The Research And Optimization Of Pressure Vessel Steel16MnR PWHT Parameters

In this study, serious of normalizing heat treatment experiments(890℃～1050℃) werecarried out on the16MnR steel welded butt joint. To make sure that normalized condition canbe regained after broken by normalizing heat treatment, experiments done in this article canprovide theoretic basses. The microstructures and hardness of different zones(welding line,heat affected zone and base metal) of butt-joint were measured and analyzed by metalloscope,SEM(scanning electronic microscope) and Vickers’s indentation tester respectively. Besides,PWHT (post weld heat treatment),which is normalizing in this study, was simulated withsysweld and visual-environment. The welding parameters and normalizing parameters weretested and verified. Deflection after welding and PWHT calculated in the simulation wasreasonable and so were the temperature field and stress field. The damage induced by residualstress was decreased.（1） In the welding experiment, SAW(submerged arc welding) was used. The size ofspecimen was30×150×500（mm） and it had a double-V weld, whose bevel anglewas60°. The welding parameters were as follows: I（current）=580—600（A），U（voltage）=35—36（V），V(welding speed)=40—42（cm/min），E(linearenergy)≤32.4（KJ/cm）.（2） The quality of the weldment was excellent and the results of tensing impacting,bending hardness tests met with the requirements in WPS(welding procedurequalification).（3） After a serious of normalizing treatment(890℃—1051℃) and one-hour thermalinsulation, the mechanical properties of different zones changed according to thefollowing rules：the grain size enlarged and the tensile strength was smaller thanwelding condition generally.（4） When the insulation temperature reached980℃,the tension strength got itsmaximum value in normalizing condition and so did the contraction of crosssectional area; Impact energy became weaker, which indicated that the brittletransition temperature rose and the impact toughness decreased; Hardness ofdifferent zones changed like HAZ>weld bead>base metal. As saw in theexperiments, a conclusion could be reached that when heated to980℃andinsulated for1hour the specimen got its integrated mechanic performance.（5） In the results of PWHT calculated by sysweld, the temperature field of X grooveindicated that heat input had a dramatic influence to former weld and the HAZcould reach800℃;the residual stress(mainly the tensile stress) value and thedistance to the weld center had an inverse relationship.（6） The residual stress mainly distributed at the root of the weld. During the multi-passwelding, each weld had a bending effect to the specimen, so under the multiple tensile ductile deflection, the root of the weld became harder and the stressconcentrated there.