【作者】 张金柱；

【导师】 徐楚韶；

【作者基本信息】 重庆大学 ， 冶金工程， 2004， 博士

【摘要】 以丰富的锰矿资源为依托,自五十年代开始,贵州已经在遵义建成中国最大的锰系铁合金生产基地。遵义铁合金有限责任公司已成为全国唯一拥有采矿、选矿、烧结和冶炼一条龙生产工艺的大型铁合金企业,也是我国冶金行业的重点铁合金企业。主要产品有高碳锰铁、中低碳锰铁、金属锰、锰硅合金、硅铁、铬铁等。年设备生产能力22万吨,其中年产中低碳锰铁2.4~ 2.5万吨,年产金属锰0.45~0.50万吨。对锰制品破碎时产生的粒度小于10 mm的中低碳锰铁和金属锰碎粒和粉末进行综合利用和产品升级,研究开发氮化锰铁和氮化锰制品,既有利于满足钢铁生产对锰氮制品的需求,又有利于进一步将资源优势转化为经济优势。同时,通过对中低碳锰铁和金属锰在不同条件下渗氮过程的研究,可进一步掌握锰氮之间的交互作用,以及氮在锰中的扩散行为和主要影响因素。在对国内外锰铁氮化及Mn-N系研究状况进行分析的基础上,应用真空电阻炉高温渗氮、X射线衍射、惰气熔融法氧氮分析等实验测试方法,实验研究了粒度、温度、时间等因素对锰铁氮化的影响。通过理论分析和热力学计算,探讨了渗氮过程的相关规律。在合理假定的基础上,提出了金属锰氮化的数学模型。主要获得如下结论。在以工业用氮气为主的渗氮气氛中,中低碳锰铁和金属锰在1 123~ 1 223 K范围内高温加热72小时,可同时发生氧化和氮化,生成氧化物MnO和氮化物Mn4N。渗氮试样的粒度愈小,试样的增重率愈高。此外,随渗氮温度的增高,试样的增重率提高,含氧量显著增高。工业用气态氮的含氧量较高,氮化的同时不可避免地要发生锰的氧化。在以工业用氮气为主的渗氮气氛中配加20%的氨气,也未能有效消除或抑制锰的氧化。为此,使用工业用氮气作为渗氮气体,应在氮气进入真空渗氮炉之前采用合适的脱氧方法将其脱除。通过对锰铁在渗氮过程中可能发生的化学反应进行热力学分析表明,生成锰氧化物的平衡氧分压极低,即使采用高纯氮气作为渗氮气体,也不可能避免锰氧化物在渗氮过程中生成,如果体系的残氧量较高,低价锰氧化物可进一步氧化为高价锰氧化物。热力学分析表明,在渗氮气体中添加一定量的氢气,可以有效避免金属锰和铁及其氮化物在渗氮过程中发生氧化,但在845 K以下的升温过程中金属锰仍然可以发生氧化,在729 K以下的降温过程中氮化物Mn4N同样可以发生氧化。应用规则溶液模型和有关热力学数据分别推导了锰氮化合物???-Mn4N和<WP=6>???-Mn4N的标准生成自由能表达式,并对合理性进行了简要分析。在以高纯氮气为主,配加少量高纯氢气的渗氮气氛中,通过对不同粒度的JMn97和DJMn-A两种金属锰试样分别在不同的温度和时间范围内进行高温渗氮研究,可得到如下结论。渗氮试样的粒度愈小,渗氮速度愈快,试样的增重率愈高。试样的增重率与时间的二分之一次方近似呈直线关系。粒度为0.37 mm的金属锰JMn97在1 173 K时高温加热6小时,就可使金属锰全部发生氮化,生成氮化物Mn4N和少量的Mn6N2.58。渗氮时间愈长,生成高价氮化物Mn6N2.58的相量愈多。粒度为0.33 mm的金属锰DJMn-A在1 173 K高温加热4小时,金属锰全部发生氮化,生成氮化物Mn4N和微量的Mn6N2.58。在温度较低的1 163 K高温加热4小时,金属锰全部生成氮化物Mn4N。试样的粒度较大和高温加热时间比较短的情况下,渗氮试样中均有未发生氮化的金属锰残余。在同样的渗氮条件下,随粒度的增大或加热时间的缩短,金属锰的残余量相应增多。检测分析表明渗氮试样中均有一定的氧含量,渗氮试样的含氧量愈低,单位时间的增氮率愈高。氧含量是影响金属锰渗氮的重要因素之一。基于原子在晶体中的扩散机理,借鉴氮原子在金属硅粉末中的扩散模型和内扩散控制的未反应核数理模型,通过合理假定,建立了氮在金属锰中的扩散模型。在上述渗氮条件下,各试样的渗氮结果均可较好地用扩散模型反映其相关规律。应用扩散模型导出了不同温度时氮原子的有效扩散系数,建立了有效扩散系数与温度间的关系,同时也导出了氮原子的扩散激活能。更多还原

【Abstract】 Based on rich manganese resource, Zunyi Ferroalloy Company Limited in Guizhou is the most enormous manganese ferroalloy base in our country, and also one of the key ferroalloy corporations in metallurgy industry of China. It is the only one that has been made mining, dressing, sintering, smelting and refining a coordinated process by 50 years building. The equipment capacity of Zunyi Ferroalloy Company Limited is about 220 kilo-ton yearly, and the main products produced by that are manganese-silicon ferroalloy, silicon ferroalloy, chromium ferroalloy, high, medium and low carbon manganese ferroalloys (about 24~25 kilo-ton yearly), metal manganese (about 4.5~5.0 kilo-ton yearly), and so on. There is a considerable amount of powder (less than 10 mm) as a result of manganese ferroalloy breaking to be exploited. Nitriding the powder may be the best one of multipurpose utilization for both meeting the requirements of steelmaking for the nitrided manganese ferroalloy and making the local rich resource into economy prosperity. Meanwhile, it is important to kwon the interaction between nitrogen and manganese, the nitrogen diffusion in solid manganese, and other effect factors by the experimental study of the metal manganese and low and medium carbon manganese ferroalloy nitrided at various conditions. Based on the researches in domestic and aboard on both the manganese ferroalloy nitriding and manganese- nitrogen system, the influence of time, temperature, and grain size on the solid metal manganese nitriding was studied by means of vacuum resistance furnace, X ray diffraction technique and LECO TC-436 Oxygen/Nitrogen Determinator. Several relationships on nitriding have been discussed by means of thermodynamics computation. Based on reasonable assumption, a mathematic model was set up for metal manganese nitriding. The conclusions are shown as follows:(1) Metal manganese and low and medium carbon manganese ferroalloy can be both nitrided and oxidized in industrial scale nitrogen atmosphere at 1 123~1 223 K for 72 hrs with the product Mn4N and MnO respectively. The finer the powder size is, the more amount nitrogen pick-ups. Moreover, with the nitriding temperature rising, the sample pick-ups increases correspondingly, and so the oxygen content.(2) It is unavoidable that manganese will be oxidized in the nitriding atmosphere because there is considerable oxygen content in the industrial scale nitrogen. Even added as much as 20% ammonia in the nitrogen, the manganese can’t be prevented from <WP=8>oxidized effectively. Therefore, it is necessary that the nitrogen as nitriding atmosphere be deoxidized before entering the vacuum resistance furnace by a suitable processing.(3) Based on the thermodynamic computation for the chemical reactions during manganese ferroalloy nitrided, it is shown that the oxygen pressure needed for manganese oxidized is especially minute, therefore, it is unavoidable that manganese will be oxidized in the nitriding atmosphere furnished even by ultrahigh purified nitrogen. Moreover, the low valence manganese oxide can be further turn into high valence oxide, if the remaining oxygen in the nitriding system is enough much. (4) Besides the temperature elevating below 845 K for Mn and lowering from 729 K for Mn4N, it is known that the hydrogen added into nitriding atmosphere can effectively inhibit the manganese, iron, and the nitrides oxidized by thermodynamics analysis. (5) The standard Gibbs energy expressions of formation for both ???-Mn4N and ??-Mn4N are deduced respectively based on the relative thermodynamic data and the regular solution model. Moreover, a precise discuss has made on the equations for reliability and reasonability. (6) The both JMn97 and DJMn-A metal manganese samples with different grain size are nitrided in ultrahigh purified nitrogen at various temperature and time in which a small amount ultrahigh purified hydrogen is added. The conclusions are shown as follows:The finer the powder size is, the faster the nitriding speed, the more amount nitrogen pick-ups. More更多还原