Study On Welding Process Of Reactor For Ship Denitrification System

With the increasingly serious pollution problem of marine diesel engine emissions,the MARPOL convention stipulates the discharge standard of ships.In order to meet the third level standard(Tire III)stipulated in the Convention,how to control the exhaust emissions of diesel engine economically and effectively has become an important topic in front of shipyards and diesel engine plants.The diesel engine by using catalytic reduction technology(Selective Catalytic Reduction,SCR),due to the small changes of the diesel engine,high conversion rate,good economic characteristics,has been that it is an effective means to control emissions in the next few years,marine construction,marine denitrification(SCR)system the research will be more mature and has been widely applied to all kinds of ships.Denitration by boat(SCR)between the system working temperature is 400 DEG ~500 DEG,therefore the main material generally low alloy Cr Mo steel,chrome molybdenum steel can work stably for a long time in high temperature environment,because compared with the high temperature oxidation resistance of ordinary carbon steel can be better,but there is a certain tendency of hardenability cold,easy to produce cracks or crack.In welding,welding,both to ensure the mechanical properties of the weld,but also to ensure that the chemical composition of weld,making the welding technology is particularly important.In this paper,the operating principle of SCR system were introduced,summed up the SCR reactor pressure part material and weld type,for the control of Cr Mo steel after welding cold crack and material delay crack,welding groove should be cleaned before welding,and 150 ? to preheat the groove near the control layer temperature during welding after welding,hydrogen heat treatment,the welded joints for nondestructive testing.On the other hand,the sample of SCR reactor for butt weld of the mechanical property test and microstructure observation of impact fracture of welded joints,part of the hardness test and the distribution of the major elements analysis,test results show that the production of welding technics and the proposed method is applied to the SCR system of the reactor,and mastered the organizational characteristics of chromium to judge the quality of the weld steel welding,and in the future to provide reference materials of Cr Mo steel welding process.