cr1mo钢稳态蠕变速率和断裂寿命的研究word格式论文.docxVIP

Abstract2.25Cr1Mo steel is a heat resistant steel which mainly contains chromium and molybdenum elements. It has higher strength and better resistance to oxidation at high temperature, as well as good weldability, being widely used in the high temperature and pressure components in electric power, nuclear energy and petrochemical industry such as the main steam pipe, the hot steam pipe, etc. However, if the steel serves in the conditions of high temperature (350~600 oC) and high pressure (e.g., 28 MPa) it will deform slowly and continuously, which will cause the failure of components. This slow and continuous deformation is called creep.The creep process is divided into three stages according to the shape of creep curve. The first stage in which the creep rate decreases continuously with time is called primary stage; the second stage in which creep curve is a straight line and the creep rate is constant is called stable stage; the third stage in which the creep rate increases with time until the rupture is called accelerated stage.Large numbers of investigations have shown that under the same stress the natural logarithm of stable creep rate ln ε is proportional to the inverse of temperature, 1/T, and at the same temperature the common logarithm of creep ratelog ε is proportional to that of stress, log σ , too. By the use of above relationshipsthe parameters of creep constitutive equation can be obtained from creep test. In addition, a lot of experimental investigations show that a relationship called Monkman-Grant relationship exists between stable creep rate and creep rupture time, and the power law is also satisfied between rupture time and stress and temperature. Making use of these relationships the creep rupture life can be predicted, such as Lason-Miller method.The creep test is divided into two groups. The first group is carried out under tensile stresses of 250 MPa and at different temperatures of 500, 550, 575,600 and 625 oC, separately; the second group i