The load softening temperature is a critical high-temperature indicator for purchasing refractory materials, directly reflecting the temperature at which the material can withstand both high temperatures and mechanical pressure without deformation. The latest standard for this test is YBT 370-2016: Refractory Materials – Test Method for Load Softening Temperature (Non-differential Heating Method), which provides detailed instructions on how to conduct the test.
Test Steps
- Dry the specimen in an electric drying oven at 110°C ± 5°C or an agreed temperature until it reaches a constant mass.
- Measure and record the dimensions of the specimen, with an accuracy of 0.1 mm.
- Place the specimen at the center of the furnace’s uniform temperature zone. Insert approximately 10 mm thick spacers between the specimen’s upper and lower surfaces and the pressure rod and support rod. The diameter of the spacers must not be less than that of the specimen.
Ensure the pressure rod, spacers, specimen, support rod, and loading system are vertically, stably, and coaxially aligned without any tilting.
- Adjust the deformation measurement device and the temperature measurement thermocouple.
- Apply the load to the specimen, including the mass of the pressure rod, spacers, and the pressure from the loading system, with an accuracy of ±2%.
The compressive stress applied should be 0.20 MPa for dense refractory materials and 0.05 MPa for insulating refractory materials, unless otherwise specified in the supply contract or technical conditions.
- Heat the specimen continuously and uniformly at the following heating rates until the test concludes:
- ≤1000°C: (5–10)°C/min
- ＞1000°C: (4–5)°C/min
- During the test, record the following information in real time:
a) Temperature and deformation every 10 minutes.
b) Maximum expansion value and the corresponding temperature.
c) Deformation and temperature when the specified compression deformation is reached.
d) If the specimen collapses, record the temperature Tb at which collapse occurs.
If the system automatically records and plots “temperature, deformation, time” curves, ensure the following are plotted:
- Temperature vs. time
- Deformation vs. time
- Deformation vs. temperature
- Terminate the test under any of the following conditions:
a) The required test temperature is reached (e.g., T0.6), where the specimen has deformed to the specified percentage from its maximum expansion.
b) The termination temperature Te is reached, where the specimen has compressed by 5% of its original height from its maximum expansion.
c) The furnace reaches its maximum operating temperature.
d) The specimen collapses.
e) Other abnormal situations occur.
