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.
- 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.
- 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.
- 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.
- Table 1: Detail of steelmaking process, form and dimension of material, processing and thermal history, grain size, and hardness;
- Table 2: Results of chemical analysis (check analysis);
- Table 3: Short-time tensile properties including lower yield or 0.2% proof stress, tensile strength, percentage elongation, and reduction of area;
- Table 4: Creep-rupture data including time to rupture, elongation, and reduction of area for each applied stress.
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.
The support of the Committee on Creep of the Iron and Steel Institute of Japan is deeply appreciated.