热冲压球壳Q235钢材高温后力学性能试验研究

为研究热冲压球壳Q235钢材高温后的力学性能，对经历400~900℃高温后由自然冷却和喷水冷却到常温空心球加工制作成的受拉试样进行拉伸试验，得到高温冷却后该材料的应力-应变曲线、弹性模量、屈服强度、抗拉强度和断后伸长率，并与普通Q235钢高温后力学性能进行了对比。研究结果表明：当经历温度不超过500℃时，钢材高温后强度与断后伸长率在两种冷却方式下变化规律基本类似，且变化很小。当经历温度超过500℃后，不同冷却方式对材料高温后强度与断后伸长率产生明显影响，且温度越高，相差越大，自然冷却方式下，随着温度的升高，强度降低而断后伸长率变大。喷水冷却方式下，抗拉强度增大而伸长率减小，屈服强度在500~700℃之间逐渐增大，700℃之后又快速下降。弹性模量受经历温度与冷却方式的影响较小。

Experimental research on mechanical properties of Q235 steel of hot stamping spherical shell after high temperatures

In order to investigate the mechanical properties of Q235 steel of hot stamping spherical shell after exposure to elevated temperatures, tensile specimens were made from hollow balls which cooled down to natural temperature via two different cooling methods: natural cooling and water cooling after experiencing high temperature of 400~900℃.The stress-strain curves, elastic modulus, yield strength, ultimate strength and elongation of the materials were obtained by tensile tests. The test results were compared with the mechanical properties of the normal Q235 steel after high temperatures. The study shows that when the temperature is below 500℃, the changing rules of strength and elongation are basically similar for two different cooling methods, and the variations are small. When the temperature is over 500℃, cooling methods have a significant effect on strength and elongation. The higher the temperature, the greater the difference. Under the condition of natural cooling, strength decreases and elongation increases as the temperature rises. On the other hand, under the condition of water cooling, the ultimate strength increases and the elongation decreases with the increase of temperature. The yield strength increases gradually between 500-700℃, and then decreases rapidly after 700℃. The elastic modulus is less influenced by temperatures and cooling methods.