| Zirconium and zirconium alloys are widely used in the nuclear industry due to their small thermal neutron absorption cross sections.With the adjustment of national energy policies in recent years,the use of nuclear energy has increased,and the demand for nuclear-grade zirconium materials has increased.Sponge zirconium is the basis of the zirconium industry and is an industrial primary product.However,because sponge zirconium itself does not use processing properties,it must be qualified dense zirconium material.Therefore,the smelting of sponge zirconium is very important.In order to overcome the small specifications of traditional VAR furnaces,the unnan Titanium Industry Co.,Ltd.launched the first EB production of zirconium sponge in China.Due to the high temperature of the billet after smelting,there are no corresponding protective measures in the process of skin cutting and sampling.As a result,the content of oxygen and nitrogen in the impurities of the smelting ingots exceeds the standard,resulting in unacceptable post-processing performance.At the same time,a large number of cutting chips and waste are produced in the production process,resulting in the waste of raw materials and low product yield.In order to solve the problem of excessive impurity elements and waste utilization in industrial production.A small sponge zirconium vacuum smelting experiment was conducted to explore the effects of smelting time,smelting temperature,and smelting system pressure on the product composition during the smelting process.The results show that under the existing vacuum melting conditions,the removal of nitrogen has no effect;when the smelting time is increased from 10 minutes to 30 minutes,the content of oxygen,nitrogen,and hydrogen will decrease as the smelting time increases.However,when the time exceeded 30 min,the contents of the three elements did not decrease significantly;with the decrease of the system pressure during the smelting process,the contents of oxygen,nitrogen,and hydrogen all decreased significantly.And the zirconia ingot with good surface quality was obtained under smelting conditions.It was verified that the spindle temperature influences the spindle surface quality.And obtained the best smelting parameters:about 1860 ?,smelting 30min,system pressure 0.01?0.1Pa,cooling under argon atmosphere.Aiming at some phenomena of the smelting of sponge zirconium in the laboratory and the utilization of waste materials,corresponding experiments were carried out to explore the behavior of single elements(O,N,H)under smelting conditions,and to provide theoretical support for reusing waste materials.Firstly,the difference in vapor pressure between zirconium oxide and zirconium under certain conditions is used.With the difference in the volatilization rate,oxygen in zirconium is volatilized and removed in the form of zirconium oxide,thereby achieving partial removal of oxygen and developing The experiment explored the effects of temperature,time,and system pressure on deoxygenation.The results show that at a temperature of 1750 K and a holding time of 30 min,the lower the system pressure,the better the removal of oxygen.In the existing laboratory conditions,the oxygen content in the ingot can be reduced from 0.098%to 0.057%,and 41%of the oxygen element can be removed.Secondly,the hydrogen behavior research was carried out.The experiment explored the best experimental parameters for the decomposition of zirconium to hydrogenated zirconium and zirconium hydride in the hydrogen zirconium system.The results show that:400 ?C,hydrogen atmosphere,30min is conducive to the zirconium hydrogen reaction,and the formation of a single phase of zirconium hydride;the best decomposition conditions of zirconium hydride is:1100 ?,30min,the system pressure is 0.0001?0.001Pa.According to the thermodynamic calculations and the existing laboratory and industrial EB furnace smelting conditions,the removal of nitrogen in zirconium cannot be achieved and this conclusion is verified by experiments.Simultaneously simulating the industrial production environment,the experiment was conducted to explore the effects of temperature,nitrogen content in the system,and time on zirconium uptake.The results show that high temperature(above 1200?)and high nitrogen content are favorable for zirconium nitrogen reaction.Finally,using the properties of zirconium hydride,dehydrogenation parameters are reasonably selected according to the particle size of the desired target product:600? to 1000?,30 minutes,0.0001 to 0.001 Pa. |
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