Study On The Tension Behavior Of Austenitic Stainless Steel Under Crvogenic Environment

Austenitic stainless steels(ASS) are widely used in manufacture of cryogenic vessels such as liquefied natural-gas storage tanks, liquid oxygen tanker and tank containers for cryogenic liquid due to its favorable low temperature ductility and excellent corrosion resistance. Playing an important role in liquid energy transportation, cryogenic pressure vessels have become popular with the development of cryogenic technology and the growing demand of energy.Cold stretching technique can reduce the wall thickness, the weight of ASS cryogenic vessels and the energy consumption, which well meet the reqirement of low carbon, green, light weight and so on. Nowdays, this technique has been brought into relative standards of ISO, Europe, Australia and US. Up to now, most researchers put more attention on the tensile behavior of ASS under room temperature. In order to improve the design method and ensure the safety of cryogenic pressure vessels, study on tensile behavior of ASS under cryogenic environments is necessary. Tensile test is an important way to investigate the plastic deformation capacity, and can be used as a qualification method for material design, material selection, welding procedure. Thereforce, study on the pre-loading materials at different temperatures is of great significance for safe operation of cold stretched pressure vessels.Based on National High Technology Research and Development Program (863project, Number:2011BAK06B02-05), International Science and Technology Cooperation Program(Number:2010DFB42960) and Zhejiang province key science and technology innovation team project(Number:2010R50001), the paper aims to investigate the tensile properties of ASS under cryogenic temperature to provide theoretical support and sufficient data for cryogenic vessel design in China. The main contents and work of this paper are:(1) Comparison and analysis of the influence of displacement control mode and extensometer control mode on the result of tensile test at room temperature and cryogenic environment. Then put forward a proper method for tensile test data detection at cryogenic environment. For the pro-loading materials, some tests with different sample processing methods at certain strain rates were performed under different temperatures and the results were analyzed. Then come up with a suitable method of sample processing method for the engineering application.(2) For the first time in China, studies on tensile properties of ASS with different pre-loadings at room temperature and cryogenic environment were carried out. Engineering stress strain curves were thus obtained and changes of macro-mechanical properties were analyzed, which were then explained though a study on the microstructure behavior.(3) Mechancial tensile datas of he materials with9%pre-loading and the materials without pre-loading at cryogenic environment were achieved though a series of tensile tests. Test datas were then compared and analyzed with the reliability and credibility of the statistical method, thus the minimum guarantee values of the proof strength and tensile strength of S30408steel at cryogenic temperature were obtained for the first time in China.(4) In order to well manage the test data, enhance data sharing and ensure the safety of the data as well, database of material low temperature performance was established, which provides sufficient supportting data for the cryogenic vessel design.