Research On The Dvelopment Of Secondary Superheater Outlet Header Of Ultra-supercritical Boiler Welding Process

With the continuous development of thermal power boiler industry,ultra-supercritical thermal power units than the efficiency of supercritical units increased by 5%.It is an effective method to improve the steam temperature and pressure parameters of power plant,especially the effect of temperature on the efficiency of the power plant is more obvious.This poses a higher requirement for boiler materials.The existing high-temperature creep strength of the material can not meet the requirements of the secondary superheater outlet header,the need to develop a new type of ferrite heat-resistant steel,in this trend P92 material came into being.As the super-supercritical boiler secondary superheater outlet header in operation at high temperature and high pressure state,coupled with the internal chamber of the gas corrosion,making the box to the problem of fatigue defects are more common,and the main defect parts for welding Near the seam.The secondary superheater outlet header of the super-supercritical boiler is determined as P92 material according to the performance calculation.Therefore,the content of alloying elements is high,and it is easy to produce defects when welding.In this contents,the influence of the welding process specification on the quality of the weld is studied in the final superheater outlet header,and how to avoid the defects in the welding process.The main contents of this paper are to study the weldability of the outlet header of the superheater and analyze the principle of the defect.From the strengthening mechanism of the material and the effect of the alloying elements,the solution to avoid the common defects is explored.Analysis of welding process parameters: the preheat temperature of welding,the welding groove form,welding,post weld heat treatment effect on the quality of the weld,the reasonable welding process parameters.Validated the welding process parameters before put into production,first verify the performance of the welding material,and then in accordance with the established process welding,the welding joint according to the requirements of ASME sampling,analysis of the macro and microorganize,ensure no weld defects;Tensile test of union parts,side bend test to ensure the required strength and plasticity,v-type notch impact test to ensure that the impact toughness of welded joint meet the design requirements.According to the experimental results were analyzed,and ensure that the use of process welding parameter can produce qualified weld.According to the construction of process parameters,the performance of its joint meet the design requirements.Ultra Supercritical Boiler secondary superheater outlet header P92 material selected for the first time in the factory header design,the conventional welding method is applicable,no mature welding technology and manufacturing experience to ensure that the production of welding weld meet the design requirement.According to the determination of the welding parameters of the header rin g to the docking test,the inspection of welded joints,the welding process,the welding parameters,Of the mechanical properties,microstructure meet the standard requirements.Ensure that the use of welding parameters in production to produce qualified welds,for the header manufacturing provides technical support.