非调质钢MFT8的高温拉伸与持久性能

High-temperature tensile and stress rupture properties of none-quenched and tempered steel MFT8

通过高温拉伸和持久实验研究了非调质钢MFT8的高温力学性能,用扫描电子显微镜观察高温拉伸和持久实验试样的断口形貌及组织演变规律。结果表明,从室温至500℃范围内,MFT8钢晶粒尺寸、析出相形貌未发生明显变化,高温强度的降低主要由于位错强化作用的减弱;在450℃条件下,MFT8钢具有以穿晶断裂和高塑性为代表的低温蠕变特点,材料内部虽然出现部分蠕变孔洞,但导致蠕变断裂的主要原因为析出相颗粒处应力集中引起的楔形开裂;对持久数据的线性外推得出,MFT8钢450℃在10万小时的持久强度为184.4 MPa。

The high-temperature mechanical properties of a none-quenched and tempered steel MFT8 were investigated by tensile and stress rupture tests.SEM was used to analyze the fractography and microstructure evolution for the samples after high-temperature tensile and stress rupture tests.The results show that there is no significant change for the grain size and morphology of precipitated phases of the steel during tensile tests from room temperature to 500 ℃.The decrease of dislocation strengthening leads to the decline of high temperature strength.MFT8 steel exhibits low-temperature creep process at 450 ℃,which featured in transgranular fracture and high ductility.Although the creep voids can been observed,the essential reason of creep rupture is the wedge cracking caused by stress concentration at the particles.The rupture strength of MFT8 steel at 450 ℃ and 100000 h is calculated to be 184.4 MPa with linear extrapolation of the tested data.