Experimental Study on Stainless Steel Dust by Reduction and Enrichment for Preparation Raw Material of Powder Metallurgy
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ORIGINAL ARTICLE
Experimental Study on Stainless Steel Dust by Reduction and Enrichment for Preparation Raw Material of Powder Metallurgy Ziyang Wang1 • Qiuju Li2 • Fanxi Yang2 • Jixin Zhang2 • Xionggang Lu1
Received: 23 July 2020 / Accepted: 24 October 2020 Ó The Indian Institute of Metals - IIM 2020
Abstract During the production of stainless steel, dust of size less than 50 lm is produced. It has been estimated that the production of one ton stainless steel can produce l8–33 kg dust, which contains a large amount of Fe, Cr, Ni and other valuable metals. In this study, according to the composition requirements of iron-based powder metallurgy friction materials on raw materials, the physicochemical properties of 400 series stainless steel dust were analyzed. The dust was magnetically selected, and the low-medium reduction magnetic separation was adopted, which was explored as a new process for the preparation of powder metallurgy friction material. Considering the magnetic material yield, TFe grade and decalcification effect, the suitable magnetic field strength ranges from 60 to 90 mT and the reduction temperature is from 800 to 900 °C. The main phases of the primary magnetic material after reduction include Fe, FeCr2O4, chromium carbides (Cr3C2 and Cr7C3), MgO and graphite (C), indicating that Fe3O4 is reduced to elemental Fe and FeCr2O4 and MgO are still present in material. Only a small part of the material reduces to chromium carbide at medium and low temperature (800–900 °C). Keywords Friction material Magnetic separation Powder metallurgy Reduction Stainless steel dust
& Qiuju Li [email protected] 1
State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai, China
2
Shanghai Key Laboratory of Modern Metallurgy & Materials Processing, Shanghai University, Shanghai, China
1 Introduction Since the beginning of the twenty-first century, the world stainless steel production has been increasing by 6%. According to the latest statistics released by BBS (ISSF), the global output of raw stainless steel in 2019 reaches 52.1 million tons, an increase in 3.3% per year [1, 2]. It is estimated that the production of one ton stainless steel can produce l8–33 kg of dust [3, 4]. The amount of dust in the electric furnace is about 1–2% of the furnace charge [5, 6] and among which is about 0.7–1% produced in AOD furnace charge [7, 8]. The particle size distribution of 400 series stainless steel dust ranges from 0.69 to 36.08 lm, with a diameter of 4.42 lm [9, 10]. The dust contains a lot of valuable metals such as Fe, Cr, Ni and some trace elements, such as Pb, C, Si, Mg, Mn, Ca and Zn. [11–13]. These metals are mostly in the form of oxides, with Fe in the form of Fe2O3, Cr in the form of CrO and Ni in the form of NiO [14–16]. The chemical composition and physical properties of the steel making dust are different due to the difference in smelting raw materials, smelting temperature, blowing amount. In general, these dusts with small particle size (more than 60% of \ 0.05 mm) has a high iron
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