strength, adequate cryogenic toughness, and excellent corrosion resistance. The steels will be suitable for a range of large-scale storage structural applications i.e., cryogenic (LNG and LH2), as well as other non-cryogenic applications (water, biogas, and digesters). A key result will be reduced carbon footprint due to the elimination of the solution annealing step in plate manufacture. Finally, the proposed application also addresses the issue of climate change i.e., by providing better LH2 storage capabilities for the hydrogen economy.

The project objectives are:

• To develop new austenitic stainless steel plate products possessing unique combinations of high yield strength (≥ 475 MPa) and cryogenic toughness (≥ 60 J/cm2 at -196°C and at -269°C), suitable for lightweight cryogenic storage (liquid hydrogen and liquified natural gas) applications.
• To employ and study thermomechanical hot rolling and accelerated cooling (TMCP i.e. pancaking) for the realisation optimised combinations of strength and cryogenic toughness.
• To employ a lean alloy selection strategy focusing on reduced costs and CO2 emissions (considering leaner grades and small microalloying additions).
• To contribute to the decarbonisation and modernisation of the manufacturing process, demonstrating the property, cost and environmental benefits of TMCP plates versus solution annealed plates.
• To facilitate the industrial implementation (manufacture) of these new plate products by simulating industrial scale TMCP rolling schedules, establishing rolling mill capacity requirements e.g., forces.
• To facilitate the industrial implementation (use) of these new cryogenic plate products by characterising critical application properties, appropriate benchmarking, and design case studies.
• To assess the potential of these new plate products for other non-cryogenic applications, requiring corrosion resistance and high strength (i.e., lightweight large storage tanks for water, selected chemicals, digesters).
• To determine the role of TMCP on corrosion resistance, austenite stability and mechanical anisotropy.
• To establish the microstructure-process-mechanical property relationships due to TMCP.