Study Of Structure And Mechanical Properties Of 10Ni5CrMoV Steel MIG Welding Joint

In this paper, the effect of the temperature on austenite grain size and the rule of structureinheritance of l0Ni5CrMoV steel was inveStigatCd .The mechanical properties andmicrostructure in the overheated zone was studied by weId therm-imulation test with threekind of weIding energy input. The microstructure and toughness of MIG welding joint with2lKJ/cm we1ding heat input was analysed. Experiment resu1t showed: the criticaltemperature that austenite grain size abruptly coarsens is 1200 C,the recrystallizationaustenite is acicular austenite at S50C --900C,but when the temperature is over 900C it issphere austenite,the structure inheritance temperature is at Acl--900'C.Weld thermbesimulation test indicated: the mixed structure mainly includes mwtensite +upper bainite+granular structure at l9KJ/cm,at 24KJ/cm and 30KJ/cm the mixed structure mainly includesmartensite +upper bainite +granular bainite,the charpy impact energy is the highest of threewelding heat input at 24KJ/cm, the impact eneny is 183J at --60C.The charpy impact anddynamic tear experiment of MIG welding joint with 2lKJ/cm weIding heat input showed:the toughness of weld meta1 is the worst in we1ding joint,at --50'C the charpy impact energyof weld metaI is 84J and the dynamic energy of weld metal is 300J,5o the weld metal has anexcellent low temperature toughness because the weId metal has so many acicular ferrite,themain mechanism of the second comp1ex phase from liquid phase is multiple directionprecipitating at the same core.