Study On Surfacing Technology For Hot Mill Backup Roll

Hot rolling backup roll is main parts of hot rolling mill, and it is an importantconsumable spare in rolling production. Adopt the method of automatic submerged arcsurfacing to surfacing repair of hot rolling backup roll, has a certain economic and socialbenefits. In the paper, according to hot rolling backup roll main failure forms andsurfacing repair technical requirements, with surfacing materials using the good thermalstability Cr-Ni-Mo-V system cored wire and the SJ400flux are selected in surfacing for60CrNiMo hot rolling backup roll.Because it is that higher carbon content in the hot rolling backup roll material, andthe thickness of surfacing welding layer metal thicker, large welding stress，in order toavoid the backup roll has a local shedding phenomenon in use process, and reduce theembrittlement tendency between the base metal and surfacing welding interface, in thesurfacing work layer material before used of the good toughness flux cored wireZY-YD241-S as a transition layer welding wire, and meanwhile, another one kind ofsurfacing flux cored wire ZY-YD243-S chosen as the working layer of welding wire,tomeet working requirements of hot rolling backup roll. The method of surfacingexperiment was studied on Q235A steel specimen in this paper, through organization ofthe surfacing layer metal related test and analysis, the results show that mechanicalproperties of surfacing layer metal is excellent, which can meet the performancerequirements of hot rolling backup roll of surfacing layer. According to the aboveexperimental results, the reasonable surfacing repair technology is worked out, itprovides theoretical basis for successful surfacing repair for60CrNiMo hot rollingbackup roll.While the hot rolling backup roll surfacing process in the field, because of the poorweldability of hot rolling backup roll, in order to achieve the purpose of eliminatingstress and avoid the generation of crack, the need for preheating before surfacing. Due tothe thickness of surfacing welding layer metal thicker, in order to avoid in the process ofsurfacing welding layer metal have a greater accumulated welding stress in the crackingphenomenon, must be in the thickness of surfacing welding layer metal reaches a certainrange to immediately stop surfacing, and take the middle way to remove the stress heattreatment, in order to reduce or eliminate the welding stress accumulation. To achieve the purpose of eliminate the welding stress and improve organization performance afterwelding, the need for backup roll for post-weld tempering heat treatment.After surfacing repair of hot rolling backup roll barrel by machining processing, andnondestructive testing without defects such as cracks, slag inclusion, porosity, and thebarrel hardness achieve HRC46.9.After surfacing of hot rolling backup roll by actuallyproduction line using to good effect, its strong toughness and wear resistancesignificantly better than the original hot rolling backup roll, the service life of more thandoubled, the achievement re-use requirements of hot rolling backup roll, andsignificantly reduce the cost of production, and achieved good economic and socialbenefits.