Q345R is the most widely used material in manufacture of pressure vessels in China. It is recently permitted in ASME Code Case 2642 for the fabrication of pressure vessels with design temperature above −10°C without concern about the low stress conditions. However, it’s allowed to be used at above −20°C in Chinese standards. For understanding its properties under low temperature, a large amount of toughness test data of Q345R were collected from recent literature, and lots of Charpy V-notched (CVN) impact tests at a series of lower temperature were also conducted. Several Ductile-Brittle Transition (DBT) curves were drawn from the test results and some reference temperatures for DBT region and CVN energies at certain temperatures were obtained and discussed. Results show that its toughness at −20°C is much better than that required both in Chinese standards and American Codes. The reference temperature of Q345R was determined as −24.7°C by using a conservative statistical estimation. And It is suggested that the allowable Minimum Design Metal Temperature (MDMT) of this material in American codes should be extended to a lower region.

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