【作者】 张鲜；

【导师】 苏旭平；

【作者基本信息】 湘潭大学 ， 材料学， 2009， 硕士

【摘要】 热浸镀锌是一种应用广泛的提高钢制件耐腐蚀性能的工艺。采用改良森吉米尔法的连续热镀锌机组在生产中时常出现锌层附着性差、严重时产生脱锌现象。大多数情况下这与连续退火炉中无氧化加热(NOF)工艺不佳有关。NOF段内气氛波动异常以及带钢出NOF炉段温度设定不合理都会影响带钢表面状态,引起带钢表面析碳或氧化,带钢表面这些残留物会造成后续镀锌过程中镀层粘附性不良。本工作通过对涟钢镀锌生产线退火炉NOF段煤气成分波动的分析,探讨了带钢表面析碳的成因,利用Factsage热化学软件的平衡模块,建立了带钢经NOF炉表面碳沉积机理的理论模型。得出了过剩空气系数、带钢温度以及带钢表面碳沉积的关系曲线,且定量地分析了焦炉煤气成分波动对碳初始析出温度的影响。模拟结果能辅助调节过剩空气系数从而控制带钢表面状态及出NOF炉温度,对合理制定工艺具有一定的理论指导意义。合金元素是影响镀层质量的至关重要的因素。通过热力学计算来研究锌合金体系和镀层生长规律,从而对生产过程进行预测和控制,这对于提高镀锌产品质量、优化镀锌工艺参数和促进镀锌工业的发展有着重要的意义。而在实际热镀锌过程中,基体、镀层以及锌液中各组元之间的反应相当激烈和复杂,因而不能简单地利用单个相图来分析、解决实际生产中所遇到的问题,结合实际生产工艺,从多元体系热力学的角度研究分析镀锌过程中镀层最佳组织的形成具有非常重要的作用。本工作收集、整理并验证了许多同热镀锌生产有关的锌合金体系热力学评估数据,并以Thermo-Calc软件数据库的形式存储了起来,初步建立了一个专门为镀锌生产服务的锌合金热力学数据库。共整理、归纳和验证了Zn-Sb、Zn-Ca、Zn-Li、Zn-Ce、Zn-Pr、Zn-Nd、Zn-Bi、Zn-Zr、Zn-Fe、Zn-Cr、Zn-Al、Zn-Sn、Zn-In、Zn-Cd、Zn-Mg二元合金体系和Zn-Al-Y、Zn-Sn-Ti、Zn-Fe-Al、Zn-Ni-Cu、Zn-Mn-Cu、Zn-Al-Pb、Zn-Fe-Si、Zn-Fe-Ni三元合金体系的热力学评估数据。并利用Therm-Calc对Sr-Si体系进行了热力学评估,得到了一套自洽的热力学模型参数,各种计算值与实验值都吻合较好。更多还原

【Abstract】 Hot-Dip galvanizing is widely used for improving atmospheric corrosion resistant of steel parts. Imperfect adhesion of coating and Dezincification of strips always occur in modified Sendzimir-type hot-process continuous galvanizing line. In most cases this phenomenon is the result of the changes of technical parameter of nonoxidizing furnace. The fluctuation of nonoxidizing furnace (NOF) ambient atmosphere and the unreasonable tapping temperature will all affect the surface condition of the strip, causing carbon precipitation on the surface of strip or excessive oxidation. These carbon grain and oxidized film could result in imperfect adhesion.By analyzing the fluctuation of Coke-Oven Gas (COG) composition in annealing furnace of continuous galvanizing production line (CGL) which belonged to Liansteel, The mechanism of carbon precipitation on the surface of strip was researched, a mathematical calculation for carbon precipitation on the surface of strip was modeled using Factsage Thermochemical Software and a complete curve of relation among air ratio, strip temperature and carbon precipitation area was derived. This model also quantificationally analyzed the influence of the fluctuation of coke oven gas (COG) composition on the temperature when carbon first precipitates. This can assist in adjust air ratio to control the strip surface condition and determine the appropriate strip tapping temperature. Those conclusions afford benefit for appropriate technology selection.Alloy elements play a key role for controlling the coating quality. The study of zinc alloy systems and the growth law of coating from thermodynamic calculation can help us to predict and control the product process. There’s very important meaning for controlling the quality of galvanizing products, optimizing the galvanizing process parameters and facilitating the development of galvanizing industry. But during the hot-dip galvanizing process, the reactions among steel base, coating and alloy elements in the zinc bath are intense and complicated, it is impossible to analyze and solve the problems in actual production just using Microstructure Transformation and Phase Relations of single phase diagram. Therefore, it is important to analyze the formation of coating from the point of multiply system thermodynamic combining with the actual production.A great deal of thermodynamic data concerning zinc-based alloy systems were collected, systematized, validated and stored after the form of Thermo-Calc database. So far, by using Thermo-Calc software, a thermodynamic database of zinc-based alloys for galvanizing production was primarily developed. 15 binary systems:Zn-Sb, Zn-Ca, Zn-Li, Zn-Ce, Zn-Pr, Zn-Nd, Zn-Bi, Zn-Zr, Zn-Fe, Zn-Cr, Zn-Al, Zn-Sn, Zn-In, Zn-Cd, Zn-Mg and 8 ternary systems: Zn-Al-Y, Zn-Sn-Ti, Zn-Fe-Al, Zn-Ni-Cu, Zn-Mn-Cu, Zn-Al-Pb, Zn-Fe-Si, Zn-Fe-Ni were included. Moreover,the Sr-Si system was optimized by Thermo-Calc software, A set of self-consistent thermodynamic model parameters was derived. Preferable agreement was obtained between the calculation and experimental results.更多还原