Study On Combustion Characteristic Of Silicon-oxygen And Application Of Homogeneous Ceramic Welding Materials

Industrial kiln was widely used in iron, non-ferrous, glass and otherindustries due to its superior properties. However, the industrial kilns would bedamaged after a period of time because of erosion underdifferent atmosphere orslag, which increasedthe costs. Usually, the repair methods include flame repair,wipe repair, wet process spray and ceramic welding. Ceramic welding was akind of method that using oxygen and weld material to repair the damagedareas.The interface of matrix and welding would well melt and weld together due tohigh heat which released by violent oxidation reaction.Ceramic weld repairsavoided the fluctuations in temperature of furnace bodycaused by process ofcooling and reheating, which was quite different from thosetraditional repairmethodsdemanding blowout furnaces. The industrial kilns could recover theproduction in a short time and save the cost at the same time. The expansioncoefficient was diverse in different materials, therefore, in order to maintain thestability of welding complement, the composition of ceramic welding materialsshould be similar with the parent as much as possible. In the process of weldingrepair, oxygen flow rate, welding materials are the major factors affecting the effects of ceramic welding repair. In these factors, oxygen flow can not onlyaffect thetransport of welding materials, but also can affect the efficiency ofcombustion. The combustion temperature of weld zonewould be reducedwithout preheating the oxygen. Nowadays, there still existingsome problemssuch as low combustion efficiency of silicon powder, low ignition efficiency andloose welding body, etc.Using silicon powder, aluminum powder, fused quartz, corundum as rawmaterials, ceramic welding repair was taken in the lab. The phase andmicrostructure of weld zone were characterized by XRD and SEM and thetemperature of reaction was taken measure by infrared thermometer.The results are as follows.(1) The mullite ceramic welding materials was developed by using siliconpowder, corundum and aluminumpowder. Mullite crystal nucleus were found inwelding complement analysed by X-ray diffraction.(2) Both of the combustion of silicon powder and delivery capacity ofwelding repair materials reach optimum when oxygen flow is0.4m3/h, at whichthe utilization rate of oxygen reached30%. When25wt%Si is used in theexperiment, the welding repair works best and the temperature of reaction is2737K. Moreover, welding repair materials are easier to burn when it isconsisted of particles with different sizes.(3) The finer the particle is, the higher the combustion efficiency of thesilicon powder is. Three kinds of additives wereused with same content in the experiment, i.e. Fe2O3, KClO3and NH4ClO3as combustion additivies. Fe2O3isthe best additive as for the combustion-improvercharacter and the combustionefficiency of silicon powder improved.