| Hydro-reactor is a kind of three kinds of pressure vessel,its operating conditions are harsh,generally in the 10-25MPa high pressure,400?480 degrees high temperature, hydrogen and hydrogen sulfide environment and other conditions of work,is the core equipment of hydrogenation unit.Traditional hydro-reactor vessels using 2.25Cr1Mo steel manufacturing,with the development of residue hydrogenation modification technology and coal liquefaction technology, epuipment for hydrogenation unit is becoming more larger,2.25Cr1Mo steel has been unable to fully meet the requirement,but 2.25Cr1MoV steel has higher strength, higher using temperature, better anti hydrogen embrittlement, used as a substitute for 2.25Cr1Mo steel of hydrogenation reactor, has become a major trend of development.2.25Cr1MoV steel by adding alloy elements vanadium amount and other trace elements,it is more difficult to weld than traditional non vanadium steel.The welding should be to slove the following four problems by choosing reasonable welding and heat treatment process.the first is the welding cold crack problem,the second is the welding reheat cracking problem,the third is the weld high strength,high hardness,low plasticity and impact toughness problem,the fourth is temper brittleness problem of welding joint.In this paper, using the method of carbon equivalent method, the oblique Y groove welding cold cracking sensitivity test and welding reheat cracking test, To research 2.25 Cr1MoV steel weldability.Research have shown that the lowest preheating temperature to prevent cold cracking is over 170 ? for 2.25 Cr1MoV steel welding and welding joint in the conditions of 650?×2h,690?×8h,705?×8h and 720?×8h post weld heat treatment are not produce reheat cracking.In this paper,the optimum welding and heat treatment process of 2.25Cr1MoV steel was to find out by studying the mechanical properties of the weld joint under different welding parameters and different heat treatment processes,choosing the narrow gap groove,submerged arc welding,AC power supply,wire diameter 4.0mm, welding current 1=480?540 A, voltage U=29-32 V, the welding speed of V=320?400 mm/min, each layer of welding two, weld metal thickness control in 3.0?4.0mm enery layer, the maximum welding line energy is less than or equal to 30KJ/cm, more than 180 degrees for preheating before welding, the welding process control layer temperature at 180 to 230 degrees, it is necessary to DHT immediately after welding, At 350 degrees keeping 4 hours.At last,the weld joint need to heat treatment after welding under 8 hours at 705 degrees in heattreat furnace.In this paper, it was studied about Welding joint properties under the optimal welding and post weld heat treatment process.Through the research of the welding joint properties under the 705? keeping 8 hour minimum heat treatment and 705? keeping 28 hour maximum heat treatment process after welding,including room temperature tensile strength,the high temperature yield strength,welding joint side bend test,micro-hardness,impact toughness at low temperature and temper brittleness,etc.The experimental results showed that used welding and heat treatment process in this paper for welding of 2.25Cr1MoV steel hydro-reactor vessles, it can be obtained welding joint which meet the technical conditions of hydro-reactor vessels manufacturing requirements. The research laid a solid foundation for 2.25 Cr1MoV steel hydro-reactor vessles manufacturing.In this paper,we research the microstructure morphology of welding joint through scanning electron microscope(SEM).It is the even small granular bainite in base metal, not found obvious coarse grain after welding and have similar microstructure morphology with base metal in HAZ,we also found tempering bainite and plate strip ferrite,coarse grains and uneven in welding metal.Through the research of this acticle we find out meet the requirements of welding and post weld heat treatment process,laid a solid foundation for 2.25 Cr1MoV steel hydro-reactor vessles manufacturing. |
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