Material and Its Sampling

 Most of the specifications employed for the tested materials were based on JIS (Japanese industrial Standard). For the materials which are not prescribed in JIS the specifications of ASTM or AMS were employed. These specifications are given in the accompanying Table.

 As a general rule, for each kind of materia] two or three separate heats or casts were sampled at random from commercial products of each of several manufacturers.

 Test specimens were taken as follows: parallel to rolling direction for plate steels, longitudinally at the center of wall thickness for tubes, radially for turbine rotor materials.

Testing Methods

  1. Tensile Test  The tensile tests at room and elevated temperatures were carried out in accordance with JIS G 0567, "Method of High Temperature Tensile Test for Iron and Steel", which corresponds to ISO R 783. A hydraulic type 30-ton tensile machine fitted with a multiple furnace arrangement was used. By means of a transducer type extensometer the actual strain rate of the specimen was controlled to 0.3%/min up to about the 1.0% proof stress level, and 7.5%/min above this level. The properties measured were the lower yield or 0.2% proof stress, tensile strength, percentage elongation and reduction of area at fracture.
  2. Creep and Creep-Rupture Test  The equipment and techniques employed for creep and creep-rupture testing are specified in JIS Z 2271, "Method of Tensile Creep Test for Metallic Materials" and JIS Z 2272, "Method of Creep Rupture Test for Metallic Materials", which correspond to ISO R 203 and R 204, and R 206, respectively. The accuracy of loading of the machines is ±0.5% of the required load. At any time during the test and at any point within the gauge length, the actual temperature of the specimen was controlled to the following limits: ±3℃ for temperatures higher than 300℃ but not higher than 600℃, ±4℃ for temperatures higher than 600℃ but not higher than 800℃, ±6℃ for temperatures higher than 800℃ but not higher than 1000℃.

     At least three temperatures at 50℃ intervals were chosen to cover the temperature range within which the stress rupture properties of the material are likely to be the main basis of design.

     The maximum planned duration for long-term rupture tests was up to 100,000 hrs for power station materials and 30,000 hrs for chemical plant and gas turbine materials.
  3. Test Specimen  In both the tensile and creep tests, round test specimens with threaded ends are used. Typical geometries of the specimens are 6 mm diameter and 30mm gauge length, or 10mm diameter and 50mm gauge length.

Presentation of Data

 All data are presented in tabular form and for each material four types of tables are included.

 The data of Tables 3 and 4 are also presented in graphical form. In the data sheets all of the data are presented in the original form. Attempts are being made to correlate or extrapolate the data at NRIM and will be reported elsewhere.

ACKNOWLEDGEMENT

 The support of the Committee on Creep of the Iron and Steel Institute of Japan is deeply appreciated.