Study On Bonding Properties Of Hardfacing Materials Of Cement Roller Press

Cement is one of the basic building materials. With the demand of cement in modernsociety, the scale of cement production expands year by year. There are four main procedures toproduce cement, namely, breaking the ore, grinding and burning the raw material and grindingthe clinker. Therefore, grinding is an important procedure. The cement roller press is animportant machine for cement production. Anti-waer metals are always hardfaced on the rollersurface to improve the wear resistance of the roller surface. Due to the performance difference ofthe deposited metal and base metal, as well as the high stress woking condition of the roller, thewear layer is detached from the base metal and the roller fails. Thereby it is significant to studyon bonding properties of hardfacing materials of cement roller press.In this paper, Tungsten Inert Gas Welding (TIG) was selected to make five kinds of weldedjoints and the welding materials were high Cr high Mn-type wire, Nb-type wire and TiC-typewire, coupled with the steel base materials. The five kinds of welded joints were welded jointsmade by high Cr high Mn-type wire, by Nb-type wire, by TiC-type wire, by Nb-type wire plushigh Cr high Mn-type transition wire and by TiC-type wire plus high Cr high Mn-type transitionwire. The bonding properties of hardfacing materials were studied through microstructures,microhardness, tensile strength and fracture morphologies of different welded joints.The bonding properties of welded joints made by high Cr and high Mn-type wire are good.Their average tensile strength is416.0MPa, which is the highest among the five kinds of weldedjoints. The microstructures of the joints are austenite with low microhardness, waving between304.5HV and383.5HV. So the weld has good ductility and toughness. Carbon moves from HAZto the fusion zone and martensite generates in the fusion zone, increasing the brittleness of thewelded joints. Most of the cracks in the stretching process originate in the HAZ. Themacro-fracture is cup-cone and SEM images of fracture show that the fracture covers withdimples, indicating that the joints are ductile fracture.The bonding properties of welded joints made by Nb-type wire and by TiC-type wire arepoor. Microstructures of the two kinds of welded joints are NbC and hypoeutectic matrix, TiCand martensite plus retained austenite matrix, respectively. Their microhardness exceeds600HV，so the brittle tendency is large. The fusion zone has brittle martensite, which leads tofusion zone becoming one of the weak parts of the welded joints. There is high welding residualstress in the welded joints, resulting in low tensile strength. The average tensile strengths of thetwo kinds of welded joints are283.0MPa and236.6MPa, respectively. During the five kinds ofwelded joints the tensile strength of TiC-type welded joints is the lowest. All the welded jointsare brittle fracture and tensile fractures appear in the weld. The fractures are composed ofcleavage planes and a number of river patterns distributing at the cleavage planes.The bonding properties of welded joints made by Nb-type wire plus high Cr high Mn–type transition layer wire and by TiC-type wire plus high Cr and high Mn-type transition layer wireare good. The average tensile strengths of the two kinds of welded joints are413.2MPa and327.2MPa, respectively. Compared with welded joints made by Nb-type wire and by TiC-typewire, the tensile strengths of welded joints made by Nb-type wire plus high Cr high Mn–typetransition layer wire and by TiC-type wire plus high Cr and high Mn-type transition layer wireimprove by44%and38%, respectively. The anti-wear layer microstructures of the two weldedjoints are NbC and hypoeutectic matrix, TiC and martensite plus retained austenite matrix，respectively. The two kinds of microstructures have high hardness and excellent wear resistance.The interface of anti-wear layer and transition layer is fine austenite, which has good toughnessand strength.The microstructures of transition layer are austenite with good ductility andtoughness. When welding the anti-wear layer plastic deformation occurs in the austenite,reducing the residual stress in welded joints and improving the bonding properties. Two kinds ofwelded joints are brittle fracture. Most fractures of Nb-type wire plus high Cr high Mn wire–type transition layer wire welded joints locate at the HAZ regions, but others in the weld. Andall fractures of TiC-type wire plus high Cr high Mn–type transition layer wire welded jointslocate at the welds.High Cr and high Mn-type wire welded joints have good bonding properties and high tensilestrength, but low hardness and poor wear resistance. Nb-type wire joints and TiC-type wire jointshave high hardness and excellent wear resistance but poor bonding properties. Therefore, whenhardfacing the roller press, choosing high Cr and high Mn-type wire as transition layer, then Nb-type wire or TiC-type wire as anti-wear layer, advantages of these wires can be combinatedtogether. And the bonding properties of anti-wear layer and base metal are improved and the lifeof the roller press is extended.