[Discussion Thread 9] For Q235C steel plates with a thickness of 16 mm, the lower limit value of their yield strength ReL is 235 MPa. ——Right or wrong...
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bg4.png【Discussion Thread 9】For Q235C steel plates with a thickness of 16 mm, the lower limit value of their yield strength ReL is 235 MPa. ——Right or wrong, or it could be either——For Q235C steel plates with a thickness of 16 mm, the lower limit value of their yield strength ReL is 235 MPa. ( ) A. Correct B. Incorrect ---------- Some users have asked about the upper yield strength ReH specified in GB/T700. Where can I find the value of ReL? ---------------Q represents the yield limit of this material, while the 235 following it indicates the yield strength of this material, which is around 235 MPa. Moreover, as the thickness of the material increases, its yield strength decreases. Due to its moderate carbon content, it possesses good overall properties, with strength, plasticity, and weldability being well balanced, which makes it the most widely used material. --------I feel that this question mainly tests the yield strength value corresponding to the critical wall thickness. As shown in the figure:
The yield limit of Q235 specifies the lower bound of the yield strength for a certain thickness range; the yield strength of Q235 is dependent on thickness
This table is derived from GB/T700-2016: handshake
I’m a bit confused about the definition of yield strength. If you examine the GBT700 table carefully, the header “Yield strength ReH, not less than” indeed represents a minimum value: dizzy:
The values given in the standards are mostly limit values (upper or lower limits), or they can be understood as range values, such as less than or equal to, greater than or equal to, etc., as reflected in the table headers shared by 2#.
The lower limit value means that it cannot be below this value; if it is below this value, the material does not meet the standards.
Rel refers to the yield strength, right? Q235C exhibits a clear yield point, so the yield strength is taken as such. On the stress-strain curve, it seems to correspond to the proportional limit – is this correct?
Rel refers to the lower yield strength; China’s steel standards require this value. ReH denotes the upper yield strength, while steel standards in Europe and America such as ASME typically refer to the upper yield strength. The upper yield strength and lower yield strength generally differ by 10–20 MPa, depending on the strength of the steel, and these values correspond to the upper and lower edges of the yield plateau in the yield curve.