| Nickel slag is a kind of slag in Fe O-SiO2 system.Presently,the stock of nickel slag has reached 10 million tons owing to the shortage of reasonable ways to dispose of,which not only occupies lot of land resources but also causes pollution to the environment.How to realize the recycling of nickel slag with high added value has became an urgent problem to be solved.Glass-ceramics is a kind of polycrystalline solid material which contains a large number of microcrystalline and glass phase.It's main properties are influenced by the type of crystal phase,grain size and quantity,the nature and quantity of the residual glass phase,that makes the glass-ceramics designable.Using the nickel slag to prepare glass-ceramics on one hand achieves the high value-added recycling of nickel slag,and protects the environment on the other.In this paper,the mix proportion of the basic glass is designed and adjusted according to the phase diagrams of CaO-MgO-Al2O3-SiO2 system.The nickel slag from Jinchuan company is used as the main material to prepare glass-ceramics with augite as the principal crystalline phase by melting method.The effects of heat treatment and nucleating agent on the performance of glass-ceramics are investigated by means of mechanical properties test,thermal expansion coefficient test,XRD,DSC,SEM.The crystallization mechanism of glass-ceramics is also studied by dynamics simulation.Finally the feasibility of glass-ceramics composite pipe being used in practical application is studied by simulation of thermal stress distribution with ANSYS.The results show that:(1)By using melting method the nickel slag glass-ceramics in CMAS system whose main materials were nickel slag is produced,and the multipurpose utilization rate of slag reached 65%.The mix proportion of basic glass contains nickel slag 32.5%?fly ash 32.5%?silica sand 9%?CaO 9%?CaF2 9%?Li2CO3 5%.The iron of nickel slag is reduced with adding graphite powder 3%(The reduction of iron is 76.23%).(2)The best heat treatment technics is 768 ? for 1.5h.The holding time and temperature has a significant effect on the microhardness and bending strengthrespectively.(3)The optimum nucleating agent is Cr2O3,the optimum dosage is 1.5% for nickel slag glass-ceramics.The microhardness and bending strength of nickel slag glass-ceramics adding Cr2O3 1.5% is 782.1HV and 97.5MPa respectively which enhances 29% and 93% compared to the nickel slag glass-ceramics without nucleating agent.The effect of nucleating agent on the microhardness of nickel slag glass-ceramics is greater than that of bending strength.The crystallization activation energy of nickel slag glass-ceramics adding Cr2O3 1.5% is 244.5KJ×mol-1,meanwhile the ??? is 2.74.Compred with other slag glass-ceramics the value of crystallization activation energy is lower.That shows the nickel slag glass-ceramics is crystallized by surface with a better ability of crystallization.The main crystal phase is augite and diopside with tiny uniform grain and compact structure.(4)The simulation analysis of ANSYS shows that the nickel slag glass-ceramics adding 1.5% Cr2O3 is the best choice to make glass-ceramics composite pipe.The structure of glass-ceramics composite pipe is stable under a constant temperature of200?.And if the temperature of cast iron is 23?,the structure of composite pipe keeps stable when the inner wall temperature of glass-ceramics is 113?,but breaks when the temperature reaches 143?.So,the temperature difference between inside and outside of composite pipe is not allowed to above 120?,when the outer wall is at room temperature. |
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