Research On The Crack Propagation Of The Refractory Temperature Tube Based On The Thermal Stress

The temperature measurement tube is molten steel continuous temperature measurement system for molten steel temperature sensing element, the fracture is the main damage form, and cracks is the primary condition for fracture. Temperature measurement tube crack not only affect its accuracy, but also affect the service life. In this paper the temperature measurement tube temperature field model, analysis of the temperature field’s change gradient, which is established on the basis of the temperature measurement tube thermal stress field model is established, and then the crack propagation model, studies the influence of the temperature measurement tube life factors and its analysis. The study on optimal temperature tube structure, improves the life of measuring tube has practical significance.(1) Establish the temperature field model of temperature tube and given boundary conditions and initial conditions to obtain the temperature field contours and temperature gradient for coupling calculation of the thermal stress.(2) Establish thermal stress model, and applied the results of the temperature field calculation to the structure field for the thermal stress coupling calculation. Research preheats temperature, temperature measuring tube wall thickness and other factors on the distribution of temperature tube stress.(3) Establish temperature tube crack model. Focus on the crack propagation mechanism and the thermal shock influence on the life of temperature tube contained the crack.The experiment results show that the established models are correct; the maximum error between measurement value and simulation value is less than6℃. In the process of temperature measurement the temperature tube is subject to serious thermal shock, and the temperature undergoes a tremendous change in a short time, particularly the temperature along the axial direction from the bottom of tube varies obviously with a step-shape distribution; Thermal stress at the exterior wall in contact with liquid steel is very small and that at the interior wall is much larger. The maximum stress value appears at the bottom of the thinnest wall. But with the advance of time the thermal stress field region gradually decreases; The higher the preheating temperature, the lower the thermal stress of the tube during temperature measurement. The increasing stress that caused by the changed wall thickness intensifies the temperature tube damage; the existence of the crack will greatly reduce the temperature of the life. If the crack length is2mm, the temperature measurement will be rupture after four times of use due to the propagation of the crack.