| Cement industry is an important branch of modern manufacturing industries. Cement production process mainly includes ore crushing, grinding raw material, calcination and clinker grinding. In the process of crushing and grinding, due to the high intensity abrasive wear and cyclical compressive stress, the wear-resistant layer on the squeeze roller will be gradually consumed and finally damaged by fatigue. In the end, early failure of squeeze roller happens to cause great economic losses to the enterprise. Thereby increasing the bonding strength between wear-resistant layer and base metals of steel roller core has an important effect on improving the squeeze roller life and reducing production costs.In this paper, different types of surfacing metals were prepared on 45 steel base metal by applying consumable metal electrode arc surfacing process with 5 commercially available wires and 6 kinds of homemade wires shielded by themselves. 5 commercially available wires were austenite steel, Nb-alloyed steel 1# and 2# wires, high-chromium hypoeutectic alloyed cast iron containing niobium wire and high-chromium hypereutectic alloyed cast iron wire respectively. 6 kinds of homemade wires were hypereutectoid alloyed steel wires with different contents of high-carbon ferrochromium. The bonding strength between each surfacing layer and 45 steel base metal was measured by the self-designed put-off test. Then the chemical compositions, micro-hardness distribution and microstructure characterization for each type of surfacing layer were studied. The fracture place and fractograph characteristics were observed and determined using metallographic microscope and scanning electron microscopy(SEM) as well.The experiments showed that the bonding properties between the austenite steel surfacing layer and base metal were best for the average value of bonding strength reached 314 MPa. The microstructure of the austenite steel surfacing layer was single-phase austenite dendrite. Furthermore, the austenite dendrite on the interface growing combined well on the pearlite in overheated zone bonded well with the base metal. The micro-hardness of the fusion line and the adjacent regions was all below 260 HV. The fracture location of the push-off specimens was located in coarse grain region in HAZ with cleavage morphology. The bonding properties between high-chromium hypereutectic alloyed cast iron surfacing layer and base metal were poor, which bonding strength only reached 61 MPa on average. The microstructure of the surfacing layer was combined by hexagonal and strip primary carbide mixed with eutectic and its micro-hardness was above 760 HV. The fusion zone was composed of pearlite lamella, disconnected M + A’ thin lamella and austenite lamella. But the fracture location was at the bottom of the surfacing layer with brittle fracture. The micro-hardness of high-chromium hypoeutectic alloyed cast iron surfacing layer containing niobium was above 730 HV. Its fusion zone was composed of pearlite lamella adjacent base metal and M + A’ thin lamella, at which micro-hardness was between 400 HV and 600 HV. Because its carbides and matrix structure formed better mutual support and protection, the bonding strength was above hypereutectic high-chromium alloyed cast iron surfacing layers, reaching 125 MPa with the fracture location mainly at the bottom of the surfacing layer. The microstructures of Nb-alloyed steel surfacing layer labeled 1# and 2# were all composed of M+A’ with Nb C granules dispersedly distributed on steel matrix. However, there was a small amount of austenite at the bottom of the 1# surfacing layer, and some intergranular mesh alloyed-cementite existed at the bottom of the 2# surfacing layer. Therefore, the micro-hardness of 1# surfacing layer was lower and its bonding strength to base metal was higher, reaching 227 MPa. But the bonding strength of 2# surfacing layer only reached 116 MPa. The fracture surfaces of two surfacing layers were not only in the surfacing layer bottom, but also in the HAZ.The bonding properties between the hyper-eutectoid alloy steel surfacing layers by homemade flux-cored welding wires with different contents of Cr Fe and the base metal were better. Their bonding strength were all above 130 MPa with the highest value of 225.3MPa. With the increase of high-carbon ferrochrome contents, the bonding strength decreased first and then increased. The microstructures of the surfacing layers changed from M+A’+Nb C to more and more A+Nb C+(M+A’). The martensite in the fusion region gradually decreased and the austenite there increased continuously. The six kinds of homemade wires were denoted as Cr Fe1 # ~ Cr Fe6 #.The micro-hardness of the fusion zone for the six surfacing layers showed downward trend. The micro-hardness of six kinds of surfacing layers also showed downward trend. However, because there were a lot of intensive Nb C particles in Cr Fe3# and Cr Fe4# surfacing layers, which became the major factor that affected the micro-hardness. So the micro-hardness of Cr Fe3# surfacing layer was the highest, and Cr Fe4# surfacing layer was the second. The macro and micro analysis for fracture showed that the fracture surfaces both Cr Fe1# and Cr Fe5# push-off samples were not only in the fusion zone, but also in the HAZ. While the fracture location of Cr Fe2# push-off sample was mainly in the fusion zone. The fracture location of Cr Fe3# and Cr Fe4# push-off samples was mainly at the bottom of surfacing layer, which was brittle fracture. The fracture location of Cr Fe6# push-off sample was mainly in the HAZ with typical cleavage fracture. |
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