Experimental Study on Steel Mechanical Properties at High Temperature

Experimental Study on Steel Mechanical Properties at High Temperature

A more accurate understanding of the mechanical properties of structural steel at high temperatures is the basis for the analysis of steel structure response under fire. S45C carbon steel square bar is a kind of structural steel. Glory Steel Work could offer structural steel like, S20C steel, S45C steel, etc. Foreign countries have done a lot of researches on the mechanical properties of structural steel under high temperature. However, due to different test methods (steady state test and transient test), different accuracy of test equipment and measurement technology, and different control mode and control selected parameters during the test with the complex effects of creep factors, there will be certain differences in test results. The structural models used in different theoretical analysis of structural fire resistance response and the calculation of various parameters are also quite different. Generally, simple segmentation models are used, and complex smooth curve models are also used. It is necessary to carry out a certain number of structural steel high-temperature material tests, and try to understand the mechanical properties of commonly used structural steels at high temperatures.

When the temperature is 200 °C, the steel still shows obvious yielding and strengthening, but the flow rate is reduced compared with normal temperature. When the temperature is 300 °C and higher, the steel does not have obvious yielding phenomenon, but when the stress level is small, there is still an approximate elastic phase. The temperature is different, and the elastic ultimate strain is also different, about 1‰. At 300 °C, the material strength is much lower than that at 200 °C. In addition, it can be seen from the stress and strain relationship of the unloading section that when the temperature is low (below 400 °C), part of the strain during the unloading process is substantially restored by the initial slope of the curve. When the temperature is high (500 °C, 600 °C), the stress level is high in a range after the start of unloading. The influence of creep causes the strain to be increased. When the stress level is low, the strain is increased. The stress starts to recover slowly and, and the slope of the curve is smaller than the initial elastic phase of loading. Of course, if the load loading and unloading rate is large during the test, the effect of creep will be smaller.

After the temperature exceeds 300 °C, there is no obvious yielding stage in the stress-strain curve of the steel, so the yield strength is not clearly defined. At higher temperatures, the stress increases very slowly with strain.