基于高硅镍铁合金生产300系列不锈钢母液的基础研究

The optimal use of low grade Nickel oxide ore (Nickel laterite ore) and chromium fine ore is one of the effective ways to solve the problem of resources lack of Ni and Cr for the stainless steel production in China. In current study, the short process for producing 300 series stainless steel through Ni-Si-Fe alloy as basement will be taken into consideration. The process could be expressed briefly as: Nickel laterite ore is smelted in a submerged arc furnace (SAF) into Ni-Si-Fe alloy with high silicon and low carbon content, which is an intermediate product. Desilicication and chromium-increase reaction will take place between the intermediate melt and the chrome ore-lime melt through SAF-Shaking ladle process; hence the mother liquor of Ni and Cr- stainless steel could be produced. This will be connected to Argon oxygen decarburization (AOD) and vacuum oxygen decarburization (VOD) processes, refining process of 300 series stainless steel then will be finished..Current study will focus on the development of new process, with in it, the thermodynamics properties of Ni-Si-Fe alloy melt and the smelting silicothermic reduction kinetics of chrome ore will be investigated. The process theory and technical parameters for decarburization and dephosphorization of Ni-Si-Fe alloy melt will be provided. The principle for slag formation from chrome ore and lime reaction and its effect to the smelting reduction rate for chrome ore will be investigated. Macrokinetics model of desilicication and chromium-increase for Ni-Si-Fe alloy melt will be set up. For special conditions of shaking ladle, which is the key process equipment, the effect of alloy melt and the change of interface characteristics of slag to 'emulsify' and 'phase-splitting' behaviors will be investigated, at the same time, the 'Scale-up Theory' for shaking ladle reactor will be completed. The process theory estimation for producing 300 series stainless mother liquior through electrosilicothermic process needs to be taken into consideration as well in this study.

低品位氧化镍矿（俗称红土矿）和铬粉矿的合理利用是解决我国不锈钢产业镍、铬资源缺乏的重要出路之一。本项目提出以镍硅铁合金为主原料的300系列不锈钢短流程冶炼工艺技术思路：红土矿用矿热炉炼制成高硅低碳镍硅铁合金中间产品，采用电炉-摇包工艺使其与铬矿-石灰熔体发生脱硅增铬反应，生产出镍、铬不锈钢母液，继而与AOD、VOD工艺衔接，完成300系列不锈钢钢液冶炼过程。.围绕新工艺开发，重点研究镍硅铁合金熔体热力学性质与铬矿熔融硅热还原动力学行为。提供镍硅铁合金熔体降碳和沉淀脱磷的工艺理论和技术参数；揭示铬矿与石灰成渣反应机理及其对铬矿熔融还原速率的影响；建立镍硅铁合金熔体脱硅增铬宏观动力学模型。针对关键工艺设备- - 摇包的特殊工况条件，研究合金熔体和炉渣界面性质变化过程对"乳化"和"分相"行为的影响规律，完善摇包冶金反应器"相似放大"理论。完成电硅热法生产300系列不锈钢母液的工艺理论计算。

本课题提出了以红土镍矿、铬精矿粉为主原料的电硅热法生产300系列不锈钢的短流程冶炼工艺技术思路，以解决红土镍矿与铬精矿粉的合理利用问题。红土镍矿用矿热炉炼制成高硅低碳的高硅镍铁合金，必要时采用还原脱磷法对高硅镍铁合金进行脱磷，然后采用电炉—摇包法工艺将低磷高硅镍铁合金与铬粉矿—石灰熔体进行反应，完成脱硅、增铬的冶炼，得到镍铬不锈钢母液，继而经成分调整后与AOD、VOD工艺衔接，完成300系列不锈钢钢液冶炼过程。相较于传统的二步法冶炼工艺，新工艺的生产原料成本降低了6.3%~7.2%，综合能耗减少了7.1%左右，CO2排放降低了6.2%左右。. 测定了不同硅含量的Fe-Ni-Si合金熔体中碳的饱和溶解度。结合还原脱磷工艺要求，确定了硅含量大于20%、碳含量小于0.5%的高硅镍铁合金中间产品，该合金可降低不锈钢液后续AOD、VOD的脱碳负荷。高硅镍铁合金中间产品可采用还原脱磷率工艺能得到磷含量小于0.03%的产品，由此实现了不锈钢钢液脱磷工序的提前，避免钢液氧化脱磷时的铬损失。. 采用CaO-CaF2 渣对Fe-Ni-Si合金熔体进行还原脱磷率，脱磷产物随Fe-Ni-Si合金中硅含量的不同而发生变化，当合金中的硅含量为10.5 %, 31.48 %, 34.71 % 和 43.15 %时，脱磷产物分别为Ca2P2, Ca10+xSi12-2xP16, Ca4SiP4和Ca10+xSi12-2xP16, 以及Ca4SiP4。相应的还原脱磷率亦随Fe-Ni-Si合金熔体中硅含量的增加而增加。. 针对电炉—摇包法工艺中的关键设备，研究了摇包内不同转速下两相液体的流型，阐述了界面平摆流型、界面荷叶状流型和界面卷混流型三种流型的发生和转化。渣金两相乳化后的分相，可通过摇包的低速摇动，促进渣相中金属液滴的聚集长大加快，比静置摇包更快实现“相分离”过程。由量纲分析方法，得出两相发生卷混的临界转速的经验公式。该式适用于摇包操作参数的放大。实验确认相际传质引起的马拉格尼效应在一定程度上可以加快液液两相流体混合。

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