不锈钢粉尘碳热还原产物金属颗粒形貌和尺寸

Morphology and size of the metallic particles generated via carbothermic reduction of stainless steel dust

为促进不锈钢粉尘资源化利用,本文提出碳热还原不锈钢粉尘制备高附加值球形超细金属粉末的新思路.为此,本文系统研究了1350℃下不锈钢粉尘碳热还原产物金属颗粒的微观结构、形貌和尺寸,以及配碳比对其的影响.配碳比从0.9经1.0增加到1.1时,还原失重率变化不明显,Fe-Cr-C金属颗粒球形度有轻微提高,金属颗粒尺寸显著细化后又粗化.粗大金属颗粒(直径约20μm以上)内包含一次和二次M7C3碳化物析出相,其球形度和圆润度均较差.细小金属颗粒(直径约20μm以下)内仅包含二次M_(7)C_(3)碳化物析出相,其球形度和圆润度均较好.热力学计算表明金属颗粒中碳含量(质量分数)超过4.85%时将析出一次M_(7)C_(3)碳化物.一次M_(7)C_(3)碳化物析出相及不锈钢粉尘还原后残留的高熔点、低变形性残渣恶化了金属颗粒球形度和圆润度.

To promote the utilization of stainless steel dust as resource, a new concept that producing high added-value ultra-fine spherical metallic powders via carbothermic reduction of SSD is proposed in this paper. Therefore, the microstructure, morphology and size of metallic particles generated via carbothermic reduction of stainless steel dust at 1 350 ℃ as well as the effect of carbon addition ratio was studied in this paper. Increasing carbon addition ratio from 0.9 via 1.0 to 1.1, the weight loss due to reduction changes non-significantly, the sphericity of the metallic particles improves slightly, and the size of the metallic particles is refined first and then coarsened again. Coarse metallic particles(the diameter is approximately above 20 μm) contain both primary and secondary M7C3 carbide with poor sphericity and roundness. Fine metallic particles(the diameter is approximately below 20 μm) contain only secondary M7C3 carbide with relatively good sphericity and roundness. Thermodynamic calculation shows that precipitation of primary M7C3 carbide occurs once carbon content in the metallic particles exceeds 4.85%. The primary M7C3 carbide together with the residual slag after stainless steel dust reduction with high melting point and poor deformability deteriorates the sphericity and roundness of the metallic particles.