【作者】 孙涛；

【导师】 刘建雄； 李松；

【作者基本信息】 昆明理工大学 ， 材料加工工程， 2009， 硕士

【摘要】 氮化钒是冶金工业中一种重要的钒添加剂,通过钒氮微合金化技术能显著提高钢的强度和降低钢的成本。2001年12月攀枝花钢铁公司申请的“氮化钒的生产方法”专利开创了国内氮化钒的产业化进程。攀钢集团钢铁研究院在2005年发明了VT包芯线(一种粉芯为按一定比例混合的氮化钒粉末和钛铁粉末而外层是钢皮包裹制成的包芯线),该包芯线用于攀钢钢水冶炼时的成分调整。但该包芯线自投产以来一直存在芯粉密度不均匀等问题,其主要原因是氮化钒原料经破碎后产生大量细粉(经统计粒径小于0.6mm的细粉占到总重量的40%-50%),在通过漏斗对钢带进行加料时,细粉在漏斗内部产生架桥,阻碍其它粉料正常均匀地下流,使粉料在钢带长度内分布不均匀。为了改善粉末的流动性和提高细粉的利用率,本文对氮化钒粉末制定了分级—造粒—干燥的工艺,即将破碎后粒径小于1 mm的细粉通过筛分选出,用圆盘造粒机进行造粒,最后进行干燥。并用红外线快速水分测定仪测定生球的含水率；用体视显微镜观察干球外观形貌；用扫描电子显微镜观察干球横截面微观结构；用自制装置测量干球搅拌强度和抗压强度,自由降落试验测量干球落下强度。经过对氮化钒造粒正交试验结果和干燥试验结果分析表明：低温淀粉粘合剂可以做为氮化钒粉末造粒时的粘合剂；通过试验确定了氮化钒造粒—干燥最佳工艺,即在粒径范围为0.2～0.6mm的氮化钒粉末中加入1.0%的淀粉粘合剂,在35r/min的圆盘转速下进行造粒,然后在110℃下干燥1h,可以得到较为理想成粒率和较高强度的干球；由体视显微镜图可知,不同造粒条件组合得到的干球外观形貌差异比较大；大粒径的氮化钒球团长大是介于成层机理和粘结机理之间,小粒径的氮化钒球团长大主要以粘结机理长大。通过干燥试验发现：生球初含水率越小,干燥总速度越快；原料粒度越细、原料中粘合剂比例越大,干燥总速度越慢；干燥速度曲线受干燥温度大小影响。通过试验得出：氮化钒生球干燥速度曲线主要有单峰型和双峰型两种类型。在单峰型生球干燥曲线中,生球的干燥过程由增速期和减速期两阶段组成,而且干燥速度由增快到减慢是个渐变过程。在双峰型生球干燥曲线中,生球的干燥过程是由第一增速期,第一减速期,第二增速期和第二减速期四个阶段构成。更多还原

【Abstract】 Vanadium nitride is an important vanadium alloy additive in metallurgical industry,V-N microalloying technology can increase the steel intensity significantly and reduce the cost of steel.A patent application for the production method of vanadium nitride had been filed by Panzhihua Iron and Steel Corporation in December,2001 and it initiated the industrialized process of vanadium nitride in China.VT cored wire(a kind of cored wire in which vanadium nitride powder and ferrotitanium powder are mixed in certain proportion and the powder is packed by steel strip) was invited by Panzhihua Iron and Steel Research Institute in 2005 and it was used to adjust the chemical element composition when melting steel by wire-feeding method.While there has been existing a problem of uneven powder core density since VT cored wire was commissioned,the main reason is that the fine vanadium nitride powders(the proportion of fine powders which particle size smaller than 0.6mm reach 40% to 50%)produced after crushing bridge in funnel by which to feed to steel strip, what hinders other powders downflowing at normal speed, so the phenomenon occurs.In order to improve the powder flowability and the fine powder utilization,the classification-granulation-drying technological process is used. In this dissertation, the fine powders after crushing which particle size smaller than lmm are sorted by sieve,then granulated by pan granulator and dried by drier.The green pellets water content is measured by infrared rapid moisture instrument;the surface morphologies of dry pellets are studied by stereomicroscope;the microstructures of dry pellets cross-section are analysed with scanning electron microscope(SEM);the dry pellets compressive intensity and dry pellets stirring intensity are measured by self-made equipments;the dry pellets drop number is determined by free drop experiments.The results of vanadium nitride granulation orthogonal experiments and drying experiments show that,the low-temperature starch adhesive is the proper binder for vanadium nitride powder granulation;the optimum process of vanadium nitride granulation-drying operation for the dry pellets with ideal granulating rate and higher strength are investigated as follows:the disc rotation speed is 35r/min,the binder addition amount is 1.0%,the material particle size distribution is 0.2～0.6mm,the drying temperature is 110℃,the drying time is 1h; the surface morphologies of dry pellets is different under different granulation conditional combinations through the stereomicroscope graphs;the growth mechanisms of large particle vanadium nitride pellets lie between stratification and coalescence, the small particle pellets grow up by the way of coalescence.Based on the results of drying experiments, it’s found that,the smaller the green pellets initial moisture content is, the faster the total drying speed is;the finer the materials particle and the larger the binder ratio in material is, the slower the total drying speed is; the drying rate curves are influenced with the drying temperature.There are two types of vanadium nitride pellets drying rate curves:one-peak type and two-peak type.The green pellets drying process of one-peak type is composed of increasing speed stage and deceleration stage and the process changes gradually.The green pellets drying process of two-peak type is composed of the fist increasing speed stage,the first deceleration stage,the second increasing speed stage and the second deceleration stage.更多还原