配碳还原氧化铁皮制备多孔不锈钢的机理研究

Iron scale is a kind of solid waste produced during the production and rolling process of continuous casting slab or ingots, which accounts for about 1.5% of the steel production in the year, and the quantity is considerable. At present, iron scale is mainly used in the preparation of steel melting agent, reducing iron powder, iron red pigment, and so on, which the recycling levels are low. Porous stainless steel has low density, large specific surface area and high strength, and is waterproof and breathable, which is widely used as structural materials and functional materials in aerospace, petrochemical, medical, environmental protection and other fields. In order to give full play to the advantages of high total iron content, low content of impurities, easy purification and recycle and so on, iron scale should be researched for the preparation of high value-added products at low cast. Therefore, it is necessary to study the mechanism of preparation of porous stainless steel by reducing iron scale with carbon. In the project, iron scale will be taken as raw materials, in which a variety of alloy elements and carbon will be added during the porous stainless steel sintering process in N2 atmosphere and under high temperature. Thus, the thermodynamic and kinetic conditions of iron scale reduced completely with decarburization and chromium yield at the same time will be revealed, while the alloying mechanism of porous stainless steel and the interaction between alloying and enhanced-nitrogen strengthened in N2 atmosphere will be proven. Meanwhile, the data support and theoretical guidance will be provided to the efficient recycle of iron scale during the sintering process of porous stainless steel.

氧化铁皮是连铸坯或钢锭生产及其轧制过程中产生的固体废弃物，其产生量占当年钢产量的1.5%左右，数量相当可观。目前，氧化铁皮主要用于生产炼钢化渣剂、还原铁粉、铁红颜料等，回收再利用水平较低。多孔不锈钢具有密度低、比表面积大、比强度高、透水、透气等特性，作为结构材料或功能材料被广泛应用于航空航天、石油化工、医疗、环保等多种领域。为了充分发挥氧化铁皮全铁含量高、杂质含量低、便于提纯等优点，回收利用氧化铁皮生产高附加值的铁基金属制品，同时降低多孔不锈钢的生产成本，本课题拟以氧化铁皮为含铁原料，添加多种合金元素及烧结助剂，在配碳还原的基础上，通过N2气氛下高温烧结制备多孔不锈钢的过程展开研究，以揭示氧化铁皮全部被碳质材料还原同时去碳保铬的热力学和动力学条件，探明烧结过程多孔不锈钢金属元素的合金化机理及其与N2气氛增氮强化的交互作用，从而为实现高效回收利用氧化铁皮生产多孔不锈钢提供数据支持和理论指导。

氧化铁皮是钢铁生产流程重要的副产品，铁品位高、杂质少、产量大，但目前主要作为烧结、还原铁原料，利用水平低，开发高附加值利用途径，是钢铁行业高质量发展的需求。项目以氧化铁皮为原料，采用真空碳还原制备多孔316不锈钢，研究了还原及渗氮过程热力学和动力学机理，以及制备参数对不锈钢碳含量、孔隙度、夹杂物和综合性能的影响。.氧化铁皮配碳真空还原制备不锈钢时，所配入的铬合金先与铁氧化物反应，生成FeCr2O4，之后转变为Cr23C6，真空下Cr23C6中碳能够参与还原，最后形成金属Cr，进入奥氏体中。真空中，600~900℃温度还原3h内，还原速率受碳的气化反应限制；大于3h时，速率受新相形核的限制。在压力为10-4atm，1200℃下保温180min还原条件下，能够获得碳含量0.025%的成分合格的316不锈钢。所制备的多孔不锈钢晶粒尺寸小于10μm，存在高Mo的σ析出相和贫铬区。.通过调整造孔剂用量，可将多孔不锈钢的孔隙率控制在42.07%和80.04%之间，而比表面积从0.38 m2/g增加至0.91 m2/g。多孔不锈钢显微硬度随孔隙率增加逐渐降低，孔隙率为42.07%时，硬度为90.34HV0.1，强度为381.15MPa。.随着渗氮温度和渗氮压力升高，多孔316不锈钢的[N]含量逐渐升高；0.08 MPa条件下，800℃以上N元素以固溶态氮和CrN形式存在，800℃以下N元素以固溶态氮形式存在。850℃、0.08MPa渗氮30min，[N]含量达到1.15%，此时显微硬度为176.35 HV。.在多孔不锈钢中加入Cu时，可以调节孔隙率，对显微组织影响较小。抗拉强度在0~3.5 % Cu含量范围内呈现先升高后稍有下降的趋势，即在Cu含量为3.0 %达到峰值。.项目利用冶金副产品制备多孔不锈钢，生产流程简单、成本较低，实现了氧化铁皮的绿色高值利用。