拉伸预应变对34CrNiMo6钢室温拉伸性能及低周疲劳性能的影响

Effects of tensile pre-strain on room temperature tensile and low cycle fatigue properties of 34CrNiMo6 Steel

自增强超高压容器在服役过程中通常需要承受循环内压作用,研究预应变对其筒体材料34CrNiMo6钢室温拉伸性能和低周疲劳性能的影响,对保障超高压容器的结构完整性具有重要意义。以国产34CrNiMo6钢为研究对象,开展不同拉伸预应变水平下的室温拉伸试验及对称应变控制条件下室温低周疲劳试验。结果表明:与原始试样相比,在6%预应变范围内,材料的屈服强度和抗拉强度随预应变水平的增加而增大,但伸长率和断面收缩率出现了连续单调下降。预应变显著改变了滞回曲线的应力幅值及形状,且预应变前后材料表现出明显的拉-压不对称和循环软化/硬化特征;在1%~4%预应变水平下,材料的低周疲劳寿命呈现出先升高后降低的趋势。

It is of great significance to study the effect of pre-strain on the room temperature tensile properties and low-cycle fatigue properties of 34CrNiMo6 steel to ensure the structural integrity of ultra-high pressure vessels,since the self-reinforced ultra-high pressure vessel is usually subject to cyclic internal pressure during service condition.In this paper,room temperature tensile tests and low-cycle fatigue tests under symmetrical strain control conditions of domestic 34CrNiMo6 steel under different tensile pre-strain levels were carried out.Results showed that compared with the as-received specimen,the yield strength and tensile strength of the material increased with the increase of the pre-strain(in the range of 6%),but the elongation and reduction in area decreased monotonically.Pre-strain significantly changed the stress amplitude and shape of the hysteresis curve,and the materials before and after pre-strain showed obvious tensile-compression asymmetry and cyclic softening/hardening characteristics.In the range of 1%-4%ed pre-strain,the low-cycle fatigue life of the material exhibited an initial increase followed by a decrease.