ISO 6892-2: Tensile test of metallic materials at elevated temperature
DIN EN ISO 6892-2 governs the tensile test on metallic materials above room temperature and specifies the conditions under which temperature-dependent properties such as yield strength, tensile strength, and elongation at break are determined when a material is subjected to stress at several hundred degrees Celsius. While the ISO 6892-1 While the first part of the standard describes the tensile test at room temperature, the second part supplements the requirements for temperature control, heating through and high-temperature strain measurement, so that test results remain reproducible and comparable between laboratories even under thermal stress.
Key facts at a glance
DIN EN ISO 6892-2 is the internationally recognized standard for the Tensile test on metallic materials at elevated temperatureIt defines the test conditions for tests above room temperature and ensures that temperature-dependent material properties are recorded reproducibly.
- The standard serves to determine temperature-dependent parameters such as Yield strength Rp0,2 and Rp1,0, tensile strength Rm, elongation at break A and reduction of area Z.
- Temperature control, sample heating, and strain measurement under heat significantly determine the quality of the results.
- At high temperatures, yield strengths are predominantly determined, since a distinct upper and lower yield strength (ReH/ReL) often no longer occurs.
- A standard-compliant test requires a High-temperature furnace, thermocouples and a high-temperatureEXTENSOMETER.
- The standard is applied in the Materials development, quality assurance and the design of thermally stressed components.
What does DIN EN ISO 6892-2 regulate?
The standard standardizes the execution of tensile tests above room temperature. It describes how the specimen is brought to, maintained at, and tested at the test temperature, and defines requirements for the testing equipment, temperature control, strain measurement technology, and data analysis. The aim is to ensure that results from different machines and laboratories remain comparable despite the additional influencing factor of temperature.
Differentiation from ISO 6892-1 and ISO 6892-3
The ISO 6892 series of standards covers various temperature ranges. The first part applies to room temperature, the second to elevated temperatures, and the third to low temperatures. ISO 6892-2 builds upon the fundamental principles of tensile testing and supplements them with requirements for temperature control, temperature distribution, and high-temperature strain measurement. A basic description of the characteristic values and test methods can be found on our website. Page for ISO 6892-1.
Why tensile tests at elevated temperatures are important
Many components operate continuously at several hundred degrees Celsius. As the temperature increases, strength and stiffness decrease, and the deformation behavior changes, sometimes significantly. Characteristic values from room temperature tests are insufficient for the design of such components. The high-temperature tensile test provides the values necessary for reliable designs and realistic service life assessments.
Typical areas of application:
- Power plant and turbine construction
- Pressure vessel and chemical plant construction
- Aerospace
- Exhaust systems and heat treatment technology
- Hydrogen technology and high-temperature materials
Temperature control and heating through
Before the test, the sample is heated to the test temperature and held there long enough until it is completely heated through. Only then is a uniform temperature present across the entire measuring range. Even slight deviations from the target temperature alter the determined parameters, which is why the standard sets strict requirements for temperature stability and temperature distribution.
The temperature is measured directly on the sample using thermocouples; for longer measurement ranges, measurements are taken at multiple points along the sample. These multiple measurement points indicate whether the sample is heated uniformly or if a temperature gradient is present. The oven control maintains a constant temperature throughout the entire test.
Test speed at elevated temperature
The strain rate has a significantly greater impact on material properties at elevated temperatures than at room temperature. The same material can exhibit different yield strengths and tensile strengths at the same temperature but with different test speeds. Therefore, the standard describes methods for controlling the test speed and recommends tightly toleranced test conditions to ensure comparable results.
The basic system of speed control with method A (strain rate control) and method B (stress rate control) corresponds to ISO 6892-1.
Requirements for the test facility
A standards-compliant high-temperature test requires more than a universal testing machine. The testing system includes a high-temperature furnace, precise temperature control, thermocouples, and an extensometer that measures reliably under heat. All components must be perfectly matched. The general requirements for force measurement and machine stiffness remain unchanged, just as with room-temperature testing.
High-temperature furnace and temperature measurement
The oven encloses the sample and heats it to the test temperature. Thermocouples on the sample measure the actual temperature and send this data back to the control system. Uniform heating along the entire length of the sample is essential for reliable results.
High-temperature extensometer
The strain is measured directly on the sample, even at several hundred degrees Celsius. Special equipment is used for this purpose. High-temperature extensometer Extensometers that operate reliably under heat radiation and thermal expansion and record the expansion profile throughout the entire experiment are required. Room temperature extensometers are not suitable for these conditions.
Measurement uncertainty in high-temperature tests
In addition to the usual influencing factors, elevated temperatures bring additional factors to bear on the result: temperature gradients across the sample, deviations from the target temperature, the accuracy of the temperature measurement, and the increased influence of the strain rate. Regular calibration of the entire testing chain, including temperature measurement, is therefore essential for reliable and reproducible characteristic values.
FAQ: Frequently asked questions
From what temperature does DIN EN ISO 6892-2 apply?
This standard applies to tensile tests above room temperature. Tests at room temperature are carried out according to ISO 6892-1, and tests at low temperatures according to ISO 6892-3.
Why are yield strengths predominantly determined at high temperatures instead of the tensile strength?
With increasing temperature, many materials no longer exhibit a distinct upper and lower yield strength (ReH/ReL). Instead of the yield strength, the proof stress Rp0,2 or Rp1,0 is determined, which corresponds to the stress at a defined permanent strain.
Why is temperature control crucial in high-temperature testing?
Even slight deviations from the test temperature alter the material properties. Complete heating of the sample and stable temperature control are prerequisites for reproducible results.
Are special extensometers required for high-temperature experiments?
Yes. Strain measurement is performed using high-temperature extensometers, which operate reliably under heat radiation and thermal expansion. Room temperature extensometers are not suitable for this purpose.
