Dissimilar Heat - Resistant Steel Tube Joint Welding Numerical Simulation

Dissimilar steel welding joint in coal-fired boiler pipe, in power plant’s working environment, tends to austenitic heat resistant steel and steel pearlite or martensite steel welded together, the austenitic dissimilar steel welded joint has at least one large difference in the fusing interface composition and organization. As the physical properties of interface on both sides of the materials do not match, there exists significant difference in the thermal expansion coefficient, thermal conductivity, and thus will produce, in the area of the welding and the fusion zone interface, more thermal stress. Meanwhile, the dissimilar steel welded joint due to thermal expansion characteristic of different material near the weld cause large thermal stress. Thus there will be weak local area on the one side of the dissimilar steel.This thesis analyzed the SYSWELD of T91 / HR3 C, HR3C/12 Cr Mo V dissimilar steel welding process in numerical simulation, in the process of the welding temperature field and transient thermal stress field distribution rule as well as the cooling process of the temperature field and welding residual stress field. Besides, this thesis also makes an detailed analysis on the sand to master the distribution of temperature field and stress field.By means of numerical simulation of welding process and welding cooling process found for HR3C/T91 dissimilar steel tube joints in terms of its surface temperature is slightly below the surface temperature, and at the side of the T91 to higher temperature, and for HR3C/12 Cr Mo V dissimilar steel pipe joint 12 Cr Mo V side to higher temperature, the temperature drop rate and faster at the same time.T91 / HR3 C dissimilar steel pipe joint of the surface of the residual stress inside the ring to the present tension between residual stress and pressure on both ends of the distribution, basic parent metal edge of the area is not affected by residual stress. Maximum stress appears at the side of the T91, a maximum of 350 MPa, HR3 C steel side smaller stress value is 200 MPa. Axial residual stress present all for tensile stress, but due to the stress in the middle is small, the welding starting position(position) in tension and tensile stress value is small, the value is 60 MPa. The maximum axial residual value is 300 MPa.HR3C/12 Cr Mo V dissimilar steel pipe inner surface residual stress of joint circular weld residual stress is tensile stress, on both sides of the heat affected zone is compressive stress, because on both sides of the parent metal hematocrit were similar, the basic distribution is symmetrical. Ring to the maximum residual stress appears in the weld of tensile stress, the maximum value of 400 MPa.HR3C steel side as compressive stress, size of 150 MPa. Outer surface of the axial residual stress is tensile stress, the maximum axial residual is 260 MPa.Last but not least, this thesis also analyzed the blind hole method of HR3C/T91, HR3C/12 Cr Mo V dissimilar metal weldments of welding residual stress measurement, compared with numerical value analysis, as well as the measured values and the error of the numerical value.