Study On The Surfacing Technique Of Extrusion Roller For Roller Press Machine

In recent years, the cement industry in China is developing rapidly, the cement enterprise production scale is widening and the use of enterprise to production equipments is also increasing. The roller press machine is the key equipment in cement production grinding, being mainly used for extrusion raw and clinker. The extrusion roller in the roller press machine is applied the huge pressure in work, will be affected by material wear and can be destroyed seriously for long-term use. Because of its cost is higher and replacing time is longer, this will give cement production enterprise to bring the economic loss. Through the surfacing repairing of extrusion roller, the damaged extrusion roller can be used again, which reduces the number of replacement of extrusion roller, improves the utilization rate of the machine itself, saves the enterprise costs to buy new equipment cost, reduces the production cost, and creats the economic benefits for the enterprise.In this paper, the gas shielded welding method was adopted for the surfacing welding, using four kinds of welding wires (Arcfcw-1003, KSW-615, KSW-626, KSW-645). The surfacing layers are divided into bottom layer,transition layer and wear-resisting layers including high chromium cast iron surfacing layer and TiC surfacing layer. The microstructures of surfacing layer and heat affected zone were studied first. The bottom layer contains ferrite and pearlite, its average hardness is 16.3 HRC, and the bottom layer has good plasticity and toughness. The transition layer consists of austenite with high Cr and Mn contents, its average hardness is 27 HRC, and the transition layer has the very good abrasion resistance and impact resistance. The high chromium cast iron surfacing layer contains hypoeutectic structure and hypereutectic structures with high hardness carbide (M7_C3), its average hardness is 53.7 HRC, and the surfacing layer has the very good abrasion resistance. TiC surfacing layer contains carbide (TiC) and austenite, high hardness carbide being embedded in the good toughness austenitic matrix, its average hardness is 51.7 HRC, and the surfacing layer not only has good abrasion resistance, but also has the very good crack-resistance. The heat affected zone consists of overheated region, fine grained region and coarse grained region. The overheated region contains widmanstatten structure and the grain becomes very coarse. The recrystallization occurs in the fine grained region and its mechanical performance is very good. The recrystallization occurs partly in the coarse grained region, it has relatively bulky ferrite and tiny pearlite with different grain sizes, and the mechanical performance of this region is poor.The effects of different welding parameters on the microstructures, hardness, dilution ratio and crack of surfacing layers were also studied in this paper. The effect of different welding parameters on microstructures of high chromium cast iron surfacing layer is mainly dendrite shape changes. When welding current increases or welding speed reduces, the dendrite becomes bulky, the distance of main dendrite reduces, the eutectic structure is very little,and the hardness of surfacing layer lowers. The effect of different welding parameters on microstructures of TiC surfacing layer is mainly the change of number and size of carbide (TiC). The number of carbide increase, the size of carbide become big, and the hardness of surfacing increases. When welding current increases, the widmanstatten structure in HAZ is very coarse due to serious overheat. When welding speed decreases, the microstructures changes from ferrite to widmanstatten, the ferrite is little, and the structure is not very rough.The changes of dilution ratio of surfacing layers with four wires are consistent. When welding current increases or welding speed reduces, the weld depth and weld width increase, weld reinforcement also incresases, and the dilution ratio of surfacing layer become large.The effect of welding parameters on the crack of high chromium cast iron surfacing layer is great. When welding current increases, the crack length decrease, quantity gradually decrease, and the crack rate has decreased trend. When welding speed increases, the number of crack increase sharply, crack length has a big change, and the crack rate also increases significantly.Based on the effect of different welding parameters on the microstructure, hardness, dilution ratio and crack of surfacing layer, the welding parameters were determined, the welding current of 200A and welding speed of 280mm/min for the bottem layer; the welding current of 300A and welding speed of 280mm/min for the transition layer; the welding current of 290A and welding speed of 360mm/min for the high chromium cast iron surfacing layer; the welding current of 340A and welding speed of 360mm/min for the TiC surfacing layer.