Study On The Material Properties And Life Prediction Of Oxygen Lance Nozzle

The oxygen lance nozzle is one of the key parts in converter steelmaking production.It is affected by the high temperature heat radiation of molten steel,the erosion and erosion of splashed steel slag and molten steel,and the cooling of circulating water flow inside,which results in a large temperature difference in the nozzle and a large thermal stress.In the process of repeated blowing,the large change of thermal stress will also cause the nozzle to contract and expand repeatedly.All of these will cause the nozzle of oxygen gun to overheat,burn and deform,shorten the service life of the nozzle directly,and reduce the economic benefits.In recent years,there are mainly two kinds of oxygen lance nozzles used in domestic steel plants,one is cast oxygen lance nozzle,the other is forged oxygen lance nozzle,and the two kinds of oxygen lance nozzles have obvious differences in service life.In this paper,starting from the research on the properties of two kinds of copper oxygen lance nozzle materials,the temperature field and stress field of the same material and the same structure oxygen lance nozzle under different processing conditions are analyzed by experimental research and numerical simulation,the key factors of high temperature damage are explored,and the thermal fatigue life prediction is carried out.The research results will be used for the maintenance and structure of oxygen lance nozzle Optimization is of great significance.In this paper,the mechanical properties of cast / forged oxygen free copper materials are obtained by tensile test at room temperature,which provides strong data support for the subsequent finite element analysis;secondly,the influence of thermal cycle times on the thermal fatigue performance of cast / forged oxygen lance nozzle is explored by high temperature thermal cycle test.Then,according to the actual working situation of the oxygen lance,ANSYS Workbench software is used to simulate the heat structure coupling of a smelting cycle of the nozzle,analyze the temperature field and stress field distribution,and get the weak link of the nozzle working in the fatigue environment,which provides basic data for the maintenance and structural optimization of the nozzle.Finally,through n Code Design Life fatigue analysis software to analyze its thermal fatigue life,get the fatigue result cloud chart and the life of each node,and determine the location and life of the oxygen gun nozzle easily damaged.It was found that the mechanical properties of cast / forged oxygen free copper decreased as a whole after high temperature thermal cycling.Before 150 cycles,the mechanical properties of cast / forged oxygen free copper increased with the increase of cycles.After 150 cycles,the properties began to decline,and the drop range of cast copper was larger,and the properties were lower than those at room temperature.The results show that the high temperature thermal cycle has more influence on the thermal fatigue properties of cast copper.The results show that the highest temperature of forging nozzle is 452.77 ℃,the highest temperature of casting nozzle is 471.75 ℃,the highest temperature of casting nozzle is higher than that of forging nozzle because the thermal conductivity of casting nozzle material is worse than that of forging nozzle material;the maximum thermal stress of forging and casting nozzle is 189.97 MPa and 177.2MPa respectively,although the maximum thermal stress of casting nozzle is lower than that of forging nozzle But the maximum thermal stress of the casting nozzle is closer to the tensile strength limit of the material,and it is more likely to be damaged.Through fatigue life analysis,the service life of forging and casting nozzles is 338.8 times and 177.6 times respectively,which is consistent with the change rule of material properties in high temperature thermal cycling experiment.At the same time,the life distribution and fatigue sensitive area of the oxygen lance nozzle are obtained,which can provide reasonable guidance for the maintenance and structural optimization of the oxygen lance nozzle,and effectively reduce the safety risk caused by the failure of the oxygen lance nozzle.